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Background: Continuous non-invasive arterial pressure measured with CNAP (CNAP) has been shown to be superior to intermittent oscillometric measurements during procedural sedation and spinal anaesthesia. We assessed the performance of CNAP during general anaesthesia by analysis of agreement with invasive measurements of arterial pressure (AP).Methods: Eighty-eight patients undergoing elective abdominal surgery, cardio-, or neurosurgery were included in the study. Systolic, diastolic, and mean AP measured by an intra-arterial catheter in the radial artery (IAP) were compared with those obtained by CNAP from the same arm. Data were analysed to determine the precision (i.e. measurement error) and accuracy (i.e. systematic error) of beat-to-beat CNAP values with respect to IAP. Also, we compared the frequency of fast changes in AP (FCAP) and hypotension (IOH) by both methods.Results: CNAP precision of 4.5, 3.1, and 3.2 mm Hg (systolic, diastolic, and mean AP, respectively) was not significantly different from IAP precision, and CNAP accuracy was +6.7, -5.6, and -1.6 mm Hg. The frequency of AP pairs having a difference within the calculated limits of agreement was 81%, 64%, and 76% for systolic, diastolic, and mean AP, respectively. The calculated limits of agreement were +/-17.6, +/-11.4, and +/-12.0 mm, Hg, respectively. CNAP and IAP detected simultaneously to 82.1% FCAP and to 84.6% IOH.Conclusions: CNAP provides real-time estimates of arterial pressure comparable with those generated by an invasive intra-arterial catheter system during general anaesthesia. [ABSTRACT FROM AUTHOR]

Background. Concentration effect relationships are commonly described with a direct response model as for example the sigmoid Emax model with one effect compartment as site of action. In this study we investigated whether models with more than one effect site, or indirect response, or counter-regulatory response models may be more appropriate for modelling the propofol effect on arterial blood pressure. Methods. Nine young healthy volunteers received propofol as target controlled infusion with predefined increasing and decreasing plasma target concentrations. Propofol concentrations were determined from arterial blood samples. Arterial blood pressure was measured invasively at radial artery site. Pharmacokinetic/-pharmacodynamic modelling was performed by population analysis with MONOLIX, testing different direct, indirect and counter-regulatory response models. Results. Propofol plasma concentrations were well described by a three-compartment model. The propofol effect on arterial blood pressure was best described by a direct sigmoid Emax model with two effect site compartments. Conclusions. Two effect sites were needed to describe the propofol effect on arterial blood pressure. This may reflect different pathways of arterial blood pressure response to propofol. [ABSTRACT FROM AUTHOR]

Background Target controlled infusion (TCI) with sufentanil is usually performed using the Gepts model, which was derived from patients undergoing general surgery. It is, however, known that pharmacokinetics of sufentanil can be changed during cardiopulmonary bypass (CPB). We tested whether TCI during coronary artery bypass surgery with CPB produces constant total, unbound sufentanil concentration–time course or both. Methods After IRB approval, written informed consent was obtained from 38 male patients (48–74 yr) undergoing coronary artery bypass surgery. Anaesthesia was managed with propofol and TCI of sufentanil, using the Gepts model, targeting plasma concentrations of 0.4 (n=18) or 0.8 ng ml−1 (n=20). Arterial blood samples were taken before, during, and after CPB. Total and unbound sufentanil concentrations were measured by HPLC with tandem mass spectrometry. The accuracy of the TCI model was assessed by the prediction error, and a pharmacokinetic model was determined by population analysis. Results The median prediction error of the TCI with the Gepts model before, during, and after CPB was 59.6, 3.9, and −10.4%, respectively. The unbound sufentanil concentrations increased significantly during CPB. Pharmacokinetic modelling showed an increase in elimination and intercompartmental clearance after initiation of CPB. Conclusions Neither total nor unbound sufentanil concentrations remained constant when performing a TCI with the Gepts model in coronary artery bypass surgery with CPB. A pharmacokinetic model derived from patients undergoing cardiac surgery with CPB might improve the performance of TCI in this population. [ABSTRACT FROM AUTHOR]

Background. Continuous non-invasive arterial pressure measured with CNAPTM (CNAP) has been shown to be superior to intermittent oscillometric measurements during procedural sedation and spinal anaesthesia. We assessed the performance of CNAP during general anaesthesia by analysis of agreement with invasive measurements of arterial pressure (AP). Methods. Eighty-eight patients undergoing elective abdominal surgery, cardio-, or neurosurgery were included in the study. Systolic, diastolic, and mean AP measured by an intra-arterial catheter in the radial artery (IAP) were compared with those obtained by CNAP from the same arm. Data were analysed to determine the precision (i.e. measurement error) and accuracy (i.e. systematic error) of beat-to-beat CNAP values with respect to IAP. Also, we compared the frequency of fast changes in AP (FCAP) and hypotension (IOH) by both methods. Results. CNAP precision of 4.5, 3.1, and 3.2 mm Hg (systolic, diastolic, and mean AP, respectively) was not significantly different from IAP precision, and CNAP accuracy was +6.7, 25.6, and 21.6 mm Hg. The frequency of AP pairs having a difference within the calculated limits of agreement was 81%, 64%, and 76% for systolic, diastolic, and mean AP, respectively. The calculated limits of agreement were ±17.6, ±11.4, and ±12.0 mm, Hg, respectively. CNAP and IAP detected simultaneously to 82.1% FCAP and to 84.6% IOH. Conclusions. CNAP provides real-time estimates of arterial pressure comparable with those generated by an invasive intra-arterial catheter system during general anaesthesia. [ABSTRACT FROM AUTHOR]

Background: Clinical benefits of measuring processed EEG during anaesthesia in adults, such as improved recovery and reduced risk of awareness, may also be valid in children. This study evaluated a rational selection of EEG variables as measures of arousal during surgical anaesthesia in children.Methods: Sixty children undergoing surgical anaesthesia with propofol and remifentanil were enrolled. The performance of 33 single EEG variables and bispectral index (BIS) was assessed by simultaneous analysis of prediction probability (Pk) of Children's Hospital of Wisconsin Sedation Scores and their signal-to-noise ratio (SNR). Variables performing best in Pk and SNR analysis were selected as potential measures of arousal. Their performance was investigated in five age groups, 0-1, 1-2, 2-5, 5-8, and 8-13 yr.Results: Single EEG variables such as relative power from frequency bands 13-20 and 20-26 Hz, SEF95, and approximate entropy performed best with Pk>0.59 and SNR>5.50. The Pk and SNR of BIS were 0.71 and 15.76, respectively. Their performance was significantly better in children aged 1-13 yr than in 0-1 yr.Conclusions: BIS may provide a measure of arousal during propofol anaesthesia in children, but its accuracy is less in infants younger than 12 months. Single EEG variables such as high-frequency components of EEG, SEF95, and approximate entropy may be of limited value to detect arousal in the individual paediatric patient. [ABSTRACT FROM AUTHOR]

Background Our objective was to evaluate the effect of intensive care treatment on the protein binding of sufentanil and hydromorphone in cardiac surgery patients during postoperative analgesia using a target-controlled infusion (TCI) and patient-controlled analgesia (PCA). Methods Fifty adult patients were enrolled in this prospective randomized study; of which, 49 completed the study (age range 40–81 yr). Sufentanil was administered as an analgesic intraoperatively, and hydromorphone was dosed after operation with TCI and PCA until 8 a.m. on the first postoperative day. Arterial plasma samples were collected for drug and protein concentration measurements up to 24 h after cardiac surgery. Corresponding patient data were collected from the electronic patient data system. After explorative data analysis with principal component analysis, multivariate regression analysis and non-linear mixed effects modelling was used to study the effect of treatment on protein binding. Results Data of 35 patients were analysed. The median protein binding of sufentanil and hydromorphone was 88.4% (IQ range 85.7–90.5%) and 11.6% (IQ range 9.5–14.3%), respectively. Free fraction of sufentanil increased towards the end of the study period, whereas hydromorphone free fraction remained nearly constant. The total sufentanil concentration and volume balance were identified as significant covariates for the protein binding of sufentanil. For the protein binding of hydromorphone, no significant covariate effects were found. Conclusions Sufentanil protein binding was significantly dependent on changes in the total drug concentration and volume balance addressing the importance of adequate dosing and fluid-guided therapy. Hydromorphone protein binding was nearly constant throughout the study period. Clinical trial registration EudraCT 2011-003648-31 and ClinicalTrials.gov: NCT01490268. [ABSTRACT FROM PUBLISHER]