Ch.18 Balanced Inhalation Anaesthesia

Question 1

Goal of equine anaesthesia

Answer 1

Maintenance of good intraoperative cardiopulmonary function, followed by calm pain-free and co-ordinated anaesthetic recovery

Question 2

What is believed to be the cause of foal deaths when using inhalant drugs (iso, servo, des) for induction

Answer 2

Rapid uptake of newer, less soluble inhaled agents in young animals with an immature cardiopulmonary system.

Question 3

What is drug potency represented by?

Answer 3

MAC
Minimum alveolar concentration -
end tidal alveolar concentration of inhalation anaesthetic that prevents movement in 50% of subjects in response to a noxious stimulus.

Question 4

MAC of Halothane

Answer 4

0.88%

Question 5

MAC of Isoflurane

Answer 5

1.31%

Question 6

MAC of Sevoflurane

Answer 6

2.31%

Question 7

MAC of Desflurane

Answer 7

7.6%

Question 8

How are Iso, sevo and des metabolised and at what rate

Answer 8

Liver
ISO - 0.2%
SEVO - 3-5%
DES - 0.02%

Question 9

How do iso, sevo and des decrease blood pressure

Answer 9

Decreased peripheral resistance

Question 10

How does Desflurane affect CO at 1 MAC

Answer 10

Does not depress CO

Question 11

What plasma levels of lidocaine are required to reduce the MAC of Halothane by 50-70%

Answer 11

> 5ug/ml

Question 12

Lidocaine at 1.3mg/kg over 15mins followed by 50ug/kg/min decreased the MAC of Sevo by what %

Answer 12

27%

Question 13

At what plasma levels are signs of ataxia seen in the standing horse

Answer 13

1.85-4.53ug/ml

Question 14

Intra op lidocaine protocol dose

Answer 14

0.65-1.3 mg/kg over 15 - 20mins
Followed by CRI 25 - 50 ug/kg/min

Question 15

Intra op CRI rate of Medetomidine

Answer 15

3.5 ug/kg/hr

Question 16

Intra op CRI rate of Dexmedetomidine

Answer 16

1.75 ug/kg/hr

Question 17

Intra op CRI rate of Xylazine

Answer 17

0.3 - 0.6 mg/kg/hr

Question 18

Intra op CRI rate of Detomidine

Answer 18

10 ug/kg/hr

Question 19

Intra op CRI rate of Romifidine

Answer 19

18 -40 ug/kg/hr

Question 20

Intra op CRI rate of Ketamine

Answer 20

0.5 - 1 mg/kg/hr

Question 21

Intra op CRI rate of S (+) Ketamine

Answer 21

0.5 - 1 mg/kg/hr

Question 22

What is the maximum length of time a Ketamine CRI is advised for owing to rough recoveries

Answer 22

1.5 hours

Question 23

Which horses are at risk of toxicosis following lidocaine

Answer 23

Ones with compromised cardiovascular function with resultant reduced liver blood flow and metabolism

Question 24

How does lidocaine decrease the MAC of inhalant anaesthetics

Answer 24

Dose dependently

Question 25

How do Alpha 2 adrenoreceptor agonists decrease the MAC of inhalant anaesthetics

Answer 25

Dose dependently

Question 26

For how long does the bolus of alpha 2 adrenoreceptor agonists negatively impact cardiopulmonary function in the anaesthetised horse

Answer 26

20 -120 mins

Question 27

Which alpha 2 adrenoreceptor agonists have the shortest half life

Answer 27

Medetomidine and dexmedetomidine

Question 28

For how long does the bolus of alpha 2 adrenoreceptor agonists negatively impact cardiopulmonary function in the standing sedated horse

Answer 28

10 mins

Question 29

Which has a better anaesthetic recovery Medetomidine CRI or Dexmedetomidine CRI

Answer 29

Dexmedetomidine

Question 30

How does recovery following a lidocaine balanced anaesthesia compare to medetomidine balanced

Answer 30

Medetomidine recovery is longer but of better quality

Question 31

How does management of a lidocaine balanced anaesthesia compare to medetomidine balanced

Answer 31

Medetomidine - fewer drugs administered during the anaesthesia

Question 32

How does monitoring a horse's eye differ when balancing anaesthesia with medetomidine

Answer 32

Brisker eye reflexes Only nystagmus may indicate the horse is light

Question 33

How does xylazine 1mg/kg/hr CRI in balanced anaesthesia affect the cardiovascular system and recovery

Answer 33

HR Lower BP Higher Recoveries longer but better quality

Question 34

On average Alpha 2 adrenoreceptor agonists reduce MAC by what%

Answer 34

30%

Question 35

What is the currently licensed form of Ketamine?

Answer 35

Racemic mixture of S-Ketamine and R-Ketamine

Question 36

What is postoperative wind up

Answer 36

A state of reactivity of the cns that can occur following tissue damage leading to maintenance of pain even after the injury has healed

Question 37

What duration of ketamine infusion has been associated with undesirable excitatory CNS effects

Answer 37

Over 1 - 2 hours or repetitive IV boluses

Question 38

Describe the emergence reactions associated with ketamine

Answer 38

Muscle tremor and rigidity Mydriasis Oculogyric movements Sweating Excitation Ataxia Schizophrenia like behaviour

Question 39

What is accountable for emergence reactions when using Ketamine

Answer 39

Plasma conc Length of drug infusion Formation of S-norketamine

Question 40

How to minimise emergence rxns when using ketamine

Answer 40

Lower dose Gradual decrease to stop 15/20 mins before end of sx Alpha 2 adrenoreceptor agonists for recovery or use 1.1mg/kg IV S-Ketamine and maintain on CRI AT 0.5 mg/kg/hr with iso and oxygen

Question 41

What is associated with better recovery when combined with guafenesin Racemic Ketamine or S-Ketamine

Answer 41

S-Ketamine

Question 42

Experimental studies of opiod use during inhalant anaesthesia shows what changes in MAC

Answer 42

No change Except for high doses of Fentanyl

Question 43

Changes in MAC from Morphine CRI

Answer 43

None

Question 44

Effects of 0.02 mg/kg Butorphanol on anaesthesia when combined with Iso

Answer 44

Deeper anaesthesia Sympathetic stimulation caused by sx is blunted

Question 45

Former name of Guaifenesin

Answer 45

Glyceryl Guaiacolate

Question 46

Advantages of using Guaifenesin

Answer 46

Potentiates other sedatives/anaesthetics drug Good relaxation of laryngeal and pharyngeal muscles Relaxation of skeletal mm Does not affect diaphragmatic or respiratory function No effect on CO or BP

Question 47

What is the dose range of Guaifenesin

Answer 47

50 - 100 mg/kg

Question 48

Risks of Guaifenesin use

Answer 48

Irritant to vessels 10% Guaifenesin very high risk (7/7) of thrombus formation and reports of hemolysis

Question 49

Do benzodiazepines have analgesic properties?

Answer 49

No but they potentiate analgesic properties of co-administered drugs

Question 50

Risks of using benzodiazepines intra-operatively and how to avoid

Answer 50

Ataxia after standing in recovery Reverse using benzodiazepine antagonist such as flumazenil

Question 51

How is lidocaine metabolized

Answer 51

By the liver

Question 52

True or False Lidocaine has a long half life?

Answer 52

False

Question 53

In healthy awake horses, lidocaine toxicity has been observed in plasma levels exceeding..

Answer 53

1.85 - 4.35 ug/ml

Question 54

True or False Alpha 2 adrenoreceptor agonists are potent analgesics

Answer 54

True

Question 55

True or False Medetomidine has a short half life

Answer 55

True

Question 56

Does Ketamine depress CO

Answer 56

No Causes sympathetic stimulation which may help maintain cardiac function when anaesthetised

Question 57

Does Guafenisin have a wide or narrow window of safety

Answer 57

wide

Question 58

Where does Guaifenesin elicit its affects

Answer 58

Brain stem - potentiating other sedative and anaesthetic drugs

Question 59

Does Guaifenesin affect respiratory function

Answer 59

No effect on diaphragm or resp function when used in clinical doses of 50-100mg/kg

Question 60

What % Guaifenesin has been assoicated with Hemolysis

Answer 60

10%