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Essential Expectations-Avoiding Hypocapnia and Hyperoxemia in Neonatal Encephalopathy

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Essential Expectations-Avoiding Hypocapnia and Hyperoxemia in Neonatal Encephalopathy Journal of Pediatrics and Neonatal Care Essential Expectations-Avoiding Hypocapnia and Hyperoxemia in Neonatal Encephalopathy Mini Review Mini Review Therapeutic hypothermia (TH) is the accepted treatment modality for newborns with moderate to severe neonatal Volume 6 Issue 5 - 2017 encephalopathy likely originating from a hypoxic-ischemic event. Numerous randomized, controlled trials and meta-analyses have shown that TH reduces that the risk of death or major Baystate Children’s Hospital, USA neurodevelopmental disability by 25-35% among treated infants *Corresponding author: Jeffrey Shenberger, Baystate [1,2]. Lung injury, with or without effective respiratory control, Children’s Hospital, Division of Newborn Medicine 759 is present in as many as 80% of infants with moderate-to-severe neonatal encephalopathy who meet the inclusion criteria for TH [3]. 009-3; Email: Although these encephalopathic newborns often require oxygen Chestnut Street Springfield, MA 01199, USA, Tel: 413-794- supplementation or ventilatory support to provide adequate Received: March 08, 2017 | Published: April 04, 2017 gas exchange, their rapidly changing pulmonary mechanics and respiratory drive makes achieving and maintaining eucapnia and normoxemia clinically challenging. Accumulating evidence from clinical trials illustrates the importance of controlling the Although hypocapnia in neonatal encephalopathy may be partial pressures of carbon dioxide (PCO2) and oxygen (PO2) in a surrogate marker for brain injury severity, PCO2 represents order to maximize neurodevelopmental outcomes and ameliorate secondary brain injury resulting from over ventilation and recovery. As many infants undergoing TH are intubated for apnea, oxygenation. frequenta readily bloodmodifiable gas monitoring factor capable and/or of transcutaneousmaximizing neurologic or end- tidal CO monitoring are essential. As respiratory drive returns, Carbon dioxide regulates cerebrovascular tone by inducing 2 many infants become tachypneic and hypocapnic. At a minimum, vasodilation and augmenting perfusion at high levels clinicians should minimize ventilator settings and foster rapid (hypercapnic) and vasoconstriction and diminishing perfusion extubation in an attempt to not inadvertently lower PCO . For during low levels (hypocapnic). Knowing that hypocapnia- 2 persistent hypocapnia, both sedation and the introduction of dead mediated vasoconstriction is maintained in hypoxic-ischemic space into the ventilator circuitry may restore PCO to “normal” encephalopathy raises concerns that low PCO may accentuate 2 2 levels. To date, however, neither strategy has been studied, secondary brain injury, not only by reducing cerebral perfusion, rendering the safety and effectiveness for improving neurologic but by reducing O delivery, increasing neuronal energy demands 2 outcomes speculative. and DNA fragmentation, and depleting neuronal energy stores [4- 7]. Indeed newborn animal models demonstrate that hypocapnia In contrast to CO2, high partial pressures of oxygen are injurious yet frequently life-sustaining. Even a brief period of with greater brain injury than observed in either eucapnic or hyperoxia/hyperoxemia following a hypoxic insult promotes lipid hypercapnicreduces cerebral animals blood [8,9]. flow More following severe asphyxia brain injury, and is detected associated on stimulates apoptosis in the CNS of newborn animals [14-16]. In vasoreactivity determined by near-infrared spectroscopy [10]. theperoxidation, pre-cooling enhances era, one expressionstudy reported of inflammatory that severe hyeroxemiagenes, and MRI, has also been identified in infants with suboptimal cerebral Several clinical series reveal that hypocapnia is correlated with (PaO2>200 mmHg) was associated with increased odds of adverse adverse neuro developmental outcomes in infants with hypoxic- outcome (OR 3.85) in newborns with intrapartum asphyxia ischemic encephalopathy (HIE). In a retrospective cohort study [11]. A similar association was found in infants qualifying for of infants with HIE prior to the use of TH, Klinger et al found TH, such that a PaO2 that severe hypocapnia (PCO2<20 mmHg) was associated with corresponded to a 4-fold increased risk of HIE and a more than increased risk of death or severe neurologic impairment (relative 2-fold greater incidence>100 of hypoxicmmHg withininjury onthe MRIfirst among hour ofthose life risk 2.3) [11]. Analysis of data from the NICHD Research Network with moderate-severe HIE [17]. Likewise, high fractional inspired whole body cooling trial found both minimum and cumulative O2 PCO2<35 mmHg were associated with poor neurodevelopment attainment of blood gases, is also associated with increased risk concentrations within the first few hours of life, often prior to outcome [12]. More recently, post hoc analysis of the CoolCap of adverse outcome [18]. Hence PO2, like PCO2, warrants close Study data estimated the probability of poor outcome based upon monitoring to maintain partial pressures at appropriate levels. PCO and 2 2 Thankfully regulating PO is relatively easily achieved clinically. the severity of neurologic outcome after controlling for pH, aEEG 2 Continuous oximetry on the right hand (pre-ductal) beginning pattern,, finding birth anweight, inverse cooling correlation status, between and Sarnat the score lowest [13]. PCO immediately following delivery is a standard component of Submit Manuscript | http://medcraveonline.com J Pediatr Neonatal Care 2017, 6(5): 00256 Essential Expectations-Avoiding Hypocapnia and Hyperoxemia in Neonatal Copyright: 2/2 Encephalopathy ©2017 Shenberger neonatal resuscitation. Blended oxygen should be available and bcl-2 proteins, DNA fragmentation, and membrane peroxidation resuscitation initiated with room air. Once stabilized, maintaining products in cerebral cortical mitochondria of newborn piglets. pre-ductal oxygen saturations between 90-97% should neither Neonatology 91(1): 20-27. heighten the risk of developing pulmonary hypertension nor 8. increase the degree of secondary injury attributable to oxidative dioxide protects the perinatal brain from hypoxic-ischemic damage: stress [19]. Experience would suggest that monitoring both pre- anVannucci experimental RC, Towfighi study J, in Heitjan the immature DF, Brucklacher rat. Pediatrics RM (1995) 95(6): Carbon 868- and post-ductal saturations in these infants is wise. 874. With the advent of TH, clinicians caring for infants with 9. Rosenberg AA (1992) Response of the cerebral circulation to hypocarbia in postasphyxia newborn lambs. Pediatric research 32(5): 537-541. capable of reducing the secondary injury from a presumed hypoxic-ischemicneonatal encephalopathy insult. wereDuring afforded the recovery the first effectivephase, evolving therapy 10. Howlett JA, Northington FJ, Gilmore MM, Tekes A, Huisman TA, et changes in respiratory control and pulmonary mechanics al. (2013) Cerebrovascular autoregulation and neurologic injury represent an additional opportunity for clinical intervention in neonatal hypoxic-ischemic encephalopathy. Pediatric research aimed at maximizing recovery. Maintenance of eucapnia and 74(5): 525-535. normoxemia, therefore, should be envisioned as “essential 11. Klinger G, Beyene J, Shah P, Perlman M (2005) Do hyperoxaemia expectations” in the care of these infants. These simple goals are and hypocapnia add to the risk of brain injury after intrapartum achievable with appropriate monitoring, attention to detail, and asphyxia? Archives of disease in childhood Fetal and neonatal individualized respiratory support. edition 90(1): F49-F52. 12. Pappas A, Korzeniewski SJ (2016) Long-Term Cognitive Outcomes References 1. Tagin MA, Woolcott CG, Vincer MJ, Whyte RK, Stinson DA (2012) Asphyxia to Cerebral Palsy. Clinics in perinatology 43(3): 559-572. of Birth Asphyxia and the Contribution of Identified Perinatal Hypothermia for neonatal hypoxic ischemic encephalopathy: 13. Lingappan K, Kaiser JR, Srinivasan C, Gunn AJ (2016) Relationship an updated systematic review and meta-analysis. Archives of between PCO2 and unfavorable outcome in infants with moderate- pediatrics & adolescent medicine 166: 558-566. to-severe hypoxic ischemic encephalopathy. Pediatric research 2. Jacobs SE, Berg M, Hunt R, Tarnow-Mordi WO, Inder TE, et al. (2013) 80(2): 204-208. Cooling for newborns with hypoxic ischaemic encephalopathy. The 14. Gill MB, Bockhorst K, Narayana P, Perez-Polo JR (2008) Bax shuttling Cochrane database of systematic reviews 31(1): CD003311. after neonatal hypoxia-ischemia: hyperoxia effects. Journal of 3. Alsina M, Martin-Ancel A, Alarcon-Allen A, Arca G, Gaya F, et neuroscience research 86(16): 3584-3604. al. (2017) The Severity of Hypoxic-Ischemic Encephalopathy 15. Sifringer M, Bendix I, Borner C, Endesfelder S, Von Haefen C, et al. Correlates With Multiple Organ Dysfunction in the Hypothermia (2012) Prevention of neonatal oxygen-induced brain damage by Era. Pediatric critical care medicine : a journal of the Society of reduction of intrinsic apoptosis. Cell death & disease 3: e250. Critical Care Medicine and the World Federation of Pediatric Intensive and Critical Care Societies 18(3): 234-240. 16. Rognlien AG, Wollen EJ, Atneosen-Asegg M, Saugstad OD (2015) 4. Mirro R, Lowery-Smith L, Armstead WM, Shibata M, Zuckerman SL, brain after hyperoxic reoxygenation. Pediatric research 77(2): 326- et al. (1992) Cerebral vasoconstriction in response to hypocapnia 333.Increased expression of inflammatory genes in the neonatal mouse is maintained after ischemia/reperfusion
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