Patients admitted to an ICU for ASBA may present with an elevation of plasma CK, CK-MB and myoglobin not related to any heart injury. CK and CK-MB are not good markers of myocardial injury in ASBA patients due to the multitude of potential confounders. Therefore, troponin should be measured instead. The degree of respiratory dysfunction is suggested by respiratory distress at rest, difficulty speaking in sentences, diaphoresis or use of accessory respiratory muscles. The intensity of wheezing is an unreliable indicator.
Subcutaneous emphysema suggests an associated pneumothorax or pneumomediastinum.
In the most severe situations, patients may develop respiratory muscle failure associated with acute respiratory acidosis. While some studies report an increase in a subset of patients with ASBA, none have looked at concomitant changes in myoglobin or troponins. It has been suggested that plasma elevation of CK measured in ASBA originates from respiratory muscles. The muscular release of CK could be explained by an intense workload during respiratory distress. The present study was designed to evaluate prospectively whether the cause of the increase of CK and CK-MB in ASBA is of cardiac origin and to determine the utility of troponin measurement in those patients.