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ASC306 > Anaesthetics, Sedatives and Analgesics > Flashcards

Anaesthetics, Sedatives and Analgesics Flashcards

1
Q

What is the textbook definition of general anaesthesia?

A

▫ 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)
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2
Q

What is the textbook definition of local anaesthesia?

A

Loss of sedation in a limited body area

-block nerve transmitters to/from particular body area

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3
Q

What is the textbook definition of sedation?

A

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)

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4
Q

What is the textbook definition of tranquilisation?

A

• Tranquilisation: (tranquilisers) Drug induced relaxation and reduction in anxiety.

Awareness of surroundings is retained!

Can still move

Will still perceive and remember pain

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5
Q

What is the definition of analgesia?

A

literally absence of pain

Drugs that REDUCE sensation of pain

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6
Q

Is it true that some drugs may have more than one property eg sedative and anesthetic etc?

A

Yes!!

and they ALL have side effects

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7
Q

What are the commonly used routes of admin for drugs?

A
  • IV
  • IM
  • SC
  • Inhalation
  • Oral
  • Transmucosal
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8
Q

What are the A/D of injection?

A

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

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9
Q

A/D of IV?

A
  • 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
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10
Q

A/D of IM?

A

▫ Simple technique

▫ Predictable onset of action (slower cf. IV)

▫ BUT:  Painful – especially with large volumes

 Can not titrate dosage

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11
Q

A/D of SC?

A

▫ 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

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12
Q

A/D of inhalation?

A

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
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13
Q

A/D of injectable anaesthesia?

A

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

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14
Q

A/D of inhalational anaesthesia?

A

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
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15
Q

A/D of oral admin?

The activity of drugs administered this way may be limited by…?

A

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

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16
Q

What are the different forms of oral admin?

A/D?

A

• 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

17
Q

A/D of transmucosal?

A

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

18
Q

What are the different phases of GA?

A
  • Premedication
  • Induction
  • Maintenance
  • Recovery
19
Q

What is premedication and why is it used?

A

• 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

20
Q

What is induction GA?

A

• 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

21
Q

What is maintenance GA?

A

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

22
Q

Describe recovery from GA

A

• 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!

23
Q

Describe the legislation surrounding anaesthetic/analgesic/sedative drugs

A

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!

24
Q

Describe the legislation surrounding anaesthetic/analgesic/sedative drugs

-additional requirements

A

• 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.

25
Q

What are the four drug classes?

A

• General Anaesthetics

▫ Injectable

▫ Inhalational

• Local Anaesthetics

• Sedatives

• Analgesics

26
Q

What are the two types of injectable GA?

A

Hypnotic Anaesthetics (Alfaxalone/Propofol)

▫ Dose dependant CNS depression

▫ Sedation -> Light Anaesthesia -> Deep anaesthesia

▫ Dose dependant CVS and respiratory depression

• Dissociative Anaesthetics (Ketamine)

▫ Disconnection rather CNS depression

▫ Less respiratory depression

▫ Analgesic effects

27
Q

Describe inhalational GA

A

Vapours or gases

  • Require accurate delivery by complex equipment
  • Very potent dose dependant CNS depression
  • Potent cardiovascular and respiratory depression
  • Require very careful monitoring – low margin for error
  • Can be easily removed from the body!
  • repeated exposure causes damage
  • most commonly used drugs for maintenance of GA
  • eg Isoflurane, Sevoflurane (anaesthesia only)
  • some have analgesic properties
  • Nitrous Oxide (NANGS!!)
  • Methoxyflurane
28
Q

What is the mode of action of LA?

A

• Block sodium channels in sensory nerves preventing signal conduction.

• Also block conduction in:

▫ Motor nerves = paralysis

▫ sympathetic nerves = vasodilation

▫ The brain leading to seizures

▫ Myocardium causing CVS depression

29
Q

What are the advantages of regional anaesthetic?

A
  • Simple to perform & minimal equipment
  • Highly effective analgesia
  • Low risk of complications (with precautions)
  • ‘Standing Surgery’
  • Adjunct to general anaesthesia
30
Q

What are the differences b/w local and regional anaesthetic?

A
  • LA small area blocked, RA whole region
  • LA simple technique, RA complex
  • LA may not block all tissues, RA blocks all layers
  • LA = lrg volume, RA = sml volume
31
Q 
Sedatives Classes:
Describe Phenothiazines (Acepromazine) and Butyrophenol (Azaperone)
A

▫ Sedative and Tranquilisers

▫ NO analgesic properties

▫ Synergistic sedation with other drugs

▫ Injectable (IV/IM/SC) and Oral formulations

▫ Main side effect = Hypotension (low blood pressure)

▫ Contraindicated in Stallions.

32
Q

Sedatives Classes:
​Describe Alpha-2 Adrenoreceptor agonsists Xylazine/Detomidine/Romifidine/Medetomidine

A

▫ Very Potent Sedatives (the most potent)

▫ Very potent analgesics

▫ Synergism with sedatives/anaesthetics/analgesics

▫ Injectable (IV/IM) and Transmucosal formulations

▫ Significant Cardiovascular and other side effects

▫ Particularly dangerous in small ruminants

Mostly used in horses

33
Q

Sedative classes:

Describe Benxodiazepines (Diazepam/Valium)

A

• Benzodiazepines (Diazepam)

▫ Dose dependant CNS depression

 Sedation – some species

 Dysphoria (excitement) in others

 Controls Seizures

 Muscle relaxation

▫ NO Analgesia

▫ Synergism with other sedatives/anaesthetics

▫ Injectable (IV/IM) and oral formulations

▫ Limited cardiovascular or respiratory effects

34
Q

Analgesic classes:

Describe opioids (morphine/methadone, butorphanol)

A

▫ CONTROLED Substances = possession without authority is illegal

▫ Not registered in production animals

▫ Powerful analgesics

▫ Mild sedation in some species

▫ Synergistic with sedatives and anaesthetics

▫ Main side effect = respiratory depression

35
Q

Analgesic classes:

Describe NSAIDS (meloxicam/flunixin/phenylbutazone)

A

▫ Effective analgesics for mild to moderate pain

▫ Acute and chronic use

▫ Synergism with opioids

▫ NO sedative effects

-mostly used post op or for chronic pain

▫ Oral and Injectable (IV/SC) formulations

▫ Main side effects = Gastrointestinal ulceration; renal failure; Delayed blood clotting.

36
Q

Name some drugs from other classes that may be used for analgesia

A

▫ Alpha-2 Agonists

▫ Ketamine (Dissociative anaesthetic)

▫ Local anaesthetics – post operative pain relief etc

▫ Nitrous Oxide – mostly during anaesthesia

▫ Methoxyflurane (human use)

37
Q
A

ASC306 (14 decks)

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