Experimental model to estimate intestinal viability using charge-coupled device microscopy

Efficacy of Assessing Intraoperative Bowel Perfusion with Near-Infrared Camera in Laparoscopic Gastric Cancer Surgery

BACKGROUND

Anastomotic leakage is a severe complication after gastric cancer surgery. Inadequate blood supply is regarded as an important risk factor. The aim of the study was to evaluate the feasibility and usefulness of intraoperative assessment of anastomotic vascular perfusion in gastric cancer surgery using near-infrared (NIR) camera imaging with indocyanine green (ICG)-enhanced fluorescence technique.

MATERIALS AND METHODS

From March 2015 to 2016, 30 patients undergoing laparoscopic gastrectomy for gastric cancer were prospectively evaluated. After completing the anastomosis, 2.5-5.0 mg of ICG was injected via peripheral veins. All anastomoses and resection margins were investigated using NIR camera to assess anastomotic perfusion. The assessment was performed using the adopted perfusion score of fluorescence activity, which ranged from 1 to 5 (1 = no uptake, and 5 = iso-fluorescent to all other segments).

RESULTS

Twenty-six distal gastrectomy (20 gastroduodenostomies, 6 gastrojejunostomies), 3 total gastrectomies (TG), and 1 pylorus-preserving gastrectomy were performed. The gap of visualization was 4.1 ± 3.2 minutes (range, 2-15) after ICG injection. Twenty-three of 30 patients (76.7%) showed technically successful ICG visualization. Among gastroduodenostomies, the average scores for gastric and duodenal sides were 3.5 and 3.7. Among gastrojejunostomies, the average scores for gastric, jejunal, and duodenal stump sides were 3.5, 4.0, and 3.8 (jejunojejunostomy, 3.5). Among TG, the average scores for esophagojejunostomy, duodenal stump, and jejunojejunostomy were 3.7, 4.0, 4.0, and 4.7. One case of leakage occurred in this study. Other complications included fluid collection and stenosis in 1 patient each.

CONCLUSIONS

This study showed intraoperative ICG angiography using NIR camera is feasible and provides imaging of anastomotic blood flow. Further studies are needed for practice.

Probe-based confocal laser endomicroscopy and fluorescence-based enhanced reality for real-time assessment of intestinal microcirculation in a porcine model of sigmoid ischemia

BACKGROUND AND AIM

Surgeons currently rely on visual clues to estimate the presence of sufficient vascularity for safe anastomosis. We aimed to assess the accuracy of endoluminal confocal laser endomicroscopy (CLE) and laparoscopic fluorescence-based enhanced reality (FLER), using near-infrared imaging and fluorescence from injected Indocyanine Green, to identify the transition from ischemic to vascular areas in a porcine model of mesenteric ischemia.

METHODS

Six pigs underwent 1-h sigmoid segmental ischemia. The ischemic area was evaluated by clinical assessment and FLER to determine presumed viable margins. For each sigmoid colon, 5 regions of interest (ROIs) were identified: ischemic (ROI 1), presumed viable margins ROI 2a (distal) and 2b (proximal), and vascular areas 3a (distal) and 3b (proximal). After injection of fluorescein, CLE scanning of the mucosa from the ischemic area toward viable margins was performed. Capillary blood samples were obtained by puncturing the serosa at the ROIs, and capillary lactates were measured with the EDGE(®) analyzer.

RESULTS

Capillary lactates were significantly higher at ROI 1 (4.91 mmol/L) when compared to resection margins (2.8 mmol/L; mean difference: 2.11; p < 0.05) identified by FLER. There was no significant difference in lactates between ROI1 and resection margins identified by clinical evaluation. In 50 % of cases, ROI 2aCLINIC-2bCLINIC were considered to match (<1 cm distance) with ROI 2aFLER-2bFLER. Confocal analysis revealed specific clues to identify the transition from ischemic to viable areas corresponding to those assessed by FLER in 11/12 cases versus 7/12 for those identified by clinical evaluation.

CONCLUSIONS

In this experimental model, FLER and CLE were more accurate than clinical evaluation to delineate bowel vascularization.

Investigating viability of intestine using spectroscopy: a pilot study

BACKGROUND

The differentiation of "viable" from "nonviable" bowel remains a challenge in the treatment of acute mesenteric ischemia. In this study, diffuse reflectance spectroscopy (DRS) was used to investigate the viability of bowel tissue after ischemia and reperfusion in an animal model in vivo and in real time.

METHODS

A total of 25 females Sprague-Dawley rats were divided into five groups based on different bowel ischemia times. In each study group for four of them, the superior mesenteric artery was occluded using a vascular clamp for a different period (i.e., 30, 45, 60, and 90 min; n = 5 for each group). Intestinal reperfusion was accomplished by releasing the clamps after the given occlusion period for each group. Spectra were acquired by gently touching the optical fiber probe to the bowel tissue before the induce ischemia, at the end of the induced ischemia, and after the reperfusion. The data acquired before the ischemia were used as a control group. Without occluding the superior mesenteric artery, the spectra were acquired on the bowel with the same time intervals of the experiments were used as a sham group (n = 5). Subsequently, the same bowel segments were sent for histopathologic examination.

RESULTS

Based on the correlation between the spectra acquired from the bowel segments and the results from the histopathologic investigation, DRS is able to differentiate the histopathologic grading that appears when the Chiu/Park score ≥5 (i.e., high-level ischemic injury) than Chiu/Park score <5. Eight out of nine low-level ischemic injury tissue samples were correctly defined using the spectroscopic classification system. All eleven high-level ischemic injury tissues that were histopathologically assigned grade 5 and above were correctly defined using the spectroscopic classification system in the ischemia-reperfusion groups.

CONCLUSIONS

DRS could potentially be used intraoperatively for the assessment of bowel viability in real time. These preliminary findings suggest that DRS has the potential to reduce unnecessary resection of viable tissue or insufficient resection of nonviable tissues may reduce the mortality and morbidity rates of intestinal ischemia-reperfusion as acute mesenteric ischemia.

Predicting the survival of experimental ischaemic small bowel using intraoperative near-infrared fluorescence angiography

BACKGROUND

Predicting the long-term viability of ischaemic bowel during surgery is challenging. The aim was to determine whether intraoperative near-infrared angiography (NIR-AG) of ischaemic bowel might provide metrics that were predictive of long-term outcome.

METHODS

NIR-AG using indocyanine green was performed on 24 pigs before, and after inducing bowel ischaemia to determine the feasibility of NIR-AG for detecting compromised perfusion. Contrast-to-background ratio (CBR) over time was measured in regions of interest throughout the bowel, and various metrics of the CBR-time curve were developed. Sixty rat small bowels, with or without strangulation, were imaged during surgery and on day 3 after operation. CBR metrics and clinical findings were assessed quantitatively for their ability to predict animal survival, histological grade of ischaemic injury and visible necrosis on day 3.

RESULTS

In ischaemic pig small bowel, various qualitative and quantitative CBR metrics appeared to correlate with bowel injury as a function of distance from normal bowel. In rats, intraoperative clinical assessment showed high specificity but low sensitivity for predicting outcome on day 3 after operation. Qualitative patterns of the CBR-time curve, such as absence of an arterial inflow peak and presence of a NIR filling defect, resulted in better prediction of survival (90 per cent), histological grade (85 per cent) and visible necrosis on day 3 (92 per cent).

CONCLUSION

Survival of ischaemic bowel was predicted by intraoperative NIR-AG with greater accuracy than clinical evaluation alone.

How to assess intestinal viability during surgery: A review of techniques

Objective and quantitative intraoperative methods of bowel viability assessment are essential in gastrointestinal surgery. Exact determination of the borderline of the viable bowel with the help of an objective test could result in a decrease of postoperative ischemic complications. An accurate, reproducible and cost effective method is desirable in every operating theater dealing with abdominal operations. Numerous techniques assessing various parameters of intestinal viability are described by the studies. However, there is no consensus about their clinical use. To evaluate the available methods, a systematic search of the English literature was performed. Virtues and drawbacks of the techniques and possibilities of clinical application are reviewed. Valuable parameters related to postoperative intestinal anastomotic or stoma complications are analyzed. Important issues in the measurement and interpretation of bowel viability are discussed. To date, only a few methods are applicable in surgical practice. Further studies are needed to determine the limiting values of intestinal tissue oxygenation and flow indicative of ischemic complications and to standardize the methods.

Lactate and glycerol released to the intestinal lumen reflect mucosal injury and permeability changes caused by strangulation obstruction

BACKGROUND

The present study evaluates whether microdialysis of glycerol and lactate reflects mucosal injury and permeability changes after strangulation obstruction of the pig small intestine.

METHODS

Strangulation obstruction was induced by tightening a rubber band around a small bowel loop until its venous pressure increased to a level just below diastolic aortic pressure (partial strangulation), or further until cessation of flow in the main feeding artery (total strangulation). Mucosal injury and permeability of marker molecules from blood to lumen and vice versa was compared to release of glycerol and lactate to the intestinal lumen.

RESULTS

Mucosal injury, hyperpermeability, and release of glycerol were more pronounced after total than after partial strangulation. In animals with partial strangulation there was a complete restitution of the surface epithelium, and luminal glycerol and lumen-to-blood permeability of polyethylene glycol 4000 remained low. Such animals showed a sustained elevation of lactate and blood-to-lumen permeability of fluorescein isothiocyanate dextran after 2 h of partial strangulation, but a decline to baseline levels of these parameters in animals with 1 h partial strangulation.

CONCLUSION

Microdialysis of lactate and glycerol in the intestinal lumen may be used to assess structural and functional changes of the intestinal mucosa after strangulation obstruction.