You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

The use of colloid fluid therapy is widespread in veterinary practice, but there are variable recommendations for the dose rates to avoid adverse side-effects.

Studies in normal dogs indicate that dextrans (and to a lesser extent hetastarches) in synthetic colloid solutions may cause coagulation problems due to :

• Decreased concentrations of von Willebrand factor
• Haemodilution
• Platelet membrane coating
• Precipitation of coagulation factors

These changes can lead to prolonged prothrombin time (PT), prolonged activated partial thromboplastin time (APTT), a lowered platelet count and haemorrhage. However, these effects can be prevented by the concurrent administration of small volumes of fresh frozen plasma.

In normal dogs colloids remain in the circulation until they are metabolised and excreted through the kidneys, and as a result volume overload has been reported to occur in normal dogs given high doses. However, overload is rare in critically ill patients which are haemorrhaging or losing fluids into effusions. Overload can be prevented by monitoring central venous pressure during fluid administration.

Based upon the occurrence of these adverse side-effects in studies in normal dogs it is usually recommended that the dose rate of colloid fluid replacement does not exceed 20mg/kg body weight/day. However, in practice some authors use much higher doses in critically ill cases (King L.G., ACVIM Proceedings 1994), particularly if hypoproteinaemia is present. Dose rates of up to 40ml/kg of hetastarch have been administered over a 6 hour period without clinical bleeding, and volume overload is reported to be rare in critically ill dogs given colloids. 

One recommendation is that colloids should be given at one third of the total fluid rate required for the patient, eg give crystalloid solutions at 200ml/hour and colloid at 100ml/hour for a dog requiring 300ml/hour.

Updated January 2016