Cardio-hepatic risk assessment by CMR imaging in liver transplant candidates.

BACKGROUND: The preoperative workup of orthotopic liver transplantation (OLT) patients is practically complex given the need for multiple imaging modalities. We recently demonstrated in our proof-of-concept study the value of a one-stop-shop approach using cardiovascular MRI (CMR) to address this complex problem. However, this approach requires further validation in a larger cohort, as detection of hepatocellular carcinoma (HCC) as well as cardiovascular risk assessment is critically important in these patients. We hypothesized that coronary risk assessment and HCC detectability is acceptable using the one-stop-shop CMR approach. METHODS: In this observational study, patients underwent CMRI evaluation including cardiac function, stress CMR, thoracoabdominal MRA, and abdominal MRI on a standard MRI scanner in one examination. RESULTS: Over 8 years, 252 OLT candidates underwent evaluation in the cardiac MRI suit. The completion rates for each segment of the CMR examination were 99% for function, 95% completed stress CMR, 93% completed LGE for viability, 85% for liver MRI, and 87% for MRA. A negative CMR stress examination had 100% CAD event-free survival at 12 months. A total of 63 (29%) patients proceeded to OLT. Explant pathology confirmed detection/exclusion of HCC. CONCLUSIONS: This study further defines the population suitable for the one-stop-shop CMR concept for preop evaluation of OLT candidates providing a road map for integrated testing in this complex patient population for evaluation of cardiac risk and detection of HCC lesions.

Exploratory use of cardiovascular magnetic resonance imaging in liver transplantation: a one-stop shop for preoperative cardiohepatic evaluation.

BACKGROUND: Preoperative cardiovascular risk stratification in orthotopic liver transplantation candidates has proven challenging due to limitations of current noninvasive modalities. Additionally, the preoperative workup is logistically cumbersome and expensive given the need for separate cardiac, vascular, and abdominal imaging. We evaluated the feasibility of a "one-stop shop" in a magnetic resonance suite, performing assessment of cardiac structure, function, and viability, along with simultaneous evaluation of thoracoabdominal vasculature and liver anatomy. METHODS: In this pilot study, patients underwent steady-state free precession sequences and stress cardiac magnetic resonance (CMR), thoracoabdominal magnetic resonance angiography, and abdominal magnetic resonance imaging (MRI) on a standard MRI scanner. Pharmacologic stress was performed using regadenoson, adenosine, or dobutamine. Viability was assessed using late gadolinium enhancement. RESULTS: Over 2 years, 51 of 77 liver transplant candidates (mean age, 56 years; 35% female; mean Model for End-stage Liver Disease score, 10.8; range, 6-40) underwent MRI. All referred patients completed standard dynamic CMR, 98% completed stress CMR, 82% completed late gadolinium enhancement for viability, 94% completed liver MRI, and 88% completed magnetic resonance angiography. The mean duration of the entire study was 72 min, and 45 patients were able to complete the entire examination. Among all 51 patients, 4 required follow-up coronary angiography (3 for evidence of ischemia on perfusion CMR and 1 for postoperative ischemia), and none had flow-limiting coronary disease. Nine proceeded to orthotopic liver transplantation (mean 74 days to transplantation after MRI). There were six ascertained mortalities in the nontransplant group and one death in the transplanted group. Explant pathology confirmed 100% detection/exclusion of hepatocellular carcinoma. No complications during CMR examination were encountered. CONCLUSIONS: In this proof-of-concept study, it appears feasible to perform a comprehensive, efficient, and safe preoperative liver transplant imaging in a CMR suite-a one-stop shop, even in seriously ill patients.

Isoflurane and desflurane uptake during liver resection and transplantation.

When reducing fresh gas flows, the course of the vaporizer dial settings required to maintain a constant end-expired concentration of a potent inhaled anesthetic becomes more dependent on the uptake pattern of the inhaled anesthetic. However, the uptake pattern of potent inhaled anesthetics during prolonged procedures remains poorly quantified. Therefore, we determined isoflurane and desflurane uptake (V(iso) and V(des), respectively) during liver resection (LR, n = 17) and orthotopic liver transplantation (OLT, n = 18) using a liquid injection closed-circuit anesthesia technique maintaining the end-expired concentration at 0.8% and 4.5%, respectively. Individual and average uptake curves were fit to a series of mathematical functions and compared with the square root of time and four-compartment models. Cumulative doses of isoflurane and desflurane after 1 and 3 h in the LR group and after 1, 3, and 8 h in the OLT group were correlated with demographic variables and each patient's average cardiac output and cardiac index. Average uptake was best described by a biexponential fit: V(iso) (LR) = 1.5 x (1 - e(-t x 0.525)) + 16.4 x (1 - e(-t x 0.00506)) (R(2) = 0.9996); V(iso) (OLT) = 1.4 + 3.1 x (1 - e(-t x 0.472)) + 26.7 x (1 - e(-t x 0.00307)) (R(2) = 0.9994); V(des) (LR) = 2.7 x (1 - e(-t x 0.763)) + 28.7 x (1 - e(-t x 0.00568)) (R(2) = 0.9984); and V(des) (OLT) = 1.4 x (1 - e(-t x 0.472)) + 26.7 x (1 - e(-t x 0.00307)) (R(2) = 0.9994). Uptake showed significant interindividual variability, and correlations between uptake variables and patient characteristics were inconsistent. The rate of uptake decreased more slowly then predicted by the uptake models. Because neither existing models nor patient characteristics accurately predict uptake in the individual patient, anesthesia techniques involving the use of low fresh gas flows will continue to have to rely on drug monitoring. However, the slowly decreasing rate of uptake during prolonged procedures suggests that the number of vaporizer adjustments to keep the end-expired concentration constant should be limited.

Effect of hemofiltration filter adsorption on circulating IL-6 levels in septic rats.

INTRODUCTION: Hemofiltration may modulate the inflammatory response in sepsis through a variety of mechanisms. We sought to distinguish clearance from adsorption as the principal mechanism responsible for reducing circulating IL-6 levels with hemofiltration. MATERIALS AND METHODS: Nine hours after cecal ligation and puncture in 18 adult male Sprague-Dawley rats, we divided the rats into three groups (6 animals each) and placed groups 2 and 3 on a hemofiltration circuit connected between the right carotid artery and femoral vein using an AN69 membrane. In the hemofiltration group (group 2), ultrafiltrate was replaced with lactated Ringer's solution; in the recirculation group (group 3), the ultrafiltrate was reinfused into the animal. A sham group (group 1) had an arteriovenous circuit inserted but no hemofiltration. Blood was obtained for measurement of IL-6 and tumor necrosis factor (TNF) at the start of hemofiltration and after 5 and 11 hours of treatment. RESULTS AND DISCUSSION: IL-6 levels increased only in the sham-treated animals (20.4 +/- 11.3 at baseline to 62.3 +/- 16.8 pg/ml at 11 hours, P = 0.03) (differences between groups 1 and 2, P = 0.015, and groups 1 and 3, P = 0.028). TNF levels were highly variable but not significantly different among the three groups. CONCLUSION: Hemofiltration-associated reductions in circulating IL-6 levels appear to be secondary to adsorption of mediators to the filter membrane. We do not know whether this is due to direct adsorption of IL-6 per se or to the absorption of other mediators with secondary downregulation of IL-6 production or release. In addition, we could not exclude an interaction between adsorption and hemofiltration.