The ABC's of managing critical problems in neonates (Proceedings)

May 1, 2011
William D. Fortney, DVM
William D. Fortney, DVM

Dr. Fortney is a consultant and speaker on geriatric and pediatric veterinary medicine in Manhattan, Kan. He worked as head of small animal medicine and director of community practice at Kansas State University. He is a 1974 graduate of the University of Missouri College of Veterinary Medicine. He completed his residency in small animal medicine in 1977 at Purdue University. The following year he began teaching at Kansas State. Throughout his career, Dr. Fortney has been an active member of the veterinary profession serving in a number of leadership roles on the state and national level. He is a noted author and lecturer on senior care.

Average puppy and kitten deaths during the first 12 weeks of life approach? 11%-34%. Still births or death within the first 24 hours account for 5% of the losses; an additional 5% loss occurs during the neonatal period; and 0%-5% loss in transitional & socialization periods. Infectious diseases are not the most common cause of neonatal or transitional period mortality.

Death loss

Average puppy and kitten deaths during the first 12 weeks of life approach 11%-34%. Still births or death within the first 24 hours account for 5% of the losses; an additional 5% loss occurs during the neonatal period; and 0%-5% loss in transitional & socialization periods. Infectious diseases are not the most common cause of neonatal or transitional period mortality.

Birth weight / weight gain

Birth weight is the single most important predictor of neonatal survival. Those neonates that are < 25% of the litter average weight are at particularly high risk for hypoglycemia, hypothermia, hypoxia, bacterial septicemia and pneumonia. Close observation and careful monitoring are paramount to their survival chances. Monitoring weight gain is a good indicator of health status. Health Monitoring: Signs of healthy vigorous neonates include; adequate weight gain, strong activated sleep patterns, firm muscle tone and strength, and not crying. Crying for over 15 minutes is a signal and should not be considered normal. Puppies cry when hungry, neglected (separated or culled), in pain, and especially when cold.

Hypothermia

Thermoregulation is problematic in the neonate. Chilling is always a major threat to the survival of the neonate. The shivering reflex and peripheral vasoconstriction response are not fully developed until at least 1 week. Their relatively large surface area, plus the lack of insulating fat, promotes rapid heat loss by conduction, convection, radiation, and evaporation. The vulnerable young must relay on warmth of the dam and litter and environment to maintain an adequate body temperature. Mothers who refuse to "gather" the young or lick the young excessively, or "cull" one or two of the young, places these individuals at high risk for hypothermia. Hypothermia is a common cause of death in the newborn and is part of a viscous down spiraling cascade of events. As the rectal temperature reaches below 94° F the neonate suckling becomes weak and ineffectual. The intestines become hypomotile and the heart rate increases. Below 85° F there is gastrointestinal stasis with bacterium, a decrease in heart rate and hypoglycemia. Once below 70° F, the neonate is motionless and appears appear dead. An occasional chest wall movement may be seen, but the heart rate is 40-60 b/min and is non-palpable. Environmental temperature can be critical as a healthy newborn can only maintain a body temperature 12°F > than that of the surrounding environment.

Hypothermic patients should be re-warmed slowly (1-2 hours) to a temperature of 98°- 99°F. Warming increases the respiratory and heart rates; increases effectual nursing and swallowing reflex; increases visceral movements; and mobilizes glycogen stores. This warming process is essential prior to attempted feeding. Maintain the neonate in a draft-free environment. Re-warming is best accomplished with a human neonatal incubator. A thermometer should be used to measure ambient temperature. Focal heat sources such as circulating hot water blankets, warmed rice bags and hot water bottles insulated with towels may also be used. Whenever a focal heat source is used, a temperature gradient should be created to allow the neonate to either move to or away from the heat source. Overheating is rarely a problem but panting with hyperemic membranes and skin is a clue. Heat lamps and electric heating pads are not recommended because of increased the risks of burns and overheating. Remember to turn the patient every 20 minutes while taking the temperature.

Hypoxia

Hypoxia is a common sequel to birthing. Many newborns would benefit from short term supplemental oxygen therapy and respiratory stimulants. Those neonates with pneumonia or sepsis often require supplemental oxygen via an oxygen tent, oxygen cage, nasal tube or face mask (short-term only). Arterial blood gases are nearly impossible to collect and unavailable to most practices. However, a pulse- oximetry can sometimes be placed on the hairless skin of the ventral abdomen. Unfortunately an accurate reading requires adequate circulation not often present in a shock neonate. The normal oxygen saturation is > 90%.

Dehydration

Dehydration is always a concern with a sick puppy or kitten. It is no surprise they are extremely susceptible to dehydration. They are >70% water with a large surface area is covered with non-cornified skin combined with an inability to concentrate their urine. Hydration status can not be accurately assessed with skin turgor. Estimates of the degree of dehydration must be determined by dryness of the mucus membranes and eyes, plus the urine specific gravity. Accurate body weight and urine specific gravity can be used to evaluate the rehydration efforts. Re-hydration fluids may be administered to the neonate orally via stomach tube, SubQ, intravenously, interosseous, or rectally depending on the severity of the problem and resources available. Regardless of the route, fluids should be pre-warmed to 95°F – 98.6°F. Maintenance fluid requirements in neonates are about 60 -100 mls/kg/day. For oral stomach tube fluid administrations use a 5 FR – 8 FR infant feeding tube. Measure from the tip of the nose to the last rib and mark the tube. The tube is filled with fluid to prevent the introduce air into the stomach. Pass the tube down the left side of the mouth as the puppy cries (exhales). After delivery of the fluid, pinch the tube prior to withdrawal and withdraw it quickly to minimize aspiration. Aspiration pneumonia is a fatal consequence of improper placement of the feeding tube. Normal stomach volume is approximately 50 mls/kg. Oral fluids and nutrition are contraindicated in hypothermic neonates because gastrointestinal motility.

Subcutaneous fluids may be given in the interscapular space similar to a mature animal. However absorption is delayed with hypothermia. The jugular vein may be catheterized for intravenous fluids using a 24ga over-the-needle catheter. The interosseous route is best method of fluid administration in the small neonate. A 22ga spinal needle or standard 20 – 22ga needle placed intramedullary in the femoral cortex (via the trochanteric fossa) or humerous is an excellent way to administer fluids or blood. The site should be clipped, aseptically prepared and blocked. The needle is rotated back and forth as it is pushed into and firmly seated in the cortex. Pain is associated with cold fluids or fluids given to rapidly. The initial fluid of choice is warmed 50:50 solution of lactated ringers and 5% dextrose or LRS. Potassium supplementation may be necessary. Monitoring the patient's weight, cardiopulmonary status, mucus membranes, and urine specific gravity can be used to evaluate the response to fluid therapy.

Hypoglycemia

Next to hypothermia, hypoglycemia is one of the most common and serious problems seen in the neonates, especially the toy breeds. Normal blood glucose for the neonate is 90-140 mg%. Maintenance of normal blood glucose requires several interrelated factors of digestive absorption, liver and muscle glycogenolysis, and liver gluconeogenesis. A fasting puppy can maintain adequate blood glucose for 24 hours initially through glycogenolysis then gluconeogenesis. After that period a precipitous drop occurs. Neonates are prone to hypoglycemia because of increased demands for glucose (in part due to low fat reserves), poor hepatic and muscle glycogen reserves and reduced precursors for gluconeogenesis. Hypoglycemia is often secondary or a consequence of some other disease process (i.e. sepsis). Because it is such a common squeal to most problems empirical treatment of hypoglycemia is recommended for all sick neonates. Clinical signs of hypoglycemia include; visual problems, vertigo, in coordination, muscle tremors, seizures, lethargy, depression, collapse, coma, death. Unfortunately these symptoms can also be associated with numerous other common and uncommon neonatal illnesses. The diagnosis of hypoglycemia is based on the clinical signs, blood glucose, and the response to dextrose therapy. Therapy options include 10% Dextrose dosed at 1-2 ml/kg given slowly intravenously or 1-2 ml/kg 10% dextrose given orally via stomach tube every 15 minutes until normo-glycemic. Owners can be instructed to give oral Nutrical(c), Nutri-Drops(c), honey, Kayro syrup but only if the patient is conscience.

Nutrition

Always one of the first things an owner is concerned about with a sick puppy or kitten, however it is one of the last items to consider in managing a sick neonate. Once the hypothermia, hypoxia, hypoglycemia and dehydration have been addressed, and then consider nutritional supplementation. Tube feeding with a commercial milk replacement formula initially diluted 50% with LRS is the next step in patient care of the sick neonate.

Neonatal septicemia

Life threatening sepsis occurs when a bacterial infection overcomes a neonates defense mechanisms. Staphylococcus, Streptococcus, E coli, Klebsiella, Enterobacter, Clostridium, and Salmonella are commonly isolated from septic neonates. Ports of entry include the gastrointestinal tract, respiratory tract infection, urinary tract, skin and the umbilical cord. Several pre-disposing issues are responsible for either a decrease in the host's immunity and/or a break in the physical protection barriers. Those co-existing factors include inadequate colostrum, hypothermia, hypoglycemia, poor nutrition, viral infection, endoparasitism, plus metritis or mastitis in the bitch or queen. The clinical sings of septicemia vary with the severity of the condition. Most findings are not pathognomonic for sepsis and may be overlooked. Occasionally death is par-acute with no symptoms noted. Typically neonates should several of the following; prolonged crying, restlessness, weakness, hypothermia, shock, cyanosis. Petechial hemorrhages may be present. In advanced cased there may be discoloration and/or sloughing of distal extremities i.e., toes, ears, tongue, ear tips and tail.

Laboratory findings are supportive of the diagnosis. Initially the hemogram will reveal a neutrophillic leukocytosis with a mild left shift. The marrow reserves are rapidly diminished resulting in a neutropenia. A thrombocytopenia is often present. An associated hypoglycemia is usually present.

A septic neonate should be managed as an emergency. Any commonly associated conditions such as hypothermia, hypoxia, hypoglycemia, shock, and dehydration need to be addressed. Prior to initiating antibacterial therapy, any cultures should be taken for submission. Antibacterial selection is empirical in the neonate as little clinical pharmacokinetic data on the appropriate dosing of antimicrobial agents is lacking. Depending on the specific drug, absorption, re-distribution, protein binding, lipid solubility, hepatic metabolism, renal clearance, and poorly developed blood brain barrier influences the dosage regimen. Potential toxicities are an issue. Because absorption of antibacterial following oral, subcutaneous, or intramuscular administration is unpredictable, the antibacterial agents used in septicemia should be administered IV or interosseous if possible. The use of oral pro-biotics should always be an adjunct to using antibacterial in the neonate.

Fading Puppy / Fading Kitten Syndrome: Puppies and kittens that slowly waste away then die during the neonatal period often referred to as a "fading puppy" or "fading kitten" syndrome. Often referred to as a "failure to thrive", the pups and kittens are born apparently healthy, but nursing slowly ceases, they fail to gain weight, become weak, thin, and eventually die, for no apparently obviously reason. The syndrome represents a myriad of causative agents. Rule outs should include congenital anomalies, nutritional deficiencies in the mother, traumatic birth injury, maternal neglect, and neonatal isoerythrolysis. Infectious agents such as Brucellosis, low grade bacterial sepsis, viral infections (herpes virus, FIP/FeLV) and toxoplasmosis have been incriminated in the "fading" syndrome. Unfortunately, some fading neonates will not survive. Obtaining complete and accurate necropsies is the most expensive and crucial aspect of identifying the cause of the "fading". A necropsy diagnosis may yield information that will be beneficial to the rest of the litter and future litters.