Laboratory Studies
Lab tests should be ordered on the basis of patient presentation. Indications for ordering labs are as follows:
Diagnosis of cocaine use
See the list below:
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Urine drug screen: Qualitative drug screens usually test for the inactive cocaine metabolite, benzoylecgonine, which may be present for as long as 36 hours after a single use. Metabolites can be demonstrated in the urine within 5 minutes after intravenous administration. With long-term use, urine metabolites may be detected for as long as 3 weeks after discontinuation of the drug. Urine drug screen in the neonate also can be used to detect possible in utero exposure to cocaine. The persistence of benzoylecgonine, which can be detected in the neonate's urine for as long as 4 days, is due to slow metabolism, probably related to immaturity or relative deficiency of plasma cholinesterases in the newborn.
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Detection: Zinc sulphate and zinc supplements may interfere with detection of cocaine analogues. [20]
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Serum level of cocaine: This can be determined but has not been found to be useful clinically because of the rapid metabolism and short half-life of the drug.
Diagnosis of neurological complications
Tests used for diagnosing neurological complications include antinuclear antibody (ANA), creatine kinase (CK), CT scan, brain MRI, magnetic resonance angiography (MRA) of neck and intracranial vessels, 4-vessel angiogram, echocardiogram (transthoracic, transesophageal), positron emission tomography (PET), and single-photon emission computed tomography (SPECT).
Creatine kinase
Urine should be evaluated routinely for the presence of myoglobin. Of patients with cocaine-induced rhabdomyolysis, 75% have a positive urine dipstick result for the orthotolidine reaction for heme, 67% yield positive findings for urine protein, and many manifest microscopic hematuria.
Imaging Studies
See the list below:
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CT scan of brain: Focal neurological deficits or alterations in mental status are indications for performing CT scan of the brain. With long-term cocaine use, significant cerebral atrophy, enlarged lateral ventricles, and widened sylvian fissures may be seen. CT scan also reveals intracerebral hemorrhage.
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MRI of brain: MRI of newborns exposed to cocaine in utero may reveal evidence of cortical infarction, major congenital malformations, and mainly midline CNS abnormalities. Prenatal cocaine exposure reveals subtle microstructural changes on diffusion tensor imaging, suggesting less mature development of frontal white matter pathways. [21] Fast fluid-attenuated inversion-recovery (FLAIR) images may also show diffuse white matter changes as seen in toxic leukoencephalopathies.
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MRA of brain and intracranial vessels: MRA is indicated in patients with ischemic stroke or subarachnoid hemorrhage. MRA may show evidence of vasculitis or aneurysm; venous phase may show evidence of venous thrombosis.
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Four-vessel angiogram: This study is indicated in patients with a history of cocaine abuse and presenting with intracerebral hemorrhage, especially subarachnoid hemorrhage. Angiogram may show underlying vascular abnormalities. Berry aneurysms of the circle of Willis are a common finding. Arteriovenous (AV) malformations or tumor may be seen as well. Rarely, superior sagittal sinus thrombosis with hemorrhagic venous infarction, dural AV fistula, rupture of multiple mycotic aneurysms, and large-vessel thrombosis have been described. Angiographic beading can be seen in patients with vasculitis.
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Neuroradiological study of newborns born to mothers who had used cocaine during pregnancy may reveal periventricular leukomalacia or holoprosencephaly. Evidence of intracerebral, intraventricular or subarachnoid hemorrhage may be observed. Sonography, CT scan, and MRI revealed cortical infarcts and midline congenital malformations in 15% of infants exposed to cocaine in utero.
Other Tests
See the list below:
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ECG: Perform ECG if patient has chest pain.
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EEG: Perform EEG in patients with seizures and a history of cocaine use. Habitual cocaine use can be associated with diffuse slowing on EEG. Focal abnormalities in the form of spikes or slowing can be seen in patients with focal seizures or intracerebral complications.
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Transthoracic and transesophageal echocardiogram: Perform transthoracic and transesophageal echocardiogram in patients with embolic stroke caused by cocaine use. These studies may show evidence of vegetations in patients with infective endocarditis.
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PET and SPECT: These studies may provide additional information in long-term cocaine users presenting with neuropsychiatric manifestations. Cerebral blood flow is reduced in habitual cocaine abusers, and abnormalities are most marked in the prefrontal cortex. Some investigators using PET have found reduced glucose metabolism over the entire cerebral cortex, thalamus, and midbrain. SPECT with iodine-123 isopropyl iodoamphetamine (IMP) revealed irregularly reduced cerebral perfusion even among asymptomatic social cocaine users who had normal findings on CT scans. In cocaine-dependent polydrug users (many of whom also used opioids and/or ethanol), some authors have found abnormal cerebral perfusion that primarily involved parietal, temporal, frontal, and basal ganglia. [22]
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Ophthalmoscopic examinations and fundus photography of the retinas of cocaine addicts have revealed increased retinal arterial branching angle and venular caliber. [23]
