Surgical Conditions of the Airways Flashcards
(22 cards)
What are the major conditions that affect the rhinarium, and how is each surgically treated?
Congenital Cleft of the Primary Palate -
Congenital failure of complete fusion/formation of the external nares and premaxilla.
No functional significance, so surgical intervention is unnecessary.
Trauma -
Trauma to the rhinarium often causes considerable bleeding, due to prominent blood supply.
Treatment either by surgical glue or sutures.
Neoplasia -
Appear as asymmetrical swellings or open wounds at the nose.
Commonly squamous cell carcinomas or mast cell tumours.
Should be surgically excised by partial nosectomy (total in cats).
Should be followed up with adjunctive radiotherapy.
What is brachycephalic obstructive airway syndrome, why does it develop, and what ways may it present clinically?
Syndrome seen in all brachycephalic dogs, due to a combination of primary and secondary pathologies that restrict normal airflow.
Generally present in one of two clinical syndromes:
Stable Respiratory Compromise -
The animal is stable and able to maintain adequate ventilation, despite increased resistance to flow.
Unstable Obstructive Crisis -
Animal is unable to maintain adequate ventilation, often under an increased demand.
Requires immediate care and probable later surgical intervention.
What is the process of development of unstable obstructive crisis in an animal, and how will this animal present?
Typically occurs in brachycephalic animals when placed under an increased respiratory demand (i.e. exercise, heat, etc).
This increased demand increases the pressure under which the animal attempts to breathe, causing a roaring inspiration.
This causes vibration of the pharyngeal and palatal tissues, stimulating oedema, further restricting airflow.
This pressure gradient may also pull the stomach through the oesophageal hiatus, causing regurgitation.
Animals also begin to overheat due to a failure of expiratory heat loss and increased muscle activity.
How should an animal in unstable obstructive crisis be treated, and what is the purpose of each treatment?
If receptive, the animal should be given oxygen supplementation to reduce the effort with which it needs to breathe.
Should not do if the animal becomes stressed by the oxygenation equipment.
If necessary, this may be done by emergency intubation/tracheostomy.
The animal should have its core temperature reduced by whole body cooling and IV administration of cool fluids.
This will minimise the risk of hyperthermia, and reduce the effort with which the animal must breathe.
The animal should be sedated, ideally with acepromazine, to reduce its anxiety to reduce its respiratory effort.
Additionally, acepromazine will stimulate peripheral vasodilation to aid heat loss.
Once an animal in unstable obstructive crisis is stabilised, what should be done to investigate and treat the underlying condition?
The animal should have a full history and physical exam to identify any co-morbidities that may impact the treatment or the initial development of the condition.
Blood tests and radiography should also be performed to investigate additional co-morbidities.
The extent of disease within the upper airways should then be assessed under light anaesthesia, prior to development of a surgical plan of treatment.
What are the primary pathologies present in brachycephalic dogs that lead to the development of brachycephalic obstructive airway syndrome, and how can each be surgically treated?
Stenotic Nares -
The diameter of the opening into the nasal passages is very small, contributing a very large resistance to airflow.
This can be corrected by the removal of a wedge of tissue from each nare, and their suturing into a wider position.
Long Soft Palate -
The soft palate extends too far back, contacting the epiglottis and obstructing the larynx.
A section of tissue can be removed to the caudal/middle aspect of the tonsils to remove this obstruction.
Aberrant Turbinates -
In some animals, the ethmoid turbinates cannot fit into the nasal passage, and grow down into the nasopharynx, interfering with airflow.
This can be removed by laser ablation, though is rarely performed unless all other treatments have failed.
Tracheal Hypoplasia -
The animals (esp bulldogs) have an abnormally narrow trachea, that can reduce total airflow, especially during exercise.
Currently, this cannot be treated.
What are the secondary pathologies present in brachycephalic dogs that lead to the development of brachycephalic obstructive airway syndrome, and how can each be surgically treated?
Lateral Laryngeal Ventricle Eversion -
Oedema of the lateral laryngeal ventricles within the larynx, due to increases in the pressure in the airways.
Severe cases can be treated by surgical excision of the ventricles.
Minor cases may be left, as mild oedema may regress with the treatment of the other factors of the condition.
Laryngeal Collapse -
Failure of the extrinsic laryngeal muscles to control the opening of the larynx.
Occurs following chronic pressures on inspiration causing exhaustion of the muscles.
Treatment may be by laryngectomy, lateralisation of the arytenoids, or by permanent tracheostomy.
What post-op care should be provided to animals following surgical treatment for brachycephalic obstructive airway syndrome?
In some cases, the animals may have a temporary tracheostomy to permit oxygenation whilst the airways heal.
Should only be used for 24 hours at most.
The animals should have a soft food diet for 3-5 days to prevent trauma to the airways.
The animal should not be exercised for at least two weeks, and then should only have gentle exercise thereafter.
As the treatment is not curative, but instead only improves quality of life.
What is laryngeal paralysis, why may it develop, and how do affected animals present?
Damage to the laryngeal nerve, preventing the normal ability to open and close the arytenoid cartilages of the larynx.
More common idiopathically in older animals, though can also be due to trauma, iatrogenic damage, general neuropathies, neoplasms, etc.
Affected animals are generally less able to inspire normally, causing exercise intolerance, stridor/dysphonia, and potential cyanosis and collapse.
These animals may present similarly to animals in unstable obstructive crisis.
Partial opening also increases the risk of aspiration pneumonia, and may cause tracheitis and coughing.
How is laryngeal paralysis corrected surgically, how is the procedure performed, and what is the outcome for the animal?
Major aim is to permanently open the arytenoids to permit airflow.
This can be done intra- or extralaryngeally.
Main approach is by unilateral arytenoid lateralisation:
One arytenoid is externally disarticulated from the thyroid and cricoid, and sutured in an open position to the thyroid and cricoid cartilages.
Generally associated with a very good improvement in the animal, though have a reasonable chance (30%) of complication.
Main complications relate to incomplete abduction of the arytenoids, iatrogenic laryngeal damage, or aspiration pneumonia (as larynx permanently opened).
What is a tube tracheostomy, and when may its use be indicated?
Insertion of a specialised tube directly into the trachea, via the neck, so to provide the patient with oxygenation whilst bypassing the upper airways.
Should not be performed preferentially to standard orotracheal intubation.
Primary indications for use include:
Formation of a temporary airway to permit surgery of the oral cavity.
Long-term ventilatory support without obstructing the oral cavity.
Emergency provision of an airway, especially following damage/collapse of a portion of the upper tract.
What are the key design features of the tracheostomy tube, and what variances may it have?
Most of the tubes are made of plastic, designed to be single-use and disposable, and are bought in sterile packaging,
Some tubes may instead be made from metal, so can be cleaned and reused, but must be completely sterilised each time.
The appropriate tube for any animal should be half the diameter of the trachea, so allowing oral airflow to additionally pass.
This provides safety, should the tube become blocked.
Some tubes have an inflatable cuff which can seal the trachea should the patient require ventilation.
Some tubes may also have a removable inner sleeve that can be removed and cleaned of any mucous that may block airflow.
For what reasons may the trachea need to be surgically accessed, and how is this done?
Most common reasons for surgical access of the trachea in animals is for the placement of a tracheostomy tube and for the placement of support rings for tracheal collapse.
Less commonly done to repair trauma or to remove tumours/foreign bodies.
To perform the surgery, first the animal must be in dorsal recumbency, with the neck extended and aseptically prepared.
A midline incision should be made at the desired level (generally fourth/fifth tracheal interspace for tracheostomy), passing through the muscle and fat layers to the level of the trachea.
Care must be made not to damage any importnat structures (vessels/nerves/thyroid/etc).
Stay sutures should be placed into the trachea to stabilise it, and the required surgery should be performed.
For tracheostomy, this is by a single transverse incision through the fourth/fifth interspace through which the tube can be placed.
Care should be taken to prevent damage to the laryngeal nerves at the lateral aspect of the trachea.
What care should be provided to an animal with a tracheostomy tube, and how long should this last?
Any animal with a tube in place must have 24 hour in-person monitoring, in case of blockage.
If present, the inner cannula of the tube should be removed and cleaned regularly to prevent this.
The animal should receive mucolytics to reduce the viscosity of their muscous, so to minimise the risk of tube blockage.
Nebulised air may also be provided to loosen these secretions.
The tube should be removed as soon as is possible, and the wound should be left to heal by secondary intention.
What is a lung lobectomy, and for what reasons may it be performed?
Surgical removal of the whole, or part, of a lung lobe.
Uncommonly performed, but may be indicated in a number of diseases, such as:
Primary (or rarely secondary) pulmonary neoplasia, for removal of the mass.
Lung lobe torsions.
Severe abscessation/infection.
Bullous disease, often to resolve or prevent a pneumothorax.
Trauma.
What is the process of performing a lung lobectomy?
Following preparation of the patient, the thorax is entered by lateral 5th/6th intercostal thoracotomy on the appropriate side.
The lung lobe should be isolated from the other lobes by ligation and division of the pulmonary artery and vein supplying the lobe.
Caudal lobes should be detached from the diaphragm by cutting the pulmonary ligament.
The bronchus supplying the lobe should be clamped, divided and oversewn.
All vessels should be checked for leaks, then the remaining open tissue should be closed with a vascular staple gun.
What is a lung lobe torsion, what may cause it to occur, and how is it treated?
Twisting of one or more of the lobes of the lung around their blood supply, causing ischaemia.
Most commonly occurs in the right cranial or right middle lobes.
May occur spontaneously, but more common with a concurrent pleural effusion.
The effusion causes the collapse of the lobe (often those with the smallest SA:V), making it denser and smaller, allowing it to twist.
If occurring spontenously, then it is likely to set up a pleural effusion itself, so it is improtant to determine which occurred first (as primary effusion will require additional treatment).
Treatment of the torsion is done by lung lobectomy of the affected lobe(s).
The lobes should not be untwisted, as this would release inflammatory mediators and toxins from the affected lobes into the systemic circulation.
What may cause the development of a diaphragmatic rupture, what are its effects on the animal, and how can this be determined diagnostically?
Typically, the only cause of a diaphragmatic rupture is trauma.
Hence, in many cases, concurrent pathologies may be present (i.e. fractures, pneumothorax, haemorrhage, etc).
Changes in pressure regulation and the presence of a hole in the diaphragm will typically cause abdominal viscera (often the liver) to displace into the thorax.
This limits the room for lung expansion, and generally causes dyspnoea in the animal.
This can be identified radiographically or by ultrasound, by the detection of additional organs in the thorax and a loss of the clear diaphragmatic boundary.
When should a diaphragmatic rupture be treated, and what are the exceptions to this?
Due to traumatic origin of the condition, the patient should be stabilised and all other co-morbidities should be treated first.
The exceptions to this are when the life of the patient is threatened as a direct result of the consequences of the rupture.
These may include the herniation and dilation of the stomach through the diaphragm, strangulation of the intestines within the rupture, or unabating haemorrhage into the abdomen or thorax.
What are the major forms of congenital diaphragmatic herniation, why do they occur, and how do they appear radiographically?
Peritoneopericardial Diaphragmatic Hernia -
Occurs due to a failure of detachment of the pericardium from the peritoneum during development.
Hence, a constant connection between the pericardium and the abdomen is formed, allowing herniation of abdominal viscera into the pericardial space.
Appear on radiograph as a massive enlargement in the apparent heart size, with a contact to the diaphragm.
Oesophageal Hiatal Hernia -
More common in shar peis, though can occur in many breeds,
Occurs due to an enlargement of the oesophageal hiatus, allowing herniation of the stomach through it and into the thorax.
More rarely may also cause herniation (and possible strangulation) of loops of small intestine also.
Can be identified radiographically by visualisation of the stomach across the diaphragm.
Can be improved by contrast medium
What is the process of surgical correction of diaphragmatic ruptures and hernias?
Should be performed from the abdomen, which is accessed by a ventral midline incision.
Any herniated viscera should be returned to the abdomen by gentle traction, and any adhesions should be removed.
In some cases, this may require enlargement of the diaphragmatic opening.
The diaphragm can then be closed, starting caudally, and working cranially.
The first suture can be used as a stay suture to improve the ease of suturing,
Care should be taken to avoid the major nerves and vessels supplying the diaphragm.
What is the process of treatment of an oesophogeal hiatal hernia, and why is it different to the closure of other diaphragmatic hernias?
Due to the physical attachment of the oesophagus and the stomach, simple closure of the hiatus could still potentially permit recurrence.
Hence, each offending structure must be secured in place.
The correction is performed via the abdomen, by a ventral midline incision.
The stomach should be returned to the abdomen by gentle traction, and should then be detached from the diaphragm by cutting the phrenoesophogeal ligament.
The stomach should then be secured to the abdominal wall by a gastropexy.
Can be a tube gastropexy to ensure nutrition of the animal during recovery.
The oesophagus should then be secured at the hiatus, and the hiatus sealed, by oesophagopexy.
