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Surgery

Intubation complication in a rabbit

15 Apr, 16 | by gmills

By Daniel Pang

A report of an unexpected and novel anaesthetic complication in a rabbit, the presence of faecal matter in the oropharynx impeding attempts at intubation, was recently published in Veterinary Record Case Reports.

The incidence of anaesthetic-­ and sedation-­related mortality in apparently healthy rabbits is 1.4 per cent, six to eight times greater than in dogs or cats, and respiratory complications represent a substantial fraction of these deaths.

Unfortunately, undiagnosed respiratory disease and hypoventilation due to anaesthetic agents can cause significant respiratory depression. Endotracheal intubation provides a secure airway, facilitating positive pressure ventilation, reducing the risk of fluid aspiration and limits workplace pollution with anaesthetic gases. However, many rabbits are maintained anaesthetised with a face mask, rather than secure airway, because they are challenging to intubate. They have a relatively large tongue, narrow oral cavity and small glottis, which combine to limit visibility of, and access to, the larynyx. Simpler, novel methods of securing an airway such as supraglottic airway devices (eg, Laryngeal Mask Airway, V­Gel) have shown promise in clinical use.

A healthy, adult New Zealand white rabbit was anaesthetised for a CT scan as part of a larger study evaluating different methods of providing a secure airway to facilitate ventilation. Following induction of general anaesthesia (intramuscular dexmedetomidine and midazolam, followed by intravenous alfaxalone), the rabbit was positioned in sternal recumbency and orotracheal intubation with an endotracheal tube was attempted with a blind technique. Initial attempts at intubation by an experienced anaesthetist were unsuccessful, with intubation finally achieved after five minutes. This contrasted with an average of two minutes to perform intubation in similar rabbits by the same anaesthetist.

The study protocol required CT scans of the oropharynx to be performed before and after intubation. These ‘pre’ and ‘post’ scans allowed us to identify the cause of the difficult intubation: faecal matter present in the oropharynx before intubation, which was pushed caudally to cause a physical obstruction during attempted intubation (Fig 1). This was also confirmed at postmortem examination.

pang pic

FIG 1: CT images (sagittal plane) of a three-month-old New Zealand White rabbit pre-intubation (top) and post-intubation (bottom) with a 2.5 mm ID endotracheal tube. The pre-intubation image shows two areas containing material of mixed gas and soft tissue attenuation. These were confirmed as faecal material at necropsy examination – a discrete faecal pellet in the oral cavity (orange arrow) and dispersed faecal material in the caudal oropharynx, immediately rostral to the larynx (orange arrowheads). The endotracheal tube (green arrowheads) is visible in the post-intubation scan (bottom) passing dorsal to the faecal pellet (orange arrow). The pellet visible in the pre-intubation scan in the oral cavity has migrated caudally to merge with, and compress, the dispersed faecal material in the laryngopharynx

The source(s) of failed orotracheal intubation attempts in rabbits are usually unknown, although there is a tendency to blame anaesthetist inexperience or anatomical impediments. This report identifies a previously undocumented source of a difficult intubation. A pre­anaesthetic examination of the oral cavity in rabbits may be warranted, but is unlikely to rule out the presence of foreign material in the oropharynx.

The full article is available here: http://vetrecordcasereports.bmj.com/content/4/1/e000265.full

Wombat fatigue: marsupial regains mobility after pioneering surgery

20 Feb, 15 | by Assistant Editor

 

If you are ever faced with a juvenile hairy-nosed wombat with a limp, the recently published case report by Gail Anderson and colleagues (published in Veterinary Record Case Reports and found here) should contain a salutary lesson.

The authors were presented with a male juvenile hand-raised southern hairy-nosed wombat, which weighed 7.5 kg and was approximately 13 months old. He had been rescued from his dead mother’s pouch about seven months earlier and raised by a carer using southern hairy-nosed wombat milk replacer (yes – it does exist!). His carer had noted he was reluctant to walk and this lameness became progressively worse.

 

Haarnasenwombat_(Lasiorhinus_krefftii)

A southern hairy-nosed wombat. Photo: Eva Hejda

 

Clinical observation showed that he was reluctant to move and, when encouraged to do so, he had severe lameness in both hindlimbs and a ‘shuffling’ gait. The wombat was placed under general anaesthesia and palpation of the stifles elicited crepitus on both sides but no obvious joint effusion. It was not possible to fully extend the stifles. No other abnormalities were found on clinical examination. Stifle radiographs revealed displacement of the distal femoral metaphyses due to bilateral type 1 Salter-Harris epiphyseal fractures.

Distal femoral metaphyses have a mottled, radiolucent, appearance. Proximal femoral epiphyses were flattened and showed delayed development consistent with epiphyseal dysplasia. The right proximal femoral epiphysis was slightly more irregular and flattened compared with the left proximal femoral epiphysis. The lower lumbar spine was normal according to radiographs.

 

F1.large

The left (top) and right (bottom) stifle joints of the wombat before surgery.

 

 

Radiographs of a normal southern hairy-nosed wombat of the same age were not available for comparison and, to the author’s knowledge, are not available in the literature. This situation is a common problem for veterinarians treating lesser-studied wildlife species.

After discussion with his carer, he was scheduled for surgery to attempt to reduce the epiphyseal fractures. If left untreated, it was unlikely that he would have regained normal mobility and function. The wombat was, however, given a guarded prognosis, partly because the injury appeared to be chronic and other radiographic changes had been observed.

Induction of anaesthesia was somewhat problematic as endotracheal intubation was difficult, probably due to the relatively small diameter of a wombat’s trachea and excessive mucus production.

The surgical procedure was similar to that commonly used for the repair of comparable fractures in dogs. Using a small osteotome and mallet, the cartilaginous and bony epiphyseal piece was elevated and freed from its caudally displaced position and gently levered back into a position more cranially. Once reduced, the epiphyseal piece was secured with two 1.5 mm diameter Kirschner wires.

 

F5.large

Radiograph of the right stifle following surgery. The white cross shows the K-wires used to immobilise the fracture. The left side looked the same as this after surgery.

 

The wombat recovered quickly and uneventfully from general anaesthesia and was given postoperative analgesia. Once he was moving freely and starting to hide in its custom-made pouch (a fleece-lined pillowcase), he was left in a quiet, dimly lit cage and closely supervised.

The wombat was discharged to his carer once he was moving normally in his pouch, with instructions to restrict his activity for two weeks. He continued to eat well, although he showed initial discomfort and limited mobility. However, he continued to improve and by four months after surgery, he was walking with good extension of his hindlimbs and normal action. His carer felt that he had made a complete recovery.

A video of the wombat four months after surgery showing excellent recovery and mobility can be viewed here: www.youtube.com/watch?v=HqstN5sS8Hg.

Similar hindlimb injuries in pouch young have been frequently observed by vets working in Australia. It is thought that forcible removal of a juvenile wombat from its dead mother’s pouch is the usual cause. However, this report, adding as it does to the limited resources available for this species, shows that excellent outcomes can be achieved following this type of injury in wombats.

More details, images and discussion about this case can be found at Veterinary Record Case Reportshttp://vetrecordcasereports.bmj.com/content/3/1/e000099.abstract

 

Searching for a needle in a…

19 Aug, 14 | by Assistant Editor

 

Veterinary Record Case Reports publishes high quality cases in all disciplines, so that clinicians and researchers can easily find important information on both common and rare conditions. Here, Alastair MacMillan, Editor of the online-only journal, highlights an interesting case involving an inquisitive labrador.

An eight-month-old female labrador retriever presented with progressive cervical hyperaesthesia after being seen coughing close to a broken sewing kit two weeks previously. She had cervical hyperaesthesia and mild proprioceptive deficits in the right thoracic and pelvic limbs. CT imaging of the neck showed a thin metallic foreign body going in a ventrodorsal direction through the vertebral canal at the atlanto-occipital junction.

F2.large

CT showing a sewing needle going in a ventrodorsal direction through the vertebral canal at the atlanto-occipital junction 

Once the needle was located, it was easily grasped using Mosquito forceps, and removed in its entirety. Marked clinical improvement was observed the day after surgery and the owner reported a complete recovery of the patient, with return to normal activities in due course.

F3.large3D reconstruction showing the needle in the atlanto-occipital junction (arrow)

Reports of foreign bodies in the vertebral canal are rare in human and veterinary medicine. Although ingestion of foreign bodies is common in companion animals, sewing needles without an associated thread rarely cause a problem, as they either fail to reach the stomach, or pass through the intestinal tract uneventfully. Although brain abscessation associated with a penetrating needle has been previously reported, this is the first report of a sewing needle penetrating the vertebral canal and being surgically removed with complete clinical recovery of the patient.

To read the full report, click here.

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