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Biomedical subjects

S Niermeyer

Publications and source records attributed to S Niermeyer.

At least 19 recordsLinked to original sources
PubMed2004

Is 100% oxygen necessary for the resuscitation of newborn infants?

This paper reproduces in detail the debate 'pro-and-con' regarding the use of 100% oxygen or room air in the resuscitation of the asphyxiated newly born infants, celebrated in Oslo at the 2002 European Association of Perinatal Medicine (EAPM) meeting, in which both co-authors participated as featured speakers. The authors describe their arguments which are based on medical tradition, clinical experience, basic science, and prospective randomized and pseudo-randomized clinical studies that have been reported in the past years. Both authors stress the importance of the long-term consequences of the use of high oxygen concentrations in the perinatal period and conclude that there is a need for further research in the way of ample prospective randomized clinical trials.

Air↗
PubMed2001

Pathophysiology of neonatal resuscitation: application in a global context.

Despite the adoption of evidence-based guidelines for neonatal resuscitation, formulated with international consensus, the process of resuscitating a newly born infant remains a uniquely local activity. Variations in the physical environment, cultural and medical beliefs, and available resources mediate significant difference in practices worldwide. Yet, the universal nature of the physiology surrounding birth, and its disturbances, provides a common basis for reference. Recognition of the importance of assistance available at the moment of birth, management of the thermal environment, and establishment of adequate ventilation is nearly universal. Differences in specific practices arise from local differences in the risks and challenges to perinatal health, which, in turn, stem from the environment or the available resources. Valuable information can be learned through comparison and evaluation of different techniques. In such a way, the evidence base for neonatal resuscitation can be strengthened and infants around the world can share in the benefits realized.

Asphyxia Neonatorum↗
PubMed2001

Medications during resuscitation -- what is the evidence?

Medication use during neonatal resuscitation is uncommon. The infrequent use of resuscitation medications has impeded rigorous investigations to determine the most effective agents and/or dosing regimens. The medications most commonly used during delivery room resuscitation include epinephrine, sodium bicarbonate, naloxone hydrochloride and volume expanders. The available evidence for each of these medications is reviewed in this article.

Asphyxia Neonatorum↗
PubMed2001

An advisory statement from the Pediatric Working Group of the International Liaison Committee on Resuscitation.

The International Liaison Committee on Resuscitation (ILCOR), with representation from North America, Europe, Australia, New Zealand, Africa, and South America, was formed in 1992 to provide a forum for liaison between resuscitation organizations in the developed world. This consensus document on resuscitation extends previously published ILCOR advisory statements on resuscitation to address the unique and changing physiology of the newly born infant within the first few hours after birth and the techniques for providing advanced life support. After careful review of the international resuscitation literature and after discussion of key and controversial issues, consensus was reached on almost all aspects of neonatal resuscitation, and areas of controversy and high priority for additional research were delineated. Consensus on resuscitation for the newly born infant included the following principles: Personnel trained in the basic skills of resuscitation should be in attendance at every delivery. A minority (fewer than 10%) of newly born infants require active resuscitative interventions to establish a vigorous cry and regular respirations, maintain a heart rate > 100 beats per minute (bpm), and maintain good color and tone. When meconium is present in the amniotic fluid, it should be suctioned from the hypopharynx on delivery of the head. If the meconium-stained newly born infant has absent or depressed respirations, heart rate, or muscle tone, residual meconium should be suctioned from the trachea. Attention to ventilation should be of primary concern. Assisted ventilation with attention to oxygen delivery, inspiratory time, and effectiveness judged by chest rise should be provided if stimulation does not achieve prompt onset of spontaneous respirations and/or the heart rate is < 100 bpm. Chest compressions should be provided if the heart rate is absent or remains < 60 bpm despite adequate assisted ventilation for 30 seconds. Chest compressions should be coordinated with ventilations at a ratio of 3:1 and a rate of 120 "events" per minute to achieve approximately 90 compressions and 30 rescue breaths per minute. Epinephrine should be administered intravenously or intratracheally if the heart rate remains < 60 bpm despite 30 seconds of effective assisted ventilation and chest compression circulation. Common or controversial medications (epineprine, volume expansion, naloxone, bicarbonate), special resuscitation circumstances affecting care of the newly born, continuing care of the newly born after resuscitation, and ethical considerations for initiation and discontinuation of resuscitation are discussed. There was agreement that insufficient data exist to recommend changes to current guidelines regarding the use of 21% versus 100% oxygen, neuroprotective interventions such as cerebral hypothermia, use of a laryngeal mask versus endotracheal tube, and use of high-dose epinephrine. Areas of controversy are identified, as is the need for additional research to improve the scientific justification of each component of current and future resuscitation guidelines.

Environment↗
PubMed2000

International Guidelines for Neonatal Resuscitation: An excerpt from the Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care: International Consensus on Science. Contributors and Reviewers for the Neonatal Resuscitation Guidelines.

The International Guidelines 2000 Conference on Cardiopulmonary Resuscitation (CPR) and Emergency Cardiac Care (ECC) formulated new evidenced-based recommendations for neonatal resuscitation. These guidelines comprehensively update the last recommendations, published in 1992 after the Fifth National Conference on CPR and ECC. As a result of the evidence evaluation process, significant changes occurred in the recommended management routines for: * Meconium-stained amniotic fluid: If the newly born infant has absent or depressed respirations, heart rate <100 beats per minute (bpm), or poor muscle tone, direct tracheal suctioning should be performed to remove meconium from the airway. * Preventing heat loss: Hyperthermia should be avoided. * Oxygenation and ventilation: 100% oxygen is recommended for assisted ventilation; however, if supplemental oxygen is unavailable, positive-pressure ventilation should be initiated with room air. The laryngeal mask airway may serve as an effective alternative for establishing an airway if bag-mask ventilation is ineffective or attempts at intubation have failed. Exhaled CO(2) detection can be useful in the secondary confirmation of endotracheal intubation. * Chest compressions: Compressions should be administered if the heart rate is absent or remains <60 bpm despite adequate assisted ventilation for 30 seconds. The 2-thumb, encircling-hands method of chest compression is preferred, with a depth of compression one third the anterior-posterior diameter of the chest and sufficient to generate a palpable pulse. * Medications, volume expansion, and vascular access: Epinephrine in a dose of 0.01-0.03 mg/kg (0.1-0.3 mL/kg of 1:10,000 solution) should be administered if the heart rate remains <60 bpm after a minimum of 30 seconds of adequate ventilation and chest compressions. Emergency volume expansion may be accomplished with an isotonic crystalloid solution or O-negative red blood cells; albumin-containing solutions are no longer the fluid of choice for initial volume expansion. Intraosseous access can serve as an alternative route for medications/volume expansion if umbilical or other direct venous access is not readily available. * Noninitiation and discontinuation of resuscitation: There are circumstances (relating to gestational age, birth weight, known underlying condition, lack of response to interventions) in which noninitiation or discontinuation of resuscitation in the delivery room may be appropriate.

Blood Volume↗
PubMed1999

The pregnant altitude visitor.

The human fetus develops normally under low-oxygen conditions. Exposure of a pregnant woman to the hypoxia of high altitude results in acclimatization responses which act to preserve the fetal oxygen supply. The fetus also utilizes several compensatory mechanisms to survive brief periods of hypoxia. While fetal heart rate monitoring data during air travel suggest no compromise of fetal oxygenation, exercise at high altitude may place further stress on oxygen delivery to the fetus. The limited data on maternal exercise at high altitude suggest good tolerance in most pregnancies; however, short-term abnormalities in fetal heart rate and subsequent pregnancy complications have been observed, as well. A survey of Colorado obstetrical care providers yielded consensus that preterm labor and bleeding complications of pregnancy are the most commonly encountered pregnancy complications among high-altitude pregnant visitors. Dehydration, engaging in strenuous exercise before acclimatization, and participation in activities with high risk of trauma are behaviors that may increase the risk of pregnancy complications. Medical and obstetrical conditions which impair oxygen transfer at any step between the environment and fetal tissue may compromise fetal oxygenation. Knowledge of the medical, obstetrical, and behavioral risk factors during pregnancy at high altitude can help the pregnant visitor to high altitude avoid such complications.

Altitude↗
PubMed1999

Resuscitation of the newly born infant: an advisory statement from the Pediatric Working Group of the International Liaison Committee on Resuscitation.

The International Liaison Committee on Resuscitation (ILCOR), with representation from North America, Europe, Australia, New Zealand, Africa, and South America, was formed in 1992 to provide a forum for liaison between resuscitation organizations in the developed world. This consensus document on resuscitation extends previously published ILCOR advisory statements on resuscitation to address the unique and changing physiology of the newly born infant within the first few hours following birth and the techniques for providing advanced life support.

Delivery Rooms↗
PubMed1999

An advisory statement from the Pediatric Working Group of the International Liaison Committee on Resuscitation.

The International Liaison Committee on Resuscitation (ILCOR), with representation from North America, Europe, Australia, New Zealand, Africa, and South America, was formed in 1992 to provide a forum for liaison between resuscitation organizations in the developed world. This consensus document on resuscitation extends previously published ILCOR advisory statements on resuscitation to address the unique and changing physiology of the newly born infant within the first few hours after birth and the techniques for providing advanced life support. After careful review of the international resuscitation literature and after discussion of key and controversial issues, consensus was reached on almost all aspects of neonatal resuscitation, and areas of controversy and high priority for additional research were delineated. Consensus on resuscitation for the newly born infant included the following principles: Common or controversial medications (epinephrine, volume expansion, naloxone, bicarbonate), special resuscitation circumstances affecting care of the newly born, continuing care of the newly born after resuscitation, and ethical considerations for initiation and discontinuation of resuscitation are discussed. There was agreement that insufficient data exist to recommend changes to current guidelines regarding the use of 21% versus 100% oxygen, neuroprotective interventions such as cerebral hypothermia, use of a laryngeal mask versus endotracheal tube, and use of high-dose epinephrine. Areas of controversy are identified, as is the need for additional research to improve the scientific justification of each component of current and future resuscitation guidelines.

Documentation↗
PubMed1998

The diagnosis of acute mountain sickness in preverbal children.

OBJECTIVE: To establish diagnostic criteria for acute mountain sickness (AMS) in preverbal children. DESIGN: Nonrandomized control trial. SETTING: Ambulatory. PARTICIPANTS: Children aged 3 through 36 months and adults from the Denver, Colo, area (altitude, 1610 m). MAIN OUTCOME MEASURES: The Lake Louise Scoring System was modified, using a fussiness score as the headache equivalent and a pediatric symptom score to assess appetite, vomiting, playfulness, and ability to sleep. Acute mountain sickness was assessed by combining the fussiness and pediatric symptom scores to produce what we termed the Children's Lake Louise AMS Score (CLLS). INTERVENTIONS: Parents recorded the fussiness score at 11 AM, 1, 3, and 5 PM, and the pediatric symptom score at 3:00 PM each day. Each subject traveled twice, with 1 day considered a control. Days 1 and 2 were measurements at home; day 3 reflected travel without altitude change to 1615 m; and 1 week later, day 4 involved travel to 3488 m. On days 3 and 4 the accompanying adults completed the Lake Louise Scoring System. RESULTS: Twenty-three subjects (14 boys; mean+/-SD age, 20.7+/-9.0 months) participated. The mean CLLS demonstrated no differences on days 1, 2, or 3. On day 4, 5 subjects (21.7%) had AMS, established as a CLLS of 7 or higher, and these scores normalized 2 hours after descent. Forty-five adults participated and 9 (20%) had AMS. CONCLUSIONS: We define AMS in preverbal children as a CLLS of 7 or higher with a fussiness score of 4 or higher and a pediatric symptom score of 3 or higher, in the setting of recent altitude gain. The incidence of AMS in preverbal children (21.7%) was similar to that in adults (20%).

Acute Disease↗
PubMed1998

Human adaptation to high altitude: regional and life-cycle perspectives.

Studies of the ways in which persons respond to the adaptive challenges of life at high altitude have occupied an important place in anthropology. There are three major regions of the world where high-altitude studies have recently been performed: the Himalayas of Asia, the Andes of South America, and the Rocky Mountains of North America. Of these, the Himalayan region is larger, more geographically remote, and likely to have been occupied by humans for a longer period of time and to have been subject to less admixture or constriction of its gene pool. Recent studies of the physiological responses to hypoxia across the life cycle in these groups reveal several differences in adaptive success. Compared with acclimatized newcomers, lifelong residents of the Andes and/or Himalayas have less intrauterine growth retardation, better neonatal oxygenation, and more complete neonatal cardiopulmonary transition, enlarged lung volumes, decreased alveolar-arterial oxygen diffusion gradients, and higher maximal exercise capacity. In addition, Tibetans demonstrate a more sustained increase in cerebral blood flow during exercise, lower hemoglobin concentration, and less susceptibility to chronic mountain sickness (CMS) than acclimatized newcomers. Compared to Andean or Rocky Mountain high-altitude residents, Tibetans demonstrate less intrauterine growth retardation, greater reliance on redistribution of blood flow than elevated arterial oxygen content to increase uteroplacental oxygen delivery during pregnancy, higher levels of resting ventilation and hypoxic ventilatory responsiveness, less hypoxic pulmonary vasoconstriction, lower hemoglobin concentration, and less susceptibility to CMS. Several of the distinctions demonstrated by Tibetans parallel the differences between natives and newcomers, suggesting that the degree of protection or adaptive benefit relative to newcomers is enhanced for the Tibetans. We thus conclude that Tibetans have several physiological distinctions that confer adaptive benefit consistent with their probable greater generational length of high-altitude residence. Future progress is anticipated in achieving a more integrated view of high-altitude adaptation, incorporating a sophisticated understanding of the ways in which levels of biological organization are articulated and a recognition of the specific genetic variants contributing to differences among high-altitude groups.

Adaptation, Physiological↗
PubMed1995

Arterial oxygen saturation in Tibetan and Han infants born in Lhasa, Tibet.

BACKGROUND: Reduced oxygen availability at high altitude is associated with increased neonatal and infant mortality. We hypothesized that native Tibetan infants, whose ancestors have inhabited the Himalayan Plateau for approximately 25,000 years, are better able to maintain adequate oxygenation at high altitude than Han infants, whose ancestors moved to Tibet from lowland areas of China after the Chinese military entered Tibet in 1951. METHODS: We compared arterial oxygen saturation, signs of hypoxemia, and other indexes of neonatal wellbeing at birth and during the first four months of life in 15 Tibetan infants and 15 Han infants at 3658 m above sea level in Lhasa, Tibet. The Han mothers had migrated from lowland China about two years previously. A pulse oximeter was placed on each infant's foot to provide measurements of arterial oxygen saturation distal to the ductus arteriosus. RESULTS: The two groups had similar gestational ages (about 38.9 weeks) and Apgar scores. The Han infants had lower birth weights (2773 +/- 92 g) than the Tibetan infants (3067 +/- 107 g), higher concentrations of cord-blood hemoglobin (18.6 +/- 0.8 g per deciliter, vs. 16.7 +/- 0.4 in the Tibetans), and higher hematocrit values (58.5 +/- 2.4 percent, vs. 51.4 +/- 1.2 percent in the Tibetans). In both groups, arterial oxygen saturation was highest in the first two days after birth and was lower when the infants were asleep than when they were awake. Oxygen saturation values were lower in the Han than in the Tibetan infants at all times and under all conditions during all activities. The values declined in the Han infants from 92 +/- 3 percent while they were awake and 90 +/- 5 percent during quiet sleep at birth to 85 +/- 4 percent while awake and 76 +/- 5 percent during quiet sleep at four months of age. In the Tibetan infants, oxygen saturation values averaged 94 +/- 2 percent while they were awake and 94 +/- 3 percent during quiet sleep at birth and 88 +/- 2 percent while awake and 86 +/- 5 percent during quiet sleep at four months. Han infants had clinical signs of hypoxemia--such as cyanosis during sleep and while feeding--more frequently than Tibetans. CONCLUSIONS: In Lhasa, Tibet, we found that Tibetan newborns had higher arterial oxygen saturation at birth and during the first four months of life than Han newborns. Genetic adaptations may permit adequate oxygenation and confer resistance to the syndrome of pulmonary hypertension and right-heart failure (subacute infantile mountain sickness).

Altitude↗
PubMed1993

Arterial oxygenation and pulmonary arterial pressure in healthy neonates and infants at high altitude.

We sought to document arterial oxygen saturation relative to changes in the right ventricular pressure/left ventricular pressure ratio (RVP/LVP ratio), an index of pulmonary arterial pressure, in infants born at high altitude. We performed pulse oximetry and echocardiography in 15 healthy infants born in Leadville, Colo. (3100 m), at 6 to 24 hours, 24 to 48 hours, 1 week, 2 months, and 4 months of age. Pulse oximetry was done under conditions of wakefulness, feeding, and active and quiet sleep. All infants received supplemental O2 at delivery and during postnatal transition; all oximetry measurements were performed with infants breathing room air. The mean arterial O2 saturation ranged from 80.6% +/- 5.3% to 91.1% +/- 1.7% during the 4 months. Values fell during the first week after birth and then rose gradually to attain near-birth values at 2 and 4 months of age. Arterial O2 saturation was uniform among behavioral states at 6 to 24 hours and 24 to 48 hours of age. After 1 week of age, values were highest during wakefulness, intermediate during feeding and active sleep, and lowest during quiet sleep. The RVP/LVP ratio remained in the normal or mildly elevated range throughout the study period. We conclude that the RVP/LVP ratio promptly becomes normal at high altitude, and despite low arterial O2 saturation in the first weeks to months after birth, healthy newborn infants at 3100 m show little evidence of acute pulmonary hypertension.

Age Factors↗