Laboratory Studies
The use of laboratory studies in the treatment of patients potentially exposed to opioid or benzodiazepine incapacitating agents should initially focus on the potential complications associated with those sedating agents. Additional laboratory tests can also be conducted in an attempt to identify the incapacitating agent if the specific agent is unknown to the clinicians.
Rapid urine drug screenings (immunoassays) are available and may assist in diagnosis. However, these immunoassays do have a number of limitations. Opioid immunoassays are directed toward morphine, and thus many synthetic opioids, such as fentanyl, show no cross-reactivity with these assays. Testing for benzodiazepines is complicated because numerous benzodiazepines have substantially different structures. Results may be positive for diazepam, but negative for other benzodiazepines (eg, clonazepam).
Performing the following tests is reasonable in any person who has potentially been exposed to an incapacitating agent:
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Complete blood cell count
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Electrolytes assay
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Clotting studies
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Renal function tests
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Liver function tests
If the patient is comatose, performing a urine myoglobin and/or creatine phosphokinase test is warranted to exclude rhabdomyolysis. Hyperkalemia, hyperphosphatemia, and hypocalcemia may occur in association with rhabdomyolysis. The lactate level may also be elevated in these patients.
If the incapacitating agent is unknown, obtain extra blood and urine samples. Subsequent testing can be performed to confirm the causative agent.
Imaging Studies
A patient who has potentially been exposed to an opioid or a benzodiazepine incapacitating agent and who is comatose may be at risk for aspiration pneumonia. Obtain a chest radiograph.
If the etiology of a patient's altered mental status is uncertain, performing a head CT scan to exclude other intracranial processes is reasonable.
Electrocardiography
Both opioids and benzodiazepines may be associated with bradycardia. However, stress occurring in response to a situation associated with an exposure to aerosolized opioids or benzodiazepines may lead to tachycardia. Patients who are exposed to these agents and have preexisting cardiac disease may be at risk for cardiac ischemia. Perform an electrocardiogram to evaluate for these potential problems.
