Evaluation and Management of Drug Overdose in Adults
By James E. McFeely, MD, Medical Director Critical Care Units, Alta Bates Summit Medical Center, Berkley, CA, is Associate Editor for Critical Care Alert.
Dr. McFeely reports no financial relationship to this field of study.
Management of patients with accidental or intentional poisoning in drug overdose is a common problem for the intensivist. The actual incidence of poisoning in the United States is unknown because of lack of adequate reporting, but a minimum of several million cases occur annually. The vast majority of these cases do not require ICU admission.1 The most common exposures that require ICU admission include analgesics, sedative hypnotics and psychotics, antidepressants, street drugs, and alcohols. Of cases that eventually result in a fatality, more than 30% are due to analgesics and narcotics (acetaminophen, oxycodone, and salicylates).
Evaluation
Initial evaluation requires a systematic approach beginning with a detailed history of ingestion (if the patient is able to provide one) and, for the critical care patient, rapid assessment for cardiovascular instability and need for airway protection.2 Patients with an unexplained altered level of consciousness should receive glucose (D50) and thiamine. There is no need to wait for an initial finger-stick glucose measurement. If there is a suggestion of narcotic overdose, naloxone (0.5-1 mg) can be administered if the patient is hypoventilating or if inadequate airway protection is suspected.
History
Obtaining an accurate history may be difficult. A history should be obtained not only from the patient, but also from anyone else with relevant information about what may have been ingested. Accessing pill vials or pharmacy records and prescription information from the patient's primary care physician may also provide useful information. The physical examination may offer further hints as to the category of drugs ingested and suggest a specific toxidrome to direct the diagnostic and therapeutic workup (see Table 1, below). Patients presenting with tachycardia, hypertension, tachypnea, mydriasis, and fever may have been exposed to some sympathomimetic, anticholinergic, or hallucinogenic medications, or may be suffering from drug withdrawal. Patients presenting with hypotension, bradycardia, hypothermia, and obtundation are more likely to have been exposed to opiates, sedative hypnotics, alcohols, or some sympatholytic medication.
Table 1. Toxidromes (presenting features of different categories of overdose). |
|
| Toxidrome | Clinical Features |
| Cholinergic (SLUDGE) |
Salivation, Lacrimation, Urination, Defecation, Gastrointestinal upset, Emesis |
| Anticholinergic | Dry skin, hyperthermia, mydriasis, tachycardia, delirium, thirst, urinary retention |
| Sympathomimetic | Hypertension, tachycardia, CNS excitation, seizures, mydriasis, diaphoresis |
| Narcotic | Miosis, respiratory depression, depressed level of consciousness, hyporeflexic |
| Sedative hypnotics | Respiratory depression, depressed level of consciousness, hyporeflexic, hypotensive |
Discrepancies between the history and physical examination may reflect an inaccurate or incomplete ingestion history. Routine laboratory data, including chemistry panels, urine toxicology screens, acetaminophen, and aspirin levels, should be measured in all patients with intentional overdose regardless of their ingestion history. Depending on the timing of the ingestion, these drug levels may need to be repeated to determine the severity of the clinical course and the need for ongoing therapy. Other specific laboratory analysis may be necessary (e.g., co-oximetry for diagnosis of carbon monoxide poisoning), depending on the toxic exposure. Measurement of anion and osmolal gaps should occur routinely: An abnormality suggests a specific differential diagnosis (see Table 2, below). A pregnancy test should be obtained from women in the appropriate age group.
Table 2. Causes of an increased osmolal gap. |
| Acetone |
| Alcohols (ethanol, isopropyl alcohol, methanol, benzyl alcohol) |
| Glycerol |
| Mannitol |
| Glycols (propylene glycol, ethylene glycol) |
| Ethers (ethyl ethers, glycol ethers) |
Decision to Admit
The need for ICU admission can be determined within the first few hours. Many patients who present to the emergency room with ingestions develop minimal or no symptoms and do not require ICU care. Typical ICU admission criteria include respiratory failure, seizures, altered level of consciousness, hypotension, or evidence of involvement of the cardiac conduction system. Patients who require emergent dialysis, whole bowel irrigation, invasive monitoring, or the potential rapid use of antidotes (e.g., digoxin immune Fab, naloxone) should also be admitted to the ICU.
Once admitted, patients require general ICU supportive care, including airway protection for depressed mental status or hypoventilation. Hypotension is initially managed with a combination of fluid and vasopressors. Hypertension and agitation can be treated with short-acting sedatives such as benzodiazepines. Hypertension should be treated with a calcium channel blocker or combination of a beta-blocker with vasodilators to avoid unopposed alpha-adrenergic effect.
Once the patient has been initially stabilized, it may be appropriate to perform a gut decontamination to minimize further absorption of the ingested agent. A combination of activated charcoal and polyethyline glycol-electrolyte solution is frequently used. Controversy remains regarding the efficacy of repetitive dosing of activated charcoal.3 Some toxic ingestions can be removed through the use of hemodialysis (see Table 3, below).
Table 3. Toxic exposures potentially treatable with dialysis. |
| Alcohols and similar substances (ethanol, isopropyl alcohol, acetone, methanol, ethylene glycol, trichloroethanol) |
| Barbiturates |
| Bromides |
| Chloral hydrate |
| Lithium |
| Procainamide |
| Theophylline |
| Salicylates |
| Atenolol, sotalol |
| Heavy metals (possibly) |
Antidotes
Some specific antidotes exist for a number of the more serious and common toxic ingestions (see Table 4, below).4-10 The decision to use these depends on an assessment of the potential benefits, risks, and predicted severity of the toxic ingestion. Some antidotes may need to be repeatedly administered depending on the half-life of the antidote and the toxic ingestion. Particular caution needs to be used with the administration of flumazenil in patients with suspected chronic ingestion of benzodiazepines, as this may precipitate seizure activity. With appropriate supportive care and judicious use of specific antidotes, the mortality rate for hospitalized patients with drug poisoning is approximately 1%-2%.
Table 4. Specific antidotes for common toxic ingestions. |
|
| Toxin | Antidote |
| Acetaminophen | Acetylcysteine (Mucomyst)4,5 |
| Anticholinergic agents | Physostigmine |
| Benzodiazepines | Flumazenil |
| Beta-blockers | Glucagon,6 calcium, insulin, glucose |
| Calcium channel blockers | Calcium, glucagon,6 insulin, glucose, lipids |
| Carbon monoxide | Oxygen, maybe hyperbaric therapy |
| Cyanide | Amyl nitrate, sodium nitrite |
| Digitalis | Digoxin immune Fab (Digibind®) |
| Ethylene glycol | Ethanol, fomepizole7 |
| Methemoglobinemia | Methylene blue |
| Opiates | Naloxone |
| Organophosphates, nerve agents | Atropine, perhaps pralidoxime8 |
| Tricyclic antidepressants | Sodium bicarbonate9,10 |
Conclusion
Throughout the course of care, it should be routine practice to contact the local poison control center to obtain expert advice in management of these patients. In the United States, the local center can be reached at (800) 222-1222.
Careful attention to the details of the history, appropriate laboratory analysis, frequent reassessment of a patient's condition, and liberal consultation with poison control all facilitate the best chance for a successful outcome.
References
- Watson WA, et al. 2004 Annual report of the American Association of Poison Control Centers Toxic Exposure Surveillance System. Am J Emerg Med 2005;23:589-666.
- Zimmerman JL. Poisonings and overdoses in the intensive care unit: General and specific management issues. Crit Care Med 2003;31:2794-2801.
- Position statement and practice guidelines on the use of multi-dose activated charcoal in the treatment of acute poisoning. American Academy of Clinical Toxicology; European Association of Poisons Centres and Clinical Toxicologists. J Toxicol Clin Toxicol 1999;37:731-751.
- Clinical policy: Critical issues in the management of patients presenting to the emergency department with acetaminophen overdose. Ann Emerg Med 2007;50:292-313.
- Brok J, et al. Interventions for paracetamol (acetaminophen) overdose. Cochrane Database Syst Rev 2006;(2):CD003328.
- Kerns W 2nd. Management of beta-adrenergic blocker and calcium channel antagonist toxicity. Emerg Med Clin North Am 2007;25:309-331; abstract viii.
- Brent J. Fomepizole for ethylene glycol and methanol poisoning. N Engl J Med 2009;360:2216-2223.
- Buckley NA, et al. Oximes for acute organophosphate pesticide poisoning. Cochrane Database Syst Rev 2005;(1):CD005085.
- Bradberry SM, et al. Management of the cardiovascular complications of tricyclic antidepressant poisoning: Role of sodium bicarbonate. Toxicol Rev 2005;24:195-204.
- Tricyclic antidepressant poisoning: Cardiovascular toxicity. Toxicol Rev 2005;24:205-214.
You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content