INCIDENCE AND RISK FACTORS FOR INTRAOPERATIVE HYPOTHERMIA IN CHILDREN UNDERGOING SURGERY FOR CANCER - A QUALITY IMPROVEMENT AUDIT.

Background:

Hypothermia is defined as core body temperature < 36ËšC(Normal body temperature: 36.5°C to 37.5°C).Hypothermia can be further classified as mild (when body temperature is 35.0-36°C, moderate (when body temperature is 33-34.9°C and severe (when body temperature is <33°C. During surgery hypothermia can result due to heat loss from the patient’s body either by conduction, radiation, convection or evaporation. Conduction is the physical transmission of heat from the patient to another item, like a bed or theatre table. Radiation is the heat that a patient’s metabolism produces and emits. Convection is the process by which air travels about the patient to dissipate heat. Evaporation, which happens continuously as the patient breathes. Exposure to the cold operating room and evaporative losses further exacerbate the issue as anaesthesia affects the body’s ability to regulate its internal temperature, causing core-heat redistribution and heat loss to the environment.

Hypothermia during surgery causes many pathophysiological changes.The circulatory, adrenergic, and respiratory systems are all affected by prolonged hypothermia. Moderate hypothermia even delays the time it takes to recover from anaesthesia and the metabolism of anaesthetics and neuromuscular blocking drugs resulting in unplanned postoperative ventilation. Ventricular dysrhythmias are more likely when the sympathetic nervous system is stimulated in response to cold and when serum potassium levels change. Additionally, hypothermia changes the coagulation cascade and platelet function, increasing bleeding. Vasoconstriction-induced tissue hypoxia can cause a wound to take longer to heal. Also patients are more vulnerable to developing an infection at the surgical site because hypothermia inhibits neutrophil activity and reduces the effectiveness of macrophages and lymphocytes.

Infants and children are at a greater risk to develop hypothermia as they have less effective regulatory capacity, limited subcutaneous fat stores and differences in body size. Few studies have reported 4.5%-50% incidence of perioperative hypothermia in children. Reports of pediatric outcomes resulting from perioperative hypothermia are limited.

Peri-operative hypothermia is a silent and often missed factor which may contribute to adverse post operative outcomes like delay in surgical site wound healing, increased risk of wound infection, delayed recovery, prolonged ICU or hospital stay and increased mortality.Therefore, perioperative temperature monitoring and use of various measures (cutaneous warming systems like under surface warming mattress and warming blankets and fluid warming devices) to avoid intraoperative hypothermia are important quality improvement measures aimed to optimize surgical care and improve perioperative outcomes.

Study Design: This study is a prospective observational study as a part of dissertation in Tata Memorial Hospital for the period of 1 year. This study will be carried out after obtaining approval from the Institutional Ethics committee and CTRI registration

Study methodology:

 Data will be collected from all eligible patients. All children will receive anaesthesia according to the current standard of care. All children coming for surgery are premedicated and taken in the OT. The OT table is pre warmed with a warming blanket before taking the patient in. Standard monitors (Electrocardiogram, noninvasive blood pressure and pulse oximetry) are attached according to the ASA guidelines. After induction of anesthesia temperature monitoring will be done with either an esophageal or surface temperature probe. The need for invasive blood pressure monitoring and regional anaesthesia techniques for pain management will be decided by the anaesthesiologist conducting the case.Forced air warming blankets and fluid warmers will be used to prevent intraoperative hypothermia. This is our current standard of care and no additional interventions will be done for the purpose of the study. We are just auditing our current practice of perioperative temperature regulation. Data will be collected from the electronic records of all the children undergoing elective surgery at Tata Memorial Centre.

 The following data will be collected

 Demographic data

 Â·         Age and gender

·         Height weight and BMI

 Intra - operative information

 -    Type of anaesthesia: General anaesthesia(GA) / Regional anaesthesia (RA) / GA+RA.

-    Temperature monitoring method – Core temperature/Surface temperature

-    Method of active warming used – fluid warmers, warming blankets, other measures

-    Temperature at the start and end of anaesthesia

-    Hourly temperature recorded for the duration of surgery

-    Minimum and maximum intra-operative temperature

-    Duration of hypothermia

-    Need to stop active warming

-    Intraoperative blood loss

-    Intraoperative complications – arrhythmia, bleeding, hypotension needing vasopressors

-    Details of surgery

o   Grade of surgery- Minor /Intermediate/Major

o   Site of surgery – Cavity surgery / surface surgery

-    Duration of surgery and anaesthesia

 Post-operative information

 -    Post op core temperature

-    Need for active warming device

-    Unplanned mechanical ventilation

-    Delay recovery

-    Complications according to Clavien Dindo classification

-    ICU stay

-    Hospital stay

All patients included in the study will be followed up by the study team till discharge from the hospital.No biological samples will be taken from the patient. No additional hospital visits will be required.There are no stop points or withdrawal criteria.

Statistical Analysis:

Categorical variables will be expressed as percentages. Data for continuous variables will be expressed as mean (SD) with range (minimum ± maximum values). Univariate and multivariate logistic regression analysis will be done to see if there is any association between intraoperative hypothermia and age, BMI, duration of surgery, grade of surgery, site of surgery, warming measures, blood loss and intraoperative complications. Data will be presented as mean value + SD unless otherwise indicated and P < 0.05 will be considered significant. Analysis will be done using SPSS version 25 (IBM Corp. Released in 2017. IBM SPSS Statistics for Windows, Version 25).