Prevention of maternal hypotension after regional anaesthesia for caesarean section.
OBJECTIVE
Hypotension during regional anaesthesia for caesarean section remains a common clinical problem, particularly for spinal anaesthesia. The purpose of this review is to evaluate recent research in this area with a focus on English language papers from the past 1-2 years.


RESULTS
Risk factors for hypotension include increased sympathetic tone, increasing age, obesity, higher blocks and higher birthweight, but not multiple gestation. Methods aimed at countering effects of aortocaval compression do not reliably prevent hypotension. Intravenous crystalloid prehydration has poor efficacy, and focus has changed toward cohydration and use of colloids. Phenylephrine is established as a first-line vasopressor, although there are limited data from high-risk patients. Initial phenylephrine bolus dose requirement may be surprisingly large. Phenylephrine infusions can be conveniently titrated to maintain blood pressure and prevent maternal symptoms. Ephedrine crosses the placenta more than phenylephrine and direct fetal effects of ephedrine may explain associated depression of fetal pH and base excess.


CONCLUSIONS
Recent research supports decreased use of crystalloid prehydration and ephedrine and increased use of cohydration, colloids, smaller spinal doses and phenylephrine. Further research is required to investigate these techniques in high-risk patients and to evaluate novel monitoring techniques.
Ngan Kee
Warwick D
WD
Department of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong, China.
D000765:Anesthesia, Conduction / Q000009:adverse effects*; D002585:Cesarean Section; D005260:Female; D005440:Fluid Therapy / Q000379:methods; D006801:Humans; D007022:Hypotension / Q000139:chemically induced / Q000517:prevention & control*; D016343:Monitoring, Intraoperative / Q000379:methods; D011187:Posture; D011247:Pregnancy; D018566:Pregnancy, High-Risk; D012307:Risk Factors; D004561:Transcutaneous Electric Nerve Stimulation / Q000379:methods; D014662:Vasoconstrictor Agents / Q000627:therapeutic use
D014662:Vasoconstrictor Agents