Clinical neuroscience: relevance to current practice
The last decade has seen a rapid expansion of our knowledge in clinical neuroscience. These developments are of relevance to everyone working in anaesthesia and intensive care because of the changes that they have brought to the management of common neurological conditions such as head injury, subarachnoid haemorrhage (SAH) and stroke. This postgraduate issue of the British Journal of Anaesthesia is dedicated to clinical neuroscience and its relevance to current elective and acute clinical practice. The reviews are written by acknowledged experts in their field and present the latest evidence for current clinical practice and identify new developments that are likely to direct future practice.There are new challenges facing anaesthetists as neurosurgical practice evolves. Controversies regarding the provision of anaesthesia for intracranial neurosurgery remain, with no ideal technique identified.1 The ‘local’ vs ‘general’ anaesthesia debate for carotid surgery also continues.2 The anaesthetic considerations for patients with SAH are changing as treatment shifts from the operating room to the neuroradiology department.3 Less invasive treatment strategies and changes in neurosurgical practice have also resulted in increasing numbers of patients with poor grade SAH presenting for anaesthesia and intensive care. The management challenges of this difficult group of patients should not be underestimated. Complex spinal surgery is the most rapidly expanding service in most neurosurgical units in the UK and also brings significant challenges for the anaesthetist. This is even more so in the paediatric population and therefore it is timely to include a review of the provision of anaesthesia for spinal surgery in children.
Head injury remains an important cause of death and disability in young adults. More than 3500 patients are admitted to UK intensive care units with severe head injury each year. Despite advances in management, 23% of severely head-injured patients still die and around 60% of those who survive have some residual neurological defect, ranging from mild cognitive impairment to severe neurological deficit.4 The importance of head injury for practicing clinicians is reflected by the extensive coverage in this issue. Basic principles and current concepts of the pathophysiology of brain injury and the pharmacological and physiological basis of cerebral protection are reviewed. The latest guidance for effective resuscitation and early management of head injury is presented. There is accumulating evidence that specialized neurocritical care, with the provision of protocolized management strategies by a multi-disciplinary team, might improve outcome after severe traumatic brain injury (TBI).5 The review on the intensive care management of head injury emphasizes a multi-faceted strategy of physiological neuroprotection based on the avoidance of secondary ischaemic injury by maintenance of cerebral perfusion and optimization of cerebral oxygenation. Advances in neuromonitoring have led to the introduction of multi-modality monitoring systems that can identify cerebral ischaemia early and guide treatment during the intensive care management of head injury. The latest techniques are discussed and, in conjunction with reviews published in the BJA postgraduate issue in 2006 6–9 and some recently published studies,10–13 represent state of the art knowledge. Sophisticated modalities are becoming more widely available and it is therefore appropriate that this issue contains a review of imaging after brain injury. The role of neuroimaging in elucidating pathophysiological changes after brain injury and the potential for neuroimaging techniques to allow refinement and optimization of existing treatment strategies and the development of new treatments are discussed. It is likely that a combination of neuromonitoring and neuroimaging will allow us to improve our understanding of the critical pathophysiological derangements that occur after brain injury and are responsible for poor outcome.14 As in other areas of medicine, the influence of genetics on outcome after head injury is now undisputed 15 and a comprehensive review of this important area is presented. A greater understanding of the interplay between environmental and genetic factors is likely to allow better risk stratification of patients, the development of new preventative and therapeutic modalities, and the possibility of ‘individualizing’ patient management based upon their genetic make-up.
Therapeutic nihilism and insufficient treatment opportunities have led to stroke being the third cause of death and major cause of disability in industrial countries. Recently, the management of stroke has moved up the political and professional agenda and it is now becoming established as an ‘acute’ area of medicine. It is appreciated that brain tissue is lost, and therefore outcome adversely affected, if time to treatment is delayed.16 The introduction of acute interventions for stroke will have implications for all anaesthetists working in accident departments and intensive care units.
The complex issues surrounding the provision of anaesthesia for patients with disorders of the neuromuscular junction are often overlooked and we are pleased to include a comprehensive review of this subject.
There are common themes in the management of the acute insult, prevention of secondary injury and brain protection in many neurological disorders. The apparent overlap between different facets of experimental and clinical neuroscience therefore has far reaching potential in terms of patient management and outcome. It is now clear that the gene polymorphism that makes us susceptible to developing Alzheimer's disease is also associated with poorer outcome after TBI.17 Recent research has also shown that cytokines play a crucial role in determining the speed and extent of damage in many neurological conditions. For example, the key role of neuroinflammation has led to head injury being described as an ‘inflammatory disease’.18 The implications of these observations for clinical care are that a ‘cure’ for one illness may have beneficial effects in another. Nowhere is this more likely than in neurological conditions, where new avenues for risk assessment and novel therapeutic interventions for limiting secondary brain injury are being tested and developed. While it is known that anaesthetic agents have effects at sub-cellular level,19–25 what is unknown is how these might interact with other sub-cellular phenomena such as cytokine expression or release. Further research in this area might offer insights into the neuroprotective effects of some anaesthetic agents and the potential for clinical application.
Neurocritical care is an evolving sub-speciality of intensive care medicine that offers specialist treatment to patients with neurological disease or injury.5 It is likely to see further expansion with the widespread introduction of targeted therapies for SAH and stroke. However, readers of this issue of the British Journal of Anaesthesia will not fail to recognize the wide gap that remains between our expanding knowledge base and its translation into clinical practice. This is nowhere more apparent than in head injury management where widely accepted consensus guidance on monitoring and management are not uniformly applied.26 27 In other areas this gap is even wider. Despite extensive experimental evidence, few neuroprotective strategies have been tested in the clinical arena and, with the exception of hypothermia after cardiac arrest,28 the results of clinical trials have been negative.29
While it is exciting to have so many new developments available to us, it is important to understand that translation into clinical practice and improved patient outcome requires further work. In the area of head injury management in the UK, gathering and sharing of information on current practice and patient outcomes, agreement of standardized management protocols, establishment of common patient pathways and encouragement of multi-centre research are required. Clinical networks have been established in many specialties to provide similar standards of care throughout the UK and with them have come improved patient outcomes. Notable successes to date are in the areas of cancer and diabetes, and perhaps the time is right to develop similar networks for the management of critically ill brain injured patients. Almost every review in this issue begins with a description of the major impact that neurological illness and injury has on the health of the nation, and a belief that adverse outcome can be minimized by timely and targeted interventions. While we should all rise to this challenge to improve outcome for our patients, determined efforts beyond those of individuals will be required to deliver this agenda. Specialist societies, charities, patient groups, the medical Royal Colleges and those who commission healthcare all have a role to play in improving services for patients with neurological disease in the UK.
1 Department of Neuroanaesthesia and Neurocritical Care
The National Hospital for Neurology and Neurosurgery
University College London Hospitals
Queen Square
London WC1 N 3BG
UK
2 University Division of Anaesthesia and Intensive Care
Queen's Medical Centre
Nottingham NG7 2UH
UK
* Corresponding author E-mail: ravi.mahajan{at}nottingham.ac.uk
References
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