vascular disease in the horse

Question 1

what are the two types of jugular thrombosis in the horse?

Answer 1

Non-septic
- Thickening “cording” of the vein
- Reduction in patency and blood flow

Septic
- Hot
- Painful
- Discharging tracts (chronic)

Question 2

what is the aetiology and what are the clinical signs of jugular thrombosis?

Answer 2

aetiology:
Most (all) cases of jugular thrombosis are associated with intravenous catheterisation or injection

Jugular thrombosis results in Venous occlusion
* Swelling in the supraorbital area
* Cheek and lips
* Tongue
◦ Leading to dysphagia
* Upper airway obstruction
◦ Nasal airflow test
* Proximal venous distension

Question 3

what are the predisposing factors of jugular thrombosis inthe horse?

Answer 3

• Systemic inflammatory response syndrome
• Multi-organ dysfunction syndrome
• Irritant drugs
• Poor catheter placement
• Poor catheter use

Question 4

how is jugular thrombosis diagnosed?

Answer 4

Ultrasonography is used to:
* Assess extent of thrombus
* Identify sepsis (cavitation)
* Assess patency of vein
* Distinguish perivenous swelling from thrombosis
* Select site for aspiration

discharging tract tracts form the thrombus to the skin

Culture
* Catheter tip
* Ultrasound-guided aspirate fluid pocket from within thrombus
* Swab from discharging tracts
* Blood

Question 5

how is jugular thrombosis treated and what is the management of a horse with thrombosis that still needs venous access?

Answer 5

Treatment:
* Broad spectrum antibiotics
* Anti-inflammatories - to prevent further clot build up
◦ Systemic
‣ Aspirin
‣ Other NSAIDs
◦ Topical
‣ DMSO
‣ Hot packs
* Heparin
◦ or analogues
* Vasodilators
◦ Glyceryltrinitrate
* raise head

Management:
Alternative venous access
* Lateral thoracic (just behind the forelimb)
* Cephalic (more difficult to manage, come out easily)

With bilateral thrombosis, tracheostomy may be required

Question 6

what are the complications of jugular thrombosis in the horse?

Answer 6

Embolic disease (parts of thrombus break off and travel to distant parts of the body) can then cause:
◦ Bacterial endocarditis
◦ Septic Pneumonia (as lodges in pulmonary vessel)

Long term poor performance due to:
◦ Recurrent laryngeal neuropathy (runs close to jugular vein, swelling in region can damage nerve)
◦ Upper airway oedema during exercise (blood flow to head increased as increased cardiac output during exercise)

Question 7

what are the catheter material options for use in the horse?

Answer 7

Cheaper but more thrombogenic
* Teflon, nylon and polyvinylchloride
* life span of 72 hours

More expensive but less thrombogenic - use for longer periods of catheterisation
* Polyurethane
* life span 7-21 days

Question 8

what are the catheter design options for use int he horse?

Answer 8

• Rigid over-the-needle catheters are more thrombogenic but are easier to place - ideal for emergency situations
• Flexible catheters are less thrombogenic but require wire-guided placement

Question 9

what ar the key aspects of catherter care to prevent jugular thrombosis?

Answer 9

• Extension sets to avoid excessive manipulation of hub
• Swab injection ports
• Change ports and fluid lines Q24hrs
• Change fluid bags in sterile manner
• Appropriate lifespan
• Covering and application of antiseptics are controversial
  ◦ Helpful in foals to stop them scratching the catheter out, may increase risk of infection

Question 10

when a catheter breaks it may be attached to jugular wall, therefore can be removed, but when not attached to jugular wall and catheter breakage (embolism) occurs it can do what?

Answer 10

◦ Adults – travel to lungs and rarely cause problems
◦ Foals – stick within heart and require surgical removal

Question 11

What is aortoilic thrombosis? what is the aetiology and clinical signs?

Answer 11

Partial or complete occlusion of the terminal aorta, and external and internal iliac arteries by an organising thrombus

Aetiology unknown
* Parasitic - unlikely

clinical signs:
* Poor performance
* Exercise-associated hindlimb lameness (i.e. exacerbated by exercise: differential for exertional rhabdomyolysis)
* Breeding failure in stallions
* After exercise
◦ Cold limb
◦ Weak pulses

Question 12

how is aortoiliac thrombosis diagnosed and treated in horses? what is the prognosis?

Answer 12

Diagnosis:
* Palpate thrombus, turgid vessel on rectal examination
* Visualise the thrombus with transrectal ultrasonography
* Vascular phase scintigraphy - not common

Treatment
* Non-steroidal anti-inflammatory drugs
* Aspirin
* Fenbendazole (larvicidal, anti-thrombotic effect?)

Prognosis - Guarded

Question 13

what are the most common sites for vascular rupture inthe horse?

Answer 13

• Any intra-abdominal or intra-thoracic vessel can rupture
  ◦ Aorta and pulmonary artery appear to be most common sites

Question 14

Vascular rupture and haemoperitoneum is an important differential in horses that present with severe distress following strenuous exercise (particularly if colic-type pain is noted), what are the other differentials that should be consided?

Answer 14

• Stress fractures
• Exertional rhabdomyolysis
• Arrhythmias
  can be confused with colic type symptoms

Question 15

what is the aetiology of vessel rupture in the horse?

Answer 15

Pre-existing aneurysm
* Tunica media degeneration
◦ Congenital
◦ Parasitic
‣ 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, and this might not be the cause of certain types of vascular rupture

Question 16

What vascular disease can occur in Periparturient broodmares, particularly immediately before or after foaling, but up to three weeks after?

what is the management?

Answer 16

Rupture of the uterine vessels - uterine artery, external iliac artery

◦ Conservative
◦ Support circulation
◦ Analgesics
◦ want to avoid excessive movement as this can dislodge clots

prognosis for a severe uterine bleeds is poor

transexamic acid to promote clotting is the most commonly used in equine medicine

Question 17

what congenital or aquired conditon can occur to the aortic wall? what is the signalment of this disease and when is it typoically seen, what are the clinical signs, how is it diagnosed and what is the prognosis?

Answer 17

Aorto-cardiac fistula
* Seen mainly in intact males
* Rupture occurs during exercise or breeding
◦ Sudden death
◦ Distress
◦ Ventricular tachycardia
◦ Loud continuous murmur

Diagnosis: Echocardiography

Prognosis: hopeless