Anesthesia and analgesia
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Anesthesia and analgesia · May 1996
Comparative StudyThe effects of propofol on the 40-Hz auditory steady-state response and on the electroencephalogram in humans.
The auditory steady-state response (ASSR) is a nearly sinusoidal electrical response of the brain to auditory stimuli delivered at fast rates. The amplitude of the response is largest for stimulus rates near 40/s, hence the label 40-Hz ASSR. We have studied the effects of propofol (1.5 mg/kg) on the 40-Hz ASSR in 14 patients. ⋯ Recovery of the 40-Hz ASSR occurs whether or not consciousness is regained, but the 40-Hz ASSR tends to be larger after the return of consciousness. An association between higher amplitude 40-Hz ASSR and the return of consciousness could not be conclusively established, perhaps because of low signal-to-noise ratio in three patients. The 40-Hz ASSR did not offer any clear advantage over the SEF in predicting the return of consciousness.
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Anesthesia and analgesia · May 1996
Tracheal extubation of children in the operating room after atrial septal defect repair as part of a clinical practice guideline.
Early tracheal extubation in the operating room after atrial septal defect (ASD) surgery was recommended as part of a clinical practice guideline (CPG) established in the Cardiovascular Program at the Children's Hospital, Boston, MA. This retrospective review was undertaken to determine whether this practice was efficient without compromising patient care. The charts and hospital charges for 102 patients undergoing secundum ASD or sinus venosus defect surgery between March 1992 and July 1994 were reviewed; 36 patients (Group I) had surgery prior to introduction of the CPG, and 66 patients were managed according to the CPG. ⋯ There was no difference among groups in the hospital charges for OR, anesthesia and CICU time. However, when the combined hospital charges for services provided both in the OR and CICU were included, patients in Group II were charged significantly less, and this primarily reflects the absence of postoperative mechanical ventilation charges. Tracheal extubation in the OR after ASD surgery in children can result in lower patient charges without significantly compromising patient care.
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Anesthesia and analgesia · May 1996
Comparative StudyHemodynamic effects of intravenous isoproterenol versus epinephrine in the chronic maternal-fetal sheep preparation.
Isoproterenol 5 micrograms may be an effective marker of accidental intravascular injection in women in labor; however, before isoproterenol can be incorporated in routinely used epidural test doses, the safety and usefulness should be determined in an animal model. This study was designed to examine the hemodynamic effects of isoproterenol in comparison with epinephrine in the pregnant ewe. Five doses of isoproterenol were tested and compared with two doses of epinephrine in a randomized cross-over fashion. ⋯ A significant increase in the cardiac output was seen after isoproterenol. Neither isoproterenol nor epinephrine affected fetal heart rate (FHR), fetal mean arterial pressure (FMAP), amniotic fluid pressure (Amn-pr), blood gases, or acid base status in the mother and the fetus. Provided that neurotoxic effects are absent, isoproterenol might be a better alternative than epinephrine as a test dose for possible intravenous placement of an epidural catheter in pregnant women.
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Anesthesia and analgesia · May 1996
Comparative StudyThe effect of thoracic epidural anesthesia on hypoxic pulmonary vasoconstriction in dogs: an analysis of the pressure-flow curve.
The aim of the present study was to examine whether hypoxic pulmonary vasoconstriction (HPV) is preserved during one-lung ventilation combined with thoracic epidural anesthesia (TEA) in dogs. Using a separately ventilated left lower lobe (LLL) in situ, the pressure-flow (P-Q) curve was obtained. The HPV response was assessed by the shift of the P-Q curve, changes in blood flow diversion rate (FDR) and decrease in PaO2 during hypoxic gas ventilation of LLL. ⋯ TEA reduced heart rate, cardiac output, mean arterial pressure, mean pulmonary arterial pressure, and mixed venous oxygen tension. Our results suggest that TEA did not affect the primary pulmonary vascular tone at baseline or during lobar hypoxia, but enhanced the diversion of blood flow and arterial blood oxygenation during lobar hypoxia. This enhanced HPV response probably reflects hemodynamic changes, such as decreased cardiac tension, due to sympathetic nerve activity blockade by TEA.
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Anesthesia and analgesia · May 1996
Auto-positive end-expiratory pressure during one-lung ventilation using a double-lumen endobronchial tube.
The present study was undertaken to investigate the possible relationships between the magnitude of autopositive end-expiratory pressure (auto-PEEP) and measured PaO2 during one-lung ventilation (OLV). Forty-one adults received OLV anesthesia using a tidal volume of 8 mL/kg and a respiratory rate of 12 breaths/min. Auto-PEEP was quantified using an end-expiratory port occlusion method. ⋯ Auto-PEEP during OLV correlated inversely with preoperative forced expiratory volume in 1 s/forced vital capacity (y = 12.5 - 0.13x, r = -.05, P < 0.005). During OLV, there was no significant correlation between auto-PEEP and measured PaO2. These findings confirm that many patients do not exhale completely to functional residual capacity during OLV.