Metabolic Response to Trauma

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Questions and Answers

What is the primary role of the ebb phase in the metabolic response to trauma?

Mobilization of energy stores

Restoration of protein and fat stores

Increase in metabolic rate

Conservation of circulating volume and energy stores (correct)

Which of the following accurately describes the flow phase of the metabolic response?

It has no impact on body weight.

It lasts for less than 24 hours.

It is marked by a significant anabolic phase. (correct)

It primarily focuses on conserving energy.

Which hormone is primarily involved in the metabolic response to trauma?

Thyroxine

Glucagon

Catecholamines (correct)

Insulin

What can occur as a result of an excessive systemic response following trauma?

Multiple organ dysfunction syndrome (MODS) Signup and view all the answers

What is the duration of the ebb phase after a traumatic insult?

24-48 hours Signup and view all the answers

Which condition is characterized by hypovolemia, decreased basal metabolic rate, and reduced cardiac output?

Ebb phase Signup and view all the answers

What primarily happens during the catabolic phase of the flow phase?

Negative nitrogen balance Signup and view all the answers

What happens to the body during severe injury or major surgery in terms of metabolism?

Simultaneous catabolism and starvation Signup and view all the answers

What is one outcome of the inflammatory response?

Increased vascular permeability Signup and view all the answers

Which factor is NOT associated with increased metabolic response to trauma?

Higher urinary output Signup and view all the answers

Which of the following is a clinical application to limit the inflammatory response?

Early enteral nutrition Signup and view all the answers

What characterizes the late metabolic response to injury?

Negative nitrogen balance Signup and view all the answers

What common electrolyte disturbance is seen due to impaired sodium pump action?

Hyponatraemia Signup and view all the answers

Which type of anaesthesia is suggested to control the inflammatory response better?

Regional anaesthesia Signup and view all the answers

What metabolic change occurs in the early phase of response to injury?

Reduction in metabolic rate Signup and view all the answers

Which condition may lead to a poorer outcome after surgery or trauma?

Pre-existing chronic inflammatory disease Signup and view all the answers

What effect does severe injury have on resting energy expenditure (REE)?

REE increases by up to 50% Signup and view all the answers

Which hormone is primarily involved in mediating catabolism following an injury?

Catecholamines Signup and view all the answers

What is the main metabolic response of the body to a rise in body temperature of 1°C?

Increased metabolic rate by 6-10% Signup and view all the answers

What is one consequence of the negative nitrogen balance following uncomplicated surgery?

Negative protein synthesis Signup and view all the answers

Which substrate is primarily used for energy by tissues, excluding the brain, during fat metabolism?

Free fatty acids Signup and view all the answers

What is one reason why severe catabolism and negative nitrogen balance cannot be easily reversed?

Provision of protein and calories can help Signup and view all the answers

What characterizes the corticoid-withdrawal phase in the anabolic phase?

Positive potassium balance Signup and view all the answers

Which metabolic pathway is primarily affected during the process of glycogenolysis?

Glucose release from glycogen stores Signup and view all the answers

Study Notes

Introduction

Metabolic response to trauma is an adaptive response that either leads to survival or death, based on if the individual receives attention.
Aims to preserve "self" and homeostasis.
An uncontrolled response may become pathological.
Similar responses seen in trauma, burns, sepsis, and surgery.
The response is both local and systemic.
The extent of the response is proportional to the severity of the insult.
An appropriate response maintains homeostasis and allows for wound healing.
An excessive response can produce a systemic inflammatory response.
This can lead to the systemic inflammatory response syndrome (SIRS).
Multiple organ dysfunction syndrome (MODS) can result from SIRS.

Phases

The metabolic response is divided into two phases: the ebb and flow phase.
The ebb phase is the survival phase, lasting for a few hours and up to 24 to 48 hours after the insult.
The main physiological role is to conserve both circulating volume and energy stores for recovery and repair.
The ebb phase is attenuated by resuscitation but not completely reversible.
The ebb phase involves:
- Hypovolemia
- Decreased basal metabolic rate
- Reduced cardiac output
- Hypothermia and lactic acidosis.
The flow phase follows if the patient survives.
The flow phase involves the mobilization of body energy stores for recovery, repair, and the subsequent replacement of damaged tissues.
The flow phase has two parts:
- Catabolic metabolic rate, which lasts about a week in moderate trauma, and longer in severe trauma.
- Anabolic phase, characterized by protein and fat store restoration and weight gain.

Metabolic / Energy Responses

Following severe injury or major surgery, catabolism and starvation occur simultaneously.
Changes in any individual patient depend on which process predominates.
TMR = Total Metabolic rate
EA = Energy of activity
Therm = Thermogenesis
BMR = Basal Metabolic Rate
Catabolism is mediated by catecholamines, cytokines, and other factors.
Following injury, physical work (EA) is usually decreased due to inactivity, although heart and respiratory muscle work may increase.
Resting energy expenditure REE (the sum of BMR and thermogenesis) is increased by up to 50% following severe injury.

Thermogenesis

Patients are frequently mildly pyrexial for 24–48 hours following injury.
This occurs because cytokines, principally IL-1, reset temperature-regulating centers in the hypothalamus.
Pyrexia may also complicate infection occurring after injury.
Metabolic rate increases by 6–10% for each 1°C change in body temperature.

Basal Metabolic Rate

There is increased activity of protein, carbohydrate, and fat-related metabolic pathways and of many ion pumps.

Changes During Catabolism

Carbohydrate metabolism
- Glycogenolysis (stores last about 10 hours)
- Hepatic gluconeogenesis
- Insulin resistance of tissues
- Hyperglycemia
Fat metabolism
- Lipolysis
- Free fatty acids used as energy substrate by tissues (except the brain)
- Some conversion of free fatty acids to ketones in the liver (used by the brain)
- Glycerol converted to glucose in the liver
- Following severe trauma, 200–500 g of fat may be broken down daily.
Protein metabolism
- Skeletal muscle breakdown
- Amino acids converted to glucose in the liver and used as substrate for acute-phase protein production
- Negative nitrogen balance

Anabolic Phase

The anabolic phase occurs in three stages:
- Corticoid-withdrawal phase: characterized by spontaneous Na+ and free-water diuresis, a positive potassium balance, and a reduction in nitrogen excretion.
- Positive nitrogen balance: characterized by weight gain, increased protein synthesis, return of lean body mass, and muscular strength.
- Final phase: characterized by slower weight gain, return of N2 equilibrium, positive carbon balance, and deposition of body fat.

Outcome of Response

The inflammatory response produces clinically apparent local and systemic effects.
Local response usually presents as the cardinal signs of inflammation.
Systemic response includes:
- Increased ECF volume and hypovolemia
- Increased vascular permeability and edema
- Early reduced urine output and increased urine osmolality
- Reduced ‘free’ water clearance
- Late diuresis and increased sodium loss
- Pyrexia in the absence of infection
- Early: reduction in metabolic rate
- Late: increased metabolism, negative nitrogen balance, and weight loss
- Lipolysis and ketosis
- Gluconeogenesis via amino acid breakdown
- Reduced serum albumin
- Hyponatraemia due to impaired sodium pump action
- Acid-base disturbance – usually a metabolic alkalosis or acidosis
- Immunosuppression
- Hypoxia and coagulopathy

Clinical Applications

The inflammatory response can be limited by:
- Reducing the degree of trauma with appropriate and careful surgery (minimally invasive surgery).
- Reducing infection with wound care and antibiotics.
- Maintaining early enteral nutrition.
- Controlling pain.
- Correcting hypovolemia.
- Correcting acid-base disturbance.
- Correcting hypoxia.
- Choice of anesthesia: regional anesthesia, local anesthesia over general anesthesia.
- Early mobilization.

Factors Associated with the Magnitude of The Metabolic Response to Injury

Patient-related Factors:
- Genetic predisposition: how an individual responds to injury and infection is related to gene subtypes.
- Coexisting disease: such as cancer and chronic inflammatory disease.
- Drug treatments: pre-existing anti-inflammatory or immunosuppressive therapy, such as steroids.
- Nutritional status: malnourished patients have decreased immune function and deficiency in important substrates.
Acute Surgical/Trauma-related Factors:
- Severity of injury: greater tissue damage is associated with a greater metabolic response.
- Nature of injury: some types of tissue injury cause a proportionate metabolic response.

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Description

Explore the metabolic response to trauma, including its adaptive nature and the consequences of uncontrolled responses. This quiz covers the phases of response, such as the ebb and flow phases, and highlights the importance of maintaining homeostasis for recovery.