Acute Circulatory failure/ Shock


Cardiology Medicine Flashcards on Acute Circulatory failure/ Shock, created by Rahul sharma on 09/11/2016.
Rahul sharma
Flashcards by Rahul sharma, updated more than 1 year ago
Rahul sharma
Created by Rahul sharma almost 8 years ago

Resource summary

Question Answer
Describe how cardiac tamponade cause shock? Accumulation of pericardial fluid raises intrapericardial pressure, hence poor ventricular filling and fall in cardiac output.
Define shock Circulatory failure resulting in inadequate organ perfusion. Often defined by low- BP--(SBP) systolic <90mmHg-- or mean arterial pressure (MAP)< 65mmHg-- with evidence of tissue hypo perfusion, e.g. mottled skin, urine output < 0.5 mL/kg for 1 hour, serum lactate> 2mmol/L Signs: GCS low/ agitation, pallor, cool peripheries, tachycardia, slow capillary refill, tachypnoea, oliguria.
What is MAP mean arterial pressure cardiac output (CO) x Systemic vascular resistance (SVR) CO = stroke volume x heart rate shock can result from inadequate CO or a loss of SVR or both.
Describe how hypovolaemia can cause shock? Hypovolemic shock refers to a medical or surgical condition in which rapid fluid loss results in multiple organ failure due to inadequate circulating volume and subsequent inadequate perfusion. Most often, hypovolemic shock is secondary to rapid blood loss (hemorrhagic shock). Bleeding: trauma, AAA, GI bleed Fluid loss: vomiting, burns, third space losses, e.g. pancreatitis, heat exhaustion.
How sepsis can cause shock? Infection with any organism can cause acute vasodilation from inflammatory cytokines. Gram -ves can produce endotoxin, causing sudden and severe shock but without signs of infection (fever, raised WCC). Classically patients with sepsis are warm and vasodilator, but may be cold and shut down.
How Anaphylaxis can cause shock Type-1 IgE- mediated hypersensitivity reaction. release of histamine and other agents causes: capillary refill leak, wheeze, cyanosis, oedema (larynx, lids, tongue, lips), urticaria.
Describe how clinical examination can be used to distinguish between the causes of shock listed? ABCDE we are dealing primarily with C. Cold and clammy suggests cariogenic shock or fluid loss. Look for signs of anaemia or dehydration, e.g. skin turgor, postural hypotension? warm and well perfused, with bounding pulse points to septic shock. Any features suggestive of anaphylaxis- history, urticaria, angio-oedema, wheeze? JVP or central venous pressure : if raised, cardiogenic shock likely. Check abdomen: any signs of trauma, or aneurysm? CVS: usually tachycardic and hypotensive. But in young and fit, or pregnant women, the SBP may remain normal, although pulse pressure will narrow, with up to 30% blood volume depletion. Difference between arms- aortic dissection?
Define CVP and normal range? Central venous pressure (CVP) is the pressure recorded from the right atrium or superior vena cava and is representative of the filling pressure of the right side of the heart CVP monitoring in the critically ill is established practice but the traditional belief that CVP reflects ventricular preload and predicts fluid responsiveness has been challenged by a large body of evidence CVP represents the driving force for filling the right atrium and ventricle normal is 0-6mmHg in a spontaneously breathing non-ventilated patient
How CVP can be used to give an indication of the cause of shock? CAUSES OF RAISED CVP Right ventricular failure Tricuspid stenosis or regurgitation Pericardial effusion or constrictive pericarditis Superior vena caval obstruction Fluid overload Hyperdynamic circulation High PEEP settings
CVP waveform analysis Dominant a wave – pulmonary hypertension, TS, PS Cannon a wave – complete heart block, VT with AV dissociation Dominant v wave – TR Absent x descent – AF Exaggerated x descent – pericardial tamponade, constrictive pericarditis Sharp y descent – severe TR, constrictive pericarditis Slow y descent – TR, atrial myxoma Prominent x and y descent – RV infarction
Use of volume expanders in the treatment of shock. In most kinds of shock, crystalloid fluids (normal saline or Ringer's lactate) should be given as boluses. Be careful with rapid fluid administration to the patient in cardiogenic shock with pulmonary oedema. Colloids are used to provide oncotic expansion of plasma volume. They expand plasma volume to a greater degree than isotonic crystalloids and reduce the tendency toward pulmonary and cerebral oedema. About 50% of the administered colloid stays intravascular.
Use of blood products in the treatment of shock Blood products may be necessary in certain types of hemorrhagic shock. If volume resuscitation does not improve the patient's hemodynamic status, vasoactive medications such as epinephrine, norepinephrine, dopamine, and vasopressin may be used.
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