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Pathophysiology of neonatal resuscitation: application in a global context
Semin Neonatol 2001; 6: 213–217 doi:10.1053/siny.2001.0050, available online at http://www.idealibrary.com on
Pathophysiology of neonatal resuscitation: application in a global context Susan Niermeyera and Jeffrey Perlmanb a
Associate Professor of Pediatrics, Section of Neonatology, University of Colorado Health Sciences Center, Denver, Colarado, USA b Professor of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas, USA
Key words: resuscitation, neonatal, cross-cultural perspectives, asphyxia, pathophysiology, ventilation, meconium, chest compressions
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. 2001 Harcourt Publishers Ltd
Introduction With publication of the Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care: International Consensus on Science [1], the foundation for neonatal resuscitation practice has taken two important steps forward. First, the 2000 Guidelines for Neonatal Resuscitation [2] have as their basis a rigorous process of evidencedbased evaluation which has led to the formulation of the final recommendations. Second, the guidelines reflect an international consensus on resuscitation science. Nonetheless, resuscitation of a newly born infant remains an activity that occurs and may vary at an undeniably local level. Thus, in many parts of the world, births take place in the household rather than in medical facilities [3]. Correspondence to: Susan Niermeyer MD, Associate Professor of Pediatrics, Section of Neonatology, University of Colorado Health Sciences Center, Denver, Colorado, USA and Visiting Research Scientist, Instituto Boliviano de Biologı´a de Altura, La Paz, Bolivia. Tel: +591 2 24 20 59 (office in La Paz); +591 2 44 10 62 (home in La Paz); Fax: +591 2 22 14 18 or 39 14 16; E-mail: [email protected]
1084–2756/01/030213+05 $35.00/0
When delivery does occur within the medical setting, these facilities vary from birthing centres to primary-care clinics or hospitals in small communities, to regional medical centres. Cultural differences and ethnic medical beliefs also shape the understanding of physiology and the approach to treatment. The above differences raise several important questions: (1) Is there sufficient concordance in the approach to the reversal of perinatal asphyxia and/or airway difficulties as well as the maintenance of an environment supportive to normal postnatal transition to provide guidelines that can be truly global? (2) What global differences must be acknowledged when considering neonatal resuscitation? (3) What lessons can be learned from the global variations in practice? (4) Can these variations serve as the substrate for future research in neonatal resuscitation?
Pathophysiology The birth of an infant is associated with abrupt cessation of the fetal–placental circulation, followed © 2001 Harcourt Publishers Ltd
214
by rapid and profound changes involving both the cardiac and respiratory systems occurring in tandem. Respiratory adaptation includes cessation of fluid production (the volume of alveolar lung fluid prior to delivery approximates 30–35 ml/kg in the term infant), and clearing of this fluid prior to the establishment of a functional residual capacity. The initiation of spontaneous respirations is critical to the initiation and completion of this process. Concurrent circulatory changes include a fall in pulmonary vascular resistance and an increase in pulmonary blood flow associated with the onset of ventilation, and an increase in systemic vascular resistance associated with umbilical arterial vasoconstriction. These resistance changes result in a reversal of blood flow which becomes predominantly left to right across the foramen ovale and the patent ductus arteriosus. This process of adaptation may be complicated by airway secretions (mucus, blood, amniotic fluid, meconium), failure to initiate respirations (secondary to maternal analgesia, central nervous system injury, sepsis, etc.), respiratory distress (secondary to pulmonary disease, space-occupying lesions, etc.), asphyxia (hypoxia with hypercarbic acidosis), perinatal infections, cardiac dysfunction ( secondary to structural or functional abnormalities), congenital anomalies and prematurity. Fortunately, the overwhelming majority of near term and term babies complete the transition spontaneously and require minimal to no interventions. However, depending on the process inhibiting normal transition, resuscitation may require action as limited as clearing oral airway secretions to interventions as intense as chest compressions and medications in order to restore circulatory function. Irrespective of the intensity of the cardiorespiratory intervention/s, resuscitation incorporates other vital activities including drying off the infant (to minimize heat loss) while maintaining body heat (skin-to-skin contact, warm towels).
Common strategies in the response to resuscitation The first tenet of neonatal resuscitation is the need for assistance at the moment of birth in order to prevent more severe problems. There is nearly universal acceptance of this concept, irrespective of whether the birth attendant is a family member, a traditional birth attendant, a medically trained mid-
S. Niermeyer and J. Perlman
wife, or a physician with a supporting team of specialized nurses and respiratory therapists [4]. Management of the thermal environment immediately after birth takes many forms, but in every birth setting it is recognized as a key step to avoid jeopardizing the process of achieving homeostasis after birth. In areas with limited resources, thermal management may receive even more emphasis than in settings with more extensive resources, when attention to fundamental concepts may be inadvertently superseded by a focus on technologically advanced airway and cardiovascular interventions. Finally, the basics of airway, breathing, and circulation are addressed in nearly every medical system (see Chapter 2), although the approaches may vary in form and degree. For example, clearing of the airway may require no intervention in settings in which delivery is unmedicated and the infant is vigorous and capable of handling his or her own secretions. When removal of secretions is required, many medical systems use wiping of the mouth with a cloth rather than suctioning as a basic method of clearing the airway. Removal of secretions with a bulb syringe or catheter is often reserved for cases in which respiratory distress occurs, because of the greater risk of provoking vagal bradycardia by stimulation of the posterior pharynx and delaying the postnatal rise in oxygen saturation [5,6].
Different strategies in the approach to resuscitation Certain fundamental differences in neonatal resuscitation are dictated by variation in infection risk, use of obstetrical analgesia/anaesthesia, route of delivery and/or management of dystocia, site of delivery or available resources. Thus the principal perinatal pathogens vary globally. For example in Asia and South America, perinatal infections with Gram-negative organisms often lead to preterm delivery or immediate, serious cardiopulmonary compromise at the time of birth. In contrast, Group B Streptococcal infections predominate in North America, where the presentation varies from asymptomatic to a more insidious onset of illness with potential cardiopulmonary collapse. In other regions of the world, such as Africa, the onset of illness maybe even more delayed in onset and yet still prove lethal, such as in the case of perinatal tetanus in Egypt.
Pathophysiology of neonatal resuscitation
Global variation in practices of obstetrical analgesia and/or anaesthesia is considerable. Natural delivery without any medications occurs not only in remote areas without resources, but in technologically advanced settings in North America and Europe. The Dutch model of home deliveries attended by specialized midwives has as its goal pain control by psychological preparation and support, without medication. Meticulous prenatal care and careful triage has resulted in one of the lowest neonatal and maternal mortality rates in the world [3,7]. Dystocia remains a major cause of perinatal asphyxia in isolated areas where transportation and lack of medical resources combine to threaten both neonatal and maternal survival. In isolated areas, there is often strict attention to early diagnosis of fetal malposition and a variety of non-invasive techniques are used to turn the fetus in a prophylactic manner, with variable degrees of success. The site of delivery relates directly to the degree of sophistication of available medical intervention. In home settings, attention to management of the thermal environment and cleanliness of instruments used in the delivery assumes paramount importance. Resuscitation devices are often unavailable in many technologically underdeveloped countries, and reliance on tactile stimulation of respirations and mouth-to-mouth or mouth-to-nose and mouth resuscitation is common. Even in the developing world where mechanical devices for positive-pressure ventilation are available, resuscitation with 100% oxygen is uncommon, due to limited supplies and distribution of compressed medical gases. In technologically advanced medical centres, where an assortment of devices for neonatal resuscitation is available, attention is now focused on improving the effectiveness of these devices. In such delivery rooms, ongoing controlled trials of automatic devices for positivepressure ventilation hold promise for better standardization and effectiveness of this key step in neonatal resuscitation. The site of delivery may, in some cases, mediate differences in the approach to neonatal resuscitation because of environmental factors. The most compelling example of environmental effect on perinatal physiology occurs at moderate (>2500 m) and extreme (>3500 m) high altitude, where lower inspired oxygen concentration, due to lower barometric pressure, results in both a slower postnatal rise in paO2 and fall in pulmonary artery
215
pressure [8,9]. In this setting, supplemental oxygen may play a key role in normalization of pulmonary artery pressure to near sea-level values [10].
Lessons to be learned Comparison of neonatal resuscitation techniques on a global scale is important in order to evaluate both the strengths and weaknesses of any one approach. This information may then serve as the substrate to study and eventually to disseminate the most effective approaches to neonatal resuscitation. For example the lack of necessity for intervention after a normal, unmedicated vaginal delivery – the usual strategy in the developing world – is gaining increased acceptance even in technologically driven delivery services in the USA. Thus, there is increasing recognition that routine oropharyngeal suctioning may be unnecessary and may possibly even have repercussions later in the establishment of breast-feeding (Gartner, Lawrence, personal communication). Adequate thermoregulation can be accomplished as effectively by thorough drying of the infant, followed by immediate skin-to-skin contact of mother and infant and covering both with warmed linens, as by placing the infant under a radiant warmer. Continued observation of the infant can be carried out under both circumstances. However the former situation does not require separation from the mother. Current management of the infant with meconium-stained amniotic fluid varies widely dependent on available facilities. Recent evidence indicates that it is the depressed and not the vigorous infant delivered in the presence meconium-stained amniotic fluid who should be managed with endotracheal intubation for suctioning [11] (and Chapter 3) However, in many regions of the world where tracheal intubation is not possible, management of the infant with meconium-stained fluid may rest solely on intrapartum suctioning of the naso- and hypopharynx before complete delivery. Improved antepartum management to minimize the asphyxial component of meconium aspiration syndrome, clarification of the role of intrapartum suctioning, and testing of the paradigm of intubation on the basis of vigour rather than consistency of meconium await further research (Chapter 3). In most of the developing world, strong emphasis is appropriately placed on establishment
216
of effective ventilation because of the limited availability of more advanced support (100% oxygen, medications or even volume expansion). Indeed, ongoing trials in the developed and developing world are presently investigating the hypothesis that room air may be equivalent or superior to 100% oxygen in neonatal resuscitation ([12] and Chapter 4). Biochemical evidence of less oxidant injury and preliminary clinical evidence for similar or more rapid return of spontaneous respirations and normalization of vital signs suggest that resuscitation with room air may someday find a role even where medical resources abound. Other methods in wider use in the developing world, such as simple mouth-to-valve devices for positivepressure ventilation may serve as models for development of more sophisticated devices that deliver better-regulated pressure and result in more effective ventilation during neonatal resuscitation [13,14]. Alternative methods of ventilation such as laryngeal mask airway, now used primarily for ventilation under anesthesia deserve further exploration in the delivery room setting as a means to minimize the need for endotracheal intubation of newly born infants [15,16]. The physiological basis of seemingly radically different approaches to stimulating respiration deserves exploration. In some parts of China the practice of treating apnoeic infants with intramuscular injections of vitamin C almost certainly results in strong tactile stimulation, but may also provide some antioxidant protection in the longer term. Finally, both traditional and technologically advanced practices should be examined for alternative approaches to the infant who fails to respond to effective ventilation alone. The fundamental practice of chest compressions has been extrapolated from the adult model of cardiopulmonary resuscitation. Although certain aspects of chest compressions have been studied rigorously (location of compressions [17], two-thumb vs two-finger technique [18], simultaneous vs interposed compression and ventilation [19]), the fundamental issues of compression-to-ventilation ratios have not been well studied under the conditions which pertain at the moment of birth (asphyxial cardiac injury, pulmonary immaturity, pulmonary function impaired by infection or aspiration). Neurological and cognitive impairment of infants who have been resuscitated after perinatal asphyxia remains one of the painful shortcomings of modern perinatal medicine. The currently accepted therapeutic arsenal of epinephrine, volume expansion, and bicarbonate
S. Niermeyer and J. Perlman
leaves much to be desired in terms of therapeutic effect and adverse consequences. Rigorous, controlled trials of hypothermia (see Chapter 5,7), glucose, antioxidants, alternative methods of volume expansion, new vasoactive agents (see Chapters 6 and 7), and electromechanical methods of supporting the circulation deserve to be supported. Perhaps the greatest variation in practice surrounding neonatal resuscitation comes in the approach to the infant who cannot be successfully revived. Whether a decision is made in advance not to resuscitate or a full resuscitation has not resulted in restoration of spontaneous circulation and respiration, the response of the persons caring for the infant is uniquely based on cultural norms and available resources. The importance of having a clear path to follow in the resuscitation and achieving an understanding with the family about their wishes cannot be overemphasized, whether in technologically advanced medical settings or traditional medical systems (see Chapter 8). As the world becomes more globalized at the level of local communities, cross-cultural understanding will become even more important.
Summary The forging of evidence-based, international guidelines for neonatal resuscitation offers an ongoing opportunity to learn from global variation in practice. Comparison of the different methods that have arisen to deal with the common features of perinatal physiology and pathophysiology can advance the understanding of the strengths and weaknesses of each method. Techniques in common use where resources are limited may have equal value in technologically advanced settings. Furthermore, comparison of approaches to resuscitation highlights steps where further research is needed at both the level of basic science and clinical application. Evaluation of innovative approaches to neonatal resuscitation, gained from diverse global perspectives, may result in improvement of outcome in areas such as neurodevelopment after perinatal hypoxic–ischemic injury, which have proven refractory to current interventions. Finally, continued cooperation on an international scale helps assure that infants around the world can rapidly benefit from advances in neonatal resuscitation.
Pathophysiology of neonatal resuscitation
Acknowledgements I would like to acknowledge the help of the people who have shaped my understanding of neonatal resuscitation with an international perspective: Drs Jacinto Hernandez and Jaime Zegarra in Peru and the USA; Nancy Villena, Guillermo Torrico, and Fernando Armaza in Bolivia; and Shamina, Yang Ping and Drolkar in The Tibet Autonomous Region, People’s Republic of China (SN).
References 1 Emergency Cardiovascular Care Committee of the American Heart Association. International Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care: A Consensus on Science. Resuscitation 2000; 46(1–3): 3–430. 2 Niermeyer S, Kattwinkel J, Van Reempts P, et al. International Guidelines for Neonatal Resuscitation: An Excerpt from the Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care: International Consensus on Science. Pediatrics 2000; 106(3) URL: http://www.pediatrics.org/cgi/content/full/106/3/ e29 and Circulation 2000; 102 (suppl I I-343–I-357). 3 Jordan, B. Birth in Four Cultures: A Crosscultural Investigation of Childbirth in Yucatan, Holland, Sweden, and the United States. Montreal: Eden Women’s Publications, 1978. 4 Trevathan W. Human Birth: An Evolutionary Perspective. New York: Aldine De Gruyter, 1987. 5 Estol PC, Piriz H, Basalo S, Simini G, Grela C. Oro-nasopharyngeal suction at birth: effects on respiratory adaptation of normal term vaginally born infants. J Perinat Med 1992; 20: 297–305. 6 Carrasco M, Martell M, Estol PC. Oronasopharyngeal suction at birth: effects on arterial oxygen saturation. J Pediatr 1997; 130: 832–834. 7 World Health Organization. Mortality Reports. URL: http://www.who.int/whosis/ 8 Niermeyer S, Shaffer EM, Thilo E, Corbin C, Moore LG. Arterial oxygenation and pulmonary arterial pressure in healthy neonates and infants at high altitude. J Pediatr 1993; 123: 767–772.
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9 Niermeyer S, Yang P, Shanmina, Drolkar Zhuang J, Moore LG. Arterial oxygen saturation in Tibetan and Han infants born in Lhasa, Tibet. N Eng J Med 1995; 333: 1248–1252. 10 Sime F, Banchero N, Penaloza D, Gamboa R, Cruz J, Marticorena E. Pulmonary hypertension in children born and living at high altitudes. Am J Cardiol 1963; 11: 143–149. 11 Wiswell RE. Meconium in the Delivery Room Trial Group: delivery room management of the apparently vigorous meconium-stained neonate: results of the multicenter collaborative trial. Pediatrics 2000; 105: 1–7. 12 Saugstad OD, Rootwelt T, Aalen O. Resuscitation of asphyxiated newborn infants with room air or oxygen: an international controlled trial: the Resair 2 Study. Pediatrics 1998; 102: e1. 13 Milner AD, Stokes GM, Tunell R, McKeugh M, Martin H. Laboratory assessment of Laerdal mouth tube mask prototype resuscitation device. J Med Biol Engineer Comput 1992; 30: 117–119. 14 Massawe A, Kilewo C, Irani S, Verma RJ, Chakrapam AB, Ribbe T, Tunell R, Fischler B. Assessment of mouth-tomask ventilation in resuscitation of asphyxic newborn babies: a pilot study. J Trop Med Int Hlth 1996; 1: 865–873. 15 Paterson SJ, Byrne PJ, Molesky MG, Seal RG, Finucane BT. Neonatal resuscitation using the laryngeal mask airway. Anesthesiology 1994; 80: 1248–1253. 16 Gandini D, Brimacombe JR. Neonatal resuscitation with the laryngeal mask airway in normal and low birth weight infants. J Anesthes Analges 1999; 89: 642–643. 17 Orlowski JP. Optimum position for external cardiac compression in infants and young children. Ann Emerg Med 1986; 15: 667–673. 18 Houri PK, Frank LR, Menegazzi JJ, Taylor R. A randomized, controlled trial of two-thumb vs two-finger chest compression during CPR in a swine infant model of cardiac arrest. Ann Emerg Med 1993; 22: 240–243. 19 Dean JM, Koehler RC, Schleien CL, Berkowitz I, Michael JR, Atchison D, Rogers MC. Age-related effects of compression rate and duration in cardiopulmonary resuscitation. J Appl Physiol 1990; 68: 554–560.
Pathophysiology of neonatal resuscitation: application in a global context Susan Niermeyera and Jeffrey Perlmanb a
Associate Professor of Pediatrics, Section of Neonatology, University of Colorado Health Sciences Center, Denver, Colarado, USA b Professor of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas, USA
Key words: resuscitation, neonatal, cross-cultural perspectives, asphyxia, pathophysiology, ventilation, meconium, chest compressions
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. 2001 Harcourt Publishers Ltd
Introduction With publication of the Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care: International Consensus on Science [1], the foundation for neonatal resuscitation practice has taken two important steps forward. First, the 2000 Guidelines for Neonatal Resuscitation [2] have as their basis a rigorous process of evidencedbased evaluation which has led to the formulation of the final recommendations. Second, the guidelines reflect an international consensus on resuscitation science. Nonetheless, resuscitation of a newly born infant remains an activity that occurs and may vary at an undeniably local level. Thus, in many parts of the world, births take place in the household rather than in medical facilities [3]. Correspondence to: Susan Niermeyer MD, Associate Professor of Pediatrics, Section of Neonatology, University of Colorado Health Sciences Center, Denver, Colorado, USA and Visiting Research Scientist, Instituto Boliviano de Biologı´a de Altura, La Paz, Bolivia. Tel: +591 2 24 20 59 (office in La Paz); +591 2 44 10 62 (home in La Paz); Fax: +591 2 22 14 18 or 39 14 16; E-mail: [email protected]
1084–2756/01/030213+05 $35.00/0
When delivery does occur within the medical setting, these facilities vary from birthing centres to primary-care clinics or hospitals in small communities, to regional medical centres. Cultural differences and ethnic medical beliefs also shape the understanding of physiology and the approach to treatment. The above differences raise several important questions: (1) Is there sufficient concordance in the approach to the reversal of perinatal asphyxia and/or airway difficulties as well as the maintenance of an environment supportive to normal postnatal transition to provide guidelines that can be truly global? (2) What global differences must be acknowledged when considering neonatal resuscitation? (3) What lessons can be learned from the global variations in practice? (4) Can these variations serve as the substrate for future research in neonatal resuscitation?
Pathophysiology The birth of an infant is associated with abrupt cessation of the fetal–placental circulation, followed © 2001 Harcourt Publishers Ltd
214
by rapid and profound changes involving both the cardiac and respiratory systems occurring in tandem. Respiratory adaptation includes cessation of fluid production (the volume of alveolar lung fluid prior to delivery approximates 30–35 ml/kg in the term infant), and clearing of this fluid prior to the establishment of a functional residual capacity. The initiation of spontaneous respirations is critical to the initiation and completion of this process. Concurrent circulatory changes include a fall in pulmonary vascular resistance and an increase in pulmonary blood flow associated with the onset of ventilation, and an increase in systemic vascular resistance associated with umbilical arterial vasoconstriction. These resistance changes result in a reversal of blood flow which becomes predominantly left to right across the foramen ovale and the patent ductus arteriosus. This process of adaptation may be complicated by airway secretions (mucus, blood, amniotic fluid, meconium), failure to initiate respirations (secondary to maternal analgesia, central nervous system injury, sepsis, etc.), respiratory distress (secondary to pulmonary disease, space-occupying lesions, etc.), asphyxia (hypoxia with hypercarbic acidosis), perinatal infections, cardiac dysfunction ( secondary to structural or functional abnormalities), congenital anomalies and prematurity. Fortunately, the overwhelming majority of near term and term babies complete the transition spontaneously and require minimal to no interventions. However, depending on the process inhibiting normal transition, resuscitation may require action as limited as clearing oral airway secretions to interventions as intense as chest compressions and medications in order to restore circulatory function. Irrespective of the intensity of the cardiorespiratory intervention/s, resuscitation incorporates other vital activities including drying off the infant (to minimize heat loss) while maintaining body heat (skin-to-skin contact, warm towels).
Common strategies in the response to resuscitation The first tenet of neonatal resuscitation is the need for assistance at the moment of birth in order to prevent more severe problems. There is nearly universal acceptance of this concept, irrespective of whether the birth attendant is a family member, a traditional birth attendant, a medically trained mid-
S. Niermeyer and J. Perlman
wife, or a physician with a supporting team of specialized nurses and respiratory therapists [4]. Management of the thermal environment immediately after birth takes many forms, but in every birth setting it is recognized as a key step to avoid jeopardizing the process of achieving homeostasis after birth. In areas with limited resources, thermal management may receive even more emphasis than in settings with more extensive resources, when attention to fundamental concepts may be inadvertently superseded by a focus on technologically advanced airway and cardiovascular interventions. Finally, the basics of airway, breathing, and circulation are addressed in nearly every medical system (see Chapter 2), although the approaches may vary in form and degree. For example, clearing of the airway may require no intervention in settings in which delivery is unmedicated and the infant is vigorous and capable of handling his or her own secretions. When removal of secretions is required, many medical systems use wiping of the mouth with a cloth rather than suctioning as a basic method of clearing the airway. Removal of secretions with a bulb syringe or catheter is often reserved for cases in which respiratory distress occurs, because of the greater risk of provoking vagal bradycardia by stimulation of the posterior pharynx and delaying the postnatal rise in oxygen saturation [5,6].
Different strategies in the approach to resuscitation Certain fundamental differences in neonatal resuscitation are dictated by variation in infection risk, use of obstetrical analgesia/anaesthesia, route of delivery and/or management of dystocia, site of delivery or available resources. Thus the principal perinatal pathogens vary globally. For example in Asia and South America, perinatal infections with Gram-negative organisms often lead to preterm delivery or immediate, serious cardiopulmonary compromise at the time of birth. In contrast, Group B Streptococcal infections predominate in North America, where the presentation varies from asymptomatic to a more insidious onset of illness with potential cardiopulmonary collapse. In other regions of the world, such as Africa, the onset of illness maybe even more delayed in onset and yet still prove lethal, such as in the case of perinatal tetanus in Egypt.
Pathophysiology of neonatal resuscitation
Global variation in practices of obstetrical analgesia and/or anaesthesia is considerable. Natural delivery without any medications occurs not only in remote areas without resources, but in technologically advanced settings in North America and Europe. The Dutch model of home deliveries attended by specialized midwives has as its goal pain control by psychological preparation and support, without medication. Meticulous prenatal care and careful triage has resulted in one of the lowest neonatal and maternal mortality rates in the world [3,7]. Dystocia remains a major cause of perinatal asphyxia in isolated areas where transportation and lack of medical resources combine to threaten both neonatal and maternal survival. In isolated areas, there is often strict attention to early diagnosis of fetal malposition and a variety of non-invasive techniques are used to turn the fetus in a prophylactic manner, with variable degrees of success. The site of delivery relates directly to the degree of sophistication of available medical intervention. In home settings, attention to management of the thermal environment and cleanliness of instruments used in the delivery assumes paramount importance. Resuscitation devices are often unavailable in many technologically underdeveloped countries, and reliance on tactile stimulation of respirations and mouth-to-mouth or mouth-to-nose and mouth resuscitation is common. Even in the developing world where mechanical devices for positive-pressure ventilation are available, resuscitation with 100% oxygen is uncommon, due to limited supplies and distribution of compressed medical gases. In technologically advanced medical centres, where an assortment of devices for neonatal resuscitation is available, attention is now focused on improving the effectiveness of these devices. In such delivery rooms, ongoing controlled trials of automatic devices for positivepressure ventilation hold promise for better standardization and effectiveness of this key step in neonatal resuscitation. The site of delivery may, in some cases, mediate differences in the approach to neonatal resuscitation because of environmental factors. The most compelling example of environmental effect on perinatal physiology occurs at moderate (>2500 m) and extreme (>3500 m) high altitude, where lower inspired oxygen concentration, due to lower barometric pressure, results in both a slower postnatal rise in paO2 and fall in pulmonary artery
215
pressure [8,9]. In this setting, supplemental oxygen may play a key role in normalization of pulmonary artery pressure to near sea-level values [10].
Lessons to be learned Comparison of neonatal resuscitation techniques on a global scale is important in order to evaluate both the strengths and weaknesses of any one approach. This information may then serve as the substrate to study and eventually to disseminate the most effective approaches to neonatal resuscitation. For example the lack of necessity for intervention after a normal, unmedicated vaginal delivery – the usual strategy in the developing world – is gaining increased acceptance even in technologically driven delivery services in the USA. Thus, there is increasing recognition that routine oropharyngeal suctioning may be unnecessary and may possibly even have repercussions later in the establishment of breast-feeding (Gartner, Lawrence, personal communication). Adequate thermoregulation can be accomplished as effectively by thorough drying of the infant, followed by immediate skin-to-skin contact of mother and infant and covering both with warmed linens, as by placing the infant under a radiant warmer. Continued observation of the infant can be carried out under both circumstances. However the former situation does not require separation from the mother. Current management of the infant with meconium-stained amniotic fluid varies widely dependent on available facilities. Recent evidence indicates that it is the depressed and not the vigorous infant delivered in the presence meconium-stained amniotic fluid who should be managed with endotracheal intubation for suctioning [11] (and Chapter 3) However, in many regions of the world where tracheal intubation is not possible, management of the infant with meconium-stained fluid may rest solely on intrapartum suctioning of the naso- and hypopharynx before complete delivery. Improved antepartum management to minimize the asphyxial component of meconium aspiration syndrome, clarification of the role of intrapartum suctioning, and testing of the paradigm of intubation on the basis of vigour rather than consistency of meconium await further research (Chapter 3). In most of the developing world, strong emphasis is appropriately placed on establishment
216
of effective ventilation because of the limited availability of more advanced support (100% oxygen, medications or even volume expansion). Indeed, ongoing trials in the developed and developing world are presently investigating the hypothesis that room air may be equivalent or superior to 100% oxygen in neonatal resuscitation ([12] and Chapter 4). Biochemical evidence of less oxidant injury and preliminary clinical evidence for similar or more rapid return of spontaneous respirations and normalization of vital signs suggest that resuscitation with room air may someday find a role even where medical resources abound. Other methods in wider use in the developing world, such as simple mouth-to-valve devices for positivepressure ventilation may serve as models for development of more sophisticated devices that deliver better-regulated pressure and result in more effective ventilation during neonatal resuscitation [13,14]. Alternative methods of ventilation such as laryngeal mask airway, now used primarily for ventilation under anesthesia deserve further exploration in the delivery room setting as a means to minimize the need for endotracheal intubation of newly born infants [15,16]. The physiological basis of seemingly radically different approaches to stimulating respiration deserves exploration. In some parts of China the practice of treating apnoeic infants with intramuscular injections of vitamin C almost certainly results in strong tactile stimulation, but may also provide some antioxidant protection in the longer term. Finally, both traditional and technologically advanced practices should be examined for alternative approaches to the infant who fails to respond to effective ventilation alone. The fundamental practice of chest compressions has been extrapolated from the adult model of cardiopulmonary resuscitation. Although certain aspects of chest compressions have been studied rigorously (location of compressions [17], two-thumb vs two-finger technique [18], simultaneous vs interposed compression and ventilation [19]), the fundamental issues of compression-to-ventilation ratios have not been well studied under the conditions which pertain at the moment of birth (asphyxial cardiac injury, pulmonary immaturity, pulmonary function impaired by infection or aspiration). Neurological and cognitive impairment of infants who have been resuscitated after perinatal asphyxia remains one of the painful shortcomings of modern perinatal medicine. The currently accepted therapeutic arsenal of epinephrine, volume expansion, and bicarbonate
S. Niermeyer and J. Perlman
leaves much to be desired in terms of therapeutic effect and adverse consequences. Rigorous, controlled trials of hypothermia (see Chapter 5,7), glucose, antioxidants, alternative methods of volume expansion, new vasoactive agents (see Chapters 6 and 7), and electromechanical methods of supporting the circulation deserve to be supported. Perhaps the greatest variation in practice surrounding neonatal resuscitation comes in the approach to the infant who cannot be successfully revived. Whether a decision is made in advance not to resuscitate or a full resuscitation has not resulted in restoration of spontaneous circulation and respiration, the response of the persons caring for the infant is uniquely based on cultural norms and available resources. The importance of having a clear path to follow in the resuscitation and achieving an understanding with the family about their wishes cannot be overemphasized, whether in technologically advanced medical settings or traditional medical systems (see Chapter 8). As the world becomes more globalized at the level of local communities, cross-cultural understanding will become even more important.
Summary The forging of evidence-based, international guidelines for neonatal resuscitation offers an ongoing opportunity to learn from global variation in practice. Comparison of the different methods that have arisen to deal with the common features of perinatal physiology and pathophysiology can advance the understanding of the strengths and weaknesses of each method. Techniques in common use where resources are limited may have equal value in technologically advanced settings. Furthermore, comparison of approaches to resuscitation highlights steps where further research is needed at both the level of basic science and clinical application. Evaluation of innovative approaches to neonatal resuscitation, gained from diverse global perspectives, may result in improvement of outcome in areas such as neurodevelopment after perinatal hypoxic–ischemic injury, which have proven refractory to current interventions. Finally, continued cooperation on an international scale helps assure that infants around the world can rapidly benefit from advances in neonatal resuscitation.
Pathophysiology of neonatal resuscitation
Acknowledgements I would like to acknowledge the help of the people who have shaped my understanding of neonatal resuscitation with an international perspective: Drs Jacinto Hernandez and Jaime Zegarra in Peru and the USA; Nancy Villena, Guillermo Torrico, and Fernando Armaza in Bolivia; and Shamina, Yang Ping and Drolkar in The Tibet Autonomous Region, People’s Republic of China (SN).
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