Examination of the Neonatal Kitten

Start with a complete medical history for the kitten in question as well as for littermates. It may also be helpful to have a medical history for the queen if available (illness, nutrition, vaccinations, etc.) and information about the labor and delivery, especially for kittens under 2 weeks of age. Investigate the kitten's home environment, noting temperature and humidity, sanitation, population density and prevalence of infectious diseases and parasites.

Kittens under 4 weeks of age should be examined with the queen present if available, and ideally in the home or cattery if possible. Neonates should be handled gently, on a clean warm surface. Wash your hands and wear gloves. Simple equipment will suffice for neonatal exams: gram scale, pediatric rectal thermometer, otoscope with infant cones, penlight, stethoscope with an infant bell and diaphragm.

Before handling the kitten, observe its body condition and response to the environment, including mentation, posture, locomotion, and respiratory rate. Healthy neonates will have a strong suckle reflex. Normal body temperature for neonates is 97-98^oF (36-37^oC). The rectal temperature rises slowly, reaching 100^oF (38^oC) by about 4 weeks of age. For the first few weeks of life, kittens are poikilothermic and lack a shiver reflex. They gradually become homeothermic by 4 weeks of age.

Attempt to establish an estimated age for the kitten by using body weight and inspection of the dentition. The typical kitten birth weight is 90 to 110g (range 80-140g). Normal kittens gain 50-100g per week (10-15 g/day) and should double their birth weight by 2 weeks of age. The first deciduous teeth to appear are the incisors and canines at 3-4 weeks of age. The premolars erupt at about 5-6 weeks of age. The dental formula for deciduous teeth is 2(I3/3, C1/1, P3/2); there are no deciduous molars.

Inspect the neonate for gross anatomic abnormalities, such as cleft palate or lip, umbilical hernia or infection (omphalophlebitis), open fontanelles, limb deformities, chest wall deformities and nonpatent urogenital or rectal openings. Kittens younger than 3 weeks of age cannot eliminate urine and feces voluntarily. Evaluate a kitten's micturition and defecation reflexes using a cotton ball with mineral oil to stimulate the anogenital area. Diarrhea is present in about 60% of sick neonatal kittens. Hematuria or pigmenturia may be signs of urinary tract infection or neonatal isoerythrolysis.

The eyes should be inspected for abnormalities of the globe or eyelids and for neonatal conjunctivitis. A menace reflex does not appear until 21 days of age or later. Pupillary light responses may appear as late as 21 days as well. A divergent strabismus may be present and is normal until about 8 weeks of age. Evaluation of the fundus is difficult until about 6 weeks of age.

The pinnae should be inspected for evidence of trauma, parasites such as ear mites, and skin disease. The ear canals are not easy to inspect with an otoscope until after 4 weeks of age. The neonate's hair coat should be clean and shiny. Healthy neonatal kittens may have hyperemic mucous membranes until 7 days of age, whereas sick neonates often have pale, gray, or cyanotic mucous membranes.

Neonatal kittens have lower blood pressure than adults, as well as greater cardiac output, and a faster heart rate. Functional murmurs may be present in neonates due to anemia, hypoproteinemia, fever or sepsis. Innocent murmurs not associated with disease are more common in puppies than kittens; murmurs present after 4 months of age should be investigated. Congenital heart disease usually produces murmurs that are loud and accompanied by a precordial thrill. The normal neonatal heart rate can be over 200 bpm (range 220-260). The normal respiratory rate is 15-35 breaths/minute.

A full abdomen is normal in well-fed kitten, but an enlarged abdomen in an ill kitten may indicate aerophagia. The normal liver and spleen may not palpable; the kidneys are always palpable. The stomach may be palpable if it is full. The intestinal tract is palpable as fluid-filled bowel loops that should be freely moveable and non-painful. The urinary bladder is also palpable, moveable, and non-painful.

Diagnostics

For venipuncture, position the kitten in dorsal recumbency with the forelegs drawn back toward the abdomen and the head and neck extended. Draw blood from the jugular vein using a 1-ml syringe with a 25-g or 26-g needle. Slow aspiration of blood is essential to avoid collapsing the vein. A small volume (0.5 ml) of blood can be used for the most critical tests:

 PCV and total solids using microhematocrit tubes and refractometer

 CBC: WBC from 1 drop whole blood directly into Unopette^®, blood smear for differential

 BUN from whole blood on reagent strip

 Blood glucose from drop of whole blood using glucometer (note these machines tend to read slightly low)

Blood chemistry and hematology values for neonates differ from the adult; most values normalize to adult levels by 4 months of age. Normal ranges for kittens may be found in the references below.

Urine is collected for chemistries, sediment and specific gravity by stimulating the perineum; cystocentesis should be performed with great care in the very young. Urine specific gravity is 1.020 or lower in the first few weeks of life; adult values are reached by about 8 weeks of age. A fecal sample should be examined for common intestinal parasites such as Giardia, Isospora, and roundworms using both centrifugation and a direct saline smear. Kittens as young as 2 weeks of age may be treated with pyrantel pamoate (5-10 mg/kg, PO, q 2 weeks).

Necropsy is under utilized as a diagnostic tool for multi-cat environments such as shelters or catteries. Necropsy results may provide information necessary to save remaining littermates or a future litter. For the best results, the whole body should be submitted (refrigerated, not frozen) to a qualified pathologist. If necessary, freezing is preferable to autolysis and some information can still be obtained.

Basic Therapeutics

Hypothermia occurs when the kitten's rectal temperature is less than 94^oF (34.4^oC) and is associated with depressed respiration, impaired function of the immune system, bradycardia, and ileus. Hypothermic kittens should be re-warmed slowly, over 30 minutes to 2 hours to a maximum rectal temperature of 101^oF (36.3^oC) to avoid dehydration. An incubator or oxygen cage is a good way to accomplish re-warming, but hot water bottles and heating lamps can also be used with very careful monitoring. For severely hypothermic kittens, fluids warmed to 95-98^oF (35-37^oC) may be administered via the intravenous (IV) or intraosseous (IO) route or as an enema. Never attempt to feed a hypothermic kitten, as aspiration pneumonia is a significant risk.

Clinical hypoglycemia occurs when the blood glucose is less than 3 mmol/L (50 mg/dL), and is a common problem for sick neonates due to the kitten's immature liver function and rapid depletion of glycogen stores. Hypoglycemia may be caused by vomiting, diarrhea, sepsis, hypothermia and inadequate nutritional intake. Kittens with hypoglycemia will be weak and lethargic, and may be anorexic. If the kitten is not hypothermic or dehydrated, administer 5-10% dextrose orally at 1 ml/100g body weight per hour by gastric tube until the kitten is stronger and normoglycemic. Then begin feedings of kitten milk replacer. Critically ill neonates may require a bolus infusion of 10-20% dextrose IV or IO (1 ml/100g) followed by 1.25 to 5% dextrose in a balanced electrolyte solution. Hypertonic dextrose solutions should not be administered subcutaneously or tissue sloughing may occur.

Dehydration occurs easily in neonatal kittens with diarrhea, vomiting, or reduced fluid intake. Neonates have poor compensatory mechanisms and immature kidney function. Hydration status may be difficult to assess in the youngest patients. Skin turgor is not a reliable test of hydration for kittens under 6 weeks of age as their skin has increased fat and decreased water content compared to adults. The kitten's mucous membranes should be moist and either hyperemic or pink. Pale mucous membranes and a decreased capillary refill time indicate at least 10% dehydration. Neonatal urine is normally colorless and clear; in dehydrated kittens, the urine is dark with a specific gravity over 1.020.

If the kitten is minimally dehydrated and normothermic with no gastrointestinal dysfunction, warmed oral or subcutaneous (SC) fluids can be administered. If the kitten is moderately to severely dehydrated, IV fluid administration is the most effective. A mini-set (60 drops/ml) is used with a fluid or syringe pump or a burette. The cephalic or jugular vein can be catheterized with a 24-g ¾-inch or 22-g 1-inch catheter. Lactated ringers solution is ideal for rehydration as lactate can be used as an energy source; 1.25-5% dextrose can be added if necessary.

Warmed IV fluids may be given as a bolus of 30-40 ml/kg (3-4 ml/100g body weight), followed by a maintenance infusion of 80 ml/kg/day (8 ml/100g) plus any ongoing losses. It is important to monitor fluid therapy closely as it is easy to over hydrate young kittens. Hydration status can be monitored by several methods, but weighing the kitten every 6-12 hours is easily accomplished. Other methods include serial PCV/total protein measurements, central venous pressure measurement, and urine output measurement with placement of a 3.5-Fr red rubber urinary catheter. Electrolyte and glucose status should also be monitored.

If it is difficult to achieve intravenous access, an alternate route for administration of fluids must be employed. The intraperitoneal route should not be used in neonatal kittens due to the risk of inducing peritonitis. Intraosseous access using the trochanteric fossa of the proximal femur is the best alternative to IV access; blood, fluids and medications can be administered in this way. Use a 20- to 22-gauge 1-inch spinal needle or 18- to 25-gauge hypodermic needle as a catheter. Flow rates of up to 11 ml/minute can be achieved by gravity. Use of cold fluids, too large a volume in a short time, or hypertonic or alkaline solutions will cause pain. IV access should be established as soon as possible. Complications of IO administration include infection, extravasation of fluids and trauma.

Immunity

Kittens receive almost all their passive immunity during the first 18 hours of life (before gut closure) with the ingestion of colostrum; there is little trans-placental transfer of immunoglobulins in the cat. The serum IgG nadir is reached at 5 weeks of age and correlates with a period of vulnerability to infection.

Failure of passive transfer can occur in orphaned kittens that have not ingested colostrum during the first critical hours. Correction of failure of passive transfer can be accomplished by SC injection of adult cat serum from a cat with compatible blood type that has been screened for infectious diseases (15 ml/100g body weight, divided into 3 doses over 24 hours). Kittens with uncorrected failure of passive transfer start to produce IgG at about 4 weeks of age; they are therefore most vulnerable to infection from birth to 6 weeks of age.

Infectious Diseases

The highest mortality rates from infectious diseases are in the first 2 weeks of life and in the post-weaning period. Common pathogens include: Mycoplasma, feline herpesvirus-1 (FHV-1), calicivirus, parvovirus, feline leukemia virus, feline infectious peritonitis, Toxoplasma, E. coli, Pasteurella, Staphylococcus, Streptococcus, Bordetella, Chlamydophila. The most important pathogens are Streptococcus canis (Group G, beta-hemolytic), coliform bacteria (e.g., E. coli), and respiratory infections, especially FHV-1.

Drug therapy in neonates is affected by several important factors that influence drug absorption, distribution, binding, and metabolism. In general, IV or IO administration is more predictable than oral, SC or intramuscular routes. Most medications have not been studied in neonatal kittens so that dose and frequency recommendations are often extrapolations. Typically, adult doses are decreased by 30-50% or the dosing interval is increased. Certain antibiotics should be avoided in young kittens such as aminoglycosides, chloramphenicol, and potentiated sulfonamides. Antibiotics recommended for use in young kittens include the quinolones and β-lactams.

References

1.  Hoskins J. Clinical evaluation of the kitten: from birth to eight weeks of age. Comp Contin Edu Pract Vet 12;1990;1215-1225.

2.  Levy J, Crawford P, et al. (2006). Effect of age on reference intervals of serum biochemical values in kittens. J Amer Vet Med Assoc 228;2006; 1033-1037.

3.  Chandler M. Pediatric normal blood values. Current Veterinary Therapy XI: Small Animal Practice. R. Kirk and J. Bonagura. Philadelphia, W.B. Saunders;1992;981-984.