Texas Equine Veterinary Association

www.texasequineva.com • 11 Table 1 Sedative Dose, route Diazepam 0.05-0.4 mg/kg IV Midazolam 0.06-0.1 mg/kg IV or IM Butorphanol 0.01-0.04 mg/kg IV or IM An important skill to develop is the sonographic evaluation of the umbilicus. When ultrasounding the umbilicus, start at the stump and work your way caudal where you can see the umbilical arteries side by side from the urachus until they reach the bladder and then scan cranially from the stump where you can see the umbilical vein until it reaches the liver. Table 2 shows the umbilical measurements of normal foals. Table 2 Structure Ideal measurement Umbilical vein Less than 1 cm Umbilical artery Less than 1.3 cm Urachus + Umbilical arteries Less than 2.5 cm (Reef. V, et al, 1988) Once a full physical exam is performed by 12–24 hours, the IgG status should be determined. There are different types of test to determine concentration levels of IgG, although the fastest and most practical test is the concentration enzyme immunoassay test (SNAP test) which has readily available results in 7–10 minutes to allow the veterinarian to make any important decisions quickly. Failure of passive transfer can be secondary to premature lactation from the mare, low quality colostrum, orphan foals, foal rejection by mare, fescue toxicity, prematurity, and PAS. Collecting blood at 12 hours allows you to have multiple options as far as replacing the immunoglobulins depending on the result of the test. The newborn foal's small intestine has specialized enterocytes that allow for absorption of large particles including antibodies present in the colostrum of the mare for the first 6–8 hours and up to 24 hours of life. A complete failure of passive transfer is considered if the IgG value is less than 400 mg/dl, partial failure if it is between 400– 800 mg/dl and adequate passive transfer if it is greater than 800 mg/dl. Although, there is lack of scientific evidence between the association of failure of passive transfer and sepsis; both complete and partial failure of passive transfer are treated. The treatment option will depend on the age of the foal. If the foal is less than 8 hours of age, there is still the chance of attempting to replace the IgG orally by administration of banked colostrum if available. If the foal is 12–24 hours old, the IgG should be replaced intravenously as the intestinal absorption will not be reliable. IgG is the most abundant antibody to protect against infections in foals. The typical dose for plasma administration is 20 ml/ kg which is equivalent to ~1L for a 45kg foal. Plasma is the ideal immunoglobulin replacement as it not only contains IgG but it contains clotting factors, provides colloidal support, and has anti-endotoxic properties. The lower the IgG the higher the chances that more than 1 L of plasma would be required to be transfused. It is important to also keep in mind that plasma transfusion may have less effect in septic foals as these sick foals will sequester IgG in sites of inflammation, intravascular spaces, and they can catabolize IgG faster causing IgG to have a shorter half-life. Intravenous administration of serum (Seramune) has been done by clinicians as well due to being less costly and more conveniently stored. Previous studies have compared the effects of both intravenous treatments on final IgG concentrations, revealing that similar concentrations are achieved with 1 unit of plasma compared to 2–3 units of serum. Thus, plasma may still be a better option despite the additional cost and difficulty of storage. (MCClure. J.T, et, al. 2001) During the process of product transfusion, close monitoring of vitals and a slow rate of administration is imperative due to possible transfusion reactions. If an increase in vitals is noted, distress, or colic, then the plasma transfusion should be discontinued and the plan re-assessed. A dose of anti-inflammatories or even steroids or epinephrine may be needed depending on the severity of the reaction. At the time of collecting blood for the IgG concentration, if the foal has any indication of being ill, a complete blood count (CBC) and chemistry (CHEM) may be helpful to evaluate further the condition of the neonate. The CBC will give you valuable information to determine or confirm if the foal has evidence of sepsis as demonstrated by a low white blood cell count, potentially immature neutrophils (bands), and toxic changes (Dohle bodies). The CHEM will be useful to determine organ function (especially kidneys), acid base status, electrolyte derangements, and protein levels. It is not uncommon for a foal born out of a mare with a degree of suspected placentitis to have elevated creatinine values due to poor perfusion of the foal's urine in utero via the placenta. This value should not be ignored as it can reach high levels and fluid therapy should be instituted in case the cause is primary renal insufficiency and not spurious hypercreatinemia. A decrease in creatinine to normal values should be reached before 72 hours of being born if it is placental in origin. Foals that have a hypoproteinemia should be treated with conservative fluid therapy as they can be easy to fluid overload. The goal of initial fluid therapy is to expand vascular volume to maintain cardiovascular function. Therefore, when electing a type of fluid to administer to keep the foal on maintenance or correct a dehydration, care should be taken as foals have a harder time regulating sodium within their system. Usually a lower sodium content fluid such as Lactate ringers or half strength saline (0.45%) is better tolerated. These fluid choices may need to be re-evaluated if there are significant electrolyte derangements in conditions such as with a bladder rupture. The fluid rate at which these are delivered depend on the hydration status of the foal but the dry maintenance rate, known as the Holliday-Segar formula, has been widely used. See table 3. Table 3 Body weight Fluid Volume For the first (1-10 kg) of body weight 100ml/kg/day For the second (11-20 kg) of body weight 50ml/kg/day For any excess of 20kg 25ml/kg/day If the foal is unable to nurse frequently, then dextrose

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