Propofol cardioprotection for on-pump aortocoronary bypass surgery in patients with type 2 diabetes mellitus (PRO-TECT II): a phase 2 randomized-controlled trial.

PURPOSE: The efficacy of myocardial conditioning strategies is compromised in patients with advanced age, diabetes, or low ejection fraction. We conducted a single-centre parallel-arm blinded randomized-controlled trial to determine whether propofol provides perioperative myocardial protection. METHODS: Patients enrolled in this study were scheduled for primary aortocoronary bypass surgery utilizing normothermic cardiopulmonary bypass (CPB) with blood cardioplegia. The participants were stratified by diabetic status and left ventricular ejection fraction and randomly assigned to receive either an elevated dose of propofol -previously associated with experimental cardioprotection- or an isoflurane preconditioning regime. The primary endpoint was the coronary sinus (CS) concentration of 15-F2t-isoprostane (isoP). Secondary endpoints included in-hospital low cardiac output syndrome (LCOS) and major adverse cardiac events, 12- and 24-hr CS cardiac troponin I (cTnI) release, and myocardial B-cell lymphoma 2 (Bcl-2) protein expression. RESULTS: Data were analyzed from 125 of 137 randomized participants. Participants receiving propofol experienced a greater mean (SD) increase from baseline in CS 15-F2t-isoP levels compared with those receiving isoflurane [26.9 (10.9) pg·mL(-1) vs 12.1 (10.4) pg·mL(-1), respectively; mean difference, 14.8; 95% confidence interval (CI), 11.0 to 18.6; P < 0.001] but a decreased incidence of LCOS (20.9% vs 57.1%, respectively; relative risk [RR],0.37; 95% CI, 0.22 to 0.62; P < 0.001). The incidence of LCOS was similar between groups in participants without type 2 diabetes mellitus (DM2) (P = 0.382) but significantly decreased in the propofol DM2 subgroup compared with the isoflurane DM2 subgroup (17.9% vs 70.3%, respectively; RR, 0.26; 95% CI, 0.13 to 0.52; P < 0.001). Propofol was associated with an increase in myocardial Bcl-2 protein expression (P = 0.005), a lower incidence of a CS cTnI threshold for myocardial infarction (P = 0.014), and fewer heart failure events (P < 0.001). CONCLUSION: Propofol may be a preemptive intraoperative cardioprotectant for patients with DM2 under conditions of normothermic CPB and blood cardioplegic arrest. The study is registered at www.clinicaltrials.gov (NCT00734383) and www.controlled-trials.com (ISRCTN70879185).

Oxidative stress and myocardial injury in the diabetic heart.

Reactive oxygen or nitrogen species play an integral role in both myocardial injury and repair. This dichotomy is differentiated at the level of species type, amount and duration of free radical generated. Homeostatic mechanisms designed to prevent free radical generation in the first instance, scavenge, or enzymatically convert them to less toxic forms and water, playing crucial roles in the maintenance of cellular structure and function. The outcome between functional recovery and dysfunction is dependent upon the inherent ability of these homeostatic antioxidant defences to withstand acute free radical generation, in the order of seconds to minutes. Alternatively, pre-existent antioxidant capacity (from intracellular and extracellular sources) may regulate the degree of free radical generation. This converts reactive oxygen and nitrogen species to the role of second messenger involved in cell signalling. The adaptive capacity of the cell is altered by the balance between death or survival signal converging at the level of the mitochondria, with distinct pathophysiological consequences that extends the period of injury from hours to days and weeks. Hyperglycaemia, hyperlipidaemia and insulin resistance enhance oxidative stress in the diabetic myocardium that cannot adapt to ischaemia-reperfusion. Altered glucose flux, mitochondrial derangements and nitric oxide synthase uncoupling in the presence of decreased antioxidant defence and impaired prosurvival cell signalling may render the diabetic myocardium more vulnerable to injury, remodelling and heart failure.

A new derivatization method coupled with LC-MS/MS to enable baseline separation and quantification of dimethylarginines in human plasma from patients to receive on-pump CABG surgery.

Asymmetric dimethylarginine (ADMA) is an inhibitor of nitric oxide synthase and a risk factor for cardiovascular events. We have developed a new derivatization method to enable baseline separation of the regio-isomers, ADMA, and symmetric dimethylarginine (SDMA), within 15 min on a C18 reverse phase column. Reacting naphthalene-2,3-dicarboxaldehyde with ADMA and SDMA in the presence of 2-mercaptoethanol produces corresponding 2,3-dihydro-benzo[f]isoindol-1-ones that are more stable than previously reported ortho-phthaldialdehyde and 2-mercaptoethanol derivatives. LC-MS/MS quantitation of these derivatives can be used to determine ADMA and SDMA concentrations in the plasma of patients to receive on-pump coronary artery bypass grafting (CABG) surgery. The LOD, LOQ and lower LOQ (LLOQ) of this method were determined to be 2.6, 8.7, and 25 nM for ADMA, and 2.5, 8.3, and 25 nM for SDMA, respectively, with consumption of only 50 µL of plasma. The relative standard deviations and relative errors of the intraday and interday determinations, as measurements of reproducibility and accuracy, are all within 15%. The ADMA and SDMA concentrations in patient plasma are 298.1 ± 11.2 nM (mean ± S.E.M., n = 123) and 457.7 ± 19.8 nM (mean ± S.E.M., n = 123), respectively. Upon unblinding of our clinical trial, these predetermined values might explain patient clinical outcomes associated with on-pump CABG surgery, as ADMA is known to inhibit nitric oxide production. Furthermore, this derivatization reaction in conjunction with LC-MS/MS analysis may open a venue to explore alternative chemical labeling modes for LC-MS/MS applications, such as analysis of other amino acids, metabolites, and peptides containing primary amine group(s).

A simple and robust LC-MS/MS method for quantification of free 3-nitrotyrosine in human plasma from patients receiving on-pump CABG surgery.

We have developed a simple, sensitive, and robust liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) method to determine free 3-nitrotyrosine concentrations in human plasma of patients receiving on-pump coronary artery bypass grafting surgery. A one-step solid-phase extraction protocol was optimized to enrich the analyte at low nanomolar concentrations. The processed samples were analyzed by LC-MS/MS with a 2.1 × 100 mm Kinetex PFP column and a triple quadrupole mass spectrometer. The method was validated for 3-nitrotyrosine concentrations close to real patient plasma levels. The relative standard deviations or relative errors of the intraday and interday determinations were all within 10%. Limit of detection and limit of quantitation were determined to be 0.034 nM and 0.112 nM, respectively, while lower limit of quantitation was below 0.625 nM. No deterioration of the column performance was noticed after running a large number of patient samples. The results showed that the 3-nitrotyrosine concentrations in coronary sinus plasma samples were elevated after cardiopulmonary bypass (CPB) procedure. The pre-CPB and post-CPB concentrations of 3-nitrotyrosine in patient plasmas were 1.494 ± 0.107 nM and 2.167 ± 0.177 nM (mean ± SEM), respectively. Application of this method to more patients in clinical studies may help validate 3-nitrotyrosine as a meaningful biomarker for nitrosative stress and link patient characteristics, clinical outcomes, and cardioprotective treatments to endogenous nitrosative stress levels.

Differences in myocardial PTEN expression and Akt signalling in type 2 diabetic and nondiabetic patients undergoing coronary bypass surgery.

OBJECTIVE: Patients with diabetes experience increased cardiovascular complications after cardiac surgery. Hyperglycaemia predicts increased mortality after myocardial infarction and may influence cardiovascular risk in humans. Impaired prosurvival phosphatase and tensin homologue on chromosome 10 (PTEN)-Akt signalling could be an important feature of the diabetic heart rendering it resistant to preconditioning. This study was designed to evaluate for differences and relationships of myocardial PTEN-Akt-related signalling and baseline glycaemic control marker in type 2 diabetic and nondiabetic patients undergoing coronary artery bypass surgery. METHODS: Right atrial biopsies and coronary sinus blood were obtained from 18 type 2 diabetic and 18 nondiabetic patients intraoperatively. Expression and phosphorylation of Akt, endothelial nitric oxide synthase (eNOS), Bcl-2 and PTEN were evaluated by Western blot. Plasma 15-F(2t) -isoprostane concentrations were evaluated by liquid chromatography-mass spectrometry. RESULTS: PTEN expression and 15-F(2t) -isoprostane concentrations were significantly higher in diabetic patients. Increased fasting blood glucose levels correlated with increased coronary sinus plasma 15-F(2t) -isoprostane concentrations. Increased cardiac 15-F(2t) -isoprostane generation was highly correlated with myocardial PTEN expression. Bcl-2 expression and eNOS phosphorylation were significantly lower in diabetic compared with nondiabetic patients. Akt phosphorylation tended to be lower in diabetic patients; however, this tendency failed to reach statistical significance. CONCLUSION: The current results suggest that prosurvival PTEN-Akt signalling is impaired in the diseased diabetic myocardium. Hyperglycaemia and increased oxidative stress may contribute to this phenomenon. These findings strengthen the understanding of the underlying biologic mechanisms of cardiac injury in diabetic patients, which could facilitate development of new treatments to prevent cardiovascular complications in this high-risk population.

Propofol protects against hydrogen peroxide-induced injury in cardiac H9c2 cells via Akt activation and Bcl-2 up-regulation.

Propofol is a widely used intravenous anesthetic agent with antioxidant properties secondary to its phenol based chemical structure. Treatment with propofol has been found to attenuate oxidative stress and prevent ischemia/reperfusion injury in rat heart. Here, we report that propofol protects cardiac H9c2 cells from hydrogen peroxide (H(2)O(2))-induced injury by triggering the activation of Akt and a parallel up-regulation of Bcl-2. We show that pretreatment with propofol significantly protects against H(2)O(2)-induced injury. We further demonstrate that propofol activates the PI3K-Akt signaling pathway. The protective effect of propofol on H(2)O(2)-induced injury is reversed by PI3K inhibitor wortmannin, which effectively suppresses propofol-induced activation of Akt, up-regulation of Bcl-2, and protection from apoptosis. Collectively, our results reveal a new mechanism by which propofol inhibits H(2)O(2)-induced injury in cardiac H9c2 cells, supporting a potential application of propofol as a preemptive cardioprotectant in clinical settings such as coronary bypass surgery.

Target-achieved propofol concentration during on-pump cardiac surgery: a pilot dose-finding study.

PURPOSE: Propofol concentrations that produce laboratory-based cardioprotective effects are generally greater than those produced under routine anesthesia during cardiac surgery. It is unknown whether experimental cardioprotective propofol concentrations can routinely be achieved during cardiopulmonary bypass (CPB) using continuous infusion. METHODS: Twenty-four patients scheduled for primary aortocoronary bypass grafting with CPB were allocated to receive one of three propofol infusion rates; 50, 100, or 150 microg x kg(-1) x min(-1) in an open-label pilot study. Data were described using a line of best fit to derive an experimental clinical maneuver predicted to produce a whole blood concentration of 5 microg x mL(-1) at reperfusion. A predetermined interim analysis of 30 patients who were receiving the derived maneuver in an ongoing study was used to evaluate the maneuver. Cardiac index (CI), systemic vascular resistance index (SVRI), and left ventricular stroke work index (LVSWI) were recorded. RESULTS: The infusion rate-concentration curve had an equation of y = 0.215e (0.0279x ), where y represents the whole blood concentration and x represents the infusion rate (r (2) = 0.781). The predicted infusion rate to achieve a mean concentration of 5 microg x mL(-1) was 113 microg x kg(-1) x min(-1). The nearest practical rate is 120 microg x kg(-1) x min(-1), producing a concentration of 5.39 (1.45) microg x mL(-1). The values for CI, SVRI, and LVSWI were similar between groups at corresponding time periods. CONCLUSIONS: An infusion rate of 120 microg x kg(-1) x min(-1) is clinically practical and capable of achieving experimental cardioprotective propofol concentrations at reperfusion.

Propofol reduces apoptosis and up-regulates endothelial nitric oxide synthase protein expression in hydrogen peroxide-stimulated human umbilical vein endothelial cells.

BACKGROUND: Vascular endothelial cells play an important role in maintaining cardiovascular homeostasis. Oxidative stress is a critical pathogenic factor in endothelial cell damage and the development of cardiovascular diseases. In this study we evaluated the effects of propofol on oxidative stress-induced endothelial cell insults and the role of serine-threonine kinase Akt modulation of endothelial nitric oxide synthase (eNOS) as a mechanism of protection. METHODS: Human umbilical vein endothelial cells were used as the experimental model. Hydrogen peroxide (H2O2, 100 microM) was used as the stimulus of oxidative stress. Study groups included 1) control; 2) cells incubated with H2O2 alone; 3) cells incubated with propofol (50 microM) alone; or 4) cells pretreated with propofol 50 microM for 30 min then co-incubated with H2O2. Cell viability was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and Trypan blue dye exclusion test. Cell apoptosis was evaluated by Hoechst 33258 staining. Caspase-3 activity was determined by the colorimetric CaspACE Assay System. Expressions of Akt, phospho-Akt, and eNOS were detected by Western blotting. RESULTS: H2O2 decreased cell viability, induced apoptosis, and increased caspase-3 activity in human umbilical vein endothelial cells. Propofol significantly protected cells from H2O2-induced cell damage, apoptosis and decreased H2O2-induced increase in caspase-3 activity. Propofol treatment significantly increased eNOS expression compared to control and H2O2-stimulated cells. There was no significant difference in phospho-Akt (Ser 473 or Thr 308) expression among the groups. CONCLUSIONS: Propofol 50 microM can reduce H2O2-induced damage and apoptosis in endothelial cells, by suppressing caspase-3 activity and by increasing eNOS expression via an Akt-independent mechanism.

Large-dose propofol during cardiopulmonary bypass decreases biochemical markers of myocardial injury in coronary surgery patients: a comparison with isoflurane.

We investigated if increasing propofol's dosage to augment its antioxidant capacity during cardiopulmonary bypass (CPB) could confer cardiac protection. Fifty-four coronary artery bypass graft surgery patients were randomly assigned to small-dose propofol (Group P; n = 18), large-dose propofol (Group HiP; n = 18), or isoflurane Group (Group I; n = 18). After the induction, anesthesia was maintained with an inspired concentration of isoflurane 1%-3.5% (Group I) or a continuous infusion of propofol 60 microg x kg(-1) x min(-1) (Group P) throughout the surgery. In Group HiP, this dose of propofol was increased to 120 microg x kg(-1) x min(-1) for 10 min before the onset of CPB until 15 min after aortic unclamping and then decreased to 60 microg x kg(-1) x min(-1) until the end of surgery. The duration of aortic cross-clamping was 83 +/- 24, 88 +/- 22, and 81 +/- 20 min in Group P, Group HiP, and Group I, respectively (P > 0.1). Plasma malondialdehyde, a marker of oxidative stress, was significantly lower at 8 h after CPB, and Troponin I was lower at 24 h after CPB in Group HiP compared with Group P and Group I (P < 0.05). There was a significant reduction in inotropic requirements for separation from CPB in Group HiP compared with Group I. Postoperative systemic vascular resistance was significantly reduced in Group HiP as compared with Group I. Mean cardiac index was significantly higher at 24 h after CPB in Group HiP compared with Group P and Group I (P < 0.05) (Group I, 2.2 +/- 0.1; Group P, 2.3 +/- 0.2; and Group HiP, 2.8 +/- 0.3 L x min(-1) x m(-2), respectively). The duration of intensive care unit stay was significantly shorter in Group Hi-P compared with Group I. We conclude that administration of a large dose of propofol during CPB attenuates postoperative myocardial cellular damage as compared with isoflurane or small-dose propofol anesthesia.

Propofol enhances ischemic tolerance of middle-aged rat hearts: effects on 15-F(2t)-isoprostane formation and tissue antioxidant capacity.

OBJECTIVE: Experimental study has shown that myocardial ischemic tolerance is reduced during middle-age. We investigated the effect of propofol on ischemic tolerance of middle-aged rat hearts. METHODS: Hearts of young adult (10 weeks old, Y) and middle-aged rats (20 weeks old, M) were assigned to propofol (P-Y, P-M) and control (C-Y, C-M) groups (n=6 each). Hearts were perfused using a Langendorff preparation with Krebs-Henseleit solution (KH) at constant flow rates. We applied propofol (P-Y, P-M) for 10 min at 12 microg/ml before inducing 40 min global ischemia. During ischemia, saline (C-Y, C-M) or propofol (P-Y, P-M) in saline was perfused through the aorta at 60 microl/min. Propofol in KH was perfused at 12 microg/ml for the first 15 min of reperfusion and subsequently reduced to 5 microg/ml in propofol treatment groups. Coronary effluent was assayed for 15-F(2t)-isoprostane after equilibration, during ischemia (T(1)) and at 0.5 (T(2)) and 5 (T(3)) min of reperfusion. After 90 min of reperfusion (T(4)), hearts were harvested to assess tissue antioxidant capacity. RESULTS: In P-Y, we observed an increased latency to ischemic-contracture and a significantly reduced contracture after 35 min ischemia compared to control groups. No ischemic contracture was observed in P-M. There were significantly lower 15-F(2t)-isoprostane levels in P-M and P-Y than in C-M and C-Y at T(1). At T(4), the recovery of left ventricular developed pressure in P-M was greater than in P-Y (P<0.05); both were greater than in C-M and C-Y. CONCLUSION: Propofol enhanced ischemic tolerance of middle-aged hearts, primarily by inhibiting lipid peroxidation.

Antioxidant therapy with Salvia miltiorrhiza decreases plasma endothelin-1 and thromboxane B2 after cardiopulmonary bypass in patients with congenital heart disease.

OBJECTIVE: The endothelium-derived vasoconstrictor endothelin-1 is increased after cardiopulmonary bypass in children with congenital heart defects. This study determines whether antioxidant therapy with Salvia miltiorrhiza injection, an herb extract containing phenolic compounds, prevents the postoperative increase of endothelin-1. The relationship between endothelin-1 and the endothelium-derived prostacyclin (prostaglandin I2) and thromboxane A2 postoperatively is also investigated. METHODS: Twenty children with congenital heart defects and pulmonary hypertension were randomly assigned to group A (placebo control, n=10) or B (200 mg/kg Salvia miltiorrhiza intravenously after anesthesia induction and at the time of rewarming, respectively; n =10) before cardiac surgery. Central venous blood samples were taken before operation (T(0)), 10 (T(1)) and 30 minutes (T(2)) after starting cardiopulmonary bypass, 10 (T(3)) and 30 minutes (T(4)) after aortic declamping, and 30 minutes (T(5)) and 24 hours (T(6)) after termination of cardiopulmonary bypass. Plasma lipid peroxidation product malondialdehyde, myocardial specific creatine kinase-MB activity, thromboxane B2, and 6-keto-prostaglandin F(1 alpha) (stable metabolites of thromboxane A2 and prostaglandin I2) were measured. RESULTS: Malondialdehyde increased significantly at T(1) in group A and remained significantly higher than in group B thereafter (P <.05). Malondialdehyde in group B did not significantly increase over time. At T(5), plasma creatine kinase-MB, thromboxane B2, and endothelin-1 in group B were lower than in group A (P <.05); malondialdehyde correlated significantly with creatine kinase-MB (r = 0.71, P =.0005). At T(6), endothelin-1 negatively correlated with the 6-keto-prostaglandin F(1 alpha)/thromboxane B2 ratio (r = -0.64, P =.0025). CONCLUSION: Antioxidant therapy reduces myocardial damage and attenuates postoperative vasoactive mediator imbalance.

[Clinical significance of plasma free 15-F2t-isoprostane concentration during coronary artery bypasses graft surgery].

OBJECTIVE: To analyse retrospectively the variation of plasma 15-F2t-isoprostane concentration during cardiac surgery and the relation with early myocardial dysfunction following normothemic cardiac surgery. METHODS: Thirty patients scheduled for coronary artery bypass graft surgery using normothermic cardiopulmonary bypass (CPB) and warm intermittent blood, crystalloid cardioplegia were enrolled. Patients were divided into two groups treated with (group II) or without (group I) positive inotropic drugs. Central venous blood was sampled at baseline, 30 minutes after global myocardial ischemia, 10, 30 and 120 minutes after aortic declamping (reperfusion). Plasma free 15-F2t-isoprostane was measured with enzyme immunoassay (EIA) using a highly specific rabbit 15-F2t-isoprostane antibody. Cardiac index (CI) was monitored intraoperatively and up to 6 hours following surgery. RESULTS: Plasma free 15-F2t-isoprostane increased significantly during ischemia, remained elevating at 10 minutes after reperfusion (P<0.05 vs. baseline) and began to decline at 30 minutes after reperfusion in the whole population. 15-F2t-isoprostane underwent exponential decay and returned to baseline at 30 minutes after reperfusion in group I that did not need any postoperative inotropic support. In contrast, 15-F2t-isoprostane further increased upon reperfusion and remained significantly higher than baseline at 30 minutes after reperfusion (P<0.05) in group II that needed two or more inotropes to maintain CI greater than 2.2 L x min(-1) x m(-2). Postoperative CI was significantly inversely correlated with the percentage change in plasma free 15-F2t-isoprostane concentration from 10 to 30 minutes after reperfusion (r=-0.95, P<0.01). CONCLUSION: It shows a close relationship between free plasma concentrations of 15-F2t-isoprostane and early postoperative cardiac function following coronary artery bypass graft surgery.

Propofol mediates signal transducer and activator of transcription 3 activation and crosstalk with phosphoinositide 3-kinase/AKT.

We previously demonstrated that propofol, an intravenous anesthetic with anti-oxidative properties, activated the phosphoinositide 3-kinase (PI3K)/AKT pathway to increase the expression of B cell lymphoma (Bcl)-2 and, therefore the anti-apoptotic potential on cardiomyocytes. Here, we wanted to determine if propofol can also activate the Janus kinase (JAK) 2/signal transducer and activator of transcription (STAT) 3 pathway, another branch of cardioprotective signaling. The cellular response of nuclear factor kappa B (NFκB) and STAT3 was also evaluated. Cardiac H9c2 cells were treated by propofol alone or in combination with pretreatment by inhibitors for JAK2/STAT3 or PI3K/AKT pathway. STAT3 and AKT phosphorylation, and STAT3 translocation were measured by western blotting and immunofluorescence staining, respectively. Propofol treatment significantly increased STAT3 phosphorylation at both tyrosine 705 and serine 727 residues. Sustained early phosphorylation of STAT3 was observed with 25~75 µM propofol at 10 and 30 min. Nuclear translocation of STAT3 was seen at 4 h after treatment with 50 µM propofol. In cultured H9c2 cells, we further demonstrated that propofol-induced STAT3 phosphorylation was reduced by pretreatment with PI3K/AKT pathway inhibitors wortmannin or API-2. Conversely, pretreatment with JAK2/STAT3 pathway inhibitor AG490 or stattic inhibited propofol-induced AKT phosphorylation. In addition, propofol induced NFκB p65 subunit perinuclear translocation. Inhibition or knockdown of STAT3 was associated with increased levels of the NFκB p65 subunit. Our results suggest that propofol induces an adaptive response by dual activation and crosstalk of cytoprotective PI3K/AKT and JAK2/STAT3 pathways. Rationale to apply propofol clinically as a preemptive cardioprotectant during cardiac surgery is supported by our findings.

The cellular and molecular origin of reactive oxygen species generation during myocardial ischemia and reperfusion.

Myocardial ischemia-reperfusion injury is an important cause of impaired heart function in the early postoperative period subsequent to cardiac surgery. Reactive oxygen species (ROS) generation increases during both ischemia and reperfusion and it plays a central role in the pathophysiology of intraoperative myocardial injury. Unfortunately, the cellular source of these ROS during ischemia and reperfusion is often poorly defined. Similarly, individual ROS members tend to be grouped together as free radicals with a uniform reactivity towards biomolecules and with deleterious effects collectively ascribed under the vague umbrella of oxidative stress. This review aims to clarify the identity, origin, and progression of ROS during myocardial ischemia and reperfusion. Additionally, this review aims to describe the biochemical reactions and cellular processes that are initiated by specific ROS that work in concert to ultimately yield the clinical manifestations of myocardial ischemia-reperfusion. Lastly, this review provides an overview of several key cardioprotective strategies that target myocardial ischemia-reperfusion injury from the perspective of ROS generation. This overview is illustrated with example clinical studies that have attempted to translate these strategies to reduce the severity of ischemia-reperfusion injury during coronary artery bypass grafting surgery.

Development and application of a LC-MS/MS method to quantify basal adenosine concentration in human plasma from patients undergoing on-pump CABG surgery.

A sensitive and robust LC-MS/MS method was developed to quantify basal adenosine concentrations in human plasma of patients undergoing on-pump coronary artery bypass grafting (CABG) surgery. A strong cation exchange (SCX) monolithic cartridge was used to enrich analyte, improve robustness, and reduce biological complexity. A simple modifier-free mobile phase was employed to improve sensitivity and reproducibility. This method exhibits consistent precision and accuracy, and the RSDs or REs of all the intraday and interday determinations were within 10%. The calibration curve was linear across the examined dynamic range from 1nM to 500nM (r(2)=0.996). LOD and LOQ were determined to be 0.257nM and 0.857nM respectively, while LLOQ was below 10nM. This method was used to monitor changes of adenosine levels in patient plasma drawn intraoperatively during on-pump CABG surgery. The analysis of 84 patients revealed that the mean concentration of adenosine in coronary sinus plasma after cardiopulmonary bypass (CPB) is higher than that in coronary sinus before CPB (p=0.0024; two-tailed t-test) and that in radial artery plasma after CPB (p=0.0409; two-tailed t-test). These findings suggest that the equilibrium between adenosine production and elimination has favored the elevation of adenosine basal level during on-pump CABG surgery and the change is specific to heart tissues. Evaluation of adenosine with a sensitive and robust analytical method has important implications on providing consistent results and meaningful insights into adenosine regulation, as well as its steady state and sustained action on the heart. Relating patient characteristics or clinical outcomes with basal adenosine concentration can be used to optimize the CABG-CPB maneuver by regulating adenosine level via pharmacological intervention, and differentiating adenosine's contribution to cardioprotection from other modulatory factors.

Rationale, design and baseline characteristics of the PRO-TECT II study: PROpofol CardioproTECTion for Type II diabetics: a randomized, controlled trial of high-dose propofol versus isoflurane preconditioning in patients undergoing on-pump coronary artery bypass graft surgery.

Diabetes mellitus is a leading cause of death globally and results in significant morbidity and mortality following surgery. After cardiac surgery, diabetic patients are especially at risk for low cardiac output syndrome, which can quadruple the risk for postoperative death. Attempts to prevent low cardiac output syndrome have focused on increasing myocardial tolerance to ischemia (preconditioning), which involves the myocardial mitochondrial ATP-regulated K(ATP) channel, G-protein initiation, nitric oxide synthase, and protein kinase C. Unfortunately, the signal transduction pathways required for preconditioning are corrupted in diabetes. Effective antioxidant intervention during ischemia-reperfusion appears important for preserving myocardial function; thus, alleviating oxidant-mediated post-ischemic injury by increasing antioxidant defenses (cardioprotection) is an alternative to preconditioning. Our previous work suggests that propofol (2,6-diisopropylphenol), an intravenous anesthetic with antioxidant potential, may confer cardioprotection. In this paper, we describe the rationale and methodology of the Pro-TECT II Study, a Phase II randomized controlled trial designed to explore the relationships of biomarkers of oxidative or nitrosative stress in diabetes, to determine the effect of propofol cardioprotection to counteract these effects in patients undergoing elective primary coronary bypass graft surgery with cardiopulmonary bypass, and to provide feasibility and sample size data needed to conduct Phase III trials.

Quantitative analysis of propofol in whole blood using capillary electrophoresis.

We have developed a straightforward capillary electrophoresis method capable of quantifying clinically relevant propofol concentrations in whole blood from patients undergoing aortocoronary bypass grafting with cardiopulmonary bypass. The method utilizes 400 microL of whole blood and is capable of detecting propofol in the ng/mL range. Factors affecting reproducibility and reliability of analytical results for clinically relevant samples are discussed. The method was used to evaluate propofol concentrations in blood samples from 30 patients. The distribution in the whole blood concentration achieved in patients advocates the need for target-achieved monitoring techniques.

Endothelin A and B receptor antagonist bosentan reduces postischemic myocardial injury in the rat: critical timing of administration.

The purpose of this study was to investigate the effects of bosentan, a mixed endothelin receptor A and B subtype antagonist, on myocardial ischemia-reperfusion injury and to explore the influence of the timing of bosentan administration on its cardioprotective effects. Adult rat hearts were perfused by the Langendorff technique with Krebs-Henseleit solution (KH) at a constant flow rate at 10 mL/min. Global myocardial ischemia was induced by stopping KH perfusion for 40 min, and this was followed by 60 min of reperfusion. Hearts were randomized to 1 of 3 experimental groups (n = 7 each): untreated control; treatment with bosentan 1 micromol/L 10 min prior to, during 40 min global ischemia, and for 15 min of reperfusion (BOS); or treatment with bosentan 1 micromol/L after 15 min of reperfusion (BOS-R). We observed that BOS-R, but not the BOS treatment regimen, significantly reduced the release of cardiac-specific creatine kinase and postischemic myocardial infarct size (P < 0.05 vs. control) without affecting myocardial contractility. Left ventricular developed pressure in the BOS group was significantly (P < 0.01) lower than that in the control group throughout reperfusion. It is concluded that pharmacologically delayed antagonism of endothelin-1 during reperfusion attenuates postischemic myocardial injury. Endothelin-1 antagonist application during early reperfusion may exacerbate postischemic myocardial dysfunction.

15-F(2t)-isoprostane exacerbates myocardial ischemia-reperfusion injury of isolated rat hearts.

Reactive oxygen species induce formation of 15-F(2t)-isoprostane (15-F(2t)-IsoP), a specific marker of in vivo lipid peroxidation, which is increased after myocardial ischemia and during the subsequent reperfusion. 15-F(2t)-IsoP possesses potent bioactivity under pathophysiological conditions. However, it remains unknown whether 15-F(2t)-IsoP, by itself, can influence myocardial ischemia-reperfusion injury (IRI). Adult rat hearts were perfused by the Langendorff technique with Krebs-Henseleit (KH) solution at a constant flow rate of 10 ml/min. 15-F(2t)-IsoP (100 nM), SQ-29548 (1 microM, SQ), a thromboxane receptor antagonist that can abolish the vasoconstrictor effect of 15-F(2t)-IsoP, 15-F(2t)-IsoP + SQ in KH, or KH alone (vehicle control) was applied for 10 min before induction of 40 min of global ischemia followed by 60 min of reperfusion. During ischemia, saline (control), 15-F(2t)-IsoP, 15-F(2t)-IsoP + SQ, or SQ in saline was perfused through the aorta at 60 microl/min. 15-F(2t)-IsoP, 15-F(2t)-IsoP + SQ, or SQ in KH was infused during the first 15 min of reperfusion. Coronary effluent endothelin-1 concentrations were significantly higher in the group treated with 15-F(2t)-IsoP than in the control group during ischemia and also in the later phase of reperfusion (P < 0.05). Infusion of 15-F(2t)-IsoP increased release of cardiac-specific creatine kinase, reduced cardiac contractility during reperfusion, and increased myocardial infarct size relative to the control group. SQ abolished the deleterious effects of 15-F(2t)-IsoP. 15-F(2t)-IsoP exacerbates myocardial IRI and may, therefore, act as a mediator of IRI. 15-F(2t)-IsoP-induced endothelin-1 production during cardiac reperfusion may represent a mechanism underlying the deleterious actions of 15-F(2t)-IsoP.