Hypothermia-induced thrombocytopenia in an elderly woman

To the editor

A 77-year old women presented to our emergency department in February with a 1-week history of lethargy and inadequate fluid intake. Her past medical history was significant for hypertension and also for oropharyngeal dysphagia and temperature dysregulation due to multi-infarct dementia and a recent massive ischemic stroke. Her vital signs at presentation were remarkable for a blood pressure of 82/61 mmHg, heart rate of 41 beats per minute and an orally measured temperature of 33.5°C. She was lethargic and cachectic. The remainder of the physical exam was normal. A 12-lead electrocardiogram (ECG) showed sinus bradycardia and a prominent Osborn J wave in leads I, II, and a VL. A complete blood count revealed a hemoglobin level of 12 g/dL, white cell count of 9200 cells/µL, and platelet count of 80 000 cells/µL. Other remarkable laboratory results included a plasma sodium concentration of 170 mmol/l, blood urea nitrogen of 85 mg/dl and plasma creatinine of 3 mg/dL. Hypotonic intravenous fluids, prophylactic antibiotics and passive rewarming were initiated.

Over the next few days, the patient's temperature, heart rate, mental status and plasma sodium concentration returned to baseline. The pre-renal azotemia and Osborn waves were resolved with appropriate fluid therapy and passive rewarming, respectively. The thrombocytopenia showed a transient worsening to 37 000 cells/µL over the next 2 days with gradual recovery to the normal range afterwards. Investigations for disseminated intravascular coagulation were negative, blood cultures remained negative and antibiotics were stopped. Interestingly, the platelet count showed a very strong correlation with body temperature over the course of hospitalization (R² = 0.91, p < 0.01; Figure 1). The patient remained unable to swallow, but the family chose comfort care only and the patient was discharged.

Figure 1. Correlation between the platelet count and body temperature in a patient with temperature dysregulation and hypothermia. Note: After a transient drop, the platelet count increased to the normal range as hypothermia was resolved.

Hypothermia is a recognized complication of therapeutic hypothermia used in the treatment of neonatal post-asphyxial encephalopathy and severe traumatic brain injury in adults [1], [2]. Hypothermia-induced thrombocytopenia in non-therapeutic settings, however, is rare. To my knowledge, only about 10 such cases have been previously reported [3–8]. The mechanism of thrombocytopenia in hypothermia seems to be related to the sequestration of platelets in the liver and spleen due to a loss of marginal microtubules, development of pseudopods, adopting a more spherical shape, and becoming more sticky [9], [10]. In all reported cases, thrombocytopenia resolved upon resolution of hypothermia.

Declaration of interest: None.