Potency of propofol for inducing loss of consciousness in end-stage kidney disease patients

It can be difficult for anesthesiologists to determine the optimal dose of propofol for end-stage kidney disease (ESKD) patients due to changes in drug disposition. The purpose of this study was to evaluate the potency of propofol for inducing loss of consciousness in ESKD patients. Patients with normal kidney function (Control group, n = 15), those with ESKD (ESKD group, n = 15), and those with ESKD undergoing cervical epidural anesthesia (ESKD-CEB group, n = 15) were administered propofol by target-controlled infusion (TCI) using the Schneider model. The effect-site concentration (Ce) of propofol started at 0.5 μg/ml and increased in increments of 0.5 μg/ml until the patient did not respond to verbal commands. The relationship between the probability (P) of loss of consciousness and the Ce of propofol was analyzed in each group using logistic regression. The Ce values of propofol at the time of loss of consciousness were 4.3 ± 0.9, 3.7 ± 0.9, and 3.3 ± 1.0 μg/ml for the Control, ESKD, and ESKD-CEB* groups, respectively (*significant difference vs. control, P < 0.05). The estimated Ce50 values for lost ability to respond to verbal command were 4.56, 3.75, and 3.21 μg/ml for the Control, ESKD, and ESKD-CEB groups, respectively. In conclusion, when inducing anesthesia in ESKD patients, we recommend using an initial dose similar to that of patients with normal kidney function, or rather starting with a lower dose.

Effect of lumbar epidural blockade and propofol on mean arterial pressure, cardiac output and bispectral index: A randomised controlled and pharmacodynamic modelling study

BACKGROUND

It is generally accepted that a neuraxial blockade strengthens the sedative effects of propofol. Deafferentation caused by neuraxial blockade is thought to play a key role.

OBJECTIVES

The objective is to determine whether epidural blockade affects the bispectral index (BIS) of propofol and two other pharmacodynamic endpoints, mean arterial pressure (MAP) and cardiac output (CO).

DESIGN

Randomised, placebo-controlled study.

SETTING

University hospital.

PATIENTS

Patients scheduled for surgery needing epidural analgesia.

INTERVENTION

28 ASA one or two patients received 0, 50, 100 or 150 mg of epidural ropivacaine. After stabilisation of the epidural blockade, propofol was given by target-controlled infusion. The propofol plasma target concentrations were increased at 6-min intervals from 0 to 1, 2.5, 4 and 6 μg ml-1. The study was performed before surgery.

MAIN OUTCOME MEASURES

Three endpoints, BIS, mean arterial blood pressure and CO were measured from baseline (prior to the administration of epidural ropivacaine) until 2 h after the start of propofol infusion. The propofol concentration-effect data were analysed to determine the interaction between epidural blockade and propofol sedation.

RESULTS

In the absence of propofol, the increase in number of epidural blocked segments from 0 to 15.5 (range 6 to 21) reduced the MAP by 30%, without affecting BIS or CO. In the absence of epidural blockade, the increase in propofol concentration to 6 μg ml-1 reduced BIS, MAP and CO. When combined, epidural anaesthesia and intravenous propofol exhibited no pharmacodynamic interaction on any of the three endpoints. In addition, epidural blockade did not affect the propofol effect-site equilibration half-life for its haemodynamic effects (11.5 ± 0.5 min) or for its effects on the BIS (4.6 ± 0.4 min).

CONCLUSION

Epidural blockade reduces the propofol requirements for sedative end points. This is not the result of a pharmacodynamic interaction.

TRIAL REGISTRATION

Dutch trial register CCMO, Central Committee on Research Involving Human Subjects, trial number NL 32295.058.10.

Investigation of single-dose thoracic paravertebral analgesia for postoperative pain control after thoracoscopic lobectomy - A randomized controlled trial

BACKGROUND

Thoracoscopic lobectomy is less painful than normal thoracotomy, but pain management is still an issue in the postoperative period. Thoracic epidural analgesia (TEA) is considered as the gold standard for post-thoracotomy pain control, but is associated with numerous risks.

METHODS

A total of 114 patients undergoing thoracoscopic lobectomy were randomly divided into three groups. Patients in the PVB-R group received a single-dose 0.5% ropivacaine paravertebral block (PVB), combined with patient-controlled intravenous analgesia (PCIA) after extubation during the 48-h postoperative period; those in the PVB-RD group received a single-dose 0.5% ropivacaine and dexmedetomidine (1 μg/kg) PVB, combined with the same PCIA scheme; and those in the TEA group received intraoperative thoracic epidural anesthesia with 0.5% ropivacaine, and a single dose of epidural morphine (0.03 mg/kg) after extubation combined with the same PCIA scheme. The dose and first time of postoperative analgesia, verbal rating score (VRS), change in catecholamine, cortisol and cytokine levels, change in hemodynamic parameters, and side effects during the postoperative period were recorded.

RESULTS

Compared to the PVB-R group, the dose of postoperative analgesia and VRS were lower and the first time of postoperative analgesia were longer in the PVB-RD and TEA group. Patients in the PVB-RD group had a lower incidence of side effects compared to those in the TEA group.

CONCLUSIONS

Single-dose 0.5% ropivacaine combined with dexmedetomidine (1 μg/kg) PVB provides satisfactory postoperative pain control after thoracoscopic lobectomy, and can reduce the incidence of postoperative side effects.

Effects of intrathecal bupivacaine on the NR2B/CaMKIIα/CREB signaling pathway in the rat lumbar spinal cord

Neuraxial anesthesia produces an anesthetic-sparing, sedative effect. The mechanism underlying this effect potentially involves decreased spinal afferent input. However, the neurochemical mechanisms at the spinal level remain unknown. The N-methyl-D-aspartate receptor 2B subunit/calcium-calmodulin-dependent protein kinase II α/cAMP response element-binding protein (NR2B/CaMKIIα/CREB) signaling pathway serves an important role in regulating the transmittance of peripheral noxious stimulation to supraspinal regions in the process of nociception. The present study investigated the effects of intrathecal bupivacaine on the NR2B/CaMKIIα/CREB signaling pathway. Following catheterization, 36 male Sprague-Dawley rats were randomly assigned to a normal saline (NS) or bupivacaine treatment group, in which each rat intrathecally received 20 µl normal saline or 0.5% bupivacaine, respectively. The expression levels of NR2B, CaMKIIα/p-CaMKIIα, and CREB/phosphorylated (p)-CREB in the lumbar spinal cord were investigated by western blotting, reverse transcription-quantitative polymerase chain reaction and immunohistochemistry (IHC). Following bupivacaine treatment, western blot analysis demonstrated that the protein expression levels of NR2B, p-CaMKIIα, and p-CREB in the spinal cord were reduced by approximately 54, 56 and 33%, respectively, compared with NS control rats. Similar alterations in expression were observed by IHC analysis. Additionally, mRNA expression levels of NR2B, CaMKIIα, and CREB were also downregulated following the intrathecal administration of bupivacaine. Therefore, the sedative effect of subarachnoid blockade with bupivacaine possibly occurs through de-afferentation, which may reduce cortical arousal by downregulating the spinal NR2B/CaMKIIα/CREB pathway in vivo, however further investigation is required in order to verify this.

Epidural Dexmedetomidine Reduces the Requirement of Propofol during Total Intravenous Anaesthesia and Improves Analgesia after Surgery in Patients undergoing Open Thoracic Surgery

The aim of this study was to assess the systemic and analgesic effects of epidural dexmedetomidine in thoracic epidural anaesthesia (TEA) combined with total intravenous anaesthesia during thoracic surgery. Seventy-one patients undergoing open thoracotomy were included in this study and randomly divided into three groups: Control group (Group C): patients received TEA with levobupivacaine alone and were intravenously infused with saline; Epidural group (Group E): patients received TEA with levobupivacaine and dexmedetomidine, and were intravenously infused with saline; Intravenous group (group V): patients received TEA with levobupivacaine alone and were intravenously infused with dexmedetomidine. The doses of propofol used in the induction and maintenance of general anaesthesia, cardiovascular response, dose and first time of postoperative analgesia and verbal rating scale were recorded. The induction and maintenance were significantly lower in the Groups E and V. Verbal rating scale and postoperative analgesic requirements were significantly lower in Group E than in Groups C and V. Patients in Group C had more severe cardiovascular responses, as compared with Groups E and V. Epidural administration of dexmedetomidine reduced the induction and maintenance of propofol, and inhibited the cardiovascular response after intubation and extubation. Moreover, epidural dexmedetomidine provided better analgesia after open thoracotomy.

Thoracic Epidural Anesthesia Reduces Right Ventricular Systolic Function With Maintained Ventricular-Pulmonary Coupling

Background:

Blockade of cardiac sympathetic fibers by thoracic epidural anesthesia may affect right ventricular function and interfere with the coupling between right ventricular function and right ventricular afterload. Our main objectives were to study the effects of thoracic epidural anesthesia on right ventricular function and ventricular-pulmonary coupling.

Methods:

In 10 patients scheduled for lung resection, right ventricular function and its response to increased afterload, induced by temporary, unilateral clamping of the pulmonary artery, was tested before and after induction of thoracic epidural anesthesia using combined pressure-conductance catheters.

Results:

Thoracic epidural anesthesia resulted in a significant decrease in right ventricular contractility (ΔESV 25 : +25.5 mL, P =0.0003; ΔEes: -0.025 mm Hg/mL, P =0.04). Stroke work, dP/dt MAX , and ejection fraction showed a similar decrease in systolic function (all P <0.05). A concomitant decrease in effective arterial elastance (ΔEa: -0.094 mm Hg/mL, P =0.004) yielded unchanged ventricular-pulmonary coupling. Cardiac output, systemic vascular resistance, and mean arterial blood pressure were unchanged. Clamping of the pulmonary artery significantly increased afterload (ΔEa: +0.226 mm Hg/mL, P <0.001). In response, right ventricular contractility increased (ΔESV 25 : -26.6 mL, P =0.0002; ΔEes: +0.034 mm Hg/mL, P =0.008), but ventricular-pulmonary coupling decreased (Δ(Ees/Ea) = -0.153, P <0.0001). None of the measured indices showed significant interactive effects, indicating that the effects of increased afterload were the same before and after thoracic epidural anesthesia.

Conclusions:

Thoracic epidural anesthesia impairs right ventricular contractility but does not inhibit the native positive inotropic response of the right ventricle to increased afterload. Right ventricular-pulmonary arterial coupling was decreased with increased afterload but not affected by the induction of thoracic epidural anesthesia.

Clinical Trial Registration:

URL: http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=2844 . Unique identifier: NTR2844.

Thiopental dose requirements for induction of anaesthesia and subsequent endotracheal intubation in patients with complete spinal cord injuries

BACKGROUND

Dose requirements of thiopental depend on patient characteristics and infusion rate. We determined thiopental dose requirements for induction of anaesthesia, and the effects of remifentanil on cardiovascular and bispectral index (BIS) responses to tracheal intubation in spinal cord-injured (SCI) patients undergoing general anaesthesia.

METHODS

Twenty patients with traumatic complete SCI undergoing elective surgery were enrolled. Twenty patients without SCI served as control. Anaesthesia was induced with thiopental, followed by remifentanil 1 μg/kg and rocuronium 0.8 mg/kg, and maintained with 2% sevoflurane and 50% nitrous oxide in oxygen after tracheal intubation. Thiopental was administered at a rate of 50 mg/15 s until abolition of the eyelash reflex. Thiopental doses, BIS values, systolic arterial blood pressure (SAP), heart rate (HR) and plasma catecholamine concentrations were measured.

RESULTS

Total thiopental dose required to abolish the eyelash reflex based on total body weight (BW) (5.26 ± 0.87 vs. 3.91 ± 1.07 mg/kg, P < 0.001) or lean BW (6.56 ± 1.37 vs. 5.24 ± 1.36 mg/kg, P < 0.01) were significantly smaller in the SCI group than in the control. SAP was decreased by induction of anaesthesia with thiopental and remifentanil, and increased by tracheal intubation in both groups. However, the peak SAP after intubation was smaller in the SCI patients. HR increased significantly above baseline values following intubation in both groups with no significant intergroup differences. Hypertension was more frequent in the control group. Norepinephrine concentrations remained unaltered following intubation in both groups.

CONCLUSIONS

These results suggest that the dose requirements of thiopental for induction of general anaesthesia and subsequent tracheal intubation are reduced in the SCI patients.

Effect of caudal block on sevoflurane requirement for lower limb surgery in children with cerebral palsy

BACKGROUND

Caudal block is a widely used technique for providing perioperative pain management in children. In this randomized double-blinded study, we evaluated the effects of preoperative caudal block on sevoflurane requirements in children with cerebral palsy (CP) undergoing lower limb surgery while bispectral index (BIS) values were maintained between 45 and 55.

METHODS

52 children undergoing Achilles-tendon lengthening were randomized to receive combined general-caudal anesthesia (caudal group, n = 27) or general anesthesia alone (control group, n = 25). Caudal block was performed with a single dose of 0.7 ml·kg(-1) of 1.0% lidocaine containing epinephrine at 5 μg·ml(-1). The control group received no preoperative caudal block. The endtidal sevoflurane concentrations (ET(sev)) were adjusted every minute to maintain the BIS values between 45 and 55.

RESULTS

The ET(sev) required to maintain the BIS values were not significantly different between the control and caudal groups after induction of anesthesia [2.1 (0.2) vs 2.2 (0.4); P = 0.773]. However, significantly higher ET(sev) was observed in the control group before surgical incision [2.0 (0.2) vs 1.8 (0.3); P = 0.013] and during the first 20 min after surgical incision [2.2 (0.3) vs 1.4 (0.3); P < 0.001]. There was no significant difference in BIS values between the control and caudal groups throughout the study period (P > 0.05). In the caudal group, the caudal block was successful in 25 of 27 (92.6%) patients.

CONCLUSIONS

Caudal block effectively reduced sevoflurane requirements by 36% compared to general anesthesia alone in children with CP undergoing lower limb surgery while BIS values were maintained between 45 and 55.