Neurologic manifestations of classic heat stroke: Description of patients from the Chicago heat wave of July 1995

Purpose: To characterize neurologic manifestations of heat stroke (HS) in intensive care unit patients. Methods: We collected and analyzed retrospectively data on HS patients from 9 Chicago hospitals. The enrollment criteria for this study were admission to the ICU between 7/12/95 and 7/20/95, mental state alteration, and rectal temperature ≥40.6°C (105°F). Patients with temp. <40.5°C were included if cooling occurred before the first recorded temp, and/or environment in which the patient was found was described by paramedics or family members as "hot without working air conditioner"; 53 patients meeting these criteria were identified. Results: CNS derangements included; coma (34), delirium (2), lethargy (8), disorientation (6), and seizures (3). Of the 10 (19%) patients who died, 8 had presented in coma. Forty-three (81%) patients survived to be discharged from hospital. Thirty-three (77%) of these surviving patients were found to have residual neurologic deficits with 22 (67%) patients requiring transfer to chronic care facilities. Mild to severe general muscular weakness was the most common finding. Twenty-nine patients had head CT and no acute disease process(es) were detected. Central pontine myelinolysis (CPM) was diagnosed by MRI in one patient; autopsy confirmed CPM and revealed petechial cerebral hemorrhage and loss of Purkinje cells. Muscle biopsy in 3 patients with profound weakness revealed axonal degeneration. Conclusions: Preliminary analysis of our data suggests patients with HS have high mortality and morbidity. Prolonged weakness may be related to axonal degeneration. CPM is a relatively uncommon complication of therapeutic interventions for electrolyte imbalance and is not usually associated with HS. Clinical Implications: Long term neurologic sequelae are common following critical illness precipitated by HS. Readily identifiable anatomic lesions are uncommon. CPM may be one such lesion.