The Relationship between Some Plasma Clearance Methods for Estimation of Glomerular Filtration Rate in Dogs with Pyometra

Abstract

The purpose of the present study was to compare different pharmacokinetic models for estimation of glomerular filtration rate (GFR) in 50 dogs with pyometra. GFR was estimated by plasma clearance (CLplasma) of iohexol by four 1-compartment methods (CL1c), a 2-compartment method (CL2c), and the trapezoidal method (CLtr). Regression analysis was performed to establish correction formulas for prediction of CLtr from the CL1c values and to find optimal times of sampling. Standardization of clearance values to body weight (kg), body surface area (m2) and extracellular fluid volume (ECFV) was compared by ranking of values. CLtr and CL2c values were similar, whereas CL1c overestimated CLtr. CLtr could be predicted from 2 samples at 2 and 3 hours after injection, using the formula CLtr = 4.52 + 0.84CL1c - 0.00080(CL1c)2 (R2 = .97). Similar relationships were found when sampling at 2 and 4 hours or at 2, 3 and 4 hours after injection, whereas predictions from the 3- and 4-hour estimates were not optimal (R2 = .79). The 2-sample methods for calculating GFR/ECFV generally produced unreliable predictions of the complete curve GFR/ECFV values. For some dogs, the choice of standardization procedure substantially changed the apparent level of renal function relative to other dogs in the study. We conclude that by applying an appropriate correction formula, GFR may be estimated using 2 blood samples at 2 and 3, or 2 and 4 hours after injection of iohexol when renal function is normal or moderately reduced. The method of standardizing the analysis with respect to body size may influence interpretation of the results substantially.

Cardiac troponin I levels in canine pyometra

“…Multiple organ dysfunctions and coagulopathies such as disseminated intravascular coagulation (DIC) are other severe complications that can induce myocard injury [21]. Further, the renal function is often negatively affected in dogs with pyometra which might lead to secondary uraemic myocardial damage [33-35]. In the present study 53% of the pyometra dogs were SIRS-positive, which is in the range of the proportion previously reported [2].…”

“…Structural damage of proximal tubuli and some decrease in glomerular filtration rate have been demonstrated in dogs with pyometra [34,35]. Increased cTnI levels have also been demonstrated in azotaemic cats and dogs [37].…”

Determination of Extracellular Fluid Volume in Healthy and Azotemic Cats

“…The relationship between slope‐intercept GFR/ECFV (β) and multisample GFR/ECFV (( A /α +  B /β)/( A /α 2  +  B /β 2 )) in cats was found to be linear in this study and a second order polynomial did not improve the fit of the regression model. This relationship is in agreement with that of 50 dogs undergoing surgery for pyometra28 but contradicts an earlier canine study in which the relationship was found to be nonlinear 15. Slope‐intercept GFR/ECFV has been shown to have a nonlinear relationship with multisample GFR/ECFV in human patients 13, 14.…”

Glomerular filtration rate in dogs as estimated via plasma clearance of inulin and iohexol and use of limited-sample methods

“…However, methods for measuring urinary clearance of a substrate require accurate collection of urine, which may be cumbersome in animals. 6 Inulin is one of the markers used for GFR estimation; however, inulin is expensive and sample handling and laboratory analysis of inulin is cumbersome. However, they have greater potential for error if there is extrarenal clearance of the filtration marker or if the pharmacokinetic model used is not appropriate.…”