Hypothermia-induced acute kidney injury in an elderly patient
A 78-year-old Korean male was admitted to our hospital in November for severe hypothermia. He had been diagnosed with hypertension at the age of 65 years, and had been treated with medications. He was found comatose on a mountaineering path 4 hours prior to admission. The temperature on the mountain, where he was lying, was reported to be 14℃. Upon admission, the patient was in deep stupor. His blood pressure, as measured in the supine position, was 80/50 mmHg, heart rate was 85 beats per minute, and respiratory rate was 19 per minute. The body temperature was below 34.0℃ (exceeding the measurement range of 34.0℃ to 44.0℃ of the thermometer, which had an error of measurement of ± 0.2℃). Electrocardiography showed J waves, prolonged QT, and occasional premature ventricular complexes (). Therefore, we estimated that his body temperature was indicative of moderate to severe hypothermia.\nChest radiography appeared normal, and ultrasonography of the kidneys showed normal echogenicity and intact corticomedullary differentiation without hydronephrosis. The patient's kidneys were within the normal range in size (the right kidney measured 9.3 × 5.4 cm, and the left kidney measured 9.9 × 4.6 cm). Renal scan (technetium-99m MAG3) indicated normal excretion and secretion functions. Urinalysis showed no proteinuria, and urine microscopic exam showed 10 to 19 red blood cells per high-power field with no casts. Blood urea nitrogen and serum creatinine concentrations were 25 mg/dL (normal range, 8 to 20) and 2.7 mg/dL (normal range, 0.6 to 1.2), respectively. In addition, fractional excretion of sodium was 4.5% and renal failure index was 2.25. The results of hormonal assays were as follow: plasma cortisol 14.6 µg/dL (normal range, 4.0 to 18.3), thyroid simulating hormone 1.43 µIU/mL (normal range, 0.17 to 4.05), free triiodothyronine 0.49 ng/dL (normal range, 0.78 to 1.82), and free thyroxine 1.25 ng/dL (normal range, 0.93 to 1.20). Anterior pituitary hormone levels were normal.\nThe results of arterial blood gas analysis were as follows: pH 7.260, pCO2 28.0 mmHg, pO2 151.0 mmHg, and HCO3- 12.6 mmol/L. Other laboratory studies produced the following results: serum calcium 8.8 mg/dL, serum phosphate 8.0 mg/dL, serum sodium 141 mEq/L, serum potassium 3.7 mEq/L, serum magnesium 3.1 mg/dL, hemoglobin A1c 5.4%, lactic acid 11.4 mmol/L, serum myoglobin 1,685.0 ng/mL, serum lactate dehydrogenase 159 IU/L, serum creatine phosphokinase 68 U/L, and serum amylase 582 U/L. Urinary concentrations of sodium, potassium, chloride were 95, 44.1, and 114 mEq/L, respectively. Urine osmolality was 537 mOsm/kg.\nUpon hospitalization, the patient was wrapped in a warm blanket. We provided him with a forced-air warming system (Warm Touch, Mallinckrodt Medical Inc., Dublin, Ireland) infused with warmed saline (42℃) by pressure infusion (Ranger, Alrizant Healthcare Inc., Eden Prairie, MN, USA). Five hours of warming resulted in an increase in body temperature to 37.3℃, and the patient regained consciousness. Subsequently, electrocardiography showed a normal sinus rhythm (). After supportive care, the serum creatinine levels decreased gradually from 2.7 to 1.1 mg/dL on the fourth day of the hospital stay. The patient was discharged after 12 days of hospitalization, and the serum creatinine and body temperature were 1.2 mg/dL and 36.5℃ at discharge ().