Jump-Starting the Dummy Foal

In his presentation "Jump Starting the Dummy Foal" at the 2003 American Association of Equine Practitioners' convention, Bill Bernard, DVM, Dipl. ACVIM, of Rood and Riddle Equine Hospital in Lexington, Ky., began by saying that the term "dummy foal" is being used less and less. A more accurate term for the foal exhibiting behavioral or neurologic abnormalities that are not related to infectious or toxic conditions, congenital or developmental abnormalities, or metabolic disorders is hypoxic ischemic encephalopathy (HIE). Sometimes the term "neonatal maladjustment syndrome" is used. These foals exhibit central nervous system (CNS) signs within the first few days of life after suffering a lack of oxygen delivery to the brain, either from a lack of blood flow (ischemia) or a lack of oxygen in the blood that is going to the brain (hypoxemia) before, during, or immediately after birth.

Cause and Clinical Signs
Bernard said that based on a study of cases admitted to Rood and Riddle, there are several risk factors associated with HIE. In 30% of cases, premature placental separation was the cause, while in another 30% of cases, placental insufficiency (any situation where the foal demands more oxygen and nutrition than the uterus is capable of) contributed to HIE. Obstruction of umbilical blood flow, decreased uterine blood flow, colic, or other medical problems of the mare during pregnancy, and prolonged or shortened gestational length can also result in the disease. Foals born after a dystocia (difficult delivery) and those delivered by Caesarean section should be monitored for signs of HIE.

Bernard noted that during a normal delivery, there is a brief time when the fetus does not receive oxygen; the healthy foal is able to compensate for this, while the compromised foal might not be able to. A cycle of events takes place that results in HIE; these events include intracellular swelling, increased cerebral (of or pertaining to the cerebrum of the brain) tissue pressure, focally decreased blood flow, generalized brain swelling, decreased cerebral blood flow, and cerebral necrosis (death).

There are a myriad of clinical signs associated with HIE that can vary in severity, which usually is related to the amount of cell damage that has occurred. "Signs can be mild, such as a loss of affinity for the mare, an inappropriate suckle reflex, wandering, intermittent depression, and stargazing," said Bernard. "Facial spasms, lip curling and chomping, or abnormal respiratory patterns may occur. Abnormal vocalizations (barking) are rarely identified. These foals may sleep deeply and may be difficult to arouse. These 'mild' signs may be all that is seen, and the patient may recover without complication."

"On the other hand," he continued, "signs may progress to more prominent and severe indications of CNS disease. Foals may become totally unaware of the environment and appear to have blindness of central origin. Seizures may follow and are usually very sudden in onset."

Bernard said that more severe cases will have severe convulsive seizures, and the foal might become stuporous or comatose.

In seizuring neonates, 90% of the time it is because of HIE, but other causes must be ruled out. Trauma, meningitis, hypoglycemia, hydrocephalus (fluid on the brain), and electrolyte abnormalities could produce similar clinical signs to HIE, said Bernard. Trauma is uncommon, and signs are usually evident on the head. A foal with meningitis might present with a fever, appear agitated, stomp his feet, grind his teeth, or sweat profusely. Diagnosis can be confirmed with a cerebrospinal fluid (CSF) tap, thus ruling out HIE.

Hypoglycemia (decreased concentration of glucose in the blood) should be considered, but it is usually a problem in older foals and is not associated with seizures. Hydrocephalus can be confused with HIE. In both problems, signs might not be present at birth. A hydrocephalus foal might not nurse, act slow, show CNS signs, or seizure at birth. Radiographs of the skull, computerized axial tomography, or magnetic resonance imaging (MRI) can be used to diagnose hydrocephalus.

Electrolyte abnormalities such as hypocalcemia (low blood calcium) and hypoproteinemia (low total protein in blood plasma) should be ruled out, said Bernard.

Other problems that must be considered during diagnosis include metabolic acidosis, generalized sepsis, parasite migration, Tyzzer's disease (a bacterial disease characterized by depression, diarrhea, and sudden death), viral encephalitis, drug-induced toxicities, liver failure, idiopathic (without apparent cause) epilepsy, and heat stroke.

Diagnosis of HIE is based on clinical signs, historical information on the foal and the mare's pregnancy, and through elimination of other similar problems. Bernard said that elevated creatinine (a waste product of protein metabolism) and elevated muscle enzyme levels are not uncommon in HIE foals. By running a chemistry panel, other diseases such as metabolic or hepatic disease can be eliminated.

There is no magic treatment for HIE, said Bernard. The first thing a veterinarian will do is control seizures. Bernard's choice in medications is Valium (diazepam), although phenobarbitol and xylazine can also be used. Other possible drugs include allopurinol, phenytoin, and sodium pentobarbital. He has also used antimicrobial therapy to prevent secondary infection. Medications to reduce brain swelling such as intravenous dimethyl sulfoxide (DMSO) or mannitol can be used. Because DMSO must be combined with fluids, it is not his top choice.

Bernard cautioned against the use of fluids, since overhydration of the foal can increase brain swelling. He might prescribe non-steroidal anti-inflammatories, but cautioned that use of steroids could result in sepsis.

Nutrition is important, with the foal requiring 5-10% of his body weight in milk each day. If he is unable to nurse, his nutrition must be provided through feedings every one to two hours. He cautioned not to overfeed the recumbent (down) foal.

Prognosis of the HIE foal depends on the severity of the initial insult, amount of swelling in the brain, and cell damage. "When recovery does occur, there does not seem to be any long-term effects on growth or development," said Bernard. "Do not give up on the foal with seizures."

About the Author

Sarah Evers Conrad

Sarah Evers Conrad has a bachelor’s of arts in journalism and equine science from Western Kentucky University. As a lifelong horse lover and equestrian, Conrad started her career at The Horse: Your Guide to Equine Health Care magazine. She has also worked for the United States Equestrian Federation as the managing editor of Equestrian magazine and director of e-communications and served as content manager/travel writer for a Caribbean travel agency. When she isn’t freelancing, Conrad spends her free time enjoying her family, reading, practicing photography, traveling, crocheting, and being around animals in her Lexington, Kentucky, home.

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