PHYSIOLOGY AND MANAGEMENT ON THE HIGH-RISK NEONATE

ASPHYXIA NEONATORUM

Instructor: Grace Adjei
Date: 2/11/2025

LESSON OBJECTIVES

By the end of the lesson, students should be able to:

• Define asphyxia neonatorum
• Enumerate the causes of asphyxia neonatorum
• Determine the types of the condition and their signs and symptoms
• Understand the management of the condition
• Demonstrate neonatal resuscitation

DEFINITION

• Asphyxia: Refers to a lack of oxygen.
• Other Names: Also known as perinatal asphyxia, neonatal/newborn asphyxia, or birth asphyxia.
• Description: It is the failure of the newborn to initiate and sustain spontaneous respiration, resulting in oxygen deprivation.
• Physiological Mechanism: Results from a reduced amount of oxygen or an increased amount of carbon dioxide in the body.

CAUSES OF ASPHYXIA NEONATORUM

MATERNAL CAUSES

• Maternal hypoxia
• Maternal hypotension, shock or adverse posture
• Maternal hypertension and vascular disease
• Pregnancy-Induced Hypertension (PIH)
• Respiratory diseases in the mother (e.g., preterm birth)
• Hypertonic uterine action
• Prolonged or obstructed labor
• Placental diseases (e.g., syphilitic placenta), dysfunction, or separation (placenta abruption/previa)
• Adverse effects of drugs administered to the mother, such as narcotic drugs or diazepam
• Severe maternal anemia

FETAL CAUSES

• Obstruction of the airway by mucus, blood, amniotic fluid, or meconium
• Underdeveloped lungs
• Postmaturity of the fetus
• Tracheal atresia
• Cord prolapse and compression; true knot in the cord
• Congenital heart disease of the baby
• Shoulder dystocia
• Depression of respiratory centers due to narcotics/anaesthetics

APGAR SCORE

TYPES OF ASPHYXIA NEONATORUM

• Mild Asphyxia (Asphyxia livida):
    - Defined as having no significant deprivation of oxygen during labor (also called primary apnoea).
• Severe Asphyxia (Asphyxia pallida):
    - Occurs when there is prolonged oxygen lack before or after delivery, indicating circulatory failure and the baby being in shock (also referred to as secondary apnoea).

SIGNS AND SYMPTOMS OF MILD AND SEVERE ASPHYXIA

GENERAL PRINCIPLES UNDERLYING THE TREATMENT OF ASPHYXIA PALLIDA

• Clear the airway passage thoroughly.
• Administer oxygen or initiate mouth-bag respiration.
• Provide warmth to the newborn.
• Inform the supervising physician of the situation.
• If response to initial measures is poor, combine cardiac massage with artificial respiration.
• Administer drugs as necessary.
• Continuously observe the baby's condition for any changes.

ASSESSING APGAR IN UTERO

• Assess fetal heart rate.
• Meconium-stained liquor is present in a cephalic presentation.
• Occasionally, the mother may report excessive fetal movement.
• Fetal blood sampling can confirm a compromised fetus and may reveal acidosis.

PREPARATION FOR THE RECEPTION OF AN ASPHYXIATED BABY

• Anticipate the possibility of birth asphyxia, though it can occur unexpectedly.
• Ensure resuscitation equipment is always available and functioning.
• Attending personnel should be familiar with resuscitation equipment, techniques, and local policies regarding medical aid provision.

RESUSCITATION EQUIPMENT

• Resuscitaire with overhead radiant heater
• Clock timer
• Two straight-bladed infant laryngoscopes
• Neonatal endotracheal tubes
• Neonatal airways
• Suction catheters
• Neonatal bag and mask

Additional Equipment

• Endotracheal tube introducer
• Magills forceps
• Syringes
• Stethoscope
• Cord clamps
• Drugs for resuscitation
• Warm, dry towels
• Adhesive tape for tube fixation

MANAGEMENT OF ASPHYXIA NEONATORUM

AIMS OF RESUSCITATION

• Establish and maintain a clear airway through efficient ventilation and oxygenation.
• Ensure effective circulation.
• Correct any acidosis.
• Prevent hypothermia, hypoglycemia, and hemorrhage.

PROCEDURE

• Start the clock immediately after birth.
• Assess the APGAR score at 1 minute.
• If there is no respiratory effort, initiate resuscitation measures.
• Clear the upper airways through gentle suctioning of the oro- and nasopharynx and verify heartbeat presence.
• Dry the baby promptly and transfer to a resuscitaire, placing it on a flat firm surface under a radiant heat source to prevent hypothermia.
• Elevate the baby's shoulders slightly with a towel, which extends the head to straighten the trachea and avoid hyperextension that might obstruct the airway.

STIMULATION

• Gentle stimulation (drying and clearing the airway) may trigger breathing.
• Techniques include a single finger flick to the sole of the foot or gentle back rubbing.
• Direct a low flow (2-4 L/min) of oxygen over the baby's face to stimulate a gasp reflex.

WARMTH

• Wet cloths should be removed, and a prewarmed blanket should cover the baby’s body and head, leaving only the chest exposed.

CLEARING THE AIRWAY

• Most babies require no airway clearance at birth; however, if there’s observable respiratory difficulty, suctioning is necessary.
• The catheter tip should not exceed 5 cm insertion depth, and each suction attempt should be limited to 5 seconds.
• In the presence of meconium-stained liquor, suction the mouth, oropharynx, and nasal passages immediately after the head emerges and before the baby takes its first breath.
• Thick meconium necessitates visual suctioning, using a laryngoscope to visualize the larynx, taking care not to trigger laryngospasm or bradycardia by touching the vocal cords.

VENTILATION AND OXYGENATION

• If the baby does not respond to airway clearance, assisted ventilation becomes necessary.
    - Methods:
      - Use a neonatal bag and mask with a properly fitted mask covering the baby’s nose and mouth without impinging on the eyes.
      - Administer oxygen or air through the mask using a bag fitted with a self-limiting pressure valve (e.g., ambu bag).
      - Hold the baby’s jaw forward and support it to maintain the airway.
      - Deliver five sustained inflations at a pressure of 30 cmH2O for 2-3 seconds, repeating five times, followed by continuous ventilation at 40 respirations per minute by squeezing the bag.
    - If ineffective, proceed with endotracheal intubation without delay if the baby shows bradycardia.
    - Mouth-to-face resuscitation may be used if specialized equipment is not available, using the operator's mouth to seal over the infant’s mouth and nose, delivering air at a rate of 20 breaths per minute, allowing the baby to exhale between breaths.

EXTERNAL CARDIAC MASSAGE

• Indicated if the heart rate drops below 60 bpm or falls between 60 and 100 bpm despite ventilation.
• Conducted by encircling the baby's chest, using fingers on the spine and thumbs on the middle to lower third of the sternum.
• Chest compressions should occur at a rate of 100-120 per minute, in a 3:1 ratio of compressions to ventilation, achieving a depth of one third of the baby’s chest (approximately 1.5-2.0 cm).
• Excessive pressure can cause rib, lung, or liver damage.
• Effectiveness should be gauged by observing color, perfusion, and the femoral pulse.
• Brief interruptions should be made to auscultate the heart periodically.

USE OF DRUGS

• If the baby remains hypotonic or unresponsive after ventilation, drug intervention is considered.
    - Naloxone Hydrochloride: A strong anti-opioid medication to counteract effects of maternal narcotics given within the previous 3 hours.
      - Establish ventilation before administration.
      - Dosage: Up to 0.1-0.2 mg/kg body weight for intramuscular injection.
      - Caution: Should not be given to infants of narcotic-addicted mothers, as it may precipitate acute withdrawal.
    - Sodium Bicarbonate: Administer if heart rate is less than 60 bpm despite effective ventilation, chest compression, and two intravenous doses of adrenaline.
      - Dosage: 4.2% solution using 2-4 ml/kg by slow intravenous injection at a rate of 1 ml/min to alleviate acidosis.
      - Ventilation must be established beforehand.
    - Adrenaline (Epinephrine): Indicated when heart rate is less than 60 despite 1 minute of effective ventilation and chest compression.
      - Initial dose: 0.1-0.3 ml/kg of 1:10,000 solution administered intravenously.
    - Calcium Gluconate: Dosing at 100 mg/kg body weight and isoprenaline (0.1-0.5 mg/kg/min) may be applicable for severe bradycardia or cardiopulmonary arrest.
    - Human Albumin: Shown to be effective if pulmonary hemorrhage or signs of shock persist after adequate resuscitation.
      - Dosage: 4.5% human albumin 10-20 ml/kg as a volume expander, administered rapidly.
    - Dextrose: 10% solution at 3 ml/kg may be given intravenously to treat hypoglycemia.
    - Konakion (Vitamin K): Up to 1 mg may be given intramuscularly to reduce hemorrhage risk.
    - Dexamethasone: 1-2 mg may be given IV or IM to minimize the risk of cerebral edema in cases of severe asphyxia.

OBSERVATION AND AFTERCARE

• Continuous monitoring and documentation of the baby's response during resuscitation procedures.
• Note the time when spontaneous respirations are established.
• Consider leaving the endotracheal tube in place for a few minutes post-establishment of breathing.
• Newborns with an APGAR score less than 6 at 5 minutes, or who are slow to respond to resuscitation, should be transferred to a neonatal unit for observation regarding potential cerebral function impairment.
• Parents must be informed about resuscitation efforts and reasons for any transfer, ensuring the mother has the chance to see and hold the baby if conditions permit.
• Babies responding quickly to resuscitation may remain with parents in the delivery room until transfer to the postnatal ward.

RESUSCITATION ACTION PLAN: KEY POINTS

• Anticipate potential problems.
• Verify the readiness of resuscitation equipment.
• Start the timing clock.
• Execute suctioning as necessary.
• Ensure the baby remains warm.
• Assess and document APGAR score.
• Provide oxygen supplementary support as needed.
• Implement bag and mask ventilation strategies.
• Facilitate endotracheal ventilation when indicated.
• Perform cardiac massage if necessary.
• Utilize specified drugs to assist resuscitation efforts.
• Address other emerging problems as they arise.

QUESTIONS OR CONTRIBUTIONS

Instructor: Grace Adjei
Date: 2/11/2025