Anesthesia and analgesia
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Anesthesia and analgesia · May 2004
Randomized Controlled Trial Comparative Study Clinical TrialA comparison of the clinical usefulness of three different electroencephalogram monitors: Bispectral Index, processed electroencephalogram, and Alaris auditory evoked potentials.
We compared the usefulness of the Bispectral Index (BIS), Processed electroencephalogram (pEEG), and Alaris auditory evoked potentials (A-AEP). Ninety females scheduled for mastectomy were divided into three groups. Anesthesia was induced with propofol and fentanyl to insert a laryngeal mask airway (LMA) and was maintained by adding nitrous oxide. EEG was monitored by either BIS, spectral edge frequency by pEEG, or A-AEP index by A-AEP. We recorded the number of patients with impedance low enough to extract good EEG signals at the first electrodes application (success rate), the number with an index outside of the range considered appropriate for general anesthesia (inappropriateness rate), changes of the index by LMA insertion or surgical incision (responsiveness), and time to return to good EEG signals after signal disturbance by electric cautery (recovery time). The success rate was larger in BIS > or = A-AEP > pEEG. The inappropriateness rate was smaller in A-AEP < or = BIS , or = pEEG. The A-AEP group showed the largest responsiveness. The recovery time was shorter in pEEG < A-AEP < BIS. In summary, the BIS had the largest success rate, the A-AEP had the least inappropriateness rate and the largest responsiveness, and the pEEG had the fastest recovery time. ⋯ We compared the usefulness of three electroencephalogram monitors. The Bispectral Index was the easiest for obtaining low impedance, the auditory evoked potential index had the least inappropriateness rate for general anesthesia and had the largest responsiveness, and the spectral edge frequency was the fastest in stabilizing measurement after electric cautery.
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Anesthesia and analgesia · May 2004
Clinical TrialDantrolene reduces the threshold and gain for shivering.
Dantrolene is used for treatment of life-threatening hyperthermia, yet its thermoregulatory effects are unknown. We tested the hypothesis that dantrolene reduces the threshold (triggering core temperature) and gain (incremental increase) of shivering. Healthy volunteers were evaluated on 2 random days: control and dantrolene (approximately 2.5 mg/kg plus a continuous infusion). In Study 1, 9 men were warmed until sweating was provoked and then cooled until arteriovenous shunt constriction and shivering occurred. Sweating was quantified on the chest using a ventilated capsule. Absolute right middle fingertip blood flow was quantified using venous-occlusion volume plethysmography. A sustained increase in oxygen consumption identified the shivering threshold. In Study 2, 9 men were given cold lactated Ringer's solution i.v. to reduce core temperature approximately 2 degrees C/h. Cooling was stopped when shivering intensity no longer increased with further core cooling. The gain of shivering was the slope of oxygen consumption versus core temperature regression. In Study 1, sweating and vasoconstriction thresholds were similar on both days. In contrast, shivering threshold decreased 0.3 +/- 0.3 degrees C, P = 0.004, on the dantrolene day. In Study 2, dantrolene decreased the shivering threshold from 36.7 +/- 0.2 to 36.3 +/- 0.3 degrees C, P = 0.01 and systemic gain from 353 +/- 144 to 211 +/- 93 mL.min(-1).degrees C(-1), P = 0.02. Thus, dantrolene substantially decreased the gain of shivering, but produced little central thermoregulatory inhibition. ⋯ Dantrolene substantially decreases the gain of shivering but produces relatively little central thermoregulatory inhibition. It thus seems unlikely to prove more effective than conventional muscle relaxants for treatment of life-threatening hyperthermia.
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We accomplished endotracheal intubation by using fluoroscopic direction in a patient presenting a difficult airway both on the basis of a preanesthetic physical examination and on the basis of a potential for cervical cord injury associated with complicated laryngoscopy. Under topical anesthesia, a multipurpose angiographic (MPA) catheter over a Bentson wire was advanced into the trachea under intermittent C-arm fluoroscopic guidance while the occiput, cervical spine, and mandible remained in a neutral position. The endotracheal tube was then easily advanced over the MPA catheter into the trachea, where the location was documented by fluoroscopic view. Because of judicious use of topical anesthesia and the small diameter and flexibility of the MPA catheter, the unsedated patient remained comfortable throughout the procedure. The stored data were later transferred to a compact disk, and a copy was provided to the patient as an adjunct to Medic-Alert. Unlike fiberoscopy, with which the view can be totally obscured by secretions, blood, and abnormal anatomy, the direction and location of the MPA catheter within the airway were easily identifiable throughout the procedure. The small diameter of the MPA (1.5-mm outer diameter) should allow placement of endotracheal tubes as small as 3.0-mm inner diameter--an option not available even with pediatric instruments. Although time was not a consideration, the procedure was accomplished in <12 min with 22 s of fluoroscopy. We believe that with experience, atraumatic intubation of a difficult airway could be accomplished routinely in less than 2 min with radiological-assisted intubation. ⋯ Radiologic-assisted intubation facilitated endotracheal intubation without sedation, instrumentation, or significant movement of the occiput, cervical spine, or mandible. The procedure was accomplished in <12 min and with only 22 s of fluoroscopy. This approach provides the ultimate adjunct to the preoperative airway physical evaluation while providing for immediate (or delayed) atraumatic endotracheal intubation. The diagnostic information and procedure can be recorded on a compact disk.
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Anesthesia and analgesia · May 2004
Clinical TrialIs bilateral monitoring of cerebral oxygen saturation necessary during neonatal aortic arch reconstruction?
In this study, we measured cerebral oxygenation in both cerebral hemispheres by using near-infrared spectroscopy before, during, and after regional low-flow cerebral perfusion (RLFP) to determine whether bilateral monitoring was necessary. Neonates undergoing aortic arch reconstruction with RLFP were studied. The bilateral regional cerebral oxygenation index was measured and recorded at 1-min intervals during the following periods: 1) before bypass, 2) during bypass before RLFP, 3) during RLFP, 4) on bypass after RLFP, and 5) post-bypass. Before bypass and on bypass before RLFP, the correlation (r = 0.979 and 0.852) and agreement (mean bias, right versus left, 0 and +2) between hemispheres were excellent. During RLFP, however, correlation (r = 0.35) and agreement (mean bias of the right versus left side, +6.3) worsened and only partially returned to baseline values after RLFP. Nine of 19 patients had sustained differences in cerebral oxygen saturation of >10%, always with the left side values less than the right. Bilateral monitoring detects desaturation in the left cerebral hemisphere during RLFP. The long-term consequences of lower saturations on the left side of the brain are unclear. ⋯ Left-sided cerebral hemisphere oxygen saturation, measured with near-infrared spectroscopy, was less than right-sided cerebral oxygen saturation during regional low-flow cerebral perfusion used for neonatal aortic arch reconstruction.
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Anesthesia and analgesia · May 2004
The failure of retrograde autologous priming of the cardiopulmonary bypass circuit to reduce blood use after cardiac surgical procedures.
Hemodilution during cardiopulmonary bypass (CPB) is a primary risk factor for blood transfusion in cardiac surgical patients. Priming of the CPB circuit with the patients' own blood (retrograde autologous priming, RAP) is a technique used to limit hemodilution and reduce transfusion requirements. We designed this study to examine the impact of RAP on perioperative blood product use. Using a retrospective cohort study design, the medical records of all patients undergoing CPB (excluding circulatory arrest cases) by a single surgeon were examined. Data were collected over a 24-mo period when RAP was routinely used as a blood conservation strategy (RAP group, n = 257). This group was compared with a cohort of patients during the 24 mo immediately preceding the introduction of RAP into clinical practice (no RAP group, n = 288). A small, statistically insignificant reduction in the percentage of patients receiving packed red blood cells was observed in the RAP group (44% versus 51% no RAP, P = 0.083). No differences were found between the groups in the number of units of packed red blood cells, platelets, or fresh frozen plasma transfused throughout the perioperative period. These results suggest that overall, RAP does not offer a clinically important benefit as a blood conservation technique. ⋯ Priming of the cardiopulmonary bypass circuit with the patients' own blood (retrograde autologous priming) resulted in insignificant reductions in blood use in a large, unselected group of patients undergoing cardiac surgical procedures.