SUPINE HYPOTENSIVE SYNDROME

Objective: To review reports of the supine hypotensive syndrome with r eference to clinical presentation, suggestions on the mechanism of ons et, and the possibility of advance detection. Data sources: We used wo rldwide obstetric, anesthesia, and general medical journals from 1922 onward, a Medline search from 1966 onward, and manual cross-referencin g for prior publications. Methods of study selection: We selected appr oximately 100 case reports of supine hypotensive syndrome and studies on supine blood pressure responses during late pregnancy. Data extract ion and synthesis: Publications that recorded novel clinical observati ons, specific hemodynamic or biochemical measurements, or associated c omplications were included. Conclusions: Supine hypotensive syndrome i s characterized by severe supine symptoms and hypotension in late preg nancy, which compel the unconstrained subject to change position. Rare ly, it may manifest even from the fifth month of pregnancy or postpart um, as well as in the pelvic tilt or sitting positions. Although infer ior vena cava compression, influenced primarily by the size of the ute rus and exact maternal and fetal position, is the major determinant in its development, other factors may also be important in modulating th e circulatory effects of such compression. Advance recognition of susc eptibility to the syndrome depends on a history of severe supine sympt oms or supine intolerance and an increase in maternal heart rate and d ecrease in pulse pressure in the supine position. As there seems to be a spectrum of severity from minimal central cardiovascular alteration s to severe syncopal shock resulting from supine inferior vena cava co mpression, it is difficult to define a cutoff point at which the syndr ome occurs. Although usually recognizable by maternal symptoms, severe hypotension without symptoms has been reported on three occasions.