discharge For example, certain congenital anomalies may be life threatening, and yet may not present until after this transition has been completed and the newborn has been discharged home Other perinatally acquired conditions may not present until days later due to their insidious onset Additional challenges include subtle neonatal presentations and more severe symptoms in response to pathogens because of immature immune function and lack of energy stores The immune system is entirely dependent on passive immunity provided from the mother during pregnancy, leaving the neonate immunocompromised and susceptible to life-threatening infections Furthermore, infants have very little in terms of cardiopulmonary reserve, so that the sick infant can go from well appearing to critically ill and cardiopulmonary arrest in a short period of time Finally, pathogens to which neonates are likely to be exposed during birth include aggressive bacteria and viruses, including Group B streptococcus (GBS), gramnegatives, and herpes simplex Regardless of the etiology of injury or illness, neonates have a very limited ability to communicate critical changes in health Infants cannot express subjective data, and often new parents are unable to identify critical changes in infant behavior As such, it is important for the caregiver to gather and interpret subtle changes in vital signs and the physical examination to avoid catastrophic injury to the ill newborn In this chapter, we will highlight the major differences between neonatal anatomy and physiology compared to that of older children We will also provide clinicians with a concise synopsis of common neonatal disorders that may be encountered in the ED Goals of Treatment Given the unique challenges of neonatal care, the primary goals of treatment are twofold: (1) to distinguish early signs of a sick infant from normal newborn behaviors and (2) to provide timely intervention to prevent permanent injury or death in the case of an ill neonate Clinical Considerations Clinical Recognition To assist in the clinical recognition of a sick infant, close attention must be paid to the vital signs obtained in triage Subtle changes in vital signs can often be the only indication of serious illness, and the early detection of these changes can alert the clinician to intervene prior to the loss of physiologic reserve and cardiopulmonary collapse