OBJECTIVES: We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (November 2005).
SELECTION CRITERIA: Three review authors independently assessed eligibility and methodological quality of studies, and extracted data.
MAIN RESULTS: We included 75 trials (a total of 4624 women). Crystalloids were more effective than no fluids (relative risk (RR) 0.78, 95% confidence interval (CI) 0.60 to 1.00; one trial, 140 women, sequential analysis) and
colloids were more effective than crystalloids (RR 0.68, 95% CI 0.52 to 0.89; 11 trials, 698 women) in preventing
hypotension following spinal anaesthesia at
caesarean section. No differences were detected for different doses, rates or methods of administering
colloids or crystalloids.
Ephedrine was significantly more effective than control (RR 0.51, 95% CI 0.33 to 0.78; seven trials, 470 women) or
crystalloid (RR 0.70, 95% CI 0.50 to 0.96; four trials, 293 women) in preventing
hypotension. No significant differences in
hypotension were seen between
ephedrine and
phenylephrine (RR 0.95, 95% CI 0.37 to 2.44; three trials, 97 women) and
phenylephrine was more effective than controls (RR 0.27, 95% CI 0.16 to 0.45; two trials, 110 women). High rates or doses of
ephedrine may increase
hypertension and
tachycardia incidence. Lower limb compression was more effective than control (no leg compression) (RR 0.69, 95% CI 0.53 to 0.90; seven trials, 399 women) in preventing
hypotension, although different methods of compression appeared to vary in their effectiveness. No other comparisons between different physical methods such as position were shown to be effective, but these trials were often small and thus underpowered to detect true effects should they exist.
AUTHORS' CONCLUSIONS: While interventions such as
colloids,
ephedrine,
phenylephrine or lower leg compression can reduce the incidence of
hypotension, none have been shown to eliminate the need to treat maternal
hypotension during spinal anaesthesia for
caesarean section. No conclusions can be drawn regarding rare adverse effects due to the relatively small numbers of women studied.