Prevention of Venous Thromboembolism in Microvascular Surgery Patients Using Weight-Based Unfractionated Heparin Infusions

Background Unfractionated heparin infusions are commonly used in microvascular surgery to prevent microvascular thrombosis. Previously, fixed-dose heparin infusions were believed to provide sufficient venous thromboembolism (VTE) prophylaxis; however, we now know that this practice is inadequate for the majority of patients. Anti-factor Xa (aFXa) level is a measure of unfractionated heparin efficacy and safety. This study evaluated the pharmacodynamics of weight-based dose heparin infusions and the impacts of real-time aFXa-guided heparin dose adjustments. Methods This prospective clinical trial enrolled adult microvascular surgery patients who received a weight-based heparin dose following a microsurgical procedure. Steady-state aFXa levels were monitored, and patients with out-of-range levels received dose adjustments. The study outcomes assessed were aFXa levels at a dose of heparin 10 units/kg/hour, time to adequate aFXa level, number of dose adjustments required to reach in-range aFXa levels, and clinically relevant bleeding and VTE at 90 days. Results Twenty-one patients were prospectively recruited, and usable data were available for twenty patients. Four of twenty patients (20%) had adequate prophylaxis at a heparin dose of 10 units/kg/hour. Among patients who received dose adjustments and achieved in-range aFXa levels, the median number of dose adjustments was 2 and the median weight-based dose was 11 units/kg/hour. The percentage of patients with in-range levels was significantly increased (65 vs. 15%, p = 0.0002) as a result of real-time dose adjustments. The rate of VTE at 90 days was 0%, and clinically relevant bleeding rate at 90 days was 15%. Conclusion Weight-based heparin infusions at a rate of 10 units/kg/hour provide a detectable level of anticoagulation for some patients following microsurgical procedures, but most patients require dose adjustment to ensure adequate VTE prophylaxis.

Microvascular cover in the lower limbIndications and timing, flap types, and technique

Providing adequate and timely soft tissue cover is essential in the treatment of injuries to the lower extremity. Microvascular free tissue transfer is a part of the algorithm of treatment. Free flaps provide the desired quantity and quality of well-vascularized tissue from numerous potential donor sites all over the body, tailored to each specific defect. Microvascular surgery allows single-stage reconstruction of composite defects and is best done early, where possible in the first 24 hours or failing this, during the first week after injury. Free tissue transfer is a complex interdisciplinary procedure and can fail in up to 5% of cases. It is not appropriate for all patients. Free muscle, or musculocutaneous, flaps are ideal for coverage of diaphyseal defects whereas free fasciocutaneous flaps are better for coverage of metaphyseal defects. Perforator free flaps experience little donor site morbidity.

Wire Myography for Continuous Estimation of the Optimal Concentration of Topical Lidocaine as a Vasodilator in Microsurgery

Background Intraoperative vasospasm during reconstructive microvascular surgery is often unpredictable and may lead to devastating flap loss. Therefore, various vasodilators are used in reconstructive microsurgery to prevent and relieve vasospasm. Lidocaine is a vasodilator commonly used in microvascular surgery. Although many reports have described its in vitro and in vivo concentration-dependent vasodilatory effects, limited studies have examined the pharmacological effects of lidocaine on blood vessels in terms of persistence and titer. Methods In this study, the vasodilatory effect of lidocaine was examined by using the wire myograph system. Abdominal aortas were harvested from female rats, sliced into rings of 1-mm thickness, and mounted in the wire myograph system. Next, 10, 5, 2, and 1% lidocaine solutions were applied to the artery, and the change in vasodilation force, persistence of the force, and time required to reach equilibrium were measured. Results The vasodilatory effect was confirmed in all groups following lidocaine treatment. Although strong vasodilation was observed in the 10% lidocaine group, it was accompanied by irreversible degeneration of the artery. Vasodilation in the 1% lidocaine group was weaker than that in the other groups 500 seconds after lidocaine addition (p < 0.05). Between the 5 and 2% lidocaine groups, 5% lidocaine showed a stronger vasodilatory effect 400 to 600 seconds after lidocaine addition (p < 0.01); however, there was no significant difference in these groups after 700 seconds. Additionally, there was no difference in the time required for the relaxation force to reach equilibrium among the 5, 2, and 1% lidocaine groups. Conclusion Although our study confirmed the dose-dependent vasodilatory effect of lidocaine, 5% lidocaine showed the best vasodilatory effect and continuity with minimal irreversible changes in the arterial tissue.

Epoprostenol & Its Use in Microvascular Surgery – A Useful Aid to Flap Salvage Secondary to Recalcitrant Vasospasm?

Systemic intravenous epoprostenol, as well as being a vasodilator, is the most potent inhibitor of platelet aggregation known. Early research carried out on its use in microvascular surgery showed promising results in preventing thrombosis and improving flap survival rates, however interest in its use in microsurgery has diminished in recent years. In this report we describe its use in successful free flap salvage and discuss its role in microsurgery.

Vasodilation by Verapamil-Nitroglycerin Solution in Microvascular Surgery

Objective Papaverine is a topical vasodilator commonly used during microvascular surgery to inhibit undesired vasoconstriction. A previous national shortage of papaverine prompted evaluation of an alternative, effective vasodilator. This study aims to assess the experience of a solution of verapamil and nitroglycerin (VG) as a potential alternative pharmacologic vasodilator. Study Design Retrospective case series. Setting Two tertiary academic medical centers. Subjects and Methods Among 298 patients, 306 consecutive free tissue transfers performed between 2014 and 2017 for head and neck defect reconstruction utilized a VG solution. Patient and flap characteristics, intraoperative patient and flap complications, and postoperative complications were reviewed. Diameter of the cervical recipient artery was measured intraoperatively before and after topical application of the VG solution in a subset of 43 patients (44 flaps). Results Flaps included fibula, radial forearm, subscapular system, and anterolateral thigh. In total, 3 (0.98%) flaps failed with varied etiology unrelated to the VG solution (venous thrombosis, arterial anastomosis thrombosis, physical damage to the perforator). Specific to topical application of the VG solution, the mean recipient artery diameter increased from 2.1 to 3.1 mm, a 48% increase ( P < .01). There were no intraoperative cardiac events or complications attributable to the VG solution. Conclusion We describe the use of a VG solution for pharmacologic vasodilation during microvascular free tissue transfer. Its use was associated with an acceptable incidence of adverse events, none of which were directly attributable to the VG solution. Apparent and sustained vasodilation was demonstrated. The VG solution represents a safe and efficacious alternative to papaverine in microvascular surgery.