Tanzeela Gala  ( Royal free Hospital, London, UK )
Noman Shahzad  ( Department of Surgery, Aga Khan University, Karachi, Pakistan. )
Ahmed Iqbal Edhi  ( Final Year MBBS Student, Aga Khan University, Karachi, Pakistan. )
Tabish Umer Chawla  ( Department of Surgery, Aga Khan University Hospital, Karachi, Pakistan. )

Objectives: To determine the incidence of hypothermia in patients undergoing colorectal surgery, and to identify factors that increase vulnerability to perioperative hypothermia.

Methods: The retrospective study was conducted at the Aga Khan University Hospital, Karachi, and comprised medical records from May 2012 to June 2017 related to all patients aged >16 years of either gender who underwent colorectal procedures. Analysis about predictors of perioperative hypothermia was done using Stata 12.

Results: Of the 100 patients, 69(69%) were males. The overall mean age was 50.2±16.7 years. Majority cases had elective presentation 72(72%). Incidence of perioperative hypothermia was noted in 74(74%) patients. Postoperative morbidity was 16(16%), while mortality was 4(4%). Elective presentation and hypothermia before surgery were significantly associated with occurrence of intraoperative hypothermia (odds ratio: 4.5 and 1.3 respectively).

Conclusion: Perioperative incidence of hypothermia was found to be quite high despite appropriate measures. Factors responsible need to be explored and rectified.

Keywords: Hypothermia, Colorectal surgeries, Perioperative. (JPMA 70: 304; 2020) https://doi.org/10.5455/JPMA.294692

 

Introduction

 

Hypothermia is defined as a core temperature of <36°C and is divided into mild (32-36°C), moderate (28-32°C) and severe (< 28°C) categories.¹ Perioperative hypothermia, which is experienced by 50-90% of surgical patients, is a preventable cause of morbidity.² During preoperative period, patients can get hypothermic while waiting for surgery. Intraoperatively during the first 30-40 minutes of anaesthesia, body temperature can drop to <35°C due to loss of thermoregulatory heat-preserving mechanisms and anaesthetics-induced peripheral vasodilation.³ Risk of adverse outcomes like wound infection, sepsis, multiple organ failure, myocardial infarction (MI) and even mortality is increased by hypothermia.⁴ Furthermore, coagulopathy in hypothermic patients is known to increase fluid and blood transfusion requirements.⁵ Moreover, patients tend to remember hypothermia as one of the worst aspects of their perioperative experiences.³ When looking at the measures that have been taken, majority of studies report methods of warming intraoperatively to successfully reduce hypothermia and its consequences. Others have suggested preoperative warming.⁶ As core temperature gradually declines into the zone of hypothermia, early intervention to prevent declining trends may be more beneficial than merely targeting absolute temperature values intraoperatively. With attention towards maintaining normothermia intra operatively, warming blankets, circulating water mattresses and prewarmed intravenous (IV) fluids have been used.⁷ The current study was planned to determine the incidence of hypothermia in patients undergoing colorectal surgery, and to identify factors that increase vulnerability to perioperative hypothermia.

 

Materials and Methods

 

The retrospective study was conducted at the Aga Khan University Hospital (AKUH), Karachi, and comprised medical records from May 2012 to June 2017 related to all patients aged >16 years of either gender who underwent colorectal procedures. AKUH is a tertiary care hospital with nine general surgeons performing colorectal surgeries. Data related to patients with missing records and those who had concomitant procedures performed with colorectal surgery were excluded. After approval was obtained from the institutional ethics review committee, patients who underwent colorectal surgeries were identified using the International Classification of Diseases (ICD) codes for colorectal surgery.⁸ Data was collected on a specifically designed questionnaire. Body temperature at five different time points perioperatively was labelled as: T1: Preoperative temperature; T2: Temperature before induction in the operation theatre; T3: The minimum intraoperative temperature: T4: Temperature at the end of surgery; and T5: Temperature after the patient's arrival in the recovery room.³ Data analysis was done using Stata 12. Means with standard deviations were calculated for continuous variables. Frequencies and percentages with Chi square, Fishers Exact and McNemar test were applied for categorical variables. Univariate logistic regression analysis was done to find significant predictors of intraoperative hypothermia. Multivariable logistic regression analysis was done to find independent predictors of intraoperative hypothermia and to adjust for potential confounders. Conditional logistic regression was used to determine factors associated with changes of temperature status from before surgery to intraoperative setting.

 

Results

 

Of the 389 records retrieved, 100(25.7%) were included and, of them, 69(69%) were males. The overall mean age was 50.2±16.7 years, and mean body mass index (BMI) was 23.87±5.7kg/m2. Majority cases had elective presentation 72(72%). All the 100(100%) patients received warming blankets intraoperatively (Table-1).

Overall incidence of perioperative hypothermia was 74(74%). None of the study patients was hypothermic preoperatively, while almost 46(46%) were hypothermic before induction in the operation theatre (OT). Intraoperative hypothermia was recorded in 69(69%) patients at which point mean temperature was 35.4±1.3°C. In the recovery room, 10(10%) patients were hypothermic (Figure-1).

Proportion of hypothermic patients admitted electively was higher than those admitted via emergency room (Figure-2).

Univariate and multivariate logistic regression analysis showed that patients who presented electively were 4.5 times more prone to developing intraoperative hypothermia, and the odds of being hypothermic intraoperatively was 1.3 times more in patients who were hypothermic before induction (Table-2).

Mode of admission and patients' age turned out to be significantly associated factors (p<0.05). Odds ratio (OR) for mode of admission was 4.25 (95% CI: 1.1-8.1) (p=0.0006), while for age interval of 10 years, OR turned out to be 1.21 and (95% CI: 1.1-2.1) (p=0.0001). Postoperative morbidity was 16(16%), while mortality was 4(4%), and all of them suffered from hypothermia at some point in the perioperative period.

 

Discussion

 

Perioperative hypothermia is one of the preventable causes of postoperative morbidity,² and, hence, reduces risk of sepsis, multiple organ failure, cardiovascular incidents, myocardial infarctions and even mortality.⁴ The current study demonstrates a high frequency of perioperative hypothermia (74%) in patients undergoing colorectal surgery despite active efforts made towards intraoperative warming. Significant drop in core temperature occurred before the start of surgery which is also reported earlier.³ The core temperature further dropped intraoperatively to as low as 35.1°C. Greater proportion of hypothermia in electively admitted patients compared to emergency admissions can be due to false sense of protection about the need to prevent hypothermia in patients admitted electively. Fewer epidurals and shorter preoperative waiting times in emergency settings could also be potential factors responsible for this finding. The benefits of pre-warming with methods including passive insulation, forced-air warming and electrically warmed blankets have been well described,^9,10 but this is yet to be adopted as routine in most centres. Age being a significant predictor of hypothermia is likely due to decreasing body's physiological reserves with age and relatively more time needed to rewarm from any decreases in core temperature.^11,12 Patients with higher BMI can conserve core heat better due to greater fat insulation and a smaller surface area-tovolume ratio, minimising heat losses through the skin. Heat conservation in obese patients may confer advantage during critical illness.¹³ Though our study was not aimed at looking at morbidity as a result of perioperative hypothermia, morbidity related to hypothermia is a known phenomenon.⁴ Careful management of preoperative core temperature may reduce the incidence of hypothermia and thus resulting in morbidity. In terms of limitations, part of variability in body temperatures could be due to core temperature having been measured intraoperatively through nasopharyngeal probe, while at the rest of the time points, the temperature was measured through oral cavity.

 

Conclusion

 

Frequency of hypothermia was found to be more intraoperatively compared to the rest of perioperative periods. Factors responsible need to be explored and rectified. Electively admitted patients having more frequency of hypothermia reflected a false sense of protection regarding the need to prevent hypothermia. This needs to be further explored.

 

Disclaimer: None.

Conflicts of Interest: None.

Source of Funding: None.

 

References

 

1. Kirkpatrick AW, Chun R, Brown R, Simons RK. Hypothermia and the trauma patient. Can J Surg. 1999; 42:333-43.

2. Weirich TL. Hypothermia/warming protocols: why are they not widely used in the OR? AORN J. 2008; 87:333-44.

3. Mehta OH, Barclay KL. Perioperative hypothermia in patients undergoing major colorectal surgery. ANZ J Surg. 2014; 1;84:550- 5.

4. Reynolds L, Beckmann J, Kurz A. Perioperative complications of hypothermia. Best Pract Res Clin Anaesthesiol. 2008; 22:645-57.

5. Lenhardt R, Marker E, Goll V, Tschernich H, Kurz A, Sessler DI, et al. Mild intraoperative hypothermia prolongs postanesthetic recovery. Anesthesiology. 1997; 87:1318-23.

6. Vanni SM, Castiglia YM, Ganem EM, Rodrigues Junior GR, Amorim RB, Ferrari F, et al. Preoperative warming combined with intraoperative skin-surface warming does not avoid hypothermia caused by spinal anesthesia in patients with midazolam premedication. Sao Paulo Med J. 2007; 125:144-9.

7. De Witte JL, Demeyer C, Vandemaele E. Resistive-heating or forced-air warming for the prevention of redistribution hypothermia. Anesth Analg. 2010; 110:829-33.

8. "ICD-10 Version:2016". apps.who.int. [Online] [Cited 2009 May 30]. Available from: URL: https://icd.who.int/browse10/2016/en

9. Horn EP, Bein B, Bohm R, Steinfath M, Sahili N, Hocker J. The effect of short time periods of pre-operative warming in the prevention of peri-operative hypothermia. Anaesthesia. 2012; 67:612-7.

10. Just B, Trevien V, Delva E, Lienhart A. Prevention of intraoperative hypothermia by preoperative skin-surface warming. Anesthesiology. 1993; 79:214-8.

11. Kimura S, Cameron JS, Kozlovskis PL, Bassett AL, Myerburg RJ. Delayed afterdepolarizations and triggered activity induced in feline Purkinje fibers by alpha-adrenergic stimulation in the presence of elevated calcium levels. Circulation. 1984; 70:1074-82.

12. Hamra M, Rosen MR. Alpha-adrenergic receptor stimulation during simulated ischemia and reperfusion in canine cardiac Purkinje fibers. Circulation. 1988; 78:1495-502.

13. Shahzad N, Alvi AR, Iqbal R, Rozi S, Mannan F, Khan MH, et al. Obesity and the Outcome of Surgical Intensive Care Unit Patients: A Prospective Cohort Study. Clin Surg. 2018;1:1-9.