Peri-Operative Hypothermia in Trauma Patients: A Retrospective Cohort Analysis at a Busy District General Hospital Within the National Health Service (NHS)

Abstract

Introduction: Perioperative hypothermia is defined as a patient's core body temperature of less than 36°C, which can lead to several complications. Even mild hypothermia increases the incidence of post-operative wound infection, post-operative ischaemic cardiac events and intra-operative blood loss and prolongs post-operative recovery. It is, hence, essential to maintain and provide normothermia during the perioperative phases for optimal surgical results and patient satisfaction. One of the most significant contributing factors to intra-operative hypothermia is the induction of general anaesthesia, where a significant amount of heat is shifted from the core to the peripheral circulation with consequent loss to an often-cold environment. The difference between the patient's skin and ambient temperature during the interval from entering the operating room through anaesthesia induction until draping and active warming may be significant. This study aims to look at the incidence of perioperative hypothermia in trauma and orthopaedics patients who present to a busy district general hospital in the National Health Service (NHS) and correlate this with the ambient theatre temperature and phases of surgery to draw a statistical significance.

Methods: This retrospective observational study conducted at the North Manchester General Hospital's trauma and orthopaedics department included 300 patients listed in the trauma surgery list from 1 July 2023 to 31 August 2023. Inclusion criteria were trauma patients aged 16-85 years. Elective orthopaedic and other surgical speciality patients were excluded. The perioperative temperature measurements were collected from the anaesthesia records. Statistical calculations were conducted using the StatsDirect software (StatsDirect Ltd, Wirral, UK) from Manchester University NHS Foundation Trust, Manchester.

Results: Among the 300 patients, the overall incidence of hypothermia was 3% pre-operative, 18% pre-induction, 21% intra-operative, 21% post-operative, 3% in recovery and 0% post-recovery. Intra-operative hypothermia incidence was significant, given that active warming was applied to patients with pre-operative hypothermia. Multivariate regression analysis showed that pre-induction temperature and theatre ambient temperature were statistically significant in predicting intra-operative hypothermia.

Conclusion: This study highlights the need for active interventions to recognise and prevent perioperative hypothermia in trauma and orthopaedics patients. Active pre-warming of patients and the operating rooms, regardless of surgery type and duration, is feasible and potentially beneficial. Further studies should include a randomised controlled trial comparing active and passive warming strategies to evaluate their effectiveness in improving perioperative outcomes.

Keywords: intra-operative hypothermia; operating theatre temperature; peri-operative hypothermia; pre-warming; trauma and orthopaedic surgery.

Figure 1. Median temperatures in various phases of surgery

Figure 2. Percentage of incidence of hypothermia in trauma patients in various phases of surgery

Figure 3. Line fit plot between duration of surgery (in minutes) and intra-operative patient temperatures (in °C)

Figure 4. Line fit plot between pre-induction temperature and intra-operative temperature in trauma patients

Figure 5. Line fit plot between the theatre ambient temperature (in °C) and intra-operative temperatures (in °C)