Journal of neurosurgical anesthesiology
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J Neurosurg Anesthesiol · Oct 1996
Comparative StudyValidation of transcranial near-infrared spectroscopy for evaluation of cerebral blood flow autoregulation.
The aim of the study was to evaluate a new noninvasive transcranial near-infrared spectroscopy (TNIRS) technique for determination of the lower limit of cerebral blood flow (CBF) autoregulation by comparing this technique with the standard cerebral arteriovenous oxygen saturation difference (AVDo2) method. In eight healthy volunteers, mean arterial blood pressure was increased by infusion of angiotensin and decreased by the combination of lower-body negative pressure and labetalol. For each 5-mm Hg change in mean arterial pressure, blood was sampled from the bulb of the internal jugular vein and a radial artery, and simultaneously, the oxygen saturation of hemoglobin in the brain was measured with an INVOS 3100 Cerebral Oximeter (Somanetics). ⋯ For all the 98 pairs of saturations registered, the correlation was 0.37 (p < 0.001), the mean difference was 16%, and the limits of agreement were -2.2 and 33.8%. We conclude that the cerebral oximeter might be useful in evaluation of the lower limit of cerebral autoregulation. This method, however, is of no value for estimation of levels of global cerebral oxygen saturation.
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J Neurosurg Anesthesiol · Oct 1996
The effect of right internal jugular vein cannulation on intracranial pressure.
Access to the central venous circulation is often necessary in patients who have elevated intracranial pressure. It has been suggested that a disadvantage of the internal jugular vein approach to the central circulation may be an elevated intracranial pressure. The purpose of this prospective study was to evaluate the effect of right internal jugular vein cannulation on intracranial pressure in patients who are at risk of intracerebral hypertension. ⋯ Furthermore, no difference was found in percentage change from baseline intracranial pressure data throughout the study period. Our results suggest that cannulation of the right internal jugular vein is a safe approach to the central circulation in patients at risk of intracranial hypertension. A description of the possible accommodating mechanisms are outlined.
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J Neurosurg Anesthesiol · Oct 1996
Comparative StudyComparative effects of propofol, pentobarbital, and isoflurane on cerebral blood flow and blood volume.
While intravenous and volatile anesthetics have widely differing effects on cerebral blood flow (CBF), clinical studies suggest that the relative differences in their effects on intracranial pressure (ICP) may be smaller. Because acute changes in ICP are determined primarily by changes in cerebral blood volume (CBV), we compared the impact of propofol, pentobarbital, and isoflurane on CBF and CBV in rats. Equipotent doses of the three agents were determined by tail-clamp studies. ⋯ CBF was 2.0-2.6 times greater with isoflurane than with propofol or pentobarbital (137 vs. 67 and 52 ml.100 g-1.min-1, respectively). By contrast, while CBV was greater in the isoflurane group than in either the propofol or pentobarbital groups, the magnitude of the intergroup differences were much smaller (propofol = 2.49 +/- 0.28 ml/100 g; pentobarbital = 2.27 +/- 0.15 ml/100 g; isoflurane = 2.77 +/- 0.24 ml/100 g, mean +/- SD). These results suggest that the simple measurement of CBF may not adequately describe the cerebrovascular effects of an anesthetic, at least with respect to predicting the magnitude of the agents likely effects on ICP.
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J Neurosurg Anesthesiol · Oct 1996
Case ReportsPercutaneous dilational tracheostomy after anterior cervical spine fixation.
After spinal cord injury, quadriplegic patients generally require tracheostomy for ventilatory support and airway clearance. Early tracheostomy has several advantages over translaryngeal intubation, but in patients who undergo anterior surgical fixation of the spine, it is often delayed until after recovery of the surgical wound. ⋯ The percutaneous dilational technique minimizes the injury to the adjacent structures of the neck and the risk of stomal infection. Therefore, it should be considered the technique of choice when an early tracheostomy is indicated for quadriplegic patients who have undergone anterior surgical fixation of the cervical spine.
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J Neurosurg Anesthesiol · Jul 1996
Comparative StudyChanges in cerebral blood flow velocity in children during sevoflurane and halothane anesthesia.
The purpose of this study was to evaluate arterial blood pressure and middle cerebral artery blood flow velocity in children during induction of anesthesia with sevoflurane. These measures were compared to findings in a control group anesthetized with halothane. Each child received mask induction of sevoflurane (n = 9) or halothane (n = 9) with 70% nitrous oxide in oxygen. ⋯ Both sevoflurane (2.4%) and halothane (1.3%) combined with 70% nitrous oxide decreased blood pressure and increased cerebral blood flow velocity. Intubation increased blood pressure and further increased cerebral blood flow velocity with both anesthetic treatments. These results indicate that sevoflurane and halothane combined with nitrous oxide decrease blood pressure and increase cerebral blood flow velocity and suggest that sevoflurane produces cerebrovascular effects similar to those of halothane during anesthetic induction.