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Shock: a review of pathophysiology and management. Part I.

OBJECTIVE
To review pathophysiology and management of hypovolaemic, cardiogenic and septic shock in a two-part presentation.


DATA SOURCES
Articles and published peer-review abstracts and a review of studies reported from 1994 to 1998 and identified through a MEDLINE search of the English language literature on septic shock, cardiogenic shock and hypovolaemic shock.


SUMMARY OF REVIEW
Shock is a clinical syndrome characterised by hypotension (i.e. a systolic blood pressure less than 90 mmHg or a mean arterial pressure less than 60 mmHg or reduced by greater than 30%, for at least 30 minutes), oliguria (i.e. a urine output less than 20 mL/hr or 0.3 ml/kg/hr for 2 consecutive hours), and poor peripheral perfusion (e.g. cool and clammy skin which demonstrates poor capillary refill). Hypovolaemic and cardiogenic shock are associated with disorders that cause an under-lying haemodynamic defect of a low intravascular volume and a reduction in myocardial contractility, respectively. The understanding and management of hypovolaemic shock has changed very little over the past 50 years with treatment requiring management of the causative lesion (i.e. surgical correction of blood loss) and replacement of the intravascular volume by infusing blood and/or 0.9% sodium containing colloid or crystalloid fluids. Due to recent developments in percutaneous coronary revascularisation techniques, management of cardiogenic shock in some centers has changed. Emergency cardiac catheterisation with urgent myocardial reperfusion (using percutaneous transluminal coronary angioplasty or coronary artery stenting in selected cases) and use of glycoprotein IIb/IIIa antagonists while supporting the circulation using an intra-aortic Balloon pump, has been reported to reduce mortality of cardiogenic shock in acute myocardial infarction. Large randomised, controlled multicentre trials are awaited.


CONCLUSIONS
Hypovolaemic shock requires urgent management of the underlying defect and replacement of the intravascular volume loss. Recent studies in management of cardiogenic shock using urgent revascularisation and intra-aortic Balloon counterpulsation in patients with acute myocardial infarction have shown a reduction in mortality in selected cases.