Poisoning: Overview of approaches for evaluation and treatment

Patients presenting to the hospital with overdoses and poisonings should undergo an initial evaluation to determine whether a specific poisoning can be detected that would lead to specific management options. History and physical examination are key to determine what poisoning, such as a toxidrome—a syndrome related to a toxic exposure (cholinergic, anticholinergic, sympathomimetic, opioid, sedative-hypnotic, or withdrawal syndromes)—could be causing a patient’s presentation. Once a poisoning or overdose has been identified, management can be determined. Management options can include gastrointestinal decontamination, enhancing elimination, and/or use of antidotes. Additionally, some poisonings and overdoses only require supportive care.

History

A thorough poison history should be obtained. Route of exposure should be obtained. Necessary elements for a suspected ingestion include suspected substance, amount ingested, time of ingestion, and any possible coingestants. Other important elements include past medical history, medication history, social history, and family history. Access to other medications in the home, including dietary and herbal supplements and over-the-counter medications, must be determined. Review of symptoms, including if vomiting was present, will also be important when determining if gastrointestinal decontamination would be useful.

Physical examination

Poisoned patients should undergo a thorough physical examination to determine if a toxidrome is present. Specific elements of the examination that allow for this determination include mental status; pupil size and reactivity; mucous membrane evaluation; cardiac and pulmonary examinations; abdominal examination for bowel sounds and presence of palpable bladder; skin examination for temperature, flushing, and perspiration; muscle tone; and neurologic examination for the presence of tremors, clonus, and reflexes. See Table 140.1 for toxidrome physical examination findings.

TABLE 140.1

Toxidrome Physical Examination Findings

Toxidrome Physical Examination	Cholinergic	Anticholinergic	Sympathomimetic	Opioid	Opioid Withdrawal	Sedative-Hypnotic	Sedative-Hypnotic Withdrawal
Mental status	Awake	Obtunded or delirious	Awake	Depressed	Awake	Depressed	Agitated, awake, delirious
Pupils	Pinpoint	Dilated	Dilated	Pinpoint	Dilated	Normal	Dilated
	Reactive	Unreactive	Reactive	Reactive	Reactive		Reactive
Mucous membranes	Wet	Dry	Normal	Normal	Normal	Normal	Normal
Cardiovascular	↓	↑	↑	Normal	Normal	Normal	↑
Cardiovascular	Heart rate	Heart rate	Heart rate	Normal	Normal	Normal	Heart rate
Pulmonary	Wheeze, rhonchi	Normal	Normal	↓	Normal	Normal	Normal
	↑			Respiratory rate
	Respiratory rate			↓
				Depth of breathing
Bowel sounds	↑	↓	Normal	↓	↑	Normal	Normal
Bladder	Not palpable	Palpable	Normal	May be palpable	Normal	Normal	Normal
Skin temperature	↓	↑	↑	Normal	Normal	Normal	↑
Skin color	Normal	Flushed	Flushed	Normal or cyanotic	Normal	Normal	Normal
Perspiration	Present	Absent	Present				Present
Antidote	Atropine
Pralidoxime	Physostigmine	Benzo-diazepines	Naloxone			Benzodiazepines

Laboratory analysis

While determining whether a poisoning has occurred or trying to determine the cause of an undifferentiated poisoning, some laboratory values can be helpful. Common laboratory studies to obtain include basic metabolic panel for electrolytes and to determine anion gap; ethanol, acetaminophen (paracetamol), and salicylate concentrations; liver function tests for transaminases; serum osmolarity if toxic alcohol is suspected; and blood gas for pH. These laboratories can aid in narrowing the differential diagnosis when a patient has overdosed or make the diagnosis in acetaminophen or salicylate poisoning.

Toxicology laboratory

Urine drug screens are usually obtained in poisoned patients; however, there is no standardized screen. The interpretation of these tests depends on the clinician’s knowledge of which toxins have been screened and whether confirmatory testing (ideally performed by a different analytic method) will follow. The length of time required to receive results varies among hospitals. Quantitative serum drug testing is done when quantitation of a toxin is clinically relevant, as is the case for acetaminophen, anticonvulsant agents, salicylates, digoxin, ethanol, ethylene glycol, methanol, iron, lithium, and theophylline. The clinician caring for the poisoned patient should discuss drug testing with the analytic toxicologist so that the results of testing can be appropriately interpreted. The clinical value of analytic toxicology testing depends on the clinician’s ability to understand and interpret the results because of limitations of the screening and other tests.

Once a poisoning has been identified, specific management options may be necessary, from gastrointestinal decontamination and enhancing elimination, to use of specific antidotes.

Gastrointestinal decontamination

The theory of gastric decontamination is that removal of toxins is done first from the stomach (where absorption is poor) before moving to the small intestine (where absorption is more rapid) so as to decrease the toxicity of the poisoning. Because of controversies regarding the role of gastrointestinal decontamination (GID), senior toxicologists from the American Academy of Clinical Toxicology and the European Association of Poison Centres and Clinical Toxicologists (EAPCCT) agreed to collaborate on the production of position statements on GID treatments. These statements, published in 1997, are systematically developed guidelines founded on a criteria-based critical review of all relevant scientific literature. All position statements were updated in 2004, with some getting new updates in 2014 ( Table 140.2 ). GID included ipecac, gastric lavage, single-dose activated charcoal, cathartics, and whole-bowel irrigation.

TABLE 140.2

Position Statement Summaries on Gastrointestinal Decontamination Treatments

Management	Recommendation
Gastric Decontamination
Ipecac	Syrup of ipecac should not be administered routinely for the management of poisoned patients.
Gastric lavage	Gastric lavage should not be employed routinely in the management of poisoned patients.
Single-dose activated charcoal	Single-dose activated charcoal should not be administered routinely in the management of poisoned patients.
Cathartic	Administration of a cathartic alone has no role in the management of poisoned patients. Routine use of a cathartic in combination with activated charcoal is not endorsed.
Whole-bowel irrigation	Whole-bowel irrigation should not be used routinely in the poisoned patient.
Enhance Elimination
Multiple-dose activated charcoal	Multiple-dose activated charcoal should be considered if a patient has ingested a life-threatening amount of carbamazepine, dapsone, phenobarbital, quinine, or theophylline.
Urinary alkalinization	Urinary alkalinization should be considered as first-line treatment in patients with moderately severe salicylate poisoning who do not meet the criteria for hemodialysis. Urinary alkalinization also should be considered for patients with severe poisoning caused by 2,4-dichlorophenoxyacetic acid or mecoprop (MCPP) poisoning. Urinary alkalinization is not recommended as first-line treatment for cases of phenobarbital poisoning, because multiple-dose activated charcoal is superior.

Ipecac

Ipecac, a prepared form of the Cephaelis acuminata or Cephaelis ipecacuanha plant, is no longer recommended for routine use in the management of poisoned patients, as there is no evidence that it improves outcomes. Vomiting within 30 minutes after administration is caused by local irritation of the gastric mucosa, and after 30 minutes vomiting is centrally induced. In experimental studies, the amount of marker removed by ipecac treatment was highly variable and diminished with time.

Gastric lavage

Gastric lavage should not be employed routinely in the management of poisoned patients, as there is little clinical evidence of benefit and no controlled trials showing benefit. If performed because of a potentially life-threatening poison ingestion, an experienced provider should perform the lavage based on the complications that can occur. Gastric lavage involves a large-bore (36F–40F) orogastric tube passed into the stomach, after which small volumes (200–300 mL) of liquid are alternately administered and aspirated. Comatose patients and those with loss of their protective airway reflexes should have an endotracheal tube placed before this procedure. An oral airway prevents biting of the tube. The amount of stomach contents removed via this procedure is highly variable and decreases with time. The procedure can actually push stomach contents into the intestine. Contraindications include loss of protective airway reflexes (unless the patient is endotracheally intubated), ingestion of a corrosive substance or a hydrocarbon, gastrointestinal pathology, and other medical conditions that could be worsened by the use of lavage. Complications of the procedure include aspiration, laryngospasm, hypoxia, hypercapnia, mechanical injury, and fluid and electrolyte imbalances in children.

Single-dose activated charcoal

Activated charcoal is made when coconut shells, peat, wood, or other materials undergo controlled pyrolysis and are subsequently activated by heating in steam or air at high temperatures. Activation creates multiple internal pores and the small particle size necessary for adsorption. The particles have a large surface area and are capable of adsorbing poisons with varying affinities. Although in vitro studies demonstrate adsorption of many drugs to activated charcoal, animal studies reveal variable reductions in the systemic uptake of marker substances. Volunteer and clinical studies have not demonstrated that single-dose administration of activated charcoal improves outcome. Therefore single-dose activated charcoal should not be administered routinely in the management of poisoned patients. Administration of activated charcoal may be considered if a patient has ingested a potentially toxic amount of poison that is known to be adsorbed to charcoal not longer than 1 hour before treatment, as its effectiveness decreases over time. There is no evidence that the administration of activated charcoal improves outcome. ^,

Contraindications to the administration of activated charcoal include decreased level of consciousness and unprotected airway, ingestion of caustic substances or hydrocarbons, gastrointestinal pathology, and medical conditions that could be further compromised by the administration of activated charcoal. Complications include aspiration and direct administration of charcoal into the lung.

Because activated charcoal is an inert substance, it is thought that lung injury after aspiration of activated charcoal is caused by gastric contents. Aspiration of gastric contents causes neutrophils to release neutrophil elastase, which increases pulmonary vascular permeability. In comparison, intratracheal administration of activated charcoal does not increase elastase in the bronchoalveolar fluid. Activated charcoal can activate alveolar macrophages, which are a potent source of oxygen radicals, proteases, and other inflammatory mediators. Charcoal also causes obstruction of small distal airways. Overdistention of alveolar segments in areas not occluded by charcoal leads to volutrauma in those areas, which increases microvascular permeability. Although case reports reveal long-term pulmonary pathology after aspiration or instillation of activated charcoal, ^, the true incidence of chronic problems after charcoal aspiration is unknown.

Cathartics

Administration of a cathartic alone has no role in the management of poisoned patients. Routine use of a cathartic in combination with activated charcoal is not endorsed.

You're Reading a Preview

Become a Clinical Tree membership for Full access and enjoy Unlimited articles

Become membership

If you are a member. Log in here