Indications and Contraindications of Nutrition Support in the Critically Ill Adult - Essay Example

Indications and Contraindications of Nutrition Support in the Critically Ill Adult Introduction Malnutrition is known to be a common problem in all hospitalized patients. It has been indicated that at the time of admission to a hospital 40% of the adult patients are compromised with their nutrition. About two-thirds of all patients encounter deterioration during their treatment in the hospitals. This is more so when the patients are acutely ill since in acute illness, the metabolic rates are enhanced, and there may be an element of impaired utilisation of nutritional substrates based on the baseline condition. It has been observed that due to different priority of treatment and management strategies, the critically ill patients tend to receive inadequate attention to nutrition. The healthcare professionals often underestimate the nutritional needs of the patients who are critically ill. Moreover, the initiation of nutritional therapy is often delayed in these patients. In the critically ill patient, nutritional status plays a key role in recovery. The extent of muscle wasting and weight loss in the ICU is inversely correlated with long-term survival. However, because conventional parenteral nutritional therapy of malnourished critically ill patients has not been demonstrated to produce anabolism, blunting of the catabolic state may be the more effective strategy. Over the top of that malnutrition in the critically ill patients have been associated with increased mortality, morbidity, and length of stay, which may be correlated to increased dependency of mechanical ventilation, enhanced rates of infection, and impairment of wound healing. Therefore, to determine the evidence in this area of care, it would be prudent to critically analyse the research findings which could justify the indications and contraindications of nutritional therapy in these patients. Bu nutritional therapy it is meant, any form of nutritional support including total parenteral nutrition (TPN), peripheral parenteral nutrition (PPN), and enteral nutritional support given orally (Heyland et al., 2003). Issues In the critically ill, the acute phase response occurs as a basic feature of the body's defenses against injury. Among the changes, the prominent are alterations in distribution and metabolism of amino acids. Concomitantly, there is an increase globulin synthesis as a part of acute phase response. Metabolically, there is noted to be increased gluconeogenesis along with reduced serum iron and zinc levels and increased copper and ceruloplasmin levels. These changes lead to fever and an associated negative nitrogen balance. There is protein breakdown invariably in all patients. There is evidence that critically ill adult patients may lose about 16-20 g of nitrogen, which are supposed to be excreted in the form of urea, which in normal individuals are about 10-12 g/d. Many acutely ill patients have septic complications, and in some of them, the nitrogen loss may account for up to 24 g of urinary urea nitrogen daily. The nutritional implications of these facts become very significant since with the loss of 1 g of urinary urea nitrogen, the nitrogen content in 6.25 g of protein is loss, which is equivalent to approximately 1 oz of lean body mass. As one can calculate, the loss of 16 g of nitrogen as urinary urea is therefore equal to the loss of about 1 lb of skeletal muscle or lean body mass per day (Doig et al., 2008). Nutritional supplementation, hence, bears an important meaning in the management of patients who are critically ill. Studies have indicated that initiation of nutritional supportive treatments in critically ill patients within 48 to 72 hours of admission has at least three important outcomes. These are improved clinical outcomes, lower rates of infectious complications, and shorter duration of hospital stay. The route of administration of nutritional supports to these patients has also important influences over clinical outcomes. Evidence indicates that enteral nutrition is favorable over parenteral nutrition in most of the cases, unless enteral nutrition is contraindicated for any reason. Enteral nutrition is generally preferred over the parenteral nutrition since this is more physiologic. The former is less prone to lead to hepatobiliary dysfunction or other metabolic derangements. The cost of enteral nutrition is substantially less than parenteral nutrition. Enteral feeding in other biologic models has been demonstrated to be associated with less incidence of bacterial translocation in the intestines. Moreover parenteral nutrition has been reported to be associated with impaired IgA dependent immune response of the respiratory tract leading to a higher propensity of respiratory infections and complications. In the critically ill patients receiving parenteral nutrition, there is a host of other complications such as immune compromise, pressure ulcers, GI bleeding, wound complications, higher rates of infections. Other studies that investigated early institution of enteral nutrition in the critically ill adults have demonstrated that it improves immune functions, decreases hypermetabolic responses to tissue injury, causes augmentation of cellular antioxidant system, preservation of the integrity of the intestine, improves would healing and nitrogen balance (Gajanayake and Chan, 2009). Enteral Alimentation Where oral diets prove impossible or inadequate, tube feeding into the gut is both the safest and the cheapest alternative. However, patients who are being enterally fed may experience problems from lack of gastric acidity, and diarrhea. Some indications of enteral nutrition includes existing nutritional deficits, high-risk of hospital-acquired malnutrition, traumatic injury or burns, adult respiratory distress syndrome, severe pancreatitis, and low-output enterocutaneous fistula. Although there are many positive aspects of enteral nutrition, it must be kept in mind during enteral nutrition in critically ill patients that continuous enteral feeding may constantly dilute the gastric acid. The gastric acid being responsible for creating a hostile environment for bacteria, enteral nutrition may predispose to enhanced bacterial colonization through constant dilution of gastric acid is the frequency of the feed is not ascertained based on the patients' conditions. Gastric emptying is an important parameter to determine the frequency of the enteral feeds. The intervals between the feeds must be sufficient enough in order to allow the stomach to empty. Many critically ill patients have reduced gut motility with prolonged gastric emptying. Many patients undergoing enteral nutrition may have a complication of diarrhea. Diarrhea associated with enteral feed may be due to increased fluid in the bowel in opposition to the allowed transit time of the feed through the intestine. The likely causes of diarrhea associated with enteral feed include excessive gut fluid, hypoalbuminemia, and contamination of feeds. There are many critically ill patients who have total paralytic ileus. In many cases paralytic ileus involves the stomach sparing the ileum where absorption occurs. In these cases feeding through a stomach tube is contraindicated; however, even then enteral nutrition can be pursued through nasojejunal or percutaneous jejunostomy tube. In patients who are having infectious complications or etiology of critical illness, this pathway must be prevented. It has been demonstrated in critically ill patients over again that use of early enteral nutrition as opposed to parenteral or delayed enteral nutrition could be associated with lower complications and better clinical outcomes. The basic considerations must involve weighing of the following facts. Dextrose infusion alone has no protein-sparing effect. Patients with severe catabolic stress require "stress doses" of protein even if renal function is compromised. Breakdown products of protein may require more frequent dialysis, but in the patient with renal dysfunction, the nitrogen-wasting metabolism of catabolic stress is the same. In contrast, in diabetic patients and patients with increased peripheral insulin resistance from stress, serum glucose levels should be aggressively controlled to levels below 180 mg/dl to maintain nitrogen homeostasis and limit infectious complications (Jones et al., 2007). While contemplating the contraindications, the patients who are hypoperfused construe a risk for which enteral nutrition is not commonly recommended. This becomes specifically important in critically ill patients who are hemodynamically unstable. Most of these patients are also treated with vasopressor agents. Although argued that many such contraindications are derived from animal studies and studies on critical illnesses based on septic or trauma parameters and there is paucity of studies done in patients undergoing cardiothoracic surgery, it is better to withhold enteral therapy for critically ill patients with hemodynamic compromise. Physiologically, enteral nutrition leads to increased blood flow to the gut mucosa. Therefore following enteral nutrition in hemodynamically unstable patients, the baseline oxygen demand may be further accentuated leading to ischemia. With vasopressors included in the support regimen, following feeding, there may be further vasoconstriction. Furthermore, the usual signs and symptoms of bowel ischemia often go unrecognized and are often interpreted as common GI symptoms in critically ill or postsurgical patients, and this carries a higher risk of mortality. Therefore to be on the safer side it is better to withhold enteral therapy for the patients who are on vasoconstrictors and are hemodynamically compromised (Jones and Heyland, 2008). Regarding the agents used for enteral nutrition, polymeric standard formulae are most widely used. These contain nutritional profiles which may resemble a normal diet. Several different concentrations are available. The highest concentration 2 kcal/mL may be used in critically ill patients who also need fluid restriction. Concentrated formulae are recommended for people needing a bolus feeding. These are indicated for meeting high caloric needs in critically ill trauma or surgical patients. However, normocaloric formula has been demonstrated to be helpful in reducing critical care unit stay for such patients. Therefore where indicated there is no need to pursue calorie-dense formula for enteral nutrition in meeting the nutritional needs of critically ill patients (Martin et al., 2004). The other contraindications that have been noted in literature are complete intestinal obstruction, failure of enteral support, and shock and presence of pressors in the therapeutic regimen. In the literature, there are certain relative contraindications which have been indicated. In these cases, a weighted decision regarding the mode of therapy must be taken by the clinician. These are severe pancreatitis, malabsorption syndrome, and ileus. Despite these enteral feeding is the nutritional therapy of choice in critically ill patients due to several advantages and favorable outcome implications (McClave et al., 2009). Total Parenteral Nutrition Literature has always recommended enteral feeding over parental nutrition in any form. Therefore as evidence suggests in the case of a functional gastrointestinal tract, even if the patient is critically ill, enteral nutrition is the first choice, and unless otherwise indicated, TPN should not be the first choice for nutritional management. Therefore absolute contraindication of total parenteral nutrition is a functional GI tract. In all patients with critical illness, it means, if the gut is functional it should be the route for feeding. The common complications cited against total parenteral nutrition are atrophy of the gut predisposing to increased bacterial and fungal colonization, which may subsequently invade the blood stream leading to bacteremia and sepsis. Sepsis thus may occur due to microbial translocation and subsequent endotoxemia from spread of toxins into the portal system. This can be a frequent source of fever in critically ill patients even without demonstrable source of infection. A study of over 200 abdominal trauma patients compared mortality rates of parenterally and enterally fed ICU patients who had similar illness severity at admission. The group that could not tolerate enteral feeding received total parenteral nutrition that averaged 35 kcal/kg/d and 1.2 g/kg/d of protein. The other group tolerated enteral feedings and received 30 kcal/kg/d and 1.1 g/kg/d of protein. Preoperative TPN should not be routinely used since the majority of prospective studies have shown no benefit and one has shown harm. However, recent evidence in malnourished cancer patients demonstrated that preoperative TPN reduces complications and may reduce mortality. Likewise, postoperative TPN should not be routinely used since the majority of prospective trials showed no benefit and some showed an increased rate of complications. This lack of benefit and increased harm may be due to failure to maintain tight glucose control (< 110 mg/dL) in critically ill patients receiving TPN. The other indications of TPN are short bowel syndrome, high-output gastrointestinal fistula, hyperemesis gravidarum, bone marrow transplantation, and nonfunctional gut with hypoalbuminemia indicated by serum albumin of < 2.8 g/dL. In some cases, where there is a perceived need for aggressive metabolic support TPN should be indicated (Brokenshire et al., 2009). The benefits of TPN includes that it can be a method of satisfactory nutrition for patients with nonfunctioning, absent, or deficient intestinal tracts. In a variety of disorders, this can be tailored to meet the specific needs of the patients with a variety of disorders. The requisite fluid restriction can be implemented without compromising the adequacy of the nutritional support. It must be borne in mind that institution of TPN would need establishment of a central venous access. While planning a TPN, the volume requirement of the patient is also an important consideration. The planning is just not mechanically providing some formulation bottles. Rather in case of the critically ill patients, there must be a calculation of maintenance requirements and ongoing losses. Critically ill patients often have changing needs and thus the volume formulation must consider the changing needs of these patients. As an example the indication of renal tubular acidosis should be considered. These sorts of metabolic acidosis can be treated by adjusting the TPN formulation. The patients with metabolic alkalosis can also be treated by TPN where through central catheters 1N HCl may be infused in nonfat bags. In critically ill patients with renal and hepatic failure, there is scope for TPN. In management of renal failure the requirement of fluid restriction becomes important. TPN can provide concentrated solutions of carbohydrate, fat, and amino acids leading to a decreased volume of infusion with liberal use of dialysis. Although patients with moderate to severe liver failure fail to tolerate TPN, it can be tolerated well by patients with mild liver failure, although this is not the method of choice. However, moderately severe hepatic dysfunction can be benefited by TPN through which branched-chain amino acids may be infused which are deficient in such conditions. Critically ill patients with cardiopulmonary failure can also be suited to TPN since the fluid can be adjusted depending on the central venous pressure. The patients with pulmonary failure due to chronic obstructive pulmonary disease may benefit from decreased respiratory quotient, increased fat, and decreased carbohydrate calories (Genton et al., 2006). Although recommended in all patients critically ill but with normal gut function, in some patients with even intact gastrointestinal tract may not tolerate enteral feeds. Some patients with even intact enteral functions would end up receiving insufficient enteral intake with inadequate protein and energy requirements. In these patients, TPN has been recommended to be a supplement or a sole source of nutritional support. Current evidence indicates many patients with critical illnesses are sedated and treated often with catecholamines. These major drug classes may cause delayed gastric emptying and gastric feeding intolerance. While the reason is not specified, although not a standard of care, in almost all critical care patients TPN is begun often as a conventional practice. TPN containing lipids are contraindicated in trauma patients due to high complication rates (Guenter et al., 2004). Peripheral Parenteral Nutrition The route of parenteral nutrition should be secondary to the principle of meeting the individual patient's calorie and protein goals. Peripheral parenteral nutrition is given through a peripheral vein. This is indicated in patients who are able to tolerate the daily 3-L fluid requirement necessary to obtain adequate calorie administration. This has also been demonstrated to be indicated in patients in the early phase of enteral nutrition as a supplement to make up for the inadequacy. Currently, it has been indicated that the permissible concentrations of nutrients such as glucose, amino acids, and other nutrients delivered via peripheral parenteral nutrition are limited by the commonest complication of phlebitis, which has been attributed mainly to the high osmolality of the alimentation solution. It has also been shown that a solution of 900 mosmoles/L can be safely administered through improved catheters, which may have the added advantage of reducing the volume of the fluid to 2 L. This is, however, inadequate for patients who would need fluid restriction, and in those patients the therapy of choice should be TPN, rather than peripheral parenteral nutrition (Naylor et al., 2004). Peripheral parental nutrition is usually only suitable for short-term use, as patients often develop thrombophlebitis despite the relatively low glucose concentrations. Peripheral nutrition can only deliver limited energy in moderately large volumes, so is unsuitable for patients needing high-energy diets or fluid restrictions (Sinuff and Cook, 2003). Conclusion In the critically ill patients, unless positive contraindications are present for enteral nutrition, all patients should be started with enteral nutrition within 48 hours of admission. The indications include all patients except those who have contraindications for enteral feeding. In other patients where hepatic and pancreatic diseases are present and where enteral absorption is compromised, the patients should be offered total parenteral nutrition specifically when long-term management and fluid restriction are important requirement of the management strategy. In cases where short term management is indicated, peripheral parenteral nutrition may be prescribed. Reference Brokenshire, E., Plank, LD., Gillanders, LK., McIlroy, K., and Parry, BR., (2009). 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