Anesthesia and analgesia
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Anesthesia and analgesia · Sep 2004
Threshold current for an insulated epidural needle in pediatric patients.
We designed this study to determine the threshold current for nerve stimulation of an insulated needle in the epidural space. The intended dermatome was identified using the bony landmarks of the spine. An 18-gauge insulated Tuohy needle was inserted perpendicularly to the skin and advanced until "loss of resistance" was felt. ⋯ Postoperative radiograph confirmed all catheter placements within 2 myotomes of the muscle twitches. Electrical stimulation may be a useful adjuvant tool to loss of resistance for confirming proper thoracic epidural needle placement. The threshold current criteria for an insulated needle (6-17 mA) would be higher than the original Tsui test criteria described for an epidural catheter (1-10 mA) in the epidural space.
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Anesthesia and analgesia · Sep 2004
Flow rates and warming efficacy with Hotline and Ranger blood/fluid warmers.
The heating capabilities of a water bath blood/fluid warmer, Hotline, have proven superior to those of other devices. The dry heat warmer Ranger has not previously been compared with the Hotline. We evaluated these devices in terms of flow rates and efficacy of warming. ⋯ Hotline was able to deliver warmer RBCs and saline at slower flow rates (1-4 L/h), but because changes in MBT were almost identical, there was no clinically important advantage, and almost no heat was transferred at these slower flow rates. At more rapid flow rates (>4 L/h), the Ranger warmed RBCs and saline better and produced smaller decreases in MBT than the Hotline. The use of the Hotline for rapid infusions, especially of cold RBCs, is not recommended because of low outflow temperatures and decreases in MBT that were three times larger than those seen with the Ranger.
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Anesthesia and analgesia · Sep 2004
Derivation of preliminary three-dimensional pharmacophores for nonhalogenated volatile anesthetics.
We investigated the molecular basis for the immobilizing activity of nonhalogenated volatile anesthetics by using comparative molecular field analysis (CoMFA). In vivo potency data (expressed as minimum alveolar anesthetic concentrations) for 38 structurally diverse drugs were obtained from the literature. The anesthetics were randomly divided into a training-set (n = 28) used to formulate the activity models and a test-set (n = 10) used to independently assess the models' predictive power. ⋯ The final CoMFA model explained 95.5% of the variance in the observed activities of the training-set anesthetics. The model had good predictive capability for both the training-set drugs (cross-validated r(2) = 0.824) and the randomly excluded test-set anesthetics (r(2) = 0.921). Pharmacophoric maps were derived by identifying the spatial distribution of key areas in which steric and electrostatic interactions are important in determining the immobilizing activity of the anesthetics considered.
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Anesthesia and analgesia · Sep 2004
The effects of cervical and lumbar epidural anesthesia on heart rate variability and spontaneous sequence baroreflex sensitivity.
A high level of neuroaxial block may produce profound bradycardia and hypotension, possibly as a result of an imbalance between sympathetic and parasympathetic control of heart rate. We designed this study to test the hypothesis that cervical epidural anesthesia would increase the high-frequency (HF) component of heart rate variability (HRV) as a result of cardiac sympathectomy, whereas lumbar epidural anesthesia would cause sympathetic predominance. HRV and spontaneous baroreflex (SBR) sensitivity were assessed before and after cervical and lumbar epidural anesthesia by using plain 1.5% lidocaine (median upper/lower sensory block: C3/T8 for cervical and T11/L5 for lumbar) in healthy patients (n = 10 each). ⋯ HF power correlated well with SBR sensitivities under most of our study conditions. Respiratory rates and Paco(2) were unchanged by either epidural technique. Our results indicate that cervical, but not lumbar, epidural anesthesia depresses phasic and tonic dynamic modulation of the cardiac cycle by the vagal nerve in conscious humans.