Friday, January 11, 2008

Toxicity, Methamphetamine PART 2

Acute Respiratory Distress Syndrome Headache, Migraine Hypertensive Emergencies Hyperthyroidism, Thyroid Storm, and Graves Disease Myocardial Infarction Myocarditis Pediatrics, Febrile Seizures Pediatrics, Tachycardia Status Epilepticus Toxicity, Amphetamine Toxicity, Anticholinergic Toxicity, Antihistamine Toxicity, Hallucinogen Toxicity, Mushroom - Hallucinogens Toxicity, Sympathomimetic Toxicity, Theophylline

WORKUP
Lab Studies:
Perform laboratory studies based on the patient's symptoms.
Obtain a baseline complete blood count (CBC) and chemistry panel for all patients.
Measure creatinine kinase (CK) and myoglobin levels to exclude rhabdomyolysis that may be present despite minimal symptoms. Obtain myocardial band enzymes of CK (CK-MB) and a troponin level if concern of myocardial ischemia from methamphetamine use exists.
Perform pregnancy tests in women of childbearing age.
Imaging Studies:
Order a chest radiograph for patients with pulmonary symptoms or chest trauma.
In patients with altered mental status, perform a head CT scan to exclude intracranial bleeding. Such bleeding may be the result of either methamphetamine-induced hypertension or associated head trauma.
Other Tests:
Obtain an ECG for all patients.
Patients with symptomatic chest pain should have myocardial infarction excluded using standard rule-out protocol.
Obtain serial ECGs, CK isoenzymes, myoglobin, and troponin (T or I) at the appropriate intervals.
TREATMENT


Prehospital Care: Patients with acute methamphetamine intoxication may be highly agitated and present a serious safety risk to prehospital personnel. Seek additional help from police or other EMS providers before patient transport, if possible. Prehospital IV access is warranted with patient consent, allowing for treatment of seizures and agitation using IV benzodiazepines according to medical direction or protocol.
Patient mental function may be sufficiently impaired, precluding the patient from making an informed decision to refuse treatment and transport.
Emergency Department Care: Most cases of amphetamine toxicity can be managed supportively. In the case of a severe overdose, immediate supportive care, including airway control, oxygenation and ventilation support, and appropriate monitoring is required. Specific treatments for heavy metal toxicity caused by contaminants in some methamphetamine preparations may be needed. Animal studies suggest that orally ingested but not IV amphetaminelike compounds can be decontaminated with oral activated charcoal. In severe overdoses, termination of amphetamine-induced seizure activity and arrhythmias are of immediate importance. Correction of hypertension, hypotension, hyperthermia, metabolic and electrolyte abnormalities, and control of severe psychiatric agitation are indicated. Consider health maintenance activities, such as testing for hepatitis and HIV disease.
Agitation
Because of the ability of methamphetamine to cause significant CNS and psychiatric activation, patients who present to EDs for acute intoxication may require pharmacologic intervention.
Treat hyperactive or agitated persons with droperidol or haloperidol. Haloperidol and droperidol are butyrophenones and dopamine blocking agents that specifically antagonize the central behavioral effects of methamphetamine. Multiple clinical reports attest to the efficacy of droperidol and haloperidol in acute amphetamine toxicity.
An animal study has shown the superiority of haloperidol over diazepam in protecting against amphetamine-induced fatality.
Patients with acute choreoathetoid syndrome associated with amphetamines may show rapid improvement with haloperidol.
The doses of these medications should be titrated to the symptoms and be given IV (see Medication).
Diazepam, a benzodiazepine that enhances GABA neurotransmission (probably nonspecifically), affects methamphetamine-induced behavioral and psychiatric intoxication. It is also used to terminate amphetamine-induced seizures.
Diazepam was found to be highly effective in antagonizing the toxic effects of cocaine but not as effective against amphetamines in animal models. In a recent study of 146 patients presenting to the ED agitated, violent, or psychotic from methamphetamine, droperidol produced more rapid and profound sedation than lorazepam. Droperidol and lorazepam produced clinically significant reductions in pulse, systolic blood pressure, respiration rate, and temperature over a 60-minute period.
Significant social and psychiatric intervention is needed to reduce long-term dependency on amphetamines.
Hypertension
If sedation fails, several antihypertensive agents, including short-acting IV beta-blockers or direct short-acting vasodilators, are effective in reversing some methamphetamine-induced hypertension.
Theoretically, IV labetalol would be the best agent because of combined anti–alpha-adrenergic and anti–beta-adrenergic effects. However, when given IV, labetalol loses much of its anti–alpha-adrenergic effect.
These drugs should be given in small IV doses and titrated to effect. However, clinical experience has shown labetalol and esmolol to be equally effective.
In rare instances, agents such as nitroprusside or fenoldopam are necessary.
Myocardial infarction
The approach to the patient with methamphetamine-induced cardiac ischemia should be no different than in other cases. Nitrates, thrombolytics, beta-blockers, and other commonly used agents can also be used in the case of methamphetamine toxicity.
Carefully monitor blood pressure to ensure that it does not exceed contraindicated levels for thrombolytics.
Beta-blockers are very helpful in reducing oxygen demand because most patients have significant tachycardia.
Seizures
Treat methamphetamine-induced seizures like other seizures of unknown etiology.
Administer benzodiazepines IV (see Medication).
In those patients who do not have IV access, an agent that has good IM absorption can be used (eg, lorazepam, midazolam).
After control of the acute episode, administer longer-acting stabilizing agents, such as phenobarbital.
All patients with methamphetamine-induced seizures are at high risk for intracranial bleeding and should receive a head CT scan as soon as possible.
Rhabdomyolysis
Suspect rhabdomyolysis, and rule it out by drawing initial CK levels in patients who present to the ED with severe agitation from amphetamines.
Aggressively treat patients with rhabdomyolysis with fluids and admit them to the hospital.
Closely monitor renal function, vital signs, and fluid input and output.
Early and aggressive fluid and electrolyte treatment of potential rhabdomyolysis can improve the clinical outcome and decrease potential nephrotoxicity.
Consultations: Consult with a regional poison control center or a local medical toxicologist (certified through the American Board of Medical Toxicology and/or the American Board of Emergency Medicine) to obtain additional information and patient care recommendations

FOLLOW-UP

Further Inpatient Care:
Critical care management may be needed for patients with persistent hypertension and those who develop severe rhabdomyolysis, seizures, stroke, coma, hyperthermia, or acute coronary ischemic syndrome.
Complications:
Rhabdomyolysis
Seizures
Stroke
Coma
Acute coronary ischemia
Ventricular arrhythmias
Death
Patients who use methamphetamine IV are at risk for HIV, hepatitis B, hepatitis C, and other infectious diseases associated with IV street drug use.
Prognosis:
Prognosis is generally good with rapid and appropriate treatment, assuming that the patient does not present with one of the above complications.
Patient Education:
For excellent patient education resources, visit eMedicine's Poisoning - First Aid and Emergency Center, Mental Health and Behavior Center, and Substance Abuse Center. Also, see eMedicine's patient education articles Drug Dependence & Abuse, Substance Abuse, Poisoning, Club Drugs, and Activated Charcoal.
MISCELLANEOUS

Medical/Legal Pitfalls:
Failure to diagnose and treat patients with methamphetamine toxicity if they have hyperthermia or rhabdomyolysis
Failure to obtain a head CT scan in patients with methamphetamine toxicity who present with mental status changes that do not normalize with pharmacologic treatment; thus, failing to diagnose an intracerebral hemorrhage
Failure to diagnose myocardial infarction or unstable angina in methamphetamine-intoxicated patients
Special Concerns:
Consider the possibility of methamphetamine or amphetamine toxicity in children who present with first-time seizures; several studies have noted amphetamine-positive drug screens in this patient population.
Healthcare personnel should be aware regarding blood-borne exposure and risk of HIV, hepatitis B, and hepatitis C.
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