TOTAL IV ANESTHESIA WITH S-(-KETAMINE I N GERIATRIC ORTHOPEDIC-SURGERY - ENDOCRINE STRESS-RESPONSE, CARDIOVASCULAR REACTIONS, AND RECOVERY())

Clinically-used ketamine is a racemic mixture of two isomers, S-(+)- a nd R-(-)-ketamine. Previous investigations showed the anaesthetic pote ncy of S (+)-ketamine to be three times higher than that of R-(-)-keta mine. It was the aim of this study to compare the effects of S-(+)-ket amine and racemic ketamine on endocrine and cardiovascular parameters, recovery, and side effects in geriatric patients during total intrave nous anaesthesia (TIVA) for orthopaedic surgery.Methods. Forty patient s over 60 years of age scheduled for elective hip or knee replacement were investigated in a double-blind, randomised design. For induction of TIVA, patients received 0.1 mg midazolam, 0.5 mg atropine, 1 mg/kg S (+)-ketamine or 2 mg/kg racemic ketamine, respectively, 2 mg vecuron ium, and 1.5 mg/kg suxamethonium. After intubation and relaxation with a total dose of 0. 1 mg/kg vecuronium, a continuous infusion of 2 mg/ kg per hour S-(+)- or 4 mg/kg per hour racemic ketamine was administer ed throughout surgery. Blood samples were taken through a central veno us catheter at seven time-points, before induction as well during and after surgery, until the 1st postoperative morning for analysis of adr enaline, noradrenaline (by high-pressure liquid chromatography with el ectrochemical detection), anti-diuretic hormone (ADH), adrenocorticotr opic hormone (ACTH), cortisol (by radioimmunoassay), glucose, and lact ate. In addition, systolic arterial pressure (SAP), heart rate (HR), a nd arterial oxygen saturation were measured, and the time intervals be tween the end of ketamine infusion and the return of consciousness and orientation were protocolled. The incidence and assessment of dreams and other side effects were reported by the patients. Results. Biometr ic data of the groups were comparable, the mean age of both groups bei ng 68 years. Plasma adrenaline, noradrenaline, ADH, ACTH, cortisol, an d glucose as well as SAP and HR increased significantly (P < 0.05) dur ing the course of anaesthesia. The influence on lactate levels was not significant. There were no differences between S (+)- and racemic ket amine with respect to these parameters. Three patients in the ketamine -racemate group showed severe arterial hypertension and were withdrawn from the study. Recovery clearly improved after administration of S ( +)-ketamine compared to the racemate. Simple orders were followed afte r 2.0 +/- 3.4 versus 4.9 +/- 6.8 min (P = 0.07), orientation with resp ect to person returned after 5.7 +/- 4.0 versus 14.6 +/- 10.0 min (P < 0.001) and spatial orientation after 8.2 +/- 5.4 versus 17.4 +/- 9.7 min (P < 0.001). After racemic ketamine, 1 patient remembered a negati ve dream and 1 patient a positive dream. In the S (+)-group, 1 positiv e dream was reported. No intraoperative awareness was reported, and al l patients would accept the same anaesthesia again. Conclusions. Incre ases in cardiovascular parameters and insufficient reduction of the st ress response with respect to ADH, ACTH, and cortisol seem to require a more potent hypnotic element during TIVA with ketamine. With regard to endocrine and cardiovascular parameters, the pharmacodynamic effect s of racemic and S-(+)-ketamine were comparable. Because of the signif icant improvement in recovery and the reduced quantitative drug load, S-(+)-ketamine offers a clinical advantage compared with currently use d racemic ketamine.