Augmented release of brain natriuretic peptide during reperfusion of the human heart after cardioplegic cardiac arrest

B-type natriuretic peptide as a surrogate marker for survival in patients undergoing cardiac surgery

Background

B-type natriuretic peptide (BNP) is a biomarker predicting morbidity and mortality in patients with congestive heart failure. However, the usefulness of pre- or postoperative BNP levels in patients undergoing cardiac surgery remains uncertain. We sought to determine the association of pre- or postoperative BNP levels on mortality in patients undergoing cardiac surgery under cardiopulmonary bypass (CPB).

Methods

This study retrospectively evaluated 1,642 patients undergoing cardiac surgery under CPB over 2 years. The primary outcomes were 30-day and overall mortality after cardiac surgery.

Results

The 30-day mortality rate was 3.0% (n=49), and the overall mortality occurred in 118 patients during the mean follow-up period of 24.9±8.9 months. In multivariable analyses, preoperative BNP level was not significantly associated with 30-day [odds ratio (OR), 1.03; 95% confidence interval (CI), 0.99–1.06; P=0.06] or overall [hazard ratio (HR), 1.01; 95% CI, 0.98–1.03; P=0.50] mortalities. However, the postoperative BNP level was significantly associated with 30-day (OR, 1.05; 95% CI, 1.02–1.09; P=0.001) and overall (HR, 1.03; 95% CI, 1.01–1.04; P=0.01) mortalities. As a sensitivity analysis, postoperative BNP levels were divided into quartiles. The top quartile (≥484 pg/mL) was identified as a strong predictor of overall mortality (HR, 2.18; 95% CI, 1.14–4.19; P=0.02).

Conclusions

Preoperative BNP level was not associated with mortality after cardiac surgery. However, postoperative BNP level was associated with mortality after cardiac surgery, especially in patients with high levels (≥484 pg/mL). Further studies in larger cohorts are necessary to validate these results.

NT-Pro BNP Secretion and Clinical Endpoints in Cardiac Surgery Intensive Care Patients

The primary objective of this study was to determine the pattern of N-Terminal pro brain natriuretic peptide (NT-pro BNP) secretion pre and post cardiac surgery and then to investigate the correlation between levels of serum NT-pro BNP and postoperative clinical and biochemical endpoints. This was a prospective observational study performed at a tertiary centre in New Zealand, examining 118 adult patients undergoing cardiac surgery. Interventions included blood samples for NT-Pro BNP and troponin-T taken 48 hours prior to operation and 12, 36 and 72 hours postoperatively. The plasma NT-pro BNP levels increased fourfold postoperatively, to plateau at 36 to 72 hours. Preoperative NT-pro BNP levels correlated with ventilation time (r=0.46), length of stay in intensive care unit (r=0.59), total perioperative noradrenaline dose (r=0.55), but not with postoperative atrial fibrillation or mortality. Using multivariate analysis, serum NT-pro BNP levels at 36 hours were associated with increased noradrenaline dose (P=0.001), decreased preoperative ejection fraction (EF) Group (P=0.013) and elevated preoperative NT-pro BNP (P <0.001). Factors not associated with NT-pro BNP levels at 36 hours include the operation type, bypass and cross-clamp times, use of milrinone and troponin-T. We conclude that NT-pro BNP levels increased markedly after cardiac surgery and that high preoperative NT-pro BNP levels are associated with a slow postoperative recovery, but do not predict the occurrence of postoperative atrial fibrillation or mortality. Myocardial ischaemia is an unlikely cause of the NT-pro BNP elevation, because no correlation existed between troponin-T and NT-pro BNP levels.

Natriuretic Peptides in Cardiac Anesthesia and Intensive Care

Natriuretic peptides, predominantly B-type, are widely used in cardiology as prognostic and diagnostic biomarkers or, much less often, as a substantive treatment tool. They are hormones that are produced mainly in the myocardium in response to overload and ischemia, and their level quite accurately reflects the degree of myocardial dysfunction. Although their use in cardiac anesthesia and intensive care setting seems to be very beneficial for assessing the risk of acute disturbance of myocardial function or its laboratory monitoring, the actual significance of natriuretic peptides in this area is not yet recognized. This is due to the lack of clear diagnostic and prognostic values for these biomarkers supported by high-quality researches. On the basis of the available data, main advantages, existing difficulties, and most effective ways of using natriuretic peptides for determining the risk of heart surgery and assessing the severity of sepsis, pneumonia, and other critical conditions have been discussed in this review. In addition, the expediency of using natriuretic peptides as target parameters for goal-oriented therapy and as a substantive tool for treatment is considered.

Atrial natriuretic factor in normothermic and hypothermic cardiopulmonary bypass

Background: To evaluate the plasmatic changes of atrial natriuretic factor (ANF) during and after cardiopulmonary bypass (CPB) in normothermia and hypothermia.

Methods: Twenty-three patients (n=23) undergoing coronary artery bypass graft surgery were randomly assigned to two groups. In Group I (n=11), the patients underwent operation in normothermia; in Group II (n=12), the operation was performed in hypothermia (268C).

Results: Plasma ANF levels were determined after induction of anaesthesia, at the end of CPB and one hour postoperatively. There were no demographic differences between the two groups, diuresis (p=0.90) and natriuresis (p=0.95). Plasma levels of ANF were significantly elevated during and after CPB in both groups (p <0.01). The groups differed significantly for plasma levels of ANF during CPB and postoperatively ( p<0.05), but did not differ prebypass (p=0.08). There was no correlation in either group between ANF release and central venous pressure, natriuresis and diuresis. There was only a borderline relationship between ANF concentration and diuresis after CPB in Group I.

Conclusion: CPB triggers the production and release of ANF. The present study demonstrates a significantly enhanced ANF release during hypothermia and reperfusion after ischaemia. Thus, these data suggest the protective role of ANF on the hypoxic myocardium, and they confirm that ANF does not play a role in diuresis and natriuresis during and after hypothermic CPB.

Clinical Implication of Atrial and Brain Natriuretic Peptide in Coronary Artery Bypass Grafting

Atrial natriuretic peptide and brain natriuretic peptide are known to be indices for heart failure. Atrial natriuretic peptide and brain natriuretic peptide changes in off-pump and on-pump coronary artery bypass grafting is hypothesized to be correlated to clinical implications of coronary artery bypass grafting. 20 consecutive off-pump and 20 consecutive on-pump coronary artery bypass grafting patients were studied. Perioperative atrial natriuretic peptide and brain natriuretic peptide values were measured and statistically analyzed in terms of 14 factors related to myocardial damage and recovery. Postoperative atrial natriuretic peptide plateaued on the third postoperative day and it decreased gradually down to the preoperative level by one month in the off-pump group. Postoperative brain natriuretic peptide plateaued, showed very slow decrease and it never reached down to the preoperative level. The peak brain natriuretic peptide level was correlated with aortic cross-clamp time, postoperative pleural effusion, and postoperative atrial fibrillation ( p < 0.01). The atrial natriuretic peptide change reflected surgical prevention of ventricular remodeling. Brain natriuretic peptide > 450 μg·mL−1 had strong predictive power for atrial fibrillation and pleural effusion and is a useful marker for management of coronary surgery patients.

B-type natriuretic peptide as prognostic marker in tetralogy of Fallot surgery

Background

B-type natriuretic peptide has been extensively studied in patients with cardiovascular disease, but its impact on the perioperative outcome of patients with cyanotic congenital heart defects is still unclear. We assessed the perioperative changes in B-type natriuretic peptide levels and their correlation with preoperative factors and clinical outcomes in a large homogenous group of patients with tetralogy of Fallot undergoing definitive repair at a tertiary care center.

Methods

A prospective study was undertaken in the cardiac operating room and intensive care unit at a single institution; 250 patients with tetralogy of Fallot undergoing intracardiac repair under cardiopulmonary bypass were studied. B-type natriuretic peptide levels were taken at 3 time points and correlated with clinical variables.

Results

Baseline B-type natriuretic peptide levels correlated with the degree of cyanosis in all 4 groups. B-type natriuretic peptide levels at 24 h after admission to the intensive care unit correlated with mortality in the adult subset of patients. B-type natriuretic peptide levels > 290 pg mL−1 in the intensive care unit predicted an increased probability of adverse clinical outcomes.

Conclusions

We demonstrated a rise in serum B-type natriuretic peptide levels in patients with tetralogy of Fallot undergoing definitive repair on cardiopulmonary bypass. B-type natriuretic peptide levels may be monitored to identify patients with cyanosis at increased risk of an augmented inflammatory response to cardiopulmonary bypass.

Changes in N-terminal pro B-type natriuretic peptide concentration: comparative study of percutaneous transluminal coronary angioplasty and off-pump coronary artery bypass graft

The goal of this study was to compare the effects of different reperfusion methods on N-terminal B-type natriuretic peptide (NT-proBNP) in percutaneous transluminal coronary angioplasty (PTCA) or off-pump coronary artery bypass (OPCAB) patients. Fifty subjects were enrolled in the study, 32 patients received PTCA and 18 OPCAB. An NT-proBNP measurement was performed before intervention and at 1, 3, and 7 days after the procedures. NT-proBNP levels were not significantly different before intervention (PTCA group 297+/-147.3 vs. OPCAB group 235+/-167.8 pg/mL, p>0.05). However, 1 day after the procedures, NT-proBNP levels were higher in the OPCAB group (PTCA 375+/-256.4 vs. OPCAB 1,415+/-737.6 pg/mL, p<0.05), after 3 days NT-proBNP reached peak levels (PTCA 480+/-363.0 vs. OPCAB 2,119+/-818.4 pg/mL, p<0.05), and levels were reduced after 7 days (PTCA 292+/-243.7 vs. OPCAB 522+/-334.0 pg/mL, p>0.05). PTCA induced a mild and transient increase in NT-proBNP concentration, but OPCAB caused sustained high NT-proBNP levels during the 7 day postoperatively. However, differences between NT-proBNP levels associated with these two modalities showed a tendency to decrease rapidly postoperatively.

B-type natriuretic peptide to assess haemodynamic status after cardiac surgery

BACKGROUND

B-type natriuretic peptide (BNP) is the most powerful hormonal marker of left ventricular dysfunction and could be considered as an indicator of ventricular preload. The aim of this prospective study was to compare the respective value of BNP and cardiac filling pressures to assess the response to volume load after cardiac surgery.

METHODS

Thirty-seven mechanically ventilated patients suffering from acute circulatory failure immediately after cardiac surgery, and equipped with a pulmonary-artery catheter were included. All haemodynamic measurements were taken before and after volume expansion using 500 ml of 4% modified fluid gelatin.

RESULTS

Fifteen patients were volume responders (CI increase>or=15%) and 22 were non-responders. Right atrial pressure, pulmonary-artery occlusion pressure and BNP before volume loading were not significantly different between the responders and non-responders. BNP concentration before volume infusion significantly correlated to preoperative left ventricular ejection fraction, aortic cross-clamping time, serum creatinine, mean pulmonary arterial pressure and intensive care unit duration whereas no correlation was found with pulmonary-artery occlusion pressure or cardiac index.

CONCLUSION

BNP level after cardiac surgery was influenced by many perioperative variables, limiting its usefulness as an indicator of cardiac preload or a predictor of volume responsiveness in this population.

Rise and fall of B-type natriuretic peptide levels in patients with coronary artery disease and normal left ventricular function after cardiac revascularization

BACKGROUND

Recently, it was shown that B-type natriuretic peptide levels are increased in patients with acute coronary syndromes.

AIMS

To assess the relation between B-type natriuretic peptide and ischemia in patients with stable and unstable angina pectoris with normal left ventricular function in relation to the extent of ischemia and response to revascularization.

METHODS

Fifty-nine consecutive patients were enrolled in the study, patients were divided into two groups: stable angina patients (group I, n=18), and unstable coronary patients (group II, n=41). Baseline characteristics were compared with 15 age-matched and sex-matched participants. B-type natriuretic peptide levels were measured at baseline and 3, 7 and 90 days after coronary revascularization in group I and II.

RESULTS

Patients with unstable angina pectoris had increased B-type natriuretic peptide levels compared with stable angina pectoris patients (B-type natriuretic peptide levels: controls 15.5+/-13 pg/ml, stable angina pectoris group 28.4+/-19 pg/ml, unstable angina pectoris group 104+/-81 pg/ml; P<0.01). A relationship between the number of affected coronary vessels and B-type natriuretic peptide was assessed (one-vessel 29.9+/-21 pg/ml, two-vessel 93.8+/-87 pg/ml, three-vessel 119+/-88 pg/ml; P<0.01). After revascularization, B-type natriuretic peptide levels decreased in groups I and II (25+/-20 vs. 39+/-28 pg/ml) and were similar after 90 days in percutaneous transluminal coronary angiograghy and in coronary artery bypass grafting groups (percutaneous transluminal coronary angiography 26+/-22 pg/ml, coronary artery bypass grafting 36+/-26 pg/ml; NS).

CONCLUSIONS

B-type natriuretic peptide levels increase in unstable angina pectoris patients and are linked to the extent of coronary disease in patients with normal left ventricular systolic function, and returned to baseline level after surgical or catheter revascularization.

Impact of cardiac surgery on plasma levels of B-type natriuretic peptide in children with congenital heart disease

OBJECTIVE

To examine prospectively the effect of cardiac surgery on plasma concentration of B-type natriuretic peptide (BNP) in children with congenital heart disease.

SETTING

Tertiary referral center.

METHODS

BNP plasma concentration was measured by sandwich immunoassay (Biosite) in 65 consecutive patients with congenital heart disease (age 4 days to 17.1 years, mean (S.D.) age 3.6 (4.7) years, median age 1.0 years) on the day before and after surgical therapy. BNP levels were compared to perioperative data and to healthy subjects.

RESULTS

BNP increased significantly (p<0.001) after cardiac surgery from median 31 pg/ml (mean 189 pg/ml) to median 453 pg/ml (mean 607 pg/ml) and remained significantly elevated during the first week (p<0.001). After a first peak mean (S.D.) 1.3 (0.7) days after surgery, there was a significant decrease of plasma BNP followed by a second peak 5.1 (1.1) days after surgery. Postoperative BNP plasma concentration was correlated to BNP before surgery (r=0.58, p<0.001), to cardiopulmonary bypass duration (r=0.52, p<0.001) and to serum lactate concentration at the first day after surgery (r=0.49, p<0.001).

CONCLUSIONS

In children with congenital heart defects plasma BNP increased immediately after cardiac surgery despite haemodynamic unloading. The correlation to cardiopulmonary bypass time and serum lactate concentration and the similarity between the pattern of BNP release after surgery and after myocardial ischaemia might be explained by a cytoprotective role for BNP after cardiac surgery.

Plasma brain natriuretic peptide and cardiac troponin I concentrations after adult cardiac surgery: Association with postoperative cardiac dysfunction and 1-year mortality*

OBJECTIVE

The purpose of the present study was to evaluate the prognostic implications of perioperative B-type natriuretic peptide (BNP) and cardiac troponin I concentrations in patients undergoing cardiopulmonary bypass for cardiac surgery.

DESIGN

Prospective observational study.

SETTING

Biochemistry laboratory and surgical care unit in a university hospital.

PATIENTS

A total of 92 consecutive patients undergoing elective coronary artery (43 patients) or valve surgery (49 patients).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

BNP and cardiac troponin I concentrations were measured before surgery (day 0), and at day 1 after surgery. Postoperative cardiac dysfunction was defined as low cardiac output or hemodynamic instability requiring inotropic support for >24 hrs or congestive heart failure until day 5. One-year survival was also evaluated. Univariate and multivariate analyses were performed. An important BNP secretion was systematically observed after cardiac surgery. Independent predictors of cardiac dysfunction were preoperative New York Health Association class and BNP and cardiac troponin I concentrations measured at day 1. Patients with an elevation of both markers have a 12-fold increased risk of postoperative heart failure. The use of both markers in combination predicted better postoperative heart failure than each one separately. Age, low preoperative left ventricular ejection fraction, and elevated BNP at day 1 (>352 pg/mL) were associated with an increased mortality rate at 1 yr. In multivariate analysis, only left ventricular ejection fraction was significantly associated with 1-yr survival.

CONCLUSIONS

Postoperative plasma BNP and cardiac troponin I levels are independent predictors of postoperative cardiac dysfunction after cardiac surgery. Simultaneous measurement of BNP and cardiac troponin I improve the risk assessment of postoperative cardiac dysfunction. However, the association between BNP levels and 1-yr outcome was no longer significant after adjustment on left ventricular ejection fraction.

Relationship of extent and nature of dysfunctional myocardium to brain natriuretic peptide in patients with ischemic left ventricular dysfunction

We studied the relationship between brain natriuretic peptide (BNP) levels and viable myocardium and ischemic myocardium, regional scar and regional contractile function. Fifty-nine patients underwent dobutamine echocardiography and magnetic resonance imaging and resting BNP levels were determined. By magnetic resonance imaging, total extent of dysfunctional myocardium correlated strongest with BNP (r = 0.60, p < 0.0001). The extent of scar, viability and ischemia also correlated. At dobutamine echocardiography, a composite of dysfunctional and ischemic myocardium was the strongest correlate of BNP (r = 0.48, p < 0.0001), with less strong correlations by global parameters. The extent of dysfunctional myocardium, rather than its nature determines BNP levels.

Effect of cardiopulmonary bypass and surgical intervention on the natriuretic hormone system in children

OBJECTIVES

We sought to determine the effect of cardiopulmonary bypass and surgical intervention on the natriuretic hormone system in children and to assess whether such changes are associated with morbidity.

METHODS

At 6 perioperative time points in 25 patients, plasma levels of atrial natriuretic peptide, brain natriuretic peptide, and guanosine 3', 5'-monophosphate were measured, and the biologic activity of the natriuretic hormone system was quantified. Relationships were sought between changes in brain natriuretic peptide levels, biologic activity, and a number of morbidity indicators.

RESULTS

There was a significant change in atrial natriuretic peptide levels (P = .037), brain natriuretic peptide levels (P = .001), and biologic activity of the natriuretic hormone system (P = .009) over the first 4 time points in the study. Atrial natriuretic peptide levels transiently decreased from baseline to 12 hours after surgical intervention. Compared with baseline values, brain natriuretic peptide levels were increased at 12 hours after surgical intervention and on postoperative day 1. The increase in brain natriuretic peptide levels from baseline to 12 hours after surgical intervention was associated with cardiopulmonary bypass time (r(s) = 0.4, P = .047). The biologic activity transiently decreased from baseline to intensive care unit admission but was not associated with any morbidity indicators.

CONCLUSIONS

Increased postoperative brain natriuretic peptide levels are associated with longer bypass times. The biologic activity of the natriuretic hormone system is transiently impaired. Larger studies should investigate brain natriuretic peptide as a predictor of postoperative morbidity and the potential for natriuretic hormone infusions to improve postoperative hemodynamics and urine output.

Brain natriuretic peptide levels during cardiac reperfusion: comparison between percutaneous coronary angioplasty and aorto-coronaric bypass

BACKGROUND

Several studies have documented brain natriuretic peptide (BNP) behavior during cardiac ischemia and after myocardial necrosis. Peptide levels have been shown to be increased during acute phase of cardiac ischemia and during late ventricular remodelling; however, there are fewer data about hormone levels during percutaneous transluminal coronary angioplasty (PTCA) and aorto-coronaric by pass (CABG).

METHODS

Aim of this study was to investigate plasma BNP during acute or sub-acute myocardial ischemia in patients undergoing to PTCA or CABG, taking blood samples before and after both procedures. We studied 59 consecutive subjects, 25 submitted to coronary by-pass and 34 submitted to coronary angioplasty. Blood BNP levels were measured the day before intervention and after 3, 7 and 90 days from the procedures.

RESULTS

Peptide levels were significantly different just before intervention (GABG group 118.7+/-81 pg/ml vs. PTCA group 34.8+/-15 pg/ml, p<0.01). This difference was increased after 3 days (CABG group 403.2+/-185 pg/ml vs. PTCA group 105.3+/-56 pg/ml, p<0.0001) and after 7 days (CABG group 252.2+/-93 pg/ml vs. PTCA group 69.8+/-36 pg/ml, p<0.00001). These results trend to converge after 90 days (CABG group +/-93 pg/ml vs. PTCA group +/-36 pg/ml, p<0.05).

CONCLUSIONS

Plasma BNP shows a different behavior during and after different myocardial reperfusion procedures. PTCA causes only mild and temporary elevation of peptide levels, otherwise CABG demonstrates a more enhancing of BNP release not only in early phase but also after one week; increased levels tend to return towards the reference range after few weeks from cardiac surgery.

Plasma brain natriuretic peptide reflects left ventricular function during percutaneous cardiopulmonary support

BACKGROUND

Plasma levels of brain natriuretic peptide (BNP), a cardiac hormone secreted predominantly from the ventricle, are elevated in patients with myocardial infarction, hypertension, and dilated cardiomyopathy. In this study, we assessed the usefulness of measuring BNP to evaluate left ventricular function in patients with severe heart failure receiving mechanical circulatory support.

METHODS

Plasma BNP and creatine kinase (CK)-MB levels were measured serially in 8 consecutive patients with cardiogenic shock who received percutaneous cardiopulmonary support (PCPS) at Osaka Police Hospital from August 1999 to March 2000. Coronary artery bypass grafting or percutaneous transluminal coronary angioplasty was also performed in 5 patients during PCPS; in addition, 1 patient underwent insertion of a left ventricular venting catheter and implantation of a left ventricular assist system after PCPS.

RESULTS

Five patients were weaned from PCPS, and 3 died. In survivors, plasma BNP and CK-MB levels correlated positively and significantly (r = 0.968, p = 0.03). After PCPS was initiated, plasma BNP levels gradually decreased in survivors, but not in patients who died (p = 0.003).

CONCLUSIONS

These results suggest that plasma BNP levels accurately reflect myocardial damage in patients undergoing PCPS. A decrease in BNP might appear to indicate improved left ventricular function and predict successful weaning from mechanical support.

Intraoperative metabolic monitoring of the heart: I. Clinical assessment of coronary sinus metabolites

Numerous clinical studies have corroborated the ability of intraoperative sampling of coronary sinus blood to measure changes in myocardial metabolism induced by ischemia and reperfusion. Among other changes, cardiac arrest induces a period of obligate myocardial lactate production that persists for an indeterminate amount of time after reperfusion. Coronary sinus lactate assays have been established as a standard method to compare various myocardial protection strategies. Current methodology requires detailed sample processing, precluding real-time feedback in the operating room. Newer devices hold promise in allowing the online assessment of myocardial metabolism; however, these methods await precise validation.

The impact of cardiac natriuretic peptide determination on the diagnosis and management of heart failure

The long-predicted endocrine function of the heart has been proven by the discovery of atrial natriuretic peptide (atrial natriuretic factor, A-type natriuretic peptide; ANP) 20 years ago. This subsequently led to the description of a whole family of structurally similar but genetically distinct peptides, the natriuretic peptide family, which contributes to cardiovascular homeostasis. These looped peptides promote natriuresis and diuresis, act as vasodilators, and exert antimitogenic effects on cardiovascular tissues. Two members, ANP and brain natriuretic peptide (B-type natriuretic peptide; BNP) are secreted by the heart mainly in response to myocardial stretch induced by volume load. The natriuretic peptides are synthesized as preprohormones. The C-terminal endocrinological active peptides (ANP, BNP) and their N-terminal prohormone fragments are found in plasma. The natriuretic peptide system is activated to its highest degree in ventricular dysfunction. However, natriuretic peptides are increased in all patients with edematous disorders which lead to an increase in atrial tension or central blood volume, such as renal failure or ascitic liver cirrhosis. It could be demonstrated that in chronic heart failure patients and during the subacute phase of myocardial infarction, of all tested neurohormones, the cardiac natriuretic peptides were best markers to identify heart failure and the most powerful predictors of morbidity and mortality. Natriuretic peptides are independent markers for risk assessment. In comparative studies BNP was superior to ANP and its N-terminal prohormone fragments in myocardial infarction as well as in chronic heart failure patients. Less data on N-terminal proBNP (NT-proBNP) is available, but BNP and NT-proBNP appear to be equivalent markers. For primary care physicians natriuretic peptide measurement is useful to decide which patient with suspected heart failure warrants further investigation, particularly when assessment of left ventricular function is not readily available. Natriuretic peptides have an excellent negative predictive value, particularly in high risk patients. An increase in BNP is serious enough to warrant follow-up examinations. For the cardiologists the natriuretic peptides are helpful for guidance of therapy and monitoring disease course in heart failure patients and for risk stratification in heart failure and myocardial infarction.

Changes in brain natriuretic peptide concentrations following open cardiac surgery with cardioplegic cardiac arrest

Elevated brain natriuretic peptide (BNP) concentration in peripheral blood reflects impaired cardiac ventricular function. We investigated the release pattern of BNP following cardioplegic cardiac arrest during heart surgery. In particular, we sought to discover whether there is an increase in peripheral BNP concentrations following reperfusion of the ischaemic heart. A secondary aim of the study was to investigate whether allopurinol, an anti-oxidant, has any effect on BNP release. A total of 29 patients scheduled for elective coronary artery bypass grafting were recruited, of whom 12 were randomly allocated to receive allopurinol with their pre-medication. Blood specimens were taken at six time points from the indwelling arterial catheter, the first before surgery and the last 2 h following the termination of cardiopulmonary bypass (CPB). BNP was found to decrease markedly when the aortic cross clamp was applied and the heart was isolated from circulation (P=0.0001). There was a slight increase in BNP following cross clamp release and myocardial reperfusion (P=0.04). A more substantial increase occurred with weaning from CPB when ventricular filling occurred (P=0.0015). Only the final BNP value, 2 h after CPB, was elevated compared with baseline (P=0.0013). Allopurinol had no demonstrable effect on changes in BNP.

Effects of intraoperative administration of atrial natriuretic peptide

BACKGROUND

Biological activity of endogenous atrial natriuretic peptide (ANP) may decrease during cardiopulmonary bypass. To evaluate the effects of intraoperative administration of exogenous ANP in patients undergoing cardiopulmonary bypass, we conducted a prospective randomized study.

METHODS

Eighteen patients undergoing mitral valve surgery were randomized to receive either ANP treatment (ANP group; n = 9) or no ANP treatment (control group; n = 9). Atrial natriuretic peptide was given immediately after initiation of cardiopulmonary bypass for 6 hours (0.05 microg x kg(-1) x min(-1)). Plasma ANP, brain natriuretic peptide and cyclic guanosine monophosphate (cGMP) levels, hemodynamic variables and renal function were assessed perioperatively.

RESULTS

Administration of ANP increased plasma cyclic guanosine monophosphate levels, urine output and fractional sodium excretion, and decreased preload, afterload and plasma brain natriuretic peptide levels significantly (p < 0.05). Plasma cyclic guanosine monophosphate levels correlated with plasma ANP levels (r = 0.95, p = 0.0001), correlated with fractional sodium excretion (r = 0.53, p = 0.02), and correlated inversely with systemic vascular resistance (r = -0.54, p = 0.02).

CONCLUSIONS

Intraoperative administration of ANP had potent effects on natriuresis and systemic vasodilation by elevating cyclic guanosine monophosphate levels. The results suggest that the technique is useful for the management of hemodynamics and water-sodium retention after cardiopulmonary bypass.