Nursing

RN/AHC Media Home Study Program CE CENTER

This activity is co-provided by AHC Media LLC and RN.

AHC Media LLC is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center's Commission on Accreditation.

This activity has been approved for 1.0 nursing contact hour using a 60-minute contact hour.

Provider approved by the California Board of Registered Nursing, Provider # 14749, for 1.0 Contact Hour.

After reading the article you should be able to:

1. Identify critical complications of malnutrition for mechanically ventilated ICU patients.
2. Compare and contrast enteral and parenteral nutrition for ICU patients.
3. Develop a plan of care to promote nutritional support for the mechanically ventilated ICU patients.

Click this button if you've already read the article and wish to take the test immediately.
You will be transferred to the AHC Media LLC site.
Should you need any assistance with the test-taking process, call (800) 888-3902.

By MARIAN RACCO, RN, MSN

MARIAN RACCO is the Clinical Coordinator in the ICU at Hunterdon Medical Center in Flemington, NJ. The author has no financial relationship to disclose. STAFF EDITOR: MARTHA K. RAYMOND, RN, BSN, BS

As many as 40% of adult patients are seriously malnourished when admitted to the hospital. In addition, two-thirds of all patients' nutritional state deteriorates during their hospital stay. Acute illness further exacerbates patients' poor nutritional status by increasing their metabolic rate and impairing the allocation of nutritional substrates.¹

Historically, the intensive care unit population has been routinely malnourished. One explanation is that nutritional issues are often not initially explored because the traditional, more obvious issues involving cardiac, pulmonary, or neurological status are deemed as more critical. Alterations in these body systems produce more immediate body responses, such as hypotension, chest pain, shortness of breath or unresponsiveness, and therefore typically garner prompt attention. In contrast, the debilitating effects of malnutrition may not be clinically apparent for several days. As such, preventable outcomes associated with malnourishment may not be noticed until patient experiences complications.

CRITICAL COMPLICATIONS Malnutrition in the critically ill, mechanically ventilated patient has an adverse effect on all physiological processes. It increases the risks for infection and pulmonary edema. Also, nutrition deficits decrease phosphorus needed to produce adenosine triphosphate for cellular energy, reduce ventilatory drive, and impair surfactant production. These malnourished patients are difficult to wean from the ventilator because of muscle fatigue caused by diaphragmatic and skeletal muscle weakness and/or reduced muscle endurance.²

One nutrient, protein, is especially vital in critical illness. Decreased protein intake associated with malnourishment decreases serum albumin level, which leads to a decreased intravascular and intracapillary oncotic pressure. This decreased pressure causes fluid to leak from the intravascular space into the interstitial space, a condition referred to as third spacing, which causes edema.³

Ultimately, malnutrition increases patient mortality and hospital cost by prolonging a patient's hospital stay.² Critically ill patients who receive prolonged mechanical ventilation without nutritional support have a 20% to 40% increased risk of developing ventilator-associated pneumonia (VAP) compared to those who are fed enterally within 48 hours of intubation. VAP is associated with a 20% to 25% increased relative mortality and an increased hospital stay of at least four days.²

With many patients admitted in a less than desirable nutritional state and considering the extensive list of serious complicationsresulting from continued malnutrition, it's essential that healthcare providers address a patient's nutrition status in an expedient manner. This can be done most effectively through the timely collaboration of the physician, nurse, and nutritionist.

EVALUATING NUTRITIONAL STATUS Although no single indicator provides an accurate depiction of a patient's nutritional status, parameters commonly used in all patients requiring a nutrition consult are body mass index (BMI), albumin/prealbumin level, nitrogen balance, and serum levels of trace elements.

An initial nutritional assessment includes a physical assessment and medical history. BMI is a common anthropometric measure of nutritional status used to diagnose obesity and under nutrition associated with clinical conditions.²

A common method of measuring a patient's protein status is the serum albumin level. Studies show that critically ill patients receiving long-term ventilation have low albumin levels during their hospitalization. These low levels are likely a reflection of both nutritional status and prolonged physiological stress associated with illness and/or ventilator weaning.

Many practitioners, however, prefer to measure the prealbumin level, because albumin changes in response to outside factors such as sepsis and surgery.⁴ Serum levels of prealbumin have a half-life of three to five days compared with 21 days for albumin. The rapid turnover of prealbumin is a reflection of its increased sensitivity to change in a body's protein status, therefore making it a more immediate indicator of physiological stress and nutrition status.²

Decreased protein intake depletes the body's nitrogen reserve, which is manifested as a negative nitrogen balance. A patient's nitrogen balance is calculated by measuring the amount of urea nitrogen excreted in urine over 24 hours and utilizing a standard formula, and then comparing that to the amount of protein ingested during that same 24-hour period.⁵

Serum levels of the trace elements of magnesium and phosphorus are biochemical indicators routinely used by clinicians to monitor nutritional status in critically ill patients. Magnesium deficiencies can be associated with acute diarrhea, a potential side effect of enteral feedings. Magnesium and phosphorus are important in energy synthesis and wound healing. Furthermore, abnormal levels of either of these electrolytes can cause cardiac, neurological, and neuromuscular disorders.²

Initial evaluation of a patient's nutritional status in a timely manner is critical. Daily ICU multidisciplinary rounding on every critically ill patient is essential as it ensures that the topic of nutrition will be discussed, thereby facilitating the prompt referral to a nutritionist. It is recommended that a nutrition referral be initiated within 24 hours of intubation so that a patient's nutritional needs are addressed quickly in an effort to prevent further nutritional compromise.

WHEN TO IMPLEMENT NUTRITION Studies suggest that initiating nutritional support within 24 to 48 hours of intubation helps maintain lean body mass and immune function, thereby improving clinical outcomes, lowering infection rates and reducing hospital length of stay.^1,6,7 Starting enteral nutrition near the beginning of an acute illness has several benefits.^1,5,6 This type of nutrition improves immune function and augments the cellular antioxidant system. There is also a decrease in the body's hypermetabolic response to tissue injury. Other advantages include better nitrogen balance and improved wound healing. For this reason, it is imperative the nurse requests a nutrition consult within 24 to 48 hours following endotracheal intubation.

ENTERAL OR PARENTERAL In ICU patients, the early use of enteral nutrition compared with either parenteral or delayed enteral nutrition is associated with lower complication rates and improved clinical outcomes.^1,6 Enteral nutrition is a therapy that allows the gastrointestinal tract to function more normally. It's also less likely to be associated with hepatobiliary dysfunction and metabolic instability. Enteral nutrition is substantially less expensive than parenteral nutrition.

Clinical studies have shown that ICU patients receiving parenteral nutrition have demonstrated a higher incidence of metabolic and infectious complications than those patients receiving enteral nutrition. Common metabolic complications include hyperglycemia, hypoglycemia, and refeeding syndrome — the body suddenly shifts from fat metabolism to carbohydrate metabolism. This shift causes a surge in insulin levels, which in turn leads to an increase in the cellular uptake of phosphorus, resulting in hypophosphatemia. Primary symptoms of hypophosphatemia are muscle weakness and wasting and general fatigue, all of which are barriers to successful ventilator weaning and healing.⁶ Acute cholecystitis is a common complication of parenteral nutrition, related to the complete lack of usage of the gastrointestinal tract resulting in biliary stasis in the gall bladder. Total parenteral nutrition must infuse through a central venous catheter, and a bacterial infection of that catheter is a serious and potentially life-threatening risk.¹

ENTERAL FEEDING RESIDUAL VOLUMES Residual volumes are routinely checked as a way to assess tube-feeding tolerance and help to assess a patient's risk for aspiration. Although checking residual volume is a common clinical practice, there is no data correlating a specific residual volume with increased aspiration events.^8,9 The single best measure a nurse can do to prevent aspiration of enteral feedings and therefore reduce the risk of VAP is to keep the patient's head of bed elevated at least 30 degrees. The American Gastroenterological Association recommends elevating the head of bed to a minimum of 30 to 45 degrees to reduce the risk of microaspiration.⁹

Gastric residual volumes greater than 200 ml to 250 ml are generally considered high in critically ill patients with an artificial airway in place. It is interesting to note that the combined secretion of saliva and gastric fluids may total up to 188 ml/hr, which brings one to question whether a tube feeding residual of 250 ml is really an accurate reflection of poor absorption. It is not recommended to automatically stop a tube feeding for an isolated high gastric residual volume. A residual recheck should be done one hour before tube feedings are held.⁹ Though the gastric residual is a factor in aspiration, ongoing studies contend there is no consistent relationship between aspiration and gastric residual volumes. However, aspiration does occur significantly more often when volumes are high.¹⁰ See Table 1 for a listing of strategies to help with gastric residual volumes.^3,6

WHEN TO USE TPN Parenteral nutrition should only be used in patients with an inaccessible or nonfunctional gastrointestinal tract. Some of the most common reasons are due to a massive gastrointestinal bleed, acute abdomen, bowel obstruction/ileus, intractable vomiting or diarrhea, or prolonged NPO status postoperatively—greater than 7 to 10 days.⁶ The potential for transitioning to enteral feedings should be reevaluated daily in patients on parenteral nutrition. The perfect time for such a reevaluation is during interdisciplinary ICU morning rounds.

Early initiation of nutritional support is integral to the recovery of a critical illness, and evidence supports that enteral nutrition is both efficient and effective in providing necessary nutrition, particularly in the mechanically ventilated population. The key to obtaining nutrition in a timely manner is interdisciplinary collaboration among the critical-care physician, critical-care nurse, and nutritionist. This collaboration is best achieved through daily interdisciplinary rounds on all critically ill patients so that all team members have input into the patient's plan of care. Critical-care nurses need to recognize they are in a powerful position to influence patient nutrition and outcomes in their practice.

References

1. Barr, J., Hecht, M., et al. (2004). Outcomes in critically ill patients before and after the implementation of an evidence-based nutritional management protocol. Chest, 125(4), 1446-1457.

2. Higgins, P., Daly, B., et al. (2006). Assessing nutritional status in chronically critically ill adult patients. Am J Crit Care,15(2), 166-176.

3. Bixby, M. (2006). Third-spacing: Where has all the fluid gone? Nursing made incredibly easy!, 4(5), 42-53.

4. Urde, L. D., Stacy, K. M., & Lough, M. E. (2004). Priorities in critical care nursing, p. 52. St. Louis: Mosby.

5. Heyland, D., Rupinder, D., et al. (2003). Canadian clinical practice guidelines for nutrition support in mechanically ventilated, critically ill adult patients. J Parenter Enteral Nutr, 27(5), 355-373.

6. American Association of Critical-Care Nurses. (2005). AACN: Essentials of critical-care nursing. Chicago: McGraw-Hill.

7. Parrish, C. R., & McCray, S. F. (2003). Nutrition support for the mechanically ventilated patient. Crit Care Nurse, 23(1), 77-80.

8. Palmer, J., & Metheny, N. A. (2008) Preventing aspiration in older adults with dysphagia. Am J Nurs, 108(2), 40-48.

9. Bourgault, A., Ipe, L., & Weaver, J. (2007). Development of evidence-based guidelines and critical care nurses' knowledge of enteral feeding. Crit Care Nurse, 27(4), 17-29.

10. Metheny, N. A., Schallom, L., et al. (2008). Gastric residual volume and aspiration in critically ill patients receiving gastric feedings. American Journal of Critical Care,17(6). 512-519.

MEASURING RESIDUAL VOLUMES DURING ENTERAL FEEDING

If gastric residuals are limiting tube feed delivery, the following steps should be considered.

» Place patient on his/her right side for 15 to 20 minutes prior to checking residual to prevent build-up of feedings in the noncontracting fundic portion of the stomach

» Seek transpyloric access of feeding tube

» Use a prokinetic agent to increase contractile force and improve gastric motility

» Switch to a more calorically dense product to decrease total volume

» Trial semi-elemental or elemental formulas

» Tighten glucose control to less than 200 mg/dL to avoid gastroparesis from hyperglycemia

» Use narcotic alternatives

Sources:

1. Bixby, M. (2006). Third-spacing: Where has all the fluid gone? Nursing made incredibly easy!, 4(5), 42-53.

2. American Association of Critical-Care Nurses. (2005). AACN: Essentials of critical-care nursing. Chicago: McGraw-Hill.

THE BODY IN CRISIS – NUTRITIONAL DEMANDS

• Critically ill patients are at risk for starvation combined with the physiologic stress from injury, major surgery, trauma, and sepsis. Often, patients face starvation because they can't take anything by mouth for surgical procedures, may be hemodynamically too unstable to be fed, or may be unable to eat because of disease-related factors. To compound the problem, physiologic stress affects hormones, increasing the metabolic rate—hypermetabolism—that raises oxygen consumption and energy expenditure.

The hormonal changes develop primarily from the sympathetic nervous system (SNS). When stimulated, the SNS causes the adrenal medulla to release the catecholamines epinephrine and norepinephrine. Other hormones released in response to stress include glucagon, adrenocorticotropic hormone, and antidiuretic hormone. In addition, glucocorticoids such as cortisol and mineralocorticoids including aldosterone are released. All these hormonal changes cause nutrient substrates, primarily amino acids, to move from peripheral tissues, such as skeletal muscle, to the liver for gluconeogenesis.

These nutrient substrates, however, mobilize at the expense of body tissue and function at a time when the body has an increased need for protein synthesis, necessary for wound healing and acute phase proteins. Hyperglycemia results from the effects of increased catecholamines, glucocoticoids, and glucagon. Loss of protein results in a negative nitrogen balance and weight loss.

Source: Urde, L. D., Stacy, K. M., & Lough, M. E. (2004). Priorities in critical care nursing, p. 52. St. Louis: Mosby.

STUDY SAYS EARLY ICU FEEDING DOES NOT IMPROVE CLINICAL OUTCOMES

• According to a study just published in the Journal of the American Medical Association's December 17 issue, providing earlier enteral nutrition to patients in intensive care units (ICUs) neither shortens their stays nor reduces their risk of death. Previous guidelines had suggested that providing nutritional support to patients within 24 hours of ICU admission reduced their mortality rates.

Between November 2003 and May 2004, researchers in Australia and New Zealand enrolled 1,118 critically ill adult patients from 27 hospitals who were expected to stay in the ICUs for more than two days. The ICUs were randomly assigned as guideline groups or control groups. The guideline groups used Browman's Clinical Practice Guideline Development Cycle and a practice-change strategy of 18 interventions that were supported by outreach visits. The study sought to determine whether evidence-based feeding guidelines would improve feeding practices and reduce mortality in ICU patients.

The study found that more patients in the guideline ICUs were fed much sooner (.75 vs. 1.37 mean days to enteral nutrition start) and reached caloric goals more often (6.10 vs. 5.02 mean days per 10 fed-patient days) than the control patients. However, the guideline and control ICUs did not show a significant difference in hospital-discharge mortality rate (28.9% vs. 27.4%) or to hospital length of stay (24.2 vs. 24.3 days) or ICU length of stay (9.1 vs. 9.9 days).

The researchers concluded that implementation of the guideline initiated significant practice change in ICUs regarding earlier nutrition and feeding processes for critically ill patients, but use of the guideline did not reduce hospital death rates.

Source: Doig, G.S., Simpson, F., et al. (2008). Effect of evidence-based feeding guidelines on mortality of critically ill adults: a cluster randomized controlled trial. JAMA, 300(23), 2731-2741.