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Poisoning and Drug Overdose
SECTION 3
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GENERAL MEDICAL CARE: Emergent Medical Care
Poisoning and Drug Overdose Kelly Young
ROLE OF THE GENERALIST 1 2 3 4 5 6
Recognize poisoning/ingestion, especially in young children and in adolescents at risk for suicide attempts. Evaluate patient, determining general medical status and the ingestant. Determine expected severity of the ingestion. Institute appropriate management. Consult regional poison center and refer to the emergency department or intensive care unit as needed. Educate parents about poisoning prevention and poison center access.
DEFINITIONS Poisoning refers to exposure to a potentially toxic substance. Poisoning may be accidental or intentional, as in suicide attempts or gestures. Table 35-1 defines types of poisonings. A toxidrome is a recognizable set of symptoms associated with a particular toxin or class of toxins (e.g., narcotics). Decontamination refers to strategies to prevent or minimize absorption of the toxin and to enhance elimination. An antidote is a drug or therapy that reverses or blocks the toxic effects of the toxin. Accidental ingestions by preschool children and intentional ingestions constitute the most frequent referrals to poison centers. Fatalities are uncommon and have been decreasing as a result of improved anticipatory guidance, child-resistant packaging, and improved recognition and
supportive treatment of serious ingestions. When fatalities occur, they are more common in intentional ingestions by adolescents. Young children tend to ingest either nontoxic substances or only small quantities of toxic substances.
FUNDAMENTALS The pathophysiology by which toxins exert their effects varies according to the specific toxin. Toxins may cause local effects as a result of tissue destruction, systemic effects on particular organ systems, or effects on overall metabolism. Toxins are absorbed, distributed throughout the body, metabolized, and excreted. Interventions focus on prevention of absorption; enhanced metabolism and excretion; occasionally prevention of metabolism into a more toxic by-product; and, if available, neutralization of the toxic effects through an antidote. Because timing of symptoms after exposure varies according to the specific toxin, knowledge of the natural time course of symptoms is key to diagnosis and management. Even without a history of poisoning, clinicians must maintain a high index of suspicion. Children and adolescents may not tell others about a toxic exposure—some because they cannot, others for fear of punishment, or others because the ingestion was secondary to suicidal ideation. Table 35-2 lists common symptoms of ingestion. Symptoms that particularly should raise suspicion of an ingestion include otherwise unexplained alterations in mental status or behavior, cardiac dysrhythmias, severe vomiting, seizures, and autonomic changes. Table 35-3 summarizes four commonly encountered ingestions and the variety of symptoms that may occur.
Table 35-2. Common Symptoms Table 35-1. Types of Poisonings Ingestion Dermal
Ophthalmologic Inhalational
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Ingestion of a potentially toxic substance, often a drug; commonly used interchangeably with the term poisoning Toxic effects from exposure to toxic substance via the skin; may cause local effects on the exposed skin and/or systemic effects from absorption of the toxin Toxic effects from exposure to the eye Toxic effects from inhaling a toxin; may cause pulmonary and/or systemic effects
Gastrointestinal Cardiac Eye Gastrointestinal Neurologic Respiratory
Distinctive breath odor, skin color change, increased or decreased skin moisture, hypothermia, hyperthermia Bradycardia or tachycardia, hypotension, hypertension, arrhythmias, electrocardiogram changes Miosis, mydriasis, nystagmus Vomiting, diarrhea, hematemesis Altered mental status, acute mood or behavior changes, headache, seizures Respiratory depression, Kussmaul breathing in acidosis
Acetaminophen* Initial: No symptoms or nausea, vomiting, and anorexia 24–48 hr: Liver toxicity with right upper quadrant abdominal pain 3–4 days: Liver failure with jaundice, coagulopathy, and encephalopathy Iron Early symptoms: Vomiting and diarrhea, often bloody, possibly with massive fluid loss. Shock and death may occur in early stage with severe ingestions Latent period: Apparent improvement over 12 hr Late symptoms: In severe ingestions, shock, coma, seizures, liver failure, disseminated intravascular coagulation, and death may occur Tricyclic Antidepressants Mental status changes, seizures, cardiac rhythm changes, and hypotension Alcohols† Early symptoms: Nausea and vomiting and symptoms of mood and behavior change progressing to severe central nervous system depression; a distinctive odor may be present Methanol ingestion does not lead to intoxication, produces blurred vision after 3–24 hr, may lead to blindness *Any patient suspected of poisoning should have an acetaminophen level checked, even if they do not disclose acetaminophen ingestion. † Ethanol, isopropyl alcohol (rubbing alcohol), ethylene glycol (antifreeze, deicer), methanol (antifreeze, solvent).
DIAGNOSIS A detailed history is a key part of the evaluation. Table 35-4 lists important historical information. The goal of the history is to determine what was ingested, the maximum possible amount ingested, when the ingestion occurred, and current symptoms. Patients and parents should be asked about all possible substances available for ingestion, including medications of visitors, herbal preparations, vitamins, alternative medications, products from other countries, household products (e.g., cleaning, personal care, products used in hobbies or work), gardening products, and alcohol or drugs of abuse. There may be coingestions of substances other than the one disclosed in the initial history. One also must probe for the possibility of a combination product (e.g., patient discloses ingestion of a pseudoephedrine cold medicine, but the product also contains acetaminophen). Table 35-4. History Questions What was taken? If unknown, what was available to the patient? How much was taken? Calculate maximum possible amount based on amount remaining. Calculate maximum dose in mg/kg When was it taken? If not disclosed, how long was the child not under observation? What symptoms have occurred? When did the symptoms begin occurring relative to the estimated time of exposure to the toxin? What other medical conditions does the patient have? Look for conditions that may increase toxicity or prohibit certain therapies
The patient’s medical history should be reviewed to determine if the patient is particularly susceptible to toxic effects (e.g., if an epileptic patient ingests a proconvulsant). Intentional ingestions and suicidal ideation are separate but important issues to assess in older children. Sleuthing methods may be required to obtain the best estimate of the amount ingested. Family members should be encouraged to bring in the container and any remains of the substance ingested, even if it requires sending someone back to the home. Prescription labels may contain useful information regarding the number of pills originally present and when the prescription was filled, allowing for calculation of the probable number of pills left at the time of ingestion. Unknown pills often can be identified by comparing them (i.e., size, shape, color, imprint) with pictures from a pharmaceutical reference. The health care provider should count remaining pills or measure remaining liquid to estimate the maximum quantity of drug that was available to the patient. The health care provider always should assume the “worst case” (i.e., that the patient ingested all of the missing drug). The approximate volume of a swallow is 0.3 mL/kg. Even the best guess may be inaccurate. Physical examination should include examination directed toward expected signs of toxicity and a general examination. Symptoms and signs not consistent with what is expected may represent an undisclosed coingestant. Particularly important aspects of the physical examination are weight (expected toxic effects may be determined by milligrams ingested per kilogram); vital signs; temperature; pupillary size and reaction; breathing pattern (e.g., Kussmaul’s breathing seen in acidosis); mental status; distinctive breath odors; and skin color, temperature, and moisture. Certain combinations of these findings along with other symptoms may suggest a toxidrome (Table 35-5). If a symptomatic patient has a typical toxidrome, empirical therapy may be initiated based on the toxidrome without confirmation of the exact substance ingested. Continual reassessment and cardiorespiratory monitoring are important because new symptoms may develop. Laboratory tests performed should be directed by the results of the history and physical examination (Table 35-6). Qualitative drug screens that report only the presence or absence of drug are available for serum or urine. These screens are used more often when poisoning is part of a broader differential diagnosis for symptoms such as altered mental status or behavioral changes. These screens rarely are helpful in a patient with known poisoning. Quantitative drug levels assist in determining the expected severity of the ingestion or in ruling out ingestion of a drug. Quantitative levels usually are available for acetaminophen, aspirin (salicylate), ethanol, methanol, ethylene glycol, iron, theophylline, lithium, common anticonvulsants, some tricyclic antidepressants, and carboxyhemoglobin and methemoglobin by blood gas analysis. Because they are common coingestants and may require acute intervention, acetaminophen and salicylate levels should be determined routinely in poisonings, even in the absence of supportive historical data or physical signs. For adolescents, ethanol is a common coingestant and should be measured routinely. When the toxin is unknown or acidosis is suspected, serum chemistries and osmolarity may offer valuable
CHAPTER 35 Poisoning and Drug Overdose
Table 35-3. Symptoms of Ingestion of Acetaminophen, Iron, Tricyclic Antidepressants, and Alcohols
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Table 35-5. Toxidromes Toxin
Symptoms
Treatment
Narcotics
Respiratory depression, miosis, altered mental status or coma SLUDGE mnemonic: salivation, lacrimation, urination, diarrhea, gastrointestinal cramping, emesis. Also bronchorrhea, bronchospasm Seizures, prolonged QRS, altered level of consciousness, dysrhythmias Flushing (“red as a beet”) Dry skin and mucous membranes (“dry as a bone”) Hyperthermia (“hot as a hare”) Delirium (“mad as a hatter”) Mydriasis, tachycardia, urinary retention Mydriasis, anxiety, tachycardia, hypertension, hyperthermia, diaphoresis
Naloxone
Organophosphates, cholinergics
Tricyclic antidepressants Anticholinergic
Sympathomimetic
Atropine, pralidoxime
Sodium bicarbonate Supportive care
Quiet environment and benzodiazepines
information. The anion gap is calculated as [Na] – ([Cl] + [HCO3]) and is normally 8 to 12 mEq/L. An elevated anion gap indicates metabolic acidosis. Differential diagnosis can be remembered using the MUDPILES mnemonic: methanol ingestion, uremia, diabetic ketoacidosis, paraldehyde or phenformin ingestion, iron or isoniazid ingestion, lactic acidosis, ethylene glycol or ethanol ingestion, salicylate or solvent (e.g., toluene) ingestion. The osmolar gap is the difference between the measured serum osmolarity and the osmolarity calculated as 2[Na] + [glucose]/18 + [blood urea nitrogen]/2.8 and is normally less than 10 mOsm. An elevated osmolar gap is seen with ingestion of the alcohols (ethanol, methanol, ethylene glycol, and isopropyl alcohol).
Table 35-6. Laboratory and Diagnostic Tests Routine Laboratory Specific drug levels as indicated Acetaminophen, salicylate, ethanol levels Serum chemistries, calculated anion gap Serum osmolarity, calculated osmolar gap Rapid bedside glucose test Urine pregnancy test in childbearing-age female Laboratory, if Indicated Arterial blood gas Urinalysis
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Diagnostic Studies, if Indicated Electrocardiogram Chest radiography Plain abdominal radiography for radiopaque tablets Endoscopy
Arterial blood gas analysis is indicated if acidosis, hypoxemia, or abnormal hemoglobins (carboxyhemoglobin or methemoglobin) are suspected. Because hypoglycemia is common to many ingestions, a rapid bedside glucose test should be done on all patients. If rhabdomyolysis is suspected or associated with the toxic exposure, urinalysis should be performed. All girls of childbearing age should have a urine pregnancy test. Other diagnostic studies include pulse oximetry and cardiorespiratory monitoring for all poisoning patients, an electrocardiogram if cardiac toxicity is suspected or abnormalities (including tachycardia) are noted on physical examination, and imaging studies. Specific imaging studies may be indicated for certain ingestions, such as a chest radiograph in hydrocarbon ingestion to assess for aspiration and pulmonary toxicity. A plain abdominal radiograph (kidney, ureter, and bladder film) may identify certain radiopaque substances, as recalled by the mnemonic CHIPETS: chloral hydrate, heavy metals, iron, phenothiazines, entericcoated medications, tricyclic antidepressants, and slowrelease medications. An abdominal radiograph is primarily useful in iron ingestions to determine whether significant amounts of drug are present or remain after gastric decontamination procedures. Other diagnostic studies may be indicated for a specific toxin (e.g., endoscopy after ingestion of caustic acids or alkalis). Table 35-7 lists thresholds for probable toxicity and expected severity of poisoning by serum levels for acetaminophen, iron, and alcohols. In acetaminophen ingestion, the Rumack nomogram is used to plot a 4-hour postingestion level for determining the severity of expected toxicity. Baseline liver function tests also should be checked. Ingestions of iron at a dose of 20 mg/kg or less are unlikely to produce symptoms. A plain abdominal radiograph may show radiopaque tablets. If tablets are present, attempts should be made to remove them through gastric decontamination and, in extreme cases, endoscopy or even surgery to prevent further absorption. Repeat iron levels should be performed at 4 to 6 hours and 8 to 12 hours postingestion to rule out bezoar formation or ingestion of a
Table 35-7. Toxicity: Threshold Dose and Expected Toxicity by Serum Level Ingestant
Ingested Dose for Probable Toxicity
Expected Toxic by Serum Levels
Acetaminophen
Child: 140 μg/kg, toxicity likely Adolescent: 6g, toxicity likely
Iron
Ethanol
<20 mg/kg, symptoms unlikely 40 mg/kg serious toxicity >60 mg/kg, potentially lethal 3–5 g/kg, toxicity likely
4-hr level: 150–200 μg/mL, possible toxicity >200 μg/mL, probable toxicity 450–500 μg/dL, toxicity likely 800–1000 μg/dL, severe toxicity
Isopropyl alcohol
2–3 g/kg
Methanol and ethylene glycol
1–2 mL/kg
100 mg/dL, significant toxicity 50 mg/dL, toxicity likely 20 mg/dL, toxicity likely
MANAGEMENT Management strategies are specific to the toxin and the symptoms of the patient. Initial management must focus on the basic ABCs (airway, breathing, circulation) of resuscitation. General management of poisoning includes decontamination methods if indicated, specific antidotes if available, and close observation and supportive care. Details of toxic exposures by the ophthalmic and dermal routes are not discussed in this chapter, but general management includes copious irrigation with water or normal saline. Exposures to acids should not be treated by attempted neutralization with bases, and vice versa. Several methods of decontamination exist (Table 35-8). Syrup of ipecac and gastric lavage theoretically decrease absorption by removing residual toxin in the stomach. Toxicologists no longer recommend their use because studies have shown these techniques to be relatively ineffective, particularly as the time since ingestion increases, and they may interfere with the use of activated charcoal. Complications include aspiration and esophageal trauma. Some toxicologists recommend use only if they can be applied within 30 minutes of ingestion of a liquid or 1 hour of ingestion of solids. The American Academy of Pediatrics no longer recommends ipecac as a home treatment strategy. Neither induction of vomiting nor lavage should be used in patients with hydrocarbon or caustic acid or alkali ingestions. Care should be taken in patients with altered mental status who may not be able to protect their airway from aspiration. Activated charcoal is the mainstay of therapy for most ingestions. Charcoal binds toxins, preventing their absorption; the charcoal-toxin complex is then eliminated. The optimal dose of charcoal is 10 times the amount of toxin ingested. Because the exact amount of toxin ingested is often unknown, charcoal usually is administered at doses of 1 to 2 g/kg. The amount of charcoal given is limited only by what the patient is able to tolerate. The mnemonic PHAILS may be used to recall the few substances not bound to charcoal: pesticides; hydrocarbons; acids, alkalis, and alcohols; iron; lithium; and solvents. Charcoal may be mixed with soda or juice to enhance voluntary administration. Because charcoal has an unappetizing black color, placement in a cup with an opaque lid and administration through a straw may be helpful. A charcoal product is available for home use. If the patient
Table 35-8. Summary of Gastric Decontamination Techniques Technique
Dose
Contraindications
Syrup of ipecac
6 mo–1yr: 10 mL (use with caution) 1–12 yr: 15 mL >12 yr: 30 mL Follow with 8 oz water
Gastric lavage
15 mL/kg aliquots normal saline to maximum of 400 mL until lavage is clear (may be several liters)
Activated charcoal
1–2 g/kg or <6 yr: 25–50 g >6 yr: 50–100 g
Cathartics
Magnesium citrate, 4 mL/kg 70% Sorbitol, 1 g/kg
Whole-bowel irrigation
Toddler and preschool age: 500 mL/hr Adolescent and adult: 1–2 L/hr Continue until rectal effluent is clear
ALOC Caustics: acids and alkalis Hydrocarbons Expected ALOC (tricyclic antidepressants) ALOC with unprotected airway Caustics: acids and alkalis Hydrocarbons Expected ALOC >1 hr since ingestion ALOC with unprotected airway Absent bowel sounds, bowel obstruction Substance not bound by charcoal Repeated doses can cause dehydration or electrolyte imbalances Bowel obstruction, ileus, perforation, hemorrhage ALOC with unprotected airway
CHAPTER 35 Poisoning and Drug Overdose
sustained-release product. Ingestion of alcohols may be suspected by the presence of an anion gap acidosis and an osmolar gap. The Breathalyzer may offer a rapid assessment of ethanol ingestion. The threshold for toxicity in tricyclic antidepressants is low; moderate-to-severe symptoms can occur with doses of 10 to 20 mg/kg. Levels may be available for some tricyclic antidepressants, but results usually are not immediately available and may be difficult to interpret. Diagnosis is by clinical suspicion. An electrocardiogram should be performed to assess cardiac toxicity, including initial sinus tachycardia; prolonged QRS interval; prolonged P-R interval; prolonged Q-T interval; and in severe toxicity, progression to potentially life-threatening wide-complex tachycardia.
ALOC, altered level of consciousness.
refuses charcoal, it may be administered through a nasogastric tube. Care must be taken with patients at risk for aspiration (young children, children with altered mental status) because it can result in serious pneumonitis. Endotracheal intubation to protect the airway may be required before charcoal administration in these patients. Correct placement of the nasogastric tube in the gastrointestinal tract should be verified before administration. Cathartics (e.g., magnesium citrate, magnesium sulfate) have been mixed with charcoal to decrease transit time, enhance elimination, and counteract the constipating effects of charcoal. No significant benefit of cathartic use has been shown. Adverse effects, including dehydration and electrolyte disturbances, may occur, especially in young children. Cathartics are not recommended, but if used, they should never be given in repeated doses. Multiple-dose charcoal, less commonly used and often referred to as gastrointestinal dialysis, involves repeated administration of activated charcoal every 4 hours. This method may promote diffusion of the drug back into the gastrointestinal tract with binding to the charcoal. Cathartics should not be given with charcoal in repeated doses. Multiple-dose charcoal may be useful for phenobarbital, theophylline, and carbamazepine overdoses. It is not recommended for overdoses of drugs that cause ileus, such as tricyclic antidepressants. Whole-bowel irrigation uses solutions prescribed to clean out the gastrointestinal tract in preparation for colon
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surgery (e.g., GoLYTELY). It may be indicated for slowrelease medications, tablets that dissolve slowly and may cause concretions (e.g., iron), and ingestions in which charcoal is not effective. Administration by nasogastric tube usually is required to accomplish a rate of 500 mL/hr in young children and 1 to 2 L/hr in older children and adolescents. The end point is clear rectal effluent. Contraindications include bowel obstruction, ileus, gastrointestinal perforation, hemorrhage, and altered mental status with an unprotected airway. Hemodialysis may be used for severe ingestions of ethylene glycol, methanol, phenobarbital, lithium, salicylate, or theophylline. Charcoal hemoperfusion involves passing blood through a charcoal cartridge instead of a dialysis machine and may be used for severe theophylline poisoning. Urinary alkalinization via administration of sodium bicarbonate intravenously can enhance elimination of weak acids. The toxin is kept in its ionic state, preventing reabsorption in the renal tubule. This method is used primarily in severe salicylate and phenobarbital poisonings. Antidotes are available for only a few ingestions (Table 35-9). Naloxone may reverse rapidly respiratory depression from narcotic overdose. N-acetyl cysteine (NAC), if administered in time, prevents severe liver toxicity in acetaminophen ingestion. Bicarbonate administration may ameliorate the cardiac toxicity of tricyclic antidepressants. Digoxin immune Fab (Digibind) is used to bind digoxin, and deferoxamine is used to chelate iron. Referral and consultation depends on the specific substance ingested and the resources available. The regional poison center should be contacted for recommendations regarding management, disposition, and length of observation time required for asymptomatic patients. Symptomatic patients and patients who require a long observation period to rule out toxic effects should be admitted to the hospital. Severely toxic patients require management in an intensive care unit (ICU). A toxicologist should be consulted on such patients if one is available. Otherwise the poison center can be used for follow-up and recommendations. Table 35-9. Common Antidotes
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Toxin
Antidote
Acetaminophen Anticoagulants (warfarin-like) Anticholinergics Benzodiazepines β-blockers Calcium channel blockers Carbamate pesticides Carbon monoxide Cyanide Digoxin Ethylene glycol Iron Isoniazid Lead Mercury Methanol Methemoglobinemia Narcotics Organophosphate pesticides Tricyclic antidepressants
N-Acetyl cysteine Vitamin K Physostigmine Flumazenil Glucagon Calcium, glucagon Atropine Oxygen Cyanide antidote kit Digibind Ethanol Deferoxamine Pyridoxine Dimercaprol, EDTA, DMSA Dimercaprol, DMSA Ethanol, fomepizole Methylene blue Naloxone Atropine, pralidoxime Sodium bicarbonate
DMSA, dimercaptosuccinic acid; EDTA, ethylenediaminetetraacetic acid
Management of acetaminophen overdose involves the antidote NAC. NAC acts as a substitute for glutathione, which normally binds the toxic metabolite of acetaminophen, but is overwhelmed in an overdose. An initial dose of 140 mg/kg orally, followed by 70 mg/kg every 4 hours for 17 doses, is the traditional protocol. In other countries, NAC may be delivered intravenously. Activated charcoal is not used if it would interfere with NAC administration. Any vomiting should be treated aggressively with antiemetics to avoid interference with NAC. Patients with potentially toxic ingestions must be observed in the ICU. Patients with severe toxicity not prevented by NAC may require transfer to a liver transplant center. Deferoxamine is given to chelate iron in potentially serious overdoses, at a rate of 10 to 15 mg/kg/hr intravenously. Activated charcoal is not effective for binding iron. Gastric lavage may be used early after ingestion or if radiopaque tablets are still visible on plain abdominal radiographs. Presence of concretions or bezoars may require whole-bowel irrigation, endoscopy, and, in rare cases, surgical removal. Dialysis is used to remove the deferoxamine-iron complex if renal failure occurs. Patients with potentially serious ingestions or undergoing chelation therapy should be admitted to the ICU. Treatment of alcohol poisoning is primarily supportive and includes airway management/protection; fluid administration; and treatment of significant acidosis, hypocalcemia, and hypoglycemia with bicarbonate, calcium, and dextrose administration. Activated charcoal is not useful for alcohols. Gastric lavage is not recommended in a patient with significant altered mental status unless the airway is protected. Ethanol has been used as an antidote for severe methanol and ethylene glycol poisonings. Fomepizole is a new antidote available for methanol overdose and is preferred over ethanol administration. Dialysis may be required for lifethreatening overdoses, severe acidosis, renal failure, and methanol overdose causing visual symptoms not reversed by fomepizole. Treatment of tricyclic antidepressant poisoning includes supportive care, close monitoring, activated charcoal, and sodium bicarbonate for cardiac toxicity. ABCs should be assessed and stabilized immediately, and the patient should be placed on a cardiorespiratory monitor. Cardiac toxicity may be treated with sodium bicarbonate, 1 to 2 mEq/kg intravenously initially, then continuous infusion to maintain a serum pH of 7.45 to 7.55. Tricyclic antidepressants block the fast sodium channel, and sodium bicarbonate administration counteracts this effect. Lidocaine, 1 mg/kg slow intravenous bolus, then continuous infusion at 20 to 50 μg/ kg/min, may be used for wide-complex tachyarrhythmias. Seizures should be treated with benzodiazepines. Hypotension should be treated with fluid boluses; Trendelenburg positioning; sodium bicarbonate; and, if needed, pressors, such as norepinephrine and low-dose dopamine. Because of the low threshold for toxicity, all patients with tricyclic antidepressant ingestion warrant admission to an ICU. Anticipatory guidance and parental education are important in prevention (Box 35-1). Management of a less serious accidental ingestion provides an excellent opportunity for parental education. Emphasis should be placed on safe storage of toxic substances and access to the regional poison
Safe Storage 1. Keep potential toxins out of reach of children. Lock cabinets storing toxic substances. 2. Never store substances in unmarked containers, especially containers that typically hold beverages (e.g., old soda bottles or cups). 3. Advise visitors (e.g., grandparents) to store medications out of reach of children. 4. Dispose of unneeded toxic substances and unused or outdated medications. Education 1. Discuss safety issues with children as developmentally appropriate (e.g., not ingesting unknown substances). 2. Do not refer to medication as “candy” to entice young children to take it. 3. Discuss risks in depressed adolescents; advise parents to keep toxins out of reach of potentially suicidal family members.
and child-safe packaging have reduced fatalities further. Prognosis is more likely to be poor in intentional ingestions if the patient does not disclose ingestion or delays disclosure. The severity of poisoning is distinct from the seriousness of suicidal intention. Patients may have been quite serious about committing suicide, yet taken an inconsequential amount of drug or a drug that is relatively safe in overdose. In contrast, patients hoping to make a suicidal gesture unwittingly may expose themselves to a potentially fatal ingestion. Follow-up involves repeated anticipatory guidance and psychiatric consultation for intentional ingestions.
Mini-index of Related Topics
CH.
■ RESUSCITATION AND BASIC LIFE SUPPORT
27
■ APPROACH TO THE ILL-APPEARING CHILD
38
Poison Center
■ APPROACH TO THE AGITATED PATIENT
39
1. Keep the regional poison center and local emergency department or pediatrician’s telephone numbers readily available. Many poison centers provide stickers for household telephones.
■ GLUCOSE AND ELECTROLYTE DISORDERS
42
Therapy 1. Consider advising parents to have activated charcoal in the home. 2. Parents should administer activated charcoal only if instructed by the poison center staff or medical staff.
center phone number. Parents should be reminded that potential toxins include not only prescription medications, but also over-the-counter medications, vitamins, herbal preparations, alternative medications, household products, toxic plants, gardening and hobby chemicals, and kitchen items such as alcohol or oil of wintergreen.
■ SUICIDE AND SUICIDE PREVENTION
CHAPTER 35 Poisoning and Drug Overdose
Box 35-1. Education Points for Anticipatory Guidance
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SUGGESTED READINGS American Academy of Pediatrics, Committee on Injury and Poison Prevention: Handbook of Common Poisonings in Children, 3rd ed. Elk Grove Village, Ill, American Academy of Pediatrics, 1994. Erickson JB: Toxicology: Ingestions and smoke inhalation. In GauscheHill M, Fuchs S, Yamamoto L (eds): APLS: The Pediatric Emergency Medicine Resource. Boston, Jones and Bartlett, 2004, pp 234–267. Perry H, Shannon H: Poisoning. Pediatr Ann 1996;25:19–29. Tenenbein M: Poisoning. In Barkin RM (ed): Pediatric Emergency Medicine Concepts and Clinical Practice. St. Louis, Mosby-Year Book, 1997, pp 527–534. Tenenbein M, Cohen S, Sitar DS: Efficacy of ipecac-induced emesis, orogastric lavage and activated charcoal for acute drug overdose. Ann Emerg Med 1987;16:838–841.
OUTCOME AND FOLLOW-UP Prognosis depends on the specific toxin but is generally good. Most ingestions are not serious, and fatalities are rare. Advances in education of the public, poison center use,
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GENERAL MEDICAL CARE: Emergent Medical Care
Poisoning and Drug Overdose Kelly Young
ROLE OF THE GENERALIST 1 2 3 4 5 6
Recognize poisoning/ingestion, especially in young children and in adolescents at risk for suicide attempts. Evaluate patient, determining general medical status and the ingestant. Determine expected severity of the ingestion. Institute appropriate management. Consult regional poison center and refer to the emergency department or intensive care unit as needed. Educate parents about poisoning prevention and poison center access.
DEFINITIONS Poisoning refers to exposure to a potentially toxic substance. Poisoning may be accidental or intentional, as in suicide attempts or gestures. Table 35-1 defines types of poisonings. A toxidrome is a recognizable set of symptoms associated with a particular toxin or class of toxins (e.g., narcotics). Decontamination refers to strategies to prevent or minimize absorption of the toxin and to enhance elimination. An antidote is a drug or therapy that reverses or blocks the toxic effects of the toxin. Accidental ingestions by preschool children and intentional ingestions constitute the most frequent referrals to poison centers. Fatalities are uncommon and have been decreasing as a result of improved anticipatory guidance, child-resistant packaging, and improved recognition and
supportive treatment of serious ingestions. When fatalities occur, they are more common in intentional ingestions by adolescents. Young children tend to ingest either nontoxic substances or only small quantities of toxic substances.
FUNDAMENTALS The pathophysiology by which toxins exert their effects varies according to the specific toxin. Toxins may cause local effects as a result of tissue destruction, systemic effects on particular organ systems, or effects on overall metabolism. Toxins are absorbed, distributed throughout the body, metabolized, and excreted. Interventions focus on prevention of absorption; enhanced metabolism and excretion; occasionally prevention of metabolism into a more toxic by-product; and, if available, neutralization of the toxic effects through an antidote. Because timing of symptoms after exposure varies according to the specific toxin, knowledge of the natural time course of symptoms is key to diagnosis and management. Even without a history of poisoning, clinicians must maintain a high index of suspicion. Children and adolescents may not tell others about a toxic exposure—some because they cannot, others for fear of punishment, or others because the ingestion was secondary to suicidal ideation. Table 35-2 lists common symptoms of ingestion. Symptoms that particularly should raise suspicion of an ingestion include otherwise unexplained alterations in mental status or behavior, cardiac dysrhythmias, severe vomiting, seizures, and autonomic changes. Table 35-3 summarizes four commonly encountered ingestions and the variety of symptoms that may occur.
Table 35-2. Common Symptoms Table 35-1. Types of Poisonings Ingestion Dermal
Ophthalmologic Inhalational
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Ingestion of a potentially toxic substance, often a drug; commonly used interchangeably with the term poisoning Toxic effects from exposure to toxic substance via the skin; may cause local effects on the exposed skin and/or systemic effects from absorption of the toxin Toxic effects from exposure to the eye Toxic effects from inhaling a toxin; may cause pulmonary and/or systemic effects
Gastrointestinal Cardiac Eye Gastrointestinal Neurologic Respiratory
Distinctive breath odor, skin color change, increased or decreased skin moisture, hypothermia, hyperthermia Bradycardia or tachycardia, hypotension, hypertension, arrhythmias, electrocardiogram changes Miosis, mydriasis, nystagmus Vomiting, diarrhea, hematemesis Altered mental status, acute mood or behavior changes, headache, seizures Respiratory depression, Kussmaul breathing in acidosis
Acetaminophen* Initial: No symptoms or nausea, vomiting, and anorexia 24–48 hr: Liver toxicity with right upper quadrant abdominal pain 3–4 days: Liver failure with jaundice, coagulopathy, and encephalopathy Iron Early symptoms: Vomiting and diarrhea, often bloody, possibly with massive fluid loss. Shock and death may occur in early stage with severe ingestions Latent period: Apparent improvement over 12 hr Late symptoms: In severe ingestions, shock, coma, seizures, liver failure, disseminated intravascular coagulation, and death may occur Tricyclic Antidepressants Mental status changes, seizures, cardiac rhythm changes, and hypotension Alcohols† Early symptoms: Nausea and vomiting and symptoms of mood and behavior change progressing to severe central nervous system depression; a distinctive odor may be present Methanol ingestion does not lead to intoxication, produces blurred vision after 3–24 hr, may lead to blindness *Any patient suspected of poisoning should have an acetaminophen level checked, even if they do not disclose acetaminophen ingestion. † Ethanol, isopropyl alcohol (rubbing alcohol), ethylene glycol (antifreeze, deicer), methanol (antifreeze, solvent).
DIAGNOSIS A detailed history is a key part of the evaluation. Table 35-4 lists important historical information. The goal of the history is to determine what was ingested, the maximum possible amount ingested, when the ingestion occurred, and current symptoms. Patients and parents should be asked about all possible substances available for ingestion, including medications of visitors, herbal preparations, vitamins, alternative medications, products from other countries, household products (e.g., cleaning, personal care, products used in hobbies or work), gardening products, and alcohol or drugs of abuse. There may be coingestions of substances other than the one disclosed in the initial history. One also must probe for the possibility of a combination product (e.g., patient discloses ingestion of a pseudoephedrine cold medicine, but the product also contains acetaminophen). Table 35-4. History Questions What was taken? If unknown, what was available to the patient? How much was taken? Calculate maximum possible amount based on amount remaining. Calculate maximum dose in mg/kg When was it taken? If not disclosed, how long was the child not under observation? What symptoms have occurred? When did the symptoms begin occurring relative to the estimated time of exposure to the toxin? What other medical conditions does the patient have? Look for conditions that may increase toxicity or prohibit certain therapies
The patient’s medical history should be reviewed to determine if the patient is particularly susceptible to toxic effects (e.g., if an epileptic patient ingests a proconvulsant). Intentional ingestions and suicidal ideation are separate but important issues to assess in older children. Sleuthing methods may be required to obtain the best estimate of the amount ingested. Family members should be encouraged to bring in the container and any remains of the substance ingested, even if it requires sending someone back to the home. Prescription labels may contain useful information regarding the number of pills originally present and when the prescription was filled, allowing for calculation of the probable number of pills left at the time of ingestion. Unknown pills often can be identified by comparing them (i.e., size, shape, color, imprint) with pictures from a pharmaceutical reference. The health care provider should count remaining pills or measure remaining liquid to estimate the maximum quantity of drug that was available to the patient. The health care provider always should assume the “worst case” (i.e., that the patient ingested all of the missing drug). The approximate volume of a swallow is 0.3 mL/kg. Even the best guess may be inaccurate. Physical examination should include examination directed toward expected signs of toxicity and a general examination. Symptoms and signs not consistent with what is expected may represent an undisclosed coingestant. Particularly important aspects of the physical examination are weight (expected toxic effects may be determined by milligrams ingested per kilogram); vital signs; temperature; pupillary size and reaction; breathing pattern (e.g., Kussmaul’s breathing seen in acidosis); mental status; distinctive breath odors; and skin color, temperature, and moisture. Certain combinations of these findings along with other symptoms may suggest a toxidrome (Table 35-5). If a symptomatic patient has a typical toxidrome, empirical therapy may be initiated based on the toxidrome without confirmation of the exact substance ingested. Continual reassessment and cardiorespiratory monitoring are important because new symptoms may develop. Laboratory tests performed should be directed by the results of the history and physical examination (Table 35-6). Qualitative drug screens that report only the presence or absence of drug are available for serum or urine. These screens are used more often when poisoning is part of a broader differential diagnosis for symptoms such as altered mental status or behavioral changes. These screens rarely are helpful in a patient with known poisoning. Quantitative drug levels assist in determining the expected severity of the ingestion or in ruling out ingestion of a drug. Quantitative levels usually are available for acetaminophen, aspirin (salicylate), ethanol, methanol, ethylene glycol, iron, theophylline, lithium, common anticonvulsants, some tricyclic antidepressants, and carboxyhemoglobin and methemoglobin by blood gas analysis. Because they are common coingestants and may require acute intervention, acetaminophen and salicylate levels should be determined routinely in poisonings, even in the absence of supportive historical data or physical signs. For adolescents, ethanol is a common coingestant and should be measured routinely. When the toxin is unknown or acidosis is suspected, serum chemistries and osmolarity may offer valuable
CHAPTER 35 Poisoning and Drug Overdose
Table 35-3. Symptoms of Ingestion of Acetaminophen, Iron, Tricyclic Antidepressants, and Alcohols
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Table 35-5. Toxidromes Toxin
Symptoms
Treatment
Narcotics
Respiratory depression, miosis, altered mental status or coma SLUDGE mnemonic: salivation, lacrimation, urination, diarrhea, gastrointestinal cramping, emesis. Also bronchorrhea, bronchospasm Seizures, prolonged QRS, altered level of consciousness, dysrhythmias Flushing (“red as a beet”) Dry skin and mucous membranes (“dry as a bone”) Hyperthermia (“hot as a hare”) Delirium (“mad as a hatter”) Mydriasis, tachycardia, urinary retention Mydriasis, anxiety, tachycardia, hypertension, hyperthermia, diaphoresis
Naloxone
Organophosphates, cholinergics
Tricyclic antidepressants Anticholinergic
Sympathomimetic
Atropine, pralidoxime
Sodium bicarbonate Supportive care
Quiet environment and benzodiazepines
information. The anion gap is calculated as [Na] – ([Cl] + [HCO3]) and is normally 8 to 12 mEq/L. An elevated anion gap indicates metabolic acidosis. Differential diagnosis can be remembered using the MUDPILES mnemonic: methanol ingestion, uremia, diabetic ketoacidosis, paraldehyde or phenformin ingestion, iron or isoniazid ingestion, lactic acidosis, ethylene glycol or ethanol ingestion, salicylate or solvent (e.g., toluene) ingestion. The osmolar gap is the difference between the measured serum osmolarity and the osmolarity calculated as 2[Na] + [glucose]/18 + [blood urea nitrogen]/2.8 and is normally less than 10 mOsm. An elevated osmolar gap is seen with ingestion of the alcohols (ethanol, methanol, ethylene glycol, and isopropyl alcohol).
Table 35-6. Laboratory and Diagnostic Tests Routine Laboratory Specific drug levels as indicated Acetaminophen, salicylate, ethanol levels Serum chemistries, calculated anion gap Serum osmolarity, calculated osmolar gap Rapid bedside glucose test Urine pregnancy test in childbearing-age female Laboratory, if Indicated Arterial blood gas Urinalysis
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Diagnostic Studies, if Indicated Electrocardiogram Chest radiography Plain abdominal radiography for radiopaque tablets Endoscopy
Arterial blood gas analysis is indicated if acidosis, hypoxemia, or abnormal hemoglobins (carboxyhemoglobin or methemoglobin) are suspected. Because hypoglycemia is common to many ingestions, a rapid bedside glucose test should be done on all patients. If rhabdomyolysis is suspected or associated with the toxic exposure, urinalysis should be performed. All girls of childbearing age should have a urine pregnancy test. Other diagnostic studies include pulse oximetry and cardiorespiratory monitoring for all poisoning patients, an electrocardiogram if cardiac toxicity is suspected or abnormalities (including tachycardia) are noted on physical examination, and imaging studies. Specific imaging studies may be indicated for certain ingestions, such as a chest radiograph in hydrocarbon ingestion to assess for aspiration and pulmonary toxicity. A plain abdominal radiograph (kidney, ureter, and bladder film) may identify certain radiopaque substances, as recalled by the mnemonic CHIPETS: chloral hydrate, heavy metals, iron, phenothiazines, entericcoated medications, tricyclic antidepressants, and slowrelease medications. An abdominal radiograph is primarily useful in iron ingestions to determine whether significant amounts of drug are present or remain after gastric decontamination procedures. Other diagnostic studies may be indicated for a specific toxin (e.g., endoscopy after ingestion of caustic acids or alkalis). Table 35-7 lists thresholds for probable toxicity and expected severity of poisoning by serum levels for acetaminophen, iron, and alcohols. In acetaminophen ingestion, the Rumack nomogram is used to plot a 4-hour postingestion level for determining the severity of expected toxicity. Baseline liver function tests also should be checked. Ingestions of iron at a dose of 20 mg/kg or less are unlikely to produce symptoms. A plain abdominal radiograph may show radiopaque tablets. If tablets are present, attempts should be made to remove them through gastric decontamination and, in extreme cases, endoscopy or even surgery to prevent further absorption. Repeat iron levels should be performed at 4 to 6 hours and 8 to 12 hours postingestion to rule out bezoar formation or ingestion of a
Table 35-7. Toxicity: Threshold Dose and Expected Toxicity by Serum Level Ingestant
Ingested Dose for Probable Toxicity
Expected Toxic by Serum Levels
Acetaminophen
Child: 140 μg/kg, toxicity likely Adolescent: 6g, toxicity likely
Iron
Ethanol
<20 mg/kg, symptoms unlikely 40 mg/kg serious toxicity >60 mg/kg, potentially lethal 3–5 g/kg, toxicity likely
4-hr level: 150–200 μg/mL, possible toxicity >200 μg/mL, probable toxicity 450–500 μg/dL, toxicity likely 800–1000 μg/dL, severe toxicity
Isopropyl alcohol
2–3 g/kg
Methanol and ethylene glycol
1–2 mL/kg
100 mg/dL, significant toxicity 50 mg/dL, toxicity likely 20 mg/dL, toxicity likely
MANAGEMENT Management strategies are specific to the toxin and the symptoms of the patient. Initial management must focus on the basic ABCs (airway, breathing, circulation) of resuscitation. General management of poisoning includes decontamination methods if indicated, specific antidotes if available, and close observation and supportive care. Details of toxic exposures by the ophthalmic and dermal routes are not discussed in this chapter, but general management includes copious irrigation with water or normal saline. Exposures to acids should not be treated by attempted neutralization with bases, and vice versa. Several methods of decontamination exist (Table 35-8). Syrup of ipecac and gastric lavage theoretically decrease absorption by removing residual toxin in the stomach. Toxicologists no longer recommend their use because studies have shown these techniques to be relatively ineffective, particularly as the time since ingestion increases, and they may interfere with the use of activated charcoal. Complications include aspiration and esophageal trauma. Some toxicologists recommend use only if they can be applied within 30 minutes of ingestion of a liquid or 1 hour of ingestion of solids. The American Academy of Pediatrics no longer recommends ipecac as a home treatment strategy. Neither induction of vomiting nor lavage should be used in patients with hydrocarbon or caustic acid or alkali ingestions. Care should be taken in patients with altered mental status who may not be able to protect their airway from aspiration. Activated charcoal is the mainstay of therapy for most ingestions. Charcoal binds toxins, preventing their absorption; the charcoal-toxin complex is then eliminated. The optimal dose of charcoal is 10 times the amount of toxin ingested. Because the exact amount of toxin ingested is often unknown, charcoal usually is administered at doses of 1 to 2 g/kg. The amount of charcoal given is limited only by what the patient is able to tolerate. The mnemonic PHAILS may be used to recall the few substances not bound to charcoal: pesticides; hydrocarbons; acids, alkalis, and alcohols; iron; lithium; and solvents. Charcoal may be mixed with soda or juice to enhance voluntary administration. Because charcoal has an unappetizing black color, placement in a cup with an opaque lid and administration through a straw may be helpful. A charcoal product is available for home use. If the patient
Table 35-8. Summary of Gastric Decontamination Techniques Technique
Dose
Contraindications
Syrup of ipecac
6 mo–1yr: 10 mL (use with caution) 1–12 yr: 15 mL >12 yr: 30 mL Follow with 8 oz water
Gastric lavage
15 mL/kg aliquots normal saline to maximum of 400 mL until lavage is clear (may be several liters)
Activated charcoal
1–2 g/kg or <6 yr: 25–50 g >6 yr: 50–100 g
Cathartics
Magnesium citrate, 4 mL/kg 70% Sorbitol, 1 g/kg
Whole-bowel irrigation
Toddler and preschool age: 500 mL/hr Adolescent and adult: 1–2 L/hr Continue until rectal effluent is clear
ALOC Caustics: acids and alkalis Hydrocarbons Expected ALOC (tricyclic antidepressants) ALOC with unprotected airway Caustics: acids and alkalis Hydrocarbons Expected ALOC >1 hr since ingestion ALOC with unprotected airway Absent bowel sounds, bowel obstruction Substance not bound by charcoal Repeated doses can cause dehydration or electrolyte imbalances Bowel obstruction, ileus, perforation, hemorrhage ALOC with unprotected airway
CHAPTER 35 Poisoning and Drug Overdose
sustained-release product. Ingestion of alcohols may be suspected by the presence of an anion gap acidosis and an osmolar gap. The Breathalyzer may offer a rapid assessment of ethanol ingestion. The threshold for toxicity in tricyclic antidepressants is low; moderate-to-severe symptoms can occur with doses of 10 to 20 mg/kg. Levels may be available for some tricyclic antidepressants, but results usually are not immediately available and may be difficult to interpret. Diagnosis is by clinical suspicion. An electrocardiogram should be performed to assess cardiac toxicity, including initial sinus tachycardia; prolonged QRS interval; prolonged P-R interval; prolonged Q-T interval; and in severe toxicity, progression to potentially life-threatening wide-complex tachycardia.
ALOC, altered level of consciousness.
refuses charcoal, it may be administered through a nasogastric tube. Care must be taken with patients at risk for aspiration (young children, children with altered mental status) because it can result in serious pneumonitis. Endotracheal intubation to protect the airway may be required before charcoal administration in these patients. Correct placement of the nasogastric tube in the gastrointestinal tract should be verified before administration. Cathartics (e.g., magnesium citrate, magnesium sulfate) have been mixed with charcoal to decrease transit time, enhance elimination, and counteract the constipating effects of charcoal. No significant benefit of cathartic use has been shown. Adverse effects, including dehydration and electrolyte disturbances, may occur, especially in young children. Cathartics are not recommended, but if used, they should never be given in repeated doses. Multiple-dose charcoal, less commonly used and often referred to as gastrointestinal dialysis, involves repeated administration of activated charcoal every 4 hours. This method may promote diffusion of the drug back into the gastrointestinal tract with binding to the charcoal. Cathartics should not be given with charcoal in repeated doses. Multiple-dose charcoal may be useful for phenobarbital, theophylline, and carbamazepine overdoses. It is not recommended for overdoses of drugs that cause ileus, such as tricyclic antidepressants. Whole-bowel irrigation uses solutions prescribed to clean out the gastrointestinal tract in preparation for colon
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surgery (e.g., GoLYTELY). It may be indicated for slowrelease medications, tablets that dissolve slowly and may cause concretions (e.g., iron), and ingestions in which charcoal is not effective. Administration by nasogastric tube usually is required to accomplish a rate of 500 mL/hr in young children and 1 to 2 L/hr in older children and adolescents. The end point is clear rectal effluent. Contraindications include bowel obstruction, ileus, gastrointestinal perforation, hemorrhage, and altered mental status with an unprotected airway. Hemodialysis may be used for severe ingestions of ethylene glycol, methanol, phenobarbital, lithium, salicylate, or theophylline. Charcoal hemoperfusion involves passing blood through a charcoal cartridge instead of a dialysis machine and may be used for severe theophylline poisoning. Urinary alkalinization via administration of sodium bicarbonate intravenously can enhance elimination of weak acids. The toxin is kept in its ionic state, preventing reabsorption in the renal tubule. This method is used primarily in severe salicylate and phenobarbital poisonings. Antidotes are available for only a few ingestions (Table 35-9). Naloxone may reverse rapidly respiratory depression from narcotic overdose. N-acetyl cysteine (NAC), if administered in time, prevents severe liver toxicity in acetaminophen ingestion. Bicarbonate administration may ameliorate the cardiac toxicity of tricyclic antidepressants. Digoxin immune Fab (Digibind) is used to bind digoxin, and deferoxamine is used to chelate iron. Referral and consultation depends on the specific substance ingested and the resources available. The regional poison center should be contacted for recommendations regarding management, disposition, and length of observation time required for asymptomatic patients. Symptomatic patients and patients who require a long observation period to rule out toxic effects should be admitted to the hospital. Severely toxic patients require management in an intensive care unit (ICU). A toxicologist should be consulted on such patients if one is available. Otherwise the poison center can be used for follow-up and recommendations. Table 35-9. Common Antidotes
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Toxin
Antidote
Acetaminophen Anticoagulants (warfarin-like) Anticholinergics Benzodiazepines β-blockers Calcium channel blockers Carbamate pesticides Carbon monoxide Cyanide Digoxin Ethylene glycol Iron Isoniazid Lead Mercury Methanol Methemoglobinemia Narcotics Organophosphate pesticides Tricyclic antidepressants
N-Acetyl cysteine Vitamin K Physostigmine Flumazenil Glucagon Calcium, glucagon Atropine Oxygen Cyanide antidote kit Digibind Ethanol Deferoxamine Pyridoxine Dimercaprol, EDTA, DMSA Dimercaprol, DMSA Ethanol, fomepizole Methylene blue Naloxone Atropine, pralidoxime Sodium bicarbonate
DMSA, dimercaptosuccinic acid; EDTA, ethylenediaminetetraacetic acid
Management of acetaminophen overdose involves the antidote NAC. NAC acts as a substitute for glutathione, which normally binds the toxic metabolite of acetaminophen, but is overwhelmed in an overdose. An initial dose of 140 mg/kg orally, followed by 70 mg/kg every 4 hours for 17 doses, is the traditional protocol. In other countries, NAC may be delivered intravenously. Activated charcoal is not used if it would interfere with NAC administration. Any vomiting should be treated aggressively with antiemetics to avoid interference with NAC. Patients with potentially toxic ingestions must be observed in the ICU. Patients with severe toxicity not prevented by NAC may require transfer to a liver transplant center. Deferoxamine is given to chelate iron in potentially serious overdoses, at a rate of 10 to 15 mg/kg/hr intravenously. Activated charcoal is not effective for binding iron. Gastric lavage may be used early after ingestion or if radiopaque tablets are still visible on plain abdominal radiographs. Presence of concretions or bezoars may require whole-bowel irrigation, endoscopy, and, in rare cases, surgical removal. Dialysis is used to remove the deferoxamine-iron complex if renal failure occurs. Patients with potentially serious ingestions or undergoing chelation therapy should be admitted to the ICU. Treatment of alcohol poisoning is primarily supportive and includes airway management/protection; fluid administration; and treatment of significant acidosis, hypocalcemia, and hypoglycemia with bicarbonate, calcium, and dextrose administration. Activated charcoal is not useful for alcohols. Gastric lavage is not recommended in a patient with significant altered mental status unless the airway is protected. Ethanol has been used as an antidote for severe methanol and ethylene glycol poisonings. Fomepizole is a new antidote available for methanol overdose and is preferred over ethanol administration. Dialysis may be required for lifethreatening overdoses, severe acidosis, renal failure, and methanol overdose causing visual symptoms not reversed by fomepizole. Treatment of tricyclic antidepressant poisoning includes supportive care, close monitoring, activated charcoal, and sodium bicarbonate for cardiac toxicity. ABCs should be assessed and stabilized immediately, and the patient should be placed on a cardiorespiratory monitor. Cardiac toxicity may be treated with sodium bicarbonate, 1 to 2 mEq/kg intravenously initially, then continuous infusion to maintain a serum pH of 7.45 to 7.55. Tricyclic antidepressants block the fast sodium channel, and sodium bicarbonate administration counteracts this effect. Lidocaine, 1 mg/kg slow intravenous bolus, then continuous infusion at 20 to 50 μg/ kg/min, may be used for wide-complex tachyarrhythmias. Seizures should be treated with benzodiazepines. Hypotension should be treated with fluid boluses; Trendelenburg positioning; sodium bicarbonate; and, if needed, pressors, such as norepinephrine and low-dose dopamine. Because of the low threshold for toxicity, all patients with tricyclic antidepressant ingestion warrant admission to an ICU. Anticipatory guidance and parental education are important in prevention (Box 35-1). Management of a less serious accidental ingestion provides an excellent opportunity for parental education. Emphasis should be placed on safe storage of toxic substances and access to the regional poison
Safe Storage 1. Keep potential toxins out of reach of children. Lock cabinets storing toxic substances. 2. Never store substances in unmarked containers, especially containers that typically hold beverages (e.g., old soda bottles or cups). 3. Advise visitors (e.g., grandparents) to store medications out of reach of children. 4. Dispose of unneeded toxic substances and unused or outdated medications. Education 1. Discuss safety issues with children as developmentally appropriate (e.g., not ingesting unknown substances). 2. Do not refer to medication as “candy” to entice young children to take it. 3. Discuss risks in depressed adolescents; advise parents to keep toxins out of reach of potentially suicidal family members.
and child-safe packaging have reduced fatalities further. Prognosis is more likely to be poor in intentional ingestions if the patient does not disclose ingestion or delays disclosure. The severity of poisoning is distinct from the seriousness of suicidal intention. Patients may have been quite serious about committing suicide, yet taken an inconsequential amount of drug or a drug that is relatively safe in overdose. In contrast, patients hoping to make a suicidal gesture unwittingly may expose themselves to a potentially fatal ingestion. Follow-up involves repeated anticipatory guidance and psychiatric consultation for intentional ingestions.
Mini-index of Related Topics
CH.
■ RESUSCITATION AND BASIC LIFE SUPPORT
27
■ APPROACH TO THE ILL-APPEARING CHILD
38
Poison Center
■ APPROACH TO THE AGITATED PATIENT
39
1. Keep the regional poison center and local emergency department or pediatrician’s telephone numbers readily available. Many poison centers provide stickers for household telephones.
■ GLUCOSE AND ELECTROLYTE DISORDERS
42
Therapy 1. Consider advising parents to have activated charcoal in the home. 2. Parents should administer activated charcoal only if instructed by the poison center staff or medical staff.
center phone number. Parents should be reminded that potential toxins include not only prescription medications, but also over-the-counter medications, vitamins, herbal preparations, alternative medications, household products, toxic plants, gardening and hobby chemicals, and kitchen items such as alcohol or oil of wintergreen.
■ SUICIDE AND SUICIDE PREVENTION
CHAPTER 35 Poisoning and Drug Overdose
Box 35-1. Education Points for Anticipatory Guidance
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SUGGESTED READINGS American Academy of Pediatrics, Committee on Injury and Poison Prevention: Handbook of Common Poisonings in Children, 3rd ed. Elk Grove Village, Ill, American Academy of Pediatrics, 1994. Erickson JB: Toxicology: Ingestions and smoke inhalation. In GauscheHill M, Fuchs S, Yamamoto L (eds): APLS: The Pediatric Emergency Medicine Resource. Boston, Jones and Bartlett, 2004, pp 234–267. Perry H, Shannon H: Poisoning. Pediatr Ann 1996;25:19–29. Tenenbein M: Poisoning. In Barkin RM (ed): Pediatric Emergency Medicine Concepts and Clinical Practice. St. Louis, Mosby-Year Book, 1997, pp 527–534. Tenenbein M, Cohen S, Sitar DS: Efficacy of ipecac-induced emesis, orogastric lavage and activated charcoal for acute drug overdose. Ann Emerg Med 1987;16:838–841.
OUTCOME AND FOLLOW-UP Prognosis depends on the specific toxin but is generally good. Most ingestions are not serious, and fatalities are rare. Advances in education of the public, poison center use,
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