19A13: Exam Report

Classify circulatory shock and provide examples (40% marks). Outline the cardiovascular responses (60%)

83% of candidates passed this question.

Answers should have included the various types of shock and provided clear examples.
Cardiovascular responses including sensor, integrator, effector mechanisms were necessary to pass.

G6 SYL2017 / 19A13: Classify circulatory shock and provide examples (40% marks). Outline the cardiovascular responses (60%)

Definition

A state of circulatory failure characterised by globally impaired tissue perfusion that is insufficient to meet body demands

Classification

  • CARDIOGENIC
  • OBSTRUCTIVE
  • HYPOVOLAEMIC
  • DISTRIBUTIVE
  • ENDOCRINE
  • ERROR

Cardiogenic

  • Impaired contractility
  • Dysrrhythmia
  • Valvular dysfunction
  • LVOT obstruction

Obstructive

    • In circulatory system → massive PE
    • External to circulatory system → Tension PTX

Hypovolaemic Shock

  • Haemorrhage
  • Fluid loss

Distributive

    • i.e. sepsis, neurogenic, liver failure, anaphylaxis

Endocrine

  • Adrenal insufficiency
  • Hypo/Hyperthyroidism

Errors

  • Arterial line transducer higher than RA

Cardiovascular Response

Sensor

Baroreceptors

MAP < 60

↓firing rate of BaroR afferents

Via CN X & IX

Chemoreceptors

↓tissue perfusion

Hypoxia

Anaerobic Metabolism

Stimulates Central & Peripheral ChemoR

Via CN X & IX

Ischaemic Cns Response

MAP < 60

Integrator

Baroreceptors

Vasomotor & cardiac centres of Lower Pons & Medulla

Chemoreceptors

Respiratory centre in RAS of lower pons & Medulla

Ischaemic Cns Response

Vasomotor & cardiac centres of Lower Pons & Medulla

Effector

Baroreceptors

ANS by negative feedback

↓BP → ↑symp. & ↓parasympathetic ouput

Chemoreceptors

↑symp outflow

↑MV

Ischaemic Cns Response

Mass SYMPATHETIC OUTFLOW

Sympathetic Stimulation:

    • Adr & NA released from adrenal medulla and sympathetic n terminals ↑x50

@ Heart

    • b1 receptor activation
    • ↑HR & FoC
    • ↑CO

@ Arteriolar

    • a1 activation
    • ↑SVR
    • Maintenance of BP
    • Mass VC of cutaneous, sk m, splanchinic vessels to redirect blood
    • Renal A VC → especially supply to outer layers of renal cortex
    • Cardiac/Cerebral vessel sparing

@Venous

    • Mobilisation of reservoirs; lungs, liver, cutaneous
    • ↑VR = ↑CO