When is vomiting or diarrhea 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.

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.

Feeding the animal with vomiting/diarrhea

How to feed

Feeding must occur - either voluntarily or by force feeding or tube feeding. Offering anorexic cats and dogs different choices f food may stimulate their appetite, However, if the food is associated with nausea or vomiting, food aversion can occur, especially in the cat. Struggling and aggressive manipulation can be debilitating or life-threatening for the critical cat and is not to be attempted if there is depressed mentation, difficulty swallowing, or potential of stress induced complications. Tube feeding can be done by orogastric intubation (reserved for neonates), nasoesophageal (NE) or nasogastric (NE) intubation, gastrostomy (G), jejunostomy (J), or esophagostomy (E) or esophagogastric (EG) intubation, depending upon the site of tube insertion.

The function and patency of the gastrointestinal tract will determine which tube site is selected. The author prefers esophagostomy intubation whenever possible, finding it to be easily accomplished and well tolerated by the cat. Most of the critical cats will have nasal oxygen tubes, making occlusion of the other nostril by nasoesophageal or nasogastric tube a profound discomfort. A radiograph should be taken to check the placement of the tip of any NG, NE, E or EG tube. If it is in the stomach too far, the tube tip may cause gastric irritation and vomiting. However, the NG or NE tube is inexpensive, fast to apply, and rarely requires general anesthesia. Placing the tip of the catheter, whether it is an esophagostomy tube or an NG tube, in the stomach, allow for gastric decompression in the vomiting patient. "Trickle flow" feeding from the esophagus or stomach, with a dilute concentration of nutrients, has been used successfully, with anitemetics and motility modifiers, in the dog and cat with vomiting and diarrhea.

What to feed

Meat-based diets should be selected that provide a good quality protein, vitamin A, thiamine and niacin. The diet should be adequately supplemented with taurine and arginine. Multiple B vitamins are commonly added to the intravenous fluids or the enteral diets. The status of the cat and the size of the tube selected will dictate which diet is selected.

Whichever tube method is selected, nutritional support is initiated using a small amount of oral glucose/electrolyte solution (e.g. Resorb ®; Pedialyte®). This is called "mircoenteral nutrition" and is provided to test the tolerance of the GI mucosa to feeding and to help protect the gastric mucosa from erosion, atrophy, and GI immune function. It is not expected to meet caloric or nutritional requirements.

Small diameter tubing (NE, NG, J tubes) will require the instillation of a veterinary liquid diet. Feline Clinicare®/Clinicare RF® (Abbott) are designed to meet the nutritional requirements of the cat. When the patient has a very sensitive GI tract, NE or NG tube feeding by trickle flow with dilute liquid diet may be used to initiate enteral feeding and build up dietary tolerance.

Larger diameter feeding tubes (E, EG, G) can accommodate thicker veterinary enteral canned diets. The diets are formulated to meet the high protein, high fat needs of the cat and are used as soon as tolerated. High calories in a low volume are ideal and can be provided by Maximum Calorie® (Eukanuba) and a/d® (Hills) diets. When the fat content needs to be lower or the cat is obese or diabetic, a high protein low carbohydrate diet, such as Purina DM ® (Nestles Purina) can be diluted and blendarized for use.

Partial parenteral nutrition (PPN) is provided when complete enteral feeding is not possible for the first 1-3 days. This is an intravenous solution of branched chain amino acids (3% to 8.5%) and electrolytes (Freeamine®; Procalamine®). Glucose is typically provided or added to make a 2.5-5% solution. The electrolyte solution is consistent with a maintenance electrolyte solution, allowing the PPN to be delivered as part of the maintenance fluid therapy. Because the osmolality is similar to plasma or only slightly greater, PPN can be delivered through a peripheral vein. This solution does not provide all of the essential nutrients and is meant to only off-set protein catabolism while weaning onto full enteral support.

How much to feed

The amount of nutrition to provide is determined by calculating the caloric needs of the patient. The resting energy requirement (RER) is determined by the following:

RER (kcal) = 30 x kg weight* + 70

*for obese cats, use an estimate of ideal body weight

During times of critical illness, the RER may increase as metabolic rate increases (estimated to be 1.2-1.5 times normal), requiring an adjustment in the RER of 1.2-1.5 times. This is particulary true for cats and dogs with head trauma or burns.

How to feed

Enteral feeding begins with microenteral nutrition using a glucose/electrolyte solution. In the vomiting dog or cat, this is best delivered by trickle flow, through the feeding tube by constant rate of infusion (CRI) (0.6-2.0 ml/kg/hr CRI). The fluid is placed in an empty IV fluid bag and administered through an IV administration set and fluid pump. It is helpful to add food coloring to the solution to prevent the nursing staff from confusing this enteral solution with intravenous solutions. In addition, the food coloring will identify this solution in fluid. During this period of microenteral feeding, PPN is often utilized to decrease catabolism of proteins while weaning onto enteral feedings.

Most patients with nausea and vomiting will benefit from trickle flow feeding of a dilute veterinary liquid diet. The diet is diluted with water (1:3 or 1:2) depending upon the degree of anticipated GI sensitivity. Food coloring is added and the solution administered as above for microenteral feeding. Food is warmed to body temperature prior to feeding. If the animal experiences vomiting, the administration rate is slowed. PPN can be used as a supplement to the enteral feedings during this weaning process.

The concentration is increased once the cat has tolerated the lower concentration and volume for 4-6 hours. Once the cat has been weaned onto concentrated diet, the volume is then increased. The goal is to administer concentrated diet (liquid or canned) by periodic bolus infusions (q4-8h) to meet total daily caloric requirements by day 3 of hospitalization. The rate of administration, volume of administration, and concentration of the diet are all variables that can be adjusted if nausea, vomiting, diarrhea or other signs of GI sensitivity occur.