Clinical description was made of a series of hypotensive patients resuscitated with and without an algorithm. Of 603 hypotensive patients, there were 114 (19%) deaths and 169 (28%) patients with complications; the average low MAP was 53 +/- 25 mm Hg. Of 169 patients with complications, 48 (28%) had shock-related (SR) complications; 25 (52%) of these patients died. There were 265 (44%) patients who had severe associated diseases and these patients comprised the group most vulnerable to complications and death; in this group, there were 41 patients with SR-complications who had significantly higher mortality, longer resuscitation times, lower MAP, more deviations from the algorithm, and more delays in resuscitation than did those with nonshock-related complications. Multiple deviations from the algorithm were associated with longer resuscitation times, and higher incidence of SR complications. Most of the delays in resuscitation of these patients and most of the SR complications could have been prevented. Seventeen percent of hypotensive patients entering the emergency department (ED) normally carried low arterial pressures, which averaged 75 +/- 3 (SD) mm Hg; this was more common, but not confined to young females. Of the 603 patients who actually were hypotensive, 6% were admitted in arrest (phase I), 18% in severe shock (phase II, MAP less than 60 mm Hg), 52% in moderate shock (phase III, MAP less than 80 mm Hg), and 24% were normotensive but subsequently became hypotensive (phase IV). The importance of various decision nodes of the algorithm were evaluated. The present algorithm, designed for these hypotensive emergency patients, provides a framework for fluid management that expedites resuscitation and reduces complications related to shock. We conclude that: (a) delays in resuscitation can be clearly related to an increased incidence of SR complications; (b) when the algorithm was satisfactorily followed, there was faster resuscitation and less SR complications; and (c) when the algorithm was satisfactorily followed in patients with severe associated illnesses, there was also shorter ICU stay, shorter hospitalization and decreased mortality.