Shock is a clinical syndrome in which
profound and widespread reduction in
the effective delivery of oxygen and
other nutrients to the tissues. In shock
condition, the individual is weak, anx-
ious with coldness of extremeties, sweet-
ing and marked fall in arterial pressure.
Physiologic mechanisms can effect the
arterial pressure by acting on one or
more of two variables i.e. preload,
impedance to blood flow (after load) and
myocardral contractility. These macha-
nisms include:
- Local release of vasodilater metabolits
e.g. adenosine - Release form the endothelium of
substances that relax (e.g. endothelium
derived relax factor, nitric oxide) or
contract (e.g. endothelium) - Activity of autonomic nervous system
and the modulation of this activity by
baroreceptor reflexes and vasomotor
centre in the brainstem. - The release of epinephrine or norepi-
nephrine by adrenal medulla and sym-
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1.4
Chapter
3.2 Treatment of Shock & Vasopressor Agents
pathetic nerve endings.- Release of vasopressin.
- Release of vasodilators, including kinin
and prostaglandins. - Two activity of renin-angiolension sys-
tem
All these mechanism can affect the
arterial pressure by altering the vascular
resistance and/or cardiac output.
FORMS OF SHOCK
The classification of shock is based on
the cause which is as under:I Cardiogenic shock- Myopathic
- Arrhythmic
- Mechanical
II Oligemic shock or hypovolaemic shock - Haemorrhage
- Fluid depletion
III Extracardiac obstructive shock - Constrictive pericarditis
- Pulmonary embolism