7. Local and general anaesthetics

Question 1

What are regional and local techniques and what are they used for?

Answer 1

They produce complete blockade of perioperative nociceptive input of a specific area.

they are the most effective way to prevent sensitisation of the CNS and the development of pathological pain

Question 2

What is the effect of stress on surgical trauma?

Answer 2

stress compromises haemostatic, metabolic and immunological function. This in turn increases morbidity and mortality

Question 3

Name some local anaesthetics and their uses:

Answer 3

• Lignocaine (topical) peripheral/epidural blockade, 5-15 min onset, 1-2 hrs
• Mepivacine- peripheral/epidural blockade, 5-15 min onset, 1.5-2.5 hrs
• Bupivacaine- peripheral/epidural blockade, onset 10-20 mins, 4-6 hrs

Question 4

What can topical anaesthesia be used for?

Answer 4

• facilitate the placement of endotracheal tube, nasal oxygen lines and urinary catheters

care must be taken in <5kg patients (systemic toxicity)

Question 5

What is infiltration anaesthesia used for?

Answer 5

used to desensitise dermal or subcutaneous tissues for minor diagnostic and surgical procedures.

particularly good for lump removal and horse castration

Question 6

What is interpleural anaesthesia?

Answer 6

Facilitated via a chest tube or specialised catheter.

used to drain fluid from the chest, high risk of toxicity and convulsions due to rapid intake of drug

Question 7

What is intra-articular anaesthesia used for?

Answer 7

(into the joint)

• diagnostic purposes in horses
• improve post-operative pain following orthopaedic surgery

Question 8

Why is intravenous regional anaesthetic used?

Answer 8

Allows for a large amount of anaesthetic- not usually used in dogs and cats or patients <5kg

Question 9

What is peripheral neural blockade used for?

Answer 9

• dental surgeries
• lump removal
• most commonly used in small animals

Question 10

Where can we peripheral blockade?

Answer 10

• maxillary and mandibular branches of the trigeminal nerve (dental)
• Cervical and thoracic nerves (surgery involving forelimb or thorax
• lumbar and sacral nerves (surgery on hindlimbs)

Question 11

what can we use peripheral blockade for in horses?

Answer 11

• diagnosis of lameness
• eye injuries
• suturing of wounds
• castration
• dental procedures
• mares with vulva conformational issues

Question 12

What happens when we use an epidural?

Answer 12

also known as a Central Neural Blockade

• complete sensory, motor and autonomic blockade
• usually used in combination with opioids (morphine)
• requires very careful management

Question 13

Which analgesics are best used for standing procedures in dogs?

Answer 13

• alpha 2 agonists alone, or in combination with opioids or phenophiazines

Question 14

What are the advantages of standing procedures?

Answer 14

• lower anaesthetic-related complications
• reduced cost
• reduced tie to complete procedure

Question 15

What are the disadvantages of standing procedures?

Answer 15

• over sedation = ataxia
• insufficient analgesia may be a problem
• less than ideal surgical conditions
• increased risk of injury to personnel

Question 16

What are the ideal properties of sedative drugs?

Answer 16

• reliable sedation
• reversible
• predictable onset and duration of action
• minimal ataxia
• analgesia
• minimal CV effects
• no allergic reactions
• can be used in combination with other sedatives/tranquilisers

Question 17

What can you use for a bolus injection?

Answer 17

Alpha 2 agonist + opioid

• xyalizine + butorphanol/morphine
• Medetomodine + methadone
• Detomodine + butorphanol/morphine
• Romifidine + butorphoanol

Question 18

What is the Constant Rate Infusion (CRI)?

Answer 18

provides a more constant state of sedation once the loading bolus has been administrated (drugs + saline) - requires IV