Unplanned Autotransplantation for Complex Multi-Valve Replacement in a Super Morbid Obese Female: The Challenge of Intraoperative Decision Making.

Cardiac autotransplantation is a rare technique typically reserved for the treatment of malignant tumors of the left atrium and left ventricle. Even when well planned, it conveys a high risk to the patient. This report discusses the intraoperative progression to an unplanned autotransplant for mitral valve repair while considering some decision making processes that cardiac surgeons make.

Ketamine anesthesia in children--exploring infusion regimens.

AIM: We aimed to produce a racemic ketamine manual infusion regimen capable of maintaining a steady-state blood concentration associated with anesthesia in children aged 1.5-12 years. METHOD: The literature was searched for a ketamine blood concentration associated with anesthesia in humans. Pharmacokinetic parameter estimates were taken from published studies of infusion data in children and used in a pharmacokinetic simulation program to predict likely ketamine blood concentrations during infusions. A variability of 10% was allowed about the chosen target concentration. RESULTS: A target concentration of 3 mg.l(-1) was chosen for simulation modeling. This target is greater than that associated with anesthesia when supplemented by nitrous oxide or midazolam in adults. Arousal to light touch or voice appears to occur at a mean plasma concentration of 0.5 mg.l(-1) in both children and adults. A loading dose of 2 mg.kg(-1) followed by an infusion rate of 11 mg.kg(-1).h(-1) for the first 20 min, 7 mg.kg(-1).h(-1) from 20 to 40 min, 5 mg.kg(-1).h(-1) from 40 to 60 min and 4 mg.kg(-1).h(-1) from 1 to 2 h resulted in a steady-state target concentration of 3 mg.l(-1) in children 1.5-12 years. Arousal, either spontaneous or to speech, is anticipated 3 h 47 min after a 2 h infusion in an average 6-year-old child. The context sensitive half-time in children was shorter than in adults after 1.5 h, rising from 30 min at 1 h to 55 min at 5 h after an infusion of 3 mg.kg(-1).h(-1) in a 10 kg child. CONCLUSION: Children require higher infusion rates than adults to maintain steady-state concentrations of 3 mg.l(-1) and have shorter context sensitive half-times than adults after prolonged infusion. These differences can be attributed to age-related pharmacokinetics. We anticipate slow return to full consciousness after prolonged infusion, suggesting that a lower target concentration with supplementation from adjuvant short acting anesthetic drugs may be advantageous.

Dosing ketamine for pediatric procedural sedation in the emergency department.

OBJECTIVE: To describe intravenous ketamine dosing regimens for children requiring brief procedural sedation. METHODS: Time-concentration and sedation profiles were simulated in children (2, 6, and 12 years old) using published pediatric pharmacokinetic and pharmacodynamic parameter estimates. Single-dose, repeat-dosing, and infusion regimens to achieve sedation level of less than 2 (arouses slowly to consciousness, with sustained painful stimulus) for 15 minutes were investigated. RESULTS: A single bolus dose of 1.5 and 1.75, 2, and 2.125 mg/kg (for adult and 12-, 6-, and 2-year-olds, respectively) was required to achieve the desired sedation. Anticipated recovery would be slow, and a sedation level of 4 (drowsy, eyes open or closed but easily arouses to consciousness with verbal stimulus) was reached only after 70 minutes. The use of a smaller initial bolus with a subsequent half-dose "top-up" at 8 minutes achieves the same sedation level but with earlier recovery. A smaller initial dose of 0.25 and 0.275, 0.3, and 0.35 mg/kg followed by an infusion 2.5 and 2.75, 3, and 3.5 mg/kg per hour (for adult and 12-, 6-, and 2-year-olds, respectively) for 15 minutes gives a more even sedation level and rapid recovery (20 minutes to sedation level 4). CONCLUSIONS: Dosing increases with decreasing age. A large single dose is associated with deep sedation, possible adverse effects, and delayed recovery. Between-subjects variability is large, and dose should be tailored to clinical monitoring and requirement. Intermittent pain insult is better suited to a top-up technique, whereas continuous pain is better suited to an infusion technique.