Anesthesiology
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An endotracheal tube with a 5 mm diameter ultrasonic transducer incorporated into its distal end was inserted into the tracheas of six anesthetized dogs. The device provides for ultrasound measurement of aortic diameter and blood velocity in the ascending aorta to obtain cardiac outputs. Because measurements are made proximal to the origins of the aortic arch vessels, total cardiac output is obtained. ⋯ R2 = .82. The results from this preliminary assessment of the feasibility of measuring cardiac output in dogs using transtracheal Doppler suggest that additional studies should be pursued. Additional issues that require investigation include confirmation of constancy of human anatomy and demonstration of lack of tracheal trauma from the Doppler equipped endotracheal tube.
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This prospective clinical study evaluated the influence of high bilirubin plasma levels on the Nellcor pulse oximeter readings (SpO2). Twenty-nine icteric patients (mean total bilirubin 19.2 mg/dl, range 2.3-84.3 mg/dl) were compared with 46 controls. The difference between SpO2 and oxyhemoglobin percentage of hemoglobin (HbO2corr) or fractional saturation as measured by a seven wavelengths Corning Co 2500 Co-oximeter and corrected for the spectral error induced by hyperbilirubinemia in that co-oximeter was greater in icteric patients (bias and precision: 2.9% +/- 2.2% vs. 1.7% +/- 2.7%, P less than 0.03). ⋯ Pulse oximeters read most of CoHb as oxyhemoglobin. After correcting SpO2 for carboxyhemoglobin in both groups of patients, the 99% confidence limits from the obtained regression line were the same in icteric patients (-0.81%, 1.03%) as in controls (-0.89%, 1.08%). There was thus no demonstrable direct influence of high bilirubin plasma levels on SpO2 as measured by a Nellcor pulse oximeter.
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Comparative Study
The dose-response relationship of mivacurium chloride in humans during nitrous oxide-fentanyl or nitrous oxide-enflurane anesthesia.
The dose-response relationships of mivacurium chloride during N2O/fentanyl or N2O/enflurane anesthesia were compared in 70 patients intraoperatively. Responses were defined in terms of percentage changes in the evoked twitch tension of the adductor pollicis muscle, and dose-response curves were constructed following probit transformation of the responses. End-tidal concentrations of enflurane during the were study were 0.9-1.2%. ⋯ Regression lines describing the relationship between the maximum depression of twitch tension (response) and the time interval between the injection of mivacurium and the return of twitch tension to 90% of the control value (duration) were constructed. The response-duration line for N2O/enflurane anesthesia was displaced significantly to the left of the line for N2O/fentanyl (P less than 0.05), indicating that enflurane anesthesia was associated with a prolongation of mivacurium-induced neuromuscular blockade. The neuromuscular blocking effect of mivacurium is both enhanced by and prolonged during N2O/enflurane compared with that during N2O/fentanyl anesthesia.