As of 2021, the life expectancy of the Korean population is 83.6 years, and the elderly population aged 65 and above constitutes 16.5% of the total population, numbering 8,537,000 individuals [1]. Cancer has maintained its position as the leading cause of death among the elderly, with cancer patients aged 65 and above showing a continuously increasing trend at a rate of 1,552 cases per 100,000 individuals [2].

Among these cases, the incidence of colorectal cancer ranked 2th in terms of occurrence according to domestic cancer incidence statistics of 2022 [3]. Laparoscopic surgery for colorectal cancer aims to reduce pain and stress after the procedure, promotes rapid recovery, and decreases hospitalization days [4]. As such, its aesthetic benefits and emphasis on immune system stability have led to its increasing preference [5].

Laparoscopic surgery for colorectal cancer is a surgical procedure involving an injection of gas through the trocar into the abdominal cavity, using a camera for visualization, and manipulating instruments to perform the surgery. During surgery, a gradual decrease in body temperature occurs due to the continuous infusion of 21°C CO₂ gas into the abdominal cavity [6]. Additionally, the elderly have higher likelihoodof experiencing disease complications due to decreased organ function, and a higher likelihood of hypothermia due to decreased thermo regulatory capacity [4]. In particular, intraoperative hypothermia is caused by the use of 15°C inhaled anesthetic gas during surgery and 21°C CO₂ gas injected into the abdominal cavity during laparoscopic surgery [6]. Intraoperative hypothermia leads to an increase in catecholamine’s, resulting in elevated blood pressure and heart rate, tissue hypoxia, and metabolic acidosis [4].

Moreover, stress-induced cortisol elevation due to stressors such as hypothermia, trauma, and the procedure itself can suppress immune function by interfering with lymphocyte and macrophage activity, resulting in immune suppression due to a decrease in lymphocytes [7,8]. During surgery, CO₂ gas injected into the abdominal cavity can lead to easy absorption and potentially cause hypercarbia, stimulating the sympathetic nervous system and inducing respiratory acidosis, leading to disturbances in acid-base balance [9]. Warmed CO₂ gas at 37°C has been reported to cause acidosis by increasing absorption of CO₂ gas in the body, based on Fick's diffusion law [10]. The utilization of CO₂ gas warmed to 37°C offers benefits such as reduced peritoneal damage, decreased postoperative pain, and a lower risk of hypothermia [11]. The evidence supporting the use of warmed CO₂ gas suggests its potential contribution to enhanced recovery and patient safety in laparoscopic surgery. Therefore, investigating the impact of warmed CO₂ gas at 37°C on acid-base balance during laparoscopic surgery is crucial. Various nursing interventions during surgery for preventing hypothermia include warming the skin, using warmed intravenous fluids, warm humidification of anesthetic gases, and applying warm insufflation of gas [12]. Previous studies have explored the differences between cold and warmed CO₂ during laparoscopic procedures [11,13]. Research indicates that cold, dry CO₂ can induce peritoneal damage and increase lymphocyte infiltration, whereas warmed and humidified CO₂ mitigates injury [11]. CO₂ gas used at room temperature can cause peritoneal injury and inflammation, primarily attributed to the cold temperature of the gas [13]. Studies examining the effects of warmed CO₂ on acid-base balance have shown minimal clinical impact on arterial pH and pCO₂ levels during laparoscopic cholecystectomy procedure [11]. In particular, the elderly has a lower threshold for vascular contractile responses compared to adults, leading to slower recovery to normal body temperature when becoming hypothermic during surgery [14,15], and despite the high risk of hypothermia during laparoscopic surgery, basic nursing interventions for maintaining body temperature have been insufficient. Therefore, nursing intervention studies supplemented by experimental studies on warm insufflation of CO₂ gas should be conducted and evidence-based and proactive nursing interventions should be provided. It is necessary to confirm the effect of combined skin warming, fluid warming, anesthetic gas warming, and undulating gas warming in elderly laparoscopic surgery subjects with a study that includes objective indicators to determine the total effect on not only body temperature but also acid-base balance and lymphocytes, which are indicators of physiological response, and to confirm the effectiveness of nursing interventions.

The results of this study demonstrated that insufflation of warmed CO₂ gas affects body temperature, acid-base balance, and lymphocytes during laparoscopic surgery in the elderly. In this study, the body temperature of the experimental group was measured to be higher than the body temperature of the control group. A temperature change of 0.2°C or more from hypothermia below 36°C is a physiologic change in the human body that has important clinical implications, [11] emphasizing the importance of nursing interventions to prevent hypothermia in laparoscopic surgery patients in this study, the use of 37°C warmed CO₂ gas resulted in a body temperature increase of 0.21~0.33°C at 30 and 60 minutes after warming compared to insufflation of 21°C CO₂ gas. The introduction of −90°C compressed CO₂ liquefied gas into the body, entering the abdomen at a low temperature of 21°C during laparoscopic surgery leads to intraoperative hypothermia [7]. Hypothermia refers to a core body temperature of 36°C or below and in surgical rooms with temperatures between 18°C and 21°C during surgery, the body temperature can reduce to 36°C or below regardless of the patient's body exposure [9]. Furthermore, large amounts of intravenous fluids at room temperature are infused, and after induction of general anesthesia, the use of inhalation anesthetics, muscle relaxants, and antipyretics can cause vasodilation and contribute to intraoperative hypothermia [7]. These results were consistent with a previous study that reported that warming carbon dioxide to 37°C elevates body temperature during laparoscopic surgery [18], but differs from other studies that reported that warming carbon dioxide was not effective in preventing hypothermia in surgical patients [6]. Furthermore, it has been observed in a study that the group undergoing laparoscopic surgery with warm insufflation of CO₂ gas experienced a more pronounced prevention of decreased body temperature compared to the group receiving regular CO₂ gas [14], and the introduction of 21°C CO₂ gas during laparoscopic surgery resulted in a temperature decrease to 35.2°C three hours post-surgery [13]. Previous studies have shown that the maintenance of normal body temperature was not achieved through skin warming, fluid warming, and humidification of anesthetic gases during laparoscopic surgery in elderly patients [14]. Therefore, it is necessary to further verify the effectiveness of maintaining normal body temperature with insufflation of CO₂ gas warmed to 37°C. This may also be related to the duration of the dwell time after insufflation of CO₂ gas, as the average dwell time of the experimental group in this study was 218 minutes, compared to 105 minutes in the study by Cheong [11], which is different from this study. Therefore, considering these findings, it can be inferred that intraperitoneal CO₂ gas insufflation during laparoscopic surgery leads to intraoperative hypothermia. Warming interventions for temperature regulation are fundamentally important nursing interventions. Based on the results of this study, we believe that insufflation of warmed CO₂ gas during laparoscopic surgery not only minimizes the decrease in intraoperative body temperature but also has the potential to be a nursing intervention to help subjects return to normal body temperature quickly in the recovery room after anesthesia has worn off. In this study, warmed CO₂ gas was used as an insufflation agent in laparoscopic surgery and was found to affect acid-base balance, which is consistent with the results of a previous study conducted on animals using CO₂ gas [20]. Based on Fick's diffusion law [20], which states that the diffusion coefficient of a substance is proportional to its temperature, Swenson et al. [21] support the theory by stating that warming carbon dioxide to 37°C increases carbon dioxide absorption through the peritoneum, resulting in decreased hemodynamic function and acid-base imbalance. These findings are similar to those of studies that have shown acid-base imbalance due to decreased body temperature during surgery [22]. Based on the above results, it is likely that acid-base imbalance is caused by a decrease in body temperature as the surgery time increases. These results suggest that warmed CO₂ gas may affect acid-base balance, which may provide scientific support for future nursing interventions in postoperative hypothermia. In this study, warm insufflation of warmed CO₂ gas was shown to affect lymphocytes. Previous studies [9] have shown that the use of insufflation of CO₂ gas in laparoscopic surgery does not affect hemodynamic function and acid-base balance in healthy adults without high-risk factors such as heart and lung disease, but considering that the subjects in this study were elderly subjects aged 65 years or older, the results may be different due to age differences. In addition, the lymphocyte count in the group with warmed CO₂ gas to 37°C was somewhat lower than that in the group with 21°C CO₂ gas at 60 minutes after warming. However, the study showed that normal lymphocyte balance was restored after the end of surgery and anesthesia, indicating the need for further research to verify these findings in elderly patients. Tochihara et al. [15] reported that hypothermia is more likely to occur in the elderly than in other age groups due to imperfect vasoconstrictor mechanisms due to decreased elasticity with increasing age, and variability in thermoregulation due to decreased sympathetic nervous system reactivity and decreased metabolic heat production. Given that the subjects in this study were also elderly patients undergoing laparoscopic surgery, it is conceivable that there may be more age-related differences in body temperature than in other previous studies in adults. However, the subjects in this study were elderly subjects aged 65 years or older, and despite their reduced ability to regulate body temperature compared to adults, their intraoperative temperature decreased less, and their recovery to normal body temperature was rapid after surgery, and we believe that these results provide evidence that warm insufflation of CO₂ gas is effective in preventing hypothermia and maintaining normal body temperature during surgery. As this study recruited subjects from a single center and the sample size was small, it is recommended that the number of subjects be expanded to a multicenter study to increase the representativeness of the sample and revalidate the effectiveness of warm insufflation of CO₂ gas. In addition, the study controlled for the type of anesthetic and the duration of the surgery to confirm the effectiveness of warm insufflation of CO₂ gas, but did not control for the effect of the experimental environment, which does not control for all factors that can increase body temperature. Therefore. we recommend further studies to control for exogenous variables that may increase body temperature and to determine changes in body temperature, acid-base balance, and lymphocytes in response to the warming effect of CO₂ gas insufflation.

This randomized controlled pre-post experimental study investigated the effects of intraperitoneal CO₂ gas warming nursing care on body temperature, acid-base balance, and lymphocyte levels in elderly patients undergoing laparoscopic surgery. The results of this studysuggest that intraoperative application of warm insufflation of CO₂ gas is an effective evidence-based nursing intervention for improving body temperature, acid-base balance, as well as lymphocyte balance in elderly laparoscopic surgery patients. This study provides nursing significance as it demonstrates the preventive effect against intraoperative hypothermia caused by general anesthesia and the stabilization of physiological indicators. By presenting theoretical evidence, it lays the foundation for practical nursing interventions applicable in clinical practice. In addition, it is hoped that in the future, insufflation of warmed CO₂ gas will be used as a foundation for basic nursing theory and practice education for elderly patients undergoing laparoscopic surgery as an essential intraoperative nursing intervention.