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Preoperative anemia predicts thrombosis and free flap failure in microvascular reconstruction.

AbstractPatients undergoing microvascular reconstruction are often anemic from a combination of iatrogenic hemodilution and acute blood losses. No major clinical study describes the impact of preoperative anemia on free flap morbidity. The plastic surgery service at a high-volume academic center performed 156 free flaps among 147 patients from December 2005 to December 2010. One hundred thirty-two had a preoperative hemoglobin (Hb) or hematocrit (Hct), with mean values of 11.8 ± 2.4 g/dL and 35.2% ± 7.0%, respectively. The overall failure rate was 9% (12/132), primarily from vascular thrombosis (6/12). Through logistic regression analysis, Hb and Hct were significant predictors of flap failure (P < 0.005) and vascular thrombosis (P < 0.05). Fisher exact test revealed a significant increase in failure risk at Hct level less than 30% (Hb < 10 g/dL) (relative risk, 4.76, P = 0.006), and probit analysis demonstrated an exposure-response relationship to decreased Hct level (P < 0.005). These findings support that preoperative anemia could significantly impact free flap morbidity.

A novel therapy to promote axonal fusion in human digital nerves.

BACKGROUND Peripheral nerve injury can have a devastating impact on our military and veteran population. Current strategies for peripheral nerve repair include techniques such as nerve tubes, nerve grafts, tissue matrices, and nerve growth guides to enhance the number of regenerating axons. Even with such advanced techniques, it takes months to regain function. In animal models, polyethylene glycol (PEG) therapy has shown to improve both physiologic and behavioral outcomes after nerve transection by fusion of a portion of the proximal axons to the distal axon stumps. The objective of this study was to show the efficacy of PEG fusion in humans and to retrospectively compare PEG fusion to standard nerve repair. METHODS Patients with traumatic lacerations involving digital nerves were treated with PEG after standard microsurgical neurorrhaphy. Sensory assessment after injury was performed at 1 week, 2 weeks, 1 month, and 2 months using static two-point discrimination and Semmes-Weinstein monofilament testing. The Medical Research Council Classification (MRCC) for Sensory Recovery Scale was used to evaluate the level of injury. The PEG fusion group was compared to patient-matched controls whose data were retrospectively collected. RESULTS Four PEG fusions were performed on four nerve transections in two patients. Polyethylene glycol therapy improves functional outcomes and speed of nerve recovery in clinical setting assessed by average MRCC score in week 1 (2.8 vs 1.0, p = 0.03). At 4 weeks, MRCC remained superior in the PEG fusion group (3.8 vs 1.3, p = 0.01). At 8 weeks, there was improvement in both groups with the PEG fusion cohort remaining statistically better (4.0 vs 1.7, p = 0.01). CONCLUSION Polyethylene glycol fusion is a novel therapy for peripheral nerve repair with proven effectiveness in animal models. Clinical studies are still in early stages but have had encouraging results. Polyethylene glycol fusion is a potential revolutionary therapy in peripheral nerve repair but needs further investigation. LEVEL OF EVIDENCE Therapeutic study, level IV.

The Clinical Role of Intraoperative Core Temperature in Free Tissue Transfer.

BackgroundLengthy microvascular procedures carry hypothermia risk, yet limited published data evaluate the overall impact of core temperature on patient and flap morbidity. Although hypothermia may contribute to complications, warming measures are challenged by conflicting reports of intraoperative hypothermia improving anastomotic patency. MethodsA retrospective review included all free flaps performed by plastic surgeons at an academic medical center from December 2005 to December 2010. Intraoperative core temperatures were measured by esophageal probe, and median values recorded over 5-minute intervals yielded a case mean (Tavg), maximum (Tmax), and nadir (Tmin). Outcomes included flap failure, pedicle thrombosis, recipient site infection and complications associated with patient, and flap morbidity. Analysis used Student t test, Fisher exact test, Probit, and logistic regression. ResultsOf 156 consecutive free tissue transfers, the median Tavg, Tmax, and Tmin were 36.5°C, 37.1°C, and 35.8°C, respectively. The flap failure rate was 7.7% (12/156) and pedicle thrombosis occurred in 9 (6%) cases. Core temperatures did not associate with overall flap failure or pedicle thrombosis but recipient site infection occurred in 21 (13%) patients who had significantly lower mean core temperatures (Tavg = 36.0°C, P < 0.01). Lower Tavg and Tmax significantly predicted recipient site infection (P < 0.01 and P < 0.05, respectively). Cut-point analysis revealed significant increases in recipient site infection risk at Tavg less than 37.0°C (P = 0.026) and Tmin less than or equal to 34.5°C (P = 0.020). ConclusionsIntraoperative hypothermia posed significant risk of flap infection with no benefit to anastomotic patency in free tissue transfer.

Adjuvant radiation therapy increases disease-free survival in stage IB Merkel cell carcinoma.

AbstractMerkel cell carcinoma (MCC) is a rare and aggressive cutaneous malignancy. Adjuvant radiation increases survival in advanced stages, but efficacy in stage I disease is unknown. A retrospective review included all patients treated for stage I MCC during a 15-year period at Vanderbilt University Medical Center. Among 42 patients, 26 (62%) had a negative sentinel lymph node biopsy (stage IA) and 16 (38%) had clinically negative lymph nodes (stage IB) at the time of resection. Analysis using Cox regression revealed that higher stage and absence of adjuvant radiation are associated with increased disease recurrence (hazard ratio, 6.29; P = 0.003 and hazard ratio, 4.69; P = 0.013, respectively). Controlling for stage, radiation therapy significantly increased disease-free survival among patients with stage IB disease (P = 0.0026) in a log-rank test comparing Kaplan-Meier curves. These findings support adjuvant radiation therapy in stage IB MCC patients with clinically negative lymph nodes who do not undergo sentinel lymph node biopsy.

Immediate Enhancement of Nerve Function Using a Novel Axonal Fusion Device After Neurotmesis

Background The management of peripheral nerve injuries remains a large challenge for plastic surgeons. With the inability to fuse axonal endings, results after microsurgical nerve repair have been inconsistent. Our current nerve repair strategies rely upon the slow and lengthy process of axonal regeneration (~1 mm/d). Polyethylene glycol (PEG) has been investigated as a potential axonal fusion agent; however, the percentage of axonal fusion has been inconsistent. The purpose of this study was to identify a PEG delivery device to standardize outcomes after attempted axonal fusion with PEG. Materials and Methods We used a rat sciatic nerve injury model in which we completely transected and repaired the left sciatic nerve to evaluate the efficacy of PEG fusion over a span of 12 weeks. In addition, we evaluated the effectiveness of a delivery devices ability to optimize results after PEG fusion. Results We found that PEG rapidly (within minutes) restores axonal continuity as assessed by electrophysiology, fluorescent retrograde tracer, and diffusion tensor imaging. Immunohistochemical analysis shows that motor axon counts are significantly increased at 1 week, 4 weeks, and 12 weeks postoperatively in PEG-treated animals. Furthermore, PEG restored behavioral functions up to 50% compared with animals that received the criterion standard epineurial repair (control animals). Conclusions The ability of PEG to rapidly restore nerve function after neurotmesis could have vast implications on the clinical management of traumatic injuries to peripheral nerves.

The correlation of matrix metalloproteinase 9-to-albumin ratio in wound fluid with postsurgical complications after body contouring.

Background: The authors’ earlier retrospective report of surgical complications after abdominal contouring surgery provided evidence that post–bariatric surgery patients are at increased risk of developing wound complications compared with a normal population. This prospective pilot study was designed as a comparative analysis of both surgical and wound healing characteristics between massive weight loss and normal patients who present for abdominal contouring surgery. Methods: Excisional wounds were created and polytetrafluoroethylene tubing was inserted during the preoperative period for later harvesting in patients undergoing abdominal contouring following Roux-en-Y gastric bypass for weight loss (n = 16) or abdominoplasty (n = 17). Wound fluids were sequentially collected from drains and subjected to matrix metalloproteinase (MMP) analysis. Standard postsurgical complications were documented. Results: Surgical complications were more common in weight loss patients (47 percent) than in control patients (25 percent). MMP analyses showed that MMP-9 levels remained significantly elevated at postoperative day 4 in patients who subsequently experienced complications in either the weight loss group (p = 0.02) or the control group (p = 0.03). Other parameters showed no significant differences between massive weight loss patients and controls. Conclusions: Although many markers were examined, the ratio of MMP-9 to albumin was the only predictor of postsurgical complications in any group. This lends further support to growing evidence that MMP-9 may be a useful biomarker of postsurgical complications. This pilot work showed no causal factors that explain the higher rates of postsurgical complications in the post–bariatric surgery patient population. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, II.

Abstract 221: SELECTIVE ENHANCEMENT OF AXONAL INGROWTH IN PROCESSED NERVE ALLOGRAFTS LOADED WITH NEUROTROPHIC FACTORS IN THE RAT SCIATIC NERVE MODEL

Background: Traumatic peripheral nerve injuries can result in lifelong disability. Primary nerve repair is used for short nerve defects. Autologous nerve can be used in longer defects but creates donor site morbidity. Nerve conduits lack an aligned internal scaffold to support and guide axonal regeneration. Peptide amphiphiles (PA) can self-assemble into aligned nano bers and promote peripheral nerve regeneration in vivo. Bioactive epitopes IKVAV (Ile-Lys-Val-Ala-Val) and RGDS (Arg-Gly-Asp-Ser) can be incorporated into PA nano bers and can promote cell adhesion, growth, and migration. There are no studies to date that examine the ability of PA nano bers to support the regeneration of injured nerves that supply the musculoskeletal system. In this preliminary study, we investigate the viability of rat Schwann cells after incorporation into PA gels.