Use of Viagra
Why Viagra on Babies?
Dr.P.K.Rajiv, Head of newborns in AIMS,Kochi says "In newborns pulmonary hypertension is usually caused by complications in delivery. Sometimes it is also caused by pneumonia". Another critical newborn which was brought for surgery for hernia into the lung (diaphragmatic hernia) had developed severe pulmonary hypertension within a few hours of birth. In the case of Sunitha's baby,the first child, when conventional ventilation failed to improve the condition Dr.Rajiv administered Sildenafil Citrate along with nitric oxide in maximum doses of 80 ppm. Suddenly the supply of nitric oxide stopped due to equipment failure, which lead to serious concern of a drastic fall in the blood oxygenation. But to everybody's surprise the baby's condition did not deteriorate and showed slow improvement over the next 24 hrs. The baby's oxygen requirements came down gradually and the baby could be taken off life support systems(ventilator) within another two days. Few doses of Viagra stabilized the pulmonary artery pressure saving the blue baby from near death.
Dr.Rajiv says " Viagra may come in handy when nitric oxide fails to deliver the goods. Nitric oxide is not freely available and there are very few centers in India which have a regular supply of the gas. However Viagra should be used only if there is nitric oxide backup.It should not be used randomly since it is not a fully evaluated drug .Viagra could lead to harmful side effects in adults with pre-existing cardiac disease, severe lung disease ,renal failure and low blood pressure.It could also inhibit the eye enzyme phosphodiestrase leading to problems in colour vision. These specific problems are a reflection of adult disease and are not generally a contraindication for use in newborn. However since it is not fully evaluated on a long term basis its use should be limited to compassionate use in life threatening severe pulmonary hypertension when maximum approved medical therapy (high frequency ventilation and nitric oxide) have failed .The main advantage over nitric oxide would be its cost and availability .Nitric oxide is expensive at Rs 300per hour while Viagra comes at Rs 25 per tablet and it is not a potentially ,accumulating drug in the body with long term effects,considering its short term use of 8 to 12 doses.This observation is extrapolated from data on long term use in adults and very high doses used over extended periods."
Dr. Rajiv used a dose of 1 to 1.5 mg per kilo every 4 to 6 hrs.The most impressive change due to sildenafil was evidenced in the third blue baby's condition who presented near death. This baby was very sick and was straight away put on high frequency ventilation due to failure of conventional ventilation. Sildenafil was started same time due to unavailability of nitric oxide.The baby general condition and oxygen levels improved so dramatically that the baby could be taken off the ventilator within three days of arrival to the newborn intensive care unit.Sildenafil was given till the baby's oxygen requirements came down to 50 percent. Generally when a dangerously ill blue baby presents to our ICU a minimum period of five days of a near death situation is evidenced when conventional ventilation and nitric oxide have been used.
The dramatic effectiveness of Sildenafil in these babies made Dr. Rajiv formulate a few observations which could be central to further studies.
1.Oral therapy though effective, definitely needs an intravenous preparation since pulmonary hypertension is a near death situation and needs rapid action .In our observation the stability of pulmonary vasculature was attained only after the third oral dose after which flip-flop when weaning down oxygen is prevented and the baby could be weaned down smoothly.
2.The optimum oral dose appears to be between 1 to 1.5 mg per kilo every 4 to 6 hourly.Doses above 2mg per kilo may cause fall in systematic blood pressure leading to deterioration of the pulmonary hypertension.
3.Sildenafil therapy works more effectively when perfusion has been optimized . Hence bolus of saline or plasma 10 to 20 ml per kilo on arrival followed by maximum inotropic support appears to be critical for sildenafil to be effective. In addition the optimization of lung volume with high frequency ventilation appears critical to its total effectiveness.
4.The introduction of sildenafil early in the treatment once pulmonary hypertension is diagnosed echocardiographicaly appears to stabilize pulmonary vasculature faster with shorter stay on the ventilator .This so called prophylaxis management rather than rescue appears to be a very important observation in the third index case.
5.The distinct possibility of sildenafil to prevent severe pulmonary hypertension which would require ventilatory support is an important avenue of research. Its a personal observation that in high risk situations, (example, severe birth asphyxia and meconium aspiration) prophylactic use of sildenafil immediately after birth could prevent development of the above mentioned catastrophe. The optimum dose and number of doses have to be determined in further studies as well as optimum blood levels.
6.Sildenafil citrate holds a lot of promise in the treatment of labile pulmonary hypertension of newborn and may have limited potential in fixed pulmonary hypertension due to remodeling of pulmonary vasculature.
