{'fraction_non_alphanumeric': 0.05838967424708052, 'fraction_numerical': 0.037492317148125384, 'mean_word_length': 4.481481481481482, 'pattern_counts': {'":': 0, '<': 3, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Electrophysiological effects of propofol on the normal cardiac conduction system.

To determine the electrophysiological effects of propofol and to explain the potential mechanism(s) whereby it causes bradyarrhythmias, 10 closed-chest pigs weighing 20-25 kg were studied. Each animal was premedicated by intramuscular administration of ketamine hydrochloride, intubated, and mechanically ventilated. Femoral arterial and venous catheters were placed, and a comprehensive electrophysiologic evaluation was performed at baseline and after two doses (1 mg/kg i.v. bolus and 0.1 mg/kg/min infusion and an extra 1- mg/kg i.v. bolus and 0.2 mg/kg/min infusion) of propofol. The electrophysiological effects obtained on low-and high-dose propofol were compared to baseline values. Propofol caused a dose-related decrease in sinus cycle length (baseline 565 +/- 36 ms, low-dose propofol 541 +/- 28, high-dose propofol 527 +/- 26 ms; p < 0.05), a prolongation of the corrected sinus node recovery time (baseline 119 +/- 35 ms, low-dose propofol 126 +/- 32, high-dose propofol 130 +/- 30 ms; p < 0.01), and an increase in the His-ventricular interval (baseline 33 +/- 4 ms, low-dose propofol 36 +/- 4, high-dose propofol 40 +/- 3 ms; p < 0.005). All other electrophysiological parameters remained unchanged, and there were no cases of spontaneous atrioventricular block or sinus pauses. We conclude that propofol causes dose-related depression of sinus node and His-Purkinje system functions, but has no effect on the atrioventricular node function and on the conduction properties of atrial and ventricular tissues in normal pig hearts.