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  • Author or Editor: C.I. Dunlop 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

Objective

To determine whether end-tidal partial pressure of carbon dioxide (Petco 2) was a reliable estimate of Paco2 in dogs undergoing thoracotomy.

Design

Case series.

Animals

18 dogs that underwent thoracotomy.

Procedure

Paco2 and Petco 2 were measured shortly after induction of anesthesia, while dogs were breathing spontaneously; 5 minutes prior to initial skin incision, while dogs were receiving intermittent positive-pressure ventilation (IPPV); 5, 30, and 60 minutes after the thoracic cavity was opened, while dogs were receiving IPPV; and after the thoracic cavity was closed and evacuated, when dogs were again breathing spontaneously. For each period, arterial-end-tidal difference in partial pressure of carbon dioxide (Paco2-Petco 2) was compared with Paco2-Petco 2 for the preceding period.

Results

Significant changes in Paco2-Petco 2 from one period to the next were not detected except when values obtained 5 minutes after the thoracic cavity was opened were compared with values obtained 5 minutes before incision. The Paco2-Petco 2 was not constant for individual dogs.

Clinical Implications

Petco 2 was not a reliable indicator of adequacy of ventilation during thoracotomy in these dogs, because it differed greatly from Paco2, and Pac02-PETC02 was not consistent. (J Am Vet Med Assoc 1998; 212:377-379)

Free access
in Journal of the American Veterinary Medical Association

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 changes that accompany markedly long periods (12 hours) of halothane anesthesia were characterized. Eight spontaneously breathing horses were studied while they were positioned in left lateral recumbency and anesthetized only with halothane in oxygen maintained at a constant end-tidal concentration of 1.06% (equivalent to 1.2 times the minimal alveolar concentration for horses). Results of circulatory and respiratory measurements during the first 5 hours of constant conditions were similar to those previously reported from this laboratory (ie, a time-related significant increase in systemic arterial blood pressure, cardiac output, stroke volume, left ventricular work, pcv, plasma total solids concentration, and little change in respiratory system function). Beyond 5 hours of anesthesia, arterial blood pressure did not further increase, but remained above baseline. Cardiac output continued to increase, because heart rate significantly (P < 0.05) increased. Peak inspiratory gas flow increased significantly (P < 0.05) in later stages of anesthesia. There was a significant decrease in inspiratory time beginning at 4 hours. Although PaO2 and PaCO2 did not significantly change during the 12 hours of study, P v ̄ O 2 increased significantly (P < 0.05) and progressively with time, beginning 6 hours after the beginning of constant conditions. Metabolic acidosis increased with time (significantly [P < 0.05] starting at 9 hours), despite supplemental iv administered NaHCO3, Plasma concentrations of eicosanoids: 6-ketoprostaglandin F (pgf a stable metabolite of pgi 1), pgf , pge, and thromboxane (TxB2, a stable metabolite of TxA2) were measured in 5 of the 8 horses before and during anesthesia. Significant changes from preanesthetic values were not detected. Dynamic thoracic wall and lung compliances decreased with time.

Free access
in American Journal of Veterinary Research