Sympathetic innervation does not contribute to glycerol release in ischemic flaps

The emerging role of microdialysis in diabetic patients undergoing amputation for limb ischemia

Lower limb ischemia in diabetic patients is a result of macro- and microcirculation dysfunction. Diabetic patients undergoing limb amputation carry high mortality and morbidity rates, and decision making concerning the level of amputation is critical. Aim of this study is to evaluate a novel microdialysis technique to monitor tissue microcirculation preoperatively and predict the success of limb amputation in such patients. Overall, 165 patients with type 2 diabetes mellitus undergoing lower limb amputation were enrolled. A microdialysis catheter was placed preoperatively at the level of the intended flap for the stump reconstruction, and the levels of glucose, glycerol, lactate and pyruvate were measured for 24 consecutive hours. Patients were then amputated and monitored for 30 days regarding the outcome of amputation. Failure of amputation was defined as delayed healing or stump ischemia. Patients were divided into two groups based on the success of amputation. There was no difference between the two groups regarding gender, ASA score, body mass index, comorbidities, diagnostic modality used, level of amputation, as well as glucose, glycerol, and pyruvate levels. However, local concentrations of lactate were significantly different between the two groups and lactate/pyruvate (L/P) ratio was independently associated with failed amputation (threshold defined at 25.35). Elevated preoperative tissue L/P ratio is independently associated with worse outcomes in diabetic patients undergoing limb amputation. Therefore, preoperative tissue L/P ratio could be used as a predicting tool for limb amputation's outcome, although more clinical data are needed to provide safer conclusions.

Ischemic injury of the liver in a porcine model of cardiac death assessed by in vivo microdialysis

This study aims to evaluate the ischemic injury of the liver in a porcine model of cardiac death assessed by in vivo microdialysis. A porcine model of cardiac death was established by the suffocation method. Metabolic indicators were monitored using the microdialysis technique during warm ischemia time (WIT) and cold ischemia time (CIT). Pathological changes in ischemic-injured livers were observed by haematoxylin-eosin staining. The predictive values of biochemical parameters regarding the liver donor were evaluated by receiver operating characteristic curve analysis. All statistical analyses were conducted using the SPSS 18.0 software (SPSS Inc, Chicago, Illinois, USA). The degree of warm ischemic injury of the livers increased with prolonged WIT. Serum glucose, glycerol, pyruvate, lactic acid levels and lactate-to-pyruvate (L/P) ratio increased gradually during WIT. Results from Pearson correlation analyses indicated that serum lactate level and L/P ratio were positively associated with the degree of warm ischemic injury of the livers. The degree of cold ischemic injury of the livers gradually increased after 12 h CIT. Serum glucose, lactic acid and L/P ratio achieved a peak after 6-8 h of CIT, but gradually decreased with prolonged CIT. The peak of glycerol occurred after 8 h of CIT, while no changes were found with prolonged CIT. Serum pyruvate level exhibited an increasing trend after 12 h CIT. Our results confirmed that serum glucose and lactate levels were negatively correlated with cold ischemic injury of the liver. However, serum glycerol and pyruvate levels showed positive correlations with cold ischemic injury of the liver. The liver donor was unavailable after 30 min WIT and 24 h CIT. The cut-off value of serum lactate level for warm ischemic injury of the livers was 2.374 with a sensitivity (Sen) of 90 % and specificity (Spe) of 95 %; while the L/P radio was 0.026 (Sen = 80 %, Spe = 83 %). In addition, the cut-off values of serum glucose, lactate, glycerol and pyruvate levels for cold ischemic injury of the livers were 0.339 (Sen = 100 %, Spe = 77 %), 1.172 (Sen = 100 %, Spe = 61 %), 56.359 (Sen = 100 %, Spe = 65 %) and 0.020 (Sen = 100 %, Spe = 67 %), respectively. Our findings provide empirical evidences that serum glucose, lactate levels and L/P ratio may be good indicators for the degree of warm ischemic injury of the livers after cardiac death; while serum glucose, lactate, glycerol and pyruvate levels may be important in predicting cold ischemic injury.