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and were not applied to the orad segment. 9 – 11 Laser Doppler flowmetry (LDF) is a technique based on detecting the Doppler shift of laser light on moving red blood cells, which can be combined with white light spectrophotometry to determine the

Open access
in American Journal of Veterinary Research

Summary

Once daily for 3 days, laser Doppler flowmetry was used in 5 healthy, nonsedated adult horses to evaluate coronary band and laminar microcirculatory blood flow (mbf) in both forelimbs. The coronary band had significantly (P < 005) higher mbf than did the laminae on the days evaluated. Significant variation in mbf was not found over the 3-day measurement period in any one site. Significant (P < 0.05) variation was found in coronary band mbf among horses. This variation was not observed in laminar mbf. On occlusion of the digital arteries at the level of the fetlock, marked decrease in coronary band and laminar mbf was observed. Twenty minutes after iv administration of acetylpromazine, marked increase in coronary band and laminar mbf was observed. The technique was easily performed in standing nonsedated horses, did not inflict discomfort, lacked complications, and measurements were repeatable. This technique provides an index of digital mbf, either intermittently or continuously, avoiding introduction of invasive variables associated with other techniques.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To use Doppler ultrasonography and singlefiber laser Doppler flowmetry (LDF) to evaluate blood flow in the dependent and nondependent hind limbs of anesthetized horses and to evaluate changes in femoral arterial blood flow and microvascular skeletal muscle perfusion in response to administration of phenylephrine hydrochloride or dobutamine hydrochloride.

Animals—6 healthy adult horses.

Procedure—Horses were anesthetized and positioned in left lateral recumbency. Doppler ultrasonography was used to measure velocity and volumetric flow in the femoral vessels. Single-fiber LDF was used to measure relative microvascular perfusion at a single site in the semimembranosus muscles. Phenylephrine or dobutamine was then administered to decrease or increase femoral arterial blood flow, and changes in blood flow and microvascular perfusion were recorded.

Results—Administration of phenylephrine resulted in significant decreases in femoral arterial and venous blood flows and cardiac output and significant increases in mean aortic blood pressure, systemic vascular resistance, and PCV. Administration of dobutamine resulted in significant increases in femoral arterial blood flow, mean aortic blood pressure, and PCV. Significant changes in microvascular perfusion were not detected.

Conclusion and Clinical Relevance—Results suggest that Doppler ultrasonography and single-fiber LDF can be used to study blood flows in the hind limbs of anesthetized horses. However, further studies are required to determine why changes in femoral arterial blood flows were not associated with changes in microvascular perfusion. (Am J Vet Res 2000;61:286–290)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To measure changes in laminar microvascular blood flow (LMBF) over time in healthy horses and horses in the prodromal stage of black walnutinduced laminitis and to determine the effects of glyceryl trinitrate application on LMBF in horses with acute laminitis.

Animals—10 healthy adult horses.

Procedure—Laser Doppler flowmetry was used to measure LMBF. Baseline measurements were obtained, horses were given deionized water via a nasogastric tube, and measurements were obtained hourly for 12 hours. Twenty-four hours later, baseline measurements were again obtained, and horses were given black walnut extract. Measurements were obtained hourly for 12 hours or until development of Obel grade-3 laminitis. At this time, 5 horses were treated with phenylbutazone, and the other 5 were treated with phenylbutazone and glyceryl trinitrate, and measurements were obtained hourly for an additional 12 hours.

Results—LMBF was significantly decreased 1 and 2 hours after administration of the black walnut extract but then returned to near-baseline values for the next 6 hours. Eight hours after extract administration, there was a second significant decrease in LMBF that persisted until the end of the study. Glyceryl trinitrate had no effect on LMBF. Clinical signs of laminitis developed 8 to 12 hours after extract administration.

Conclusions and Clinical Relevance—Results suggest that in horses with black walnut-induced laminitis, there is an early decrease in LMBF followed by reperfusion prior to onset of clinical signs. Treatment with glyceryl trinitrate after development of clinical signs of laminitis did not have a significant effect on LMBF. (Am J Vet Res 2000;61:862–868)

Full access
in American Journal of Veterinary Research

SUMMARY

Perfusion and viability of island axial pattern skin flaps were tested in 37 healthy New Zealand white rabbits, using laser Doppler monitoring of blood flow in the capillary loops and the subpapillary plexus of the dermis. Skin flaps, selected on the basis of the caudal superficial epigastric vein and artery, were lifted and replaced in their original locus after selective occlusion of their vascular pedicles. Subjects were allotted into groups: control group (n = 10); arterial occlusion (n = 7); venous occlusion (n = 10); and arterial and venous occlusion (n = 10). The rabbits were monitored from 48 hours before surgery until euthanasia 48 to 72 hours after replacement of the flap. Flap viability was assessed on a clinical basis, using a comparative scoring method based on a numeric scale. The degree of necrosis in histologic sections was evaluated, using a scoring system. Laser Doppler measurements were obtained on 3 consecutive days before surgery, to establish the normal basal blood flow in the skin. Post-surgical measurements were obtained at 2-hour intervals for the first 8 hours and at 24, 48, and 72 hours after surgery. Measurements of basal blood flow varied significantly (P < 0.05) from site to site on the surface of individual flaps and over time. When laser Doppler flowmetric (ldf) measurements from 6 sites on a flap were used as a measure of laser Doppler flow for the total flap, there was no significant difference between contralateral flap areas outlined on the abdomen of the rabbits. Temporal variations over 3 days for each rabbit or among rabbits were not significant.

The ldf measurements detected acute vascular occlusion when compared with the controls, and were able to differentiate between control and arterial occlusion groups, control and venous occlusion groups, control and arterial and venous occlusion groups, arterial and venous occlusion groups, venous and arterial and venous occlusion groups (P < 0.05), but not between arterial and arterial and venous occlusion groups. Evaluation of ldf values at 4 hours proved to be a better predictor than clinical assessment at 4 or 8 hours in evaluating skin flap viability.

Free access
in American Journal of Veterinary Research

Schmidhammer JL , et al . Laminar microvascular flow, measured by means of laser Doppler flowmetry, during the prodromal stages of black walnut-induced laminitis in horses . Am J Vet Res 2000 ; 61 : 862 – 868 . 10.2460/ajvr.2000.61.862 10. Hood DM

Full access
in American Journal of Veterinary Research

SUMMARY

Objective

To measure blood flow in the palmar digital artery and laminae corium, using ultrasonic and laser Doppler flowmetry, respectively.

Animals

6 healthy horses.

Procedure

Digital blood flow and laminar perfusion, respectively, were measured by placing a flow probe around the palmar digital artery and a laser Doppler flow probe in a hole in the dorsal aspect of the hoof wall. All horses were given saline (0.9% NaCI) solution (1 L, IV, during a 30-minute period). Seven days later, each horse was given endotoxin (0.1 μg/kg of body weight, IV, in 1 L of saline solution, during a 30-minute period). Digital blood flow, laminar perfusion, heart and respiratory rates, body temperature, and clinical signs of endotoxemia were recorded throughout a 240-minute period. Repeated-measures ANCOVA was used to evaluate changes in outcome variables.

Results

Treatment with saline solution did not cause a change in measured variables. All horses had mild clinical signs of endotoxemia. Endotoxin treatment caused a significant decrease in digital blood flow and increases in heart rate and body temperature. Laminar perfusion decreased after endotoxin treatment.

Conclusions

Endotoxin administration caused a profound transient decrease in digital blood flow and a less substantial decrease in laminar perfusion.

Clinical Relevance

Horses with clinical endotoxemia were likely to have decreased digital blood flow and, possibly, decreased laminar perfusion, potentially predisposing them to vascular alterations within the digits. (Am J Vet Res 1998;59:192–196)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the hemodynamic effects of dobutamine hydrochloride (0.5 µg/kg of body weight/min) in halothane-anesthetized horses.

Animals—6 adult Thoroughbred horses.

Procedure—Anesthesia was induced by use of romifidine (100 µg/kg) and ketamine (2.2 mg/kg), IV. Anesthesia was maintained by halothane (end-tidal concentration 0.9 to 1.0%). Aortic, left ventricular, and right atrial pressures were measured, using cathetermounted strain gauge transducers. Cardiac output (CO), velocity time integral, maximal aortic blood flow velocity and acceleration, and left ventricular preejection period and ejection time were measured from aortic velocity waveforms obtained by transesophageal Doppler echocardiography. Velocity waveforms were recorded from the femoral vessels, using Doppler ultrasonography. The time-averaged mean velocity and early diastolic deceleration slope (EDDS) were measured. Pulsatility index (PI) and volumetric flow were calculated. Microvascular perfusion was measured in the semimembranosus muscles by laser Doppler flowmetry. Data were recorded 60 minutes after induction of anesthesia (control) and at 15 and 30 minutes after start of an infusion of dobutamine (0.5 µg/kg/min).

Results—Aortic pressures were significantly increased during the infusion of dobutamine. No change was observed in the indices of left ventricular systolic function including CO. Femoral arterial flow significantly increased, and the PI and EDDS decreased. No change was observed in the femoral venous flow or in microvascular perfusion.

Conclusions and Clinical Relevance—At this dosage, dobutamine did not alter left ventricular systolic function. Femoral blood flow was preferentially increased as the result of local vasodilatation. The lack of effect of dobutamine on microvascular perfusion suggests that increased femoral flow is not necessarily associated with improved perfusion of skeletal muscles. (Am J Vet Res 2000;61:1282–1288)

Full access
in American Journal of Veterinary Research

Abstract

Objective

To evaluate the effect on intramuscular blood flow (IMBF) and hemodynamic variables of 4 antihypotensive agents given during anesthesia.

Animals

8 ponies.

Procedure

Halothane-anesthetized ponies (n = 6) positioned in lateral recumbency received, on separate occasions, infusions of each of the following 4 agents in serially increasing dosages or saline solution: phenylephrine hydrochloride (0.25, 0.5, 1, and 2 μg/kg of body weight), dopamine (2.5, 5, 10, and 20 μg/kg), dobutamine (1, 2.5, 5, and 10 μg/kg), and dopexamine (0.5, 1, 5, and 10 μg/kg). Changes in IMBF (by laser-Doppler flowmetry) in nondependent and dependent triceps brachii muscles and cardiopulmonary variables were measured.

Results

Phenylephrine at all dosages failed to improve IMBF or cardiac index (CI), but increased mean arterial pressure (MAP) and systemic vascular resistance (SVR); 2 ponies had forelimb lameness on recovery. Dopamine (10 μg/kg/min) increased Cl, MAP, and IMBF in the dependant muscle. A higher dose (20 μg/kg/min) caused cardiac arrhythmias and muscular tremor. Dobutamine increased Cl, MAP, and IMBF of both forelimbs, effects being significant for 2.5 μg/kg/min, with further improvement as the dosage increased. In 2 ponies, 10 μg of dobutamine/kg/min caused cardiac arrhythmias. Dopexamine (1 and 5 μg/kg/min) increased Cl, MAP, and IMBF in the nondependent muscle, and 10 μg/kg/min caused muscular tremor, sweating, and arrhythmias. SVR was reduced after infusion of dopamine, dobutamine, or dopexamine.

Conclusion

During anesthesia of equids, an increase in CI and MAP is necessary to improve IMBF in the dependant forelimb.

Clinical Relevance

Of the agents investigated, dobutamine proved the most consistent in improving IMBF. (Am J Vet Res 1998;59:1463–1472)

Free access
in American Journal of Veterinary Research
Authors and

flowmetry and pulse oximetry. 6,14 Unfortunately, testing tooth vitality in awake animals is not realistic and reports 15 on advanced vitality testing in the veterinary literature are limited. The present case illustrates that in dogs with obvious signs

Full access
in Journal of the American Veterinary Medical Association