Emergency Neonatal Triage for Sepsis: An AAEP Presentation Recap
The second session from the AAEP Convention I’d like to summarize was by Dr. Nathan Slovis of Hagyard Equine Medical Institute on "Emergency Neonatal Triage for Sepsis". (My first presentation recap was on Dystocia Triage.)
Foals that are ill are true emergencies and are often seen by field practitioners prior to referral to hospitals. Dr. Slovis aimed to help ambulatory veterinarians recognize and begin management of these critical foals in order to give them the greatest chance of survival.
Dr. Slovis began by describing the transformation from fetus to neonate as "a series of rapid and dramatic physiologic changes" as the lungs replace the placenta as the primary organ used for gas exchange. While the percentage is unknown in equine medicine, active intervention by a skilled individual or team is needed in human medicine 10 percent of the time to make sure newborns receive the appropriate care to undertake independent survival as soon as possible.
Low risk foals have no maternal, neonatal, or environmental risk factors identified (which will be reviewed later in this summary).
These foals also have a normal duration of gestation: 320 to 345 days in pony breeds, 320 to 360 days in Thoroughbreds, and 360 to 380 days in donkeys. Parturition, or birthing, was of normal duration with no significant manipulation of the foal needed for delivery. The placenta is normal visually and should be at least 10 to 12 percent of the weight of the foal.
These foals should at least receive a thorough "new foal" examination and have their IgG levels tested at 12 to 24 hours post-foaling. If any abnormalities are noted, further diagnostics should be performed. To better understand the normal timing of foaling events and to identify a normal foal, read Recognizing Problems in Neonatal Foals.
Moderate risk foals have only have one risk factor of maternal, environmental, or foal origin. If these foals are not recognized and treated appropriately, they can quickly become high risk foals.
High risk foals have more than one risk factor.
Many risk factors can be identified prior to the foal’s delivery and early intervention can be anticipated and planned. In addition to a thorough clinical examination, Dr. Slovis recommended the following measures:
- Frequent monitoring of the foal for signs of deterioration or absence of normal developmental steps (failure to nurse, urinate, etc.)
- Serum chemistry with electrolyte evaluation
- Serial monitoring of complete blood count (CBC)
- Serum IgG levels, as IgG levels may be rapidly consumed in these foals; repeat analysis is advisable
- Frequent monitoring of body weight, as foals should gain an average of 2 pounds daily
- Determine whether chemoprophylaxis (antibiotic treatment) is warranted:
- Low white blood cell (WBC) count
- Placental pathology
- Mare with significant risk factors
- Foal with failure of passive transfer
Dr. Slovis identified the following "Maternal Risk Factors" that are associated with the mare:
- Dystocia (difficulty foaling)
- Caesarian section
- Partial or complete premature placental separation ("red bag")
- Medically-induced labor
- Foaling prior to 320 days gestation (prematurity)
- Placentitis (inflammation of the placenta)
- Concurrent illness or fever
- Recent medical or surgical event
- Recent transport stress
- Twin pregnancy
- Vaginal discharge
- Chronic lameness or incoordination
- Premature lactation
- Agalactia (no milk production)
- Prolonged gestation with oversized foal (uncommon)
- Pelvic abnormalities (such as previous fracture)
- Drug related: sedatives, beta-2agonists, NSAIDs
- Previous history of dystocia, delivery of septic foal, or neonatal isoerythrolysis (NI) foal
The following "Neonatal Risk Factors" are directly related to the foal:
- Death of the dam
- Meconium (first feces) staining – indicates stress in utero
- Foals that do not stand and nurse by 3 hours of age
- Failure of passive transfer of maternal antibodies
The "Environmental Risk Factors" identified relate to where the foal was born:
- Foaling in a contaminated area
- Foaling in cold or wet conditions
- Infectious disease on the premises
- Disrupted foaling
Hematology and Serum Biochemistry
Dr. Slovis stressed that knowing the normal blood values of the foal is extremely important when assessing bloodwork so that proper interpretation can be achieved. Leukocytosis, or increased white blood cells, is characteristic of a foal that had an infection in utero. Leukopenia, or decreased white blood cells, is always pathologic. If a foal has a white blood cell count of greater than 15,000 or less than 5,000, an absolute neutrophil count of less than 1,000 cells/uL, and has one or more risk factors, it should be a candidate for antimicrobial therapy.
Serum Amyloid A (SAA) testing can be used as an acute marker for inflammation on high risk foals. Dr. Slovis considers a result above 100 ug as a risk factor for a foal to develop clinical disease. Badger Equine recently acquired a stall-side test for SAA which will be incorporated into new foal examinations in the future.
Serum creatinine is normally a value used to assess renal function in the adult horse. Because the placenta is the primary organ of waste elimination in the fetus, an increased level is more indicative of placental dysfunction. If levels continue to elevate or do not decrease within 2 to 3 days, kidney problems may be to blame.
Dr. Slovis monitors creatine kinase routinely in foals due to subtle increases being a marker for perinatal asphyxia (deprivation of oxygen to the foal during birthing process). The elevation could be due to oxygen deprivation to tissues during foaling or placental insufficiency, or it could be due to trauma from foaling or prolonged time laying down.
Alkaline phosphatase (ALP) is found in every tissue in the body with high activities in the liver, bone, intestine, kidney, and placenta. Newborn foals can normally have elevated values of 100 times that of adult horses for the first 10 days of life, especially after ingesting colostrum. GGT is a specific liver enzyme that can also be normally elevated in comparison to adult values, though this is more due to the hepatic weight to total body weight ratio that is highest in foals and decreases with age. Sorbitol dehydrogenase (SDH) should be used as a marker to determine risk of perinatal asphyxia.
Neonatal Sepsis, otherwise known as Systemic Inflammatory Response Syndrome or Multiple Organ Dysfunction Syndrome (MODS), is still the major cause of sickness and death in newborn foals, despite advancements in neonatal care. Sepsis is the development of a systemic inflammatory response to a confirmed infection.
Clinical signs are nonspecific and do not point to any certain infectious agent. Blood cultures have been the gold standard for diagnosing the causative pathogen, but clinical signs in the face of negative cultures is common. This is referred to as "clinical sepsis," and it may be due to a suppression of culture growth from antibiotics given to the dam or from a noninfectious triggering of the immune system similar in humans known as the "inflammatory baby".
Treatment and management of the foal with neonatal sepsis remains grounded in the same cornerstones that were established more than 20 years ago: infection control, hemodynamic (fluid) supportive therapies, respiratory support, and nutritional support.
- Infection Control: Broad spectrum antibiotics are used to cover the most likely causative organisms. As practitioners in the field, we can begin antibiotic therapy before referral to a hospital. If the hospital is very close, however, blood cultures should be taken prior to starting antibiotic therapy. The author recommends starting antibiotics if the trip to the referral hospital is more than 45 minutes.
- Hemodynamic Support: Fluid therapy is considered the second most important component in treating equine neonatal sepsis. Hypovolemia, or decreased blood volume, can occur in cases of severe sepsis, septic shock, diarrhea, or acute bleeding, and demands immediate attention. The author recommends using fluids that are lower in chloride levels to avoid renal dysfunction and avoiding high chloride fluids such as isotonic saline. Dr. Slovis then outlined his recommendations for fluid rate and additives such as dextrose.
- Respiratory Support: The author recommended nasal oxygen at the rate of 5 to 8 L/min. Oxygen is not always available in the field, however.
- Nutritional Support: These foals are usually too sick to stand up and nurse on their own. Indwelling feeding tubes can be inserted on the farm and left indwelling. Dr. Slovis recommended initially feeding 5 to 8 percent of the foal’s body weight for the first 12 hours, then slowly increase feedings by 1 to 2 percent every 12 hours until you have reached 15 to 18 percent of the foal’s body weight. Some foals need additional supplementation of lactase to be able to break down the milk until their gastrointestinal tract is healthy enough to produce their own.
Ambulatory veterinarians are often the first line of defense when dealing with critical foals. Dr. Slovis’s presentation was a good review of how to recognize and approach initial treatment of these foals in order to give them the best shot at recovery.