Inhaled nitric oxide for preterm infants--still an experimental therapy

Early inhaled nitric oxide improves oxidative balance in very preterm infants

Inhaled nitric oxide (iNO) improves oxygenation in premature infants, but concern has been raised about its potential oxidative toxicity. We designed this study to assess the oxidative balance in premature infants who were exposed to low dose iNO and the relationship with their clinical outcome on day 28 of life. A total of 274 infants who were <32 wk gestation were randomized at birth to receive 5 ppm of iNO if they presented with hypoxemic respiratory failure. Nonhypoxemic infants were studied as the reference group. Blood samples were withdrawn 24 h apart, within the first 4 d of life, to assess malondialdehyde (MDA) concentration as oxidative stress marker and total plasmatic glutathione (GSH), intraerythrocyte GSH peroxidase, and GSH reductase activities as antioxidant defenses. After 24 h, the rise in MDA was blunted in the iNO group compared with controls and was close to the reference infants. Conversely, GSH was more stable in the iNO group, when there was no difference for the GSH peroxidase and GSH reductase activities. On day 28, Oxygen dependence was linked with a higher increase in MDA as was the risk for death, whereas intraventricular hemorrhage was associated with a higher initial drop in GSH. Early low-dose iNO in hypoxemic preterm infants improves oxidative balance and seems to be clinically beneficial up to day 28 of life.

Nitric oxide in critical respiratory failure of very low birth weight infants

Inhaled nitric oxide (iNO) is a selective pulmonary vasodilator. In randomised trials, iNO increased gas exchange modestly and had no effect on the outcome (survival, chronic lung disease, CLD) in very low birth-weight (VLBW) infants. NO is an important component of the innate immune system and a lipid- soluble free radical scavenger that interacts with the surfactant system. VLBW infants with pneumonia and therapy-resistant, severe respiratory failure soon after birth were studied. Despite their infection, there was no detectable alveolar inducible NO synthase or nitrotyrosine, which is a toxic oxidation product of NO. These infants do not respond to exogenous surfactant and demonstrate severe pulmonary hypertension. However, they require exogenous surfactant prior to iNO. In most cases the disease is complicated by pneumonia and prolonged rupture of fetal membranes. We have shown evidence that iNO given within a few hours after birth reverses the progressive course of respiratory failure and pulmonary hypertension in VLBW infants.

Places and health

This glossary aims to provide readers with some key conceptual tools with which to address the issue of place and health; it is hoped that it will provoke thought and debate on the range of ways that places are connected to health.

Bronchopulmonary dysplasia-oxidative stress and antioxidants

There is increasing evidence that oxidative stress is implicated in the development of bronchopulmonary dysplasia. Several important factors contribute to augmented oxidative stress in the newborn and especially the preterm infant: first, because of its immaturity, the lung of preterm infants is frequently exposed to oxygen therapy and hyperoxia. Second, the antioxidant defense and its ability to be induced during an hyperoxic challenge are impaired. Third, the preterm infant has an increased susceptibility to infection and inflammation, which increases oxidative stress. Fourth, free iron, which catalyzes the production of toxic reactive oxygen species, can be detected in preterm infants. The molecular and cellular mechanisms for free radical-induced injury are now understood in more detail, and it is clear that oxidative stress plays an important role in triggering apoptosis, in serving as second messenger and in signal transduction. This new insight might lead to novel and efficient therapies. So far, there has been no significant breakthrough regarding antioxidant therapies. Care should, however, be exercised in supplementing the preterm infant with antioxidants since this may affect growth and development.

Inhaled nitric oxide: more than a selective pulmonary vasodilator

Because of its high diffusing capacity through the alveolar-blood barrier and its high selectivity for the pulmonary vasculature, inhaled nitric oxide (NO) has been recently shown to be a viable and efficient approach to restore pulmonary NO deficiency. The most relevant applications of inhaled NO are in infants with primary pulmonary hypertension or hypoxia. In these patients, inhaled NO improves gas exchange and ventilation-perfusion matching, reduces the length of hospitalization and is without severe detrimental effects. The use of inhaled NO has also been extended to adults with pulmonary hypertension and the acute respiratory distress syndrome. In addition, recent clinical evidence supported by data from animal models, shows beneficial extra-pulmonary effects of inhaled NO, including protection against myocardial ischaemia-reperfusion injury.

Sir Humphry Davy; his researches in respiratory physiology and his debt to Antoine Lavoisier

This article shows how the original works of the French scientist Antoine Lavoisier were developed by Humphry Davy, a trainee surgeon from Cornwall, while he was working as a physiologist. Antoine Lavoisier had worked out how oxidation involved the consumption of oxygen and the release of energy. Davy's book, Researches Chemical and Philosophical, Chiefly Concerning Nitrous Oxide, published in 1799, describes the measurement of his own lung volumes, including the first recorded measurement of the residual volume. He measured his own rates of oxygen consumption and carbon dioxide production. He is famous for his investigations into nitrous oxide, but he also investigated the effects of breathing nitric oxide and carbon monoxide. He made these observations with a gasometer and analysis of his expired air, and his work anticipates the invention of blood gas analysis.

Sudden infant death syndrome: neonatal hypodynamia (reduced exercise level)

Sudden infant death syndrome (SIDS) has been described as a silent unexpected death during sleep. Infants with near-miss SIDS have shown a higher heart rate and diminished heart rate variability during sleep. Non-rapid-eye-movement (NREM) sleep rate variability was related to respiration. A decreased heart rate variability was also observed in infants with respiratory distress syndrome (RDS) or prenatal hypoxia. It was hypothesized that decreased heart rate variability and decreased body measurement during sleep were related to a decreased arousal response. Cardiac output is greater in the supine position. Acetylcholine slows the heart beat. Postural changes modify the acute baroreflex control of the heart rate. The cerebellum also contributes to the reflex anti-orthostatic (supine) cardiovascular response to postural change. Delayed myelination of various areas of the brain occurred in SIDS victims and it was suggested that the defect in central respiratory control could be a motor rather than a sensory problem, and that the search for abnormalities should be extended to regions in the cerebellum and pre-frontal-temporal-limbic systems. The cerebellum exercises control over motor neuron impulses from the cerebral cortex to lower structures. An extended period of neonatal decreased body movement has its counterpart in the astronaut exposed to the deconditioning effect of zero gravity. Hypodynamia induces hyperglycemia, insulin resistance, renal inositoluria and impaired nerve conduction. Myoinositol is 20 times higher in fetal-like tissue than in adults. The insecticide lindane (gammexane) is an inositol antagonist. Lindane administration to neonatal rats induced low levels of specific components of myelin proteins in oligodendrocytes in the brain. The activity of these specific enzymes was reduced in oligodendrocytes in the brain of SIDS victims. It is hypothesized that lindane administration to laboratory neonatal animals is a laboratory model for studying delayed development of the brain in SIDS.

[Jargon of the neonatal intensive care unit]

Jargon, the specialized vocabulary and idioms, is frequently used by people of the same work or profession. The neonatal intensive care unit (NICU) makes no exception to this. As a matter of fact, NICU is one place where jargon is constantly developing in parallel with the evolution of techniques and treatments. The use of jargon within the NICU is very practical for those who work in these units. However, this jargon is frequently used by neonatologists in medical reports or other kinds of communication with unspecialized physicians. Even if part of the specialized vocabulary can be decoded by physicians not working in the NICU, they do not always know the exact place that these techniques or treatments have in the management of their patients. The aim of this article is to describe the most frequent jargon terms used in the French NICU and to give up-to-date information on the importance of the techniques or treatments that they describe.