Jacobs Journal of Anesthesiology and Research

Pulse Transit Time as an Indicator of Changes in Systemic Blood Pressure and Cardiac Output

*Dmitri Bystriski
Department Of Anesthesiology Critical Care And Pain Medicine, The Lady Davis Carmel Medical Center , Haifa, Israel

*Corresponding Author:
Dmitri Bystriski
Department Of Anesthesiology Critical Care And Pain Medicine, The Lady Davis Carmel Medical Center , Haifa, Israel
Email:dmitribi@clalit.org.il

Published on: 2018-12-27

Abstract

Introduction: Pulse transit time (PuTT) is the interval between R-wave on electrocardiogram (ECG) and upstroke on peripheral arterial blood pressure (BP) waveform or pulse plethysmographic waveform. It has been suggested that changes in PuTT reflect changes in arterial BP and cardiac output (CO). The study tested the hypothesis that changes in PuTT reflect CO changes in anesthetized ventilated surgical patients. Materials and Methods: Surgical patients monitored with direct BP and non-invasive cardiac outputs were included in study. Patients with hypotension and normal CO were treated by phenylephrine (phenylephrine group, n= 41). Patients who required volume loading received bolus of colloid solution (volume loading group, n=22). Arterial and plethysmographic PuTT changes were compared with stroke volume index (SVI) and BP changes. Results: Although systolic BP increased in both groups, it increased to a greater extent following phenylephrine therapy. SVI increased following volume loading but did not change after phenylephrine administration. Arterial and plethysmographic PuTTs shortened in both groups following treatment. There was a weak but significant correlation between arterial PuTT changes and systolic BP changes (β = – 0.314; P = 0.006) and SVI (β = – 0.289; P = 0.01) as well as between plethysmographic PuTT changes and systolic BP changes (β = -0.374; P = 0.001). Correlation between changes of plethysmographic PuTT and SVI was non-significant. Conclusion: Low correlation coefficients demonstrate that PuTT changes do not correlate closely with changes either in BP or in CO. As such, we therefore conclude that PuTT changes do not reflect changes in CO or BP, and PuTT is not applicable for estimation of CO or BP changes in anesthetized ventilated patients.

Keywords

Pulse Transit Time; Cardiac Output; Cardiac Index; Systemic Blood Pressure

Introduction

Cardiac Output (CO) is an important hemodynamic variable that is rarely measured despite the fact it has been suggested that guiding perioperative therapy according to CO may improve outcome. Despite its perceived importance, CO is not measured routinely because of the complexity and the invasiveness it entails. Less invasive as well as noninvasive methods to measure cardiac output are available but they are less reliable and robust than invasive measurements. Among these techniques the thoracic bioreactance was evaluated intensively. In a multicentre study the non-invasive cardiac output monitor (NICOM) was assessed in mixed population of patients in cardiac care units, ICUs, and cardiac catheterization laboratories in comparison with pulmonary artery catheter derived cardiac output (either continuous cardiac output measurements or intermittent bolus pulmonary artery thermodilution measurements), a low bias has been observed. Comparable results were obtained in studies in post cardiac surgery patients when using cardiac output measurements obtained with transpulmonary thermodilution and calibrated pulse contour analysis or with pulmonary artery thermodilution as the criterion standard.