Utility of cardiac troponin measurement after cardiac surgery

The Perioperative Use of Levosimendan as a Means of Optimizing the Surgical Outcome in Patients with Severe Heart Insufficiency Undergoing Cardiac Surgery

BACKGROUND

Postoperative myocardial dysfunction following cardiac surgery is a relatively common occurrence. Levosimendan, a calcium sensitizer and inotropic drug, has shown potential in improving outcomes for patients with low preoperative ejection fraction (EF) and myocardial dysfunction after cardiac surgery. This study aims to evaluate the efficacy of levosimendan in optimizing the surgical outcome for such patients.

METHODS

A retrospective analysis was conducted on 314 patients with preoperative severe heart failure who underwent cardiac surgery. Among them, 184 patients received perioperative adjunctive therapy with levosimendan, while a comparable group of 130 patients received conventional treatment.

RESULTS

The use of levosimendan demonstrated several advantages in postoperative outcomes. It significantly improved short- and long-term survival rates after cardiac surgery, enhanced hemodynamic stability, reduced the requirement for inotropic support, and facilitated faster weaning from ventilator support. Patients who received levosimendan reported reduced angina and dyspnea symptoms, as well as fewer postoperative arrhythmias. Furthermore, levosimendan helped minimize myocardial injury inevitable after cardiac surgery. The levosimendan group also exhibited a notable reduction in hospital readmissions.

CONCLUSIONS

This study provides evidence of several benefits associated with the perioperative use of levosimendan. However, further prospective randomized studies are warranted to standardize and comprehensively document the other perioperative therapies, in order to validate these findings and establish stronger conclusions.

High-sensitivity cardiac troponin release after conventional and minimally invasive cardiac surgery

After cardiac surgery, a certain degree of myocardial injury is common. The arbitrarily proposed biomarker cut-off point in the Third Universal Definition for diagnosing coronary artery bypass grafting (CABG)–related perioperative myocardial infarction (PMI) is controversial and unvalidated for non-CABG surgery. Minimally invasive cardiac surgery is often thought to be associated with less myocardial damage compared to conventional surgical approaches. We conducted a real-life prospective study with serial sampling of high-sensitivity cardiac troponin T (hs-cTnT) in patients undergoing conventional and minimally invasive cardiac surgery. Four different types of cardiac surgery were performed in 400 patients (February 2014–January 2015): CABG, aortic valve replacement, minimally invasive mitral/tricuspid valve surgery through the HeartPort (HP) technique and combined CABG/valve surgery. Each group was further subdivided for comparison between the different surgical techniques. Blood samples were collected consecutively at intensive care unit (ICU) admission and 3, 6, 9, 12, 18, 24 and 48 h thereafter. The hs-cTnT values by peak timepoint differed significantly depending on the surgical approach. The overall peak timepoint for hs-cTnT occurred 6 h after ICU admission. The combined surgery and multiple-valve HP groups had the highest values (medians of 1067.5 (744.9–1455) ng/L and 1166 (743.7–2470) ng/L, respectively). The peak hs-cTnT values for patients developing PMI showed high variability. Differentiation between cardiac surgery–related necrosis and PMI remains challenging. This study emphasizes the importance of a clinically reliable biomarker cut-off value in addition to electrocardiography and echocardiography to optimize PMI diagnosis.

Post-Procedural Troponin Elevation and Clinical Outcomes Following Transcatheter Aortic Valve Implantation

Background

Biomarkers of myocardial injury increase frequently during transcatheter aortic valve implantation (TAVI). The impact of postprocedural cardiac troponin (cTn) elevation on short‐term outcomes remains controversial, and the association with long‐term prognosis is unknown.

Methods and Results

We evaluated 577 consecutive patients with severe aortic stenosis treated with TAVI between 2007 and 2012. Myocardial injury, defined according to the Valve Academic Research Consortium (VARC)‐2 as post‐TAVI cardiac troponin T (cTnT) >15× the upper limit of normal, occurred in 338 patients (58.1%). In multivariate analyses, myocardial injury was associated with higher risk of all‐cause mortality at 30 days (adjusted hazard ratio [HR], 8.77; 95% CI, 2.07–37.12; P=0.003) and remained a significant predictor at 2 years (adjusted HR, 1.98; 95% CI, 1.36–2.88; P<0.001). Higher cTnT cutoffs did not add incremental predictive value compared with the VARC‐2–defined cutoff. Whereas myocardial injury occurred more frequently in patients with versus without coronary artery disease (CAD), the relative impact of cTnT elevation on 2‐year mortality did not differ between patients without CAD (adjusted HR, 2.59; 95% CI, 1.27–5.26; P=0.009) and those with CAD (adjusted HR, 1.71; 95% CI, 1.10–2.65; P=0.018; P for interaction=0.24). Mortality rates at 2 years were lowest in patients without CAD and no myocardial injury (11.6%) and highest in patients with complex CAD (SYNTAX score >22) and myocardial injury (41.1%).

Conclusions

VARC‐2–defined cTnT elevation emerged as a strong, independent predictor of 30‐day mortality and remained a modest, but significant, predictor throughout 2 years post‐TAVI. The prognostic value of cTnT elevation was modified by the presence and complexity of underlying CAD with highest mortality risk observed in patients combining SYNTAX score >22 and evidence of myocardial injury.

Cardiac troponin I and creatine kinase-MB release after different cardiac surgeries

AIMS

To conduct a comparative study of cardiac troponin I (cTnI) and MB isoenzyme of serum creatine kinase (CK-MB) after different cardiac surgeries.

METHODS

Consecutive cardiac operations under cardiopulmonary bypass (200 adults, 144 men, 68 ± 11 years): 67 coronary artery bypass graft (CABG), 27 aortic valve surgery, 21 mitral valve surgery, 11 thoracic aorta surgery, and 74 combined surgery. Postoperative cTnI and CK-MB were measured on admission to the ICU and at fixed time until the fifth postoperative day.

RESULTS

Peak values of cTnI (median 5.8 ng/ml; interquartile range 3.6-11.9) and CK-MB (29.0 ng/ml; 15.6-60.4) were reached mainly within 18 h after the end of surgery (85% of cTnI and 95% of CK-MB highest determinations) without differences among groups. Cardiopulmonary bypass and cross-clamp time significantly correlated with markers' peak values. At multivariate analysis, mitral valve surgery showed greater cTnI, CK-MB, and their cumulative area under the curve than other isolated procedures. Thoracic aorta surgery showed lower cumulative area under the curve for both markers than CABG and combined surgery. Mitral valve surgery had significant later reduction of both markers in comparison with other procedures. No patient in mitral valve surgery group reached cTnI values in the normal laboratory range within 5 postoperative days.

CONCLUSION

Release pattern of cTnI and CK-MB after heart surgery depends on the type of procedure. Mitral valve surgery was characterized by highest and longest elevation of postoperative markers' concentration. Determinants of differences in myocardial injury biomarkers and their prognostic value after valve surgery should be accurately assessed.

Changes of cardiac troponin I and operative mortality of coronary artery bypass

Background

Recently, cardiac troponin I has been used to detect myocardial injury because of its superior cardiac specificity. However, there has been debate about the appropriate timing and cutoff level of cardiac troponin I to detect perioperative myocardial injury after coronary artery bypass grafting. The objective of this study was to define the relationship between operative mortality and changes in cardiac troponin I after isolated coronary artery bypass.

Patients and methods

A retrospective analysis was carried out on data of 218 isolated coronary artery bypass patients who were operated on between June 2009 and February 2012. All patients followed an institutional perioperative management protocol that included 6 cardiac troponin I measurements (preoperatively and 0, 12, 24, 36, and 48 h after coronary artery bypass). According to the patterns of cardiac troponin I, the patient cohort was divided into 2 groups. Group 1 was patients in whom cardiac troponin I levels decreased 24 h after the operation, and group 2 comprised the patients with cardiac troponin I levels that did not decrease or even increased after 24 h.

Results

The operative mortality was 4.1% (9/218). Group 2 showed significantly higher mortality (5/25, 20%) than group 1 (4/193, 2.1%).

Conclusion

An elevated cardiac troponin I level is common after coronary artery bypass. A persistently high level of cardiac troponin I after 24 h is an important predictor of operative mortality after coronary artery bypass surgery.

Cystatin C: influence of perfusion and myocardial injury on early (<24 h) renal function after pediatric cardiac surgery

BACKGROUND

Cardiopulmonary bypass (CPB)-associated renal dysfunction following cardiac surgery is well recognized. In patients with renal disease, cystatin C has emerged as a new biomarker which in contrast to creatinine (Cr) is sensitive to minor changes in glomerular filtration rate (GFR).

AIM

We utilized cystatin C to investigate the association of CPB perfusion parameters with acute renal injury after pediatric cardiac surgery.

METHODS

Twenty children, aged 4-58 months (AVSD, n = 7; VSD, n = 9; and ASD, n = 4), were prospectively studied. Glomerular filtration rate was quantified postoperatively by creatinine clearance (first and second 12-h periods; CrCl(0-12) and CrCl(12-24) ). Serum cystatin C and Cr were measured preoperatively and on days 0-3. Recorded CPB parameters included bypass duration (BP), perfusion pressure (PP), lowest pump flow (Q(min) ), lowest hematocrit, and corresponding lowest oxygen delivery (DO(2 min) ). Myocardial injury was determined by troponin-I.

RESULTS

Postoperatively, GFR remained unchanged (CrCl(0-12) 63.6 ± 37.0 vs CrCl(12-24) 65.1 ± 27.5; P = 0.51) and only correlated with cystatin C (CrCl(0-12) vs cystatin C(Day 0) [r = 0.58, P = 0.018] and Cr(Day 0) [r = 0.09, P = 0.735]). Cr and cystatin C increased postoperatively to peak on days 2 and 3, respectively (Cr(PreOp) 31 ± 6.9 vs Cr(Day 2) 36.9 ± 12.2, P = 0.03; cystatin C(Day 0) 0.83 ± 0.27 vs cystatin C(Day 3) 1.45 ± 0.53, P = 0.02). Increased cystatin C was significantly associated with BP (P = 0.001), mean PP (P = 0.029), Q(min) (P = 0.005), troponin-I (P < 0.001), and DO(2 min) <300 ml·min(-1) ·m(-2) (P = 0.007). Receiver-operator cutoff >1.044 mg·l(-1) for cystatin C exhibited 100% sensitivity and 67% specificity for detecting renal dysfunction, defined as GFR <55 ml·min(-1) ·1.73 m(-2).

CONCLUSIONS

Cystatin C is a sensitive marker of early renal dysfunction following pediatric heart surgery. Variations in bypass parameters, myocardial injury, and ultimately critical oxygen delivery are significantly associated with the degree of renal impairment.

Patterns and prognostic value of troponin, interleukin-6, and leptin after pediatric open-heart surgery

PURPOSE

Leptin and interleukin-6 (IL-6) are inversely correlated and associated with decreased survival in critically ill patients. We investigated changes in leptin, IL-6, and troponin in children undergoing open-heart surgery, hypothesizing that IL-6 and troponin will increase after cardiopulmonary bypass (CPB) and will be negatively correlated with leptin.

PATIENTS AND METHODS

Serial blood samples were collected from 21 patients 24 hours before and up to 48 hours after surgery.

RESULTS

Leptin levels decreased by 50% during CPB (P < .001), then gradually increased, reaching baseline levels 12 hours after surgery. The IL-6 levels increased (P < .001) during CPB, peaking 2 hours after surgery and remaining slightly elevated at 24 hours after surgery (P < .001). Leptin and IL-6 were negatively correlated (R = -0.448, P < .001). Troponin levels increased during CPB (P < .001). Postoperative leptin and troponin were inversely correlated (r = -0.535, P < .001). Patients with modest elevations in troponin levels (<20 microg/L) had a shorter aortic clamp and CPB time (P < .01), lower IL-6 peak levels (P = .03), and shorter duration of ventilation and inotropic support compared with patients with peak troponin levels greater than 20 microg/L.

CONCLUSIONS

Lower leptin and higher IL-6 levels correlated with troponin, a marker of myocardial injury. Because leptin may have cardioprotective effects, the postoperative drop in its levels may further contribute to myocardial dysfunction.

Levosimendan reduces cardiac troponin release after cardiac surgery: a meta-analysis of randomized controlled studies

OBJECTIVES

The authors performed a meta-analysis to investigate the effects of levosimendan in cardiac surgery. Inotropic drugs have never shown beneficial effects on outcome in randomized controlled studies, with the possible exception of levosimendan.

DESIGN

A meta-analysis.

SETTING

Hospitals.

PARTICIPANTS

A total of 139 patients from 5 randomized controlled studies were included in the analysis.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Four investigators independently searched BioMedCentral and PubMed. Inclusion criteria were random allocation to treatment, and comparison of levosimendan versus control performed on cardiac surgery patients. Exclusion criteria were duplicate publications, nonhuman experimental studies, and no outcome data. The endpoint was postoperative cardiac troponin release. Levosimendan was associated with a significant reduction in cardiac troponin peak release (weighted mean difference = 2.5 ng/dL [-3.86, -1.14], p = 0.0003) and in time to hospital discharge (weighted mean difference = -1.38 days [-2.78, 0.03], p = 0.05). No other relevant outcome (mortality, myocardial infarction, atrial fibrillation, time on mechanical ventilation, and intensive care unit stay) was improved in those patients receiving levosimendan.

CONCLUSIONS

Levosimendan has cardioprotective effects, resulting in reduced postoperative cardiac troponin release.

Determination of the threshold of cardiac troponin I associated with an adverse postoperative outcome after cardiac surgery: a comparative study between coronary artery bypass graft, valve surgery, and combined cardiac surgery

Introduction

The objective of the present study was to compare postoperative cardiac troponin I (cTnI) release and the thresholds of cTnI that predict adverse outcome after elective coronary artery bypass graft (CABG), after valve surgery, and after combined cardiac surgery.

Methods

Six hundred and seventy-five adult patients undergoing conventional cardiac surgery with cardiopulmonary bypass were retrospectively analyzed. Patients in the CABG (n = 225) and valve surgery groups (n = 225) were selected after matching (age, sex) with those in the combined surgery group (n = 225). cTnI was measured preoperatively and 24 hours after the end of surgery. The main endpoint was a severe postoperative cardiac event (sustained ventricular arrhythmias requiring treatment, need for inotropic support or intraaortic balloon pump for at least 24 hours, postoperative myocardial infarction) and/or death. Data are presented as the median and the odds ratio (95% confidence interval).

Results

Postoperative cTnI levels were significantly different among the three groups (combined surgery, 11.0 (9.5–13.1) ng/ml versus CABG, 5.2 (4.7–5.7) ng/ml and valve surgery, 7.8 (7.6–8.0) ng/ml; P < 0.05). The thresholds of cTnI predicting severe cardiac event and/or death were also significantly different among the three groups (combined surgery, 11.8 (11.5–14.8) ng/ml versus CABG, 7.8 (6.7–8.8) ng/ml and valve surgery, 9.3 (8.0–14.0) ng/ml; P < 0.05). An elevated cTnI above the threshold in each group was significantly associated with a severe cardiac event and/or death (odds ratio, 4.33 (2.82–6.64)).

Conclusion

The magnitude of postoperative cTnI release is related to the type of cardiac surgical procedure. Different thresholds of cTnI must be considered according to the procedure type to predict early an adverse postoperative outcome.

Plasma Troponins as Markers of Myocardial Damage during Cardiac Surgery with Extracorporeal Circulation

All types of cardiac surgery involve considerable injury to the myocardium. However, it is difficult to differentiate, in the immediate post-operative state, between ischemic alterations associated with the cardiac surgery itself and the pathological alterations of a peri-operative myocardial infarction. The diagnosis of damaged myocardium, classically performed with the enzymatic markers creatine kinase (CK) and its muscle fraction (CK-MB), has become more precise with the option of measuring cardiac troponins T and I. We measured these markers in 58 patients undergoing elective cardiac surgery with extra-corporeal circulation (ECC). The patients included 37 cases undergoing valve surgery, 14 for coronary revascularization, 6 for mixed procedures, and 1 for closure of an inter-atrial communication. The markers were measured in plasma at baseline (at anesthesia initiation), 5 min post-ECC commencement, following aorta de-clamping, during the surgical closure, and 6, 18 and 42 hrs after surgery. All the markers were increased significantly relative to the baseline values. Troponin I, CK and CK-MB values peaked between 6 and 18 hrs after surgery, troponin T between 18 and 42 hrs, and myoglobin at the surgical closure. The values of all markers were higher in patients undergoing coronary surgery compared to those in patients undergoing valve surgery. In the evaluation of myocardial damage after surgery, the measurement of classical markers such as CK and myoglobin remain valid, but other markers such as troponins provide significant additional diagnostic benefit and, thus, need to be included in the routine biochemical measurements for monitoring myocardial damage associated with the surgical procedure.

Cardiac Troponin T Levels for Risk Stratification in Pediatric Open Heart Surgery

BACKGROUND

Cardiac troponin T has been found to be accurate predictor of complications and adverse clinical events after pediatric cardiac surgery. Contrary to adult cardiac surgery, the relationship of troponin T to patient survival after pediatric heart surgery has not been previously studied. The purpose of this study was to determine whether troponin T could predict death after pediatric open cardiac surgery.

METHODS

This was a retrospective cohort study in which data from 1001 consecutive children having cardiac surgery during a 5-year period were studied. Perioperative variables that could influence death at 30 postoperative days were evaluated.

RESULTS

Multivariate analysis, using a forward stepwise logistic regression, showed that troponin T measured on the first postoperative day was a strong independent predictor of death at 30 days. Level of troponin T greater than 5.9 microg/L on the first postoperative day predicted death (odds ratio, 10.7; 95% confidence interval: 5.2 to 22.1) as did admission lactate level greater than 5.2 mmol/L (odds ratio, 22.2; 95% confidence interval: 9.7 to 50.8) No other variable, including postoperative creatine kinase-MB mass concentration, age, diagnosis, surgical procedure, presence of cyanosis, chromosomal anomaly or ventriculotomy, duration of cardiopulmonary bypass, or aortic cross-clamp, had any independent effect on 30-day survival.

CONCLUSIONS

Cardiac troponin T level on the first postoperative day is a powerful independent risk marker of death in pediatric cardiac surgery.

Dosage des isoformes cardiaques des troponines T ou I : intérêt en cardiologie et en anesthésie–réanimation

Measurement of cardiac troponin I or T in serum (highly specific for the myocardium) have replaced classical markers, such as creatine kinase MB. Cardiac troponins are preferred markers because of their high specificity and sensitivity. This had led to modifications of the original World Health Organization criteria for acute myocardial infarction. Furthermore, the place of the troponins as superior markers of subsequent cardiac risk in acute coronary syndrome has now become firmly established, for both diagnostic and risk stratification purposes. The use of C-reactive protein and/or other inflammatory biomarkers may add independent information in this context. After non cardiac surgery, the total cardiospecificity of cardiac troponins explains why other biomarkers of necrosis should no longer be used. Recent studies suggest that any elevation of troponin in the postoperative period is indicative of increased risk of long-term cardiac complications. This prognostic value has been previously demonstrated in other clinical settings such as invasive coronary intervention (surgical myocardial revascularization and percutaneous coronary intervention) and after heart valve surgery. Increases of troponin indicate cardiac damage, whatever the mechanism (ischemic or not). Other causes of cardiac injury include: pulmonary embolism, myocarditis, pericarditis, congestive heart failure, septic shock, myocardial contusion. In most cases, elevation of troponins has been shown to be associated with a bad outcome.

La troponine et les autres marqueurs de souffrance myocardique, quelle signification en médecine interne ?

PURPOSE

Troponin is now the gold standard for the diagnosis of myocardial infarction. Aiming at improving the management of a patient suspect of an acute coronary syndrome, this article will point the interpretation of troponin dosages according to the clinical presentation and concomitant diseases.

ACTUALITIES

First, the interest of troponin dosage as compared with other markers of myocardial ischemia will be underlined. Then, the literature available about troponin in cardiovascular diseases but also in extracardiac diseases will be analysed. Finally, the difficulties of assay will be discussed.

PERSPECTIVES

The availability of a sensitive and specific marker such as troponin is definitively a progress in the management of patients with an acute coronary syndromes. But it remains a biological contribution to the global management of the patient. It is important to know the causes susceptible to increase the levels of troponin to avoid a wrong interpretation of the dosage, leading to diagnostic but also therapeutic mistakes.

The comparison and validity of troponin I assay systems in diagnosing myocardial ischemic injury after surgical coronary revascularization

OBJECTIVE

A prospective observational study was conducted to test the agreement between 2 commercially available automated cardiac troponin-I immunoassay systems (Opus Plus, Behring Diagnostics UK Ltd, Hounslow, UK; AxSYM, Abbott Laboratories, Abbott Park, IL) and to determine a normal reference range and threshold value indicative of perioperative myocardial infarction (PMI) after elective coronary artery bypass graft (CABG) surgery for the Opus Plus system.

DESIGN

Prospective, observational study. Setting : Single institution, cardiothoracic specialty hospital.

PARTICIPANTS

Seventy patients undergoing elective CABG surgery.

INTERVENTIONS

After institutional review board approval, patients received standardized anesthetic, surgical, and myocardial preservation techniques. Serial electrocardiographs, creatine kinase-MB, troponin-I, and perioperative outcome data were collected. Correlation between the immunoassay systems was tested using 124 duplicate samples from the first 18 patients. The normal reference range and threshold value indicative of PMI were tested for the Opus Plus system using duplicate samples from all 70 patients.

MEASUREMENTS AND MAIN RESULTS

Peak troponin-I concentrations (median [interquartile range]) differed significantly when measured by the Opus Plus and AxSYM immunoassay systems (5.61 [3.20-22.35] microg/L v 46.50 [14.55-70.95] microg/L, respectively; p < 0.001). There was clear proportional bias that was corrected with log transformation of the raw data. By using confidence interval and receiver operating characteristic curve analysis, the authors showed that a value > or =15 mug/L was indicative of PMI (Opus Plus system) and accordingly report a 35.7% (2.9% Q-wave) overall incidence of PMI in this study population (n = 70).

CONCLUSIONS

These data highlight differences between commercially available troponin-I assay systems. The authors recommend that each institution establish a local reference range and threshold indicative of perioperative myocardial infarction for its specific patient population and assay system and provide sample methodology.

Early postoperative function of the heart after coronary artery bypass grafting is not predicted by myocardial necrosis and glutathione-associated oxidative stress

BACKGROUND

To investigate whether cardioplegia-related myocardial necrosis, lactate and glutathione release are predictive for early postoperative cardiac function after coronary artery bypass grafting (CABG).

METHODS

Twelve patients with stabile angina scheduled for elective CABG were included. Myocardial release of troponin I (Tn I), creatine kinase MB isoenzyme mass (CK-MB), oxidized glutathione (GSSG) and lactate in blood were measured before cardioplegia, and up to 20 min thereafter. Cardiac function was assessed for 12 postoperative hours.

RESULTS

Release of Tn I and CK-MB peaked at 20 min (-14.5+/-24.1 ng/ml and -23.9+/-30.6 ng/ml, respectively) and lactate at 1 min of reperfusion (-1.5+/-0.6 mmol/l). Significant GSSG release occurred at 5 min, with concomitant increase of glutathione redox ratio. The changes were not correlated to ischemic time. Cardiac index was increased after CPB and remained higher than preoperative value until the first postoperative morning. No correlations between postcardioplegic heart function and markers of tissue injury were found.

CONCLUSIONS

The extent of myocardial reversible and irreversible injury does not predict early postoperative contractile function of the heart.

Beneficial Effect of the Addition of Nitroglycerin to the Cardioplegic Solution on Lipid Peroxidation During Coronary Artery Bypass Surgery

The effects of the addition of a nitric oxide (NO) donor to the cardioplegic solution on reperfusion injury and lipid peroxidation (LPO) in coronary artery bypass grafting (CABG) are not known. Therefore, this work was conducted to determine the possible effects of nitroglycerin on LPO and reperfusion injury as a result of CABG. A prospective double-blind, placebo-controlled study was conducted in 30 consecutive patients with coronary artery disease who underwent CABG with cardiopulmonary bypass. The patients were randomly assigned to receive 3 microg/kg of nitroglycerin added to the cardioplegic solution (NTG group) or 3 microg/kg of placebo added to the cardioplegic solution (placebo group). MDA increased significantly in the placebo group compared to the NTG group during the ischemic (P < 0.01) and reperfusion periods (P < 0.01). The level of troponin I decreased significantly in the NTG group compared to the placebo group during the ischemic and reperfusion periods (P < 0.001). The level of NO increased significantly in the NTG group compared to the placebo group during the ischemic and reperfusion periods (P < 0.01). LPO was increased in response to CPB during CABG, together with simultaneous decreases in serum nitric oxide levels, whereas LPO was significantly decreased in response to CPB with nitroglycerin, together with simultaneous increases in the levels of serum nitric oxide.