Method of ephedrine administration and nausea and hypotension during spinal anesthesia for cesarean section

Abstract

Sixty healthy parturients, scheduled for elective primary or repeat cesarean section at term, were studied. Patients were assigned to one of three groups according to the response of the blood pressure. In Group A (n=22), there was no change from the baseline blood pressure and none received ephedrine. In Group B (n=18), because of hypotension (defined as a fall of more than 30 mmHg or below 100 mmHg) ephedrine was given intravenously in repeated doses of 10 mg each until the blood pressure rose to at least 100 mmHg. In Group C (n=20), intravenous ephedrine (10-30 mg) was administered as soon as any fall from baseline pressure was detected. The two treatment groups (Group B and Group C) were done in sequence. There were no differences in gestational age, maternal age, height, weight, or infant birth weight among the groups. In no patient did baseline systolic blood pressure exceed 140 mmHg. Sensory block was adequate and extended to T4 for most patients using pin prick for evaluation. There were no differences in the induction-delivery intervals or the uterine incision-delivery intervals among the groups. The incidence of nausea alone or with vomiting was clearly correlated with development of maternal hypotension. None of the parturients in Group A complained of nausea alone or with vomiting, two mothers (10%) had these symptoms in Group C, whereas two-thirds of all patients (66%) in Group B developed nausea or both nausea and vomiting (P<0.01). Acid-base data showed normal maternal values with no differences among the groups. The infants of mothers who developed hypotension (Group B) had significantly lower average pH values in umbilical artery and umbilical vein blood at birth (P<0.001) compared with babies of mothers who did not develop hypotension (Groups A and C). Umbilical artery base-deficit and Δ base deficit also were higher in Group B (P<0.001). The percentage of newborns with low Apgar scores (<7) was higher in Group B (80%) at 1 min; however there were no differences in Apgar scores at 5 min among the groups. No patient in any group developed postpartum hypertension.