Evaluating visual perception for assessing reconstructed flap health.

BACKGROUND: Detecting failing tissue flaps before they are clinically apparent has the potential to improve postoperative flap management and salvage rates. This study demonstrates a model to quantitatively compare clinical appearance, as recorded via digital camera, with spatial frequency domain imaging (SFDI), a noninvasive imaging technique using patterned illumination to generate images of total hemoglobin and tissue oxygen saturation (stO2). METHODS: Using a swine pedicle model in which blood flow was carefully controlled with occlusion cuffs and monitored with ultrasound probes, throughput was reduced by 25%, 50%, 75%, and 100% of baseline values in either the artery or the vein of each of the flaps. The color changes recorded by a digital camera were quantified to predict which occlusion levels were visible to the human eye. SFDI was also used to quantify the changes in physiological parameters including total hemoglobin and oxygen saturation associated with each occlusion. RESULTS: There were no statistically significant changes in color above the noticeable perception levels associated with human vision during any of the occlusion levels. However, there were statistically significant changes in total hemoglobin and stO2 levels detected at the 50%, 75%, and 100% occlusion levels for arterial and venous occlusions. CONCLUSIONS: As demonstrated by the color imaging data, visual flap changes are difficult to detect until significant occlusion has occurred. SFDI is capable of detecting changes in total hemoglobin and stO2 as a result of partial occlusions before they are perceivable, thereby potentially improving response times and salvage rates.

Role of coronary artery calcium score in identifying occult coronary artery disease in patients evaluated for deceased-donor liver transplant - a preliminary report.

Coronary artery disease may affect cirrhotic patients regardless of age and etiology of the underlying liver disease. Early identification of coronary artery disease is important to be able to achieve the best posttransplant outcomes and survival. The coronary artery calcium score can be used as a screening tool to supplement the results of cardiac stress tests to identify a subgroup of patients who may benefit from further investigation with coronary arteriogram. Arteriogram is an invasive test and may cause renal compromise and risk of bleeding associated with coagulopathy. The present retrospective study showed that coronary artery calcium score > 250 Agatston units may help select the subgroup of patients who will benefit from further investigation with cardiac catheterization, and determining this score may limit the risks of catheterization.

Diagnosing hepatitis C virus and improved outcomes in overall and kidney graft survival among simultaneous liver-kidney transplant recipients in the post-MELD era.

OBJECTIVES: We compared survival outcomes among simultaneous liver-kidney transplants after model for end-stage liver disease (MELD) according to their specific diagnosis and hepatitis C virus versus nonhepatitis C virus. MATERIALS AND METHODS: Clinical data review was performed for all patients who underwent combined liver-kidney transplants at Johns Hopkins Hospital from January 31, 1995, to October 31, 2012. Differences in demographics and characteristics among 2 groups were compared using independent samples t test. Survival analysis and distributions were calculated using Kaplan-Meier and Mantel-Cox log-rank test. RESULTS: Of 48 combined liver-kidney transplants, 31 simultaneous liver-kidney transplants cases were included; nonsimultaneous liver-kidney transplants and patients with prior transplants were excluded. Proportions of age, sex, ethnicity, pre-MELD score, pretransplant renal replacement therapy requirement, hypertension, diabetes mellitus, and follow-up were similar in both groups. Median follow-up was 30 months. Overall and graft survival rates among simultaneous liver-kidney transplants recipients in the pre-MELD era were significantly superior to simultaneous liver-kidney transplants patients in the post-MELD era (P = .0473). However, overall and graft survival rates among simultaneous liver-kidney transplants recipients who had hepatitis C virus and non-hepatitis C virus causes were not statistically different. CONCLUSIONS: We demonstrated a statistically significant difference in overall and kidney graft survival between the post-MELD era and the pre-MELD era. Subgroup analyses of this group showed no statistically significant difference in overall and kidney-graft survival when compared with their specific diagnosis of hepatitis C virus. This must be further studied and verified in a larger cohort of patients to fully identify the effect of hepatitis C virus infection in this group of patients because it can affect both liver and kidney grafts after transplant.

Quantitative assessment of partial vascular occlusions in a swine pedicle flap model using spatial frequency domain imaging.

The use of tissue transfer flaps has become a common and effective technique for reconstructing or replacing damaged tissue. While the overall failure rate associated with these procedures is relatively low (5-10%), the failure rate of tissue flaps that require additional surgery is significantly higher (40-60%). The reason for this is largely due to the absence of a technique for objectively assessing tissue health after surgery. Here we have investigated spatial frequency domain imaging (SFDI) as a potential tool to do this. By projecting wide-field patterned illumination at multiple wavelengths onto a tissue surface, SFDI is able to quantify absolute concentrations of oxygenated and deoxygenated hemoglobin over a large field of view. We have assessed the sensitivity of SFDI in a swine pedicle flap model by using a controlled vascular occlusion system that reduced blood flow by 25%, 50%, 75%, or 100% of the baseline values in either the vein or artery. SFDI was able to detect significant changes for oxygenated hemoglobin, deoxygenated hemoglobin, or tissue oxygen saturation in partial arterial occlusions of at least 50% and partial venous occlusions of at least 25%. This shows SFDI is sensitive enough to quantify changes in the tissue hemoglobin state during partial occlusions and thus has the potential to be a powerful tool for the early prediction of tissue flap failure.