Page 326 - Clinical Application of Mechanical Ventilation

292 Chapter 10

TABLE 10-9 Ventricular Preloads and Afterloads

Main Device Implication Examples
(Measurement)

Arterial catheter (Left Condition of systemic Arterial pressure is increased in systemic
ventricular afterload) arterial pressure hypertension or fluid overload.
Arterial pressure is decreased in systemic
hypotension or fluid depletion.
Central venous catheter Condition of systemic Central venous pressure (CVP) is
(Right ventricular venous return increased in systemic hypertension or
preload) hypervolemia.
CVP is decreased in systemic hypotension
or hypovolemia.
Pulmonary artery catheter Condition of pulmonary Pulmonary artery pressure (PAP) is
(Right ventricular artery increased in pulmonary hypertension
afterload) or blood flow obstruction in left heart
(e.g., mitral valve stenosis).
PAP is decreased in pulmonary
hypoperfusion as in right-sided heart
failure.

Pulmonary artery catheter Condition of left heart Pulmonary capillary wedge pressure
(Balloon inflated) (Left (PCWP) is increased in left heart
ventricular preload) flow obstruction.
PCWP is decreased in severe
hypotension or dehydration.
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(C.O.) by body surface area (BSA). The cardiac index (C.I.) is normally 2.5 to
cardiac index (C.I): A cardiac 2
output measurement relative to a 3.5 L/min/m and it is calculated as follows:
person’s body size.
C.I. 5 C.O. / BSA

SUMMARY OF PRELOADS AND AFTERLOADS

Each ventricle has its own preload and afterload measurements. Their meaning and
common pathologic implications are summarized in Table 10-9.

CALCULATED HEMODYNAMIC VALUES

systemic vascular resistance: From the CVP, PAP, and other related measurements, the following parameters
Resistance of the arterial system
into which the left heart is pump- may be calculated: stroke volume and stroke volume index, oxygen consump-
ing. Normal range is 800–1,500 tion and oxygen consumption index, pulmonary vascular resistance, and systemic
dynes.sec/cm . 5
vascular resistance.

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