RESUMO
BACKGROUND AND OBJECTIVES: The subarachnoid administration of fentanyl to laboring parturients may decrease maternal blood pressure. The hemodynamic effects of subarachnoid fentanyl (SAF) in laboring women was studied by impedance cardiography. METHODS: Following a 500 mL fluid bolus, 15 healthy women received 25 micrograms of SAF for labor analgesia by a combined spinal-epidural technique. Maternal systolic, mean, and diastolic blood pressure, heart rate, cardiac index, stroke index, and end-diastolic index were measured before SAF administration (baseline) and every 5 minutes for 30 minutes after administration. Prelabor blood pressure values were obtained from the patient's last office visit. Data were analyzed by analysis of variance at P < .05. RESULTS: Following SAF administration, pain scores decreased and pruritus scores increased (based on 100-mm visual analog scales). Maternal systolic, diastolic, and mean blood pressures, heart rate, and cardiac index decreased significantly by 12, 18, 17, 12, and 14%, respectively, as compared with baseline values, with no significant change in stroke index. Cardiac preload (end-diastolic index) decreased by 10% 25 minutes following SAF administration but otherwise did not significantly change. Compared with prelabor blood pressure values, the diastolic pressure decreased significantly only 9% at 20 minutes and the mean arterial pressure decreased only 7 and 8% at 20 and 25 minutes, respectively; the systolic pressure did not change. In 53% of patients, at least one hypotensive episode (systolic pressure of < or = 100 mm Hg or a > 30% decrease in systolic pressure) occurred, following SAF administration. However, only two of these episodes (systolic pressures of 93 and 96 mm Hg) lasted longer than 1 minute, and these were easily treated with intravenous ephedrine. CONCLUSIONS: Vasodilation due to sympathectomy causes a decrease in preload (end-diastolic index) and in stroke index and an increase in heart rate. Since the end-diastolic index and stroke index remained relatively stable and the heart rate decreased, it was concluded that the observed decrease in blood pressure was not due to vasodilation.
