Maintaining optimal patient conditions, including the core temperature, is paramount to successful outcomes for patients post surgery. Developing hypothermia at any stage of the patient pathway (before, during, or after surgery) can significantly impact the success of the surgery and the patient’s recovery.
Studies show that up to 20% of patients experience unintended perioperative hypothermia. Patients whose core body temperature drops below 36C face an increased risk of surgical site infections, blood loss, increased pain, prolonged recovery, and more.
NICE guidelines recommend warming patients at least 30 minutes before anaesthesia is administered. However, this often gets overlooked due to the impracticality of using current warming methods for all patients.
We explore the role of perioperative hypothermia in the prevalence and severity of surgical site infections, as well as the overall recovery time of patients.
Understanding perioperative hypothermia
To comprehend the impact hypothermia has on SSIs and recovery times, we need to understand why and how perioperative hypothermia occurs.
Several external factors influence the likelihood of perioperative hypothermia occurring. These are:
Cold operating environment
An operating theatre is generally kept cooler than other areas in a hospital, such as the wards. Due to the high stress levels of an operating room, and the layers of clothing worn, surgical staff require a cooler working temperature to ensure the safety of the patient. [1]
The combination of a colder temperature, exposed skin, and the administration of anaesthesia contribute to the risk of perioperative hypothermia. [2]
Anaesthesia
General anaesthetic alters thermoregulatory mechanisms, meaning that patients cannot regulate their temperature. This leads to vasodilation, which further increases the heat lost from the body.
Given the circumstances, patients cannot move to a warmer area or increase the temperature in the operating room. Therefore, their temperature will continue to drop without intervention.
Exposure and length
There are multiple ways exposure can lead to perioperative hypothermia. Firstly, prolonged skin exposure to the cold operating room can decrease a patient’s core temperature. Another risk factor is open surgical wounds, exposure of the body tissues during surgery can cause a loss of heat. [3]
The length of the surgery plays a key role in the risk of perioperative hypothermia. The longer the surgery, the more likely it is to develop.
Some patients face a higher risk of developing hypothermia during surgery than others. For example, advanced age, low blood pressure, low BMI, and female gender all influence the level of risk. [1]
The role of hypothermia in surgical site infections
Inadvertent hypothermia is one of the most common complications during the perioperative period. It has been recognized to contribute to not only SSIs, but also prolonged recovery times, delayed wound healing, increased blood loss, and patient discomfort. [4]
SSIs are a leading cause of nosocomial infections, accounting for 14-16% of all hospital-acquired infections. They are the leading cause of nosocomial infections among surgical patients specifically. [5] One study found that “only 1.9C core hypothermia triples the incidence of surgical wound infection following colon resection and increases the duration of hospitalisation by 20%.” [6]
Several mechanisms explain why hypothermia increases the risk of SSIs:
Impaired immune function
Hypothermia suppresses the immune system by reducing the activity of neutrophils. This is a type of white blood cell crucial for fighting infections.
At lower body temperatures, neutrophils become less effective at destroying bacteria, which increases the risk of infection at the surgical site.
Decreased oxygen delivery to tissues
Vasoconstriction is a result of hypothermia. This limits the blood flow to the skin and peripheral tissues. Adequate oxygenation of tissues is essential for wound healing and immune function.
When tissues do not receive enough oxygen, our body’s ability to heal is compromised, and the risk of infection increases.
Slower metabolism and cellular activity
Hypothermia slows down metabolic processes, including those involved in wound healing. Reduced levels of oxygen in tissue “impair oxidative killing by neutrophils and decrease the strength of the healing wound by reducing the deposition of collagen.” [8]
Prolonged recovery times due to perioperative hypothermia
The effects of hypothermia on surgical outcomes extend beyond SSIs. Patients who experience perioperative hypothermia also tend to have longer recovery times. Prolonged time spent in the hospital negatively impacts the patient, uses more hospital resources, and is more costly.
Some key factors that contribute to longer recovery times include:
Delayed wound healing
As hypothermia impairs the body’s natural healing processes, hypothermic patients face a higher risk of postoperative complications, including delayed wound healing. In turn, this increases the duration of hospital stays, uses more resources, and contributes to patient discomfort.
Increased postoperative pain and complications
Hypothermic patients have a higher incidence of complications such as bleeding, due to impaired clotting mechanisms. Both of these factors can cause postoperative pain, significantly slow recovery, and prolong the time needed to return to normal activities.
Longer hospitalisation and readmission rates
The prolonged recovery times require extended hospital stays. Patients with a postoperative temperature of below normothermia (36C) face a greater risk of SSIs, and increased mortality, among other complications. These complications increase the need for additional treatment, medications, or even more surgery. In addition, these patients have higher 30-day readmission rates. [9]
Preventing hypothermia in patients pre and post operatively
Given the significant impact of hypothermia on SSIs and recovery times, it is essential to prevent hypothermia before, during and after surgery. Warming intraoperatively has been standard practice for years and typical warming methods including intravenous fluid warmers, forced air warming blankets and heat mattresses.
Whilst these are popular methods, they may not be suitable for administering to patients during the pre-operative period or during recovery due to a number of reasons:
- time constraints, space constraints, lack of equipment, or something as simple as the availability of electrical sockets on the ward.
One simple way to reduce the risk of perioperative hypothermia is to use passive warming solutions for pre-warming and recovery.
Passive warming with THERMARMOUR Medical Blankets
THERMARMOUR Medical Blankets can be used for pre-warming patients, warming patients intraoperatively and during recovery.
Using THERMARMOUR perioperatively
Our Medical Blankets can be used throughout the patient pathway, minimising potential disruptions. They are a cost-effective, simple-to-use solution for preventing perioperative hypothermia.
Pre-warming in particular has been shown to reduce the risk of perioperative hypothermia and associated surgical site infections in various types of surgeries.
Generally, prewarming is recommended for a minimum of 30 minutes (up to 60 minutes). However, some studies have found that “prewarming for 10-30 minutes also effectively reduced the incidence of hypothermia in adult patients compared to the control group. Short-term prewarming is recommended to prevent hypothermia in clinical situations where prewarming for >30 minutes is not easy.” [10]
Monitoring Body Temperature
Continuous monitoring of core body temperature throughout surgery allows the surgical team to detect and respond to any early signs of hypothermia. Early intervention with warming techniques can prevent the cascade of complications associated with hypothermia.
See how THERMARMOUR can be used at each stage of the patient pathway:
Get access to our how-to guide: How to prevent inadvertent perioperative hypothermia.
Clinical evidence
THERMARMOUR has been thoroughly tested by clinicians and independent experts who have confirmed its effectiveness at maintaining normothermia in a perioperative setting.
Clinical trials demonstrate that THERMARMOUR works as well as FAW solutions at maintaining normothermia for elective surgeries in stable patients whilst providing a multitude of cost and operational efficiencies.
Read clinical evidence reports
Environmental Ergonomics Research Centre Loughborough University: Measurement of heat resistance of THERMARMOUR vs traditional blanket.
Hull University Teaching Hospitals NHS Trust: Report on post-operative warming (2019).
Robert Jones & Agnes Hunt Orthopaedic Hospital NHS Trust: Temperature management in major spine surgery.
The Leeds Teaching Hospitals NHS Trust: Managing perioperative normothermia in post-anaesthetic care.
The Robert Jones and Agnes Hunt Orthopaedic Hospital: An evaluation of Thermarmour warming blanket for temperature management in hip replacement.
Get in touch
If you’re a Trust interested in the THERMARMOUR Medical Blankets, you get in touch with our team to discuss your requirements and quantity needs.
You can also purchase the Medical Blanket via the NHS Supply Chain.
Sources
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3179201/
- https://www.aorn.org/outpatient-surgery/article/2022-February-perioperative-hypothermia
- https://pubmed.ncbi.nlm.nih.gov/20636552/#:~:text=A%20heat%2Dsensitive%20camera%20measured,wound%20infections%20in%20the%20future.
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5356209/#:~:text=For%20example%2C%20an%20awake%20patient,patient%20disease%20(e.g.%20sepsis).
- https://www.sciencedirect.com/science/article/abs/pii/B9780444640741000410
- https://www.sciencedirect.com/science/article/abs/pii/S152168960800061X#:~:text=Mild%20hypothermia%20significantly%20increases%20perioperative,and%20needs%20to%20be%20avoided.
- https://www.sciencedirect.com/science/article/abs/pii/B9780444640741000410
- https://pubmed.ncbi.nlm.nih.gov/8606715/#:~:text=Reduced%20levels%20of%20oxygen%20in,also%20directly%20impairs%20immune%20function.
- https://pubmed.ncbi.nlm.nih.gov/37527171/#:~:text=Postoperatively%2C%20patients%20with%20tem
- https://www.medsci.org/v19p1548.htm
Categories: Medical
Tags: hypothermia in surgery, medical blanket, normothermia, perioperative hypothermia, surgery
