Evaluation of pre-emptive intramuscular phenylephrine and ephedrine for reduction of spinal anaesthesia-induced hypotension during Caesarean section

Abstract

Pre-emptive intramuscular (i.m.) vasopressors were evaluated in 108 patients undergoing elective Caesarean section under spinal anaesthesia, assigned to four groups in a randomized, double-blind, placebo-controlled study. Group 1 received pre-emptive phenylephrine 4 mg i.m., group 2 received phenylephrine 2 mg i.m., group 3 received ephedrine 45 mg i.m., while controls received an i.m. injection of saline, all given immediately after induction of spinal anaesthesia. Hypotension was defined as a 25% decrease in mean arterial pressure (MAP). Rescue intravenous (i.v.) boluses of ephedrine were given if the patient was hypotensive or reported nausea, vomiting or dizziness. The incidence of hypotension was 33% in the phenylephrine 4 mg group compared with 70% in the control and phenylephrine 2 mg groups (P=0.03), and 48% in the ephedrine 45 mg group. The phenylephrine 4 mg and ephedrine 45 mg groups had a significantly lower percentage reduction in MAP (-21 (SD 14)% and -22 (14)%) compared with controls (-32 (18)%, P=0.04). They also had a lower total dose of rescue i.v. ephedrine (15.7 (15.7) mg and 15.8 (15.6) mg) compared with controls (28.8 (20.6) mg, P=0.02). We conclude that pre-emptive i.m. phenylephrine 4 mg and ephedrine 45 mg reduce the severity of hypotension and the total dose of rescue i.v. ephedrine during spinal anaesthesia for Caesarean section.

Prophylactic ephedrine prevents hypotension during spinal anesthesia for Cesarean delivery but does not improve neonatal outcome: a quantitative systematic review

“…4,5,11(trial 1, trial 2), 22 Ephedrine was given before hypotension developed in 13 of 14 RCTs. 1,[4][5][6][7]11,[21][22][23][24][25][26] The authors administered ephedrine before spinal anesthesia in three trials, 7,21,24 during induction of spinal anesthesia in one trial 6 and immediately after induction of spinal anesthesia in other trials. 1,4,5,11,22,23,[25][26][27] In one trial, ephedrine was given immediately after there was any decrease in arterial pressure to less than the baseline.…”

“…Drugs used for spinal anesthesia included tetracaine, 7,21,22 bupivacaine, 5,6,27 and hyperbaric bupivacaine. 1,4,11,[23][24][25][26] The combined spinal-epidural anesthesia technique was used in two trials. 1,26 All trials specified the use of uterine displacement.…”

“…1,4,11,[23][24][25][26] The combined spinal-epidural anesthesia technique was used in two trials. 1,26 All trials specified the use of uterine displacement. Iv fluid prehydration was given in all trials except one in which the ephedrine group was not given prehydration.…”

“…25 There was adequate allocation concealment (A) in four trials. 1,4,5,26 Despite attempts to contact the primary author, we were uncertain whether randomization occurred in the earliest trial 7 but the groups appeared comparable. All other trials were classified as Kangas-Saarela having unclear allocation concealment (B) because the randomization procedure was not described.…”

“…There was double-blinding in seven trials. 1,[4][5][6][7]24,26 There was no blinding in three trials. 21,11 (trial 1, trial 2) All other trials were single-blinded.…”