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Pathophysiology of Shock

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Pathophysiology of Shock Sherwan R Sulaiman MD MSc PhD What do we mean by appropriate environment ? Treatment objectives Early recognition Accurate diagnosis ... – PowerPoint PPT presentation

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Title: Pathophysiology of Shock


1
Pathophysiology of Shock
  • Sherwan R Sulaiman
  • MD MSc PhD

2
Objectives
  • Definition of shock
  • Pathophysiology of shock
  • Classification of shock
  • Grades of shock
  • Recognition of shock
  • Treatment objectives in shock

3
Definition of shock
A clinical state in which tissues do not receive
adequate blood flow and O2 to meet their
metabolic needs.
4
Physiological principles
  • Systemic blood pressure
  • Systemic vascular resistance
  • Cardiac output
  • Oxygen supply

Blood flow
5
Systemic blood pressure
  • SBP CO x SVR
  • This relationship equates well to Ohmss Law
  • V IR

6
Systemic blood pressure
  • Control of BP in the acute phase
  • Intrinsic regulatory properties of the heart
  • Autonomic pathways
  • Hormonal mechanisms

7
Systemic vascular resistance
  • SVR SPB
  • CO
  • Which is rearranged as
  • SVR (MAP CVP) x 80
  • CO

8
Cardiac output
  • Cardiac output is the volume of blood being
    pumped by the heart per minute.
  • CO HR x SV

9
Which does not affect SV?
  1. Preload
  2. Heart rate
  3. Contractility
  4. Afterload

10
Cardiac output
  • CO SV x HR
  • SV
  • Preload Contractility Afterload

11
Cardiac output
12
Supply v demand
  • O2 supply CO x (arterial O2 content)
  • O2 demand is dependent upon temperature,
    metabolic status and hormonal status

13
Pathophysiology of shock
  • Inadequate tissue perfusion
  • Decreased oxygen supply
  • Anaerobic metabolism
  • Accumulation metabolic waste
  • Cellular failure

14
Compensatory mechanisms
  • Sympathetic compensatory mechanisms may preserve
    organ perfusion initially.

15
How do adrenoceptors work?
  1. Alter ion permeability
  2. Regulate gene transcription
  3. Produce intermediate messengers

16
ß1 Adrenoceptor
Adrenaline
Adenyl cyclase
G - Protein
Increased heart muscle contractility
cAMP
ATP
17
Sympathetic 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

18
Autoregulation
  • Auto-regulation of
  • Renal
  • Cerebral
  • Coronary Arterial Blood Flow

19
Compensatory mechanism and shock
PRE-LOAD
AFTER-LOAD
Fluid Volume (CVP/JVP)
Vascular Diameter (SVR)
Cardiac Output (SV x HR)
20
Hypovolaemic shock
PRE-LOAD
AFTER-LOAD
Fluid Volume (CVP/JVP)
Vascular Diameter (SVR)
Cardiac Output (SV x HR)
1
21
Hypovolaemic shock
PRE-LOAD
AFTER-LOAD
Fluid Volume (CVP/JVP)
Vascular Diameter (SVR)
Cardiac Output (SV x HR)
1
2
22
Hypovolaemic shock
PRE-LOAD
AFTER-LOAD
Fluid Volume (CVP/JVP)
Vascular Diameter (SVR)
Cardiac Output (SV x HR)
3
1
2
23
Cardiogenic shock
PRE-LOAD
AFTER-LOAD
Fluid Volume (CVP/JVP)
Vascular Diameter (SVR)
Cardiac Output (SV x HR)
1
24
Cardiogenic shock
PRE-LOAD
AFTER-LOAD
Fluid Volume (CVP/JVP)
Vascular Diameter (SVR)
Cardiac Output (SV x HR)
2
1
25
Cardiogenic shock
PRE-LOAD
AFTER-LOAD
Fluid Volume (CVP/JVP)
Vascular Diameter (SVR)
Cardiac Output (SV x HR)
3
2
1
26
Distributive shock
PRE-LOAD
AFTER-LOAD
Fluid Volume (CVP/JVP)
Vascular Diameter (SVR)
Cardiac Output (SV x HR)
1
27
Distributive shock
PRE-LOAD
AFTER-LOAD
Fluid Volume (CVP/JVP)
Vascular Diameter (SVR)
Cardiac Output (SV x HR)
2
1
28
Distributive shock
PRE-LOAD
AFTER-LOAD
Fluid Volume (CVP/JVP)
Vascular Diameter (SVR)
Cardiac Output (SV x HR)
3
2
1
29
Which group of individuals cope poorly with shock?
  1. Children
  2. Pregnant women
  3. The elderly
  4. Young adults

30
Classification of shock
  • Hypovolaemic Shock
  • Cardiogenic shock
  • Distributive shock

31
Causes 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

32
Recognition 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

33
Avoid over reliance on invasive haemodynamic
monitoring
Pulse rate Capillary fill time Core-toe
temperature Blood pressure Level of
consciousness Blood-gas estimation
34
Treatment objectives
  • Early recognition
  • Accurate diagnosis
  • Optimise tissue oxygen delivery early
  • Blood gas estimation guides metabolic status
  • Urinary catheter
  • Appropriate environment
  • Invasive haemodynamic monitoring

35
Is this the appropriate environment?
36
Treatment objectives
  • Specific treatment will depend on the underlying
    cause
  • ABC approach
  • Volume replacement Hypovolaemic or septic
  • Inotropes Cardiogenic
  • Vasopressors Septic
  • Adrenaline Anaphylactic

37
Summary
  • Definition of shock
  • Causes
  • Oxygen supply-demand balance
  • Early recognition of shock EWS
  • Assess, intervene, reassess and seek help

38
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