Body temperature is an avital sign for all living organisms, and any minor defect in this leads to severe consequences. During the perioperative period, perioperative hypothermia is defined as (core body temperature < 36˚C) and can be classified into mild (32˚C - 36˚C), moderate (28˚C - 32˚C), and severe (28˚C) groups. Hypothermia is one of the most challenging problems that anesthesiologists face during surgical procedures [1].

Hypothermia is characterized by the severity of its effects on the human body, although even minor changes in core body temperature (dropping) can result in a number of negative consequences for the individual [2] [3] [4], such as postoperative cardiovascular problems after surgery [5] [6], coagulopathy and bleed in the postoperative period [7] [8], drug metabolism is disrupted [9] [10], wound contamination and non-healing after surgery [11] [12] [13] [14], and hypothermia might potentially result in a more extended stay in the PACU or ICU [15]. The balance between generated and lost heat is critical for maintaining body temperature stability; any divergence from this equation has negative consequences [16] [17] [18].

There are a variety of ways to keep patients at a stable temperature during surgery, including blankets, circulating water mattresses, forced air warming, and pre-warmed IV fluids that are widely employed [1] [19]. Preventing perioperative hypothermia during intraoperative time is essential for the well-being of sedative patients. Therefore, many various studies have been conducted on patient core temperature and techniques to preserve perioperative normothermia.

Over the last few years, researchers have focused on the effects of low fresh gas flow on perioperative hypothermia [20]. If the flow rate is 4 L/min or higher, rebreathing increases by 20%; if the flow rate is 2 L/min or lower, rebreathing increases by 50% or more [21]. When anesthetic gases are properly humidified and warmed, they have a considerable impact on respiratory tract function and integrity. When the inspired gas is too dry or too humid, it leads to mucus retention and dry mucus discharges. We hypothesized that using different fresh gas flow techniques (0.7, 1, 1.5, and 2 L/min) might do the same thing in maintaining a perioperative patient’s core temperature in normothermia.

The purpose of this study was to determine the impacts of different fresh gas flow techniques (0.7, 1, 1.5, and 2 L/min) on perioperative normothermia maintenance among adults undergoing elective open or laparoscopic digestive surgery and to find clinically valuable values.

This study is prospective, randomized, controlled, single-blind. Qilu Hospital of Shandong University’s Ethical Committee gave its approval (approval number: KYLL-202008-080). This randomized controlled trial was registered at clinicaltrials.gov, with the number ChiCTR2100046399. This study was conducted from April 1 2021 to September 15 2021.

During the five-month study period, data were collected from patients at the same workplace. 15 of the 255 patients enrolled in the trial were eliminated after screening for inclusion and exclusion criteria. Two hundred forty patients underwent elective open or laparoscopic digestive surgeries during the research period. To compare the effects of different fresh gas flow techniques (0.7, 1, 1.5, and 2 L/min) on maintaining perioperative normothermia in adult patients undergoing open and laparoscopic digestive operations, we chose 120 patients who had open digestive operations and were exposed to different fresh gas flow rates (0.7, 1, 1.5, or 2 L/min) for each subgroup (n = 30), as well as 120 patients who had laparoscopic digestive operations. Figure 1 illustrates the study’s design.

In a normal physiological condition, human beings can preserve an average core temperature within a restricted range of 37˚C ± 0.2˚C [23]. Heat gain and heat loss are balanced by a central system to control and regulate core body temperature. Internal heat is generated by cellular metabolism and lost through one of the following mechanisms: radiation, conduction, convection, or evaporation [24]. A core body temperature below 36˚C is defined as perioperative hypothermia [25].

Among the benefits of low-flow anesthesia are reduced anaesthetic gas consumption, less ambient pollution with inhaled anaesthetics, preservation of heat and humidity in the respiratory system, and a large reduction in expenses due to the reduction in gas consumption [26] [27]. The physical and chemical properties of inhalational drugs employed in low-flow anesthesia procedures are critical [28]. Volatile anaesthetic substances such as sevoflurane, isoflurane, and desflurane are utilized in low-flow anaesthesia nowadays, as are other volatile anaesthetic agents [29] [30]. Isik et al. [31] used desflurane and sevoflurane in low-flow anaesthesia for children. Neither hepatic nor renal function was impaired. Our study found steady hemodynamics in both open and laparoscopic groups.

In recent years, a low fresh gas supply with a closed-circuit rebreathing device to preserve perioperative normothermia has sparked interest in anesthetic approaches [32]. Significant clinical improvement is possible by raising the fraction of rebreathed gas and lowering the quantity of cool, dry, fresh gas inhaled. As we focus on this method in our study, this approach can prevent perioperative hypothermia. Some anesthesiologists prefer it over high-flow anesthesia because low-flow anesthesia preserves heat and humidity while reducing gas consumption [18]. This information is in agreement with what has previously been discovered. Due to this observation, we used varying fresh gas flow rates to keep the core temperature from dropping too much. FGFs may be able to adjust for redistribution-induced temperature gradients between the core and the periphery.

We chose digestive surgeries for this study because they have a higher risk of perioperative hypothermia due to prolonged duration, extensive surgical site exposure, fluid evaporation, significant blood loss, and recurrent lavage with large quantities of room temperature saline [1]. Additionally, massive volumes of cool, dry CO₂ (about 21˚C) are delivered intra-abdominally during laparoscopic surgery [33]; it was the combination of all of the above risk factors, rather than the protective factor, that revealed the study’s significance.

Anesthesia care includes knowing how to monitor one’s body temperature. Constant monitoring of temperature variations in sedated patients enables the diagnosis of unintentional heat loss or malignant hyperthermia [24]. You can assess your core temperature by inserting small sensors into the esophagus, ear canals, trachea, and nasopharynx [34]. Also, pulmonary artery blood temperature reflects core body temperature [24]. However, we chose the nasopharyngeal probe because other devices were insufficiently accurate, inconvenient, or invasive [34] [35].

As is well known, when air passes through the nose and upper airways during spontaneous breathing, an atypical physiological mechanism moisturizes and warms it to meet the body temperature, preventing any disruption in the body’s thermal system [36]. When mechanical ventilation fails, the gases reach the lower airway directly without being warmed, resulting in heat loss through the respiratory tract’s airways, Unless proper humidification and heating methods are used [37] [38]. In our research, we use gas rebreathing to solve the problem and create heat and humidity gases.

In our study, operating room temperatures were set to 23˚C from the start, similar to the findings of Morris RH et al. [39].

Kleemann et al. [40] found that the temperature of inspired gas during low-flow anesthesia was higher at all times when compared to high-flow anesthesia. They also reported that the temperature increased to approximately 28˚C during the first 30 min. Kleemann 15 showed that the mean inspired gas temperature was 31.5˚C after 2 h of anesthesia with a fresh gas flow rate of 0.6 L/min. Bengtson et al. [41] used a re-breathing ring system to measure the gas temperature, which was found to be 28.5˚C after 30 min with a fresh gas flow rate of 0.5 L/min; this was approximately 6.8˚C above the room temperature.

Perioperative temperature reductions in our study were lower than those reported by others [42]. A previous study showed that during the first hour of anesthesia, over half of the sedated individuals had core temperatures of less than 36˚C, which steadily rose after that [43]. This demonstrates that the first hour’s fall in core temperature is due to heat redistribution, consistent with our data, which shows that the temperature drops faster in the first hour than in the second [44]. According to our data, most operations required more than two hours, and heat redistribution was the primary cause of the temperature drop in this condition [45]. Matsukawaetal et al. reported the body’s core temperature decrease in the first hour of general anesthesia by 1.6˚C ± 0.3˚C, with a heat redistribution of 81%. Over the second and third hours, the core body temperature continues to fall by 1.1˚C ± 0.3˚C with 43% heat restructuring [45]. This 81% heat redistribution may be caused by general anesthesia-induced fast peripheral vascular dilatation, which causes heat to be transported from the core to the periphery. The core temperature begins a steady decrease in the second and third hours because the loss of body heat exceeds the metabolic generation of heat. As a result, we believe that core-to-peripheral redistribution should be reduced or compensated for to avoid the negative consequences of perioperative hypothermia. In our study, we tried to balance generated and lost heat to maintain body temperature stability.

One-third degree Celsius temperature decline with two-liter infusion of room-temperature crystalloid in normal normothermic adults, according to Barthel et al. [46], this is consistent with our findings. We found a correlation between fluid infusion rate and perioperative temperature decrease. Unwarmed fluids should be avoided, according to recent studies.

Previous research has shown that elderly patients may be more susceptible to hypothermia [42] [47]. This data is consistent with ours; most patients (71.6%) in our analysis were under 65 years, and all patients were classified as 1 or 2 by the American Society of Anesthesiologists.

In 2011, Castro demonstrated that a heat and moisture exchanger could be used to increase the heat generated by human breathing gas [48], which is consistent with our study; patients were treated with Aestiva Datex Ohmeda anesthesia workstations, which are more modern and efficient in warming and humidifying rebreathing gas than other aesthetic workstations. With the advent of modern workstations, anesthesia has shifted to be a more friendly and safe approach.

Hypothermia happens during surgery due to various factors, but the rate of occurrence varies according to the factor. We attempted to control the significant risk variables and compensate for lost heat in the current investigation, which explains why the incidence of perioperative hypothermia was not documented.

Individuals undergoing laparoscopic and open operations had similar body temperature fluctuations, according to several studies. Patients undergoing laparoscopic and open cholecystectomy exhibited similar drops in core temperature, according to Makinen et al. [49] [50]. We also found similar findings: no significant differences in intraoperative temperature variations between open and laparoscopic digestive operations.

Many prior studies reported that maintaining body temperature under general anesthesia was problematic if the fresh gas flow was greater than 1 L/min. However, our findings show that FGFs of (0.7, 1, 1.5, and 2 L/min) yield similar results. We found no differences in FGF levels (0.7, 1, 1.5, and 2 L/min) after comparing them, indicating that FGFs (0.7, 1, 1.5, and 2 L/min) can be used safely, more pleasantly, and physiologically for patients to alleviate perioperative hypothermia while under general anesthesia.

Limitations

There are some limitations of the current study. The study’s sample size can be considered an initial limitation since the number of patients was relatively small. Another limitation of our study was a single-center study, and the results should not be generalized. Additional research is required to evaluate the influence of fresh gas flows on patients’ core temperature during the peri/postoperative period with higher precision.

In this study, it was concluded that sevoflurane anesthesia is used with the fresh gas flow with one of these values (0.7, 1, 1.5, or 2 L/min) can provide safe anesthetic techniques and a powerful method to use in daily practice without affecting patient care to maintain perioperative normothermia for patients undergoing general anesthesia with open or laparoscopic surgery. When attempts were taken to minimize perioperative hypothermia, our study data also demonstrated that the core peri-operative temperature did not significantly differ between the laparoscopic and open operations.

I want to express my heartfelt gratitude to my teacher (prof. Feng Qi) and (Qiya Hu, Yuanyuan Meng, Yu Liu, Lianying Zhao, Shuqin Wang, Amir Muse Mohamud) for providing me with the beautiful opportunity to work on this beautiful project on the topic (The impact of fresh gas flow anesthesia on perioperative hypothermia in adult patients undergoing elective open or laparoscopic digestive surgery), which also helped me to learn about so many things.

Second, I’d want to thank my parents and friends for their assistance in completing this project within the time constraints.

Qilu Hospital of Shandong University’s Ethical Committee approved our study [approval number: KYLL-202008-080]. Written informed consent was obtained from each participant.

All data used and/or analyzed during the current study are available from the corresponding author on reasonable request.

This RCT was registered at clinicaltrials.gov and assigned the following identifier: ChiCTR2100046399 submitted on 15\5\2021.

Ahmed Badughaish: drafted and conducted the research. Qiya Hu, Yuanuan Meng, Yu Liu, Lianying Zhao, Shuqin Wang, Amir Muse Mohamud, and Feng Qi revised and supervised this manuscript.

No conflicts of interest were declared with this article.

Badughaish, A., Hu, Q.Y., Zhao, L.Y., Meng, Y.Y., Liu, Y., Wang, S.Q., Mohamud, A.M. and Qi, F. (2022) The Impact of Fresh Gas Flow Sevoflurane Anesthesia on Perioperative Hypothermia in Adult Patients Undergoing Elective Open or Laparoscopic Digestive Surgery: A Prospective Randomized Controlled Trial. Open Journal of Anesthesiology, 12, 34-48. https://doi.org/10.4236/ojanes.2022.121004

FGF: Fresh Gas Flow; PLOS: Postoperative hospital Length-Of-Stay; ICU: Intensive Care Unit.