Chapter 7
SHOCK, LOW CARDIAC OUTPUT, AND INOTROPIC SUPPORT
Pramod S. Puligandla, MD
I. Introduction
Shock is a clinical syndrome of inadequate tissue perfusion, oxygen
utilization and cellular energy production that ultimately leads to irreversible
cellular damage. While shock manifests as an acute functional derangement of
the macro- and microcirculatory systems, it is important to emphasize that it is
not equivalent to hypotension. The diagnosis of shock is made clinically, and is
based on assessments of volume status (e.g. urine output), cardiac function (e.g.
heart rate, blood pressure), and vascular tone (e.g. capillary refill time).
Shock is classified in many different ways and its presentation may vary
significantly over time. In general, shock is classified as (a) hypovolemic (lack of
circulating intravascular volume), (b) distributive (loss of vascular tone primarily
or secondarily related to neurologic or neurohormonal disturbances), and (c)
cardiogenic/obstructive (cardiac pump failure). There is significant overlap
between the different types. For example, “septic shock” has clinical
characteristics of all three of the above.
A good understanding of the basics of myocardial function and oxygen
delivery is vital for the timely diagnosis and management of patients with shock.
(See Chapter 1)