Physiology of Life & Death PDF

EHS201 Introduction to Trauma Physiology of Life & Death 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 1 Introduction Body systems o Interrelated o Interdependent Every cell and every organ work together to: o Sustain cellular energy producti...

EHS201 Introduction to Trauma Physiology of Life & Death 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 1 Introduction Body systems o Interrelated o Interdependent Every cell and every organ work together to: o Sustain cellular energy production o Maintain vital metabolic processes 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 2 Energy Energy powers all body functions o 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 patient’s body maintains energy production 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 4 Systems & Components Airway o Must be patent Breathing (lungs) o Adequate oxygen must: Reach alveoli Cross alveolar/capillary wall Enter the circulation o Carbon dioxide (CO2) must be removed 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 5 Systems & Components Circulation o Distributes red blood cells (RBCs) o Ensures adequate number of RBCs o Transports oxygen to every cell in every organ 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 6 What are the key components the body requires to produce energy? 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 7  Glucose and oxygen 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 8 Airway An open airway is essential to deliver air (oxygen) to the alveoli 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 9 Airway Normal air movement o Inhalation results from negative intrathoracic pressure as the chest expands Air fills the alveoli 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 10 Airway Normal air movement o Exhalation results from increased intrathoracic pressure as the chest relaxes Forces air out of the alveoli 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 11 Breathing When air reaches the alveoli: o Oxygen crosses the alveolar–capillary membrane Oxygen o Enters the RBCs o Attaches to hemoglobin for transport 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 12 Breathing CO2 in the plasma and cells o A by-product of aerobic metabolism and energy production o Crosses the alveolar–capillary membrane into the alveoli o Is removed during exhalation 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 13 Circulation Oxygen-enriched RBCs are pumped through the blood vessels of the body to deliver oxygen to target organs Oxygen is then off-loaded from the RBCs to fuel the metabolic processes of the cell CO2 is transferred from the cells to the plasma for elimination via the lungs 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 14 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 Aerobic o Carbon dioxide Metabolism o Water ATP 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 15 Aerobic Metabolism Aerobic metabolism is dependent upon: o Adequate and continuous supply of oxygen o Patent airway o Functioning lungs o Functional heart o Intact vascular system o Adequate supply of RBCs Aerobic Metabolism ATP 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 16 Anaerobic Metabolism 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 Anaerobic Metabolism ATP 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 17 Anaerobic Metabolism 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 Anaerobic o 19-fold decrease in energy Metabolism o Increased lactic acid as a by-product ATP 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 18 Shock Inadequate energy production required to sustain life Change from aerobic to anaerobic metabolism o Secondary to hypoperfusion o Delivery of oxygen is inadequate to meet metabolic demands o Decreased energy production Cellular and organ death 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 19 Consequences of Hypoperfusion Cellular hypoxia Decreased ATP (energy) production Cell dysfunction o Lactic acid buildup o Low pH 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 20 Consequences of Hypoperfusion Cell dysfunction o Autodigestion of cells Leads to cellular death and organ failure o Entry of sodium and water into the cell Cellular edema (swelling) worsens with overhydration o Continuation of cycle Unless oxygenated red blood cells reach the capillaries o If further loss of intravascular (blood) volume The cycle continues 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 21 Consequences of Hypoperfusion Inadequate ATP Cells and organs do not function properly o Hypothermia Decreased heat production o Acidosis What little ATP is being produced is used to shiver Lactic acid production increases o Coagulopathy As body temperature drops, blood clotting becomes impaired 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 22 Triangle of Death 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 23 Cascade of Death 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 24 Types of Shock Hypovolemic o Dehydration o Burns Trauma-Related o Hemorrhage Distributive o Neurogenic o Septic o Anaphylactic o Psychogenic Cardiogenic o Pump failure (intrinsic versus extrinsic) 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 25  What are the shock-related causes of coagulopathy? 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 26  Hypothermia and acidosis 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 27  Hemorrhagic Shock Most common cause of hypoperfusion after trauma Internal or external blood loss Class I Class II Class III Class IV Blood loss 2000 ml (40%) Pulse rate 140 Respiratory rate 14-20 20-30 30-40 >35 Blood pressure Normal Normal Decreased Decreased Pulse pressure Normal or increased Decreased Decreased Decreased Mental status Slightly anxious Mildly anxious Anxious, confused Confused, lethargic 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 28 Hemorrhagic Shock Most common cause of hypoperfusion after trauma Internal or external blood loss 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 29 Pathophysiology of Shock Shock is progressive Changes in shock include: o Hemodynamic o Cellular (metabolic) o Microvascular Compensatory mechanisms o Short-term o Will fail without interventions 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 30 Pathophysiology of Shock The heart must be an effective pump o Primed by return of blood through the vena cavae Starling’s Law Stroke volume (SV) o Amount of blood ejected with each contraction o Depends on adequate return of blood o If blood volume decreases SV will decrease Cardiac output (CO) will decrease unless the heart rate (HR) increases 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 31 Pathophysiology of Shock Adequate blood pressure o Required to maintain cellular perfusion CO is one factor in maintaining blood pressure (BP) If CO falls o Vasoconstriction occurs o Systemic vascular resistance (SVR) increases in an attempt to maintain BP 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 32 Pathophysiology of Shock Vasoconstriction leads to the ischemic phase of shock Microvascular changes o Early Precapillary and postcapillary sphincters constrict Resulting in ischemia in the tissues Must then produce energy anaerobically 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 33 Pathophysiology of Shock As acidosis increases: o The precapillary sphincters relax o The postcapillary sphincters remain constricted o This results in stagnation of blood in the capillary bed 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 34 Pathophysiology of Shock Finally: o The postcapillary sphincters relax o Results in washout o Releases micro emboli o Aggravates acidosis o Causes infarction of organs by micro emboli 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 35 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 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 36 Cardiogenic Shock (Extrensic) Results from external compression of the heart Ventricles cannot fully expand o Less blood is ejected with each contraction Blood return to the heart is decreased Causes from trauma include: o Pericardial tamponade o Tension pneumothorax 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 37 Signs Associated with Types of Shock Vital Sign Hypovolemic Neurgenic Cardiogenic Skin temperature Cool, clammy Warm, dry Cool, clammy Skin color Pale, cyanotic Pink Pale, cyanotic Blood pressure Drops Drops Drops Level of Altered Lucid Altered consciousnes Use history and mechanism of injury to differentiate Consider hemorrhagic shock first 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 38 Organ Sensitivity to Hypoperfusion Extremely sensitive o Brain, heart, lungs o Minutes Moderately sensitive o Kidneys, liver, gastrointestinal tract o 1-1.5 hours Least sensitive o Muscle, bone, skin o 4-6 hours 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 39 Organ System Failure If not recognized and promptly corrected, shock will lead to organ dysfunction: o First in oxygen-sensitive organs o Then in other less oxygen-sensitive organs This cascading effect will lead to multi-organ dysfunction syndrome and patient death o Failure of one major organ system Mortality rate of approximately 40% o As additional organ systems fail, mortality approaches 100% 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 40 Organ System Failure Acute renal failure o May result if oxygen delivery is impaired for more than 45–60 minutes o Will result in: Decreased renal output Reduced clearing of toxic products 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 41 Organ System Failure Acute respiratory distress syndrome (ARDS) o Results from: Damage to the alveolar cells Hyper-resuscitation (fluid overload) o Results in: Leakage of fluid into the interstitial spaces and alveoli 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 42 Organ System Failure Hematologic failure o Impaired clotting cascade May result from: Hypothermia Dilution of clotting factors from fluid administration Depletion of clotting factors 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 43 Organ System Failure Hepatic failure o Results from prolonged shock Overwhelming infection o Results from decreased function of the immune system due to ischemia and loss of energy production 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 44  What are the signs for compensated hemorrhagic shock? 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 45  Sinus tachycardia, tachypnea, normal systolic, narrowed pulse pressure, mild anxiety, cool and pale skin 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 46 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 47 Summary 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: o Patent airway o Functioning lungs o Functioning heart o Intact circulation 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 48 Summary 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 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 49 Summary 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. 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 50 Reference(s) American College of Surgeons Committee on Trauma (2020). Prehospital Trauma Life Support, Ninth Edition. Jones & Bartlett Learning. 8/24/2023 PHYSIOLOGY OF LIFE & DEATH 51