RESUMO
OBJECTIVE: To determine blood flow patterns in the common carotid artery and external jugular vein in cows before and after sedation achieved by administration of xylazine hydrochloride. ANIMALS: 30 clinically normal Swiss Braunvieh cows. PROCEDURE: A 5.0-MHz sector transducer was used to examine the common carotid artery and external jugular vein before and after cows were sedated by administration of xylazine. Several variables were calculated, including diameter of the blood vessels, blood flow velocity, and flow-time volume. RESULTS: The common carotid artery before sedation had a maximum systolic velocity of 89 +/- 8.5 cm/s, maximum diastolic velocity of 36 +/- 6.0 cm/s, mean velocity of 35 +/- 5.4 cm/s, and flow-time volume of 28.2 +/- 3.48 cm3/s. In all cows, sedation achieved by administration of xylazine resulted in a significant decrease in velocity of arterial blood flow and flow-time volume. The external jugular vein before sedation had a maximum velocity of 65 +/- 8.3 cm/s, maximum velocity of retrograde venous blood flow of 20 +/- 6.6 cm/s, and flow-time volume of 29.7 +/- 5.42 cm3/s. These values decreased significantly after cows were sedated by administration of xylazine. CONCLUSIONS AND CLINICAL RELEVANCE: Doppler ultrasonography is particularly suitable for evaluation of blood flow patterns in the common carotid artery and external jugular vein of healthy cows. The results reported here provide a basis for use in examination of cows with cardiac and blood vessel disease.
