Blood pressure
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Transcript Blood pressure
Acute Care Workshop
Dr Stephanie Sim
Dr Sharon Christie
Dr James Shaw
Dr Lysa Owen
Plan for today
Learning Objectives
Powerpoint presentation (on Blackboard)
Demonstration of ABCDE
Split into 2 groups
Simulation
Break at half time then swap
Outcomes Acute care Workshop
Describe the pathophysiology of hypoxia
and hypotension
Identify when a patient is acutely unwell
Demonstrate ability to assess an acutely
unwell patient using ABCDE
Initiate appropriate management
Demonstrate awareness of specific
treatment regimens
Hypoxia
Oxygen cascade
• Series of steps: atmospheric air
•
pO2 at any stage
mitochondria
in subsequent steps
25
Dry atmospheric gas,
(~21)
20
15
pO2
(kPa)
Humidified tracheal
gas, (~19.8)
Alveolar gas, (~14)
Arterial blood, (~13.3)
10
Capillary blood, (~7)
5
Mitochondria, (~4)
0
Remember
Context is really important….
A patient with ‘normal values’ when breathing at a rate
of 40 bpm, is not as well as someone breathing at a
rate of 12bpm
A patient with Sats of 96% on 60% O2 is not as well as
someone breathing air with the same O2 sats!
A patient with PaO2 of 9kPa is getting better if it was 8
before and he is on the same concentration of O2,but
getting worse if it was previously 10kPa!
Blood pressure
Related to
Arterial & venous system with organ autoregulation
Blood Pressure
Cardiac Output (CO) X Systemic vascular resistance (SVR)
Heart Rate X Stroke Volume
Blood pressure
Related to
Arterial & venous system with organ autoregulation
Blood Pressure
Myocardial contractility ↓↓
CARDIOGENIC SHOCK
Afterload ↓↓ SEPSIS/
ANAPHYLAXIS/
NEUROGENIC
Cardiac Output (CO) X Systemic vascular resistance (SVR)
Heart Rate X Stroke Volume
Preload ↓↓HYPOVOLAEMIA/ HAEMORRHAGE
Blood pressure
THEREFORE
Blood Pressure depends on
Circulating blood volume
↓ in hypovalaemia/ haemorrhage
Pump function
↓ in cardiogenic shock
Systemic vascular resistance
↓ in sepsis
↓ in anaphylaxis
Response to shock
Tachycardia, Tachypnoea
Progressive peripheral vasoconstriction
(if possible)
Shift to anaerobic metabolism for hypoxic
cells, then lose the ability to generate
ATP, loss of electrical gradient and cell
death
Causes of Shock
Haemorrhagic (70Kg man)
Class I
Class II
Class III
Class IV
Blood loss (ml)
Up to 750
750-1500
1500-2000
>2000
Blood loss
(% volume)
Up to 15%
15-30%
30-40%
>40%
Pulse rate
<100
>100
>120
>140
Blood pressure
Normal
Normal
Decreased
Decreased
Pulse pressure
Normal or
increased
Decreased
Decreased
Decreased
Respiratory Rate
14-20
20-30
30-40
>35
Urine Output ml/hr
>30
20-30
5-15
Negligible
CNS/Mental status
Slightly
anxious
Mildly
anxious
Anxious,
confused
Confused,
lethargic
Signs of shock
Tachycardia, tachypnoea and vasoconstriction
=> Diagnosis of shock until proven otherwise
(relying on BP drop delays diagnosis)
Urine output – indicator of renal blood flow
Relative to normal (kids, young adults, elderly)
Varying ability to mount response (B blocker, Ca
channel blocker, paced, etc)
Should be >0.5ml/Kg/hour
Acid Base Abnormality
Respiratory alkalosis initially> Metabolic Acidosis
Assessment of shock
Airway
Breathing – give O2, RR, SpO2, Breath Sounds
Circulation – stem bleeding/obtain adequate iv
access/assess tissue perfusion (P,BP,CRT) ?Fluids
required (likely to be)
Disability – AVPU, BM, Pupils
Exposure – Complete examination re possible
cause, temp, TPAR
?Catheterisation
Fluid Homeostasis
Normal 70 Kg male = 42litre (60%) Water
Extracellular
Intracellular Fluid (ICF)
28 litres
Fluid (ECF)
9.4
litres
4.6
litres
Interstitial
Plasma
Normal Physiology
Compartment volume maintained by
Oncotic pressure (retains fluid)
Hydrostatic pressure (forces fluid out of vessel)
Osmotic gradients
Electrolyte pumps
Types of fluid replacement
Crystalloids
Colloids
Blood
Crystalloids
Eg. Dextrose, Saline, Hartmans
True solutions - substances which will diffuse through
a semi-permeable membrane
Pros/Cons:
Easily available
Cheap
Variable volume of distribution (can end up in undesirable
spaces!)
Colloids
Eg. Gelofusine,
“glue” – Greek
Substance which does not diffuse through a
semipermeable membrane.
Large particles (protein or carbohydrate) that are
suspended in water
Pros/Cons :
Stays in intravascular space
Relatively expensive
Risk of anaphylaxis
No proven benefit over saline in hypovolaemia
Blood
Pros/Cons : Well recognised
Replaces ‘like with like’
Carries oxygen well!
Expensive
Risk of transfusion reactions
Infection risk etc
Distribution of Fluids
5%Dextrose
(essentially WATER)
Circulation
Interstitial Fluid
ICF
ECF
0.9% Saline
Blood
Colloid (expands plasma
volume due to oncotic pressure)
Main points
Recognise patient is unwell
Treat early (ideally before hypoxic, hypotensive)
Optimise what you can (ABCDE)
*Remember Oxygen*
General measures to improve blood pressure
*Fluids* ( in almost all cases)
Inotropes
Specific measures to treat cause
Monitor response
Urine output, ABGs
Blood pressure/ cardiac monitor
Central lines etc
Etc
Any Questions?
Outcomes Acute care Workshop
Describe the pathophysiology of hypoxia
and hypotension
Identify when a patient is acutely unwell
Demonstrate ability to assess an acutely
unwell patient using ABCDE
Initiate appropriate management
Demonstrate awareness of specific
treatment regimens