Measurements of hindlimb blood flow recorded using Doppler ultrasound during administration of vasoactive agents in halothane-anesthetized horses.
The purpose of the study was to determine the ability of Doppler ultrasound to detect changes in femoral blood flow during pharmacologic manipulation of arterial blood pressure. Doppler ultrasonography was performed in the femoral vessels of six halothane-anesthetized horses before and during administration of phenylephrine HCI and sodium nitroprusside. The time-averaged mean velocity and volumetric flow were calculated. The contour of the velocity waveform was assessed, and the early diastolic deceleration slope (EDDS) and pulsatility index (PI) were calculated. Administration of phenylephrine HCI resulted in increased mean aortic blood pressure (MABP) by 40% (29.3-53.0%). This caused significant decrease in cardiac output (26.8 to 13.5 l/min), femoral arterial velocity (left artery 7.20 to 4.00 cm/s; right artery 5.01 to 3.39 cm/s) and volumetric flow (left artery 556 to 221 ml/min; right artery 397 to 193 ml/min) in the femoral vessels and significant increase in systemic vascular resistance (163 to 433 dyn-s/cm5), EDDS (1a: 285 to 468: ra: 250 to 481) and PI (1a: 9.38 to 20.4; ra 17.1 to 29.1). Administration of sodium nitroprusside resulted in a decreased MABP of 27.2% (22.5-33%). This increased cardiac output (20.8 to 32.4 L/min), however, no significant changes were observed in femoral blood flow. Despite obvious changes in the waveform contour, no significant change occurred in EDDS or PI. These results suggest that Doppler ultrasound may be useful for measuring femoral blood flow in anesthetized horses. However, waveform analysis appears to be limited when multiple changes occur in central and peripheral haemodynamics.
Raisis
A L
AL
Centre for Equine Studies, The Animal Health Trust, Lanwades Park, Kentford, Newmarket, Suffolk. anthea.raisis@aht.org.uk
Young
L E
LE
Meire
H B
HB
Taylor
P M
PM
Blissitt
K J
KJ
Marlin
D
D
Lekeux
P
P
D018685:Anesthetics, Inhalation / Q000008:administration & dosage*; D000818:Animals; D001011:Aorta / Q000000981:diagnostic imaging / Q000187:drug effects; D016280:Atrial Function, Right / Q000187:drug effects; D001783:Blood Flow Velocity / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D001810:Blood Volume / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D003971:Diastole; D005260:Female; D005263:Femoral Artery / Q000000981:diagnostic imaging / Q000187:drug effects*; D005268:Femoral Vein / Q000000981:diagnostic imaging / Q000187:drug effects*; D006221:Halothane / Q000008:administration & dosage*; D006614:Hindlimb / Q000098:blood supply* / Q000000981:diagnostic imaging; D006736:Horses / Q000033:anatomy & histology* / Q000502:physiology; D008297:Male; D009599:Nitroprusside / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011673:Pulsatile Flow / Q000187:drug effects; D012039:Regional Blood Flow / Q000187:drug effects; D013318:Stroke Volume / Q000187:drug effects; D018608:Ultrasonography, Doppler / Q000662:veterinary*; D014655:Vascular Resistance / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D014665:Vasodilator Agents / Q000494:pharmacology*; D016277:Ventricular Function, Left / Q000187:drug effects; D017725:Ventricular Pressure / Q000187:drug effects
D018685:Anesthetics, Inhalation; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D009599:Nitroprusside; D010656:Phenylephrine; D006221:Halothane