Peri-Operative Considerations of Dementia, Delirium, and Cognitive Decline

As the elderly population increases, so will the number of surgical patients with dementia and other cognitive disorders. Laboratory evidence suggests that some commonly used anaesthetic agents may accelerate the Alzheimer’s disease (AD) process, but robust clinical research is still needed. This chapter discusses the need for peri-operative guidelines for patients with dementia, and the many opportunities for further research to inform such guidelines. It also covers postoperative delirium and its association with longer hospital and intensive care unit stays, cognitive decline after surgery, and higher mortality. Finally, it covers postoperative cognitive dysfunction (POCD), how standardized definitions and study methodology are lacking, and that studying cognitive trajectory after anaesthesia and surgery is often confounded by various clinical elements that cannot be accounted for methodologically.

Paediatric Neuroanaesthesia

The anaesthetic management of infants and children undergoing neurosurgical procedures should be based on the developmental stage of the patient. For the safe conduct of anaesthesia, the evolving maturational changes of the various organ systems must be considered when choosing drugs and techniques in the peri-operative period. This chapter on paediatric neuroanaesthesia discusses the developmental aspects of the central nervous system (CNS), pre-operative assessment and planning, intra-operative management (including induction of anaesthesia, vascular access and positioning, maintenance of anaesthesia, and management of fluids and blood loss), anaesthetic management of specific neurosurgical procedures (e.g., congenital disorders, neoplasms, epilepsy, cerebrovascular disease, neuroendoscopy), and postoperative course.

Awake Craniotomy for Tumour, Epilepsy, and Functional Neurosurgery

An awake craniotomy for tumour and epilepsy surgery allows for the mapping of eloquent brain function to minimize its injury and/or for the localization of an epileptic focus. The insertion of deep brain stimulators for the treatment of functional neurosurgical disorders is also frequently performed with an awake patient. The role of the anaesthetist is important in order to have a comfortable and cooperative patient, for the use of appropriate sedation to allow for mapping, and careful vigilance to rapidly diagnose and treat any complication. This chapter discusses the overall rationale for, and the anaesthetic management of, patients undergoing awake craniotomy for tumours, epilepsy surgery, or deep brain stimulator placement.

Pituitary and Neuroendocrine Surgery

Surgeries on the pituitary and neuroendocrine system are commonly encountered in neuroanaesthesia practice. Pituitary tumours are the third most common brain tumour, comprising about 10–15% of all primary brain tumours. Patients with pituitary tumours pose unique challenges to the anaesthestist caring for them in the peri-operative period, and they require the care of a multi-disciplinary team to accurately diagnose and manage their disease process as they undergo surgical resection. This chapter on pituitary and neuroendocrine surgery includes sections on anatomy and physiology, systemic changes associated with pituitary tumours, pre-operative evaluation (including intra-operative management), and common complications (for example, diabetes insipidus).

Neurologic Emergencies

The primary goal of the neuroanaesthetist and neurointensivist is to preserve brain structure and function, especially in the setting of neurologic insults. Neurologic emergencies can also develop peri-operatively in patients undergoing non-neurosurgical procedures, which the general anaesthetist should be prepared to manage. This chapter on neurologic emergencies discusses herniation syndromes (including pathophysiology of intracranial hypertension, symptoms of herniation, and therapies to reduce intracranial pressure and reverse herniation). It also covers coma (including differential diagnoses of postoperative coma, clinical evaluation of the comatose patient, CT imaging, advanced tests, and directed therapies). Finally, it discusses key aspects of ischaemic stroke, status epilepticus, and transition of care.

Neurotoxicity of General Anaesthetics

This chapter covers the neurotoxicity of general anaesthetics. It discusses how a large body of preclinical evidence shows an association of anaesthetic exposure with neural cell injury and death in the developing brain. Several putative mechanisms have been demonstrated in vitro and in in vivo animal models. Furthermore, these exposures have been associated with impaired behavioural and cognitive development in young animals. Several retrospective human studies of neurocognitive and behavioural disorders following childhood exposure to anaesthesia suggest a similar association, and prospective studies in humans are currently ongoing. The implication of this information on anaesthetic practise remains to be seen.

Anaesthesia for Complex Spine Surgeries

This chapter discusses the pre-operative evaluation of the patient scheduled for complex spine surgery, and focuses on functional capacity, neurological assessment, and upper airway examination. In patients undergoing cervical spine surgery, awake fibreoptic intubation may be the safest technique for upper airway management, especially in patients with significant spinal cord compression or unstable cervical spine. Increased intra-ocular pressure during spine surgery in the prone position may compromise the ocular perfusion pressure. Maintaining proper ocular perfusion pressure is crucial to avoid postoperative vision loss or impairment. Avoiding muscle relaxants and high concentrations of inhalation anaesthetics are important for the anaesthetic management during intra-operative electrophysiological monitoring. Avoiding hypervolaemia is important to avoid endothelial glycocalyx damage.

Interventional Neuroradiology

Neuroradiology is a rapidly evolving field in the diagnosis and treatment of cerebrovascular diseases. This chapter reviews fundamental principles for providing care to patients undergoing interventional neuroradiology (INR) surgical procedures from the viewpoint of the patient, the neuro-interventionalist, the anaesthetist, and the neuro-intensivist. It provides a background of endovascular treatment of cerebral disorders and then focuses on the treatment of three disorders that are treated by endovascular therapy: cerebral aneurysms, carotid artery stenosis, and acute ischaemic stroke. It also covers intracranial pressure monitoring and treatment, motor deficit, management of blood pressure and ICP, and anaesthetic care for patients with acute ischaemic stroke.

Neurophysiologic Monitoring for Neurosurgery

Intra-operative neurophysiological monitoring (IOM) has evolved substantially since its beginnings in the 1970s with somatosensory evoked potentials (SSEP) and facial nerve electromyography (EMG). The introduction of new techniques (especially motor evoked potentials [MEP]) and refinements of older techniques have become important tools that the surgeon can use to enhance intra-operative decision making and improve patient outcome of surgical (e.g., intracranial, neurovascular, skull base and brainstem, spine and spinal cord, peripheral nerve) procedures. These monitoring modalities are used to map the anatomic location of neural structures and monitor the functional status of the neural tracts. The anaesthetist plays a key supportive role in monitoring and management when IOM indicates potential neural compromise.

Principles of Neuroprotection

This chapter on the principles of neuroprotection includes information on cerebral metabolism, energy failure and pathophysiologic mechanisms, oxidative stress, acidosis, cell death, and difficulties encountered in the translation of neuroprotective strategies from animals to humans. It also covers peri-operative neuroprotective strategies (including barbiturates, volatile anaesthetics, etomidate, propofol, ketamine, and xenon), physiologic management and neuroprotection (including systemic temperature, neonatal hypothermia, induced hypothermia after cardiac arrest, hypothermia and spinal cord injury, hypothermia and traumatic brain injury (TBI), hypothermia and focal ischaemic stroke, arterial oxygen tension, arterial carbon dioxide tension, glucose management, cerebral perfusion pressure, and tPA). Finally, it covers interventional procedures (including mechanical thrombectomy) to treat acute ischaemic stroke.