Relief of severe pulmonary hypertension after closure of a large ventricular septal defect using low dose inhaled nitric oxide

Cardiopulmonary Resuscitation in Infants and Children With Cardiac Disease: A Scientific Statement From the American Heart Association

Cardiac arrest occurs at a higher rate in children with heart disease than in healthy children. Pediatric basic life support and advanced life support guidelines focus on delivering high-quality resuscitation in children with normal hearts. The complexity and variability in pediatric heart disease pose unique challenges during resuscitation. A writing group appointed by the American Heart Association reviewed the literature addressing resuscitation in children with heart disease. MEDLINE and Google Scholar databases were searched from 1966 to 2015, cross-referencing pediatric heart disease with pertinent resuscitation search terms. The American College of Cardiology/American Heart Association classification of recommendations and levels of evidence for practice guidelines were used. The recommendations in this statement concur with the critical components of the 2015 American Heart Association pediatric basic life support and pediatric advanced life support guidelines and are meant to serve as a resuscitation supplement. This statement is meant for caregivers of children with heart disease in the prehospital and in-hospital settings. Understanding the anatomy and physiology of the high-risk pediatric cardiac population will promote early recognition and treatment of decompensation to prevent cardiac arrest, increase survival from cardiac arrest by providing high-quality resuscitations, and improve outcomes with postresuscitation care.

[Recommendations for inhaled nitric oxide treatment in the newborn]

The recommendations in this document describe the current indications for inhaled nitric oxide (iNO) treatment in the newborn and clearly distinguish between those supported by scientific evidence and those for which evidence is still lacking, such as its use in preterm infants. The methodology for iNO administration, its dosage and the main secondary effects are discussed, and the reasons for lack of response to this treatment are analyzed.

Effects of Inhaled Nitric Oxide Administration on Early Postoperative Mortality in Patients Operated for Correction of Atrioventricular Canal Defects

OBJECTIVE

Postoperative pulmonary hypertension (POPH) substantially increases mortality after repair of congenital heart diseases. Inhaled nitric oxide (NO) has been reported as an effective and specific means of controlling POPH crisis. No randomized, placebo-controlled study has addressed the ability of NO administration to reduce mortality. Such a trial could raise ethical questions.

DESIGN

Observational study with historical control subjects based on multivariate confounder scores.

SETTING

Surgical pediatric ICU in a university hospital.

PATIENTS

Two hundred ninety-four records of patients operated on for atrioventricular (AV) canal between 1984 and 1994 who presented with severe POPH.

INTERVENTIONS

All variables found to be predictive for death by univariate tests were entered in a multivariate forward stepwise logistic regression model. Two paired groups regarding risk factors for death and only differing for POPH treatment (NO or conventional treatment) were constructed on the basis of predicted values obtained from this model. Twenty-five patients received NO, and 39 control patients, operated on between 1984 and 1994, received conventional treatment for POPH.

MEASUREMENTS AND RESULTS

Postoperative pulmonary pressure, date of operation, and occurrence of an infectious complication were retained in the model. The comparison between the two paired groups showed a significant difference in mortality (24%; 95% confidence interval [CI], 7 to 41%; vs 56%; 95% CI, 37 to 75%, respectively; p = 0.02).

CONCLUSIONS

This study suggests that there is a high probability for postoperative mortality reduction associated with administration of inhaled NO when severe POPH occurs in children operated for complete repair of AV canal.

Comparison of hyperventilation and inhaled nitric oxide for pulmonary hypertension after repair of congenital heart disease

BACKGROUND

Pulmonary hypertension is associated with congenital heart lesions with increased pulmonary blood flow. Acute increases in pulmonary vascular resistance (PVR) occur in the postoperative period after repair of these defects. These increases in PVR can be ablated by inducing an alkalosis with hyperventilation (HV) or bicarbonate therapy. Studies have shown that these patients also respond to inhaled nitric oxide (iNO), but uncertainty exists over the relative merits and undesirable effects of HV and iNO.

HYPOTHESIS

Alkalosis and iNO are equally effective in reducing PVR and pulmonary artery pressure (PAP) in children with pulmonary hypertension after open heart surgery.

SETTING

Critical care unit of a tertiary care pediatric hospital.

DESIGN

Prospective, randomized, crossover design.

PATIENTS

Twelve children with a mean PAP > 25 mm Hg at normal pH after biventricular repair of congenital heart disease.

INTERVENTIONS

Patients were assigned to receive iNO or HV (pH > 7.5) in random order, and the effect on hemodynamics was measured. Each treatment was administered for 30 mins with a 30-min washout period between treatments. Finally, both treatments were administered together to look for a possible additive effect.

MEASUREMENTS AND MAIN RESULTS

Cardiac output and derived hemodynamic parameters using the dye dilution technique. Hyperventilation, achieved by an increase in ventilator rate without a change in mean airway pressure, decreased Pa(CO2) from a mean (SD) of 43.7+/-5.3 to 32.3+/-5.4 mm Hg and increased pH from 7.40+/-0.04 to 7.50+/-0.03. This significantly altered both pulmonary and systemic hemodynamics with a reduction in PAP, PVR, central venous pressure, and cardiac output and an increase in systemic vascular resistance. In comparison, iNO selectively reduced PAP and PVR only. The reduction in PVR was comparable between treatments, although addition of iNO to HV resulted in a small additional reduction in PVR. An additional decrease in PAP was seen when HV was added to iNO, attributable to a reduction in cardiac output rather than a further decrease in PVR.

CONCLUSIONS

Inhaled NO and HV are both effective at lowering PAP and PVR in children with pulmonary hypertension after repair of congenital heart disease. The selective action of iNO on the pulmonary circulation offers advantages over HV because a decrease in cardiac output and an increase in SVR are undesirable in the postoperative period.

Preoperative and postoperative response to inhaled nitric oxide

The preoperative dose response to inhaled nitric oxide (NO) was compared with the need for and response to NO after cardiac surgery in patients with congenital heart defect and secondary pulmonary hypertension. In a preoperative vasodilator test with inhaled NO 20, 40 and 80 ppm and oxygen, mean pulmonary artery pressure (PAP) was at least 40 mmHg and/or the pulmonary vascular resistance index (PVRI) 4 Wood units. Preoperatively, NO 40 ppm and FiO2 0.9 reduced systolic pulmonary/systemic arterial pressure (PAPs/SAPs) from 0.89 (SD 0.10) to 0.80 (0.18) and pulmonary/systemic vascular resistance (PVR/SVR) from 0.26 (0.13) to 0.13 (0.08). Haemodynamic assessment was repeated in 11 patients postoperatively. NO treatment was started if PAPs/SAPs rose to 0.8 or the pulmonary oximetry fell below 40%. Postoperatively, eight of 11 patients, including 6 patients with Down's syndrome, needed NO. PAPs/SAPs decreased more than preoperatively: 48.5% vs 11.2, p = 0.0045. Pulmonary oximetry increased by 15.7%, p = 0.02. The degree of preoperative response to NO did not differ between the patients with postoperative pulmonary hypertension and the other children. Patients with early pulmonary hypertensive crisis (first 24 h; n = 6) had a higher PVRI (7.6 vs 4.4 Um2; p = 0.003) and PVR/SVR (0.34 VS 0.17; p = 0.02) preoperatively. Two patients died in pulmonary hypertensive crisis.

Treatment of pulmonary hypertension during surgery with nitric oxide and vasodilators

PURPOSE

To describe the effects of the combination of several therapies on the pulmonary circulation and cardiac function in a patient with severe pulmonary hypertension.

CLINICAL FEATURES

We report the case of a female patient with chronic secondary pulmonary hypertension and cardiac failure who underwent right hemicolectomy under general anesthesia. Insertion of a pulmonary artery catheter before the operation revealed pulmonary artery pressure (PAP) of 55/24 mm Hg which was lowered moderately by 40 parts per million (ppm) inhNO. During surgery, the patient presented an episode of atrial fibrillation with a slow, irregular heart rate of 45-50 min(-1) and variable systemic pressure. A dipyridamole DPD (0.2 mg x kg(-1)) bolus stabilized systemic pressure and increased heart rate and cardiac output. However, PAP did not change. Nitroglycerine infusion was started at 10 mg x hr(-1) shortly after the initiation of DPD. The patient responded favourably to combined inhNO, intravenous DPD and NTG therapy with a marked and sustained reduction of PAP and a systemic hemodynamic stability.

CONCLUSION

We conclude that: 1) in combination with inhNO, DPD does not augment the inhNO-induced decrease in PAP; 2) DPD improves the hemodynamic profile and elevates cardiac output; 3) therapeutic combination (inhaled NO, NTG, DPD) has a potent effect on pulmonary pressure in cardiac failure patients.

Fluctuations of inspired concentrations of nitric oxide and nitrogen dioxide during mechanical ventilation

BACKGROUND: Nitric oxide (NO) is a very reactive agent with potentially toxic oxidation products such as nitrogen dioxide (NO2). Therefore, during NO inhalation a constant inspired concentration and accurate measurement of NO and NO2 concentrations are essential. The objective of this study was to test the NO concentrations at various positions along the inspiratory limb of the breathing circuit using a recently developed system to administer NO in phase with inspiratory flow during mechanical ventilation (Servo 300 NO-A, Siemens, Sweden). Furthermore, we tested whether an active heating system would interfere with inspired NO concentrations. RESULTS: A sharp decline in the NO concentration was found between the respirator's inspiratory outlet and more distal points along the inspiratory limb of the circuit. This finding was most evident when an active heating system was mounted between those points. CONCLUSIONS: The concentrations of NO and NO2 should be measured as near to the patient as possible, as significant fluctuations of these concentrations might be found along the inspiratory limb of the respiratory circuit especially when an active heating system is used.

The Utility of Nitric Oxide in the Postoperative Period

Inhaled nitric oxide (iNO) is a pulmonary-selective vaso dilator with minimal bronchodilator activity in humans. NO also inhibits platelet and neutrophil activation and adhesion and inhibits ischemia-reperfusion injury. The pulmonary vasodilatory property of iNO causes a reduc tion in pulmonary vascular resistance and improvement in arterial oxygenation in a wide spectrum of diseases characterized by pulmonary hypertension and hypox emia. Promising examples of diseases for which NO may provide beneficial physiologic effects are primary and secondary pulmonary hypertension, right ventricu lar failure, cardiac transplantation, pulmonary embo lism, protamine reactions, acute respiratory distress syndrome, lung transplantation and, perhaps, chronic obstructive airways disease. The usefulness of iNO may be improved by concomitant therapy with pulmonary- selective intravenous vasoconstrictors (eg, Almitrine; Vectarian, Neuilly, France) and cGMP phosphodiester ase V inhibitors (eg, Zaprinast; Research Biochemicals International, Natick, MA). Almitrine improves oxygen ation, synergistically with iNO, and may be useful in disease states characterized primarily by hypoxemia. Zaprinast may be useful for weaning iNO and avoidance of rebound pulmonary hypertension.

Nitric oxide, oxygen, and prostacyclin in children with pulmonary hypertension

OBJECTIVE

To test the vasodilatory response of the pulmonary vascular bed in children with pulmonary hypertension.

DESIGN

Prospective dose response study in which the effects of inhaled nitric oxide (NO) are compared with those of oxygen and intravenous prostacyclin.

PATIENTS AND INTERVENTIONS

The vasodilator test was performed in 20 patients in whom mean pulmonary artery pressure (PAPm) was > or = 40 mm Hg and /or pulmonary vascular resistance index was > or = 4 Um2. Haemodynamic effects of inhaled NO (20, 40, and 80 ppm) at a fractional inspired oxygen (FiO2) value of 0.3, pure oxygen, oxygen at FiO2 0.9-1.0 combined with NO as above or with intravenous prostacyclin at 10 and 20 ng/kg/min were measured.

RESULT

NO decreased PAPm with a dose response from 20 to 40 ppm (mean change at 40 ppm-5.50, 95% confidence interval (CI) -7.98 to -3.02 mm Hg. Maximal decrease in the ratio of pulmonary to systemic vascular resistance was achieved with a combination of NO 80 ppm and oxygen (-0.18, 95% CI -0.26 to -0.10). Increase in the pulmonary flow index was greatest with pure oxygen in those with an intracardiac shunt (8.52, 95% CI -0.15 to 17.20 l/min/m2). Neither NO nor oxygen altered systemic arterial pressure but intravenous prostacyclin lowered systemic arterial pressure and resistance.

CONCLUSIONS

NO selectively reduces pulmonary vascular resistance and pressure maximally at 40 ppm. Oxygen reduces pulmonary vascular resistance and NO potentiates this reduction without affecting the systemic circulation. Prostacyclin vasodilates the pulmonary and the systemic circulations.

The role of nitric oxide in cardiac surgery

The release of nitric oxide (NO) from coronary endothelial cells is impaired following reperfusion; however, several experimental studies have found that it exerts a cardioprotective effect during myocardial ischemia-reperfusion. Thus, attempts have been made to supplement NO production exogenously during reperfusion when endogenous NO release may be diminished. Conversely, other studies suggest that NO exacerbates reperfusion injury by inducing the production of peroxynitrite. NO has also been reported to provide beneficial effects as a selective pulmonary vasodilator to relieve pulmonary hypertension. A loss of NO-mediated relaxation caused by the dysfunction of endothelial cells is characteristic of intimal hyperplasia, and nitrosovasodilators have proven efficient against atherosclerotic coronary heart disease, which may be attributable to their antiplatelet effects as well as to vasodilation. Furthermore, protamine sulfate, which is rich in L-arginine, is thought to augment NO production by supplying exogenous L-arginine, or to act on endothelial cell receptors to stimulate the production of NO. This review summarizes the current role of NO in cardiac surgery.

Inhaled low-dose nitric oxide for postoperative care in patients with congenital heart defects

Postoperative pulmonary hypertensive crisis is a major problem that may account for a substantial part of the postoperative mortality and morbidity. We, therefore, evaluated the effect of inhalation of low-dose nitric oxide (NO) on postoperative care in pediatric patients with pulmonary hypertension. We studied 10 infants and children ages 1-108 months (median age, 11 months) with congenital heart disease associated with pulmonary hypertension. The NO and N2 gas mixture was then mixed with varied quantities of air and oxygen and delivered into a respirator instead of an inspiratory tube. Patients were treated with inhaled NO for 38.6 +/- 19.6 h (range 1-200 h). All patients were eventually weaned from high level sedation and respirator. The NO concentration ranged from 2 to 5 parts per million. During NO inhalation patients demonstrated a statistically significant reduction in systolic pulmonary arterial pressure by approximately 26%; from 55 +/- 10 to 41 +/- 20 mm Hg. Inhalation of NO resulted in a significant increase of Pao2 from 110 +/- 16 to 149 +/- 29 mm Hg. A-aDo2 significantly decreased from 284 +/- 27 to 247 +/- 31 mm Hg. In conclusion, we have shown that a low-dose NO inhalation acted as pulmonary vasodilator in patients with preexisting pulmonary hypertension.

Hemodynamics and oxygenation changes induced by the discontinuation of low-dose inhalational nitric oxide in newborn infants

OBJECTIVE

To assess changes associated with nitric oxide (NO) discontinuation in neonates receiving inhalational NO therapy as a treatment for pulmonary hypertension of the neonate (PPHN).

DESIGN

Prospective study.

SETTING

A pediatric PICU in a university hospital.

PATIENTS AND METHODS

Ten neonates were included. NO discontinuation was attempted when the oxygenation index fell below 10. The mean NO concentration was 4.9 +/- 0.8 ppm. Each infant was studied over three successive 5-min periods and was assigned to either group 1 (NO1+, NO2+, NO-) or group 2 (NO1+, NO-, NO2+).

MEASUREMENTS AND RESULTS

Postductal transcutaneous PO2 (tcPO2), postductal oxygen saturation with pulse oxymetry (SpO2), systolic and diastolic blood pressure (BP), heart rate (HR), left ventricular shortening fraction (LVSF), cardiac output (CO), and ratio of pulmonary artery time to peak velocity and right ventricular ejection time (TPV/RVET) were similar during the two successive NO+ periods (group 1), thus demonstrating that the measurements were reproducible. NO removal (groups 1 and 2) did not modify systolic or diastolic BP, HR, CO, or LVSF but did induce a significant decline in SpO2, tcPO2 (- 25 +/- 5%) and TPV/RVET ratio (- 25 +/- 3%). No reinstitution reversed the effects of NO withdrawal on tcPO2, SpO2 and TPV/RVET ratio (group 2) without any changes in systemic hemodynamics.

CONCLUSION

The shut-off of low-dose NO induced in each patient a decrease in oxygen delivery that may be due to increased pulmonary vascular resistances and/or redistribution of pulmonary blood flow with ventilation-perfusion mismatching. The optimum weaning-off procedure of inhalational NO remains to be determined.

Atrial natriuretic peptide and nitric oxide in children with pulmonary hypertension after surgical repair of congenital heart disease

ANP causes pulmonary vasodilation in some children with pulmonary hypertension secondary to congenital heart disease. In a small group of patients, ANP lowered mean pulmonary artery pressure and pulmonary vascular resistance index > 20% without changing systemic vascular resistance index. Inhaled NO is an effective pulmonary vasodilator and is a more selective pulmonary vasodilator than ANP. The utility of ANP may be limited by its nonselective effects as more selective vasodilator agents are available.

Quantitative measurement of nasal production of nitric oxide in awake humans

The aim of this study was to determine, quantitatively, the production of nitric oxide (NO) in the nose and nasopharynx. Subjects were instructed to perform a Valsalva manoeuvre with their mouth open as gas was aspirated from a closely fitting nasal CPAP mask by a chemiluminescence analyser (Sievers 270B, Sievers Instrument Corp. Boulder, Colorado, U.S.A.). Room air was free to flow in through the mouth and out through the nose and hence to the analyser. The manoeuvre was continued until a smooth plateau of at least 20 seconds in duration was achieved on a chart recorder. The mean plateau concentrations were 176 (+/- 39.6) parts per billion (ppb) for males and 135.8 (+/- 24.4) ppb for females. The mean male production of NO was 15.8 nanomol/min which was significantly different from that of females of 12.5 nanomol/min (Mann-Whitney U Test; P < 0.01). By measuring the concentration of NO in gas aspirated from the nose during Valsalva manoeuvre, we excluded the respiratory tract below the glottis from our sampling and as such results represent the portion of NO produced in the nose and nasopharynx. These findings suggest that nasally produced NO is produced in sufficient quantities to act as a continuous pulmonary vasodilator, being inspired preferentially into areas of greatest ventilation, thus perhaps acting to continually match ventilation to perfusion.

Nitric oxide treatment for pulmonary hypertension after neonatal cardiac operation

This report describes a newborn with transposition of the great arteries who underwent a Blalock-Taussig shunt with transient improvement in oxygenation, but required emergent insertion of a central shunt later the same day due to progressive hypoxia and cardiac arrest. Two hours after central shunt insertion, sudden episodes of hypoxia and hypotension developed that were resistant to all pharmacologic therapy. Inhaled nitric oxide (25 ppm) was then administered with dramatic improvement in oxygenation and hemodynamics within minutes. The patient's condition stabilized after these measures, and nitric oxide therapy was discontinued after 2 days.

Dose-response to inhaled nitric oxide in acute hypoxemic respiratory failure of newborn infants: a preliminary report

In acute hypoxemic respiratory failure of term and near-term neonates, extra- and intrapulmonary right-to-left shunting contribute to refractory hypoxemia. Inhaled nitric oxide (NO) decreases pulmonary arterial pressure and improves ventilation-perfusion mismatch in a variety of animal models and selected human patients. We report on 10 consecutive term and near-term newborns with severe acute hypoxemic respiratory failure due to diaphragmatic hernia, meconium aspiration syndrome, group B streptococcus sepsis, pneumonia or acute respiratory distress syndrome, who received increasing doses of inhaled NO (up to 80 ppm) to improve the arterial partial pressure of oxygen (PaO2). The response to NO and the optimum NO concentration which improved PaO2 varied considerably between patients. Improvement of PaO2 was absent or poor (less than 10 mm Hg) in the 4 newborns with meconium aspiration syndrome and in 1 patient with congenital diaphragmatic hernia, while in the other 5 patients inhaled NO increased the mean (+/- SE) PaO2 from 41 +/- 6 to 57 +/- 9 mm Hg (P < 0.05). Optimum NO concentrations determined by dose-response measurements performed during the first 8 hr of NO inhalation were 8-16 ppm except for 2 newborns with congenital diaphragmatic hernia who required 32 ppm to effectively increase PaO2. Four of the 5 patients in whom the PaO2 rose by more than 10 mm Hg received inhaled NO for extended periods of time (5 to 23 days) with no signs of tachyphylaxis. The optimum NO concentration dropped to less than 3 ppm after prolonged mechanical ventilation or when intravenous prostacyclin was given concomitantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Near-patient measurements of methemoglobin, oxygen saturation, and total hemoglobin: evaluation of a new instrument for adult and neonatal intensive care

OBJECTIVES

a) To evaluate the performance of a compact, new instrument that uses disposable cuvettes to measure total hemoglobin concentration, oxygen content, and the relative concentrations of oxy- and methemoglobin in 50-microL blood samples; b) to determine whether the instrument can be used for near-patient assessment of methemoglobinemia; and c) to ascertain whether problems commonly encountered in neonatal blood samples affect the instrument's performance.

DESIGN

Prospective study, in which the test instrument was compared with a standard method. Samples of whole blood with and without bilirubin, fetal hemoglobin, and hemolysis were analyzed on the new (test) instrument and on a widely used cooximeter (OSM3 hemoximeter, Radiometer; reference instrument).

SETTING

In vitro analyses of blood samples in clinical and university laboratories.

MEASUREMENTS AND MAIN RESULTS

There was a close linear correlation between the methomoglobin measurements of the test instrument and those measurements of the reference instrument (slope = 0.989; r2 = .989). The average difference in mean assay values between the reference instrument and the test instrument was -0.59%, i.e., < 1% methemoglobin. Repeated measurements indicated the precision was 0.5% methemoglobin. Complete hemolysis of the sample reduced the methemoglobin reading by only 0.40%. Adding bilirubin (10 to 11 mg/dL [171 to 188.1 mumol/L]), increased the methemoglobin reading by 0.23%, increased the oxyhemoglobin reading by 0.45%, and increased total hemoglobin by 0.21 g/dL. Fetal hemoglobin also had minimal effects on the readings.

CONCLUSIONS

The test instrument is fast and easy to operate. No sample preparation or pipetting is required. To operate the instrument, the user simply connects a syringe containing the blood sample to one of the disposable cuvettes, injects 50 microL of blood into the cuvette, and inserts the cuvette into the instrument. The test instrument automatically detects the presence of the cuvette, analyzes the sample, and displays the results in < 10 secs. The findings in this study indicate that the test instrument has sufficient accuracy for near-patient testing in intensive care units. The errors introduced by hemolysis, fetal hemoglobin, and bilirubin were too small to be of clinical importance. Thus, the test instrument is essentially unaffected by complications commonly encountered in neonatal blood. The capacity of the test instrument to measure methemoglobin makes it particularly useful if inhaled nitric oxide therapy becomes a standard clinical practice.

Continuous low dose inhaled nitric oxide for treatment of severe pulmonary hypertension after cardiac surgery in paediatric patients

OBJECTIVE

To assess the effect of inhaled nitric oxide (NO) on severe postoperative pulmonary hypertension in children after surgical repair of a congenital heart defect.

DESIGN

A pilot study of NO administration to 7 consecutive children who required adrenergic support and in whom postoperative mean pulmonary artery pressure was more than two thirds of mean systemic pressure and persisted despite alkalotic hyperventilation.

SETTING

Routine care after cardiac surgery for congenital heart disease in a multidisciplinary paediatric intensive care unit.

METHODS

Continuous inhalation of NO, initially at 15 ppm. Therefore, daily attempts at complete weaning or at reducing NO to the lowest effective dose.

RESULTS

In 6 of the 7 children NO inhalation selectively decreased mean (SD) pulmonary artery pressure from 51 (12) to 31 (9) mm Hg (P < 0.05) while mean systemic arterial pressure was unchanged (68 (10) v 71 (7) mm Hg) (NS) and the arteriovenous difference in oxygen content decreased from 6.7 (0.9) to 4.8 (0.8) vol% (P < 0.05). Concomitantly PaO2 increased from 158 (98) to 231 (79) mm Hg) (P < 0.05). The seventh child showed no response to NO up to 80 ppm, could not be weaned from cardiopulmonary bypass, and died in the operating room. In responders, attempts at early weaning from NO inhalation always failed and NO at concentrations of less than 10 ppm was continuously administered for a median of 9.5 days (range 4 to 16 days) until complete weaning was possible from a mean dose of 3.9 (2.9) ppm. Methaemoglobinaemia remained below 2% and nitrogen dioxide concentrations usually ranged from 0.1 to 0.2 ppm. One child later died and five were discharged. A few months after surgery Doppler echocardiography (and catheterisation in one) showed evidence of regression of pulmonary hypertension in all 5.

CONCLUSIONS

Inhalation of NO reduced pulmonary artery pressure in children with severe pulmonary hypertension after cardiac surgery and this effect was maintained over several days at concentrations carrying little risk of toxicity.

Guidelines for the safe administration of inhaled nitric oxide

Inhaled nitric oxide (NO) is a selective pulmonary vasodilator, potentially useful in the treatment of pulmonary hypertension and ventilation-perfusion mismatch. High doses of inhaled NO and its oxidative product nitrogen dioxide (NO2) may cause acute lung injury. Using a standard infant ventilator, ventilator circuit and test lung, an administration and monitoring strategy has been defined for inhaled NO and these observations validated in eight ventilated infants. In 90% oxygen, doses of inhaled NO > or = 80 parts per million may result in toxic NO2 concentrations.

An appraisal of techniques for administration of gaseous nitric oxide

Gaseous nitric oxide (NO) is a potent selective pulmonary vasodilator. When mixed with O2 for more than 10-15 minutes it forms toxic amounts of nitrogen dioxide (NO2). We describe two techniques to administer 20 parts per million (ppm) during mechanical ventilation. A technique using flows of NO and O2 at low pressure to drive a Siemens Servo 900C ventilator provided a constant inspired concentration of NO. Another technique in which NO was added to the inspiratory limb of a Siemens Servo 900C ventilator driven by high pressure oxygen provided a highly variable concentration (9-53 ppm) of inspired NO.