Journal of neurosurgical anesthesiology
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We present two patients who each had a retained subarachnoid drain catheter broken during postoperative removal. Management of these fragments should be individualized. The fragment remained in one patient, but was removed in the other because of further procedures required for hydrocephalus. We discuss possible causes of this complication as well as suggestions for prevention.
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J Neurosurg Anesthesiol · Apr 1997
Intact cerebral blood flow reactivity during remifentanil/nitrous oxide anesthesia.
Remifentanil hydrochloride is a new opioid rapidly metabolized by blood and tissue esterases. The swift degradation accounts for the elimination half-life (t1/2 beta) of < 10 min. An anesthetic agent allowing more rapid postoperative assessment of the neurosurgical patient would be beneficial. ⋯ Electroencephalographic monitoring showed a spectral edge frequency of 26 +/- 1 Hz before induction, 25 +/- 1 Hz during maintenance of the remifentanil/N2O anesthetic (0.32 +/- 0.15 microgram/kg/ min), 24 +/- 1 Hz during hypocapnic CBF determination, and 24 +/- 2 Hz during normocapnic CBF determination. At the completion of the procedure, the patients responded to commands within 3.6 +/- 2.5 min and were extubated 7.2 +/- 4.5 min after the remifentanil/N2O was discontinued. In conclusion, absolute CBF values during remifentanil/N2O are similar to previously reported CBF values during fentanyl/N2O and isoflurane/N2O anesthesia, and cerebrovascular reactivity to CO2 remains intact.
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J Neurosurg Anesthesiol · Apr 1997
Comparative StudyPredictive accuracy of continuous propofol infusions in neurosurgical patients: comparison of pharmacokinetic models.
The performance of 10 pharmacokinetic models in predicting blood propofol concentrations was evaluated in patients during neurosurgical anesthesia. Eight patients-ASA category I or II, aged 49 +/- 18-years, weighing 71 +/- 20 kg, and scheduled for routine neurosurgery-were anesthetized with propofol and sufentanil using Ohmeda pumps controlled with a personal computer. Sufentanil was administered as a bolus of 0.3 microgram.kg-1, 5 min before induction of anesthesia, and infused at a constant rate of 0.5 microgram.kg-1.h-1 throughout the study. ⋯ The models of Gepts et al. (Anesth Analg 1987; 66:1256-1263, Anaesthesia 1988; 43(suppl):8-13), Tackley et al. (Br J Anaesth 1989;62:46-53), and Cockshott (Postgrad Med J 1985;61:55), derived from healthy patients receiving continuous propofol infusions, provided the best agreement between expected and measured propofol concentrations; they showed bias and inaccuracy lower than 17%. In conclusion, the accurate prediction of blood propofol concentrations from different continuous infusion rates in ASA I or II patients requires the selection of appropriate pharmacokinetic models derived from similar categories of patients and using a similar technique of propofol administration. However, in clinical practice, the selection of a specific set among the appropriate models is balanced by the interindividual variability in blood propofol concentrations adjusted to clinical effects.
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J Neurosurg Anesthesiol · Apr 1997
Comparative StudyFurosemide decreases cerebrospinal fluid formation during desflurane anesthesia in rabbits.
Previous studies suggest that desflurane may increase cerebrospinal fluid (CSF) formation rate (Vf) and volume, particularly during conditions of hypocapnia combined with elevated CSF pressure. The present study was designed to determine whether treatments routinely used in patients during anesthesia for neurological surgery would decrease Vf during desflurane anesthesia in rabbits. Three groups of six rabbits each were examined at four experimental conditions. ⋯ During the combination of desflurane, hypocapnia, and elevated CSF pressure, furosemide decreased Vf to 3.2 +/- 1.7 microliters.min-1, mannitol increased plasma osmolality and decreased plasma sodium concentration, and fentanyl decreased heart rate and increased plasma potassium concentration. Values for Ra and brain water content did not differ between groups. Of the four treatments examined, only furosemide decreased Vf during the combination of desflurane, hypocapnia, and elevated CSF pressure.
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J Neurosurg Anesthesiol · Apr 1997
Effects of normo- and hypocapnic nitrous-oxide-inhalation on cerebral blood flow velocity in patients with brain tumors.
Nitrous oxide (N2O) use during anesthesia for intracranial procedures has been a subject of controversy in the past. To date, the isolated influence of N2O on mean cerebral blood flow velocity in the middle cerebral artery (VMCA) has not been investigated during hypocapnia in patients with brain tumors. We compared VMCA during normocapnic (ETCO2: 40 mm Hg) and hypnocapnic (ETCO2: 25 mm Hg) inhalation of air and 50% nitrous oxide in oxygen N2O/O2 in eight patients with unilateral brain tumors on both the tumor side and the healthy side. ⋯ Mean VMCA increased during normocapnic inhalation of N2O/O2 (tumor side: 86 +/- 16 cm sec-1; healthy side: 74 +/- 17 cm sec-1) when compared with air (tumor side: 72 +/- 18 cm sec-1; healthy side: 62 +/- 14 cm sec-1, p < 0.01), whereas during hyperventilation VMCA decreased on both sides (p < 0.001). Mean VMCA values were quite similar during hypocapnic inhalation of 50% N2O/O2 (tumor side: 50 +/- 12 cm sec-1; healthy side: 45 +/- 13 cm sec-1) and air (tumor side: 51 +/- 14 cm sec-1; healthy side: 45 +/- 12 cm sec-1). The data of our study suggest that in patients with cerebral tumors the N2O-induced increase in mean VMCA can be completely reversed by hyperventilation.