Practice pattern of perioperative temperature management in patients undergoing major abdominal surgery

Introduction

 Inadvertent perioperative hypothermia is a common complication of perioperative period. Perioperative hypothermia is defined as core body temperature less than 36°C. The incidence ranges between 60-90% of all surgical patients. Perioperative inadvertent hypothermia results from a combination of impaired regulation of temperature control mechanisms secondary to anaesthesia and exposure of body surface and cavities to cold operation room environment over a period. Inadvertent hypothermia is associated with increased bleeding, cardiovascular events, postoperative shivering and increased oxygen consumption, thermal discomfort, increased rate of surgical site infections (SSI) and delayed wound healing. Patients at high risk for developing perioperative inadvertent hypothermia fulfil any two of the following criteria.(1)

a) American Society of Anesthesiologists (ASA) grade II to V (the higher the grade, the greater the risk)

b) Preoperative temperature below 36.0°C (and preoperative warming is not possible because of clinical urgency)

c) Use of combined general and regional anaesthesia

d) Major or intermediate surgery

e) At risk of cardiovascular complications.

 In patients with cardiac disease undergoing non-cardiac surgery, perioperative normothermia was associated with reduced rates of major cardiac events and ventricular tachycardia.(2)American College of Cardiology and American Heart Association recommends maintenance of normothermia to reduce perioperative cardiac events in patients undergoing noncardiac surgery as class IIb.(3) Hypothermia within 2 hours of induction of anaesthesia (delayed hypothermia) was identified as an independent risk factor for developing severe hypothermia (temperature <35°C). Delayed hypothermia is associated with increased SSI and organ space infection (4).

 Pre-warming initiated 30 min before induction of anaesthesia prevents rapid decline of core temperature that occurs due to redistribution.(5,6) Prewarming was also associated with normothermia in recovery (7). In a meta-analysis of RCT’s, active body surface warming systems (ABSW) (heating using air, water or gel) was associated with reduced blood loss, significant reduction in SSI, postoperative shivering and thermal discomfort. Forced air warming system was associated with reduced major cardiovascular events in patients with heart disease.(8) ABSW are associated with reduced blood loss, significant reduction in SSI, postoperative shivering and thermal discomfort (9). Therefore, active warming is superior to passive warming (10).

In addition to active warming, administration of warm fluids is associated with less shivering (11), in patients requiring >500 ml fluid volume.(12) National Institute for Health and Care Excellence (NICE) guidance recommends irrigation fluids used intraoperatively by surgeons should be warmed in a thermostatically controlled cabinet to a temperature of 38-40°C.(1). The purpose of this study is to audit current practice regarding perioperative temperaturemanagement in patients undergoing major abdominal surgery.

 Aim

To audit practice pattern of perioperative temperature management in patients undergoing major abdominal surgery.

 Primary Objective:

1. Incidence of hypothermia within 2 hours of anaesthesia induction

 Secondary Objectives:

1. Proportion of patients shifted to recovery/ ICU with hypothermia (Temperature <36°C)

2. Practice pattern of perioperative hypothermia management (use of active warming, grade of hypothermia during and after surgery, presence of shivering during recovery)

3. Unplanned ventilation secondary to hypothermia (Temperature <36°C)

 Study design

Prospective observational audit.

 Material and Methods

This study is a prospective observational study of perioperative temperature management following major abdominal surgery in Tata Memorial Hospital over a period of 5 months. Post Institutional ethics committee approval and CTRI registration; we will audit our current practice regarding perioperative temperature management in patients undergoing elective liver, pancreatic, urology, gynaecology, retroperitoneal resections and CRS with or without HIPEC procedures. Perioperative hypothermia is defined as follows:

Normothermia - > 36°C

Mild Hypothermia – 35.5°C-35.9°C

Moderate Hypothermia – 35°C-35.4°C

Severe hypothermia – <35°C

 Inclusion criteria

1. Consenting patients > 18 years of age, undergoing elective major abdominal procedures (gastrointestinal, urology, gynaecology, retroperitoneal resections and CRS with or without HIPEC.

2. Duration of surgery > 2 hours

 Exclusion criteria

1. Patients <18 years age.

2. Pregnant women.

3. Patients in whom core temperature cannot be monitored

 We will record the following patient variables after the patient arrives in the operation room (OR).

1. Demographic details

2. Comorbidities if any

3. ASA grade

4. Duration of anaesthesia

5. Duration of surgery

6. Minimally invasive surgery

7. Axillary temperature on arrival in the OR

8. Core temperature 2 hours after induction of anaesthesia

9. Intraoperative lowest temperature and duration since induction of anaesthesia

10. Maximum intraoperative temperature

11. Grade of hypothermia intraoperative (Lowest reading will be considered)

12. Devices used for perioperative temperature management

13. Intraoperative blood loss

14. Temperature before shifting to Recovery room/ ICU

15. Grade of hypothermia following RR/ICU admission

16. Warming devices used intraoperatively

17. Unplanned ventilation due to hypothermia (Temp <36°C)

18. Presence of shivering in recovery room/ ICU

19. Need for medication to control shivering if any

20. Use of active warming in Recovery room/ICU

21. Postoperative complications in patients undergoing pancreatic resections.

 Patients undergoing pancreatic resections will be followed up until discharge for postoperative complications if any by the study team. This is a non-interventional study with no patient contact. Source document for recording all parameters will be anaesthesia and ICU/RR monitoring charts and EMR notes.

 Sample size

We will include consecutive patients undergoing major abdominal surgery over a period of 5 months. We will screen approximately 600 patients and enrol 400 patients during the study period (or whichever is earlier).

 Statistical Methods

Data will be presented as mean ± (SD), median (range), and frequency (percentage) where appropriate. We will analyse categorical data using the chi-square test or Fisher Exact test (for binary data). Similarly, for comparisons of two groups we will use independent sample t-test or Mann-Whitney U test as per the distribution of data. We will evaluate association between hypothermia and grades of hypothermia and postoperative complications in patients with pancreatic resection using categorical tests chi-square/ Mann Whitney U test depending on the distribution of data. Statistical significance is defined as P-value <0.05. For the purpose of thesis, data will be analysed in May 2024