Summary An experimental model of postoperative ileus was developed in ponies using trauma to, and exposure of, a length of small intestine which gave rise to a reproducible and reversible set of changes in gut activity. This was assessed by recordings of electrical and mechanical activity and by propulsion of spheres from stomach to anus. Activity was depressed, especially in the stomach and colon, and transit was slowed. All drugs given increased electromechanical activity but propranolol was the least effective and did not alter the delayed transit of spheres. Yohimbine was more effective and the addition of bethanechol produced a little extra propulsive action. Metoclopramide had the best effect, virtually returning transit to normal and was the only drug fully restoring coordination of gastric and small intestinal activity which was disrupted by the ileus procedure. Loss of gastroduodenal coordination is probably the central lesion in equine ileus and may be mediated by dopamine.

The Limulus amoebocyte lysate assay was used to test for the presence of endotoxin in 37 clinical cases of equine colic. Positive plasma titres were detected in 10 cases and the presence of endotoxin was significantly correlated with a high heart rate, a high packed cell volume and a poor prognosis. High levels of endotoxin were detected in gut contents taken from several sites in the gastrointestinal tract of normal horses.

Restriction of free movement of the flexor tendons through the fetlock canal results in lameness. The commonest cause was chronic synovitis of the digital sheath. The condition is characterised by an unremitting lameness, synovial distenslon and a notch on the caudal aspect of the limb. The condition can be relieved by section of the annular ligament of the fetlock. In a series of 24 cases 16 horses returned to work with no recurrence of lameness, three cases were lost to follow up and five animals remained lame; three of these had intercurrent disease.who referred the cases to us. We are grateful to our colleagues annular ligament of the fetlock in the horse. Vet. Med. SmaN Anim. Mr (3. B. Edwards and Dr J. V. Davies for permission to Clin. 69, 327-329.report three of their cases.Verschooten, F. and De Moor, A. (1978) Tendonitis in the horse: its Referencesradiographic diagnosis with air tendograms. J. Am. vet. Radio/. Webbon. P. M. (1977) A Dost mortem studv of eouine digital flexor SOC. 19, 23-30. Adams, 0. R. (1974) Constriction of the palmar (volar) or plantar tendons. Equine ver. J . -9, 61-67. I ABSTRACT Surgery Effects of extensive resection of the small intestine in the pony TATE, L. P., RALSTON, S. L., KOCH, C. M. and EVERITT, J. I. (1983) Am. J. vet. Res. 44, 1187-1 191.

Summary Post operative ileus (POI) is a common and serious complication of colic surgery in the horse. There is a high correlation between the incidence of POI and the presence of ischaemic bowel, suggesting a role for endotoxin. 0.1μg/kg endotoxin was administered intravenously to six ponies with chronically implanted gastrointestinal electromechanical recording devices. It produced profound disruption of normal fasting bowel motility patterns, with an inhibition of gastric contraction amplitude and rate, left dorsal colon contraction product and small colon spike rate. In the small intestine an increase in abnormally arranged regular activity and a decrease in irregular activity was observed. There was no significant prolongation in stomach to anus transit time as assessed by the passage of plastic spheres. The bowel motility patterns induced by endotoxin could be mimicked by the intravenous infusion of PGE2 and less potently by PGI2 (prostacyclin), but not by PGF2α. This study provides evidence that systematic endotoxin present in clinical cases of colic may play a role in the pathogenesis of equine ileus. The acute effects of endotoxin on bowel motility appear to be mediated indirectly by prostaglandins, and the inhibitory effects may be mediated mainly by PGE2.

Summary Phenylbutazone was given orally to 2 groups of horses and the plasma levels of the drug and its 2 principal metabolites oxyphenbutazone and γ‐hydroxyphenylbutazone measured by high performance liquid chromatography. Animals in Group 1 received single oral doses in a range from 1.1 to 13.2 mg/kg and were sampled over the succeeding 24 h. Considerable individual variation was observed both in timing and magnitude of the plasma drug responses between horses, but 24 h after dosing a dear dose response relation was recorded. Group 2 horses were given the recommended therapeutic dosage regimen and sampled over 24 h periods twice weekly. After 4 days at 8.8 mg/kg in 2 divided doses mean peak plasma levels of phenylbutazone reached 24 μg/ml and showed evidence of cumulation. After 4 days at 4.4 mg/kg, peak plasma concentrations had fallen to 10 γg/ml and mean peak levels just failed to reach 4 γg/ml 3 days after reducing dosage to 2.2 mg/kg once daily. Plasma concentrations of oxyphenbutazone did not exceed 25 per cent of the parent drug and the y‐hydroxy metabolite was only just detectable and never exceeded 1 μg/ml. Résumé Du phénylbutazone a été administré oralement à deux groupes de chevaux, puis la concentration de la drogue et de ses deux principaux métabolites, I'oxyphenbutazone et l'hydroxyphénylbutazone, dans le plasma, a été mesurée à l'aide d'un chromatographe en phase liquide à hautes performances. Les animaux du groupe 1 ont reçu des doses orales uniques allant de 1, 1 à 13, 2 mg/kg, les échantillons étant prélevés au cours des 24 heures suivantes. On a pu observer des variations individuelles considérables au point de vue du moment d'apparition et de. l'amplitude des concentrations plasmiques entre les animaux, mais 24 heures après le dosage, une relation nette entre dose et réponse apparaît. Les bêtes du groupe 2 ont reçu la posologie thérapeutique recommandée et des prélèvements ont été effectués deux fois par semaine sur des périodes de 24 heures. Après quatre jours de traitement à 8, 8 mg/kg en deux doses séparées, les concentrations plasmiques de pointe moyennes de phénylbutazone atteignaient 24 μg/ml et on notait des signes d'effet cumulatif. Après quatre jours à 4 μg/kg, les concentrations plasmiques de pointe avaient baisséà 10 μg/ml; trois jours après avoir réduit le dosage à 2, 2 mg/kg pris une fois par jour, ces mêmes concentrations étaient juste en‐dessous de 4 μg/ml. Les concentrations plasmiques d'oxyphenbutazone ne dépassèrent pas 25% de celles de la drogue‐mère, tandis que l'hydroxymétabolite γétait juste détectable et ne dépassa jamais 1 μg/ml. Zusammenfassung Phenylbutazon wurde oral 2 Gruppen von Pferden verabreicht. Anschließend wurden die Plasmawerte der Droge und ihrer beiden wichtigsten Stoffwechselprodukte, Oxyphenbutazon und Hydroxyphenylbutazon, mit Hilfe eines Hochleistungs‐Chromatographen gemessen. Die Pferde der Gruppe 1 erhielten jeweils eine einzelne Dosis von 1, 1 bis 13, 2 mg/kg mit anschließender Probenentnahme während eines Zeitraums von 24 Stunden. Der zeitliche V...

Summary Post operative ileus is a serious complication of abdominal surgery in horses and there is evidence that endotoxin plays a significant role in its pathogenesis. Pre‐treatment with intravenous (iv) flunixin (1.1 mg/kg bodyweight [bwt]) or phenylbutazone (4.4 mg/kg bwt) significantly antagonised the acute disruption of gastric, small intestinal and large intestinal motility induced by 0.1 μg/kg bwt iv endotoxin in ponies implanted with gastrointestinal strain gauges. Phenylbutazone was more effective than flunixin and this was significant (P<0.01) for the stomach and left dorsal colon. Both drugs reduced the acute systemic side‐effects of the endotoxin and flunixin was slightly more effective than phenylbutazone in antagonising the cardiovascular effects. These results suggest that the acute effects of endotoxin on bowel motility are mediated at least in part by a cyclooxygenase dependant pathway. Flunixin and phenylbutazone showed a relative selectivity for the cardiovascular and gastrointestinal effects of endotoxin, respectively. Phenylbutazone may be of use clinically in acute colic cases, antagonising the disruptive effects of endotoxin on bowel motility, without entirely blocking the cardiovascular effects which can indicate that the patient has a condition requiring surgery.

The effect of cisapride was evaluated on the normal fasting bowel motility of four ponies with chronically implanted electromechanical transducers. Cisapride was infused over 60-min periods at 0.05 mg/kg (n = 4), 0.1 mg/kg (n = 5) and 0.25 mg/kg (n = 5). It produced marked and prolonged increases in electrical and mechanical activity at all sites examined. In the stomach there was increased total contraction activity with increased contraction amplitude and a slight reduction in rate. In the small intestine there was an increase in irregular (phase II) activity with an increase in number and amplitude of contractions and a decrease in the number of regular (phase III) activity fronts. There was a decrease in the number of phase III fronts that spread distally from the jejunum to the ileum. The phase II activity was coordinated temporally with prolonged activity in the stomach. Cisapride increased electrical and contractile activity in the left dorsal colon with increased contraction amplitude and an increase in electrical activity in the small colon. In the stomach and small intestine cisapride produced dose-dependent increases in activity but in the left dorsal and small colon the intermediate dose (0.1 mg/kg) produced the largest and most consistent responses. Side-effects observed were increased bowel sounds and frequency of defaecation, a slight increase in heart rate and transient signs of discomfort at the highest (0.25 mg/kg) dose rate.

Prostaglandin E1 was infused intravenously (25, 50 and 75 ng/kg/min) in three ponies. Changes in gastrointestinal mechanical and electrical activity were recorded from chronically implanted strain-gauge force transducers and electrodes. Dose-dependent responses were obtained: there were significant decreases in electrical spiking activity in the stomach, left large colon and small colon, with a corresponding decrease of activity in the left dorsal colon mechanogram. The small intestine was also affected, showing a decrease in both contraction rate and amplitude, which was more marked in the proximal jejunum than in the ileum. There was an association between these changes in gastrointestinal activity and the presence of discomfort and diminished gut sounds.