(2) Approach to Shock Flashcards
Definition of shock
Circulatory shock: an abnormality of the circulatory system that results in reduced organ perfusion and tissue oxygenation
causes of shock are broadly caused by
- reduced cardiac output e.g. hypovolaemic, cardiogenic, obstructive
- reduced systemic vascular resistance e.g. septic shock, anaphylactic shock
summary of 4 main types of shock
CHOD
Cardiogenic
Hypovolaemic
Obstructive
Distributive
causes of hypovolaemic shock
- haemorrhage
- vomiting
- diarrhoea
- diuresis e.g. post catheter
- burns
- third spacing e.g. pancreatitis, severe sepsis, anaphylaxis)
causes of cardiogenic shock
- Myocardial infarction
- Cardiomyopathy
- Cardiac arrhythmia
- Tachy or brady
- Negatively inotropic drug overdose (e.g. beta blockers or CCB)
cause sof Obstructive shock
- Tension pneumothorax
- Massive PE
- Cardiac tamponade
causes of Reduced systemic vascular resistance (SVR):
- Septic shock
- Anaphylactic shock
- Neurogenic shock
why treat shock as early as possible
- Effects of shock are initially reversible, but rapidly become irreversible, resulting in multiorgan failure and death
- Initiate treatment early
Features of shock
- Hypotension
- Tachycardia
- Oliguria
- Abnormal mental state
- Tachypnoea
- Cool, clammy, cyanotic skin]
- Metabolic acidosis
- Hyperlactatemia
- Others
o Chest pain and ECG changes e.g. anterior wall MI
o Fever and cough or history of ongoing UTI
o RTA and patient has head and spinal cord injuries, quadriparesis and paraplegia
o History of insect bite, lip swelling and rash
o Central abdominal pain, patient unresponsive
o Abdominal pain, vomiting and diarrhoea since 3 days
o History of AF, presented with HR 180, sweating and SOB
blood pressure is related to
BP = CO x SVR
c
cardiac output
CO is the volume of blood pumped by the heart per minute and is in turn related to heart rate (HR) and stroke volume (SV) as follows:
CO = HR x SV
stroke volume
is the volume of blood pumped by the heart per contraction and is determined by
* Preload
* Myocardial contractility
* Afterload
Preload
- Preload is the ventricular wall tension at the end of diastole and reflects the degree of myocardial muscle fibre stretch; it is determined by volume status, venous capacitance and the difference between mean venous pressure and right atrial pressure
- Preload is related to SV by the Frank-Starling mechanism; increased fibre length initially leads to an increased SV but above a certain point, the fibres become overstretched and further filling results in a decreased SV, as is the case in cardiac failure
Myocardial contractility
is the intrinsic ability of the heart to work independently of preload and afterload; positive inotropes increase the contractility, shifting the Frank-Starling curve upwards
afterload
Afterload is the pressure that the heart must work against to eject blood during systole.
