Perioperative hypothermia and coagulopathy
Stem
A 52-year-old man, 90 kg, is brought to the operating room 90 minutes after a motorcycle crash for fixation of an unstable pelvic fracture. He has received 2 units of red cells in the emergency department. His core temperature is 35.4 °C, blood pressure 96/58, heart rate 112, and the room is set at 19 °C. The surgeon expects a long case with significant blood loss.
Question
How will you manage his temperature, and why does it matter for this operation?
Ideal answer
HeadlineA cold patient bleeds, and he is already below 36 °C before I start, so I warm while I work and treat cold and bleeding as one problem.
- Room to at least 21 °C, forced air from induction, and all fluids and blood warmed to 37 °C through a rapid infuser.1
- Core temperature by distal esophageal probe, recorded at least every 30 minutes,1 because peripheral sites lag the core and hide the trend.
- Treat bleeding and cold together: aggressive rewarming toward 36 °C, correcting acidosis and calcium, balanced component therapy.
- Viscoelastic testing run at his temperature, because standard tests warmed to 37 °C hide the defect.
- Tell the surgeon early that hypothermia, acidosis and coagulopathy feed each other; if they appear, we move to damage control.
Watch for: the temperature, the gas, the ionized calcium and the field.
Breaking down the answer
- Prewarming — shrinks the core-to-periphery gradient so redistribution costs less heat: the single most effective preventive step, for 30 minutes in holding. Prevention before reaction is the judgment examiners look for. Changes if: elective, I do not induce below 36.0 °C.1
- Core site — esophageal, nasopharyngeal, bladder or pulmonary artery temperature;2 skin and axillary readings lag and underestimate.
- Why cold bleeds — clotting factor activity falls about 10% per degree, platelets fail, fibrinolysis rises.3 Even mild hypothermia under 1 °C raises blood loss about 16% and transfusion risk about 22%;4 in massively transfused trauma, below 34 °C independently predicts death.3
- The lab lies — PT and aPTT run at 37 °C, so a cold patient's coagulopathy looks normal on paper. I ask for TEG or ROTEM and tell the lab his temperature, or I treat clinically.
- Damage control — the strategic answer to the lethal triad in trauma: short surgery, rewarm in the ICU, return later.
- Calcium — citrate in transfused blood binds ionized calcium, and a cold liver clears citrate slowly. I keep it at 1.1–1.3 mmol/L,3 because calcium is factor IV and low calcium also depresses contractility.
- Rewarming targets — at least 36 °C before emergence and ward transfer,1 because postoperative hypothermia increases myocardial events and wound infection and prolongs neuromuscular block and drug action.
Follow-up question
After 8 units of red cells the field is oozing everywhere. Temperature is 33.8 °C, pH 7.21, ionized calcium 0.85 mmol/L, and the lab INR is 1.4. What do you do?
Follow-up answer
HeadlineThe lethal triad, and the INR understates it because the lab warms the sample; I tell the surgeon and ask for packing and damage control.
Calcium chloride 1 g; plasma and platelets continued at 1:1:1; cryoprecipitate or fibrinogen concentrate if fibrinogen is 150 mg/dL or less;3 TEG. Tranexamic acid if within 3 hours of injury and not yet given, because later doses increased bleeding deaths in CRASH-2.5 I raise the room temperature, add an underbody pad, run every fluid through a warmer, warm the irrigation, and consider a bladder or esophageal warming device. Temperature, gas and coagulation every 30 minutes; ICU transfer intubated.
Pitfalls that cost points
- Extubating a cold patient: shivering raises oxygen consumption up to several-fold, and residual block is prolonged.
- Treating each part of the triad in isolation, one lab value at a time.
Rapid-fire
Q: Why is the first-hour drop larger than later losses? A: It is redistribution, not loss: vasodilation lets core heat flow to the cooler periphery, 1–1.5 °C in the first hour,2 then a slower linear loss from radiation and convection.
Q: When is deliberate hypothermia acceptable? A: Targeted temperature management after cardiac arrest and some cardiac or neurosurgical cases; otherwise normothermia is the standard.
Q: Why does shivering matter after surgery? A: It increases oxygen consumption and CO2 production; in a patient with coronary disease it provokes ischemia. Meperidine 12.5–25 mg IV stops it.
Q: Which patients cool fastest? A: Neonates, the elderly, burn patients, and those with large exposed body cavities or major regional plus general anesthesia, because both central and peripheral thermoregulation are impaired.
Q: How much do unwarmed patients cool? A: Typically 1–2 °C, from redistribution followed by ongoing heat loss.2
Numbers to know
| Item | Value |
|---|---|
| First-hour core drop | 1–1.5 °C (redistribution) |
| Hypothermia definition | Core < 36.0 °C1 |
| Blood loss | Rises ~16% with < 1 °C of hypothermia4 |
| Before induction and ward transfer | ≥ 36.0 °C1 |
| Ionized calcium target | 1.1–1.3 mmol/L3 |
| Intraoperative warming | Forced air if > 30 min; fluids ≥ 500 mL warmed to 37 °C1 |
Links
- Temperature monitoring and intraoperative hypothermia, Massive hemorrhage and transfusion, Trauma: initial management and damage control, dic, Arterial blood gas and acid-base interpretation
- ASA Practice Guidelines for Perioperative Blood Management; ACS TQIP Massive Transfusion in Trauma Guidelines
Sources
- 1.Hypothermia: prevention and management in adults having surgery (CG65), recommendations · NICE, 2016 · nice.org.uk
- 2.Perioperative thermoregulation and heat balance · The Lancet, 2016 · pubmed.ncbi.nlm.nih.gov
- 3.The European guideline on management of major bleeding and coagulopathy following trauma: sixth edition · European multidisciplinary task force (Crit Care), 2023 · pmc.ncbi.nlm.nih.gov
- 4.The effects of mild perioperative hypothermia on blood loss and transfusion requirement · Anesthesiology, 2008 · pubmed.ncbi.nlm.nih.gov
- 5.The importance of early treatment with tranexamic acid in bleeding trauma patients: an exploratory analysis of the CRASH-2 randomised controlled trial · The Lancet, 2011 · researchonline.lshtm.ac.uk
Facts on this page were checked against these sources on Oct 14, 2026. Guidelines change; confirm doses against current institutional protocols.