Hemodynamic Disorders, Thromboembolism, and Shock PDF

Fatima Obeidat MD  Occurs in 90% of individuals with severe skeletal injuries (long bone fracture) but less than 10% show any clinical findings.  Fat microemboli occlude pulmonary and cerebral microvasculature  Fat embolism syndrome:  pulmonary insufficiency.  Neurologic sympto...

Fatima Obeidat MD  Occurs in 90% of individuals with severe skeletal injuries (long bone fracture) but less than 10% show any clinical findings.  Fat microemboli occlude pulmonary and cerebral microvasculature  Fat embolism syndrome:  pulmonary insufficiency.  Neurologic symptoms.  Anemia.  Thrombocytopenia.  Diffuse petechial rash.  Fatal in 10% of cases  Clinical signs and symptoms appear 1 to 3 days after injury.  Sudden onset of  Tachypnea.  Dyspnea.  Tachycardia.  Irritability, and restlessness,  Can progress rapidly to delirium or coma.  Gasbubbles within the circulation can coalesce and obstruct vascular flow and cause distal ischemic injury.  Airmay enter the circulation a. During obstetric procedures b. Chest wall injury. c. A particular form, called decompression sickness, occurs when individuals are exposed to sudden changes in atmospheric pressure  Deep-sea divers, and underwater construction workers are at risk. When air is breathed at high pressure (e.g., during a deep-sea dive), increased amounts of gas (particularly nitrogen) become dissolved in the blood and tissues.  If the diver then ascends (depressurizes) too rapidly, the nitrogen bubbles comes out of solution in the blood to form gas emboli that can induce focal ischemia in a number of tissues, including brain and heart  The rapid formation of gas bubbles within skeletal muscles and supporting tissues in and about joints is responsible for the painful condition called the bends In the lungs, gas bubbles in the vasculature cause edema, hemorrhages, leading to respiratory distress, called the chokes.  Treatingacute decompression sickness requires placing the affected individual in a compression chamber to increase barometric pressure and force the gas bubbles back into solution.  Ischemic necrosis caused by occlusion of the vascular supply to the affected tissue.  Examples:  Myocardial or cerebral infarction.  Pulmonary infarction  Bowel infarction  Ischemic necrosis of distal extremities (gangrene) esp. in the diabetics.  Arterial thrombosis or arterial embolism underlies the vast majority of infarctions.  Less common causes  Vasospasm.  Expansion of an atheroma  Extrinsic compression of a vessel, by tumor.  Venous thrombosis thus usually occur only in organs with a single efferent vein (e.g., testis or ovary).  Infarcts may be either red (hemorrhagic) or white (anemic). Red infarcts occur in:  (1) with venous occlusions (such as in ovarian torsion);  (2) in loose tissues (e.g., lung)  (3) in tissues with dual circulations such as lung and small intestine,;  (4) in previously congested tissues (as a consequence of sluggish venous outflow).  (5) when flow is reestablished after infarction White infarcts occur with :  Arterial occlusions in solid organs with end-arterial circulations (e.g., heart, spleen, and kidney)  ischemic coagulative necrosis.  in the central nervous system results in liquefactive necrosis  Most infarcts are replaced by scar.  Is characterized by systemic hypoperfusion of tissues.  It can be caused by :  1. diminished cardiac output.  2. reduced effective circulating blood volume  Consequences are impaired tissue perfusion and cellular hypoxia (organ failure)  Cardiogenic shock results from low cardiac output due to myocardial pump failure.  It may be caused by myocardial damage (infarction), ventricular arrhythmias, extrinsic compression (cardiac tamponade), or outflow obstruction (e.g., pulmonary embolism).  Hypovolemic shock results from low cardiac output due to loss of blood or plasma volume (e.g., due to hemorrhage or fluid loss from severe burns).  Septic shock results from arterial vasodilation and venous blood pooling that stems from the systemic immune response to microbial infection. gram-positive bacteria constitute the most common cause of septic shock