Preoperative medication and its effect on blood gases.

Abstract

The effect of preoperative medication on blood gases was studied in two groups of patients undergoing open heart surgery using a cardiopulmonary bypass. One group of 16 patients (meperidine group) received meperidine hydrochloride, promethazine hydrochloride, and pentobarbital as premedication; the second group of 16 patients (control group) received pentobarbital only. The meperidine group showed significant reduction in arterial oxygen pressure (Po 2 ) after premedication with insignificant changes in arterial carbon dioxide pressure (Pco 2 ), and pH. The control group showed no change in Po 2 , Pco 2 , and pH. Thus, narcotics can produce arterial hypoxemia in the premedicated surgical patient in the presence of normal values of pH and Pco 2 before the induction of anesthesia. Narcotics reduce the normal sighing frequency and may depress the reflex urge to maintain normal pulmonary mechanisms. Satisfactory sedation can be attained with barbiturates alone.