The influence of age on hemodynamics and the dose requirements of propofol and buprenorphine in total intravenous anesthesia

A retrospective study was performed to determine the influence of age on hemodynamics and awakening time in total intravenous anesthesia (TIVA) with propofol and buprenorphine for spinal surgery. Twenty patients (26-79 yr) were studied and allocated into following four groups by age: 26-49 yr, 50-59 yr, 60-69 yr, and elderly 70-79 yr. All patients were premedicated with midazolam (2.5-5 mg) i.m. Anesthesia was induced (60-180 ml.h-1) and maintained (20-60 ml.h-1) with propofol infusion with 40% oxygen in air, added with vecuronium and one single dose of buprenorphine (0.08-0.2 mg; 1.37-2.63 micrograms.kg-1) before incision. Mean arterial pressure was stable and did not differ in four groups. Heart rate was decreased (P < 0.01) in the elderly group compared with the group younger than 50 yr. Bradycardia (below 50 beat.min-1) occurred in 60% of the elderly group. An adequate dose of buprenorphine (microgram) was proposed as: 208 - 1.8 x age (yr) + 0.3 x weight (kg) (r = 0.90, P < 0.01). The induction and maintenance rates (ml.h-1) of propofol were decreased with age and increased with weight (P < 0.05). However, the maintenance dose of propofol (3.9-8.5 mg.kg-1.h-1) did not correlate with age. Awakening time was prolonged (P < 0.05) in the elderly group (17.0 +/- 7.2 min) as compared with the group of younger than 50 yr (8.0 +/- 3.9 min). The three patients requiring postoperative analgesics were younger than 60 yr. This study suggests that we should reduce the dose of buprenorphine with age in TIVA using propofol. About 50% of the dose given to the patient younger than 50 yr was considered adequate in the elderly group.