The role of adrenaline in the management of obstetric spinal hypotension during caesarean section: a systematic review

Abstract

Background: Obstetric spinal hypotension is a common complication. After considerable research, phenylephrine infusion has been established as the first-line agent for its management. Adrenaline is sometimes recommended for use when phenylephrine is unavailable in low-resource settings; however, little research informs this recommendation.

Methods: We conducted a systematic review of all randomised controlled trials comparing adrenaline to other vasoconstrictors for the management of spinal hypotension during caesarean section. Primary study outcomes were the incidence of maternal hypotension and fetal acidosis. Secondary outcomes were maternal bradycardia, tachycardia, nausea, vomiting, hypertension, requirement for cardiac resuscitation, loss of consciousness, and Apgar scores.

Results: Participants were 20–40 years of age, American Society of Anesthesiologists (ASA) grade I–II, undergoing elective caesarean section. Of 1 935 publications identified, six were extracted for full-text review, of which three were included in the final data synthesis. There was significant heterogeneity between studies, and only one was of high quality, which precluded metaanalysis. Comparator vasoconstrictors included ephedrine, phenylephrine, and noradrenaline, administered either by bolus or infusion.

Primary outcomes: adrenaline did not result in an absolute blood pressure difference when compared to the other agents. One study reported a lower mean venous cord bicarbonate level, and a second reported a lower base excess in the adrenaline group. 

Secondary outcomes: compared to ephedrine, adrenaline resulted in a lower heart rate. Compared to phenylephrine and noradrenaline, adrenaline had a lower and a similar incidence of bradycardia, respectively. There were no between-group differences in the other secondary outcomes.

Conclusion: Small trials provided limited support for the efficacy and safety of adrenaline in the management of obstetric spinal hypotension. However, there is insufficient evidence to inform recommendations for the use of this vasopressor. Therefore, the use of adrenaline should be limited to situations where phenylephrine, supplemented as necessary by less potent agents, is unavailable. In view of the proven safety and efficacy of phenylephrine, ethical justification for further research on adrenaline could be questioned.