68. Anaesthesia in small ruminants

Question 1

Types of anaesthetia?

Answer 1

Local (infiltration)

• Loss of sensation in a limited body area

Regional (nerve block)

• Loss of sensation in a limited, but larger body area, than for local anaesthesia

Epidural

General

• Loss of consciousness, decreased sensitivity and motor response

Question 2

Types of anaesthetia(in detail)?

Answer 2

Anaesthesia in ruminants

Regional (nerve block)

• Abdominal Wall:

o Proximal Lumbar Paravertebral Nerve Block (Kalchschmidt)

o Distal Lumbar Paravertebral Nerve Block

o Inverted L Paralumbar Anaesthesia

• Distal Limb Via Vascular (IV) Infusion
• Horn (Cornual Nerve Block)
• Eye and Eyelid:

o Peterson Eye Block, Retrobulbar and Auriculopalpebral Nerve, Auriculopalpebral Nerve

• Teat:

o Ring Block, Inverted V Block, Teat Cistern Infusion &Vascular (Local) Infusion

• Sacral and Subsacral Paravertebral Blocks

o Sacral Paravertebral Alcohol Block

Epidural

o High caudal (sacrococcygeal)

o Low caudal (coccigo-coccigeal)

o Lumbo-sacral

General

o Intravenous

o Inhalation

Question 3

Most common ovine surgical procedures?

Answer 3

Introduction

• The most common ovine surgical procedures

o CS

o Vasectomy

o Digit amputation

• non-steroidal anti-inflammatory drug (NSAID), 5–10 minutes prior to surgery

Question 4

Lidocaine side effect?

Answer 4

Lidocaine side effect

• “Sting” of the lidocaine solution: 1 ml of sterile bicarbonate solution in 20 ml of 2% lidocaine
• Animals — especially small ruminants — injected with more than 6 mg/kg (3 mg/lb = 6.6 mg/kg)

lidocaine may exhibit central nervous system signs with generalized twitching and recumbency

Example:

• Goat kid:
• 15lb (6.8 kg)
• 2%=20 mg/ml
• 45 mg = 2.25 ml! of 2% lidocaine

Question 5

Intravenous use?

Answer 5

Intravenous

• Should be used less frequently
• Risk factors:

o regurgitation of rumen content → aspiration → pneumonia

o ruminal bloat → respiratory function

o remove concentrate feeding for 24 hours prior to any elective procedure

o sheep positioned in sternal recumbency with the head held lowered

Question 6

Sedation drugs used?

Answer 6

Sedation

• Xylazine

o unpredictable

o stress prior to sedation → poor sedative effects → isolated after injection

o 0.05–0.07 mg/kg im., iv, 10 min. (0.25 ml), above 0.07 mg/kg could cause bradycardia and

respiratory depression

• Medetomidine

o 10 μg/kg iv.

o much more predictable sedation

Question 7

Induction and maintenance drugs used?

Answer 7

Induction and maintenance

• Ketamine

o 3 mg/kg iv. 10–15 minutes surgical anaesthesia → 2–3 mg/kg ketamine → further 10

minutes of surgical anaesthesia

• Alphaxalone

o 2.2–4.4 mg/kg iv. → inhalation anaesthesia

o very safe but its short duration

o lamb: 4.4 mg/kg, 10 min. → forelimb fracture reduction

Question 8

Sacrococcygeal details of use and drugs?

Answer 8

Sacrococcygeal

• standing sheep
• The area over the tailhead is clipped and disinfected
• digital palpation during slight vertical movement of the tail
• 25 mm 20 gauge needle directed at 10–20° to the tail
• Lidocaine 0.5 mg/kg or
• Lidocaine 0.5 mg/kg and xylazine (max.) 0.07 mg/kg, 10-15 min.

o Example: 65-80 kg: 2 ml 2% lidocaine inj. + 0.25 ml 2% xylazine inj.

o more effective analgesia and less effect on motor innervation

o 2 min. → loss of tail tone, but 10 min. for perineal area

o Does not cause significant sedation ↔ cattle, llamas, and horses

o complication: into fascia and/or surrounding tissues → causes mild sedation (xylazine)

lasting 2–3hours

o second inj. but only lidocaine

o mild hindlimb paresis may persist for up to 48 hours

o rectal, cervical or uterine prolapses

• Xylazine (max.) 0.07 mg/kg in 2.5 ml

o 40-50 min. surgery

o CS

o Vasectomy