**3.4 Gastric conduit perfusion evaluation-intraoperative fluorescence angiography**

During gastric conduit creation and pullup, ligation of the left gastric, left gastroepiploic, and short gastric vessels is necessary, leaving the right gastroepiploic artery as the main feeding vessel of the gastric conduit. This may lead to insufficient arterial supply or venous congestion at the anastomotic site, leading consequently to anastomotic complications, such as anastomotic leakage, benign stricture, and graft necrosis [38]. Esophagogastric anastomotic strength and, thus anastomotic complications after esophagectomy depend mainly on the preservation of the right gastric and right gastroepiploic arteries, which provide adequate perfusion to gastric conduit [39]. In addition, the tip of the gastric conduit is the most vulnerable site of ischemia due to insufficient perfusion by the gastroduodenal artery. Apart from adequate arterial perfusion, gastric conduit perfusion may be affected by rough manipulations, poor preparation, and suboptimal surgical technique [10].

Numerous intraoperative methods have been proposed for the assessment of gastric conduit perfusion and optimal anastomotic site selection. Among them, fluorescence angiography (FA) using indocyanine green has been adopted widely. Slooter and colleagues tried to identify a threshold of FA using ICG for facilitating intraoperative decision-making and identifying high-risk patients for anastomotic leakage. For Ivor-Lewis esophagectomy, FA was performed after gastric pullup into the thorax and decision of anastomotic site. After intravenous ICG injection, the first fluorescent enhancement time point in the lungs, at the base of the gastric conduit, at the planned anastomotic site, and at the ICG watershed or in the tip of the gastric conduit were recorded. Follow-up revealed anastomotic leakage in 9 out of 67 patients (13.4%) with intrathoracic anastomosis. In conclusion, the authors suggest that the time between ICG injection and enhancement at the tip of the gastric conduit, with a cut-off value of 98 seconds, can be used as a threshold to predict anastomotic leakage after esophagectomy. However, it should be highlighted that anastomotic leakage was noticed in two out of two patients who underwent additional gastric conduit resection based on FA findings. In other words, excessive gastric resection based on FA outcomes may lead to anastomotic leakage due to tension at the anastomosis [38].

Using the Near-Infrared (NIR) laparoscopic PINPOINT® endoscopic fluorescence imaging system (NOVADAQ®, Mississauga, ON, Canada), which provides ICG fluorescence angiography images over white light in a dynamic fashion, Pather et al. reported their experience in indocyanine green fluorescence angiography-assisted minimally invasive Ivor-Lewis esophagectomy. After intravenous administration of 7.5 ml of ICG, a surgeon-based assessment of conduit perfusion was performed, as good perfusion, when visualization of the ICG-FA up to the tip of the gastric conduit was noticed, or non-perfusion, if any area of perfusion demarcation was noticed. In the latter category, the operative plan was changed and the poorly-enhanced part of gastric conduit was resected before anastomosis. Anastomotic leak was noticed in 6 out of 100 patients and was managed with endoscopic stent placement. The authors conclude that non-perfusion was independently associated with anastomotic leak postoperatively. However, anastomotic leakage remains a multifactorial complication, and ICG-FA should be used as a tool for recognizing high-risk patients, parallel to patient preoperative optimization [39].

FA with ICG is also proposed to be of great value for the assessment of gastric fundus perfusion in patients who previously received neo-adjuvant radiation [16]. Apart from perfusion assessment, Gubric et al. use FA with ICG for anastomosis tension assessment, where delayed perfusion in a previously well-perfused gastric conduit tip reveals excessive tension [29]. However, this technique also presents a series of limitations. First of all, interpretation of the outcomes is mainly subjective and no consensus has been reached regarding perfusion-related cut-off point for

*Prevention of Anastomotic Leak in Minimally Invasive Esophagectomy: The Role of Anastomotic… DOI: http://dx.doi.org/10.5772/intechopen.106041*

fluorescence. In addition, gastric conduit fluoresces green under circumstances of venous congestion, since arterial perfusion is intact [38]. In conclusion, a FA threshold may be used for detecting high-risk patients for anastomotic leakage and adopting prophylactic measures to avoid it [38].

#### **3.5 Ischemic preconditioning of the stomach**

The concept of gastric ischemic pre-conditioning preoperatively to reduce anastomotic leakage was first introduced by Akijama et al., who performed preoperative embolization therapy (PET). After femoral artery catheterization, embolization of the left gastric artery was performed and the right gastroepiploic artery was the remaining feeding artery of the stomach. Blood flow of the gastric tube was measured to be 67% of the measure just after laparotomy was performed, compared to the non-PET group, where the respective value of blood flow was 33%. Similar outcomes were noticed regarding the anastomotic leakage rate among the two groups [39]. Nowadays, the idea of ischemic preconditioning has been extended apart from preoperative embolization also to pre-operative laparoscopic ligation of the left gastric and left gastroepiploic arteries during the staging laparoscopy in type II junction tumors [16]. Occasionally, ligation or embolization of short gastric vessels is also performed [2].

The pathophysiological mechanism is based on preoperative redistribution of gastric blood supply and increased tissue perfusion at the site of the esophagogastric anastomosis. Michalinos et al. performed a systematic review and meta-analysis to investigate the role of gastric ischemic preconditioning, including both techniques of embolization and ligation, to postoperative anastomotic leakage rate, as well as morbidity and mortality. Outcomes revealed a statistically significant association between gastric preconditioning and reduced overall rate of anastomotic leakage, as well as severe anastomotic leakage. On the contrary, no statistically significant relationship was established between ischemic precondition and anastomotic stricture, major postoperative morbidity, or mortality. Results were similar among the two methods of ischemic preconditioning, while authors also suggest that increasing the interval time period between preconditioning and esophagectomy as well as the number of vessels embolized or ligated may lead to better outcomes regarding conduit perfusion [2]. In addition, it is investigated whether patients with calcifications of the thoracic aorta and stenosis of the celiac trunk, who are at risk of higher anastomotic leakage rate due to reduced micro or macro perfusion of the gastric conduit, may benefit significantly from gastric ischemic preconditioning performance [40].
