Accuracy and Reliability of a Disposable Vascular Pressure Device for Arterial Pressure Monitoring in Critical Care Transport.

OBJECTIVE: Arterial catheterization is a commonly performed procedure in intensive care units to guide the management of critically ill patients who require precise hemodynamic monitoring; however, this technology is not always available in the transport setting because of cumbersome and expensive equipment requirements. We compared the accuracy and reliability of a disposable vascular pressure device (DVPD) with the gold standard (ie, the transducer pressure bag invasive arterial monitoring system) used in intensive care units to determine if the DVPD can be reliably used in place of the traditional pressure transducer setup. METHODS: This study was a single-center, prospective, observational study performed in the adult intensive care unit of a large academic university hospital. A convenience cohort of hemodynamically stable, adult critically ill patients with femoral, brachial, or radial arterial catheters was recruited for this study. The Compass pressure device (Centurion Medical Products, Williamston, MI) is a disposable vascular pressure-sensing device used to assure venous access versus inadvertent arterial access during central line placement. The DVPD was attached to an in situ arterial catheter and measures the mean intravascular pressure via an embedded sensor and displays the pressure via the integrated LCD screen. Using a 3-way stopcock, the DVPD was compared with the standard arterial setup. We compared the mean arterial pressure (MAP) in the standard setup with the DVPD using Bland-Altman plots and methods that accounted for repeated measures in the same subject. RESULTS: Data were collected on 14 of the 15 subjects enrolled. Five measurements were obtained on each patient comparing the DVPD with the standard arterial setup at 1-minute intervals over the course of 5 minutes. A total of 70 observations were made. Among the 15 subjects, most (10 [67%]) were radial or brachial sites. The average MAP scores and standard deviation values obtained by the standard setup were 83.5 mm Hg (14.8) and 81.1 mm Hg (19.3) using the DVPD. Just over half (51.4%) of the measurements were within a ± 5-mm Hg difference. Using Bland-Altman plotting methods, standard arterial measurements were 2.4 mm Hg higher (95% confidence interval, 0.60-4.1) than with the DVPD. Differences between the 2 devices varied significantly across MAP values. The standard arterial line measurements were significantly higher than the DVPD at low MAP values, whereas the DVPD measurements were significantly higher than the standard arterial line at high MAP values. CONCLUSION: The DVPD provides a reasonable estimate of MAP and may be suitable for arterial pressure monitoring in settings where standard monitoring setups are not available. The DVPD appears to provide "worst-case" values because it underestimates low arterial blood pressure and overestimates high arterial blood pressure. Future trials should investigate the DVPD under different physiological conditions (eg, hypotensive patients, patients with ventricular assist devices, and patients on extracorporeal membrane oxygenation), different patient populations (such as pediatric patients), and in different environments (prehospital, air medical transport, and austere locations).

Comparison of three haemodynamic monitoring methods in comatose post cardiac arrest patients.

OBJECTIVES: Haemodynamic monitoring during post arrest care is important to optimise treatment. We compared stroke volume measured by minimally-invasive monitoring devices with or without thermodilution calibration, and transthoracic echocardiography (TTE), and hypothesised that thermodilution calibration would give stroke volume index (SVI) more in agreement with TTE during targeted temperature management (TTM). DESIGN: Comatose out-of-hospital cardiac arrest survivors receiving TTM (33 °C for 24 hrs) underwent haemodynamic monitoring with arterial pulse contour analyses with (PiCCO2®) and without (FloTrac®/Vigileo® monitor®) transpulmonary thermodilution calibration. Haemodynamic parameters were collected simultaneously every fourth hour during TTM (hypothermia) and (normothermia). SVI was measured with TTE during hypothermia and normothermia. Bland-Altman analyses were used for determination of SVI bias (±1SD). RESULTS: Twenty-six patients were included, of whom 77% had initial shockable rhythm and 52% discharged with good outcome. SVI (bias ±2SD) between PiCCO (after thermodilution calibration) vs FloTrac/Vigileo, TTE vs FloTrac/Vigileo and TTE vs PiCCO were 1.4 (±25.8), -1.9 (±19.8), 0.06 (±18.5) ml/m2 during hypothermia and 9.7 (±23.9), 1.0 (±17.4), -7.2 (±12.8) ml/m2 during normothermia. Continuous SVI measurements between PiCCO and FloTrac/Vigileo during hypothermia at reduced SVI (<35 ml/m2) revealed low bias and relatively narrow limits of agreement (0.5 ± 10.2 ml/m2). CONCLUSION: We found low bias, but relatively wide limits of agreement in SV with PiCCO, FloTrac/Vigileo and TTE during TTM treatment. The methods are not interchangeable. Precision was not improved by transpulmonary thermodilution calibration during hypothermia.

Validity of the Polar V800 monitor for measuring heart rate variability in mountain running route conditions.

PURPOSE: This study was conducted to test, in mountain running route conditions, the accuracy of the Polar V800™ monitor as a suitable device for monitoring the heart rate variability (HRV) of runners. METHOD: Eighteen healthy subjects ran a route that included a range of running slopes such as those encountered in trail and ultra-trail races. The comparative study of a V800 and a Holter SEER 12 ECG Recorder™ included the analysis of RR time series and short-term HRV analysis. A correction algorithm was designed to obtain the corrected Polar RR intervals. Six 5-min segments related to different running slopes were considered for each subject. RESULTS: The correlation between corrected V800 RR intervals and Holter RR intervals was very high (r = 0.99, p < 0.001), and the bias was less than 1 ms. The limits of agreement (LoA) obtained for SDNN and RMSSD were (- 0.25 to 0.32 ms) and (- 0.90 to 1.08 ms), respectively. The effect size (ES) obtained in the time domain HRV parameters was considered small (ES < 0.2). Frequency domain HRV parameters did not differ (p > 0.05) and were well correlated (r ≥ 0.96, p < 0.001). CONCLUSION: Narrow limits of agreement, high correlations and small effect size suggest that the Polar V800 is a valid tool for the analysis of heart rate variability in athletes while running high endurance events such as marathon, trail, and ultra-trail races.

The patient with chronic heart failure undergoing surgery.

PURPOSE OF REVIEW: Congestive heart failure (CHF) is one of the most common diseases of the elderly patient. The underlying pathophysiology varies considerably and approximately 50% of the patients suffer from CHF with reduced left ventricular ejection fraction. Mortality in the perioperative period is increased in patients with CHF and this holds true for both minor and major surgeries. This review will summarize recent literature in the field of CHF and perioperative outcome in patients undergoing surgery with a special emphasis on actual guidelines, preoperative assessment and appropriate perioperative therapy. RECENT FINDINGS: In the past 18 months, new insights in the short and long-term effects of CHF in the perioperative period have been published. The role of left ventricular ejection fraction has been studied in noncardiac surgical patients and it has been demonstrated that an ejection fraction less than 30% is associated with a significant increase in mortality and myocardial infarctions. Moreover, in 25% of patients, acute exacerbation of heart failure takes place in the perioperative period. The European Society of Anesthesiology published new guidelines on the preoperative evaluation of patients with CHF. The role of adequate preoperative evaluation and preparation of patients with CHF is discussed widely. It becomes clear that parameters like brain natriuretic peptide play a crucial role in risk stratification and prediction of outcome. Also, the treatment of patients with low cardiac output was a topic, and it became clear that established therapies including the use of ß-mimetics and PDE-III inhibitors should only be initiated in very selected patient groups. However, adequately powered studies in patients with CHF are still missing and the majority of knowledge is based on patient undergoing cardiac surgery. SUMMARY: CHF is a source of considerable perioperative morbidity and mortality and in contrast to coronary artery disease, knowledge is very limited and additional research urgently needed.

[Intra-operative continuous non-invasive blood pressure monitoring].

Intra-operative hypotension is associated with increased risk of 30-day mortality and organ ischaemia. Thus, a reliable monitoring of blood pressure is desirable. New clinical studies indicate, that monitoring of middle arterial pressure with continuous non-invasive monitoring during stable haemodynamic conditioning provides accurate changes in blood pressure. The potential of continuous non-invasive monitoring is promising, but not fully developed.