Nutritional Issues in the ICU Case File
Eugene C. Toy, MD, Manuel Suarez, MD, FACCP, Terrence H. Liu, MD, MPH
Case 42
A 46-year-old man was admitted to the ICU for the management of severe acute pancreatitis. The patient developed acute respiratory insufficiency requiring intubation and mechanical ventilator support. His respiratory status remains unimproved on hospital day 4. At this point, his hemodynamic status has improved, and he no longer requires vasoactive agents for support of his blood pressure.
⯈How would you initiate nutritional support for this patient?
⯈What are the potential limitations in your ability to deliver nutritional support?
⯈What are the factors that contribute to the increase in this patient's nutritional requirements?
ANSWER TO CASE 42:
Nutritional Issues in the ICU
Summary: A 46-year-old man is hospitalized in the ICU with severe acute pancreatitis.
He is now hemodynamically stable, but is still requiring ventilatory support
on hospital day 4.
- Initiating nutritional support: Begin appropriate enteral nutritional support based on his nutritional status and projected needs. This nutrition plan needs to take into account his ongoing severe inflammatory response and his associated respiratory dysfunction.
- Potential limitations to deliver nutritional support: For this patient with severe acute pancreatitis requiring mechanical ventilator support and large volume fluid resuscitation, traditional nutritional intake by mouth may not be possible. In addition, the intestinal edema associated with his resuscitation may contribute to impaired intestinal motility and absorption.
- Factors contributing to increased nutritional requirements: Hyper metabolism and increased catabolism from his pancreatitis will contribute to marked increase in amino acid requirement and decreased ability to utilize glucose.
ANALYSIS
Objectives
- To learn the approaches to nutritional assessments and strategies of monitoring responses to nutritional support.
- To learn the nutritional management of patients with pancreatitis and renal insufficiency (with and without concurrent hemodialysis).
- To learn the principles of nutritional support specifically designed for the modulation of host inflammatory and immune responses.
Considerations
This is a 46-year-old man who has been in the hospital for 4 days. The severe inflammatory response in pancreatitis can generate large fluid shifts between the intravascular and extravascular space leading to hemodynamic instability as well as edema and respiratory failure. Patients with severe pancreatitis require aggressive fluid resuscitation to maintain adequate intravascular volume to support end-organ perfusion. This patient's hypotension did not respond initially to fluid resuscitation alone and required pressor support, but now his BP has improved. Typically, these patients will have large net positive fluid balance, to which the lungs are most sensitive, especially in the setting of ARDS. This type of lung injury requires prolonged mechanical respiratory support beyond the initial resuscitation phase. In addition, his initial hypotension may have decreased his end-organ perfusion, which can lead to acute kidney injury. This patient's source of acute pancreatitis is unknown, but based on statistics, alcoholic pancreatitis is highly probable. If his pancreatitis is due to alcohol, he may also have a poor baseline nutritional status due to chronic excess alcohol consumption. Additionally, he may have deficiencies that would benefit from specific vitamin and mineral supplementation in addition to caloric and protein provision. Enteral nutritional support will target the delivery of 25 to 30 kcal/kg of nonprotein calories and 1.5 to 2.0 g/kg of proteins per day. Close monitoring to avoid hyperglycemia (glucose >140- 160) should be implemented. Similarly, if nasogastric feeding is initiated, the patient should be closely monitored for signs of intolerance such as abdominal distension, and/or high gastric residual volumes ( >500 mL).
Approach To:
Nutritional Issues in the ICU
DEFINITIONS
ENTERAL NUTRITION: Nutrition provided through the gastrointestinal tract via a tube, catheter, or stoma that delivers nutrients distal to the oral cavity.
PARENTERAL NUTRITION: The intravenous administration of nutrition, either via central or peripheral access.
PROTEIN-CALORIE MALNUTRITION: A recent weight loss of >10% to 15% or actual body weight <90% of ideal body weight.
TROPHIC FEEDING: Low-volume enteral feeding (usually 10-30 mL/h) mean to prevent mucosal atrophy but insufficient to provide adequate calorie and protein requirements.
CLINICAL APPROACH
Critical illness is associated with a catabolic response because of changes in the hormonal milieu related to cytokine responses that occur following major physiological insults. The increased metabolic response continues into a later anabolic phase of tissue healing. Both of these increase the patient's nutritional requirements. The goals of nutrition therapy are to modify (most cases down-regulate) the metabolic response to stress, to prevent oxidative cellular injury, and to up-regulate the host immune responses. Initiation of early nutritional support, primarily enteral nutrition, is a proactive strategy directed at reducing some of the deleterious effects produced by the host's hypermetabolic responses, which in turn should reduce complications, ICU length of stay, and mortality.
In the majority of critically ill patients, it is practical, safe, and less expensive to utilize enteral nutrition over parenteral nutrition. Results from the various clinical trials comparing enteral versus parenteral nutrition in critically ill patients have shown that enteral nutrition is associated with the reduction in infectious complications, specifically central-line infections and pneumonia. Enteral nutrition is also associated with cost savings from reduced adverse events and savings from reduced hospital length of stay. It appears that critically ill ICU patients with hemodynamic compromise and requiring high doses of vasoactive agents and large volume of blood products may have an increased risk of intolerance to enteral nutritional support and increased risk of gut-related complications. Therefore, it is generally advisable to withhold enteral feeding until the patients are fully resuscitated.
Enteral nutrition utilizes the gut barrier to control water and electrolyte absorption. It also supports the functional integrity of the gut by maintaining tight junctions between the intraepithelial cells, stimulating blood flow, and inducing the release of trophic endogenous agents (ie, cholecystokinin, gastrin, bombesin, and bile salts). Furthermore, the structural integrity of the gut, including villous height and mass of secretory IgA-producing immunocytes, is better maintained with enteral nutrition. Loss of functional integrity can adversely affect gut permeability producing increase in bacterial challenge, perpetuation of systemic inflammatory response syndrome (SIRS), increase in the risk for systemic infection, and increase in the likelihood of multiorgan dysfunction syndrome (MODS) development.
In a previously healthy patient with no evidence of malnutrition, the use of parenteral nutrition may be withheld until after 7 to 1 0 days of hospitalization without nutrition. This is mostly due to concerns with infectious complications associated with parenteral nutrition. If, however, there is preexisting protein-calorie malnutrition and enteral nutrition support is not feasible, it is appropriate to initiate parenteral nutrition much earlier after adequate resuscitation has taken place. Parenteral nutrition is indicated primarily for patients in whom enteral nutrition is not feasible or not tolerated, and in severely malnourished patients who are about to undergo major upper GI surgery.
Initiating nutritional therapy first requires an assessment of the patient's nutritional status by determining weight loss and previous nutrient intake prior to admission, level of disease severity, comorbid conditions, and function of the gastrointestinal (GI) tract. Estimates of calorie requirement of the patient's basic metabolic rate is done with the Harris-Benedict equation. This can also be measured via indirect calorimetry with the aid of a respiratory therapist. Protein requirements are estimated from the patient's degree of illness and monitored with 24-hour nitrogen-balance measurements. Traditional markers (albumin, pre-albumin, transferrin, retinolbinding protein) are a reflection of the acute phase response and do not accurately represent nutrition status in the ICU patient. These markers by themselves have too low specificity, but may, together along with body weight changes, provide an estimate of general nutrition status.
Enteral nutrition should be started within 24 to 48 hours following admission, or as soon as fluid resuscitation is completed and the patient is hemodynamically stable. Feeding started within this time frame is associated with less gut permeability and diminished activation and release of inflammatory cytokines; early enteral feeding has also been shown to reduce infectious morbidity and hospital length of stay. Either gastric or small bowel feeding is acceptable in the ICU patient but small bowel is preferable in patients with high risk of aspiration and patients with severe brain injury (intracranial hypertension is associated with decreased gastric emptying).
The use of "trickle" or trophic feeds may prevent mucosal atrophy, but has not been shown to improve outcomes from the standpoint of immune modulation. Feedings should be increased toward goal or at least to >50% to 65% of caloric goal over the first 48 to 72 hours following initiation for maximal benefits. Gastric residuals <500 mL in the absence of other signs of intolerance are acceptable and do not increase the risk of aspiration or pneumonia. In critically ill patients, protein is the most important macronutrient for supporting immune function and wound healing. Assessment of the adequacy of protein nutrition is estimated from nitrogen balance (needs to be 1.2-2.0 g/kg/d) or nonprotein calorie:nitrogen ratio (70:1 to 100:1). Phosphate levels should be monitored closely and replaced when needed in respiratory failure patients for optimal pulmonary function.
Many enteral formulations are available to meet the needs of different patients. In patients with ARDS or lung injury, enteral formulations characterized by an anti inflammatory lipid profile and antioxidants should be used (ie, omega-3 fish oils, borage oil) for they have been shown to reduce ICU length of stay, duration of mechanical ventilation, organ failure, and mortality. Patients with respiratory failure can receive calorically dense formulations if fluid restriction is needed. Antioxidant vitamins (including vitamin E and ascorbic acid) and trace minerals (including selenium, zinc, and copper) may also improve ICU patient outcomes. Thiamine and folate supplementation for individuals with history of chronic alcohol abuse is important. Formulations with low glucose concentrations are available for diabetics as well to improve glycemic control.
Special considerations regarding enteral nutrition should be made for patients with renal failure. Acute kidney injury (AKI) usually develops in the setting of multiple organ failure in the critically ill individual. These patients also require the standard enteral formulations described previously with continued adherence to the protein and calorie provisions as before. If significant electrolyte abnormalities develop, formulations with appropriate electrolyte profiles may be considered. In AKI patients receiving renal replacement therapy (RRT), increased protein provision should be considered. RRT results in amino acid loss of approximately 10 to 20 g/d depending on the method, length of time, and type of filters used. These patients require formulations with 1.5 to 2.0 g/kg/d of protein, and some studies suggesting as high as 2.5 g/kg/d of protein to preserve a positive nitrogen balance.
Patients with severe acute pancreatitis should have a nasogastric (NG) tube placed on admission and enteral nutrition started as soon as fluid volume resuscitation is complete. Three meta-analyses showed that use of enteral nutrition compared to parenteral nutrition reduces infectious morbidity, hospital length of stay, need for surgical interventions, multiple organ failure, and mortality. Outcome benefits are seen in patients with acute pancreatitis when enteral nutrition is initiated within 24 to 48 hours. There has been no significant difference seen in outcomes of feeding by the gastric versus jejunal route; however, jejunal feeding may be better tolerated in these patients as severe pancreatitis can be associated with poor gastric emptying. To improve tolerance to enteral nutrition higher in the GI tract, low-fat elemental formulations in continuous infusion rather than bolus feeding should be used.
CLINICAL CASE CORRELATION
- See also Case 26 (Fluid/Electrolyte Abnormalities) and Case 40 (Postoperative Care in ICU).
COMPREHENSION QUESTIONS
42.1 You are making your nutritional rounds in the ICU. Which of the following patients is the best candidate for enteral rather than parenteral nutrition?
A. A 72-year-old woman on her eighth ICU day with sepsis from a ventilator associated pneumonia requiring 2 vasoactive agents for support of her blood pressure.
B. A 62-year-old malnourished man with an obstructing esophageal cancer about to undergo an lvor-Lewis esophagectomy.
C. A 75-year-old healthy man who underwent an uncomplicated right hemicolectomy for a malignancy 7 days ago. He is ambulating but still has abdominal distension and has not had flatus yet.
D. A 26-year-old man with multiple gunshot wounds to the abdomen and extensive small bowel injury who has just undergone extensive small bowel resection and now has only 45 cm of small bowel left and no ileocecal valve.
E. A 60-year-old woman who underwent a subtotal gastrectomy for stage 2 adenocarcinoma of the stomach 8 days ago and has developed an anastomotic leak.
42.2 Which of the following methods is the best for assessing nutritional status in a critically ill patient?
A. History and physical examination
B. Albumen, pre-albumin, and retinol-binding protein
C. Triceps skin fold
D. Harris-Benedict equation
E. Percent body fat estimation
42.3 Which of the following is the most accurate statement regarding enteral and parenteral nutrition?
A. Both enteral and parenteral nutrition help preserve structural integrity of the gut.
B. The cost savings of enteral over parenteral nutrition is from the direct cost of the cheaper generic enteral solutions versus the more expensive parenteral nutrition solutions.
C. There is a clear mortality benefit of using enteral nutrition versus parenteral nutrition in the ICU patient.
D. In patients with severe acute pancreatitis, enteral rather than parenteral nutrition is the preferred method of nutrition.
E. Peripheral TPN administration is associated with lower complications than enteral nutritional support.
42.4 A 57-year-old woman who weighs 132 lb (60 kg) is admitted to the ICU for acute pancreatitis complicated by acute kidney injury. She is requires hemodialysis every other day. Which of the following is the best nutrition regimen for this patient?
A. Place a nasojejunal (NJ) tube and feed continuous enteral 2000 kcal/d solution containing 120 g of protein daily.
B. Place a NO tube and feed continuous enteral 2000 kcal/d solution containing 80 g of protein daily.
C. Place a surgical jejunostomy tube and feed enteral 2000 kcal/d solution containing 115 g of protein daily in bolus fashion.
D. Place a peripherally inserted central line and give parenteral 2000 kcal/d solution containing 120 g of protein daily.
E. Place a NO tube and begin feeding to deliver 1800 kcal/d and 60 g of protein a day.
42.5 A-56-year-old man is admitted to the ICU for respiratory failure due to acute lung injury after a motor vehicle accident. The patient is placed on the ventilator. Which of the following is the most accurate management principle in this patient?
A. Calorie-dense, low volume enteral solutions should be used.
B. Anti-inflammatory lipid profile and antioxidants such as omega-3 fish oils and borage oil are typically avoided.
C. Uric acid supplementation is needed to help with ventilation.
D. High caloric intake and hyperglycemia are usually not issues in this type of patient.
E. Close aspiration monitoring and cease enteric feeding if gastric residuals are > 100 mL.
ANSWERS TO QUESTIONS
42.1 C. The best candidate for enteral nutrition is patient (C), because he underwent a right hemi-colectomy 7 days ago. Candidate (A) is still requiring 2 vasopressor agents which is a relative contraindication. Patient (B) is about to undergo major GI surgery and parenteral nutrition is a better option. Patients (D) and (E) have functional issues with their GI tract: (D) had small bowel surgery and possibly a short gut, and patient (E) has an anastomotic leak of his stomach. In a previously healthy patient with no evidence of malnutrition, parenteral nutrition should not be given until after 7 to 10 days of hospitalization without nutrition if the duration of parenteral nutrition is expected to be >5 to 7 days. This can be started earlier if there is an evidence of malnutrition. Enteral nutrition should be given unless patients do not have a functioning GI tract or if they have hemodynamic compromise, specifically those requiring high-dose catecholamine agents, large volume, or blood products. Parenteral nutrition is also recommended in patients in whom enteral nutrition is not feasible and who are about to undergo major upper GI surgery under the following conditions: (1) if the patient is malnourished, give parenteral nutrition 5 to 7 days preoperatively and continue postoperatively; (2) if nutrition is normal, delay parenteral nutrition 5 to 7 days postoperatively, should enteral nutrition continue not to be feasible and duration of parenteral nutrition is expected to be >5 to 7 days. Special circumstances such as short bowel syndrome and high-output proximal GI enterocutaneous fistulas would also be indications for parenteral nutrition.
42.2 A. Assessment of nutritional status is done best by evaluating patient's weight loss and previous nutrient intake prior to admission, level of disease severity, comorbid conditions, and function of the gastrointestinal tract. Albumin, pre-albumin, trasnferrin, and retinol-binding protein are a reflection of the acute-phase response and do not accurately represent nutrition status in the ICU. Triceps skin fold and other anthropometry may be affected by edema. The Harris-Benedict equation is an estimation of basal metabolic caloric requirements based on weight, not an assessment tool for nutritional status.
42.3 D. Even in severe acute pancreatitis, initiation of enteral nutrition after acute resuscitation is the preferred method of nutrition delivery. Only enteral nutrition helps preserve villous height and structural integrity of the gut. The majority of cost savings from enteral nutrition is from its decreased infection rate and hospital stay. There is a clear infectious benefit with enteral nutrition, but no clear mortality benefit has been found.
42.4 A. The ideal regimen for a renal failure patient undergoing renal replacement therapy in the ICU is one with 1.5 to 2.0 g/kg/d of protein. In severe acute pancreatitis, enteral nutrition is preferred and there is no outcome difference between using gastric versus jejunal feeding but placing surgical jejunostomy tubes carry their own inherent risks. Furthermore, patients tolerate continuous feeds easier than they tolerate bolus feeding in this situation.
42.5 A. The feedings should be calorie-dense, low-volume enteral solutions. Enteral solutions characterized by an anti-inflammatory lipid profile and antioxidants such as omega-3 fish oils and borage oil are desirable. Phosphate supplementation (not uric acid) are needed to help with ventilation. Excess caloric intake and hyperglycemia should be avoided to decrease infectious complications. Gastric residuals <500 mL in the absence of other signs of intolerance are acceptable and do not increase the risk of aspiration or pneumonia.
CLINICAL PEARLS
⯈ Enteral nutrition is practical, safe, less expensive, and leads to fewer infections than parenteral nutrition.
⯈ Enteral nutrition should be started within 24 to 48 hours following admission or as soon as fluid resuscitation is completed and the patient is hemodynamically stable.
⯈ In patients receiving renal replacement therapy (RRT), increased protein should be considered.
⯈ Markers such as albumin, pre-albumin, trasnferrin, and retinol-binding protein are a reflection of the acute-phase response and do not accurately represent nutrition status in the ICU patient; however, the serial measurements can help determine progress with nutritional therapy.
References
Latifi R. Nutritional therapy in critically ill and injured patients. Surg Clin N Am. 2011;91:579-593.
McClave SA, Martindale RG , Vanek VW, et al. Guidelines for the provision and assessment of nutrition support therapy in the adult critically ill patient: Society of Critical Care Medicine and American Society for Parenteral and Enteral Nutrition. Crit Care Med. 2009;37:1-30.
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