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Summary

Histomorphologic/morphometric evaluation, leukocyte scintigraphy, and myeloperoxidase activity were used to determine whether neutrophils accumulate in the large colon of horses during low-flow ischemia and reperfusion. Twenty-four adult horses were assigned to 1 of 3 groups: group 1, sham-operated (n = 6); group 2, 6 hours of ischemia (n = 9); and group 3, 3 hours of ischemia and 3 hours of reperfusion (n = 9). Low-flow ischemia of the large colon was induced in horses of groups 2 and 3 by reducing colonic arterial blood flow to 20% of baseline. Radiolabeled (99mTc) autogenous neutrophils were injected at 175 minutes, which corresponded to 5 minutes prior to reperfusion in group-3 horses. Full-thickness biopsy specimens of the left ventral colon were collected at baseline and at 30-minute intervals for 6 hours; a portion of the biopsy specimen was placed in formalin for histologic examination, and the remainder was used to measure mucosal radioactivity and myeloperoxidase activity. There were no differences in baseline mucosal neutrophil index, mucosal neutrophil numbers, submucosal venular neutrophil numbers, mucosal radioactivity, or mucosal myeloperoxidase activity among groups, or over time in group-1 horses. Neutrophils accumulated in the colonic mucosa during ischemia and further increased at reperfusion, as indicated by neutrophil index (morphology) and mucosal neutrophil numbers (morphometry); mucosal neutrophil index was significantly (P < 0.05) greater in group-3 horses during reperfusion than at the corresponding periods of ischemia in group-2 horses. Neutrophil numbers were significantly (P < 0.05) increased in submucosal venules at 10 minutes of reperfusion in group-3 horses and were significantly (P < 0.05) greater in group-3 than in group-2 horses during the interval from 3 to 6 hours. Mucosal radioactivity significantly (P < 0.05) increased at reperfusion in group-3 horses; there was a trend (P = 0.076) toward greater mucosal radioactivity in group-3, compared with group-2 horses, throughout the 3- to 6-hour interval. There were no differences in mucosal myeloperoxidase activity among or within any of the 3 groups over time.

Neutrophils accumulated in the large colon of horses during low-flow ischemia and reperfusion. Neutrophil infiltration was detected by histologic examination and leukocyte scintigraphy, but not by measurement of myeloperoxidase activity. The accumulation of neutrophils during ischemia and the further neutrophil infiltration during reperfusion indicate that neutrophils may contribute to reperfusion injury of the large colon.

Free access
in American Journal of Veterinary Research

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

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 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

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

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

Xylazine (0.05 mg/kg of body weight diluted to a 5-ml volume, using 0.9% NaCl) or 5 ml of 0.9% NaCl was administered epidurally into the first caudal intervertebral space (Co1-Co2) in 8 cows (mean ± sd body weight, 583 ± 150 kg). Cows were observed for responses to deep needle pricking of the caudal dermatomes (S3 to Co), sedation, and ataxia. Heart rate, respiratory rate, body temperature, rate of ruminal contractions, coccygeal arterial blood pressure, pHa, blood gas tension (Pa o 2 , Pa co 2 ), base excess, total solids concentration, and pcv were determined before and after xylazine administration. Epidurally administered xylazine induced sedation and selective (S3 to Co) analgesia for at least 2 hours. Mild ataxia of hind limbs was observed in 6 cows, but all cows remained standing. Heart rate, respiratory rate, rate of ruminal contractions, arterial blood pressure, Pa o 2 , pcv, and total solids concentration were significantly (P < 0.05) decreased, and Pa co 2 , base excess, and bicarbonate concentration were significantly (P < 0.05) increased after xylazine administration. Epidurally administered 0.9% NaCl did not alter sensory perception to needle pricking and did not affect any of the physiologic variables determined. Although epidural administration of xylazine induced analgesia and sedation in healthy cows, it should be avoided for epidural analgesia in cattle with heart disease, lung disease, and/or gastrointestinal disease because of its potent cardiopulmonary and ruminal depressant effects.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate anesthetic effects of 4 drug combinations used for total intravenous anesthesia of horses undergoing surgical removal of an abdominal testis.

Design—Clinical trial.

Animals—32 healthy cryptorchid horses.

Procedure—Horses were sedated with xylazine and butorphanol and were randomly assigned to 1 of 4 groups: induction of anesthesia with ketamine and diazepam and maintenance with bolus administration of ketamine and xylazine (KD/KX); induction and maintenance of anesthesia with bolus administration of tiletamine-zolazepam, ketamine, and detomidine (TKD); induction and maintenance of anesthesia with continuous infusion of xylazine, guaifenesin, and ketamine; and induction and maintenance of anesthesia with continuous infusion of guaifenesin and thiopental. Horses that moved 3 consecutive times in response to surgical stimulation or for which surgery time was > 60 minutes were administered an inhalant anesthetic, and data from these horses were excluded from analysis.

Results—Quality of induction was not significantly different among groups. Muscle relaxation and analgesia scores were lowest for horses given KD/KX, but significant differences among groups were not detected. Horses anesthetized with TKD had a significantly greater number of attempts to stand, compared with the other groups, and mean quality of recovery from anesthesia for horses in the TKD group was significantly worse than for the other groups. Anesthesia, surgery, and recovery times were not significantly different among groups.

Conclusions and Clinical Relevance—Results suggest that all 4 drug combinations can be used to induce short-term anesthesia for abdominal cryptorchidectomy in horses. However, horses receiving TKD had a poorer recovery from anesthesia, often requiring assistance to stand. (J Am Vet Med Assoc 2000;217:869–873)

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the effects of rapid small-volume fluid administration on arterial blood pressure measurements and associated hemodynamic variables in isoflurane-anesthetized euvolemic dogs with or without experimentally induced hypotension.

Design—Prospective, randomized, controlled study.

Animals—13 healthy dogs.

Procedures—Isoflurane-anesthetized dogs were randomly assigned to conditions of nonhypotension or hypotension (mean arterial blood pressure, 45 to 50 mm Hg) and treatment with lactated Ringer's solution (LRS) or hetastarch (3 or 10 mL/kg [1.4 or 4.5 mL/lb] dose in a 5-minute period or 3 mL/kg dose in a 1-minute period [4 or 5 dogs/treatment; ≥ 10-day interval between treatments]). Hemodynamic variables were recorded before and for up to 45 minutes after fluid administration.

Results—IV administration of 10 mL/kg doses of LRS or hetastarch in a 5-minute period increased right atrial and pulmonary arterial pressures and cardiac output (CO) when dogs were nonhypotensive or hypotensive, compared with findings before fluid administration; durations of these effects were greater after hetastarch administration. Intravenous administration of 3 mL of hetastarch/kg in a 5-minute period resulted in an increase in CO when dogs were nonhypotensive. Intravenous administration of 3 mL/kg doses of LRS or hetastarch in a 1-minute period increased right atrial pressure and CO when dogs were nonhypotensive or hypotensive.

Conclusions and Clinical Relevance—Administration of LRS or hetastarch (3 or 10 mL/kg dose in a 5-minute period or 3 mL/kg dose in a 1-minute period) improved CO in isoflurane-anesthetized euvolemic dogs with or without hypotension. Overall, arterial blood pressure measurements were a poor predictor of the hemodynamic response to fluid administration.

Full access
in Journal of the American Veterinary Medical Association