When is vomiting an emergency? (Proceedings)

Vomiting is one of the most common medical presentations to the emergency room. It is not uncommon for the dog or cat to eat grass or their food and vomit – and subsequently go about their lives unaffected. So – when is vomiting an emergency? While there are no simple, nor clear cut answers, the simple guidelines in the box can guide the triage nurse or doctor.

Vomiting is an emergency when the cause of vomiting can be associated with

• a potentially life-threatening etiology (eg. toxins, GDV, foreign body, sepsis)

• possible decompensation of a chronic serious disease (eg. renal failure, diabetes);

OR the effect of vomiting causes compromise of

• airway

• breathing

• circulation

The gastrointestinal (GI) signs can be caused by pathology initiated within the GI tract (primary) or caused by systremic problems (secondary). Catastrophic problems related to vomiting can include: cardiac arrest (vasovagal reflex bradycardia), upper airway obstruction, aspiration pneumonia, profound hemorrhage, severe hypovolemic, distributive and/or septic shock, and ischemia of GI organs. The animal must be rapidly stabilized and causes requiring surgical correction rapidly investigated.

Vomiting is a reflex expulsion of gastric contents. Vomiting can be active with GI contractions or passive. It is important to understand the mechanisms of vomiting center stimulation to identify the cause and best therapeutic approach (see Figure 1).

Figure 1. Mechanisms of vomiting and site of antiemetic action.

The color of the vomitus will locate the origin. Clear vomitus is swallowed saliva from stomach;. yellow reflects refluxed digested bile from stomach;. green suggests undigested bile from the upper duodenum due to obstruction or ileus; and brown fluid with a fetid odor is from the small intestines suggesting total obstruction or generalized ileus. Blood in the vomitus from primary GI causes typically appears as red colored fluid or as "coffee grounds". This "hematemesis" suggests a serious underlying pathology. Streaks of blood within the clear or yellow vomitus is from gastric irritation due to vomiting and is not indicative of specific pathology.

The timing and force of vomiting can suggest the location : shortly after eating indicates gastric inflammation or obstruction; large amounts of undigested food up to 6 hours post prandial suggests pyloric obstruction or gastric atony; projectile vomiting indicates pyloric or upper duodenal outflow obstruction or ileus; and non-productive vomiting or retching may indicate the presence of gastric dilatation-volvulus.

There are four mechanisms of diarrhea that can occur in any combination: osmotic diarrhea; secretory diarrhea; increased intestinal permeability; and abnormal gastrointestinal motility. Bacterial endotoxins can inhibit the ion pumps in GI epithelium resulting in secretory diarrhea. Any cause of GI mucosal erosions (eg severe shock, toxins, hyperthermia, foreign body) or blunting of GI epithelium (e.g. viral or baterial agents) can cause diarrhea by any or all mechanisms listed above: osmotic due to cellular debris in the intestinal lumen; secretory due to bacterial endotoxins or other pump inhibitors; motility due to ileus; and increased permeability. The presence of blood [melena (digested) or hematochezia(fresh)] indicates that the intestinal barrier is damaged and increased protein loss and bacterial translocation anticipated. Small intestinal diarrhea typically results in greater fluid, electrolyte, protein, and acid-base abnormalities than large intestinal diarrhea and is characterized by liquid projectile feces. Large bowel diarrhea generally has a "pudding" consistency with mucous or fresh blood.

The systemic inflammatory response syndrome (SIRS) can be associated any cause of vomiting and/or diarrhea..The increase in capillary permeability can lead to third spacing of fluid and electrolytes into the intestinal tract. Vomiting associated with gastric outflow or upper duodenal obstruction (mechanical or physiologic) can cause hypochloremic metabolic alkalosis. Other causes usually result in metabolic acidosis depending upon the perfusion status of the animal.

Resuscitation: Hypovolemia should be rapidly resuscitated with a combination of isotonic replacement crystalloids and synthetic colloids. Isotonic balanced buffered crystalloids (0.9% saline if metabolic acidosis) (10-20mls/kg IV) are administered with hetastarch or dextran-70 (5-20 ml/kg dogs; 5 ml/kg cats) titrated to supranormal end-points. When abdominal hemorrhage or brain pathology is suspected, fluids are titrated using small volume resuscitation techniques to hypotensive resuscitation end-points. Analgesia is provided using narcotic injections: 0.4mg/kg butorphanol, 0.2mg/kg hydromorphone IV, 0.05-0.1mg/kg , or oxymorphone IV, with or without a sedative.

Measures necessary to prevent vomiting and aspiration are used to include antiemetic (see Figure 1) and/or promotility agents and nasogastric tube suctioning. When vomiting is associated with an unobstructive ileus or stimulation of the vomiting center or CRTZ zone, antiemetics are indicated alone or in combination: metoclopramide 0.2-0.4 mg/kg SQ q6-8h or followed by a 1.0-2.0 mg/kg/24h IV by constant rate infusion; ondansetron 0.1-0.2 mg SQ q 8h, or 0.5 mg IV load followed by 0.5 mg/kg/h IV by constant rate infusion; chlorpromazine 0.05 mg/kg IV, 0.01-0.025 mg/kg IV (cats) q 4-6h if cardiovascularly stable; ranitidine 2 mg/kg IV q 12 h. When an unobstructive ileus is occurring, administration of promotility agents is indicated, such as metoclopramide or cisapride (dog: 0.1-0.5 mg/kg PO q8-12h, cat: 0.5-1 mg/kg PO q 8h). When esophageal or gastric ulceration is suspected, sucralfate (0.5-1 gram q 4-8h) and one of the H2-antagonsits or hydrogen pump inhibitors are indicated: ranitidine (2-2.5mg/kg q 12 h); or cimetadine (4mg/kg IV q 6-8h); or omperazole (0.7 mg/kg, up to 20mg PO q 24h). Intestinal motility suppressants are not recommended for routine use. Most anti-diarrheal medications decrease peristalsis which may lead to severe intestinal bacterial overgrowth and translocation.

Diagnostics

Laboratory samples are collected, prior to fluids when possible, for an immediate database (PCV, TS, Glucose, labstick BUN, electrolytes, venous blood gas), and samples to be run for a CBC, serum chemistry, urinalysis, coagulation profile, Parvo test, and ethylene glycol as indicated. Culture the feces for Salmonella and Campylobacter if contagious cause of diarrhea is suspected. Free T4 levels (feline) and ACTH stimulation (canine) are run if endocrine causs are suspected.

The mental status and cranial nerves are evaluated for abnormalities, and the cervical neck palpated for pain, which may indicate CNS pathology and/or meningoencephalitis. This might indicate an etiology as well as require that special care be taken to prevent aspiration of vomitus. The oropharynx is examined for presence of a linear foreign body around the base of the tongue. Auscult the abdomen for gastric and bowel sounds. Absence of bowel sounds suggests hypomotility, ileus, fluid accumulation, or diffuse peritonitis. Palpation of the abdomen will evaluate the abdominal organs; gastrointestinal distension, thickening, or plication may indicate an obstruction from a foreign body or mass. A tympanic cranial abdomen suggests a gastric dilatation-volvulus Focal pain or retching/vomiting during palpation suggests involvement of local structures. Feces are evaluated for diarrhea, foreign objects and the presence of blood. Dark blood (melena) is associated with upper GI bleeding and frank hemorrhage is associated with lower intestinal bleeding. Rectal temperature can reflect possible inflammation or infection if elevated, or poor perfusion or toxins if low.

If gastric distension with gas is present, fluid resuscitation and gastric decompression are performed prior to obtaining radiographs. Radiographs and ultrasound of the abdomen are evaluated for detail, presence of gas, organ enlargement, organ displacement, and mineralized/calcified lesions. Generalized loss of intraabdominal detail is a sign of diffuse peritoneal disease. Diffuse gas dilation of the stomach with a "shelf" sign is diagnostic for gastric dilatation-volvulus. Segmental gas dilation of the intestines with or without evidence of a foreign object suggests obstruction. Intraabdominal gas is a sign of a gastrointestinal rupture or intraabdominal infection with a gas-producing bacteria. Mineralized and calcified lesions of the urinary or biliary tract can indicate possible inflammation or obstruction. Changes in organ size and shape is a sign of organ dysfunction. Loss of detail in the right upper quadrant and a duodenal loop sign can suggest pancreatic inflammation. Ultrasound evaluation can be used to evaluate for peritoneal fluid, Gi obstruction or intussusception, detect subtle organ enlargement, mass lesions, metastatic disease, vascular occlusion, urinary tract obstruction, and pancreatitis. Aspiration of mass and cytologic examination of fluid can be done with ultrasound.

Continued support

Interstitial fluid deficits and on-going fluid losses are replaced using balanced isotonic replacement crystalloids or 0.9% saline if there is hypochloremic metabolic alkalosis. If it is expected that resolution of signs will take time, if SIRS is occurring, and/or an on-going need for colloid support is anticipated, hetastarch is administered (0.8ml/kg/hr) in addition to crystalloid maintenance infusion to support intravascular colloid osmotic pressure and volume. Administer antibiotics if suspect bacterial translocation and/or bacterial etiology. First generation cephalosporin (cefazolin 20 mg/kg IV q8h) and metronidazole (10 mg/kg IV q8h) will provide broad spectrum coverage of aerobes and anaerobes.

On-going life-threatening gastric hemorrhage can be controlled by placing a nasogastric tube and performing cold water gastric lavage until bleeding subsides or the animal is prepared for surgical intervention. Evaluate the need for transfusion. Emergency surgical intervention is required for uncontrolled hemorrhage, intestinal obstruction, perforation of the gastrointestinal tract, presence of intraabdominal gas, septic peritonitis, bile peritonitis, intussusception, linear foreign bodies, ruptured tumors, torsion of the spleen, testicles, uterus, or intestines, gastric dilatation-volvulus, mesenteric volvulus, organ abscess, pyometra, or if unable to stabilize with appropriate aggressive resuscitative measures.

Monitoring

Physical parameters, blood pressure and central venous pressure are used to evaluate intravascular volume and hydration status. Temperature body weight, mentation, and frequency and characterization of the vomitus and diarrhea are recorded. Frequent monitoring of PCV/TP, albumin, glucose and electrolytes are necessary. Follow the Rule of 20. Any sudden change in mentation should prompt the nursing staff to suspect hypoglycemia.