Objective—To quantify and compare intracellular
magnesium concentrations (Mgi) in clinically normal
dogs (control dogs) and dogs that have gastric dilatation-
volvulus (GDV dogs) and to determine whether
there is a difference in Mgi and serum magnesium
concentrations (Mgs) between GDV dogs with and
without cardiac arrhythmias.
Animals—41 control dogs and 21 GDV dogs.
Procedure—Rectus abdominis muscle specimens
were obtained from control and GDV dogs for determination
of Mgi. Blood samples were obtained from
GDV dogs for determination of Mgs, and dogs were
monitored for 48 hours for cardiac arrhythmias.
Muscle specimens were frozen at –40 C, oven dried
at 95 C, and digested with concentrated nitric acid.
Multielemental analyses were performed by simultaneous/
sequential inductively coupled plasma-atomic
emission spectroscopy with fixed-cross flow nebulization.
The Mgi was standardized to sulfur content to
correct for the amount of fat and fascia in the muscle
specimen. Mean (± SEM) values were recorded in
parts per million (ppm).
Results—There were no significant differences in
Mgi between control (627 ± 11.1 ppm) and GDV (597
± 20.5 ppm) dogs, in Mgi between GDV dogs with
(590 ± 34 ppm) and without (584 ± 29 ppm) cardiac
arrhythmias, and in Mgs between GDV dogs with
(1.77 ± 0.26 ppm) and without (1.51 ± 0.09 ppm) cardiac
arrhythmias. There was no correlation between
Mgs and Mgi ( R2=0.0001).
Conclusions and Clinical Relevance—Results indicate
that Mg depletion is not pathophysiologically
important in dogs with GDV and does not play a role
in the cardiac arrhythmias detected in these patients.
(Am J Vet Res 2000;61:1415–1417)
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)