RESUMO
BACKGROUND: The prevention of maternal hypotension by traditional crystalloid preloading prior to spinal anesthesia in obstetric patients undergoing spinal anesthesia has recently been questioned by many. A review of published data with unbiased comparison comparing preloading and no preloading prior to spinal anesthesia was attempted to assess the relative benefits and side-effects in terms of incidence of maternal hypotension, dose of vasopressors given and APGAR scores at one and 5 minutes. METHODS: A medline search of published randomized controlled trials (RCT) from 1966-1997 comparing crystalloid and no crystalloid preloading prior to spinal anesthesia in patients for cesarean section was done. Search for available meta-analysis on preloading, only three met the criteria for analysis. The outcome measures were limited to three due to lack of available data for comparison. RESULTS: Using the Peto Odds Ratio, analysis of the three studies showed no significant difference in the incidence of hypotension between those who were preloaded and those who were not. But a trend towards a lower incidence of hypotension among those who were preloaded was seen. Using the weighted means difference (WMD) to analyze the dose of vasopressors given, there was no significant difference between preloading and no preloading but a trend towards a greater total dose of vasopressors was seen in those not preloaded. There was no significant difference in APGAR scores in the three studies. CONCLUSION: There is no sufficient evidence to support a change in practice to no preloading prior to spinal anesthesia for elective cesarean section based on the results of this meta-analysis. Further studies must be done to increase the validity and precision of results comparing preloading and no preloading.