Shock Flashcards
Anoxia
Total depletion/absence of oxygen
Hypoxemia
Low oxygen in the blood
Hypoxia
Abnormally low oxygen content in any tissue or organ
What is shock?
- A state of inadequate tissue perfusion resulting in inadequate oxygen delivery to the cell
- Caused by many factors including anything that alters heart function, blood pressure, or blood volume
What results when unable to to correct or reverse shock?
Inability to correct and reverse shock results in increasing oxygen debt/deficit, acidosis, organ system dysfunction and eventually death
What are the keys to preventing shock?
Key to prevention is rapid recognition and intervention before a refractory or irreversible shock state occurs
What happens at the cellular level in shock?
Inadequate tissue perfusion results in impaired cellular metabolism
This results in:
1. Impaired oxygen use
2. Impaired glucose use (i.e. impaired uptake which can be caused by impairment of Na/K pump)
3. Buildup of metabolic end products (such as lactic acid and nitrous oxide which can rapidly build up in high concentrations in the cell and blood thus lowering the pH and causing acidosis)
What occurs with impaired oxygen use ?
- In shock states, without adequate oxygen, cells must use the less efficient anaerobic pathway
- This pathway generates an insufficient amount of ATP to maintain normal cellular metabolism
- Acidosis results
- With limited ATP, cells lose their ability to maintain an electrochemical gradient and the sodium-potassium pump fails
What occurs with impaired glucose use?
- Due to impaired glucose delivery or from impaired glucose uptake by the cell
- Hormonal and neurochemical release during shock states also increase the amount of glucose available
Cortisol: increases blood sugar through gluconeogenesis
Growth hormone: anti-insulin activity
Catecholamines: NE inhibits insulin
Net result is a buildup of glucose in the extracellular environment resulting in hyperglycemia
What occurs with a build-up of metabolic end products?
- Impaired cellular metabolism results in a buildup of metabolic end products (i.e. lactic acid) that are toxic to cells
- This buildup results in further disruption to cellular function and membrane integrity
- Lactic acidosis: Lactate levels >5 mmol/L and serum pH <7.35
What are the systemic effects of shock on your lungs?
- Circulatory deprivation results in tissue hypoxia and anoxia
Shock causes: - Decreased gas exchange
- Tachypnea
- Pulmonary edema (ARDS: Acute respiratory distress syndrome)
- Respiratory failure is a major cause of death in shock
ARDS is when the alveoli inflame, fills with liquid and collapses, gas exchange is unable to occur
What are the systemic effects of shock on your heart?
Myocardial deterioration is one of the major causes of death in shock
Shock causes:
- Decreased cardiac output
- Hypotension
- Release of myocardial depressants (MDF - myocardial depressant factor) – causes significant reduction in cardiac output
What are the systemic effect of shock in the blood?
Coagulation abnormalities
- During shock, hypoxia is caused by the slow-movement of blood in the capillaries; anaerobic metabolism begins and increases the production of lactic acid
- Slow-moving acidic blood is hypercoagulable
- When clotting factors are present along with the acidic blood of shock, widespread intravascular clotting may occur in the vessels (DIC)
What is DIC?
DIC (Disseminated Intravascular Coagulation)
- Causes multiple thrombi or emboli in microvascular circulation
- Body attempts to break down clots, but this also includes normal clot formation (in response to traumatic bleeding)
- Treatment includes: treating the precipitating cause, anticoagulant therapy, replacement of clotting factors (blood transfusion)
What are some lab tests used to diagnose DIC?
Lab findings: Thrombocytopenia; Prolonged PT, aPTT, thrombin time; Decreased fibrinogen; Elevated D-dimers
- Thrombocytopenia indicates a low blood platelet count
- PT is a blood test that measures the amount of time it takes for your blood to clot (often prolonged)
- Thrombin time this is a screening coagulation test designed to test fibrin formation from fibrinogen and plasma (also prolonged)
- Fibrinogen or factor I is a glycoprotein that helps in the formation of blood clot and normally we see decreased fibrinogen
- D-dimer is fibrin degradation product – a small protein fragment present in the blood after a blood clot is degraded by fibrinolysis and these levels are usually elevated
What are some neuroendocrine manifestations and mechanisms in shock? (i.e. tachycardia in shock)
- Cool, pale skin, increased BP: SNS stimulation, NE release -> vasoconstriction
- Tachycardia: SNS stimulation, epinephrine release
- Hyperglycemia: SNS stimulation, epinephrine release, growth hormone release
- Altered immune response: the release of glucocorticoids -> increase in ACTH
- Water retention (weight gain): Increase in ADH & aldosterone leads to sodium and water retention
- Oliguria: Decreased tissue perfusion
How does shock affect the immune system?
Depression of immune function; shock severely depresses macrophages
- Macrophages are located in the blood and tissues, shock reduces the capacity of macrophages to remove bacteria and toxins from the bloodstream
- Therefore people suffering shock are more susceptible to bacteria and endotoxins
How does shock affect the renal system?
Decreased UO -> reflective of status of circulation through vital organs
- the rate of urinary production reflects visceral blood flow and body fluid imbalance
How does shock affect the GI system?
Ileus, hypoxia -> tissue necrosis and sepsis; impaired liver function
- Under sympathetic stimulation, vagal stimulation to the GI tract slows or stops resulting in ileus with an absence of peristalsis
- A lack of nutrient blood supply to the intestines increases the risk of tissue necrosis and sepsis
- The liver is also at risk for impaired circulation, during shock – the liver has an impaired ability to detoxify and may also release vasoactive substances
What three components does adequate circulating volume depend on?
- Heart
- Vascular tone
- Blood volume
- A minor impairment in one can be compensated by the other two
- If prolonged or severe impairments occur, this leads to shock
How is blood circulation controlled and driven? Where is blood from the heart is delivered? Where is circulation slowest?
- Blood flows throughout body due to the driving pressure as it exits the left ventricle
- The size of the body’s larger vessels is controlled by the autonomic nervous system (ANS)
- Blood is delivered into arterioles where it can be stored and released more consistently into the capillaries
- Blood flows slowly through capillaries (greatest demand)
What controls microcirculation?
- Microcirculation is controlled locally by vasoactive substances released in the area by the actions of various types of cells
- ## Blood flow through capillary bed is influenced by the needs of the cells near the vessels
Arterial baroreceptor & chemoreceptor responses to changes in arterial pressure
- When there is blood loss, there is a decrease in arterial blood pressure
- The body can quickly detect a fall in blood pressure through its arteriole
- Cardiopulmonary baroreceptors and then activate the sympathetic adrenergic system to stimulate the heart increasing heart rate and contractility and constrict blood vessels thereby increasing systemic vascular resistance
- Reduced organ blood flow caused by vasoconstriction and reduced arteriole pressure leads to systemic acidosis that is sensed by the chemoreceptors
- The chemoreceptor system further stimulates the sympathetic adrenergic system thereby reinforcing the baroreceptor reflex
