32 - Haemorrhage and Shock Flashcards by Haleema D

What is clinical shock

Acute circulatory failure - inadequate or inappropriately distributed tissue perfusion resulting in cellular hypoxia

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How is tissue perfusion usually maintained

CO - 5l/min
BP - 120mmHg
MAP - 100mmHg

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What are the signs of shock

MAP <60mmHg and hypo perfusion of vital organs (tachycardia, tachypnea, mental confusion , pallor)

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What causes low BP

Low cardiac output

Low vascular resistance

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What are the effects of cellular hypoxia

Cells switch to anaerobic metabolism
Lactic acid produced
Cell function ceases and swells
Membrane becomes more permeable
Electrolytes and fluids seep in and out
Na+/K+ pump impaired
Cells swell 
Mitochondria damagge
Cell death

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What are the factors controlling heart rate

Baroreceptors in carotid sinus

Arousing stimuli - ANS

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What are factors controlling stroke volume

Blood in heart before it contracts

Myocardial contractility

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What is starling’s law of the heart

Greater the preload, the greater the force of contraction
Greater the stroke volume
(If preload decreases then SV decreases)

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What increases myocardial contractility

Sympathetic NS
Circulating catecholamines
Ionotrope drugs - B1 agonists

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What decreases myocardial activity

Cardiac disease
Hypoxia/hypercapnia
Ph or electrolyte disturbance
Drugs - BB, CCB

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What is prostacyclin

(PG12) produced from

Produced in endothelial cells from arachidonic acid

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What is the action of prostacyclin

= Prevents formation of platelet plug –inhibits platelet activation
= Local vasodilator – reduces Ca entry into smooth muscle to reduce contractility

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What is the action of thromboxane

local vasoconstriction and platelet aggregation

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What causes shock

SVR not maintained - arterioles no longer constrict

Preload decreases - loss of blood volume or obstruction

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What is compensation

The initial stage where homeostatic mechanisms are activated

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What is decompensation

When • Arterioles cannot maintain constriction/preload too great, end organs start to fail

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What is distributive shock

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Loss of vasoconstriction
Excess blood flow
poor perfusion of other organs

What are causes of distributive shock

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Sepsis
Anaphylaxis
Neurogenic

What are signs of distributive shock

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Low BP
Tachycardia
Fatigue

What is septic shock

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Type of distributive shock

Sepsis is when the host response leads to micro vascular damage in one or more end organs

What causes lack in vasoconstriction in sepsis

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Neutrophils and monocytes release cytokines that prevent normal vasoconstricion
may be severe enough to reduce BP to shock level

What is hypovolemic shock

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Due to haemorrhage (often called haemorrhagic shock)

What are some causes of hypovolemic shock

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Haemorrhage
Burns
Surgery or trauma
Loss of fluid and electrolytes

Signs of hypovolemic shock

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Confusion/anxiety
Cold
Low BP
High HR
Slow capillary refill 
(Make sure you check the history as internal bleeding is not as obvious)

What is life threatening blood loss values

Total body water is 45 litres (IC 27 and EC 18) | So if Blood volume is 4.5-5 litres – loss >40% (>2 litres ) is life threatening

What is the | immediate compensatory response to haemorrhage

Immediate = baroreceptors increase sympathetic outflow, increase HR and contractlity, vasomotor centre in medulla signals to hypothalamus to release vasopressin to reduce preload and release ANP so urine flow and excretion decrease

What is the long term compensatory response to haemorrhage

``` Increased renin release Aldosterone released from adrenal cortex by angiotensin II Thirst is stimulated Increase in water intake Na+ and H20 retention is increased Albumin is stimulated ```

What is class I of hypovolemic shock

– Loss of <15% blood volume (blood donation, minor injury, fully compensated, fatigue/slightly normal)

What is class II of hypovolemic shock

- Loss of 15-30% of blood (tachycardia, tachypnea, dc in PP, slight anxiety, delayed cap refill, rest and water/food, will compensate)

What is class III of hypovolemic shock

- Loss of >30% of blood (persistent drop in BP, anxious patient, confused, require plasma volume expanders or blood transfusion, may have end-organ damage)

What is class IV of hypovolemic shock?

Loss of >40% of blood volume (confused/unconscious, tachycardia, no urine output, severely decreased systolic pressure, life threatening hemorrhage, need blood transfusion)

What is cardiogenic shock

Failure of the heart to pump efficiently and supply blood to the body

Causes of cardiogenic shock

 myocardial infarction, heart failure, arrhythmia, ventricular septal rupture, Ischaemic Cardiomyopathy, Valvular Disease

What are signs of cardiogenic shock

AMI = Chest pain, SOB, Nausea | Pulmonary oedema, acute circulatory collapse

What pathways are disrupted in neurogenic shock

Automatic pathways in SC

How do you manage shock if the cause is hypovolemia

Restore circulating BV with IV colloids (gelatins, dextrans, hydroxyethyl starches, or 4% or 20% albumin) or crystalloids (isotonic or hypertonic saline, or Ringer lactate solution)

What drugs restore BP

Vasopressor drugs - Dopamine, noradrenaline, phenylephrine, ADH

What do you give to a patient if the cause of shock is sepsis

Antimicrobials

central venous pressure

8 – 12 mmHg

Mean arterial pressure

≥ 65 mmHg

Urine output

0.5 mL/kg/h

Mixed venous oxygen saturation

≥ 70%

32 - Haemorrhage and Shock Flashcards

(42 cards)