Anaesthetics, Sedatives and Analgesics Flashcards
What is the textbook definition of general anaesthesia?
▫ General Anaesthesia: ‘Drug induced unconsciousness characterised by controlled and reversible depression of the central nervous system’
- No perception (awareness) or recall of noxious (painful) stimuli
- Immobility
- BODY MAY STILL REACT TO PAIN
- GA is controlled and reversible (it is not poisonous)
What is the textbook definition of local anaesthesia?
Loss of sedation in a limited body area
-block nerve transmitters to/from particular body area
What is the textbook definition of sedation?
Depression of the central nervous system resulting in decreased awareness of surroundings.
Induces a ‘feeling’ of drowsiness and reduced responses
Can still move (i.e. NOT immobilised)
Will still perceive pain (may or may not remember)
What is the textbook definition of tranquilisation?
• Tranquilisation: (tranquilisers) Drug induced relaxation and reduction in anxiety.
Awareness of surroundings is retained!
Can still move
Will still perceive and remember pain
What is the definition of analgesia?
literally absence of pain
Drugs that REDUCE sensation of pain
Is it true that some drugs may have more than one property eg sedative and anesthetic etc?
Yes!!
and they ALL have side effects
What are the commonly used routes of admin for drugs?
- IV
- IM
- SC
- Inhalation
- Oral
- Transmucosal
What are the A/D of injection?
Accurate and reliable drug delivery
• Bypass stomach and hepatic metabolism (liver)
- drugs may be inactivated by acidic stomach
- may be removed by presystemic elimination (liver)
- some drugs not absorbed well the GIT wall
- Pain on injection and patient compliance?
- Risk of injury around injection site?
-dont inject in wrong place! eg some irritant drugs may only be administered IV
A/D of IV?
- Rapid onset with predictable effect ▫
- Dose can be ‘titrated to effect’
- slowly give, with syringe see how animal goes under sedation eg showing blink reflex may need more
- ▫ Technically demanding
A/D of IM?
▫ Simple technique
▫ Predictable onset of action (slower cf. IV)
▫ BUT: Painful – especially with large volumes
Can not titrate dosage
A/D of SC?
▫ Simple technique
▫ Slow onset and longer duration of action
▫ Less painful than IM
▫ BUT: Onset and intensity of effect are less predictable
-as blood flow not as predictable
Can not titrate dose
A/D of inhalation?
Rapid uptake and elimination of the drug
- Can be titrated to effect
- ONLY drugs where we can take the drug out as well as put it in
-can vary amount we put in
• For drugs treating respiratory disease allows direct targeting to the site of action
- avoids side effects in other parts of body
- avoids metabolism and stomach
A/D of injectable anaesthesia?
Injectable Anaesthesia Inhalational Anaesthesia
- Rapid Onset
- IV injection = Very accurate control of onset
- IM injection- can be delivered remotely (dart guns etc)
- Titrate to effect
- Offset requires metabolism
- Accumulation with repeated doses
- Requires injection (needles)
- Simple equipment
Can dart animal
A/D of inhalational anaesthesia?
Onset depends on breathing
- Smell etc may cause distress during induction (not a problem during maintenance)
- Titrate to effect
- Offset by exhalation
- Little accumulation
- No injections
- Complex equipment required for safe use
A/D of oral admin?
The activity of drugs administered this way may be limited by…?
Very slow onset of action
- Potentially long duration of action
- Pain free administration
- Activity of drugs may be limited by:
▫ Variable absorption from the GIT
▫ Metabolism by the liver
▫ Delayed emptying from the stomach by food etc
▫ Rumen will destroy many drugs
▫ Taste: Bad taste = poor compliance