The effect site for injectable anesthesia?
Rout of admin for wildlife/zoo animals, usually suboptimal?
Route of admin for very small animals?
Relative to IV, drawbacks of using IM for anasthetics (6):
- Slow Onset
- Higher dose required
- Less Predictable
- No secure Venous Access
- Must use small volume
- Must be non-irritant
What factors affect the seed of onset (5)?
- Rate of admin
- P factors
What drug properties affect the speed of onset (4)?
- Lipid Solubility
- Molecular Weight
- Protein Binding
What P factors affect the speed of onset?
- Acid-Base balance
- Electrolyte Balance
- Plasma Protein Concentration
What influence does lipid solubility have on drug?*
+lipid solubility-> crosses membranes faster
What influence does molecular weight have on drug?
Smaller MW -> Cross BB faster
What influence does Protein binding have on drug?*
Determines how much drug can leave vascular space and exert effects (hypoalbuminaemia= greater Fx)
What influence does Ionization have on drug?*
- Ionized drugs cannot cross membrane
- (pH changes can cause ionization of drug)
What factors influence Distribution?
- Organ Perfusion
- Protein Binding
- Lipid Solubility
After Admin, plasma concentrations fall b/c of... (3)
- Redistribution (to vessel rich tissues, muscle, fats)
- Elimination (through metab and excretion)
What factors affect recovery?
- Duration of admin
- Distribution to other tissues
- Elimination 1/2 Life
How are barbiturates categorized?
What is Thiopental classified as?
Thiopental, not in solution, is classified as..... (pH)
Weak Organic Acid
Thiopental, IN solution, is classified as ... (pH)
10.5, HIGHLY ALKALI
Once injected, what happens to Thiopental?
The pH falls (blood is 7.4) and becomes UN-IONIZED
One reconstituted, what is the shelf life of Thiopental?
7 Days (High pH = bactericidal)
Thiopental concentrations greater than ____%, can cause sloughing, pain and self trauma
- (Dilute w/ SQ ++NaCl if accidental peri-vascular injection)
Thiopental Mechanisms of Action (3):
- Interacts with GABA to increase the duration of GABAa dependent Cl channel in the CNS= Hyperpolarzation and Neurolnal Inhibition
- Depresses the reticular activating system in the brainstem => sleepy
- Depresses transmission in sympathetic ganglia
Speed of onset:
Speed of Redistribution:
- Onset: VERY rapid (<30 sec)
- Redistribution: Rapid
- recovery: Slow
What increases the effects of barbiturates?
- Hypoproteinaemia (active form unbound)
Ionized VS Unionize
Which is in plasma?
Which is Active?
- Both are in plasma
- Un-ionized is active (highly lipid soluble, crosses BB)
What technique can increase the rate of induction and recovery?
Rapid Inj using Minimal Effective Dose
Why isnt thiopental used for maintenance?
It is cumulative
Two determinants of thiopental induction dose requirements:
Avoid Thiopental in...
- Sight Hounds
- Thin Animals (little depot)
- Use caution in hypovolemia/shock/cardio Dz
Thiopental CNS Fx (3):
- Rapidly Crosses BBB
- No alangesia
Thiopental Cardio Fx (4):
- Drop CO
Thiopental Respiratory Fx:
- Post-induction Apnea
Advantages of Thiopental (2):
- Potent & Short Acting
- Long history of use in many species
Disadvantages of Thiopental (7):
- CVS and Resp Depression
- Fx depend of admin technique
- Tissue Irritation
- Solutions dont mix with other drugs
Barbiturate used for ET:
Pentobarbital +/- Phenytoin
Propofol is classified as a...
Lipid Solubility of Propofol:
HIGHLY lipid Soluble
Protein Binding of Propofol
High Protein Binding
Shelf life of Propofol:
- 12-24 hrs, in fridge
- (NO PRESERVATIVES)
Propofol is available as...
- 1% or 2% emulsion in
- 10% soybean oil
- 2.2% glycerol
- 1.25 purified egg phosphatide
Propoclear is a _____ formulation of propofol
- B) Redistribution: Rapid
- Metabolised: Rapid
- Clearance: Exceeds Hepatic Flow
- Recovery: Rapid (except in cats) & No hangover
Propoclear should be administered____
Proprclear CNS Fx (4):
- Inhibits NMDA
- Anti-convulsant (give w/ Propofol)
- Central Anti-Emetic
Propoclear Cardiovascular Fx(4):
- Depress CO
- Vasodilation= hypotension
- Inhibit/Reset Baroreceptor Reflex
- Splenic Engorgement
Propoclear Respiratory Fx(2):
- Post-Induction Apnea
Important Propoclear Side Fx(4):
- CVS Depression
- Respiratory Depreassion
- Pain on Injection
Administration of Propofol slowly => (2)
- Min hypotension
- Min Respiratory Depression
Tx for persistant Propofol Shakes
Which is used for epileptic dogs that don't respond to Valium?
Cats should not anesthetized on consecutive days with...