Plasma B-type natriuretic peptide monitoring to evaluate cardiovascular function prior to organ procurement in patients with brain death.

BACKGROUND

The natriuretic peptide system plays an active role in the regulation of fluid balance and systemic vascular resistance. Assays of plasma concentrations of B-type natriuretic peptide (BNP) may have a diagnostic role in evaluating myocardial function. We present our experience with BNP monitoring to assess myocardial function after the proclamation of brain death in potential organ donors.

METHODS

After the proclamation of brain death and prior to organ donation, a plasma BNP or aminoterminal pro-BNP level was obtained. Additional information from the donor included shortening fraction (SF) or ejection fraction, central venous pressure (CVP) reading, and renal function including blood urea nitrogen and creatinine. When available, data from the pulmonary artery (PA) catheter including pulmonary capillary wedge pressure (PCWP) and cardiac index were also collected.

RESULTS

The cohort for the study included eight patients (age range: 6 months to 21 years). The diagnosis of brain death by clinical or radiological examination had been completed in all patients and the patients were scheduled for organ procurement. Myocardial contractility as assessed by echocardiogram using SF was within normal limits. The CVP varied from 7 to 12 mmHg (9 +/- 2) and the PCWP was 10-11 mmHg in the two patients who had PA catheters in place. No patient was receiving inotropic medications. In five of the six patients, the BNP value was above the upper limit of normal (100 pg x ml(-1)). In two patients, an NT-pro-BNP value was obtained and found to be higher than the upper limits of normal (450 pg x ml(-1)). All eight patients were acceptable cardiac donors and the transplanted hearts functioned without difficulty in the recipients.

CONCLUSIONS

Assays of plasma BNP concentrations have been shown to be helpful in differentiating myocardial dysfunction from primary lung disease in both the adult and pediatric population. However, our data demonstrate that mechanisms other than myocardial performance may regulate BNP levels in patients with severe central nervous system injury who progress to brain death. Our preliminary data suggest that these assays appear to be of limited value in assessing myocardial performance in this population.