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Obstetrics Simplified - Diaa M. EI-Mowafi

Foetal Asphyxia

It is a state of inadequate oxygenation and inadequate elimination of carbon dioxide.

Intrauterine Asphyxia

Aetiology

  • Maternal causes:
    • Anoxia due to:
      • Cardiac failure.
      • Pulmonary diseases.   
      • Anaesthetic agents causing hypotension.
      • Severe anaemia.
      • Eclamptic fit.
  • Placental causes:
    • Placental compression as in:
      • Tonically contracted uterus.
      • Prolonged labour after rupture of membranes.
      • The old method to control bleeding from a placenta praevia.
    • Placental insufficiency: due to acute causes as separation or infarcts.
  • Umbilical cord:
    • True knots.
    • Tight coils around the neck.
    • Prolapsed cord leading to its compression and vasospasm of its vessels.
    • Compression by the forceps’ blades.
    • Rupture of vasa praevia.
    • Haematoma of the cord.
    • Avulsion of the cord.
  • Foetal causes:
    • Cerebral oedema and ischaemia leading to decreased blood supply to the respiratory centre in the medulla. This may result from:
      • Intracranial haemorrhage.
      • Depressed skull fracture.

Diagnosis = Signs of Foetal Distress

  • Foetal heart rate changes: in the form of;
    • Tachycardia: > 160 beats / min. due to sympathetic stimulation caused by mild hypoxia.
    • Bradycardia: < 100 beats / min due to vagal stimulation caused by moderate hypoxia.
    • Cardiac arrhythmia (irregular FHR): due to severe hypoxia. It is the most dangerous one.
    • Late deceleration.
    • Loss of beat - to - beat variation.
  • Meconium stained amniotic fluid:

Asphyxia causes increased intestinal movement and relaxation of the foetal anal sphincter with passage of the intestinal contents

Grades of meconium and its management:

Grade Description Management
I A good volume of liquor, lightly stained with meconium. Review the clinical presentation e.g. FHR. Stop oxytocin + left lateral position.
II A reasonable volume of liquor with a heavy suspension of meconium. Foetal blood sample is indicated.
III Thick undiluted meconium resembles sieved spinach. Caesarean section unless easy vaginal delivery is imminent.

N.B. The fresh thick dark brown meconium that is seen on the examining fingers in breech presentation is not an indicator of foetal distress.

  • Foetal acidosis: scalp blood pH < 7.2.
  • Foetal movements: increased in early distress.
  • Cord pulsation: is weak, if cord is prolapsed.

Management

  • Conservative:
    • Stop oxytocin drip: if it is in use.
    • Left lateral position of the mother: to relieve aorto-caval compression → improves venous return → improves cardiac output → improves uteroplacental blood flow.
    • Oxygen: is given by mask to the mother in a rate of 6 litres / min. increases the O2 supply to the foetus.
  • Immediate delivery:
    • is indicated if the foetal distress is not improved by the conservative methods. This is achieved by:
      • Vacuum extraction, forceps delivery or breech extraction: if the cervix is fully dilated and vaginal delivery is amenable.
      • Caesarean section: if rapid vaginal delivery is not amenable.

Asphyxia Neonatorum

Aetiology

  • Causes in the respiratory centre:
    • Paralysis: due to cerebral haemorrhage.
    • Depression: by drugs as morphine, pethidine or anaesthesia.
  • (Causes in the lungs:
    • Congenital atelectasis.
    • Respiratory distress syndrome: due to deficient lung surfactant.
  • Causes in the respiratory passages:
    • Obstruction by: meconium, liquor, blood, mucus.
  • Causes in the respiratory muscles:
    • Congenital debility.
    • Weakness in prematures.

Diagnosis

Clinical features:

It depends upon the type (stage) of asphyxia:

  ASPHYXIA LIVIDA ASPHYXIA PALLIDA
Degree Mild (early stage) Severe (late stage)
Colour of skin Blue Pale white
Respiratory efforts May be present Absent
Heart beats Strong, 80-120/ min Weak, <80 /min
Eyes Reactive pupils Dilated pupils
Muscle tone A degree of muscle tone Flaccid
Reflexes Present Absent
Prognosis Good, easy resuscitation Bad, difficult resuscitation.

Apgar score: It is a clinical assessment of the newborn’s condition, its need for resuscitation and the response to it. It is done at 1 and 5 minutes from delivery.

Sign 0 1 2
Heart rate Absent <100 >100
Respiratory effort Absent Slow, irregular Good, crying
Muscle tone Flaccid Some limb flexion Active movement
Reflex (Response to nasal catheter) No response Grimace Cough or sneeze
Colour Blue or pale Body pink, limbs blue Completely pink

The score at 1 minute determine the need for resuscitation:

Score Condition Resuscitation
7-10 Good. Only nasopharyngeal aspiration.
4-6 Moderate asphyxia Position the baby + O2 mask.
0-3 Severe asphyxia Endotracheal intubation + cardiac massage + drugs.

The 5 minutes-score is an indicator of future CNS efficiency.

Prophylaxis of Asphyxia Neonatorum

  • Proper antenatal care.
  • Proper intranatal monitoring.
  • No morphia 4 hours or pethidine 2 hours before delivery.
  • Minimise the foetal exposure to anaesthesia during labour and ensure adequate oxygenation with it.
  • Episiotomy in proper time.
  • Avoid birth trauma.
  • Vitamin K 10 mg to the mother during labour.
  • Clear the air passages of the foetus immediately after delivery.

Treatment

It is remembered by ABCD arrangement:

  • Air passages suction:
    • immediately after birth by suction of mouth, pharynx and nose with the head 15o lower down.
  • Breathing:
    • is stimulated by slapping the soles of the foetus, flexion and extension of the legs and rubbing the back.
    • Mouth to mouth breathing: A one layer piece of gauze is placed on the infant’s mouth close its nose with the fingers and expire gently into the mouth. The expired O2 and CO2 will stimulate the respiratory centre.
    • Oxygen mask.
    • Endotracheal intubation and intermittent positive pressure ventilation not exceeding 20 cm water.
  • Cardiac massage.
    • If the heart rate is below 60 beats/ min. the thumb is pressed at the junction of the middle and lower third of the sternum in a rate of 120/min.
  • Drugs:
    • Sodium bicarbonate: 1 mEq/kg is given IV to correct acidosis.
    • Naloxone: 10 m g/kg is given IV as an antidote to morphine or pethidine
    • Epinephrine: 0.1 ml/kg of 1:10.000 dilution is injected into the umbilical vein or intracardiac.
    • Antibiotics: to guard against pneumonia which is liable to develop after prolonged resuscitation.

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