Near-fatal heat stroke during the 1995 heat wave in Chicago

Background: In July 1995, Chicago sustained a heat wave that resulted in more than 600 excess deaths, 3300 excess emergency department visits, and a substantial number of intensive care unit admissions for near-fatal heat stroke. Objective: To describe the clinical features of patients admitted to an intensive care unit with near-fatal classic heat stroke. Patients were followed for 1 year to assess delayed functional outcome and mortality. Design: Observational study. Setting: Intensive care units in the Chicago area. Patients: 58 patients admitted to the hospital from 12 July to 20 July 1995 who met the case definition of classic heat stroke. Measurements: The data collection tool was designed to compile demographic and survival data and to permit analysis of organ system function by abstracting data on physical examination findings, electrocardiography and echocardiography results, fluid resuscitation, radiography results, and laboratory findings. Data on functional status at discharge and at 1 year were collected by using a modified Stanford Health Assessment Questionnaire. Results: Patients experienced multiorgan dysfunction with neurologic impairment (100%), moderate to severe renal insufficiency (53%), disseminated intravascular coagulation (45%), and the acute respiratory distress syndrome (10%); Fifty-seven percent of patients had evidence of infection on admission. In-hospital mortality was 21%. Most survivors recovered near-normal renal, hematologic, and respiratory status, but disability persisted, resulting in moderate to severe functional-impairment in 33% of patients at hospital discharge. At 1 year, no patient had improved functional status, and an additional 28% of patients had died. Conclusions: Near-fatal classic heat stroke is associated with multiorgan dysfunction. A high percentage of patients had infection at presentation. A high mortality rate was observed during acute hospitalization and at 1 year, in addition, substantial functional impairment at discharge persisted 1 year. The degree of functional disability correlated highly with survival at 1 year.