Why You Should Ask Your Doctor To Keep You Warm During Surgery – Dr Raveenthiran Rasiah

How to prevent hypothermia during surgery

In the medical profession, the role of an anaesthesiologist is often referred to as the silent force behind the scene. Going beyond the administration of anaesthesia, the responsibilities of an anaesthesiologist include overall patient management during surgery and optimizing the comorbid conditions of the patient for the safe outcome of the patient in the perioperative period [1].

But first, let’s understand what happens before a patient goes for surgery.

Different surgical procedures will have different mandates that are required to be followed before surgery. Some routinely followed procedures before surgery could include an associated period of fasting, undergoing certain medical examinations like electrocardiogram (ECG), blood tests, X-rays and other tests, depending on the procedure.

This is also followed by a consultation with the doctor who will describe the procedure to the patient while making clear notes about their medical history, allergies and medications, if any. In many instances, some doctors provide medication to relieve anxiety before the surgery.

On the day of the procedure, the patient will have an encounter with their anaesthesiologist. Depending on the surgical procedure, the anaesthesiologist will determine the anaesthesia dosage the patient requires and for how long the anasesthesia can be safely administered. Before the induction of anaesthesia, he/she will also check the patient’s history and allergies to reduce any risk associated with the anaesthesia[2].

An unintended drop in temperature during surgery can induce a state of ‘hypothermia.’

According to medical standards, an anaesthesiologist will monitor four important parameters for patients under anaesthesia — pulse oximetry, non-invasive blood pressure, end-tidal COz and your electrocardiogram (ECG)[3]. Additionally, your doctor will also keep a watch on your body’s temperature. Depending on what the procedure warrants, an anaesthesiologist will also monitor your intraarterial monitoring and central venous pressure.

However, as a general practice, most anaesthesiologists will monitor a patient’s temperature during the procedure to ensure that a patient does not wake up with chills.

Operating rooms function at a lower temperature for several reasons. These include improving the shelf life of surgical fluids, keeping the surgeon and other staff comfortable during the procedure and most importantly to prevent surgical site infections (SSI) that might occur at site of incision.

An unintended drop in temperature during surgery can induce a state of ‘hypothermia’ that can lead to a plethora of other associated conditions including patient discomfort and delayed healing of wounds.[4] It is therefore important for patients to understand the role of temperature and why is it necessary to stay warm during surgeries.

Patients under anaesthesia lose the body’s thermoregulatory functions.

When a patient is wheeled into the operation theatre, his or her normal body temperature is within 36.5 to 37°C. But an hour later the temperature can drop to 36°C. This drop in temperature is contributed by several factors namely the anaesthesia itself, low operating temperatures in the operating theatre, dry anaesthesia gases, laminar air flow of the operating room and exposed body surface area.

The drop in temperature starts to affect several other systems as the body tries its level best to conserve heat. Eventually after all the mechanisms of the body fail, vasoconstriction at the periphery sets in, the body starts to shiver to produce more heat and to increase oxygen demand. Under anaesthesia, a patient loses the shivering mechanism failing to signal how cold they really are. As the temperature drops even further, a plateau stage is soon reached where the body conserves heat only for vital organs such as the liver, kidneys, lungs, heart and brain.[5]

As the patient starts to wake up post-surgery, the shivering mechanism is restored and in a temperature compromised state, the patient starts to shiver uncontrollably adding to their physical discomfort.

Shivering is not the only by-product of hypothermia. A drop in temperature can lead to several major and minor complications.[6]

Patients often report that postoperative shivering is the worst part of their hospitalization experience. Occurring in 40% unwarmed patients[7], hypothermia can also prolong hospital recovery and aggravate pain post-surgery. This means longer hospitalization and increased medical expenses.

Hypothermia may increase the probability of Surgical Site Infections (SSI) taking a longer period to heal wounds.[8] The drop in temperature also increases the risk of blood loss and in extreme cases have also been known to increase the incidence of cardiac events.[9]

Hypothermia can be prevented by active and passive warming methods.

Conventionally when the temperature of the patient dropped, medical practitioners often resort to passive warming methods whereby they would wrap the hands and feet of the patient in cloth or use blankets to cover the patients in an attempt to keep them warm. Even today, in clinics where resources are limited, passive warming methods are used to keep the patients warm.

However, occurrence of hypothermia can be prevented by using active and passive warming methods that work earnestly to keep the patient warm in pre, intra, and postoperative stages of the surgery. In fact, the NICE guidelines[10] recommend using active warming methods like forced air warming to keep patients in a stable temperature state throughout the surgery and prevent the risk of hypothermia.

Forced air warming is a comfortable therapy that can keep you warm under the knife.

Also known as convective warming, forced air warming works on the principle of radiation and convection. With this therapy, heat is transferred from the movement of warm air around the patient’s skin, which allows more heat transfer at lower temperatures reducing the risk of overheating.[11]

Developed in 1987 by Bair Hugger, forced air warming is a preferred therapy for medical professionals. The 3M™ Bair Hugger™ is an easy and cost-effective way to prevent hypothermia and the many complications revolving around it. This therapy utilises a blanket, almost resembling a bear hug through which warm air is circulated around the patient maintaining optimal temperature. Along with comfort, the 3M™ Bair Hugger™ also provides flexibility in conforms giving doctors unrestricted access and flexible positioning for any procedure while maintaining optimal temperatures.

A Bair Hugger. CREDIT: 3M

Forced air warming also has positive implications on helping with healing wounds, reducing Surgical Site Infections (SSI) and blood loss. Not to mention reducing the risk of shivering post-surgery and making the experience less traumatic for patients.

Medical practitioners are now looking at forced air warming as one of the methods that can be employed for ERAS (Enhanced Recovery After Surgery)[12], a medical movement geared to improving efficiency by decreasing hospital stays and readmissions and combating complications with evidence-based therapies.

Talk to your anaesthesiologist before the surgery to discuss various warming options available for you, understand the benefits and risks associated with the therapy and share your medical history with them to ensure a speedy recovery.

Dr Raveenthiran Rasiah is a consultant anaesthesiologist and critical care specialist with wide expertise and experience in the field of anaesthesia administration.

Disclaimer: Kindly note that the above article is not intended to be a substitute for independent professional medical advice. Please seek the advice of your physician or other qualified health provider with any questions or concerns you may have. The article is was contributed on doctor personal experience based etc. The doctor does not and is not tied with any medical companies in sharing information

[1] Rajan Verma, Brij Mohan, Joginder Pal Attri, Veena Chatrath, Anju Bala, and Manjit Singh, Anesthesiologist: The silent force behind the scene, Anaesthesia essays and research. Sept 2015; 9(3): 293-297.

[2] WHO Guidelines for Safe Surgery 2009: Safe Surgery Saves Lives.

[3] Checketts MR, Alladi R, Ferguson K, Gemmell L, Handy JM, Klein AA, Love NJ, Misra U, Morris C, Nathanson MH, Rodney GE, Verma R, Pandit JJ. Recommendations for standards of monitoring during anaesthesia and recovery 2015: Association of Anaesthetists of Great Britain and Ireland. Anaesthesia. 2016;71(1):85-93.

[4] Kasai T, Hirose M, Yaegashi K, Matsukawa T, Takamata A, Tanaka Y. Preoperative risk factors of intraoperative hypothermia in major surgery under general anesthesia. Anesth Analg. Nov 2002;95(5):1381-1383

[5] Diaz M, Becker DE. Thermoregulation: physiological and clinical considerations during sedation and general anesthesia. Anesthesia progress. 2010;57(1):25-33.

[6] Madrid E, Urrutia G, Roqué i Figuls M, Pardo-Hernandez H, Campos JM, Paniagua P, Maestre L, Alonso-Coello P. Active body surface warming systems for preventing complications caused by inadvertent perioperative hypothermia in adults. The Cochrane Library. 2016;4(CD009016):1-217.

[7] Just B, Delva E, Camus Y, Lienhart A. Oxygen Uptake during Recovery Following Naloxone Relationship with Intraoperative Heat Loss. Anesthesiology. 1992;76(1):60-64.

[8] Kurz A, Sessler Di, Lenhardt R. Perioperative normothermia to reduce the incidence of surgical-wound infection and shorten hospitalization. Study of Wound Infection and Temperature Group. N Eng/ J Med. 1996;334(19):1209-1215.Kurz A. NEJM. 1996 May 9;334(19):1209-16

[9] Frank SM, Fleisher LA, Breslow MJ, Higgins MS, Olson KF, Kelly S, Beattie C. Perioperative maintenance of normothermia reduces the incidence of morbid cardiac events. A randomized clinical trial. JAMA. Apr 9 1997;277(14):1127-1134.

[10] National Institute for Health and Care Excellence. Hypothermia: Prevention and management in adults having surgery. Vol CG65: NICE London; 2008.

[11] Nieh HC, Su SF. Meta-analysis: effectiveness of forced-air warming for prevention of perioperative hypothermia in surgical patients. Journal of Advanced Nursing. 2016;72(10):2294-2314.

[12] Bernard H. Patient warming in surgery and the enhanced recovery. British Journal of Nursing. 2013;22(6):319-325.

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