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Objective-To determine the hematologic, serum biochemical, rheological, hemodynamic, and renal effects of IV administration of lactated Ringer's solution (LRS) to healthy anesthetized dogs. Design-4-period, 4-treatment cross-over study. Animals-8 healthy mixed-breed dogs. Procedures-Each dog was anesthetized, mechanically ventilated, instrumented, and randomly assigned to receive LRS (0, 10, 20, or 30 mL/kg/h [0, 4.5, 9.1, or 13.6 mL/lb/h]), IV, on 4 occasions separated by at least 7 days. Blood hemoglobin concentration and serum total protein, albumin, lactate, and electrolyte concentrations; PCV; colloid osmotic pressure; arterial and venous pH and blood gases (Po2 Pco2); whole blood and plasma viscosity; arterial and venous blood pressures; cardiac output; results of urinalysis; urine production; glomerular filtration rate; and anesthetic recovery times were monitored. Oxygen delivery, vascular resistance, stroke volume, pulse pressure, and blood and plasma volume were calculated. Results-Increasing rates of LRS administration resulted in dose-dependent decreases in PCV; blood hemoglobin concentration and serum total protein and albumin concentrations; colloid osmotic pressure; and whole blood viscosity. Plasma viscosity; serum electrolyte concentrations; data from arterial and venous blood gas analysis; glomerular filtration rate; urine production; heart rate; pulse, central venous, and arterial blood pressures; pulmonary vascular resistance; and oxygen delivery did not change. Pulmonary artery pressure, stroke volume, and cardiac output increased, and systemic vascular resistance decreased. Conclusions and Clinical Relevance-Conventional IV infusion rates of LRS to isoflurane-anesthetized dogs decreased colligative blood components; increased plasma volume, pulmonary artery pressure, and cardiac output; and did not change urine production or oxygen delivery to tissues. [ABSTRACT FROM AUTHOR]

Objective--To evaluate the effect of medetomidine on minimum alveolar concentration (MAC), respiratory rate, tidal volume, minute volume (VM), and maximum inspiratory occlusion pressure (IOCPmax) in halothane- and isoflurane-anesthetized dogs. Animals--6 healthy adult dogs (3 males and 3 females). Procedure--The MAC of both inhalants was determined before and 5, 30, and 60 minutes after administration of medetomidine (5 μg/kg, IV). Dogs were subsequently anesthetized by administration of halothane or isoflurane and administered saline (0.9% NaCI) solution IV or medetomidine (5 μg/kg, IV). Respiratory variables and IOCPmax were measured at specific MAC values 15 minutes before and 5, 30, and 60 minutes after IV administration of medetomidine while dogs breathed 0% and 10% fractional inspired carbon dioxide (FICO2). Slopes of the lines for VM/FICO2 and IOCPmax/FICO2 were then calculated. Results--Administration of medetomidine decreased MAC of both inhalants. Slope of VM/FICO2 increased in dogs anesthetized with halothane after administration of medetomidine, compared with corresponding values in dogs anesthetized with isoflurane. Administration of medetomidine with a simultaneous decrease in inhalant concentration significantly increased the slope for VM/FICO2, compared with values after administration of saline solution in dogs anesthetized with halothane but not isoflurane. Values for IOCPmax did not differ significantly between groups. Conclusions and Clinical Relevance--Equipotent doses of halothane and isoflurane have differing effects on respiration that are most likely attributable to differences in drug effects on central respiratory centers. Relatively low doses of medetomidine decrease the MAC of halothane and isoflurane in dogs. [ABSTRACT FROM AUTHOR]

The article studies the N-methyl-D-aspartate receptors (NMDAR) that are important components in the development of central sensitization and secondary hyperalgesia. The NMDAR were first discovered in the late 1980's when it was demonstrated that NMDAR antagonists inhibited hyper-excitability in nociceptive neurons of the dorsal horn of the spinal cord. Their role in the development of central and peripheral sensitization resulted to the administration of drugs with pharmacologic properties. Development of hyperalgesia and allodynia can be limited by decreasing NMDAR activity.

Objective-To estimate the prevalence and characteristics of pain in dogs and cats examined by an emergency service at a veterinary teaching hospital and evaluate the response of dogs and cats with signs of pain to analgesic treatment. Design-Cross-sectional study. Animals-317 dogs and 112 cats. Procedure-A questionnaire was used to categorize the characteristics of pain. The location, cause, and signs of pain were determined by obtaining a thorough history and conducting a physical examination. Pain was categorized by type (superficial somatic, deep somatic, or visceral), mechanism (inflammatory, neuropathic, or both), severity (mild, moderate, or severe), and duration. Evidence for primary or secondary hypersensitivity and hyposensitivity to manipulation was determined. The response to single or multiple analgesic drug administration was assessed. Results-179 (56%) dogs and 60 (54%) cats had signs of pain. In most of these dogs and cats, pain was classified as acute (< 24 hours' duration) and of moderate severity and was associated with primary hypersensitivity. Most dogs had deep somatic pain; most cats had visceral pain. Inflammation was the most common mechanism. One hundred nineteen (66%) dogs and 41 (68%) cats were treated with analgesic drugs. Analgesic treatment was considered effective in 73 (61%) dogs and 31 (76%) cats. Conclusions and Clinical Relevance-Results suggest that moderate to severe acute somatic pain caused by inflammation is common in dogs and cats examined by an emergency service and that a combination of multiple analgesic drugs is more effective than any single analgesic drug in the treatment of pain in these dogs and cats. [ABSTRACT FROM AUTHOR]

Objective--To compare the effects of lactated Ringer's solution (LRS) with those of a physiologically balanced 6% hetastarch plasma expander administered to isoflurane-anesthetized dogs with hypotension induced by blood withdrawal. Animals--12 healthy Beagles. Procedure--Blood was withdrawn from isoflurane-anesthetized dogs (volume withdrawn measured) to a systolic arterial blood pressure (SAP) of 80 mm Hg. Six dogs each received either LRS or hetastarch solution (90 mL/kg/h, IV). Hemodynamic variables, pH, blood gas concentrations, PCV, serum electrolyte and total protein concentrations, and colloid osmotic pressure (COP) were determined at baseline, while SAP was 80 mm Hg, and after fluid treatment. The volume of fluid administered and rate of return of SAP to within 10% of baseline values were recorded. Results--Mean ± SD volume of blood withdrawn to decrease SAP to 80 mm Hg was 173 ± 38 mL. Hemodynamic variables decreased after blood withdrawal but returned to baseline values more rapidly after infusion of a smaller volume of hetastarch solution, compared with the response to LRS infusion. Whereas PCV and serum total protein concentration decreased after administration of either solution, COP decreased only after administration of LRS. The total volume of hetastarch solution and LRS required to restore and maintain SAP to within 10% of baseline values was 1.1 ± 0.9 and 4.4 ± 1.7 times greater than the volume of blood removed, respectively. Conclusions and Clinical Relevance--Compared with LRS infusion, smaller volumes of hetastarch solution normalized and maintained SAP without lowering COP in isoflurane-anesthetized dogs after blood withdrawal. [ABSTRACT FROM AUTHOR]

Presents a study on the prevalence and characteristics of pain in dogs and cats examined as outpatients at a veterinary teaching hospital. Method of determining cause, anatomic location and type of pain; Significance of age; Administration of analgesics.

Objective--To determine the effects of xylazine on canine coronary artery smooth muscle tone. Sample Population--Hearts of 26 healthy dogs. Procedure--Dogs were anesthetized with pentobarbital, and vascular rings of various diameters were prepared from the epicardial coronary arteries. Vascular rings were placed in tissue baths to which xylazine was added (cumulative concentrations ranging from 10-10 to 10-4M), and changes in vascular ring tension were continuously recorded. Effects of the nitric oxide inhibitor NG-nitro-Larginine methyl ester (L-NAME; 5mM), the α1-adrenoceptor antagonist prazosin (10mM), and the α22-adrenoceptor antagonist atipamezole 10mM) on xylazine-induced changes in vascular ring tension were determined. Results were expressed as percentage of maximal contraction for each vascular ring preparation. Results--Xylazine induced vasoconstriction of small (< 500-µm-diameter) and medium (500- to 1,000-µm-diameter) vascular rings but not of large (> 1,000-µm-diameter) rings. For large vascular rings, L-NAME, atipamezole, and prazosin did not significantly affect the contractile response to xylazine. For small vascular rings, the contractile response following addition of xylazine to rings treated with L-NAME was not significantly different from the contractile response following addition of xylazine to control rings, except at a xylazine concentration of 10-6M. Xylazine-induced vasoconstriction of small vascular rings was blocked by atipamezole, but the addition of prazosin had no effect on xylazine-induced vasoconstriction. Conclusions and Clinical Relevance--Results suggest that xylazine increases smooth muscle tone of small canine coronary arteriesand that this effect is predominantly mediated by stimulation of α2adrenoceptors. [ABSTRACT FROM AUTHOR]

Objective--To determine the effects of IV administration of perzinfotel and a perzinfotelfentanyl combination on the minimum alveolar concentration (MAC) of isoflurane in dogs. Animals--6 healthy sexually intact Beagles (3 males and 3 females). Procedures--All dogs were instrumented with a telemetry device for continuous monitoring of heart rate, arterial blood pressure, and core body temperature (at a femoral artery). Dogs were anesthetized with propofol (6 mg/kg, IV) and isoflurane. Isoflurane MAC values were determined in 3 experiments in each dog, separated by at least 7 days, before (baseline) and after the following treatments: no treatment (anesthetic only), perzinfotel (20 mg/kg, IV), fentanyl (5 µg/kg bolus, IV, followed by a continuous IV infusion at 0.15 µg/kg/ min), and a fentanyl-perzinfotel combination (20 mg of perzinfotel/kg, IV, plus the fentanyl infusion). Bispectral index and oxygen saturation as measured by pulse oximetry were also monitored throughout anesthesia. Results--Without treatment, the mean ± SD isoflurane MAC for all 6 dogs was 1.41 ± 0.10%. Baseline MAC was 1.42 ± 0.08%. Intravenous administration of perzinfotel, fentanyl, and the perzinfotel-fentanyl combination significantly decreased the MAC by 39%, 35%, and 66%, respectively. Perzinfotel and perzinfotel-fentanyl administration yielded significant increases in the bispectral index. Mean, systolic, and diastolic arterial blood pressures significantly increased from baseline values when perzinfotel was administered. Systolic arterial blood pressure significantly increased from the baseline value when perzinfotel-fentanyl was administered. No adverse effects were detected. Conclusions and Clinical Relevance--IV administration of perzinfotel, fentanyl, or a perzinfotel- fentanyl combination reduced isoflurane MAC in dogs and increased arterial blood pressure. [ABSTRACT FROM AUTHOR]

Objective--To determine the effect of IV administration of crystalloid (lactated Ringer's solution [LRS]) or colloid (hetastarch) fluid on isoflurane-induced hypotension in dogs. Animals--6 healthy Beagles. Procedures--On 3 occasions, each dog was anesthetized with propofol and isoflurane and instrumented with a thermodilution catheter (pulmonary artery). Following baseline assessments of hemodynamic variables, end-tidal isoflurane concentration was increased to achieve systolic arterial blood pressure (SABP) of 80 mm Hg. At that time (0 minutes), 1 of 3 IV treatments (no fluid, LRS [80 mL/kg/h], or hetastarch [80 mL/kg/h]) was initiated. Fluid administration continued until SABP was within 10% of baseline or to a maximum volume of 80 mL/kg (LRS) or 40 mL/kg (hetastarch). Hemodynamic variables were measured at intervals (0 through 120 minutes and additionally at 150 and 180 minutes in LRS- or hetastarch-treated dogs). Several clinicopathologic variables including total protein concentration, PCV, colloid osmotic pressure, and viscosity of blood were assessed at baseline and intervals thereafter (0 through 120 minutes). Results--Administration of 80 mL of LRS/kg did not increase SABP in any dog, whereas administration of ≤ 40 mL of hetastarch/kg increased SABP in 4 of 6 dogs. Fluid administration increased cardiac index and decreased systemic vascular resistance. Compared with hetastarch treatment, administration of LRS decreased blood viscosity. Treatment with LRS decreased PCV and total protein concentration, whereas treatment with hetastarch increased colloid osmotic pressure. Conclusions and Clinical Relevance--Results indicated that IV administration of hetastarch rather than LRS is recommended for the treatment of isoflurane-induced hypotension in dogs. [ABSTRACT FROM AUTHOR]

Objective--To evaluate the accuracy of a commercial ultrasonographic cardiac output (CO) monitoring system (UCOMS) in anesthetized Beagles as assessed by comparison with thermodilution CO (TDCO). Animals--8 healthy anesthetized Beagles. Procedures--Simultaneous UCOMS and TDCO measurements of CO were obtained during 4 hemodynamic states: baseline anesthesia (0.5% to 1.5% isofiurane), a higher depth of anesthesia (2% to 3.5% isoflurane) to yield a ≥ 15% reduction in systolic arterial blood pressure, IV infusion of-colloidal solution to a mean right atrial pressure of ≥ 15 mm Hg, and IV infusion of dobutamine at 5 µg/kg/min. Measurements were obtained at 2 probe positions: the subxiphoid region and the right thoracic inlet. Correlation and agreement of results between methods were determined via linear regression analysis and Bland-Altman plots. Results--A significant positive correlation was detected between UCOMS and TDCO measurements obtained at the subxiphoid (ρ = 0.86) and thoracic inlet (ρ = 0.83) positions. Bland-Altman plots revealed minimal bias between methods (bias ± SD, -0.03 ± 0.73 L/min and -0.20 ± 0.80 L/min for subxiphoid and thoracic inlet measurements, respectively). However, the percentage error associated with UCOMS measurements made at the 2 positions was > 45%. Conclusions and Clinical Relevance--When compared with the results of TDCO, CO measured with the UCOMS exceeded commonly accepted limits of error in healthy dogs, The UCOMS was, however, able to track changes in CO across hemodynamic states. Additional research is needed to assess the usefulness of the UCOMS for monitoring CO in critically ill dogs. [ABSTRACT FROM AUTHOR]

Objective--To determine the effect of IV administration of perzinfotel on the minimum alveolar concentration (MAC) of isoflurane in dogs. Animals--6 healthy sexually intact male Beagles. Procedures--Dogs were instrumented with a telemetry device that permitted continuous monitoring of heart rate, arterial blood pressure, and body temperature. Dogs were anesthetized with propofol (4 to 6 mg/kg, IV) and isoflurane for 30 minutes before determination of MAC of isoflurane. Isoflurane MAC values were determined 4 times, separated by a minimum of 7 days, before and after IV administration of perzinfotel (0 [control], 5, 10, and 20 mg/kg). Bispectral index and percentage hemoglobin saturation with oxygen (Spo2) were monitored throughout anesthesia. Results--Isoflurane MAC was 1.32 ± 0.14%. Intravenous administration of perzinfotel at 0, 5, 10, and 20 mg/kg decreased isoflurane MAC by 0%, 24%, 30%, and 47%, respectively. Perzinfotel significantly decreased isoflurane MAC values, compared with baseline and control values. The bispectral index typically increased with higher doses of perzinfotel and lower isoflurane concentrations, but not significantly. Heart rate, body temperature, and Sp% did not change, but systolic, mean, and diastolic arterial blood pressures significantly increased with decreases in isoflurane MAC after administration of perzinfotel at 10 and 20 mg/kg, compared with 0 and 5 mg/kg. Conclusions and Clinical Relevance--IV administration of perzinfotel decreased isoflurane MAC values. Improved hemodynamics were associated with decreases in isoflurane concentration. [ABSTRACT FROM AUTHOR]

Objective--To evaluate the cardiovascular effects of total IV anesthesia with propofol (P-TIVA) or ketamine-medetomidine-propofol (KMP-TIVA)in horses. Animals--5 Thoroughbreds. Procedures--Horses were anesthetized twice for 4 hours, once with P-TIVA and once with KMP-TIVA. Horses were medicated with medetomidine (0.005 mg/kg, IV) and anesthetized with ketamine (2.5 mg/kg, IV) and midazolam (0.04 mg/kg, IV). After receiving a loading dose of propofol (0.5 mg/kg, IV), anesthesia was maintained with a constant rate infusion of propofol (0.22 mg/kg/min) for P-TIVA or with a constant rate infusion of propofol (0.14 mg/kg/min), ketamine (1 mg/kg/h), and medetomidine (0.00125 mg/kg/h) for KMP-TIVA. Ventilation was artificially controlled throughout anesthesia. Cardiovascular measurements were determined before medication and every 30 minutes during anesthesia, and recovery from anesthesia was scored. Results--Cardiovascular function was maintained within acceptable limits during P-TIVA and KMP-TIVA. Heart rate ranged from 30 to 40 beats/min, and mean arterial blood pressure was > 90 mm Hg in all horses during anesthesia. Heart rate was lower in horses anesthetized with KMP-TIVA, compared with P-TIVA. Cardiac index decreased significantly, reaching minimum values (65% of baseline values) at 90 minutes during KMP-TIVA, whereas cardiac index was maintained between 80% and 90% of baseline values during P-TIVA. Stroke volume and systemic vascular resistance were similarly maintained during both methods of anesthesia. With P-TIVA, some spontaneous limb movements occurred, whereas with KMP-TIVA, no movements were observed. Conclusions and Clinical Relevance--Cardiovascular measurements remained within acceptable values in artificially ventilated horses during P-TIVA or KMP-TIVA. Decreased cardiac output associated with KMP-TIVA was primarily the result of decreases in heart rate. [ABSTRACT FROM AUTHOR]

Objective—To compare the anesthetic and cardiorespiratory effects of total IV anesthesia with propofol (P-TIVA) or a ketamine-medetomidine-propofol combination (KMP-TIVA)in horses. Design—Randomized experimental trial. Animals—12 horses. Procedure—Horses received medetomidine (0.005 mg/kg [0.002 mg/lb], IV). Anesthesia was induced with midazolam (0.04 mg/kg [0.018 mg/lb], IV) and ketamine (2.5 mg/kg [1.14 mg/lb], IV). All horses received a loading dose of propofol (0.5 mg/kg [0.23 mg/lb], IV), and 6 horses underwent P-TIVA (propofol infusion). Six horses underwent KMP-TIVA (ketamine [1 mg/kg/h {0.45 mg/lb/h}] and medetomidine [0.00125 mg/kg/h {0.0006 mg/lb/h}] infusion; the rate of propofol infusion was adjusted to maintain anesthesia). Arterial blood pressure and heart rate were monitored. Qualities of anesthetic induction, transition to TIVA, and maintenance of and recovery from anesthesia were evaluated. Results—Administration of KMP IV provided satisfactory anesthesia in horses. Compared with the P-TIVA group, the propofol infusion rate was significantly less in horses undergoing KMP-TIVA (0.14 ± 0.02 mg/kg/min [0.064 ± 0.009 mg/lb/min] vs 0.22 ± 0.03 mg/kg/min [0.1 ± 0.014 mg/lb/min]). In the KMP-TIVA and P-TIVA groups, anesthesia time was 115 ± 17 minutes and 112 ± 11 minutes, respectively, and heart rate and arterial blood pressure were maintained within acceptable limits. There was no significant difference in time to standing after cessation of anesthesia between groups. Recovery from KMP-TIVA and P-TIVA was considered good and satisfactory, respectively. Conclusions and Clinical Relevance—In horses, KMP-TIVA and P-TIVA provided clinically useful anesthesia; the ketamine-medetomidine infusion provided a sparing effect on propofol requirement for maintaining anesthesia. [ABSTRACT FROM AUTHOR]