Longing for the QT

A 58-year-old man presented to the ED with a reported overdose of an unknown medication. The patient was agitated, combative, and altered. Initial vital signs included a heart rate of 115 beats/min, blood pressure of 154/93 mm Hg, respirations of 22/min, and temperature of 99.5°F. The patient was difficult to evaluate because he was agitated, and he was given 5 mg of haloperidol IV and 2 mg of lorazepam IV. The patient continued to be agitated, and was given another 10 mg of haloperidol IV, followed by a repeat dose of 10 mg IV 15 minutes later. The patient then became unresponsive, and his cardiac monitor demonstrated the rhythm below.​What is the mechanism of drug-induced QT prolongation?The causes of QT prolongation can be divided into congenital and acquired. These two entities occur by different mechanisms. Congenital prolonged QT syndrome is caused by, mutations in ion channel subunits or protein coding genes. The acquired form is more prevalent with drug-induced QT prolongation being the most frequent cause.Most drugs that prolong the QT interval act by blocking the delayed rectifier potassium channel encoded by the human ether à go-go related gene (hERG). This inhibits the flow of potassium ions through the outward potassium channel, thereby delaying depolarization. Contributing factors include higher drug serum levels, polypharmacy, electrolyte abnormalities (hypokalemia, hypomagnesemia, hypocalcemia), genetic factors, intrinsic heart disease, and dysrhythmias.Wh...
Source: The Tox Cave - Category: Emergency Medicine Tags: Blog Posts Source Type: blogs