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FOCUS POINTS
The cranial vault changes structurally from birth through the first 2 years of life. Eighty percent of the intracranial volume consists of brain and interstitial fluid, with blood and cerebrospinal fluid (CSF) making up the remainder. Intracranial compliance is the change in intracranial pressure (ICP) relative to the volume.
The open fontanelles and sutures in infancy results in increased intracranial compliance and allows for slow expansion of contents.
The Munro-Kellie hypothesis states that the sum of all intracranial volumes is always a constant. Infants are an exception to this rule because of the increased compliance and pliability of the skull. Mass effect of a slow growing tumor or hemorrhage can thus be masked by this compensation.
Acute changes in volume due to hemorrhage or obstruction of the CSF flow are not attenuated and can lead to life-threatening consequences.
Cerebral perfusion pressure (CPP), the pressure gradient across the brain, is the difference between mean arterial pressure (MAP) at the entrance to the brain and the mean exit pressure (i.e. central venous pressure), or intracranial pressure (ICP) if elevated. It is a more reliable estimate of cerebral perfusion.
In adults, cerebral autoregulation maintains a constant brain perfusion despite moderate changes in MAP or ICP. The lower absolute limits of cerebral autoregulation in infants and children is unclear and the range is believed to be narrower in neonates.
Acceptable MAP for a neonate is the gestational age in mmHg. Tight blood pressure control is essential in the management of neonates to minimize both cerebral ischemia with hypotension, and intraventricular hemorrhage with hypertension.
Certain pediatric disease states have specific anesthetic considerations and require tailoring of the intraoperative anesthetic management to the unique disease condition.
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The practice of anesthesia for pediatric neurosurgical conditions requires understanding of the distinct differences in children compared to adults, and is made more challenging by the unique management considerations. There are age-related differences in the incidence, anatomy, and pathology of surgical lesions in this population, which translate into the need for an individualized approach to the pediatric neurosurgical patient. Differences in the physiological responses to surgery and anesthesia from adults are what set children apart, and make management decisions different from what is considered the norm of adult neuroanesthetic practice. Over the last couple of decades, the numerous technological advances in neurosurgery coupled with subspecialization, and a better understanding of the postoperative needs of pediatric patients have dramatically improved outcomes in infants and children with neurosurgical lesions.1
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COMMON PEDIATRIC NEUROSURGICAL CONDITIONS
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Congenital anomalies and malformations
Tumors
Hydrocephalus
Epilepsy
Craniosynostosis
Vascular anomalies—arteriovenous malformations, vein of Galen, moyamoya syndrome
Neuroimaging and interventional neuroradiological procedures
Neurotrauma
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NEUROANATOMY, DEVELOPMENTAL CONSIDERATIONS, AND NEUROPHYSIOLOGY
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The infant cranial vault undergoes several structural and physiological changes in the first 2 years of life. The intracranial space is compliant owing to open fontanelles and sutures, allowing for a ...