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26th February 2024

Understanding perioperative hypothermia

The term perioperative simply means “around the time of surgery”. The length of this time period may vary, but generally concerns the time before, during and after surgery. Such as from the time the patient enters the hospital for surgery, to the time the patient is discharged.

Perioperative hypothermia occurs when a patient’s body temperature has dropped below 36°C. Unfortunately, patients developing hypothermia can be common before, during, and after major surgery, which is why we developed Thermarmour.

Our mission is to protect and prevent patients from inadvertent hypothermia during surgery by using simple, effective, and innovative products. Learn more about Thermarmour medical products.


Perioperative hypothermia complications

The effects of hypothermia can range from mild to fatal, depending on the patient, and the scenario. Within a surgical setting, even a mild case of hypothermia can have serious consequences.

Risks include surgical site infections, blood loss, cardiac arrhythmias, altered medication metabolism and increased pain. The danger of developing hypothermia during the perioperative period is not limited to the surgery itself. It may also cause post-operative complications and lengthen recovery time.


How does perioperative hypothermia develop?

A mixture of personal and environment factors can influence how a patient regulates their body temperature. Age, health, and medication use can increase a patient’s risk of developing hypothermia.

perioperative normothermia

However, the physical environment and practices of the hospital can also play a role.

An environmental example would be exposing a patient’s skin for prolonged periods, or a cold operating room. Both of these things can contribute to a lower body temperature.
Another opportunity for heat loss is during transportation from the ward to the operating room.

Without appropriate coverage from clothing or gowns, patients core temperature can begin to drop.

For these reasons, we recommend that Thermarmour medical blankets are applied from the time of consent, right through to after post-surgery recovery.




How does anaesthesia contribute to developing hypothermia?

Though every patient is different, the administration of anaesthesia and the body’s reaction to it is a major contributor to a person developing perioperative hypothermia.

An article in the Anaesthesia Progress journal tells us that when anaesthesia is administered, the core body heat redistributes to the skins surface through “anaesthetic-induced vasodilation and depression of hypothalamic thermoregulatory centres”.

This means that due to a lack of thermoregulatory control, heat is taken away from the body’s core and vital organs and is redistributed closer to the skins surface.

The balance of heat is another issue in surgery. The journal article “Inadvertent perioperative hypothermia” tells us that to maintain normothermia, heat that is lost must be regained.
During surgery, and whilst under anaesthesia, regaining heat without external aids is unlikely.

Our metabolic rate decreases during anaesthesia, and heat production is a function of metabolism. It is thought that around 60% of the heat generated during our metabolic processes is used to maintain a normal body temperature.

Therefore, the reduction of our metabolic rate during surgery can result a negative heat balance, potentially causing hypothermia.




How is perioperative hypothermia prevented?

Preventing perioperative hypothermia is determined by the circumstances of the surgery. Such as the patient, the type of surgery, as well as the available space and resources.

A simple yet effective solution is passive warming, such as the Thermarmour medical blanket. Suitable for most environments due to its ease of use, simply remove from the packaging and place around the patient.

perioperative normothermia

Passive warming promotes heat retention, using the patients own body temperature to recirculate heat.

In contrast to active warming solutions such as forced air warming, these medical blankets work to alleviate the heat lost, rather than adding heat. They also don’t need to be plugged in to a machine to function, so there’s no cables getting in the way of surgical staff.

Thermarmour medical blankets are a convenient, easy and efficient way to maintain perioperative normothermia.

Read more about Thermarmour clinical evidence.



Pre-warming with Thermarmour

Our medical blankets are efficient and simple to use. As they do not require any electricity or any other additional heat source, they are suitable for any size operating room or pre-op waiting area.

The Thermarmour material is a multi-layered system, consisting of four layers that work cohesively together to maintain patient normothermia.

perioperative normothermia

To reduce perioperative hypothermia, Thermarmour should be given to the patient 30-45 minutes before their procedure to start the pre-warming process.

Patients should remain under the blanket until they are in position for surgery.

Thermarmour can be used to wrap exposed extremities, helping to prevent the initial redistribution temperature drop (RTD) and inadvertent perioperative hypothermia.

After surgery, we recommend continuing with the use of the same Thermarmour blanket in the recovery room and during the transition back to the ward or discharge for day cases.

Learn more about the Thermarmour medical blanket.



Register your email address to receive the link to the How-To Guide: Understanding Perioperative Hypothermia

Download your copy



  1. Inadvertent perioperative hypothermia
  2. Thermoregulation: Physiological and Clinical Considerations during Sedation and General Anesthesia

  3. Perioperative Hypothermia—A Narrative Review

  4. Understanding the Dangers of Perioperative Hypothermia

  5. Is Normothermia Maintained in the Operating Room? 

  6. Maintaining perioperative normothermia

  7. Biochemistry, Heat and Calories



Categories: Medical

Tags: hypothermia in surgery, normothermia, perioperative hypothermia, perioperative normothermia

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