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The normal neonate: What is normal and abnormal? (Proceedings)

May 01, 2011

The neonatal period is the first 4 week of life. During this critical period, the puppy or kitten has a different physiology and rate of development and than during the rest of the pediatric period. Once the puppy or kitten is 6- 8 weeks of age, then all of the development is complete and the youngster can be considered a "growing" adult. There are significant differences between the newborn and weanling. Understanding these differences is very important is caring for the newborn puppy or kitten.

A physical examination is a good starting point for evaluating the health of a newborn. Accurate observations of the animal's body general condition, body movements, mentation, posture, locomotion, and breathing patterns should all done be done prior to ever handling the neonate.

The complete physical exam findings will help determine the overall health of the patient.

Weight

Monitoring weight gain is a good indicator of health status. Adequate weight gain for both species has been reported during the neonatal period. On average, nursing puppies should double their weight in 10 days; the puppy should gain 5-10% / day; or the puppy should gain 2 Gms/Kg of the expected adult weight/day. Nursing kittens should also double their weight in 10 days; normal kittens gain 10 - 15 Gms / day; and the kittens should weigh 1 pound/month for the first 4 months. Formula fed neonates grow at significantly slower rate despite the identical caloric intake only doubling their weight in 14 days.

Thermoregulation

An accurate rectal temperature in neonates requires a digital thermometer that reads to 95°F or lower. Thermoregulation is problematic in the neonate and a common cause for infant death. The shivering reflex and peripheral vasoconstriction response are not fully developed until at least 1 week. Their relatively large body surface area of non-cornified skin, plus the lack of insulating fat, promotes rapid heat loss by conduction, convection, and radiation. The vulnerable young must relay on the ambient temperature, the dam's mothering instincts, and/or littermates for warmth. Orphaned puppies or kitten only the ambient temperature of the nesting box. Environmental temperature exposure can be critical as a healthy newborn can only maintain a body temperature 12° > than that of the surrounding environment.

Hydration Assessment

Dehydration is always a concern with a sick puppy or kitten. It is no surprise the newborns are extremely susceptible to dehydration. Neonates are 75% water with a disproportionately large body surface area is covered with non-cornified skin combined with an inability to concentrate their urine. Water turn over is 2-3X that of an adult. Unlike an adult, hydration status can not be accurately assessed using skin turgor. Estimates of the degree of dehydration must be determined by dryness of the oral mucus membranes and eyes, plus the urine specific gravity measurements.

Skin

The skin should be checked for wounds and bruising. Premature puppies and kittens have high mortalities. Spare or absence of hair on the dorsal feet is usually indicative of prematurely.

Head/Skull

Examine the skull for shape and for an open fontanelle. Many toy breeds are born with a palpable open fontanelle and a small opening may be normal in the Persian. Most openings should be closed by 9-12 weeks although in is not uncommon for the opening to persist in certain breeds (Chihuahuas, Miniature Daschunds) without obvious consequence. Chihuahua the open fontanel is referred to as a "molera" and is considered to be a breed standard. The simple fact that a Chihuahua has a domed head with an open molera does not predispose it to hydrocephalus. A study done by Greene and Braund in 1989 concluded that "Many clinically normal toy breeds and brachycephalic (short faced) breeds also may have open fontanelle without associated hydrocephalus." Also, "There did not appear to be any relationship between the presence or size of the fontanelle and the concomitant presence of hydrocephalus." When the dog seems normal but displays enlarged ventricles of the brain (under ultrasound), its hydrocephalus is termed "occult" (having no clinical signs).