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Emergency stabilization of gastric dilatation and volvulus (Proceedings)

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Aug 01, 2009

Gastric dilatation and volvulus (GDV) is an acute, life-threatening condition which requires immediate medical and surgical intervention. It occurs in susceptible dogs when the stomach becomes distended with air, and then while dilated, twists on itself.

Signalment, risk factors and prognosis

It most commonly occurs in adult, large to giant breed dogs with a deep chest conformation. Overrepresented breeds include the Great Dane, St. Bernard, Weimeraner, Standard Poodle, Bassett Hound, and various setter breeds. Additional risk factors include having a first degree relative with GDV and increasing age. Mortality rates for dogs with GDV are quite variable and range from 10-90%. Risk factors associated with increased mortality include duration of clinical signs prior to treatment; the presence of gastric necrosis, cardiac arrhythmia, or increased serum lactate concentration; and the need for splenectomy.

Pathophysiology

Gastric distention and volvulus occurs when a distended stomach twists on its long axis and occludes the esophageal hiatus and pylorus, thereby trapping stomach contents. Clockwise rotation is most common (as viewed from caudal to cranial with the dog in dorsal recumbency). Gastric distention results in decreased venous return to the heart, congestion of the splanchnic vessels, and increased gastric wall pressure. Decreased venous return leads to obstructive shock. Splanchnic congestion results in breakdown of the gut mucosal barrier and consequential bacterial translocation, activation of systemic inflammatory mediators (SIRS), and disseminated intravascular coagulation (DIC). Increased gastric wall pressure leads to gastric mucosal ischemia, infarction, ulceration, perforation and peritonitis. The spleen, attached to the stomach via the gastrosplenic ligaments and the short gastric blood vessels, commonly rotates with the stomach to the right ventral abdomen. This may lead to congestion, splenomegaly, infarction and thrombosis, torsion, and significant hemoperitoneum when the gastric branches of the splenic arteries are avulsed.

Clinical signs

The classic presentation is that of a large, deep chest dog with an acute history of agitation and non-productive retching that has a distended, tympanic abdomen, ptyalism, and shock. However, it is important to remember that GDV can occur in atypical breeds and species and that the stomach can be hidden under ribs. Additionally, these patients can present with varying degrees of shock, from well compensated to terminal.

Diagnosis and therapy

An emergency database should include the quick assessment tests of packed cell volume, total solids, blood glucose and azotemia estimate (QATs); a venous blood gas; serum or plasma lactate; and coagulation profile. QATs establish baseline values and aid in monitoring individual patient trends. A venous blood gas provides acid base status which is important as decreased venous return results in vascular stasis, lactic acid accumulation, and ultimately metabolic acidosis. Additionally, compression of the respiratory tract may result in a respiratory acidosis. Correction of acid base or electrolyte abnormalities is important prior to induction of general anesthesia. Lactate is used to evaluate the adequacy of perfusion. It is produced when anaerobic metabolism occurs and is considered an early indicator of tissue hypoxia. It should be interpreted in conjunction with clinical perfusion parameters such as pulse quality, mucus membrane color, capillary refill time, and rectal temperature. Lactate has been evaluated in dogs with GDV [Plasma lactate concentration as a predictor of gastric necrosis and survival among dogs with GDV: 102 cases (1995-1998). JAVMA, 215 (1), 1999]. In this retrospective study a low serum lactate was a better predictor of survival than high lactate was a predictor of death. For this reason a single lactate may have minimal value whereas serial lactate measurements are far most useful. Various coagulation parameters including platelet count, prothrombin and activated partial thromboplastin times, fibrinogen, antithrombin, and fibrin degradation products have also been evaluated in GDV patients [Abnormal hemostatic profiles and gastric necrosis in canine GDV. Vet Surgery. 1993, 22(2):93-7]. In this prospective study, none of the 10 dogs with fewer than 2 abnormal hemostatic test results had evidence of gastric necrosis at surgery or necropsy.