**5. Intraoperative factors that interfere with the outcome of the anastomosis: testing methods of blood flow and patency at the level of the colorectal anastomosis**

Assessing intraoperative perfusion with indocyanine green (ICG) and nearinfrared (NIR) visualization can aid in selecting the degree of intestinal transection and subsequent anastomotic vascular sufficiency, according to the theory.

In a prospective study of nonselected patients undergoing any elective colorectal surgery with anastomosis in three tertiary hospitals over a 3-year span, NIR-ICG was used to look at anastomosis perfusion.

In addition to standard operator visual evaluation alone, a standard procedure was followed to evaluate NIR-ICG perfusion before and after anastomosis construction.

The researchers looked at 540 patients (median age 64 years, 279 men) who had surgery for neoplastic (330) and benign (174) pathology.

A total of 425 operations (853%) were initiated laparoscopically, with a 59% conversion rate.

In total, 220 patients (437%) had high anterior resection or reversal of Hartmann's procedure, and 90 patients (179%) had low anterior resection.

ICG angiography was effective in every patient, with leak rates of 24% (12 of 504) overall, 26% for colorectal anastomoses, and 3% for low anterior resection.

The anastomotic leak rates were lower when NIR-ICG imaging was used than in the participating centers from over 1000 related operations conducted with the same technique but without NIR-ICG technology. As a result, the study's findings were as follows:

Patients undergoing elective colorectal surgery should have their NIR-ICG levels checked on a regular basis.

The use of NIR-ICG can alter intraoperative decisions, potentially lowering anastomotic leak rates.

Kryzauskas conducted a systematic review and meta-analysis of publications, which included a total of 23 studies, with a total of 7115 patients, that were conducted to see whether intraoperative testing of the mechanical integrity and perfusion of the colorectal anastomosis could minimize the risk of AL. Intraoperative checks for the integrity (OR: 0.52, 95% CI: 0.34–0.82, P.001) and perfusion (OR: 0.40, 95% CI: 0.22–0.752, P.001) of the lower gastrointestinal tract anastomoses are linked to a substantially lower AL rate, according to a pooled study. The researchers came to the conclusion that intraoperative monitoring for anastomosis integrity or perfusion both reduced the AL dose. Studies combining these two anastomosis testing methods, especially intraoperative endoscopy and indocyanine green fluorescence angiography, could be very promising for further AL reduction. Since diabetes is a well-established independent factor that results in higher anastomotic leakage rates, the effects of biological sealants on colorectal anastomosis and their potential impact in patients with severe diabetes were studied in depth.

Fibrin sealants have been used to avoid anastomotic dehiscence in both laboratory and clinical trials.

We looked for existing evidence in the field by searching Medline (1966–2016) and Scopus (2004–2016). There is no evidence to support the use of fibrin sealants as a supplement in diabetic patients undergoing colorectal surgery at this time.

Experimental animal models with severe diabetes may be very useful in this area, and more research is required before fibrin sealants are used in a clinical environment.

In a systematic study and meta-analysis, Wu and team [16] analyzed the air leak test conducted intraoperatively.

The intraoperative air leak test (ALT) is a standard intraoperative test used to detect anastomosis that is mechanically inadequate.

The aim of this meta-analysis is to see whether ALT can help reduce postoperative colorectal anastomotic leakage (CAL).

The report included 22 experiments, with the following being the most notable.

According to the data, conducting an ALT using the recorded technique does not substantially reduce the clinical CAL rate, but it is still important due to the increased risk of CAL in ALT(+) cases.

Additional repairs, unfortunately, may not be successful in reducing this risk using current methods.

The findings of this study call for the standardization of ALT methodology and the creation of successful methods for repairing ALT(+) anastomoses.

A meta-analysis of randomized controlled trials on the use of suction drains following rectal surgery was conducted by Guerra and coauthors [17], and after looking at 760 patients from four RCTs that were eligible (RCT comparing drained with undrained anastomoses following rectal surgery), the use of drains showed little benefit in terms of anastomotic leak, pelvic complications, or reintervention.

On the other hand, the drained party had a slightly higher rate of postoperative bowel obstruction.

The researchers concluded that using pelvic drains routinely does not provide a major benefit in preventing postoperative complications following rectal surgery with extraperitoneal anastomosis.

Furthermore, a higher risk of bowel obstruction following surgery should be considered.

Non-surgery-based intraoperative risk factors for anastomotic healing also influence surgical outcome.

After analyzing 117 papers, a review by van Rooijen and team [18] provided an overview of potential modifiable risk factors that could play a role during the operation, and the results (the main outcome measure was the risk of anastomotic leakage and other postoperative complications during colorectal surgery) revealed that diabetes mellitus, hyperglycemia and a high HbA1c, anemia, and data on blood pressure, inotropes/vasopressors, oxygen supplementation, form of analgesia, and goal-directed fluid therapy are all unequivocal.

There was no research that looked into the effect of body core temperature or mean arterial pressure on CAL.

Subjective considerations including the surgeon's own evaluation of local perfusion and the visibility of the operating field have not been studied for incidence in CAL patients.

The findings revealed that in order to enhance colorectal treatment, both surgery-related and non-surgery-related risk factors that can be changed must be established.

In their ongoing attempt to minimize the number of CAL, surgeons and anesthesiologists can collaborate on these issues.

In the Netherlands, a multicenter cohort study is currently being conducted to determine individual intraoperative risk factors for CAL.
