Neonatology by Gomella

Author:Gomella
Format: epub
Published: 0101-01-01T00:00:00+00:00

considered early. There are a few reports (albeit uncontrolled) suggesting that the use of HFO is of benefit and may even prevent some neonates from requiring extracorporeal membrane oxygenation (ECMO).

E. Surfactant. In infants with RDS, administration of surfactant is associated with a fall in PVR. Surfactant may also be of benefit in various other pulmonary disorders (eg, meconium aspiration), although it is unknown whether its actions in these is related to a reduction in PVR.

F. Pressor agents. Some infants with PPHN have reduced cardiac output. In addition, increasing systemic blood pressure will reduce the right-to-left shunt. Hence, at least normal blood pressure should be maintained, and some recommend maintaining blood pressure of ≥40 mm Hg. Dopamine is the most commonly used drug for this purpose. Dobutamine has the disadvantage, in this context, that, although it may improve cardiac output, it has less of a pressor effect than dopamine. A simple nonpharmacologic measure to increase systemic vascular resistance is to inflate blood pressure cuffs on all four extremities. In a small study using this technique, inflating the blood pressure cuffs was associated with a 10- to 25- mm Hg increase in arterial oxygen tension. Moreover, administration of tolazoline to these infants resulted in a further 10- to 20-mm Hg increase and did not precipitate hypotension (see Rhodes et al, 1995).

G. Sedation. The lability of these infants has been mentioned previously, and hence sedation is commonly used. Nembutal (1-5 mg/kg) or Versed (0.1 mg/kg) is frequently used, and analgesia with morphine (0.05-0.2 mg/kg) is also used.

H. Paralyzing agents. The use of these agents is controversial. It is reasonable to use a paralyzing agent in infants who have not responded to sedation and are still labile or who appear to "fight" the ventilator. Pancuronium is the drug most commonly used, although it may increase PVR to some extent and worsen ventilation-perfusion mismatch. Vecuronium (0.1 mg/kg) has also been used.

I. Alkalinization. In the past, it had been noted that hyperventilation, with the resulting hypocapnia, improved oxygenation secondary to pulmonary vasodilation. Subsequently, it was shown that the beneficial effect of hypocapnia was actually a result of the increased pH rather than of the low PaCO2 values achieved. Furthermore, follow-up of infants with PPHN had suggested that hypocapnia was related to poor neurodevelopmental outcome (especially sensorineural hearing loss). Hypocapnia is known to reduce cerebral blood flow. Hence, it may be advisable to increase pH using an infusion of sodium bicarbonate (0.5-1 mEq/kg/h) if possible. Serum sodium should be monitored so as to avoid hypernatremia. Improvement in oxygenation is often seen with arterial pH 7.50-7.55 (sometimes levels as high as 7.65 are required).

J. Intravenous pulmonary vasodilators. Various intravenous pulmonary vasodilators have been tried in the past (tolazoline, prostaglandin E1, prostacyclin, nitroglycerin, nitroprusside, and others). All of these are also systemic vasodilators and often cause systemic hypotension with little, if any, net benefit. Tolazoline is probably the most commonly used drug of this class. It is an α-adrenergic antagonist with histaminergic action. It is given as a loading dose of 1-2 mg/kg followed by continuous infusion of 1-2 mg/kg/h.

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