What is the role of lab testing in the workup of heroin toxicity?

Updated: Dec 16, 2018
  • Author: Rania Habal, MD; Chief Editor: Jeter (Jay) Pritchard Taylor, III, MD  more...
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Answer

The diagnosis of heroin poisoning is usually made clinically, and laboratory analysis does not alter therapy in the emergent setting. Additional tests and further workup are indicated if the patient's condition does not respond to naloxone or if the patient's course of treatment is complicated.

Qualitative analysis may be helpful in confirming heroin use, as well as concomitant use of other drugs. Co-ingestion of alcohol, benzodiazepines, cocaine, and amphetamines is common and may contribute to morbidity and mortality. If the patient is taking prescription narcotics, which commonly contain acetaminophen or aspirin, serum drug levels should be obtained.

Heroin is quickly metabolized to 6-MAM and morphine. Most qualitative toxicologic studies screen for morphine only and use the presence of morphine in the urine as a surrogate for heroin use. In criminal and legal cases, however, testing for specific compounds is necessary, and—because 6-MAM can be generated only from heroin metabolism—the presence of 6-MAM on a drug screen is taken as evidence for heroin use.

In mild-to-moderate heroin overdoses, arterial blood gas (ABG) analysis reveals respiratory acidosis. In more severe overdoses, tissue hypoxia is common, leading to mixed respiratory and metabolic acidosis. The presence of unexplained metabolic acidosis should prompt a search for a co-ingestion or contamination with poisonous substances such as cyanide and clenbuterol. [20]

Hypoglycemia must be diagnosed at the bedside and treated immediately. A complete metabolic panel is indicated if the patient's coma persists despite the infusion of naloxone (Narcan), dextrose, and thiamine (the coma protocol).

Other studies to consider include the following:

  • Liver function tests (LFTs) and coagulation studies are indicated if hepatitis is suspected and can determine ammonia levels if hepatic encephalopathy is suspected.
  • Renal function should be monitored in patients with rhabdomyolysis, shock, or prolonged coma and in the setting of sepsis, severe hypertension, and preexisting renal insufficiency.
  • Complete blood cell (CBC) count is indicated if infection, blood loss, or immunodeficiency is suspected.
  • Creatine kinase (CK) level determination is indicated when rhabdomyolysis or compartment syndrome is suspected; an elevated CK level may denote cardiac injury in comatose patients.
  • A pregnancy test should be considered in women of childbearing age.
  • Cerebrospinal fluid (CSF) analysis is indicated when an infectious process is suspected.

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