Equine neonatology (Proceedings)


Equine neonatology (Proceedings)

Apr 01, 2009

"07 Slow to go" is a 48 hour old Thoroughbred filly that was born to a 15 year old Thoroughbred mare. The foal was found in the stall with the mare at 6 am on day 355 of gestation and was standing but was wet to the touch. The foal was first seen to nurse about 1 hour later. The foal passed meconium within 30 minutes. The owner checked the foal at 4PM that day and she was following the mare and nursed immediately after he approached the stall and again about 15 minutes later.

The mare has had 4 uncomplicated pregnancies previously with healthy foals delivered between 350 and 357 days of gestation. The mare foaled in the stall and that the mare and the placenta appeared normal when discovered.

The owner again checked on the pair at around 11PM on the night of delivery and all appeared well. However, at 6 am the following morning, the foal was recumbent in the stall and did not get up when first approached. The owner walked next to the foal and the foal got up but did not nurse. The owner went back out to check the foal before leaving for work and the foal nursed for a short time. When the owner returned from work at 5:30 PM, the foal was recumbent and did not rise until he assisted the foal to stand. At this time the foal did not nurse at all, so a veterinarian was called. The foal is now 24 to 36 hours old.

Examination reveals injected sclera, petechiation in the pinna of the ear, hyperemia of the oral mucous membranes and hyperemia of the coronet. Body temperature is 102.6 degrees F, heart rate is 100 beats/minute, and respiratory rate is 36 breaths per minute. The umbilicus and joints palpate normally and thoracic auscultation is normal. Loose yellow feces are adhered to the perineum and tail.

This foal exhibits clinical signs of sepsis causing bacteremia from bacterial infection via the intestinal tract, lungs, or umbilicus. The prodromal signs of sepsis are subtle and are often not recognized by caretakers. Knowledge of normal foal behavior and frequent monitoring are paramount for early identification of illness. During the first week of life, healthy foals suckle for 2 minutes 5 to 7 times an hour. Healthy foals nearly always suckle when approached by humans. Therefore, it is very unlikely that a healthy foal will not nurse each time they are observed by caretakers. Failure to nurse during checks should alert caretakers to a problem a veterinary examination is warranted. Complete blood count and immunoglobulin concentrations should be assessed during this examination.

Sepsis rapidly progresses as the bacterial infection stimulates production of inflammatory mediators in an exaggerated fashion resulting in the systemic inflammatory response syndrome (SIRS). As the inflammatory response intensifies, changes in blood pressure, vascular resistance, cardiac output, vascular permeability, clotting function, and body temperature occur that manifest as altered mental status, hypo- or hyperthermia, shivering, cold extremities, mucous membrane pallor, hyperemia, or cyanosis, bradycardia or tachycardia, poor pulse quality, poor capillary refill, and petechiation. Further progression can result in complete loss of suckle, recumbency with inability to rise, coma and death due to septic shock. Because the SIRS usually results from progression of bacteremia in the early stages of sepsis, clinical signs of localization of infection (nasal discharge, coughing, joint swelling, umbilical swelling) are rarely identified in this stage. Identification of secondary sites of infection is usually delayed by 1 to several days if the foal survives the septic shock. In some cases, localization to secondary sites occurs without development of septic shock. Pneumonia, omphalophlebitis, and septic arthritis are the most common sites of secondary infection. Meningitis, nephritis, endocarditis, and hepatic abscesses occur much less frequently.

Diagnosis of sepsis involves identifying foals in the early stages when treatment is most successful. Early intervention is essential but diagnosis in this stage is often not definitive. Proof positive requires identification of organisms in blood culture and false negatives commonly occur. Blood culture results are not available for 5-7 days which is well into treatment. Regardless, blood culture is a useful diagnostic test to confirm sepsis retrospectively and to guide antimicrobial therapy for secondary sites of infection. Historical facts, examination findings, and laboratory tests are used to make a presumptive diagnosis of sepsis on an emergency basis in order to guide life saving therapy. These findings are tabulated in a scoring system (sepsis score)1 to identify results that are statistically associated with sepsis.