Shock Flashcards
Define Shock
A syndrome of inadequate tissue perfusion
What is the pathogenesis of shock
Decreased perfusion leads to decreased O2 delivery
Tissue O2 requirements exceeds O2 delivery
Cellular hypoxia leads to cell dysfunction
What are the two main determinants of tissue perfusion?
Cardiac Output
Peripheral Vascular Resistance
What is the formula for Cardiac Output
Stroke volume x Heart Rate
What are the three factors that affect cardiac output
Preload
Contractility
Afterload
What are the two factors that affect Peripheral Vascular Resistance
Blood vessel diameter
Blood viscosity
What are the 4 main types of shock
- Hypovolemic
- Cardiogenic
- Obstructive
- Distributive
What is the etiology of a hypovolemic shock
Excess Fluid Loss
What can cause a hypovolemic shock
Hypovolemic shock can be classified as Hemorrhagic or non-hemorrhagic
List some causes of hemorrhagic Hypovolemic shock
Hemorrhagic:
- Post partum hemorrhage
- upper GI bleed
- penetrating trauma
- A/V fistula
-
List some causes of non-hemorrhagic Hypovolemic shock
GI loss
Increased insensible fluid loss (burn)
Renal fluid loss (adrenal insufficiency, drug induced diuresis)
Third space fluid loss (SBO/LBO, pancreatitis)
What is the pathophysiology of Hypovolemic Shock?
< intravascular volume = <preload + SV= < Cardiac Output= compensatory inc. in vascular resistance and heart rate
What is the pathophysiology of cardiogenic shock?
An underlying pathology causes dysfunction of the heart =
< contractility/ <stroke volume leading to < cardiac output
List 9 causes of cardiogenic shock
- MI
- Arrythmias
- HF
- Cardiomyopathy
- Myocarditis
- VSD
- Valve Defect (aortic/mitral regurgitation)
- blunt cardiac trauma
- drugs (Beta blockers, CCBs)
What is the pathophysiology of obstructive shock
Obstruction of the heart and its Great Vessels> inability of the heart to circulate blood > dec. Cardiac Output > compensatory inc. in Systemic vascular resistance >
What are 3 main causes of obstructive shock?
Dec. diastolic filling
Dec. venous return
Inc. Ventricular afterload
List 3 pathologies that can lead to decreased diastolic filling and then obstructive shock
Cardiac Tamponade
Constrictive Pericarditis
Restrictive Cardiomyopathy
List 3 pathologies that can lead to decreased venous return and then obstructive shock
Tension pneumothorax
Intrathoracic tumour
List 3 pathologies that can lead to increased ventricular afterload and then obstructive shock
Massive PE
Aortic Dissection
Aortic Stenosis
Severe pulmonary hypertension
List 4 types of Distributive Shock
- Septic Shock
- Anaphylactic Shock
- Neurogenic Shock
- Acute Adrenal insufficiency
What is the classical presentation in neurogenic shock
- hypotension
- bradycardia
- vasodilation
What is the main pathophysiology underlying Distributive Shock
Vasodilation (relative hypovolemic state)
Define Neurogenic Shock
This is a type of shock that is caused by sudden loss of signals from the sympathetic system caused by upper spinal cord damage
(Leading to systemic vasodilation)
What drug can be administered to correct bradycardia
Atropine
List 3 vasopressors
Norepinephrine
Epinephrine
Phenylepinephrine
What are the two specific mechanisms associated with septic shock
Dysregulated host response to infection leading to capillary leakage and systemic vasodilation leading to organ dysfunction
Circulating inflammatory cytokines lead to myocardial depression
Describe the pathophysiology of anaphylactic shock
Immunologic anaphylaxis leads to degranulation of mast cells > massive histamine release> systemic vasodilation and increased capillary leakage
What are the two important parts of the history in diagnosing shock
- Initial/ Focus hx
- hx of end organ function
List 6 signs/ symptoms of shock
- tachycardia
- tachypnoea
- hypotension
- altered mental status
- decrease urine output
- low output: cold clammy
- high output: warm dry
What determines the investigations done in shock patients
Determined by the possible cause
What investigations should be done in the event of septic shock
Vitals
CBC, UnEs
Blood Culture sensitivity
What investigations should be done in the event of cardiogenic shock
Vitals
CBC
UnEs
Cardiac Enzymes
ECG
Echo
CXR
What general investigations should be done in the event of shock
Vital Signs
CBC + UnEs
Urine Output
GCS
CVP/PCWP
Evaluation of tissue oxygenation
How do you evaluate tissue oxygenation
Arterial Blood Gas
Which drugs are useful in distributive shock
Vasopressors (to stimulate vasoconstriction)
Noradrenaline, Vasopressin
