The use of the Spy Elite Intraoperative Perfusion Assessment System (intraoperative laser fluorescence angiography) to determine bowel perfusion in the morbidly obese patient.

Steven C Tizio, MD, Marisela Messenger, RN, BSN, MBA, Seema Izfar, MD, Mario Alcantara, MD, James C Connaughton, MD, Jaime Mayoral, MD. Methodist Healthcare System of San Antonio.

Objective of the technology or device:  Increased mesenteric fat is a risk factor for anastomotic dehiscence, which may be due to decreased perfusion. Morbid obesity has been implicated as a possible risk factor for anastomotic leak in several studies. The only subjective means of evaluating bowel perfusion is to check for discoloration of the bowel, active peristalsis, and bleeding at the cut edge of the bowel.  An objective method of assessing bowel integrity, near-infrared fluorescence (NIR) imaging, can be utilized to assess the microvascular circulation of the bowel.  

Description of the technology and method of its use or application: A fluorescent dye (e.g. indocynanine green, 0.2-0.5 mg/kg) is injected in a bolus dose into the patient intravenously and after a delay of time, the dye fluoresces using NIR laser light allowing analysis of the tissue of interest.  The amount of light emitted is directly proportional to the amount of tissue perfusion.  A map of isofluorescence can be created using the pixel intensity from the images, allowing assessment of perfusion.

Preliminary results:  15 patients with a low BMI (range 16.6 to 26.5 kg/m2) were compared with 15 patients with a high BMI (range 35.1 to 63.7 kg/m2) with regards to bowel perfusion using the SPY Elite system.  Perfusion was determined by an average intensity of maximal fluorescence based on 256 shades of gray, with 256 being the maximum value. The average perfusion was 159.9 and 167.4 (p=.77), for the low and high BMI groups respectively.  We have not been able to correlate a significant difference in tissue perfusion for morbidly obese patients.

Conclusions / future directions: The use of NIR fluorescence technology is a novel technique for estimating perfusion in the morbidly obese. Surgery in the morbidly obese is fraught with challenges, one of which is a possible increased risk of anastomotic leak. In our study, we were not able to demonstrate a statistical significance in mesenteric perfusion in patients with morbid obesity as compared to patients with a normal BMI.  It is possible that increasing the number of patients in the study may be able to demonstrate a statistical difference in perfusion in the future.  SPY angiography remains a novel technique for intraoperative estimation of bowel perfusion and may lead to decreased risk of anastomotic leak in obese and non-obese patients with more widespread adoption.

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