Vasopressin improves oxygen levels in newborns with acute PH: Study

Blood flow also boosted by the hormone treatment in difficult-to-treat babies

Margarida Maia, PhD avatar

by Margarida Maia, PhD |

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The hormone vasopressin may help improve oxygen levels and blood flow in newborns with acute pulmonary hypertension who fail to respond to treatment with inhaled nitric oxide, a study suggests.

About two-thirds of newborns treated with vasopressin in the study, however, developed hyponatremia (a low level of sodium in the blood), suggesting the need for careful monitoring of sodium status during infusion of the hormone.

The study, “Vasopressin in newborns with refractory acute pulmonary hypertension,” was published in the journal Pediatric Research.

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Pressure in lungs normally drops to allow newborns to breathe

When a baby is born and takes a first breath, the pressure in the lungs falls to adapt to breathing outside of the mother’s womb. This allows blood to travel to the lungs to get oxygen and deliver it to the rest of the body.

In babies with acute pulmonary hypertension, or persistent pulmonary hypertension of the newborn (PPHN), the pressure in the lungs stays high. As a result, there is a limit on how much oxygen reaches the body’s organs, including the brain, heart, and kidneys.

Treatment usually involves breathing support in combination with inhaled nitric oxide, a molecule that causes blood vessels to widen and blood pressure to drop. However, not all newborns respond in the same way to inhaled nitric oxide.

Vasopressin regulates blood pressure by fine-tuning the balance of sodium and body fluids. Previous reports have suggested vasopressin may ease symptoms in newborns with difficult-to-treat acute pulmonary hypertension.

Now, a team of researchers in Canada looked at the safety of add-on vasopressin and its effectiveness in newborns younger than 1 month who experienced acute pulmonary hypertension but failed to respond to inhaled nitric oxide.

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Study included 25 newborns who started on vasopressin days after birth

The study included 25 newborns (14 girls, 11 boys) who were started on vasopressin at a median age of 2 days. Eleven were preterm babies, meaning they were born before 37 weeks of pregnancy. Pulmonary hypertension developed right after birth in 23 newborns, and after the first week of life in two.

Vasopressin was started due to low levels of oxygen (32%), cardiovascular compromise (8%), or both (60%). Cardiovascular compromise occurs when the heart in unable to pump enough blood to the rest of the body.

The hormone was infused continuously at a median dose of 0.3 micro-units per kilogram of body weight per minute via a central line, which usually goes all the way up to a vein near or just inside the heart. The infusion was given for a median of 72 hours (three days).

After 12 hours of treatment with vasopressin, the median oxygenation index, a measure of how much breathing support is needed to maintain a healthy oxygen level, dropped from 28.4 to 14.4, indicating an improvement. After 24 hours, it had further dropped to 12.5.

The fraction of inspired oxygen, which refers to the concentration of oxygen in the gas mixture supplied by a ventilator, decreased from 0.91 to 0.5 after 12 and 24 hours post-treatment with vasopressin.

“One of the key observations in our study was the improvement in oxygenation indices after twelve and twenty-hours of vasopressin infusion,” the researchers wrote, noting the observation is in line with previous reports.

At the same time, the mean blood pressure increased from 41 millimeters of mercury before to 51 post-treatment at 12 and 24 hours, indicating an improvement of blood flow.

Before treatment, the median level of sodium in the blood was 135 millimoles per liter (mmol/L). During treatment with vasopressin, however, 17 (68%) newborns experienced an episode of hyponatremia, as sodium reached a level lower than 130 mmol/L.

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Call for monitoring of sodium levels for newborns receiving vasopressin

While hyponatremia did not appear to result in any damage to the liver or kidneys, “careful monitoring of serum sodium levels are warranted in newborns who are receiving vasopressin infusion,” the researchers wrote.

None of the newborns required extracorporeal membrane oxygenation, a type of support wherein part of the patient’s blood is diverted through an artificial lung for gas exchange (oxygenation and removal of carbon dioxide ) and then returning it to the patient. Nine newborns (36%) died, including six due to their initial diagnosis and three following a decision to redirect care.

“The use of vasopressin may be associated with improvement in oxygenation and hemodynamic [blood flow] status of neonatal patients” with acute pulmonary hypertension that failed to respond to initial therapy, the researchers concluded.

“However, larger, prospective studies [conducted over time] are needed to validate these findings and establish optimal treatment protocols for [acute pulmonary hypertension] in neonates,” they wrote.

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