Journal of neurosurgical anesthesiology
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J Neurosurg Anesthesiol · Apr 1999
Influence of fentanyl, alfentanil, and sufentanil on motor evoked potentials.
The effects of the opioids fentanyl, alfentanil, and sufentanil on motor pathways were studied in a total of 30 rabbits. Compound muscle action potentials (CMAP) were recorded from the extensor muscles of the upper extremity as well as evoked spinal cord potentials (ESCP) from the thoracic epidural space in response to electrical stimulation of the motor cortex. After establishing stable baseline values, an equipotent intravenous bolus of one of the three opioids was applied that abolished reflex motor response to noxious stimulation. ⋯ We hypothesize that the descending volleys within motor pathways are mainly inhibited at a spinal level, because ESCP, particularly the number of spinal I-waves, are not severely affected even when CMAP are completely suppressed. In conclusion, intraoperative monitoring of descending pathways by means of MEP during anesthesia with opioids is feasible at anesthetic plasma concentrations maintaining a surgical level of analgesia. Even with high opioid plasma levels, a valid MEP monitoring could be performed evaluating neural activity of spinal MEP.
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J Neurosurg Anesthesiol · Apr 1999
The effect of magnesium sulfate on cerebral blood flow velocity, cardiovascular variables, and arterial carbon dioxide tension in awake sheep.
Although there are data demonstrating reversal of cerebral vasospasm with magnesium sulfate, there is little information on the effects of magnesium on the normal intact cerebral vasculature. This study investigated the actions of magnesium on cerebral blood flow (CBF) velocity, cardiovascular variables, and arterial gas tensions. Magnesium sulfate was infused into awake, adult sheep at rates of 3 and 6 mmol/min to a total of 15 and 30 mmol, respectively. ⋯ Infusion of both 15 and 30 mmol of magnesium increased CBF velocity by 14% (P = .056) and 24% (P = .023), respectively. These increases were accompanied by increases in arterial carbon dioxide tension (PaCO2) of 12% (P = .033) and 17% (P = .048). Multiple linear regression analysis revealed that both PaCO2 (P = .00037) and magnesium (P = .0012) were important predictors of CBF velocity.
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J Neurosurg Anesthesiol · Jan 1999
Fiberoptic intubation in 327 neurosurgical patients with lesions of the cervical spine.
In patients with lesions of the cervical spine, direct laryngoscopy for endotracheal intubation entails the risk of injuring the spinal cord. In an attempt to avoid this complication, the authors used flexible fiberoptic nasal intubation in a series of 327 patients with cervical lesions undergoing elective neurosurgical procedures. The nasal route was preferred for laryngeal intubation because it is easier than the oral route and a restraining collar or halo device does not impair the intubating maneuver. ⋯ Cervical stabilizers did not have to be removed for intubation in any patient. None of the patients had postoperative neurologic deficits attributable to the intubation procedure. The authors consider fiberoptic transnasal intubation to be a useful alternative to direct laryngoscopic tracheal intubation in patients undergoing elective surgical procedures on the cervical spine to avoid potential injury to the cervical spinal cord.
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J Neurosurg Anesthesiol · Jan 1999
Comparative StudyCerebral glucose metabolism in acute and persistent vegetative state.
Regional cerebral glucose metabolism (rCMRglc) was investigated with 18F-2-fluoro-2-deoxy-D-glucose (FDG) and positron emission tomography (PET) in 24 patients with acute (AVS, duration <1 month, n=11) or persistent (PVS, duration >1 month, n=13) vegetative state (VS) following prolonged anoxia due to cardiorespiratory arrest. After a follow-up period of twelve months, 8 patients had died, 13 remained in a permanent vegetative state and three showed moderate improvement of consciousness, without however regaining independence for activities of daily life. As expected, overall glucose utilization (CMRglc) was significantly reduced in VS in comparison to age matched controls. ⋯ A statistically significant correlation between the degree of evoked potential or EEG alterations in VS and the reduction of global or regional cortical metabolic rates for glucose could not be established. Cortical metabolic rates in patients with PVS were significantly reduced when compared to patients studied in AVS (p<0.05 for all cortical regions of interest except the frontal lobe). This phenomenon reflects the progressive loss of residual cortical function following anoxic brain injury that corresponds to the neuropathological findings of progressive Wallerian and transsynaptic degeneration as sequelae of anoxic brain injury in PVS.
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J Neurosurg Anesthesiol · Jan 1999
Case ReportsSudden asystole during craniotomy: unrecognized phenytoin toxicity.
The authors report a case of intraoperative sinus arrest in an otherwise healthy patient undergoing craniotomy for aneurysm clipping after mild subarachnoid hemorrhage. The sinus arrest was precipitated by a rapid infusion of 1500 mg phenytoin and was successfully treated with standard resuscitative measures. The differential diagnosis of intraoperative cardiac arrest and the mechanisms of action of phenytoin are discussed. The authors emphasize the role of phenytoin in cerebral protection.