Emergency Medicine Written Board Exam Sample Questions
Book 1 - 2006
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QUESTION

132.    A 37-year-old woman with a history of depression is brought in after a suicide attempt. She was found at home with altered mental status and an empty bottle of amitriptyline. Her vital signs are BP 110/78, HR 126, RR 14, and T 37.2° C. Her electrocardiogram is shown below. 

Figure from:
Harrigan RA, Brady WJ. ECG abnormalities in tricyclic antidepressant ingestion. Am J Emerg Med. 1999 Jul;17(4):387-93.

Which statement regarding her management is LEAST accurate?

A) Hypotension should be treated with fluids, sodium bicarbonate, and then a direct-acting vasopressor
B) Immediate intravenous sodium bicarbonate is indicated
C) In the event of ventricular dysrhythmia, lidocaine will further block sodium channels and is absolutely contraindicated
D) This patient is likely to have a seizure and should be observed closely
E) This patient’s mental status is likely to decline rapidly and early airway control should be considered

ANSWER

132.           C          In the event of ventricular dysrhythmia, lidocaine will further
                               block sodium channels and is (absolutely) contraindicated

The use of tricyclic antidepressants for the treatment of depression has declined in recent years, mainly due to the introduction of safer antidepressant medications. These medications, however, are still frequently prescribed for refractory cases of depression and chronic pain control. In the past, tricyclic antidepressants have been associated with more overdose deaths than any other class of prescription medication. In overdose, TCAs cause a multitude of pharmacological effects that result in their toxic profile. The therapeutic effect is the result of blockade of norepinephrine and serotonergic reuptake. In addition, TCAs are antagonists at muscarinic acetylcholine receptors (antimuscarinic toxidrome), postsynaptic alpha adrenergic blockers (hypotension), voltage-dependent sodium channel blockers (cardiotoxicity), and secondary antagonists at GABA-A receptors (seizures). By far, the most important life-threatening effect is cardiotoxicity from cardiac sodium channel blockade. Sodium channel blockade initially manifests itself as QRS prolongation and terminal 40 milliseconds right axis deviation (terminal R wave in lead aVR and S wave in lead I), but ultimately may cause ventricular dysrhythmias and death.

While the electrocardiogram cannot be used to rule out TCA poisoning, it can be helpful in risk stratifying patients who do have symptoms of toxicity. Patients with a QRS duration greater than 100ms are at risk for seizures and ventricular dysrhythmias. In previous studies, 33% of patients with QRS >100ms and 50% of patients with QRS >160ms developed seizures. As QRS duration increases, the risk for ventricular dysrhythmia also increases. In patients with QRS >160ms, 50% will develop ventricular dysrhythmia.

Any patient who presents with suspected TCA overdose should receive an immediate electrocardiogram. Sinus tachycardia is often found on ECG as a result of the antimuscarinic toxidrome. Any QRS prolongation should prompt immediate intravenous sodium bicarbonate administration. In previous studies, hypertonic saline loading and alkalosis have both been shown to improve the sodium channel blockade associated with TCA poisoning, but sodium bicarbonate (sodium load and alkalosis) is more effective than hypertonic sodium or alkalosis alone. Should ventricular dysrhythmias develop, the first-line therapy is aggressive, intravenous sodium bicarbonate. While class Ia and Ic antidysrhythmics can worsen sodium channel blockade and are contraindicated, lidocaine (a class Ib) can be given. Hypotension in the setting of tricyclic antidepressant overdose may be the result of cardiac sodium channel blockade and/or alpha-adrenergic blockade. First-line therapy for hypotension is intravenous fluid administration followed by sodium bicarbonate (regardless of QRS width), then direct-acting vasopressor. Direct-acting pressors (like norepinephrine) are traditionally more effective than indirect-acting agents (like dopamine) and should be used preferentially.

Patients presenting after TCA overdose may have mental status ranging from normal to frankly comatose. Agitation is a common due to the antimuscarinic effects of tricyclics. Classically TCA-related coma develops very rapidly. Therefore, these patients require close observation and consideration of early airway protection. Early airway protection should be of particular concern in patients receiving activated charcoal for gastric decontamination.

Physostigmine is a carbamate, cholinesterase inhibitor agent that has been used in the past as an antidote for tricyclic antidepressant overdose. Although this medication was used for this indication for years, several reports of sudden-onset asystole following physostigmine administration has caused physostigmine to be considered absolutely contraindicated in the setting of tricyclic antidepressant overdose.

1. Mills KC: Tricyclic Antidepressants, in Tintinalli, JE (ed): Emergency Medicine: A Comprehensive Study Guide, 6th ed. New York, NY, McGraw-Hill 2004:1025.

226.      Which of the following statements is LEAST accurate concerning urinary tract infections (UTI) in children?

A) A negative urinalysis rules out UTI in children < 2 years of age.           
B) Children with multiple UTIs should be evaluated for abuse.      
C) Infants younger than 3 months of age with a UTI should be admitted for intravenous antibiotics.
D) Neonatal boys are more prone to UTIs than girls.
E) Well appearing children > 3 months old with pyelonephritis may be treated as outpatients.

ANSWER

226.                 A          A negative urinalysis rules out UTI in children < 2 years of age

In children younger than 2-years-old, a negative urinalysis does not rule out a urinary tract infection.  Up to 50% of children with UTIs can have a false negative urinalysis. Nitrite and leukocyte esterase presence in urine dipstick have the highest combined sensitivity for UTI. In addition, if both are positive, the false positive rate is less than 4%. Most consider young girls to be at the highest risk for UTI. This is in fact true except for the neonatal period, when neonatal boys actually have a higher risk than girls. Children with UTIs are managed differently based on the age of the child. The very young are treated conservatively, and those under 3 months of age are generally admitted to the hospital for IV antibiotics. Pyelonephritis used to be commonly managed as an inpatient, but in well appearing children, this infection can be treated as an outpatient with oral antibiotics.

1. McCollough M, Sharieff G.  Renal and Genitourinary Tract Disorders.  arx, JA, et al (eds): Rosen's Emergency Medicine Concepts and Clinical Practice, 5th ed. 2002:2331-2333.

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