Population-based volume kinetics of crystalloids and colloids in healthy volunteers.

We characterized the volume kinetics of crystalloid solutions (Ringer's lactate solution and 5% dextrose water) and colloid solutions (6% tetrastarch and 10% pentastarch) by nonlinear mixed-effects modeling in healthy volunteers. We also assessed whether the bioelectrical impedance analysis parameters are significant covariates for volume kinetic parameters. Twelve male volunteers were randomly allocated to four groups, and each group received the four fluid solutions in specified sequences, separated by 1-week intervals to avoid any carryover effects. Volunteers received 40 ml/kg Ringer's lactate solution, 20 ml/kg 5% dextrose water, 1000 ml 6% tetrastarch, and 1000 ml 10% pentastarch over 1 h. Arterial blood samples were collected to measure the hemoglobin concentration at different time points. Bioelectrical impedance spectroscopy (BIS, INBODY S10, InBody CO., LTD, Seoul, Korea) was also carried out at preset time points. In total, 671 hemoglobin-derived plasma dilution data points were used to determine the volume kinetic characteristics of each fluid. The changes in plasma dilution induced by administration of crystalloid and colloid solutions were well-described by the two-volume and one-volume models, respectively. Extracellular water was a significant covariate for the peripheral volume of distribution at baseline in the volume kinetic model of Ringer's lactate solution. When the same amount was administered, the colloid solutions had ~4 times more plasma expansion effect than did the crystalloid solutions. Starches with larger molecular weights maintained the volume expansion effect longer than those with smaller molecular weights.

Predictive performance of a new pharmacokinetic model for propofol in underweight patients during target-controlled infusion.

BACKGROUND: In a previous study, the modified Marsh and Schnider models respectively showed negatively- and positively-biased predictions in underweight patients. To overcome this drawback, we developed a new pharmacokinetic propofol model-the Choi model-for use in underweight patients. In the present study, we evaluated the predictive performance of the Choi model. METHODS: Twenty underweight patients undergoing elective surgery received propofol via TCI using the Choi model. The target effect-site concentrations (Ces) of propofol were 2.5, 3, 3.5, 4, 4.5, and 2 µg/mL. Arterial blood samples were obtained at least 10 minutes after achieving pseudo-steady-state. Predicted propofol concentrations with the modified Marsh, Schnider, and Eleveld pharmacokinetic models were obtained by simulation (Asan pump, version 2.1.3; Bionet Co. Ltd., Seoul, Korea). The predictive performance of each model was assessed by calculation of four parameters: inaccuracy, divergence, bias, and wobble. RESULTS: A total of 119 plasma samples were used to determine the predictive performance of the Choi model. Our evaluation showed that the pooled median (95% CI) bias and inaccuracy were 4.0 (-4.2 to 12.2) and 23.9 (17.6-30.3), respectively. The pooled biases and inaccuracies of the modified Marsh, Schnider, and Eleveld models were clinically acceptable. However, the modified Marsh and Eleveld models consistently produced negatively biased predictions in underweight patients. In particular, the Schnider model showed greater inaccuracy at a target Ce ≥ 3 µg/mL. CONCLUSION: The new propofol pharmacokinetic model (the Choi model) developed for underweight patient showed adequate performance for clinical use.

Differential Postoperative Effects of Volatile Anesthesia and Intraoperative Remifentanil Infusion in 7511 Thyroidectomy Patients: A Propensity Score Matching Analysis.

Although remifentanil is used widely by many clinicians during general anesthesia, there are recent evidences of opioid-induced hyperalgesia as an adverse effect. This study aimed to determine if intraoperative remifentanil infusion caused increased pain during the postoperative period in patients who underwent a thyroidectomy. A total of 7511 patients aged ≥ 20 years, who underwent thyroidectomy between January 2009 and December 2013 at the Asan Medical Center were retrospectively analyzed. Enrolled patients were divided into 2 groups: group N (no intraoperative remifentanil and only volatile maintenance anesthesia) and group R (intraoperative remifentanil infusion including total intravenous anesthesia and balanced anesthesia). Following propensity score matching analysis, 2582 patients were included in each group. Pain scores based on numeric rating scales (NRS) were compared between the 2 groups at the postoperative anesthetic care unit and at the ward until 3 days postoperation. Incidences of postoperative complications, such as nausea, itching, and shivering were also compared. The estimated NRS pain score on the day of surgery was 5.08 (95% confidence interval [CI] 4.97-5.19) in group N patients and 6.73 (95% CI 6.65-6.80) in group R patients (P < 0.001). There were no statistically significant differences in NRS scores on postoperative days 1, 2, and 3 between the 2 groups. Postoperative nausea was less frequent in group R (31.4%) than in group N (53.5%) (P < 0.001). However, the incidence of itching was higher in group R (4.3%) than in group N (0.7%) (P < 0.001). Continuous infusion of remifentanil during general anesthesia can cause higher intensity of postoperative pain and more frequent itching than general anesthesia without remifentanil infusion immediately after thyroidectomy. Considering the advantages and disadvantages of continuous remifentanil infusion, volatile anesthesia without opioid may be a good choice for minor surgeries, such as thyroidectomy.

Comparison of the Efficacy and Safety of a Pharmacokinetic Model-Based Dosing Scheme Versus a Conventional Fentanyl Dosing Regimen For Patient-Controlled Analgesia Immediately Following Robot-Assisted Laparoscopic Prostatectomy: A Randomized Clinical Trial.

Conventional, intravenous, patient-controlled analgesia, which is only administered by demand bolus without basal continuous infusion, is closely associated with inappropriate analgesia. Pharmacokinetic model-based dosing schemes can quantitatively describe the time course of drug effects and achieve optimal drug therapy. We compared the efficacy and safety of a conventional dosing regimen for intravenous patient-controlled analgesia that was administered by demand bolus without basal continuous infusion (group A) versus a pharmacokinetic model-based dosing scheme performed by decreasing the dosage of basal continuous infusion according to the model-based simulation used to achieve a targeted concentration (group B) following robot-assisted laparoscopic prostatectomy.In total, 70 patients were analyzed: 34 patients in group A and 36 patients in group B. The postoperative opioid requirements, pain scores assessed by the visual analog scale, and adverse events (eg, nausea, vomiting, pruritis, respiratory depression, desaturation, sedation, confusion, and urinary retention) were compared on admission to the postanesthesia care unit and at 0.5, 1, 4, 24, and 48 h after surgery between the 2 groups. All patients were kept for close observation in the postanesthesia care unit for 1 h, and then transferred to the general ward.The fentanyl requirements in the postanesthesia care unit for groups A and B were 110.0 ±â€Š46.4 µg and 77.5 ±â€Š35.3 µg, respectively. The pain scores assessed by visual analog scale at 0.5, 1, 4, and 24 h after surgery in group B were significantly lower than in group A (all P < 0.05). There were no differences in the adverse events between the 2 groups.We found that the pharmacokinetic model-based dosing scheme resulted in lower opioid requirements, lower pain scores, and no significant adverse events in the postanesthesia care unit following robot-assisted laparoscopic prostatectomy in comparison with conventional dosing regimen.

The accuracy of the new landmark using respiratory jugular venodilation and direct palpation in right internal jugular vein access.

BACKGROUND: Although ultrasonography is recommended in internal jugular vein (IJV) catheterization, the landmark-guided technique should still be considered. The central landmark using the two heads of the sternocleidomastoid muscle is widely used, but it is inaccurate for IJV access. As an alternative landmark, we investigated the accuracy of the new landmark determined by inspection of the respiratory jugular venodilation and direct IJV palpation in right IJV access by ultrasonography. METHODS AND FINDINGS: Thirty patients were enrolled. After induction of anesthesia, the central landmark was marked at the cricoid cartilage level (M1) and the alternative landmark determined by inspection of the respiratory jugular venodilation and direct palpation of IJV was also marked at the same level (M2). Using ultrasonography, the location of IJV was identified (M3) and the distance between M1 and M3 as well as between M2 and M3 were measured. The median (interquartile range) distance between the M2 and M3 was 3.5 (2.0-6.0) mm, compared to 17.5 (12.8-21.3) mm between M1 and M3. (P<0.001) The dispersion of distances between M2 and M3 was significantly smaller than between M1 and M3. (P<0.001) The visibility of respiratory jugular venodilation was associated with CVP more than 4 mmHg. Limitations of the present study are that the inter-observer variability was not investigated and that the visibility of the alternative landmark can be limited to right IJV in adults. CONCLUSION: The alternative landmark may allow shorter distance for the right side IJV access than the central landmark and can offer advantages in right IJV catheterization when ultrasound device is unavailable. TRIAL REGISTRATION: Clinical Research Informational Service KCT0000812.