Comparison of the ViOptix Intra.Ox Near Infrared Tissue Spectrometer and Indocyanine Green Angiography in a Porcine Bowel Model

Clinical and computational development of a patient-calibrated ICGFA bowel transection recommender

INTRODUCTION

Intraoperative indocyanine green fluorescence angiography (ICGFA) aims to reduce colorectal anastomotic complications. However, signal interpretation is inconsistent and confounded by patient physiology and system behaviours. Here, we demonstrate a proof of concept of a novel clinical and computational method for patient calibrated quantitative ICGFA (QICGFA) bowel transection recommendation.

METHODS

Patients undergoing elective colorectal resection had colonic ICGFA both immediately after operative commencement prior to any dissection and again, as usual, just before anastomotic construction. Video recordings of both ICGFA acquisitions were blindly quantified post hoc across selected colonic regions of interest (ROIs) using tracking-quantification software and computationally compared with satisfactory perfusion assumed in second time-point ROIs, demonstrating 85% agreement with baseline ICGFA. ROI quantification outputs detailing projected perfusion sufficiency-insufficiency zones were compared to the actual surgeon-selected transection/anastomotic construction site for left/right-sided resections, respectively. Anastomotic outcomes were recorded, and tissue lactate was also measured in the devascularised colonic segment in a subgroup of patients. The novel perfusion zone projections were developed as full-screen recommendations via overlay heatmaps.

RESULTS

No patient suffered intra- or early postoperative anastomotic complications. Following computational development (n = 14) the software recommended zone (ROI) contained the expert surgical site of transection in almost all cases (Jaccard similarity index 0.91) of the nine patient validation series. Previously published ICGFA time-series milestone descriptors correlated moderately well, but lactate measurements did not. High resolution augmented reality heatmaps presenting recommendations from all pixels of the bowel ICGFA were generated for all cases.

CONCLUSIONS

By benchmarking to the patient's own baseline perfusion, this novel QICGFA method could allow the deployment of algorithmic personalised NIR bowel transection point recommendation in a way fitting existing clinical workflow.

Assessment of Anastomotic Viability With Spectroscopic Real-time Oxygen Saturation Measurement in a Porcine Study

OBJECTIVE

Anastomotic leakage (AL) is a severe complication following intestinal procedures. Intra.Ox™ by ViOptix Inc (Newark, CA, USA) is a novel, FDA-approved spectroscopic device which enables real-time measurement of mixed tissue oxygen saturation (StO₂). Using a porcine model, this study explores the correlation between StO₂ measurements and AL formation as well as investigates the applicability of Intra.Ox™ in the clinical setting.

METHODS

Eleven female swine were divided into 3 groups to explore AL formation in different ischemic conditions. Group 1: 100% mesenteric-vascular ligation, n = 3; Group 2: 50% ligation, n = 5; Group 3: No mesenteric ligation, n = 3. StO₂ at the anastomotic line was measured before and after vessel ligation and anastomosis. Measurements were taken at 6 distinct locations along afferent and efferent loops. AL was evaluated on postoperative day 5 by re-laparotomy.

RESULTS

AL rate was 100%, 60% and 0% in groups 1, 2 and 3, respectively. Post-anastomotic StO₂ in group 1 (22.9 ± 18.5%) and 2 (39.2 ± 20.1%) were significantly lower than in group 3 (53.1 ± 8.3%, p<.0001). Post-anastomotic StO₂ readings ≤40% indicated AL potential with 100% sensitivity,+ 80% specificity, positive predictive value of 85.7% and negative predictive value of 100%.

CONCLUSION

This study demonstrates the value of Intra.Ox™ in assessing local perfusion and indicate the association between low StO₂ and AL by providing accurate, real-time, noninvasive tissue oxygenation measurements at anastomotic sites. Further studies are required to investigate the clinical application of this novel device in intestinal surgery.

The use of tissue oxygen measurements compared to indocyanine green imaging for the assessment of intraoperative tissue viability of human bowel

BACKGROUND

Adequate tissue oxygenation and perfusion remain fundamental to safe bowel resection surgery. Near infrared (NIR) imaging using indocyanine green has proven itself superior to clinical evaluation alone in assessing bowel perfusion, but requires expensive equipment not readily available in many centers.

METHODS

We studied the IntraOx device (Vioptix Inc, Newark, CA USA), a handheld, tissue oxygen saturation assessment tool, to assess whether tissue bed oxygen saturation (StO2) is comparable to NIR assessment of bowel viability. Patients undergoing elective colon resection for benign and malignant disease were included. After choosing a clinical margin (CM) and dividing the mesentery, StO2 was measured at 5-cm intervals along the colon. A tissue oxygen saturation margin (TOM) was assigned where StO2 dropped off by at least 10 percentage points. NIR perfusion was then assessed to determine NIR margin (NIRM). Intraoperative and postoperative data were collected.

RESULTS

32 consecutive patients undergoing colectomies were analyzed. IntraOx sensitivity was 90.6%, specificity was 94.3%. The mean StO2 difference across the NIRM was 23.1%. In all but one case, the TOM matched the NIRM. In 3 cases, the TOM and NIRM concurred, but were a mean of 3.3 cm proximal to the CM and altered the surgical plan. At 4-week follow-up, no significant complications were reported.

CONCLUSIONS

The IntraOx device consistently identified a margin of significant saturation "drop-off" which correlated with the findings on NIR perfusion and clinical assessment. These early data indicate that StO2 measurement may be equivalent to NIR assessment of bowel perfusion. In addition, the IntraOx device may be a more cost-effective solution for surgeons looking for adjunctive evaluation of bowel viability. More study is warranted in a larger group of patients to confirm these preliminary findings and to judge the impact of StO2 assessment on reducing anastomotic leaks.

Intraoperative Near-Infrared Spectroscopy Monitoring of Renal Allograft Reperfusion in Kidney Transplant Recipients: A Feasibility and Proof-of-Concept Study

Conventional renal function markers are unable to measure renal allograft perfusion intraoperatively, leading to delayed recognition of initial allograft function. A handheld near-infrared spectroscopy (NIRS) device that can provide real-time assessment of renal allograft perfusion by quantifying regional tissue oxygen saturation levels (rSO₂) was approved by the FDA. This pilot study evaluated the feasibility of intraoperative NIRS monitoring of allograft reperfusion in renal transplant recipients (RTR). Intraoperative renal allograft rSO₂ and perfusion rates were measured in living (LDRT, n = 3) and deceased donor RTR (DDRT, n = 4) during the first 50 min post-reperfusion and correlated with renal function markers 30 days post-transplantation. Intraoperative renal allograft rSO₂ for the DDRT group remained significantly lower than the LDRT group throughout the 50 min. Reperfusion rates were significantly faster in the LDRT group during the first 5 min post-reperfusion but remained stable thereafter in both groups. Intraoperative rSO₂ were similar among the upper pole, renal hilum, and lower pole, and strongly correlated with allograft function and hemodynamic parameters up to 14 days post-transplantation. NIRS successfully detected differences in intraoperative renal allograft rSO₂, warranting future studies to evaluate it as an objective method to measure ischemic injury and perfusion for the optimization of preservation/reperfusion protocols and early prediction of allograft function.