Journal of neurosurgical anesthesiology
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Local cerebral blood flow (LCBF) maps produced by 33% xenon-enhanced computed tomographic scanning (Xe/CT LCBF) are useful in the clinical diagnosis and management of patients with cerebrovascular disorders. However, observations in humans that 25-35% xenon (Xe) inhalation increases cerebral blood flow (CBF) have raised concerns that Xe/CT LCBF measurements may be inaccurate and that Xe inhalation may be hazardous in patients with decreased intracranial compliance. In contrast, 33% Xe does not increase CBF in rhesus monkeys. ⋯ The halothane MAC was 0.99 +/- 0.12% (M +/- SD), and the Xe MAC was 98 +/- 15%. These results suggest that the MAC of Xe in rhesus monkeys is higher than the reported human Xe MAC value of 71%. Thus the absence of an effect of 33% Xe on CBF in the rhesus monkey may be related to its lower anesthetic potency.
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J Neurosurg Anesthesiol · Oct 1994
Comparative StudyCSF, sagittal sinus, and jugular venous pressures during desflurane or isoflurane anesthesia in dogs.
Previous studies to determine whether desflurane increases cerebrospinal fluid (CSF) pressure are inconclusive because none have included all of the following: multiple doses of desflurane, administration for at least several hours, examination at normo- and hypocapnia, a concurrent comparison group, direct measurement of both intra- and extracranial CSF pressures, and measurement of venous pressures that influence CSF pressure. The present study was designed to determine whether CSF pressure increases during 4.0 h desflurane anesthesia using a study design that included the above elements. Catheters were placed in the lateral cerebral ventricle, cisterna magna, sagittal sinus, and jugular vein of 12 dogs anesthetized with thiopental 12 mg.kg-1.h-1 and halothane 0.5 to 0.8%. ⋯ CSF and sagittal sinus pressures, but not jugular venous pressure, increased with both desflurane and isoflurane. The greater increase of CSF pressure with 4.0 h desflurane (to 40.2 +/- 12.7 cm H2O) than with 4.0 h isoflurane (to 26.2 +/- 11.5 cm H2O) was attributable to an increase of CSF pressure that was greater during 2.0 h desflurane and normocapnia than during 2.0 h isoflurane and normocapnia, and to an increase of CSF pressure during 2.0 h desflurane and hypocapnia that was similar to that during 2.0 h isoflurane and hypocapnia. The greater increase of CSF pressure during desflurane may have resulted, in part, from increased CSF volume as indicated by a positive CSF-sagittal sinus pressure gradient (in contrast, there was little or no CSF-sagittal sinus pressure gradient during isoflurane) and a steeper slope of the gradient to CSF pressure relationship.
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J Neurosurg Anesthesiol · Oct 1994
Sevoflurane versus halothane anesthesia after acute cryogenic brain injury in rabbits: relationship between arterial and intracranial pressure.
The relationship between intracranial pressure and arterial blood pressure during sevoflurane or halothane anesthesia was evaluated in New Zealand white rabbits after cryogenic brain injury. Fourteen rabbits were randomized to be anesthetized with 1.5 MAC of sevoflurane or halothane in oxygen. All animals were paralyzed with pancuronium, and mechanically ventilated. ⋯ Intracranial pressure in the halothane anesthesia group increased from 9 +/- 1 to 32 +/- 3 mm Hg during the same range of blood pressure. Linear regressions of intracranial pressure on mean arterial pressure were performed for each of the two anesthetic groups. The slope of the regression line for the sevoflurane animals (0.491) was significantly greater than that for the halothane animals (0.323, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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J Neurosurg Anesthesiol · Jul 1994
Comparative StudyDoppler sensor placement during neurosurgical procedures for children in the prone position.
Precordial ultrasonic Doppler devices are effective monitors for detecting venous air emboli (VAE). However, placing an ultrasonic probe on the anterior part of the chest of a prone patient can lead to dislodgment or pressure sores and makes the probe inaccessible to the anesthesiologist. The purpose of this study was to compare placement of a Doppler probe on the patient's back with the traditional precordial site for the ability to detect VAE. ⋯ Positive tests were obtained from the posterior site in 23 of 24 (96%) children < 10 kilograms (group I), 28 of 39 (72%) children between 10 and 20 kg (group II), and 6 of 22 (27%) children > 20 kilograms (group III). This study demonstrates that a posterior Doppler probe can be effective for monitoring infants at risk of VAE. However, this method is not reliable in children weighting > 10 kg.
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J Neurosurg Anesthesiol · Jul 1994
Case ReportsDetection of site of air entry in venous air embolism: role of Valsalva maneuver.
Venous air embolism in posterior fossa surgery is a well-documented complication. Various highly sensitive devices help in early detection of air embolism. In management of air embolism, sealing the site of air entry is an important step in preventing further episodes. Here we discuss the importance of inspiratory hold after lung inflation (Valsalva maneuver) in helping to localize the site of air entry and its role in the management of venous air embolism observed in two cases of posterior fossa mass, operated in sitting position.