Simplified Methods for Estimation of Plasma Clearance of Iohexol in Dogs and Cats

Abstract

The purpose of this study was to evaluate simplified methods for iohexol plasma clearance estimation in dogs and cats. Serial blood samples were taken before and 5, 20, 40, 60, 80, 100, 120, 150, 180, and 240 minutes after a bolus injection of iohexol in 51 dogs and 25 cats. Iohexol plasma concentration was determined with X-ray fluorescence. Clearance was calculated by dividing the injected dose by the area under the plasma tracer elimination curve estimated with a 2-compartment pharmacologic model. Clearance was normalized to body surface area (BSA). The 10-point clearance was used as a reference for the evaluation of simplified methods. A 2-sample method based on a single exponential fit and a single-sample method based on a linear quadratic model were investigated. Simplified methods were evaluated by calculating the standard deviation of the difference (SDD) between the clearances obtained with the simplified methods and the 10-point reference method. All combinations of sampling times were evaluated. The best sampling times were chosen for dogs and cats as the ones yielding the lowest SDD. Linear regression analysis was performed between the reference method and the optimized simplified methods. The best combination of time for the 2-sample method was 5 and 120 minutes in dogs and 20 and 180 minutes in cats. The best time for sampling in the single-sample method was 120 minutes in dogs and 80 minutes in cats. Plasma clearance of iohexol can be estimated in dogs and cats from 1 or 2 blood samples with a reasonable margin of error.

Effect of MK‐467 on organ blood flow parameters detected by contrast‐enhanced ultrasound in dogs treated with dexmedetomidine

“…Although glomerular filtration rate (GFR) was not calculated in this study, the differences in iohexol plasma concentrations between the treatments suggested that the decrease in the GFR after DEX was alleviated by MK‐467, as GFR inversely correlates with iohexol plasma concentration (Gleadhill & Michell ; Goy‐Thollot et al. ). Thus, the addition of MK‐467 could be beneficial for kidneys and GFR since this compound alleviates the effects of DEX on renal blood flow.…”

Determination of Glomerular Filtration Rate in Adult Horses and Donkeys by Single IV Administration of Iohexol

“…Moreover, it is stressful for animals and not well accepted by the owner. In the present article, threepoint simplified models have been evaluated for horses and donkeys, as in other species [31][32][33]. The three-sample plasma clearance of IOX was chosen because it is the minimum number of samples required to calculate plasma clearance with a one-compartment pharmacokinetic model, to decrease the chance of errors and increase the accuracy of the GFR estimation [11,34].…”

An overview of glomerular filtration rate testing in dogs and cats

“…In people, body surface area is used for standardization rather than body weight. Some veterinary studies have applied this method (Moe and Heiene, 1995; Goy-Thollot et al, 2006a; Goy-Thollot et al, 2006b); however, the most appropriate formula for estimating body surface area in veterinary species is unknown. Extracellular fluid volume (ECFV) has also been used as a method of standardization, (Bexfield et al, 2008; Heiene et al, 2009) because ECFV regulation is closely related to GFR; however, results have been variable and this method needs to be evaluated more before its use can be recommended.…”

“…Obtaining two plasma samples 5 and 120 min following marker injection in dogs and 20 and 180 min after injection in cats allows assessment of GFR with an acceptable margin of error (Goy-Thollot et al, 2006a). In addition, a 3-sample plasma clearance of iohexol protocol in healthy dogs of various body sizes also demonstrated good results (Bexfield et al, 2008) comparable to previous studies (Moe and Heiene, 1995; Brown et al, 1996a; Finco et al, 2001; Goy-Thollot et al, 2006a). In cats, two-and four-sample plasma clearance of iohexol has also provided accurate results when compared with plasma clearance of exogenous creatinine (Heiene et al, 2009).…”