Don't rely on BNP levels to detect CHF for trauma
B-type natriuretic peptide (BNP), a neurohormone secreted by the heart in response to fluid overload, has been shown to be elevated in medical patients with left ventricular dysfunction, which speeds diagnosis of congestive heart failure (CHF) patients. But can it also detect CHF in critically ill trauma patients?
Researchers looked at 50 trauma patients and found that there was no relationship between elevated BNP levels and echocardiographic evidence of CHF.1 "The BNP is a great test for medical patients, to decide if the cause of their hypoxia is CHF or pulmonary disease," says Kenneth Waxman, MD, one of the study's authors and director of surgical education and trauma services medical director at Santa Barbara (CA) Cottage Hospital. "It's a wonderful test and it's verified, but it hasn't really been looked at in trauma patients."
Therefore, BNP is not a good way to differentiate the causes of hypoxia or determine whether a trauma patient has CHF, he says. "There is a trend to do a lot of BNPs in the ED, to kind of screen for heart failure," Waxman says. "Nurses should keep in mind that the BNP just doesn't work for trauma patients. For example, in head-injured patients, we found elevated BNPs in people who didn't have heart failure."
At Santa Barbara Cottage Hospital, ED nurses obtain the blood sample for CHF patients, administer medication for the patient as ordered by the ED physician, and monitor the effects of these medications, says Kelly Kam, RN, trauma and pre-hospital manager.
"BNP is a very useful test in helping to diagnose why a patient may be short of breath," Kam says. "Continuous monitoring of airway, breathing, and circulation are the No. 1 priority. Any intervention to maintain these should not be withheld while awaiting this lab value."
The test has become standard of care in the ED and is used "on a daily basis" to help make or confirm a diagnosis of CHF, says Kam. "This test also acts as a marker to determine the severity of the heart failure if the test is positive," she says. "It will also show how well the prescribed treatment is working."
Frequently reassess the CHF patient's airway, breathing, circulation, and neurological status and their response to any medications given, says Kam. Document and report these findings, she says. "Any compromise in these particular areas is cause for alarm and requires immediate intervention," Kam says.
- Stewart D, Waxman K, Brown C, et al. B-type natriuretic peptide levels may be elevated in the critically injured trauma patient without congestive heart failure. J Trauma-Injury Inf Crit Care 2007; 63:747-750.