Shock Flashcards
Shock definition
Abnormality in circulatory system that results in inadequate organ perfusion
Types of shock
Hypovolaemic (Haemorrhagic)
Cardiogenic
Distributive (Septic, Anaphylactic)
Obstructive
Neurogenic
Most common cause of shock in trauma patients
Haemorrhage
Cardiac output equation
CO = Stroke volume x Heart rate
Factors contributing to stroke volume
Preload
Myocardial contractility
Afterload
Definition of preload
Volume of venous blood return to the left and right sides of the heart
Effect of haemorrhage on preload
Haemorrhage reduces preload
Starling’s law
Muscle fibre length of the myocardium is related to the myocardial muscle contractility
Effect of preload on myocardial contractility
Volume of preload determines myocardial muscle fibre length after ventricular filling at the end of diastole
(Starling’s law)
Afterload definition
Resistance to the forward flow of blood
Early physiologic responses to blood loss
Release of catecholamines
Increase peripheral vascular resistance and diastolic BP
Progressive vasoconstriction to preserve blood flow to kidneys, heart and brain
Increased HR to preserve cardiac output
Shift from aerobic to anaerobic cellular metabolism
Useful marker of severity of shock and to monitor response to treatment
Lactate
Base deficit
Focus of management for haemorrhagic shock
Locate and stop haemorrhage
Diagnostic adjuncts for identifying source of haemorrhage
CXR
Pelvic XR
FAST scan
Diagnostic Peritoneal Lavage
Bladder catheterisation
4 views in FAST scan
Pericardial view
RUQ view
LUQ view
Suprapubic view
RUQ view of fast scan
Liver
Interface between liver and diaphragm
Morrison’s pouch
Morrison’s pouch
Interface between liver and right kidney
(Hepatorenal fossa)
LUQ view of FAST scan
Spleen
Interface between spleen and diaphragm
Interface between spleen and left kidney
Suprapubic view of FAST scan
Area behind bladder looking for fluid
Fluid posterior to the bladder is abnormal
Pericardial view of FAST scan
Sub-xiphoid view
Parasternal view
Looking for tamponade
Major haemorrhage protocol ratio to give products for major trauma initially
RBC : Platelets : FFP
1:1:1
Major haemorrhage protocol ratio to give products for major trauma initially
RBC : Platelets : FFP
1:1:1
What guides ongoing blood products to give by monitoring coagulation
Where available:
Thromboelastography (TEG)
or
Rotational Thromboelastometry (ROTEM)
Consequence of massive crystalloid resuscitation in haemorrhagic shock
Coagulopathy due to dilution of platelets and clotting factors
Poiseuille’s law equation
Interpretation of Poiseuille’s law
Flow rate of IV fluids through a cannula / tube is:
- Proportional to the Radius^4
- Inversely proportional to the length
Ideal size and shape of a cannula according to Poiseuille’s law
Short and large calibre (diameter)
Normal adult blood volume in Litres
Approximately 7% body weight in Kg
(ideal body weight in obese adults)
Normal paediatric blood volume in Litres
Approximately 8-9% body weight in Kg
Classification of Haemorrhagic shock
Class I
Class II
Class III
Class IV
Class I Haemorrhagic shock definition
Blood volume loss <15%
Eg someone who has donated 1 unit of blood
Class I Haemorrhagic shock signs
Minimal tachycardia
Normal BP, pulse pressure, RR
Base deficit 0 to -2
Class II Haemorrhagic shock definition
Blood volume loss 15 - 30%
Uncomplicated haemorrhage
Requires crystalloid fluid resuscitation
Class II Haemorrhagic shock signs
Raised HR and RR
Decreased pulse pressure
Urine output 20 - 30 ml/hr
Base deficit -2 to -6
Subtle central nervous system signs (anxiety, fear)
Class III Haemorrhagic shock definition
Blood volume loss 30 - 40%
Complicated haemorrhagic state
Requires blood replacement often, but minimum crystalloids
Class III Haemorrhagic shock signs
Marked increased HR and RR
Changes in mental state
Significant hypotension
Inadequate perfusion
Base deficit -6 to -10
Class IV Haemorrhagic shock definition
Blood volume loss >40%
Preterminal event
Patient will die within minutes unless aggressive measures taken
Class IV Haemorrhagic shock signs
Marked tachycardia
Significant hypotension
Very narrow pulse pressure
Minimal Urine output
Cold, pale skin
Base deficit -10 or more
Confounding factors that alter haemodynamic response
Age
Injury severity
Time lapse between injury and treatment
Prehospital fluid resus
Medications
Implanted cardiac devices
Athletes
Causes of hypovolaemia with soft tissue injures
Blood loss at site of injury
Oedema in injured soft tissue from fluid shifts
Methods for haemorrhagic control
Direct pressure
Splint fractures
Pelvic binder
Tourniquet
Surgery
Angio-embolisation
Role of NG tube in trauma
For gastric decompression
Gastric distention can cause hypotension, dysrhythmia and increase aspiration risk
How to deliver fluid / blood
Warmed and high flow rates via Belmont
Balanced / Controlled resuscitation
Aka permissive hypotension
Refraining from aggressive fluid resuscitation until source is controlled to reduce further bleeding
Not acceptable for suspected head injuries
Minimum urine output indicating adequate perfusion in Adults
0.5 ml/kg/hr
Minimum urine output indicating adequate perfusion in Children
1 ml/kg/hr
Minimum urine output indicating adequate perfusion in Infants
2 ml/kg/hr
Categories of response to initial fluid bolus
Rapid response
Transient response
Minimal / No response
Ongoing management of rapid response
No further bolus needed but can switch to maintenance regime
Have types and matched blood ready in case
Ongoing management of transient response
Respond to initial bolus but then deteriorate again
- Transfusion of blood and blood products
- Consider major haemorrhage protocol
- Obtain source control
Ongoing management of minimal / no response
Massive haemorrhage protocol
Immediate, definitive intervention
Most common cause for a transient response to fluid bolus
Undiagnosed source on bleeding
Definition of massive transfusion
> 10 units packed cells in first 24 hrs
OR
> 4 units packed cells in 1 hr
When to use tranexamic acid
Within 3 hours of injury give 1g TXA stat
Followed by 1g TXA infusion
How common is coagulopathy in trauma patients
Occurs in 30% severely injured pts
Baseline clotting studies and platelets are useful
Calcium replacement target range
Free / Ionised Calcium > 1.0
This figure is obtained on a blood gas
Consideration of pregnancy and haemorrhage
Normal hypervolaemia masks perfusion abnormalities
Decreased foetal perfusion may indicate maternal hypovolaemia
