Anesthesiology
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Comparative Study
In vivo comparison of two mixed venous saturation catheters.
The accuracy and stability of mixed venous saturation pulmonary arterial catheters under adverse physiologic conditions has not been assessed. Either a Shaw Opticath catheter (three-wavelength) or a Swan-Ganz oximetry TD catheter (two-wavelength) was calibrated in vitro and positioned in the pulmonary artery in each of ten mongrel dogs. The in vivo saturations were compared to measured saturations from anaerobically collected mixed venous blood analyzed with a reference cooximeter at each step in the protocol. ⋯ The two-wavelength catheter tended to drift under the same conditions (R = .808; SEE = 10.6%). At the conclusion of the experiment, the two-wavelength system was uniformly higher then the cooximeter by 5-31% with a mean of 21% (P less than or equal to .003 as compared with the initial difference by paired Student's t test). Pending further analysis of the tendency of the two-wavelength system to drift it would seem prudent to limit its clinical application.
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Lung densities (atelectasis) and pulmonary gas exchange were studied in 13 supine patients with no apparent lung disease, the former by transverse computerized tomography (CT) and the latter by a multiple inert gas elimination technique for assessment of the distribution of ventilation/perfusion ratios. In the awake state no patient had clear signs of atelectasis on the CT scan. Lung ventilation and perfusion were well matched in most of the patients. ⋯ Both the density area and the shunt increased after muscle paralysis. PEEP reduced the density area in all patients but did not consistently alter the shunt. It is concluded that the development of atelectasis in dependent lung regions is a major cause of gas exchange impairment during halothane anesthesia, during both spontaneous breathing and mechanical ventilation, and that PEEP diminishes the atelectasis, but not necessarily the shunt.
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Comparative Study
Comparison of sufentanil-N2O and fentanyl-N2O in patients without cardiac disease undergoing general surgery.
Sufentanil (mean total dose 2 micrograms/kg) was compared with fentanyl (mean total dose 15 micrograms/kg) as a supplement to 60% N2O anesthesia in 30 adult patients undergoing general surgical procedures. Comparisons were made with respect to stability of hemodynamic variables (heart rate and systolic and diastolic blood pressure), changes in stress hormones (cortisol, antidiuretic hormone, epinephrine, norepinephrine, and dopamine), recovery of alertness and orientation, time to extubation, postoperative analgesia, and measures of respiratory depression (resting end-tidal carbon dioxide tension [PETCO2], CO2 response curve for minute ventilation [delta VE/delta PETCO2]). Hemodynamic variables remained stable and similar in both groups throughout the study. ⋯ Small but significant elevations in resting PETCO2 were seen in both groups postoperatively (P less than 0.05), but postoperative delta VE/delta PETCO2 responses were significantly depressed only in patients receiving fentanyl (P less than 0.05). The results of this study demonstrate that sufentanil-N2O anesthesia is as effective as fentanyl-N2O in attenuating the hemodynamic and hormonal responses to the stress of general surgery. Because continuous intraoperative PETCO2 monitoring was not employed in this study, intraoperative hypocapnea cannot be strictly excluded as a possible influence on the postoperative measures of ventilatory drive.(ABSTRACT TRUNCATED AT 250 WORDS)
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Minute ventilation (VE), tidal volume (VT), carbon dioxide elimination (VCO2), and end-tidal (PETCO2) and arterial CO2 tensions (PaCO2) were measured in 39 anesthetized infants and children with body weights ranging from 3.1 to 31 kg. Eighteen children had normal cardiopulmonary function, seven had acyanotic congenital heart disease, and 11 had cyanotic congenital heart disease. One child had left heart failure and pulmonary congestion, and two had severe parenchymal lung disease. ⋯ In children with cyanotic congenital heart disease, however, correlation between PETCO2 and PaCO2 was relatively poor (r = 0.61). Mean values for PaCO2 were significantly higher than PETCO2 in the cyanotic children (P less than 0.01), resulting in significant underestimation of physiologic dead space (P less than 0.05) and significant overestimation of alveolar ventilation (P less than 0.01). In three patients with pulmonary disease, large differences between PaCO2 and PETCO2 were comparable with those observed in the children with cyanotic congenital heart disease.(ABSTRACT TRUNCATED AT 250 WORDS)