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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 Blood was withdrawn from the carotid artery through a densitometer cuvette to measure the dye concentration.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

Abstract

Objective

To study biomechanical characteristics of the normal and surgically altered canine thoracolumbar vertebral column to determine the effects of surgery and trauma on lateral stability.

Animals

The T13-L1 vertebral motion units of 48 mixed-breed dogs were dissected free of surrounding musculature and prepared for biomechanical testing by cross-pinning the vertebral bodies and mounting in polymethylmethacrylate.

Procedure

Normal and surgically altered spinal specimens were subjected to lateral bending. The mean slope of the bending moment versus angular displacement curve and the load to failure were compared between treatment groups and significance was determined by the method of least squares (P < 0.05). Specimens were surgically altered by facetectomy, lateral fenestration, diskectomy, and combinations of these procedures. Each specimen was subjected to lateral bending to failure at a rate of 2.5 cm/min in a swing arm bending jig designed to simulate 4-point bending and subject the specimen to pure bending.

Results

Only specimens undergoing diskectomy had a significant decrease in slope and load at failure. Unilateral and bilateral facetectomies and fenestration induced a nonsignificant decrease in stiffness, compared with control specimens.

Conclusions

Fenestrations and facetectomies do not appear to increase the risk of injury to the canine thoracolumbar spinal cord during lateral bending.

Clinical Relevance

Fenestrations and facetectomies, as used in routine laminectomies, may be performed without concern for significant destabilization of the spine in lateral bending; however, it is possible that thoracolumbar spinal fractures involving only the vertebral body may significantly destabilize the spine in all modes of bending. (Am J Vet Res 1996;57:1228-1232)

Free access
in American Journal of Veterinary Research