The key role of pulse wave transit time to predict blood pressure variation during anaesthesia induction

Objective To establish the relationship between pulse wave transit time (PWTT) before anaesthesia induction and blood pressure variability (BPV) during anaesthesia induction. Methods This prospective observational cohort study enrolled consecutive patients that underwent elective surgery. Invasive arterial pressure, electrocardiography, pulse oximetry, heart rate and bispectral index were monitored. PWTT and BPV were measured with special software. Anaesthesia was induced with propofol, sufentanil and rocuronium. Results A total of 54 patients were included in this study. There was no correlation between BPV and the dose of propofol, sufentanil and rocuronium during anaesthesia induction. Bivariate linear regression analysis demonstrated that PWTT ( r = –0.54), age ( r = 0.34) and systolic blood pressure ( r = 0.31) significantly correlated with systolic blood pressure variability (SBPV). Only PWTT ( r = –0.38) was significantly correlated with diastolic blood pressure variability (DBPV). Patients were stratified into high PWTT and low PWTT groups according to the mean PWTT value (96.8 ± 17.2 ms). Compared with the high PWTT group, the SBPV of the low PWTT group increased significantly by 3.4%. The DBPV of the low PWTT group increased significantly by 2.1% compared with the high PWTT group. Conclusions PWTT, assessed before anaesthesia induction, may be an effective predictor of haemodynamic fluctuations during anaesthesia induction.

Correlation of Pulse Wave Transit Time with Pulmonary Artery Pressure in a Porcine Model of Pulmonary Hypertension

For the non-invasive assessment of pulmonary artery pressure (PAP), surrogates like pulse wave transit time (PWTT) have been proposed. The aim of this study was to invasively validate for which kind of PAP (systolic, mean, or diastolic) PWTT is the best surrogate parameter. To assess both PWTT and PAP in six healthy pigs, two pulmonary artery Mikro-Tip™ catheters were inserted into the pulmonary vasculature at a fixed distance: one in the pulmonary artery trunk, and a second one in a distal segment of the pulmonary artery. PAP was raised using the thromboxane A2 analogue U46619 (TXA) and by hypoxic vasoconstriction. There was a negative linear correlation between PWTT and systolic PAP (r = 0.742), mean PAP (r = 0.712) and diastolic PAP (r = 0.609) under TXA. During hypoxic vasoconstriction, the correlation coefficients for systolic, mean, and diastolic PAP were consistently higher than for TXA-induced pulmonary hypertension (r = 0.809, 0.778 and 0.734, respectively). Estimation of sPAP, mPAP, and dPAP using PWTT is feasible, nevertheless slightly better correlation coefficients were detected for sPAP compared to dPAP. In this study we establish the physiological basis for future methods to obtain PAP by non-invasively measured PWTT.

Comparison of the ability of two continuous cardiac output monitors to detect stroke volume index: Estimated continuous cardiac output estimated by modified pulse wave transit time and measured by an arterial pulse contour-based cardiac output device

BACKGROUND: Estimated continuous cardiac output (esCCO), a non-invasive technique for continuously measuring cardiac output (CO), is based on modified pulse wave transit time, which is determined by pulse oximetry and electrocardiography. OBJECTIVE: We examined the ability of esCCO to detect stroke volume index (SVI) and changes in SVI compared with currently available arterial waveform analysis methods. METHODS: We retrospectively reanalysed 15 of the cases from our previous study on esCCO measurement. SVI was calculated using an esCCO system, measured using the arterial pressure-based CO (APCO) method, and compared with a corresponding intermittent bolus thermodilution CO (ICO) method. Percentage error measurement and statistical methods, including concordance analysis and polar plot analysis, were performed. RESULTS: The difference in the SVI values between esCCO and ICO was -3.0 ± 8.8 ml (percentage error, 33.5%). The mean angular bias was 0.8 and the radial limits of agreement were ± 27.3. The difference in the SVI values between APCO and ICO was 0.9 ± 11.2 ml (percentage error, 42.6%). The mean angular bias was -6.8 and the radial limits of agreement were ± 44.1. CONCLUSION: This study demonstrated that the accuracy, precision, and dynamic trend of esCCO are better than those of APCO.

Continuous Estimation of Cardiac Output in Critical Care: A Noninvasive Method Based on Pulse Wave Transit Time Compared with Transpulmonary Thermodilution

Purpose. Estimation of cardiac output (CO) and evaluation of change in CO as a result of therapeutic interventions are essential in critical care medicine. Whether noninvasive tools estimating CO, such as continuous cardiac output (esCCOTM) methods, are sufficiently accurate and precise to guide therapy needs further evaluation. We compared esCCOTM with an established method, namely, transpulmonary thermodilution (TPTD). Patients and Methods. In a single center mixed ICU, esCCOTM was compared with the TPTD method in 38 patients. The primary endpoint was accuracy and precision. The cardiac output was assessed by two investigators at baseline and after eight hours. Results. In 38 critically ill patients, the two methods correlated significantly (r = 0.742). The Bland–Altman analysis showed a bias of 1.6 l/min with limits of agreement of −1.76 l/min and +4.98 l/min. The percentage error for COesCCO was 47%. The correlation of trends in cardiac output after eight hours was significant (r = 0.442), with a concordance of 74%. The performance of COesCCO could not be linked to the patient’s condition. Conclusion. The accuracy and precision of the esCCOTM method were not clinically acceptable for our critical patients. EsCCOTM also failed to reliably detect changes in cardiac output.

Are Noninvasive Continuous Cardiac Output Monitoring Interchangeable with Esophageal Doppler?

Objective: To compare the trending ability, accuracy, and precision of non-invasive stroke volume (SV) measurement based on a bioreactance technique and measurement of the pulse wave transit time (PWTT) versus the esophageal Doppler monitoring (EDM). Materials and Methods: Two hundred twenty-seven paired measurements from 10 patients who underwent abdominal surgery under general anesthesia were included for SV measurements. Pearson’s correlation coefficient was calculated, and Bland-Altman analysis was performed to evaluate the agreement between EDM and bioreactance (EDM-bioreactance) and between EDM and PWTT (EDM-PWTT). Results: EDM-bioreactance had a correlation coefficient of 0.75 (95% confidence interval [CI] 0.62 to 0.78; p<0.001), bias of 0.28 ml (limits of agreement –30.92 to 31.38 ml), and percentage error of 46.82%. EDM-PWTT had a correlation coefficient of 0.48 (95% CI 0.44 to 0.72; p<0.001), bias of –0.18 ml (limits of agreement –40.28 to 39.92 ml), and percentage error of 60.17%. A subgroup analysis of data from patients who underwent crystalloid loading was performed to detect the trending ability. The four-quadrant plot analysis between EDM-bioreactance and EDM-PWTT demonstrated concordance rates of 70.00% and 73.68%, respectively. Conclusion: SV measurement based on bioreactance technique and measurement of PWTT are not interchangeable with EDM. Trial registration: Thai Clinical Trials Registry, TCTR 20181217003 Keywords: Stroke volume, Cardiac output, Doppler, Perioperative care, Pulse, Time

Does vascular stiffness predict white matter hyperintensity burden in ischemic heart disease with preserved ejection fraction?

This study found that patients with ischemic heart disease (IHD) with preserved ejection fraction and normal blood pressures exhibit greater carotid β-stiffness, as well as middle cerebral artery pulsatility and resistive indexes, than controls. White matter lesion volume (WMLv) was not different between vascular pathology groups. Cerebrovascular pulse wave transit time (ccPWTT) and carotid β-stiffness independently associate with WMLv in pooled participant data, suggesting that regardless of heart disease history, ccPWTT and β-stiffness are associated with structural white matter damage.