WORKUP	Section 5 of 10
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Lab Studies:

• The diagnosis of PCP intoxication is a difficult one to make without some sort of history of drug use from the patient. It should be considered in patients with bizarre behavior, hypertension, and nystagmus, or coma unresponsive to naloxone in a substance abuser. One of the very typical scenarios involves a nude patient walking on the street or between moving vehicles.

• Exposure to PCP can be confirmed by qualitative urine toxicology screening. Serum screening for PCP is not useful clinically because the test is not readily available. In addition, quantitative serum PCP level does not correlate with the symptoms.

• A fingerstick should be performed in all patients with altered mental status. McCarron et al found that 20% of patients with acute PCP intoxication were hypoglycemic.

• No laboratory tests are specific for PCP intoxication, but, in addition to hypoglycemia, elevations in WBC count and BUN and creatinine levels may be seen.

• Serum creatine phosphokinase and urine myoglobin levels should also be measured to rule out rhabdomyolysis, especially in the patients with severe agitation.

• Consider an arterial blood gas (ABG) to assess for hypoxemia and metabolic acidosis in unresponsive patients.

• Urine pregnancy tests are indicated for female patients of childbearing age.

Imaging Studies:

• No imaging studies are necessary for the evaluation of acute PCP intoxication.

• Consider a CT scan of the head to rule out an intracranial cause for altered mental status.

• Consider specific imaging to evaluate traumatic injuries associated with PCP intoxication.

Procedures:

• For patients who are unable to protect their airway or have evidence of respiratory compromise, endotracheal intubation and mechanical ventilation may be needed.

• Consider lumbar puncture in patients with altered mental status and fever in whom the diagnosis is unclear.

	TREATMENT	Section 6 of 10
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Prehospital Care:

• Evaluate and stabilize the patient's airway, breathing, and circulation (ABCs) including cervical spine immobilization if traumatic injury is suspected.

• Physical restraints may be required to prevent self-injury and to protect the medical staff. These patients should be monitored closely due to several death reports of PCP-intoxicated patients while being physically restrained.

• Chemical restraints may also be used. Establish intravenous access and administer benzodiazepines for cases of severe agitation. Intramuscular benzodiazepines are an alternative if intravenous access is unobtainable.

Emergency Department Care:

• After addressing and stabilizing the ABCs, treatment of PCP intoxication starts with initial supportive measures (IV, O₂, cardiac monitor). ECG may be indicated to assess for dysrhythmias.

• Obtain a fingerstick to rule out hypoglycemia.

• Place patients in a dark, quiet room under continuous observation to minimize environmental stimuli.

• Consider activated charcoal for oral ingestions and co-ingestions. Multiple doses of charcoal may be beneficial in the case of large overdose. Only one dose of sorbitol should be given, usually with the initial dose.

• Extreme violent psychotic behavior requires sedation with parenteral benzodiazepines. Seizures should be treated with benzodiazepines. Butyrophenones and phenothiazines should be avoided in moderate and severe intoxications because they can lower seizure threshold, cause dystonic reactions and hypotension, and worsen anticholinergic symptoms, including hyperthermia. Haldol should be reserved for the patients with mild, predominately psychotic symptoms, with normal vital signs.

• Patients with respiratory insufficiency or failure may require endotracheal intubation.

• Hyperthermia may be treated by conventional cooling methods.

• Rhabdomyolysis is treated with intravenous hydration and urine alkalinization. Possible caveat: a theoretical, but clinically unproven, concept of increase PCP reabsorption secondary to the urine alkalinization.

• For hypertensive emergencies, try to control agitation first with parenteral benzodiazepines. For persistent hypertension, intravenous nitroprusside is the agent of choice. Because of the theoretical concept of unopposed alpha effect (worsening of hypertension) and the availability of other antihypertensive agents (eg, calcium-channel blockers, intravenous nitroglycerin), pure beta-blockade should be avoided. Labetalol, however, which has both alpha and beta blockade, may be beneficial.

• New research is centered about the development of antibodies to neutralize the toxic effects of PCP.

• Acute PCP toxicity can usually be managed conservatively with an observation period of a few hours. More serious ingestions may require admission to an intensive care unit for days to weeks.

	MISCELLANEOUS	Section 9 of 10
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Medical/Legal Pitfalls:

• The acute toxicity of PCP is often misdiagnosed because of its similarity to schizophrenic episodes. In fact, PCP-induced psychosis may respond to antipsychotics, which may further confound the diagnosis.

• Do not rely on the urine toxicology screen to diagnose acute PCP intoxication. Chronic PCP users can have positive test results for weeks after their last use. Cases of false-positive results for PCP have also been reported with diphenhydramine (Benadryl) and dextromethorphan, an agent in over-the-counter cough formulations that can produce clinical effects similar to PCP when taken in high doses.

• Failure to diagnose or address hypoglycemia, hyperthermia, traumatic injuries, or rhabdomyolysis is medical malpractice.