Impact of Intraoperative Hypothermia on Early Postoperative Anastomotic Leak in Patients Undergoing Elective Colorectal Surgery

Colorectal surgery is widely conducted to cure a broad range of benign and malignant gastrointestinal diseases and is associated with significant morbidity in the postoperative period.[1] Despite the innovation in the surgical practices, perioperative care, and improved recovery measures, anastomotic leak (AL) is one of the most dreaded and severe complications after colorectal resection.[2] In addition to raising postoperative morbidity and mortality, anastomotic leakage prolongs the hospital stay and increases the costs of care, and negatively impacts long-term oncological results and quality of life.[3]

The incidence of anastomotic leak (AL) following elective colorectal surgery is reported to be between 3% and 15%, depending on patient factors, surgery method, level of anastomosis, and perioperative care.[4] The mortality rates of AL can be up to 10%-20%, especially among older patients and patients with comorbidities.[5] They have identified several risk factors of AL, such as malnutrition, smoking, steroid use, poor tissue perfusion, tension at the anastomotic site, and intraoperative hemodynamic instability. Nonetheless, there are potentially adjustable perioperative factors that are gaining more clinical focus.[6]

A common yet underappreciated complication of a major abdominal surgery is intraoperative hypothermia, or core body temperature reaching or falling below 36 °C.[7] Research indicates that approximately 50-70% of patients who have long-term abdominal surgeries develop certain levels of unwanted hypothermia.[8] Hypothermia has been demonstrated to disrupt coagulation, hinder tissue oxygenation, silence immune activity, and weaken collagen production, biologically plausible mechanisms that have been shown to contribute to poor anastomotic healing.[9] Regardless of these associations, the direct effect of intraoperative hypothermia on early postoperative anastomotic leak has not been adequately investigated, especially in elective colorectal surgery.[10]

Since intraoperative hypothermia is a preventable and reversible risk factor, a better comprehension of its contribution to anastomotic integrity is of a high clinical interest. Knowing a definite relation between intraoperative hypothermia and anastomotic leak may affect the perioperative temperature management behavior and lead to a better outcome. Nevertheless, the current literature is sparse and without conclusive results, and specialized clinical assessment of the field is necessary. The current investigation attempted to determine the effect of intraoperative hypothermia on early postoperative anastomotic leak in patients undergoing elective colorectal surgery.

The study involved 180 patients; among them, 78 (43.3) patients had intraoperative hypothermia and 102 (56.7) patients had normothermia. Both groups were similar in regard to baseline demographic/ clinical factors such as age, sex distribution, BMI, comorbidities, ASA classification, and smoking history, which did not show significant preoperative differences that could confound the main outcome (Table 1).

There was also a general similarity in perioperative variables among the two groups. The majority of the patients were subjected to open surgery, and laparoscopic operations were balanced in distribution. Even though the duration of surgery was also a little higher in the hypothermia group, there were no significant differences in other intraoperative aspects, including estimated blood loss and total fluid intake (Table 2).

The cases of early postoperative anastomotic leak were more prevalent in patients who experienced intraoperative hypothermia than in normothermic patients. In the same manner, reoperations involving leaks were higher in the hypothermia group, but 30-day mortality did not have significant differences between the groups (Table 3).

In multivariate logistic regression analysis, intraoperative hypothermia remained an independent predictor of early anastomotic leak after the adjustment of possible confounders, such as age, BMI, ASA class, duration of surgery, and estimated blood loss (Table 4). The independent relationship between other variables and the risk of leak was not significant.

Perioperative variables that were continuous over time, including age, BMI, duration of operation, estimated blood loss, intraoperative fluid, and minimum intraoperative temperature, were summarized and compared between the two groups. The duration of surgery and minimum core temperature showed significant differences, with the finding that hypothermia was related to longer surgery and lower intraoperative temperature without significant differences in other variables (Table 5).

Table 1. Baseline Demographic and Clinical Characteristics of Patients

Table 2. Perioperative Characteristics

Table 3. Early Postoperative Anastomotic Leak

Table 4. Multivariate Logistic Regression for Anastomotic Leak

In the present prospective cohort study, patients having intraoperative hypothermia had a considerably increased rate of early postoperative anastomotic leak following an elective colorectal operation than normothermic patients. Intraoperative hypothermia was also an independent predictor of anastomotic leakage after correction of possible confounding factors like age, BMI, ASA score, operative duration, and blood loss, and this indicates how intraoperative hypothermia could be considered a modifiable perioperative variable.

Our results are aligned with an increasing amount of evidence indicating that perioperative temperature control has an impact on surgical outcomes. A recent prospective observational study of patients undergoing rectal surgery reported intraoperative hypothermia as a risk of early anastomotic leakage and excessive inflammatory markers (e.g., IL 17), suggesting biological processes that associate hypothermia with poor tissue healing and inflammatory processes (e.g., suppressed immune response and collagen deposition), which can weaken anastomotic integrity.[12]

Most studies on intraoperative hypothermia have been done on non-colorectal surgery, but the patterns are consistent. As an example, a multicentric study of esophagectomy patients revealed that lower intraoperative temperature was associated with significantly higher risks of postoperative anastomotic failure, such as leaks and severe morbidity, which confirms the hypothesis that hypothermia negatively affects anastomotic healing in various gastrointestinal operations.[13] A similar investigation involving Ivor Lewis esophagectomy revealed that the only independent predictor of anastomotic leak on a multivariate analysis was severe intraoperative hypothermia (<35 o C).[14] These studies are in non-colorectal populations, but the studies point in the right direction as they indicate the general applicability of temperature control in anastomotic surgeries.

In colorectal surgery specifically, the DoubleCheck trial focused on modifiable intraoperative risk factors such as hypothermia and found that perioperative optimisation decreased the incidence of colorectal anastomotic leak, although not exclusively due to the use of temperature control.[15] This is consistent with our discovery of the link between hypothermia and leak risk but underscores the idea that more complex perioperative care packages can be required to achieve leak reduction.

In addition to anastomotic leak, the perioperative outcomes of hypothermia have been reported to have more extensive negative consequences. A 2025 meta-analysis of the literature in BMC Anesthesiology discovered an effect of low body temperature (intraoperative hypothermia) with a tendency towards increased risk of surgical site infection, particularly when the body temperature was reduced to ≤35 °C or below, which could be an indirect factor in impaired wound and anastomotic healing.[16] Equally, hypo or normothermia has been associated with increased duration of hospitalization and other postoperative complications among general surgery patients, which suggests that temperature deregulation has systemic consequences related to recovery.[17]

The concept that hypothermia is a negative influence on surgical outcomes is also supported by research conducted on other forms of abdominal anastomoses. As an example, clinically relevant postoperative pancreatic fistula after pancreaticoduodenectomy was greater in cases of severe intraoperative hypothermia, indicating that hypothermia can have a wide-range of deleterious effects on anastomotic healing in digestive tract surgery.[18] A related retrospective study revealed hypothermia to be linked with pancreatic fistula following PD, which once again affirms this deleterious association.[19]

Even though work in reconstructive surgery does not directly measure anastomotic leaks, studies have demonstrated that intraoperative hypothermia elevates the rates of wound complications, hematoma, and impaired healing, which then supports the mechanistic plausibility of hypothermia impacting tissue repair.[20]

However, other historical meta-analyses, primarily of superficial surgical complications, have also shown mixed evidence, no significant overall relationship between hypothermia and poor outcome in all forms of surgery, but significant risk at temperatures below certain critical values, or in specific operations.[16] The results indicate a multifaceted and contextualized role of intraoperative temperature with significant effects, especially in major abdominal and anastomotic surgery.

Along with hypothermia, both the demographic and perioperative profiles of your cohort were typically reflective of other colorectal anastomotic leak studies where multifactorial risk profiles such as operative time, comorbidity, and immunologic status have been implicated.[21] Although the studies did not necessarily explicitly address the use of temperature, they reiterated the complexity of anastomotic complications and how the inclusion of temperature monitoring in perioperative risk assessment may be advantageous.

The strengths of our study are a prospective study design, core temperature measurements, and multivariate adjustment of core temperature measurements with the most important confounders that provided strong evidence that intraoperative hypothermia is an independent predictor of anastomotic leak. This is clinically significant because of the need to be more vigilant in ensuring intraoperative warming protocols (e.g., forced air warming, fluid warming) are affordable and modifiable protocols to enhance surgical outcomes. Although there have been constant associations, causal inference is also hampered by observational design. Also, the lack of universal temperature thresholds and heterogeneity of definitions of hypothermia across studies make it more difficult to directly compare studies, and larger multicenter prospective and interventional studies are warranted.

The significance of intraoperative hypothermia is a predictive factor and an independent one in the early occurrence of anastomotic leak in elective colorectal surgery patients. Normothermia in surgical practice helps to minimize the likelihood of this dangerous complication, as well as to promote the healthy growth of tissues and the overall recovery of the patient after surgery. These results highlight the importance of close integration of perioperative temperature as a basic, inexpensive, and adjustable intervention to enhance surgical outcomes. Active warming and continuous monitoring of core temperature should be seen as routine practice when performing elective colorectal surgeries to improve patient safety and minimize postoperative morbidity.

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