Thiopental Disposition as a Function of Age in Female Patients Undergoing Surgery

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Abstract
The effect of age on the disposition kinetics of thiopental was studied in 22 lean female patients having a body mass index (wt (kg)/height(m)2) < 30 and whose age ranged between 25-83 yr. Patients underwent primarily abdominal surgery. A strong positive correlation between age and the apparent volumes of distribution, V.beta. and Vss, was found (P < 0.001). No significant relationship was found betweeen total body clearance and age. The elimination half-life (t1/2) of thiopental increased with age and was primarily a function of volume of distribution. The free or unbound fraction of thiopental in serum (.alpha.) ranged from 0.168-0.276 and was significantly correlated with age (P < 0.05). Multiple regression analysis indicated that age was the independent variable which contributed most to the variability in t1/2, V.beta. and Vss. No conclusion can be reached concerning the potential differences in anesthetic induction doses required as a function of age. Apparently, care may be required in the use of a balanced anesthetic technique in the elderly as a result of prolonged elimination.