Shock Flashcards
When does shock occur?
When there is insufficient tissue perfusion
What is septic shock?
Infection that triggers a particular Systemic Inflammatory Response Syndrome (SIRS)
Characteristics of septic shock
Body temperature outside 36 oC - 38 o C
HR >90 beats/min
Respiratory rate >20/min
WBC count >12,000/mm3 or < 4,000/mm3
Patients with infections and ______ elements of SIRS meet the diagnostic criteria for sepsis
2 ore more elements
Those with organ failure have severe sepsis and those with refractory hypotension have..
Septic shock
The overall hallmarks of septic shock are..
Excessive inflammation, coagulation and fibrinolytic suppression
Key areas for attention in septic shock
Prompt administration of antibiotics
Haemodynamic stabilisation
Modulation of the septic response
In surgical patients, the main groups with septic shock include..
Anastomotic leaks, abscesses and extensive superficial infections such as necrotising fasciitis
The average adult blood volume comprises 7% of body weight. Thus in the 70 Kg adult this will equate to..
5 litres
T or F: Average adult blood volume changes in children and is slightly lower in the elderly
True
Blood loss of <750ml is classed as class __ of haemorrhagic shock
One
Blood loss of 750-1500ml is classed as class __ of haemorrhagic shock
Two
Blood loss of 1500-2000ml is classed as class __ of haemorrhagic shock
Three
Blood loss of >2000ml is classed as class __ of haemorrhagic shock
Four
The main groups with haemorrhagic shock include..
Trauma
Tension pneumothorax
Spinal cord injury
Myocardial contusion
Cardiac tamponade
When assessing trauma patients it is worth remembering that in order to generate a palpable femoral pulse an arterial pressure of _________ is required
> 65mmHg
Once bleeding is controlled and circulating volume normalised the levels of transfusion should be to maintain a Hb of _______ in those with no risk factors for tissue hypoxia and Hb of _____ for those who have such risk factors
Once bleeding is controlled and circulating volume normalised the levels of transfusion should be to maintain a Hb of 7-8 in those with no risk factors for tissue hypoxia and Hb 10 for those who have such risk factors.
Neurogenic shock often occurs following a..
Spinal cord transection (usually at a high level)
Neurogenic shock results in..
Decreased sympathetic tone or increased parasympathetic tone
How does neurogenic shock relate to Starling’s law?
There is a decrease in peripheral vascular resistance mediated by marked vasodilation. This results in decreased preload and thus decreased cardiac output. There is decreased peripheral tissue perfusion and shock is thus produced
In neurogenic shock, peripheral vasodilators/ vasoconstrictors are used to return vascular tone to normal
Vasoconstrictors
In medical patients, the main cause of cardiogenic shock is..
Ischaemic heart disease
In the traumatic setting, the main cause of cardiogenic shock is..
Direct myocardial trauma or contusion
In cardiogenic shock, evidence of ECG changes and overlying sternal fractures or contusions should raise the suspicion of..
Injury
In cardiogenic shock, ________________ should be used to determine evidence of pericardial fluid or direct myocardial injury
Transthoracic echocardiography
When cardiac injury is of a blunt nature and is associated with cardiogenic shock the right/left side of the heart is the most likely site of injury with chamber and or valve rupture
Right
Surgial Tx for right side injury/chamber or valve rupture in cardiogenic shock
Cardiopulmonary bypass
Some may require intra-aortic balloon pump as a bridge to surgery
Life-threatening, generalised or systemic hypersensitivity reaction
Anaphylactic shock
Most important drug in anaphylactic shock?
Adrenaline - can be repeated every 5 minutes if necessary
The best site for IM injection is the..
Anterolateral aspect of the middle third of the thigh
Common identified causes of anaphylaxis
Food (e.g. Nuts) - the most common cause in children
Drugs
venom (e.g. Wasp sting)
What three things does normal tissue perfusion rely on?
Cardiac Function
Capacity of vascular bed
Circulating blood volume
Surrogate markers for normal perfusion
Blood pressure
Consciousness (Brain perfusion)
Urine output (Renal perfusion)
Lactate (General tissue perfusion)
What is Hypovolaemic shock?
Acute haemorrhage - “Fluid deplete” states
Severe dehydration, burns
Physiology of Hypovolaemic shock?
Volume depletion – leading to reduced SVR
Reduced volume returning to heart – reduced pre-load and hence reduced CO
In cardiogenic shock, if due to MI, suggests that >40% of ___ is involved
LV
Examples of obstructive shock
Direct obstruction to cardiac output (PE, Air/Fat/Amniotic fluid-embolism)
Restriction of cardiac filling (Tamponade, Tension pneumothorax)
Examples of Distributive shock
Septic, anaphylaxis, acute
liver failure, spinal cord injuries
Physiology of distributive shock
Due to disruption of normal vascular autoregulation, and
profound vasodilatation. Poor perfusion – despite increased cardiac output
What is Endocrine shock?
Severe uncorrected hypothyroidism, Addisonian
crisis – both reduced CO and vasodilation
Most common cause of shock
Distributive (septic)
What does the neuroendocrine response release?
Pituitary hormones – adrenocorticotrophic hormone, anti-diuretic hormone, endogenous opioids
Cortisol – fluid retention, antagonises insulin
Glucagon
The inflammatory response is often followed by secondary..
Immune suppression, leaving predisposition to secondary infection
Function of nitric oxide?
Regulation of blood flow, coagulation, neural activity and immune function
Where is nitric oxide produced?
Produced in minute (picomolar) concentrations in
endothelial and other cells by cNOS
T or F: Inflammation pathways activiate nitric oxide’s inducible
isoform iNOS in vessel smooth walls leading to
1000 fold increase in NO production
True
Haemodynamic changes
Gold standard for monitoring cardiac output
Thermodilution with a PA catheter – rarely used outside specialist units
Fluid challenge
300-500ml over 10-20 mins
Fluid choices
Crystalloids - need significantly larger volumes
Colloids - can cause anaphylaxis
Blood - will stay in circulation but scarce and has multiple risks
Drugs used if fluid management does not work
Adrenaline (Epinephrine)
Noradrenaline (Norepinephrine)
Vasopressin (ADH)
Dopamine
Dobutamine/Dopexamin
Next step if both fluids and drugs don’t work
Mechanical support options
* In cardiogenic shock: balloon pumps, L-VADs,R-VADs
* In severe cases – VA-ECMO
Consequences of resuscitation
Volume delivered never remains intra-vascular
Extra-vascular overload, in an intra-vascularly “dry” patient
Sub-cutaneous oedema obvious
Less obvious – “wet” lungs/ARDS, bowel oedema
De-Escalation / “De-Resucitation”
Spontaneous, Diuretic, Dialysis
