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Hypothermia Coagulation Lab Error — FRCA Final MCQ

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HardIntensive Care MedicineHypothermia Coagulation Lab ErrorFRCA Final

A patient in ICU has a core temperature of 34.0°C. The coagulation cascade is impaired by hypothermia. Standard laboratory coagulation tests (PT/APTT) are performed at 37°C. What is the clinical implication?

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Correct answer: E — Lab tests UNDERESTIMATE the degree of coagulopathy because the assays are warmed to 37°C

Standard laboratory coagulation assays (PT, APTT, INR) are performed at 37°C regardless of the patient's actual temperature. At 34°C, enzyme kinetics of the coagulation cascade are significantly slowed, causing worse coagulopathy in vivo than the lab tests suggest. Therefore, lab results UNDERESTIMATE the true degree of coagulopathy in hypothermic patients. This is clinically important in trauma resuscitation (the 'lethal triad' of hypothermia, acidosis, and coagulopathy). Thromboelastography (TEG/ROTEM) can be performed at the patient's actual temperature to better reflect in vivo haemostasis.

Reference: RCOA – 2023 – Haematology in anaesthesia; NICE – 2016 – CG65 Hypothermia