USING NIRS TO ASSESS OXYGENATION & PERFUSION IN THE PRE-OPERATIVE TRIAGE OF SURGICAL PROCEDURES
Ronald Ray, DPM, Sandeep Gopalakrishnan, PhD, MAPWCA, Jonathan A. Niezgoda, BS, CHWS and Jeffrey A. Niezgoda, MD, FACHM, MAPWCA, CHWS
In this case series, three patients with diabetic foot ulcers, who were in consideration for invasive wound care procedures, were imaged with SnapshotNIR to assess their healing potential. SnapshotNIR is an imaging device that uses reflectance-based technology to measure tissue oxygenation (StO2) in superficial vessels 2-3 mm below the surface of the wound.
Treatment process:
Patients were imaged with near-infrared technology (NIRS) using SnapshotNIR at admission for immediate StO2 assessment. The NIRS images were then supported with X-ray and CTA studies. Depending on the results of the studies, the desired amputation or surgical debridement was scheduled or postponed. The postponed patient was instead enrolled in hyperbaric oxygen therapy (HBOT) to facilitate an increase in tissue oxygenation, resulting in a better response to an amputation procedure.
CASE 1
Patient Details
A 52-year-old male presented to the emergency room with multiple areas of Wagner IV dry ulcerations. The patient had a history of Type II Diabetes (T2DM) with neuropathy, peripheral vascular disease (PVD), hypertension, and was an active smoker of more than 1 pack per day. He had no prior history of ulcerations. The patient reported that the discoloration and ulceration started about a month prior.
Case Details
The patient underwent femoral-popliteal bypass, 36 HBOT treatments, and aggressive wound care procedures, including the removal of toes D1 and D2. Pre-, intra- and, post-operative NIRS images were captured using SnapshotNIR to measure StO2 at that time. The pre-operative images demonstrated that this patient would respond well to an invasive procedure as shown by the average StO2 values of 64-73%.
Intra-operative imaging showed that while there was a slight decrease in tissue oxygen saturation on the dorsal aspect of the foot, the planter aspect remained well-oxygenated and perfused.
Post-operative imaging with SnapshotNIR showed a slight decrease in StO2 from the dorsal toward the medial aspect of the incision. This information proved to be significant because during a follow-up visit, a superficial dehisce was noted along the same area. Full closure of the superficial dehiscence was facilitated with negative pressure wound therapy (NPWT).
Impact
SnapshotNIR was used throughout the patient’s treatment plan, aiding in the clinical decision-making process. The table below shows how taking multiple images throughout the treatment, and noting the average oxygenation status, can provide additional support for surgical intervention, helping to understand the treatment prognosis. NIRS provides immediate tissue assessment of StO2 and can be used pre-operatively to screen for patients at risk for complications due to underlying peripheral arterial disease (PAD).
Case 2
Patient Details
A 68-year-old male presented with a grade-IV dry ulceration to the medial aspect of the 1st metatarsal phalangeal joint of the left foot reported to be present for 1-2 months with no history of trauma. Previous treatment included debridement (which resulted in necrotic changes), a femoral-femoral bypass in 2013, a failed left lower extremity transluminal intervention in 2018 and a healed partial amputation of the second digit (D2) in 2022. The patient had diabetes Type II (DMT2), hypertension, hyperlipidemia, Grade I diastolic heart failure, chronic obstructive pulmonary disease (COPD) and pulmonary hypertension, and had quit smoking 10 years ago.
Case Details
Imaging studies obtained were negative for any bone involvement, but they did show significant atrophic vessels below the popliteal artery. This aligned with the patient’s complaint of calf pain. NIRS images of the wound obtained with SnapshotNIR showed low tissue oxygenation and perfusion values in the peri-wound area, ranging from 55% to 76%.
Impact
Having the ability to assess wound and peri-wound StO2 provided additional objective data to aid in the clinical decision-making process for the treatment of this patient. Ongoing NIRS imaging was used to monitor the patient’s response to HBOT.
Case 3
Patient Details
A 68-year-old male presented with a grade III-IV necrotic ulceration on the lateral aspect of the 5th metatarsal head of the left foot. There was no exposed bone but there were possible indications of osteomyelitis. Degrative bone changes at the distal end of the 5th metatarsal were confirmed with X-ray and MRI studies.
The patient was a type II diabetic with neuropathy, hypertension, and hyperlipidemia. The patient had a history of coronary artery disease and previously had coronary artery bypass grafting and aortic valve replacement. Previous lower limb treatment included right hallux (big toe) and left 5th digit (D5) amputation, in addition to peripheral vascular disease (PVD) transluminal angioplasty intervention with stenting of the left superficial femoral artery and popliteal artery.
Case Details
SnapshotNIR images were taken to assess the tissue perfusion and oxygenation of the area. StO2 values of the peri-wound ranged from the mid-60s to 80s (%), and on the plantar aspect of the foot from the high-50s to mid-70s (%). These values captured by Snapshot indicated adequate perfusion of the tissue in question. The patient qualified for surgical debridement and negative pressure wound therapy (NPWT). Following NPWT treatment, granulation tissue was achieved over the entire wound bed and the patient eventually fully healed.
Impact
SnapshotNIR provided confirmation of patient eligibility for surgical debridement, with adequate StO2 values of the wound and peri-wound, helping the clinician in the decision-making process. Vascular assessment and intervention, when necessary, can help to monitor and optimize the vascular status of patients prior to surgical procedures to ultimately enhance outcomes and limit the risk of complications.
How does SnapshotNIR help pre-operatively?
Surgical interventions including tissue resection, debridement and amputation all increase the metabolic demands on the involved tissues. Adequate tissue perfusion and oxygenation are critical to support tissue healing following these interventions. Tissue that lacks sufficient blood flow is at a higher risk for desiccation, necrosis and post-operative complications, leading to healing failure following surgical intervention at the incision. Proper preoperative assessment of vascular perfusion is critical in patient selection and screening.
Until recently, ankle-brachial studies and transcutaneous oximetry have been used to assess blood flow and by association healing potential before invasive treatments. These studies are labor-intensive and do not accurately or fully assess tissue oxygenation and perfusion. NIRS imaging is a modality that provides instantaneous and actionable information regarding a patient’s tissue oxygenation. SnaphotNIR, a reflectance-based, non-invasive device, can screen patients for vascular insufficiency and thus prompt preoperative vascular optimization. This process complements preoperative patient selection and enhances surgical decision-making to decrease the potential for post-surgical complications.
References:
1.Gopalakrishnan S, Niezgoda J, Hoffman B, Niezgoda JA. Using near infrared spectroscopy imaging to manage critical limb ischemia. Today’s Wound Clinic®. 2019;13(9):12-15.
2.Arnold J, Marmolejo VL. Interpretation of Near-Infrared Imaging in Acute and Chronic Wound Care. Diagnostics. 2021;11(5).
3. Wahab N, Lapucha MA. Clinical applications of near-infrared spectroscopy in the modern wound care clinic. Today’s Wound Clinic®. 2021;15(2)