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filling, and the amount of abdominal fat. The position
of the penis caudal to testicles makes a pre-scrotal 3 approach with a single incision on the midline possible.
Guinea pig sows possess paired ovaries and a bicornuate uterus, consisting of paired uterine horns,
a short uterine body, and a single cervical canal which opens into the vagina2, 3. The ovaries are located in a craniodorsal position, immediately caudal to the kidneys.
Mature male guinea pigs possess paired, large, ovoid testes with a well-developed epididymis, located on either side of the perineum in distinct, shallow scrotal sacs, often with a large amount of surrounding fat. The testicles are usually fully descended into the scrotum by 3 months. If the testes have not descended by 4 months of age, the guinea pig should be considered cryptorchid. The wide inguinal canals remain open for life. Reproductive glands, located within the abdomen, include the seminal vesicles (vesicular glands), coagulating glands, bulbourethral glands, and the prostate.
Analgesia and anaesthesia
Both rabbits and guinea pigs have low pain tolerance thresholds, often responding to pain by inactivity and inappetence. Both of these may, if untreated, result
in intestinal ileus which may in turn lead to the death
of the patient. It is therefore important that a sound analgesic plan is developed to manage both surgical and post-operative pain. The use of opioids, non- steroidal anti-inflammatory drugs and local anaesthesia can be combined to produce multimodal analgesia. It is important that analgesia be continued for several days to ensure the patient is comfortable and eating well.
There are several factors to consider when formulating an anaesthetic plan
Anaesthetic plans should therefore include the following: 1. Minimal / no fasting
2. Washing the mouth out before anaesthetic induction
3. Pre-medication should include analgesia and, if possible, be reversible
4. Induction can be given IM, IV or via mask. In rabbits, mask induction should only be used in a well-sedated and calm rabbit
5. Ventilation support can be given via a well- sealed face mask (guinea pigs, small rabbits), endotracheal tube (rabbits), or laryngeal mask (rabbits)
6. Pre- and post-oxygenation of the patient is essential
7. Patients should be encouraged to eat as soon as possible after recovery
Male rabbits and guinea pigs can be castrated via either an open or closed technique. The initial incision may either be scrotal (a 1-1.5 cm incision through the scrotum longitudinally on each side of the midline about midway along the length of the scrotum) or a single pre-scrotal incision
Closed: The tunic is grasped and the testicle is removed from the scrotum with the tunic intact. The tunic is
tightly adhered to the end of the scrotum by the proper ligament of the testis. This ligament must be broken down to allow exteriorization of the testicle. Caudal traction is applied to the testicle and dry gauze is used to strip the facial attachments allowing the narrow portion of the cord to be exteriorized. Once the testicle has been exteriorized adequately the cord is ligated using a 2 or 3 clamp technique.2
Open: The vaginal tunic is incised to allow exteriorization of the testicle, spermatic cord, and vascular supply. The tail of the epididymis will still be attached to the tunic. This attachment must be broken down freeing the testicle
for removal. The spermatic cord is double ligated and the testicle is removed. The vascular pedicle is traced cranially and the inguinal canal is identified. A single interrupted suture is placed across the inguinal canal being careful not to compress the blood vessels passing through the canal. The vascular pedicle is ligated prior to transection. (It is not necessary to pull the testicle out far from the body, risking accidentally tearing the vessels. The surgeon only needs the entire testicle exposed
and the vessels can be ligated close to the testicle.) Once transected (or torn) the vascular pedicle retracts
· Their small body size
· Large surface area to body mass ratio
can lead to rapid temperature drops
· Rapid metabolic rate means that there
is a high demand for oxygen and energy
· This metabolic rate affects the dose rate and frequency of many drugs
· They are obligate nasal breathers
· Intubation can be difficult
· A rapid recovery with minimal ‘hangover’ effects is needed to ensure a rapid return to eating, minimising the risk of ileus
· Rabbits, in particular, can have a catastrophic re- lease of catecholamines when stressed, leading to cardiac arrhythmias and arrest
· They cannot vomit
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