general anaesthetic. Radiographs are frequently neglected, often with
undesirable consequences down the line.
A concurrent septic physitis or osteomyelitis may continuously “reseed” a septic joint, and may be easily missed if serial radiographs are
not taken. The septic arthritis will then most likely not resolve, and the
treatment will be deemed a failure. Septic physitis and osteomyelitis
requires surgical debridement together with targeted antimicrobial
therapy (local and systemic) for resolution. It may save a lot of hassle
down the line, if you routinely radiograph all septic joints at the time of
presentation, and in selected cases, take serial views during the course
of treatment.
Don’t top up an epidural
Epidural anaesthesia is an extremely useful technique in the standing
horse for surgery of the perineal area and tail. It can also be used for
adjunctive analgesia during general anesthesia for surgery of these same
anatomical areas and the hind limbs, as well as postoperative pain
management. It is used both acutely around the time of surgery, and also
for weeks of afterwards (via an epidural catheter) in horses with long-term
pain. It is most logical to administer epidural analgesia prior to induction of
anaesthesia, to gain all the benefits of pre-emptive analgesia.
The epidural route of administration targets specific receptors in the
dorsal horn of the spinal cord. It has the advantage of reducing unwanted
systemic effects and using much smaller doses of drugs. The analgesic
effect generally lasts longer than systemic administration, as uptake into
the circulation is relatively slow.
The meninges reach the midsacral region in horses, and the spinal cord
extends to the caudal half of S2. Hence use of the lumbosacral space
runs the risk of a spinal injection. The caudal epidural (C1–C2 space) is
the preferred technique in the horse.
i. No risk of dural puncture
ii. Less risk of motor blockade and ataxia.
However, a large volume of injectate can cause the drug to move forward
and result in a cranial epidural block. Depending on the drug and dose
used, rostral areas may be affected. Drugs used for epidural analgesia
include lignocaine, morphine, detomidine, and occasionally ketamine.
Combinations of these are in frequent use eg lignocaine + detomidine or
morphine + detomidine.
Local anaesthetics cannot be used alone to supply hindlimb analgesia in
the standing horse, as the animal will become ataxic or recumbent. These
drugs produce local anaesthesia, hence it is essential that an appropriate
volume is used or the hindlimbs will become paralysed. Volume is more
15-‐18
February
2016
East
London
Convention
Centre,
East
London,
South
Africa
78