Viscosity and rheologic properties of blood from clinically normal horses

Frank M. Andrews From the Department of Rural Practice (Andrews, Korenek), College of Veterinary Medicine and Statistical and Computing Services, Agricultural Experiment Station (Sanders), University of Tennessee, PO Box 1071, Knoxville, TN 37901-1071, and Department of Physiology and Pharmacology, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210 (Hamlin).

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Nancy L. Korenek From the Department of Rural Practice (Andrews, Korenek), College of Veterinary Medicine and Statistical and Computing Services, Agricultural Experiment Station (Sanders), University of Tennessee, PO Box 1071, Knoxville, TN 37901-1071, and Department of Physiology and Pharmacology, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210 (Hamlin).

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William L. Sanders From the Department of Rural Practice (Andrews, Korenek), College of Veterinary Medicine and Statistical and Computing Services, Agricultural Experiment Station (Sanders), University of Tennessee, PO Box 1071, Knoxville, TN 37901-1071, and Department of Physiology and Pharmacology, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210 (Hamlin).

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Robert L. Hamlin From the Department of Rural Practice (Andrews, Korenek), College of Veterinary Medicine and Statistical and Computing Services, Agricultural Experiment Station (Sanders), University of Tennessee, PO Box 1071, Knoxville, TN 37901-1071, and Department of Physiology and Pharmacology, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210 (Hamlin).

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Summary

Blood viscosity (bv) was measured in 32 healthy horses at 6 spindle speeds (60, 30, 12, 6, 3, and 1.5 rpm) and for pcv of 40%, using a digital rotational cone and plate microviscometer. Also, in 7 of 32 horses, bv was measured 3 times each, for 3 pcv values (20, 40, and 60%), and at each spindle speed to determine effect of pcv on bv and machine and among-horse variations. Total plasma protein and fibrinogen concentrations were measured in all horses, using a standard refractometer and heat precipitation, respectively. In 7 of 32 horses, quantitative fibrinogen concentration was measured, using a quantitative fibrinogen assay. Plasma protein and fibrinogen concentrations were measured to determine their effect on bv.

Plasma total protein (6.0 to 7.5 g/dl) and fibrinogen (100 to 400 mg/dl) concentrations were within normal reference range for our laboratory. In this study of healthy horses, mean (± sd) bv values obtained for each pcv value and at each spindle speed were: for pcv of 20%, 2.39 ± 0.33 centipoise (cp) at 60 rpm, 2.52 ± 0.35 cp at 30 rpm, 2.80 ± 0.37 cp at 12 rpm, 2.96 ± 0.48 cp at 6 rpm, 3.04 ± 0.62 cp at 3 rpm, and 2.93 ± 0.96 cp at 1.5 rpm; for pcv of 40%, 3.98 ± 0.29 cp at 60 rpm, 4.40 ± 0.38 cp at 30 rpm, 5.26 ± 0.59 cp at 12 rpm, 6.36 ± 0.93 cp at 6 rpm, 7.34 ± 1.46 cp at 3 rpm, and 8.33 ± 2.61 cp at 1.5 rpm; and for pcv of 60%, 7.21 ± 0.91 cp at 60 rpm, 8.27 ± 1.05 cp at 30 rpm, 10.46 ± 1.38 cp at 12 rpm, 13.69 ± 1.82 cp at 6 rpm, 18.12 ± 2.81 cp at 3 rpm, and 23.44 ± 3.45 cp at 1.5 rpm.

Blood viscosity increased with decreasing rpm and shear rate. Blood viscosity also increased with increasing pcv at each spindle speed. The bv for healthy horses at pcv of 40% was fitted to an asymptotic model. The estimated coefficients were:
BV(PCV=40%)=4.346+4.877e-0.116.rpm

Significant (P < 0.05) correlation between total plasma protein concentration and bv was found for pcv of 40% at all spindle speeds. Furthermore, significant (P < 0.05) correlation between quantitative plasma fibrinogen concentration and bv was found for pcv of 60% at the lower spindle speeds (6, 3, and 1.5 rpm).

The sd of measurement error and the among-horse sd for the digital rotational cone and plate microviscometer were greatest at the low spindle speeds for all pcv. The least variation was found for pcv of 20%.

The digital rotational cone and plate microviscometer is an accurate instrument for measuring bv at multiple pcv and spindle speeds in horses. Packed cell volume, plasma protein concentration, and fibrinogen concentration appear to affect bv in horses. Blood viscosity values obtained in this study will give insights into factors affecting bv in horses and will serve as a baseline for comparison with values in diseased horses.

Summary

Blood viscosity (bv) was measured in 32 healthy horses at 6 spindle speeds (60, 30, 12, 6, 3, and 1.5 rpm) and for pcv of 40%, using a digital rotational cone and plate microviscometer. Also, in 7 of 32 horses, bv was measured 3 times each, for 3 pcv values (20, 40, and 60%), and at each spindle speed to determine effect of pcv on bv and machine and among-horse variations. Total plasma protein and fibrinogen concentrations were measured in all horses, using a standard refractometer and heat precipitation, respectively. In 7 of 32 horses, quantitative fibrinogen concentration was measured, using a quantitative fibrinogen assay. Plasma protein and fibrinogen concentrations were measured to determine their effect on bv.

Plasma total protein (6.0 to 7.5 g/dl) and fibrinogen (100 to 400 mg/dl) concentrations were within normal reference range for our laboratory. In this study of healthy horses, mean (± sd) bv values obtained for each pcv value and at each spindle speed were: for pcv of 20%, 2.39 ± 0.33 centipoise (cp) at 60 rpm, 2.52 ± 0.35 cp at 30 rpm, 2.80 ± 0.37 cp at 12 rpm, 2.96 ± 0.48 cp at 6 rpm, 3.04 ± 0.62 cp at 3 rpm, and 2.93 ± 0.96 cp at 1.5 rpm; for pcv of 40%, 3.98 ± 0.29 cp at 60 rpm, 4.40 ± 0.38 cp at 30 rpm, 5.26 ± 0.59 cp at 12 rpm, 6.36 ± 0.93 cp at 6 rpm, 7.34 ± 1.46 cp at 3 rpm, and 8.33 ± 2.61 cp at 1.5 rpm; and for pcv of 60%, 7.21 ± 0.91 cp at 60 rpm, 8.27 ± 1.05 cp at 30 rpm, 10.46 ± 1.38 cp at 12 rpm, 13.69 ± 1.82 cp at 6 rpm, 18.12 ± 2.81 cp at 3 rpm, and 23.44 ± 3.45 cp at 1.5 rpm.

Blood viscosity increased with decreasing rpm and shear rate. Blood viscosity also increased with increasing pcv at each spindle speed. The bv for healthy horses at pcv of 40% was fitted to an asymptotic model. The estimated coefficients were:
BV(PCV=40%)=4.346+4.877e-0.116.rpm

Significant (P < 0.05) correlation between total plasma protein concentration and bv was found for pcv of 40% at all spindle speeds. Furthermore, significant (P < 0.05) correlation between quantitative plasma fibrinogen concentration and bv was found for pcv of 60% at the lower spindle speeds (6, 3, and 1.5 rpm).

The sd of measurement error and the among-horse sd for the digital rotational cone and plate microviscometer were greatest at the low spindle speeds for all pcv. The least variation was found for pcv of 20%.

The digital rotational cone and plate microviscometer is an accurate instrument for measuring bv at multiple pcv and spindle speeds in horses. Packed cell volume, plasma protein concentration, and fibrinogen concentration appear to affect bv in horses. Blood viscosity values obtained in this study will give insights into factors affecting bv in horses and will serve as a baseline for comparison with values in diseased horses.

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