vascular disease

• The most important vascular diseases are…

  • Jugular thrombosis
  • Aortoiliac thrombosis
  • Vascular aneurysms and rupture
• There are two types of jugular thrombosis…

  A) thickening

  B) reduction

  C) hot

  D) painful

  E) discharging

  
• • Venous occlusion occurs with jugular thrombosis which can lead to…
  • Swelling in the supraorbital area, cheek, lips and tongue (due to the jugular vein being the main vessel for drainage of the head). This can then lead to dysphagia and upper airway obstruction.
  • Nasal airflow tests should be considered where there is URT obstruction
  • Proximal venous distension across the face may also be noted
• Most (all) cases of jugular thrombosis are associated with intravenous catheterization or injection

  • Predisposing factors include…
  • Systemic inflammatory response syndrome, SIRS
  • Multi-organ dysfunction syndrome, MODS
  • Irritant drugs (most IV drugs are and lead to vasculitis and thrombosis)
  • Poor catheter placement
  • Poor catheter use
• Ultrasonography is used to confirm the diagnosis of jugular thrombosis and allows…

  • Assessment of the extent of the thrombus
  • Identification of sepsis (cavitation)
  • Assessment of the patency of the vein (i.e., is there blood flow or a complete obstruction)
  • Distinguishing perivenous swelling from thrombosis
  • Selection of the site for aspiration (for culture)
• Culture allows confirmation of bacterial involvement in jugular thrombosis and can be performed with…

  • Catheter tip (easy to do)
  • Ultrasound-guided aspirate fluid pocket from within the thrombus
  • A swab from discharging tracts
  • Blood
• Treatment of jugular thrombosis involves…

  • Broad spectrum antibiotics
  • Anti-inflammatories (which prevent further platelet aggregation)
  • Heparin or analogues (as an anti-coagulant)
  • Vasodilators e.g., Glyceryl trinitrate to improve blood flow around the thrombus
  • Raising the head to reduce the swelling around the head and proximal neck
• • Management of jugular thrombosis involves…
  • Obtaining alternative venous access e.g., via the lateral thoracic (just behind the forelimb) or cephalic (more difficult to manage as it is around the limb). Depending on the situation (needs to be done for those that need IVFT or IV medication), the Placement of these catheters can be blind or US guided.
  • With bilateral thrombosis, a tracheostomy may be required due to swelling around the larynx and pharynx caused by oedema in the head/neck.
  • Surgical procedures to strip and/or graft the vein have been described but are rarely done
• • Complications of jugular thrombosis include…
  • Embolic disease (part of the thrombus breaks off and collects in another region of the body) a sequelae is bacterial endocarditis (affecting the cardiac valves) and septic pneumonia (pulmonary vessel lodging)
  • Long term poor performance due to…
  • Recurrent laryngeal neuropathy (the recurrent laryngeal nerve lies near the jugular vein and hence swelling of the vein can impact the nerve)
  • Upper airway oedema during exercise (blood flow is increased due to the increased cardiac output that occurs during exercise leading to the oedema)
• Aortoiliac thrombosis can cause a partial or complete occlusion of the terminal aorta, and external and internal iliac arteries by an organizing thrombus. The cause is unknown

  • Parasitic causes are unlikely despite previous theories
  • This can cause…
  • Poor performance
  • Exercise-associated hindlimb lameness (i.e. exacerbated by exercise)
  • This is also a differential for exertional rhabdomyolysis as the clinical signs are also exacerbated by exercise
  • Breeding failure in stallions
  • Cold limbs and weak pulses after exercise
• Aortoiliac thrombosis diagnosis involves…

  • Palpation of the thrombus, turgid vessel on rectal examination (distended turgid vessels)
  • Visualisation of the thrombus with transrectal ultrasonography (blood is not anechoic due to the cellular content)
  • Vascular phase scintigraphy but this is not common in practise
• Aortoiliac thrombosis has a guarded prognosis but treatment involves…

  • Non-steroidal anti-inflammatory drugs
  • Aspirin
  • Fenbendazole (larvicidal with possible anti-thrombotic effects)
  • While it is not thought that parasites are involved (Strongyles vulgaris) this is not known for certain and hence they are treated with an anthelmintic as a precaution
• The thrombus is in a distended vessel and the appearance is more hyperechoic than normal

  A) thrombus

  
• Vascular rupture is the most common form of sudden death during exercise in horses. Any intra-abdominal or intra-thoracic vessel can rupture but the aorta and pulmonary artery appear to be the most common sites

  • Vascular rupture and hemoperitoneum is an important differential in horses that present with severe distress following strenuous exercise (particularly if colic-type pain is noted). Other differential diagnoses include…
  • Stress fractures
  • Exertional rhabdomyolysis
  • Arrhythmias
• • Vascular Rupture is caused by a pre-existing aneurysm which can be due to…
  • Medial degeneration
  • Congenital
  • Parasites
  • Large strongyles are more likely to affect the cranial mesenteric arteries and be associated with colic. The role of migrating strongyles in other vascular diseases may have been over-emphasised (hence may not always be the underlying cause of vascular rupture)
• fill in the blanks

  A) periparturient

  B) colic

  C) broad

  D) poor

  E) entire

  F) males

  G) tachycardia

  H) continuous

  I) echocardiography

  
• When performing an IV injection be sure to inject in the proximal third of the neck as this avoids the carotid artery (less superficial the artery is the more proximal you are). Remove the needle from the syringe (to assess blood flow after injection - if pulsatile and high flow redirect the needle) and push the needle right into the hub (which increases stability of the needle).

  • 18 Guage, 1/5 inch needle should be used
• Important factors with intravenous catheterisation are…

  • Catheter insertion should be done under a sterile technique
  • Ensure minimal trauma to the skin and surrounding tissues
  • Secure appropriately in the jugular furrow
• There are different types of catheter material…

  • Cheaper but more thrombogenic e.g., Teflon, nylon and polyvinylchloride
  • More expensive but less thrombogenic e.g., Polyurethane. These should be used in periods of long catheterization
• There are also different types of catheter design…

  • Rigid over-the-needle catheters
  • These are more thrombogenic but are easier to place. Hence may be the catheter of choice in emergency situations.
  • Flexible catheters
  • These are less thrombogenic but require wire-guided placement. These are often placed in foals or sick animals where the risk of thrombosis is higher
• tips when using intravenous catheterisation…

  • Use extension sets to avoid excessive manipulation of hub
  • Swab injection ports before injection
  • Change ports and fluid lines every 24 hrs in a sterile manner to prevent bacterial contamination
  • bags should also be changed ina sterile manner
  • Ensure an appropriate lifespan for the type of catheter used.
  • Covering and application of antiseptics are controversial
  • These are helpful in foals to stop them scratching the catheter out (as they spend more time lying down)
  • However doing this may increase risk of infection
• • PCV catheters should only be in place for a maximum of 72 hours
  • Polyurethane catheters can be in place for 7-21 days with good care
• Complications of IV catheterization include…

  • Jugular thrombosis
  • Catheter breakage.
  • This breakage may be attached to the jugular wall and therefore can be removed. However, if it is not attached…
  • In adults, they can travel to the lungs but they rarely cause problems
  • In foals, they can stick within the heart and require surgical removal