Intraoperative partial pressure of oxygen measurement to predict flap survival

Abstract

ABSTRACT Introduction: Flap monitoring using partial pressure of oxygen (pO2) is a proven modality. Instruments needed are expensive and are not readily available to a clinician. Here, pO2 of flap has been determined using readily available and cheap methods, and a cut-off value is calculated which helps in predicting flap outcome. Methods and Results: Total 235 points on 84 skin flaps were studied. Capillary blood was collected from flap and fingertip using 1-ml syringes after at least 30 min of flap inset, and pO2 analysed using blood gas analyser. Fall/change of pO2 (difference of mean of pO2 [diff-pO2]) was also calculated by subtracting the flap pO2 from the finger pO2. Flap was monitored clinically in post-operative period and divided into two groups depending on its survival with Group 1 – dead points and Group 2 – alive points. pO2 and diff-pO2 amongst both the groups were compared and found to be statistically different (P = 0.0001). Cut-off value calculated for pO2 was found to be <86.3 mmHg with a sensitivity of 100% and specificity of 89.05%. The difference of >68.503 mmHg of flap pO2 compared from finger pO2 was calculated as a cut-off with sensitivity of 94.12 and specificity of 79.60%. Conclusions: Flap areas having intra-operative pO2 value <86.3 mmHG have higher chances (60.71%) of getting necrosis later. Similarly, if diff-pO2 compared to fingertip is >68.5 mmHg, chances of those points getting necrosed in post-operative period are high.