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Near-Fatal Heat Stroke during the 1995 Heat Wave in Chicago

Jane E. Dematte, MD; Karen O'Mara, DO; Jennifer Buescher, BS; Cynthia G. Whitney, MD, MPH; Sean Forsythe, MD; Turi McNamee, MD; Raghavendra B. Adiga, MD; and I. Maurice Ndukwu, MD, MPH
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For author affiliations and current author addresses, see end of text. Acknowledgments: The authors thank Drs. Alan R. Leff, J. Iasha Sznajder, and Gregory A. Schmidt for insightful comments and advice during the preparation of this manuscript and Dr. Phil Schumm for statistical advice. They also thank the Office of the Cook County Medical Examiner, Little Company of Mary Hospital, Christ Hospital Medical Center, St. Bernard Hospital, Jackson Park Hospital, Mount Sinai Hospital Medical Center, South Shore Hospital, and Mercy Hospital Medical Center, Chicago, Illinois, for their assistance. Grant Support: In part by the Park Ridge Health Foundation and the University of Chicago Clinical Research Center (grant no. M01 RR00055). Requests for Reprints: I. Maurice Ndukwu, MD, MPH, Section of Pulmonary and Critical Care Medicine, University of Chicago, 5481 South Maryland Avenue, MC 6076, Chicago, IL 60637. Current Author Addresses: Dr. Dematte: Michael Reese Hospital and Medical Center, 2929 South Ellis Avenue, RC-216, Chicago, IL 60521.

Copyright ©2004 by the American College of Physicians

Ann Intern Med. 1998;129(3):173-181. doi:10.7326/0003-4819-129-3-199808010-00001
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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.


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Figure 1.
Relation between admissions to the intensive care unit (ICU) (bar graph) and the heat index (line chart) during the height of the heat wave.[1]

Admissions increased 24 hours after the peak heat index on 13 July 1995. The peak admission rate occurred 2 days later, on 15 July 1995. Intensive care unit admissions coincided with heat-related deaths reported by the Cook County Medical Examiner's office .

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Figure 2.
Kaplan-Meier plot showing 1-year survival based on the level of functional disability at the time of discharge, as determined by the modified Stanford Health Assessment score.P

Black circles represent survival in patients with minimal disability, white box represents patients with moderate disability, and black triangles represent patients with severe disability. Patients with severe disability had significantly decreased survival (Mantel-Cox log-rank = 0.04).

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Figure 3.
Kaplan-Meler plot showing survival from the time of presentation through 1 year of follow-up on the basis of age.P

Patients in category 1 were younger than 60 years of age (circles); patients in category 2 were 60 to 69 years of age (triangles); and patients in category 3 were older than 70 years of age (squares). Survival did not differ among the groups (Mantel-Cox log-rank chi-square > 0.2).

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