Title: Pathophysiology of Shock
1Pathophysiology of Shock
- Sherwan R Sulaiman
- MD MSc PhD
2Objectives
- Definition of shock
- Pathophysiology of shock
- Classification of shock
- Grades of shock
- Recognition of shock
- Treatment objectives in shock
3Definition of shock
A clinical state in which tissues do not receive
adequate blood flow and O2 to meet their
metabolic needs.
4Physiological principles
- Systemic blood pressure
- Systemic vascular resistance
- Cardiac output
- Oxygen supply
Blood flow
5Systemic blood pressure
- SBP CO x SVR
- This relationship equates well to Ohmss Law
- V IR
6Systemic blood pressure
- Control of BP in the acute phase
- Intrinsic regulatory properties of the heart
- Autonomic pathways
- Hormonal mechanisms
7Systemic vascular resistance
- SVR SPB
- CO
- Which is rearranged as
- SVR (MAP CVP) x 80
- CO
8Cardiac output
- Cardiac output is the volume of blood being
pumped by the heart per minute. - CO HR x SV
9Which does not affect SV?
- Preload
- Heart rate
- Contractility
- Afterload
10Cardiac output
- CO SV x HR
- SV
- Preload Contractility Afterload
11Cardiac output
12Supply v demand
- O2 supply CO x (arterial O2 content)
- O2 demand is dependent upon temperature,
metabolic status and hormonal status
13Pathophysiology of shock
- Inadequate tissue perfusion
- Decreased oxygen supply
- Anaerobic metabolism
- Accumulation metabolic waste
- Cellular failure
14Compensatory mechanisms
- Sympathetic compensatory mechanisms may preserve
organ perfusion initially.
15How do adrenoceptors work?
- Alter ion permeability
- Regulate gene transcription
- Produce intermediate messengers
16ß1 Adrenoceptor
Adrenaline
Adenyl cyclase
G - Protein
Increased heart muscle contractility
cAMP
ATP
17Sympathetic activation
- Tachycardia
- Increased myocardial contractility (ß1)
- a-adrenergic receptor-mediated vasoconstriciton
(ß2-receptor-mediated vasodilatation in skeletal
muscle, coronary, pulmonary and renal
circulations) - Overall increased CO and redistribution of flow
cardiac, cerebral, hepatic and muscle vascular
beds
18Autoregulation
- Auto-regulation of
- Renal
- Cerebral
- Coronary Arterial Blood Flow
19Compensatory mechanism and shock
PRE-LOAD
AFTER-LOAD
Fluid Volume (CVP/JVP)
Vascular Diameter (SVR)
Cardiac Output (SV x HR)
20Hypovolaemic shock
PRE-LOAD
AFTER-LOAD
Fluid Volume (CVP/JVP)
Vascular Diameter (SVR)
Cardiac Output (SV x HR)
1
21Hypovolaemic shock
PRE-LOAD
AFTER-LOAD
Fluid Volume (CVP/JVP)
Vascular Diameter (SVR)
Cardiac Output (SV x HR)
1
2
22Hypovolaemic shock
PRE-LOAD
AFTER-LOAD
Fluid Volume (CVP/JVP)
Vascular Diameter (SVR)
Cardiac Output (SV x HR)
3
1
2
23Cardiogenic shock
PRE-LOAD
AFTER-LOAD
Fluid Volume (CVP/JVP)
Vascular Diameter (SVR)
Cardiac Output (SV x HR)
1
24Cardiogenic shock
PRE-LOAD
AFTER-LOAD
Fluid Volume (CVP/JVP)
Vascular Diameter (SVR)
Cardiac Output (SV x HR)
2
1
25Cardiogenic shock
PRE-LOAD
AFTER-LOAD
Fluid Volume (CVP/JVP)
Vascular Diameter (SVR)
Cardiac Output (SV x HR)
3
2
1
26Distributive shock
PRE-LOAD
AFTER-LOAD
Fluid Volume (CVP/JVP)
Vascular Diameter (SVR)
Cardiac Output (SV x HR)
1
27Distributive shock
PRE-LOAD
AFTER-LOAD
Fluid Volume (CVP/JVP)
Vascular Diameter (SVR)
Cardiac Output (SV x HR)
2
1
28Distributive shock
PRE-LOAD
AFTER-LOAD
Fluid Volume (CVP/JVP)
Vascular Diameter (SVR)
Cardiac Output (SV x HR)
3
2
1
29Which group of individuals cope poorly with shock?
- Children
- Pregnant women
- The elderly
- Young adults
30Classification of shock
- Hypovolaemic Shock
- Cardiogenic shock
- Distributive shock
31Causes of shock
- Significant blood loss Haemorrhagic shock
- Loss of ECF Hypovolaemic shock
- Myocardial infarction Cardiogenic shock
- High spinal injuries Neurogenic shock
- Severe infections Septic shock
- Anaphylaxis Anaphylactic shock
- Poisoning Cytotoxic shock
32Recognition of shock
- Tachycardia
- Tacypnoea
- Impaired tissue blood flow
- Capillary fill time
- Cold peripheries?
- Hypotension
- Oliguria lt0.5ml/kg/hr
- Increased serum lactate
- Low venous saturation .lt70
33Avoid over reliance on invasive haemodynamic
monitoring
Pulse rate Capillary fill time Core-toe
temperature Blood pressure Level of
consciousness Blood-gas estimation
34Treatment objectives
- Early recognition
- Accurate diagnosis
- Optimise tissue oxygen delivery early
- Blood gas estimation guides metabolic status
- Urinary catheter
- Appropriate environment
- Invasive haemodynamic monitoring
35Is this the appropriate environment?
36Treatment objectives
- Specific treatment will depend on the underlying
cause - ABC approach
- Volume replacement Hypovolaemic or septic
- Inotropes Cardiogenic
- Vasopressors Septic
- Adrenaline Anaphylactic
37Summary
- Definition of shock
- Causes
- Oxygen supply-demand balance
- Early recognition of shock EWS
- Assess, intervene, reassess and seek help
38Any questions?