Complications in Equine Surgery. Группа авторов

The energy requirement in an adult healthy horse is approximately 40 kcal/kg/day. A 5% dextrose solution contains 0.17 kcal/mL. An infusion rate of 10 mL/kg/h would be required to provide the daily energy requirement. This is a much higher rate than maintenance fluid requirements and potentially does result in fluid overload. A 5% dextrose solution is therefore not adequate to provide enough dextrose to cover the energy requirements of a horse long term.

A 50% dextrose solution contains 1.7 kcal/mL and can provide approx. 41 kcal/kg/day when used at 1 ml/kg/h and may meet short‐term energy requirements. It should be kept in mind that this form of parenteral nutrition does not cover amino acid (protein) needs. Some patients also do not tolerate this amount of dextrose and respond with hyperglycemia. Therefore, parenteral or partial parenteral nutrition with solutions containing carbohydrates, amino acids and lipids should be considered in adult horses where parenteral nutrition is required for >48–72 h (foals >24 h).

       Diagnosis

      Clinical signs and blood glucose concentrations are used for diagnosis. Hyperglycemia has been shown to be detrimental and causes increased morbidity and mortality in human and equine patients. Clinical signs of hyperglycemia only occur in chronic cases. Clinical signs of hyperglycemia are vague (reduced wound healing, etc.) but polyuria and polydipsia can occur if glucosuria is present. Hypoglycemia can lead to weakness, and when severe to seizures.

       Treatment

      In patients with hyperglycemia, discontinue administration of glucose‐containing fluids if possible. If glucose‐containing fluids are necessary as a form of parenteral nutrition, insulin can be added to the fluid regimen to decrease blood glucose. See later in this chapter for further complications, monitoring and prevention of hyperglycemia associated with the use of carbohydrate‐containing solutions as parenteral nutrition.

       Expected outcome

       Depends on severity.

       Animals can potentially die from seizures in hypoglycemia.

       Persistent hyperglycemia in human medicine has been associated with higher morbidity and poor outcomes overall.

       If treatment is instituted and the animal responds, full recovery is possible.

Complications Associated with Intravascular Plasma Administration

      Plasma transfusion has become part of the standard of care for critically ill adult horses and foals in equine hospitals. The most common indication in the peri‐operative period is to achieve an increase in colloid osmotic pressure to treat hypoproteinemia. This often occurs associated with gastrointestinal disease in colic patients. Other indications for surgical patients include presence of coagulopathies and foals with failure of transfer of passive immunity. Homemade and commercial plasma from commercial plasma banks are being used [28–30]. Complications associated with administration of plasma include immunogenic and non‐immunogenic reactions, serum hepatitis, transmission of disease and septicemia due to bacterial contamination. Severity or reactions range from mild urticaria to severe anaphylaxis with occasional death.

      Immunological Reactions

       Definition

      Immunogenic transfusion reactions are classified as acute or delayed. Acute reactions include hemolysis, non‐hemolytic systemic fever reactions and anaphylaxis. The only delayed immunologic transfusion reaction reported in veterinary medicine is post‐transfusion purpura occurring in a previously blood transfused dog with hemophilia.

       Risk factors

       Foals <7 days [31]

       Patients that have received multiple previous transfusions

       Multiparous mares

       Hypernatremic animals

       Pathogenesis

      The immunogenicity of blood products stems from proteins and from other cellular material not completely removed during production. Generally hemolytic transfusion reactions are the result of antibodies in the recipient plasma reacting with the erythrocytes of the donor. These types of reaction should therefore not occur if the plasma is free of red blood cells. Minor reactions can occur when antibodies present in the plasma of the donor react with the red blood cells of the recipient. Non‐hemolytic febrile reactions are thought to occur due to leukocyte antigens on transfused lymphocytes, granulocytes or platelets and antibodies in previously sensitized recipients. Urticarial reactions are not well understood but are believed to occur due to proteins in the donor blood and antibodies in the recipient blood. There is usually not a specific antigen against which the recipient is reacting. Systemic anaphylaxis is the most severe form, which in humans is linked to IgA antibodies but unknown in horses. Immunological transfusion reactions are reported as <10% in horses [29, 31]. Plasma can also contain large amounts of sodium, which could lead to clinically significant hypernatremia in small patients (e.g. neonates).

       Prevention

       Type of plasma

       It has been suggested that commercial plasma leads to fewer adverse side effects than home‐made plasma, although this was not supported by a clinical study in a hospital setting [31].

       Method of plasma preparation could play a role in incidence of adverse effects. Plasma prepared by gravity or centrifuge sedimentation contains a greater amount of cellular material compared to plasma obtained by plasmapheresis. Therefore, the latter preparation method could potentially lead to a lower incidence of immunological reactions [30]. Plasmapheresis is well tolerated by horses and used for collection of plasma without complications but requires specialized equipment.

       Cross‐matching before plasma transfusion would only be able to prevent hemolytic transfusion reactions, which are the result of antibodies in the recipient plasma reacting with the erythrocytes of the donor. This is a very rare occurrence. Cross matching before plasma transfusion is rarely performed.

       Using blood products from a “universal donor” negative for Aa and Qa antigen can help prevent severe reactions. While horses have many different blood antigens, only Aa and Qa are responsible for the majority of severe hemolytic reactions.

       Plasma from geldings or maiden mares is preferred over stallions and mares with prior pregnancies.

       Administration of plasma

       Frozen plasma should be thawed at 30–37°C, in a water bath prior to administration to avoid precipitation of proteins which can occur when thawed at a higher temperature, (e.g. in a microwave).

       Plasma transfusions should be administered using a blood administration set with a filter to reduce the number of clots transfused. Blood clots travel through the systemic circulation and lead potentially to cardiac side effects or pulmonary artery obstruction resulting in fatal incidents.

       The plasma transfusion should be started at a rate of 0.3–0.5 mL/kg/ for the first 10–20 minutes. During this time the horse should be continuously monitored for signs of adverse reactions and a brief physical examination should be performed every 5 minutes. Parameters that should be monitored and should not increase during that time include heart rate, respiratory rate and temperature. The occurrence of respiratory distress, cardiac arrhythmias, urticaria, muscle tremors, salivation and coughing should also be monitored. If no reaction occurs, the plasma can be administered faster.

       Other

       If multiple plasma transfusions are required within a short period of time, preferably