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Abstract

Objective—To determine the anesthetic-sparing effects of perzinfotel when administered as a preanesthetic via IV, IM, or SC routes or IM in combination with butorphanol.

Animals—6 healthy sexually intact Beagles (4 males and 2 females; age, 18.5 to 31 months; body weight, 9.8 to 12.4 kg).

Procedures—After administration of a placebo, perzinfotel (10 to 30 mg/kg), or a perzinfotel-butorphanol combination, anesthesia was induced in dogs with propofol and maintained with isoflurane in oxygen. The following variables were continuously monitored: bispectral index; heart rate; systolic, diastolic, and mean arterial blood pressures; end-tidal concentration of isoflurane; end-tidal partial pressure of CO2; oxygen saturation as measured by pulse oximetry; rectal temperature; and inspiration and expiration concentrations of isoflurane. A noxious stimulation protocol was used, and the minimum alveolar concentration (MAC) was determined twice during anesthesia.

Results—IV, IM, and SC administration of perzinfotel alone decreased the mean isoflurane MAC values by 32% to 44% and significantly increased bispectral index values. A dose of 30 mg of perzinfotel/kg IM resulted in significant increases in heart rate and diastolic arterial blood pressure. The greatest MAC reduction (59%) was obtained with a combination of 20 mg of perzinfotel/kg IM and 0.2 mg of butorphanol/kg IM, whereas administration of butorphanol alone yielded a 15% reduction in the isoflurane MAC.

Conclusions and Clinical Relevance—SC, IM, or IV administration of perzinfotel prior to induction of isoflurane anesthesia improved anesthetic safety by reducing inhalant anesthetic requirements in healthy dogs.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate effects of infusion of guaifenesin, ketamine, and medetomidine in combination with inhalation of sevoflurane versus inhalation of sevoflurane alone for anesthesia of horses.

Design—Randomized clinical trial.

Animals—40 horses.

Procedure—Horses were premedicated with xylazine and anesthetized with diazepam and ketamine. Anesthesia was maintained by infusion of guaifenesin, ketamine, and medetomidine and inhalation of sevoflurane (20 horses) or by inhalation of sevoflurane (20 horses). A surgical plane of anesthesia was maintained by controlling the inhaled concentration of sevoflurane. Sodium pentothal was administered as necessary to prevent movement in response to surgical stimulation. Hypotension was treated with dobutamine; hypoxemia and hypercarbia were treated with intermittent positive- pressure ventilation. The quality of anesthetic induction, maintenance, and recovery and the quality of the transition to inhalation anesthesia were scored.

Results—The delivered concentration of sevoflurane (ie, the vaporizer dial setting) was significantly lower and the quality of transition to inhalation anesthesia and of anesthetic maintenance were significantly better in horses that received the guaifenesin-ketamine-medetomidine infusion than in horses that did not. Five horses, all of which received sevoflurane alone, required administration of pentothal. Recovery time and quality of recovery were not significantly different between groups, but horses that received the guaifenesin-ketamine-medetomidine infusion required fewer attempts to stand.

Conclusions and Clinical Relevance—Results suggest that in horses, the combination of a guaifenesin-ketamine- medetomidine infusion and inhalation of sevoflurane resulted in better transition and maintenance phases while improving cardiovascular function and reducing the number of attempts needed to stand after the completion of anesthesia, compared with inhalation of sevoflurane. (J Am Vet Med Assoc 2002;221:1150–1155)

Full access
in Journal of the American Veterinary Medical Association

Abstract

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 (Po 2; Pco 2); 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.

Full access
in Journal of the American Veterinary Medical Association

Objective

To determine effects of low doses of medetomidine administered with and without butorphanol and glycopyrrolate to middle-aged and old dogs.

Design

Prospective randomized clinical trial.

Animals

88 healthy dogs ≥ 5 years old.

Procedure

Dogs were assigned randomly to receive medetomidine (2, 5, or 10 pa/kg [0.9, 2.3, or 4.6 μg/lb] of body weight, IM) alone or with glycopyrrolate (0.01 mg/kg [0.005 mg/Ib], SC), medetomidine (10 μg/kg) and butorphanol (0.2 mg/kg [0.1 mg/lb], IM), or medetomidine (10 μg/kg), butorphanol (0.2 mg/kg), and glycopyrrolate (0.01 mg/kg). Anesthesia was induced with thiopental sodium and maintained with isoflurane. Degree of sedation and analgesia were determined before and after medetomidine administration. Respiratory rate, heart rate, and mean arterial blood pressure were determined 10 and 30 minutes after medetomidine administration. Adverse effects and amounts of thiopental and isoflurane used were recorded.

Results

Sedation increased after medetomidine administration in 79 of 88 dogs, but decreased in 7 dogs that received 2 or 5 μg of medetomidine/kg. Mean postsedation analgesia score and amounts of thiopental and isoflurane used were less in dogs that received medetomidine and butorphanol, compared with other groups. Respiratory rate, heart rate, and blood pressure were not different among groups. Significantly more adverse effects developed in dogs that did not receive glycopyrrolate.

Conclusions and Clinical Relevance

Administration of medetomidine (10 μg/kg, IM) and butorphanol (0.2 mg/kg, IM) induced sedation and analgesia and reduced amounts of thiopental and isoflurane required for anesthesia in middle-aged and old dogs. Glycopyrrolate decreased frequency of medetomidine-associated adverse effects. (J Am Vet Med Assoc 1999;215:1116–1120)

Free access
in Journal of the American Veterinary Medical Association

Summary

The hemodynamic effects of hypertonic saline solution (hss) resuscitation on endotoxic shock were examined in pentoharhital-anesthetized calves (8 to 20 days old). Escherichia coli (055:B5) endotoxin was infused iv at dosage of 0.1 μg/kg of body weight for 30 minutes. Endotoxin induced large decreases in cardiac index, stroke volume, maximal rate of change of left ventricular pressure (+ dP/dtmax), femoral and mesenteric arterial blood flow, glomerular filtration rate, urine production, and mean aortic pressure. Severe pulmonary arterial hypertension and increased pulmonary vascular resistance were evident at the end of endotoxin infusion. Treatment with hss (2,400 mosm of NaCl/L, 4 ml/kg) or an equivalent sodium load of isotonic saline solution (iss: 300 mosm of NaCl/L, 32 ml/kg) was administered 90 minutes after the end of endotoxin administration. Both solutions were infused iv over a 4- to 6-minute period.

Administration of hss induced immediate and significant (P < 0.05) increase in stroke volume and central venous pressure, as well as significant decrease in pulmonary vascular resistance. These effects were sustained for 60 minutes, after which all variables returned toward preinfusion values. The hemodynamic response to hss administration was suggestive of rapid plasma volume expansion and redistribution of cardiac output toward splanchnic circulation. Plasma volume expansion by hss was minimal 60 minutes after resuscitation.

Administration of iss induced significant increase in cardiac index, stroke volume, femoral arterial blood flow, and urine production. These effects were sustained for 120 minutes, at which time, calves were euthanatized. Compared with hss, iss induced sustained increase in mean pulmonary arterial pressure and only a small increase in mesenteric arterial blood flow. The rapid administration of large-volume iss appears superior to small-volume hss for initial resuscitation of acutely endotoxemic, anesthetized calves. At this time, we do not advocate rapid infusion of iss to septicemic calves because exacerbation of pulmonary hypertension may potentially depress respiratory function, and rapid increase in preload may hemodynamically compromise calves with depressed cardiac contractility.

Free access
in American Journal of Veterinary Research

Summary

The respiratory, renal, hematologic, and serum biochemical effects of hypertonic saline solution (hss) treatment were examined in 12 endotoxic, pentobarbitalanesthetized calves (8 to 20 days old). Escherichia coli endotoxin (055:B5) was infused iv at a rate of 0.1 μg/kg of body weight over 30 minutes. Endotoxin induced severe respiratory effects, with marked hypoxemia and increases in arterial-alveolar O2 gradient (P[A —a]O2), physiologic shunt fraction (Qs/Qt), and physiologic dead space to tidal volume ratio (Vd/Vt). Oxygen consumption was decreased, despite an increase in the systemic O2 extraction ratio. Peak effects were observed at the end of endotoxin infusion. The renal response to endotoxemia was characterized by a decrease in free-water reabsorption and osmotic clearance, as well as a decrease in sodium and phosphorus excretion. Endotoxemia induced leukopenia, thrombocytopenia, hyperphosphatemia, hypoglycemia, acidemia, and increased serum alkaline phosphatase concentrations.

Calves were treated with hss (2,400 mosm/L of NaCl, 4 ml/kg, n = 4) or an equivalent sodium load of isotonic saline solution (iss; 300 mosm/L of NaCl, 32 ml/kg, n = 4) 90 minutes after the end of endotoxin administration. Both solutions were infused over a 4- to 6-minute period. A control group (n = 4> was not treated. Infusion of hss or iss failed to induce a significant change in Pao2 , P(A-a)o2, (Qs/Qt), (Vd/Vt), or oxygen consumption. Both solutions increased systemic oxygen delivery to above preendotoxin values. Hypertonic saline infusion induced significant (P < 0.05) increases in serum Na and Cl concentrations and osmolality, whereas iss induced a significant increase in serum Cl concentration and a significant decrease in serum phosphorus concentration. Both hss and iss reversed the endotoxin-induced changes in renal function, with increases in free water reabsorption and osmotic clearance, as well as increases in sodium and phosphorus excretion. Sodium retention was greater following hss administration. On the basis of these findings, hypertonic saline solutions can be rapidly and safely administered to endotoxic calves.

Free access
in American Journal of Veterinary Research

Summary

Atrial premature complexes (apc) were identified in 16 cows over a 2-year period. Fourteen cows had concurrent gastrointestinal disease. Variation in the intensity of the first heart sound and an occasionally irregular heart rhythm were evident during thoracic auscultation. Neither cardiac murmurs nor pulse deficits were detected in any cows, and clinical signs of heart failure were lacking. Three cows had apc immediately prior to or after development of atrial fibrillation.

The heart rate when apc were diagnosed ranged from 48 to 124 beats/min (mean, 77 ± 20 beats/min), and the apc frequency ranged from < 1 to 23/min (mean 9.4 ± 8.0). The P-wave morphologic characteristics in 4 cows with apc was abnormal. The coupling index of the apc varied between 0.44 and 0.95, with a mean of 0.73. Aberrant ventricular activation was usually associated with a short coupling interval (coupling index < 0.60) and was observed in 3 cows.

Ten cows were determined to be hypocalcemic and 4 cows hypokalemic when apc were identified. Atrial ectopic activity could not be detected in 12 cows after resolution of the concurrent gastrointestinal disorder or electrolyte abnormality. Atrial premature complexes may be a functional cardiac disorder in cattle, unrelated to structural heart disease. The potential for apc to progress to sustained atrial arrhythmias such as atrial fibrillation should be considered.

Free access
in Journal of the American Veterinary Medical Association

SUMMARY

Objectives

To describe the acute cellular response, inflammatory mediator release, and effect on chondrocyte metabolism of interleukin 1β (IL-1β) in isolated innervated or denervated equine metacarpophalangeal joints.

Animals

One metacarpophalangeal joint of 24 adult horses.

Procedures

The metacarpophalangeal joint was isolated for 6 hours in a pump-perfused, auto-oxygenated, innervated or denervated metacarpophalangeal joint preparation. Isolated joints were assigned to 4 groups: control, control-denervated, inflamed, and inflamed-denervated, and inflammation was induced by intra-articular injection of IL-1β. Synovial fluid was collected for cytologic examination and determination of IL (IL)-1β, (IL-6), prostaglandin E2 (PGE2), and substance P (SP) values. Synovial membrane was immunostained with SP and nerve-specific enolase (NSE) antibodies. Cartilage was collected for determination of proteoglycan (PG) synthesis and degradation.

Results

IL-1β induced significant neutrophilic leukocytosis in synovial fluid and synovial membrane. IL-1β concentration had returned to baseline by 5.5 hours, but IL-6 concentration significantly increased throughout the study. Total SP content was significantly higher in inflamed joints. There was a significant increase in 24- and 48-hour PG degradation in inflamed innervated joints.

Conclusion

Cellular response to IL-1β was rapid and sustained; joint clearance of IL-1β was rapid, and endogenous production of IL-1β did not follow. The IL-6 and PGE2 concentrations significantly increased, and SP content was increased in association with inflammation but not denervation. A degradative response of cartilage to IL-1β was observed, and was enhanced by innervation. This model was useful for investigation of the articular response to acute inflammation and the influence of denervation in modulating this response. (Am J Vet Res 1998;59:88–100)

Free access
in American Journal of Veterinary Research