Cross-comparisons of trending accuracies of continuous cardiac-output measurements: pulse contour analysis, bioreactance, and pulmonary-artery catheter.

We compared the similarity of cardiac-output (CO) estimates between available bolus thermodilution pulmonary-artery catheters (PAC), arterial pulse-contour analysis (LiDCOplus™, FloTrac™ and PiCCOplus™), and bioreactance (NICOM™). Repetitive simultaneous estimates of CO obtained from the above devices were compared in 21 cardiac-surgery patients during the first 2 h post-surgery. Mean and absolute values for CO across the devices were compared by ANOVA, Bland-Altman, Pearson moment, and linear-regression analyses. Twenty-one simultaneous CO measurements were made before and after therapeutic interventions. Mean PAC CO (5.7 ± 1.5 L min) was similar to LiDCO™, FloTrac™, PiCCO™, and NICOM™ CO (6.0 ± 1.9, 5.9 ± 1.0, 5.7 ± 1.8, 5.3 ± 1.0 L min, respectively). Mean CO bias between each paired method was -0.10 (PAC-LiDCO), 0.18 (PAC-PiCCO), -0.40 (PAC-FloTrac), -0.71 (PAC-NICOM), 0.28 (LiDCO-PiCCO), 0.39 (LiDCO-FloTrac), -0.97 (NICOM-LiDCO), 0.61 (PiCCO-FloTrac), -1.0 (NICOM-FloTrac), -0.73 (NICOM-PiCCO) L/min, with limits of agreement (1.96 SD, ±95% CI) of ± 2.01, ±2.35, ±2.27, ±2.70, ±1.97, ±2.17, ±3.51, ±2.87, ±2.40, and ± 3.14 L min, respectively, and the percentage error for each of the paired devices was 35, 41, 40, 47, 33, 36, 59, 50, 42, and 55%, respectively. From Pearson moment analysis, dynamic changes in CO, estimated by each device, showed good cross-correlations. Although all devices studied recorded similar mean CO values, which dynamically changed in similar directions, they have markedly different bias and precision values relative to each other. Thus, results from prior studies that have used one device to estimate CO cannot be used to validate others devices.

Monitoring patients with continuous-flow ventricular assist devices outside of the intensive care unit: novel challenges to bedside nursing.

Ventricular assist devices provide therapeutic options for patients with severe heart failure who have exhausted available medical therapies. With restoration of organ perfusion with ventricular assist devices, the heart failure resolves and quality of life and functional status improve. The current generation of continuous-flow devices present novel challenges to the clinical assessment of patients by substantially reducing or nearly eliminating any palpable pulse. Patients therefore generally have inadequate arterial pulsatility for most noninvasive monitoring devices such as pulse oximeters or automated blood pressure cuffs to work accurately. This article describes the function of continuous-flow devices and how this function affects common monitoring options, as well as how to clinically assess recipients of continuous-flow devices to promptly identify those whose condition may be deteriorating or who may be receiving inadequate perfusion.

Bariatric surgery for a patient with a HeartMate II ventricular assist device for destination therapy.

A patient with a HeartMate II left ventricular assist device who had a body mass index of 52 needed gastric bypass surgery in order to qualify for a heart transplant. Unlike previous experience in which the surgery was performed at the implant hospital, the gastric bypass surgery in this case was performed at a bariatric center of excellence that was a separate facility from the implant hospital. The artificial heart program of the University of Pittsburgh Medical Center worked with the bariatric center of excellence in scheduling the gastric bypass surgery using a multidisciplinary team approach at 2 hospitals to coordinate safe, high-quality patient care in a unique situation.

Cross-comparison of cardiac output trending accuracy of LiDCO, PiCCO, FloTrac and pulmonary artery catheters.

INTRODUCTION: Although less invasive than pulmonary artery catheters (PACs), arterial pulse pressure analysis techniques for estimating cardiac output (CO) have not been simultaneously compared to PAC bolus thermodilution CO (COtd) or continuous CO (CCO) devices. METHODS: We compared the accuracy, bias and trending ability of LiDCO™, PiCCO™ and FloTrac™ with PACs (COtd, CCO) to simultaneously track CO in a prospective observational study in 17 postoperative cardiac surgery patients for the first 4 hours following intensive care unit admission. Fifty-five paired simultaneous quadruple CO measurements were made before and after therapeutic interventions (volume, vasopressor/dilator, and inotrope). RESULTS: Mean CO values for PAC, LiDCO, PiCCO and FloTrac were similar (5.6 ± 1.5, 5.4 ± 1.6, 5.4 ± 1.5 and 6.1 ± 1.9 L/min, respectively). The mean CO bias by each paired method was -0.18 (PAC-LiDCO), 0.24 (PAC-PiCCO), -0.43 (PAC-FloTrac), 0.06 (LiDCO-PiCCO), -0.63 (LiDCO-FloTrac) and -0.67 L/min (PiCCO-FloTrac), with limits of agreement (1.96 standard deviation, 95% confidence interval) of ± 1.56, ± 2.22, ± 3.37, ± 2.03, ± 2.97 and ± 3.44 L/min, respectively. The instantaneous directional changes between any paired CO measurements displayed 74% (PAC-LiDCO), 72% (PAC-PiCCO), 59% (PAC-FloTrac), 70% (LiDCO-PiCCO), 71% (LiDCO-FloTrac) and 63% (PiCCO-FloTrac) concordance, but poor correlation (r(2) = 0.36, 0.11, 0.08, 0.20, 0.23 and 0.11, respectively). For mean CO < 5 L/min measured by each paired devices, the bias decreased slightly. CONCLUSIONS: Although PAC (COTD/CCO), FloTrac, LiDCO and PiCCO display similar mean CO values, they often trend differently in response to therapy and show different interdevice agreement. In the clinically relevant low CO range (< 5 L/min), agreement improved slightly. Thus, utility and validation studies using only one CO device may potentially not be extrapolated to equivalency of using another similar device.

The Joint Commission's disease-specific care certification for destination therapy ventricular assist devices.

The Centers for Medicare and Medicaid Services announced that all hospitals implanting ventricular assist devices are required to have certification from the The Joint Commission for disease-specific care destination therapy with a ventricular assist device effective March 27, 2009, in order to receive Medicare reimbursement for services rendered to patients who have devices implanted for destination therapy. On February 23, 2007, The Joint Commission released the certification requirements for ventricular assist devices implanted for destination therapy in an 8-page document so that hospitals could prepare to meet the 2009 certification deadline. The Artificial Heart Program of the University of Pittsburgh Medical Center undertook a multidisciplinary project, under the guidance of the nurse coordinator, to prepare the hospital and program for a precertification survey by The Joint Commission for disease-specific destination therapy ventricular assist device certification. The Presbyterian Hospital Artificial Heart Program was awarded The Joint Commission's device-specific certification for destination therapy with ventricular assist devices in June 2008.

Evaluation of a Health Care Performance Improvement Initiative to Facilitate Optimal Clinical Outcomes in Patients Receiving Ventricular Assist Device Support.

BACKGROUND: Ventricular assist device (VAD) patients are at high risk for morbidities and mortality. One potentially beneficial component of the Joint Commission VAD Certification process is the requirement that individual VAD programs select 4 performance measures to improve and optimize patients' clinical outcomes. PROBLEM STATEMENT: Review of patient data after our program's first certification visit in 2008 showed that, compared to national recommendations and published reports, our patients had suboptimal outcomes in 4 areas after device implantation: length of hospital stay, receipt of early (<48 hours) postsurgical physical therapy, driveline infection incidence, and adequacy of nutritional status (prealbumin ≥18 mg/dL). METHODS: Plan-Do-Study-Act processes were implemented to shorten length of stay, increase patient receipt of early physical therapy, decrease driveline infection incidence, and improve nutritional status. With 2008 as our baseline, we deployed interventions for each outcome area across 2009 to 2017. Performance improvement activities included staff, patient, and family didactic, one-on-one, and hands-on education; procedural changes; and outcomes monitoring with feedback to staff on progress. Descriptive and inferential statistics were examined to document change in the outcomes. OUTCOMES: Across the performance improvement period, length of stay decreased from 40 to 23 days; physical therapy consults increased from 87% to 100% of patients; 1-year driveline infection incidence went from 38% to 23.5%; and the percentage of patients with prealbumin within the normal range increased from 84% to 90%. IMPLICATIONS: Performance improvement interventions may enhance ventricular assist device patient outcomes. Interventions' sustainability should be evaluated to ensure that gains are not lost over time.

Ability of pulse power, esophageal Doppler, and arterial pulse pressure to estimate rapid changes in stroke volume in humans.

INTRODUCTION: Measures of arterial pulse pressure variation and left ventricular stroke volume variation induced by positive-pressure breathing vary in proportion to preload responsiveness. However, the accuracy of commercially available devices to report dynamic left ventricular stroke volume variation has never been validated. METHODS: We compared the accuracy of measured arterial pulse pressure and estimated left ventricular stroke volume reported from two Food and Drug Administration-approved aortic flow monitoring devices, one using arterial pulse power (LiDCOplus) and the other esophageal Doppler monitor (HemoSonic). We compared estimated left ventricular stroke volume and their changes during a venous occlusion and release maneuver to a calibrated aortic flow probe placed around the aortic root on a beat-to-beat basis in seven anesthetized open-chested cardiac surgery patients. RESULTS: Dynamic changes in arterial pulse pressure closely tracked left ventricular stroke volume changes (mean r .96). Both devices showed good agreement with steady-state apneic left ventricular stroke volume values and moderate agreement with dynamic changes in left ventricular stroke volume (esophageal Doppler monitor -1 +/- 22 mL, and pulse power -7 +/- 12 mL, bias +/- 2 sd). In general, the pulse power signals tended to underestimate left ventricular stroke volume at higher left ventricular stroke volume values. CONCLUSION: Arterial pulse pressure, as well as, left ventricular stroke volume estimated from esophageal Doppler monitor and pulse power reflects short-term steady-state left ventricular stroke volume values and tract dynamic changes in left ventricular stroke volume moderately well in humans.

Thresholded area over the curve of spectrometric tissue oxygen saturation as an indicator of volume resuscitability in porcine hemorrhagic shock.

BACKGROUND: A rapid, reliable, and noninvasive functional measure of responsiveness to resuscitation in posttraumatic hemorrhagic shock could prove useful in guiding therapy, especially under circumstances such as the battlefield and civilian mass casualties. Tissue oxygen saturation (Sto2) is a promising candidate for this application. We therefore explored the value of peripheral muscle Sto2 in predicting systemic responsiveness to colloid volume resuscitation in a porcine model of hemorrhagic shock. METHODS: Fourteen isoflurane-anesthetized piglets were subjected to a standardized hemorrhage protocol that maintained mean arterial pressure (MAP) between 30 and 40 mm Hg. Asanguineous resuscitation with a volume of Hextend equal to the total volume bled was initiated when compensation was exhausted (MAP <30 mm Hg). We recorded continuous MAP and Sto2 values, and calculated the contiguous area over the Sto2 curve yet below a given threshold of Sto2 (TAOC) as a function of this threshold before the selected timepoint for timepoints up to 30 minutes before resuscitation. RESULTS: Hemorrhage resulted in significant fluctuations of MAP and high interindividual variability of disease dynamics and outcome: 4 nonsurvivors and 10 survivors at 2 hours postresuscitation. Sto2 measurements reflected hemodynamic conditions in most animals, with a pronounced drop preceding final decompensation in 7 of 14 animals. TAOC discriminated three of four nonresuscitable (nonsurvivor) animals from the survivors, with group differences reaching significance even for the earliest examined timepoint (30 minutes before resuscitation), depending on the choice of TAOC threshold. CONCLUSIONS: Sto2 may serve as a marker of decompensation, whereas TAOC, a physiologically motivated correlate of perfusion debt and cumulative hypoperfusion injury, may be a useful early indicator of responsiveness to volume resuscitation in hemorrhagic shock.

Usefulness of angle corrected tissue Doppler to assess segmental left ventricular function during dobutamine stress echocardiography in patients with and without coronary artery disease.

The application of angle correction to tissue Doppler (TD) during dobutamine stress echocardiography (DSE) extends the application of TD to all left ventricular segments, improves the differentiation of abnormal from normal segmental responses to stress, and has promise to improve its clinical utility for objectively evaluating wall motion during DSE.

Regional correlation by color-coded tissue Doppler to quantify improvements in mechanical left ventricular synchrony after biventricular pacing therapy.

Cardiac resynchronization therapy (CRT) can improve cardiac function in patients with heart failure and left bundle branch block. To test a new synchrony index derived from mitral annular velocity by color tissue Doppler, 19 subjects were studied: 9 patients with heart failure and left bundle branch block at baseline and at 1, 3 and 6 months after CRT and 10 normal controls. The synchrony index in patients with heart failure was less than that in controls at baseline (r = 0.60 +/- 0.13 vs 0.94 +/- 0.02; p <0.01), but improved at 6 months after CRT (r = 0.77 +/- 0.09; p <0.05 vs baseline).

Second-generation tissue Doppler with angle-corrected color-coded wall displacement for quantitative assessment of regional left ventricular function.

To test the hypothesis that a new tissue Doppler (TD) approach using angle-correction and transformation of velocity data to color-coded displacement data may objectively quantify regional left ventricular function, in vitro experiments were first performed with an oscillating echo target precisely controlled by a microstepping motor. Displacement varied from 1 to 15 mm (60 to 130 cycles/min) at angles of 0 degrees and 45 degrees to the echo transducer. Custom software transformed TD data to displacement data. Sixty-five subjects were then studied: 35 with wall motion abnormalities and 30 normal controls. Results were compared with independent visual assessment and caliper measurements of endocardial excursion from gray-scale images. In vitro displacement imaging strongly correlated with true displacement (r = 0.99, p <0.0001). In humans, peak transmural displacement discriminated normal results (6.3 +/- 3.2 mm) from hypokinesia (2.7 +/- 1.8 mm, p <0.05), akinesia (0.4 +/- 1.2 mm, p <0.05) from hypokinesia, and dyskinesia (-1.9 +/- 1.2 mm, p <0.05) from akinesia. Normal subendocardial displacement was 5.9 +/- 2.9 versus 4.0 +/- 3.9 mm in the epicardial layer (p <0.01). This displacement gradient was absent in abnormal segments. Displacement data correlated with endocardial excursion by calipers (parasternal views: r = 0.86, all views: r = 0.79, both p <0.0001). Overall accuracy of displacement imaging was 82% (kappa = 0.71) versus 66% (kappa = 0.43) for visual assessment with caliper data as the standard of reference. Angle-corrected displacement imaging was superior to routine visual assessment and is a promising new method to quantify regional left ventricular function.

The effects of vasoactive drugs on pulse pressure and stroke volume variation in postoperative ventilated patients.

INTRODUCTION: Although pulse pressure variation (PPV) and stroke volume variation (SVV) during mechanical ventilation have been shown to predict preload responsiveness, the effect of vasoactive therapy on PPV and SVV is unknown. METHODS: Pulse pressure variation and SVV were measured continuously in 15 cardiac surgery patients for the first 4 postoperative hours. Pulse pressure variation was directly measured from the arterial pressure waveform, and both PPV and SVV were also calculated by LiDCO Plus (LiDCO Ltd, Cambridge, United Kingdom) before and after volume challenges or changes in vasoactive drug infusions done to sustain cardiovascular stability. RESULTS: Seventy-one paired events were studied (38 vasodilator, 10 vasoconstrictor, 14 inotropes, and 9 volume challenges). The difference between the measured and LiDCO-calculated PPV was 1% ± 7% (1.96 SD, 95% confidence interval, r(2) = 0.8). Volume challenge decreased both PPV and SVV (15% to 10%, P < .05 and 13% to 9%, P = .09, respectively). Vasodilator therapy increased PPV and SVV (13% to 17% and 9% to 15%, respectively, P < .001), whereas increasing inotropes or vasoconstrictors did not alter PPV or SVV. The PPV/SVV ratio was unaffected by treatments. CONCLUSION: Volume loading decreased PPV and SVV; and vasodilators increased both, consistent with their known cardiovascular effects. Thus, SVV and PPV can be used to drive fluid resuscitation algorithms in the setting of changing vasoactive drug therapy.

The influence of hemodynamics and wall biomechanics on the thrombogenicity of vein segments perfused in vitro.

This study addresses the hypothesis that exposure to peripheral arterial (ART) or coronary (COR) hemodynamics and wall biomechanics affect platelet deposition on vein segments. Intact human saphenous vein (HSV) and porcine internal jugular vein (PIJV) segments were studied under venous (VEN), ART, and COR environments using in vitro perfusion systems. Wall shear stress (tau) and circumferential wall stress (sigma(theta)) were calculated for PIJV segments. Platelet deposition was measured using a radioactive assay. PIJV ART segments exhibited a 14% increase in inner diameter over time (P < 0.05). tau, acting on PIJV ART specimens, was less at 6 h compared with time 0 (P < 0.05). sigma(theta) was lower in the VEN specimens compared with ART and COR groups (P < 0.01). Platelet deposition decreased by 40% on PIJV ART segments (P < 0.05) but increased 3.2-fold on PIJV COR segments (P < 0.05) versus VEN control segments. Platelet deposition was increased 1.75-fold in COR HSV cases versus VEN segments. These data indicate that short-term exposure to COR conditions lead to enhanced platelet deposition, whereas ART conditions decrease platelet deposition.