Alkalosis

Alkalosis

Alkalosis refers to a physiological process which, if unopposed, would lead to a rise in blood pH. Alkalemia is defined as an arterial blood pH greater than 7.45 (or venous pH over 7.5). Alkalosis can be either respiratory (secondary to hyperventilation) or metabolic (secondary to increased bicarbonate retention, a result of exogenous ingestion or in certain syndromes).

Respiratory Alkalosis

Respiratory alkalosis is caused by hyperventillation which drives down pCO₂. Etiologies include:

A ventilator providing excessive minute ventilation secondary to either too high a frequency or volume.
Anxiety and hyperventilation.
CNS disorders
Psychiatric disorders

The physiologic response to lowered pCO₂ is decreased cerebral blood flow. Symptoms include dizziness and confusion. Rarely, seizures and loss of consciousness can occur. In chronic respiratory alkalosis, the kidney will recover less bicarbonate and serum bicarbonate levels will be decreased. Acute treatment for hyperventilation is rebreathing CO₂, for example by having the patient breath in and out of a bag.

Metabolic Alkalosis

Alkalosis occurs when either base is gained or acid is lost through some mechanism. Physiologically, the result is tissue hypoxia, CNS changes and muscular irritability. Symptomatically, patients may have lethargy, confusion, neuromuscular irritability, arrythmias, and seizures. As a compensatory mechanism, the patient's respiratory rate may decrease.

Treatment

Treatment of alkalosis is based on treatment of the underlying derangement. Just as bicarbonate can be administered to immediately correct a severe acidosis, hydrochloric acid can be administered to correct an extreme alkalosis. It can be infused as dilute solution or in the form of ammonium chloride or arginine hydrochloride (counterindicated in hepatic and renal disease, respectively).

Acid-Base

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Last modification: April 30, 1998