Objective—To determine whether a limited sampling time method based on serum iohexol clearance (Cliohexol) would yield estimates of glomerular filtration rate (GFR) in clinically normal horses similar to those for plasma creatinine clearance (Clcreatinine).
Animals—10 clinically normal adult horses.
Procedures—A bolus of iohexol (150 mg/kg) was administered IV, and serum samples were obtained 5, 20, 40, 60, 120, 240, and 360 minutes after injection. Urinary clearance of exogenous creatinine was measured during three 20-minute periods. The GFR determined by use of serum Cliohexol and plasma Clcreatinine was compared with limits of agreement plots.
Results—Values obtained for plasma Clcreatinine ranged from 1.68 to 2.69 mL/min/kg (mean, 2.11 mL/min/kg). Mean serum Cliohexol was 2.38 mL/min/kg (range, 1.95 to 3.33 mL/min/kg). Limits of agreement plots indicated good agreement between the methods.
Conclusions and Clinical Relevance—Use of serum Cliohexol yielded estimates of GFR in clinically normal adult horses similar to those for plasma Clcreatinine. This study was the first step in the evaluation of the use of serum Cliohexol for estimating GFR in adult horses.
Objective—To determine whether pharmacokinetic
analysis of data derived from a single IV dose of
iohexol could be used to predict creatinine clearance
and evaluate simplified methods for predicting serum
clearance of iohexol with data derived from 2 or 3
blood samples in clinically normal foals.
Animals—10 healthy foals.
Procedure—Serum disposition of iohexol and exogenous
creatinine clearance was determined simultaneously
in each foal (5 males and 5 females). A 3-compartment
model of iohexol serum disposition was
selected via standard methods. Iohexol clearance calculated
from the model was compared with creatinine
clearance. Separate limited-sample models were
created with various combinations of sample times
from the terminal slope of the plasma versus time
profile for iohexol. Correction factors were determined
for the limited-sample models, and iohexol
clearance calculated via each method was compared
with exogenous creatinine clearance by use of
method comparison techniques.
Results—Mean exogenous creatinine clearance was
2.17 mL/min/kg. The disposition of iohexol was best
described by a 3-compartment open model. Mean
clearance value for iohexol was 2.15 mL/min/kg and
was not significantly different from mean creatinine
clearance. A method for predicting serum iohexol
clearance based on a 2-sample protocol (3- and 4-hour
samples) was developed.
Conclusions and Clinical Relevance—Iohexol clearance
can be used to predict exogenous creatinine
clearance and can be determined from 2 blood samples
taken after IV injection of iohexol. Appropriate
correction factors for adult horses and horses with
abnormal glomerular filtration rate need to be determined.
(Am J Vet Res 2003;64:1486–1490)