PLASMA POTASSIUM RESPONSE TO ACUTE RESPIRATORY ALKALOSIS

Acute respiratory alkalosis (hyperventilation) occurs in clinical settings associated with electrolyte-induced complications such as cardiac arrhythmias (such as myocardial infarction, sepsis, hypoxemia, cocaine abuse). To evaluate the direction, magnitude and mechanisms of plasma potassium changes, acute respiratory alkalosis was induced by voluntary hyperventilation for 20 (18 and 36 liter/min) and 35 minutes (18 liter/min). The plasma potassium response to acute respiratory alkalosis was compared to time control, isocapnic and isobicarbonatemic (hypocapnic) hyperventilation as well as beta- and alpha-adrenergic receptor blockade by timolol and phentolamine. Hypocapnic hypobicarbonatemic hyperventilation (standard acute respiratory alkalosis) at 18 or 36 liter/min (Delta PCO2 - 16 and -22.5 mm Hg, respectively) resulted in significant increases in plasma potassium (ca + 0.3 mmol/liter) and catecholamine concentrations. During recovery (post-hyperventilation), a ventilation-rate-dependent hy pokalemic overshoot was observed. Alpha-adrenoreceptor blockade obliterated, and beta-adrenoreceptor blockade enhanced the hyperkalemic response. The hyperkalemic response was prevented under isocapnic and isobicarbonatemic hypocapnic hyperventilation. During these conditions, plasma catecholamine concentrations did not change. In conclusion, acute respiratory alkalosis results in a clinically significant increase in plasma potassium. The hyperkalemic response is mediated by enhanced alpha-adrenergic activity and counterregulated partly by beta-adrenergic stimulation. The increased catecholamine concentrations are accounted for by the decrease in plasma bicarbonate.