ABSTRACT
<p><b>BACKGROUND</b>Bispectral index (BIS) is considered very useful to guide anesthesia care in elderly patients, but its use is controversial for the evaluation of the adequacy of analgesia. This study compared the BIS changes in response to loss of consciousness (LOC) and loss of somatic response (LOS) to nociceptive stimuli between elderly and young patients receiving intravenous target-controlled infusion (TCI) of propofol and remifentanil.</p><p><b>METHODS</b>This study was performed on 52 elderly patients (aged 65-78 years) and 52 young patients (aged 25-58 years), American Society of Anesthesiologists physical status I or II. Anesthesia was induced with propofol administered by TCI. A standardized noxious electrical stimulus (transcutaneous electrical nerve stimulation, [TENS]) was applied (50 Hz, 80 mA, 0.25 ms pulses for 4 s) to the ulnar nerve at increasing remifentanil predicted effective-site concentration (Ce) until patients lost somatic response to TENS. Changes in awake, prestimulus, poststimulus BIS, heart rate, mean arterial pressure, pulse oxygen saturation, predicted plasma concentration, Ce of propofol, and remifentanil at both LOC and LOS clinical points were investigated.</p><p><b>RESULTS</b>BISLOCin elderly group was higher than that in young patient group (65.4 ± 9.7 vs. 57.6 ± 12.3) (t = 21.58, P < 0.0001) after TCI propofol, and the propofol Ce at LOC was 1.6 ± 0.3 μg/ml in elderly patients, which was significantly lower than that in young patients (2.3 ± 0.5 μg/ml) (t = 7.474, P < 0.0001). As nociceptive stimulation induced BIS to increase, the mean of BIS maximum values after TENS was significantly higher than that before TENS in both age groups (t = 8.902 and t = 8.019, P < 0.0001). With increasing Ce of remifentanil until patients lost somatic response to TENS, BISLOSwas the same as the BISLOCin elderly patients (65.6 ± 10.7 vs. 65.4 ± 9.7), and there were no marked differences between elderly and young patient groups in BISawake, BISLOS, and Ce of remifentanil required for LOS.</p><p><b>CONCLUSION</b>In elderly patients, BIS can be used as an indicator for hypnotic-analgesic balance and be helpful to guide the optimal administration of propofol and remifentanil individually.</p><p><b>TRIAL REGISTRATION</b>CTRI Reg. No: ChiCTR-OOC-14005629; http://www.chictr.org.cn/showproj.aspx?proj=9875.</p>
Subject(s)
Adult , Aged , Female , Humans , Male , Middle Aged , Electroencephalography , Movement Disorders , Pain , Piperidines , Pharmacology , Propofol , Pharmacology , Transcutaneous Electric Nerve Stimulation , UnconsciousnessABSTRACT
<p><b>BACKGROUND</b>In this prospective randomized study, we compared the predicted blood and effect-site C 50 for propofol and remifentanil target-controlled infusion (TCI) and the bispectral index (BIS) values at loss of consciousness (LOC) and response to a standard noxious painful stimulus (LOS) in elderly and young patients, respectively. We hypothesized that the elderly patients will require lower target concentration of both propofol and remifentanil at above two clinical end-points.</p><p><b>METHODS</b>There were 80 American Society of Anesthesiologists (ASA) physical status I-II unpremedicated patients enrolled in this study, they were divided into elderly group (age ≥65 years, n = 40) and young group (aged 18-64 years, n = 40). Propofol was initially given to a predicted blood concentration of 1.2 μg/ml and thereafter increased by 0.3 μg/ml every 30 s until Observer's Assessment of Alertness and Sedation score was 1. The propofol level was kept constant, and remifentanil was given to provide a predict blood concentration of 2.0 ng/ml, and then increased by 0.3 ng/ml every 30 s until loss of response to a tetanic stimulus. BIS (version 3.22, BIS Quattro sensor) was also recorded.</p><p><b>RESULTS</b>In elderly group, the propofol effect-site C 50 at LOC of was 1.5 (1.4-1.6) μg/ml, was significantly lower than that of young group, which was 2.2 (2.1-2.3) μg/ml, the remifentanil effect-site C 50 at LOS was 3.5 (3.3-3.7) ng/ml in elderly patients, was similar with 3.7 (3.6-3.8) ng/ml in young patients. Fifty percent of patients lost consciousness at a BIS value of 57.3 (56.4-58.1), was similar with that of young group, which was 55.2 (54.0-56.3).</p><p><b>CONCLUSION</b>In elderly patients, the predicted blood and effect-site concentrations of propofol at LOC were lower than that of young patients. At same sedation status, predicted blood and effect-site concentrations of remifentanil required at LOS were similar in elderly and young patients. BIS were not affected by age. Low-propofol/high-opioid may be optional TCI strategy for elderly patients.</p>