Mechanisms of heat loss explained

In this essential episode of the Prolonged Field Care (PFC) Podcast, host Dennis sits down with CRNA Kevin to dive deep into one of the most overlooked yet critical issues in trauma care: Hypothermia prevention and management. Even in warm environments, trauma patients can rapidly become hypothermic—leading to coagulopathy, increased bleeding, wound infections, and worse outcomes. Dennis and Kevin break down the science, real-world lessons from deployments, and practical strategies for austere and prolonged field care settings.

Whether you're a medic, provider, or anyone involved in combat casualty care, this episode will change how you approach keeping patients warm under fire or in remote locations.

Episode Highlights:

• The four main mechanisms of heat loss: radiation (40-60% of total loss), convection, conduction, and evaporation—and how to counter each one effectively.
• Why even healthy patients cool rapidly under anesthesia, and why trauma patients in the field are at much higher risk.
• Practical tips for austere environments: using tents, inflatable structures, insulation from the ground, wool blankets, and body heat to raise ambient temperature.
• Common mistakes that actively cool patients: wet clothing, cold airways (LMAs/ventilation), uncovered exposure, and cold blood/fluid administration.
• Best bang-for-buck interventions: covering the head, minimizing exposure, drying the patient, using HME filters, and insulating from the ground.
• Real deployed experiences: keeping trauma bays warm, pre-warming gear, using camping pads on litters, and limitations of Ready-Heat and HPMKs at altitude or in extreme cold.
• Advanced rewarming techniques (when available): fluid warming, bladder lavage, peritoneal lavage, and ECMO.
• Temperature monitoring challenges in the field: esophageal, nasopharyngeal, rectal, Foley, and forehead strips—plus how to interpret trends.

Chapters:

• 00:00 – Introduction & Why Hypothermia Matters in Trauma Care
• 02:30 – Heat Loss in Anesthesia: Vasodilation and the First-Hour Temperature Drop
• 04:50 – Mechanisms of Heat Loss: Radiation, Convection, Conduction, Evaporation
• 07:10 – OR Strategies: Room Temperature, Head Covering, Fluid Warming, Bear Huggers
• 09:29 – Environmental Control in the Field: Raising Ambient Temperature & Reducing Wind
• 11:52 – Using Tents and Structures to Trap Body Heat
• 14:14 – Insulation from the Ground: Litters, Wool Blankets, Camping Pads, Air Mattresses
• 17:53 – Preventing Conduction & Pressure Sores with Padding
• 19:56 – Avoid Actively Cooling Patients: Cold LMAs, Unheated Ventilation, Wet Clothing
• 22:21 – Heat Moisture Exchangers (HME) & Humidified Gas
• 26:40 – Blood Resuscitation: Cold Fluids vs. Hypovolemia—What Kills First?
• 31:17 – Team-Based Rewarming: Minimize Exposure, Pre-Warm Gear, Dry HPMKs
• 35:22 – Limitations of Battery-Powered Warmers & Bear Huggers in Austere Settings
• 40:04 – Prevention First: Insulate, Cover, Dry—Then Active Rewarming Works Better
• 42:24 – Downstream Effects of Hypothermia: Lethal Triad & Wound Infections
• 44:51 – Aggressive Rewarming Options: Chest Tubes, Gastric/Bladder Lavage, ECMO
• 47:15 – Temperature Monitoring in the Field: Probes, Strips, and Trend Interpretation

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