The combination of impaired homeostatic mechanisms and the high prevalence of drug use and disease in the elderly make acid-base disturbances common. 5.5 with metabolic acidosis suggests distal tubular inability to acidify the urine and occurs with type 1 or type 4 renal tubular acidosis. In the elderly, type 1 renal tubular acidosis may be caused by amphotericin therapy or by tubular dysfunction due to the myeloma protein in multiple myeloma. Type 4 renal tubular acidosis is characterized by tubular dysfunction that is worse than that in type 1. The added tubular dysfunction is suggested by concomitant hyperkalemia.
Initial treatment aims to correct the underlying disease process.
Acute complete correction of arterial pH is not a goal of therapy, and caution must be used to avoid volume and sodium overload. Metabolic alkalosis results from net acid loss or alkali gain in the extracellular fluid. Acid loss can result from vomiting, prolonged gastric suctioning, and diuretic use. Treatment is directed toward mineralocorticoid antagonism. Lethargy and stupor may occur from adverse effects on the cerebral circulation.