Feeding Tubes and Nutritional Intervention in the Critically Ill Patient

Feeding Tubes and Nutritional Intervention in the Critically Ill Patient

International Veterinary Emergency and Critical Care Symposium 2004

Elisa M. Mazzaferro, MS, DVM, PhD, DACVECC
Denver Veterinary Specialists
Wheat Ridge, CO, USA

A nutritional assessment should be part of the regular history and treatment for any hospitalized patient, regardless of illness. Too frequently, history of the type and amount of food and patient's appetite are overlooked in the emergency situation and critically ill hospitalized patients. In addition to diet history, the physical examination should carefully evaluate the patient for its body condition score, muscle atrophy, peripheral edema, ascites, pleural effusion, risk factors for anorexia or vomiting. Additionally, laboratory markers of malnutrition are all important considerations when formulating a feeding plan for each patient. In simple non-stressed starvation, the body uses carbohydrates and fat stores for energy purposes. However, during the stressed starvation that is associated with a variety of illnesses, the body's normal mechanisms to compensate and preserve lean muscle mass are superceded by the massive release of inflammatory cytokines, glucocorticoids, and catecholamines that cause peripheral insulin resistance and allow proteolysis, muscle wasting, and lipolysis. Providing nutritional supplementation is of paramount importance in any patient that cannot or will not eat, cannot tolerate enteral feeding because of protracted vomiting, or cannot digest and absorb nutrients because of intestinal malfunction. Too frequently, lack of nutritional support contributes to protein-calorie malnutrition, leading to increased length of hospital stay, increased patient morbidity, depressed immune function, delayed wound healing, as well as increased patient mortality. Energy requirement can vary with the duration and degree of illness.

The resting energy expenditure (RER) is the amount of calories necessary for a nonstressed animal in the postprandial state in a calm, thermoneutral environment. In other words, it is the amount of energy necessary for basic functions not including obtaining and digesting foodstuffs. In patients over 2 kg, the linear formula (30 x BWkg) + 70 = Kcal/day = RER, can be used to calculate daily resting energy expenditure. The metabolic energy requirements (MER) is the amount of calories required for an animal in a thermoneutral environment with basic activity to obtain, digest and absorb foodstuffs. The IER, is the energy requirement associated with illness, injury, infection, and inflammation. The IER is an arbitrary number multiplied by the RER to combat the proposed increase in caloric requirements associated with various forms of illness. This number is largely subjective in nature. Research conducted in the critical care unit at ColoradoStateUniversity documented no increase in RER in numerous patients hospitalized in the critical care unit. In fact, the researchers documented an increase in RER in septic patients and those with suspected systemic inflammatory response syndrome (SIRS). Because of the down-regulation of metabolism and associated euthyroid sick syndrome that often occurs with critical illness, many hospitalized patients often have caloric needs that approximate their resting energy expenditures. Overfeeding, particularly carbohydrates, can contribute to respiratory acidosis and increased patient morbidity. Overfeeding early in the course of illness, particularly after a long period of anorexia or weight loss, can result in hyperalimentation and so-called "refeeding syndrome". Because of this, nutritional assessment of each patient should occur on an individual basis, depending on the patient's primary illness, the expected time that the patient will need nutritional supplementation, the patient's tolerance to enteral or parenteral feeding, anesthetic risks, and underlying illnesses including pancreatitis, gastric stasis or atony, esophageal motility disorders, and severe diarrhea.

Enteral nutrition is the preferred method of feeding as long as the GI tract can tolerate it. Any portion of the gastrointestinal tract that can be used should be used, as enterocyte atrophy occurs within 48 hours of anorexia and lack of trophic stimuli within the gut lumen. Early enteral nutrition has been shown to decrease patient morbidity in patients with parvoviral enteritis. Within 24 hours of hospitalization, fluid, acid-base, and electrolyte balance should be normalized, and exogenous nutritional support should commence in any anorectic patient or patient that is not tolerating oral feeding. In a patient that is not vomiting, one of the first things to try to stimulate an animal's appetite is to moisten and warm to food, to stimulate the senses. In some cases, an animal will eat moistened or wet diets when they will not voluntarily eat dry diets. If any animal won't eat a moistened or wet diet, adding flavor to the food in the form of spices, meat baby food, yogurt, or cottage cheese sometimes entices their appetite. Intravenous diazepam (0.2 mg/kg IV in dogs, 1-2 mg IV in cats) and cyproheptadine (2-4 mg/cat once to three times daily) sometimes will stimulate the patient's appetite, as well. If such tactics do not work, or if the patient is unable to prehend food due to orofacial trauma or disease, then force-feeding can be considered. I do not recommend this practice, as it is often very stressful for the patient, and it is difficult to force feed the required amount of calories, even when feeding nutrient-dense formulations. Additionally, the stress of force-feeding can affect the patient's will to voluntarily eat. Some patients become nauseated when a human approaches after several episodes of force-feeding or administration of oral medications. Enteral feeding tubes are so well tolerated, easy to place, and inexpensive, that enteral nutrition via various forms of feeding tubes should strongly be considered in any inappetant patient. Liquid diets are available in monomeric or polymeric formulations. Elemental or monomeric diets are predigested proteins and sugars, and are a mixture of amino acids, di- and tri-peptides, and monosaccharide sugars. Due to their high osmolality, monomeric diets often have the associated complication of causing diarrhea. Polymeric diets require that polypeptides, proteins, and polysaccharides are digested in the gastrointestinal tract prior to the nutrient absorption. Many polymeric formulations are isoosmolar and are not associated with as frequent diarrhea as monomeric diets. This author prefers Clinicare (Abbott Laboratories, North Chicago, IL), a polymeric liquid diet that is 1 kcal/ml, and is an excellent choice for enteral feeding by a variety of different routes of administration.

Nasoesophageal and nasogastric tubes are among the easiest and least expensive forms of feeding tubes available for use by veterinary practitioners. 3-5 Fr Argyle infant feeding tubes are ideal, are soft and pliable, and are well tolerated after placement by most patients. A nasoesophageal feeding tube should be placed in patients with expected or known short-term anorexia that are not vomiting, and have no problems with esophageal motility or strictures. A 3 ½-6 French tube can be placed in patients that weigh less than 10 kg, and an 8 French tube placed in patients that weight > 10 kg. After the appropriately sized tube is chosen, the patient's nostril and nasal passage should be anesthetized with a topical anesthetic agent such as lidocaine or proparacaine. The patient's head should be tilted caudally to allow the entire nasal passage to be lubricated with the topical anesthetic agent. The tube can be placed in a freezer to chill it and make it slightly more rigid for ease of placement. A stay suture should be place at the lateral aspect of the external nares before attempting to place the tube. The tube should then be measured to the level of the carina to avoid passing it past the level of the lower esophageal sphincter. The tube should be marked from the tip of the tube to the level at the tip of the nose, and marked with a permanent marker or a piece of white tape. The distal tip of the tube should be lubricated, and then passed on the ventral floor of the nasal cavity, tilting the nose upwards and passing along the ventromedial floor of the nasal passage, past the pharynx, until the patient swallows. Once the patient has swallowed, the tube can quickly be passed to the level of the tape, then secured with a finger-trap suture attached to the stay suture. The rest of the tube can be secured in between the eyes and on the dorsal nasal planum with sutures or surgical staples. The placement of the tube can be checked by auscultating over the thorax and injecting 10-15 mls of air into the tube, listening carefully for borborygmi. Alternatively, a lateral thoracic radiograph can be performed to check tube placement. The purpose of not allowing the tube to pass through the lower esophageal sphincter is to avoid gastric reflux of hydrochloric acid and possible esophagitis. Alternatively, a nasogastric tube can be placed for both enteral nutrition and for gastric decompression in cases of gastric atony, as seen with severe parvoviral enteritis and pancreatitis or ileus. Liquid diets can easily be fed through the tube as a bolus infusion or as a constant rate infusion, as tolerated by the patient. All patients with a nasogastric or nasoesophageal feeding tube should have a firm Elizabethan collar placed to avoid displacing the tube. Topical anesthetic agents such as topical proparacaine or lidocaine can be placed in the nostrils as necessary to help prevent irritation and sneezing. Potential complications of nasogastric or nasoesophageal feeding include aspiration pneumonitis, vomiting, diarrhea, and tube obstruction.

Esophagostomy tubes are an excellent method of feeding patients with severe head or facial trauma, oral oropharyngeal masses, and anorexia. Esophagostomy tubes are easy to place and are well tolerated by most patients. Client compliance is very positive, and there is a minimal risk of complication compared with percutaneous gastrostomy feeding tubes. Contraindications of an esophageal feeding tube include esophageal motility disorders or strictures, protracted vomiting, or a history of esophageal reflux or esophagitis. Depending on the type of tube placed, minimal equipment is necessary. Typically tube sizes range from 8-16 French, depending on the size of the patient. To place a tube, place the patient in right lateral recumbancy and clip the fur on the lateral cervical region from the ramus of the mandible caudally to the thoracic inlet and dorsally and ventral to midline. Measure a red rubber catheter from the level of the mid cervical region to the thoracic inlet. Cut the distal portion of the tube on an angle with a scissors to make the hole as large as possible to avoid occlusion. Mark the proximal segment of the tube at the level where it will leave the skin, to avoid pushing the tube in too far past the lower esophageal sphincter. Following routine anesthetic induction and intubation, place a curved forceps (Carmalt) into the mouth and down the throat to the level of the mid cervical area. Turn the tips of the Carmalt laterally to the level of the skin and open the tips. Palpate the open tips of the Carmalt, and make a stab incision over the open tips through the skin and underlying tissue. Direct the tips of the Carmalt through the skin. Grasp the distal end of the red rubber catheter in the tips of the Carmalt and clamp. Pull the distal end of the red rubber tune into the esophagus and rostrally out the mouth. The proximal end of the tube will be facing the caudal half of the patient. Turn the distal end of the tube into the mouth and continue to push with either your finger or a forceps until the proximal portion of the tube flips rostrally. Twist the tube gently, then push caudally to the level of the marker. You can secure the tube with sutures in the wing of the atlas, a pursestring and finger-trap suture at the point that the tube enters the skin. Always check tube placement with a lateral thoracic radiograph. Unlike PEG tubes, the E-tube can be used immediately, with fluid or a blenderized diet. The author's preference is to feed Eukanuba Maximum Calorie diet, warmed slightly warmer to room temperature. This diet is well tolerated and causes minimal to no diarrhea in most patients. An added benefit is that the diet becomes fluid enough to be administered through the E-tube without the hassle of being blenderized with additional water.

Gastrostomy tubes can be placed percutaneously with or without endoscopic assistance, or intra-operatively. The different procedures are beyond the scope of the monograph, but highlights of gastrostomy tube placement are discussed. Most clinicians prefer to wait a minimum of 12 to 24 hours prior to using a PEG tube, to allow appropriate time to create a seal and minimize the risk of iatrogenic peritonitis by introducing food into the abdominal cavity. The patient's caloric requirements should be calculated, and approximately 1/3 of the caloric requirement fed over a 24-hour period during the first day. The caloric needs should gradually be increased over a three-day period, until the patient's full caloric requirements are being met. Ideally, meals should be fed every 6 hours, gradually increasing the amount fed and decreasing the frequency of feedings as tolerated by the patient. It is important to remember to include the patient's water requirements daily, as well. Prior to any feeding, the tube should be aspirated, and if more than 1/3 of the volume instilled during the previous meal remains, the meal should be skipped. The meal should be warmed to body temperature, then fed over a period of 15-30 minutes as tolerated by the patient. The meal should be discontinued if vomiting, retching or salivation or any sign of discomfort occurs during feeding. After each meal, the tube should be flushed with a minimum of 15 mls of tap water to prevent tube occlusion. If tube occlusion occurs, Coca Cola can be instilled and allowed to sit in the tube to try to dissolve any cot that has formed. Clinical signs of oozing around the site of entry, redness or swelling, fever, weakness, lethargy or abdominal pain should alert the clinician to the possibility of infection. Even if the tube is not being used, it should be left in place for a minimum of 5-7 days prior to its removal, to decrease the risk of peritonitis.

Intraoperatively, jejunostomy tubes can be placed in any patient with a history of vomiting or proximal gastrointestinal obstruction, resection, or pancreatitis that will need continued nutritional support in the immediate post-operative period. A jejunostomy tube (5-8 French polyvinylchloride feeding tube) can be placed into the proximal to mid-jejunum, or alternatively can be placed through a gastrostomy tube and used until the patient is ready for gastric feedings. Any liquid diet can be placed through the jejunostomy tube either as a constant rate infusion or as bolus feedings, as tolerated by the patient. J-tubes are relative easy to place, although have the risk of peritonitis if they come loose. Other potential complications include orad migration of the tube into the stomach, tube clogging, and diarrhea.

Parenteral nutrition can be partial or total, depending on the percentage of total daily nutrient requirements that is administered to the patient. As their name implies, partial parenteral nutrition (PPN) provides only a portion of the daily nutrient needs, while total parenteral nutrition (TPN) provides all of the patient's daily nutritional needs. Total parenteral nutrition provides a combination of dextrose, amino acids, and lipids intravenously, to be administered when the gastrointestinal tract must be bypassed due to illness, injury or surgery, or is not tolerating enteral feeding due to protracted vomiting and diarrhea. In some cases, partial or total parenteral nutrition can be mixed with enteral nutrition, to provide all of the patient's nutritional requirements as needed. Parenteral nutrition can be administered through a peripheral catheter if the osmolarity of the fluid is less than 550 mOsm/L. If parenteral nutrition is to be used long-term, or if the osmolarity of the solution is greater than 550 mOsm/L, the fluid should be infused via a central catheter, to decrease the risk of thrombophlebitis. Although parenteral nutrition provides nutrients, enterocytes undergo atrophy due to lack of luminal nutrition. Bacterial translocation can occur as a result of lack of enteral nutrition, although the body is being fed by an alternate route. Because of the risk of infection, catheters used for administration of parenteral nutrition should be designated lines for the sole purpose of TPN or PPN, and not for infusion of other drugs or obtaining blood samples. Potential complications of parenteral nutrition include thrombophlebitis, kinks in the catheter, and catheter related sepsis at the time of catheter insertion, or hematogenous seeding of the catheter tip, potentially from translocation of gastrointestinal bacteria. TPN can be formulated and made in any clinic, provided that extreme attention to sterility is adhered to. First, calculate the patient's resting energy expenditure (RER), using the formula in paragraph 1 of this monograph. Next, 20% of the patient's RER should be provided as dextrose, and 80% of the RER provided as lipid. For dogs, 3 grams of protein should be provided for every 100 kilocalories of energy. For cats, 4 grams of protein per 100 kilocalories of energy should be provided. Supplemental potassium chloride and vitamins can be added as necessary. Procalamine already contains 24.5 mEq of KCl per liter. The following guidelines should be used when calculating individual patient formulations: 5% Dextrose contains 0.17 kcal/ml, 20% lipid solution contains 2 kcal/ml, 8.5% Amino Acid solution contains 0.86 g/ml, and 3% Amino Acid solution (Procalamine) contains 0.03 g/mL.