Abstract
INTRODUCTION: Our goal was to assess the diagnostic utility and temporal kinetics of serum creatine kinase (CK) measurement as a predictor of acute kidney injury (AKI) in emergency department (ED) patients who present with possible substance-use related conditions. METHODS: This was a retrospective chart review of ED patients with a urine drug screen (UDS) ordered and resulted between 2009-2013. Data was extracted electronically from EPIC Systems electronic health records, populated into a Microsoft Excel file, and includes demographics, chief complaint, vital signs, neuro-psychiatric physical examination findings, laboratory findings, psychiatric consult order time, ED medications given, orders, disposition and its time, and diagnosis. RESULTS: Of 74,970 patients with an ED UDS, 22,101 (29%) had at least one CK measured. After inclusion and exclusion criteria, 2858 (13%) remained. Mean (standard deviation [SD]) age was 43.3 (12.5) years, 73% were male, 61% Black, 22% White, and 17% Hispanic. Mean (SD) ED length of stay was 10.4 (5.8) hours, and 56.7% were hospitalized. On average, CK was higher at 6-12 hours (p<0.001) and 12-18 hours (p=0.016) compared to 6 hours. CK was lower at 42-56 hours (p = 0.011), 72 hours (p<0.001), and over 72 hours (p<0.001), compared to 6 hours. Maximum CK was determined in those with >2 CK measures. We defined AKI risk as a creatinine of >1.4 milligrams per deciliter based on RIFLE criteria. AKI risk was calculated among those with at least two creatinine values in 522 patients. We identified five (1%) patients as having AKI risk. The odds of AKI risk were not associated with increase in CK over time. CONCLUSION: In 74,970 ED patients undergoing UDS testing for potential substance abuse, there was no identifiable CK level associated with AKI risk. In patients with possible substance-use conditions, CK continued to trend up even after six hours from door time and began to decrease after 42 hours. We found no value in repeated ED CK measures. Disposition should not be based solely on CK levels.