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C HAP TE R 2 1 / Hemodynamic Monitoring 483

110.0 SBP PP
100.0 max SBP min max
Ps PP
90.0 min
∇
80.0
70.0
DBP
60.0
50.0
A
130.0
120.0
110.0
100.0
90.0
B
■ Figure 21-19 Example of SPV and PPV. (A) This analog tracing was obtained from the bedside monitor
with the paper speed decreased to 6.25 mm/s. In this case, the patient is demonstrating marked variation in
their SPV (e.g., SPV 9 mm Hg) indicating fluid responsiveness. (B) In this case, there is minimal variation
in the functional indices (e.g., SPV 4 mm Hg) indicating that the patient would not be fluid responsive and
other methods, such as a vasopressor, should be considered to treat the patient’s hypoperfusion.

studies suggest that it may be artificially increased during hy- Pulse Pressure Variation
potension, 245 uses the following equation:
Arterial pulse pressure is the difference between the arterial sys-
(SBP max SBP min ) tolic and diastolic pressure (Fig. 21-19). Pulse pressure variation
SPV% 100 254
[(SBP max
SBP min )> 2 ] (PPV) is measured using the following equation :
The absolute SPV and SPV% are directly related to the tidal (PP max PP min )
PPV% 100
volume (Table 21-8). In patients with acute circulatory failure [(PP max
PP min )> 2 ]
caused by sepsis who were receiving an 8 to 11 mL/kg VT, SPV
greater than 10 mm Hg was predictive of fluid responsiveness. 234 Three factors affect the pulse pressure: LV SV, arterial resist-
Additional research is needed to identify a threshold for these in- ance, and arterial compliance. Of note, the latter two factors do
dices with smaller tidal volumes ( 8 mL/kg). not change significantly during a single breath 255 ; therefore, the

Table 21-8 ■ FUNCTIONAL HEMODYNAMIC INDICATOR THRESHOLDS
Response
Population Threshold VT (mL/kg) Threshold Sensitivity Specificity
Septic shock 234 ↑SV 15% 8–11 SPV 10 mm Hg NR NR
PAOP 11 mm Hg NR NR
ARDS or septic ↑CI 15% 8–12 PPV 13% 94% 96%
shock 233 PAOP (no threshold) — —
CVP (no threshold) — —
Critically ill 246 ↑CI 15% 8 PPV 12% 39% 65%
8 PPV 8% 66% 65%
8 PPV 12% 88% 89%
All VT PPV 12% 60% 74%
Acute circulatory ↑SV 15% 8 PPV 10% 89% 83%
failure 247
Postcardiac ↑CO 12% 8–10 PPV% 11% 100% 93%
surgery y 248 SPV% NR NR
PAOP (no threshold) — —
CVP (no threshold) — —
Postcardiac surgery ↑SVI 5% 10 SVV 9.5% 71% 80%
LVEF 35% 249 PAOP 7 mm Hg 79% 70%
CVP 6 mm Hg 50% 90%
LVEF 50% SVV 9.5% 79% 85%
PAOP 8 mm Hg 59% 75%
CVP 10 mm Hg 71% 62%
Septic shock 250 ↑CI 10% PS SVV—no threshold — —
Postcardiac surgeryy 251 ↑CI 15% 8–10 PPV 11.8% 95% 92%
SVV—no threshold
ARDS 252 ↑CI 15% 5–8 PPV 11.8% 68% 100%
Postcardiac surgeryy 253 ↑CI 15% 8 PPV 12% 97% 95%

NR not reported; PS pressure support; LVEF, left ventricular ejection fraction.