Browsing by Author "Anderson, Brian J."

Now showing 1 - 8 of 8
  • Thumbnail Image
    Item
    A manual propofol infusion regimen for neonates and infants
    (2019) Morse, James; Hannam, Jacqueline A.; Cortínez Fernández, Luis Ignacio; Allegaert, Karel; Anderson, Brian J.
  • Thumbnail Image
    Item
    Absorption characteristics of epidural levobupivacaine with adrenaline and clonidine in children
    (2013) Chalkiadis, George; Abdullah, Farah; Bjorksten, Andrew; Clarke, Alexander Linden; Cortínez Fernández, Luis Ignacio; Udayasiri, Sonal; Anderson, Brian J.
  • Thumbnail Image
    Item
    Advances in pharmacokinetic modeling: target controlled infusions in the obese
    (2018) Cortínez Fernández, Luis Ignacio; Anderson, Brian J.
  • Thumbnail Image
    Item
    Dexmedetomidine pharmacokinetics in the obese
    (2015) Cortínez Fernández, Luis Ignacio; Anderson, Brian J.; Holford, Nick H. G.; Puga, Valentina; De La Fuente, Natalia; Auad, Hernán; Solari Gajardo, Sandra; Allende, Fidel; Ibacache Figueroa, Mauricio Enrique
  • No Thumbnail Available
    Item
    Levobupivacaine plasma concentrations following repeat caudal anesthetics
    (2022) Frawley, Geoff; Ignacio Cortinez, Luis; Anderson, Brian J.; Bjorksten, Andrew; King, Sebastian
    Aim A single caudal anesthetic at the start of lower abdominal surgery is unlikely to provide prolonged analgesia. A second caudal at the end of the procedure extends the analgesia duration but total plasma concentrations may be associated with toxicity. Our aim was to measure total plasma levobupivacaine concentrations after repeat caudal anesthesia in infants and to generate a pharmacokinetic model for prediction of plasma concentrations after repeat caudal anesthesia in neonates, infants and children. Methods Infants undergoing definitive repair of anorectal malformations or Hirschsprung's disease received a second caudal anesthesia at the end of the procedure. Total levobupivacaine concentrations were assayed 3-4 times in the first 6 h after the initial caudal. These data were pooled with data from four studies describing plasma concentrations after levobupivacaine caudal or spinal anesthesia. Population pharmacokinetic parameters were estimated using nonlinear mixed-effects models. Covariates included postmenstrual age and body weight. Parameter estimates were used to simulate concentrations after a repeat levobupivacaine 2.5 mg kg(-1) caudal at 3 or 4 h following an initial levobupivacaine 2.5 mg kg(-1) caudal. Results Twenty-one infants (postnatal age 11-32 weeks, gestation 37-39 weeks, weight 5.2-8.6 kg) were included. The measured peak plasma concentration after repeat caudal levobupivacaine 2.5 mg kg(-1) 4 h after initial caudal was 1.38 mg L-1 (95% prediction interval 0.60-2.6 mg L-1) and 3 h after initial caudal was 1.46 mg L-1 (0.60-2.80) mg L-1. Simulation of total plasma concentrations in neonates (7 kg, 57 weeks postmenstrual age) given caudal levobupivacaine 4 h after the initial caudal were 1.76 mg L-1 (0.68-3.50) mg L-1 if 2.5 mg kg(-1) levobupivacaine was used and 0.88 mg L-1 (0.34-1.73) mg L-1 if 1.25 mg kg(-1) of 0.125% levobupivacaine was used. In simulated older children (20 kg, 6 years), the mean maximum concentration was 1.43 mg L-1 (0.60-2.70) mg L-1 if 2.5 mg kg(-1) levobupivacaine was repeated at 3 h. Conclusion Repeat caudal levobupivacaine 2.5 mg kg(-1) at 3 h after an initial 2.5 mg kg(-1) dose does not exceed the concentration associated with systemic local anesthetic toxicity. In 2.5% of simulated neonates (weight 3.8 kg, PMA 40 weeks), repeat caudal anesthesia demonstrates broaching of the lower concentration limit associated with toxicity at both 3 and 4 h after initial caudal.
  • Thumbnail Image
    Item
  • No Thumbnail Available
    Item
    Pharmacokinetics of methadone in adult patients undergoing cardiac surgery with cardiopulmonary bypass
    (2024) Salas, Wilbaldo E.; Cortinez, Luis Ignacio; López Barreda, Rodrigo; Rolle, Augusto; Elgueta, Francisca; Godoy, César; Giordano Villatoro, Ady; Contreras Ibacache, Víctor; Anderson, Brian J.
    Cardiopulmonary bypass (CPB) induces profound physiological changes that may alter the pharmacokinetics of methadone. We aimed to describe the pharmacokinetics of an intravenous bolus of methadone racemate in adult patients undergoing heart surgery with CPB. METHODS: We prospectively studied 29 patients aged 45 to 75 years scheduled for cardiac surgery with CPB who received methadone 0.2 mg/kg after anesthesia induction. Arterial blood samples (n = 10) were taken, before, during, and after CPB. Pharmacokinetic analysis was undertaken using nonlinear mixed effects models. RESULTS: All patients completed the study. The median [interquartile range] methadone concentrations decreased from 34.8 [23.9–48.2] ng/mL (10 minutes before CPB) to 18.2 [9.9–26] ng/mL after 60 minutes of CPB (P < .001). A 3-compartment model adequately described the observed changes in methadone concentrations. The influence of CPB on methadone pharmacokinetics was best described by hemodilution in a fixed volume of 1.5 L (CPB circuit volume) and by sequestration from the CPB components (CLSEQ = 93.4 L/h, 95%CI 59–124, P < .01). The observed effect of CPB in methadone pharmacokinetics can be compensated by giving a supplementary bolus dose of 0.05 mg/kg at the end of CPB. CONCLUSIONS: Our results confirmed a decay in methadone concentrations during CPB, which, in our modeling analysis, was attributed to hemodilution and sequestration within the CPB components.
  • No Thumbnail Available
    Item
    Prediction of levobupivacaine concentrations in neonates and infants following neuraxial rescue blocks
    (2021) Frawley, Geoff; Ignacio Cortinez, Luis; Anderson, Brian J.
    Aim Pharmacokinetic simulation was used to characterize levobupivacaine disposition after regional anesthetic rescue for failed spinal anesthesia in neonates and infants.