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Study Objectives: To determine the combined effects of aging and propofol on autonomic nervous system activity using heart rate variability (HRV) analysis. Design: Prospective, two-parallel group, repeated-measures study. Setting: Operating room of an academic hospital. Patients: ASA physical status 1, 2, and 3 patients, including 14 young (< 65 yrs) and 14 elderly (> 65 yrs) patients. All patients were scheduled for general surgical procedures with general anesthesia. Interventions: Each patient received two successive propofol doses during induction (0.5 mg/kg and 1.5 mg/kg) with a time interval allowing the return of Bispectral Index (BIS) to awake values. Measurements: Primary outcomes were HRV parameters, which included normalized power spectral density at low frequency (LFnorm) and high frequency (HFnorm) bands and the ratio LF/HF. Secondary outcomes were BIS values, blood pressure, heart rate, respiratory rate, and body temperature. Main Results: The interaction of age and propofol dose level was significant [multivariate analysis of variance, F (3,74) = 4.72, P = 0.005], representing a combined effect of age and propofol dose level on the mean HRV parameters. Propofol induction decreased the HFnorm component and enhanced LFnorm and LF/HF in the younger group, but had no significant effect in the older group. Such an effect was not associated with a significant difference in systolic blood pressure (SBP) decrements between the younger and older groups. Within each group, propofol caused significant decreases in SBP compared with preinduction values. Heart rate did not change significantly during propofol administration between groups or within groups. Conclusions: Propofol and aging act in synergy to depress the activity of the cardiovascular component of the autonomic nervous system. However, a compensatory increase in sympathetic outflow was seen in young patients. Such counterbalance was not observed in the older group. [ABSTRACT FROM AUTHOR]

: Study objectiveTo demonstrate the effect of administering a precurarizing dose of cisatracurium or rocuronium on the speed of onset of cisatracurium, and to review the possible mechanisms and value of the priming principle.: DesignDouble-blind, randomized, controlled trial.: SettingInpatient anesthesia in a university teaching hospital.: Patients90 ASA physical status I and II patients undergoing elective surgery requiring endotracheal intubation.: InterventionsThree groups of 30 patients each were investigated. Following induction of anesthesia with fentanyl and propofol, Group 1 received cisatracurium 0.015 mg.k–1, Group 2 received rocuronium 0.09 mg · kg–1, and Group 3 (control) received normal saline. Six minutes after priming, Groups 1 and 2 received cisatracurium 0.135 mg · kg–1 whereas Group 3 received cisatracurium 0.15 mg · kg–1.: Measurements and main resultsIn each group, first twitch height and the train-of-four ratios were recorded every 10 seconds after the initial priming dose. Intubation was attempted after the first twitch height became less than 15% of baseline. The decrease in the train-of-four ratios at 6 minutes was 0.97 for cisatracurium and 0.85 for rocuronium. The onset of muscle relaxation was significantly faster after priming with cisatracurium and rocuronium (71.7 ± 21.3 and 65 ± 19.8 sec, respectively) compared with control (148.7 ± 43.1 sec). Females receiving both muscle relaxants had a faster onset of paralysis than did males (65.9 ± 20.6 vs. 79.2 ± 20.6 and 55 ± 14.5 vs. 71.7 ± 20.4 sec). Intubation conditions were either excellent or satisfactory in all patients.: ConclusionsSix minutes after precurarization, there is no significant difference between rocuronium and cisatracurium when used as priming drugs. An even faster onset time with both drugs was demonstrated in females. The use of priming doses of 25% to 30% of ED95 may cause symptomatic muscle weakness. The mechanisms of the priming principle are discussed. [Copyright &y& Elsevier]