Toxicology
James F. Wiley II
Diane P. Calello
GASTRIC DECONTAMINATION
Administration of activated charcoal is the preferred method of gastric decontamination. Whole bowel irrigation and gastric lavage play a much lesser role in the management of the poisoned patient but may still be of benefit in selected patients. Syrup of ipecac is not recommended for most poisonings.
Activated Charcoal
Indications and Contraindications
Activated charcoal is indicated for all ingestions if administration can occur within 1 hour of ingestion, unless specifically contraindicated. Contraindications include the following:
Compromised, unprotected airway (aspiration risk)
Gastrointestinal bleeding or perforation
Caustic ingestions (charcoal impedes endoscopic visualization)
Aliphatic hydrocarbon ingestion (may promote vomiting and aspiration)
TABLE 83-1 Agents with Limited or Uncertain Binding to Activated Charcoal | |||||||||||||||||||||||||||||||||
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Administration
The dose is 1 g/kg, up to 60 g total of activated charcoal. Mixing the charcoal with flavored syrups and putting it in a covered cup with a straw facilitates oral administration. Nasogastric intubation is required in alert but uncooperative patients, but should be done with extreme caution as it increases the risk of charcoal aspiration. Patients with altered mental status should not receive activated charcoal unless their airway is first secured.
Complications
Complications of activated charcoal use include vomiting and aspiration, constipation or obstipation, desorption of poison from charcoal, and late absorption in patients with delayed gastrointestinal motility (e.g., those taking drugs with anticholinergic properties). Death has occurred in a child who aspirated activated charcoal mixed with a magnesium cathartic.
Whole Bowel Irrigation
Whole bowel irrigation involves copious irrigation of the gastrointestinal tract, via nasogastric tube, to force the poisons rapidly through the bowel before significant absorption can occur. The solution used, polyethylene glycol 3,500 MW iso-osmotic bowel solution (GoLYTELY), causes no significant fluid or electrolyte loss in the gut.
Indications and Contraindications
Potential indications, to date, have been limited to agents that do not adsorb well to charcoal or that have the potential for absorption distally in the gastrointestinal tract, such as iron, heavy metals such as lead, lithium, and sustained-release
products (e.g., many antiarrhythmics, theophylline). Other scenarios may be amenable to whole bowel irrigation as an adjunct to activated charcoal administration, such as ingestions of patch medications, and delayed presentation of high-lethality toxic ingestions. In addition, whole bowel irrigation is used to treat body packers (people who ingest large numbers of packets of cocaine or heroin wrapped in latex condoms). Whole bowel irrigation is contraindicated in patients with evidence of ileus or bowel perforation.
products (e.g., many antiarrhythmics, theophylline). Other scenarios may be amenable to whole bowel irrigation as an adjunct to activated charcoal administration, such as ingestions of patch medications, and delayed presentation of high-lethality toxic ingestions. In addition, whole bowel irrigation is used to treat body packers (people who ingest large numbers of packets of cocaine or heroin wrapped in latex condoms). Whole bowel irrigation is contraindicated in patients with evidence of ileus or bowel perforation.
Administration
GoLYTELY is administered at a dose of 500 mL/hour in young children and at a dose of up to 2 L/hour in adolescents and adults, usually via nasogastric tube. The patient should be sitting up during treatment. The endpoint for stopping whole bowel irrigation is a clear rectal effluent and recovery from poisoning.
Complications
The major complications reported from whole bowel irrigation are vomiting and abdominal pain. Further, patients should not be permitted to “drink” whole bowel irrigation as the required volume per hour cannot be achieved voluntarily and the treatment will fail.
Gastric Lavage
Gastric lavage removes 10% to 25% of ingested toxin when performed within 30 to 60 minutes of ingestion.
Indications and Contraindications
Gastric lavage may not be useful more than 1 hour after ingestion unless the ingested poison delays gastric emptying. It has been shown to improve outcome in patients who are comatose and receive gastric lavage within 60 minutes. In other patients, the potential risks of gastric lavage must be weighed heavily against its benefit.
Gastric lavage should be reserved for the critically ill poisoning patient or a patient who is likely to undergo rapid decompensation. Patients who ingest liquid medicines may benefit from nasogastric lavage if it is performed within 30 to 60 minutes.
Gastric lavage should not be performed in patients with airway compromise before endotracheal intubation. Other contraindications include the ingestion of caustic alkaline substances or small amounts of acids or hydrocarbons, abnormal esophageal anatomy, and bleeding diatheses.
Administration
Gastric lavage requires the placement of a large-bore (24 to 36 French) orogastric tube followed by repeated infusion and withdrawal of room temperature normal saline in 50- to 200-mL aliquots. Before lavage, one must ensure a protected airway: Position the patient on the left side with the head below the feet, and determine correct gastric tube position.
Syrup of Ipecac
Syrup of ipecac, derived from the ipecacuanha plant, causes vomiting by direct gastric irritation and through a direct central effect at the chemotactic trigger zone in the medulla. Up to 93% of patients who receive ipecac vomit within 30 to 60 minutes.
Indications and Contraindications
Indications are now limited to patients within 30 to 90 minutes after ingestion who are at substantial risk of toxicity, do not have a contraindication to ipecac administration, who will be delayed beyond 1 hour before receiving emergency care, and for whom syrup of ipecac will not delay or adversely affect definitive treatment. Except for rural residents, these guidelines severely limit the potential use of syrup of ipecac, and the American Academy of Pediatrics no longer recommends routine prescribing of syrup of ipecac as part of well child care. It is almost never used in the hospital setting.
Contraindications to ipecac use consist of altered mental status (lethargy, coma, seizures—either existing or impending) and ingestion of caustic substances, aliphatic hydrocarbons, or drugs with a high likelihood of rapid serious effects (e.g., cyclic antidepressants, antiarrhythmics, clonidine, isoniazid, lithium, alcohol). In addition, patients who have already spontaneously vomited will not receive any further benefit from syrup of ipecac administration.
Administration
Dose is based on age: for children 6 months to 1 year of age, give 10 mL (2 tsp); 1 to 12 years, 15 mL (1 tbsp); and >12 years, 30 mL (2 tbsp). Give the child 10 mL/kg of water, up to 240 mL (8 oz), after administering the syrup of ipecac. Repeat the dose if no vomiting occurs within 30 minutes.
Complications
Complications include excessive vomiting, Mallory-Weiss tears, pneumomediastinum, and delayed delivery of activated charcoal or other oral antidotes. Chronic use of syrup of ipecac or inadvertent administration of the much more concentrated extract of ipecac has caused myocardial and neuromuscular toxicity.
Cathartics
Indications and Contraindications
Cathartics have no demonstrated efficacy in poisoning treatment. Coadministration of cathartic with activated charcoal in patients >12 years of age may prevent obstipation. Cathartics are contraindicated in patients with bowel perforation, ileus, or diarrhea.
Administration
Cathartics should only be given as a single dose when administered with activated charcoal; multiple doses of cathartics should be avoided except as outlined in
section on “Elimination Enhancement.” If a cathartic is given, sorbitol 35% is the preferred agent because it has a rapid onset of catharsis. The dose of sorbitol 35% is 1 g/kg (3 mL/kg).
section on “Elimination Enhancement.” If a cathartic is given, sorbitol 35% is the preferred agent because it has a rapid onset of catharsis. The dose of sorbitol 35% is 1 g/kg (3 mL/kg).
Complications
Complications include electrolyte imbalance and dehydration. Sorbitol also increases the likelihood of vomiting when given with activated charcoal. Death has occurred in several patients who received 4 to 6 doses of sorbitol over 24 hours.
ELIMINATION ENHANCEMENT
Extracorporeal clearance of toxin can be achieved by administering multiple-dose activated charcoal, inducing alkaline diuresis, or by performing hemodialysis or charcoal hemoperfusion.
Multiple-Dose Activated Charcoal
Multiple doses of activated charcoal increase the clearance of theophylline, carbamazepine, phenytoin, phenobarbital, and some cyclic antidepressants. The dose is 1 g/kg with cathartic for the initial dose, followed by 0.5 to 1 g/kg of activated charcoal without cathartic every 4 hours until the patient has nontoxic blood levels, has shown clinical improvement, and has passed charcoal-laden stool.
Alkaline Diuresis
Alkaline diuresis can enhance the excretion of weak acids, especially salicylates and phenobarbital (but not other barbiturates). This procedure promotes conversion of these drugs to their ionized form within the proximal renal tubule and prevents distal tubular resorption (ion trapping). Sodium bicarbonate is given intravenously until a urine pH greater than 7.0 is achieved. Care must be taken to avoid fluid overload, hypernatremia, hypokalemia, hypocalcemia, and hypomagnesemia during alkaline diuresis.
Hemodialysis
Hemodialysis can remove toxins with low molecular weight (200 Da), low plasma protein binding, and low tissue binding as expressed by the volume of distribution (Vd):
Vd (L/kg) = Dose absorbed (mg/kg)/plasma concentration (mg/L) Hemodialysis is most effective for drugs with a Vd <1 L/kg (Table 83-2).
Hemoperfusion
Hemoperfusion diverts the patient’s circulation through a charcoal filter where the toxin binds to an activated charcoal cartridge. Charcoal hemoperfusion is technically more difficult and less available than hemodialysis. Furthermore, ingestions of theophylline and phenobarbital, the drugs most amenable to removal with hemoperfusion, are now more typically managed using multiple-dose activated charcoal or hemodialysis.
TABLE 83-2 Toxins Removed by Hemodialysis | ||||||||||||||||||||||||||||||
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HINT: Less than 1% of all pediatric poisoning patients require hemodialysis or hemoperfusion.APPROACH TO THE POISONED PATIENT
Stabilization
Airway, breathing, circulation, and disability must be assessed in order, and compromise in any of these areas requires prompt attention. Complete exposure of the patient occurs as part of the rapid assessment. Vital signs, including temperature, continuous monitoring of the heart rate, respiratory rate, blood pressure, and pulse oximetry, should be initiated. Supplemental oxygen in an inspired concentration of 100% should be administered.
Administration of Substrates and Antidotes
Dextrose and Thiamine
The glucose level should be determined in any poisoned child with a depressed level of consciousness, using a rapid reagent strip. Hypoglycemia suggests certain ingestants (Table 83-3) and requires correction with 0.5 to 1 g/kg dextrose administered as an intravenous bolus. Children who have ingested oral hypoglycemic agents should also receive octreotide (Table 83-4). Thiamine (100 mg intramuscularly or intravenously) should precede dextrose infusion in a patient who is suspected to be alcoholic.
TABLE 83-3 Agents Causing Hypoglycemia in Overdosed Children | |||||
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HINT: Hypoglycemia is the one metabolic abnormality that can cause focal neurologic findings.Naloxone
Naloxone (2 mg intravenously, intramuscularly, or via endotracheal tube) reverses coma caused by opioids. It may also help some patients who have ingested clonidine. It should be given to any child with a depressed level of consciousness because it has few adverse effects in this setting and may prevent the need for aggressive intervention, such as endotracheal intubation. Response to naloxone occurs within 1 to 2 minutes of administration. After 30 minutes, the naloxone will wear off and resedation may occur. Repeated naloxone administration or continuous intravenous naloxone infusion is often required to prevent further depressed mental status.
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