Real-time intraoperative detection of tissue hypoxia in gastrointestinal surgery by wireless pulse oximetry

Abstract

Objective Dehiscence or leakage following bowel anastomoses is associated with high morbidity and mortality. Perfusion and local tissue oxygenation (StO2), independent of systemic oxygen saturation, are fundamental determinates of anastomotic viability. As current technology is limited for monitoring local StO2 at bowel anastomoses, we aimed to construct a wireless pulse oximeter (WiPOX) to monitor real-time intraoperative tissue oxygenation, permitting identification of compromised anastomotic perfusion. Methods We have: (a) designed a handheld device capable of real-time monitoring of serosal and mucosal StO2 through endoscopic ports with wireless data transmission to standard intraoperative monitors, (b) constructed the WiPOX using materials meeting FDA regulations for intraoperative use and re-use, (c) performed accuracy testing in humans by comparing the WiPOX to standard pulse oximeters, and (d) tested WiPOX efficacy for detecting early tissue hypoxia in stomach, intestines, and kidneys in anesthetized rats and swine. Results In humans, WiPOX demonstrated accuracy within 3% when compared to commercially available pulse oximeters. Application of the WiPOX in rats and swine demonstrated normal serosal and mucosal StO2 and pulse rates in healthy small bowel and stomach. Within 30 seconds of compromised perfusion, the WiPOX detected bowel hypoxia over a wide range of oxygen saturation (p<0.005). A greater degree of hypoxia was detected in mucosal versus serosal measurements during early ischemia, despite normal appearance of tissue. The onboard sensor-processor unit permitted non-invasive pulse oximetry and integration with current intraoperative monitoring. The contact pressure-sensing head allowed for consistent, high quality StO2 waveform readouts despite the presence of body fluids. Conclusions We have constructed, validated, and successfully tested a novel wireless pulse oximeter capable of detecting intraoperative tissue hypoxia in open or endoscopic surgery. This device will aid surgeons in detecting anastomotic vascular compromise and facilitate choosing an ideal site for bowel anastomosis by targeting well-perfused tissue with optimal healing capacity.

A collaborative review of the current concepts and challenges of anastomotic leaks in colorectal surgery

“…Several attempts have been made to apply more sophisticated means of assessing anastomotic perfusion. Such methods include analysis of tissue oxygenation using light spectroscopy [62] and modified pulse oximetry [63,64]. A fall in tissue oxygen tension appears to be associated with subsequent AL.…”

Cerebral and tissue oximetry

“…Emerging data also support the possibility of using tissue oximetry to measure renovascular reactivity during hemorrhagic shock [93, 94]. Lastly, tissue oximetry could be used as an early marker to detect intraoperative tissue hypoxia during abdominal surgery that involves the intestines, pancreas, or kidneys [95, 96]. The major drawback to evaluating oxygenation of superficial organs with NIRS methodology is the large inter-individual variability in distance between the body surface and the organ of interest, secondary to overlying fat and muscle.…”

Systematic review of methods to predict and detect anastomotic leakage in colorectal surgery

“…The levels of oxygenation were found to be stable and reproducible, suggesting that this technique may have merit as a predictive test. Two animal studies support these findings, comparing tissue oxygenation over a range of staple sizes and using a novel wireless pulse oximeter to assess colonic tissue perfusion [26,27]. To date, the level of tissue oxygenation that unavoidably leads to ischaemia has not been clearly defined and further work to stratify the risk of anastomotic leakage is required.…”