Toxicology



Toxicology





Overview


Poisonings



  • Event resulting from the ingestion of, or contact with, a harmful substance.


  • May be the result of an overdose or incorrect use of a medication.


  • Children <3 years of age account for approximately 46% of poisonings.


  • Male predominance <13 years of age.


  • Female predominance >13 years of age.


  • More than 90% of poisonings occur inside the child’s residence.


Poison Control Centers



  • National poison control hotline.



    • 1-800-222-1222.


    • Consultation is free to health care professionals and the general public.


    • Most callers are not referred to a health care facility.



      • Results in significant health care cost savings.


Selected Poisonings


Acetaminophen

Shawna Mudd


Background



  • Also known as N-acetyl-p-aminophenol and paracetamol.


  • Commonly used and widely available analgesic and antipyretic.


  • Dispensed as a single product, but also found in many combination preparations.


  • Common in pediatric overdoses.


Etiology



  • Commonly occurs through dosing errors.


  • Unintentional ingestions are common in young children.


  • Intentional ingestions occur more often in older children/adolescents.



Clinical Presentation



  • Initial symptoms, mild.



    • Vomiting.


    • Malaise.


  • >24 hours, symptoms progress.



    • Increased alanine transaminase (ALT) and aspartate transaminase (AST).


  • >72 hours, peak toxicity.



    • Coagulopathy.


    • Encephalopathy.


    • Liver failure.


    • Cerebral edema (some cases).


    • Possibly, death.


Diagnostic Evaluation



  • Determine quantity and dosage form ingested.


  • Determine time of ingestion.


  • Refer to an emergency department (ED) for:




    • Children <6 years of age.



      • >200 mg/kg in children <6 years of age in a 24-hour period.


      • >150 mg/kg per 24-hour period for the preceding 48 hours.


      • >100 mg/kg per 24-hour period for 72 hours or longer.


  • Acetaminophen level.



    • Draw 4 hours after ingestion, or immediately on presentation if more than 4 hours has elapsed since ingestion.


    • If presenting <4 hours after ingestion, consider waiting to draw level until 4 hours has passed.


    • A 4-hour postingestion level is the first value plotted on the acetaminophen serum level nomogram.


    • Serum acetaminophen levels should be drawn, as well as liver function tests.







      FIGURE 13.1 • Rumack-Matthew Nomogram for Acetaminophen Poisoning. Acetaminophen concentration plotted versus time after exposure to predict potential toxicity and antidote use.


    • If the ingestion occurred over time, obtain the level 4 hours after the first dose was taken or immediately on presentation if >4 hours have elapsed.



      • Example: Child began ingesting acetaminophen at 4 p.m. and continued taking additional medication until 7 p.m.; the 4-hour mark will be considered from the 4 p.m. time of first ingestion, and the first level should be obtained at 8 p.m. (or immediately if the child is presenting later than 4 hours after the ingestion).


  • Acetaminophen serum level nomogram.



    • Used to assist in determining severity of toxicity and therapy.



      • Stratifies risk level of ingestion.


      • Based on serum level and time after ingestion.



    • First level is 4 hours after ingestion.


    • Limitations:



      • Levels obtained prior to 4 hours after ingestion are not interpretable on the nomogram.


      • Patients presenting late may no longer have a detectable level or may have a low level and may have ingested a lethal dose.


      • Less predictive in chronic ingestion (rather than acute ingestion).


      • Less predictive in extended-release formulations.


Management



  • Antidote: N-acetylcysteine (NAC).



    • Available formulations.



      • Intravenous (IV) (Acetadote).


      • Oral (Mucomyst).


    • Mechanism of action.



      • Unclear; likely maintains or restores glutathione levels, allowing for metabolism of acetaminophen without development of hepatocellular necrosis, or may act as an alternative substrate for conjugation with acetaminophen toxic metabolites.


    • Administer within 8 hours of acetaminophen ingestion for greatest efficacy.


    • Administer in cases with any signs of hepatotoxicity, even if the acetaminophen level is low or undetectable.


    • Any child with an unknown amount of acetaminophen ingestion or questionable history should have an acetaminophen level drawn and consideration for NAC administration.


  • Activated charcoal (AC).



    • Consider administration if child presents to medical attention immediately after ingestion (<2 hours postingestion; ideally <1 hour postingestion).


    • May also be beneficial in cases of multidrug ingestion.


Alcohols (Ethanol, Methanol, Ethylene Glycol)

Shawna Mudd


Background



  • Toxic symptoms result from either intentional or accidental ingestion of alcohol-containing products.


  • Many alcohol products exist that are intended for human consumption; however, some are not intended for human consumption.


  • All can pose serious health risks for children.


Etiology/Types



  • Ethyl alcohol (ethanol).



    • The alcohol most commonly recognized; produced by the fermentation of grains, “grain alcohol.”


    • Alcoholic beverages and distilled spirits.


    • Found in accessible household products—hand sanitizer, mouthwash, colognes, and others.


  • Methyl alcohol (methanol).



    • Produced from the distillation of wood, “wood alcohol.”


    • Found in industrial solvents, gasoline blends, plastic products, windshield wiper fluid, paint strippers, glass cleaners, hobby and craft adhesives, food warming cans used under chafing dishes (e.g., Sterno), and others.


  • Ethylene glycol.



    • Used in various solvents.


    • Primary component of automobile antifreeze.


    • Found in herbicides/pesticides, liquid detergents, paints and paint products, among others.


    • May have a sweet taste and attractive color which can pose a particular danger to children.



Clinical Presentation



  • All present with generalized nonspecific CNS depression.


  • Ethanol.



    • Symptoms similar to other sedatives.


    • Vomiting due to GI distress.


    • Slurred speech, ataxia, lethargy, and coma.


    • Respiratory depression.


    • Hypotension.


    • Bradycardia.


    • Facial flushing.


    • Profound hypoglycemia secondary to impaired gluconeogenesis can be problematic, and often is a delayed presentation.


    • An odor to the breath can sometimes be detected.


  • Methanol.



    • Similar to ethanol intoxication in its initial presentation, but the initial inebriation period may diminish for periods ranging from 6 to 30 hours, during which the patient is fairly asymptomatic despite the fact that toxic metabolism is occurring.


    • Severe metabolic acidosis.


    • Visual complaints (e.g., blurred vision or seeing spots), headache, seizures.


    • Tachypnea or hyperpnea.


    • Pulmonary edema and renal failure.


    • Coma.


  • Ethylene glycol.



    • Similar to ethanol intoxication in its initial presentation, except that no odor is generally present on the breath.



    • CNS depression may worsen over time.


    • Tachypnea and hyperpnea.


    • Shock.


    • Pulmonary edema.


    • Acute renal failure.


    • Acute respiratory failure.


    • Cerebral edema.


    • Ocular complaints are generally not present.


Diagnostic Evaluation



  • Any symptomatic patient or any patient suspected of ingesting methanol or ethylene glycol should be managed in the ED/hospital setting.


  • Patients require cardiorespiratory monitoring and supportive treatment as appropriate (e.g., airway, breathing, and circulation).


  • Laboratory.



    • Serum ethanol (blood alcohol), ethylene glycol, and methanol levels.


    • In cases of suspected methanol or ethylene glycol ingestions, laboratory evaluation for metabolic acidosis is necessary.


    • Electrolytes with calcium and anion gap calculation.


    • Serum osmolality (a large serum osmolality gap should raise suspicion for ingestion of methanol or ethylene glycol).


    • Arterial or venous blood gas values.


    • Blood glucose level.


    • BUN and creatinine level.


    • Hepatic panel/Liver function tests.


    • Additional testing may include urinalysis and amylase, lipase, and creatine kinase levels.


Management



  • Ethanol.



    • Conservative observation with cardiorespiratory monitoring.


    • Supportive treatment as appropriate.



      • Supplemental oxygen.


      • IV fluids.


      • Glucose (if hypoglycemia is present).


      • Electrolyte monitoring (particularly if frequent vomiting/diarrhea).


      • Gastric decontamination or emptying is not recommended.


  • Methanol and ethylene glycol.



    • Supportive cardiovascular and respiratory care.


    • Prompt treatment of hypoglycemia.


    • Key to treatment of methanol and ethylene glycol toxicity is to interfere in the production of toxic metabolites through the IV administration of fomepizole or by the oral or IV administration of ethanol.


    • Dialysis effectively clears alcohols; however, it is infrequently needed unless the patient is deteriorating with the administration of fomepizole or ethanol.



      • May be needed in the cases of concomitant renal failure.


Metformin

Mark D. Weber


Background



  • Overdose of oral hypoglycemic agents, such as metformin and sulfonylureas, is rare in children.


  • Metformin overdose leads to lactic acidosis but rarely hypoglycemia.


  • Sulfonylureas (e.g., glipizide, glyburide, glimepiride) can cause rapid decrease in glucose levels.


Etiology



  • Inadvertent or accidental ingestion.


  • Suicide attempt.



Clinical Presentation



  • Nausea, abdominal pain, diarrhea.


  • Dizziness.


  • Hypoglycemia; rare in metformin overdose (common in other classes of oral antihyperglycemic agents).


  • Lactic acidosis is primarily noted in adults with preexisting liver and renal insufficiencies.


Diagnostic Evaluation



  • Baseline blood glucose level.


  • Comprehensive metabolic panel.


  • Hepatic function panel.


  • Lactic acid level.


Management



  • Gastric lavage with AC; depending on time of presentation related to ingestion.


  • Glucose-level monitoring.


  • Hemofiltration, in cases of severe lactic acidosis.



β-Blockers

Melanie Muller


Background



  • Most ingestions are acute, accidental, occur in a residence and in children <6 years of age.




Clinical Presentation



  • Widely variable depending on the amount ingested and the specific drug that was ingested.


  • Ranges from asymptomatic to cardiac arrest.


  • Most patients become symptomatic within 2 hours after the ingestion, except in the case of extended-release medications in which symptomatology can be delayed for up to 24 hours.


  • Most common presentations include:



    • Bradycardia.


    • Hypotension.


  • Ventricular dysrhythmias can be associated with the ingestion of β-blockers with MSA properties.


  • Seizures and neurologic sequelae can occur if patient experiences severe hypotension or if medication ingested possesses lipophilicity.


Diagnostic Evaluation



  • Accurate history.



    • Name of agent ingested.


    • Approximation of number of pills ingested and concentration.


    • Approximate time of ingestion.


    • Possibility of co-ingestion.


    • Any interventions performed prior to seeking assistance.


Evaluation



  • EKG.


  • Serum electrolytes.


  • Urine and serum toxicology screen.


  • Acetaminophen and salicylate levels to evaluate for co-ingestion.


Management



  • Depends on the amount ingested and patient symptomatology.


  • First, evaluate airway, breathing, and circulation.


  • Consider AC (1 g/kg/dose) if within 1 hour of ingestion.


  • Fluid bolus (normal saline 20 mL/kg) for hypotension.


  • Atropine administered IV for bradycardia.


  • Glucagon infusion for moderate to severe ingestions.


  • Sodium bicarbonate if the β-blocker ingested possesses MSA properties.



    • Helps to prevent dysrhythmias.



Bath Salts/Spice

Mark D. Weber


Background



  • Bath salts are compounds that originate from the khat plant (Catha edulis).


  • Marketed as “bath salts” or “plant food.”


  • Labeled as “not to be used for human consumption” in order to avoid legislative regulation.


  • Effects are similar to that of cocaine or amphetamines.



Clinical Presentation



  • Initial effects include:



    • Hypertension.


    • Tachycardia.


    • Euphoria.


    • Alertness.


    • Hyperactivity.



  • Additional effects may include acute coronary vasospasm, myocardial infarction, esophagitis, gastritis, liver dysfunction, and increase of preexisting psychosis.


Diagnostic Evaluation



  • Not detected by standard drug/toxicology screen analysis.


  • Advanced detection can be performed by mass spectrometry.


Management



  • Low-dose benzodiazepines to manage agitation.


  • Benzodiazepines to treat seizures.


  • Surface cooling and/or dantrolene to treat hyperthermia.



    • Prevention of rhabdomyolysis.


  • Nitroglycerine, morphine, and antiplatelet drugs for coronary vasospasm.


Benzodiazepines

Dana L. Lerma


Background



  • Class of medications that provide a sedative-hypnotic effect.


  • Used in the treatment of anxiety, seizures, procedural sedation, withdrawal states, and as muscle relaxants.


  • While benzodiazepine overdose is relatively common, they generally involve a co-ingested agent.


  • Overall, patient outcomes are generally good when benzodiazepine ingestion occurs alone.


Pharmacology



  • Benzodiazepines act on γ-aminobutyric acid A receptors, an inhibitory neurotransmitter in the CNS.


Clinical Presentation



  • Mild to moderate toxicity:



    • CNS depression.



      • Drowsiness, fatigue, confusion, memory loss, ataxia, and slurred speech.


    • Paradoxical excitement is not uncommon in children.


    • Respiratory depression is uncommon, but may occur.


    • Tachycardia or bradycardia may be present; although with mild toxicity, vital signs are normally stable.


    • Nausea and vomiting.


  • Severe toxicity.



    • More profound CNS depression.


    • Respiratory depression and/or arrest.


    • Hypothermia and hypotension are common.


    • Possible coma or death.


Diagnostic Evaluation



  • Urine toxicity screen should be sent. However, not all benzodiazepines are detected on routine urine drug/toxicology tests, including midazolam, lorazepam, and clonazepam.


  • Routine laboratory testing should be completed, including glucose to evaluate for hypoglycemia as cause of decreased mental status.


  • Acetaminophen, salicylate, and ethanol are common co-ingestions.



    • Evaluation of these serum levels is indicated.


Management



  • Primarily supportive.


  • Flumazenil is a rapid benzodiazepine receptor antagonist; only indicated in iatrogenic oversedation or respiratory depression.


  • Intubation may be required in patients with respiratory depression and loss of airway reflexes.


  • Fluid resuscitation for hypotension.


  • Rarely, vasopressors are required to maintain adequate blood pressure.


  • AC is generally only beneficial when benzodiazepines are co-ingested with another toxic substance.



Carbon Monoxide

Mark D. Weber


Background



  • Inhalation of carbon monoxide (CO) from surrounding environment, leading to tissue hypoxia.



Etiology



  • Exposure to:



    • Smoke inhalation.


    • Space heaters; fuel burning.


    • Furnaces, charcoal grills, fireplaces, portable generators.


    • Water heaters.


    • Cooktop ranges.


    • Wood-burning stoves.



      • Typically, exposure to these is not of concern unless they are not kept in proper working order or if used in a close or partially closed space.


    • Car/truck exhaust.



      • Typically not a concern unless running a car/truck in a closed garage/space with inadequate ventilation.




Clinical Presentation



  • Symptoms include headache, nausea, dizziness, vomiting, seizures, shortness of breath, hypotension, confusion, loss of consciousness (moderate to severe poisonings).


  • May initially seem like a flu-like illness.


  • Can lead to cardiopulmonary arrest, coma, and death.


  • Cherry-red skin is a rare finding.


Diagnostic Evaluation



  • Arterial or venous blood gas analysis to assess COHb percentage—normal <2%.


  • Traditional pulse oximetry may be unable to detect CO binding to hemoglobin, resulting in falsely elevated oxygen saturation reading.



    • Hemoglobin is saturated, however, with a mixture of oxygen and CO.


    • Pulse oximeters are unable to discern what substance is bound to the hemoglobin and report a total percentage of saturation; in cases of CO toxicity, the combination of oxygen and CO bound to hemoglobin.


Management



  • Supplemental oxygen.



    • Preferably, non-rebreather to maximize oxygen concentration.


  • Intubation if level of consciousness and respiratory rate indicate.


  • Hyperbaric oxygen therapy.



    • Controversial, but may speed recovery and removal of CO.



Caustic Agents

Andrea M. Kline-Tilford



Etiology



  • Determined by the identity of the agent, amount consumed, concentration, and duration of exposure to the tissue.


  • Tissue injury is caused by a chemical reaction.


  • Greatest concern is acids with a pH <3 and alkalis with a pH >11 (Table 13.1).


Clinical Presentation



  • Injuries often present hours to days after the ingestion.



    • Appearances may change after initial presentation; initial presentation may appear deceptively harmless.


  • Injuries divided into three categories:



    • Airway/facial burns.


    • Esophageal/GI burns.


    • Splash burns.


  • Burning sensation in the mouth, perioral edema.


  • Esophageal/pharyngeal edema.



    • Esophageal injury is rapid.


    • Acute tissue penetration and deep tissue injury continues for hours.


    • Injury progresses for the first week after the ingestion.



      • Inflammation.


      • Vascular thrombosis.


      • Ulceration, fibrous crust formation, and granulation tissue develop in the first few days after the event.








    TABLE 13.1 Commonly Ingested Caustic Agents

















    Type of Agent


    Examples of Agents


    Acid


    Hydrochloric acid, nitric acid, sulfuric acid (e.g., swimming pool cleaners, rust removers, toilet bowl cleaners), acetic acid (e.g., descaling agents).


    Alkali


    Potassium hydroxide, sodium hydroxide (e.g., liquid drain cleaners, oven cleaners, disk batteries), ammonia (household cleaning agents), sodium metasilicate (e.g., dishwashing agents), lithium and calcium hydroxide (hair relaxers).


    Other


    Bleach/Hypochlorous acid. Peroxide (Mildew cleaners).


    Adapted from Lupa, M., Magne, J., Guarisco, L., & Amedee, R. (2009). Update on the diagnosis and treatment of caustic ingestion. The Ochsner Journal, 9, 54-59.



  • Dyspnea, dysphagia, drooling.


  • Stridor.


  • Recurrent emesis.


  • Hematemesis.


Diagnostic Evaluation



  • History and physical examination.


  • Nothing by mouth.



    • Aggressive IV hydration.


  • Chest and abdominal radiographs.



    • Evaluate for free air in mediastinum (esophageal perforation), air under diaphragm (gastric perforation) (see Figure 13.3).


    • Baseline chest radiograph in anticipation that aspiration pneumonia may develop.


  • Laryngoscopy: often fiber-optic, to reduce the likelihood of bleeding or increased damage to area associated with procedure.



    • Surgical airway may be required (e.g., tracheostomy) in some cases.


  • Endoscopy (airway, esophageal).


  • Barium esophagram.



    • More useful in long-term evaluation of esophagus, especially stricture formation.


    • High false-negative rate in early stages of injury (e.g., prior to stricture formation).


  • Technetium-labeled sucralfate (nuclear medicine study) (Figures 13.4A & B).






FIGURE 13.3 • Pneumomediastinum Due to Esophageal Perforation. Posteroanterior chest radiograph shows extensive air within the mediastinum, as well as lucencies around the aortic arch and along the tracheal air column and associated subcutaneous air.







FIGURE 13.4 • Corrosive Esophagitis Esophagram. A: Dilated, boggy esophagus with ulceration 8 days after the ingestion of a caustic agent. B: Stricture formation is evident on an esophagram obtained 3 months after the caustic injury.


Management



  • Pain control.


  • Nasogastric tube may be required as a stent for injured area and provide nutrition.



    • Placed under endoscopic guidance.


    • Generally left in place for 14 to 21 days.


  • Strictures often require repeated balloon dilation via endoscopy.


  • Antibiotics often used, though no evidence to support that they affect stricture formation or rates of infection.


  • Steroids, controversial.


  • Avoid induction of emesis; may lead to worse injury from additional exposure to corrosive agent.



Calcium Channel Blockers

Lara G. Smith

Mark D. Weber



Jan 30, 2021 | Posted by in NURSING | Comments Off on Toxicology
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