[Prehydratation and anaesthesia in obstetrics: state of the art]

All epidural or spinal techniques using local anaesthetics causes some degree of sympathetic blockade resulting in peripheral vasodilatation and possibly hypotension or reduction in cardiac output. In the practical clinic, administration of fluids intravenously prior spinal and epidural anaesthesia is required to prevent maternal hypotension and fetal hypoxia. We evaluated in this review the efficacy of volume preloading on the incidence of hypotension after spinal or epidural anaesthesia for caesarean delivery. Randomized controlled trials investigating volume preloading before the initiation of obstetric anaesthesia were sought by using MEDLINE (1966-2001). The primary outcome was the incidence of hypotension. Secondary outcomes included: ephedrine use, Apgar scores, umbilical cord pH values, and maternal nausea and vomiting. Crystalloid preload was inconsistent in preventing hypotension, whereas colloid appeared to be effective in all studies. A colloid solution, such as hydro-xyethyl starch (HES) might be preferable considering the capacity to stay intravasculary for a longer period. Few differences in fetal outcomes or maternal nausea and vomiting were reported. Increasing central blood volume by using colloid decreases the incidence of hypotension before loco-regional anaesthesia for cesarean delivery. Implications. We performed a review to determine whether fluid loading reduced the incidence of low blood pressure after spinal or epidural anaesthesia for caesarean delivery. Although no technique totally eliminates the occurrence of hypotension, colloid administration (starch or gelatin containing fluids) was the most effective.