: Difference between hypovolemic shock and heart arrest caused by hypovolemia? Is there a difference between hypovolemic shock and heart arrest caused by hypovolemia ?

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Hypovolemic shock may be a reversible cause of cardiac arrest (5)
Mechanisms:

Acute cardiac ischemia and myocardial infarction: these are due to decreased oxygen supply to the heart itself (remember that shock itself represent global ischemia)(1)(2)

pH changes, especially acidemia: when shock reaches to a irreversible state so much acidosis has developed(1) which itself can cause a cardiac arrest.(2)

Electrolyte abnormalities, most notably hypokalemia, hyperkalemia, and hypomagnesemia: ischemia (untreated) leads infarction leads necrosis leads loss of cell membrane leads ions and enzymes to leak and and produce toxic effects.(2) (3)

Heart Failure:The incidence of sudden cardiac death appears to be increased during periods of worsening HF symptoms.4.

While Hypovolemic Shock itself does not involve cardiac arrest,

if uncompensated will ultimately cause tissue damage, release of destructive enzymes, acidosis, depletion of cellular ATP. (1)

Pathophysiology:

As volume status continues to decrease, systolic blood pressure drops. As a result, oxygen delivery to vital organs is unable to meet oxygen demand. Cells switch from aerobic metabolism to anaerobic metabolism, resulting in lactic acidosis.
As sympathetic drive increases, blood flow is diverted from other organs to preserve blood flow to the heart and brain.
This propagates tissue ischemia and worsens lactic acidosis. If not corrected, there will be worsening hemodynamic compromise and, eventually, death.(4)

References:

Guyton and Hall Medical Physiology
www.uptodate.com/contents/pathophysiology-and-etiology-of-sudden-cardiac-arrest#H1240264379
Robbins and Cotran Pathologic Basis of Diseases
www.ncbi.nlm.nih.gov/books/NBK513297/ en.m.wikipedia.org/wiki/Hs_and_Ts