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  • Author or Editor: J. L. Grandy x
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Summary

Gastric dilatation was experimentally induced in 6 anesthetized dogs maintained with constant-dose isoflurane in oxygen. An intragastric balloon was used to distend the stomach with a constant 30 mm of Hg pressure for 3.5 hours. The Pa co 2 was maintained between 35 and 45 mm of Hg, using intermittent positive-pressure ventilation. Cardiopulmonary measurements prior to stomach distension (baseline) were compared with measurements taken during 0.1, 0.5, 1.0, 1.5, 2.5, and 3.5 hours of stomach distension by analyzing the change from baseline in a randomized-block analysis with each dog as a block. After distending the stomach, cardiac index increased (P < 0.01) from 1.5 to 3.5 hours. Stroke volume did not change, thus the increase in the cardiac index was attributable to an increase in heart rate. During inflation, increases were observed in systemic arterial, pulmonary arterial, and right atrial pressure. Respiratory frequency was unchanged; however, to maintain Pa co 2 constant, it was necessary to progressively increase peak airway pressure. Although Pa co 2 tended to decrease during gastric dilation, the dogs were never hypoxemic. These results indicate that when our methods are used to maintain a constant anesthetic dose of isoflurane in oxygen, an observed increase in cardiovascular performance is expected. This differs from other studies in anesthetized dogs that have shown reduction in cardiovascular performance following gastric dilatation.

Free access
in American Journal of Veterinary Research

Summary

The accuracy of the Doppler technique for indirect systolic blood pressure measurement was assessed in 16 anesthetized cats. Eight cats were anesthetized with isoflurane and 8 were anesthetized with halothane. Anesthetic depth and mode of ventilation were varied to obtain a wide range of arterial blood pressure. A Doppler transducer was placed on the palmer surface of the left forelimb over the common digital branch of the radial artery to detect blood flow, and a blood pressure monitoring cuff with a width 37% the limb circumference was placed half way between the elbow and the carpus. To enable direct arterial pressure measurements, the left femoral artery was catheterized and the blood pressure waveforms recorded simultaneously.

Systolic blood pressure measured by use of the Doppler ultrasonic technique was significantly lower than that obtained from the femoral artery catheter. Using linear regression, we determined a clinically useful calibration adjustment for Doppler indirect blood pressure measurement in cats: femoral systolic pressure = Doppler systolic pressure + 14 mm of Hg.

Free access
in American Journal of Veterinary Research

SUMMARY

The purpose of this study was to compare the thermodilution technique for estimation of cardiac output with the indocyanine green dye dilution technique at flows between 10 and 39 L/min in halothane-anesthetized horses. The estimation of area of dye dilution cardiac output curves was made by using the fore-’n-aft (fa) triangle method. This shorthand technique was compared with logarithmic exponential extrapolation and summation (extrapolated area), using 64 cardiac output curves. Then, 256 simultaneous thermodilution measurements were compared with dye dilution measurements calculated by use of the fa technique. Forty milliliters of iced 0.9% NaCl solution containing 15 mg of indocyanine green dye was used as the indicator. This was delivered in < 1 second to the right atrium, using a power injector. A thermistor positioned in the pulmonary artery detected the thermal indicator. Blood was withdrawn from the carotid artery through a densitometer cuvette to measure the dye concentration. The fa estimations of area were higher than those determined by use of extrapolated area. A multiplicative adjustment of 0.837 was estimated. On average, thermodilution estimates of cardiac output exceeded the adjusted fa determinations. Using a weighted linear regression, we determined the following calibration adjustment: thermal dilution cardiac output/1.048 = indocyanine green dye dilution cardiac output.

Free access
in American Journal of Veterinary Research

SUMMARY

Cardiovascular and respiratory functions were serially characterized in 7 healthy, spontaneously breathing, adult horses (from which food had been withheld) during 5 hours of constant 1.06% alveolar halothane (end-expired halothane concentration of 1.06%; equivalent to 1.2 times the minimal alveolar anesthetic concentration for horses). To enable comparison of temporal results in relation to 2 body postures, horses were studied in lateral recumbency (lr) and dorsal recumbency (dr) on separate occasions. Temporal changes in results of measures of circulation previously reported from this laboratory for horses in lr were confirmed (ie, a time-related increase in systemic arterial blood pressure, cardiac output, stroke volume, and pcv). During dr, systemic arterial blood pressure was initially significantly (P < 0.05) greater and pulmonary artery pressure less than results at comparable periods during lr. Differences ceased to exist with duration of anesthesia. Except for a greater heart rate at hour 5 of dr, no other significant differences in circulation were found between lr and dr. In general, except for PaO2 measures of ventilation did not change with time in either lr or dr. The PaO2 was significantly greater during lr, compared with dr, but the average did not change significantly with time in either body posture.

Free access
in American Journal of Veterinary Research

Summary

Maximal conduction velocities of compound action potentials evoked by stimuli of 2 times threshold in the caudal cutaneous sural (ccsn) and medial cutaneous antebrachial (mcan) nerves were determined by averaging potentials evoked and recorded through percutaneous needle electrodes. Mean maximal conduction velocities of compound action potentials were: ccsn = 61.3 ± 2.0 meters/second (m/s) and mcan = 56.4 ± 2.8 m/s. To confirm accuracy of our percutaneous recordings, compound action potentials were recorded through bipolar chlorided silver electrodes from the exposed surfaces of fascicles of the ccsn and the mcan. The maximal conduction velocities of these potentials were in agreement with the conduction velocities of compound action potentials that were evoked and recorded through percutaneous needle electrodes. The specificity of stimulating and recording sites was verified by recording before and after section of the nerves. Stimuli from 3 to 5 times threshold evoked a second, longer latency, compound action potential that consisted of a variable number of components in the ccsn and mcan. The configurations and conduction velocities of the shorter latency potentials were the same as those of the single compound action potentials evoked by stimuli of 2 times threshold. Mean conduction velocities of the longer latency potentials were: ccsn = 24.4 ± 2.6 m/s and mcan = 24.5 ± 2.2 m/s. Needle electrode and direct stimulation of either the ccsn or the mcan at 3 to 5 times threshold failed to evoke contractions of limb muscles. Therefore, action potentials that contributed to the evoked compound potentials recorded in these horses arose, most likely, from afferent nerve fibers.

Free access
in American Journal of Veterinary Research