Anesthesia and analgesia
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Anesthesia and analgesia · Jul 1995
Comparative StudyPropofol concentration monitoring in plasma or whole blood by gas chromatography and high-performance liquid chromatography.
We compared the measurement of propofol concentrations in plasma or whole blood by high-performance liquid chromatography (HPLC) to that of gas chromatography (GC). Blood samples were collected from patients who had received bolus injection or continuous infusion of propofol. The results showed that the two methods correlated well both in plasma and whole blood samples. ⋯ This discrepancy in concentrations resulted from the infusion or clearance of propofol, and the lag of redistribution across blood cell membranes. In conclusion, monitoring of propofol concentrations by the methods of GC and HPLC gives equivalent results. For propofol concentration monitoring, plasma samples are preferred, but immediate centrifugation is needed.
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Anesthesia and analgesia · Jul 1995
Comparative StudyThe effects of differing concentrations of bupivacaine on the epidural somatosensory evoked potential after posterior tibial nerve stimulation.
The somatosensory evoked potential (SEP) recorded from the cervical epidural space in response to stimulation of the posterior tibial nerve is often used to monitor spinal cord integrity during scoliosis surgery. Epidural analgesia may be used as part of the anesthetic technique for scoliosis surgery, but the effects of the local analgesic on the evoked potential must be determined to ensure that it does not interfere with the monitoring of spinal cord function. Therefore, we compared the effects of the administration of 10 mL of 0.25% (n = 8), 0.5% (n = 8), or 0.75% (n = 8) bupivacaine injected into the L3-4 epidural space on the somatosensory evoked potential to posterior tibial nerve stimulation in patients anesthetized with a propofol infusion, nitrous oxide and oxygen, immediately before scoliosis surgery. ⋯ There were no significant differences between 0.25% bupivacaine and the control group, but both 0.5% and 0.75% bupivacaine were associated with clinically and statistically significant decreases in overall amplitude (P < 0.002, 0.5% bupivacaine; P < 0.001, 0.75% bupivacaine). Latency increased similarly in all groups. We conclude that bupivacaine in concentrations greater than 0.25% is not suitable for scoliosis surgery, if spinal somatosensory evoked potentials (SSEP) are to be measured.
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Anesthesia and analgesia · Jul 1995
The reliability of quantitative electroencephalography as an indicator of cerebral ischemia.
The electroencephalogram (EEG) has been used to detect episodes of cerebral ischemia during various surgical procedures. Recently, computerized systems for recording and interpreting the quantitative EEG (QEEG) have been used by anesthesiologists because of their ease of application, clarity of display, and reported ability to identify ischemic EEG changes. However, the extent to which automated techniques of QEEG interpretation reliably differentiate cerebral ischemia from the confounding effects of anesthetics and other sources of "artifact" is not completely established. ⋯ The CIMON technique identified episodes which met previously defined criteria for QEEG cerebral dysfunction and ischemic pattern in both groups, despite the presumed absence of cerebral ischemia in the control patients. Since there was no evidence of cerebral ischemia in the raw EEGs of either the ICD patients or the controls, these QEEG changes were not confirmed by conventional techniques of EEG interpretation. Our results suggest that caution is warranted when using automated systems for intraoperative interpretation of EEG.
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Anesthesia and analgesia · Jul 1995
Ketamine does not increase cerebral blood flow velocity or intracranial pressure during isoflurane/nitrous oxide anesthesia in patients undergoing craniotomy.
Ketamine's effect on cerebral hemodynamics is controversial. We hypothesized that ketamine would not increase intracranial pressure (ICP) and cerebral blood flow (CBF) velocity in anesthetized, ventilated patients. Twenty patients requiring craniotomy for brain tumor or cerebral aneurysm were studied. ⋯ ICP decreased from 16 +/- 1 mm Hg to 14 +/- 1 mm Hg (mean +/- SE; P < 0.001) and VMCA decreased from 44 +/- 4 cm/s to 39 +/- 4 cm/s (P < 0.001). Total EEG power decreased (P < 0.02). These results suggest that ketamine can be used in anesthetized, mechanically ventilated patients with mildly increased ICP without adversely altering cerebral hemodynamics.
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Anesthesia and analgesia · Jul 1995
Comparative StudyHeparin neutralization by recombinant platelet factor 4 and protamine.
Protamine is the only available drug to reverse heparin-induced anticoagulation. Platelet factor 4 (PF4) is a basic polypeptide stored in platelets that reverses heparin. To investigate its potential as a reversal drug, we studied recombinant PF4 on anticoagulated blood obtained during cardiac surgery. ⋯ PF4 reversal ratios of 3:1 and 3.5:1 and protamine reversal ratios of 1:1, 1.5:1, 2:1 were not statistically different from heparinase-ACT values. There were no significant differences in viscoelastic measurements of clot formation between protamine and PF4. Recombinant PF4 at a 3.0:1 ratio reverses heparin-induced anticoagulation after cardiopulmonary bypass, and represents a potential alternative, especially for the protamine allergic patient.