Extra information

Bradycardia

• Heart abnormally slow

• Reduces the amount of blood pumped into the circulation each minute

• Can reduce cardiac output and oxygen delivery

Tachycardia

• Occurs when the heart rate is abnormally fast

• Reduces the time available for the ventricles to fill

• Can reduce stroke volume

• May eventually reduce cardiac output despite the increased heart rate

Stroke volume

• amount of blood ejected by the ventricle with each contraction

Vasoconstriction

• Narrows the blood vessels

• Increase resistance

• Helps maintain blood pressure during blood loss

Vasoconstriction causes

• Sympathetic nervous system stimulation

• Adrenaline

• Noradrenaline

Vasodilation

• Widens the blood vessels

• Reduces vascular resistance

Heart rate and perfusion

• Tachycardia is often an early sign of inadequate perfusion

• The body increases the heart rate to help maintain cardiac output

• Tachycardia must be distinguished from responses to pain or anxiety

Blood pressure and perfusion

• May be an unreliable early indicator of inadequate perfusion

• The body can maintain blood pressure through compensatory mechanisms

• Hypotension is generally considered a late sign of inadequate perfusion

Skin and perfusion

• Cool, pale, and clammy skin may indicate sympathetic vasoconstriction

• Blood is being redirected away from less essential organs to vital organs

Consciousness and perfusion

• Altered consciousness may be a late sign of hypovolaemia

• It can occur earlier when the brain is deprived of oxygen or glucose

Fill and squeeze principle

• Fill: restore adequate circulating volume and preload

• Squeeze: use medications to improve cardiac contractility or vascular tone if perfusion remains inadequate

What is TXA used for

• Severe traumatic haemorrhage

• Antifibrinolytic medication

• Helps preserve formed clot

How does TXA work

• Synthetic lysine analogue

• Reduced plasminogen/plasmin activity

• Decreases fibrinolysis

• Decreases breakdown of fibrin clot

When should TXA be considered

• Severe trauma with significant haemorrhage

• Early administration within 3 hours

Calcium in major haemorrhage

• Blood products contain citrate

• Citrate binds with ionised calcium

• Decreased calcium can worsen

  • Coagulopathy

  • Myocardial function

• Calcium chloride 10% at 10mL in case of transfusion

Noradrenaline used in cardiogenic shock

• Significant hypotension with poor perfusion.

• Primarily causes α₁ vasoconstriction.

• ↑ systemic vascular resistance

• ↑ mean arterial pressure

• Some β₁ activity supports contractility.

Adrenaline used in cardiogenic shock

• Inopressor support in selected severe cases.

  • Α₁:

  • Vasoconstriction

  • ↑ SVR.

• Β₁:

  • ↑ HR.

  • ↑ contractility.

• Can increase BP and cardiac output.

Dobutamine pathophysiology

• Predominantly β₁ agonist.

• ↑ myocardial contractility.

• ↑ stroke volume.

• ↑ cardiac output.

• Most useful when reduced contractility is the major problem and BP can tolerate it.

Why are fluids used cautiously in cardiogenic shock

• Excess fluid can worsen pulmonary oedema.

• Can increase workload on a failing heart.

Why does PE cause hypoxaemia

• Ventilated areas become poorly perfused.

• Causes ventilation perfusion mismatch.

How does noradrenaline work

• Mainly α₁ agonism.

• Vasoconstriction.

• ↑ systemic vascular resistance.

• ↑ MAP.

• Supports organ perfusion pressure

Why does bradycardia occur in neurogenic shock

• Loss of sympathetic cardiac stimulation.

• Relative/unopposed parasympathetic influence.

• The patient fails to mount expected compensatory tachycardia.

Medication for hypotension in neurogenic shock

• Noradrenaline.

• α₁ vasoconstriction replaces lost vascular tone.

• ↑ systemic vascular resistance and MAP.

Adrenaline pathophysiology AI receptors

• Vasoconstriction.

• ↑ systemic vascular resistance.

• ↑ blood pressure.

• ↓ mucosal oedema.

Adrenaline pathophysiology B1 receptors

• ↑ heart rate.

• ↑ myocardial contractility.

• ↑ cardiac output.

Adrenaline pathophysiology B2 receptors

• Bronchodilation.

• Helps reverse bronchospasm.

What does salbutamol do in anaphylaxis

• β₂ agonist.

• Relaxes bronchial smooth muscle.

• Produces bronchodilation.

Maintaining critical perfusion pressure

• MAP <40 = brain damage

• MAP of 50 = minimum target

• MAP of 65 = heart perfusion

• MAP 65-67 = kidney confusion

mean arterial pressure calculation

• Diastolic BP + ⅓ systolic BP - diastolic BP

• Pressure maintained in the vascular system

Blood pressure formula

• Cardiac output x pulmonary vascular resistance

Cardiac output formula

• Heart rate x stroke volume

What happens to coagulation in severe haemorrhage

• Severe shock and tissue injury can cause trauma-induced coagulopathy.

• Increased fibrinolysis.

• Clotting becomes impaired.

• Ongoing bleeding worsens.

• Hypothermia further impairs coagulation.

• Hypocalcaemia can impair coagulation and myocardial function.

What is traumatic brain injury main goal

prevent secondary brain injury

Why are hypoxia and hypotension dangerous in TBI

• Both reduce oxygen delivery to injured brain tissue.

• Can markedly worsen secondary brain injury.

• Even short episodes may worsen outcome

Cerebral perfusion pressure

CPP = MAP - ICP

What happens to cerebral perfusion pressure when ICP increases

• MAP stays the same.

• ICP rises.

• CPP falls.

• Brain perfusion decreases.

What happens if MAP falls while ICP is raised

• CPP falls dramatically.

• Cerebral ischaemia risk increases.

• Hypotension is therefore particularly dangerous in severe TBI

Why loosen items and elevate head in TBI

• Items:

  • They may impair cerebral venous drainage.

  • This may increase ICP.

• Head:

  • May improve cerebral venous drainage.

  • May reduce ICP where clinically appropriate.

Unreliable patient

• Acute stress reaction

• head/brain injury

• Altered mental status

• Intoxication with drugs and/or alcohol

• Distracting injuries

Intracranial volume consists of

• Brain

• CSF

• Blood vessel volume

What is ICP

• Intracranial pressure

• Pressure exerted by the brain on the contents within the skull

What is CCP

• Cerebral perfusion pressure

• Pressure required to perfuse the brain

What is MAP

• Mean arterial pressure

• Pressure maintained in the vascular system

Airway obstruction important in

• Reduced LOC.

• Facial trauma.

• Vomiting/secretions.

• Foreign bodies.

• Burns/inhalation injury.

Suction time

• Only 10-15 seconds at a time

• Use eyewear, mask, gloves

Oxygen flow vs FiO2

• Flow rate

  • Amount of oxygen delivered per minute

• FiO2

  • fraction/concentration of oxygen actually inhaled

What happens when respiratory distress increases

• Peak inspiratory flow increases.

• More room air may be entrained.

• Actual FiO₂ may decrease despite unchanged oxygen flow.

high-yield concept

• Flow rate ≠ FiO₂.

• Actual FiO₂ depends partly on whether the delivery system meets the patient's inspiratory flow demand.

Confirm placement of advanced airways

• Ascultation

• ETCO2

• Evaluate chest rise and fall

• Pulse oximetry

• Monitor vitals (HR, BP)a