Objective—To evaluate cyclooxygenase (COX) selectivity
of several nonsteroidal anti-inflammatory drugs
(NSAID) in canine blood in vitro.
Animals—11 healthy adult male hound crosses.
Procedure—9 NSAID were studied at 5 concentrations.
Thromboxane B2 (TxB2) was assayed as a
measure of COX-1 activity in clotted blood.
Prostaglandin E2 (PGE2) was assayed as a measure
of COX-2 activity in heparinized, lipopolysaccharide
(LPS)-stimulated blood. All assays were competitive
ELISA tests. Cyclooxygenase selectivity was
expressed as a ratio of the concentration of an
NSAID that inhibited 50% of the activity (IC50) of
COX-1 to the IC50 of COX-2. A separate ratio of the
concentration that inhibited 80% of COX activity
(IC80) was also determined. A ratio of
< 1.0 indicated selectivity for COX-1, whereas a
ratio of > 1.0 indicated COX-2 selectivity.
Results—Ketoprofen, aspirin, and etodolac were
COX-1 selective. Piroxicam, meloxicam, and carprofen
had COX-2 selectivity. The IC50 and IC80 values
were similar for most NSAID.
Conclusion and Clinical Relevance—This methodology provides repeatable
data from individual dogs and is comparable to results
of previous in vitro and ex vivo models. Findings are
also consistent with those of canine studies performed
in vivo, suggesting that this is a viable in vitro
assessment of the COX selectivity of NSAID in dogs.
(Am J Vet Res 2002;63:91–94)
Procedure—Cardiac output was measured in 6 anesthetized
horses as lithium dilution cardiac output
(LiDCO), thermodilution cardiac output (TDCO), and
transesophageal Doppler echocardiographic cardiac
output (DopplerCO). For the LiDCO measurements,
lithium chloride was administered IV, and cardiac output
was derived from the arterial lithium dilution curve.
Sodium nitroprusside, phenylephrine hydrochloride,
and dobutamine hydrochloride were used to alter cardiac
output. Experiments were divided into 4 periods.
During each period, 3 LiDCO measurements, 3
DopplerCO measurements, and 3 sets of 3 TDCO
measurements were obtained.
Results—70 comparisons were made between
LiDCO, DopplerCO, and triplicate TDCO measurements
over a range of 10 to 43 L/min. The mean
(± SD) of the differences of LiDCO – TDCO was –0.86
± 2.80 L/min; LiDCO = –1.90 + 1.05 TDCO (r = 0.94).
The mean of the differences of DopplerCO – TDCO
was 1.82 ± 2.67 L/min; DopplerCO = 2.36 + 0.98
TDCO (r = 0.94). The mean of the differences of
LiDCO – DopplerCO was –2.68 ± 3.01 L/min; LiDCO =
–2.53 + 0.99 DopplerCO (r = 0.93).
Conclusions and Clinical Relevance—These results
indicate that lithium dilution is a suitable method for
measuring cardiac output in horses. As well as being
accurate, it avoids the need for pulmonary artery
catheterization and is quick and safe to use.
Monitoring cardiac output during anesthesia in horses
may help reduce the high anesthetic mortality in this
species. (Am J Vet Res 2000;61:731–737)