Renal response to lower body positive pressure produced by military anti-shock trousers

Military anti-shock trousers (MAST) are extensively used in the management of various forms of clinical shock and are presumed to produce their antihypotensive effect by the autotransfusion of blood from the lower extremities. In the present studies we documented the renal response to (1) four hours of recumbency; (2) 4 h of MAST inflation at a pressure of 45 mm Hg over the lower extremities and 15 mm Hg over the abdomen, and (3) 4 h of thermoneutral head-out water immersion in a group of salt replete normal subjects. Similar studies were performed in a group of adults with nephrotic syndrome and edema. In both normal and nephrotic subjects only water immersion produced a natriuresis that was significantly greater than during recumbency. The mean natriuresis following MAST inflation in normal subjects was somewhat greater than that during recumbency but the difference was neither consistent nor statistically significant. We conclude that MAST inflation does not lead to central translocation of more fluid than what would be expected from the assumption of recumbent posture. Thus, MAST are unlikely to be of therapeutic benefit in the relief of edema in patients with nephrotic syndrome and a critical evaluation of their mechanisms of action in the management of hypotension is required.