Neurological Critical Care

Introduction

Neurological critical care has evolved rapidly over the past 25 years. A rational amalgamation of the science of critical care with developments in neurosciences has paved way for a modern neurological intensive care unit (ICU). Comprehensive general medical care combined with specialized neurological care through management of intracranial pressure (ICP) and blood flow dynamics, advanced neuromonitoring [e.g., electroencephalography (EEG), brain tissue oxygen (PbtO ₂ ), and microdialysis], and newer therapeutic modalities, is intended to decrease the mortality and improve the functional outcomes of the patients. Given the complexity of cerebral function in health and disease, it is intuitive that specialized expertise is required at all levels of staffing including physicians, nurses, and technologists to manage a neurocritical care unit.

History of Neurocritical Care

The critical care units developed in the 1950’s to cater to the requirements of the victims of poliomyelitis in the Europe may be considered as the forerunners of modern neurocritical care units. A rapid increase in the volume of neurosurgical work and the complexity of neurosurgical and neuroanesthesia procedures called for increase in dedicated neurocritical care units. Advent of specialized therapies with definite outcome benefit (e.g., plasmapheresis for immunomodulation and thrombolysis for stroke) has necessitated creation of critical care facilities for neuromedical patients. The specialized needs of patients with neurotrauma demanded dedicated beds for neurotrauma, especially in the light of anticipated outcome benefit with modern-day cerebral physiology monitors.

Critical care, in general, was rather late to develop in India. Critical care services for neurological and neurosurgical patients started in major academic centers like National Institute of Mental Health and Neurosciences (NIMHANS), All India Institute of Medical Sciences (AIIMS), and Postgraduate Institute of Medical Education and Research (PGIMER) in the 1970’s and the 1980’s.

Design of a Neurocritical Care Unit

Design of critical care facilities has an impact on organizational performance, clinical outcomes, and cost of care delivery. Organizations involved in design and construction projects are advised to engage experienced consultants who will collaborate with the users and make key design decisions on the basis of best current evidence. The design of the unit should take into account the requirements of the patients, staff, and the families. The construction should provide adequate space for patient care activities, offices, academic activities, and the staff and family necessities. The administration should commit itself to providing the requisite equipment, consumables, and other supplies. A realistic planning should be made of manpower depending on the nature of patients. There is little literature on the guidelines for a neurocritical care unit. However, the guidelines for a general ICU published in Critical Care Medicine journal could form the baseline document over which any other specific needs of a neurological ICU can be built up.

Clinical Conditions Requiring Admission to Neurocritical Care Unit

Critical care is an expensive resource, hence should be used very judiciously. It is all the more precious in case of neurocritical care, as the available beds are limited and the demands are high. Although absolute objectivity is not possible, prioritization of the services in favor of those patients who are salvageable avoids futile prolongation of the ICU care. With advances in technology and concepts of pathophysiology, many conditions that were considered nonsalvageable earlier have a good prognosis now.

The most common diagnostic entities in a neurological ICU are traumatic brain injury (TBI), subarachnoid hemorrhage (SAH), stroke, postoperative care after major neurological surgery, neuromuscular paralysis due to polyneuropathy, and neuromuscular junction disorders. A comprehensive list of the clinical conditions admitted to NIMHANS neurological ICUs over a 1-year period is shown in Table 34.1 . In the current day practice, a neurological ICU should not be equated with a routine postoperative care unit for neurological patients. Over the years, there has been a progressive change in the patterns of admission to neurological ICUs. The demographic and epidemiological trends in neurological ICU are showing an overall increase in yearly admissions particularly in certain disease categories such as cardiac arrest, intracerebral hemorrhage (ICH), spine diseases, seizures, and TBI implying a trend for more aggressive management of these conditions. Also, there seems to be an increase in ICU length of stay (LOS) reflecting the implementation of aggressive therapeutic measures and the expanding role of critical care in health care delivery. The financial considerations of such aggressive therapy are a matter of serious concern and debate.

Justification for Neurological Critical Care Units

Critical care requirements in neurologically ill patients are inherently different and more complex from those of general critical care units. While many of the issues related to systemic physiology are similar to those in general ICU’s, understanding and management of specific neurological derangements are more complex and need specialized knowledge and skills. The margin of safety is low as the brain is very highly vulnerable to ischemic/hypoxic complications. Delays in identification of even subtle problems have a major impact on the outcome while the monitoring technology is complex and expensive. Ambiguity about the utility of the monitored information and uncertainty about the efficacy of certain treatment strategies further complicates the matters.

The benefits of specialized neurological critical care units have been evaluated in several studies. Patel et al. documented that specialist neurocritical care with protocol-driven therapy is associated with a significant improvement in outcome for patients with severe head injury, including those who require complex therapeutic interventions. In another study, introduction of a neurocritical care team, including a full-time neurointensivist, who coordinated care, significantly reduced in-hospital mortality and LOS without changes in readmission rates or long-term mortality. Critical care unit stay and length of hospital stay were shortened and disposition of patients improved in those with strokes admitted to a neurological ICU. Certain clinical entities seem to benefit more than the others; improvements in clinical outcomes associated with neurointensivist-driven care are more definitive in SAH than in ICH. The improved outcomes in the neuro-ICUs are probably related to more invasive intracranial and hemodynamic monitoring, lower threshold for tracheostomy, good nutritional support, and less intravenous (IV) sedation when compared to general ICUs. Finally, patients with ICH brought directly to neurological emergency department had significantly better outcomes than patients admitted to the other services and subsequently transferred to neurological ICU. The difference is probably accounted for by delays in optimizing management prior to arrival at the dedicated neurological ICU.

Pathophysiological Issues in Neurological Critical Care

The pathology in a patient in the neurological ICU may involve the brain and spinal cord or the peripheral nervous system. Irrespective of the primary cause, ischemia and inadequate oxygen delivery form the basis of the neurological dysfunction in the majority of patients with encephalopathy (e.g., trauma, SAH, stroke) ( Fig 34.1 ). Several factors determine the delicate balance between cerebral oxygen demand (CMRO ₂ ) and oxygen supply [cerebral metabolism, arterial blood pressure (BP), cardiac output, PaO ₂ , PaCO ₂ , pH, hemoglobin, ICP, drugs, and vasospasm]. Management of these patients revolves around optimization of these factors. Correction of the CMRO ₂ /cerebral blood flow (CBF) imbalance calls for optimization of hemodynamic, respiratory, and other systemic physiology, in addition to management of ICP and CBF dynamics.

Neuromuscular diseases requiring critical care are generally caused by reversible demyelination (e.g., acute or chronic inflammatory demyelinating polyneuropathy) or reversible pathology of the neuromuscular junction (e.g., myasthenia gravis). At times, the pathological processes involved may be degenerative in nature but have a high probability of therapeutic success (e.g., multiple sclerosis). Patients with more complex underlying pathologies and documented poor prognosis are generally not candidates for neurological ICU admission, except when the ICU admission is intended to treat a reversible intercurrent problem (e.g., chest infection, cardiac failure) of short duration.

Management of Patients in a Neurological Intensive Care Unit

ICU management of patients involves optimization of general systemic physiology and disease-specific therapy ( Table 34.2 ).

Management of General Systemic Physiology

Systemic insults account for a major proportion of the secondary neurological deterioration both in traumatic injury and non-TBI. While definitive treatment relevant to the primary pathology is in progress (e.g., evacuation of a mass lesion in TBI, thrombolysis in cerebrovascular accidents), efforts should be made to optimize the systemic physiology. Some practical issues in the management of these factors are discussed.