Abbreviations/Definitions

• Shock: a critical condition brought on by a sudden drop in blood flow through the body – the circulatory system fails to maintain adequate blood flow, drastically reducing the delivery of oxygen and nutrients to vital organs – it also compromises the kidneys, which restricts waste removal from the body
• Refeeding Syndrome: the metabolic alterations that may occur during nutritional repletion of underweight, severely malnourished, or starved individuals – the hallmark of refeeding syndrome is hypophosphatemia – other electrolyte abnormalities include hypokalemia and hypomagnesemia
• ARDS: AcuteRespiratoryDistressSyndrome– respiratory failure resulting from an acute insult to the lungs that occurs when the respiratory system is no longer able to perform its normal functions
• Pancreatitis: inflammation of the pancreas
• Respiratory Quotient: the ratio of the volume of carbon dioxide evolved to that of oxygen consumed by an organism, tissue, or cell in a given time
• Ileus: decreased or absent motility of the bowel and forward movement of bowel contents
• Pulmonary Edema: the accumulation of excess fluid in the lungs – leads to impaired gas exchange and may cause respiratory failure
• Sepsis: a systemic inflammatory response and immunosuppressive process that prevents an adequate response to infection or trauma – it may result in organ dysfunction or hypoperfusion abnormalities

Pathophysiology

Describe the physiologic and biochemical changes which occur during the post-operative period for a patient having major surgery. How might this impact plans for nutrition support?

Patient’s undergoing major surgery will go through the cycle of metabolic stress (ebb phase ⇒ flow phase ⇒ recovery or resolution phase) during the post-operative period. During this time, energy and protein needs are increased to help promote proper healing. Enteral and parenteral feeding may be initiated to meet theses increased nutritional needs if the patient’s ability to meet them by an oral diet is inhibited or precluded by post-op status of the GI tract, pain, or other systemic effects of a major surgery.

Describe the physiologic and biochemical changes which occur during sepsis/septic shock. How might this impact plans for nutrition support?

Sepsis is an immunosuppressive process that prevents an adequate response to infection. Septic shock is severe sepsis with hypotension that cannot be reversed with fluid resuscitation, and it is associated with organ dysfunction or hypoperfusion abnormalities. The clinical signs of sepsis include increased white blood cell count, increased heart rate, increased respiratory rate, fever or hypothermia, and elevation of positive acute phase proteins. Sepsis is initiated by a source of infection and/or trauma, resulting in the systemic response that causes the release of inflammatory mediators. Inflammation results in vascular permeability, mediated by the major vasodilator nitric oxide (NO), leading to a shift of fluid into the lungs and other interstitial spaces. As sepsis continues, there is a shift from an inflammatory to an anti-inflammatory response (immunosuppression), leading to organ dysfunction. There is an increased rate of gluconeogenesis which results in significant catabolism of skeletal muscle mass, which can result in hyperglycemia and increased serum lactate. Planning nutrition support can be challenging due to abnormalities of metabolism, difficulty estimating and/or measuring nutritional requirements, fluid/volume restrictions, and multi-system organ dysfunctions. However, the goals of nutrition support for every patient is to provide adequate protein and calories, and correct micronutrient/vitamin deficiencies. Current guidelines recommend initiating enteral nutrition 24-48 hours after ICU admission. Enteral formulas are not recommended for patients with sepsis because arginine catabolism produces nitric oxide.

What effect can malnutrition have on respiratory function? How might this impact plans for nutrition support?

Protein-energy malnutrition has been shown to affect the strength and endurance of respiratory muscles, particularly the diaphragm, lung structure, defense mechanisms, and control of ventilation. Persistent malnutrition causes depressed immune function, which can lead to an increased incidence of pulmonary infection. Nutrition support can help provide the energy and protein the person needs to increase their body weight and muscle strength, allowing the lungs to rest and repair themselves. If the patient’s respiratory function is impaired (e.g. pulmonary infection), consider providing 30-45% of calories from fat to help reduce metabolic CO₂production.

Nutritional Management

Describe the different routes for administration of enteral feedings (PEG, NG, and PEJ). Include indications for each route of administration in your description.

PEG (Percutaneous Endoscopic Gastrostomy)– The feeding tube is inserted through the skin and into the stomach. Indicated for patients with difficulty swallowing, poor appetite or inability to consume adequate nutrition by mouth, and a feeding tube is only indicated for 3-4 weeks of use (no longer than 28 days).

NG (Nasogastric)– The feeding tube is inserted through the nose into the stomach. Indicated for short term use in patients with a functioning GI tract.

PEJ (Percutaneous Endoscopic Jejunostomy)– The feeding tube is inserted through the abdominal wall into the jejunum. Indicated when the stomach is not functioning properly and cannot tolerate feeds to the stomach. Also indicated in patients with difficulty swallowing or are at risk of food going into the lungs.

Review the enteral feeding formulary for your institution and discuss appropriate enteral feeding formula use for each route. (You may want to do this in chart form.)

For enteral feedings, West Nassau Dialysis primarily uses Nepro. It is appropriate for dialysis patients because it is low in potassium and phosphorus. Patients are given Nepro if they need to increase their protein intake, have no appetite, and/or are not consuming anything by mouth. Ensure is another enteral feeding formula used by West Nassau Dialysis, but very rarely.

Discuss re-feeding syndrome. Include in your discussion, the role of phosphorus in respiratory function. What are some possible consequences of over feeding a patient who requires mechanical ventilation?

Refeeding syndrome (RS) describes the metabolic alterations that occur during nutrition repletion of underweight, severely malnourished, or starved individuals. Some of the consequences of RS include hypoxia, respiratory failure, weakness, nausea, vomiting, diarrhea, encephalopathy, cardiac arrhythmias, coma, and death.

The hallmark of RS is hypophosphatemia. Other electrolyte abnormalities include hypokalemia and hypomagnesemia. The hypophosphatemia of RS is caused by a sudden shift back to glucose as the predominant fuel source, creating a high demand for the production of phosphorylated intermediates of glycolysis, which leads to hypophosphatemia. The hypokalemia and hypomagnesemia are due to potassium and magnesium shifting intracellularly in response to anabolism and increased insulin release. Sodium retention also occurs and is caused by extracellular fluid expansion. Additionally, thiamine depletion can occur as a result of an increased use for carbohydrate metabolism.

It is important to identify patients at risk of developing RS and taking steps to prevent it. Before initiating feeding in an at-risk patient, check for and correct any existing electrolyte abnormalities (e.g. K⁺, PO₄^–, Mg²⁺). Once feeding is initiated, it is essential to avoid over feeding by starting low and going slow (e.g. start at 25% of estimated goals, then increase to goal at 3-5 days). Throughout re-nourishment, supplement electrolytes, and monitor electrolyte and glucose levels. Provide any additional supplementation needed for specific vitamins (e.g. thiamine or folic acid), or alternatively, a multivitamin supplement.

Phosphorus plays several different roles in respiratory function. It is involved in cellular metabolic pathways such as glycolysis and oxidative phosphorylation, as well as the regulation of the dissociation of oxygen from hemoglobin and the delivery of oxygen to tissues throughout the body.

As I mentioned before, phosphorus plays an important role in respiratory function and the hallmark of over feeding a patient is hypophosphatemia. Symptoms of hypophosphatemia include hypoxia, respiratory muscle weakness, impaired pulmonary function, and respiratory failure. Therefore, if a patient on mechanical ventilation is over-fed and develops hypophosphatemia, the process of weaning them off of mechanical ventilation may be affected.

What is propofol (Diprivan)? How might use of this drug impact recommendations for nutrition support?

Propofol is an anesthetic drug that causes relaxation and sleepiness. It is used to sedate intubated, mechanically ventilated patients in the ICU or the maintenance of general anesthesia. It is a lipid-based solution and provides 1.1kcal/mL. It is important to consider this when calculating the patient’s nutritional needs. Since it provides additional calories from fat, the type of formula, volume, initial rate, and goal rate you recommend may be different from the recommendation you would make if the patient was not on Propofol.

What is the rationale for using MCT oil in the diets of patients with malabsorption syndrome?

MCT oil provides lipids that are more easily digested and absorbed. The structure of MCTs allows them to be more readily absorbed into the bloodstream from the GI tract than other lipids. Another reason is that their absorption from the GI tract does not require bile or pancreatic enzymes. For patients with malabsorption syndrome, MCT oil should be given if their colon is still functioning and the malabsorption is occurring somewhere else. In these patients, MCT oil can help reduce fat malabsorption and help the patient obtain sufficient calories to optimize their nutritional status.

Nutrition Support Practice Calculations

Using the enteral feeding formulary at your clinical placement, complete the following care plans:

(a)  Pt A. is an 80-year-old F admitted to the ICU with CHF. Ht: 5’5” Wt: 50 kg. She required intubation secondary to pulmonary edema. A naso-jejunal feeding tube has been placed. You are consulted to suggest an appropriate feeding. Calculate her estimated calorie and protein needs. Write a feeding prescription for this patient.

Nutritional needs are based on current body weight (50kg):

• Calorie needs = 1250-1500 kcals (25-30kcal/kg)
• Protein needs = 60-100g protein (1.2-2.0g/kg)
• Fluid needs = 1000-1250 mL/d (20-25mL/kg)

Feeding prescription:

• Volume based feeding with Jevity 1.5 (Adult Standard Formula)
• Goal rate: 40 mL/hour – provides 1440 calories and 61 g protein
• Initiate at 20 mL/hour and advance to goal as tolerated

(b)  Pt B. is a 74year old M s/p CVA 7 days ago. Ht: 68” Wt: 160 pounds. He is NPO x 1 week. A PEG was placed yesterday. You are consulted to suggest an appropriate feeding. Calculate his estimated calorie and protein needs. Write a diet prescription for this patient.

Nutritional needs are based on current body weight (73kg):

• Calorie needs = 1825-2190 kcals (25-30kcal/kg)
• Protein needs = 73-88 g protein (1-1.2g/kg)
• Fluid needs = 1825-2190 mL/d (25-30mL/kg)

Feeding prescription:

• Volume based feeding with Jevity 1.5 (Adult Standard Formula)
• Goal rate: 55 mL/hour – provides 1980 calories and 84 g protein
• Initiate at 14 mL/hour and advance to goal as tolerated