European Journal of Cardiovascular Medicine

In ancient times the word “anesthesia” was only known to few people. As the world developed with its technology, the medical field techniques were also developed mainly in the field of anesthesia. There were many inventions in the equipment and methods to deliver anesthesia. One side, there was development in induction agents, volatile liquids, vaporizers etc. and on the other hand there were many inventions on the influencing factors of intra-op monitoring during anesthesia like BP monitoring, hemodynamic changes, pulse oximetry monitoring, neuromuscular monitoring, and temperature monitoring.

This made many to make a study about the factors that affecting the anesthesia and the factors influencing during the intra-op monitoring. So that is why we have got my answers for many unknown questions. Among those factors we are going to see about how the temperature varies in patients who are performing surgeries under General Anesthesia and Spinal Anesthesia.

Accidental hypothermia may happen in gentler climes and is not just a problem in places or at very low temperatures^[1]. The severity of hypothermia will influence the symptoms. A body temperature decrease below 35C that occurs uncontrollably is referred to as hypothermia. Mild (core temperature of 32 to 35⁰C), moderate (28 to 32 ⁰C), and severe (less than 28 ⁰C) severity levels are determined by these ranges. Furthermore, some professionals categorize certain people as having deep hypothermia (temperature below 24 ⁰C). A decline in hypothermia's severity is associated with more severe side effects, gloom, and death^.[2]

There are several factors that contribute to unintentional hypothermia in patients undergoing medicines, comorbid conditions, trauma, the environment's temperature, the kind of anesthetic used, and the extent of surgery has impact on body's core temperature. The coagulation process, blood loss and transfusion requirements, drug metabolism, infection at the surgical site and leaving the post-anesthesia care unit are all negatively impacted by perioperative hypothermia. To reduce the risk of perioperative hypothermia, Active temperature control is required before to, during, and following surgery. Accurate and continuous probes should be used to measure temperature. Warming tool such as warmer, blankets and warm fluids can be used for patients.⁽³⁾

The mechanism known as thermoregulation allows mammals to carefully manage their internal body temperature regardless of the ambient temperature. To make due, temperature guideline is a type of homeostasis and a method for keeping a consistent interior temperature^.(4)

Extracted fat tissue has a poorer heat conductivity than expelled lean tissue. Theoretically, subcutaneous fat could hinder heat loss and alter thermoregulation abilities. Obesity hinders fat persons are more prone to heat stress than lean people due to heat loss, despite its advantage in cold conditions ⁽⁵⁾. Hence the obese patients will have an advantage over the thermoregulation than non-obese patients. Obese patients can maintain their heat producing capacity due to their adequate amount of brown fat and so they are less prone to hypothermia and shivering. Non- obese patients are more prone to hypothermia and shivering as they have low heat producing capacity.

It was an observational study was performed on 100 patients. All patients who had surgery with general anesthesia and spinal anesthesia in general surgery, OBG, ENT, ortho and dental. Patients with age more than 18 years, ASA status I, II, III, patients who performed surgery under general anesthesia and spinal anesthesia and all elective and emergency surgeries were included.

Patients who didn't gave their consent for study, patient who had neuromuscular disorder and patient who had a history of malignant hyperthermia and Rayodine receptor defect were excluded from the study. After the approval of institutional human ethics human ethics this study committee, this study had been conducted in department of anesthesiology, CHRI.

In this study first patients BMI, were calculated and then patients body core temperature was measured in pre anesthetic period. After inducing the patients, the patients core temperature was measured in axilla, in variation of 10 minutes throughout the surgery procedure. In this study, the temperature changes had been compared with general anesthesia and spinal anesthesia with BMI.

Among one hundred study population we calculated the percentage of gender population among sample we collected. We found that Female population (62%) is more than the male population (38%).

As our study is on General anesthesia versus Spinal anesthesia, we divided the study population into two major groups. To get an accurate result we divided them into half of the population, we collected data in 50% of patients got general anesthetic, and 50% underwent spinal anesthesia.

In this study we are going compare the temperature changes with BMI in both general and spinal anesthesia. As per guidelines, it has six categories, to make it easy we segregated them into two larger groups as per our convenient. First group will be BMI with<30 (71%) and Second group will be BMI with >30(29%).

To make it clear, we divided the type of anesthesia with two larger categories of BMI. Hence we divided BMI with <30 and BMI with >30 among general anesthesia and spinal anesthesia separately. We found in general anesthesia, BMI with <30 were 40 patients and BMI with >30 were 10 patients and in spinal anesthesia, BMI with <30 were 31 patients and BMI with >30 were 19 patients.

Firstly, we calculated data in general anesthesia, we took BMI with <30 and BMI with >30. Among them, here we recorded the readings of mild hypothermia alone. Later we compared it with BMI. In that 54% of the patients with BMI<30 were in mild hypothermia and 14% of the patients with BMI >30 were in mild hypothermia.

Secondly, we calculated data in moderate hypothermia with general anesthesia population. We recorded the readings as we did for mild hypothermia and we compared it with BMI and the results were, 20% of the patients with BMI<30 were in moderate hypothermia and 12% of the patients with BMI >30 were in moderate hypothermia.

Finally, we compared the readings with mild hypothermia and moderate hypothermia in general anesthesia for the evaluation of chi-square. 

To find the chi-square value we found the observed value first, the observed will be the frequency of patients who underwent mild and moderate hypothermia with BMI <30 and with BMI >30 in general anaesthesia. Secondly with observed value we found the expressed value. Finally, we assembled all the values in the formula of “(O -E)² / 2” to get chi-square value.

We did calculation for spinal anesthesia as same as we did for General anesthesia, here we calculated the percentage of mild hypothermia in spinal anesthesia. We got 32% of patients with BMI<30 were in mild hypothermia and 8.3% of patients with BMI >30 were in mild hypothermia

Out of 100 study population, we divided into two sub- groups. Each group consists of 50 members. The two sub-groups were General and Spinal Anesthesia. We collected 50 in general anesthesia, 50 in spinal anesthesia. As per our study we have to correlate the data with Body Mass Index (BMI) to see the temperature variation or changes in both the population with BMI. So, to make it easy we classified BMI into two major groups for our convenient one is BMI with <30 and another one is BMI >30. Now we collected the readings of temperature via nasopharyngeal pathway and axillary centers. Decrease in normal body core temperature is defined as hypothermia. Hence we are classifying the hypothermia that is mild and moderate for accurate results.

The range of mild hypothermia (35⁰ C – 33⁰ C) and moderate hypothermia (32 ⁰C- 28 ⁰C). Classified the hypothermia according to the readings we collected. Mild and Moderate hypothermia in General anesthesia with BMI<30 and BMI >30 as a separate group as above mentioned in table. Similarly, for Spinal anesthesia, Mild and Moderate hypothermia with BMI<30 and with BMI >30 as above mentioned in table. To get a clear view we even noted the duration of surgery whether the duration is with the cause of hypothermia.

In our study sample, we got 38% of male gender and 62% of female gender, BMI<30 was 71%and BMI >30 was 29%. In general anesthesia, we observed Mild hypothermia was present in 54%,  Moderate hypothermia was in 20% of patients in BMI with <30 and in BMI with >30, Mild hypothermia was present in 14% and 12% of patients got moderate hypothermia. In spinal anesthesia we found Mild hypothermia in 32% of patients and got moderate hypothermia in 36% of patients with BMI <30 and in BMI with >30 , mild hypothermia got in 8.3% of patients, moderate hypothermia was present in 22% of patients with BMI >30. Finally to calculate chi- square we took the frequency values, in first subgroup we noted mild hypothermia in 27 patients (F=27), Moderate hypothermia was observed in 10 patients (F=10) with BMI <30 and For BMI>30 mild hypothermia was noticed in 7 patients (F=7), Moderate hypothermia was in 6 patients (F= 6) among 50 patients who underwent general anesthesia. Similarly in second sub group, the frequency of mild hypothermia was 16 patients (F=16) and moderate hypothermia was in 18 patients (F=18) with BMI <30 and in BMI>30 mild hypothermia resulted in 5 patients (F= 5), and moderate hypothermia was observed in 11 patients (F= 11) among 50 patients who underwent spinal anesthesia. We even compared the time duration, we monitored the incidence of hypothermia in duration of surgery. We found that in 1^ST hour of duration 21 patients were in mild hypothermia and 9 patients were in moderate hypothermia. As the duration of surgery increased to 2^ND hour we noticed 15 patients were in mild hypothermia and 13 patients were moderate hypothermia. In long procedure the duration of surgery even increased to 3^RD hour, observed 10 patient were found to be in mild hypothermia and 32 patients were found to be in moderate hypothermia. We found only the incidence of hypothermia and not the chi –square in duration surgery. From this, we understood that as duration surgery increases the chances for moderate hypothermia increases.

A research by Fernandes LA, Braz LG, Koga FA, et al 2012. compared the effects of active heating techniques on 10 non-obese women with BMIs between 18.5 and 24.9 who had undergone abdominal surgery with 10 obese patients with BMIs between 30.0 and 34.9. He discovered that obesity lowers the incidence of intraoperative hypothermia, raises core body temperature after waking, and increases core body temperature intraoperatively. A research by Kurz et al. included 40 participants who had elective colonoscopies. They revealed an inverse correlation between body fat percentage and surface area (10%-24%, 25%-35%, and 36%-50%) and 35, 36-44, and >45 kg/m2 respectively, as well as the degree of redistributed hypothermia and the drop in temperature.

Savastano et al. focused on the relationship between adiposity and regional internal heat levels in both resting and thermoneutral situations, They compared 23 individuals with BMIs >30 to 13 patients with BMIs between 18 and 25. They found no differences in the core temperature using an infrared thermography approach, but they did find that the stomach skin temperature and finger bed temperature were lower and higher in big patients. They claimed that the stout's large stomach subcutaneous fat tissue formed a blockage that prevented heat transfer and protected against normothermia. In this research, we discovered that the heart rate decreased in non-obese individuals and that normothermia was better protected during sedation, a recognized thermo- neutrality disruptor.

Many studies discovered that spinal anesthesia is also a reason to cause hypothermia. In our studies we found similar observation with spinal anesthesia. Body mass index (BMI) is also a one of the factor to cause hypothermia in patients undergoing surgery. We also observed that whether the duration of surgery increases the chance of hypothermia. We found that spinal anesthesia are more prone to hypothermia even in BMI<30 (P=0.01025492). General anesthesia are is less prone to hypothermia even if the BMI is >30 (P=0.008523498).