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Questions and Answers
What primarily mediates catabolism in the body?
What is a common metabolic change following severe injury?
What effect does a 1°C increase in body temperature have on metabolic rate?
Which metabolic process occurs in the liver to provide glucose during catabolism?
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What is commonly observed during prolonged sepsis or burns regarding nitrogen balance?
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What is a key characteristic of the corticoid-withdrawal phase in the anabolic process?
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What happens to fat and muscle mass during the process of catabolism?
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What is the primary physiological role of the ebb phase in the metabolic response to trauma?
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Following uncomplicated surgery, how long does negative nitrogen balance typically last?
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What physiological condition is NOT typical during the ebb phase following trauma?
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Which phase follows the ebb phase in the metabolic response to trauma?
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During the flow phase, what type of balance is associated with the catabolic part of the response?
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What is a potential consequence of an excessive metabolic response to trauma?
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Which of the following is NOT a typical characteristic of the flow phase?
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What can result if the metabolic response to trauma is uncontrolled?
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Which hormone is associated with the metabolic response phase following trauma?
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What is the outcome of a positive nitrogen balance associated with weight gain?
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Which of the following is a systemic response to an inflammatory reaction?
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What metabolic changes occur during the late phase of an inflammatory response?
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Which factor is NOT associated with a greater magnitude of metabolic response to injury?
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How can the inflammatory response be limited in clinical practice?
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What is a common acid-base disturbance associated with inflammation?
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What role does hypovolaemia play in the systemic inflammatory response?
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Which factor is considered patient-related and influences the metabolic response to injury?
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Study Notes
Introduction
- The metabolic response to trauma is an adaptive response that aims to preserve homeostasis and promote survival.
- The magnitude of the response is directly proportional to the severity of the insult.
- The response can be local or systemic, and a severe response can lead to Systemic Inflammatory Response Syndrome (SIRS) and Multiple Organ Dysfunction Syndrome (MODS).
Phases
- The metabolic response to trauma is divided into two phases: the ebb phase and the flow phase.
- The ebb phase, or survival phase, is characterized by decreased metabolic rate, decreased oxygen consumption, and decreased cardiac output.
- The ebb phase lasts approximately 24-48 hours.
- The flow phase, or recovery phase, involves the mobilization of body energy stores to repair damaged tissues.
- There is a transition from the ebb phase to the flow phase if the patient survives the initial insult.
Metabolic / Energy Responses
- The metabolic response to trauma is a complex interplay between catabolism, thermogenesis, and basal metabolic rate.
- Catabolism: Breakdown of body tissues to release energy. This is mediated by catecholamines and cytokines.
- Thermogenesis: Increased heat production due to the release of cytokines, particularly IL-1.
- Basal Metabolic Rate (BMR): The rate at which the body burns calories at rest. BMR increases during trauma due to increased activity of protein, carbohydrate, and fat metabolic pathways.
Changes During Catabolism
- Carbohydrate metabolism: Decreased glycogen stores and increased hepatic gluconeogenesis. The body becomes insulin resistant.
- Fat metabolism: Increased lipolysis and utilization of free fatty acids as energy substrates. Some free fatty acids are converted to ketones in the liver, which can be used by the brain.
- Protein metabolism: Skeletal muscle breakdown, amino acids used for gluconeogenesis and acute phase protein production.
- Total energy expenditure: Increased as the magnitude of trauma increases.
- Negative nitrogen balance occurs: The body breaks down more protein than it builds.
Anabolic Phase
- Stage 1: The corticoid-withdrawal phase, characterized by spontaneous sodium and free water diuresis, a positive potassium balance, and a reduction in nitrogen excretion.
- Stage 2: Positive nitrogen balance, weight gain, increased protein synthesis, and the return of lean body mass and muscle strength.
- Stage 3: Slower weight gain, return of nitrogen equilibrium, positive carbon balance, and body fat deposition.
Outcome of Response
- Local response: The classical signs of inflammation: redness, swelling, heat, and pain.
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Systemic response:
- Increased extracellular fluid volume and hypovolemia.
- Increased vascular permeability and edema.
- Early reduction in urine output and increased urine osmolality.
- Reduced free water clearance.
- Late diuresis and increased sodium loss.
- Pyrexia (fever).
- Early reduction in the metabolic rate.
- Late increased metabolism, negative nitrogen balance, and weight loss.
- Lipolysis and ketosis.
- Gluconeogenesis via amino acid breakdown.
- Reduced serum albumin.
- Hyponatremia due to impaired sodium pump action.
- Acid-base disturbance - usually a metabolic alkalosis or acidosis.
- Immunosuppression.
- Hypoxia and coagulopathy.
Clinical Applications
- Strategies to limit the inflammatory response:
- Minimize surgical trauma: Utilize minimally invasive surgery techniques.
- Reduce infections: Implement proper wound care and antibiotic therapy.
- Early enteral nutrition: Provides essential nutrients.
- Pain control: Reduces stress and improves outcomes.
- Correct hypovolemia: Restore blood volume.
- Correct acid-base disturbances: Maintain electrolyte balance.
- Correct hypoxia: Ensure adequate oxygen supply.
- Choice of anesthesia: Regional or local anesthesia over general anesthesia whenever possible.
- Early mobilization: Promotes recovery and reduces complications.
Factors Associated with the Magnitude of the Metabolic Response to Injury
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Patient-related factors:
- Genetic predisposition: Individual variations alter the response to injury and infection.
- Coexisting diseases: Conditions like cancer and chronic inflammatory disease can influence the response.
- Drug treatments: Pre-existing anti-inflammatory or immunosuppressive drugs, such as steroids, can modify the response.
- Nutritional status: Malnutrition decreases immune function and reduces vital substrates.
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Acute surgical/trauma-related factors:
- Severity of injury: Greater tissue damage leads to a larger metabolic response.
- Nature of injury: Different types of tissue injury trigger a proportional metabolic response.
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Description
Test your understanding of the metabolic response to trauma and its two distinct phases: the ebb and flow phases. This quiz covers key concepts such as the body's adaptive mechanisms to injury and the consequences of severe trauma. Challenge yourself on the intricacies of metabolic and energy responses associated with traumatic conditions.
