A man in his 30s comes to your emergency department at 3 a.m. profoundly diaphoretic and reporting severe 10/10 chest pain. He has been at a party all night, and the chest pain started about 30 minutes earlier. He had a previous heart attack, but cannot remember many of the details. He reports no medication or drug use. No doubt this is a concerning presentation, and you immediately order an ECG, blood work, and an aspirin.
While this is in process, you review the electronic medical information, which reveals that the previous “heart attack” was actually observation for chest pain rule-out. The ECG showed nonspecific ST/T-wave changes, and serial troponin measurements were negative. He had undergone a stress echocardiogram, which was a good quality study, and demonstrated no inducible ischemia or reproducible symptoms. The patient had a urine drug screen during that previous admission, however, that was positive for cocaine.
With that information, cocaine-associated chest pain is high on your differential, but you have many questions and are not sure how to proceed.
How useful is a urine drug screen for determining if the patient used cocaine?
The urine drug test for cocaine is highly specific (95%) and sensitive (99%). Cocaine itself is eliminated from urine in about 12 hours, but this can be delayed up to 72 hours in chronic or heavy users. The standard ELISA assay, however, does not test for cocaine, but instead for the metabolite benzoylecgonine, which is detectable in urine in as little as two hours after use and remains detectable for three to four days. Amoxicillin was previously thought to cause false-positives, but recent studies show that is less likely. Despite similar endings, other -caine drugs such as lidocaine, procaine, and articaine lack the central ecgonine structure, and therefore are not registered as false-positives.
How certain should you be that the positive urine cocaine test is related to the patient's current chest pain?
The cardiac effects of cocaine are seen rapidly after ingestion. The majority of patients develop myocardial infarction within an hour, usually by three hours after cocaine use. The cocaine metabolites, however, may cause delayed or waxing-waning coronary vasoconstriction, and therefore the ischemic chest pain can occur up to four days afterwards. If a patient can give you an accurate history of cocaine ingestion that falls within the window, you should have a very high suspicion that the chest pain symptoms are cocaine-related.
Find a complete discussion of cocaine chest pain, including the physiologic effects of cocaine, evaluating for cocaine chest pain, and treating cocaine-associated myocardial infarction, in the EMN iPad app and in the Spontaneous Circulation blog on www.EM-News.com, where the app can also be downloaded for free.Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.