M. Hynynen et al., PLASMA-CONCENTRATION AND PROTEIN-BINDING OF ALFENTANIL DURING HIGH-DOSE INFUSION FOR CARDIAC-SURGERY, British Journal of Anaesthesia, 72(5), 1994, pp. 571-576
We have studied plasma protein binding of alfentanil in 10 patients gi
ven a mean total dose of 949 mu g kg(-1) as the principal anaesthetic
agent for coronary artery bypass grafting. The mean unbound fraction o
f plasma alfentanil increased from 0.09 to 0.16 after administration o
f heparin and to 0.26 after beginning cardiopulmonary bypass (CPB). Af
ter CPB until the end of surgery, the unbound fraction decreased to 0.
12. These changes in the unbound fraction were associated with signifi
cant changes in plasma total and unbound concentrations of alfentanil
also. Within the first I min of CPB, total alfentanil concentration ha
d decreased by more than the unbound concentration and the decrease ob
served in the latter disappeared rapidly. From induction of anaesthesi
a until awakening of the patient, plasma protein binding of alfentanil
was related significantly (P = 0.0166) to the serum concentration of
orosomucoid (alpha(1)-acid glycoprotein).