Pediatric emergencies (Proceedings) - Veterinary Healthcare
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Pediatric emergencies (Proceedings)


CVC IN WASHINGTON, D.C. PROCEEDINGS


Physiology



Neonate vitals

Respiratory Rate: 15-35 breaths/min until 4 weeks

Blood Pressure:
  • birth: 54/30 (40) mmHg
  • 4 weeks: 70/45 (60) mmHg
  • Adult: 130/80 (100) mmHg

Cardiac

At birth, the autonomic nervous system and the baroreceptor reflexes are immature, with the ANS maturing by day 10 and the baroreceptor system maturing by 4 weeks. Due to this immature state, it is difficult for the neonate to respond to changes in blood pressure. The cardiac function of a newborn is at a high resting function, which also makes it difficult for the heart to respond to acute changes in pressure by increasing stroke volume or heart rate. Instead of increasing cardiac output, the newborn increases oxygen extraction and redistributes blood flow to the heart, brain, diaphragm and adrenal glands, and away from the spleen, gastrointestinal tract, skin, and kidneys.

Pulmonary

In the fetus, there is increased pulmonary vascular resistance, which causes blood to shunt through the ductus arteriosus to the aorta and the systemic circulation. The fetal alveoli are collapsed until the first breath taken by the neonate. With the expansion of the lungs, prostacyclins are released that increase pulmonary blood flow. The decrease in pulmonary vascular resistance causes closure of the ductus arteriosus. Additionally, type II epithelial cells in the lungs produce a large amount of surfactant in response to lung expansion and the stress of birth, and thus reduce the tension of the air-fluid interface in the alveoli. Normal neonatal respiratory rates are higher than adults, but with a lower minute ventilation and tidal volume.

Hypoxia will occur at birth if the lungs fail to expand or the pulmonary vascular resistance does not decrease adequately. The fetal response to hypoxia is to decrease respiratory movements, which may further delay spontaneous breathing at birth. Briskly rubbing the newborn with a clean, dry towel or administering Doxapram stimulates respiration.

Urogenital

Micturition should occur within the first 24 hours. Neonate urine specific gravity is 1.006 to 1.017, and neonates cannot fully concentrate urine until 8 weeks old. Glucosuria also occurs commonly in newborns.

Daily fluid requirements are up to 100 ml/kg/d. To treat hypotension or shock, a fluid rate of 50-100 ml/kg/hr can be given providing that cardiopulmonary and renal function are monitored frequently. Once a shock dose is administered, severely dehydrated puppies or kittens should be maintained at 100ml/kg/day.

Testicles should descend by 4-6 weeks in male puppies.

Gastrointestinal

Neonates are born with a strong sucking reflex, but the swallowing reflex does not fully develop until they are 3 weeks old. Meconium is the neonate's first stools, comprised of amniotic fluid, mucous, bile, and cells shed from the intestinal tract. It is typically dark and thick and should be passed within the first 48 hours. Often, you will not observe neonatal feces if the mother is quick to clean her young.

Gastrointestinal contraction rates increase until 10 days after birth, and the normal flora colonizes the GI tract shortly after birth.

Liver

The liver goes through two periods of development—"rapid maturation" until 4 weeks old during which time the microsomal enzyme system develops, and "continued maturation" until 10 weeks old after which the liver is considered fully mature.


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Source: CVC IN WASHINGTON, D.C. PROCEEDINGS,
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