Persistent Pulmonary Hypertension of the Newborn
(PPHN)

 		 Reviewed by Simon Rowley and Carl Kuschel
January
2001
Clinical Guidelines Back Newborn Services Home Page
Pathogenesis Diagnosis Investigations
Management Aims Specific Therapies References

Infants with Persistent Pulmonary Hypertension of the Newborn (PPHN) are exceptionally unstable and difficult to manage. After initial resuscitation the management should always be discussed with the consultant on call.

Pulmonary hypertension of the newborn with right to left shunt occurs in a variety of clinical situations. These include Meconium Aspiration Syndrome, hypoplastic lungs, transient tachypnoea of the newborn, congenital pneumonia and hyaline membrane disease. Secondary disturbances such as polycythaemia and myocardial failure are contributory. There is frequently a history of chronic in utero hypoxia, but some cases remain idiopathic.

Pathogenesis

Diagnosis

Investigations

Necessary investigations include

Aims of Management

  1. Lower pulmonary vascular resistance.
  2. Maintain systemic blood pressure.
  3. Reverse right-to-left shunting.
  4. Improve arteriolar oxygen saturation and oxygen delivery to the tissues.
  5. Minimise barotrauma.

Specific Therapies

1. Oxygen and ventilation
  1. 100% O2
    Always start with 100% oxygen and reduce the FiO2, rather than starting on 25% and increasing.  In the short term there is no risk to a term baby using such measures.
  2. Normo-ventilation i.e. pO2 7-12 kpa is acceptable if baby stable
  3. pCO2 5-7 kpa if this can be achieved
  4. Use of HFOV, particularly in combination with inhaled Nitric Oxide, has been shown to reduce the need for ECMO.

2. Normotension
  1. Myocardial function is frequently poor, despite reasonable blood pressures.
  2. Aim to keep the mean arterial pressures above 50mm Hg in term infants
  3. Use volume (initially normal saline) and dopamine -starting with 5-10 mcg/kg/min and/or dobutamine 5-10 mcg/kg/min if systemic pressure raises and pulmonary pressure stays the same, R-L shunt will diminish .
  4. Adrenaline infusions may be indicated if there is severe myocardial dysfunction

3. Avoid polycythaemia
  1. Aim to keep the PCV between 0.40 and 0.45.

4. Alkalosis
  1. Establish the critical pH- preferably 7.45 but may be higher.  If there is no dramatic improvement in PaO2 at a pH >7.6, the infant can be deemed to be "pH unresponsive".
  2. Use small boluses of bicarbonate (1-2 mmol/kg) or a continuous infusion (0.5mmol/kg/hour initially).  Liberal bicarbonate use may result in hypernatraemia and hypokalaemia.

5. Sedation
  1. Many babies are very unstable.
  2. Consider early use of narcotic infusions.

6. Muscle Relaxation
  1. This may be necessary to gain initial control in very vigorous babies who are not adequately sedated with narcotics and are fighting the ventilator to their detriment.
  2. Use pancuronium 100micrograms/kg/dose PRN preferably for 24 hours or less.

7. Pulmonary vasodilators
  1. Inhaled nitric oxide (iNO) is the vasodilator of choice.
    iNO should be started at 20ppm and reduced to 5ppm as able, according to response and to stability.
    Methaemoglobin levels should be monitored (these are measured automatically on blood gases).
    Nitrogen dioxide (NO2) levels should be monitored and kept below 1ppm.
  2. Magnesium sulphate may be used in refractory cases.  The use of MgSO4 is controversial but may be indicated in selected instances.
  3. Prostacyclin may also be used in severe and refractory cases, although it is difficult to obtain and its use is controversial.
  4. Tolazoline is no longer used at NWH.  It is a non-registered medication.  It has an unpredictable effect and frequently results in systemic hypotension and collapse.

8. Hyperventilation
  1. Inducing alkalosis by hyperventilation often creates as many problems as it solves and is best avoided. There can be an improvement in PO2.

9. ECMO
  1. This is essentially prolonged cardio-pulmonary bypass and is provided via PICU at Starship Hospital.
  2. Usual criteria are infants who have an Oxygenation Index (OI) >40 but it may be appropriate to discuss infants who may potentially require ECMO with the PICU specialist early rather than when ECMO or death are imminent.  This will be done specialist-to-specialist.  The neurological status of the infant may be an important factor in determining if ECMO is offered.
OI =         MAP x100       x FiO2 Click here to open the OI calculator
PaO2 (mmHg)
where MAP is Mean Airway Pressure,
PaO2 is the arterial oxygen tension in mmHg (1kPa = 7.5mmHg), and
FiO2 is the fraction of inspired oxygen (100% = 1.0, air = 0.21)

10. Weaning
  1. Weaning such babies is invariably difficult. Steps should be taken one at a time and by small increments once lability appears to have stabilised.

Other

References

1 Drummond WH. Persistent pulmonary hypertension of the neonate (Persistent fetal circulation syndrome). 1984, Year Book Medical Publishers, In. pg 61-85.
2 Fox WW, Duara S. Persistent pulmonary hypertension in the neonate: Diagnosis and management. J Pediatr 1983; Vol 103:4 pg 505-514.
3 Drummond WH, Gregory GA, et al. The independent effects of hyperventilation, tolazoline, and dopamine on infants with persistent pulmonary hypertension. J Pediatr 1981; 9(4): 603-611
4 Wung J, James LS, et al. Management of infants with severe respiratory failure and persistence of the fetal circulation, without hyper- ventilation. Pediatrics 1985; 76:4, pg488-494.
5 Hansen and Corlet from "Diseases of the Newborn" : Disorders of the transition. Taeusch Ballard Avery 6th edition -Chapter VIII.
6 Finer NN, Barrington KJ.  Nitric oxide for respiratory failure in infants born at or near term.  Cochrane Database of Systematic Reviews 2000; Issue 2.  Update Software.
7 UK Collaborative ECMO Trial Group.  UK collaborative randomised trial of neonatal extracorporeal membrane oxygenation.  Lancet 1996; 348:75-82.