Continuous infusions of propofol administered to dogs: effects on ICG and propofol disposition

We have studied the effects of stepwise increasing infusion rates of propofol 200-500 micrograms kg-1 min-1 on blood concentrations of propofol and the disposition and clearance of a bolus dose of indocyanine green (ICG) 0.5 mg kg-1 in 10 acutely instrumented dogs. Drug concentrations and ICG clearance were measured 30 min after each change of infusion rate and after reverting for 60 min to the basal propofol infusion rate. Increasing infusion rates resulted in significant prolongation of the elimination half-life of ICG and decrease in ICG clearance at the largest infusion rate (500 micrograms kg-1 min-1) compared with the basal rate. Similarly, there were greater than predicted blood concentrations of propofol at the largest infusion rate. When the infusion rate reverted to 200 micrograms kg-1 min-1, and continued for 60 min, there was a significant difference between the initial blood concentration of propofol at this basal infusion rate and this latter value (P < 0.01). These changes reflect the persistent myocardial depression observed during the recovery phase.