anaesthesiaThere are two major techniques commonly used in
castrating a horse, one requiring only
local anaesthesia and the other requiring
general anaesthesia. Each technique has advantages and disadvantages.
Standing castration Standing castration is a technique where a horse is sedated and local anaesthesia is administered, without throwing the horse to the ground or putting him completely "under". It has the benefit that
general anaesthesia (GA) is not required. This method is advocated for simple procedures because the estimated
mortality for GA in horses at a modern clinic is low, approximately one or two in 1000. Mortality in the field (where most horse castrations are performed) is probably higher, due to poorer facilities. For standing castration, the
colt or
stallion is
sedated, typically with
detomidine with or without
butorphanol, and often physically restrained.
Local anaesthetic is injected into the
parenchyma of both
testes. An incision is made through the
scrotum and the testes are removed, then the
spermatic cord is crushed, most commonly with either
ligatures or
emasculators, or both. The emasculators are applied for two to three minutes, then removed, and a careful check is made for signs of
haemorrhage. Assuming that bleeding is at a minimum, the other side is castrated in the same manner. Most
veterinarians remove the testis held most "tightly" (or close to the body) by the
cremaster muscle first, so as to minimize the risk of the horse withdrawing it to the point where it is inaccessible. The horse, now a gelding, is allowed to recover. Standing castration can be performed in more complicated cases. Some authorities have described a technique for the removal of
abdominally retained testes from
cryptorchid animals, but most surgeons still advocate a recumbent technique, as described below. The primary drawback to standing castration is the risk that, even with sedation and restraint, the horse may object to the procedure and kick or otherwise injure the individual performing the operation.
Recumbent castration Putting a horse under
general anaesthesia for castration is preferred by some veterinarians because "surgical exposure is improved and it carries less (overall) risk for surgeon and patient". For simple castration of normal animals, the advantages to recumbent castration are that the horse is prone, better
asepsis (sterile environment) can be maintained, and better
haemostasis (control of bleeding) is possible. In addition, there is significantly less risk of the surgeon or assistants being kicked. In a more complex situation such as castration of
cryptorchid animals, the
inguinal canal is more easily accessed. There are several different techniques (such as "open", "closed", and "semi-closed") that may be employed, but the basic surgery is similar. However, general anaesthesia is not without risks, including post-anaesthetic
myopathy (muscle damage) and
neuropathy (nerve damage), respiratory dysfunction (V/Q mismatch), and cardiac depression. These complications occur with sufficient frequency that castration has a relatively high overall mortality rate.
Aftercare With both castration techniques, the wound should be kept clean and allowed to drain freely to reduce the risk of
hematoma formation, or development of an
abscess. The use of
tetanus antitoxin and
analgesics (painkillers) are necessary and
antibiotics are also commonly administered. The horse is commonly walked in hand for some days to reduce the development of
edema.
Possible complications Minor complications following castration are relatively common, while serious complications are rare. According to one in-depth study, for standing castration the complication rate is 22%, while for recumbent castration it is 6% (although with a 1%
mortality). • Scrotal/incisional infection – local seroma/abscess formation is relatively common, when the skin seals over before the deeper pocket has time to seal. This requires reopening the skin incision, to establish adequate drainage. To prevent the wounds from closing too quickly the horse needs to be exercised at least once daily after the procedure. It is common to treat the horse with a
nonsteroidal anti-inflammatory drug to reduce the swelling and sometimes it is necessary to give
antibiotics. •
Chronic infection leads to a
schirrous cord – the formation of a
granuloma at the incision site, that may not be obvious for months or even years •
Evisceration, a condition where the
abdominal organs "fall out" of the surgical incision, is uncommon, and while the survival rate is 85–100% if treated promptly, the mortality rate is high for those not dealt with immediately. ==See also==