Vasopressor therapy for hypotension due to epidural anesthesia for cesarean section

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Abstract
Maternal hemodynamic changes and neonatal acid-base status were assessed in 127 healthy patients undergoing elective cesarean section under epidural anesthesia. An impedance cardiography was used to measure stroke volume (SV), ejection fraction (EF) and end-diastolic volume (EDV). In addition, neonatal umbilical venous and arterial Po2 Pco2 pH, base excess, lactate pyruvate, excess lactate, and L/P ratio were measured at birth. Patients were divided into three groups. Group 1 (n = 53) required no vasopressor (normotensive controls), In Group 2 (n= 37), nean blood pressure (BP) decreased from 90 mmHg to 67 mmHg (12.0 to 8.9 kPa), and ephedrine was given in 5-mg increments to maintain systolic BP > 100 mmHg (13.3 kPa). In Group 3 (n = 37), BP decreased from 83 mmHg to 62 mmHg (11.1 to 8.2 kPa), and phenylephrine was administered in 100 .mu.g increments to maintain systolic BP > 100 mmHg (13.3 kPa). In Group 2 and 3 the SV and EDV decreased 43% and 33% respectively when hypotension developed. Both vasopressors restored BP, SV and EDV to near baseline values. Neonatal Apgar scores and acid-base profiles were not significantly different among the three groups of neonates, nor were they different between the two hypotensive groups. It is concluded that: 1) transient maternal hypotension does not affect neonatal acid-base status; 2) both ephedrine and phenylephrine increase cardiac preload; and 3) an a agent like phenylephrine does not cause fetal acidosis when used for treating maternal hypotension.