Monitoring Oxygen Toxicity in the Preterm Infant:
Mechanisms, Critical Questions and Clinical Challenges
T. Allen Merritt, MD, MHA and Jan Mazela, MD, PhD
Throughout human evolution, physiologic gases vital for survival (oxygen, nitric oxide, carbon dioxide, and hydrogen sulfide) have been our allies, yet also our enemy when given or produced in excess because of their multiple toxic effects, especially in neonates with limited antioxidant defenses. Oxygen was discovered by the Polish alchemist, Michael Sedziwej as a "spiritus" emitted by the heating of "salpetre." The discovery was later reported by Scheele in 1773 but credited to Priestley in 1774 (as "dephlogistated air") and named "oxygen" by Lavoisier in 1777. Supplemental oxygen was administered to humans by Chaussier using a bellows ventilator in 1777, and remains the most commonly used drug in neonatal medicine.1 Since the 1930s oxygen therapy has been a mainstay of neonatal care,2 yet as commented by Tin in 2002, "Oxygen must have been given to more infants than any other medicinal product…despite that, we still know very little about how much infants actually need, or how much it is wise to give. Given that we have also known for nearly 50 years that it is easy to damage the eyes of preterm infants by giving too much oxygen, especially in the first weeks of life, the depth of our ignorance is really quite embarrassing."3 Silverman further commented that oxygen therapy for neonatologists has been an "albatross."4

Steps Towards a More Rational Use of Supplemental Oxygen: Lessons from the Experts
Meeting the metabolic demands of the developing brain and nervous system by providing adequate substrates for cellular energy requirements has been an elusive goal of neonatologists. Sufficient oxygen delivery to the developing brain – a critical goal for neonatologists – is a function of hemoglobin type and content, SpO2 level, paO2, and cerebral blood flow, along with adequate glucose and alternative fuels. Dr. Kimura provides an enlightening discussion of how the developing brain is affected both by reactive oxygen species, and hyperoxia.
Neonatologists and pediatric cardiologists care for infants with congenital cyanotic heart disease who have hypoxemia, based on conventional SpO2 limits even with prostaglandin treatment, and who await surgical correction. In the panel discussion, Dr. Dudell reviews lessons learned from the care of infants managed by necessity with "restrictive" oxygen saturation levels until surgical intervention.

 

Rapid Response.

This one-hour computer based learning module has been designed for the bedside healthcare provider and members of the RRT as a primer on the importance of early identification of a patient in crisis, effective team communication during a crisis and rapid assessment and stabilization of the patient.