Section 7: Gastroenterology/Nutrition/Hepatology

Critical Care Nutrition

INTRODUCTION

Nutrition support intervention varies depending on which phase of illness a patient may be in. Three phases of critical illness are highlighted.^1–3

FIRST PHASE OF ILLNESS: ACUTE PHASE

• Duration: 6 to 8 hours after onset of illness or trauma

• Characteristics: Fever, tachycardia, hypoglycemia

• Nutrition intervention: Usually NPO during resuscitation with fluids, inotropes, pressors, and/or blood products

Please note, though, that growth is inhibited at this time. Energy metabolism is diverted toward the stress or injury.

SECOND PHASE OF ILLNESS: EBB PHASE

• Duration: Varies

• Characteristics:

  • INCREASED: Catecholamines, counterregulatory hormones (glucagon, cortisol) → hyperglycemia, growth hormone, cytokine production, free fatty acids → possible hypertriglyceridemia, antidiuretic hormone (ADH), gluconeogenesis

  • DECREASED: Insulin level, insulin growth factor-1, acute decrease in metabolic rate

• Nutrition intervention: These metabolic and hormonal changes are not reversed or impaired by providing an increased amount of calories. Calories should be limited because providing an excess amount of nutrients could be deleterious.

Weights most likely will reflect increased fluid status due to increased ADH and not reflect the true somatic status of the patient.

THIRD PHASE OF ILLNESS: FLOW PHASE

TWO SUBCATEGORIES: CATABOLIC AND ANABOLIC

Catabolic Flow Phase

• Duration: Varies

• Characteristics: Hypermetabolism due to endogenous catabolism of fat, carbohydrate, and protein stores; active inflammatory processes; hyperglycemia; glucose intolerance; lipolysis; and negative nitrogen balance

• Nutrition intervention: Until the metabolic and hormonal alterations subside, nutrient provision should remain toward basal metabolic needs with the exception of providing an increased amount of protein as permissible per renal and liver status. Amino acids are pulled from muscle, connective tissue, and the gut (if inactive) to promote gluconeogenesis and production of acute-phase proteins, such as C-reactive protein (CRP).

There will be a decrease in synthesis of visceral protein stores of albumin and prealbumin.

Anabolic Flow Phase

• Duration: Varies

• Characteristics: Restoration of tissue composition, depleted energy reserves, and positive nitrogen balance

• Nutrition intervention: Nutrient provision should now be increased to promote nutrition repletion. Patient is now approaching convalescence and growth will resume; thus, more calories will be needed.

COMPONENTS OF ENERGY EXPENDITURE

Total energy expenditure = Basal metabolic rate + Energy from thermogenesis + Energy for activity* + Energy for growth* + Energy for healing process⁴

*Please note patients in the PICU are usually not active nor are they growing, so these components are excluded in determining energy needs.⁵

CONSIDERATIONS FOR DETERMINING ENERGY NEEDS

1. Phase of illness

2. Severity and duration of illness

3. Respiratory status: intubated vs. O₂ (mask ventilation/nasal cannula) vs. room air

4. Sedation status

5. Muscle relaxed or pentobarbital coma

6. Injury or stress factors, such ...