Production Animal Sedation, Anaesthesia & Analgesia 1 Flashcards
Considerations of prod animal sedation?
- Cost/benefit – value of animal, cost of procedure and aftercare, slaughter value if the animal can be transported
- Safety – animal, surgeon, others
- Welfare
- Anaesthesia – local, regional, general
- Fluid therapy
- Aftercare - fly control, access to food and
water, isolation box, re-introduction to
herd/pen - Analgesia – NSAID, limit movement, support
- Informed owner and signed consent form
Causes of Pain in farm animals?
- Injury
- Diseases
- Surgery
- Husbandry procedures
- Obstetrics
common surgical procedures?
» Left displaced abomasum correction
» Right displaced abomasum correction
» Caesarean section
» Exploratory laparotomy/rumenotomy
» Displaced/torsion of caecum
» Open castration
» Closed castration
» Disbudding/dehorning
» Digital amputation
» Enucleation
» Wound repair
Claw amputation?
Surgical procedures in alpaca?
Castration
Tooth root abscess
Fractures
Wound repair
Surgical Procedures sheep?
Caesarean section
Claw amputation
Surgical castration
Wound repair
Surgical procedures pigs?
» Castration – Commercial boars prior to slaughter or pet pigs
» Hernia repairs
» Caesarean
» Digital amputation
Aftercare pigs procedures?
– beware mixing with other pigs
Thermoregulation
Pet pig procedures?
OVH & ENtropion
Restraint?
what does chronic pain result in ?
a reduction in the pain threshold with a heightened response to
a painful stimulus (hyperalgesia) or a pain response to a previously non-painful stimulus
(allodynia).
examples of painful procedures
Bhvr cues of pain in pigs?
Trembling
Leg shaking
Head shaking
Pawing the ground
Huddling
Stiffness
Postural changes
Reduced feed intakes
Vocalisation
Aggression
Restlessness
Bhvr changes in ruminants?
Reduced feed intake
Reduced rumination
Reluctance to move
Grinding teeth
Abnormal posture
what things proposed. by Huxley et al suggested for eval of pain in cattle?
- Decreased movement/locomotion;
- Decreased interaction with other animals in the group;
- Decreased feed intake (‘hollow’ left flank)
- Changes relevant to the source of the pain being experienced- altered locomotion, flank watching or kicking, or ear twitching;
- Level of mental activity/responsiveness (animals in severe pain often show reduced responsiveness to stimuli);
- Changes in normal postures associated with pain - lateral recumbency, not moving or drooping of the ears);
- Increased heart rate, increased pupil size, altered rate and depth of respiration or trembling;
- Bruxism (tooth grinding);
- Poor coat condition (
how can we reduce pain in practial terms?
▪ Reduced walking distances to the milking parlour and minimising competition for food and
water will bring some relief in lame cows or post-operative patients.
▪ Support dressings, splints and castes will minimise the trauma and pain following a fracture.
▪ Hoof blocks, which lift a painful claw off the ground so that it is no longer is weight bearing,
are commonly used and are a very cost-effective method of reducing pain.
▪ Pressure bandages can be used to reduce pain.
timing of analgesia?
- Pre-emptive administration before the exciting cause of pain should be possible in most
elective procedures. - In other situations administration as soon as possible after the onset of pain is advisable to
reduce the severity and time period of discomfort.
Multimodal analgesia?
- Using a combination of analgesic drugs, which act on different pathways, it is sometimes
possible to increase and optimise the pain control. This is called multimodal analgesia. - An example is the combined use of a systemic NSAID and a local anaesthetic line block in a
caesarean section.
time to effect of various drugs?
Reminder of cascade?
Withdrawal times
multimodal analgesia in cattle?
local anaesthesia?
- 4-5% Procaine + adrenaline (epinephrine)
- Toxic dose – 10-20mg/kg
Toxic effects with increasing dose?
- Neurological toxicity
Nausea
Muscle twitching
Sedation
Seizures
Unconsciousnes
Respiratory arrest - Cardiac toxicity
Cardiac arrythmia
Cardiac arrest
What practical considerations - pigs ?
- Handling facilities available
- Other people to provide assistance
- Anatomy of the animal
- Adverse effects
Anatomy in pigs?
▪ Limited access to veins
▪ Vast layer of fat
▪ Prone to respiratory obstruction
▪ Difficult to intubate
Adverse effects
▪ Recovery can be prolonged/dramatic
▪ Poor thermoregulation
▪ Malignant hyperthermia
what drugs can we give?
Sedation in pigs?
Azaperone (1-2mg/kg depp IM)
- Light-mod sedation
- Low dose in boars intended for breeding
- Leave alone to work
Alpha-2 agonist
- Xylazine
- Detomidine
Pigs - PRe-med?
- Atropine sulphate at a dose rate of 0.02-0.04 mg/kg i/m, sc, or iv 30 minutes before general anaesthesia will reduce the risk of bradycardia and reduce salivation
- Ophthalmic ointment can be instilled into both eyes immediately following induction of anaesthesia to provide corneal protection particularly in pet pigs.
Pigs - what injectables?
Ketamine
Describe ketamine induction?
- Azaperone pre-medication OR ketamine + other agent in one syringe
- Dose dependent on premed used
- Higher doses associated with muscle rigidity
- ≈40mins of anaesthesia from induction
Maintenance ketamine?
- 5mg/kg IV
- 30 mins after induction
- IV access from cathertising ear vein
Licensing of ketamine as injectable?
Licenced @ 15-20mg/kg
Off licence at lower
doses
Pigs GA?
Mask induction using isoflurane followed by intubation is commonly used option in
smaller pigs particularly pet pigs which are brought to the surgery.
For small and large pigs of all sizes on farm intramuscular injections are preferable for
sedation or anaesthesia.
Where to give IM in pig?
neck
Venipuncture in ear vein pigs?
- In potbellied pigs the ear vein may or may not be detected as it runs dorsally along the anterior margin of the
ear. - A rubber band placed at the base of the ear will raise the vein and increase its visibility.
- The vein can be catheterised using a 21-22 gauge butterfly needle if required. Pigs flick their ears when the
ear is pricked with a sharp needle. - The ear needs to be held securely to minimise this problem. The use of topical local anaesthetic gel on the
skin over the vein to be punctured is helpful in this regard if availble.
Intubation pigs?
- Intubation is difficult and requires the use of a laryngoscope to depress the tongue and epiglottis. Placement
of the intubation tube is sometimes assisted by the use of a plastic stylet - The stylet is placed inside the tube to direct the tube through the larynx and is then removed
ALWAYS for long procedures
face masks in pigs?
If the pig is quietly restrained isoflurane using a tightly fitting mask around the pig’s snout can be used to anaesthetise pigs for short procedures.
Food & water witholding for pig surgery?
withheld for 24 hours and water for 4 hours if general anaesthesia is to be used.
Thermoreg in pigs?
Thermoregulation in the pig under sedation/general anaesthesia is relatively poor and the animal should
be kept in a comfortable ambient temperature to prevent hypothermia or hyperthermia both during and
after the procedure. Heating pads, blankets and hot water bottles can be used to good effect in
preventing or treating this problem.
Malignant hyperthermia ?
The sensitivity of potbellied pigs to isoflurane to induced malignant hyperthermia is thought to be low.
Isoflurane and other stresses can trigger malignant hyperthermia in genetically pre-disposed pigs i.e.
Landrace, pietrain, duroc
The clinical signs include a sudden increase in body temperature with muscle rigidity, tachycardia and
tachypnoea. Gaseous anaesthetics should be discontinued combined, and the pig cooled by the use of
ice-packs.
Longer recovery - why ?
The pig and particularly the pet pig has a higher proportion of body fat relative to muscle and may have
prolonged recovery periods.
Risk fo muscle damage in recovery pigs?
non-slippery surface to prevent uncoordinated ,
abnormal movements which can result in torn muscles. The most common of these is
lateral abduction of both hind legs with both legs being splayed outwards into the ‘splits’
position with tearing of the adductor muscles.
Isolation pigs post-op?
Confinement following surgical procedures with healing wounds for 10-14 days is
advisable to avoid wound break down and interference from group
re-introduction post-op?
Re-introduction of a pig to a group must be done with extreme care and close supervision
to avoid fighting. The use of azaperone sedation may be advisable.
overall what multimodal analgesia in pigs?
