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

Dehiscence or leakage after 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. Because current technology is limited for monitoring local StO₂ at bowel anastomoses, our goal was to construct a wireless pulse oximeter (WiPOX) to monitor real-time intraoperative tissue oxygenation, permitting identification of compromised anastomotic perfusion.

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 reuse, (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.

In humans, WiPOX demonstrated accuracy within 3% compared with 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 s 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 noninvasive 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.

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.