The effect of hyperbaric oxygen on compromised grafts and flaps.

The use of grafts and flaps serves as an integral tool in the armamentarium of the reconstructive surgeon. Proper planning and surgical judgment are critical in the ultimate success of these procedures. However, there are situations when grafts and/or flaps can become compromised and require urgent intervention for salvage. These instances can include irradiated or otherwise hypoxic wound beds, excessively large harvested grafts, random flap ischemia, venous or arterial insufficiency, and ischemia-reperfusion injury. Alternatively, compromised grafts and flaps can be inadvertently created secondary to trauma. It is in these types of cases, hyperbaric oxygen (HBO2) therapy can serve as a useful adjunct in the salvage of compromised flaps and grafts. This review outlines the extensive basic science and clinical evidence available in support of the use of HBO2 therapy for compromised grafts and flaps. The literature demonstrates the benefit of adjunctive HBO2 therapy for multiple types of grafts and flaps with various etiologies of compromise. HBO2 therapy can enhance graft and flap survival by several methods including decreasing the hypoxic insult, enhancing fibroblast function and collagen synthesis, stimulating angiogenesis and inhibiting ischemia-reperfusion injury. The expedient initiation of hyperbaric oxygen therapy as soon as flap or graft compromise is identified maximizes tissue viability and ultimately graft/flap salvage.

Hyperbaric Oxygen Therapy for the Compromised Graft or Flap.

Significance: Tissue grafts and flaps are used to reconstruct wounds from trauma, chronic disease, tumor extirpation, burns, and infection. Despite careful surgical planning and execution, reconstructive failure can occur due to poor wound beds, radiation, random flap necrosis, vascular insufficiency, or ischemia-reperfusion (IR). Traumatic avulsions and amputated composite tissues-compromised tissue-may fail from crush injury and excessively large sizes. While never intended, these complications result in tissue loss, additional surgery, accrued costs, and negative psychosocial patient effects. Recent Advances: Hyperbaric oxygen (HBO) has demonstrated utility in the salvage of compromised grafts/flaps. It can increase the likelihood and effective size of composite graft survival, improve skin graft outcomes, and enhance flap survival. Mechanisms underlying these beneficial effects include increased oxygenation, improved fibroblast function, neovascularization, and amelioration of IR injury. Critical Issues: Common strategies for the compromised graft or flap include local wound care, surgical debridement, and repeated reconstruction. These modalities are associated with added costs, time, need for reoperation, morbidity, and psychosocial effects. Preservation of the amputated/avulsed tissues minimizes morbidity and maximizes the reconstructive outcome by salvaging the compromised tissue and obviating additional surgery. HBO is often overlooked as a potential tool that can limit these issues. Future Directions: Animal studies demonstrate a benefit of HBO in the treatment of compromised tissues. Clinical studies support these findings, but are limited to case reports and series. Further research is needed to provide multicenter prospective clinical studies and cost analyses comparing HBO to other adjunctive therapies in the treatment of compromised grafts/flaps.

Lidocaine-induced ASC apoptosis (tumescent vs. local anesthesia).

BACKGROUND: The purpose for the present study was to determine which anesthetic method, local anesthesia versus tumescent, is superior for liposuction in terms of adipose-derived stem cell (ASC) survival in lipoaspirate; which component, lidocaine versus lidocaine with epinephrine, in anesthetic solutions could affect ASC survival; and which mechanism, necrosis versus apoptosis, is involved in lidocaine-induced ASC death. METHODS: Human lipoaspirates were harvested using standard liposuction technique. Individuals scheduled for liposuction on bilateral body areas gave consent and were included in the study. On one area, liposuction was conducted under local anesthesia with lidocaine/epinephrine. On the contralateral area, liposuction was accomplished with tumescent wetting solution containing lidocaine/epinephrine. Lipoaspirates were processed for the isolation of stromal vascular fraction (SVF). ASC survival was determined by the number of adherent ASCs after 24 h of SVF culture. Lidocaine dose-response (with or without epinephrine) on cultured ASCs was examined. Lidocaine-induced ASC apoptosis and necrosis was determined by Annexin V-FITC/Propidium Iodide (PI) assay and analyzed by flow cytometry. RESULTS: All of the participants were female adults. The average age was 45 ± 4.0 years (±SEM) and the average BMI was 28 ± 1.0 (±SEM). Lipoaspirate samples (n = 14) treated by local anesthesia (n = 7/group) or tumescent anesthesia (n = 7/group) were investigated. Liposuction sites were located in the hip or thigh. The average number of adherent ASCs was 1,057 ± 146 k in the local anesthesia group, which was significantly lower than the 1,571 ± 111 k found in the tumescent group (P = 0.01). ASC survival was significantly lower in the lidocaine group and in a dose-dependent manner as compared to the correspondent PBS controls (P < 0.05 or P < 0.01). ASC survival was significantly lower in both the lidocaine and lidocaine with epinephrine groups when compared to PBS controls. Annexin/PI assay showed that ASC apoptosis (but not necrosis) in the lidocaine group was significantly higher than that in the corresponding PBS control (P = 0.026). CONCLUSIONS: Tumescent anesthesia is the superior method for liposuction with respect to ASC preservation compared to local anesthesia. Lidocaine could cause significant ASC apoptosis.

The effect of hyperbaric oxygen on nitric oxide synthase activity and expression in ischemia-reperfusion injury.

BACKGROUND: Hyperbaric oxygen (HBO) mitigates ischemia-reperfusion (IR) injury via a nitric oxide mechanism that is nitric oxide synthase (NOS) dependent. The purpose of this study was to investigate this NOS-dependent mechanism by examining isoform-specific, tissue-specific, and time-specific upregulation of NOS mRNA, protein, and enzymatic activity. METHODS: We raised a gracilis flap in Wistar rats that were separated into early and late phases. Treatment groups included nonischemic control, IR, HBO-treated ischemia-reperfusion (IR-HBO), and nonischemic HBO control. We harvested tissue-specific samples from gracilis, rectus femoris, aorta, and pulmonary tissues and processed them by reverse transcription polymerase chain reaction and Western blot to determine upregulation of isoform-specific NOS mRNA and protein. We also harvested tissue for NOS activity to investigate upregulation of enzymatic activity. Data are presented as mean ± standard error of the mean with statistics performed by analysis of variance. P ≤ 0.05 was considered significant. RESULTS: There was no increase in NOS mRNA in the early phase. In the late phase, there was a significant increase in endothelial-derived NOS (eNOS) mRNA in IR-HBO compared with IR in gracilis muscle (79.4 ± 22.3 versus 36.1 ± 4.5; P < 0.05) and pulmonary tissues (91.0 ± 31.2 versus 30.2 ± 3.1; P < 0.01). There was a significant increase in the late-phase eNOS pulmonary protein IR-HBO group compared with IR (235.5 ± 46.8 versus 125.2 ± 14.7; P < 0.05). Early-phase NOS activity was significantly increased in IR-HBO compared with IR in pulmonary tissue only (0.049 ± 0.009 versus 0.023 ± 0.003; P < 0.05). CONCLUSIONS: The NOS-dependent effects of HBO on IR injury may result from a systemic effect involving an early increase in eNOS enzymatic activity followed by a late-phase increase in eNOS protein expression within the pulmonary tissues.

Pneumomediastinum following hyperbaric oxygen therapy for carbon monoxide poisoning: case report.

A 5-year-old boy trapped in a house fire was transported to the emergency department, unconscious with suspected carbon monoxide poisoning. The patient underwent a difficult intubation, but did not initially demonstrate any radiographic abnormalities. The patient remained intubated and underwent hyperbaric oxygen therapy using the carbon monoxide treatment protocol. Immediate post-therapy chest radiograph revealed the development of occult pneumomediastinum. The patient remained stable on positive-pressure ventilation and the pneumomediastinum resolved spontaneously. The patient was extubated on post-injury Day #2 and was discharged post-injury Day #4 with no residual clinical sequelae. The development of pneumomediastinum associated with hyperbaric oxygen therapy for carbon monoxide poisoning appears to be a rare phenomenon. However, clinicians should be aware of the risk factors that predispose patients to developing pneumomediastinum and have a low threshold for obtaining routine pre- and post-procedure screening chest radiographs in intubated and critically ill patients, particularly in children.

The effect of hyperbaric oxygen on compromised grafts and flaps.

The use of grafts and flaps serves as an integral tool in the armamentarium of the reconstructive surgeon. Proper planning and surgical judgment are critical in the ultimate success of these procedures. However, there are situations when grafts and/or flaps can become compromised and require urgent intervention for salvage. These instances can include irradiated or otherwise hypoxic wound beds, excessively large harvested grafts, random flap ischemia, venous or arterial insufficiency and ischemia-reperfusion injury. Alternatively, compromised grafts and flaps can be inadvertently created secondary to trauma. It is in these types of cases that hyperbaric oxygen therapy (HBO2T) can serve as a useful adjunct in the salvage of compromised flaps and grafts. This review outlines the extensive basic science and clinical evidence available in support of the use of HBO2T for compromised grafts and flaps. The literature demonstrates the benefit of adjunctive HBO2T for multiple types of grafts and flaps with various etiologies of compromise. HBO2T can enhance graft and flap survival by several methods including decreasing the hypoxic insult, enhancing fibroblast function and collagen synthesis, stimulating angiogenesis and inhibiting ischemia-reperfusion injury. The expedient initiation of hyperbaric oxygen therapy as soon as flap or graft compromise is identified maximizes tissue viability and ultimately graft/flap salvage.

Nitrite attenuates ischemia-reperfusion-induced microcirculatory alterations and mitochondrial dysfunction in the microvasculature of skeletal muscle.

BACKGROUND: Recently, nitrite has been rediscovered as a physiologically relevant storage reservoir of nitric oxide in blood and it can readily be converted to nitric oxide under hypoxic and acidic conditions. In this study, the authors evaluated the therapeutic efficacy of nitrite on reperfusion-induced microcirculatory alterations and mitochondrial dysfunction in the microvasculature of skeletal muscle. METHODS: The authors used a vascular pedicle isolated rat cremaster model that underwent 4 hours of warm ischemia followed by 2 hours or 17 hours of reperfusion. At 5 minutes before reperfusion, normal saline, sodium nitrite (0.20 µM/minute/kg), or nitrite mixed with 2-(4-carboxyphenyl)-4,5-dihydro-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl (potassium salt) (0.2 mg/minute/kg) was infused into the microcirculation of ischemic cremaster by means of intraarterial infusion. Ischemia-reperfusion-induced microcirculatory alterations were measured after 2 hours of reperfusion. Microvasculature of the cremaster muscle including the vascular pedicle was harvested to determine the mitochondrial dysfunction. The blood concentration of methemoglobin was also measured to determine the toxicity of nitrite. RESULTS: The authors found that nitrite significantly attenuated ischemia-reperfusion-induced vasoconstriction, arteriole stagnation, and capillary no-reflow in the early phase of reperfusion and the depolarization of mitochondrial membrane potential and cytochrome c release in the late phase of reperfusion. Nitrite-induced protection was significantly blocked by a nitric oxide scavenger (potassium salt). The methemoglobin results showed that the doses of nitrite we used in the present study were safe. CONCLUSION: The supplementation of a low dose of nitrite, directly into the microcirculation of ischemic muscle through local intraarterial infusion, significantly attenuated ischemia-reperfusion-induced microcirculatory alterations in vivo and mitochondrial dysfunction in vitro in the microvasculature of skeletal muscle.

Microcirculatory effects of melatonin in rat skeletal muscle after prolonged ischemia.

The purpose of this study was to determine microcirculatory effects and response of nitric oxide synthase (NOS) to melatonin in skeletal muscle after prolonged ischemia. A vascular pedicle isolated rat cremaster muscle model was used. Each muscle underwent 4 hr of zero-flow warm ischemia followed by 2 hr of reperfusion. Melatonin (10 mg/kg) or saline as a vehicle was given by intraperitoneal injection at 30 min prior to reperfusion and the same dose was given immediately after reperfusion. After reperfusion, microcirculation measurements including arteriole diameter, capillary perfusion and endothelial-dependent and -independent vasodilatation were performed. The cremaster muscle was then harvested to measure endothelial NOS (eNOS) and inducible NOS (iNOS) gene expression and enzyme activity. Three groups of rats were used: sham-ischemia/reperfusion (I/R), vehicle + I/R and melatonin + I/R. As compared with vehicle + I/R group, administration of melatonin significantly enhanced arteriole diameter, improved capillary perfusion, and attenuated endothelial dysfunction in the microcirculation of skeletal muscle after 4 hr warm ischemia. Prolonged warm ischemia followed by reperfusion significantly depressed eNOS gene expression and constitutive NOS activity and enhanced iNOS gene expression. Administration of melatonin did not significantly alter NOS gene expression or activity in skeletal muscle after prolonged ischemia and reperfusion. Melatonin provided a significant microvascular protection from reperfusion injury in skeletal muscle. This protection is probably attributable to the free radical scavenging effect of melatonin, but not to its anti-inflammatory effect.