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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine changes in splanchnic oxygen extraction ratio during experimentally induced portal hypertension in dogs.

Animals—6 clinically normal dogs.

Procedure—Standard midline laparotomy and median sternotomy were performed in anesthetized dogs. Baseline measurements of arterial blood pressure, aortic blood flow, portal vein blood flow, and portal vein pressure were acquired, and arterial, venous, and portal vein blood samples were obtained to determine systemic and splanchnic oxygen extraction ratios. The portal vein was gradually occluded until a pressure of 18 cm of H2O was reached; this pressure was maintained for 30 minutes, and measurements and collection of blood samples were repeated.

Results—Portal vein blood flow decreased significantly from 457 ± 136 ml/min before to 266 ± 83 ml/min after induction of portal hypertension. Oxygen content in the portal vein significantly decreased from 12.3 ± 1.85 to 8.2 ± 2.31%, and splanchnic oxygen extraction ratio significantly increased from 15.8 ± 6.2 to 37.4 ± 10.9% during portal hypertension. There was a significant inverse correlation between portal vein blood flow and splanchnic oxygen extraction ratio at baseline and during portal hypertension.

Conclusion and Clinical Relevance—An increase in splanchnic oxygen extraction ratio is evident with partial attenuation of the portal vein and the concurrent decrease in portal vein blood flow. Correlation of oxygen extraction ratio with portal vein blood flow may be a more important indicator for determination of an endpoint to prevent congestion and ischemia of the gastrointestinal tract and pancreas during ligation of portosystemic shunts. (Am J Vet Res 2002;63:15–18)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the effect of sevoflurane on cardiac energetic and hemodynamic parameters in ferrets.

Animals—7 healthy domesticated ferrets.

Procedure—Sevoflurane was used as the sole anesthetic agent for general anesthesia in ferrets. Standard midline laparotomy and median sternotomy were performed to permit instrumentation. Myocardial blood flow was determined by use of colored microsphere technology. Measurements and blood samples were obtained at 1.25%, 2.5%, and 3.75% expired concentration of sevoflurane.

Results—A dose-dependent decrease in arterial blood pressure, left ventricular pressure, systemic vascular resistance, aortic flow, and dp/dt (an index of contractility) was detected as expired concentration of sevoflurane increased. Heart rate, central venous pressure, coronary vascular resistance, myocardial oxygen extraction ratio, and (the time constant of relaxation) were unchanged. Cardiac external work decreased, as did myocardial oxygen consumption, causing increased cardiac efficiency at higher concentrations of sevoflurane.

Conclusions and Clinical Relevance—Sevoflurane caused minimal and predictable cardiovascular effects in ferrets without increasing myocardial metabolic demands. Data obtained from this study have not been previously reported for a species that is being commonly used in cardiovascular research. These findings also support use of sevoflurane as a safe inhalant anesthetic in ferrets for clinical and research settings. ( Am J Vet Res 2004:65:653–658)

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in American Journal of Veterinary Research
in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate effects of one-lung ventilation on oxygen delivery in anesthetized dogs with an open thoracic cavity.

Animals—8 clinically normal adult Walker Hound dogs.

Procedure—Each dog was anesthetized and subjected to one-lung ventilation during a period when it had an open thoracic cavity. A Swan-Ganz catheter was used to measure hemodynamic variables and obtain mixed-venous blood samples. A catheter was inserted in the dorsal pedal artery to measure arterial pressure and obtain arterial blood samples. Oxygen delivery index was calculated and used to assess effects of one-lung ventilation on cardiopulmonary function. Effects on hemodynamic and pulmonary variables were analyzed.

Results—One-lung ventilation caused significant decreases in PaO2, arterial oxygen saturation (SaO2), mixed-venous oxygen saturation, and arterial oxygen content (CaO2). One-lung ventilation caused significant increases in PaCO2, physiologic dead space, and alveolar-arterial oxygen difference. Changes in SaO2, CaO2, and PaCO2, although significantly different, were not considered to be of clinical importance. One-lung ventilation induced a significant increase in pulmonary arterial wedge pressure, mean pulmonary artery pressure, and shunt fraction. One-lung ventilation did not have a significant effect on cardiac index, systemic vascular resistance index, pulmonary vascular resistance index, and oxygen delivery index.

Conclusions and Clinical Relevance—One-lung ventilation affected gas exchange and hemodynamic function, although oxygen delivery in clinically normal dogs was not affected during a period with an open thoracic cavity. One-lung ventilation can be used safely in healthy dogs with an open thoracic cavity during surgery. (Am J Vet Res 2003;64:443–448)

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in American Journal of Veterinary Research

Abstract

Objective—To evaluate effects of injection with a nonsteroidal anti-inflammatory drug (NSAID) followed by oral administration of an NSAID on the gastrointestinal tract (GIT) of healthy dogs.

Animals—6 healthy Walker Hounds.

Procedures—In a randomized, crossover design, dogs were administered 4 treatments consisting of an SC injection of an NSAID or control solution (day 0), followed by oral administration of an NSAID or inert substance for 4 days (days 1 through 4). Treatment regimens included carprofen (4 mg/kg) followed by inert substance; saline (0.9% NaCl) solution followed by deracoxib (4 mg/kg); carprofen (4 mg/kg) followed by carprofen (4 mg/kg); and carprofen (4 mg/kg) followed by deracoxib (4 mg/kg). Hematologic, serum biochemical, and fecal evaluations were conducted weekly, and clinical scores were obtained daily. Endoscopy of the GIT was performed before and on days 1, 2, and 5 for each treatment. Lesions were scored by use of a 6-point scale.

Results—No significant differences existed for clinical data, clinicopathologic data, or lesion scores in the esophagus, cardia, or duodenum. For the gastric fundus, antrum, and lesser curvature, an effect of time was observed for all treatments, with lesions worsening from before to day 2 of treatments but improving by day 5.

Conclusions and Clinical Relevance—Sequential administration of NSAIDs in this experiment did not result in clinically important gastroduodenal ulcers. A larger study to investigate the effect of sequential administration of NSAIDs for longer durations and in dogs with signs of acute and chronic pain is essential to substantiate these findings.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To compare indicators of postoperative pain and behavior in dogs with and without a lowdose ketamine infusion added to usual perioperative management.

Design—Prospective, randomized, blinded clinical study.

Animals—27 dogs undergoing forelimb amputation.

Procedure—Dogs were anesthetized with glycopyrrolate, morphine, propofol, and isoflurane. Thirteen dogs were treated with ketamine IV, as follows: 0.5 mg/kg (0.23 mg/lb) as a bolus before surgery, 10 µg/kg/min (4.5 µg/lb/min) during surgery, and 2 µg/kg/min (0.9 µg/lb/min) for 18 hours after surgery. Fourteen dogs received the same volume of saline (0.9% NaCl) solution. All dogs received an infusion of fentanyl (1 to 5 µg/kg/h [0.45 to 2.27 µg/lb/h]) for the first 18 hours after surgery. Dogs were evaluated for signs of pain before surgery, at the time of extubation, and 1, 2, 3, 4, 12, and 18 hours after extubation. Owners evaluated their dogs' appetite, activity, and wound soreness on postoperative days 2, 3, and 4.

Results—Dogs that received ketamine infusions had significantly lower pain scores 12 and 18 hours after surgery and were significantly more active on postoperative day 3 than dogs that received saline solution infusions.

Conclusions and Clinical Relevance—Results suggest that perioperative administration of low doses of ketamine to dogs may augment analgesia and comfort in the postoperative surgical period. (J Am Vet Med Assoc 2002;221:72–75)

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate the effects on oxygen delivery (DO2) of 2.5 and 5 cm H2O of positive end-expiratory pressure (PEEP) applied to the dependent lung during one-lung ventilation (OLV) in anesthetized dogs with a closed thoracic cavity.

Animals—7 clinically normal adult Walker Hound dogs.

Procedure—Dogs were anesthetized, and catheters were inserted in a dorsal pedal artery and the pulmonary artery. Dogs were positioned in right lateral recumbency, and data were collected during OLV (baseline), after application of 2.5 cm H2O of PEEP for 15 minutes during OLV, and after application of 5 cm H2O of PEEP for 15 minutes during OLV. Hemodynamic and respiratory variables were analyzed and calculations performed to obtain DO2, and values were compared among the various time points by use of an ANOVA for repeated measures.

Results—PEEP induced a significant decrease in shunt fraction that resulted in a significant increase in arterial oxygen saturation. However, it failed to significantly affect arterial oxygen content (CaO2) or cardiac output. Thus, DO2 was not affected in healthy normoxemic dogs as a net result of the application of PEEP.

Conclusions and Clinical Relevance—The use of PEEP during OLV in anesthetized dogs with a closed thoracic cavity did not affect DO2. Use of PEEP during OLV in dogs with a closed thoracic cavity is recommended because it does not affect cardiac output and any gain in CaO2 will be beneficial for DO2 in critically ill patients. (Am J Vet Res 2005;66:978–983)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the effects of one-lung ventilation (OLV) on oxygen delivery (DO2) in anesthetized dogs with a closed thoracic cavity.

Animals—7 clinically normal adult Walker Hound dogs.

Procedure—Dogs were anesthetized. Catheters were inserted in a dorsal pedal artery and the pulmonary artery. Dogs were positioned in right lateral recumbency. Data were collected at baseline (PaCO2 of 35 to 45 mm Hg), during two-lung ventilation, and 15 minutes after creating OLV. Hemodynamic and respiratory variables were analyzed and calculations performed to obtain DO2 , and values were compared among the various time points by use of an ANOVA for repeated measures.

Results—OLV induced a significant augmentation of shunt fraction that resulted in a significant reduction in PaO2, arterial oxygen saturation, and arterial oxygen content. Cardiac index was not significantly changed. The net result was that DO2 was not significantly affected by OLV.

Conclusions and Clinical Relevance—Use of OLV in healthy dogs does not induce significant changes in DO2, which is the ultimate variable to use when evaluating tissue oxygenation. One-lung ventilation can be initiated safely in dogs before entering the thoracic cavity during surgery. Additional studies are necessary to evaluate OLV in clinically affected patients and variations in age, body position, and type of anesthetic protocol. (Am J Vet Res 2005;66:973–977)

Full access
in American Journal of Veterinary Research