Neonatology Notes

Neonatology

The Normal Newborn

Physiology

• In the fetus:

  • Lungs are filled with fluid

  • Oxygen is supplied by the placenta

  • There is a high pulmonary vascular resistance

  • LA pressure is low due to limited return from the lungs

  • RA>LA, due to RA receiving venous return including blood from the placenta maintains foramen ovale (right to left shunt)

  • SEE pg 142 of Illustrated for Fetal Circulation diagram

• The first breath occurs (on average) 6 seconds after delivery with regular breathing after about 30 seconds

• Pulmonary expansion at birth is associated with a rise in oxygen tension, and with falling pulmonary vascular resistance the pulmonary blood flow increases sixfold

  • Increased LA filling and reduced pressure in the RA due to exclusion of the placenta closes the foramen ovale

• After an elective CS – mother has not gone through labour and the infant’s chest has not been squeezed, it may take several hours for pulmonary fluid to be reabsorbed leading to rapid, labored breathing transient tachypnea of the newborn.

• Failure to breath at birth – causes include

  • Asphyxia

  • Birth trauma

  • Maternal analgesia or anaesthetic agents

  • Retained lung fluid, preterm infant or congenital malformation

• Asphyxia may be:

  • Continous asphyxia – abruption or cord prolapse

  • Intermitten asphyxia – prolonged and frequent contractions. Etc.

• A fetus deprived of oxygen in utero will try to breath – when this fails primary apnoea, HR is maintained

• Primary apnoea may be followed by irregular gasping and a second period of apnoea secondary or terminal apnoea – HR and BP fall

  • Requires CPAP

Apgar Score

Routine Examination of the Newborn

• Birthweight, gestational age and birthweight noted

• General observation

• Head circumference normal at term is 33-37cm

• Fontanelle and sutures are palpated anterior normally is 4 x 4cm

  • Tense fontanelle when the baby isn’t crying may indicate raised ICP

  • May also be a sign of meningitis

• Face is observed

  • Characteristic facies in certain syndromes

• If plethoric or pale – check hematocrit to identify polycythaemia or anaemia

• Jaundice within 24 hours required further evaluation

• Eyes are checked for a red reflex

  • Absent may be due to cataracts, retinoblastoma and corneal opacity

• Palate needs to be inspected

• Breathing and chest movement

  • RR normally 40-60 per minute

• Auscultate the heart

  • Normal rate is 110-160 bpm in term babies

• Palpate the abdomen

  • Liver extends 1-2cm below the costal margin

  • Spleen tip may be palpable as may the left kidney

• Femoral pulses are palpated

  • Reduced in coarction confirm by measuring the blood pressure in the arms and legs

• Inspect genitalia and anus

  • Clitoris and labia

  • Descent of testes in males

• Muscle tone assess by observing limb movements

• Whole of the back and spine inspected

• Hips are checked for DDH

  • Barlow manoeuvre and Ortolani manoeuvre

Vitamin K Therapy

• Vitamin K deficiency can result in haemorrhagic disease of the newborn

• Can occur early during the first week of life or between 1 and 8 weeks

• Haemorrhage can be mild bruising, haematemesis, malaena or prolonged bleeding from the umbilical stump

• Some suffer from intracranial haemorrhage – resulting in disability or death

• Breast milk is a poor source of vitamin K Vs. formula feed

• Disease can be prevented by IM vitamin K immediately after birth

Guthrie Screening

• Heel prick is taken on day 5-9

• In the UK all infants are screened for:

  • PKU (phenylalanine)

  • Hypothyroidism

  • Haemoglobinopathies (sickle cell and thalassaemia)

  • CF – measure serum immunoreactive trypsin (raised if there is pancreatic duct obstruction) – if raised DNA analysis

  • MCAD (medium chain acyl-CoA dehydrogenase) deficiency

Know the Important Time Frames for the Newborn

• Bowels – usually within 6 hours - up to 24 hours

• Bladder – up to 24 hours

• Weight – newborns lose around 7-10% of weight but should regain it by 2 weeks

Hypoxic-Ischaemic Encephalopathy

• Perinatal asphyxia gas exchange (placental or pulmonary) is compromised

  • Respiratory depression hypoxia, hypercarbia and respiratory acidosis

  • Circulatory depression low CO, reduced tissue perfusion, ischaemia, metabolic acidosis, capillary leak and oedema

• Leads to Hypoxic Ischaemic Encephalopathy (HIE) with multi organ dysfunction

  • Encephalopathy abnormal neurology and seizures

  • Respiratory failure persistent pulmonary hypertension of the newborn (PPHN)

  • Myocardial dysfunction hypotension

  • Metabolic hypoglycaemia, hypocalcaemia, hyponatraemia

  • Other organ dysfunction renal failure, D

• Occurs in 0.5-1 per 1000 infants develop HIE and 0.3 per 1000 have significant disability

• Causes include:

  • Failure of placental gas exchange – excessive contractions, abruption, ruptured uterus

  • Interruption of umbilical blood flow – cord compression (shoulder dystocia, cord prolapse)

  • Inadequate maternal placental perfusion – maternal hypo- or hypertension

  • Compromised fetus – anaemia, IUGR

  • Failure of cardiorespiratory adaptation at birth

• Clinical manifestations occur 48 hours after asphyxia

  • Mild irritable, responds excessively to stimulation, staring eyes, hyperventilation and impaired feeding

  • Moderate marked abnormal tone and movement, cannot feed, may have seizures

  • Severe no normal spontaneous movements or response to pain, fluctuating hypo- and hypertonia, seizures are prolonged and refractory to treatment, multi organ failure

• Management

  • Respiratory support

  • Amplitude-integrated electroencephalogram (aEEG)

  • Treat seizures

  • Fluid restriction due to renal impairment

  • Treat hypotension by volume and inotrope support

  • Monitor and treat hypoglycaemia and electrolyte imbalance

  • Mild hypothermia may be beneficial if started within 6 hours

• Prognosis

  • If MILD complete recovery may be expected

  • If...

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