Background and purpose: The association between hyperthermia and early neurological deterioration, increased morbidity, and mortality in acute ischemic stroke is well known. However, the timing at which the cerebral lesion may be aggravated by high temperature has not been firmly established. The aim of this study was to determine the prognostic value of body temperature measured at different times after onset of stroke.
Methods: Axillary temperature was recorded every 2 hour hours for 72 hours in 260 patients with a hemispheric cerebral infarction of <24 hours' duration. A potential infectious focus was examined in all patients with hyperthermia (temperature >37.5 degreesC in any of the assessments). Stroke severity was quantified with the Canadian Stroke Scale on admission. The relationship between the highest temperature recorded in each 6-hour interval from stroke onset and stroke outcome (Canadian Stroke Scale and Barthel Index at 3 months) or infarct volume was evaluated by correlation analyses. The importance of the time at which hyperthermia was first detected was assessed by logistic regression analysis.
Results: During the first 72 hours, 158 patients (60.8%) had hyperthermia, and in 57.6% of them an infectious cause was identified. Mortality rate at 3 months was 1% in normothermic patients and 15.8% in hyperthermic patients (P<0.001). The correlation coefficients between the final infarct volume, Canadian Stroke Scale and Barthel Index scores at 3 months, and each temperature recording decreased progressively over time from symptom onset. Hyperthermia initiated within the first 24 hours from stroke onset, but not afterward, was independently related to larger infarct volume (odds ratio [OR]=3.23, 95% CI=1.63 to 6.43; P<0.001) and higher neurological deficit (OR=3.06, 95% CI=1.70 to 5.53; P<0. 001) and dependency (OR=3.41, 95% CI=1.69 to 6.88; P=0.002) at 3 months. The infectious origin of hyperthermia was not associated with poorer outcome or greater infarct volume.
Conclusions: The relationship between brain damage and high temperature is greater the earlier the increase in temperature occurs. However, only body temperature within the first 24 hours from stroke onset is associated with poor outcome and large cerebral infarcts.