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SU2.1-3 | Shock and Resuscitation — Practice Quiz
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Arterial blood pressure is the product of cardiac output and systemic vascular resistance (BP = CO x SVR). In which type of shock is the PRIMARY defect a fall in systemic vascular resistance, with the patient classically warm and vasodilated?
Correct. Distributive shock (septic, anaphylactic, neurogenic) is characterised by pathological vasodilatation — a fall in systemic vascular resistance — producing the warm, vasodilated 'warm shock' picture in the early phase. Hypovolaemic, cardiogenic and obstructive shock instead reduce cardiac output and are typically cold and vasoconstricted.
Distributive shock (septic, anaphylactic, neurogenic) lowers SVR and is classically warm; hypovolaemic, cardiogenic and obstructive shock lower CO and are cold and clamped down.
A primary fall in systemic vascular resistance with a warm, vasodilated patient is distributive shock (septic/anaphylactic/neurogenic). The others fail by reducing cardiac output and present cold and vasoconstricted.
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A 25-year-old man has lost an estimated 30-40% of his blood volume from a pelvic fracture. He is markedly tachycardic, his systolic blood pressure has fallen, his pulse pressure is narrowed, his respiratory rate is raised and he is confused. Using the standard classification of haemorrhagic shock, which class does this BEST represent?
Correct. Class III haemorrhage (roughly 30-40% blood-volume loss) is the point at which hypotension, marked tachycardia, a clearly narrowed pulse pressure, tachypnoea and altered mental state appear together. Class I and II maintain systolic pressure; class IV (>40%) is immediately life-threatening with profound hypotension and obtundation.
Haemorrhagic shock classes: I (<15%), II (15-30%, tachycardia/narrowed pulse pressure but normal systolic BP), III (30-40%, hypotension appears), IV (>40%, life-threatening).
Hypotension with marked tachycardia, narrowed pulse pressure, tachypnoea and confusion at an estimated 30-40% loss is Class III. Class I-II preserve systolic pressure; Class IV (>40%) is more profound, with collapse and obtundation.
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A trauma patient is tachycardic at 118/min, has cool clammy peripheries, a urine output of 15 mL/h and is mildly confused, yet his systolic blood pressure reads 116 mmHg. What is the MOST appropriate interpretation?
Correct. Tachycardia, cool clammy peripheries, oliguria and altered mentation in the face of a near-normal systolic pressure define compensated shock. Hypotension is a LATE sign; catecholamine-driven vasoconstriction holds the pressure up until compensation fails. Treat the trajectory, not the single reassuring number.
Shock is inadequate tissue perfusion, diagnosed at the bedside; hypotension is a LATE sign. A normal BP in a tachycardic, cold, oliguric patient is compensated shock.
This is compensated shock. Hypotension is a late sign — a normal systolic pressure does not exclude shock when the patient is tachycardic, cold, oliguric and confused. Treat the trajectory, not the snapshot.
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In the resuscitation of a patient with major traumatic haemorrhage requiring massive transfusion, which approach to blood-product replacement is now standard?
Correct. Damage-control resuscitation of major haemorrhage uses balanced transfusion in an approximately 1:1:1 ratio of red cells, plasma and platelets to replace whole-blood components and limit dilutional and trauma-induced coagulopathy, while minimising large-volume crystalloid. Definitive control of bleeding remains essential.
Damage-control resuscitation of major haemorrhage: balanced 1:1:1 transfusion of red cells, plasma and platelets, limit crystalloid, and achieve early haemorrhage control.
Standard massive-transfusion practice is balanced 1:1:1 red cells, plasma and platelets, not crystalloid alone or red cells alone. Vasopressors do not replace blood and source control in haemorrhage.
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In the early resuscitation of a patient with uncontrolled (ongoing) haemorrhage before definitive surgical control, the concept of 'permissive hypotension' is sometimes applied. Which statement BEST describes its rationale?
Correct. Permissive (or hypotensive) resuscitation accepts a lower target blood pressure in selected patients with uncontrolled haemorrhage, because driving the pressure up before surgical control can dislodge clot and increase blood loss. It is a bridge to definitive control — not a substitute for it — and is generally avoided in traumatic brain injury, where perfusion pressure must be protected.
Permissive hypotension: a deliberately lower BP target in uncontrolled haemorrhage to avoid clot disruption, as a bridge to surgical control; avoided in traumatic brain injury.
Permissive hypotension means accepting a deliberately lower target BP until bleeding is controlled, to avoid clot disruption — not withholding all fluid or aggressively normalising pressure. It is avoided, not preferred, in traumatic brain injury.
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A patient presents with shock, distended neck veins, muffled heart sounds and hypotension after blunt chest trauma; the lung fields are clear. Cardiac tamponade is suspected. Into which mechanistic category of shock does cardiac tamponade fall?
Correct. Cardiac tamponade (like tension pneumothorax and massive pulmonary embolism) causes obstructive shock — a mechanical obstruction to cardiac filling or output. Although it impairs the pump, the defect is extrinsic obstruction, not intrinsic myocardial failure, and the treatment is to relieve the obstruction (pericardiocentesis/drainage).
Obstructive shock = mechanical obstruction to filling/output: cardiac tamponade, tension pneumothorax, massive pulmonary embolism. Treatment relieves the obstruction.
Cardiac tamponade impairs ventricular filling by external compression — this is obstructive shock (with tension pneumothorax and massive PE). It is distinguished from cardiogenic shock, where the myocardium itself fails; treatment is to relieve the obstruction.
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