{"id":7699,"date":"2024-12-05T16:18:04","date_gmt":"2024-12-05T21:18:04","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/pathology\/chapter\/diagnosis-of-acid-base-disorders\/"},"modified":"2025-11-11T23:45:21","modified_gmt":"2025-11-12T04:45:21","slug":"diagnosis-of-acid-base-disorders","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/pathology\/chapter\/diagnosis-of-acid-base-disorders\/","title":{"raw":"Diagnosis of Acid-Base Disorders","rendered":"Diagnosis of Acid-Base Disorders"},"content":{"raw":"<div class=\"textbox textbox--learning-objectives\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Learning Objectives<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nBy the end of this section, you will be able to:\r\n<ul>\r\n \t<li>Differentiate between acid-base disorders, including mixed disorders.<\/li>\r\n \t<li>Follow a basic framework for Identifying acid-base disorders.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\nIn addition to patient history and their clinical manifestations, we clinically diagnose acid base imbalance with a venous or arterial blood gas. A blood gas is a direct measurement of pH and PaCO<sub>2<\/sub>, the Henderson-Hasselbalch equation is used to infer bicarbonate. <sup>[3]<\/sup> Thus, diagnosis of acid base disturbances rely on blood levels of pO<sub>2<\/sub>, pH, pCO<sub>2<\/sub>, and HCO<sub>3<\/sub><sup>-<\/sup>.\u00a0 The pO<sub>2<\/sub> level first determine is hypoxemia is present which sheds a lot of information as to why there is a pH disturbance.\u00a0 A change in pH will have a value associated with the cause and, if the body compensates, a value to indicate the extent of compensation. Because pCO<sub>2<\/sub> is an indicator of carbonic acid, its level determines how much acid is present in the blood.\u00a0 Similarly HCO<sub>3<\/sub><sup>-<\/sup> is a marker of how much base is circulating in the blood.\r\n\r\nIn metabolic acidosis, we will see a decrease in pH &lt;7.35 (i.e. acidosis), which the cause is either a either a gain of acid (that is NOT from CO<sub>2<\/sub>) or loss of base (i.e. abnormally low HCO<sub>3<\/sub><sup>-<\/sup>).\u00a0 If the body compensates, it will do so by trying to get rid of acid in the form of CO<sub>2<\/sub>, making it abnormally low in blood.\u00a0 However, if the body does not compensate, the blood CO<sub>2<\/sub> level will not change from normal range.\r\n\r\nIn respiratory acidosis, we will see a decrease in pH &lt;7.35 (i.e. acidosis), which the cause is respiratory, thus an increased blood pCO<sub>2<\/sub> level will be seen.\u00a0 If the body compensates, the kidneys will try to reabsorb base leading to an increase in blood HCO<sub>3<\/sub><sup>-<\/sup> , above the normal range.\u00a0 However, if the body does not compensate, the HCO<sub>3<\/sub><sup>-<\/sup> levels will not change from its normal range.\r\n\r\nIn metabolic alkalosis, we will see an increase in pH &gt;7.45 (i.e. alkalosis), which the cause is either a gain of base (HCO<sub>3<\/sub><sup>-<\/sup>\u00a0will be increased) or loss of H<sup>+<\/sup> (which is NOT in CO<sub>2<\/sub> form). If the body compensates, the lungs are quick to change respiratory rate to retain CO<sub>2<\/sub> (i.e. acid) such that pCO<sub>2<\/sub> levels will increase to above normal range.\u00a0 However, if the body does not compensate, the pCO<sub>2<\/sub> levels will not change from its normal range.\r\n\r\nIn respiratory alkalosis, we will see an increase in pH &gt;7.45 (i.e. alkalosis), which the cause is loss of pCO<sub>2<\/sub> to abnormally low levels.\u00a0 If the body compensates, the kidneys will try to retain acid and lose HCO<sub>3<\/sub><sup>-<\/sup>, as such HCO<sub>3<\/sub><sup>-<\/sup> will increase to above normal range.\u00a0 However, if the body does not compensate, the HCO<sub>3<\/sub><sup>-<\/sup> levels will not change from its normal range.\r\n\r\nThere are many methods to interpret blood gases to determine the type of acid base disturbance.\u00a0 We highlight 3 different methods.\r\n<h3>Method 1:\u00a0 Tic-Tac-Toe<\/h3>\r\nThe aforementioned summary is written out in a chart which can be used as a form of Tic-Tac-Toe (or Connect Four!!)\u00a0 Thus, when presented with blood gases, you use this chart to make the match.\r\n<table id=\"tbl-ch27_03\" class=\"top-titled\" style=\"height: 75px\">\r\n<tbody>\r\n<tr style=\"height: 15px\">\r\n<th style=\"width: 195.633px;height: 15px\" scope=\"col\"><\/th>\r\n<th style=\"width: 33.0333px;height: 15px\" scope=\"col\">pH<\/th>\r\n<th style=\"width: 87.15px;height: 15px\" scope=\"col\">PCO<sub>2<\/sub><\/th>\r\n<th style=\"width: 121.817px;height: 15px\" scope=\"col\">Total HCO<sub>3<\/sub><sup>\u2013<\/sup><\/th>\r\n<\/tr>\r\n<tr style=\"height: 15px\">\r\n<td style=\"width: 196.133px;height: 15px\">Metabolic acidosis<\/td>\r\n<td style=\"width: 34.0333px;height: 15px\">\u2193<\/td>\r\n<td style=\"width: 88.15px;height: 15px\">N, then \u2193<\/td>\r\n<td style=\"width: 122.317px;height: 15px\">\u2193<\/td>\r\n<\/tr>\r\n<tr style=\"height: 15px\">\r\n<td style=\"width: 196.133px;height: 15px\">Respiratory acidosis<\/td>\r\n<td style=\"width: 34.0333px;height: 15px\">\u2193<\/td>\r\n<td style=\"width: 88.15px;height: 15px\">\u2191<\/td>\r\n<td style=\"width: 122.317px;height: 15px\">N, then \u2191<\/td>\r\n<\/tr>\r\n<tr style=\"height: 15px\">\r\n<td style=\"width: 196.133px;height: 15px\">Metabolic alkalosis<\/td>\r\n<td style=\"width: 34.0333px;height: 15px\">\u2191<\/td>\r\n<td style=\"width: 88.15px;height: 15px\">N, then\u2191<\/td>\r\n<td style=\"width: 122.317px;height: 15px\">\u2191<\/td>\r\n<\/tr>\r\n<tr style=\"height: 15px\">\r\n<td style=\"width: 196.133px;height: 15px\">Respiratory alkalosis<\/td>\r\n<td style=\"width: 34.0333px;height: 15px\">\u2191<\/td>\r\n<td style=\"width: 88.15px;height: 15px\">\u2193<\/td>\r\n<td style=\"width: 122.317px;height: 15px\">N, then \u2193<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<div class=\"textbox textbox--exercises\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Tic Tac Toe method<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nLet's use the example of blood gas results\r\n\r\npH = 7.34 (normal: 7.35-7.45)\r\n\r\npCO<sub>2<\/sub> = 60 mmHg (normal: 35-45 mmHg)\r\n\r\nHCO<sub>3<\/sub><sup>-<\/sup>= 29 mmol\/L (normal: 22-26 mmol\/L)\r\n<ul>\r\n \t<li>1.\u00a0 pH is less than 7.34 --&gt; pH\u2193 .<\/li>\r\n \t<li>2. pCO<sub>2<\/sub> is above normal range --&gt; pCO<sub>2<\/sub>\u2191<\/li>\r\n \t<li>3.\u00a0 HCO<sub>3<\/sub><sup>-<\/sup> is above normal range --&gt; HCO<sub>3<\/sub><sup>-<\/sup>\u2191<\/li>\r\n \t<li>Look at the grid and highlight which matches<\/li>\r\n \t<li>\r\n<table id=\"tbl-ch27_03\" class=\"top-titled\" style=\"height: 75px\">\r\n<tbody>\r\n<tr style=\"height: 15px\">\r\n<th style=\"width: 175px;height: 15px\" scope=\"col\"><\/th>\r\n<th style=\"width: 52.9924px;height: 15px\" scope=\"col\">pH<\/th>\r\n<th style=\"width: 86.9981px;height: 15px\" scope=\"col\">PCO<sub>2<\/sub><\/th>\r\n<th style=\"width: 120.994px;height: 15px\" scope=\"col\">Total HCO<sub>3<\/sub><sup>\u2013<\/sup><\/th>\r\n<\/tr>\r\n<tr style=\"height: 15px\">\r\n<td style=\"width: 175.303px;height: 15px\">Metabolic acidosis<\/td>\r\n<td style=\"width: 53.5985px;height: 15px\">\u2193<\/td>\r\n<td style=\"width: 87.6042px;height: 15px\">N, then \u2193<\/td>\r\n<td style=\"width: 121.297px;height: 15px\">\u2193<\/td>\r\n<\/tr>\r\n<tr style=\"height: 15px\">\r\n<td style=\"width: 175.303px;height: 15px\"><span style=\"background-color: #ffff00\">Respiratory acidosis<\/span><\/td>\r\n<td style=\"width: 53.5985px;height: 15px\"><span style=\"background-color: #ffff00\">\u2193<\/span><\/td>\r\n<td style=\"width: 87.6042px;height: 15px\"><span style=\"background-color: #ffff00\">\u2191<\/span><\/td>\r\n<td style=\"width: 121.297px;height: 15px\"><span style=\"background-color: #ffff00\">N, then \u2191<\/span><\/td>\r\n<\/tr>\r\n<tr style=\"height: 15px\">\r\n<td style=\"width: 175.303px;height: 15px\">Metabolic alkalosis<\/td>\r\n<td style=\"width: 53.5985px;height: 15px\">\u2191<\/td>\r\n<td style=\"width: 87.6042px;height: 15px\">N, then\u2191<\/td>\r\n<td style=\"width: 121.297px;height: 15px\">\u2191<\/td>\r\n<\/tr>\r\n<tr style=\"height: 15px\">\r\n<td style=\"width: 175.303px;height: 15px\">Respiratory alkalosis<\/td>\r\n<td style=\"width: 53.5985px;height: 15px\">\u2191<\/td>\r\n<td style=\"width: 87.6042px;height: 15px\">\u2193<\/td>\r\n<td style=\"width: 121.297px;height: 15px\">N, then \u2193<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<\/li>\r\n<\/ul>\r\nLooks like we have partially compensated respiratory acidosis. We say partially compensated because pH isn't quite in normal range.\r\n\r\n<\/div>\r\n<\/div>\r\n<h3>Method 2: ROME = Respiratory Opposite; Metabolic Equal<\/h3>\r\nThe acronym R means that in respiratory disorders and O means opposite. This means that the pH will be in the opposite direction of the cause.\u00a0 For\u00a0 example, respiratory acidosis will have a pH going down with a pCO<sub>2<\/sub> going up. The M means metabolic disorder and E means equal.\u00a0 This means the direction the pH goes will be the same direction as the cause.\r\n\r\nOnce you figure out the cause, signs of compensation will be the other blood gas value.\u00a0 So, if it's a respiratory cause (ie pCO<sub>2<\/sub> is moving out of range in the opposite direction as pH), then you'll see the HCO<sub>3<\/sub><sup>-<\/sup> move out of normal range IF there is compensation.\u00a0 Similarly, if it's a metabolic cause (i.e. HCO<sub>3<\/sub><sup>-<\/sup> is out of range in the same direction as pH), they you'll see pCO<sub>2<\/sub> move out of normal range IF there is compensation.\r\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">ROME method<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nLet's use the previous example of blood gas results\r\n\r\npH = 7.34 (normal: 7.35-7.45)\r\n\r\npCO2 = 60 mmHg (normal: 35-45 mmHg)\r\n\r\nHCO3 = 29 mmol\/L (normal: 22-26 mmol\/L)\r\n<ul>\r\n \t<li>1.\u00a0 pH is going <span style=\"background-color: #ffff00\">\u2193<\/span> . This suggests we are in an acidotic condition.<\/li>\r\n \t<li>2. pCO<sub>2<\/sub> is going <span style=\"background-color: #ffff00\">\u2191<\/span>, in the <span style=\"background-color: #ffff00\">opposite<\/span> direction as pH. (\"R\" &amp; \"O\") Thus, this is a <span style=\"background-color: #ffff00\">respiratory<\/span> acidosis.<\/li>\r\n \t<li>3.\u00a0 If we have acidosis, we want to retain more base to compensate.\u00a0 We see that HCO<sub>3<\/sub><sup>-<\/sup>\u2191 which will help raise the pH. Yes, we have compensation.<\/li>\r\n<\/ul>\r\nLooks like we have partially compensated respiratory acidosis. We say partially compensated because pH isn't quite in normal range.\r\n\r\n<\/div>\r\n<\/div>\r\n<h3>Method 3: Matching pH with Cause<\/h3>\r\nBecause we know high pCO<sub>2<\/sub> means a lot of acid, we use pCO<sub>2<\/sub> as an indicator for acidosis in respiratory situations.\u00a0 Because we know high HCO<sub>3<\/sub><sup>-<\/sup> means a lot of base and that it's reabsorbed &amp; generated in the kidneys (ie not the lungs), we use this high HCO<sub>3<\/sub><sup>-<\/sup> as an indicator for alkalosis in metabolic situations (ie not the lungs). Once we know which indicator matches the abnormal pH, the other indicator will be moving if there is compensation.\u00a0 So, in respiratory causes, the HCO<sub>3<\/sub><sup>-<\/sup> will go up (in the case of respiratory acidosis) or down (respiratory alkalosis) when the body can compensate.\u00a0 For metabolic pH disturbances, the lungs will quickly change respiratory rate to either tachypnea for pCO<sub>2<\/sub> to go down (in situations of metabolic acidosis) and bradypnea for pCO<sub>2<\/sub> to go up (during metabolic alkalosis)\r\n<div class=\"textbox textbox--exercises\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Matching the pH to the Cause<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nLet's use the previous example of blood gas results\r\n\r\npH = 7.34 (normal: 7.35-7.45)\r\n\r\npCO<sub>2<\/sub> = 60mmHg (normal: 35-45 mmHg)\r\n\r\nHCO<sub>3<\/sub><sup>-<\/sup> = 29mmol\/L (normal: 22-26 mmol\/L)\r\n<ul>\r\n \t<li>1.\u00a0 pH is &lt;7.35. Thus, it is an <span style=\"background-color: #ffff00\">acidotic<\/span> condition.<\/li>\r\n \t<li>2. Which blood gas is also in acidotic range?\u00a0 Well, <span style=\"background-color: #ffff00\">pCO<sub>2<\/sub> is high<\/span> and we know that means lots of acid.\u00a0 So the <span style=\"background-color: #ffff00\">pCO<sub>2<\/sub> level matches the pH<\/span> we have.\u00a0 Thus, this is a respiratory acidosis.<\/li>\r\n \t<li>3.\u00a0 If we have acidosis, we want to retain more base to compensate.\u00a0 We see that\u00a0 HCO<sub>3<\/sub><sup>-<\/sup>\u00a0is increasing which will help raise the pH. Yes, we have compensation<\/li>\r\n<\/ul>\r\nLooks like we have partially compensated respiratory acidosis. We say partially compensated because pH isn't quite in normal range.\r\n\r\n<\/div>\r\n<\/div>\r\n&nbsp;\r\n<div class=\"textbox textbox--exercises\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Steps in Venous Blood Gas Interpretation<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n<ol>\r\n \t<li>Assess the pH alkalotic or acidotic<\/li>\r\n \t<li>Assess the CO<sub>2<\/sub> levels<\/li>\r\n \t<li>Assess for compensation<\/li>\r\n \t<li>Check with the Henderson-Hasselbalch<\/li>\r\n \t<li>Calculate expected compensation<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n<h2>Diagnosis of Mixed Acid-Base Disorders:\u00a0 What If I Have Both a Respiratory AND Metabolic Cause to pH Disturbance?<\/h2>\r\nSo far, we've introduced pH disturbances which are due to one cause - either a respiratory (i.e. lungs) or metabolic (i.e. any tissue other than lungs).\u00a0 However, it is possible for one to have two causes for the pH disturbance. This is definitely evident with patients under medical care. For example, a patient who has sustained hypoxemia from obstruction in the airway (say, for example, pulmonary edema) would be the cause of respiratory acidosis.\u00a0 However, the prolonged hypoxemia means that all of the tissues are getting insufficient oxygen for aerobic metabolism. As a result, the tissues switch to anaerobic metabolism which lactic acid is generated as a byproduct. This accumulation of lactic acid would be a cause of metabolic acidosis.\u00a0 \u00a0Thus, you have both respiratory (carbonic acid from the impaired ventilation) and metabolic acidosis (lactic acid as a result of hypoxemia).\u00a0 This is what we call a mixed condition or mixed disorder.\r\n\r\nIn addition to a thorough medical history and assessing clinical manifestations, blood tests again help the health care team to determine what the cause of the pH disturbance is so that an appropriate treatment plan can be proposed.\r\n<h2>A Step-Wise Method For Diagnosing Disorders Mixed Acid-Base Disorders <sup>[2]<\/sup><\/h2>\r\n1: Obtain ABG\/VBG and Blood Electrolyte Panel\r\n\r\n2: Check Validity of pH using Henderson Hasselbalch\r\n\r\nIf there is discrepancy, consider faulty reading or HAGMA\r\n\r\n3: Identify the primary disorder (metabolic\/respiratory, acidosis\/alkalosis) using the above chart\r\n\r\n4: Calculate Anion gap\r\n\r\n5: Consider the cause\r\n\r\n6: Calculate expected compensation, use the Winter formula, or given values\r\n\r\n7: Consider the presence of mixed acid-base disorder\r\n\r\n8: Consider the Delta-Delta gap\r\n<h2>Mixed Conditions, Winter Formula and Compensation<\/h2>\r\nIf we have established our patient has a metabolic acidosis should utilize the Winter formula to determine if the respiratory compensation is within normal ranges or if it is outside of what is expected. If it is outside what is expected, then we suspect a mixed acid base disorder in our patient, meaning the disorder is driven both by a Metabolic and a Respiratory pathology.\r\n\r\nThe Winter Formula\r\n\r\nExpected PCO<sub>2<\/sub> = (1.5 * HCO<sub>3<\/sub><sup>-<\/sup>)+8\r\n\r\nOur expected PCO<sub>2<\/sub> should be within +\/- 2 of our measured PCO<sub>2<\/sub> on our VBG to be considered normal compensation. <sup>[1]<\/sup>\r\n\r\nExpected compensation. The Winter formula gives us the expected respiratory compensation in the case of a metabolic acidosis, however, you are probably wondering what the expected metabolic compensation is for a respiratory acidosis, and the respective compensations for alkalotic processes. The following chart will provide some reference figures.\r\n\r\nMetabolic alkalosis <sup>[2]<\/sup>\r\nFor each mEq\/L increase in HCO<sub>3<\/sub><sup>-<\/sup>, pCO<sub>2<\/sub> increases by 0.7 mmHg\r\n\r\nRespiratory acidosis: Acute\r\nFor each mmHg increase in pCO<sub>2<\/sub>, HCO<sub>3<\/sub><sup>-<\/sup> increases by 0.1 mEq\/L\r\n\r\nRespiratory acidosis: Chronic\r\nFor each mmHg increase in pCO<sub>2<\/sub>, HCO<sub>3<\/sub><sup>-<\/sup> increases by 0.4 mEq\/L\r\n\r\nRespiratory alkalosis: Acute\r\nFor each mmHg decrease in pCO<sub>2<\/sub>, HCO<sub>3<\/sub><sup>-<\/sup> decreases by 0.2 mEq\/L\r\n\r\nRespiratory alkalosis: Chronic\r\nFor each mmHg decrease in pCO<sub>2<\/sub>, HCO<sub>3<\/sub><sup>-<\/sup> decreases by 0.4 mEq\/L\r\n<h1>Mixed Conditions, Anion Gap, and The Delta Gap<\/h1>\r\nIf a patient is presenting with HAGMA, we must calculate the Delta Gap. If decrease in bicarbonate is greater than the increase in Anion Gap we know that in addition to all the bicarb lost due to an increase in organic acids in the serum, some is being lost by some other mechanism, so therefore we have a mixed HAGMA and NAGMA. When this is the case the Delta Gap will return as &gt;-6. If the increase in Delta Gap is within normal ranges, [6 &gt;x&gt; -6], only a high anion gap acidosis exists. if Delta Gap &gt; 6 that means that for every organic acid added, Bicarbonate levels are not dropping equally. This suggests an underlying metabolic alkalosis mixed with the HAGMA\r\n\r\nDelta Gap = Delta AG - Delta HCO<sub>3<\/sub><sup>-<\/sup>\r\nDelta AG = Observed AG - upper normal AG (12 mmol\/L)\r\nDelta HCO<sub>3<\/sub><sup>-<\/sup> = Lower normal HCO<sub>3<\/sub><sup>-<\/sup> - observed HCO<sub>3<\/sub><sup>-<\/sup> (22 mmol\/L)<sup>[3]<\/sup>\r\n<h1>Case Studies<\/h1>\r\nBelow are 3 case studies with a small clinical picture and blood test results.\u00a0 The goal of these case studies are for interpretation of blood gases, chemistry panel, clinical manifestations, and medical history. With this information, management and treatment options can be discussed to stabilize the patient while the health care team can address the underlying cause.\r\n\r\nReference Ranges\r\n<table class=\"grid\" style=\"border-collapse: collapse;width: 100%;height: 125px\" border=\"0\">\r\n<tbody>\r\n<tr style=\"height: 15px\">\r\n<td style=\"width: 33.3333%;height: 15px\">ABG<\/td>\r\n<td style=\"width: 27.4322%;height: 15px\">Serum Chemistry<\/td>\r\n<td style=\"width: 39.2344%;height: 15px\">Vitals<\/td>\r\n<\/tr>\r\n<tr style=\"height: 110px\">\r\n<td style=\"width: 33.3333%;height: 110px\">pH 7.35-7.45\r\nPaCO<sub>2<\/sub> 35mmHg - 45 mmHg\r\nHCO<sub>3<\/sub><sup>-<\/sup>\u00a022 - 26 mEq\/L\r\nPaO<sub>2<\/sub> 80 mmHg - 100 mmHg<\/td>\r\n<td style=\"width: 27.4322%;height: 110px\">Na<sup>+<\/sup> 135-145 mEq\/L\r\nCl<sup>-<\/sup> 98 - 106 mEq\/L\r\nHCO<sub>3<\/sub><sup>- <\/sup>22 - 26 mEq\/L<\/td>\r\n<td style=\"width: 39.2344%;height: 110px\">BP: 90-120 mmHg \/ 60-80 mmHg\r\nHR: 60-100 bpm\r\nRR: 12-20 breaths per minute\r\nSpO<sub>2<\/sub>: 95%-100%\r\nTemperature (oral): 36.5 - 37.5 <sup>o<\/sup>C<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<h2>Case Study 1<\/h2>\r\n42 year old man is brought into the emergency, found down by paramedics. He has a decreased level of consciousness and is rousable to pain.\r\nThe following vitals and labs are obtained.\r\n<table class=\"grid\" style=\"border-collapse: collapse;width: 100%\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 33.3333%\">ABG<\/td>\r\n<td style=\"width: 33.3333%\">Serum Chemistry<\/td>\r\n<td style=\"width: 33.3333%\">Vitals<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"width: 33.3333%\">pH 7.19\r\nPaCO<sub>2<\/sub> 60mmHg\r\nHCO<sub>3<\/sub><sup>-<\/sup>\u00a020 mEq\/L\r\nPaO<sub>2<\/sub> 68 mmHg<\/td>\r\n<td style=\"width: 33.3333%\">Na<sup>+<\/sup> 140 mEq\/L\r\nCl<sup>-<\/sup> 100 mEq\/L\r\nHCO<sub>3<\/sub><sup>-<\/sup>\u00a020 mEq\/L<\/td>\r\n<td style=\"width: 33.3333%\">BP: 105\/68 mmhg\r\nHR: 112\r\nRR: 8 breaths per minute, shallow and even\r\nSpO<sub>2<\/sub>: 89% on room air\r\nTemp: 36.7<sup>o<\/sup>C<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<h2>Case Study 2<\/h2>\r\n63 year old man walks himself into the emergency. He is experiencing nausea, fatigue, and shortness of breath. He has known Chronic Kidney Disease.\r\nThe following vitals and labs are obtained.\r\n<table class=\"grid\" style=\"border-collapse: collapse;width: 100%;height: 95px\" border=\"0\">\r\n<tbody>\r\n<tr style=\"height: 15px\">\r\n<td style=\"width: 33.3333%;height: 15px\">ABGs<\/td>\r\n<td style=\"width: 33.3333%;height: 15px\">Serum Chemistry<\/td>\r\n<td style=\"width: 33.3333%;height: 15px\">Vitals<\/td>\r\n<\/tr>\r\n<tr style=\"height: 80px\">\r\n<td style=\"width: 33.3333%;height: 80px\">pH 7.27\r\nPaCO<sub>2<\/sub> 31mmHg\r\nHCO<sub>3<\/sub><sup>-<\/sup>\u00a014 mEq\/L\r\nPaO<sub>2<\/sub> 86 mmHg<\/td>\r\n<td style=\"width: 33.3333%;height: 80px\">Na<sup>+<\/sup> 128 mEq\/L\r\nCl<sup>-<\/sup> 104 mEq\/L\r\nHCO<sub>3<\/sub><sup>-<\/sup>\u00a014 mEq\/L<\/td>\r\n<td style=\"width: 33.3333%;height: 80px\">BP: 148\/86 mmhg\r\nHR: 90\r\nRR: 22\r\nSpO<sub>2<\/sub>: 99% on room air\r\nTemp: 36.9<sup>o<\/sup>C<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<h2>Case Study 3<\/h2>\r\n22 year old woman brought into emergency by a friend. Experiencing a sudden onset of persistant vomiting for 36 hours, denies ingestion of toxins. Reports dizziness, weakness.\r\nThe following vitals and labs are obtained.\r\n<table class=\"grid\" style=\"border-collapse: collapse;width: 100%\" border=\"0\">\r\n<tbody>\r\n<tr>\r\n<td style=\"width: 33.3333%\">ABGs<\/td>\r\n<td style=\"width: 33.3333%\">Serum Chemistry<\/td>\r\n<td style=\"width: 33.3333%\">Vitals<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"width: 33.3333%\">pH 7.50\r\nPaCO<sub>2<\/sub> 44mmHg\r\nHCO<sub>3<\/sub><sup>-<\/sup>\u00a032 mEq\/L\r\nPaO<sub>2<\/sub> 92 mmHg<\/td>\r\n<td style=\"width: 33.3333%\">Na<sup>+<\/sup> 134 mEq\/L\r\nCl<sup>-<\/sup> 95 mEq\/L\r\nHCO<sub>3<\/sub><sup>- <\/sup>32 mEq\/L<\/td>\r\n<td style=\"width: 33.3333%\">BP: 90\/60 mmhg\r\nHR: 110\r\nRR: 14\r\nSpO<sub>2<\/sub>: 97% on room air\r\nTemp: 36.5<sup>o<\/sup>C<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<h1>Video Solution: Case Study 1<\/h1>\r\n[h5p id=\"439\"]\r\n\r\n[h5p id=\"438\"]\r\n\r\n[h5p id=\"437\"]\r\n\r\n[h5p id=\"436\"]\r\n<h1>Solution to Case Study 2<\/h1>\r\n1. Obtain ABG\/VBG and Blood Electrolyte Panel\r\n\r\npH 7.27\r\nPaCO<sub>2<\/sub> 31mmHg\r\nHCO<sub>3<\/sub><sup>-<\/sup>\u00a014 mEq\/L\r\nPaO<sub>2<\/sub> 86 mmHg\r\n\r\n2: Check Validity of pH using Henderson Hasselbach\r\n\r\nHenderson Hasselbach calculation of pH = 6.1 + log ([HCO<sub>3<\/sub><sup>-<\/sup>]\/ [CO<sub>2<\/sub>]) where CO<sub>2<\/sub> is 31 mmHg\u00a0 and HCO<sub>3<\/sub><sup>-<\/sup> 14 mmol\/L.\r\n<ul>\r\n \t<li>Recall that we need to use the CO solubility coefficient\u00a0 of 0.03 to convert mmHg to mmol\/L (ie determine how much CO<sub>2<\/sub> is dissolved in blood)\r\n<ul>\r\n \t<li>[CO<sub>2<\/sub>] = 31 mmHg * 0.03 = 0.93 mmol\/L<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li>pH = 6.1 + log (14\/0.93) = 7.27<\/li>\r\n \t<li>\u00a0The measured pH is equal to the calculated pH (via Henderson Hasselbalch).<\/li>\r\n<\/ul>\r\n3: Identify the primary disorder (metabolic\/respiratory, acidosis\/alkalosis) using the Tic Tac Toe method\r\n\r\nTic Tac Toe method reveals Metabolic Acidosis\r\n<div align=\"left\">\r\n<table style=\"height: 76px\">\r\n<tbody>\r\n<tr style=\"height: 16px\">\r\n<td style=\"height: 16px;width: 280.609px\"><\/td>\r\n<td style=\"height: 16px;width: 50.1719px\">pH<\/td>\r\n<td style=\"height: 16px;width: 132.984px\">PCO<sub>2<\/sub><\/td>\r\n<td style=\"height: 16px;width: 172.984px\">Total HCO<sub>3<\/sub><sup>-<\/sup><\/td>\r\n<\/tr>\r\n<tr style=\"height: 15px\">\r\n<td style=\"height: 15px;width: 280.609px\"><span style=\"background-color: #ffff00\">Metabolic acidosis<\/span><\/td>\r\n<td style=\"height: 15px;width: 50.1719px\"><span style=\"background-color: #ffff00\">\u2193<\/span><\/td>\r\n<td style=\"height: 15px;width: 132.984px\"><span style=\"background-color: #ffff00\">N, then \u2193<\/span><\/td>\r\n<td style=\"height: 15px;width: 172.984px\"><span style=\"background-color: #ffff00\">\u2193<\/span><\/td>\r\n<\/tr>\r\n<tr style=\"height: 15px\">\r\n<td style=\"height: 15px;width: 280.609px\">Respiratory acidosis<\/td>\r\n<td style=\"height: 15px;width: 50.1719px\">\u2193<\/td>\r\n<td style=\"height: 15px;width: 132.984px\">\u2191<\/td>\r\n<td style=\"height: 15px;width: 172.984px\">N, then \u2191<\/td>\r\n<\/tr>\r\n<tr style=\"height: 15px\">\r\n<td style=\"height: 15px;width: 280.609px\">Metabolic alkalosis<\/td>\r\n<td style=\"height: 15px;width: 50.1719px\">\u2191<\/td>\r\n<td style=\"height: 15px;width: 132.984px\">N, then\u2191<\/td>\r\n<td style=\"height: 15px;width: 172.984px\">\u2191<\/td>\r\n<\/tr>\r\n<tr style=\"height: 15px\">\r\n<td style=\"height: 15px;width: 280.609px\">Respiratory alkalosis<\/td>\r\n<td style=\"height: 15px;width: 50.1719px\">\u2191<\/td>\r\n<td style=\"height: 15px;width: 132.984px\">\u2193<\/td>\r\n<td style=\"height: 15px;width: 172.984px\">N, then \u2193<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<\/div>\r\n4: Calculate Anion gap\r\n\r\nNa<sup>+<\/sup> 128 mEq\/L\r\nCl<sup>-<\/sup> 104 mEq\/L\r\nHCO<sub>3<\/sub><sup>-<\/sup>\u00a014 mEq\/L\r\n\r\n128 - (104+14) = 10\r\n\r\nAnion gap is less than 12, no HAGMA\r\n\r\n5: Consider the cause\r\n\r\nMetabolic acidosis with a low anion gap, or NAGMA. we use the following pneumonic.\r\n\r\nHARDUP\r\n\r\nH - Hyperchloremia\r\nA - Acetazolamide, Addison's disease\r\nR - Renal Tubular Acidosis\r\nD - Diarrhea, Ileostomies, Fistulae\r\nU - Ureteroenterostomies\r\nP - Pancreatoenterostomies\r\n\r\nOur patient is mildly hyperchloremic but likely to maintain electroneutrality in the face of a dropping bicarbonate level. There is no way for us to know if bicarbonate is dropping due to retention of H+ or GI loss at this stage, so there is little to rule out at the moment. However given the history of CKD and the potential for dilutional hyponatremia (our sodium is a little low and our BP is a little high), we may want to obtain kidney labs\r\n\r\n6: Calculate expected compensation, use Winters formula, or given values\r\n\r\nThe Winter Formula\r\n\r\nExpected PCO<sub>2<\/sub> = (1.5 * HCO<sub>3<\/sub><sup>-<\/sup>)+8\r\n\r\nPaCO<sub>2<\/sub>: 31mmHg\r\nHCO<sub>3<\/sub><sup>-<\/sup>: 14 mEq\/L\r\n\r\nExpected PCO<code>2<\/code> = (1.5*14mmHg) +8\r\nExpected PCO<sub>2<\/sub> = 29mmHg\r\n\r\nActual PCO<sub>2<\/sub> = 31mmHg\r\n\r\nOur expected PCO<sub>2<\/sub> should be within +\/- 2 of our measured PCO<sub>2<\/sub> on our VBG to be considered normal compensation<sup> [1]<\/sup>\r\n\r\nOur expected PCO<sub>2<\/sub> is within +\/-2 and is therefore normal compensation.\r\n\r\nIt is worth noting that our patient has a respiratory rate of 22 which is rapid (tachypnea). This extra ventilation is bringing down our CO<sub>2<\/sub> levels and causing this normal respiratory compensation\r\n\r\n7: Consider the presence of mixed acid-base disorder\r\n\r\nWe do not suspect mixed respiratory disorder in this patient, compensation is as expected.\r\n\r\n8: Consider the Delta-Delta gap\r\n\r\nPatient is not presenting with HAGMA therefore the delta delta gap is not relevant\r\n\r\nFinal solution\r\n\r\nOur patient is experiencing a NAGMA Metabolic Acidosis with partial respiratory compensation and no suspicion of mixed disorder\r\n<h1>Solution to Case Study 3<\/h1>\r\n1: Obtain ABG\/VBG and Blood Electrolyte Panel\r\n\r\npH 7.50\r\nPaCO<sub>2<\/sub> 44mmHg\r\nHCO<sub>3<\/sub><sup>-<\/sup>\u00a032 mEq\/L\r\nPaO<sub>2<\/sub> 92 mmHg\r\n\r\n2: Check Validity of pH using Henderson Hasselbalch\r\n\r\nHenderson Hasselbalch calculation of pH = 6.1 + log ([HCO<sub>3<\/sub><sup>-<\/sup>]\/ [CO<sub>2<\/sub>]) where CO<sub>2<\/sub> is 44 mmHg\u00a0 and HCO<sub>3<\/sub><sup>-<\/sup> 32 mmol\/L.\r\n<ul>\r\n \t<li>Recall that we need to use the CO solubility coefficient\u00a0 of 0.03 to convert mmHg to mmol\/L (ie determine how much CO<sub>2<\/sub> is dissolved in blood)\r\n<ul>\r\n \t<li>[CO<sub>2<\/sub>] = 44 mmHg * 0.03 = 1.32 mmol\/L<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li>pH = 6.1 + log (32\/1.32) = 7.48<\/li>\r\n \t<li>\u00a0The measured pH is equal to the calculated pH (via Henderson Hasselbach). Within the acceptable margin of error.<\/li>\r\n<\/ul>\r\n3: Identify the primary disorder (metabolic\/respiratory, acidosis\/alkalosis) using the Tic Tac Toe\r\n<table id=\"tbl-ch27_03\" class=\"top-titled\">\r\n<tbody>\r\n<tr>\r\n<th style=\"width: 291px\" scope=\"col\"><\/th>\r\n<th style=\"width: 65px\" scope=\"col\">pH<\/th>\r\n<th style=\"width: 144px\" scope=\"col\">PCO<sub>2<\/sub><\/th>\r\n<th style=\"width: 189px\" scope=\"col\">Total HCO<sub>3<\/sub><sup>\u2013<\/sup><\/th>\r\n<\/tr>\r\n<tr>\r\n<td style=\"width: 291.5px\">Metabolic acidosis<\/td>\r\n<td style=\"width: 66px\">\u2193<\/td>\r\n<td style=\"width: 145px\">N, then \u2193<\/td>\r\n<td style=\"width: 189.5px\">\u2193<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"width: 291.5px\">Respiratory acidosis<\/td>\r\n<td style=\"width: 66px\">\u2193<\/td>\r\n<td style=\"width: 145px\">\u2191<\/td>\r\n<td style=\"width: 189.5px\">N, then \u2191<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"width: 291.5px\"><span style=\"background-color: #ffff00\">Metabolic alkalosis<\/span><\/td>\r\n<td style=\"width: 66px\"><span style=\"background-color: #ffff00\">\u2191<\/span><\/td>\r\n<td style=\"width: 145px\"><span style=\"background-color: #ffff00\">N, then\u2191<\/span><\/td>\r\n<td style=\"width: 189.5px\"><span style=\"background-color: #ffff00\">\u2191<\/span><\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"width: 291.5px\">Respiratory alkalosis<\/td>\r\n<td style=\"width: 66px\">\u2191<\/td>\r\n<td style=\"width: 145px\">\u2193<\/td>\r\n<td style=\"width: 189.5px\">N, then \u2193<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nTic Tac Toe method reveals Metabolic Alkalosis\r\n\r\n4: Calculate Anion gap\r\n\r\nThis step may be somewhat unnecessary in our alkalotic patients, as we use it to detect the presence of underlying HAGMA, and differentiate between HAGMA and NAGMA. However it is a quick calculation, and easily done here.\r\n\r\n134 - (95+32) = 6\r\n\r\nAnion gap is less than 12, no HAGMA\r\n\r\n5: Consider the cause\r\n\r\nThe cause of this metabolic alkalosis is likely secondary to GI loss of protons due to the vomiting\r\n\r\n6: Calculate expected compensation, use Winters formula, or given values\r\n\r\nExpected compensation for metabolic alkalosis:\r\n\r\nFor each mEq\/L increase in HCO<sub>3<\/sub><sup>-<\/sup>, pCO<sub>2<\/sub> increases by 0.7 mmHg\r\n\r\n\u0394pCO2 = Current \u2013 Original = 44 mmHg \u2013 40 mmHg = 4 mmHg = \u0394pCO<sub>2<\/sub>\r\n\r\n4 * 0.7 = expected compensation = 2.8\r\n\r\nActual compensation = \u0394pCO<sub>2<\/sub> = 4\r\n\r\nWithin an acceptable margin of expected compensation.\r\n\r\n7: Consider the presence of mixed acid-base disorder\r\n\r\nNo indication of mixed disorder, compensation is as expected.\r\n\r\n8: Consider the Delta-Delta gap\r\n\r\nPatient is not presenting with HAGMA therefore the delta delta gap is not relevant\r\n\r\nFinal solution:\r\n\r\nSo finally we can say we have a metabolic alkalosis with partial respiratory compensation which we suspect is secondary to the GI loss of H+ due to the persistent vomiting.\r\n<h1>References<\/h1>\r\n<ol>\r\n \t<li style=\"list-style-type: none\">\r\n<ol>\r\n \t<li><span style=\"color: #000000\" data-darkreader-inline-color=\"\"><a href=\"https:\/\/www.ncbi.nlm.nih.gov\/books\/NBK482146\/\" data-darkreader-inline-color=\"\">Metabolic Acidosis - StatPearls <\/a><\/span><\/li>\r\n \t<li><span style=\"color: #000000\" data-darkreader-inline-color=\"\"><a style=\"color: #000000\" href=\"https:\/\/doi.org\/10.1007\/978-3-031-25810-7\" data-darkreader-inline-color=\"\"> Fluid, Electrolyte and Acid-Base Disorders: Clinical Evaluation and Management <\/a><\/span><\/li>\r\n \t<li><span style=\"color: #000000\"><a style=\"color: #000000\" href=\"https:\/\/www.ncbi.nlm.nih.gov\/books\/NBK507807\/\">Physiology, Acid Base Balance - StatPearls 4<\/a><\/span><\/li>\r\n<\/ol>\r\n<\/li>\r\n<\/ol>","rendered":"<div class=\"textbox textbox--learning-objectives\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Learning Objectives<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>By the end of this section, you will be able to:<\/p>\n<ul>\n<li>Differentiate between acid-base disorders, including mixed disorders.<\/li>\n<li>Follow a basic framework for Identifying acid-base disorders.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<p>In addition to patient history and their clinical manifestations, we clinically diagnose acid base imbalance with a venous or arterial blood gas. A blood gas is a direct measurement of pH and PaCO<sub>2<\/sub>, the Henderson-Hasselbalch equation is used to infer bicarbonate. <sup>[3]<\/sup> Thus, diagnosis of acid base disturbances rely on blood levels of pO<sub>2<\/sub>, pH, pCO<sub>2<\/sub>, and HCO<sub>3<\/sub><sup>&#8211;<\/sup>.\u00a0 The pO<sub>2<\/sub> level first determine is hypoxemia is present which sheds a lot of information as to why there is a pH disturbance.\u00a0 A change in pH will have a value associated with the cause and, if the body compensates, a value to indicate the extent of compensation. Because pCO<sub>2<\/sub> is an indicator of carbonic acid, its level determines how much acid is present in the blood.\u00a0 Similarly HCO<sub>3<\/sub><sup>&#8211;<\/sup> is a marker of how much base is circulating in the blood.<\/p>\n<p>In metabolic acidosis, we will see a decrease in pH &lt;7.35 (i.e. acidosis), which the cause is either a either a gain of acid (that is NOT from CO<sub>2<\/sub>) or loss of base (i.e. abnormally low HCO<sub>3<\/sub><sup>&#8211;<\/sup>).\u00a0 If the body compensates, it will do so by trying to get rid of acid in the form of CO<sub>2<\/sub>, making it abnormally low in blood.\u00a0 However, if the body does not compensate, the blood CO<sub>2<\/sub> level will not change from normal range.<\/p>\n<p>In respiratory acidosis, we will see a decrease in pH &lt;7.35 (i.e. acidosis), which the cause is respiratory, thus an increased blood pCO<sub>2<\/sub> level will be seen.\u00a0 If the body compensates, the kidneys will try to reabsorb base leading to an increase in blood HCO<sub>3<\/sub><sup>&#8211;<\/sup> , above the normal range.\u00a0 However, if the body does not compensate, the HCO<sub>3<\/sub><sup>&#8211;<\/sup> levels will not change from its normal range.<\/p>\n<p>In metabolic alkalosis, we will see an increase in pH &gt;7.45 (i.e. alkalosis), which the cause is either a gain of base (HCO<sub>3<\/sub><sup>&#8211;<\/sup>\u00a0will be increased) or loss of H<sup>+<\/sup> (which is NOT in CO<sub>2<\/sub> form). If the body compensates, the lungs are quick to change respiratory rate to retain CO<sub>2<\/sub> (i.e. acid) such that pCO<sub>2<\/sub> levels will increase to above normal range.\u00a0 However, if the body does not compensate, the pCO<sub>2<\/sub> levels will not change from its normal range.<\/p>\n<p>In respiratory alkalosis, we will see an increase in pH &gt;7.45 (i.e. alkalosis), which the cause is loss of pCO<sub>2<\/sub> to abnormally low levels.\u00a0 If the body compensates, the kidneys will try to retain acid and lose HCO<sub>3<\/sub><sup>&#8211;<\/sup>, as such HCO<sub>3<\/sub><sup>&#8211;<\/sup> will increase to above normal range.\u00a0 However, if the body does not compensate, the HCO<sub>3<\/sub><sup>&#8211;<\/sup> levels will not change from its normal range.<\/p>\n<p>There are many methods to interpret blood gases to determine the type of acid base disturbance.\u00a0 We highlight 3 different methods.<\/p>\n<h3>Method 1:\u00a0 Tic-Tac-Toe<\/h3>\n<p>The aforementioned summary is written out in a chart which can be used as a form of Tic-Tac-Toe (or Connect Four!!)\u00a0 Thus, when presented with blood gases, you use this chart to make the match.<\/p>\n<table id=\"tbl-ch27_03\" class=\"top-titled\" style=\"height: 75px\">\n<tbody>\n<tr style=\"height: 15px\">\n<th style=\"width: 195.633px;height: 15px\" scope=\"col\"><\/th>\n<th style=\"width: 33.0333px;height: 15px\" scope=\"col\">pH<\/th>\n<th style=\"width: 87.15px;height: 15px\" scope=\"col\">PCO<sub>2<\/sub><\/th>\n<th style=\"width: 121.817px;height: 15px\" scope=\"col\">Total HCO<sub>3<\/sub><sup>\u2013<\/sup><\/th>\n<\/tr>\n<tr style=\"height: 15px\">\n<td style=\"width: 196.133px;height: 15px\">Metabolic acidosis<\/td>\n<td style=\"width: 34.0333px;height: 15px\">\u2193<\/td>\n<td style=\"width: 88.15px;height: 15px\">N, then \u2193<\/td>\n<td style=\"width: 122.317px;height: 15px\">\u2193<\/td>\n<\/tr>\n<tr style=\"height: 15px\">\n<td style=\"width: 196.133px;height: 15px\">Respiratory acidosis<\/td>\n<td style=\"width: 34.0333px;height: 15px\">\u2193<\/td>\n<td style=\"width: 88.15px;height: 15px\">\u2191<\/td>\n<td style=\"width: 122.317px;height: 15px\">N, then \u2191<\/td>\n<\/tr>\n<tr style=\"height: 15px\">\n<td style=\"width: 196.133px;height: 15px\">Metabolic alkalosis<\/td>\n<td style=\"width: 34.0333px;height: 15px\">\u2191<\/td>\n<td style=\"width: 88.15px;height: 15px\">N, then\u2191<\/td>\n<td style=\"width: 122.317px;height: 15px\">\u2191<\/td>\n<\/tr>\n<tr style=\"height: 15px\">\n<td style=\"width: 196.133px;height: 15px\">Respiratory alkalosis<\/td>\n<td style=\"width: 34.0333px;height: 15px\">\u2191<\/td>\n<td style=\"width: 88.15px;height: 15px\">\u2193<\/td>\n<td style=\"width: 122.317px;height: 15px\">N, then \u2193<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<div class=\"textbox textbox--exercises\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Tic Tac Toe method<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>Let&#8217;s use the example of blood gas results<\/p>\n<p>pH = 7.34 (normal: 7.35-7.45)<\/p>\n<p>pCO<sub>2<\/sub> = 60 mmHg (normal: 35-45 mmHg)<\/p>\n<p>HCO<sub>3<\/sub><sup>&#8211;<\/sup>= 29 mmol\/L (normal: 22-26 mmol\/L)<\/p>\n<ul>\n<li>1.\u00a0 pH is less than 7.34 &#8211;&gt; pH\u2193 .<\/li>\n<li>2. pCO<sub>2<\/sub> is above normal range &#8211;&gt; pCO<sub>2<\/sub>\u2191<\/li>\n<li>3.\u00a0 HCO<sub>3<\/sub><sup>&#8211;<\/sup> is above normal range &#8211;&gt; HCO<sub>3<\/sub><sup>&#8211;<\/sup>\u2191<\/li>\n<li>Look at the grid and highlight which matches<\/li>\n<li>\n<table id=\"tbl-ch27_03\" class=\"top-titled\" style=\"height: 75px\">\n<tbody>\n<tr style=\"height: 15px\">\n<th style=\"width: 175px;height: 15px\" scope=\"col\"><\/th>\n<th style=\"width: 52.9924px;height: 15px\" scope=\"col\">pH<\/th>\n<th style=\"width: 86.9981px;height: 15px\" scope=\"col\">PCO<sub>2<\/sub><\/th>\n<th style=\"width: 120.994px;height: 15px\" scope=\"col\">Total HCO<sub>3<\/sub><sup>\u2013<\/sup><\/th>\n<\/tr>\n<tr style=\"height: 15px\">\n<td style=\"width: 175.303px;height: 15px\">Metabolic acidosis<\/td>\n<td style=\"width: 53.5985px;height: 15px\">\u2193<\/td>\n<td style=\"width: 87.6042px;height: 15px\">N, then \u2193<\/td>\n<td style=\"width: 121.297px;height: 15px\">\u2193<\/td>\n<\/tr>\n<tr style=\"height: 15px\">\n<td style=\"width: 175.303px;height: 15px\"><span style=\"background-color: #ffff00\">Respiratory acidosis<\/span><\/td>\n<td style=\"width: 53.5985px;height: 15px\"><span style=\"background-color: #ffff00\">\u2193<\/span><\/td>\n<td style=\"width: 87.6042px;height: 15px\"><span style=\"background-color: #ffff00\">\u2191<\/span><\/td>\n<td style=\"width: 121.297px;height: 15px\"><span style=\"background-color: #ffff00\">N, then \u2191<\/span><\/td>\n<\/tr>\n<tr style=\"height: 15px\">\n<td style=\"width: 175.303px;height: 15px\">Metabolic alkalosis<\/td>\n<td style=\"width: 53.5985px;height: 15px\">\u2191<\/td>\n<td style=\"width: 87.6042px;height: 15px\">N, then\u2191<\/td>\n<td style=\"width: 121.297px;height: 15px\">\u2191<\/td>\n<\/tr>\n<tr style=\"height: 15px\">\n<td style=\"width: 175.303px;height: 15px\">Respiratory alkalosis<\/td>\n<td style=\"width: 53.5985px;height: 15px\">\u2191<\/td>\n<td style=\"width: 87.6042px;height: 15px\">\u2193<\/td>\n<td style=\"width: 121.297px;height: 15px\">N, then \u2193<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/li>\n<\/ul>\n<p>Looks like we have partially compensated respiratory acidosis. We say partially compensated because pH isn&#8217;t quite in normal range.<\/p>\n<\/div>\n<\/div>\n<h3>Method 2: ROME = Respiratory Opposite; Metabolic Equal<\/h3>\n<p>The acronym R means that in respiratory disorders and O means opposite. This means that the pH will be in the opposite direction of the cause.\u00a0 For\u00a0 example, respiratory acidosis will have a pH going down with a pCO<sub>2<\/sub> going up. The M means metabolic disorder and E means equal.\u00a0 This means the direction the pH goes will be the same direction as the cause.<\/p>\n<p>Once you figure out the cause, signs of compensation will be the other blood gas value.\u00a0 So, if it&#8217;s a respiratory cause (ie pCO<sub>2<\/sub> is moving out of range in the opposite direction as pH), then you&#8217;ll see the HCO<sub>3<\/sub><sup>&#8211;<\/sup> move out of normal range IF there is compensation.\u00a0 Similarly, if it&#8217;s a metabolic cause (i.e. HCO<sub>3<\/sub><sup>&#8211;<\/sup> is out of range in the same direction as pH), they you&#8217;ll see pCO<sub>2<\/sub> move out of normal range IF there is compensation.<\/p>\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">ROME method<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>Let&#8217;s use the previous example of blood gas results<\/p>\n<p>pH = 7.34 (normal: 7.35-7.45)<\/p>\n<p>pCO2 = 60 mmHg (normal: 35-45 mmHg)<\/p>\n<p>HCO3 = 29 mmol\/L (normal: 22-26 mmol\/L)<\/p>\n<ul>\n<li>1.\u00a0 pH is going <span style=\"background-color: #ffff00\">\u2193<\/span> . This suggests we are in an acidotic condition.<\/li>\n<li>2. pCO<sub>2<\/sub> is going <span style=\"background-color: #ffff00\">\u2191<\/span>, in the <span style=\"background-color: #ffff00\">opposite<\/span> direction as pH. (&#8220;R&#8221; &amp; &#8220;O&#8221;) Thus, this is a <span style=\"background-color: #ffff00\">respiratory<\/span> acidosis.<\/li>\n<li>3.\u00a0 If we have acidosis, we want to retain more base to compensate.\u00a0 We see that HCO<sub>3<\/sub><sup>&#8211;<\/sup>\u2191 which will help raise the pH. Yes, we have compensation.<\/li>\n<\/ul>\n<p>Looks like we have partially compensated respiratory acidosis. We say partially compensated because pH isn&#8217;t quite in normal range.<\/p>\n<\/div>\n<\/div>\n<h3>Method 3: Matching pH with Cause<\/h3>\n<p>Because we know high pCO<sub>2<\/sub> means a lot of acid, we use pCO<sub>2<\/sub> as an indicator for acidosis in respiratory situations.\u00a0 Because we know high HCO<sub>3<\/sub><sup>&#8211;<\/sup> means a lot of base and that it&#8217;s reabsorbed &amp; generated in the kidneys (ie not the lungs), we use this high HCO<sub>3<\/sub><sup>&#8211;<\/sup> as an indicator for alkalosis in metabolic situations (ie not the lungs). Once we know which indicator matches the abnormal pH, the other indicator will be moving if there is compensation.\u00a0 So, in respiratory causes, the HCO<sub>3<\/sub><sup>&#8211;<\/sup> will go up (in the case of respiratory acidosis) or down (respiratory alkalosis) when the body can compensate.\u00a0 For metabolic pH disturbances, the lungs will quickly change respiratory rate to either tachypnea for pCO<sub>2<\/sub> to go down (in situations of metabolic acidosis) and bradypnea for pCO<sub>2<\/sub> to go up (during metabolic alkalosis)<\/p>\n<div class=\"textbox textbox--exercises\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Matching the pH to the Cause<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>Let&#8217;s use the previous example of blood gas results<\/p>\n<p>pH = 7.34 (normal: 7.35-7.45)<\/p>\n<p>pCO<sub>2<\/sub> = 60mmHg (normal: 35-45 mmHg)<\/p>\n<p>HCO<sub>3<\/sub><sup>&#8211;<\/sup> = 29mmol\/L (normal: 22-26 mmol\/L)<\/p>\n<ul>\n<li>1.\u00a0 pH is &lt;7.35. Thus, it is an <span style=\"background-color: #ffff00\">acidotic<\/span> condition.<\/li>\n<li>2. Which blood gas is also in acidotic range?\u00a0 Well, <span style=\"background-color: #ffff00\">pCO<sub>2<\/sub> is high<\/span> and we know that means lots of acid.\u00a0 So the <span style=\"background-color: #ffff00\">pCO<sub>2<\/sub> level matches the pH<\/span> we have.\u00a0 Thus, this is a respiratory acidosis.<\/li>\n<li>3.\u00a0 If we have acidosis, we want to retain more base to compensate.\u00a0 We see that\u00a0 HCO<sub>3<\/sub><sup>&#8211;<\/sup>\u00a0is increasing which will help raise the pH. Yes, we have compensation<\/li>\n<\/ul>\n<p>Looks like we have partially compensated respiratory acidosis. We say partially compensated because pH isn&#8217;t quite in normal range.<\/p>\n<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<div class=\"textbox textbox--exercises\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Steps in Venous Blood Gas Interpretation<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<ol>\n<li>Assess the pH alkalotic or acidotic<\/li>\n<li>Assess the CO<sub>2<\/sub> levels<\/li>\n<li>Assess for compensation<\/li>\n<li>Check with the Henderson-Hasselbalch<\/li>\n<li>Calculate expected compensation<\/li>\n<\/ol>\n<\/div>\n<\/div>\n<h2>Diagnosis of Mixed Acid-Base Disorders:\u00a0 What If I Have Both a Respiratory AND Metabolic Cause to pH Disturbance?<\/h2>\n<p>So far, we&#8217;ve introduced pH disturbances which are due to one cause &#8211; either a respiratory (i.e. lungs) or metabolic (i.e. any tissue other than lungs).\u00a0 However, it is possible for one to have two causes for the pH disturbance. This is definitely evident with patients under medical care. For example, a patient who has sustained hypoxemia from obstruction in the airway (say, for example, pulmonary edema) would be the cause of respiratory acidosis.\u00a0 However, the prolonged hypoxemia means that all of the tissues are getting insufficient oxygen for aerobic metabolism. As a result, the tissues switch to anaerobic metabolism which lactic acid is generated as a byproduct. This accumulation of lactic acid would be a cause of metabolic acidosis.\u00a0 \u00a0Thus, you have both respiratory (carbonic acid from the impaired ventilation) and metabolic acidosis (lactic acid as a result of hypoxemia).\u00a0 This is what we call a mixed condition or mixed disorder.<\/p>\n<p>In addition to a thorough medical history and assessing clinical manifestations, blood tests again help the health care team to determine what the cause of the pH disturbance is so that an appropriate treatment plan can be proposed.<\/p>\n<h2>A Step-Wise Method For Diagnosing Disorders Mixed Acid-Base Disorders <sup>[2]<\/sup><\/h2>\n<p>1: Obtain ABG\/VBG and Blood Electrolyte Panel<\/p>\n<p>2: Check Validity of pH using Henderson Hasselbalch<\/p>\n<p>If there is discrepancy, consider faulty reading or HAGMA<\/p>\n<p>3: Identify the primary disorder (metabolic\/respiratory, acidosis\/alkalosis) using the above chart<\/p>\n<p>4: Calculate Anion gap<\/p>\n<p>5: Consider the cause<\/p>\n<p>6: Calculate expected compensation, use the Winter formula, or given values<\/p>\n<p>7: Consider the presence of mixed acid-base disorder<\/p>\n<p>8: Consider the Delta-Delta gap<\/p>\n<h2>Mixed Conditions, Winter Formula and Compensation<\/h2>\n<p>If we have established our patient has a metabolic acidosis should utilize the Winter formula to determine if the respiratory compensation is within normal ranges or if it is outside of what is expected. If it is outside what is expected, then we suspect a mixed acid base disorder in our patient, meaning the disorder is driven both by a Metabolic and a Respiratory pathology.<\/p>\n<p>The Winter Formula<\/p>\n<p>Expected PCO<sub>2<\/sub> = (1.5 * HCO<sub>3<\/sub><sup>&#8211;<\/sup>)+8<\/p>\n<p>Our expected PCO<sub>2<\/sub> should be within +\/- 2 of our measured PCO<sub>2<\/sub> on our VBG to be considered normal compensation. <sup>[1]<\/sup><\/p>\n<p>Expected compensation. The Winter formula gives us the expected respiratory compensation in the case of a metabolic acidosis, however, you are probably wondering what the expected metabolic compensation is for a respiratory acidosis, and the respective compensations for alkalotic processes. The following chart will provide some reference figures.<\/p>\n<p>Metabolic alkalosis <sup>[2]<\/sup><br \/>\nFor each mEq\/L increase in HCO<sub>3<\/sub><sup>&#8211;<\/sup>, pCO<sub>2<\/sub> increases by 0.7 mmHg<\/p>\n<p>Respiratory acidosis: Acute<br \/>\nFor each mmHg increase in pCO<sub>2<\/sub>, HCO<sub>3<\/sub><sup>&#8211;<\/sup> increases by 0.1 mEq\/L<\/p>\n<p>Respiratory acidosis: Chronic<br \/>\nFor each mmHg increase in pCO<sub>2<\/sub>, HCO<sub>3<\/sub><sup>&#8211;<\/sup> increases by 0.4 mEq\/L<\/p>\n<p>Respiratory alkalosis: Acute<br \/>\nFor each mmHg decrease in pCO<sub>2<\/sub>, HCO<sub>3<\/sub><sup>&#8211;<\/sup> decreases by 0.2 mEq\/L<\/p>\n<p>Respiratory alkalosis: Chronic<br \/>\nFor each mmHg decrease in pCO<sub>2<\/sub>, HCO<sub>3<\/sub><sup>&#8211;<\/sup> decreases by 0.4 mEq\/L<\/p>\n<h1>Mixed Conditions, Anion Gap, and The Delta Gap<\/h1>\n<p>If a patient is presenting with HAGMA, we must calculate the Delta Gap. If decrease in bicarbonate is greater than the increase in Anion Gap we know that in addition to all the bicarb lost due to an increase in organic acids in the serum, some is being lost by some other mechanism, so therefore we have a mixed HAGMA and NAGMA. When this is the case the Delta Gap will return as &gt;-6. If the increase in Delta Gap is within normal ranges, [6 &gt;x&gt; -6], only a high anion gap acidosis exists. if Delta Gap &gt; 6 that means that for every organic acid added, Bicarbonate levels are not dropping equally. This suggests an underlying metabolic alkalosis mixed with the HAGMA<\/p>\n<p>Delta Gap = Delta AG &#8211; Delta HCO<sub>3<\/sub><sup>&#8211;<\/sup><br \/>\nDelta AG = Observed AG &#8211; upper normal AG (12 mmol\/L)<br \/>\nDelta HCO<sub>3<\/sub><sup>&#8211;<\/sup> = Lower normal HCO<sub>3<\/sub><sup>&#8211;<\/sup> &#8211; observed HCO<sub>3<\/sub><sup>&#8211;<\/sup> (22 mmol\/L)<sup>[3]<\/sup><\/p>\n<h1>Case Studies<\/h1>\n<p>Below are 3 case studies with a small clinical picture and blood test results.\u00a0 The goal of these case studies are for interpretation of blood gases, chemistry panel, clinical manifestations, and medical history. With this information, management and treatment options can be discussed to stabilize the patient while the health care team can address the underlying cause.<\/p>\n<p>Reference Ranges<\/p>\n<table class=\"grid\" style=\"border-collapse: collapse;width: 100%;height: 125px\">\n<tbody>\n<tr style=\"height: 15px\">\n<td style=\"width: 33.3333%;height: 15px\">ABG<\/td>\n<td style=\"width: 27.4322%;height: 15px\">Serum Chemistry<\/td>\n<td style=\"width: 39.2344%;height: 15px\">Vitals<\/td>\n<\/tr>\n<tr style=\"height: 110px\">\n<td style=\"width: 33.3333%;height: 110px\">pH 7.35-7.45<br \/>\nPaCO<sub>2<\/sub> 35mmHg &#8211; 45 mmHg<br \/>\nHCO<sub>3<\/sub><sup>&#8211;<\/sup>\u00a022 &#8211; 26 mEq\/L<br \/>\nPaO<sub>2<\/sub> 80 mmHg &#8211; 100 mmHg<\/td>\n<td style=\"width: 27.4322%;height: 110px\">Na<sup>+<\/sup> 135-145 mEq\/L<br \/>\nCl<sup>&#8211;<\/sup> 98 &#8211; 106 mEq\/L<br \/>\nHCO<sub>3<\/sub><sup>&#8211; <\/sup>22 &#8211; 26 mEq\/L<\/td>\n<td style=\"width: 39.2344%;height: 110px\">BP: 90-120 mmHg \/ 60-80 mmHg<br \/>\nHR: 60-100 bpm<br \/>\nRR: 12-20 breaths per minute<br \/>\nSpO<sub>2<\/sub>: 95%-100%<br \/>\nTemperature (oral): 36.5 &#8211; 37.5 <sup>o<\/sup>C<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>Case Study 1<\/h2>\n<p>42 year old man is brought into the emergency, found down by paramedics. He has a decreased level of consciousness and is rousable to pain.<br \/>\nThe following vitals and labs are obtained.<\/p>\n<table class=\"grid\" style=\"border-collapse: collapse;width: 100%\">\n<tbody>\n<tr>\n<td style=\"width: 33.3333%\">ABG<\/td>\n<td style=\"width: 33.3333%\">Serum Chemistry<\/td>\n<td style=\"width: 33.3333%\">Vitals<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 33.3333%\">pH 7.19<br \/>\nPaCO<sub>2<\/sub> 60mmHg<br \/>\nHCO<sub>3<\/sub><sup>&#8211;<\/sup>\u00a020 mEq\/L<br \/>\nPaO<sub>2<\/sub> 68 mmHg<\/td>\n<td style=\"width: 33.3333%\">Na<sup>+<\/sup> 140 mEq\/L<br \/>\nCl<sup>&#8211;<\/sup> 100 mEq\/L<br \/>\nHCO<sub>3<\/sub><sup>&#8211;<\/sup>\u00a020 mEq\/L<\/td>\n<td style=\"width: 33.3333%\">BP: 105\/68 mmhg<br \/>\nHR: 112<br \/>\nRR: 8 breaths per minute, shallow and even<br \/>\nSpO<sub>2<\/sub>: 89% on room air<br \/>\nTemp: 36.7<sup>o<\/sup>C<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>Case Study 2<\/h2>\n<p>63 year old man walks himself into the emergency. He is experiencing nausea, fatigue, and shortness of breath. He has known Chronic Kidney Disease.<br \/>\nThe following vitals and labs are obtained.<\/p>\n<table class=\"grid\" style=\"border-collapse: collapse;width: 100%;height: 95px\">\n<tbody>\n<tr style=\"height: 15px\">\n<td style=\"width: 33.3333%;height: 15px\">ABGs<\/td>\n<td style=\"width: 33.3333%;height: 15px\">Serum Chemistry<\/td>\n<td style=\"width: 33.3333%;height: 15px\">Vitals<\/td>\n<\/tr>\n<tr style=\"height: 80px\">\n<td style=\"width: 33.3333%;height: 80px\">pH 7.27<br \/>\nPaCO<sub>2<\/sub> 31mmHg<br \/>\nHCO<sub>3<\/sub><sup>&#8211;<\/sup>\u00a014 mEq\/L<br \/>\nPaO<sub>2<\/sub> 86 mmHg<\/td>\n<td style=\"width: 33.3333%;height: 80px\">Na<sup>+<\/sup> 128 mEq\/L<br \/>\nCl<sup>&#8211;<\/sup> 104 mEq\/L<br \/>\nHCO<sub>3<\/sub><sup>&#8211;<\/sup>\u00a014 mEq\/L<\/td>\n<td style=\"width: 33.3333%;height: 80px\">BP: 148\/86 mmhg<br \/>\nHR: 90<br \/>\nRR: 22<br \/>\nSpO<sub>2<\/sub>: 99% on room air<br \/>\nTemp: 36.9<sup>o<\/sup>C<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>Case Study 3<\/h2>\n<p>22 year old woman brought into emergency by a friend. Experiencing a sudden onset of persistant vomiting for 36 hours, denies ingestion of toxins. Reports dizziness, weakness.<br \/>\nThe following vitals and labs are obtained.<\/p>\n<table class=\"grid\" style=\"border-collapse: collapse;width: 100%\">\n<tbody>\n<tr>\n<td style=\"width: 33.3333%\">ABGs<\/td>\n<td style=\"width: 33.3333%\">Serum Chemistry<\/td>\n<td style=\"width: 33.3333%\">Vitals<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 33.3333%\">pH 7.50<br \/>\nPaCO<sub>2<\/sub> 44mmHg<br \/>\nHCO<sub>3<\/sub><sup>&#8211;<\/sup>\u00a032 mEq\/L<br \/>\nPaO<sub>2<\/sub> 92 mmHg<\/td>\n<td style=\"width: 33.3333%\">Na<sup>+<\/sup> 134 mEq\/L<br \/>\nCl<sup>&#8211;<\/sup> 95 mEq\/L<br \/>\nHCO<sub>3<\/sub><sup>&#8211; <\/sup>32 mEq\/L<\/td>\n<td style=\"width: 33.3333%\">BP: 90\/60 mmhg<br \/>\nHR: 110<br \/>\nRR: 14<br \/>\nSpO<sub>2<\/sub>: 97% on room air<br \/>\nTemp: 36.5<sup>o<\/sup>C<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h1>Video Solution: Case Study 1<\/h1>\n<div id=\"h5p-439\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-439\" class=\"h5p-iframe\" data-content-id=\"439\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Answer to Case Study 1\"><\/iframe><\/div>\n<\/div>\n<div id=\"h5p-438\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-438\" class=\"h5p-iframe\" data-content-id=\"438\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Primary cause and Anion Gap\"><\/iframe><\/div>\n<\/div>\n<div id=\"h5p-437\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-437\" class=\"h5p-iframe\" data-content-id=\"437\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Cause and delta gap\"><\/iframe><\/div>\n<\/div>\n<div id=\"h5p-436\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-436\" class=\"h5p-iframe\" data-content-id=\"436\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Mnemonics for high and non anion gap\"><\/iframe><\/div>\n<\/div>\n<h1>Solution to Case Study 2<\/h1>\n<p>1. Obtain ABG\/VBG and Blood Electrolyte Panel<\/p>\n<p>pH 7.27<br \/>\nPaCO<sub>2<\/sub> 31mmHg<br \/>\nHCO<sub>3<\/sub><sup>&#8211;<\/sup>\u00a014 mEq\/L<br \/>\nPaO<sub>2<\/sub> 86 mmHg<\/p>\n<p>2: Check Validity of pH using Henderson Hasselbach<\/p>\n<p>Henderson Hasselbach calculation of pH = 6.1 + log ([HCO<sub>3<\/sub><sup>&#8211;<\/sup>]\/ [CO<sub>2<\/sub>]) where CO<sub>2<\/sub> is 31 mmHg\u00a0 and HCO<sub>3<\/sub><sup>&#8211;<\/sup> 14 mmol\/L.<\/p>\n<ul>\n<li>Recall that we need to use the CO solubility coefficient\u00a0 of 0.03 to convert mmHg to mmol\/L (ie determine how much CO<sub>2<\/sub> is dissolved in blood)\n<ul>\n<li>[CO<sub>2<\/sub>] = 31 mmHg * 0.03 = 0.93 mmol\/L<\/li>\n<\/ul>\n<\/li>\n<li>pH = 6.1 + log (14\/0.93) = 7.27<\/li>\n<li>\u00a0The measured pH is equal to the calculated pH (via Henderson Hasselbalch).<\/li>\n<\/ul>\n<p>3: Identify the primary disorder (metabolic\/respiratory, acidosis\/alkalosis) using the Tic Tac Toe method<\/p>\n<p>Tic Tac Toe method reveals Metabolic Acidosis<\/p>\n<div style=\"text-align: left;\">\n<table style=\"height: 76px\">\n<tbody>\n<tr style=\"height: 16px\">\n<td style=\"height: 16px;width: 280.609px\"><\/td>\n<td style=\"height: 16px;width: 50.1719px\">pH<\/td>\n<td style=\"height: 16px;width: 132.984px\">PCO<sub>2<\/sub><\/td>\n<td style=\"height: 16px;width: 172.984px\">Total HCO<sub>3<\/sub><sup>&#8211;<\/sup><\/td>\n<\/tr>\n<tr style=\"height: 15px\">\n<td style=\"height: 15px;width: 280.609px\"><span style=\"background-color: #ffff00\">Metabolic acidosis<\/span><\/td>\n<td style=\"height: 15px;width: 50.1719px\"><span style=\"background-color: #ffff00\">\u2193<\/span><\/td>\n<td style=\"height: 15px;width: 132.984px\"><span style=\"background-color: #ffff00\">N, then \u2193<\/span><\/td>\n<td style=\"height: 15px;width: 172.984px\"><span style=\"background-color: #ffff00\">\u2193<\/span><\/td>\n<\/tr>\n<tr style=\"height: 15px\">\n<td style=\"height: 15px;width: 280.609px\">Respiratory acidosis<\/td>\n<td style=\"height: 15px;width: 50.1719px\">\u2193<\/td>\n<td style=\"height: 15px;width: 132.984px\">\u2191<\/td>\n<td style=\"height: 15px;width: 172.984px\">N, then \u2191<\/td>\n<\/tr>\n<tr style=\"height: 15px\">\n<td style=\"height: 15px;width: 280.609px\">Metabolic alkalosis<\/td>\n<td style=\"height: 15px;width: 50.1719px\">\u2191<\/td>\n<td style=\"height: 15px;width: 132.984px\">N, then\u2191<\/td>\n<td style=\"height: 15px;width: 172.984px\">\u2191<\/td>\n<\/tr>\n<tr style=\"height: 15px\">\n<td style=\"height: 15px;width: 280.609px\">Respiratory alkalosis<\/td>\n<td style=\"height: 15px;width: 50.1719px\">\u2191<\/td>\n<td style=\"height: 15px;width: 132.984px\">\u2193<\/td>\n<td style=\"height: 15px;width: 172.984px\">N, then \u2193<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>4: Calculate Anion gap<\/p>\n<p>Na<sup>+<\/sup> 128 mEq\/L<br \/>\nCl<sup>&#8211;<\/sup> 104 mEq\/L<br \/>\nHCO<sub>3<\/sub><sup>&#8211;<\/sup>\u00a014 mEq\/L<\/p>\n<p>128 &#8211; (104+14) = 10<\/p>\n<p>Anion gap is less than 12, no HAGMA<\/p>\n<p>5: Consider the cause<\/p>\n<p>Metabolic acidosis with a low anion gap, or NAGMA. we use the following pneumonic.<\/p>\n<p>HARDUP<\/p>\n<p>H &#8211; Hyperchloremia<br \/>\nA &#8211; Acetazolamide, Addison&#8217;s disease<br \/>\nR &#8211; Renal Tubular Acidosis<br \/>\nD &#8211; Diarrhea, Ileostomies, Fistulae<br \/>\nU &#8211; Ureteroenterostomies<br \/>\nP &#8211; Pancreatoenterostomies<\/p>\n<p>Our patient is mildly hyperchloremic but likely to maintain electroneutrality in the face of a dropping bicarbonate level. There is no way for us to know if bicarbonate is dropping due to retention of H+ or GI loss at this stage, so there is little to rule out at the moment. However given the history of CKD and the potential for dilutional hyponatremia (our sodium is a little low and our BP is a little high), we may want to obtain kidney labs<\/p>\n<p>6: Calculate expected compensation, use Winters formula, or given values<\/p>\n<p>The Winter Formula<\/p>\n<p>Expected PCO<sub>2<\/sub> = (1.5 * HCO<sub>3<\/sub><sup>&#8211;<\/sup>)+8<\/p>\n<p>PaCO<sub>2<\/sub>: 31mmHg<br \/>\nHCO<sub>3<\/sub><sup>&#8211;<\/sup>: 14 mEq\/L<\/p>\n<p>Expected PCO<code>2<\/code> = (1.5*14mmHg) +8<br \/>\nExpected PCO<sub>2<\/sub> = 29mmHg<\/p>\n<p>Actual PCO<sub>2<\/sub> = 31mmHg<\/p>\n<p>Our expected PCO<sub>2<\/sub> should be within +\/- 2 of our measured PCO<sub>2<\/sub> on our VBG to be considered normal compensation<sup> [1]<\/sup><\/p>\n<p>Our expected PCO<sub>2<\/sub> is within +\/-2 and is therefore normal compensation.<\/p>\n<p>It is worth noting that our patient has a respiratory rate of 22 which is rapid (tachypnea). This extra ventilation is bringing down our CO<sub>2<\/sub> levels and causing this normal respiratory compensation<\/p>\n<p>7: Consider the presence of mixed acid-base disorder<\/p>\n<p>We do not suspect mixed respiratory disorder in this patient, compensation is as expected.<\/p>\n<p>8: Consider the Delta-Delta gap<\/p>\n<p>Patient is not presenting with HAGMA therefore the delta delta gap is not relevant<\/p>\n<p>Final solution<\/p>\n<p>Our patient is experiencing a NAGMA Metabolic Acidosis with partial respiratory compensation and no suspicion of mixed disorder<\/p>\n<h1>Solution to Case Study 3<\/h1>\n<p>1: Obtain ABG\/VBG and Blood Electrolyte Panel<\/p>\n<p>pH 7.50<br \/>\nPaCO<sub>2<\/sub> 44mmHg<br \/>\nHCO<sub>3<\/sub><sup>&#8211;<\/sup>\u00a032 mEq\/L<br \/>\nPaO<sub>2<\/sub> 92 mmHg<\/p>\n<p>2: Check Validity of pH using Henderson Hasselbalch<\/p>\n<p>Henderson Hasselbalch calculation of pH = 6.1 + log ([HCO<sub>3<\/sub><sup>&#8211;<\/sup>]\/ [CO<sub>2<\/sub>]) where CO<sub>2<\/sub> is 44 mmHg\u00a0 and HCO<sub>3<\/sub><sup>&#8211;<\/sup> 32 mmol\/L.<\/p>\n<ul>\n<li>Recall that we need to use the CO solubility coefficient\u00a0 of 0.03 to convert mmHg to mmol\/L (ie determine how much CO<sub>2<\/sub> is dissolved in blood)\n<ul>\n<li>[CO<sub>2<\/sub>] = 44 mmHg * 0.03 = 1.32 mmol\/L<\/li>\n<\/ul>\n<\/li>\n<li>pH = 6.1 + log (32\/1.32) = 7.48<\/li>\n<li>\u00a0The measured pH is equal to the calculated pH (via Henderson Hasselbach). Within the acceptable margin of error.<\/li>\n<\/ul>\n<p>3: Identify the primary disorder (metabolic\/respiratory, acidosis\/alkalosis) using the Tic Tac Toe<\/p>\n<table id=\"tbl-ch27_03\" class=\"top-titled\">\n<tbody>\n<tr>\n<th style=\"width: 291px\" scope=\"col\"><\/th>\n<th style=\"width: 65px\" scope=\"col\">pH<\/th>\n<th style=\"width: 144px\" scope=\"col\">PCO<sub>2<\/sub><\/th>\n<th style=\"width: 189px\" scope=\"col\">Total HCO<sub>3<\/sub><sup>\u2013<\/sup><\/th>\n<\/tr>\n<tr>\n<td style=\"width: 291.5px\">Metabolic acidosis<\/td>\n<td style=\"width: 66px\">\u2193<\/td>\n<td style=\"width: 145px\">N, then \u2193<\/td>\n<td style=\"width: 189.5px\">\u2193<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 291.5px\">Respiratory acidosis<\/td>\n<td style=\"width: 66px\">\u2193<\/td>\n<td style=\"width: 145px\">\u2191<\/td>\n<td style=\"width: 189.5px\">N, then \u2191<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 291.5px\"><span style=\"background-color: #ffff00\">Metabolic alkalosis<\/span><\/td>\n<td style=\"width: 66px\"><span style=\"background-color: #ffff00\">\u2191<\/span><\/td>\n<td style=\"width: 145px\"><span style=\"background-color: #ffff00\">N, then\u2191<\/span><\/td>\n<td style=\"width: 189.5px\"><span style=\"background-color: #ffff00\">\u2191<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 291.5px\">Respiratory alkalosis<\/td>\n<td style=\"width: 66px\">\u2191<\/td>\n<td style=\"width: 145px\">\u2193<\/td>\n<td style=\"width: 189.5px\">N, then \u2193<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Tic Tac Toe method reveals Metabolic Alkalosis<\/p>\n<p>4: Calculate Anion gap<\/p>\n<p>This step may be somewhat unnecessary in our alkalotic patients, as we use it to detect the presence of underlying HAGMA, and differentiate between HAGMA and NAGMA. However it is a quick calculation, and easily done here.<\/p>\n<p>134 &#8211; (95+32) = 6<\/p>\n<p>Anion gap is less than 12, no HAGMA<\/p>\n<p>5: Consider the cause<\/p>\n<p>The cause of this metabolic alkalosis is likely secondary to GI loss of protons due to the vomiting<\/p>\n<p>6: Calculate expected compensation, use Winters formula, or given values<\/p>\n<p>Expected compensation for metabolic alkalosis:<\/p>\n<p>For each mEq\/L increase in HCO<sub>3<\/sub><sup>&#8211;<\/sup>, pCO<sub>2<\/sub> increases by 0.7 mmHg<\/p>\n<p>\u0394pCO2 = Current \u2013 Original = 44 mmHg \u2013 40 mmHg = 4 mmHg = \u0394pCO<sub>2<\/sub><\/p>\n<p>4 * 0.7 = expected compensation = 2.8<\/p>\n<p>Actual compensation = \u0394pCO<sub>2<\/sub> = 4<\/p>\n<p>Within an acceptable margin of expected compensation.<\/p>\n<p>7: Consider the presence of mixed acid-base disorder<\/p>\n<p>No indication of mixed disorder, compensation is as expected.<\/p>\n<p>8: Consider the Delta-Delta gap<\/p>\n<p>Patient is not presenting with HAGMA therefore the delta delta gap is not relevant<\/p>\n<p>Final solution:<\/p>\n<p>So finally we can say we have a metabolic alkalosis with partial respiratory compensation which we suspect is secondary to the GI loss of H+ due to the persistent vomiting.<\/p>\n<h1>References<\/h1>\n<ol>\n<li style=\"list-style-type: none\">\n<ol>\n<li><span style=\"color: #000000\" data-darkreader-inline-color=\"\"><a href=\"https:\/\/www.ncbi.nlm.nih.gov\/books\/NBK482146\/\" data-darkreader-inline-color=\"\">Metabolic Acidosis &#8211; StatPearls <\/a><\/span><\/li>\n<li><span style=\"color: #000000\" data-darkreader-inline-color=\"\"><a style=\"color: #000000\" href=\"https:\/\/doi.org\/10.1007\/978-3-031-25810-7\" data-darkreader-inline-color=\"\"> Fluid, Electrolyte and Acid-Base Disorders: Clinical Evaluation and Management <\/a><\/span><\/li>\n<li><span style=\"color: #000000\"><a style=\"color: #000000\" href=\"https:\/\/www.ncbi.nlm.nih.gov\/books\/NBK507807\/\">Physiology, Acid Base Balance &#8211; StatPearls 4<\/a><\/span><\/li>\n<\/ol>\n<\/li>\n<\/ol>\n","protected":false},"author":1076,"menu_order":10,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":["callen05-k8vhifn0ur","jen-2-8b3ju00vg8"],"pb_section_license":""},"chapter-type":[],"contributor":[265,349],"license":[],"class_list":["post-7699","chapter","type-chapter","status-publish","hentry","contributor-callen05-k8vhifn0ur","contributor-jen-2-8b3ju00vg8"],"part":7690,"_links":{"self":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/pressbooks\/v2\/chapters\/7699","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/wp\/v2\/users\/1076"}],"version-history":[{"count":25,"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/pressbooks\/v2\/chapters\/7699\/revisions"}],"predecessor-version":[{"id":8563,"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/pressbooks\/v2\/chapters\/7699\/revisions\/8563"}],"part":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/pressbooks\/v2\/parts\/7690"}],"metadata":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/pressbooks\/v2\/chapters\/7699\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/wp\/v2\/media?parent=7699"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/pressbooks\/v2\/chapter-type?post=7699"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/wp\/v2\/contributor?post=7699"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/wp\/v2\/license?post=7699"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}