Metabolic Changes in Trauma

Question 1

What is Shock?

Answer 1

• Shock is a major medical emergency. It is common after serious injury and is brought on by a sudden drop in blood flow through the body.
• There is failure of the circulatory system to maintain adequate blood flow. Inadequate blood flow to body organs and tissue causes lifethreatening cellular dysfunction. Shock can be due to a number of different mechanisms. One common type of shock is hypovolemic shock. Hypovolemic shock occurs when the body does not have enough blood volume for adequate circulation. This may occur with massive hemorrhage after significant trauma. Signs and symptoms of shock include low blood pressure (hypotension), over breathing (hyperventilation), a weak rapid pulse, cold clammy grayish-bluish (cyanotic) skin, decreased urine output (oliguria), and mental status changes (confusion, combativeness, etc).

Question 2

Effects of Shock on Cardiovascular System

Answer 2

•Initially: slight tachycardia, normal blood pressure progresses to decreased blood pressure, rapid pulse with dysrhythmia

Question 3

Effects of Shock on Respiratory System

Answer 3

•Initially: Increased respiratory rate, but gas exchange is often impaired; this leads to anaerobic metabolism and development of acidosis; Acute Respiratory Distress Syndrome (ARDS): complication of decreased lung perfusion

Question 4

Effects of Shock on GI and Hepatic Systems

Answer 4

•Decreased blood flow to the GI organs due to blood preferentially shunting to the heart and brain. Organs may become ischemic which may then lead to renal failure, Stress Ulcers Paralytic Ileus, etc.

Question 5

Effects of Shock on Neurologic System

Answer 5

•Varies from restlessness to confusion to lethargy and coma. Possible cerebral hypoxia

Question 6

Effects of SHock on Renal System

Answer 6

•Decreased kidney perfusion leads to oliguria and renal failure

Question 7

Ebb Phase

Answer 7

•The Ebb phase is the early post trauma period of hypotension and decreased energy consumption.

This is a protective response that is usually within the first 24 hours following trauma and shock.

• This hemodynamic response is an adaptive mechanism that is meant to maintain perfusion to all vital organs (heart, brain, and kidneys). Yet, this results in inadequate perfusion to other tissues that forces the body to switch to anaerobic metabolism forming lactic acid.
• If not reversed, acidosis develops and if untreated, progresses to organ hypoxia, ischemia and death.
• Patients usually die during this phase unless appropriately resuscitated.

Question 8

Ebb Phase - Hormonal Changes

Answer 8

• In the Ebb phase, changes in glucagon, cortisol and insulin parallel starvation, but changes in other hormones are unique to trauma. T
• hese changes are transient, lasting up to 18 hours.
• Metabolic adaptations in the ebb phase include a catabolic response of protein metabolism, and increased glycogenolysis, gluconeogenesis and lipolysis.

Question 9

Ebb Phase - Increase in Catabolic Hormones

Answer 9

• Glucagon –ADH
• Cortisol –Aldosterone
• Epinephrine –Thyroid

Question 10

Ebb Phase - Decrease in Anabolic Hormones

Answer 10

• Insulin
• Sex Hormones

Question 11

Flow (recovery) Phase

Answer 11

• The Flow phase follows the Ebb phase and appropriate resuscitation.
• This period is characterized by the repair of damaged tissues.
• It is marked by a period of negative nitrogen balance and increased energy consumption.
• It is highly catabolic with increased protein degradation.
• Increased gluconeogenesis is induced by elevated levels of cortisol and glucagon and increased protein degradation is elevated in response to cortisol.
• Hyperglycemia results from peripheral insulin resistance of non-damaged tissues and diminished uptake and use of glucose.
• Since insulin normally stimulates protein synthesis, this resistance pattern contributes to decreased protein synthesis.

Question 12

Flow Phase - Hormonal Changes

Answer 12

• Hormonal changes in the flow phase are such that epinephrine is at normal levels whereas glucagon insulin and cortisol are increased.
• Although this response is necessary for survival in the short term, if it persists over a long period of time or if the response is severe it leads to the onset of tissue and organ damage and even failure.

Question 13

Flow Phase - Increased Hormones

Answer 13

• Glucagon
• Cortisol
• Insulin

Question 14

Flow Phase - Normal Hormones

Answer 14

-epinephrine

Question 15

Protein Metabolism

Answer 15

• All proteins in the body are constantly being synthesized and simultaneously degraded.
• This protein turnover is a result of a continuous exchange of amino acids between the protein and free amino acid pool.
• In an average healthy 70kg person, skeletal muscle accounts for approximately 7 kg of protein and free amino acids are estimated at 200-230 g.
• Only 5 g of free amino acids are estimated to be present in the circulation.

Question 16

Proteins Metabolized at Different Rates

Answer 16

• Different proteins are metabolized at different rates. In the non-diseased state, it takes ~80 days for newly synthesized proteins in muscle to fully turn over whereas 10% of albumin is turned over each day.
• Apolipoprotein B-100, which is responsible for assembly of VLDL that carry triglycerides and cholesterol from the liver, turns over approximately six times per day!
• Surprisingly, muscle contributes to only about 25% to whole-body protein turnover.

Question 17

Protein Metabolism in Trauma

Answer 17

• As mentioned above, whole-body protein turnover increases and shifts towards catabolism in conditions of trauma, surgery or infection.
• Studies have shown a 20-25% increase in metabolic rates after trauma, and that the size of the metabolic increase is associated with the severity of trauma.
• The catabolic response to stress is facilitated by catabolic hormones such as glucagon, catecholamines and corticosteroids coupled with by insulin resistance.
• Cytokines, oxygen radicals and other local mediators are also involved in this process.
• These have both anabolic and catabolic effects.
• The catabolic effects usually develop in peripheral tissues such as muscle, fat and skin that are used to create the necessary substrate flow for healing of the wounded tissues.
• The hyper-catabolic state after severe injury is generally characterized by an increased muscle wasting and an increased excretion of urinary nitrogen.
• The net loss of nitrogen is associated with an increase in protein synthesis and breakdown with the latter the greater of the two.
• Accompanying this is an increased amino acid transfer from the periphery to the liver and kidney to provide precursors for accelerated gluconeogenesis and for the synthesis of acute phase proteins.
• Systemic proteolysis is mediated primarily by the action of cortisol.
• Excretion of urinary nitrogen can rise as high as 30 g/day. This translates to an average of 1.5% daily loss in body mass.
• For example, a trauma patient with no oral nutrition can lose 15% of their body mass in 10 days.

Question 18

Lipid Metabolism in Trauma

Answer 18

• Lipolysis is the primary source of energy for liver cells; 80-90% of the energy required for gluconeogenesis is derived from fat oxidation.
• The metabolites necessary for the increased gluconeogenesis is provided from either lactate or amino acids in the liver.
• Lipolysis is accelerated because of increased levels of cortisol, catecholamine and glucagon.

-Additional factors are the overall decrease level of insulin action (although levels are higher, peripheral tissues are resistant) and decreased sympathetic activity.

• The activity of lipoprotein lipase is reduced in fat and muscle by the action of increased proinflammatory cytokines (TNF) in trauma and sepsis.
• During the ebb phase, plasma fatty acid increase through lipolysis.
• Lipolysis continues in the flow phase and the increased free fatty acids inhibit glycolysis.
• The rate of ketogenesis following trauma is inversely proportional to injury severity.
• Ketogenesis is reduced in major trauma, shock and sepsis due to an increase in insulin and increased use of free fatty acids.
• In minor trauma, ketogenesis is increased but this increase will not reach the level of starvation ketosis.

Question 19

Nutritional Support

Answer 19

• Oral or IV Nutrition

– Optimize not excessive

• Can promote optimal healing.
• Excessive nutrition does not reverse catabolic state or negative nitrogen balance. (differs from the fasting state)

– Hepatotoxicity; renal injury

• Excess protein through dietary means typically wasted and can be harmful

Question 20

Strategy of Trauma Care - Ebb Phase

Answer 20

Treat underlying cause of hypovolemic shock to stop the progress of the Ebb phase. The goal is to improve arterial oxygenation and tissue perfusion.

• Stop hemorrhage
• Administer oxygen
• Administer intravascular volume
• Repair injury

Question 21

Strategy of Trauma Care - Recovery Phase

Answer 21

• Requires a multi-team approach.
• Prevent developing complications (renal failure, blood clots, etc)
• Prevent hospital acquired infections
• Nutritional supplementation/exogenous insulin.
• Strengthening therapy/rehabilitation.