LAUSR

BACKGROUND Electrolyte disturbances can result from targeted temperature treatment (TTM) in out-of-hospital cardiac arrest (OHCA) patients. This study explores electrolyte changes in blood and urine in OHCA patients treated with TTM. METHODS This is a sub-study of the TTH48 trial, with the inclusion of 310 unconscious OHCA patients treated with TTM at 33°C for 24 or 48 hours. Over a three-day period, serum concentrations were obtained on sodium potassium, chloride, ionized calcium, magnesium, and phosphate, as were results from a 24-hour diuresis and urine electrolyte concentration and excretion. Changes over time were analysed with a mixed-model multivariate analysis of variance with repeated measurements. RESULTS On admission, mean ± SD sodium concentration was 138 ± 3.5 mmol/l, which increased slightly but significantly (p < 0.05) during the first 24 hours. Magnesium concentration stayed within the reference interval. Median ionised calcium concentration increased from 1.11 (IQR 1.1-1.2) mmol/l during the first 24 hours (p < 0.05), whereas median phosphate concentration dropped to 1.02 (IQR 0.8-1.2) mmol/l (p < 0.05) and stayed low. During rewarming, potassium concentrations increased, and magnesium and ionises calcium concentration decreased (p < 0.05). Median 24-hour diuresis results on days one and two were 2,198 and 2,048 ml respectively, and the electrolyte excretion mostly stayed low in the reference interval. CONCLUSIONS Electrolytes mostly remained within the reference interval. A temporal change occurred in potassium, magnesium and calcium concentrations with TTM's different phases. No hypothermia effect on diuresis was detected, and urine excretion of electrolytes mostly stayed low.