Postoperative increase in B-type natriuretic peptide levels predicts adverse outcome after cardiac surgery

NT-proBNP and postoperative heart failure in surgery for aortic stenosis

Objective

Postoperative heart failure (PHF) after aortic valve replacement (AVR) for aortic stenosis (AS) may initially appear mild and transient but has serious long-term consequences. Methods to assess PHF are not well documented. We studied the association between N-terminal pro-B-type natriuretic peptide (NT-proBNP) and PHF after AVR for AS.

Methods

This is a prospective, observational, longitudinal study of 203 patients undergoing elective first-time AVR for AS. Plasma NT-proBNP was assessed at preoperative evaluation, the day before surgery, and the first (POD1) and third postoperative morning. A clinical endpoints committee, blinded to NT-proBNP results, used prespecified haemodynamic criteria to diagnose PHF. The mean follow-up was 8.6±1.1 years.

Results

No patient with PHF (n=18) died within 30 days after surgery, but PHF was associated with poor long-term survival (HR 3.01, 95% CI 1.45 to 6.21, p=0.003). NT-proBNP was significantly higher in patients with PHF only on POD1 (6415 (3145-11 220) vs 2445 (1540-3855) ng/L, p<0.0001). NT-proBNP POD1 provided good discrimination of PHF (area under the curve=0.82, 95% CI 0.72 to 0.91, p<0.0001; best cut-off 5290 ng/L: sensitivity 63%, specificity 85%). NT-proBNP POD1 ≥5290 ng/L identified which patients with PHF carried a risk of poor long-term survival, and PHF with NT-proBNP POD1 ≥ 5290 ng/L emerged as a risk factor for long-term mortality in the multivariable Cox regression (HR 6.20, 95% CI 2.72 to 14.1, p<0.0001).

Conclusions

The serious long-term consequences associated with PHF after AVR for AS were confirmed. NT-proBNP level on POD1 aids in the assessment of PHF and identifies patients at particular risk of poor long-term survival.

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.

Absolute Postoperative B-Type Natriuretic Peptide Concentrations, but Not Their General Trend, Are Associated With 12-Month, All-Cause Mortality After On-Pump Cardiac Surgery

BACKGROUND

B-type natriuretic peptide (BNP) is a predictor of mortality after on-pump cardiac surgery. However, previous limited and heterogeneous studies have focused on peak concentrations at 3 to 5 days after surgery and may not offer clinicians much help in early decision-making. After confirming the predictive value of first-postoperative-day BNP in a preliminary analysis, we explored the association between isolated second-postoperative-day BNP concentrations, second-day BNP concentrations in conjunction with first-day BNP concentrations, and the change in BNP (ie, ΔBNP) from the first to the second postoperative day and 12-month, all-cause mortality.

METHODS

We included consecutive patients undergoing on-pump cardiac surgery in this observational, secondary analysis of prospectively collected data. We analyzed biomarkers on the first and second postoperative day. ΔBNP was defined as BNP on the second postoperative day minus BNP on the first postoperative day. The primary end point was 12-month, all-cause mortality. The secondary end point was a composite of major adverse cardiac events (MACEs) at 12 months and/or all-cause mortality at 12 months. MACE was defined as nonfatal cardiac arrest, myocardial infarction, and congestive heart failure. The association between BNP and outcomes was examined by receiver operating characteristic curves, as well as univariate and multivariable logistic regression, adjusting for the EuroSCORE II, cross-clamp time, and first-postoperative-day troponin T.

RESULTS

We included 1199 patients in the preliminary analysis focused on BNP on postoperative day 1. In the analyses examining BNP variables requiring second-postoperative-day BNP measurement (n = 708), we observed 66 (9.3%) deaths, 48 (6.8%) MACE, and 104 (14.7%) deaths and/or MACE. Both first- and second-postoperative-day BNP were significant independent predictors of all-cause, 12-month mortality per 100 ng/L increase (adjusted odds ratio [aOR], 1.040 [95% confidence interval (CI), 1.019-1.065] and 1.064 [95% CI, 1.031-1.105], respectively). When used in conjunction with one another, first-day BNP was not significant (aOR, 1.021 [95% CI, 0.995-1.048]), while second-day BNP remained significant (aOR, 1.046 [95% CI, 1.008-1.091]). The ΔBNP per 100 ng/L increase was not associated with 12-month, all-cause mortality in the univariable (OR, 0.977 [95% CI, 0.951-1.007]) or multivariable analysis (aOR, 0.989 [95% CI, 0.962-1.021]).

CONCLUSIONS

Both absolute concentrations of first- and second-postoperative-day BNP are independent predictors of 12-month, all-cause mortality. When modeled together, second-postoperative-day BNP is more predictive of 12-month, all-cause mortality. Although intuitively appealing, the change in BNP from the first to the second postoperative day is a complex variable and should not routinely be used for prognostication.

Differential Release Kinetics of Cardiac Biomarkers in Patients Undergoing Valve Replacement Surgery

BACKGROUND

Differential release kinetics of cardiac biomarkers including brain natriuretic peptide (BNP), Troponin-I, and CK-MB following valve replacement (VR) are not well characterized.

METHODS AND RESULTS

We serially measured these biomarkers 24 hours prior, six hours, 24 hours, 48 hours, and one month following mitral/aortic VR in 100 patients. Baseline BNP, Tn-I, and CK-MB levels were 304.01 pg/mL, 0.03 ng/mL, and 0.99 ng/mL, respectively. While BNP levels decreased at six hours, and then peaked at 24 hours, Tn-I and CK-MB levels increased within six hours and then showed declining trends by 24 hours. While Tn-I and CK-MB levels normalized at one month, 33% patients still had BNP >200 pg/mL. Those with baseline BNP >200 pg/mL more commonly had AF, higher RV systolic pressure, longer inotrope and ventilator duration, and longer mean ICU/hospital stay as compared to those with lower BNP, although echocardiographic left ventricular ejection fraction and Tn-I/CK-MB levels were similar. Inotrope duration >42 hours, ventilation time >29 hours, and ICU stay >4 days was seen in 42% versus 19%, 30% versus 9%, and 33% versus 14%, respectively, in those with BNP >/<200 pg/mL. Baseline BNP had a significant positive correlation with mean inotrope duration, ICU, and hospital stay. Baseline BNP was also a significant predictor of inotrope duration (odds ratio [OR]=5.9, 95% confidence interval [CI]=1.20-29.68, p=0.01) and ventilation time (OR=4.7, 95% CI=1.76-17.21, p=0.02).

CONCLUSION

Release kinetics of cardiac biomarkers is significantly different following VR; BNP levels increase following an initial transient decline. Only BNP was a predictor of postoperative variables.

High levels of B-type natriuretic peptide predict weaning failure from mechanical ventilation in adult patients after cardiac surgery

OBJECTIVE

The failure to wean from mechanical ventilation is related to worse outcomes after cardiac surgery. The aim of this study was to evaluate whether the serum level of B-type natriuretic peptide is a predictor of weaning failure from mechanical ventilation after cardiac surgery.

METHODS

We conducted a prospective, observational cohort study of 101 patients who underwent on-pump coronary artery bypass grafting. B-type natriuretic peptide was measured postoperatively after intensive care unit admission and at the end of a 60-min spontaneous breathing test. The demographic data, hemodynamic and respiratory parameters, fluid balance, need for vasopressor or inotropic support, and length of the intensive care unit and hospital stays were recorded. Weaning failure was considered as either the inability to sustain spontaneous breathing after 60 min or the need for reintubation within 48 h.

RESULTS

Of the 101 patients studied, 12 patients failed the weaning trial. There were no differences between the groups in the baseline or intraoperative characteristics, including left ventricular function, EuroSCORE and lengths of the cardiac procedure and cardiopulmonary bypass. The B-type natriuretic peptide levels were significantly higher at intensive care unit admission and at the end of the breathing test in the patients with weaning failure compared with the patients who were successfully weaned. In a multivariate model, a high B-type natriuretic peptide level at the end of a spontaneous breathing trial was the only independent predictor of weaning failure from mechanical ventilation.

CONCLUSIONS

A high B-type natriuretic peptide level is a predictive factor for the failure to wean from mechanical ventilation after cardiac surgery. These findings suggest that optimizing ventricular function should be a goal during the perioperative period.

Preoperative serum brain natriuretic peptide and risk of acute kidney injury after cardiac surgery

BACKGROUND

Acute kidney injury (AKI) after cardiac surgery is associated with poor outcomes and is difficult to predict. We conducted a prospective study to evaluate whether preoperative brain natriuretic peptide (BNP) levels predict postoperative AKI among patients undergoing cardiac surgery.

METHODS AND RESULTS

The Translational Research Investigating Biomarker Endpoints in Acute Kidney Injury (TRIBE-AKI) study enrolled 1139 adults undergoing cardiac surgery at 6 hospitals from 2007 to 2009 who were selected for high AKI risk. Preoperative BNP was categorized into quintiles. AKI was common with the use of Acute Kidney Injury Network definitions; at least mild AKI was a ≥0.3-mg/dL or 50% rise in creatinine (n=407, 36%), and severe AKI was either a doubling of creatinine or the requirement of acute renal replacement therapy (n=58, 5.1%). In analyses adjusted for preoperative characteristics, preoperative BNP was a strong and independent predictor of mild and severe AKI. Compared with the lowest BNP quintile, the highest quintile had significantly higher risk of at least mild AKI (risk ratio, 1.87; 95% confidence interval, 1.40-2.49) and severe AKI (risk ratio, 3.17; 95% confidence interval, 1.06-9.48). After adjustment for clinical predictors, the addition of BNP improved the area under the curve to predict at least mild AKI (0.67-0.69; P=0.02) and severe AKI (0.73-0.75; P=0.11). Compared with clinical parameters alone, BNP modestly improved risk prediction of AKI cases into lower and higher risk (continuous net reclassification index; at least mild AKI: risk ratio, 0.183; 95% confidence interval, 0.061-0.314; severe AKI: risk ratio, 0.231; 95% confidence interval, 0.067-0.506).

CONCLUSIONS

Preoperative BNP level is associated with postoperative AKI in high-risk patients undergoing cardiac surgery. If confirmed in other types of patients and surgeries, preoperative BNP may be a valuable component of future efforts to improve preoperative risk stratification and discrimination among surgical candidates.

Clinical Use of Natriuretic Peptides

Either B-type natriuretic peptide (BNP) or NT-proBNP may be used as a diagnostic, screening, prognostic and therapeutic tool for CHF. The Food and Drug Administration (FDA) cleared the cut-off point for BNP at 100 pg/mL, and that of NT-proBNP at 125 pg/mL for patients <75 years and 450 pg/mL for those >75. A steadily rising titre even below the cut-off value should be raised as a concern as heart failure is progressive if left untreated and may result in cardiac death. Both biomarkers are also featured in lab investigations for patients with acute coronary syndrome (ACS).