The effects of an increase of central blood volume before spinal anesthesia for cesarean delivery: a qualitative systematic review.

Abstract

We evaluated in this qualitative systematic review the efficacy of increasing central blood volume on the incidence of hypotension after spinal anesthesia for elective cesarean delivery. Randomized controlled trials investigating any method of increasing central blood volume before the initiation of obstetric spinal anesthesia were sought by using MEDLINE (1966-2000), Embase (January 1988-April 2000), and the Cochrane Library (Issue 1, 2000). Additional reports from retrieved and review articles, hand searching of non-MEDLINE journals, and abstracts of major anesthesia meetings (1994-1999) were located. The primary outcome was the incidence of hypotension. Secondary outcomes included: ephedrine use, Apgar scores, umbilical cord pH values, and maternal nausea and vomiting. Twenty-three articles met our inclusion criteria with the use of crystalloid preload, colloid preload, and mechanical methods of increasing central volume. Crystalloid preload was inconsistent in preventing hypotension, whereas colloid appeared to be effective in all but one study. Leg wrapping and thromboembolic stockings decreased the incidence of hypotension compared with leg elevation or control. Few differences in fetal outcomes or maternal nausea and vomiting were reported. Increasing central blood volume by using colloid and leg wrapping decreases but does not abolish the incidence of hypotension before spinal anesthesia for elective cesarean delivery. We performed a systematic review to determine whether fluid loading reduced the incidence of low blood pressure after spinal anesthesia for cesarean delivery. Although no technique totally eliminates the occurrence of hypotension, colloid administration (starch or gelatin containing fluids) and leg wrapping were the most effective.