No abstract

A 42-year-old woman who underwent single lung transplantation who received tacrolimus and a 58-year-old woman with pneumonia and multiple comorbidities who received haloperidol both experienced drug-induced prolongation of cardiac repolarization. The second woman also developed torsade de pointes. Critically ill patients are particularly susceptible to developing torsade de pointes due to various comorbidities, electrolyte disturbances, and receipt of numerous drugs. These two case reports illustrate the increased risk for drug-induced cardiotoxicity in the critically ill patient. They also indicate the need for current knowledge derived from basic research and retrospective case reports on drug-induced torsade de pointes to be integrated into the existing body of knowledge. Guidelines can then be developed to help prospectively reduce the frequency of adverse effects in intensive care patients. Research is necessary regarding identification of high-risk patients before drugs are administered, and clarification of the proper role of therapeutic QT monitoring in clinical practice.

Nitrates may be used for pharmacological stimulation during tilt testing for the diagnosis of vasovagal syncope. In this study we assessed the diagnostic value of intravenous nitrates during tilt testing in patients with a typical history of vasovagal syncope. Twenty patients and 23 controls were tilted at 700 for a maximum duration of 30 minutes. After a 10-minute baseline supine phase, the test started with a continuous nitrate infusion at 1 microg/kg/min and increased every 5 minutes by 1 microg/kg/min, to a maximum of 6 microg/kg/min at the end of the test. The test was ended if the subjects developed a positive response (syncope or presyncope). Nineteen patients (95%) and 17 (74%) of the controls had a positive response. At test end sensitivity was 95%, but specificity was 26% and accuracy was 58%. Receiver operator characteristics (ROC) analysis revealed a maximum accuracy of 79% at 18 minutes, with a sensitivity of 80% and a specificity of 78%. Intravenous nitrates during tilt testing in patients with typical clinical criteria of vasovagal syncope is highly effective in provoking vasovagal syncope. Based on the ROC analysis, a maximum accuracy of 79% was attained at 18 minutes (at a dose of 4 microg/kg/min), suggesting a good diagnostic performance when tilt duration is limited to this point. A positive result requiring more than 18 minutes of stimulated tilting should be interpreted with caution, due to the accompanying considerable decrease of specificity.