depending on severity of disease. Concentrations of pCO2 and sodium should be particularly closely monitored.
Treatment
Immediately stop infusion of NaHCO3 if signs or respiratory distress or tachypnea occur. Measure blood sodium levels and administer isotonic replacement fluids (e.g. Lactated Ringer’s) at a rate slightly higher than maintenance if Na levels are within normal limits; otherwise, follow recommendation in the paragraph on Sodium Imbalances.
Expected outcome
The outcome depends on the severity of the case. Animals can potentially die from respiratory failure or worsening of acid–base and electrolyte abnormalities. If treatment is instituted and the animal responds, full recovery is usually observed.
Complications Due to Glucose‐/Dextrose‐Containing Fluids
Definition
Abnormal blood glucose levels (reference range: 3.7–6.7 mmol/L). The terms glucose and dextrose can be used interchangeably. Glucose exists as two isomers. L‐glucose is the isomer circulating in the blood of animals and humans, while D‐glucose (known as dextrose) is the isomer occurring widely in nature.
Risk factors
Neonates (hypoglycemia)
Patients with metabolic disease are at high risk of hyperglycemia (Equine metabolic syndrome, pituitary pars intermedia dysfunction)
Sepsis (both hypo‐ and hyperglycemia can occur)
Pathogenesis
Carbohydrate‐containing solutions are commonly used to provide additional energy as a simple means of parenteral nutrition. If administration of glucose exceeds the utilization by tissues, hyperglycemia ensues. Animals with metabolic disease or sepsis have impaired glucose uptake by cells due to insulin resistance contributing to hyperglycemia. Hypoglycemia very rarely occurs in adult horses. Neonates however, have low glucose storage capability and are at risk of hypoglycemia if glucose intake is reduced. In septic animals, particularly neonates, glucose consumption by bacteria and increased cell demands due to inflammatory mediators leads to hypoglycemia.
Prevention
Recommendations are to maintain serum glucose within narrow margins and avoid hypo‐ or hyperglycemia [27]. To avoid hyperglycemia, glucose‐containing fluids should not be administered for initial large‐volume fluid resuscitation. This can lead to profound hyperglycemia with a diuretic effect causing massive diuresis. If milk is withheld for more than 12 hours in neonatal foals, glucose‐containing fluids should be administered. In horses, it is reasonable to use a 2.5–5% dextrose‐containing polyionic fluid as maintenance therapy. Isotonic Glucose (5% glucose in water) should not be used as a general maintenance fluid due to the absence of electrolytes. This solution is useful for providing large amounts of water to patients with hyperosmolar syndrome but does have in vivo acidifying effects.
If a fluid amount higher than the maintenance rate has to be administered to a horse or foal to cover additional losses or treat dehydration, it is often better to give a glucose‐free polyionic crystalloid solution separately and to add 50% dextrose as a separate infusion set using an infusion pump. In this way, the amount of glucose can be titrated properly and separately from the amount of other fluids infused. Polyionic crystalloid glucose‐free fluids should always be given simultaneously through the same catheter as the 50% dextrose, to dilute the hyperosmolar solution and avoid endothelial injury. An infusion pump should always be used for infusion of 50% dextrose to avoid glucose overload. 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.
