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  • Author or Editor: Doris H. Dyson x
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Abstract

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.

Full access
in American Journal of Veterinary Research

SUMMARY

A controlled study of the cardiovascular responses in horses anesthetized with acepromazine (0.05 mg/kg of body weight, iv), guaifenesin (100 mg/kg, iv), thiamylal (5.0 mg/kg, iv), and halothane in O2 (1.2 to 1.4% end-expired concentration) was performed to determine whether hypotension could be prevented by use of various treatments. Six horses were given 5 treatments in a randomized sequence; no treatment (control), methoxamine (0.04 mg/kg, iv), lactated Ringer solution (20.0 ml/kg, iv), 7.5% hypertonic saline solution (4.0 ml/kg, iv), or constant infusion of dobutamine (5.0 mg/kg/min, iv) during anesthesia. Heart rate, ECG, blood pressure, central venous pressure, cardiac output, blood gas analysis, pcv, and plasma total protein concentration were measured during the study.

Compared with the control value, an increase in blood pressure during halothane administration was observed after administration of lactated Ringer solution, hypertonic saline solution, or dobutamine (P < 0.05). The improved blood pressure response to hypertonic saline solution and dobutamine was related to an increase in cardiac output, which was statistically significant (P < 0.05). Other statistically significant differences in cardiopulmonary responses among treatments were not observed during anesthesia. The pcv was increased in response to dobutamine infusion, and plasma total protein concentration was reduced in response to administration of hypertonic saline or lactated Ringer solution.

Free access
in American Journal of Veterinary Research

Abstract

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.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether administration of the nonsteroidal anti-inflammatory drugs meloxicam or carprofen to healthy dogs that were subsequently anesthetized and subjected to painful electrical stimulation has adverse effects on renal function as measured by glomerular filtration rate (GFR) and evaluation of serum concentrations of urea and creatinine.

Animals—6 male and 6 female healthy young-adult Beagles.

Procedure—A study was conducted in accordance with a randomized crossover Latin-square design. One of 3 treatments (saline [0.9% NaCl] solution, 0.2 mg of meloxicam/kg, or 4.0 mg of carprofen/kg) was administered IV 1 hour before anesthesia was induced by use of drugs in accordance with a standard anesthetic protocol (butorphanol tartrate and acepromazine maleate as preanesthetic medications, ketamine hydrochloride and diazepam for induction, and maintenance with isoflurane). Anesthetized dogs were subjected to intermittent electrical stimulation for 30 minutes. Direct, mean arterial blood pressure; heart rate; and respiratory rate were monitored. End-tidal isoflurane concentration was maintained at 1.5 times the minimum alveolar concentration. The GFR, as measured by plasma clearance of 99mTc-diethylenetriaminepentaacetic acid, and serum concentrations of serum and creatinine were determined 24 hours after induction of anesthesia.

Results—Neither meloxicam nor carprofen significantly affected GFR or serum concentrations of urea and creatinine, compared with values for the saline treatment.

Conclusions and Clinical Relevance—When administered 1 hour before onset of anesthesia and painful electrical stimulation, meloxicam or carprofen did not cause clinically important alterations of renal function in young healthy dogs. (Am J Vet Res 2004;65:1384–1390)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To compare induction with hydromorphone and diazepam (HydroD) or oxymorphone and diazepam (OxyD) followed by maintenance with isoflurane in dogs with induced hypovolemia.

Animals—6 healthy mixed-breed dogs.

Procedure—The study used a crossover design. Measurements were obtained in normovolemic dogs during isoflurane. Hypovolemia was induced (blood loss of 30 mL/kg) and measurements repeated following recovery from anesthesia, after HydroD (hydromorphone, 0.1 mg/kg; diazepam, 0.2 mg/kg; IV) or OxyD (oxymorphone, 0.05 mg/kg; diazepam, 0.2 mg/kg; IV), after another dose of the same opioid, during administration of isoflurane (end-tidal concentration, 0.9%), and after glycopyrrolate (0.01 mg/kg, IV). Significant changes were identified.

Results—Induction effect was evident within 1 minute. All dogs were intubated after the second dose of opioid. No significant differences were found between inductions. The HydroD decreased heart rate (mean ± SEM, –41 ± 9.8 beats/min), whereas both inductions increased stroke index (0.4 ± 0.09 mL/kg/beat) and caused moderate respiratory depression. Cardiac index was decreased (±30.2 ± 6.04 mL/kg/min) and there was minor metabolic acidosis during isoflurane following HydroD, compared with values for anesthetized normovolemic dogs. Glycopyrrolate increased heart rate (50 ± 8.6 beats/min) and decreased systolic blood pressure (–23.2 ± 4.87 mm Hg) in dogs induced with HydroD and decreased stroke index (–0.3 ± 0.08 mL/kg/beat) for both inductions.

Conclusions and Clinical Relevance—Similar effects were detected after administration of HydroD or OxyD in hypovolemic dogs. Either combination should be safe for use in hypovolemic dogs. Administration of glycopyrrolate was not beneficial. (Am J Vet Res 2005;66:1227–1237)

Full access
in American Journal of Veterinary Research

Abstract

Objective

To evaluate cardiovascular effects of epidurally administered oxymorphone (OXY) and an OXY-bupivacaine combination (O/B) in halothaneanesthetized dogs.

Animals

6 dogs.

Procedure

In a randomized crossover design study, dogs were anesthetized with halothane and given OXY, O/B, and saline solution (SAL). Eucapnia and end-tidal halothane concentration of 1.2% were established. Heart rate (HR), systemic and pulmonary arterial pressures, central venous pressure (CVP), and cardiac output were measured at baseline and 5, 15, 30, 45, 60, and 75 minutes after treatment. At 90 minutes, glycopyrrolate was administered IV, and measurements were repeated at 95 minutes. Cardiac index (CI), stroke volume, stroke index, systemic vascular resistance (SVR), and left ventricular work were calculated. End-tidal halothane concentration was decreased to 0.8% from 17 to 45 minutes and to 0.5% from 47 to 95 minutes for OXY and O/B, where-as for SAL, it was maintained at 1.5 and 1.2%, respectively. Samples were obtained at 0, 2, 5, 15, 30, 45, 60, and 95 minutes for measurement of serum opiate concentration and comparison with values after IM administration of OXY.

Results

HR decreased, but CVP and SVR increased in response to OXY and O/B. These changes were reversed after IV administration of glycopyrrolate, resulting in significant increase in CI, compared with that in response to SAL. Serum opiate concentration increased markedly and peaked within 15 minutes after OXY and O/B administration but did not differ from values after IM administration.

Conclusions

Epidural administration of OXY results in rapid systemic uptake and decreased HR. Glycopyrrolate administration improves HR, resulting in improved CI at equipotent halothane concentrations. (Am J Vet Res 1999;60:194–200)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To assess the usefulness of glycopyrrolate (GLY) in preventing the decrease in cardiac index (Cl) usually caused by xylazine (XYL)/ketamine (KET)-induced anesthesia in horses.

Animals

6 healthy horses.

Procedure

Horses were treated with saline solution or 2.5 μg of GLY/kg of body weight, administered IV. 15 minutes later, XYL (1 mg/kg) was administered IV followed 5 minutes later by KET (2 mg/kg) administration. The horses were positioned in left lateral recumbency, insufflated with 15 L of oxygen/min, and maintained for 30 minutes on the infusion of 0.05 mg of XYL and 0.1 mg of KET/kg/min. Mean, systolic, and diastolic arterial blood pressures, mean pulmonary arterial and central venous pressures, heart rate, Cl, and arterial and mixed venous blood gas tensions were recorded up to 40 minutes after anesthesia induction. Intestinal motility was assessed by auscultation of 4 abdominal quadrants for 24 hours after induction. Data were analyzed by Wilcoxon's rank-sum test for nonparametric observations, and by ANOVA for repeated measures and Scheffe's test for continuous parametric variables.

Results

Horses given GLY had significantly higher heart rate; mean, systolic, and diastolic arterial blood pressures; Cl; oxygen delivery; and mixed venous oxygen tensions, with significantly less tissue oxygen extraction, compared with saline-treated horses. Both groups had complete loss of intestinal motility associated with general anesthesia.

Conclusions

GLY significantly reduced the cardiovascular dysfunction attributable to general anesthesia with XYL and KET. The return of intestinal motility was delayed by 3 to 6 hours without causing any serious side effects. (Am J Vet Res 1996;57:1762–1770)

Free access
in American Journal of Veterinary Research

SUMMARY

Midazolam HCl (1.0 or 2.0 mg/kg of body weight) was administered im to 6 Canada geese to determine a sedative dose that would allow positioning for radiologic examination. The effects of both test doses on cardiopulmonary function were evaluated at 5, 10, 15, 20, 30, and 40 minutes after drug administration and were compared with 2 end-tidal isoflurane concentrations (1.5 and 2.5%). The 2.0 mg/kg dosage induced moderate sedation at 15 and 20 minutes; sedation was adequate for positioning the geese. Sedation induced by the 1.0 mg/kg dosage was inadequate. The effects of both test doses on blood pressure, heart rate, and temperature were not significantly different from each other and from baseline data. Respiratory rate increased significantly (P < 0.05) at 10, 15, 20, and 30 minutes with the 2.0 mg/kg dosage, and at 15 and 20 minutes with the 1.0 mg/kg dosage. Blood pressure and respiratory rate were significantly (P < 0.05) decreased with isoflurane when compared with baseline data and the midazolam test doses. The results of this study indicate that midazolam at a dosage of 2.0 mg/kg induces adequate sedation with minimal cardiopulmonary changes, and, as an alternative to general anesthesia with isoflurane, provides a satisfactory level of restraint for radiography.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the cardiopulmonary effects of anesthetic induction with thiopental, propofol, or ketamine hydrochloride and diazepam in dogs sedated with medetomidine and hydromorphone.

Animals—6 healthy adult dogs.

Procedures—Dogs received 3 induction regimens in a randomized crossover study. Twenty minutes after sedation with medetomidine (10 μg/kg, IV) and hydromorphone (0.05 mg/kg, IV), anesthesia was induced with ketamine-diazepam, propofol, or thiopental and then maintained with isoflurane in oxygen. Measurements were obtained prior to sedation (baseline), 10 minutes after administration of preanesthetic medications, after induction before receiving oxygen, and after the start of isoflurane-oxygen administration.

Results—Doses required for induction were 1.25 mg of ketamine/kg with 0.0625 mg of diazepam/kg, 1 mg of propofol/kg, and 2.5 mg of thiopental/kg. After administration of preanesthetic medications, heart rate (HR), cardiac index, and PaO 2 values were significantly lower and mean arterial blood pressure, central venous pressure, and PaCO 2 values were significantly higher than baseline values for all regimens. After induction of anesthesia, compared with postsedation values, HR was greater for ketamine-diazepam and thiopental regimens, whereas PaCO 2 tension was greater and stroke index values were lower for all regimens. After induction, PaO 2 values were significantly lower and HR and cardiac index values significantly higher for the ketamine-diazepam regimen, compared with values for the propofol and thiopental regimens.

Conclusions and Clinical Relevance—Medetomidine and hydromorphone caused dramatic hemodynamic alterations, and at the doses used, the 3 induction regimens did not induce important additional cardiovascular alterations. However, administration of supplemental oxygen is recommended.

Full access
in American Journal of Veterinary Research