A 57-year-old man is brought to the emergency department after being found confused and agitated in a park. Medical records indicate that he has a history of schizophrenia, alcohol use disorder, and liver cirrhosis. The patient states that he has not been taking his medications "because they never help." Temperature is 37.2 C (99 F), blood pressure is 160/80 mm Hg, pulse is 118/min, and respirations are 24/min. On examination, the patient is disheveled and disoriented, claiming that FBI agents have been chasing him. His breath smells of alcohol. Pupils are equal and reactive, and the neck is supple. The abdomen is distended but nontender. The skin and mucous membranes are dry. There is mild edema in both lower extremities but no deformity. Laboratory results are as follows: During evaluation, the patient is initially cooperative but becomes increasingly aggressive and combative. For safety reasons, he is given intravenous haloperidol and lorazepam. Shortly afterward, the cardiac monitor displays the rhythm shown in the exhibit. Which of the following most likely contributed to this patient's abnormal rhythm?

Question

A 57-year-old man is brought to the emergency department after being found confused and agitated in a park.  Medical records indicate that he has a history of schizophrenia, alcohol use disorder, and liver cirrhosis.  The patient states that he has not been taking his medications "because they never help."  Temperature is 37.2 C (99 F), blood pressure is 160/80 mm Hg, pulse is 118/min, and respirations are 24/min.  On examination, the patient is disheveled and disoriented, claiming that FBI agents have been chasing him.  His breath smells of alcohol.  Pupils are equal and reactive, and the neck is supple.  The abdomen is distended but nontender.  The skin and mucous membranes are dry.  There is mild edema in both lower extremities but no deformity.  Laboratory results are as follows:  During evaluation, the patient is initially cooperative but becomes increasingly aggressive and combative.  For safety reasons, he is given intravenous haloperidol and lorazepam.  Shortly afterward, the cardiac monitor displays the rhythm shown in the exhibit.  Which of the following most likely contributed to this patient's abnormal rhythm?

Quizplus · Accepted Answer

11ec25c8_d766_adb7_bc81_4d4b4a62aa4e_MD0003_00 This patient with altered mental status (AMS) in the setting of alcohol use disorder (AUD) and likely nonadherence with schizophrenia medications developed cardiac arrhythmia shortly after receiving intravenous medications. The cardiac rhythm shows torsade de pointes (TdP), suggesting excessive QT interval prolongation due to a medication adverse effect. QT-interval prolongation is the ECG manifestation of delayed ventricular repolarization, which occurs due to impaired function of voltage-gated potassium channels. Significantly delayed repolarization can trigger TdP, a polymorphic ventricular tachycardia that can lead to cardiac arrest. Many medications, including some antipsychotic agents (eg, intravenous haloperidol), block the outward delayed rectifier potassium current to prolong the QT interval and increase the risk of TdP. QT-interval prolongation The risk of TdP is also increased with electrolyte derangements that prolong the QT interval (eg, hypokalemia, hypomagnesemia), which are common in patients with AUD due to poor nutrition. When possible, patients receiving intravenous haloperidol or other QT-prolonging medications, particularly individuals at increased risk for arrhythmia, should undergo ECG testing prior to administration. The medication must be withheld if the baseline-corrected QT interval is prolonged (eg, >450 msec). Other medications administered intravenously for chemical restraint include lorazepam (a benzodiazepine) (Choice D) and diphenhydramine (an antihistamine); these drugs cause sedation but are not associated with QT prolongation and can be safely used to sedate an agitated or a combative patient until an ECG is obtained. Many benzodiazepines are hepatically metabolized and should be administered with care due to the risk for respiratory depression. (Choice A) Although an elevated blood alcohol level causes CNS depression and sedation, it does not prolong the QT interval and does not increase the risk for TdP. (Choice B) An elevated blood ammonia level is often present in patients with decompensated cirrhosis (eg, distended abdomen suggesting ascites, edema suggesting hypoalbuminemia). It may contribute to AMS (ie, hepatic encephalopathy) but does not increase the risk for TdP. (Choice E) AUD and poor nutrition may predispose to hypoglycemia, which should be excluded in patients with AMS. However, hypoglycemia does not predispose to TdP. (Choice F) Significant hyponatremia can cause AMS, but it is not known to increase the risk of TdP. Educational objective: Antipsychotic agents (eg, haloperidol) can cause QT-interval prolongation; therefore, an ECG should be obtained prior to administering these agents to avoid causing a life-threatening arrhythmia (ie, torsade de pointes). References: QTc prolongation by psychotropic drugs and the risk of torsade de pointes. (http://www.ncbi.nlm.nih.gov/pubmed/22114630)

A 57-Year-Old Man Is Brought to the Emergency Department After