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See Chapter 3: Complications of Intravascular Injections and Catheterization.

Definition

Thrombophlebitis

Risk factors

 Self‐made solutions carry a higher risk of bacterial contamination

 Use of small veins for parenteral nutrition

 Single lumen catheter used for all medication, fluid therapy and parenteral nutrition

Pathogenesis

Parenteral nutrition solutions are hyperosmolar and can therefore lead to an increased risk of thrombophlebitis, particularly when peripheral small veins are used. The nutrients in parenteral solution provide a breeding environment for bacteria, leading to an increased risk of catheter‐associated sepsis/toxemia.

Prevention

Self‐made solutions should be prepared aseptically under a lamellar flow hood under aseptic conditions. A sterile bag should be used and injection ports should be wiped with alcohol to reduce bacterial contamination. Dextrose and amino acids should be added first followed by lipids to avoid lipids coming out of emulsion. Once compounded the solutions should be refrigerated and used within 24 hours. Commercial solutions have a longer shelf‐life (~2 years) and can be kept in stock. They are also less likely to become contaminated but are more costly than self‐made solutions. Factors such as pH, sunlight and addition of other solution can affect the stability of the lipid emulsion. This can lead to lipid droplets coalescing; the large lipid droplets cannot be cleared and could lead to lipid embolization of small vessels.

Initially, recommendations were to use large central veins; however, due to the size of the jugular vein and its accessibility, this vein is commonly used and few complications have been reported in horses. The lumen of the catheter should be designated for parenteral nutrition only. If only one catheter can be placed, a double lumen catheter can be used to allow for concurrent administration of medication and fluid therapy. Bags and tubing should be changed every 24 hours to avoid contamination of bacteria. The bag and tubing should not be detached from the horse during the day. If the horse has to be walked, the tubing and bag should go with the horse.

Diagnosis and clinical signs

Clinical signs of thrombophlebitis are fever, heat and swelling around the catheter insertion or distal to the catheter insertion, distended jugular vein and reduced emptying or prolonged filling of the jugular vein. Inflammatory parameters in the blood such as leukocytes, serum amyloid A and fibrinogen are often elevated.

Treatment

Parenteral nutrition through the affected vein has to be discontinued and the catheter removed. The reader is referred to Chapter 3: Complications of Intravascular Injection and Catheterization, for treatment and expected outcome of thrombophlebitis.