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
What are the different forms of oral admin?
A/D?
• Tablets/Pastes/Liquids
▫ Accurate known dosing of single identified patient
▫ May be resented by some animals
• In Feed medication
▫ Stress free administration
▫ Actual dose consumed may be unknown
▫ Accidental consumption by the wrong animal/s
A/D of transmucosal?
Relies on drug being absorbed across mucous membranes eg under tongue or through gums ** key diff b/w transmucosal and oral
• Drug is absorbed across mucous membranes
▫ EG under the tongue or on the gums
- Pain free and low stress administration
- Bypasses the stomach and liver
▫ Some drugs may be inactivated by stomach/liver
▫ Rapid onset cf. True oral administration
• Only effective for some drugs
What are the different phases of GA?
- Premedication
- Induction
- Maintenance
- Recovery
What is premedication and why is it used?
• Drugs given to ‘prepare’ for general anaesthesia
• Potential reasons:
▫ Sedation to facilitate safe handling
▫ Analgesia
▫ Keep the animal calm during induction process, lowering stress
▫ Reduces the dose of anaesthetic drugs = reduce side effects
▫ Disease or condition specific treatments
What is induction GA?
• Process of administering a general anaesthetic resulting in loss of consciousness etc
- High RISK period
- Anaesthetic drugs have dangerous side effects
- Ideally given slowly to effect = Anaesthesia induced with lowest dose effective dose & therefore least side effects.
-not always possible eg. when dartinh wild animals
What is maintenance GA?
Continued delivery of anaesthetic drug to maintain unconsciousness and immobility.
-other drugs to provide analgesia and muscle relaxation may also be used
• Ideally use short acting drugs that can be eliminated rapidly
▫ Titrate to effect as requirements change
- different amount due to different levels of stimulation
- phases of procedure
▫ Avoid delayed recovery
• Animal MUST be monitored continually during the maintenance period
Describe recovery from GA
• Recovery time affected by many factors
▫ Type of drugs used
▫ Duration of anaesthesia
▫ Body temperature
▫ Health of the patient
▫ Temperament of the patient
• High RISK period!
-partly due to complacency eg you think its all done and good but nahhh
• Approximately half of all anaesthetic related DEATHS occur during recovery!
Describe the legislation surrounding anaesthetic/analgesic/sedative drugs
ALL anaesthetic/analgesic/sedative drugs are:
▫ S4 (Prescription Animal Remedy) or
▫ S8 (Controlled Drugs)
• Therefore may only be administered by or following the directions of a veterinarian.
-vet must be physically in the room watching
-WA and UK require nurse to be registered
• Anaesthetic drugs can only be administered by or under direct supervision of a veterinarian!
Describe the legislation surrounding anaesthetic/analgesic/sedative drugs
-additional requirements
• Additional requirements:
▫ Appropriate and continuous monitoring
▫ Maintenance of a permanent anaesthetic record
▫ Ability to administer oxygen (in a veterinary hospital)
▫ Facilities for resuscitation
• S8 (Controlled Drugs) have many additional restrictions and record keeping requirements.
