Short-Term Effects of Ketamine and Isoflurane on Left Ventricular Ejection Fraction in an Experimental Swine Model

Background. General anesthesia is an essential element of experimental medical procedures. Ketamine and isoflurane are agents commonly used to induce and maintain anesthesia in animals. The cardiovascular effects of these anesthetic agents are diverse, and the response of global myocardial function is unknown. Methods. In a series of 15 swine, echocardiography measurements of left ventricular ejection fraction (LVEF) were obtained before the animals received anesthesia (baseline), after an intramuscular injection of ketamine (postketamine) and after inhaled isoflurane (postisoflurane). Results. The mean LVEF of an unanesthetized swine was 47 ± 3%. There was a significant decrease in the mean LVEF after administration of ketamine to 41 + 6.5% (P = 0.003). The addition of inhaled isoflurane did not result in further decrease in mean LVEF (mean LVEF 38 ± 7.2%, P = 0.22). Eight of the swine had an increase in their LVEF with sympathetic stimulation. Conclusions. In our experimental model the administration of ketamine was associated with decreased LV function. The decrease may be largely secondary to a blunting of sympathetic tone. The addition of isoflurane to ketamine did not significantly change LV function. A significant number of animals had returned to preanesthesia LV function with sympathetic stimulation

LEFT VENTRICULAR HYPERTROPHY IN ATHLETES: THE "GRAY-ZONE" REVISITED

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743-5 Evaluation of the Accuracy of New Quantitative Image Processing Methods in Measuring the Size of Ventricular Septal Defects Directly on Three-dimensional Echocardiograms and Factors Influencing its Reliability

Volume-rendered 3-D echocardiography(3DE) can display the shape and size of various ventricular septal defects (VSD). Quantitation of VSD size directly from 3DE images has not been possible and measurements (M) could be performed only in 2DE slices derived from 3DE and required tedious efforts to obtain the correct 2DE slice orientation, Newly developed image processing (IP) algorithms permitdirect M on 3DE imagesbut the reliability of this method in sizing VSDs is unclear, Also, the effects of operator-dependent IP factors such as thresholding (TH) and opacification (OP) on quantitation are unknown. In this study, we examined the accuracy ofdirect 3DE quantificationof VSDs and the influence of TH and OP. We created 17 VSDs of various types and shapes in 9 pig hearts and acquired 2-D images with a transducer mounted on a parallel scanning device (216 image slices over 60mm distance). 3DE reconstructions were accomplished anden-face viewsof the VSDs were derived. Using the new quantitation tool, we measured the maximum and minimum diameters (Max D and Min D), directly on the 3DE image under optimal IP settings and compared them to independent direct M from the anatomic specimens. M were also performed with changes in TH and OP.ResultsThe VSD site, shape and size on 3DE corresponded well with anatomic specimens. Max D (Mean±SD) by anatomy was 10±4mm (range 4–16), and by 3DE was 10±4 (range 4–15); Min D by anatomy was 9±3 mm (range 4–15). and by 3DE was 8 ± 4 (range 5-19). The correlations between 3DE (y) and anatomy were: Max D: y=1.0x + 0.3, r = 0.88, P<0.001; Min D: y = 1.0x – 1.4, r = 0.89, P<0.001. Increased TH by 10 units led to overestimation of the VSD size by 6±18%, while TH decrease by 10 units resulted in 8±13% under-estimation. Increased OP by 10 and 20 units led to overestimation of VSD size by 11±29% and 17±23%.Conclusion3DE provides unique en-face views of VSDs unavailable by 2DE. VSD size can be measured directly on the 3D image. Inappropriate processing steps can result in unreliable data, however with optimal processing VSDs can be quantified accurately