[The evaluation of total body water composition during caesarean section under spinal anesthesia]

Hypotension is a common adverse effect of spinal anesthesia (SA). Preoperative fluid infusion is recommended to prevent hypotension during caesarean section. The aim of this study is to document relationship between preoperative total body water (TBW) and the amount of the vasopressors given intraoperatively and to evaluate the change of maternal body water composition (BWC).

In 57 patients scheduled for caesarean section under SA, maternal BWC was measured by bioelectrical impedance analysis method. SA was performed using 0.5% isobaric bupivacaine 2 ml and fentanyl 20 microg at L3-4 intervertebral space. After this procedure, the impedance was measured again. We investigated the correlation between TBW and the amount of the vasopressor and the change of maternal BWC before and after SA.

No positive linear correlation existed between the preoperative TBW and the amount of vasopressors given intraoperatively. SA produced a 3.8% increase in TBW and a 4.7% increase in extracellular water (ECW, P < 0.01).

Preoperative TBW does not affect the amount of vasopressors given during caesarean section, which suggested massive fluid infusion can not always prevent hypotension after SA. A slight changes in TBW and ECW may be induced by SA, while the exact physiological and clinical significance of these observation remains to be elucidated.