New horizons (Baltimore, Md.)
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Sedative and neuromuscular blocking (NMB) drugs are used to facilitate care of head trauma patients requiring mechanical ventilation or therapy of intracranial hypertension. Because no specific regimen is appropriate in all patients, drug selection and utilization exhibit significant regional variation. Sedatives are used to decrease anxiety and diminish awareness of noxious stimuli. ⋯ Increasingly more information is available to guide the use of NMB drugs for patients suffering head trauma. Broad concerns about these drugs include their use as adjunctive therapy to control intracranial hypertension, the incidence of prolonged weakness or myopathy, the potential for direct neurologic toxicity, and their effect on outcome. Resolution of these issues will improve the use of sedative and NMB drugs in intensive care.
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Moderate systemic hypothermia has been shown to improve neurologic outcomes in both fluid-percussion and cortical contusion models of experimental brain injury. Based upon initial clinical work, it was concluded that at temperatures < 32 degrees C, patients with severe brain injury were at increased risk of ventricular arrhythmias, and that rapid rewarming immediately postinjury predisposed to intracranial pressure increases. Subsequent clinical studies of moderate hypothermia (32 degrees C) for 24- to 48-hr duration with slow rewarming in human brain injury showed indications of neurologic improvement and a low incidence of hypothermia-related complications. ⋯ The efficacy of hyperbaric oxygen administered every 8 hrs for 1-hr duration for a 2-wk period has also been tested in patients after severe brain injury. While the mortality rate was reduced in the treated group, the percentage of favorable outcomes was unchanged. Further studies are in progress.
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The management of brain swelling that frequently occurs following severe traumatic brain injury (TBI) presents a difficult challenge for physicians treating these patients. A traditional cornerstone for the treatment of post-traumatic brain swelling has been prophylactic hyperventilation to reach PaCO2 levels of 25 to 28 torr. While there are anecdotal reports of improvement in intracranial pressure (ICP) and neurologic functioning following institution of this therapy, the only prospective, randomized trial of its use has found worse outcomes in those treated with prophylactic hyperventilation therapy for 5 days. ⋯ In some cases, TBI also causes an increase in cerebral vascular responsivity to hypocapnia, increasing the drop in regional CBF that occurs with hyperventilation. Thus, there is a well defined physiologic basis for expecting hyperventilation to cause worsened clinical outcomes following TBI. While this therapy clearly is indicated for the management of acute neurologic deterioration or intracranial hypertension refractory to all other forms of medical therapy, hyperventilation is no longer recommended as a first-line therapy for intracranial hypertension or as prophylactic therapy following severe TBI.
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Following severe head injury, derangements of the cerebral vasculature and cerebral blood flow (CBF) often occur, rendering the brain at risk of secondary ischemia. Therefore, monitoring of CBF in head-injured patients is considered useful for understanding the pathophysiology and effects of therapy, although such monitoring has not yet become part of routine patient management in most centers. In this article, we review the current research on CBF in head injury. ⋯ Disturbances of cerebrovascular CO2 reactivity and autoregulation appear to be less frequent than previously assumed. However, when present, such derangements do have consequences for therapy, in particular the management of blood pressure and cerebral perfusion pressure. Potential implications for patient management are discussed.
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Monitoring and management of intracranial pressure (ICP) are fundamental to modern neurotraumatology. Although never formally proven to independently improve outcome in prospective, randomized, placebo-controlled trials, there is such a predominance of indirect support for this modality that most neurotrauma protocols are impossible with-out its inclusion and ethical considerations virtually preclude placebo-controlled trials of its efficacy. In addition to the question of improving outcome, ICP monitoring is also useful in guiding the use of potentially harmful treatment modalities such as hyperventilation, mannitol, and barbiturates, and also provides important prognostic data. ⋯ Cerebral autoregulation generally remains at least partially preserved after severe head injury, although the CPP value at which it is activated appears to be shifted upward. Therefore, maintaining adequate CBF appears to require using an elevated minimal CPP threshold when treating the injured brain. A generally accepted value of 70 mm Hg is suggested.