Anesthesia and analgesia
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Anesthesia and analgesia · Dec 2004
Randomized Controlled Trial Clinical TrialParamedian lumbar epidural catheter insertion with patients in the sitting position is equally successful in the flexed and unflexed spine.
Positioning for placement of an epidural catheter can be quite painful for patients with lower limb injuries. We randomly allocated 50 patients scheduled for surgery after lower limb injuries for placement of a lumbar epidural catheter in the sitting position with the back in the neutral unflexed position by either the midline or paramedian approach. If the approach failed after two attempts, patients were placed in a flexed-spine position, and the procedure was attempted again. ⋯ The incidences of resistance to catheter insertion (eight versus one), paresthesia (seven versus zero), and appearance of blood in the catheter (six versus zero) were significantly more frequent in the midline compared with the paramedian approach. The midline group also experienced more discomfort than the paramedian group. We conclude that, with the patient sitting with an unflexed spine, it is usually possible to insert an epidural catheter with the paramedian approach.
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Anesthesia and analgesia · Dec 2004
Clinical TrialThe intravenous ketamine test: a predictive response tool for oral dextromethorphan treatment in neuropathic pain.
IV infusion tests performed to predict subsequent response to oral analgesics are an increasingly popular method used to enhance medical care and conserve resources. Because no infusion test is completely accurate, the potential benefits of these tests must be weighed against the frustration and waste in resources encountered with false-positive results, and the failure to use a potentially beneficial treatment with false-negative results. In recent years, drugs that act antagonistically at N-methyl-d-aspartate receptors have been shown to be valuable adjuncts in the treatment of pain. ⋯ However, when >/=67% relief with ketamine was used as an outcome measure (as determined by a receiver operating characteristic curve), the positive predictive value was 90%, the negative predictive value 80%, and the observed agreement increased to 84%. Based on these results, we conclude that an IV ketamine test may be useful in predicting response to oral DX. More research is needed to determine the ideal candidates for such a test, and the optimal dose and cutoff value for the response to ketamine.
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Anesthesia and analgesia · Dec 2004
Apoptosis is not enhanced in primary mixed neuronal/glial cultures protected by isoflurane against N-methyl-D-aspartate excitotoxicity.
Volatile anesthetics reduce acute excitotoxic cell death in primary neuronal/glial cultures. We hypothesized that cells protected by isoflurane against N-methyl-d-aspartate (NMDA)-induced necrosis would instead become apoptotic. Primary mixed neuronal/glial cultures prepared from fetal rat brain were exposed to dissolved isoflurane (0 mM, 0.4 mM [1.8 minimum alveolar anesthetic concentration], or 1.6 mM [7 minimum alveolar anesthetic concentration]) and NMDA (0 or 100 microM) at 37 degrees C for 30 min. ⋯ At 48 h, no evidence was found to indicate that cells protected by isoflurane had become apoptotic or apoptotic-like. However, cells protected by dizocilpine against necrosis showed evidence of caspase-3-mediated apoptosis. These in vitro data do not support the hypothesis that isoflurane protection against acute excitotoxic necrosis results in apoptosis.
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Anesthesia and analgesia · Dec 2004
Comparative StudyThe mechanical properties of continuous spinal small-bore catheters.
Continuous spinal anesthesia (CSA) has a nearly 100-yr history. In situations of difficult removal of a CSA small-bore catheter, mechanical properties of the different catheters might be important, because breakage could occur. We compared 5 different CSA small-bore catheters, 22- to 28-gauge from 3 manufacturers, for tensile strength, tensile stress, distension, and yield strength. ⋯ The material characteristics of different CSA small-bore catheters for maximal tensile strength were: 22-gauge = 29.56 +/- 1.56 (mean +/- sd) Newton (N), 24-gauge = 16.77 +/- 1.61 N, 25-gauge = 9.20 +/- 0.48 N, 27-gauge = 4.61 +/- 0.25 N, 28-gauge = 5.07 +/- 0.59 N at room temperature. A strong correlation between maximal tensile strength and the outer diameter (r = 0.957, P < 0.001) and maximal tensile strength and the wall thickness (r = 0.9, P < 0.001) was observed. Although extrapolation from experimental studies to clinical routine should be made with care, our data suggest that catheters with higher-strength characteristics may reduce the risk of catheter breakage in patients, although clinical correlations are lacking.
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Anesthesia and analgesia · Dec 2004
Measuring depth of sedation with auditory evoked potentials during controlled infusion of propofol and remifentanil in healthy volunteers.
Avoiding excessively deep levels of sedation is a major problem in intensive care patients. We studied whether clinically relevant levels of sedation can be objectively assessed using long latency auditory evoked potentials. We measured the auditory evoked potentials at 100 ms after the stimulus (N100) in 10 healthy volunteers during stepwise increasing, clinically relevant levels of sedation (Ramsay score [RS] 2-4). ⋯ During both propofol-induced and propofol/remifentanil-induced sedation, the N100 amplitude decreased similarly without an effect on the latencies as the level of sedation increased from Ramsay score 2 to Ramsay score 4 (P < 0.01). At the same clinical level of sedation, propofol plasma concentrations were larger when sedation was achieved by propofol alone (propofol versus propofol/remifentanil, RS 3: 2.12 mug/mL +/- 0.51 versus 1.32 +/- 0.43, P < 0.01; RS 4: 3.37 +/- 0.47 versus 1.86 +/- 0.34, P < 0.01). Our results suggest that long latency auditory evoked potentials provide an objective electrophysiological analog to the clinical assessment of sedation independent of the sedation regime used.