Neurocritical care
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Review
Physiological and biochemical principles underlying volume-targeted therapy--the "Lund concept".
The optimal therapy of sustained increase in intracranial pressure (ICP) remains controversial. The volume-targeted therapy ("Lund concept") discussed in this article focuses on the physiological volume regulation of the intracranial compartments. The balance between effective transcapillary hydrostatic and osmotic pressures constitutes the driving force for transcapillary fluid exchange. ⋯ Pressure autoregulation of cerebral blood flow is likely to be impaired in these conditions. A high cerebral perfusion pressure accordingly increases intracapillary hydrostatic pressure and leads to increased intracerebral water content and an increase in ICP. The volume-targeted "Lund concept" has been evaluated in experimental and clinical studies to examine the physiological and biochemical (utilizing intracerebral microdialysis) effects, and the clinical experiences have been favorable.
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Experimental evidence and clinical experience suggest that mild hypothermia protects numerous tissues from damage during ischemic insult. However, the extent to which hypothermia becomes a valued therapeutic option will depend on the clinician's ability to rapidly reduce core body temperature and safely maintain hypothermia. To date, general anesthesia is the best way to block autonomic defenses during induction of mild-to-moderate hypothermia; unfortunately, general anesthesia is not an option in most patients likely to benefit from therapeutic hypothermia. ⋯ In an effort to inhibit thermoregulation in awake humans, several agents have been tested either alone or in combination with each other. For example, the combination of meperidine and buspirone has already been applied to facilitate induction of hypothermia in human trials. However, pharmacological induction of thermoregulatory tolerance to cold without excessive sedation, respiratory depression, or other serious toxicity remains a major focus of current therapeutic hypothermia research.
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Guillain-Barré Syndrome is the leading cause of nontraumatic acute paralysis in industrialized countries. About 30% of patients have respiratory failure requiring intensive care unit (ICU) admission and invasive mechanical ventilation. Progressive weakness of both the inspiratory and the expiratory muscles is the mechanism leading to respiratory failure. ⋯ They include rapidly progressive motor weakness, involvement of both the peripheral limb and the axial muscles, ineffective cough, bulbar muscle weakness, and a rapid decrease in vital capacity. Specific treatments (plasma exchange and intravenous immunoglobulins) have decreased both the number of patients requiring ventilation and the duration of ventilation. The need for mechanical ventilation is associated with residual functional impairments, although all patients eventually recover normal respiratory muscle function.
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Several neurological conditions may present to the emergency department (ED) with airway compromise or respiratory failure. The severity of respiratory involvement in these patients may not always be obvious. Proper pulmonary management can significantly reduce the respiratory complications associated with the morbidity and mortality of these patients. ⋯ Several precautions must be taken when using these drugs to minimize potentially fatal complications. Noninvasive positive pressure ventilation may obviate the need for intubation in a select population of patients. This article reviews airway management, with a particular emphasis on the use of RSI for common neurological problems presenting to the ED.
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The acceptance of brain death by society has allowed for the discontinuation of "life support" and the transplantation of organs. The standard clinical criteria for brain death, when rigorously applied, ensure that the brainstem is destroyed. Because more rostral structures are more vulnerable than the brainstem, these are almost invariably devastated when brainstem function is irreversibly lost as a result of whole brain insults. ⋯ Ancillary tests are also required in very young children. In addition, some societies require their use as a matter of principle. Only tests of whole-brain perfusion adequately serve these purposes.