ch 18 critical illness

critical illness

The Stress Response

• The body’s attempt to promote healing and resolve inflammation when homeostasis is disrupted

• Intensity depends to some extent on the cause and/or severity of the initial injury

• Metabolic stress

  • Changes in metabolic rate (Usually increases)

  • HR (may increase or decrease depending on the situation)

  • BP (may increase or decrease depending on the situation)

  • Nutrient metabolism

Hormonal response to stress - Ebb phase

• Immediate postinjury phase

• Typically lasts 24-48 hrs

• ends when the patient is hemodynamically stable

• Characterized by:

  • shock with hypovolemia and diminished tissue oxygenation

  • fall in CO, oxygen consumption, urinary output, and body temp

  • rise in glucagon and catecholamine levels

  • activation of immune system

Hormonal response to stress - Treatment goals

• Restore blood flow to organs

• Maintain adequate oxygenation to all tissues

• Stop bleeding

• Fluids replaced

Hormonal response to stress - Catabolic flow phase

• Metabolic response to stress

• Counterregulatory hormones

  • Makes energy available to carry on essential bodily functions by breaking down nutrient stores

• State of hypercatabolism and hypermetabolism created

• Generally lasts 3-10 days depending on severity/complications

• Oxygen consumption, CO, CO₂ production, and body temp increase

• Fight or flight response

  • Insulin resistance → hyperglycemia

• Promotes breakdown of stored nutrients to meet energy needs

  • glucose from glycogen

  • amino acids from skeletal muscle tissue

  • fatty acids from adipose

Hormonal response to stress - Anabolic flow phase

• Characterized by a positive nitrogen balance as protein synthesis begins.

• The body preserves its remaining stores, but we still need to supply it with nutrients.

• Body is returning to normal here (stress response decreases)

• Nutrition goals: achieve and maintain fluid and electrolyte balance; minimize body protein catabolism; and meet calorie, protein and micronutrient needs

Inflammatory response - Acute-phase response

• The body fights infection and prevents tissue damage through acute inflammation, marked by changes in acute-phase proteins

  • C-reactive protein increases with inflammation (and vise versa), while negative acute-phase proteins like albumin decrease

    • Cytokines regulate these proteins and trigger systemic symptoms (anorexia, fever, lethargy, and weight loss)

• Prolonged cytokine exposure = accelerated catabolism (problem)

  • Acute inflammation is beneficial but problematic if prolonged or excessive.

Inflammatory response - Systemic inflammatory response syndrome (SIRS)

• Life-threatening condition

• May occur when severe inflammation lasts longer than a few days

• HR, RR, WBC count, and/or body temp become critically elevated

• caused by infection → sepsis → excessive fluid accumulation → low BP → impaired blood flow

• Inadequate oxygenation of tissues can lead to septic shock, multiple organ failure, and death

The Stress Response - Nutritional needs/support

• Considered after the patient is hemodynamically stable

• Protein catabolism

  • impaired immune system functioning, increased risk of infection, impaired/delayed wound healing, and increased mortality

• Primary goal is to protect lean body mass and prevent or alleviate malnutrition

The Stress Response - Calorie needs/support

• an adequate amount means we can spare the protein being provided

• Indirect calorimetry rarely used

• Resting metabolic rate (RMR)

  • We could calculate this to estimate approx. how many calories someone needs at that time

• Multiply the patient’s weight in kilograms by a specified calorie level

  • Adjusted upward or downward based on the patient’s response

  • Usually 20-30 calories per kg but different in obese or critically ill patients

• pts should be underfed; Hypocaloric intake is maintained for 3-5 days

  • Excessive calorie → increased metabolism, oxygen consumption, CO₂ production → increases burden on the heart and lungs to regulate blood gases

The Stress Response - Protein needs/support

• 1.2-2.5 g/kg depending on BMI

• severe burns = 2.0-2.5 g/kg

• Specific types of amino acids given may influence the stress response and recovery

• Arginine and glutamine, two nonessential amino acids, may become conditionally essential during periods of stress

The Stress Response - Carb and fat needs/support

• Should provide 50-60% of total calorie needs

• Fat may provide up to 40% of total calories

  • Fat is more calorie dense so if we are providing a more calorically dense meal, they can meet their goal in less volume

The Stress Response - Fluid needs/support

• Highly individualized requirements according to losses that occur through exudates, hemorrhage, emesis, diuresis, diarrhea, and fever

• Avoid overhydration

• Decreased renal output is a frequent complication of metabolic stress

The Stress Response - Micronutrient needs/support

• requirements during stress are unclear

• Trauma and burn pts have high urinary and tissue losses of the trace elements selenium, zinc, and copper

  • When replaced, pts experienced significantly fewer infections and improved wound healing

The Stress Response - Method of feeding

• EN is recommended over PN in critically ill pts who are hemodynamically stable with a functional GI tract

  • Common complication in critically ill patients is gastroparesis

  • PN is required when the GI tract is nonfunctional

    • Associated with increased rate of hyperglycemia

• Oral diets are provided as soon as possible

• Nutrition support, either complete or supplemental tube feedings, is necessary when calorie needs are not met through an oral intake

The Stress Response - Nutrition during recovery

Oral diets are provided as soon as possible

• goal = preserve lean body mass and prevention of our body from breaking down all of its nutrient stores

Burns

• Extensive ones are the most severe form of metabolic stress

• Fluid and electrolyte replacement = priority

  • maintain adequate blood volume and BP

• Degree of hypermetabolism and hypercatabolism in the metabolic response phase correlates with the extent of burn

  • higher extent = higher degree

Burns - Nutrition therapy

• if covering less than 20% of TBSA = oral high-protein, high-calorie diet

  • may be needed for years after burn incident

• Priority is to meet calorie and protein needs

  • Protein needs = 2.0-2.5 g/kg, especially if burns cover more than 10% of TBSA

  • needs increase if complications develop

• Vitamin C, vitamin A, and zinc plus a multivitamin are recommended

• if calorie intake is below 75% of needs for 3 days, consider EN if GI tract is functional

• start EN within 4-6 hours of injury if oral intake isnt possible but GI tract is functioning

  • Early initiation = improved structure and function of the GI tract, fewer episodes of infection and may also blunt the hypermetabolic response to burns

• Use PN only if EN isnt feasible or tolerated

Respiratory Stress

• Acute respiratory distress syndrome (ARDS) is a severe lung disease; Acute lung injury (ALI) is a less severe form of lung disease

• Occurs when gas exchange between the air and blood is impaired due to:

  • inflammation of the lung parenchyma

  • increased pulmonary capillary permeability

    • Pulmonary edema

    • Respiratory acidosis

      • Labored breathing and HR increases → cyanosis, confusion, drowsiness, heart arrhythmias, and coma

• most often part of systemic inflammatory processes: sepsis, pneumonia , trauma, burn, aspiration, and pancreatitis

Ventilator Dependency and Carbohydrate Restriction

Patients on ventilator support may benefit from a restricted carb intake

• carbs produce more CO₂ when they are metabolized compared to proteins or fats

  • creates a greater burden on the lungs