Haloperidol and lorazepam are commonly used to sedate ethanol (E)-intoxicated patients in emergency departments. This study was conducted to explore the role of ethanol in altering the potency of haloperidol and lorazepam with respect to cardiac conduction and contraction. For mechanical studies, isolated rat hearts were studied under isovolumetric conditions by using standard Langendorff technique. Hearts were perfused with Krebs-Heinseleit-Bicarbonate buffer containing haloperidol or lorazepam in concentrations ranging from 100 to 750 ng/ml (one heart per drug concentration). For both haloperidol and lorazepam individually, significant reductions in Left ventricular-generated pressure (LVGP) were observed at a concentration of 750 ng/ml (haloperidol = 2,250 nM and lorazepam = 2,000 nM). The addition of 20 and 65 mM ethanol shifted the concentration-response effect of haloperidol such that LVGP was significantly reduced at haloperidol = 500 and 300 ng/ml, respectively (p < 0.05 vs. basal control; paired t test). Ethanol produced no observable shift on the lorazepam concentration-response for LVGP. For electrophysiologic studies, hearts were perfused with haloperidol and lorazepam (300 ng/ml) +/- 65 mM ethanol. Compared with basal control, E + H significantly decreased heart rate (-74 +/- 12 beats/min) and increased His-ventricular conduction time (+7.6 +/- 1.5 ms vs. +1.7 +/- 0.6 ms for control hearts). Both haloperidol and EH significantly increased atrioventricular (AV) effective refractory period and the atrioventricular-His (AH) conduction interval. No significant changes in any electrophysiologic parameter were observed with ethanol or lorazepam perfused individually or with the combination of ethanol and lorazepam. Ethanol potentiates haloperidol-induced electromechanical depression of isolated rat hearts. Ethanol had no such effect on lorazepam.
Objective: To evaluate whether measures that lower cytosolic calcium (Ca) can reverse propranolol (PROP) toxicity in the isolated, perfused rat heart. Methods: Isolated rat hearts were perfused on a Langendorff apparatus with Krebs-Henseleit-bicarbonate (KHB) buffer solution. Toxicity was produced by perfusing the hearts with PROP (5 pg/mL) for 30 minutes. Subsequently, the hearts were treated for 30 minutes with buffer containing PROP plus experimental treatment. Three treatments were chosen: hypertonic sodium (Na) (1 60 mmol), to stimulate Na-Ca exchange, dantrolene (DAN) (10 pmol), to inhibit Ca release from sarcoplasmic reticulum, and combined hypertonic Na and DAN. The hearts were paced after 20 minutes of treatment. Heart rate (HR), left ventricular peak systolic pressure (LVP), the first derivative of LVP (dP/dt), and coronary flow were measured. Results: PROP decreased HR and rendered the hearts refractory to pacing. PROP did not alter dP/dt. PROP increased LVP consistent with increased cytosolic Ca. Combined hypertonic Na and DAN treatment restored the ability to pace PROP-toxic hearts to the basal HR. Individually, hypertonic Na or DAN treatment partially restored the ability to pace toxic hearts. As experimental treatments increased HR, dP/dt and LVP decreased, consistent with decreased cytosolic Ca availability. Conclusion: These data are consistent with the hypothesis that bradycardia during (3-blocker cardiotoxicity is mediated by altered Ca homeostasis.
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