Shock Flashcards
What is shock?
A syndrome where tissue perfusion is inadequate for the tissue’s metabolic requirements
What causes hypovolaemic shock?
Loss of plasma or blood volume
= acute haemorrhage, severe dehydration, burns)
How does hypovolaemia affect cardiac output?
Volume depletion → reduced SVR → reduced pre-load → decreased CO
What causes cardiogenic shock?
Pump failure due to reduced contractility, heart rate, or stroke volume
= MI, cardiomyopathies, valvular issues).
What is the mortality rate in cardiogenic shock after MI involving >40% of the LV?
> 75%
How do CO and perfusion differ in distributive shock?
CO may increase, but perfusion is poor due to regional differences and impaired oxygen extraction
What causes distributive shock?
Disruption of vascular autoregulation and profound vasodilation
= sepsis, anaphylaxis)
Name causes of obstructive shock
(1) PE
(2) air/fat/amniotic embolism tamponade
(3) tension pneumothorax
What endocrine disorders can cause shock?
(1) Severe hypothyroidism
(2) Addisonian crisis
(3) Thyrotoxicosis (can lead to A Fib)
What is the common end pathway of shock?
Cellular ischemia triggers inflammatory mediators → vasoconstriction, oedema, cytotoxic damage
Name key inflammatory mediators in shock
Cytokines, TNF-alpha, nitric oxide, platelet-activating factor, lysosomal enzymes
How does nitric oxide contribute to vascular reactivity loss in shock?
Inflammatory pathways induce iNOS → 1000x NO increase → smooth muscle relaxation, vasodilation
What is a common feature of all types of shock?
Hypotension
What are signs of cardiogenic shock?
Myocardial failure signs:
(1) chest pain
(2) fatigue
(3) SOB
(4) oedema
How is hypovolaemic shock present?
Pale, cold skin, prolonged capillary refill
What are the signs of distributive shock in sepsis vs anaphylaxis?
Sepsis: Pyrexia, vasodilation, rapid capillary refill.
Anaphylaxis: Erythema, bronchospasm, profound vasodilation
What is the gold standard for measuring cardiac output in shock?
Thermodilution with a pulmonary artery catheter
What surrogate markers assess perfusion?
Blood pressure, consciousness, urine output, lactate levels
What is the first step in managing shock?
ABCDE approach and wide-bore IV access
How is a fluid challenge administered?
300-500 mL over 10-20 minutes, with targets like ↑MAP, ↓HR, or ↑urine output
Which drug is a low-dose beta-adrenergic agonist and high-dose alpha-agonist?
Adrenaline
What drugs are used for vasoconstriction in severe shock?
(1) Noradrenaline
(2) Vasopressin
(3) Dopamine
(4) Dobutamine
What are the mechanical options for cardiogenic shock?
Balloon pumps
Why is “de-resuscitation” important?
To remove excess fluid after resolving shock, using diuretics, dialysis, or spontaneous means
What are the types of shock?
Hypovolaemic (blood loss)
Septic (severe systemic infections)
Anaphylactic
Cardiogenic (poor cardiac output)
Neurogenic
Anaphylactic shock
A 30-year-old man comes into the emergency department. His blood pressure is 80/60 mmHg, and his heart rate is 105 bpm. He is pale and cool. On auscultation, crackles can be heard at both bases.
What kind of shock is this?
Cardiogenic shock
What is the blood loss in millilitres for (1) Class 1 shock
(2) Class 2 shock
(3) Class 3 shock
(4) Class 4 shock
(1) <750 mL
(2) 750-1500mL
(3) 1500-2000mL
(4) >2000mL
What percentage of blood loss is associated with;
(1) Class 1 shock
(2) Class 2 shock
(3) Class 3 shock
(4) Class 4 shock
(1) <15%
(2) 15-30%
(3) 30-40%
(4) >40%
At what pulse rate does
(1) Class 1 shock
(2) Class 2 shock
(3) Class 3 shock
(4) Class 4 shock
occur?
(1) <100
(2) >100
(3) >120
(4) >140
How does blood pressure change in Class’s I - IV shock?
I - normal
II - normal
III - decreased
IV -decreased
> 35 resp rate indicates what class shock?
IV
What are the symptoms associated with class I - IV shock?
Class I - normal
Class II - anxious
Class III - confused
Class IV - letsargic
A 32-year-old man is admitted to hospital following a road traffic accident. Initial assessment reveals extensive pelvic injury. The patient is drowsy and speaking incoherently.
A set of observations are performed during initial resuscitation:
Heart rate 128 bpm Blood pressure 83/68 mmHg Respiratory rate 36 /min Oxygen saturations 98% on room air Temperature 36.5 °C
What stage of hypovolaemic shock is the patient most likely to be in?
and why?
Stage 3
= The patient has all the features of stage 3 shock, confusion, tachycardia, hypotension, tachypnoea and reduced pulse pressure
A 29-year-old man is admitted to the emergency department having been stabbed in the right flank. On examination, he is mildly anxious, with a heart rate of 110 bpm, blood pressure of 130/65mmHg, RR 25 with normal urine output.
What likely class of haemorrhagic shock is this patient presenting with?
and why?
Class II
= Class II haemorrhagic shock describes an estimated blood loss of 750-1500ml (15-50%). The heart rate is typically 100-120 BPM. Blood pressure remains normal. The respiratory rate is typically 20-30/min. Urine output is slightly low i.e. 20-30ml/hr. The patient may appear mildly anxious
