Neurocritical care
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Aneurysmal subarachnoid hemorrhage (SAH) affects 30,000 patients per year, causing neurologic morbidity and mortality. The etiology of hypoxemia and its role in comorbidity are controversial and unknown. ⋯ Oxygenation abnormalities after SAH occur more frequently than previously suspected. They are frequently the result of noncardiogenic and hydrostatic causes and contribute to an increased length of hospital stay.
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Recent evidence suggests that magnesium may be neuroprotective in the setting of cerebral ischemia, and therapeutic magnesium infusion has been proposed for prophylaxis and treatment of delayed ischemic neurological deficit (DIND) resulting from vasospasm in patients with aneurysmal subarachnoid hemorrhage (SAH). We studied the association between serum magnesium levels, the development of DIND, and the outcomes of patients with SAH. ⋯ We identified no relationship between serum magnesium levels and the development of DIND or outcome following aneurysmal SAH. Based on these data, magnesium supplementation to normal or high-normal physiological ranges seems unlikely to be beneficial for DIND resulting from vasospasm. However, no inference can be made regarding the value of therapeutic infusion of magnesium to supraphysiological levels.
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Clinical Trial
Prediction of intracranial pressure from noninvasive transocular venous and arterial hemodynamic measurements: a pilot study.
Continuous measurement of intracranial pressure (ICP) requires the invasive placement of epidural, parenchymal, or intraventricular devices. For critical single-point assessments, lumbar puncture may not always be practical. An accurate, reliable, portable and noninvasive method to estimate absolute ICP remains an elusive goal. The arteries that perfuse and the vein that drains the orbit are exposed to the ambient ICP while coursing through the cerebrospinal fluid or optic nerve. ⋯ The feasibility to estimate ICP from transocular sonographic and dynamometric data is suggested by these preliminary data. Retinal arterial properties are important in modeling the effect of ICP on the venous outflow pressure. Our pilot results serve as a basis on which to conduct a larger prospective and blinded study.
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It is controversial whether a low cerebral blood flow (CBF) simply reflects the severity of injury or whether ischemia contributes to the brain's injury. It is also not clear whether posttraumatic cerebral hypoperfusion results from intracranial hypertension or from pathologic changes of the cerebral vasculature. The answers to these questions have important implications for whether and how to treat a low CBF. ⋯ In patients with CBF<18 mL/100 g/minutes, intracranial hypertension plays a major causative role in the reduction in CBF. Treatment would most likely be directed at controlling intracranial pressure, but the early, severe intracranial hypertension also probably indicates a severe brain injury. For levels of CBF between 18 and 40 mL/100 g/minutes, the presence of regional hypoperfusion was a more important factor in reducing the average CBF.
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Physicians have an ethical duty to accurately determine and clearly communicate a patient's prognosis because a patient's or surrogate's decision whether to consent for aggressive treatment rests largely on their understanding of the patient's diagnosis and prognosis. Pitfalls in determining prognosis include uniformed summary judgement based on faulty pattern recognition, inadequate outcome data, utter reliance on retrospective studies, statistical limitations, nongeneralizability of outcome data, and the fallacy of the self-fulfilling prophecy. Pitfalls in physicians' communication of prognosis include inadequate time spent in discussion, use of technical jargon, biased framing of decisions, unjustified physician bias, patient innumeracy, ethnicity barriers, and surrogates' unfounded intuitions about critical illness and death. Improving the recognition of and surmounting the barriers to accurate determination and clear communication of prognosis can make critical care physicians more scientific and virtuous.