Review Article DOI: 10.18231/2394-4994.2018.0001 Indian Journal of Clinical Anaesthesia, January-March, 2018;5(1):1-8 1 Anesthesia for Neurosurgery (Part I) Lalit Gupta 1 , Bhavna Gupta 2,* 1 Assistant Professor, 2 Senior Resident, Dept. of Anaesthesia, Maulana Azad Medical College, New Delhi, Delhi, India *Corresponding Author: Email: bhavna.kakkar@gmail.com Received: 09 th January, 2018 Accepted: 18 th January, 2018 Abstract The central nervous system (CNS) deserves special consideration in the perioperative setting for several reasons for an anesthetist. An understanding of neuroanatomy is essential because neuro anesthesia continues to develop and evolution of neurosurgical practice is accompanied by new challenges for the anesthetist. Basic knowledge and expertise of the neuro-anesthetist can directly influence patient outcome. With the recent advancement in functional and minimally invasive procedures, there is an increased emphasis on the provision of optimal operative conditions, preservation of neurocognitive function, minimizing interference with electrophysiological monitoring, and a rapid, high-quality recovery. So, during neuro anesthesia, anesthesiologist needs to know physiology of CNS including cerebral metabolism and cerebral blood flow. Neuro anesthesia can be challenging, because sometimes apparently contradictory demands must be managed, for example, achieving optimal conditions for neurophysiological monitoring while maintaining sufficient anesthetic depth, or maintaining oxygen delivery to neuronal tissue and simultaneously preventing high blood pressures that might induce local bleeding. One of the peculiarities of neuro anesthesia has always been that as much importance is attached to wakening the patient as sending them to sleep. A. Cerebral Anatomy for Anesthetists 1. The brain and spinal cord are surrounded by protective but non-distensible bony structure called cranium. 2. Cranium is divided into supra-tentorial and infra- tentorial compartments. The supra-tentorial compartment contains the cerebral hemispheres and diencephalon (thalamus and hypothalamus), whereas the brainstem and cerebellum make up the infra-tentorial compartment. 3. The intracranial volume is fixed, thereby providing little room for anything other than the brain, cerebrospinal fluid (CSF), and blood contained in the cerebral vasculature. It is in the context of the restrictive nature of the space that needs urgent interventions. 4. The anterior cerebral circulation originates from the carotid artery, the posterior circulation results from the vertebral arteries, and the system of collateralization is known as the circle of Willis. 5. The spinal column is the bony structure made up of the seven cervical, 12 thoracic, and five lumbar vertebrae, as well as the sacrum. The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column. The brain and spinal cord together make up the central nervous system (CNS) 6. The spinal cord exits the skull through the foramen magnum and enters the canal formed by the vertebral bodies. In adults, the spinal cord typically ends at the lower aspect of the first lumbar vertebral body. 7. The anterior spinal artery arises from the vertebral arteries and supplies the anterior two thirds of the spinal cord. This vessel runs the length of the cord, receiving contribution from radicular arteries via intercostal vessels. The artery of Adamkiewich is the most important radicular artery 8. The posterior third of the cord is supplied by two posterior spinal arteries, which arise from the vertebral arteries and also receive contribution from radicular arteries 9. The term “blood-brain barrier” was coined, by Lewandowsky in 1898. The blood-brain barrier is composed of capillary endothelial cells with tight junctions that prevent free passage of macromolecules or proteins. In contrast, lipid- soluble substances (carbon dioxide, oxygen, anesthetic drugs) cross the blood-brain barrier easily. The blood-brain barrier may be disrupted by acute systemic hypertension, trauma, infection, arterial hypoxemia, severe hypercapnia, tumors, or sustained seizure activity. B. Neurophysiology The brain, although being 2% of the total body weight (~1350 gm), receives a disproportionately large share of cardiac output. Normal cerebral blood flow (CBF) is approximately 50 ml/100 g/min and represents 12% to 15% of total cardiac output. Despite dependence on such high cardiac output, brain is not an energy storehouse. Nearly 40% of total cerebral energy utilization is used to maintain the cellular homeostatic activities of brain tissues (i.e. basic functions of cell). While remaining 60% of the total cerebral energy utilization is needed to maintain the electrophysiological