Simultaneous determinations of blood pressure and blood pH in cases of suspected pheochromocytoma

Eight hundred fifty-seven determinations of the pH of venous blood with simultaneous blood pressure observations were carried out on 590 patients. The pH of venous blood of the patients who had been under medication for a long period before the tests did not vary significantly from that of patients who had had no medication. The most consistent result was the rise in the pH of venous blood 30 minutes after a dose of phentolamine hydrochloride (Regitine). The oral administration of 40 grains of sodium bicarbonate did not increase the response of the blood pressure during the histamine test, irrespective of the type of previous medication, even though the pH of the venous blood was low initially and rose to normal levels after the administration of the sodium bicarbonate. This may be due to the fact that none of the patients had pheochromocytomas with excessive release of pressor amines.