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Anaesthesia > 5. Premedication and Sedation > Flashcards

5. Premedication and Sedation Flashcards

1
Q

When are animals premedicated?

what is sedation used for?

A

The majority of animals are premedicated before induction of anaesthesia. It is important to select drugs based on the needs of the individual patient (dont rely on protocols).

Sedation is often used as an alternative to GA for minor surgical or diagnostic procedures.

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2
Q

What are the aims of premedication and sedation?

A
  • Quieten or immobilise a patient sufficiently to allow procedures.
  • Facilitate animal handling and restraint
  • Contribute to balanced anaesthetic (can reduce the dose of of other agents)
  • Provision of analgesia
  • Contributes to a smooth and quiet induction
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3
Q

Which properties do we ideally want from drugs?

A
  • Produce reliable sedation and anxiolysis
  • Have minimal cardiovascular effects
  • Cause minimal respiratory depression
  • Produce analgesia
  • Be reversible if possible
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4
Q

What are the 5 classes of commonly used drugs?

A
  • Phenothiazines (tranquiliser) - Acepromazine
  • Alpha-2 (adrenoreceptor) agonists (analgesia)- xylazine, romifidine, medetomidine
  • Benzodiazepines (muscle relaxants) diazepam
  • Opioids (sedation) Bupernorphine, morphine, methadone
  • Anticholinergics (prevents unwanted effects of other agents) Atropine
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5
Q

How can you maximise drug effects?

A
  • Ensure the animal is in a darkened, quiet environment
  • do not disturb the animal until the drugs have reached peak effect
  • gentle, quiet handling
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6
Q

What is the synergist effect?

A

Different classes of drugs combined to allow for a balanced approach to anaesthesia- eg pre-empetive analgesia

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7
Q

Which factors can influence the choice of premediate used?

A
  • ASA score of the patient
  • Species/breed/age
  • Reason for GA and procedure
  • Degree of pain expected from procedure
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8
Q

What must we monitor during GA?

A

Assessment of HR, RR, presence/absence of reflexes and response to arousal.
Body temperature and blood glucose levels in young patients or rabbits.

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9
Q

What supportive measures can we put in place?

A
  • Oxygen (prevents hypoxaemia)
  • Body temperature (prevents hypothermia)
  • Fluid therapy (sedated animals cannot regulate their own fluid balance)
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10
Q

What methods of induction are there?

A

IV, IM, SC

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11
Q

What is the induction of general anaesthesia process?

A

Injectable anaesthetics are used for induction followed by maintenance with a volatile agent.

Accuracy of dosing is vital

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12
Q

What is the Total Intravenous Anaesthesia (TIVA)?

A

repeated boluses or infusion of an anaesthetic in conjunction with an analgesic

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13
Q

What considerations are there when it comes to venous access?

A

Proper premedication and handling should allow for placement of an IV catheter, without forceful restraint.

Accidental perivascular injection of highly irritant drugs can lead to cellulitis.

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14
Q

What are Barbiturates?

A

Injectable anaesthetic.

  • Thiopental- rapid smooth induction, irritant, slow injection poor analgesia, treatment of seizures
  • Pentobarbital - higher concentrations available as euthanasia solutions, treatment of seizures
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15
Q

What are non-Barbiturates?

A

Propofol- smooth induction/recovery, discard open vials after 24hrs, poor analgesia, supplement oxygen needed, excitatory signs occur during induction and recovery.

Avoid in hypovolaemic, heart failure, pancreatitis patients

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16
Q

What is Etomidate?

A

Painful on injection- induction agent, short infusion.

needs to be kept refrigerated and discarded after 24hrs.

poor analgesia, good CV stability, avoid in animals with known adrenal insufficiency

17
Q

What are dissociative agents?

A

Ketamine- induction gent (IV, IM, SC, PO, TIVA)

To be combined with benzodiazepine, alpha-2 agonist or acepromazine.

CV stimulant, apnoea with high doses, avoid in epileptics and animals with increased cranial pressure (ICP)

18
Q

What do we use Tiletamine- Zolazepam for?

A

Dissociative Induction agent (IV) or in aggressive cats/dogs (IM). specifically good for cats

Sole anaesthetic agent only for diagnostic or minor surgical procedures. Avoid in epileptics, ICP. Apnoea in high doses.

Premedicate with ACP, alpha-2 or benzodiazepine

19
Q

What do we use Steroid Anaesthetics (Alfaxalone and saffran) for?

A

Alfaxan- induction (IV), can be used as a maintenance agent

Saffran- (IV) do not use in dogs or in conjunction with barbiturates. Causes hypotension in cats and facial and paw oedema

20
Q

Advantages of using Inhalant Anaesthetics for maintenance of GA?

A
  • Administered in O2
  • Can be administrated by ET tube or mask
  • Greater patient safety
  • Isoflurane and sevoflurane acts rapidly
  • Minimally metabolised by the liver
  • Rapid elimination from the body
21
Q

Disadvantages of using Inhalant Anaesthetics for maintenance of GA?

A
  • Need an anaesthetic machine, breathing system and vaporiser
  • User needs to be able to use and trouble shoot
  • Carbon monoxide can be produced by the interaction of volatile gas with soda lime (rebreathing system)
  • Dose-dependant cardiopulmonary depression causes
22
Q

What are minimum alveolar concentration values (MAC)?

A

Used when using volatile gases.
Concentration in the alveoli required to prevent 50% of a group of animals from responding with purposeful movement to a noxious stimulant.

A value is obtained using lab techniques to give the vet an idea of the % concentration to set the vaporiser at to maintain an appropriate depth of anaesthesia

23
Q

What are some factors which affect MAC values?

A
  • Pre-anaesthetic sedatives/injectables/analgesics
  • Hypoxaemia
  • Haematocrit (PCV) less than 10%
  • Increasing age
  • Hypothermia
  • Pregnancy
  • Concurrent illness
24
Q

What will affect your choice/amount of volatile gas ?

A

The concentration of inhalant in the system will depend on the choice of anaesthetic breathing system and fresh gas flow rates.

Monitors can measure inhaled and exhaled concentrations

25
Q

what can influence the uptake of inhaled gases

A
  • patient positioning
26
Q

What volatile gases are there and what are their properties?

A

Halothane, Isoflurane, sevoflurane, desflurane. nitrous oxide.

All produce a dose dependant decrease in CO and BP, depression of the CNS and poor analgesia.

Degree of respiratory depression varies between each agent

27
Q

What is nitrous oxide and how is it used?

A

Used as an analgesic alongside more potent inhalants.

Second gas effect- occurs when two

Anaesthesia (18 decks)

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