1. Three Compartment Model

2. Remifentanil vs. other opioids
100 10
Percent of peak plasma opioid concentration
fentanyl 1
sufentanil
alfentanil
remifentanil
0.1
120
240
360
480
600
Minutes since bolus injection
Minto et al, Anesthesiology, in press

3. Three Compartment Model plus an “Effect Site”

4. Remifentanil vs. other opioids
100
sufentanil 80
fentanyl 60
Percent of peak effect site opioid concentration 40
alfentanil 20
remifentanil 2 4 6 8 10
Minutes since bolus injection
Minto et al, Anesthesiology, in press

5. 50% effect site decrement curves

6. V1 and Clearance decrease with age
V1 decreases about 20% from age 20 to 80
Common finding for anesthetic drugs
Clearance decreases about 30% from age 20 to 80
Mechanism unknown

7. EC50 decreases with age EC50 is a measure of brain sensitivity
Decreased EC50 means increased sensitivity
Decreased EC50 with age also reported for:
fentanyl
alfentanil
sufentanil

8. t 1/2 ke0 increases with age
t 1/2 ke0 is the time required for the brain to equilibrate with the plasma
an increase in t 1/2 ke0 would be expected to result in a slower onset of drug effect

9. Age delays onset but does not affect peak concentration

10. Bolus doses should be reduced by 50% in the elderly
The reduction in bolus dose is because of the 50% increase in sensitivity in the elderly
Adjusting the bolus for age is at least as important as adjusting it for body weight

11. Age effects on bolus dose
Minto et al, Anesthesiology, in press

12. Infusion rates should be reduced by 2/3’s in the elderly
The infusion rate is decreased because of increased sensitivity and decreased clearance
Adjusting the infusion rate for age is more important than adjusting it for weight

13. Age effects on infusion rate
Minto et al, Anesthesiology, in press

14. Age does not affect average time to emergence

15. Age affects variability in time to emergence
Minto et al, Anesthesiology, in press

16. Hemodynamics in Elderly
Blood pressure may decrease percent in elderly (>70 yrs).
Easily treated with ephedrine.
May be associated with ST changes if patient has coronary artery disease.

17. Hemodynamics in Elderly
Heart rate is usually stable but may increase abruptly on emergence.
May be associated with ST changes if patient has coronary artery disease

18. Propofol/Alfentanil Interaction
Adapted from Vuyk et al, Anesthesiology 83:8-22, 1995
Characterizes the concentrations for
intubation
maintenance
on emergence
Concentrations are 50% response level

19. Propofol/Opioid Technique

20. Propofol/Opioid Time to Awakening

21. Propofol/Opioid Infusion rates