Download Gastric Dilatation Volvulus - Aspen Meadow Vets

Gastric Dilatation Volvulus
Josie Mallinckrodt, DVM, DACVS
What is Gastric Dilatation Volvulus?
GDV is defined by an abnormal entrapment and accumulation of fluid and air within the
gastric lumen that results in extreme, traumatic distention of the stomach and variable
rotation of the stomach on its long axis. The cause of this fluid and air entrapment within
the stomach is unknown. Risk factors include a deep-chested conformation and a
nervous/anxious temperament.
In a normal canine abdomen, the pylorus is usually situated on the right side. With GDV the
pylorus moves ventrally and to the left side of the body. This is also a “clockwise” position
from the surgeon’s perspective. The spleen is often rotated to the right side of the body
along with the gastric rotation due to the tight connection with the stomach via the short
gastric vessels. Most commonly the stomach rotates between 240-270 degrees, however
any amount of rotation can occur.
What are the physiologic consequences of GDV?
GDV causes three major physiologic changes within the body: decreased inspiration,
decreased venous return, and compromised gastric function. As the stomach fills with air,
there is increased pressure on the diaphragm, which results in a decreased tidal volume. A
mismatch of ventilation and perfusion follows resulting in a decreased partial pressure of
oxygen. Poor oxygenation of the blood results in poor oxygenation of the peripheral tissues
and tissue hypoxia. This can lead to myocardial ischemia, acute renal injury and lactic
acidosis.
Decreased venous return is primarily due to compression of the abdominal vessels,
particularly the vena cava and portal vein, secondary to gastric distension. If the spleen is
involved there is further loss of volume as blood collects within the splenic parenchyma.
Cardiac output is decreased due to the decreased venous return, which then leads to further
compromise in organ perfusion. This further adds to the myocardial ischemia, the source of
arrhythmias poor cardiac function during GDV. Other organs compromised include the
stomach and the kidneys.
Gastric function is compromised for three reasons; the poor perfusion, decreased venous
return, and mechanically from the physical dilation of the tissues. Dilation of the stomach
results in ileus, which can lead to fluid and gas accumulation in other areas of the small
intestine and colon. Ileus can lead to electrolyte imbalances. In addition, the gastric hypoxia
leads to necrosis of the stomach starting with the mucosa, resulting in translocation of
bacteria. Endotoxins and bacteria are allowed to enter the systemic bloodstream resulting in
endotoxic shock. Further gastric necrosis can lead to gastric perforation and septic
peritonitis.
Additional systemic concerns include ischemia, oxidative injury and reperfusion injury.
While there are ways to measure these processes, these tests are not available for the
standard clinician and are not of value as a sole measurement.
Clinical presentation of GDV and initial management
ASPEN MEADOW VETERINARY SPECIALISTS, PC | ANIMAL EMERGENCY AND CRITICAL CARE, LLC
104 S. Main Street Longmont, CO 80501 | Phone 303-678-8844 | Fax 303-678-8855 | www.AspenMeadowVet.com
Patients with GDV will present with the primary complaints of abdominal distention, anxiety,
panting, drooling and a nonproductive retch. There is a continuum as to the level of clinical
affectation at presentation extending from walking and bright to laterally recumbent and
minimally responsive.
A right lateral abdominal radiograph should confirm the
diagnosis of GDV – if there is a need, a VD radiograph
can be taken, it should be avoided however due to the
increased pressure it will place on he vena cava and
portal veins. The classic signs on the lateral radiograph
are compartmentalization of the stomach with the
pylorus in a dorsal position – also known as the double
bubble or Popeye’s arm.
Placement of two cephalic catheters is important for
fluid resuscitation – cephalic catheters will allow the IV
fluids to reach the heart and help with cardiac output,
whereas catheters placed in the saphenous veins will
have a lesser effect. A central line is also an option.
It is important to obtain blood pressure readings as well as an ECG. Many of our GDV
patients will present with hypotension and arrhythmias – resolving these issues prior to
anesthesia will improve their prognosis and help to decrease post-operative complications.
Treatment for hypotension includes crystalloid fluid boluses, colloid support and plasma or
blood products if indicated. Sometimes additional support via vasopressors is needed, but
should only be reached for if fluid volume resuscitation is not sufficient. Ventricular
arrhythmias are the most commonly identified during GDV and should be treated with
lidocaine if indicated (ventricular tachycardia with heart rate greater than 160, multiform
ventricular premature contractions, R on T, or ventricular premature contraction bigeminy
or trigeminy).
Gastric decompression is an essential step for successful
outcome. The two pre-operative methods are passing of
a gastric tube and trocharization. Often times with an
opiod on board it is possible to pass a gastric tube. You
can use a roll or tape in the mouth as both a mouth gag
and a perfectly sized hole for the gastric tube – if the
tube is able to pass into the stomach it allows excellent
decompression, gastric lavage and can help to untwist
the stomach. Placing the patient into different positions,
such as changing recumbency or holding in an upright
position, can help to get the gastric tube to pass. If a
stomach tube can’t be passed, then trocharization can be
used – a large bore catheter, preferable a 14 or 16
gauge, is passed at the point of greatest tympany with
the dog in lateral recumbency. The amount of
decompression achieved with this technique is variable; sometimes applying slight pressure
to the abdomen can help.
Obtaining blood work prior to surgery is also important– many patients have normal blood
work in the early phases of this disease, but this will provide a baseline for accurately
assessing your patient. Normal acid/base status can be misleading because accumulation of
fluid within the stomach results in a metabolic alkalosis, while vascular stasis and tissue
hypoxia result in metabolic acidosis. This is further compounded by tachypnea, which can
cause respiratory acidosis. So while the pH and electrolytes may appear normal initially,
these patients are actually in a severely altered metabolic state. Clotting times are also an
important value to have prior to surgery.
Lactate is a blood measurement that has gotten increased attention over the past several
years. It is used in humans as a measure of response to treatment and does have
prognostic value. In dogs with GDV, there are many disagreeing studies as to a specific
lactate value that helps with both prognosis and ability to predict gastric necrosis. The key
point from all of the studies is that a single lactate value is not a prognostic indicator and
should not be used to decide if a patient will or will not have gastric necrosis or survive after
GDV. Serial lactate measurements do have value for prognosis, as well as for a measure to
the response to treatment. A decrease of about 40-50% in serial lactate measurements
indicates a good response to treatment and may have value as a predictor of survival.
Surgery
Surgery is the recommended treatment for GDV, even if the volvulus is resolved after
passing of a gastric tube. Recurrence rates for GDV without surgical gastropexy are up to
54%; with surgical gastropexy recurrence is less than 4.3%. A full ventral midline celiotomy
should be performed – a large incision allows for easier derotation of the distended
stomach, as well as a full explore. The first step of surgery is to derotate the stomach and
get it back into normal position, from the surgeons standpoint this usually requires
counterclockwise rotation of the stomach. Once the stomach is back in normal position a
gastric tube should be passed and the surgeon should use their hand to feel and guide the
tube passing into the distal esophagus and stomach. The spleen usually derotates with the
stomach. After gastric decompression and lavage is complete, it is time to assess the health
of the gastric tissues and the spleen. Palpating the seromuscular slip of the gastric tissues is
very helpful; pinch the stomach between two fingers and pull back allowing the layers to
slide between your fingers. If you can easily palpate when the mucosal layer “slips” away
from your fingers, that area of the stomach is viable. When the gastric layers are
devitalized, the “slip” of the mucosa is no longer palpable. Serosal color is a good indicator
of gastric wall integrity as well because about 80% of the blood supply goes to the mucosa,
while 20% goes to the submucosa, muscularis and serosa. If the serosa is blackened that
section of the stomach needs to be resected. Always be sure to check the dorsal aspect of
the cardia near the distal esophageal sphincter. Gastric color and health can improve
significantly after derotation of the stomach, so be sure to give it some time prior to making
decisions about resection.
Some free blood in the peritoneal cavity at the time of surgery is common due to tearing of
the short gastric vessels. Be sure to evaluate those vessels, usually the bleeding has
stopped prior to surgical intervention, but intermittently they may require ligation.
It is also important to assess the spleen. Splenic congestion usually resolves after
derotation. You can palpate the splenic artery, if pulses are absent and the spleen color
does not improve after several minutes, splenectomy is indicated.
After full assessment of the gastric tissue and spleen health, don’t forget to perform a full
explore. Gastric foreign bodies have been noted to increase the incidence of GDV, so
palpate the stomach fully. Also, assess the other abdominal organs and the remaining
intestinal tract. Many of our GDV patients are older and can have concurrent disease, such
as liver masses.
Gastropexy is the last step of surgery prior to closure. Multiple types of gastropexy exist.
The most commonly performed are incisional, beltloop and circumcostal. All of these are
appropriate options and have the same holding power after the adhesion has formed. We no
longer recommend incorporating the gastropexy into the midline incision closure.
Remember to lavage and suction out the peritoneal cavity prior to closure.
Post-operative care
Post-operative care of GDV patients is highly variable depending on several factors including
response to gastric decompression, presence of acute renal failure, arrhythmias, continued
hypotension, electrolyte and acid base abnormalities, and presence of disseminated
intravascular necrosis. Even patients who are stable at presentation may decompensate and
require extensive post-operative care. Tailor your care to each patient as needed.
Mortality of GDV
The most recent study on survival and mortality of GDV came out in 2010 in the Journal of
the American Animal Hospital Association by Mackenzie et al. It was a retrospective study of
306 GDV patients. Factors that did not affect mortality were breed, age, sex, duration of
clinical signs, preoperative ventricular tachycardia, surgical time or the need for partial
gastrectomy. Factors that increased mortality were post-operative ventricular tachycardia,
preoperative intermittent ventricular arrhythmia, the need for splenectomy, as well as the
need for splenectomy and partial gastrectomy. Interestingly, the factor that decreased
mortality was a longer time between initial presentation and surgery, likely because those
patients received improved stabilization prior to surgery. Overall mortality rate was 10%.
Mortality increased to 15% if a patient required a splenectomy and to 20% if splenectomy
and partial gastrectomy was required. Patients who required partial gastrectomy alone had
a mortality of 9.5%.
Conclusions
GDV is a very complex disease process involving many systems and types of injury on both
a cellular and complete organ level. We continue to work to find additional prognostic
indicators for these patients to help guide owners in their decision-making, but so far we are
unable to accurately gauge how these patients will do. Serial lactate measurements help
with both prognosis and to assess response to treatment, but a single value alone is not
diagnostic or prognostic. There are new avenues being explored for therapeutic options,
including lidocaine treatment at presentation, antioxidant supplementation and other
methods to prevent reperfusion injury. Intense pre, intra and post-operative treatment with
pain medications, crystalloids, colloids, anti-arrhythmia medications, gastroprotectants and
blood products remain the treatments of choice in these patients. Monitoring, including
blood pressure, ECG, blood work, blood gas and clinical response to treatment, are all
important for success. Stabilization prior to surgical intervention is important for overall
survival in these patients – so while we need to get them into the operating room quickly,
we also need to ensure they are adequately stabilized. Overall mortality with GDV is greatly
improved over the past 20 years, improving from 18-20% down to 10%. Prophylactic
gastropexy should always be considered in our large breed patients when they are
undergoing an elective procedure, such as a spay or neuter.