The influence of diabetes on free flap transfer: II. The effect of ischemia on flap survival

Inducible Nitric Oxide Synthase and L-Arginine Optimizes Nitric Oxide Bioavailability in Ischemic Tissues Under Diabetes Mellitus Type 1

BACKGROUND

The mechanisms influencing the balance of nitric oxide (NO) bioavailability in tissues are negatively affected under diabetic and also under ischemic conditions. Free tissue transplantation for diabetic patients has to deal with both ischemic and diabetic circumstances, which lead to a significantly decrease in providing NO, thus increasing ischemia-reperfusion injury. In previous studies, we could prove that enhancing NO bioavailability leads to attenuated ischemia-reperfusion injury macrocirculatory and microcirculatory alterations in healthy and also in diabetes type 2 rats. This study is evaluating the role of inducible nitric oxide synthase in different dosages and L-arginine under diabetes type 1 conditions.

METHODS

Diabetic type 1 conditions were established via streptozotocin over a period of 4 weeks and verified via blood sugar, insulin, and C-peptide levels. Vascular pedicle isolated rat skin flap model that underwent 3 hours of ischemia was used. At 30 minutes before ischemia, normal saline, inducible nitric oxide synthase (NOS) (1/2 IE), and L-arginine (50 mg/kg body weight) were administered systemically. Ischemia/reperfusion (I/R)-induced alterations were measured 5 days after the operation.

RESULTS

The inducible NOS (iNOS) attenuated I/R-induced alterations under diabetic type 1 conditions significantly with vitality rates of 16.1% compared with control group (5.5%). Best results could be achieved with the combination of iNOS (1 IE) and L-arginine displaying vitality rates of 43%. Increased dosage of inducible nitric oxide (2 IE) led to decreased vitality rates (22.2%/27.4% without/with L-arginine).

CONCLUSIONS

Supporting the mechanisms of NO bioavailability via exogenous application of iNOS and L-arginine significantly attenuated I/R-induced alterations in a skin flap rat model. This pharmacologic preconditioning could be an easy and effective interventional strategy to uphold conversation of L-arginine to NO even on ischemic and type 1 diabetic conditions.

Diabetes is not associated with increased rates of free flap failure: Analysis of outcomes in 6030 patients from the ACS-NSQIP database

BACKGROUND

Diabetes affects a significant proportion of the population in the United States. Microsurgical procedures are common in this patient population, and despite many conflicting reports in the literature, there are no large studies evaluating the direct association between diabetes and outcomes, specifically failure, following free flap reconstruction. In this study, we sought to determine the impact of diabetes on postoperative outcomes following free flap reconstruction using a national multi-institutional database.

METHODS

We reviewed the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database to identify patients undergoing free flap reconstruction from 2010 to 2015. Preoperative variables and outcomes were compared between diabetic and nondiabetic patients. Univariate and multivariate analyses were performed to control for confounders.

RESULTS

We identified 6030 eligible patients. No significant difference in flap failure rates was observed. However, diabetic patients presented significantly higher rates of wound complications, including deep incisional surgical site infection (SSI) (OR = 1.35; P = .01) and wound dehiscence (OR = 1.17; P = .03). Diabetic patients also presented a significantly longer hospital length of stay (LOS) (β = .62; P < .001).

CONCLUSIONS

Our study evaluated the largest national cohort of free flap procedures. These results suggest that diabetes is not associated with increased rates of flap failure. However, diabetic patients are at significantly higher risk of postoperative deep incisional SSI, wound dehiscence, and longer LOS. Our findings provide the most concrete evidence to date in support of free flap reconstruction in diabetic patients, but highlight the need for heightened clinical vigilance and wound care for optimal outcomes.

Ghost cell odontogenic carcinoma on right mandible and its respective surgical reconstruction: a case report

Calcifying cystic odontogenic tumor (CCOT) is defined as an odontogenic cyst-like benign neoplasm that characteristically contains several ghost cells, ameloblastoma-like epithelium, and occasional calcification. Ghost cell odontogenic carcinoma (GCOC), a malignant form of CCOT, is an exceptionally rare malignant tumor. In this report, we present a case of a 53-year-old man whose chief complaint was a solitary mass on the right mandible area. The mass was completely removed through an extraoral surgical approach and reconstructive surgery was performed in two phases.

A Random-Pattern Skin-Flap Model in Streptozotocin Diabetic Rats

BACKGROUND

Flap operations are frequently performed in diabetic patients. Nevertheless, we could find no experimental study examining diabetes mellitus's effect on the flaps' survival. For this reason, we designed this study as a random-pattern skin-flap model of diabetic rats in 1999.

METHODS

We used 72 rats weighing about 200 g each. The animals were divided into 2 groups, 1 experimental (diabetic) and 1 control (nondiabetic). Following their diabetic periods, we elevated the rats' modified McFarlane flaps and measured their viable flap areas.

RESULTS

The mean percentage of the flap area surviving was 51.40% in the 2-week experimental group. It was 48.20% in the 4-week experimental group and 36.70% in the 8-week experimental group. The mean percentage of flap area surviving was 65.87% in the united control group (the total of all control groups). The mean surviving skin-flap area in the united control group was significantly higher than in the 4- and 8-week experimental groups. Moreover, the mean surviving flap area in the 8-week experimental group was significantly lower than in the 2-week and 4-week experimental groups.

CONCLUSIONS

Our study demonstrated that a 4-week diabetic duration for rats is sufficient to observe diabetes' deleterious effects on the flaps' viability. These effects were significantly established, however, after 8 weeks of diabetes. To obtain definitive results, at least 8 weeks of diabetic duration are preferred for similar studies.

Factors Associated with Anastomotic Failure after Microvascular Reconstruction of the Breast

The prevalence of anastomotic failure resulting in return to the operating room and flap necrosis after microvascular breast reconstruction ranges from 1 to 5 percent. The purpose of this study was to review a set of factors that may be associated with this occurrence. Microvascular reconstruction of the breast was performed in 198 women from January of 1998 to July of 2002. The mean age for all women was 47.7 years. There were 158 unilateral and 41 bilateral reconstructions, for a total of 240 flaps. The specific flaps included the free transverse rectus abdominis musculocutaneous flap (n = 176), the deep inferior epigastric perforator flap (n = 58), and the superior gluteal artery perforator flap (n = 6). Upon recognition of anastomotic failure, women were immediately returned to the operating room. Factors that were considered relevant to anastomotic failure included the choice of recipient vessel, timing of reconstruction, previous chest wall radiation therapy, previous axillary lymph node dissection, tobacco use, diabetes mellitus, patient age, and hematoma. Patient follow-up ranged from 5 to 59 months. Descriptive statistics, Fisher's exact test, and exact logistic regression were used for analyses and to summarize data. Of the 240 flaps, return to the operating room was necessary for 20 (8.3 percent), total necrosis occurred in nine (3.8 percent), and the rate of flap salvage was 55 percent (11 of 20 flaps). Venous occlusion was responsible for 16 of the 20 returns and eight of the nine failures. Statistical analysis demonstrated that both return to the operating room and flap necrosis were significantly associated with venous occlusion, delayed reconstruction, and hematoma. Previous lymph node dissection and previous radiation therapy had only a weak association with return to the operating room. The results of this study demonstrate that venous occlusion is responsible for return to the operating room and flap necrosis in the majority of cases. Age, tobacco use, choice of recipient vessel, and diabetes mellitus were not associated with anastomotic failure. The significance of delayed reconstruction may be related to its frequent association with previous lymph node dissection and/or radiation therapy resulting in perivascular fibrosis.

Recipient Vessel Analysis for Microvascular Reconstruction of the Head and Neck

The selection of recipient vessels that are suitable for microvascular anastomosis in the head and neck region is one of many components that is essential for successful free tissue transfer. The purpose of this study was to evaluate a set of factors that are related to the recipient artery and vein and to determine how these factors influence flap survival. A retrospective review of 102 patients over a 5-year consecutive period was completed. Indications for microvascular reconstruction included tumor ablation (n = 76), trauma (n = 13), and chronic wounds or facial paralysis (n = 13). The most frequently used recipient artery and vein included the facial, superficial temporal, superior thyroid, carotid, and jugular. Various factors that were related to the recipient vessels were analyzed and included patient age, recipient artery and vein, diabetes mellitus, tobacco use, the timing of reconstruction, the method of anastomosis, previous radiation therapy, creation of an arteriovenous loop, and use of an interposition vein graft. Successful free tissue transfer was obtained in 97 of 102 flaps (95%). Flap failure was the result of venous thrombosis in 4 and arterial thrombosis in 1. Statistical analysis demonstrated that anastomotic failure was associated with an arteriovenous loop (2 of 5, P = 0.03) and tobacco use (3 of 5, P = 0.03). Flap failure was not related to patient age, choice of recipient vessel, diabetes mellitus, previous irradiation, the method of arterial or venous anastomosis, use of an interposition vein graft, or the timing of reconstruction.

Free flap transplantation in mice

A new model is presented that adapts the standard experimental groin free flap model to the mouse. The femoral vessels upon which the microvascular anastomoses are based are very small (0.2-0.4 mm diameter in the artery), making this a technically challenging exercise. A 100% patency was achieved for flap replantation in ICR (outbred) mice. Success rates for flap transplantation in Balb/C (syngeneic) mice rose from 20 to 75% with modification of the anastomoses from end-to-end to end-to-side procedures. This model offers new avenues of investigation when combined with recently developed transgenic mouse models.

Rat strain differences in flap tolerance to ischemia

The rat epigastric island flap model is commonly used to explore ischemia-related phenomena. We sought to evaluate strain differences in tolerance to ischemia using two commonly used rat strains: Sprague-Dawley and Lewis. Epigastric flaps (3 x 6 cm) based on the superficial epigastric artery and vein were raised bilaterally in each rat (2 flaps/rat). Ischemia was induced for 10,12,14, or 16 hours by placing temporary occlusion clamps on each vessel of the vascular pedicle. Surviving flap areas were assessed planimetrically after 7 days. The average area of surviving flap tissue was greater in the Lewis rats for all ischemia times; this achieved significance for 12 hours and 14 hours of ischemia (P < 0.005). These findings indicate that comparisons among studies on rat flap ischemia must take into account the particular strain used. Furthermore, these findings suggest an inherent capacity of Lewis rat tissue to withstand ischemia better than tissue of the Sprague-Dawley rat strain.

Cutaneous manifestations of diabetes mellitus

Diabetes mellitus (DM) is a heterogeneous group of disorders characterized by a high serum glucose level and by disturbances of carbohydrate and lipid metabolism. It is estimated that 11 million persons in the United States have DM, 90% of whom have non-insulin-dependent DM. At least 30% of persons with diabetes have some type of cutaneous involvement during the course of their chronic disease. This review classifies the cutaneous findings in DM into four categories: (1) skin diseases with strong to weak association with DM; (2) cutaneous infections; (3) cutaneous manifestations of diabetic complications; and (4) skin reactions to diabetic treatment. Each of these categories is reviewed as well as the pathophysiology of the normal and diabetic basement membrane for a better understanding of the cutaneous manifestations of DM.

Effects of combined cold and hyperbaric oxygen storage on free flap survival

We have previously reported that hyberbaric oxygen (HBO) improved the survival rate of experimental free flaps. The purpose of this study was to evaluate the effects of combined hypothermia and HBO administered during storage on free flaps and on the xanthine oxidase system in rats. Epigastric skin flaps were stored cold for 48 and 72 hours either in room air or under HBO (2.9 atmospheres absolute, 100% oxygen) before free flap transfer. The success rates of free flaps were 80% (8/10) after 48 hours and 20% (2/10) after 72 hours of cold storage in room air. HBO produced no effect after 48 hours but significantly increased the success rate to 70% (7/10) after 72 hours of cold storage. Tissue hypoxanthine (plus xanthine) levels increased to 210% of normal after 48 hours of cold storage in room air and to 176% in HBO. Elevated hypoxanthine levels returned toward normal by 72 hours of cold storage in room air, while the increased levels remained under HBO. Xanthine oxidase activities significantly increased by 60 to 80% during 72 hours of room air storage. HBO treatment inhibited xanthine oxidase activity to 48% of normal by 72 hours of storage. Free flaps exhibited no significant alterations in GR and G6PDH activity after 48 hours of cold storage in room air or HBO. After 72 hours of cold storage, the room air control displayed a trend of decreasing GR activity and a significant 20% decrease in G6PDH activity, while HBO groups showed no significant alterations in both GR and G6PDH activity compared to normal. Protection of the antioxidative enzymes by hypothermia and inhibition of the xanthine oxidase activity by HBO appear to be one of the mechanisms of improved skin flap survival in free flaps.

Flap tolerance to ischaemia in streptozotocin-induced diabetes mellitus

The effects of diabetes mellitus (DM) on skin flap tolerance to 3 h of secondary venous ischaemia were evaluated. Epigastric island flaps were elevated 3, 6 and 12 weeks after induction of DM in rats. In the non-diabetic control groups, the flap survival was 85% in the 3-week group, 72% in the 6-week, and 78% in the 12-week. In untreated DM groups, the flap survival significantly decreased to 40% in the 3-week group, 25% in the 6-week, and 17% in the 12-week (P < 0.05 in all groups). Flap survival in the DM/insulin group decreased to 31% in the 3-week group. Effects of insulin therapy, however, were observed in later stages of DM: 71% and 62% survival in the 6- and 12-week group, respectively. Significant linear correlations between enzymatic responses and the flap survival were found. The results suggest that DM is detrimental to flap tolerance and is associated with the lack of metabolic responses to secondary ischaemia.

Effect of pre-existing health conditions on the results of reconstructive microvascular surgery

The effect of different pre-existing health conditions on the results of reconstructive microvascular surgery are reviewed. These conditions include: age, vital organ failure, diabetes, arterial and venous diseases, medications, smoking, wound healing disorders, epidermolysis bullosa, hematological diseases, multiple injury patients, pregnancy, and neuropsychiatric disease.