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  • Author or Editor: L. K. Cullen x
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SUMMARY

Myoelectric activity was monitored from the terminal ileum, cecum, and colonic pelvic flexure by use of Ag-pAgCl bipolar electrodes in 4 adult horses before, during, and after general anesthesia. Horses were anesthetized by way of 3 commonly used regimens, including xylazine (1.1 mg/kg of body weight) and ketamine hydrochloride (2.2 mg/kg); thiopental sodium (7.7 mg/kg), followed by halothane vaporized in oxygen; and thiopental sodium (2.5 g) in guaifenesin (100 mg/ml) solution given to effect, followed by halothane in oxygen. All 3 anesthetic regimens decreased intestinal spike-burst activity in the areas monitored. The slowest return to preanesthetic myoelectric activity was observed after xylazine and ketamine administration. After both of the barbiturate/halothane anesthetic regimens, there was a rebound increase in spike-burst frequency, without alteration in the proportion of propagative myoelectric events. All 3 anesthetic regimens appeared to reset the timing of the small and large intestinal migrating myoelectric complexes. By 9 hours after recovery from anesthesia, the effects of anesthesia, irrespective of regimen, had disappeared. Although anesthesia significantly (P < 0.05) altered intestinal myoelectric activity, no particular anesthetic regimen had a prolonged effect. Results of our study indicate that the particular chosen regimen of general anesthesia is unimportant in development of motility disturbances in horses after anesthesia.

Free access
in American Journal of Veterinary Research

SUMMARY

Microcytosis is a common laboratory finding in dogs with congenital portosystemic shunt (pss), although its pathogenesis is not yet understood. Because the most common cause of microcytosis in dogs is absolute or relative iron deficiency, iron status was evaluated in 12 young dogs with pss. Complete blood counting was done before surgical correction in all dogs, and in 5 dogs after surgery, by use of an automated hematology analyzer. Serum iron concentration and total iron-binding capacity (tibc) were determined coulometrically, and percentage of transferrin saturation was calculated. Erythrocyte protoporphyrin content was quantified by use of front-face fluorometry. Serum ferritin concentration was measured by use of elisa. Serum ceruloplasmin content was determined colorimetrically (with p-phenylene-diamine dihydrochloride as substrate) as an indirect indicator of subclinical inflammation, which may result in impaired iron utilization. Special stains were applied to liver (10 dogs; Gomori's) and bone marrow aspiration biopsy (7 dogs; Prussian blue) specimens for qualitative assessment of tissue iron content. Nonpaired Student's t-tests were used to compare serum iron concentration, tibc, percentage of transferrin saturation, and erythrocyte protoporphyrin, ferritin, and ceruloplasmin concentrations in dogs with pss with those in clinically normal dogs. All dogs had microcytosis before surgery; microcytosis resolved in 3 dogs after surgical correction. Serum iron concentration and tibc were significantly lower in pss-affected dogs than in clinically normal dogs. Erythrocyte protoporphyrin, ferritin, and ceruloplasmin concentrations in pss-affected dogs were not significantly different from those in healthy dogs. Excess iron was not detected consistently in liver or bone marrow samples. These results suggest that relative iron deficiency, perhaps associated with altered iron transport and not absolute iron deficiency, is related to microcytosis in dogs with pss.

Free access
in American Journal of Veterinary Research

SUMMARY

The effects of different arterial carbon dioxide tensions (PaCO2 ) on cerebrospinal fluid pressure (csfp) and intraocular pressure (iop) were studied in 6 male halothane-anesthetized horses positioned in left lateral recumbency. Steady-state anesthetic conditions (1.06% end-tidal halothane concentration) commenced 60 minutes following anesthetic induction with only halothane in oxygen. During atracurium neuromuscular blockade, horses were ventilated, and respiratory rate and peak inspiratory airway pressure were maintained within narrow limits. The csfp and iop were measured at 3 different levels of PaCO2 (approx 40, 60, and 80 mm of Hg). The PaCO2 sequence in each horse was determined from a type of switchback design with the initial PaCO2 (period 1), established 30 minutes after the commencement of steady-state anesthesia, being repeated in the middle (period 3) and again at the end (period 5) of the experiment. Measurements taken from the middle 3 periods (2, 3, and 4) would form a Latin square design replicated twice. The interval between each period was approximately 45 minutes.

Data from periods 2, 3, and 4 indicated that csfp (P < 0.05) and mean systemic arterial pressure increased significantly (P < 0.05) with high PaCO2 . Mean central venous pressure, heart rate, and iop did not change significantly during these same conditions. Measurements taken during periods 1, 3, and 5 were compared to assess the time-related responses to anesthesia and showed a significant increase in csfp, a significant decrease in mean central venous pressure, and a small (but not statistically significant) increase in mean systemic arterial pressure.

Free access
in American Journal of Veterinary Research

Summary

Cardiovascular and respiratory changes that accompany markedly long periods (12 hours) of halothane anesthesia were characterized. Eight spontaneously breathing horses were studied while they were positioned in left lateral recumbency and anesthetized only with halothane in oxygen maintained at a constant end-tidal concentration of 1.06% (equivalent to 1.2 times the minimal alveolar concentration for horses). Results of circulatory and respiratory measurements during the first 5 hours of constant conditions were similar to those previously reported from this laboratory (ie, a time-related significant increase in systemic arterial blood pressure, cardiac output, stroke volume, left ventricular work, pcv, plasma total solids concentration, and little change in respiratory system function). Beyond 5 hours of anesthesia, arterial blood pressure did not further increase, but remained above baseline. Cardiac output continued to increase, because heart rate significantly (P < 0.05) increased. Peak inspiratory gas flow increased significantly (P < 0.05) in later stages of anesthesia. There was a significant decrease in inspiratory time beginning at 4 hours. Although PaO2 and PaCO2 did not significantly change during the 12 hours of study, P v ̄ O 2 increased significantly (P < 0.05) and progressively with time, beginning 6 hours after the beginning of constant conditions. Metabolic acidosis increased with time (significantly [P < 0.05] starting at 9 hours), despite supplemental iv administered NaHCO3, Plasma concentrations of eicosanoids: 6-ketoprostaglandin F (pgf a stable metabolite of pgi 1), pgf , pge, and thromboxane (TxB2, a stable metabolite of TxA2) were measured in 5 of the 8 horses before and during anesthesia. Significant changes from preanesthetic values were not detected. Dynamic thoracic wall and lung compliances decreased with time.

Free access
in American Journal of Veterinary Research