Evaluation of Hyperspectral Imaging for Follow-Up Assessment after Revascularization in Peripheral Artery Disease

Effects of volume management on free flap perfusion and metabolism in a large animal model study

Free flap failure represents a substantial clinical burden. The role of intraoperative volume management remains controversial, with valid studies lacking. Here, using a large animal model, we investigated the influence of volume management on free flap perfusion and metabolism. Autotransfer of a musculocutaneous gracilis flap was performed on 31 German domestic pigs, with arterial anastomosis and catheterization of the pedicle vein for sequential blood sampling. Flap reperfusion was followed by induction of a hemorrhagic shock with maintenance for 30 min and subsequent circulation stabilization with crystalloid solution, crystalloid solution and catecholamine, autotransfusion or colloidal solution. Flap perfusion and oxygenation were periodically assessed using hyperspectral imaging. Flap metabolism was assessed via periodic blood gas analyses. Hyperspectral imaging revealed no difference in either superficial or deep tissue oxygen saturation, tissue hemoglobin or tissue water content between the test groups at any time point. Blood gas analyses showed that lactate levels were significantly increased in the group that received crystalloid solution and catecholamine, after circulatory stabilization and up to 2 h after. We conclude that, in hemorrhagic shock, volume management impacts acid-base balance in free flaps. Crystalloid solutions with norepinephrine increase lactate levels, yet short-term effects on flap perfusion seem minimal, suggesting that vasopressors are not detrimental.

Prognostic Performance of the Maximal Systolic Acceleration at the Hallux in Healing of Foot Ulcers: A Retrospective Cohort Study

BACKGROUND

The accurate prediction of foot ulcer healing remains a major challenge in clinical practice. To date, no reliable bedside tests are available. The primary aim of this study was to determine the prognostic performance of the maximal systolic acceleration (ACCmax) to predict ulcer healing. Secondary objectives comprised the investigation of the prognostic accuracy in patients prone to medial arterial calcification and to assess the potential risk of amputation.

METHODS

A single-center retrospective cohort study was conducted. Patients aged ≥18 years who presented with a new-onset ulcer (i.e. Fontaine IV and neuropathic ulcers) on the foot and underwent an ACCmax measurement at the hallux were included. Ulcer healing was defined as an intact skin with epithelialization after 3 or 12 months of follow-up. Prognostic performance was calculated by using sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (PLR), and negative likelihood ratio (NLR).

RESULTS

In total, 136 patients with 143 wounds were included. Almost half of the patients were diagnosed with diabetes mellitus (47%), and wound infection was present in 42% of cases. After 3 months of follow-up, an NPV of 97.9%, PLR of 3.25, and NLR of 0.19 were found when applying an ACCmax threshold of 0.5 m/s2. When looking at 12 months, these numbers were 85.6%, 2.72, and 0.50, respectively. Subgroup analysis for patients with diabetes mellitus and chronic kidney disease showed comparable results. The risk of amputation increased significantly when a measurement below 1.0 m/s2 was present (odd ratio 5.3, P = 0.010).

CONCLUSIONS

ACCmax measurements at the hallux can have additional prognostic value in patients with foot ulcers. An ACCmax below 1.0 m/s2 is associated with nonhealing of an ulcer and a higher risk of amputation, while higher ACCmax values are associated with limb salvage. Therefore, ACCmax could be used for grading ischemia in a wound classification system.

Effects of Lower Limb Revascularization on the Microcirculation of the Foot: A Retrospective Cohort Study

Background: Current assessment standards in chronic limb-threatening ischemia (CLTI) focus on macrovascular function while neglecting the microcirculation. Multispectral near-infrared spectroscopy (NIRS) provides hemodynamic characteristics of the microcirculation (i.e., capillaries) and may be a powerful tool for monitoring CLTI and preventing extremity loss. The aims of this study were to (1) investigate the effects of lower limb revascularization on the microcirculation and (2) determine if macrovascular and microvascular assessments correlate. Methods: An observational, retrospective cohort study of 38 endovascular interventions in 30 CLTI subjects was analyzed pre- and post-intervention for arterial Doppler acceleration times (AcT; macrovascular) and NIRS metrics (microvascular). Pre-intervention ankle-brachial index (ABI) was also analyzed. Results: AcT significantly decreased (p = 0.009) while oxyhemoglobin (HbO) significantly increased (p < 0.04) after endovascular intervention, indicating treatment efficacy. However, macrovascular measurements (ABI, AcT) and NIRS metrics of oxygenation and perfusion did not correlate (p > 0.06, r2 < 0.15, n = 23) indicating that macro- and microvascular assessment are not congruent. Conclusion: These findings suggest that macrovascular and microvascular assessments can determine interventional efficacy in their corresponding vasculature. Their lack of correlation, however, suggests the need for simultaneous assessment as independent use may cause diagnostic information to be missed.