Effective doses of cisatracurium. Potentiation by sevoflurane and increasing requirements with age.

BACKGROUND: The aim of the study was to investigate whether or not sevoflurane at different concentrations influenced the ED(effective dose) 50, 90 and 95 of cisatracurium and whether there is any relationship with age. METHODS: Individual dose response curves for cisatracurium were constructed in 80 consecutive patients randomly assigned to four groups: group 1 TIVA with fentanyl and propofol; group 2, 3 and 4 sevoflurane 1, 1.5, 2 MAC respectively, MAC age adjusted and with N2O 65%. Patients were premedicated with diazepam and induction accomplished with fentanyl (1.5-2 micrograms/kg) and propofol (1.5-2 mg/kg); following intubation with succinylcholine (0.4 mg/kg), TIVA or sevoflurane at the desired MAC was maintained until equilibration occurred and then cisatracurium administered in 8-10 micrograms/kg boluses until the attainment of ED95. Neuromuscular monitoring utilized TOF stimulation and ratio evaluation between Ist twitch of the train and basal twitch (T1/Tc) and continuous recording of accelerometry (Tof-guard). Single dose response curves were analyzed with sigmoid equations; the Eds and other parameter means were subjected to analysis of variance for parametric and non parametric data. RESULTS: More boluses were required under TIVA and sevo 1 MAC anesthesia (8.3 and 7.1 vs 4.9 of sevo 1.5 and 2 MAC); maximal depression (94.95%) was reached more frequently with sevo, while under TIVA an average 90% depression only was obtained. Mean ED50 (microgram/kg) where 22 (sevo) vs 34 (TIVA): ED90 averaged 36 (sevo) vs 53 (TIVA); ED95 averaged 39 (sevo) vs 56 (TIVA), with significant differences (p < 0.05) between Eds obtained from TIVA group in comparison with sevoflurane groups, but without differences between averaged EDs obtained with different MAC values among sevoflurane groups. The investigation of the relationship between age and Eds demonstrated a linear regression for all groups considered together (p = 0.000) for all Eds (50, 90, 95). CONCLUSIONS: In conclusion, the presence of MAC multiples of sevoflurane potentiated only slightly the dosages of cisatracurium and EDs linearly increase with age, particularly under sevoflurane anesthesia.