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Signa Vitae

Journal of Intensive Care and Emergency Medicine

Comparıng pulse pressure varıatıon and pleth varıabılıty ındex in the semı-recumbent and trendelenburg posıtıon ın crıtıcally ıll septıc patıents

Abstract

Introduction. Dynamic tests for predicting fluid responsiveness have generated increased interest in recent years. One of these tests, pulse pressure variation (PPV), is a parameter calculated from respiratory variations of pulse pressure. Another test, pleth variability index (PVI), is based on respiratory variations of the perfusion index and can be measured non-invasively by pulse oximeter. Previous studies have shown that both tests are valuable in determining fluid responsiveness.

Methods. In this observational prospective study, our aim was to compare the PVI and PPV in order to identify a convenient tool for determining fluid responsiveness. Our study was performed in a surgical and reanimation intensive care unit. We enrolled one hundred mechanically ventilated adult patients diagnosed with sepsis. Exclusion criteria included brain death, spontaneous breathing, cardiac arrhythmia, and impaired peripheral circulation. We measured the PPV by arterial monitorization and the PVI by using Masimo Radical 7 in the 45° semi-recumbent position (SP) and then 15° Trendelenbug position (TP). We performed correlation and ROC analysis using a >13% fluid responsiveness cut-off value for the PPV and >14% for the PVI.

Results. Between the SP and the TP, we did not observe significant decreases in PPV (from 14.17 ± 10.57 to 12.66 ± 9.64; p > 0.05), while we did observe significant decreases in PVI (from 21.91 ± 13.99 to 20.46 ± 14.12; p < 0.05). The PPV fluid responsiveness cut-off value in the SP and TP was 20% (78.95% sensitivity, 77.05% specificity) and 18% (76.67% sensitivity, 72.46% specificity), respectively. The PVI fluid responsiveness cut-off value in the SP and TP was 20% (80.49% sensitivity, 81.03% specificity) and 16% (81.25% sensitivity, 62.69% specificity), respectively. The area under the ROC of the PPV and PVI was 0.843 and 0.858 in the SP, respectively, and 0.760 and 0.747 in the TP, respectively. The PPV and PVI were correlated in the SP (r = 0.578; p = 0.001) and the TP (r = 0.517; p = 0.001).

Conclusions. Our results showed that the PPV and PVI were correlated independent of position change in sepsis patients. Both tests appear to be equivalently reliable. However, the ability of the PPV and PVI to predict fluid responsiveness decreased in the TP in our study.

Key words: pulse pressure variation, pleth variability index, fluid responsiveness, sepsis

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Mini invasive hemodynamic monitoring: from arterial pressure to cardiac output

Abstract

To evaluate the Cardiac Output (CO) the standard invasive pulmonary artery catheter (PAC) is considered today the gold standard. The major criticism to the PAC is that its level of invasiveness is not supported by an improvement in patient’s outcome. The interest to lesser and lesser invasive techniques is high. Therefore, the alternative techniques have been recently developed.
Cardiac Output can be monitored continuously by different devices that analyze the arterial waveform to track changes in stroke volume (SV) and CO. The analysis of the arterial pressure wave to determine cardiac output is classified as Pulse Contour analysis or Pulse Pressure Analysis. Starting from a similar principle three main devices are now available on the market, with different algorithms and features:

• PiCCO System (Pulsion Medical System, Munich, Germany)
• LiDCOTM plus System (LidCO, Cambridge, UK)
• Flotrac technology and Vigileo Monitor (Edwards Lifesciences, Irvine, CA, USA).

The algorithm used by all these devices has been also implemented even with the analysis of the variation of stroke volume (SVV) and of the pulse pressure (PPV). SVV and PPV represent the variation of stroke volume and of the pulse pressure during the respiratory cycle. In sedated ventilated patients these indexes have proven to predict the response to a fluid challenge. A high variation (>10-12%) identifies with good sensitivity and specificity responders and not responders.

Key words: cardiac output, arterial pressure, stroke volume variation, pulse pressure variation

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