Journal of neurosurgical anesthesiology
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J Neurosurg Anesthesiol · Jul 1999
Randomized Controlled Trial Clinical TrialEffects of clonidine on human middle cerebral artery flow velocity and cerebrovascular CO2 response during sevoflurane anesthesia.
The present study was designed to evaluate the effects of clonidine on human middle cerebral artery flow velocity and the cerebrovascular CO2 response during sevoflurane anesthesia using transcranial Doppler ultrasonography. The subjects were nine awake volunteers (group A) and 18 patients receiving oral preanesthetic medication of clonidine, 3-4 mcg/kg, (group C), or placebo (group S). In groups C and S, anesthesia was induced with inhalation of sevoflurane-nitrous oxide. ⋯ The Vmca value of group C was significantly lower than that of group S in hypercapnia, but not in hypocapnia or normocapnia. The CO2 response slope of group C was significantly lower than those of groups A and S. The results indicate that clonidine, administered as an oral preanesthetic medication, reduces Vmca in hypercapnia but not in hypocapnia or normocapnia, and reduces the cerebrovascular CO2 response during sevoflurane anesthesia.
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J Neurosurg Anesthesiol · Apr 1999
Rebound intracranial hypertension in dogs after resuscitation with hypertonic solutions from hemorrhagic shock accompanied by an intracranial mass lesion.
We compared intracranial pressure (ICP) and cerebral blood flow (CBF) in dogs after inflating a subdural intracranial balloon to increase ICP to 20 mm Hg, inducing hemorrhagic shock (mean arterial pressure [MAP] of 55 mm Hg), and infusing a single bolus of fluid consisting of either 54 mL/kg of 0.8% saline (SAL), 6 mL/kg of 7.2% hypertonic saline (HS), 20% hydroxyethyl starch (HES) in 0.8% SAL, or a combination fluid (HS/HES) containing 20% HES in 7.2% saline. Twenty-six dogs were ventilated with 0.5% halothane in N2O and O2 (60:40 ratio). As ICP was maintained at 20 mm Hg, rapid hemorrhage reduced MAP to 55 mm Hg (time interval of zero [T0]) which was maintained at that level for 30 minutes (until T30). ⋯ At T35, ICP in the HS group was significantly lower than in the SAL group (P < .05) but subsequently increased. ICP in the HS/HES group exceeded that in all other groups at T95 and T125 (P < .05). After a severe reduction in cerebral perfusion pressure (CPP), HS solutions (both HS and HS/HES) were associated with a delayed rise in ICP and did not improve global forebrain CBF in comparison with conventional saline solutions.
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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
Randomized Controlled Trial Comparative Study Clinical TrialEffects of two calculated plasma sufentanil concentrations on the hemodynamic and bispectral index responses to Mayfield head holder application.
The effects of two calculated plasma sufentanil (SUF) concentrations on the hemodynamic and bispectral index (BIS) responses to Mayfield head holder (MH) application were studied in 20 patients scheduled for intracranial surgery. Premedication consisted of hydroxyzine, alprazolam, and atropine given orally 1 hour before surgery. Anesthesia was provided with propofol (PPF) and SUF using a target-controlled infusion device. ⋯ In conclusion, MH application was associated with a significant, although not clinically relevant, increase in hemodynamic variables whatever the calculated plasma SUF concentration (0.5 or 1.0 ng/mL(-1)). In contrast, the increase in BIS observed at pinning was significantly higher in patients with the lowest calculated plasma SUF concentrations. This suggests that the BIS response to noxious stimulation is modulated by the analgesic regimen.
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J Neurosurg Anesthesiol · Apr 1999
Comparative Study Clinical Trial Controlled Clinical TrialThe effect of anticonvulsant therapy on two doses of rocuronium-induced neuromuscular blockade.
Larger and more frequent doses of steroidal neuromuscular blocking agents are required to paralyze patients taking anticonvulsants (carbamazepine and phenytoin). We compared the effects of rocuronium on onset, duration, and speed of recovery from neuromuscular blockade (NMB) in anticonvulsant-treated (Tx) and untreated (C or control) patients. Thirty-eight neurosurgical patients were enrolled: 11 Tx and 8 C patients received 0.6 mg/kg rocuronium; 9 Tx and 10 C patients received 1.2 mg/kg rocuronium. ⋯ Duration (recovery to 25% of T1) of NMB was significantly shorter in the Tx patients than in the C patients who received rocuronium 0.6 mg/kg (21+/-9 versus 45+/-20 minutes), but similar in Tx and C patients who received 1.2 mg/kg rocuronium (56+/-24 versus 69+/-21 minutes). The speed of recovery (time from 10 to 25% recovery of T1) was significantly slower in Tx patients who received 1.2 mg/kg rocuronium (9+/-5 minutes) than in those who received 0.6 mg/kg (5+/-3 minutes) and not different from controls who received 0.6 (9+/-4 minutes) or 1.2 mg/kg (12+/-7 minutes) rocuronium. We recommend the use of rocuronium 1.2 mg/kg and very frequent monitoring of NMB in anticonvulsant-treated patients to avoid premature and extremely rapid recovery after the standard 0.6 mg/kg rocuronium.