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Volume 50, Issue 11
Whether you perform surgery yourself or refer your patient to a specialty veterinary facility, aggressive stabilization can make all the difference.
Just before closing time, a large-breed dog arrives at your clinic with a history of nonproductive retching, lethargy and a progressively distending abdomen. You know gastric dilatation-volvulus (GDV) is likely, but where do you begin? Should you refer the patient straightaway? Will you need to perform surgery yourself?
If this scenario makes your palms sweat and your adrenals squeeze, fear not. GDV is a true medical and surgical emergency, but with a logical diagnostic and treatment approach and a focus on thorough preoperative stabilization, a good outcome can be achieved in the majority of cases. Even if you intend to refer the case to a specialist or emergency facility, the early stabilization procedures you perform can make a big difference to your patient's success, and your clients will appreciate your help in their decision-making process as they grapple with a very stressful situation.
Patients that present with a history suggestive of GDV should be brought immediately to the treatment area and assessed as soon as possible by a veterinarian. In the meantime, the owners should be asked to sign a consent form authorizing initial stabilization procedures and diagnostics. Remember that although middle-aged, large- and giant-breed, deep-chested dogs are the poster children of GDV, dogs of any breed between 10 months and 14 years of age-and even cats-may be affected.
Patients with GDV are often hyper-salivating with a painful abdomen, and a tympanic quality can be auscultated on abdominal percussion. Patients may present in a critical condition with an unstable cardiovascular status. Heart rate, respiratory rate, temperature, blood pressure and pulse quality should be evaluated immediately.
The first priority in treating patients with suspected GDV is to stabilize their cardiovascular status. The sooner you treat shock and restore oxygen delivery to the tissues, the less likely it is that the patient will require resection of necrotic gastric wall and the better the overall prognosis. Although it can be tempting to perform radiographs immediately, this step should be postponed until after initial resuscitation.
Use initial physical exam findings to guide your stabilization efforts and be aware that patients may present in varying degrees of shock. Those presented earlier in the disease process will have signs consistent with hyperdynamic, hypovolemic shock due to their blood volume being restricted to the caudal half of their body by the enlarged stomach compressing the caudal vena cava. These dogs will be tachycardic and tachypneic, with normal femoral pulses, pale mucous membranes and a slow capillary refill time.
As the syndrome progresses, dogs will develop injected mucous membranes and weak femoral pulses-signs of endotoxemic shock. Eventually, patients will decompensate to a point where they are hypotensive and bradycardic with white mucous membranes; at this stage they often present laterally recumbent.
Fluid resuscitation is the most important component of GDV patient stabilization. Place two venous catheters in the cranial half of the body (cephalic or jugular veins can be used). Select the largest size catheters possible to allow rapid delivery of fluids. Provide crystalloid fluid therapy (e.g. lactated Ringer's solution, Plasmalyte or 0.9% sodium chloride) initially at a dose of 40-90 ml/kg over the first 30 to 60 minutes. As a rule of thumb, a large-breed (30-kg) dog will require 1.5 to 3 L crystalloids, while a giant-breed (60-kg) dog will require 2.5 to 5.5 L. Alternatively, you can use colloid fluids (e.g. hydroxyethyl starch) at a dose of 10-20 ml/kg combined with crystalloids at 10-40 ml/kg. Titrate fluids to effect until you note improvements in heart rate, respiratory rate, mucous membrane color and refill, and blood pressure.
Patients with GDV can be painful, so administration of opioid analgesia is helpful. Pure mu agonists (fentanyl, methadone, hydromorphone) are preferred over agonist-antagonists (buprenorphine) or partial agonists (butorphanol), as these can interfere with the effects of pure mu agonists administered perioperatively. Nonsteroidal anti-inflammatory drugs (NSAIDs) are always contraindicated in cases of GDV.
Gastric decompression is an important part of stabilization as it relieves pressure on the caudal vena cava, thus allowing blood to flow from the caudal half of the body back to the heart (improved preload). It also helps to improve gastric perfusion and patient comfort. Decompression can be performed either via orogastric intubation or trocharization. Although orograstric intubation is more effective in decompressing the stomach, it can be challenging in awake patients and is generally reserved for those that are sedated or recumbent. Take care to protect the airway; intubation may be required to avoid aspiration pneumonia. Premeasure a large-bore, smooth tube to the last rib and lubricate it. Note that often the tube cannot be passed past the lower esophageal sphincter due to the torsion, and care must be taken not to force the tube as esophageal perforation is possible.
If orogastric intubation is not possible or not safe, you can perform trocharization over the region of greatest gastric tympany, usually over the right lateral abdomen caudal to the last rib. Clip and aseptically prepare the skin, insert a 14- to 18-ga over-the-needle catheter, and remove the stylette. You may need to repeat trocharization if surgery is delayed as the stomach will continue to fill with gas.
An electrocardiogram should be performed on GDV patients prior to surgery. Up to 70% of dogs with GDV develop cardiac arrhythmias,1 which are frequently ventricular in origin. Arrhythmias may occur up to 72 hours postoperatively. Patients with ventricular tachycardia, R on T complexes, multiform ventricular premature complexes, or clinical hypotension related to their arrhythmia should be treated with lidocaine (2 mg/kg slow intravenous bolus, then constant rate infusion [CRI] of 25-80 μg/kg/min).
A right lateral abdominal radiograph is the view of choice to diagnose GDV and is important to differentiate dogs with gastric dilatation from those with true dilatation and volvulus. In the latter, a soft tissue band will be present between the distended pylorus and the fundus-the so-called “double bubble” or “Popeye arm.” Dogs with gastric dilatation without volvulus will have a distended stomach without the soft tissue fold between the two regions.
The radiograph should also be evaluated for free peritoneal gas, which may indicate gastric perforation, a poor prognostic indicator. Note that patients that received gastric trocharization prior to radiographs may develop some scant free peritoneal gas in the absence of perforation. Thoracic radiographs may be indicated for patients in which aspiration pneumonia is suspected or for elderly patients in which GDV may be secondary to neoplastic causes.
Initial bloodwork should include packed cell volume and total solids, blood glucose and venous blood gas with electrolytes if available. In patients that will undergo surgery, complete blood count and serum biochemistry are indicated to assess platelet number, leukogram, liver and kidney function, and albumin levels. Coagulation testing (PT and aPTT) can help to identify patients that are coagulopathic or trending towards disseminated intravascular coagulation (DIC) preoperatively.
Ultimately, patients with GDV require surgery after medical stabilization. The decision to proceed with surgery can be difficult for owners, and family veterinarians play an important role when they're able to provide accurate information about the pet's prognosis to help with the process. Historically, GDV was thought to carry a poor prognosis, but the most recent studies report improved rates of survival of 73% to 90%.2-4
The variable most consistently associated with a poor prognosis is gastric necrosis,1-5 but unfortunately there is no way of definitively determining whether gastric necrosis is present until surgery is performed. However, several prognostic factors have been identified that can offer insight into whether your patient is likely to have a successful outcome.
In general, dogs that present with clinical signs of less than six hours' duration and those that “walk in” to the clinic do better than those that present laterally recumbent. Dogs that present with sepsis, gastric perforation or DIC have a worse prognosis.1,2,4,5 In one study, dogs with an increased amount of time between presentation and surgery had a decreased mortality rate, which speaks to the importance of aggressive preoperative stabilization.3
Blood lactate has been evaluated in several studies as an indicator of gastric necrosis. Normal canine lactate is <2.5 mmol/L, and increased lactate indicates poor tissue perfusion. If a blood lactate meter is available, measuring trends in lactate (rather than absolute values) can reflect the success of your stabilization efforts. A change (decrease) in lactate of greater than 42.5% after fluid resuscitation was associated with a survival rate of 100% in one study.6
Once you've made the decision to pursue surgery, the next consideration is whether to refer the case to a specialty or 24-hour facility or perform surgery at your own clinic. There are a number of factors that affect this decision, but referral is strongly recommended in all cases where gastric necrosis is suspected. Gastrectomy greatly increases the technical difficulty of the surgery, surgical stapling equipment available in specialty practices improves the efficiency and safety of the procedure, and postoperative care is significantly more intensive in patients that have undergone gastrectomy. Of course it's not possible to know for sure preoperatively that a gastrectomy will be required, but using the prognostic indicators above can give a reasonable idea of which cases will be more complicated.
Anesthesia for GDV patients should prioritize maintaining blood pressure and tissue oxygenation and avoiding arrhythmogenic agents. Therefore, alpha-2 agonists (dexmedetomidine, medetomidine), acepromazine and ketamine should be avoided. If possible, patients should remain in lateral recumbency for as long as possible during preparation for surgery to avoid additional pressure on the caudal vena cava, and preoxygenation is beneficial.
A common protocol is premedication with a benzodiazepine (e.g. midazolam or diazepam) and an opioid (e.g. hydromorphone or fentanyl), induction with propofol or alfaxalone, rapid intubation and endotracheal tube cuff inflation, and maintenance with isoflurane and oxygen. A fentanyl CRI of 5-10 μg/kg/h can be helpful to reduce the minimum alveolar concentration of isoflurane required. A lidocaine CRI can be administered concurrently with fentanyl-this has the dual effect of treating cardiac arrhythmias and providing analgesia.
Perioperative antibiotics are indicated in all cases of GDV, and a first-generation cephalosporin (e.g. cefazolin) or ampicillin-sublactam is appropriate. Administer the first dose at anesthetic induction and then every 90 minutes intraoperatively.
Be sure to clip a wide area-the caudal half of the thorax and the entire abdomen to the pubis should be prepared aseptically. The surgeon stands to the patient's right side. Perform a ventral midline celiotomy from the xyphoid to the fourth mammary glands or prepuce. Be prepared to encounter a hemoabdomen, as avulsion of the short gastric arteries from the greater curvature of the stomach has often occurred. In most cases, hemorrhage is self-limiting or can be addressed after gastric derotation. In patients with GDV, the greater omentum will be draped over the stomach upon entering the abdomen. Occasionally the stomach has derotated itself, in which case you will encounter the ventral surface of the stomach and spleen first, without omentum covering them.
In most cases, the stomach has rotated 180 to 270 degrees. To derotate the stomach, it may be necessary to first decompress it, which can be performed either by having an assistant pass an orogastric tube or by trocharizing the stomach with a needle intraoperatively. Then use your right hand to reach the pylorus, which is usually located dorsal to the esophagus on the patient's left side. With your left hand, form a fist and push the distended fundus (malpositioned on the dog's right side) dorsally while you pull the pylorus ventrally and to the right. The spleen will usually derotate with the stomach.
After derotation, perform complete exploration of the abdomen. Residual hemorrhage from the short gastric arteries may need to be controlled with ligatures. Palpate the stomach carefully for a gastric foreign body-gastrotomy is required in this case. Assess the color of the spleen-splenic engorgement is expected and the spleen should return to a dark purple color following derotation. If the spleen is black in color or thrombosis of the splenic artery has occurred (or both), a splenectomy is indicated.
Next, assess the gastric wall. This is a subjective assessment; accuracy improves with surgeon experience. When gastric wall color, thickness, peristalsis and bleeding on incision are evaluated in combination, accuracy of assessment is about 85%.7 The most common region affected by ischemic injury is the fundus along the greater curvature. Be sure to evaluate the stomach all the way to the lower esophageal sphincter. If the gastric wall remains black without improvement following reperfusion, if the serosal surface is pale greenish or grey, if there is absence of the normal mucosal “slip” or the wall is very thin, or if the serosal surface does not bleed when a partial thickness incision is made, partial gastrectomy is required. Gastrectomy can be performed by either a cut-and-sew technique with an inverting suture pattern, the use of surgical stapling equipment, or invagination of the ischemic gastric wall. The procedure is well described elsewhere.8
If you have performed a gastrectomy, lavage the abdomen with warm sterile saline and suction it, then exchange gloves and instruments for a sterile set. The next step is gastropexy. Incisional gastropexy is technically simple and highly effective, with reported rates of GDV recurrence almost 0%.9 Gastropexy takes place between the pylorus and the patient's right abdominal wall, so it's easiest if the surgeon moves to stand on the patient's left side. The pexy site on the stomach is located 2 to 3 cm oral to the pylorus, on the ventral surface, between the greater and lesser curvatures. The pexy site on the body wall is located in the right transverse abdominis, caudal to the last rib, parallel to the skin incision and approximately one-third of the distance from ventral to dorsal. In some larger dogs it may be necessary to place the pexy slightly more cranial, over the last ribs, but take care not to pass the insertion of the diaphragm on rib 11 to avoid an inadvertent thoracotomy!
It is helpful to have an assistant stand on the patient's right side, grasp the right abdominal wall along the linea alba with towel clamps and elevate it toward the ceiling for better visualization. A description of one way to perform the procedure is below:
Patients will require 24-hour care postoperatively, so transfer to a referral facility may be necessary. Continue fluid resuscitation and address electrolyte imbalances. Continue analgesia with pure mu agonists until the patient is able to tolerate oral analgesia. NSAIDs are contraindicated. You can continue to provide a lidocaine CRI to provide analgesia as well as to treat cardiac arrhythmias. Continuous ECG is helpful to screen for ventricular arrhythmias, which may persist for 48 to 72 hours postoperatively. Discontinue antibiotics within 24 hours of surgery unless gastric necrosis was present.
Patients can be fed within 12 to 24 hours of surgery, either via nasogastric (NG) feeding tube or orally. Small meals of a bland or gastrointestinal diet are ideal. Prokinetic therapy (e.g. metoclopramide or cisapride) and intermittent suctioning of the NG tube may be necessary in cases of ileus, and an antiemetic (e.g. maropitant) is helpful to prevent vomiting secondary to ischemic gastritis. H2 antagonists (e.g. famotidine) or proton pump inhibitors (e.g. omeprazole, pantoprazole) can be administered to treat gastric ulceration.
Major complications of surgery following GDV include peritonitis, sepsis and DIC.8 Peritonitis is most often due to ongoing gastric necrosis that was not adequately assessed initially and repeat surgery is required.
Did you know that Great Danes have a 42% of developing GDV in their lifetime?10 Other large and giant breeds have a lifetime risk of 4% to 37%.11 Prophylactic gastropexy in predisposed dogs reduces their mortality rate by 29 times,3 and incidence of GDV after incisional gastropexy is nearly 0%.12
Gastropexy can be performed at the time of spay or neuter and is recommended once dogs are close to adult size. Pexy can be performed either via a traditional “open” approach (as described above) or via laparoscopy or laparoscopic-assisted techniques. Minimally invasive approaches result in less postoperative pain and a faster return to normal activity than open approaches and are equally as effective.12,13 Next time you meet a puppy of a predisposed breed or are performing abdominal surgery for another reason on a large- or giant-breed dog, consider recommending prophylactic gastropexy-it may just save a life.
GDV is a true medical and surgical emergency, but most patients can do well with aggressive early stabilization and prompt surgical care. Taking the time to stabilize your patient prior to surgery will greatly improve postoperative outcomes, whether you plan to perform surgery yourself or transfer the patient to a referral facility. Palpating as many normal stomachs as possible and performing gastropexy in a prophylactic setting first will improve your technical expertise and confidence if and when you are required to perform surgery on a clinical GDV case.
Client education plays a major role in both the prevention of GDV through prophylactic gastropexy and rapid identification of the condition, which allows for timely veterinary care. Treating patients with GDV can be challenging, so don't hesitate to seek advice from your local emergency or specialist veterinary facility.
Dr. Bronwyn Fullagar, originally from Brisbane, Australia, is a locum small animal surgeon and veterinary educator based in Canmore, Alberta. This article was adapted from a lecture given at the Fetch dvm360 conference in Kansas City. Dr. Fullagar performs all types of surgery but particularly enjoys complex soft tissue surgery, minimally invasive surgery and surgical oncology. In her spare time she enjoys trail running with her dog, skiing, adventure travel and surfing.