L4: Total INtravenous Anesthesia (Garcia)

Question 1

Volume of distribution (Vd) of a drug =

Answer 1

Vd = dose/plasma concentration

Question 2

Dose =

Answer 2

Vd x (clinical plasma concentration)

Question 3

Steady state concentration of a drug occurs when:

Answer 3

Loading bolus has distributed and clinical dose is achieved with saturation of distribution tissue

once achieved, add more drug in as quickly as it is metabolized and leaves to maintain steady state

Question 4

Phases of redistribution to achieve steady state

Answer 4

• reaches vasorich group rapidly –> muscle –> fat
• fat poorly vascular so takes long time to saturate
• takes several hours to saturate muscle
• every time you re-dose the animal, the final conc. After redistribution increases b/c now drug is accumulated
• goal is to maintain plasma conc. In the CNS

Question 5

Properties of Propofol

Answer 5

• commonly used in SA
• good CV stability as a CRI (not induction)
• CNS protectant
• must control ventilation PRN
• blood pressure can drop off quickly after giving (but most bounce back quickly)
• Wide dose range

Question 6

Why should you not hyperventilate the brain tumor patient?

Answer 6

Interfere’s w/ brain’s own ability to self-regulate CO2; low CO2 –> vasoconstriction –> hypoxia of normal healthy brain

should maintain CO2 at low normal only; only hyperventilate if brain about to herniate

Question 7

Properties of alfaxalone

Answer 7

• cyclodextrin based steroid anesthetic
• similar CV effects to propofol
• must control ventilation PRN
• more expensive than propofol, but has faster onset and can be given IM and has longer shelf-life
• good for crazy cats
• requires higher induction dose than propofol

Question 8

Properties of diazepam

Answer 8

• used in ICU to maintain patients on ventilator
• allows for good m. Relaxation
• CV friendly
• reversible
• DON’T give IM!!!
• saturates into plastic
• may require propofol infusions

Question 9

Properties of Fentanyl

Answer 9

• used in ICU to maintain patients on ventilator
• causes some degree of unconsciousness
• CV friendly
• reversible
• may require propofol infusions

Question 10

Properties of dexmedetomidine

Answer 10

• commonly used for sedation
• can be used as adjunct to propofol CRIs
• very expensive, but only small doses needed
• vasoconstricts
• caution w/ long-term wound care
• decreases CO, therefore decreasing distr. of propofol

Question 11

Common CRI drugs

Answer 11

Propofol
Alfaxalone
Diazepam
Fentanyl
Dexmedetomidine

Question 12

Advantages of CRIs

Answer 12

• don’t require vaporizer
• titration may provide CV stable anesthesia
• requires less drugs than bolus
• less vasodilation
• smoother recoveries

Question 13

Disadvantages of CRIs

Answer 13

• more cumbersome to less experienced anesthetist
• termination of effect dependent on metabolism and elimination
• drug accumulates –> longer recoveries w/ longer infusions

Question 14

See compartmental models pic

Answer 14

:)