| The patient was admitted at 45 days of life (day 0) in our unit due to moderate-severe dermatitis caused by acute gastroenteritis. | |
| Data of interest include: preterm newborn of 32 weeks gestational age with adequate birth weight (2.060 g) and Down syndrome, diagnosed in the first week of life of FT. | |
| He had not presented any hypoxic crisis before admission. | |
| His curve was adequate. | |
| On ultrasound (Snos 100 CF, Hewlett Packard and 50percent nasal oscillatory oscillating, USA), a gradient of 70 mmHg was observed, the basal O2 saturation for ABG was 92%. | |
| On the third day she presented acute hypovolemic shock due to severe diarrhea, requiring volume expansion, intubation and connection to mechanical ventilation (MV). | |
| After a good clinical response, the patient was discharged after 6 hours with good clinical and gasometric tolerance. | |
| On the fifth day he began with progressive dyspnea, chronic cough, bilateral crackles without wheezing, requiring reintubation and connection to MV (Baby Medilog 8000techn plus, Dräger | |
| Lübeck, Germany). | |
| Respiratory syncytial virus (RSV) determination in nasal mucus was negative. | |
| On the eighth day she developed progressive oligoanuria with generalized edema (maximum weight gain of 16% on the ninth day) and increased oxygen requirements (FiO2: 100%), with significant reduction in pulmonary compliance. | |
| Invasive AMT remained above 45 mmHg (percentile 5 for age: 43 mmHg): there was no pathological thermal gradient or coagulopathy. | |
| On auscultation, the heart murmur changed in characteristics, becoming shorter and less intense (suggesting suprasystemic PHP). | |
| Prone ventilation only achieved mild improvement for 2-3 hours (degree feedback index [IO] from 19 to 16) and the patient did not tolerate increased positive pressure at the end) (higher systemic hypotension (PEO) 8 cmH2O). | |
| After ruling out infundibular spasm on ultrasound and checking for PPH (contrast-enhancement shunt [CIV]), treatment with ONI was started at 40 ppm. | |
| After good response, it was maintained at 20 ppm. | |
| The INR and nitrous oxide (ppmNOxMP plus, Bedfont Scientific Ltd, Upchurch Kent, England) were continuously monitored and maintained in ranges less than 3 years. | |
| 1. | |
| The patient was also treated with dopamine infusion at 8 μg/kg/minute. | |
| Chest X-ray showed bilateral alveolar infiltrates and mild pulmonary oligoperfusion. | |
| In bronchoalveolar lavage, Pseudomonas aeruginosa was isolated and antibiotic treatment was initiated. | |
| On day 12, resolution of acute renal failure and oedemas was observed without treatment with renal function tests. | |
| Since day 30, progressive improvement in respiratory dynamics was observed, tolerating progressive weaning from ONI (previously could not be reduced to less than 15 ppm for not tolerating the patient). | |
| On day 35, the patient was extubated. | |