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Persistent Pulmonary Hypertension of the Newborn By Jennifer Stevenson.

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1 Persistent Pulmonary Hypertension of the Newborn By Jennifer Stevenson

2 PPHN zAlso known as Persistent fetal circulation. zPPHN is the failure of PVR to fall at birth. zThe transition from fetal circulation to extra uterine circulation is not complete. zR-L shunting occurs through a patent ductus arteriosus and foramen ovale.

3 Typically seen in: zFull term or post term infants z37-41 weeks gestational age zwithin the first hours after birth.

4 Primary PPHN zClassical PPHN yidiopathic zHypoxemia develops in a baby with normal lungs. zBreath sounds and CXR are usually normal.

5 Possible causes zchronic intrauterine hypoxia zasphyxia zmaternal ingestion of prostaglandin ypremature ductal closure zhypoglycemia zhypothermia zmaternal hypertension

6 Prostaglandin ingestion zMothers who took aspirin near term caused repeated intrauterine closure of the ductus with redirection of blood into the pulmonary vasculature.

7 Secondary PPHN zPPHN secondary to lung disease. ymeconium aspiration syndrome ycongenital diaphragmatic hernia ygroup B streptococcal pneumonia yrespiratory distress syndrome ysepsis yhypoplasia

8 In Utero zFetal gas exchange occurs through the placenta instead of the lungs. zPVR > SVR causes blood from the right side of the heart to bypass the lungs through the ductus arteriosus and foramen ovale.

9 Fetal Shunts zDuctus arteriosus yR-L shunting of blood from pulmonary artery to the aorta bypasses the lungs. yUsually begins to close hours after birth. zForamen ovale yOpening between left and right atria. yCloses when there is an increased volume of blood in the left atrium.

10 At Birth zFirst breath yDecrease in PVR yIncrease in pulmonary blood flow and PaO 2 zCirculatory pressures change with the clamping of the cord. ySVR >PVR allowing lungs to take over gas exchange. yIf PVR remains higher blood continues to be shunted and PPHN develops.

11 Signs of PPHN zInfants with PPHN are born with Apgar scores of 5 or less at 1 and 5 minutes. zCyanosis may be present at birth or progressively worsen within the first hours.

12 Later developments zWithin a few hours after birth ytachypnea yretractions ysystolic murmur ymixed acidosis, hypoxemia, hypercapnia zCXR ymild to moderate cardiomegaly ydecreased pulmonary vasculature

13 Pulmonary Vasculature zPulmonary vascular bed of newborn is extremely sensitive to changes in O 2 and CO 2. zPulmonary arteries appear thick walled and fail to relax normally when exposed to vasodilators. zCapillaries begin to build protective muscle. (remodeling)

14 Diagnosis zHyperoxia Test zPlace infant on 100% oxyhood for 10 minutes. yPaO 2 > 100 mmHg parenchymal lung disease yPaO 2 = mmHg parenchymal lung disease or cardiovascular disease yPaO 2 < 50 mmHg fixed R-L shunt cyanotic congenital heart disease or PPHN

15 Hyperoxia Test (cont.) zIf fixed R-L shunt yneed to get a preductal and postductal arterial blood gases with infant on 100% O 2. xPreductal- R radial or temporal artery xPostductal- umbilical artery yIf > 15 mmHg difference in PaO 2 then ductal shunting yIf < 15 mmHg difference in PaO 2 then no ductal shunting

16 Hyperoxia-Hyperventilation Test zHyperinflate baby with manual resuscitator and 100% O 2 until PaCO 2 reaches mmHg. yPaO 2 = 100 mmHg with hyperinflation xPPHN yPaO 2 < 100 mmHg with hyperinflation xR/O congenital heart disease with echocardiogram. abnormal Echo = congenital heart disease normal Echo = PPHN

17 Echocardiography zR ventricle may be larger than normal. zRatio of pre-ejection period (PEP) to ejection time (ET) is used to evaluate left and right ventricle performance. yPPHN causes a prolonged R ventricle PEP/ET ratio xincreased pulmonary artery pressure xincreased pulmonary vascular resistance

18 Echo (cont.) zPPHN can be identified early if R and L ventricular PEP/ET ratios are measured soon after birth. zBabies with R ventricular ratio >.50 and L ventricular ratio >.38 developed PPHN within hours after birth.

19 Cardiac Catheterization zIn past, cardiac catheterization was used to diagnose infants with PPHN by monitoring pulmonary artery pressures. zToday this is not recommended because it is traumatic to the baby and it is no longer needed to make a diagnosis.

20 Treatment zGoals: yTo maintain adequate oxygenation. xThese babies are extremely sensitive xHandling them can cause a decrease in PaO 2 and hypoxia xCrying also causes a decrease in PaO 2 xTry to coordinate care as much as possible yTo maintain neutral thermal environment to minimize oxygen consumption.

21 Medication zTolazine (Priscoline)- pulmonary and systemic vasodilator ypulmonary response needs to assessed by giving 1-2 mg/kg through peripheral scalp vein xif positive response- start continuous infusion of mg/kg/hr

22 Tolazine (cont.) zMonitor closely for GI bleeding, pulmonary hemorrhage and systemic hypotension. zMay need to also give Dopamine or Dobutamine to maintain systemic blood pressure and to increase CO.

23 Mechanical Ventilation zTCPLV (Time cycled pressure limited ventilation) may be used with PPHN. zWant to use low peak inspiratory pressures zMonitor PaO 2 and PaCO 2 with a transcutaneous monitor

24 Hyperventilation zHyperventilation helps promote pulmonary vasodilation zRespiratory Alkalosis- decrease PAP to level below systemic pressures to improve oxygenation by helping to close the shunts yTry to keep pH =7.5 and PaCO 2 = yAlkalizing agents - sodium bicarbonate or THAM

25 Hyperventilation (cont.) zBabies often become agitated when they are hyperventilated zMay need to administer muscle relaxants and sedation yusually given pancuronium and morphine xpancuronium- q 1-3 hours IV at mg/kg xmorphine- continuous infusion 10 micrograms/kg/hr

26 HFOV zHigh frequency oscillatory ventilation ydecrease risk of barotrauma yeffective alveolar ventilation yalveolar recruitment xNitric Oxide more effective zHFOV more effective in PPHN babies with lung disease

27 Nitric Oxide (NO) zPotent pulmonary vasodilator ydecrease pulmonary artery pressure yincrease PaO 2 zDoes not cause systemic hypotension zNO more effective in PPHN babies without lung disease zBaby must be weaned slowly off NO or may have rebound hypertension

28 Effects of NO zNO is metabolized to nitrogen dioxide (NO 2 ) which can cause acute lung injury. zNO 2 is potentially toxic. zNO reacts with hemoglobin to form methemoglobin.

29 ECMO zExtra corporeal membrane oxygenation zForm of cardiorespiratory support that allows the lungs to rest so also called extracorporeal life support (ECLS). zECMO has increased survival rate significantly

30 ECMO (cont.) zECMO is given as a last resort when everything else has failed. zRequirements y> 33 weeks gestational age ypotentially reversible lung disease yno bleeding disorders yno intraventricular hemorrhages

31 Two Routes zVenovenous route yblood taken from R jugular vein and returned to the venous system. zVenoarterial route yblood taken from R jugular vein and returned through R carotid artery zGas exchange takes place as the blood is pumped through a membrane oxygenator

32 Outcome zPPHN may last anywhere from a few days to several weeks. zMortality rate is 20-50%. yDecreased by HFOV and NO yDecreased by ECMO zBabies treated with hyperventilation may develop sensorineural hearing loss.

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