Monitoring and evaluating the physiological changes in the horse with acute abdominal disease.

Initial examination and therapy, and the avoidance of maltreatment are emphasized. Gastric decompression is of prime importance, after which no compound should be administered via stomach tube. Where large amounts of high starch grains are fed, primary acute gastric dilatation must be differentiated from that secondary to small bowel dilatation, by immediate gastric intubation and irrigation of the cardia with lidocaine. If cessation of pain and improvement of peristalsis and general attitude follow, the former state may be assumed. If pain persists and peristalsis does not improve markedly, one should assume small bowel displacement. Rectal examination is helpful in initial evaluation: impactions, inguinal herniation and ileocaecal intussusception may be diagnosed and small bowel displacement suspected. Palpation of one or more distended loops of bowel in the ventral middle third of the abdomen indicates small bowel displacement or ileus and flaccid distension. Distinction by rectal palpation alone is difficult. Palpation of the gas-distended apex of the caecum in the middle third of the abdomen is virtually pathognomonic for 180 degrees rotation of the large bowel. Abdominal paracentesis yielding true sanguineous effusion indicates a necrotizing segment of the bowel. If negative, such a segment is absent, or there is an infarcted segment, not yet damaged to the point of leaching whole blood, or the necrotizing segment is outside the peritoneal cavity, i.e., in the thorax, intussuscepted into the caecum, or herniated into the inguinal canal. Recurrent colics frequently may be due to verminous arteritis but the relationship to diet should be investigated. Recurrent colics after grain ingestion with occult blood in the faeces may be due to ulcers; such cases respond well to grain withdrawal. The advantages and disadvantages of phenothiazine-derived tranquillizers are discussed. They are contra-indicated if there is any evidence of circulating volume insufficiency but are benefical in many instances through improved peripheral perfusion of organs provided circulating volume is adequate, i.e., early in acute abdominal disease prior to development of circulatory insufficiency. They should not be administered if immediate surgery is contemplated because of hypotensive effects. The administration of oral antibiotics (Neomycin) early in the course of the disease is encouraged. This is contra-indicated if the horse is already toxic, when it should receive parenteral antibiotics, preferably chloromycetin. Tetracyclines may predispose to the later development of salmonella diarrhoea. Absolute analgesia should be provided; our preference is the magnesium sulphate-chloral hydrate solutions. Administration of mineral oil is desirable in initiation of peristalsis, depression of Gram-negative overgrowth and softening of impactioning obstructions but nothing should be administered per os if the stomach has required decompression.