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Lesson 2 Physiology of Life and Death

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Maintenance of Life Body systems Interrelated Interdependent Every cell and every organ work together to: Sustain cellular energy production Maintain vital metabolic processes

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Energy Energy powers all body functions Energy sustains cellular and organ functions Cells make energy from oxygen and glucose Energy is stored in the form of adenosine triphosphate (ATP) molecules Without energy, cellular functions cease The goal is to help ensure that the patients body maintains energy production

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Systems and Components (1 of 2) Airway Must be patent Breathing (lungs) Adequate oxygen must: Reach alveoli Cross alveolar/capillary wall Enter the circulation Carbon dioxide (CO 2 ) must be removed

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Systems and Components (2 of 2) Circulation Distributes red blood cells (RBCs) Ensures adequate number of RBCs Transports oxygen to every cell in every organ

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Airway (1 of 3) An open airway is essential to deliver air (oxygen) to the alveoli

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Airway (2 of 3) Normal air movement Inhalation results from negative intrathoracic pressure as the chest expands Air fills the alveoli

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Airway (3 of 3) Normal air movement (contd) Exhalation results from increased intrathoracic pressure as the chest relaxes Forces air out of the alveoli

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Breathing (Lungs) (1 of 2) When air reaches the alveoli: Oxygen crosses the alveolarcapillary membrane Oxygen Enters the RBCs Attaches to hemoglobin for transport

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Breathing (Lungs) (2 of 2) CO 2 in the plasma and cells A by-product of aerobic metabolism and energy production Crosses the alveolarcapillary membrane into the alveoli Is removed during exhalation

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Circulation (1 of 2) Oxygen-enriched RBCs are pumped through the blood vessels of the body to deliver oxygen to target organs

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Circulation (2 of 2) Oxygen is then off-loaded from the RBCs to fuel the metabolic processes of the cell CO 2 is transferred from the cells to the plasma for elimination via the lungs

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Cellular Metabolism Aerobic (1 of 3) Aerobic metabolism Most efficient method of energy production Uses oxygen and glucose to produce energy via chemical reactions known as glycolysis and the Krebs cycle Produces large amounts of energy Waste products Carbon dioxide Water

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Cellular Metabolism Aerobic (2 of 3) Aerobic metabolism is dependent upon: Adequate and continuous supply of oxygen Patent airway Functioning lungs (pulmonary system) Functional heart Pump blood to the cells

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Cellular Metabolism Aerobic (3 of 3) Aerobic metabolism is dependent upon (contd): Intact vascular system Adequate supply of RBCs Carry and transport oxygen Remove waste

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Aerobic Metabolism

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Cellular Metabolism Anaerobic (1 of 2) An injury that affects any of these three components of the oxygen delivery system will affect energy production Anaerobic metabolism is a metabolic process that functions in the absence of oxygen

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Metabolism without adequate oxygen Uses stored glucose in the form of glycogen for energy production Capable of sustaining energy requirements only for a short time Produces only small amounts of energy 19-fold decrease in energy Increased lactic acid as a by-product Cellular Metabolism Anaerobic (2 of 2)

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Anaerobic Metabolism

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Shock Inadequate energy production required to sustain life Change from aerobic to anaerobic metabolism Secondary to hypoperfusion Delivery of oxygen is inadequate to meet metabolic demands Decreased energy production Cellular and organ death

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Consequences of Hypoperfusion (1 of 4) Cellular hypoxia Decreased ATP (energy) production Cell dysfunction Lactic acid buildup Low pH

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Cell dysfunction (contd) Autodigestion of cells Leads to cellular death and organ failure Entry of sodium and water into the cell Cellular edema (swelling) worsens with overhydration Continuation of cycle Unless oxygenated red blood cells reach the capillaries If further loss of intravascular (blood) volume The cycle continues Consequences of Hypoperfusion (2 of 4)

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Inadequate ATP Cells and organs do not function properly Hypothermia Decreased heat production Consequences of Hypoperfusion (3 of 4)

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Cells and organs do not function properly Acidosis What little ATP is being produced is used to shiver Lactic acid production increases Coagulopathy As body temperature drops, blood clotting becomes impaired Consequences of Hypoperfusion (4 of 4)

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Triangle of Death

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Cascade of Death

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Types of Shock Shock is any condition that causes decreased cellular energy production Hypovolemic Dehydration Hemorrhage Distributive Neurogenic Septic Anaphylactic Psychogenic Cardiogenic Pump failure (intrinsic versus extrinsic)

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Trauma-Related Types of Shock Hypovolemic Dehydration Hemorrhage Distributive Neurogenic Septic Anaphylactic Psychogenic Cardiogenic Pump failure (intrinsic versus extrinsic)

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Hemorrhagic Shock Most common cause of hypoperfusion after trauma Internal or external blood loss Classes of shock

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Neurogenic Shock Associated with spinal cord injury Interruption of the sympathetic nervous system resulting in vasodilation Patient has normal blood volume but vascular container has enlarged, thus decreasing blood pressure

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Cardiogenic Shock Extrinsic Results from external compression of the heart Ventricles cannot fully expand Less blood is ejected with each contraction Blood return to the heart is decreased Causes from trauma include: Pericardial tamponade Tension pneumothorax

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Pathophysiology of Shock (1 of 6) Shock is progressive Changes in shock include: Hemodynamic Cellular (metabolic) Microvascular Compensatory mechanisms Short-term Will fail without interventions

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Pathophysiology of Shock (2 of 6) The heart must be an effective pump Primed by return of blood through the vena cavae Starlings Law Stroke volume (SV) Amount of blood ejected with each contraction Depends on adequate return of blood If blood volume decreases SV will decrease Cardiac output (CO) will decrease unless the heart rate (HR) increases CO = SV HR

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Pathophysiology of Shock (3 of 6) Adequate blood pressure Required to maintain cellular perfusion CO is one factor in maintaining blood pressure (BP) If CO falls Vasoconstriction occurs Systemic vascular resistance (SVR) increases in an attempt to maintain BP BP = CO SVR

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Pathophysiology of Shock (4 of 6) Vasoconstriction leads to the ischemic phase of shock Microvascular changes Early Precapillary and postcapillary sphincters constrict Resulting in ischemia in the tissues Must then produce energy anaerobically

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Pathophysiology of Shock (5 of 6) As acidosis increases: The precapillary sphincters relax The postcapillary sphincters remain constricted This results in stagnation of blood in the capillary bed

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Pathophysiology of Shock (6 of 6) Finally: The postcapillary sphincters relax Results in washout Releases microemboli Aggravates acidosis Causes infarction of organs by microemboli

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Signs Associated with Types of Shock

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Organ System Failure Due to Shock If not recognized and promptly corrected, shock will lead to organ dysfunction: First in oxygen-sensitive organs Then in other less oxygen-sensitive organs This cascading effect will lead to multi-organ dysfunction syndrome and patient death Failure of one major organ system Mortality rate of approximately 40% As additional organ systems fail, mortality approaches 100%

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Organ Sensitivity to Hypoxia Extremely sensitive Brain, heart, lungs Moderately sensitive Kidneys, liver, gastrointestinal tract Least sensitive Muscle, bone, skin

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Organ System Failure Due to Shock (1 of 4) Acute renal failure May result if oxygen delivery is impaired for more than 4560 minutes Will result in: Decreased renal output Reduced clearing of toxic products

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Acute respiratory distress syndrome (ARDS) Results from: Damage to the alveolar cells Hyper-resuscitation (fluid overload) Results in: Leakage of fluid into the interstitial spaces and alveoli Organ System Failure Due to Shock (2 of 4)

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Hematologic failure Impaired clotting cascade May result from: Hypothermia Dilution of clotting factors from fluid administration Depletion of clotting factors Organ System Failure Due to Shock (3 of 4)

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Hepatic failure Results from prolonged shock Overwhelming infection Results from decreased function of the immune system due to ischemia and loss of energy production Organ System Failure Due to Shock (4 of 4)

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Summary (1 of 3) Cellular function depends on adequate energy production Adequate energy production depends on a continuous and adequate supply of oxygen A continuous and adequate supply of oxygen depends on: Patent airway Functioning lungs Functioning heart Intact circulation

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Summary (2 of 3) Interruption of the oxygen supply for any reason will lead to anaerobic metabolism Anaerobic metabolism provides insufficient energy to sustain cellular function for any length of time This leads to cellular dysfunction and cell death, organ dysfunction and organ death, and ultimately patient death

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Summary (3 of 3) Knowledge, understanding, and early recognition of impaired energy production resulting from airway compromise, pulmonary injury, and impaired circulation are key to early recognition of shock. Prompt intervention by prehospital care providers to correct these conditions can prevent the cascade of cellular dysfunction that leads to organ death. This will improve the survival rate for victims of traumatic injury.

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Questions?