[MAC-awake and wake-up time of isoflurane and sevoflurane with reference to the concentration of gas, duration of inhalation and patient's age and obesity].

We evaluated the influence of the concentration of volatile anesthetics, the duration of inhalation time, the patient's age and degree of obesity on MAC-awake (the end-tidal concentration of volatile anesthetics on awakening) and Wake-up time (the period from stopping inhalation to eye-opening in response to verbal command) following isoflurane (Iso) or sevoflurane (Sev) anesthesia in 240 patients (ASA I or II, age 17-84 yr). The patients were anesthetized with 50% oxygen, 50% nitrous oxide and various concentrations of Iso or Sev. They were divided into 6 groups in respect to the end-tidal concentration of Iso or Sev: Iso 0.7% (1 MAC), Iso 1.0% (1.5 MAC), Iso 1.4% (2 MAC), Sev 0.9% (1 MAC), Sev 1.3% (1.5 MAC) and Sev 1.8% (2 MAC). After operation all anesthetics were discontinued and MAC-awake and Wake-up time were measured under 100% oxygen inhalation. MAC-awake value of Iso was 0.14 +/- 0.05% (SD)% in all groups and that of Sev was 0.17 +/- 0.05% in Sev 0.9% group, 0.16 +/- 0.05% in Sev 1.3%, 0.17 +/- 0.06% in Sev 1.8%, respectively. All of them became smaller in aged groups than in younger groups but they were not influenced by the concentration of gas, the duration of inhalation nor the degree of obesity.(ABSTRACT TRUNCATED AT 250 WORDS)