INTRODUCTION:Previous studies have documented a high frequency of endotoxemia associated with cardiopulmonary bypass (CPB). Endotoxemia may be responsible for some of the complications associated with cardiac surgery. The purpose of the study was to examine the prevalence of endotoxemia during cardiopulmonary bypass supported aortocoronary bypass grafting surgery (ACB) using a new assay, the Endotoxin Activity Assay (EAA), and explore the association between endotoxemia and post-operative infection.METHODS:The study was a single center prospective observational study measuring EAA during the perioperative period for elective ACB. Blood samples were drawn at induction of anesthesia (T1), immediately prior to release of the aortic cross-clamp (T2), and on the first post-operative morning (T3). The primary outcome was the prevalence of endotoxemia. Secondary outcomes assessed included infection rates, intensive care unit (ICU) and hospital length of stay. An EAA of < 0.40 units was interpreted as "low", 0.41 to 0.59 units as "intermediate", and ≥ 0.60 units as "high".RESULTS:A total of 57 patients were enrolled and 54 patients were analyzable. The mean EAA at T1 was 0.38 +/- 0.14, at T2 0.39 +/- 0.18, and at T3 0.33 +/- 0.18. At T2 only 13.5% (7/52) of patients had an EAA in the high range. There was a positive correlation between EAA and duration of surgery (P = 0.02). In patients with EAA ≥ 0.40 at T2, 26.1% (6/23) of patients developed post-operative infections compared to 3.5% (1/29) of those that had a normal EAA (P = 0.0354). Maximum EAA over the first 24 hours was also strongly correlated with risk of post-operative infection (P = 0.0276).CONCLUSIONS:High levels of endotoxin occur less frequently during ACB than previously documented. However, endotoxemia is associated with a significantly increased risk of the development of post-operative infection. Measuring endotoxin levels during ACB may provide a mechanism to identify and target a high risk patient population.

Hemodilution in perioperative patients has been associated with neurological morbidity and increased mortality by undefined mechanisms. This study assesses whether hemodilutional anemia up-regulated inflammatory cerebral gene expression (microarray) to help define the mechanism.

Liver cirrhosis is associated with malnutrition and often, after liver transplantation, with the development of obesity and the inability to gain lean body mass. We have previously shown that peripheral blood mononuclear cell (PBMNC) complex I activity could be an appropriate marker for nutritional assessment. In this context, we hypothesized that a low pretransplant PBMNC complex I activity may predict a poor nutritional status in cirrhotic patients undergoing liver transplantation. Fifteen cirrhotic patients (CP) (8 men and 7 women) were recruited and investigated before and 4 months after liver transplantation. Body weight, body composition by DEXA, anthropometric measures (triceps skinfold thickness and midarm muscle circumference), resting energy expenditure, respiratory quotient and PBMNC complex I activity were measured on both time points. Patients were divided into 2 groups depending on their pretransplant PBMNC complex I activity (low vs high complex I activity [CP(low CI) vs CP(high CI)]), using as an arbitrary cutoff value-the mean complex I activity observed in age-matched healthy controls. Before transplantation, the CP(low CI) group who showed a lower complex I activity (2.11 +/- 0.53 vs 4.54 +/- 0.98 nmol/min per milligram of protein, P < .01) was significantly younger (44 +/- 9 vs 62 +/- 8 years old, P < .01); no differences were observed for any other nutritional parameters when compared to the CP(high CI) group. After transplantation, only the CP(low CI) group demonstrated a significant increase of complex I activity (+77%, P < .01), respiratory quotient (+10.5%, P < .02), triceps skinfold thickness (+126%, P < .005), and a significant decrease of fat-free mass (-8%, P < .01). In summary, our findings indicate that a low pretransplant PBMNC complex I activity in cirrhotic patients could be a useful marker of poor nutritional status despite the lack of traditional indicators of malnutrition by predicting metabolic disturbances and an inability to regain fat-free mass after liver transplantation.

BACKGROUND AND AIM:We evaluated the impact of triple nutrient supplementation (TNS: carnitine, taurine and coenzyme Q(10)) vs. carnitine alone (CARN) or placebo on survival, infarct size, cardiac function and metabolic gene expression using a model of myocardial infarction (MI) in rats. METHODS AND RESULTS:Male Wistar rats were randomized to three groups divided in two independent studies prior to ligation of the left anterior descending coronary artery (LAD): TNS vs. Placebo and TNS vs. CARN. Nutrient supplementation [L-carnitine (300 mg/day), coenzyme Q(10) (15 mg/kg body weight/day) and taurine (0.1M)] was administered daily for four weeks prior to and for 10 days after MI. At that time, cardiac function and infarct size were measured. Metabolic gene (mRNA) expression in the peri-infarct tissue of left ventricle from TNS, placebo or corresponding time-control rats (TNS or placebo without LAD ligation) was measured 10 days after MI. When compared to placebo, TNS significantly improved survival (60% vs. 34%, p<0.02), cardiac function, and reduced infarct size (30+/-7% vs. 42+/-9%, p<0.001). Although CARN improved survival like TNS (45% vs. 50%, not significant), it did not reduce infarct size (32+/-14% vs. 19+/-10%, p<0.05) or delay myocardial remodeling. In the placebo group, MI was associated with a significantly altered pattern of metabolic gene expression (glucose transporter 1, liver carnitine palmitoyl transferase 1, medium-chain acyl-CoA dehydrogenase; p<0.01 for all three) in the left ventricle peri-infarct tissue. In contrast, gene expression was normalized in the group receiving TNS. CONCLUSIONS:Our results support the potential cardioprotective impact of TNS during myocardial ischemia. In contrast to carnitine supplementation alone, TNS improved survival as well as cardiac function, gene expression and delayed remodeling.

INTRODUCTION: Renal failure is a serious complication of cardiopulmonary bypass (CPB) surgery, with significant morbidity and mortality¹.Anemia is an independent predictor of RF following CPB², possibly due to inadequate renal oxygen delivery.We investigated the effects of CPB and anemia on renal cortical and medullary tissue oxygen tension (pO2), blood flow (RBF) and eNOS protein expression.METHODS: With Animal Care Committee approval, anesthetized rats (ketamine, isoflurane, fentanyl, propofol) underwent 1h of normothermic CPB.Two groups of animals were studied in which the target hemoglobin concentration (Hb) was either 100g/L (CPB) or 65g/L (CPB-Anemia).Combined oxygen sensing microelectrodes and laser Doppler flow probes (Oxford Optronix) were placed in the renal cortex and medulla in each rat for simultaneous measurement of RBF and pO2.Absolute pO2 values (mmHg) or relative increases in RBF (%) were measured.Different groups of rats were sacrificed immediately after bypass, or 6h post-bypass, to assess renal eNOS expression by immunohistochemistry. Statistical analysis was performed using ANOVA on ranks and Mann-Whitney rank sum tests.RESULTS: There were no differences in physiologic variables between groups at baseline.Hb decreased from a baseline of 116±17 to 97±7 in the CPB group, and further decreased to 64±7 in the CPB-Anemia group (p<0.05).Basal renal cortical pO2 values (16.1±9.2mmHg) were higher than medullary pO2 values (4.9±3.0mmHg,n=8, p<0.001).Renal cortical pO2 decreased during CPB (7.0±3.6,n=4) and CPB-Anemia (6.9±5.2, n=4) (p=0.031).Renal medullary pO2 was decreased during CPB (2.7±1.7,n=4) and further decreased with CPB-Anemia (1.2±0.9, n=4) (p=0.015).Renal cortical and medullary blood flow did not change significantly during CPB but increased during CPB-Anemia (151±50% and 221±92%, n=8, p<0.05).Immunohistochemical analysis demonstrated eNOS staining in renal blood vessels immediately after CPB and increased eNOS staining 6 hours post-CPB in both groups (n=4).DISCUSSION: In this model, tissue pO2 was significantly lower in renal medulla compared with cortex prior to CPB.During CPB, pO2 was reduced in both renal cortex and medulla with maintained RBF.CPB with anemia caused a further reduction in renal medullary pO2, despite a significant increase in medullary blood flow.These data suggest that the renal medulla is more susceptible to hypoxic injury during CPB with anemia.Increased renal eNOS expression may play a role in mediating RBF during CPB and anemia.

Objective: Hemodilution and endothelial nitric oxide synthase genetic polymorphism may contribute to cerebral and renal injury after cardiopulmonary bypass. This study tested the hypothesis that cardiopulmonary bypass and anemia stimulate an increase in cerebral and renal endothelial nitric oxide synthase gene expression in an experimental model of cardiopulmonary bypass.Methods: Anesthetized rats underwent a sham procedure without cardiopulmonary bypass (sham, n = 5), normothermic bypass for 1 hour (CPB, n = 7), or bypass plus hemodilutional anemia (CPB anemia, n = 9). After 24 hours of recovery, RNA was extracted from the cerebral cortex, renal cortex, and renal medulla. Quantitative reverse transcriptase polymerase chain reaction was used to assess endothelial nitric oxide synthase messenger RNA levels in brain and kidney tissues.Results: The hemoglobin concentration of anemic CPB rats was significantly lower than that of nonanemic rats on bypass (64 +/- 5 vs 99 +/- 8 g(.)L(-1), P < .001). Cerebral cortical endothelial nitric oxide synthase messenger RNA levels were increased after cardiopulmonary bypass relative to those of the sham group (11.2 +/- 4.2 vs 6.3 +/- 1.5 fg, P = .031), without a further increase in anemic rats. Renal medullary endothelial nitric oxide synthase messenger RNA levels were significantly higher in the CPB anemia group than in the sham and CPB groups (7.1 +/- 4.4 fg vs 1.8 +/- 0.4 fg vs 3.0 +/- 0.6 fg, P < .001). Renal cortical endothelial nitric oxide synthase messenger RNA levels did not change significantly.Conclusions: Normothermic cardiopulmonary bypass was associated with higher endothelial nitric oxide synthase messenger RNA levels in kidney and brain than was the sham procedure 24 hours after cardiopulmonary bypass. Anemia accentuated the increase in renal medullary, but not cerebral cortical, endothelial nitric oxide synthase expression. These data provide an approach for exploring potential mechanisms by which endothelial nitric oxide synthase may contribute to renal and cerebral dysfunction after cardiopulmonary bypass and anemia.

INTRODUCTION: Renal failure (RF) occurs in up to 30% of patients undergoing cardiopulmonary bypass (CPB).Patients requiring dialysis have a 20-fold increase in mortality¹.Mechanisms of RF are not completely understood, although animal models have potentially identified anemia, hypoxia, ischemia, and acute inflammation².We investigated in rats the effect of CPB on renal gene expression using microarray analysis and on renal blood flow using laser doppler probes.METHODS: With ACC approval, Sprague-Dawley rats were anesthetized with ketamine and isoflurane.Study rats underwent normothermic CPB for 1 hour with a neonatal membrane oxygenator.Sham animals were instrumented but did not undergo CPB.Animals were sacrificed the next day and RNA was extracted from renal cortex and medulla.In separate experiments, OxyFlo laser doppler microvascular perfusion probes (Oxford Optronix) were placed under direct vision to measure relative blood flow in renal cortex and medulla.Gene expression was measured using Affymetrix GeneChip Rat 230.2, GeneSpring filtering, and GeneSifter analysis.A 2-fold change in gene expression compared to sham was considered significant.Physiologic data was analyzed using ANOVA.RESULTS: There were no significant differences between groups in physiologic variables.Blood flow data were normalized to pre-CPB, expressed as percent±SD.During CPB, blood flow was unchanged in both cortex (95±37%) and medulla (96±18%) (n=4).Microarray analysis identified 2-fold changes in the expression of 787 genes in cortex and 883 in medulla (n=2).Of these genes, over 50% were involved in physiological processes: metabolism (195 vs 161 genes, cortex vs medulla), stress response (43,36), inflammation (11,10), and nitric oxide pathway (5,1).Data for selected genes associated with hypoxia, ischemia and inflammation are shown in the table, expressed as fold-change compared to sham (mean±SD).Of genes associated with hypoxia and ischemia, kidney injury molecule 1 (KIM-1) was significantly up-regulated while neutrophil gelatinase-associated lipocalin (NGAL) was significantly downregulated.Up-regulation of inflammation-related genes also occurred after CPB.These include tumor necrosis factor (TNF) receptor-12, glycosylation-dependent cell adhesion molecule-1 (GlyCAM-1), and ICAM-1.DISCUSSION: In this model, CPB was associated with altered regulation of genes associated with mechanisms of RF. 24 hours post-CPB, acute inflammatory genes and KIM-1, a marker of acute ischemic injury, were significantly up-regulated despite maintenance of renal blood flow during CPB.Future research will identify the cellular localization and time course of renal gene expression, and the effect of other common interventions during CPB.This will further enhance our understanding of the mechanism of renal dysfunction associated with CPB.

INTRODUCTION Acute renal failure is one of the major complications of cardiac surgery and CPB, occurring in approximately 5% of patients. Postoperative renal dysfunction increases the risk of mortality more than 20 fold, and triples the hospitalization costs. Although the mechanism is not clear, lower hematocrit and urine pO2 level are predictive of renal injury, suggesting that reduced oxygen delivery may be important. Hypoxia is known to cause changes in expression of a number of genes, including NOS (nitric oxide synthase) and VEGF (vascular endothelial growth factor). The purpose of this study was to determine if CPB results in hypoxic gene expression in the kidney.