Efecto de dosis bajas de ketamina en la analgesia postoperatoria y consumo de morfina tras cirugía de revascularización miocárdica

Abstract

Objectives To assess the efficacy of ketamine in low doses by continuous infusion (8 μg/kg/min) given during surgery and the reduction in morphine use in the first 24 h after coronary bypass surgery with remifentanil based anaesthesia. Material and method Randomised, prospective, double blind study on 60 patients, ASA III–IV, scheduled to have off-pump myocardial revascularisation surgery. A standard anaesthetic technique with propofol and remifentanil between 0.5−1 μg/kg/min, after induction of anaesthesia, the ketamine (K) group (n=30) received a continuous infusion of 8 μg/kg/min and the propofol and remifentanil (P) group (n=30) received 0.9% physiological saline intravenously at the same infusion rate. Before the end of the surgery 0.15 mg/kg of morphine was given intravenously. Post-operative analgesia consisted of 3 mg of morphine every 5 min when the simple verbal scale was <1 (SVS<1). The intra-operative use of remifentanil–propofol was determined, as well as, the time to giving the first analgesic, pain intensity using the SVS and visual analogue scale (VAS), haemodynamic and respiratory parameters, level of sedation and adverse effects. Results No statistically significant differences were found between the demographic parameters, or in the mean use and infusions of remifentanil and propofol by both groups. The patients from the K group significantly delayed the time of requesting the first analgesic dose compared to the P group ( P<0.03). There were no significant differences between both study groups in the use of morphine in recovery and the total use in the first 24 h. The haemodynamic and respiratory parameters, and the sedation level remained stable during the whole period of the study, with no statistically significant differences between both groups. Post-operative pain control was adequate in both groups VAS<30, SVS<2), with no significant differences during the 24 h of the study. There no significant differences between groups, in the incidence of adverse effects. The incidence of nausea and post-operative vomiting was 20% in group K and 30% in group P. None of the patients had hallucinations or dysphoria. Conclusions Low doses of ketamine in continuous infusion during the intra-operative period of coronary surgery prolongs the time of demanding the first morphine dose, without reducing the use of intra-operative remifentanil, or the total use of morphine in the first 24 h after surgery.