Emergency and critical care applications of interventional radiology (Proceedings)
Following the trends in human medicine, there is an ongoing effort to adapt and develop minimally invasive therapeutics for the management of various problems facing veterinary patients. Minimally invasive therapeutics offer the advantages of smaller incisions, decreased pain, shortened anesthesia times and shorter length-of-stay compared to traditional open surgical approaches. Currently in veterinary medicine, laproscopy, thoracoscopy, minimally invasive orthopedic procedures, endourology, and interventional radiology (IR) are meeting this demand.
Interventional radiology (IR) involves the use of contemporary imaging modalities such as fluoroscopy, endoscopy, ultrasound, CT, and MRI (or combinations thereof) to gain access to different structures in order to deliver materials for therapeutic purposes. IR is a subspecialty of radiology in human medicine. IR techniques have been widely utilized in human medicine for the past 20-30 years to effect minimally invasive diagnostic and therapeutic outcomes. Applications of IR in veterinary medicine are just being realized. The purpose of these proceedings is to present current applications of IR in veterinary medicine with an emphasis on applications of IR in Emergency and Critical Care Settings.
Equipment & Training:Many IR procedures require advanced imaging modalities. Fluoroscopy is a critical tool for performing most IR procedures. In IR, an array of guide wires with various properties, catheters specifically adapted for individual procedures, stents composed of different materials and configurations, embolic coils, embolic particles, drainage devices, surgical glue, oils, chemotherapeutic agents, occlusion devices, balloons, etc. replace the standard surgical pack.
Because IR is so new to veterinary medicine, there are only few formal IR programs in the country. They are at Michigan State University and the Animal Medical Center in New York City. However, many training opportunities exist for specific procedures through various continuing education meetings and organizations.
IR Applications in the Emergency and Critical Care Setting:
Tracheal collapse: Tracheal collapse is a common affliction of small breed dogs. Traditional management of tracheal collapse is centered on medical management (cough suppressants, corticosteroids, management of concurrent problems). Surgical management using prosthetic rings placed around the cervical trachea is an option in patients with cervical tracheal collapse that fail medical management. Surgical management of tracheal collapse tends to be invasive and is associated with a significant incidence of acute complications and limitations including but not limited to disruption of the tracheal blood supply, injury to the recurrent laryngeal nerve causing laryngeal paralysis, and the inability to access the intrathoracic trachea.
Tracheal stent placement involves the placement of an intraluminal self-expanding metallic stent that holds the trachea open.1 Placement requires the use of fluoroscopy. Tracheal stenting offers a very rapid, non-surgical (everything is done through the airway) treatment option for animals with tracheal collapse. The incidence of acute complications is very low when compared to prosthetic ring placement provided the stent is sized and deployed appropriately. Long-term complications may include shortening of the stent as it expands to its nominal diameter with subsequent collapse cranial to the stent, stent fracture (likely precipitated by coughing and excessive over sizing of the stent during placement), and inflammatory tissue formation at the ends of the tracheal stent. As a result, ongoing medical management is still important although most patients require a much less rigorous medication protocol.
In the emergency setting, some dogs with acute respiratory embarrassment secondary to tracheal collapse require intubation and positive pressure ventilation when traditional measures to stabilize them fail (sedatives, oxygen therapy, corticosteroid therapy, and cough suppression). In this setting, attempts are generally made to extubate the dog while facilitating a slow recovery from anesthesia in an effort to minimize respiratory effort. When the patient is unable to be extubated, definitive care is necessary. Placement of a tracheal stent is a technique that provides this patient population with a rapid, minimally invasive, and effective technique to restore the patency of the tracheal lumen.
Overall, the author recommends tracheal stent placement for dogs with tracheal collapse that are not having good quality of life in the face of medical management, those with intrathoracic tracheal collapse, and those whose owner does not wish to pursue a surgical treatment option. Dogs with intrathoracic tracheal collapse and mainstem bronchial collapse often benefit significantly from tracheal stent placement although they often continue to cough due to the mainstem bronchial collapse. Cervical tracheal collapse may be treated through traditional surgical techniques or placement of a tracheal stent. The entire procedure takes approximately 30minutes and usually requires only 24 hours total hospitalization. It is important for clients to recognize that tracheal collapse is a progressive condition. This being said, tracheal stent placement offers an excellent palliative treatment option. Tracheal stent placement also offers an excellent palliative treatment for animals with airway obstruction due to neoplasia.2