Obstructive Jaundice does not Change the Population Pharmacokinetics of Etomidate in Patients who Underwent Bile Duct Surgery.

BACKGROUND: Etomidate is commonly used in the induction of anesthesia. We have previously confirmed that etomidate requirements are significantly reduced in patients with obstructive jaundice and that etomidate anesthesia during Endoscopic Retrograde Cholangiopancreatography (ERCP) results in more stable hemodynamics compared to propofol. The aim of the present study is to investigate whether obstructive jaundice affects the pharmacokinetics of etomidate in patients who underwent bile duct surgery. METHODS: A total of 18 patients with obstructive jaundice and 12 non-jaundiced patients scheduled for bile duct surgery were enrolled in the study. Etomidate 0.333 mg/kg was administered by IV bolus for anesthetic induction. Arterial blood samples were drawn before, during, and up to 300 minutes after the bolus. Plasma etomidate concentrations were determined using a validated high-performance liquid chromatography-tandem mass spectrometry assay. A nonlinear mixed-effects population modeling approach was used to characterize etomidate pharmacokinetics. The covariates of age, gender, height, weight, Body Surface area (BSA), Body Mass Index (BMI), Lean Body Mass (LBM), Total Bilirubin (TBL), Alanine Aminotransferase (ALT), aspartate aminotransferase (AST), total bile acid (TBA), creatinine (CR), and blood urea nitrogen (BUN) were tested for significant effects on parameters using a multiple forward selection approach. Covariate effects were judged based on changes in the Objective Function Value (OFV). RESULTS: A three-compartment disposition model adequately described the pharmacokinetics of etomidate. The model was further improved when height was a covariate of total clearance [Cl1=1.30+0.0232(HT-162), ΔOFV=-7.33; P<0.01)]. The introduction of any other covariates, including bilirubin and total bile acids, did not improve the model significantly (P>0.01). For the height of 162cm, the final pharmacokinetic parameter values were as follows: V1=1.42 (95% CI, 1.01-1.83, L), V2=5.52 (95% CI, 4.07-6.97, L), V3=63.9 (95% CI, 41.95-85.85, L),Cl1= 1.30 (95% CI, 1.19-1.41, L/min), Cl2= 1.21 (95%CI, 0.95-1.47, L/min), and Cl3=0.584 (95%CI, 0.95-1.21, L/min), respectively. CONCLUSION: A 3-compartment open model might best describe the concentration profile of etomidate after bolus infusion for anesthesia induction. The pharmacokinetics of etomidate did not change by the presence of obstructive jaundice.

Population Pharmacokinetic Modeling of Remifentanil in Infants with Unrepaired Tetralogy of Fallot.

BACKGROUND: Although there is literature suggesting that pathophysiologic changes in children with congenital heart disease alter the pharmacokinetics of anesthetics and may result in dosage adjustment, limited information exists regarding the pharmacokinetics of remifentanil in infants with unrepaired tetralogy of Fallot (TOF). The objectives of the current analysis were to characterize the population pharmacokinetics of remifentanil in infants, and to evaluate the effects of TOF on remifentanil's pharmacokinetics. METHODS: Twenty-seven infants (16 with TOF and 11 with normal cardiac anatomy; aged 114-360 days) scheduled to undergo elective surgery under general anesthesia were recruited in the study. All children received remifentanil 1 µg/kg/min intravenously for anesthesia induction and early maintenance [until ~ 20 min before cardiopulmonary bypass (CPB) for patients with TOF]. Serial arterial blood samples were drawn and analyzed. Population pharmacokinetics of remifentanil was characterized using NONMEM software. The estimates were standardized to a 70-kg adult using a per-kilogram model. RESULTS: A two-compartment disposition model adequately described the pharmacokinetics of remifentanil. Besides body weight, the introduction of any other covariates, including TOF status, did not improve the model significantly (P > 0.05). The population parameter estimates for systemic clearance (Cl1) and inter-compartment clearances (Cl2) were 6.03 × (WT/70 kg) and 1.23 × (WT/70 kg) L/min, respectively, and central volume of distribution (V1) and peripheral volumes of distribution (V2) were 19.6 × (WT/70 kg) and 21.7 × (WT/70 kg) L, respectively. CONCLUSIONS: Unrepaired TOF does not change the pharmacokinetics of remifentanil, suggesting a similar dosage for infants with TOF compared to normal cardiac anatomy infants. CLINICAL TRIAL REGISTRATION: The patient enrollment in this study started at 2012, so we do not have clinic trial number, but we still think this is a valuable research and hope it could be considered for publication.

The pharmacokinetics of dexmedetomidine in patients with obstructive jaundice: A clinical trial.

OBJECTIVES: Dexmedetomidine, a highly selective central α2-agonist, undergoes mainly biotransformation in the liver. The pharmacokinetics of dexmedetomidine were significantly affected by hepatic insufficiency. The clearance of dexmedetomidine in patients with severe hepatic failure decreased by 50% compared with controls. We tested the hypothesis that the pharmacokinetics of dexmedetomidine would be affected by obstructive jaundice. The prospective registration number of clinical trial is ChiCTR-IPR-15007572. METHODS: 18 patients with obstructive jaundice and 12 non-jaundiced patient controls received dexmedetomidine, 1 µg/kg, over 10 min. Arterial blood samples were drawn before, during, and up to 5 h after the infusion. Plasma dexmedetomidine concentrations were determined by 1290 infinity high performance liquid chromatography coupled with 6470 tandem mass spectrometry. The relevant pharmacokinetic parameters were calculated by non-compartmental analysis using Phoenix WinNonlin 7.0. RESULTS: Plasma clearance of dexmedetomidine was decreased by 33.3% in the obstructive jaundice group as compared with the control group (0.0068±0.0017 vs. 0.0102±0.0033 L/kg/min; P = 0.002). Volume of distribution was decreased by 29.2% in the obstructive jaundice group as compared with the control group (1.43±0.58 vs. 2.02±0.84 L/kg; P = 0.041). CONCLUSIONS: This study demonstrates that the clearance and distribution volume of dexmedetomidine were decreased in patients with obstructive jaundice. It may be advisable to adjust the dose of dexmedetomidine in those patients.

[Cardiovascular depression and intravascular hemolysis secondary to ethanol injection for arteriovenous malformation].

Ethanol is the only liquid embolization agent which can cure arteriovenous malformation. Complications of ethanol embolization are not rare including local tissue injury, intravascular hemolysis and cardiovascular depression even collapse, etc. This report presented a case of long time cardiovascular depression and intravascular hemolysis secondary to ethanol embolotherapy of right ear. In order to avoid the fatal complications that are associated with ethanol sclerotherapy, anesthesiologists should consider the use of continuously invasive hemodynamic monitoring while surgeons should carefully choose the dose of ethanol.

The agreement between oscillometric and intra-arterial technique for blood pressure monitoring in the lower extremities for infants and toddlers undergoing aortic coarctation repair.

OBJECTIVE: Anesthetic management for patients undergoing surgical repair of aortic coarctation (CoA) should include constant blood pressure monitoring of the right upper extremity and a lower extremity. The delayed or absent pulse in the lower limbs often leads to unsuccessful arterial cannulation in infants and the oscillometric technique used for blood pressure measurement. The aim of this study was to evaluate the agreement between the oscillometric method and intra-arterial technique for blood pressure monitoring in the lower limbs of infants undergoing CoA. METHODS: A total of 45 infants diagnosed with isolated CoA were initially enrolled in this study and five were excluded because of cannulation failure. Thus, 40 patients had their blood pressure measured simultaneously by both oscillometric technique on the thigh and femoral artery catheterization. After induction and intubation, five pairs of blood pressure readings from each patient were collected in an interval of 3 min. Statistical analysis was accomplished by revised Bland-Altman analysis. RESULTS: There was a strong correlation between oscillometric and invasive blood pressure measurements [systolic blood pressure (SBP) r = 0.771, diastolic blood pressure (DBP) r = 0.704 and mean artery pressure (MAP) r = 0.850]. The mean difference and 95% limits of agreement (95% LOA) between oscillometric and femoral artery blood pressure readings was 3.830 mmHg (-19.297, 26.957) for SBP, -8.725 mmHg (-26.236, 8.786) for DBP, and -3.235 mmHg (-18.842, 12.372) for MAP. There were only one pair of MAP (1/40) and two pairs of SBP readings (2/40) out of range (95% LOA), and all of paired DBP readings were within 95% LOA. CONCLUSION: There was a good agreement between oscillometric and invasive blood pressure measurements of lower extremities in infants with isolated CoA statistically. However, the oscillometry-measured SBP showed a tendency to overestimate the intra-arterial blood pressure reference, while oscillometry-measured DBP underestimated its reference. MAP measurement provided the most accurate and reliable results in this study.

Unrepaired Tetralogy of Fallot-related Pathophysiologic Changes Reduce Systemic Clearance of Etomidate in Children.

BACKGROUND: Pathophysiologic changes in children with congenital heart disease may alter the effect of drugs by influencing the pharmacokinetics (PK). Considering the limited literature that describes the PK of etomidate in pediatric patients, especially in those with tetralogy of Fallot (TOF), our aim was to characterize the PK of etomidate and explore the effects of TOF. METHODS: Twenty-nine pediatric patients (15 with TOF and 14 with normal cardiac anatomy) scheduled to undergo elective surgery under general anesthesia were recruited in the study. All children received etomidate 60 µg/kg/min intravenously until a bispectral index of ≤50 was reached for 5 seconds during anesthesia induction. Arterial blood samples were drawn and analyzed. Population analysis was performed by using NONMEM to define PK characteristics. The estimates were standardized to a 70-kg adult using a per-kilogram model. RESULTS: Data consisting of 244 samples from 29 children with a mean age of 236 days (range, 86-360 days) were used, including a TOF group with a mean age of 250 days (range, 165-360 days) and a normal cardiac anatomy group with a mean age of 221 days (range, 86-360 days). A 3-compartment disposition model was best fitted to describe the PK of etomidate. The introduction of TOF as a covariate for systemic clearance (Cl1) improved the model and resulted in a significant reduction of objective function (Δobjective function = -7.33; P = .0068), which means that TOF was a significant covariate of Cl1, and the etomidate Cl1 in children with TOF (1.67 × (weight [WT]/70 kg) L/min) was lower than those with normal cardiac anatomy (2.28 × (WT/70 kg) L/min). Other PK parameter values were as follows: V1 = 8.05 × (WT/70 kg) L; V2 = 13.7 × (WT/70 kg) L; V3 = 41.3 × (WT/70 kg) L; Cl2 = 3.35 × (WT/70 kg) L/min; Cl3 = 0.563 × (WT/70 kg) L/min. CONCLUSIONS: A decreased systemic clearance for etomidate in children with TOF resulted in a lower required infusion rate and variation with time to achieve the same plasma concentration and maintain an equivalent target concentration or have longer sedation and recovery times after bolus or continuous infusion than normal children.

The sedative effects and the attenuation of cardiovascular and arousal responses during anesthesia induction and intubation in pediatric patients: a randomized comparison between two different doses of preoperative intranasal dexmedetomidine.

OBJECTIVE: Premedication with intranasal dexmedetomidine (DEX) has shown to be an effective sedative in pediatric patients. This prospective, randomized, and controlled investigation was designed to evaluate whether the difference in intranasal DEX dosing would produce different beneficial effects on the attenuation of cardiovascular and arousal responses during anesthesia induction and intubation. METHODS: Forty children, aged from 3 to 6 years, of American Society of Anesthesiologists physical status I or II and scheduled for elective adenotonsillectomy randomly received intranasal DEX 1 µg·kg(-1) (group D1) or 2 µg·kg(-1) (group D2) 30 min before anesthesia induction. Anesthesia was induced with sevoflurane in oxygen flow. Mean arterial pressure (MAP) and heart rate (HR) as measurements of cardiovascular response and bispectral index (BIS) as an index of arousal response were recorded every 5 min after intranasal DEX administration and measured every 1 min for 5 min after intubation. Sedation status, behavior scores, and mask induction scores were also assessed. RESULTS: Mean arterial pressure did not show statistical differences during the anesthesia induction, but did demonstrate significantly milder responses to laryngoscopy and intubation in group D2 compared with group D1. Change in HR was consistent with MAP during laryngoscopy and intubation. Patients who received 2 µg·kg(-1) DEX presented with deeper sedation and less anxiety by the assessments of the alertness scale, behavior score, and BIS scores. Group D2 dosing achieved more favorable scores in children undergoing mask induction. CONCLUSION: Intranasal DEX 2 µg·kg(-1) administered 30 min before anesthesia induction provides considerable effect to attenuate the increase in MAP caused by intubation response. Changes in HR and BIS also demonstrate that this kind of premedication provides effective attenuation of intubation response. And preoperative intranasal DEX 2 µg·kg(-1) produces optimal-sedation, more favorable anesthesia induction course in pediatric patients. Premedication of intranasal DEX is a considerable way to blunt cardiovascular and arousal responses to endotracheal intubation.

Population pharmacokinetics of intravenous bolus etomidate in children over 6 months of age.

BACKGROUND: Information has been very limited on the population pharmacokinetics (PK) of etomidate in pediatric patients. The purpose of this study was to characterize the PK of etomidate in children. METHODS: Forty-nine children aged over 6 months undergoing elective surgery received etomidate 0.3 mg·kg(-1) bolus i.v. within 15 s for anesthesia induction. Arterial blood samples were collected for 2 h after injection. A population nonlinear mixed effects modeling approach was used to characterize etomidate PK. Estimates were standardized to a 70-kg adult using allometric size models. RESULTS: Children had a median age of 4 years (0.53-13.21 years) and weight 15.7 kg (7.5-52 kg). PK of etomidate was best estimated using a three-compartment model with weight on systemic (Cl(1)) and inter-compartmental clearances (Cl(2), Cl(3)), central (V(1)), and peripheral compartment volumes (V(2), V(3)). The most significant PK covariate was age, with increasing age having reduced size-adjusted Cl(1), V(1), and V(3) (all P < 0.01). The estimates of PK parameter (standardized to 70-kg adult) for a typical 4-year-old children were Cl(1) = 1.50 l·min(-1), Cl(2) = 1.95 l·min(-1), Cl(3) = 1.23 l·min(-1), V(1) = 9.51 l, V(2) = 11.0 l, and V(3) = 79.2 l, respectively. CONCLUSIONS: Owing to enhanced clearance and increased central compartment volume of etomidate, smaller (younger) children will require higher etomidate bolus dose than larger (older) children to achieve equivalent plasma concentrations. The dependence of Cl(1) and V(1) on age does not support weight-based etomidate dosing in smaller children.