Toxidromes: What Every Critical Care Nurse Should Know

An Expert Interview With Ann Lystrup, RN, BSN, CEN, CFRN, CCRN

Elizabeth McGann, DNSc, RN

June 08, 2011

June 8, 2011 (Chicago, Illinois) — Editor's note: Toxidromes are recognizable syndromes related to drug toxicity. Assessment and treatment of a patient with a toxidrome is essential knowledge for critical care nurses. "Oh, Grandma, What a Very Big Medication List You Have: Toxidromes Every Critical Care Nurse Should Know" was featured as a podium presentation here at the American Association of Critical-Care Nurses (AACN) 2011 National Teaching Institute & Critical Care Exposition, held from April 30 to May 5.

To find out more about how critical care nurses can best care for patients with major toxidromes, Medscape Medical News interviewed Ann Lystrup, RN, BSN, CEN, CFRN, CCRN.

Ms. Lystrup is a specialist in poison information at the Utah Poison Control Center in Salt Lake City. She has 30 years of experience in critical care, emergency, and trauma nursing as a flight nurse.

Medscape: What is a toxidrome?

Ms. Lystrup: The word toxidrome describes a group of signs and symptoms and/or characteristic effects associated with exposure to a particular substance or class of substances.

Toxidromes are analogous to groups of symptoms associated with certain medical conditions. For example, a patient who is having an acute myocardial infarction will likely experience chest pain, nausea, shortness of breath, and/or diaphoresis.

Similarly, if a patient presents with dilated pupils, confusion, agitation, flushed and dry skin, dry mouth, and tachycardia — all of which are symptoms associated with the anticholinergic toxidrome — healthcare providers should recognize that the patient may be experiencing toxicity caused by one or more substances that block cholinergic receptors in the body. Because seizures are another effect characteristic of the anticholinergic toxidrome, therapies — such as administration of benzodiazepine medication to prevent the onset of seizures — can be initiated while assessment and diagnostic evaluation studies are completed.

Medscape: What are the major toxidromes?

Ms. Lystrup: The major toxidromes most commonly associated with therapeutic use of medications, overdose exposures, substance abuse, and/or poisonings are cholinergic toxidrome, anticholinergic toxidrome, sympathomimetic/stimulant toxidrome, opioid/narcotic toxidrome, and sedative/hypnotic toxidrome.

The following is a brief description of the major toxidromes:

Cholinergic toxidrome

Signs and symptoms Causative agents
Bradycardia, urination, bronchospasm, bronchorrhea, lacrimation, emesis, diarrhea/defecation, miosis, salivation, sweating, muscle weakness, and muscle fasciculations Organophosphates, pilocarpine, carbamates, muscarinic mushrooms


Note the similarity between sympathomimetic/stimulant toxidrome and anticholinergic toxidrome (a few major differences are indicated in bold).

Anticholinergic toxidrome

Signs and symptoms Causative agents
Dry mucous membranes, flushed/dry/hot skin, visual disturbances, tachycardia, urinary retention, constipation, seizures, and decreased bowel sounds Diphenhydramine, antihistamines, atropine, antipsychotics, baclofen, phenothiazines, Jimson Weed, tricyclic antidepressants

Sympathomimetic/stimulant toxidrome

Signs and symptoms Causative agents
Excessive speech, excessive motor activity, tremor, insomnia, anorexia, hyperreflexia, seizures, rhabdomyolysis, tachycardia, hyperactive bowel sounds, and diaphoresis Amphetamines, methamphetamine, caffeine, cocaine, ephedrine, LSD, methylphenidate, nicotine, PCP


Note the similarity between sedative/hypnotic toxidrome and opioid/narcotic toxidrome, except for a few major differences (indicated in bold).

Opioid/narcotic toxidrome

Signs and symptoms Causative agents
CNS AND respiratory depression, confusion, somnolence, coma, shallow respirations, bradypnea, bradycardia, hypotension, hypothermia, decreased bowel sounds, hyporeflexia, and miosis Clonidine, codeine, buprenorphine, dextromethorphan, heroin, methadone, morphine, meperidine, hydrocodone, oxycodone, imidazoline eye drops, tramadol

Sedative/hypnotic toxidrome

Signs and symptoms Causative agents
Sedation – with progressive CNS depression and minimal or no respiratory depression, ataxia, delirium, hallucinations, hypotension, bradycardia, nystagmus, hyporeflexia, decreased bowel sounds, miosis or mydriasis Anticonvulsants, benzodiazepines, barbiturates, ethanol, methocarbamol, propoxyphene, trazodone, zolpidem, zaleplon, eszopiclone

Although not always called toxidromes specifically, exposures to other substances or classes of substances that often result in the development of common characteristic effects like those of a toxidrome include acetaminophen, salicylates, beta blockers and calcium-channel blockers, cardiac glycosides, tricyclic antidepressants, alcohols, heavy metals, iron, carbon monoxide, simple asphyxiants, and hydrocarbons.

Medscape: What challenges do nurses face in providing care to critically ill adults with a major toxidrome?

Ms. Lystrup: The major challenges nurses and other healthcare providers face in caring for critically ill patients with major toxidromes is being able to recognize that the patient has symptoms consistent with a toxidrome, and then being able to identify or differentiate which toxidrome the symptoms indicate.

Toxidromes often result from ingestion of overdose amounts or accumulation of medications with resultant elevated serum levels, but can also be seen as a result of adverse drug reactions and interactions between 2 or more medications. Thus, the ability to recognize those medications and/or combinations of medications that are most commonly associated with toxidromes for any of these reasons helps alert nurses to the potential that the patient is at risk of developing a toxicity-related syndrome.

This early detection is crucial in order to anticipate symptoms and effects rapidly, identify them when they do occur, and be prepared to initiate appropriate interventions as needed and without delay.

Medscape: Are there special considerations related to caring for critically ill older patients with toxidromes?

Ms. Lystrup: One special consideration related to caring for critically ill patients of all ages who have effects that may or may not be indicative of a toxidrome is the complicated clinical picture commonly associated with these patients.

They often present with multiple pathophysiological processes, 1 or more comorbidities, and an extensive list of medications. These create significant challenges for nurses as they attempt to "sort out" and identify what might actually be going on with these patients. Because older patients oftentimes have more preexisting medical conditions and are frequently taking higher numbers of medications, their clinical presentations are typically the most complicated and challenging.

In addition, critically ill patients have a decreased ability to further compensate for any additional physiological stressors that occur, so rapid recognition of the signs of a toxidrome and early institution of appropriate interventions is even more of a priority in these patients, despite how much more complicated that process is likely to be.

Thus, it is essential that nurses and other healthcare providers have an understanding of the conditions and medications that make patients most susceptible to major toxidromes, what signs and symptoms are likely to be seen, and what monitoring parameters and interventions are appropriate for each one.

Medscape: Are evidence-based interventions available?

Ms. Lystrup: Evidence-based interventions are available for treatment of many toxidromes, and research on additional interventions is ongoing. Administration of naloxone (Narcan) to reverse the CNS and respiratory depression associated with the opioid/narcotic toxidrome has been proven to be an effective intervention for several decades. In contrast, the use of intralipid/intravenous lipid emulsion therapy for treatment of the hypotension and bradycardia associated with beta blocker, calcium-channel blocker, and tricyclic antidepressant toxicity is relatively new; research into its effectiveness, side effects, and outcomes is ongoing.

Medscape: Can you recommend any Web-based resources with practice guidelines related to toxidromes?

Ms. Lystrup: There are several Web-based resources that give recommendations and/or guidelines for specific treatments and therapies associated with particular toxidrome-related conditions. LipidRescue provides the proposed dosing for intralipid/intravenous lipid emulsion therapy in tricyclic antidepressant, calcium-channel blocker, and beta blocker toxicity. Other Web-based resources can be found by searching specific therapies and for individual poison control centers.

There are very few practice guidelines for treatment of toxidrome that can be applied to patients universally. Treatment recommendations should be based on the particular circumstances and specific characteristics associated with each individual patient and situation. For that reason, it is advisable to contact a poison control center for consultation with a toxicologist regarding important considerations and recommendations for treatment in specific patient situations.

Early consultation with a toxicology-specialized physician is even more important for critically ill patients because of the limited ability of these patients to compensate for physiological stress and the potential for their rapid deterioration and/or adverse outcomes if appropriate treatments are delayed or inappropriate therapies are initiated.

Medscape: What can be done to prevent toxidromes?

Ms. Lystrup: Toxidromes cannot be prevented completely since they are the manifestations or symptoms that are seen following exposure to a toxic substance or in response to an adverse reaction to or elevated level of medications, drugs, or substances. In addition, patients will continue to be exposed to substances that result in toxicity and onset of symptoms associated with the particular related toxidrome, whether intentionally or unintentionally. However, as prescribers and healthcare providers gain increased knowledge about the potential for adverse drug reactions and drug–drug interactions in specific patient populations, medical conditions, and specific dosing regimens, adjustments can be made to decrease the occurrence of toxidromes.

Nurses with an understanding of toxidromes can play a significant role in educating patients about the potential for adverse effects and toxicity associated with their particular medications and medical conditions, and can teach them to watch for early signs that a toxidrome is developing.

Appropriate monitoring of patients at high risk for toxicity-related complications, and heightened awareness of the effects and symptoms that are expected will enhance early recognition of problems. Early identification of complications will hopefully result in rapid initiation of appropriate treatments and therapies, which will, in turn, result in improved patient outcomes. Continued research into and application of consistent evidence-based treatments and interventions aimed at prevention is also important.

Medscape: What predictions can you make for the future?

Ms: Lystrup: The ever-increasing availability and use of medication therapies will likely lead to increased occurrence of more complicated toxicity-related syndromes — or toxidromes. As research into new medication therapies and interactions between medications progresses, new treatments and antidotes will likely be recognized as well.

In order to provide patients with safe, high-quality care, it is critical that nurses and other healthcare providers have an understanding of the basic principles of pharmacology, drug metabolism, and medication therapies, so that we can identify patients most at risk for toxidromes, anticipate potential complications, recognize effects early, and rapidly institute appropriate treatment therapies and/or antidotes as needed.

I anticipate an increased demand for pharmacological education for healthcare providers in general, and especially for nurses, as well as a need for patient education even greater than what we have seen in the past.

Medscape: What was the most important point of your presentation?

Ms. Lystrup: Toxidromes are not only seen in patients with poisonings or overdose exposures, but can develop in any patient receiving therapeutic doses of commonly prescribed medications as well. Since critically ill patients are least likely to be able to compensate for the physiologic stressors associated with toxidromes, critical care nurses play a pivotal role in patient education, early recognition, and rapid institution of appropriate treatments of toxidrome-related complications — preventing them as much as possible and improving patient outcomes when they do occur.

Medscape: Is there anything else that you would like to add?

Ms. Lystrup: Basic pharmacologic and/or toxicologic reference texts are likely the best for obtaining information about different toxidromes, their causative agents, and their recommended treatments/antidotes. Two such textbooks are Goldfrank's Toxicologic Emergencies [Goldfrank LR, Flomenbaum NE, Hoffman RS, et al. 2011. 9th ed. New York: McGraw-Hill] and Gilman's Manual of Pharmacology and Therapeutics [Goodman LS, Gilman A, Brunton LL. 2008. New York: McGraw-Hill Medical].

Ms. Lystrup has disclosed no relevant financial relationships.


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