Abstract
Purpose
To describe the serum concentrations of ketamine following a clinically relevant dosing schedule during cardiopulmonary bypass (CPB).
Methods
Design: Prospective case series. Setting: Tertiarycare teaching hospital. Patients: Six patients undergoing coronary artery bypass grafting and over age 60 yr. Intervention: Following induction of anaesthesia each patient received a bolus of ketamine 2 mg· kg−1 followed by an infusion of 50 μg· kg−1 · min−1 which ran continuously until two hours after bypass. Main Outcome Measures: Ketamine serum concentrations were measured at five minutes after bolus, immediately following aortic cannulation, 10 and 20 min on CPB, termination of CPB, termination of the drug infusion and three and six hours after infusion termination.
Results
At the time of aortic cannulation, ketamine concentrations were 3.11 ± 0.81μg · ml−1, these levels decreased by one third with the initiation of CPB. By the end of CPB the concentrations had returned to levels roughly equivalent to those observed at the time of aortic cannulation. Following cessation of the infusion, ketamine concentration declined in a log-linear fashion with a half-life averaging 2.12 hr. (range 1.38–3.09 hr).
Conclusions
This dosage regimen maintained general anaesthetic concentrations of ketamine throughout the operative period. These levels should result in brain tissue concentrations in excess of those previously shown to be neuroprotective in animals. Thus we conclude that this infusion regimen would be reasonable to use in order to assess the potential neuroprotective effects of ketamine in humans undergoing CPB.
Résumé
Objectif
Faire connaître les concentrations sériques de la kétamine procurées par un schéma posologique approprié à la circulation extracorporelle (CEC).
Méthodes
Type d’étude: Prospective. Endroit: Hôpital de soins tertiaires et d’enseignement. Patients: revascularisation du myocarde chez six patients âgés de plus de 60 ans. Intervention: Après l’induction de l’anesthésie chacun des patients a reçu un bolus de kétamine 2 mg· kg−1 suivi d’une perfusion de 50 μg· kg−1· h−1 en permanence, arrêtée deux heures après l’intervention. Principales mesures de résultats: Les concentrations sériques de kétamine mesurées après la canulation de l’aorte, 10 et 20 min après le début de la CEC, à l’arrêt de la CEC et trois et six heures après l’arrêt de la perfusion.
Résultats
Les concentrations de kétamine qui étaient de 3,11 ± 0,81 μg· ml−1 au moment de la canulation de l’aorte ont diminué du tiers avec le début de la CEC. A la fin de la CEC, elles sont revenues à peu près à ce qu ’elles étaient au moment de la canulation de l’aorte. Après l’arrêt de la perfusion, la concentration de la kétamine a diminué de façon linéaire logarithmique avec une demi-vie moyenne de 2,12 h (écart de 1,38 à 3,09h).
Conclusions
Ce schéma posologique a permis de maintenir des concentrations anesthésiques de kétamine pendant l’intervention. Ces niveaux devraient produire des concentrationscérébrales plus élevées que celles qui ont été démontrées comme neuroprotectrices chez l’animal. Les auteurs concluent que ce schéma devrait être pertinent pour l’évaluation des propriété neuroprotectrices de la kétamine chez les humains qui subissent une CEC.
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McLean, R.F., Baker, A.J., Walker, S.E. et al. Ketamine concentrations during cardiopulmonary bypass. Can J Anaesth 43, 580–584 (1996). https://doi.org/10.1007/BF03011770
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DOI: https://doi.org/10.1007/BF03011770