Shock is a A physiological state characterized by a significant, systemic reduction in tissue perfusion, resulting in decreased tissue oxygen delivery and insufficient removal of cellular metabolic products, resulting in tissue injury.

Hypovolemic Shock
Decreased preload->small ventricular end-diastolic volumes -> inadequate cardiac generation of pressure and flow
Causes:
 -- bleeding: trauma, GI bleeding, ruptured aneurysms,    hemorrhagic pancreatitis
 -- protracted vomiting or diarrhea
 -- adrenal insufficiency; diabetes insipidus
 -- dehydration
 -- third spacing: intestinal obstruction, pancreatitis, cirrhosis

Septic/Inflammatory Shock
Mechanism: release of inflammatory mediators leading to
Disruption of the microvascular endothelium
Cutaneous arteriolar dilation and sequestration of blood in cutaneous venules and small veins
Causes:
Anaphylaxis, drug, toxin reactions
Trauma: crush injuries, major fractures, major burns.
infection/sepsis: G(-/+ ) speticemia, pneumonia, peritonitis, meningitis, cholangitis, pyelonephritis, necrotic tissue, pancreatitis, wet gangrene, toxic shock syndrome, etc.

Cardiogenic Shock
Mechanism: Intrinsic abnormality of heart -> inability to deliver blood into the vasculature with adequate power
Causes:
Cardiomyopathies: myocardial ischemia, myocardial infarction, cardiomyopathy, myocardiditis, myocardial contusion
Mechanical: cardiac valvular insufficiency, papillary muscle rupture, septal defects, aortic stenosis
Arrythmias: bradyarrythmias (heart block), tachyarrythmias (atrial fibrillation, atrial flutter, ventricular fibrillation)
Obstructive disorders: PE, tension peneumothorax, pericardial tamponade, constrictive pericaditis, severe pulmonary hypertension
Characterized by high preload (CVP) with low CO
Signs/SXS: Dyspnea, rales, loud P2 gallop, low BP, oliguria
Monitor/findings: CXR pulm venous congestion, elevated CVP, Low CO.


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