Shock Flashcards
What is the medical definition of shock?
Failure of the circulation that results in INADEQUATE TISSUE PERFUSION
Where are baroreceptors found?
They are found within the aortic arch and carotid bodies
What is the role of baroreceptors?
- They detect blood pressure, they stimulate the cardiac vagal (vagus) motor neurons which has an inhibitory effect on heart rate (stimulating the vagus nerve slows the heart rate down)
- If there is a drop in blood pressure, baroreceptors decrease firing, which decreases the stimulation of the vagus nerve, alleviating the inhibitory effect on the heart rate (>HR and >BP) - Inhibitory effect on the catecholamine neurones
- These neurones normally cause vasoconstriction and also vasopressin release
- Inhibiting these neurones will therefore decrease blood pressure
- A drop in BP will cause a reduction of this inhibitory effect, allowing vasoconstriction and vasopressin release –> Increased blood pressure
How can you test autoregulation?
Valsalva manoeuvre
- Forceful expiration against a closed glottis, this increases intrathoracic pressure which prevents venous return
What are the 3 ways that the body autoregulates blood pressure?
- The RAAS
- Barorceptor response
- Localised tissue response
Different types of shock
- Anaphylaxis: secondary to a bee sting or antibiotics
- Cardiogenic: secondary to an MI or heart failure (pump failure)
- Hypovolaemic: lost blood volume
- Neurogenic: spinal cord transection
- Septic: following meningococcal sepsis
Equation for cardiac output?
CO = stroke volume vs heart rate
Equation for mean arterial pressure/blood pressure?
MAP = CO x systemic vascular resistance
Alternate equation for cardiac output? (*not SV x HR)
CO = MAP /SVR
What is the definition of hypotension?
SBP <90mmHg
- SBP 20mmHg below patients normal
NOTE SLIDE: For each type of shock there exists:
- A prime problem
- Compensatory changes
- Clinical consequences
What are the following for hypovolaemia?
- A prime problem
- Compensatory changes
- Clinical consequences
- Prime problem = inadequate volume or fall in cardiac output
- Compensation = increased resistance, tachycardia (but cardiac output falls), hypotension = THIS IS THE BARORECEPTOR RESPONSE
- Clinical consequences = Cold & clammy peripheries, tachycardia, prolonged cap refill time, empty veins
What are the following for pump failure?
- A prime problem
- Compensatory changes
- Clinical consequences
- Prime problem = fall in cardiac output
- Compensatory changes = baroreceptor response = increased resistance and tachycardia
- Clinical consequences = cold & clammy peripheries, tachycardia, prolonged cap refill time, raised JVP
What are the following for vasodilatation?
- A prime problem
- Compensatory changes
- Clinical consequences
- Prime problem = vasodilatation
- Compensatory changes = tachycardia, >cardiac output, autoregulation
- Clinical consequences = warm & dry peripheries, tachycardia (due to >CO), short cap refill time and BOUNDING pulse
Clinical manifestations of shock
- Signs = related to poor tissue perfusion (skin, gut, liver, kidneys, brain, heart)
- Oliguria
- Altered conscious level (particularly in those with meningococcal sepsis)
- Cold, clammy skin but could also be warm and dry depending on the case
- Cyanosis
- Rapid pulse
- Nausea/vomiting
- Fatigue
- Enlarged pupils - Signs of compensation
- Fright, fight or flight response - Signs of correction of acidosis
- Tachypnoea
Initial assessment/management of shock
ABC response
A) Airway with OXYGEN therapy
- Give high flow oxygen
B) Breathing with VENTILATORY assessment/assistance
- Resp exam
C) Circulation with FLUID RESUSCITATION
- Check peripheral perfusion — cool and clammy vs warm and dry
- Pulse - volume/rate
- IV access
- Fluid challenge is nearly always the first ‘C’ treatment - crystalloids vs colloids
D) Disability
- Conscious level — AVPU vs GCS
- Pupils
E) Exposure, environment and other examination
- Causes: revealed bleeding, concealed bleeding, peripheral oedema
Is hypotension required for shock to exist?
No it is not, but it is frequently a sign of de-compensation which means that you are in trouble and things will happen quickly
Explain the circulatory features of hypovolaemia
- Perfusion = cold & clammy vs warm & dry?
- Pulse = weak vs bounding?
- Veins = empty vs full?
- Perfusion = cold and clammy
- Pulse = weak
- Veins = empty
Explain the circulatory features of pump failure
- Perfusion = cold & clammy vs warm & dry?
- Pulse = weak vs bounding?
- Veins = empty vs full?
- Perfusion = cold and clammy
- Pulse = weak (poor CO)
- Veins = full, note JVP
Explain the circulatory features of vasodilation
- Perfusion = cold & clammy vs warm & dry?
- Pulse = weak vs bounding?
- Veins = empty vs full?
- Perfusion = warm and dry
- Pulse = bounding
- Veins = full
What are different causes of hypovolaemia?
- Intravascular
- Blood loss: revealed (visual bleeding seen) or concealed (e.g. femoral fracture) - Extravascular
- Evaporation
- GI losses
- Polyuria
Different causes of pump failure, intrinsic vs extrinsic
- Intrinsic
- Muscle
- Conduction tissue
- Valves - Extrinsic
- Obstruction: PE
- Compression: tamponade
- Blood supply
What is systemic inflammatory response syndrome (SIRS) defined as?
2 or more of:
- Heart rate >90
- Fever >38 or <36
- WCC >12000 or <4000
- Respiratory rate >20 or pCO2 <32
What is septic shock defined as?
Septic shock is sepsis with refractory hypotension
- Evidence of infection
- End organ failure
- Refractory hypotension: hypotension that does not respond to fluid
- Mortality = 43-54%
What is sepsis defined as?
SIRS + confirmed or presumed infections
- Mortality = 10-15%
What is severe sepsis defined as?
Sepsis with organ dysfunction
- Mortality = 17-20%
What can cause a SIRS response?
- Trauma
- Burns
- Pancreatitis
- Other
What can cause a sepsis response?
Infection:
- Bacteria (bacteria predominantly cause sepsis)
- Fungi
- Parasites
- Viruses
- Other
What is the response of alpha receptor stimulation, in short?
Peripheral vasoconstriction
What is the response of B2 receptor stimulation, in short?
Arteriolar vasodilatation
What is the response of B1 receptor stimulation, in short?
- Inotropy
- Chronotropy
- Renin secretion
What are the actions of adrenaline? (B1receptor, B2receptor, alpha receptor)
> HR
SV
Vasoconstrictor — >BP
What are the actions of dobutamine? (B1R, B2R)
> HR
SV
Vasodilator
What are the actions of dopexamine? (B2R, DA receptor)
> HR
Splanchnic vasodilator
What are the actions of noradrenaline? (alpha receptor)
Vasoconstrictor
What is the principle management for patients with shock: reduced capacitance
Fluids (crystalloids or colloids)
What is the principle management for patients with shock: pump failure
- This is your MI patient: cardiogenic shock
- Inotropes
- Possible vasodilators: because these patients are very vasoconstricted
What is the principle management for patients with shock: reduced resistance (distributive)
Vasopressors: NA
- Maybe fluids
How does noradrenaline cause a drop in heart rate if its main action is vasoconstriction?
Vasoconstriction —> Increased blood pressure —> baroreceptor response —> increased vagal tone —> decreased heart rate
What are the main treatments for sepsis?
- Antibiotics
- Crystalloids
- Vasopressors
- SEPSIS 6
What is the sepsis six?
BUFALO
- Give O2 sats above 94%
- Take blood cultures
- Give IV antibiotics
- Give a fluid challenge
- Measure lactate
- Measure urine output
