Key Clinical Questions
What information is important in the history to define a toxidrome?
What are the key areas of focus for the physical examination in the unknown poison/overdosed patient?
What are common toxidromes to consider?
What are the effective decontamination procedures to consider?
How do you determine appropriate disposition of the poisoned/overdosed patient?
When should you be concerned about delayed toxicity?
What is the role of a poison center and poison information specialist?
A 27-year-old man was observed stumbling in a local park. The police brought him to the emergency department (ED) for evaluation of his altered mental status and possible drug intoxication. A history was difficult to obtain because he was mumbling incoherently, hallucinating, and extremely agitated. It was unknown whether the patient had an underlying psychiatric disorder. Due to increasing agitation and combativeness, the patient was placed in physical restraints. Initial vital signs included a BP 158/94, HR 133, RR 20, T101.5 F, and O2 saturation 98%. Pupils were symmetric and approximately 6 mm. They reacted poorly to light. A limited physical examination was notable for dry oropharynx, absence of cardiac murmurs, clear lungs, and a soft, nontender abdomen. Bowel sounds were present but very infrequent. Neurologically he was confused and combative but moving all extremities with good strength equal bilaterally. Occasional myoclonic jerks of the upper and lower extremities were noted. The skin was warm and dry, and flushing noted at the face and neck. A finger stick glucose was 100mg/dL. Cardiac monitor revealed sinus tachycardia. Complete blood cell count, kidney function, and electrolytes were within normal limits. He received a normal saline fluid bolus and required a total of 4 milligrams of midazolam for sedation. The patient continued to be tachycardic and combative. He was admitted to the telemetry unit for monitoring and further treatment. How would you further manage this patient? |
Introduction
Nearly 2.5 million human exposures were reported in 2007 to U.S. poison control centers. The majority of these exposures involved analgesics, sedative-hypnotics, and antipsychotics. Substances more frequently involved in fatalities of adults include sedative/hypnotics/antipsychotics, opioids, antidepressants, acetaminophen in combination, cardiovascular drugs, stimulants, and street drugs. As this database is dependent upon calls to the poison center, the incidence of poisonings by overdose and deaths due to overdose and exposures are likely underestimated, since not all exposures are reported.
Of cases reported to the poison center, approximately 1.8 million (73%) are managed at the site of exposure, 15% are treated and released from the health care facility, but 5.7% are admitted for medical care. Many of these patients will be managed and stabilized by hospitalists. A systematic approach to overdosed and poisoned patients is needed to provide effective and efficient care. In most cases the basic stabilization measures involving airway, breathing, and circulation will have occurred in the emergency department. However, continued supportive care is required until each patient is medically stable and ready for discharge or transfer to psychiatry. Supportive care of the overdosed patient may involve administering oxygen, intravenous fluids, antidotes, vasopressor, anticonvulsants, or continuing decontamination of the gut.
The Initial Evaluation
Toxidromes are defined as signs and symptoms associated with toxicity from a class of drugs (eg, opiate, cholinergic, etc). When assessing the unknown overdose patient, a common challenge is obtaining a coherent history either from the patient, his or her relatives, or from first responders. The key elements in the toxicology history include what medications or substances were ingested; the amount ingested, and/or the concentration if applicable; the time of ingestion; whether emesis occurred and if pill fragments were noted by the patient or other persons at the scene; and the reasons why the patient ingested the substance. Was this a suicide attempt, recreational use, accidental, or malicious?
Determining the patient’s current symptoms is also helpful in defining a possible toxidrome and assists in management. Common toxidromes to consider include opiate, sympathomimetic, anticholinergic, cardiovascular, and anticholinergic (See Table 98-1). Looking for signs and symptoms of serotonin and neuroleptic malignant syndromes is also important in the management and disposition of these patients.
| Mental Status | Vital Signs | Pupils | Skin | |
|---|---|---|---|---|
| Sympathomimetic | Increased | Increased | Enlarged | Wet |
| Anticholinergic | Increased | Increased | Enlarged | Dry |
| Opiate | Decreased | Decreased | Small | |
| Sedative-hypnotic | Decreased | Decreased | Small | |
| Cardiovascular | Decreased | Decreased | Midsize | |
| Serotonin | Increased/Decreased | Increased/Decreased | Enlarged | Wet |
Key points in the toxicology history of ingestions The toxicology history “MATTERS”
|
The physical examination findings in overdosed and poisoned patients may rapidly change. The mental status, vital signs, pupil size, and skin are important; and in some case, odors can point to the diagnosis. The mental status may range from severe somnolence to extreme agitation or hallucinations. It is important to note whether the vital signs are elevated, normal, or depressed. Pupils are typically reported as (Pupils Equal Round React to Light and Accomodate) “PERRLA” without reporting size. Whether the pupils are pinpoint, mid-size, or large may help with distinguishing the toxidrome. Skin changes may not be immediately noted, but specifically look for findings such as flushing or cyanosis, diaphoresis or dryness, needle track marks or bullous lesions, and note whether the skin is hot or cool to touch.
Several toxins may have a characteristic odor and will alert the provider to a possible diagnosis. Garlic odor in the breath of a patient with an unknown overdose may indicate thallium, organophosphate, arsenic, dimethyl-sulfoxide, selenium, or a phosphide ingestion; the odor of wintergreen is highly suspicious of a methylsalicylate ingestion; and, of course, the odor of distilled spirits may indicate an ethanol-containing beverage or substance. The odor of bitter almonds signifies the presence of cyanide; unfortunately only about 50% of people can detect this odor.
It is important not to get anchored to the initial one or two aspects of the patient’s presentation (anchoring bias). There are numerous medical conditions that can mimic an overdose and vice versa. When the history is unclear, unreliable, or simply unknown, one must consider medical or traumatic causes for the patient’s altered state. Attempt to obtain collateral history from relatives, medics, or others who may know the patient or found him unresponsive. Computerized tomography of the head may be needed to rule out intracranial hemorrhage or mass lesions. Chest or abdominal radiographs should be considered based on the clinical scenario and physical findings. Laboratory tests to consider based on clinical presentation include thyroid stimulating hormone, blood cultures, arterial or venous blood gases, salicylate level, hepatic function tests, pregnancy test, lactate, and creatinine kinase (CK).
Laboratory tests important in the evaluation of the unknown overdose patient include basic metabolic panel, acetaminophen level, serum osmolality, hepatic function tests, and urinalysis. Monitoring organ function by periodically assessing liver and renal laboratory values, CK, and possibly serial electrocardiograms may allow early detection of the delayed toxidrome and assist in providing expeditious management. A pregnancy test is routinely obtained in the altered female of childbearing age.
One issue that has been a source of controversy is the utility of toxicology screening tests or the urine drug screens. Kellerman et al conducted a prospective study of 582 consecutive emergency department patients with suspected drug overdose and found that more than 95% of cases had no significant change in treatment or disposition in response to routine toxicologic screening1. Another test that is typically ordered indiscriminately is the salicylate concentration. In a retrospective case review of patients with salicylate concentrations obtained, and the presence of salicylates, Wood and colleagues concluded that “routine measurement of plasma salicylate concentrations is not required” unless there is a history of salicylate ingestion or the history and physical are unreliable and the patient has clinical features of salicylate poisoning2
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