Management of Acid Base Disorders

pH disturbances can occur gradually or alarmingly acutely, dependent on both the cause and degree of compensation the body can do. Thus, a health care team must have multiple tools on hand to diagnose, identify, and then manage pH disturbances in an acute vs longer time frame.

As mentioned earlier, the rapid diagnosis and identification of the pH disturbance is done by a critical analysis of combination of history, clinical manifestations, and blood gases. Thus, the most ideal form of management is to identify the underlying cause of the pH disturbance and resolve it. For example, if the cause of the acidosis is due to generation of ketones during diabetic crisis, management is focussed on treating the diabetic crisis. However, sometimes pH disturbances are too acute a problem to wait for the underlying cause to resolve. Thus, below are general guidelines on how pH disturbances can be managed.

Metabolic Acidosis

The approach for managing acid-base disorders is primarily to treat the underlying cause.

In acute acidosis of critically ill patients we can use alkali treatment to balance their serum proton levels. Sodium bicarbonate is often administered as a life saving intervention. Sodium bicarbonate can put patients into hypernatremia, it can also cause vasodilation and hypertonicity. Due to the fact that CO₂ diffuses into cells more easily than bicarbonate, adding bicarbonate to the serum can actually increase intracellular CO₂ levels and temporarily worsen intracellular CO₂ levels, which can cause additional CNS depression secondary to CNS acidosis.^{[1] [2]}

There is some debate as to the efficacy of sodium bicarbonate treatment in critically ill patients with diabetic ketoacidosis or lactic acidosis.

Diabetic ketoacidosis will respond best by addressing the cause of ketone generation. Thus, management with insulin administration will help switch tissue metabolism away from ketone generation.

Lactic acidosis due to hypoxemia is also due anaerobic metabolism. Thus, administration of oxygen may also help in this regard as it will encourage fully saturated oxygen delivery to tissues.

Similarly, lactic acid accumulation causing acidosis due anaerobic metabolism due to perfusion can be managed by promoting better perfusion to all tissues (e.g. address problems with blood pressure, cardiac output, etc) . This promotes better delivery of oxygen-saturated RBC to all tissues for aerobic metabolism, thus shutting down the anaerobic metabolism which is generating the lactic acid.

Metabolic Alkalosis

Metabolic alkalosis is more commonly driven by the loss of protons moreso than the introduction of additional base. Therefore, we will find more success in correcting the proton loss.

Recall that one of the most common cause of proton loss is via loss of gastric acid – whether by vomiting or nasogastric suction. This means administration of anti-emetics and review of nasogastric practice will help with the alkalosis. Note that chloride correction may also be needed since Cl^– is lost with H⁺ during emesis.

Metabolic alkalosis is also caused by diuretics. Thus a medication review of diuretic usage may help address this cause.

Recall that hypokalemia is both a cause and a result of metabolic alkalosis. Thus, administration of potassium chloride (KCl).

If possible, the metabolically alkalotic patient may compensate naturally by reducing their respiratory rate, so recognizing an abnormally low respiratory rate is appropriate in situations of metabolic alkalosis. ^[4]

Respiratory Acidosis

Respiratory acidosis is due to CO₂ retention in the lungs. To treat this we can increase ventilation, and the patient will slough off additional CO₂ restoring an ideal acid base equilibria. This approach is non-invasive, and effective.^[1]

Thus, management will be both methods to improve ventilation AND help the body retain base. Depending on the cause of CO₂ retention, management can include bronchodilators to improve exhalation, diuretics to address alveolar blockage due to pulmonary edema, or antimicrobials/mucolytics to manage infectious causes of alveolar blockage.

If respiratory acidosis is pervasive and symptomatic – despite attempts of management, discussions on administration of bicarbonate should be considered.

Respiratory Alkalosis

In respiratory alkalosis, we treat the underlying condition that is driving the hyperventilation. The most common causes of hyperventilation can be:

Anxiety – Management: Grounding exercises, breathing coaching, administration of anti-anxiety medication
Pain – Management: Administration of analgesics, distraction (effective for pediatric patients), cold/heat therapy, position/splinting, social and environmental supports.
Mechanical Ventilation – Management: reduce ventilation
Damage to respiratory centres (e.g. Acute Traumatic Brain Injury) – as this is a complicated situation with multiple CNS tissue being injured, management will be more neurology focused more than respiratory. ^{[1] [3]}

Review Questions

This patient has the following venous blood gases:

pH = 7.50

pCO₂ = 30 mmHg

HCO₃^– = 23 mmol/L

1. What pH disturbance is this patient experiencing (if any?)
2. What clinical manifestation might you expect to see in this patient?
3. You have a patient with a respiratory rate of 60, they are panicked and report ” starting to feel like it is harder and harder to breath”. Their fingers are tingling and their fists are clenched. What are you concerned about, and what are you going to do?

Review Question Answers

1. Respiratory alkalosis. pH is >7.45 (alkalosis). pCO₂ is abnormally low, suggesting an alkalotic state = respiratory alkalosis. Bicarbonate is in normal range even though we would expect a loss of HCO3- to manage the respiratory alkalosis. Thus, there is no compensation.

2. Light headedness, confusion, panic, and most importantly hyperventilation.

3. This is an extremely high respiratory rate. There is evidence of increased panic and possibly altered mental status. Eventually alkalosis can lead to electrolyte imbalances such as hypokalemia and hypocalcemia which can lead to nervous complications (e.g. tingling, muscle spasms). The quickest way to manage this is by coaching their breathing to slow their resp rate. Manage pain and/or anxiety if necessary. ^[1]

References

1. 1. Rational Treatment Of Acid-Base Disorder
   2. Fluid, Electrolyte and Acid-Base Disorders: Clinical Evaluation and Management
   3. Respiratory Alkalosis
   4. Metabolic Alkalosis