We performed an open, prospective, randomized, controlled study of the incidence of major organ complications in 420 patients undergoing routine coronary artery bypass graft surgery with or without thoracic epidural anesthesia and analgesia (TEA). All patients received a standardized general anesthetic. Group TEA received TEA for 96 h. Group GA (general anesthesia) received narcotic analgesia for 72 h. Both groups received supplementary oral analgesia. Twelve patients were excluded-eight in Group TEA and four in Group GA-because of incomplete data collection. New supraventricular arrhythmias occurred in 21 of 206 patients (10.2%) in Group TEA compared with 45 of 202 patients (22.3%) in Group GA (P = 0.0012). Pulmonary function (maximal inspiratory lung volume) was better in Group TEA in a subset of 93 patients (P < 0.0001). Extubation was achieved earlier (P < 0.0001) and with significantly fewer lower respiratory tract infections in Group TEA (TEA = 31 of 206, GA = 59 of 202; P = 0.0007). There were significantly fewer patients with acute confusion (GA = 11 of 202, TEA = 3 of 206; P = 0.031) and acute renal failure (GA = 14 of 202, TEA = 4 of 206; P = 0.016) in the TEA group. The incidence of stroke was insignificantly less in the TEA group (GA = 6 of 202, TEA = 2 of 206; P = 0.17). There were no neurologic complications associated with the use of TEA. We conclude that continuous TEA significantly improves the quality of recovery after coronary artery bypass graft surgery compared with conventional narcotic analgesia.
SummaryTarget controlled infusion (TCI) pumps function using a programme based on a pharmacokinetic ⁄ pharmacodynamic model. We compared the Marsh and Schnider models to find out which better correlates with the clinically observed effect of propofol as assessed by the Observer Assessment of Alertness ⁄ Sedation (OAAS) score and the Bispectral index. We assessed the sedation score and Bispectral index score in 40 un-premedicated patients undergoing surgical procedures under spinal anaesthesia with propofol sedation to a target concentration of 2 lg.ml. Half of the patients received TCI propofol driven by the Schnider model in effect site control, the other half were sedated with TCI propofol driven by the Marsh model in plasma control. We calculated the effect site concentration predicted by both models for all the patients. Changes in the sedation score and Bispectral index correlated better with the Marsh than with the Schnider effect site prediction in both study groups. Target controlled infusion (TCI) systems are designed to facilitate the delivery of intravenous anaesthetics. The anaesthetist sets the desired target blood or effect site concentration and the TCI pump adjusts the rate of delivery of the anaesthetic agent according to a pharmacokinetic ⁄ pharmacodynamic (PK ⁄ PD) model. Different PK ⁄ PD models predict different rates of drug transfer and effect site equilibration. The Diprifusor manufactured by AstraZeneca (Macclesfield, UK) was the first available propofol TCI pump which was based on 'the Marsh PK ⁄ PD model' [1]. More recently, a different PK ⁄ PD model, 'the Schnider model ' [2], has been introduced into clinical practice. During induction of anaesthesia, the Schnider model predicts faster propofol effect site equilibration than the Marsh model.A sedation score can be used to assess the hypnotic effect of anaesthetic drugs. The rate of achieving a certain level of sedation or the time course of the sedation score should reflect the rate of effect site equilibration. The responsive component of the Observer Assessment of Alertness ⁄ Sedation (OAAS) score (Table 1) can be used for this purpose [3,4]. This allows the effect site prediction from a PK ⁄ PD model to be compared with the evolution of the OAAS over time.Bispectral index (BIS) monitoring measures the hypnotic effect of anaesthetics [5,6]. Although more often used to assess the depth of anaesthesia, BIS has also been used to evaluate the depth of sedation [6,7].We aimed to study which of the two PK ⁄ PD models better correlates with the clinically observed effect of propofol, as assessed by the OAAS score and BIS monitoring.
MethodsAfter obtaining ethics committee approval and signed informed consent, we recruited 40 un-premedicated, ASA I-III patients undergoing orthopaedic surgery under spinal anaesthesia with propofol sedation. Exclusion criteria were as follow: age less than 18 years, any
The system was able to provide clinically adequate anesthesia in 9 of 10 patients. Further studies are required to determine whether control performance can be improved by alterations to the gain factors or by using an effect site-targeted, target-controlled infusion propofol system.
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