Anesthesia and analgesia
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Anesthesia and analgesia · Nov 2003
Randomized Controlled Trial Comparative Study Clinical TrialOxygenation using tidal volume breathing after maximal exhalation.
We compared, in volunteers, the oxygenation achieved by tidal volume breathing (TVB) over a 3-min period after maximal exhalation with that achieved by TVB alone. Twenty-three healthy volunteers underwent the two breathing techniques in a randomized order. A circle absorber system with an oxygen flow of 10 L/min was used. The end-expiratory oxygen concentration (EEO(2)) was monitored at 15-s intervals up to 3 min. TVB after maximal exhalation produced EEO(2) values of 68% +/- 5%, 75% +/- 5%, and 79% +/- 4% at 30, 45, and 60 s, respectively, which were significantly larger (P < 0.05) than the corresponding values obtained with TVB alone (58% +/- 5%, 66% +/- 6%, and 71% +/- 5%, respectively). In both techniques, the EEO(2) increased exponentially, with time constants of 35 s during TVB after maximal exhalation versus 58 s during TVB without prior maximal exhalation. In conclusion, maximal exhalation before TVB can hasten preoxygenation by decreasing the nitrogen content of the functional residual capacity, with a consequent increase of EEO(2) to approximately 70% in 30 s and 80% in 60 s. ⋯ Oxygenation by using maximal exhalation before tidal volume breathing produced a significantly faster increase in end-expiratory oxygen concentration than oxygenation with tidal volume breathing alone.
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Anesthesia and analgesia · Nov 2003
Clinical TrialUltrasound-guided supraclavicular brachial plexus block.
In this study, we evaluated state-of-the-art ultrasound technology for supraclavicular brachial plexus blocks in 40 outpatients. Ultrasound imaging was used to identify the brachial plexus before the block, guide the block needle to reach target nerves, and visualize the pattern of local anesthetic spread. Needle position was further confirmed by nerve stimulation before injection. The block technique we describe aligned the needle path with the ultrasound beam. The block was successful after one attempt in 95% of the cases, with one failure attributable to subcutaneous injection and one to partial intravascular injection. Pneumothorax did not occur. Our preliminary data suggest that a high-resolution ultrasound probe can reliably identify the brachial plexus and its neighboring structures in the supraclavicular region. The technique of real-time guidance during needle advancement can quickly localize nerves. Distinct patterns of local anesthetic spread observed on ultrasound can further confirm accurate needle location. ⋯ Real-time ultrasound imaging during supraclavicular brachial plexus blocks can facilitate nerve localization and needle placement and examine the pattern of local anesthetic spread.
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Anesthesia and analgesia · Nov 2003
Case ReportsIntrathecal clonidine and severe hypotension after cardiopulmonary bypass.
The use of intrathecal clonidine as an adjunct for the management of chronic pain, intra- and postoperative analgesia is gaining an increase in popularity. However, antinociceptive doses of intrathecal clonidine may produce pronounced hemodynamic side effects, including hypotension and bradycardia. ⋯ We postulate that the intrathecally administered alpha 2-agonist clonidine reduced our patient's ability to tolerate the hemodynamic lability that is present during the separation from cardiopulmonary bypass by potentially inhibiting sympathetic nervous system activity, renin-angiotensin system, or vasopressin release. The authors report a case of severe hypotension after cardiopulmonary bypass in a patient receiving intrathecal clonidine infusion for chronic neuropathic pain.
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Anesthesia and analgesia · Nov 2003
Case ReportsSciatic nerve block in a child: a sonographic approach.
Ultrasound technology can facilitate peripheral nerve blocks in clinical practice. In this case report, ultrasound imaging was used to identify the sciatic nerve and guide local anesthetic injection in the subgluteal region of a child undergoing Achilles tendon lengthening. Sonographic guidance may be especially useful for peripheral nerve blocks in children because the neural imaging is often excellent and reference landmarks are variable. ⋯ In this case report, ultrasound was used to identify the sciatic nerve and guide local anesthetic injection in the subgluteal region of a child. Sonographic guidance may be especially useful for peripheral nerve blocks in children because the neural imaging is often excellent and reference landmarks are variable.
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Anesthesia and analgesia · Nov 2003
Clinical TrialThe prevalence of preoperative diastolic filling abnormalities in geriatric surgical patients.
Preoperative assessment of heart function has typically focused on evaluating left ventricular ejection fraction (LVEF). Recent evidence suggests that diastolic heart failure is common and may cause substantial morbidity and mortality. We designed this study to examine the prevalence and potential clinical correlates of diastolic filling abnormalities as measured by echocardiography in geriatric surgical patients. Patients >=65 yr of age undergoing coronary artery surgery without concomitant valvular surgery or those with one or more risk factors for cardiovascular disease undergoing noncardiac surgery were prospectively studied. Preoperative precordial echocardiography was performed for patients undergoing noncardiac surgery, and intraoperative transesophageal echocardiography was performed for those undergoing cardiac surgery. LVEF and diastolic filling properties including E/A ratio and deceleration time were measured. Overall, 251 patients were enrolled. The mean age was 72 +/- 7 yr. Multiple linear regression analyses showed that patients with a history of myocardial infarction P = 0.021), angina pectoris (beta = -6.09, 95% CI: -9.66, -2.52; P = 0.01), and valvular heart disease (beta = -5.05, 95% CI: -9.56, -0.55; P = 0.028) had lower LVEF than those without such conditions. Of the patients with normal LVEF, 61.5% had diastolic filling abnormalities. Diastolic filling indices including E/A ratio (beta = -1.11, 95% CI -6.02, 3.78; P = 0.65) and deceleration times (beta = -3.42, 95% CI -31.28, 24.45; P = 0.81) contributed no additional predictive value for LVEF. No clinical predictors could be identified to predict diastolic filling abnormalities. For patients undergoing noncardiac surgery, analysis of variance demonstrates that the clinical assessment of LVEF using history and physical examination data was able to grossly discriminate the different levels of LVEF as compared with echocardiography (P = 0.0004). However, under-estimation of LVEF occurred more frequently than over-estimation. Although physicians' clinical assessment of systolic ejection fraction was generally accurate, geriatric patients with normal LVEF often had isolated diastolic filling abnormalities that could not be predicted by clinical factors. These results suggest that evaluation of LV systolic function alone is not discriminatory in comprehensively characterizing LV function in geriatric surgical patients. ⋯ Although physicians' clinical assessment of systolic ejection fraction was generally accurate, geriatric patients with normal left ventricular (LV) ejection fraction often had isolated diastolic filling abnormalities that could not be predicted by clinical factors. These results suggest that evaluation of LV systolic function alone is not discriminatory in comprehensively characterizing LV function in geriatric surgical patients.