Serum sodium abnormalities during nonexertional heatstroke: incidence and prognostic values.

BACKGROUND: Although heatstroke is often associated with dehydration, the clinical significance of serum sodium abnormalities in patients with heat-related illness during heat wave has been poorly documented. METHOD: We evaluated 1263 patients (age, 82±15 years; body temperature, 40.1°C+1.2°C) admitted to emergency departments during the August 2003 heat wave in Paris, having a core temperature greater than 38.5°C and measurement of serum sodium concentrations. Patients were classified according to our previously described risk score of death. RESULTS: Hyponatremia (<135 mmol/L) was reported in 409 (32%) and hypernatremia (>145 mmol/L) in 220 patients (17%). One-year survival was significantly decreased in patients with hypernatremia (45%; P=.004) but not in those with hyponatremia (58%; P=.86) as compared with patients with serum sodium concentration in the reference range (57%). Using Cox regression, only hypernatremia was an independent prognostic factor (hazard ratio, 1.35; 95% confidence interval, 1.09-1.36) when risk score was taken into account. Using logistic regression, 2 variables were independently associated with hyponatremia (heatstroke severity score and blood urea nitrogen-creatinine ratio<100). Conversely, 5 variables were independently associated with hypernatremia (living in an institution, dementia, serum creatinine>120 µmol/L, a blood urea nitrogen-creatinine ratio >100, and absence of long-term diuretic intake). CONCLUSIONS: Serum sodium abnormalities are frequently observed in patients with a nonexertional heatstroke during heat wave; however, only hypernatremia should be considered as an independent risk factor of death. Rapid measurement of serum sodium concentration is mandatory to appropriately guide electrolyte resuscitation.

Elevation of cardiac troponin I during non-exertional heat-related illnesses in the context of a heatwave.

INTRODUCTION: The prognostic value of cardiac troponin I (cTnI) in patients having a heat-related illness during a heat wave has been poorly documented. METHODS: In a post hoc analysis, we evaluated 514 patients admitted to emergency departments during the August 2003 heat wave in Paris, having a core temperature >38.5 degrees C and who had analysis of cTnI levels. cTnI was considered as normal, moderately elevated (abnormality threshold to 1.5 ngxmL-1), or severely elevated (>1.5 ngxmL-1). Patients were classified according to our previously described risk score (high, intermediate, and low-risk of death). RESULTS: Mean age was 84 +/- 12 years, mean body temperature 40.3 +/- 1.2 degrees C. cTnI was moderately elevated in 165 (32%) and severely elevated in 97 (19%) patients. One-year survival was significantly decreased in patients with moderate or severe increase in cTnI (24 and 46% vs 58%, all P < 0.05). Using logistic regression, four independent variables were associated with an elevated cTnI: previous coronary artery disease, Glasgow coma scale <12, serum creatinine >120 micromolxL-1, and heart rate >110 bpm. Using Cox regression, only severely elevated cTnI was an independent prognostic factor (hazard ratio 1.93, 95% confidence interval 1.35 to 2.77) when risk score was taken into account. One-year survival was decreased in patients with elevated cTnI only in high risk patients (17 vs 31%, P = 0.04). CONCLUSIONS: cTnI is frequently elevated in patients with non-exertional heat-related illnesses during a heat wave and is an independent risk factor only in high risk patients where severe increase (>1.5 ngxmL-1) indicates severe myocardial damage.

Prognostic factors in non-exertional heatstroke.

PURPOSE: To identify the prognostic factors associated with mortality in heat-related illness. METHODS: Multi-center observational cohort-study in 16 emergency departments (ED) belonging to the teaching hospital network of the Paris area. The cohort comprised all patients admitted to one of the EDs during the August 2003 heat wave in Paris and having a core temperature >38.5 degrees C. Baseline clinical and biological data in ED, patient's course and 1-year survival rate were recorded. Potential prognostic factors associated with death were assessed by Cox proportional-hazards analysis. RESULTS: A total of 1,456 patients were included. Mean age was 79 +/- 19 years. Critically ill conditions were noted in 391 patients (27%), but only 72 (5%) were admitted into an intensive care unit. The survival rate was 57% at 1 year as compared to an expected 90% (P < 0.001). Nine independent prognostic factors were identified: previous treatment with diuretics, living in an institution, age >80 years, cardiac disease, cancer, core temperature >40 degrees C, systolic arterial pressure <100 mmHg, Glasgow coma scale <12 and transportation to hospital by ambulance. We defined three risk groups: low, intermediate and high risk, with a 1-year survival rate of 85, 61 and 18%, respectively. CONCLUSIONS: We observed a low survival rate and developed a risk score based on easily obtained variables that may be useful to clinicians managing casualties from future heat waves.