Home Books Katzung & Trevor's Pharmacology: Examination & Board Review, 12e

Chapter 58: Management of the Poisoned Patient

A 2-year-old girl presented with lethargy, increased respiratory rate, and an elevated temperature that appeared to result from a drug poisoning. Laboratory testing revealed the following serum concentrations: glucose, 36 mg/dL; Na⁺, 148 mEq/L; K⁺, 5 mEq/L; Cl⁻, 111 mEq/L; HCO₃⁻, 12 mEq/L; BUN, 21 mg/dL; osmolality, 300 mOsm/L.

The anion gap in this patient is

(A) −60 mEq/L

(B) −20 mEq/L

(C) +5 mEq/L

(D) +30 mEq/L

(E) +304 mEq/L

Anion gap is calculated by subtracting measured serum anions (bicarbonate plus chloride) from cations (potassium plus sodium). Increases in anion gap above normal are due to the presence of unmeasured anions that accompany acidosis. The gap in this case is 30 mEq/L, a value that is well in excess of the normal gap (12–16 mEq/L). The answer is D.

The osmolal gap in this patient is

(A) −40 mOsm/L

(B) −5 mOsm/L

(C) +15 mOsm/L

(D) +60 mOsm/L

(E) +305 mOsm/L

The osmolar gap is the difference between the measured serum osmolality and the osmolality calculated from the serum sodium, glucose, and BUN concentrations according to the equation above for calculating the osmolal gap. In this case, the measured osmolality is 300 mOsm/L, whereas the calculated osmolality is 305 mOsm/L; the difference is −5 mOsm/L. The answer is B.

The patient’s signs, symptoms, and laboratory values are most consistent with an overdose of

(A) Acetaminophen

(B) Aspirin

(C) Ethylene glycol

(D) Lead

(E) Phencyclidine

Of the drugs listed, the 2 that are likely to cause an anion gap are aspirin and ethylene glycol. However, if the child had ingested ethylene glycol, she would be expected to exhibit a significant osmolal gap. The anion gap, lethargy, tachypnea, and hyperthermia all are consistent with aspirin poisoning. The answer is B.

An 18-month-old boy presented in a semiconscious state with profound hypotension and bradycardia after ingesting a number of his grandmother’s metoprolol tablets. In this case, the most appropriate antidote is

(A) Atropine

(B) Esmolol

(C) Glucagon

(D) Naloxone

(E) Neostigmine

Glucagon (Chapter 41) stimulates heart rate and contractility through cardiac glucagon receptors that are coupled to adenylyl cyclase and the cAMP signaling pathway. This ability to increase cardiac cAMP without requiring access to β receptors makes it valuable for β-blocker overdose. The answer is C.

An 81-year-old woman with type 2 diabetes presents to the emergency department in a coma and with tachypnea, tachycardia, hypotension, and severe lactic acidosis approximately 9 h after ingesting a number of her metformin tablets. Her serum glucose concentration is 148 mg/dL. Metformin is a base with a pK_a of 12.4. The procedure that is most likely to improve her condition is

(A) Administration of activated charcoal

(B) Administration of glucagon

(C) Administration of syrup of ipecac

(D) Gastric lavage

(E) Hemodialysis

In this woman with severe signs of poisoning due to the ingestion of metformin, hemodialysis can be used to accelerate the elimination of both metformin and lactic acid. Since most of the metformin has been absorbed by the time she presented (9 h after drug ingestion), efforts to decontaminate her gastrointestinal tract with activated charcoal, gastric lavage, or syrup of ipecac are unlikely to be beneficial. Furthermore, syrup of ipecac has fallen out of favor and should not be used in unconscious patients. Unlike other drugs used to treat type 2 diabetes, metformin in overdose is unlikely to cause hypoglycemia (see Chapter 41), and this patient’s serum glucose is in the normal range so that glucagon administration is not required. The answer is E.

A 24-year-old female was rushed to the emergency department after she was found in her room hypotensive, with seizures. In the emergency department, the electrocardiogram confirmed ventricular arrhythmias. An overdose of which of the following drugs is the most likely cause of her symptoms?

(A) Acetaminophen

(B) Amitriptyline

(C) Diazepam

(D) Ethylene glycol

(E) Morphine

Tricyclic antidepressants such as amitriptyline are extremely toxic in overdose because of their effects in the CNS and cardiovascular system. In addition to hypotension, seizures, and cardiac arrhythmias, the tricyclics have strong antimuscarinic effects. The answer is B.

A patient with heart failure has accidentally taken an overdose of digoxin. The blood concentration of the drug is 8 times the threshold for toxicity. Pharmacokinetic parameters for digoxin in this patient include a clearance of 7 L/h and an elimination half-life of 56 h. If no procedures are instituted to decontaminate this patient, the time taken to reach a safe level of digoxin will be approximately

(A) 3.5 d

(B) 7 d

(C) 14 d

(D) 28 d

(E) 56 d

Estimations of the time period required for drug or toxin elimination may be of value in the management of the poisoned patient. If no procedures were used to hasten the elimination of digoxin in this patient, the time taken to reach a safe plasma level of the drug (12.5% of the measured level) is 3 half-lives, or approximately 7 d. The answer is B.

A patient is brought to the emergency department having taken an overdose (unknown quantity) of a sustained-release preparation of theophylline by oral administration 2 h previously. He has marked gastrointestinal distress with vomiting, is agitated, and exhibits hyperreflexia and hypotension.

The plasma level of theophylline measured immediately upon hospitalization was 80 mg/L. If the oral bioavailability of theophylline is 98%, the clearance is 50 mL/min, volume of distribution is 35 L, and the elimination half-life is 7.5 h, the amount ingested must have been at least

(A) 0.3 g

(B) 0.6 g

(C) 1.6 g

(D) 2.8 g

(E) 8.0 g

Estimations of the quantity of a drug or toxin ingested may be of value in the management of the poisoned patient. Applying toxicokinetic principles, a rough estimate of ingested dose of theophylline could be made by multiplying the peak plasma level of the drug (80 mg/L) by its volume of distribution (35 L) to give a value of 2800 mg, or 2.8 g. Because only about one-fourth of a half-life has passed since ingestion, the amount eliminated since that time will be rather small. The answer is D.

A short-acting antidote that can reduce this patient’s tachycardia is

(A) Acetylcysteine

(B) Deferoxamine

(C) Esmolol

(D) Fomepizole

(E) Pralidoxime

The short-acting β blocker esmolol helps reverse the tachycardia and possibly the vasodilation associated with an overdose of theophylline. The answer is C.

A contraindication to the use of gastric lavage for the removal of drugs from the stomach of a victim of poisoning is

(A) An overdose of iron pills

(B) An unconscious patient

(C) Ingestion of a corrosive

(D) Overdose with a sustained-release formulation

Neither gastric lavage nor syrup of ipecac should be used in patients who have ingested a corrosive because of the risk of esophageal damage. Gastric lavage can be used in a comatose patient if the airway has been protected with a cuffed endotracheal tube. The answer is C.

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.

Chapter 58: Management of the Poisoned Patient

Send Email

Citation

Jump to a Section

Chapter 58: Management of the Poisoned Patient

Pop-up div Successfully Displayed