Hemodynamic and acid-base effects of meperidine on unanesthetized pregnant sheep and fetus.

Meperidine hydrochloride (MHCl) is one of the most widely used analgesics today. Its effect upon maternal and fetal sheep hemodynamics and acid base were investigated in 13 experiments following maternal IV administration of 100 mg (approximately 2 mg/kg) of the drug. Blood samples were taken at baseline and at 7.5, 15, 30, 45, 60, 75, 90, and 120 minutes postinfusion. Significant changes were an increase in maternal pH at 45 minutes, P less than 0.01 and 120 minutes, P less than .01 accompanied by a decrease in pCO2 at 45 minutes, P less than .01. No changes in maternal pO2, O2 saturation (O2%), base excess (BE), hemoglobin (Hb), heart rate (HR), blood pressure (BP), and uterine blood flow (ut. BF) were noted. Fetal PH, pO2, pCO2, O2%, bicarbonate, BE, Hb, HR, and BP remained unchanged. It is suggested that MHCl causes transient maternal respiratory alkalosis without any significant changes in uterine blood flow. With the dose used in this study, no adverse effect was observed in the fetus. Therefore, based upon this study, MHCl seems to be tolerated well by both ewe and her fetus.