Small Animal Surgical Emergencies. Группа авторов

tube is advanced slowly into the pharynx and the dog is allowed to swallow so that it enters the esophagus. The tube is advanced to the stomach carefully and upon entering, gas should be released. Once the stomach has been decompressed, the tube should be removed. Some authors recommend lavaging the stomach at this point [42]. If the tube cannot be advanced into the stomach, trocharization should be attempted. The tube should not be forced into the stomach as there is a risk of perforation. If perforation does occur, this is probably an indicator of preexisting gastric or esophageal necrosis. In some cases, gastric decompression may not be possible until the dog has been anesthetized for surgery.

Figure 8.5 Measuring stomach tube prior to orogastric intubation. The end of the stomach tube is measured to the last rib and a tape marker is placed to identify how far it should be inserted.

Figure 8.6 Bandage roll placed in dog's mouth as a gag and to facilitate passage of stomach tube, which is inserted through the hole in the center of the bandage.

      Some authors have suggested a role for management of ischemia–reperfusion injury to prevent subsequent complications [10, 25, 26]. Suggested interventions have included desferoxamine, dimethyl sulphoxide and allopurinol. All have been evaluated in experimental GDV, although none have been evaluated clinically [24, 26]. Lidocaine, however, has been evaluated retrospectively and prospectively as part of the management of GDV in dogs [10, 25]. Retrospective evaluation failed to show a survival benefit associated with lidocaine, but use was uncontrolled, and it is likely that lidocaine use was biased toward more seriously affected dogs [10]. In a prospective study, GDV dogs were treated with lidocaine and a historical population of dogs with GDV was used as a retrospective control [25]. Dogs received an intravenous bolus of lidocaine (2 mg/kg) immediately on presentation, followed by a lidocaine constant rate infusion (50 μg/kg/min) given over 24 hours. A reduced rate of arrhythmias and acute kidney injury, and shorter hospitalization time were reported with lidocaine therapy. Although it is unclear if other factors played a role in the decreased complication rate, the administration of lidocaine may be warranted in the management of GDV.

      While surgical intervention is considered mandatory for management of GDV, medical management of the condition, consisting of orogastric intubation, trocarization if necessary and treatment for shock, has been evaluated [44, 45]. A high mortality (66%) [44] and recurrence rate of 71–76% has been reported [44, 45]. The authors do not recommend medical management alone for the treatment of GDV.

Operative Techniques

      Anesthesia using a cardiovascular sparing protocol is recommended. Dogs should be preoxygenated. Premedication with a pure mu‐agonist opioid is useful if not already given. Fentanyl (2–5 ug/kg) is short acting, has a fast onset and can be used immediately prior to induction to reduce the dose of induction agent required. The induction agent chosen should have a rapid onset of action (e.g., propofol or alfaxalone). Compromised dogs require less induction agent than normal animals. The dog should be maintained in sternal recumbency and the head held elevated until the animal has been intubated. Nitrous oxide should be avoided as this may cause increased gas accumulation in the stomach. Clipping should be performed with the dog in lateral recumbency. Dorsal recumbency is avoided unless the stomach has been decompressed as this may worsen hypoperfusion.

      Goals of Surgery

      Surgical treatment of GDV consists of several distinct steps that must be performed to ensure the best outcome for the dog:

       Decompression and repositioning of the stomach.

       Assessment of gastric and splenic viability.

       Resection of devitalized tissue.

       Gastropexy.

      The dog is aseptically prepared for surgery and a standard midline laparotomy is performed. The incision should be as long as necessary to allow adequate inspection and manipulation of the stomach and to perform a gastropexy. Care should be taken on incising the linea alba to prevent inadvertent trauma to the stomach which may be compressed against the ventral body wall. Abdominal retractors (e.g., Balfour) are invaluable in increasing exposure and facilitating surgery.

      Repositioning of the Stomach

      The initial aim of surgery is to decompress and reposition the stomach. This will help to address continuing hypoperfusion caused by the distended stomach and allow subsequent assessment of tissue viability and a gastropexy to be performed.

Typically, the stomach is twisted between 90 and 360 degrees in a clockwise direction [46]. The direction of torsion is assessed intraoperatively from the caudal aspect of the dog in dorsal recumbency. For a clockwise torsion, the pylorus of the stomach moves ventrally and toward the left side of the abdomen. Owing to the direction of this movement, the stomach enters the omental bursa and is therefore covered by a single layer of omentum (Figure 8.7a).

      Repositioning can be facilitated by further gastric decompression. An assistant passes an orogastric tube and the surgeon should be able to manually guide the tube through the cardiac sphincter. If this is not possible, needle gastrocentesis can be performed to reduce the distension. Repeated gastric lavage with warm tap water via the orogastric tube can help to decompress the stomach further. If there is a large amount of food present in the stomach, a gastrotomy may be necessary to allow repositioning.

      To derotate a clockwise rotated stomach, the surgeon stands on the right‐hand side of the dog and uses their right hand to grasp the pylorus of the stomach, lying in the cranial aspect of the abdomen on the left‐hand side. The pylorus is then gently retracted ventrally and toward the right‐hand side of the abdomen. At the same time, the surgeon should exert downward pressure with the left hand on the visible portion of the stomach, encouraging it to move dorsally (Figure 8.7b). This movement may need to be performed several times to fully derotate the stomach.

Figure 8.7 Series of intraoperative images showing derotation of the stomach at exploratory laparotomy in a dog with gastric dilatation and volvulus. (a) Initial appearance of the dilated stomach. The stomach is covered by omentum, which is indicative of a clockwise torsion. (b) Appearance of the stomach during derotation. The pylorus (P) is identified. (c) The dilated stomach, which has been restored to a normal position.

Once the stomach has returned to a normal position (Figure 8.7c), further decompression and lavage can be performed using the orogastric tube. If a gastric foreign body is present, a gastrotomy may be necessary.

      Assessment of Gastric Viability

Once the stomach is decompressed and repositioned, the gastric wall should be evaluated for evidence of necrosis. The greater curvature, at the junction between the fundus and the body, is the most common site for necrosis. The serosa is often bruised and, following repositioning, it should be monitored for 5–10 minutes prior