Page 608 - Cardiac Nursing

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584 PA R T I V / Pathophysiology and Management of Heart Disease
cardiogenic shock, cool, moist skin with barely perceptible periph- RA pressure; and PA systolic, diastolic, and wedge pressures. The
eral pulses is commonly observed. Capillary refill and peripheral cardiac output is decreased in HF, whereas the RA pressure or cen-
pulses are other indicators of the relative adequacy of cardiac out- tral venous pressure is elevated. The PAWP indirectly measures
put. Normal capillary refill is almost instantaneous; in cardiogenic the LV end-diastolic pressure, which is a measure of end-diastolic
shock, capillary refill is often prolonged. volume or preload and is elevated in HF.
Derived parameters that may be obtained by the use of the PA
Diagnostic Tools catheter include CI and SVR. Body surface area (BSA), measured
The primary measurements that document the relative adequacy in square meters, is correlated with the volume of cardiac output
of blood flow include continuous monitoring of arterial blood (CO) to establish the CI:
pressure and monitoring of the ECG with rhythm analysis. The CI CO
ECG can be diagnostic in the setting of MI. Most patients in BSA
5
shock are tachycardic and may show evidence of supraventricular SVR, measured in dynes/s/cm , reflects the pressure difference
or ventricular arrhythmias. Low QRS voltage and/or electrical al- of the systemic arteries to the veins.
ternans can be seen in cardiac tamponade. 199 MAP RAP
Transthoracic echocardiography is an excellent tool to obtain SVR CO 80
noninvasive information regarding the overall and regional sys-
tolic and diastolic function, intravascular volume, cardiac hemo- Besides offering diagnostic information, hemodynamic vari-
dynamics, myocardial abnormalities. 46 Echocardiography can ables show a strong prognostic value for short-term survival.
201
rapidly assess for mechanical causes, such as severe mitral regurgi- Forrester et al. classified patients with acute MI into four sub-
tation and papillary muscle rupture, acute VSD, free-wall rupture, sets with different mortality rates (see Fig. 24-18). They showed
and tamponade. Predictors of short- and long-term mortality that clinical signs of hypoperfusion occur with a CI of less than
2
from cardiogenic shock relate to the LVEF and mitral regurgita- 2.2 L/min per m and clinical signs of pulmonary congestion
tion on presentation, supporting early use of echocardiography in occur with a PAWP greater than 18 mm Hg. Subset I shows a
the course of cardiogenic shock. 46 patient with normal CI and normal PAWP with no evidence of
Chest radiography may suggest a specific diagnosis. Continu- pulmonary congestion or peripheral hypoperfusion (warm and
ous measurement of urine output and mental status are good in- dry). Subset III shows a patient with a low CI and PAWP, re-
dicators of adequate organ perfusion. A complete blood count and flecting peripheral hypoperfusion without pulmonary conges-
serial cardiac enzymes should be obtained. Serial measurements of
arterial blood gases reflect the overall metabolic state of the pa-
tient, the adequacy of ventilation, and the adequacy of the circu-
lation in providing for oxygen and metabolic needs. Measurement
of mixed venous oxygen content ( ) by direct blood sampling
or by continuous invasive monitoring reflects peripheral oxygen
extraction and use. Serial arterial lactate levels can also be meas-
ured because the presence of lactic acidosis helps identify critical
hypoperfusion as marked by anaerobic metabolism. 46
Measurement of serum BNP has become a recent laboratory
value that is measured as a means to identify those patients with
LV dysfunction 28 (see Figure 24-11). Elevation of other sub- Warm and wet
Warm and dry
stances in the blood that reflect the function of specific organs,
such as blood urea nitrogen, creatinine, bilirubin, aspartate
aminotransferase, and lactate dehydrogenase, may be useful in the
diagnosis of shock.
In seriously ill patients, direct determination of intra-arterial
pressure with an arterial line is necessary because systemic arterial
pressure determines the perfusion pressure of various organ sys-
tems and is predominantly the product of cardiac output and Cold and wet
SVR. In HF, a drop in cardiac output is compensated for by an in- Cool and dry
creased SVR in an attempt to maintain the arterial blood pressure
in normal range.
Right-sided heart catheterization with a PA quadruple lumen
thermodilution catheter can aid in the diagnosis and assessment of
the severity of HF (Chapter 21). This invasive hemodynamic
monitoring can be useful in excluding volume depletion, RV in-
farction, and mechanical problems (e.g., acute mitral regurgita-
tion). It is also useful for monitoring the response to treatment
(including volume, diuretics, inotropic support, vasoactive agents,
natriuretic peptide) and manipulation of the variables of cardiac
output, preload, and afterload. 190 The hemodynamic variables ■ Figure 24-18 Forrester subsets: clinical states and therapy. IABP,
measured by this catheter are cardiac output by thermodilution; intra-aortic balloon pumping.