Anesthesia and analgesia
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Anesthesia and analgesia · Apr 2003
Randomized Controlled Trial Clinical TrialClinical results with the acoustic puncture assist device, a new acoustic device to identify the epidural space.
Sixty patients scheduled for lumbar epidural anesthesia were included in a study in which we evaluated the efficacy of localizing the epidural space by means of an acoustic signal. A prototype of an acoustic puncture assist device, connected to the epidural needle by an extension tube, generated the pressure needed to perform the epidural puncture and translated this pressure into corresponding acoustic and visible signals. The device frees the anesthesiologist to handle the epidural needle with both hands and to detect the epidural space by means of these signals. In all 60 patients (100%), the epidural space was successfully located by using the acoustic signal. In all cases, this was confirmed by the pressure measurement, which proved to be a reliable indicator for correct identification of the epidural space. We conclude that it is possible to locate the epidural space by means of the acoustic puncture assist device. The method proved to be reliable, safe, and simple in this study. The benefits of this new epidural puncture technique include better needle control, teaching, control of correct catheter placement, and documentation. The last can be an important adjunct to anesthesia practice. ⋯ The authors demonstrate that it is possible to identify the epidural space by an acoustic and visible signal. An experimental setup constructed for this purpose makes the epidural puncture procedure audible and visible.
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Anesthesia and analgesia · Apr 2003
Comparative StudyThe memory effects of general anesthesia persist for weeks in young and aged rats.
Studies demonstrate lasting cognitive impairment in elderly persons after anesthesia and surgery. We tested the hypothesis that general anesthesia contributes to this cognitive impairment. Six- and 18-mo-old Fischer 344 rats were trained in a 12-arm radial arm maze and were then randomized to anesthesia for 2 h with 1.2% isoflurane/70% nitrous oxide/30% oxygen or a control treatment consisting of 30% oxygen. Rats recovered for 24 h and then were tested daily on the radial arm maze for 8 wk. Performance of young control rats was stable throughout the experiment. In contrast, aged control rats improved their performance as measured by time to complete the maze but not by error rate. After anesthesia, time to complete the maze did not change in young rats, but error rate decreased (P < 0.05 at 1 and 3 wk), indicating improved performance. In contrast, previously anesthetized aged rats failed to improve with repeated testing and took longer to complete the maze than aged control rats (P < 0.05 at 1 and 3 wk). These data demonstrate that general anesthesia with isoflurane and nitrous oxide improves the memory performance on an established spatial memory task in young rats, but in aged rats it attenuates the improvement in performance that otherwise occurs with repeated testing. Therefore, isoflurane and nitrous oxide anesthesia produces a sustained learning impairment in aged rats. ⋯ This study demonstrates that general anesthesia with isoflurane and nitrous oxide improves spatial memory in young rats but impairs it in aged rats for at least 3 wk, indicating that it can influence memory for much longer than previously recognized and may adversely affect memory processes in the aged.
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Anesthesia and analgesia · Apr 2003
Clinical TrialThe effect of epidural neostigmine combined with ropivacaine and sufentanil on neuraxial analgesia during labor.
Spinal neostigmine produces analgesia without respiratory depression or hypotension but provokes major gastrointestinal side effects. Epidural injection of this drug, however, appears to induce analgesia devoid of such side effects. In this study, we evaluated the effect of a bolus of epidural neostigmine on the duration and magnitude of analgesia in early labor and assessed its eventual sparing effect on subsequent local anesthetic requirements. Epidural neostigmine methylsulfate (maximal dose 4 microg/kg) was added to 10 mL of ropivacaine 0.1%, with and without sufentanil 10 microg, to initiate analgesia. Twenty minutes after injection, pain score, sensory level, and motor block were assessed. Time until request for supplemental epidural medication was also recorded. Patient-controlled epidural analgesia with ropivacaine 0.1% was used for epidural supplementation. Maternal and fetal side effects were closely recorded. Neostigmine (4 microg/kg), when added to ropivacaine 10 mg, provided equivalent analgesia to ropivacaine 20 mg but was less effective than sufentanil 10 microg for the initiation of labor epidural analgesia. Further, neostigmine did not modify the subsequent patient-controlled epidural analgesia local anesthetic requirements during labor. No hemodynamic instability, additional motor block, or bothersome side effects were recorded. ⋯ The combination of epidural neostigmine (4 microg/kg) with the local anesthetic ropivacaine, with or without sufentanil, does not significantly enhance neuraxial analgesia during labor. Such a dose, however, has no bothersome side effects.
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Anesthesia and analgesia · Apr 2003
Isoflurane action in spinal cord indirectly depresses cortical activity associated with electrical stimulation of the reticular formation.
Anesthetics act in the spinal cord to ablate both movement and the ascending transmission of nociceptive information. We investigated whether a spinal cord action of isoflurane affected cortical activity as determined by the electroencephalogram desynchronization that occurs after electrical stimulation of the midbrain reticular formation (MRF). Six goats were anesthetized with isoflurane, and neck dissections were performed to permit differential isoflurane delivery to the head and torso. The electroencephalogram was recorded before, during, and after focal electrical stimulation (0.05, 0.1, 0.2, 0.3, and 0.4 mA) in the MRF; in each animal, the brain isoflurane was maintained constant ( approximately 1%). When the torso isoflurane was 0.3% +/- 0.1%, the spectral edge frequency after MRF electrical stimulation (15.3 +/- 1.7 Hz, averaged across all stimulus currents) was more than the spectral edge frequency when the torso isoflurane was 1.2% +/- 0.2% (12.9 +/- 1.0 Hz, averaged across all stimulus currents; P < 0.05). Bispectral index values were similarly affected: 60 +/- 6 when torso isoflurane was low versus 53 +/- 7 at high torso isoflurane (P < 0.05). These results suggest that a spinal depressant action of isoflurane on ascending somatosensory transmission can modulate reticulo-thalamocortical arousal mechanisms, hence possibly reducing anesthetic requirements for unconsciousness and amnesia. ⋯ Isoflurane action in the spinal cord indirectly reduces the cortical activity associated with electrical stimulation of the reticular formation, an effect that might contribute to anesthetic-induced amnesia and unconsciousness.
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Anesthesia and analgesia · Apr 2003
The influence of induced hypothermia for hemostatic function on temperature-adjusted measurements in rabbits.
In hypothermic patients, a tendency to bleed may be observed even when hemostatic tests seem to be normal. Coagulation and platelet function tests are usually performed at 37 degrees C. We investigated the influence of induced hypothermia on temperature-adjusted hemostasis function testing using Sonoclot Analyzer (Sonoclot) and Thromboelastography (TEG). Anesthesia was induced and maintained with IV ketamine and fentanyl on 15 male New-Zealand White rabbits. A water blanket was used to induce hypothermia to 30 degrees C and to rewarm to 37 degrees C. Blood samples were obtained at four points: before hypothermia, at 34 degrees C, at 30 degrees C, and after rewarming. Standard coagulation tests were performed at 37 degrees C (C method), and simultaneously, real temperature hemostasis function tests (R method) were run. In Sonoclot(R), activated clotting time and time to peak increased and clot rate decreased significantly at 30 degrees C in the R method compared with those in the C method. In TEG(R), reaction time and clot formation time were prolonged and clot formation rate was diminished at 30 degrees C in the R method compared with those in the C method. Induced hypothermia delayed the coagulation cascade and reduced platelet function. During hypothermia, hemostatic measurements should be performed at real temperature to avoid overestimating patient hemostatic function based on results measured at the standard 37 degrees C. ⋯ We investigated the influence of induced hypothermia on temperature-adjusted hemostasis function tests in rabbits using Sonoclot Analyzer and Thromboelastography. Induced hypothermia delayed the coagulation cascade and reduced platelet function. The conventional coagulation tests performed at 37 degrees C failed to detect these hypothermia-induced degradations in hemostasis performance.