Objective—To determine the cardiovascular effects of dopamine and dobutamine infusions during nor-movolemia, hypovolemia (HV) through blood loss of 10 mL/kg (HV10), further loss to 25 mL/kg (HV25), and volume replacement (VR) in isoflurane-anesthetized dogs.
Animals—7 healthy young dogs.
Procedures—Dogs were anesthetized with isoflurane 2 times (3 weeks apart). Cardiovascular measurements were obtained for each volume state. The cardiac index (CI) determined by the lithium dilution technique was compared with CI assessed by the arterial pulse contour technique. At each volume state, random treatment with dobutamine or dopamine was assessed (CI by the arterial pulse contour technique). Ten-minute treatments with 3 and6 μg of dobutamine/kg/min or 7 and 14 μg of dopamine/kg/min (low and high doses, respectively) were administered sequentially. Differences from baseline were determined for volume, drug, and dose effects.
Results—Significant proportional changes in blood pressure (BP), stroke index (SI), and CI were evident with changes in volume state. Systemic vascular resistance (SVR) decreased after VR. Dobutamine induced little change in BP; increased heart rate (HR), SI, and CI; and decreased SVR (high dose). Dopamine increased BP and SI, did not change CI, and increased SVR (high dose). The arterial pulse contour technique underestimated changes in CI associated with volume changes.
Conclusions and Clinical Relevance—Isoflurane eliminates clinically obvious compensatory increases in HR during HV. Dopamine is suitable for temporary management of blood loss in isoflurane-anesthetized dogs. Dobutamine increased CI without an associated improvement in BP. The arterial pulse contour monitor should be recalibrated when volume status changes.
Objective—To evaluate the dose-related cardiovascular and urine output (UrO) effects of dopamine hydrochloride and dobutamine hydrochloride, administered individually and in combination at various ratios, and identify individual doses that achieve target mean arterial blood pressure (MAP; 70 mm Hg) and cardiac index (CI; 150 mL/kg/min) in dogs during deep isoflurane anesthesia.
Animals—10 young clinically normal dogs.
Procedures—Following isoflurane equilibration at a baseline MAP of 50 mm Hg on 3 occasions, dogs randomly received IV administration of dopamine (3, 7, 10, 15, and 20 μg/kg/min), dobutamine (1, 2, 4, 6, and 8 μg/kg/min), and dopamine-dobutamine combinations (3.5:1, 3.5:4, 7:2, 14:1, and 14:4 μg/kg/min) in a crossover study. Selected cardiovascular and UrO effects were determined following 20-minute infusions at each dose.
Results—Dopamine caused significant dose-dependent responses and achieved target MAP and CI at 7 μg/kg/min; dobutamine at 2 μg/kg/min significantly affected only CI values. At any dose, dopamine significantly affected UrO, whereas dobutamine did not. Target MAP and CI values were achieved with a dopamine-dobutamine combination at 7:2 μg/kg/min; a dopamine-related dose response for MAP and dopamine- and dobutamine-related dose responses for CI were identified. Changes in UrO were associated with dopamine only.
Conclusions and Clinical Relevance—In isoflurane-anesthetized dogs, a guideline dose for dopamine of 7 μg/kg/min is suggested; dobutamine alone did not improve MAP. Data regarding cardiovascular and UrO effects indicated that the combination of dopamine and dobutamine did not provide greater benefit than use of dopamine alone in dogs.
Objective—To evaluate the use of laparoscopic-assistedjejunostomy feeding tube (J-tube) placement in healthy dogs under sedation with epidural and local anesthesia and compare cardiopulmonary responses during this epidural anesthetic protocol with cardiopulmonary responses during general anesthesia for laparoscopic-assisted or open surgical J-tube placement.
Animals—15 healthy mixed-breed dogs.
Procedures—Dogs were randomly assigned to receive open surgical J-tube placement under general anesthesia (n = 5dogs; group 1), laparoscopic-assisted J-tube placement under general anesthesia (5; group 2), or laparoscopic-assisted J-tube placement under sedation with epidural and local anesthesia (5; group 3). Cardiopulmonary responses were measured at baseline (time 0), every 5 minutes during the procedure (times 5 to 30 minutes), and after the procedure (after desufflation [groups 2 and 3] or at the start of abdominal closure [group 1]). Stroke volume, cardiac index, and O2 delivery were calculated.
Results—All group 3 dogs tolerated laparoscopic-assisted J-tube placement under sedation with epidural and local anesthesia. Comparison of cardiovascular parameters revealed a significantly higher cardiac index, mean arterial pressure, and O2 delivery in group 3 dogs, compared with group 1 and 2 dogs. Minimal differences in hemodynamic parameters were foundbetween groups undergoing laparoscopic-assistedandopen surgical J-tube placement under general anesthesia (ie, groups 1 and 2); these differences were not considered to be clinically important in healthy research dogs.
Conclusions and Clinical Relevance—Sedation with epidural and local anesthesia provided satisfactory conditions for laparoscopic-assisted J-tube placement in healthy dogs; this anesthetic protocol caused less cardiopulmonary depression than general anesthesia and may represent a better choice for J-tube placement in critically ill patients.
Objective—To assess agreement between arterial
pressure waveform–derived cardiac output (PCO) and
lithium dilution cardiac output (LiDCO) systems in
measurements of various levels of cardiac output
(CO) induced by changes in anesthetic depth and
administration of inotropic drugs in dogs.
Animals—6 healthy dogs.
Procedure—Dogs were anesthetized on 2 occasions
separated by at least 5 days. Inotropic drug administration
(dopamine or dobutamine) was randomly
assigned in a crossover manner. Following initial calibration
of PCO measurements with a LiDCO measurement,
4 randomly assigned treatments were
administered to vary CO; subsequently, concurrent
pairs of PCO and LiDCO measurements were
obtained. Treatments included a light plane of anesthesia,
deep plane of anesthesia, continuous infusion
of an inotropic drug (rate adjusted to achieve a mean
arterial pressure of 65 to 80 mm Hg), and continuous
infusion of an inotropic drug (7 µg/kg/min).
Results—Significant differences in PCO and LiDCO
measurements were found during deep planes of
anesthesia and with dopamine infusions but not during
the light plane of anesthesia or with dobutamine
infusions. The PCO system provided higher CO measurements
than the LiDCO system during deep
planes of anesthesia but lower CO measurements
during dopamine infusions.
Conclusions and Clinical Relevance—The PCO system
tracked changes in CO in a similar direction as
the LiDCO system. The PCO system provided better
agreement with LiDCO measurements over time
when hemodynamic conditions were similar to those
during initial calibration. Recalibration of the PCO system
is recommended when hemodynamic conditions
or pressure waveforms are altered appreciably. (Am J Vet Res 2005;66:1430–1436)
Objective—To determine the disposition of a bolus of meloxicam (administered IV) in horses and donkeys (Equus asinus) and compare the relative pharmacokinetic variables between the species.
Animals—5 clinically normal horses and 5 clinically normal donkeys.
Procedures—Blood samples were collected before and after IV administration of a bolus of meloxicam (0.6 mg/kg). Serum meloxicam concentrations were determined in triplicate via high-performance liquid chromatography. The serum concentration-time curve for each horse and donkey was analyzed separately to estimate standard noncompartmental pharmacokinetic variables.
Results—In horses and donkeys, mean ± SD area under the curve was 18.8 ± 7.31 μg/mL/h and 4.6 ± 2.55 μg/mL/h, respectively; mean residence time (MRT) was 9.6 ± 9.24 hours and 0.6 ± 0.36 hours, respectively. Total body clearance (CLT) was 34.7 ± 9.21 mL/kg/h in horses and 187.9 ± 147.26 mL/kg/h in donkeys. Volume of distribution at steady state (VDSS) was 270 ± 160.5 mL/kg in horses and 93.2 ± 33.74 mL/kg in donkeys. All values, except VDSS, were significantly different between donkeys and horses.
Conclusions and Clinical Relevance—The small VDSS of meloxicam in horses and donkeys (attributed to high protein binding) was similar to values determined for other nonsteroidal anti-inflammatory drugs. Compared with other species, horses had a much shorter MRT and greater CLT for meloxicam, indicating a rapid elimination of the drug from plasma; the even shorter MRT and greater CLT of meloxicam in donkeys, compared with horses, may make the use of the drug in this species impractical.
Objective—To evaluate feasibility of performing
laparoscopic-assisted placement of a jejunostomy
feeding tube (J-tube) and compare complications
associated with placement, short-term feedings, and
medium-term healing with surgically placed tubes in
Animals—15 healthy mixed-breed dogs.
Procedure—Dogs were randomly allocated to
undergo open surgical or laparoscopic-assisted J-tube
placement. Required nutrients were administered by
a combination of enteric and oral feeding while monitoring
for complications. Radiographic contrast studies
documented tube direction and location, altered
motility, or evidence of stricture.
Results—Jejunostomy tubes were successfully
placed in the correct location and direction in all dogs.
In the laparoscopic group, the ileum was initially
selected in 2 dogs, 2 dogs developed moderate hemorrhage
at a portal site, and 2 J-tubes kinked during
placement but were successfully readjusted postoperatively.
All dogs tolerated postoperative feedings.
All dogs developed minor ostomy site inflammation,
and 1 dog developed bile-induced dermatitis at the
ostomy site. Despite mild, transient neutrophilia, no
significant difference was noted in WBC counts
between groups. No dog had altered gastric motility
or evidence of stricture, although the jejunopexy site
remained identifiable in several dogs at 30 days.
Conclusions and Clinical Relevance—Requirements
for successful J-tube placement were met by use of a
laparoscopic-assisted technique, and postoperative
complications were mild and comparable to those
seen with surgical placement. Laparoscopic-assisted
J-tube placement compares favorably to surgical
placement in healthy dogs and should be considered
as an option for dogs requiring enterostomy feeding
but not requiring a celiotomy for other reasons. (J Am
Vet Med Assoc 2004;225:65–71)