Shock

Shock
Essence
Circulatory failure resulting in inadequate organ perfusion. Generally systolic BP is <90mmHg. Signs: pallor, pulse, capillary return (press a nailbed), air hunger, oliguria. Causes are either pump failure or peripheral circulation failure.

A)Pump failure
Cardiogenic shock
Secondary: pulmonary embolism, tension pneumothorax, cardiac tamponade.
Peripheral circulation failure
Hypovolaemia
Bleeding: trauma, ruptured aortic aneurysm, ruptured ectopic pregnancy. Fluid loss: Vomiting (eg GI obstruction), diarrhoea (eg cholera), burns, pools of sequestered (unavailable) fluids (third spacing, eg in pancreatitis). Heat exhaustion may cause hypovolaemic shock (also hyperpyrexia, oliguria, rhabdomyolysis, consciousness, hyperventilation, hallucination, incontinence, collapse, coma, pin-point pupils, LFT up, and DIC,
Anaphylaxis
Sepsis: Gram -ve (or +ve) septicaemic shock from endotoxin-induced vasodilatation may be sudden and severe, with shock and coma but no signs of infection (fever, WCC elevated).
Neurogenic: eg post-spinal surgery.
Endocrine failure: Addison's disease or hypothyroidism;
Iatrogenic: Drugs, eg anaesthetics, antihypertensives.
Assessment
ABC.
ECG: rate, rhythm, ischaemia?
General: cold and clammy cardiogenic shock or fluid loss. Look for signs of anaemia or dehydration skin turgor, postural hypotension? Warm and well perfused, with bounding pulse septic shock. Any features suggestive of anaphylaxis—history, urticaria, angio-oedema, wheeze?
CVS: usually tachycardic (unless on B-blocker, or in spinal shock and hypotension. But in the young and fit, or pregnant women, the systolic BP may remain normal, although the pulse pressure will narrow, with up to 30% blood volume depletion. Difference between arms—aortic dissection?
JVP or central venous pressure: If raised, cardiogenic shock likely.
Check abdomen: any signs of trauma, or aneurysm? Any evidence of GI bleed? check for melaena.