Body Heat Loss in the Operating Room:

Body Heat Loss in the Operating Room:

Understanding Radiation, Conduction, Convection, and Evaporation Heat Loss

In the highly controlled environment of the operating room (OR), every detail — from airflow to lighting to sterility — is meticulously managed to ensure optimal patient outcomes. Yet, one of the most fundamental physiological aspects often underestimated is body temperature regulation.

Hypothermia, defined as a core body temperature below 96–99°F (with severe hypothermia considered 96°F or lower), is a common occurrence during surgical procedures. It’s especially prevalent in extended surgeries or among high-risk populations such as small breeds or trauma patients.

Unintended perioperative hypothermia is associated with a wide range of complications:

  • Increased risk of surgical site infections

  • Impaired coagulation leading to bleeding

  • Altered drug metabolism

  • Delayed recovery from anesthesia

  • Prolonged hospitalization

  • Increased mortality

A core contributor to intraoperative hypothermia is the loss of body heat through four primary mechanisms: radiation, conduction, convection, and evaporation.

Understanding these mechanisms is crucial for perioperative teams aiming to optimize thermoregulation strategies. Let’s take a closer look at how these heat loss processes occur in the OR and what you can do to mitigate them.

1. Radiation: The Primary Mode of Heat Loss

What Is Radiation?

Radiation is the emission of infrared heat from a warmer body (the patient) to cooler surrounding surfaces (walls, lights, equipment) without direct contact. In the OR, radiation accounts for 50–60% of total heat loss.

How It Happens in the OR

When a patient is anesthetized and positioned on the operating table, their body begins to radiate heat to surrounding cooler objects. Anesthesia inhibits natural thermoregulation mechanisms like vasoconstriction and shivering, making the patient more vulnerable.

How to Mitigate Radiative Heat Loss

  • Increase OR ambient temperature, especially for small breeds and trauma patients.

  • Use thermal insulation: Cover non-operative areas with ConRad Thermal Blankets.

  • Employ forced-air warming systems like the HoverHeat Patient Warming System.

  • Pre-warm the patient: Use the HoverHeat Cage Warming Combo for 30+ minutes before anesthesia.

  • Warm during anesthetic induction: Have the patient lay on an active HoverHeat forced-air warming pad during prep. Up to 80% of heat loss occurs in the first 30–45 minutes post-induction.

 

HoverHeat Cage Warming Combo - VetORSolutions

2. Conduction: Heat Transfer Through Direct Contact

What Is Conduction?

Conduction is the transfer of heat through direct physical contact. In the OR, this usually involves the patient losing heat to the cold surfaces they come in contact with — such as the OR table or surgical tools.

Examples in the OR

  • Cold metal OR tables

  • ECG leads and surgical retractors

  • Unwarmed IV fluids or irrigation solutions

Strategies to Reduce Conductive Heat Loss

  • Warm the OR table with ConRad Thermal Blankets, electric warming pads, or HoverHeat.

  • Use fluid warmers for IV and blood products.

  • Warm irrigation solutions, especially in abdominal procedures.

  • Pre-warm surgical instruments, particularly in surgeries involving prolonged tissue exposure.

HoverHeat Warming Pad - VetORSolutions

3. Convection: The Role of Airflow in Heat Loss

What Is Convection?

Convection is the transfer of heat via moving air. As warm air around the patient’s body rises, cooler air replaces it, leading to heat loss. ORs often have active air circulation systems, which increases this effect.

How It Happens in the OR

  • Positive pressure ventilation systems

  • Staff movement and door openings
    Convection accounts for about 15–20% of total heat loss.

Convection-Reducing Measures

  • Minimize unnecessary exposure with surgical drapes and ConRad Thermal Blankets

  • Use convective warming devices like the HoverHeat Patient Warming System

  • Reduce air movement near the patient; limit door openings and foot traffic when possible

4. Evaporation: The Cooling Effect of Fluid Loss

What Is Evaporation?

Evaporation occurs when liquids on the body (blood, prep solutions, tissue fluid) evaporate, drawing heat away. It contributes to 10–15% of total heat loss.

Examples of Evaporative Loss

  • Evaporation from surgical sites during abdominal or thoracic surgeries

  • Cold alcohol-based antiseptic solutions

  • Insensible losses through breathing dry anesthetic gases

  • Moist, exposed tissues during long surgeries

Preventing Evaporative Heat Loss

  • Use warmed, humidified anesthetic gases during prolonged intubation

  • Warm surgical prep solutions, especially alcohol-based ones

  • Minimize open exposure by keeping incisions small and covering tissues

  • Use humidified insufflation gases during laparoscopy

  • Cover non-surgical areas with ConRad Thermal Blankets

An Integrated Approach to Heat Conservation

Preventing intraoperative hypothermia requires a multimodal strategy that addresses all pathways of heat loss. Tailor the approach to the surgical procedure, duration, and patient vulnerability.

Best Practices for OR Teams:

Preoperative

  • Pre-warm patients for 30 minutes with HoverHeat Cage Warming Combo

Anesthetic Induction

  • Use HoverHeat forced-air warming pads during prep and monitor application

  • Remember: 80% of heat loss occurs within the first 30–45 minutes post-induction

Intraoperative

  • Maintain appropriate ambient OR temperature

  • Use thermal retention blankets, forced-air warming systems, and fluid warmers

  • Continuously monitor core temperature (esophageal or rectal probes)

Postoperative

  • Continue warming until the patient regains normothermia and consciousness

  • Train staff on thermoregulation protocols and device usage

HoverHeat Warming Pad - VetORSolutions

Conclusion

Thermoregulation is a critical yet often overlooked aspect of surgical care. By understanding and addressing the four main mechanisms of heat loss — radiation, conduction, convection, and evaporation — veterinary teams can improve surgical outcomes, reduce complications, and shorten recovery times.

With the right tools, protocols, and awareness, intraoperative hypothermia doesn’t have to be inevitable — it can be prevented.

References

  • Sessler DI. Perioperative thermoregulation and heat balance. Anesthesiology. 2008.

  • NICE Guidelines: Inadvertent Perioperative Hypothermia. National Institute for Health and Care Excellence.

  • Kurz A, Sessler DI, Lenhardt R. Perioperative normothermia to reduce the incidence of surgical-wound infection. NEJM. 1996.

HoverHeat Cage Warming Combo - VetORSolutions

 HoverHeat Cage Warming Combo

HoverHeat Complete Set - VetORSolutions

HoverHeat Set

General Use | Thermal Blanket Set - VetORSolutions

ConRad Thermal Blanket Set

See the short (30-second) product videos for the above products by clicking on the image.

Back to blog