May House Staff Quiz Answers



May House Staff Quiz Answers

Poisoning/Hazardous Substances

1. 2010 Question 32 – Answer C. The single most useful diagnostic and prognostic test in the setting of a TCA overdose is electrocardiography. In a study from 1985, toxicologists found that a QRS duration of greater than 100 msec predicted seizures in 34% and dysrhythmias in 14% of patients who had TCA overdoses. The QRS widening is related to fast sodium channel blockade caused by direct TCA effects and exacerbated by acidemia. These effects can be overcome by the administration of sodium bicarbonate boluses. Sodium bicarbonate should be administered until the QRS duration is less than 100 msec. The exact mechanism for this effect is unknown.

Adenosine and synchronized cardioversion are treatments for supraventricular tachycardia. Amiodarone is a drug of choice for ventricular arrhythmias. External pacing is appropriate treatment for refractory, symptomatic bradycardia.

2. 2011 Ques. #161. Answer C. In most cases, gastric foreign bodies may be managed conservatively, but esophageal impactions require urgent removal. Button batteries present a unique problem because they contain toxic heavy metals as well as alkaline compounds (eg, sodium and potassium hydroxide) that are caustic to esophageal mucosa. Significant esophageal injury (including perforation) has been reported from button batteries lodged in the esophagus for as few as 6 hours. Most complications are caused by larger batteries (20 to 23 mm diameter), although significant esophageal injury has been reported with batteries as small as 8 mm in diameter. Symptoms of dysphagia (including feeding refusal, excessive drooling, difficulty swallowing) or emesis suggest esophageal impaction. Regardless of the presence or absence of symptoms, a radiograph of the neck, chest, and abdomen should be obtained in all patients who present with a history of possible battery ingestion.

A coin lodged in the esophagus must be removed emergently if the patient is unable to handle secretions. Otherwise, endoscopy may be carried out within 12 to 24 hours, by which time up to 30% of coins (mostly those in the distal third of the esophagus) will have passed into the stomach.

3. 2010 Ques. #64 Answer A. The progressive lethargy, ataxia, seizures, anion gap metabolic acidosis of 30 mEq/L, and osmolar gap of 53 mmol/L described for the boy in the vignette are highly suggestive of alcohol poisoning. This is a particular diagnostic possibility because the boy may have had access in the garage to such potential toxic alcohols as ethylene glycol (antifreeze) and methanol (windshield wiper fluid). The hypocalcemia suggests ethylene glycol exposure because the metabolism of ethylene glycol uses the patient's calcium stores to create calcium oxalate, which is excreted in the urine as crystals. Other findings in ethylene glycol poisoning may include flank pain, hematuria, and acute renal failure.

Rapid diagnosis is critical for a patient who has symptomatic ethylene glycol poisoning because delay in treatment can lead to renal damage, cerebral herniation, multiple organ system failure, and death. Many household products are toxic and frequently accessible to young children. Gasoline and turpentine are volatile hydrocarbons that cause pulmonary injury after aspiration. Motor oil also is a hydrocarbon, but because of its high viscosity and low volatility, it poses little risk for aspiration or toxicity. Organophosphate insecticides inhibit acetylcholinesterase and cause a cholinergic crisis manifested by bradycardia, hypersalivation, bronchorrhea, diarrhea, and muscle weakness.

4. 2010 Ques. #192 Answer E. Nausea, headache, bleeding from the external auditory canal, and hearing loss in the setting of blunt head trauma, as described for the boy in the vignette, are consistent with a temporal bone fracture. Other findings may include facial paralysis, cerebrospinal oto- or rhinorrhea, and vertigo. Because temporal bone fractures result from significant force, many patients have multiple other intracranial and orthopedic injuries.

Although temporal bone fractures can be associated with other skull fractures, an occipital fracture usually is characterized by occipital scalp swelling, and an orbital floor fracture is characterized by maxillary tenderness, periorbital swelling, and abnormal extraocular movements. A subdural hematoma or diffuse axonal injury causes altered mental status.

Know that temporal bone fractures are commonly manifested by bleeding from the external auditory canal or hemotympanum, hearing loss, facial paralysis, and cerbrospinal fluid otorrhea.

5. 2011 Ques.#25 Answer A. Acute respiratory failure remains a significant cause of morbidity and mortality in hospitalized pediatric patients. The most severe forms of acute respiratory failure are acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), which are defined by: acute onset, severe arterial hypoxemia (PaO2/FiO2 ratio ................
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