By Courtney Peck, DVM, DACVECC
MSPCA-Angell West, Waltham
Gastric dilatation-volvulus (GDV) is an acute, life-threatening condition caused by distension and malpositioning of the stomach that leads to several pathophysiological complications. Various risk factors (large/giant breed dogs, body conformation, temperament, eating habits) have been identified, however the exact pathogenesis of this condition remains unclear. Once gastric dilatation and displacement occur, progressive gastric distension leads to increased intra-abdominal pressure, decreased cardiac venous return, diminished gastric perfusion, and increased diaphragmatic pressure. Further sequelae include a combination of hypovolemic, obstructive and distributive shock, myocardial ischemia resulting in cardiac arrhythmias and dysfunction, and gastric necrosis. More recently, the role that ischemia-reperfusion injury contributes to morbidity and mortality in dogs with GDV has been evaluated.
Over the past decade, studies have been published evaluating various aspects of this syndrome, leading to updated considerations and recommendations for the management of GDV. The goal of this article is to briefly discuss these more recent findings, in an attempt to improve our management and outcome of this disease.
Preoperative Thoracic Radiographs
GDV commonly occurs in geriatric dogs, and preoperative thoracic radiographs are often pursued to screen for metastatic pulmonary disease prior to proceeding with surgery. Green et al (JVECC 2012) retrospectively evaluated findings of preoperative thoracic radiographs in dogs with GDV. This study found that only 4% of dogs had pulmonary nodules, however 14% of dogs had radiographic evidence of aspiration pneumonia. Antibiotic therapy is not routinely used or recommended beyond the peri-operative period (unless there has been leakage of gastric contents), and thus some patients with unidentified aspiration pneumonia may benefit from appropriate antibiotic therapy. This finding suggests that preoperative thoracic radiographs may be warranted in all dogs prior to surgical correction of GDV.
Lactate has been extensively evaluated as a prognostic indicator for outcome in dogs with GDV, since the first paper on this subject was published in 1999 (de Papp et al, JAVMA). Originally, the degree of initial hyperlactatemia and its relation to gastric necrosis and survival were investigated. More recently, attention has focused on degree of reduction of lactate with therapy in relation to outcome. While an elevated lactate may be associated with a poorer outcome, the degree of reduction in lactate in response to therapy may also be prognostic. Green et al (JVECC 2011) found that a decrease in lactate ≥ 50% within 12 hours of presentation was associated with a positive outcome. Santoro Beer et al (JAVMA 2013) evaluated lactate as a predictive biomarker, and found that an initial lactate cutoff of 7.4 mmol/L was 80% accurate for predicting gastric necrosis and 88% accurate for predicting outcome. While these studies provide helpful information, specific recommendations to owners about their dog’s prognosis based on an initial lactate concentration should be made cautiously. Many dogs with elevated initial lactate values will survive, and some dogs with a lower lactate will not.
Gastric decompression: Gastric trocharization versus orogastric intubation
Initial stabilization of GDV includes fluid resuscitation and gastric decompression. Gastric decompression reduces intra-abdominal pressure, improving venous return and cardiac output; it also significantly improves patient comfort. Gastric trocharization and orogastric intubation have both been described as techniques for gastric decompression. Gastric trocharization can be performed rapidly and without sedation, and may be safer in hemodynamically unstable patients. Orogastric intubation requires sedation, but allows evaluation of gastric contents and/or gastric lavage. Goodrich et al (JSAP 2013) retrospectively compared both methods, and found that both techniques had high success rates and minimal complications. Neither method was found to be superior to the other.
Recent attention has focused on the role ischemia-reperfusion injury (IRI) plays in the outcome of dogs with GDV. IRI is suspected to contribute to the development of acute kidney injury (AKI), systemic inflammatory response syndrome (SIRS), and cardiac arrhythmias. During inadequate perfusion and oxygen delivery, cells develop abnormally high levels of hypoxanthine and calcium. Increased cytosolic calcium results in intracellular changes that lead to the production of xanthine oxidase (XO). When return of tissue perfusion occurs with stabilization, oxygen reenters previously ischemic cells and reacts with hypoxanthine in the presence of XO, creating reactive oxygen species. Reactive oxygen species (ROS) cause lipid peroxidation, damaging cell membranes and cellular proteins, resulting in massive cell damage and potentially cell death.
Lidocaine is a class Ib anti-arrhythmic, which acts on cardiac fast sodium channels, inhibiting their depolarization. Lidocaine’s effects on IRI likely occur via multiple mechanisms, including sodium/calcium pump inhibition, ROS scavenger, and inflammatory modulator. Lidocaine has been shown in human and laboratory animal studies to reduce the severity of IRI and SIRS. Bruchim et al (JVECC 2012) found that an initial bolus (2 mg/kg) of lidocaine at time of presentation (prior to intravenous fluid resuscitation and gastric decompression), followed by a continuous rate infusion (0.05 mg/kg/min) for 24 hours, reduced the occurrence of AKI and cardiac arrhythmias, and shortened hospitalization length. This study also found no adverse effects associated with lidocaine administration.
Association between previous splenectomy and GDV
A few studies have been released recently evaluating the association between previous splenectomy and development of GDV in dogs. Grange et al (JAVMA 2011) did not identify an increased incidence of GDV in dogs with previous splenectomies. A few years later, Sartor et al (JAVMA 2013) found contrasting results: dogs with a previous splenectomy were 5.3 times more likely to develop GDV than those without a history of splenectomy. At this time, there is not enough data to support a definitive recommendation, however it is clinically reasonable to offer a prophylactic gastropexy in at-risk dogs if they are undergoing abdominal surgery for another reason.
The current reported mortality rate for dogs with GDV ranges from 15-28%. As our understanding of the pathophysiology of this disease and its sequelae improves, we can ideally improve our outcomes. Whether your hospital performs stabilization and surgical correction of GDV, or whether emergency stabilization is provided prior to transport to another facility, awareness and incorporation of current considerations will only serve to improve our clinical acumen.
Bruchim Y, Itay S, Shira BH et al. Evaluation of lidocaine treatment on frequency of cardiac arrhythmias, acute kidney injury, and hospitalization time in dogs with gastric dilatation volvulus. JVECC 2012; 22(4): 419-427.
Goodrich ZJ, Powell LL, Hulting KJ. Assessment of two methods of gastric decompression for the initial management of gastric dilatation-volvulus. JSAP 2013; 54: 75-79.