Shock Flashcards
What is shock?
The clinical syndrome of tissue hypoperfusion due to circulatory failure.
Common, life threatening (40-80%), acute
What is the pathophysiology behind shock?
MAP below necessary (approx. 50-60mmHg, higher in diseased atherosclerotic vessels)
Slow flow to organs (even leading to thrombus formation-Virchow’s)
Inadequate perfusion for cellular metabolic requirements (Leading to acidosis and lactate formation)
What does inadequate perfusion cause?
Systemic Acidosis (pH < 7.35), further worsening global enzyme function and cellular performance
Microcapillary thrombus with patchy tissue injury and even large vessel thrombus with organ infarction
Eventual cellular necrosis results in mortality
In survivors, a degree of tissue injury may be irreversible, contributing to chronic morbidity
What micro-circulatory changes can occur in shock?
Capillary blood flow is reduced, intermittent or terminated
How is shock recognised?
Immediate Impression:
Mottling
Glasgow Coma Score- <15– Confusion, Agitation
Urine Output <0.5ml/kg/h
How is shock confirmed?
Lactate Levels:
0.75mmol/L higher than normal carries a worse prognosis
>2mmol/L arguably diagnostic
>4mmol/L significant mortality
Describe cardiogenic shock
Reduced force of cardiac contraction and stroke volume and therefore cardiac output and mean arterial pressure
Compensatory increase in SVR, resulting in cool, clammy peripheries
What is the pathophysiology involved in cardiogenic shock?
HR reduced in some caes SV reduced due to low contractility Leads to CO reduced SVR increased to compensate MAP likely decreased
What is the treatment of cardiogenic shock due to decreased HR?
Arrythmia- Drugs +- cardioversion
Poisoning- Drugs +- dialysis
What is the treatment of cardiogenic shock due to decreased SV?
MI- Drugs +- PCI
Cardiomyopathy- Drugs
Valve failure- Drugs +- surgery
Describe obstructive shock
Obstruction to cardiac outflow (otherwise similar to cardiogenic)
Evidence of raised JVP and distended neck veins may be prominent
What is the pathophysiology behind obstructive shock?
Similar to cardiogenic
CO blocked
Leading to venous back pressure
How is obstructive shock due to cardiac tamponade treated?
Trauma/Aortic Dissection: Pericardiocentesis +- Thoractomy +- Surgery
How is obstructive shock due to tension pneumothorax treated?
Trauma/Pleural Pathology: Thoracocentesis + Thoracostomy +- Surgery
How is obstructive shock due to PE treated?
Stasis (post op/partum): Anticoagulation +- Thrombolysis or direct lysis
Describe hypovolaemic shock
Reduced blood volume
Lower venous return to the heart (ventricular filling = end-diastolic volume)
Reduced force of cardiac contraction and Cardiac Output (Frank-Starling law)
What is the pathophysiology in hypovolaemic shock?
HR increased to compensate SV reduced due to low preload CO may be reduced SVR increased to compensate Likely reduction in MAP
What signs of haemorrhage will occur in class I volume loss (<15%=750ml)?
Normal RR Normal HR Normal (Or increased) BP No change in mental state Urine output >30ml/h
What signs of haemorrhage will occur in class II volume loss (<30%=1500ml)?
>20 RR >100 HR Decreased pulse pressure Anxious Urine output <30ml/h
What signs of haemorrhage will occur in class III volume loss (<40%=2000ml)?
>30 RR >120 HR Decreased BP Confused Urine output <315ml/h
What signs of haemorrhage will occur in class IV volume loss (>40%=over 2000ml)?
>35 RR >140 HR Decreased BP Lethargic Urine output negligible
What can cause haemorrhage, in turn causing hypovolaemia?
Trauma- Overt Haemorrhage, Pelvic Fracture, Long Bone Fracture, Abdominal Visceral, Intrathoracic
Gastrointestinal Bleeding
Post-operative Bleeding
How is haemorrhage treated?
Temporising Measures (Pressure, Splint, Binding Sengstaken) Find & Stop Bleeding (Surgery, Endoscopy) Cross-match, Blood, Blood Products
What can cause dehydration, in turn causing hypovolaemia?
Gastrointestinal Loss (Diarrhoea, Stoma, Vomiting, Starvation) Epithelial Loss (Burns) Renal/Cellular Loss (Addisonian Crisis, Diabetic Ketoacidosis)
How is dehydration treated?
Fluids, Electrolytes
Specialist Unit Care
Steroids/Insulin
Describe distributive shock
Reduced Systemic Vascular Resistance due to Vasodilatation with warm, red peripheries
Reduced Mean Arterial Pressure
Compensatory increase in Cardiac Output
What may be the aetiology of an inflammatory cause of distributive shock (may be complicated by hypovolaemia or cardiogenic shock)?
Sepsis (Lung, Kidney, Intra-abdominal…)
SIRS, including Pancreatitis and Burns
Anaphylactic shock
How would an inflammatory cause of distributive shock be treated?
Antibiotics +/- Noradrenaline (Vasopressor)
Supportive Therapy
Adrenaline (Vasopressor and Inotrope)
How would a neurogenic cause of distributive shock be treated?
Spinal cord damage: Neurosurgery
Iatrogenic (spinal/epidural): Support +- vasopressors
