Non-invasive venous waveform analysis (NIVA) for volume assessment in patients undergoing hemodialysis: an observational study.

BACKGROUND: Accurate assessment of volume status to direct dialysis remains a clinical challenge. Despite current attempts at volume-directed dialysis, inadequate dialysis and intradialytic hypotension (IDH) are common occurrences. Peripheral venous waveform analysis has recently been developed as a method to accurately determine intravascular volume status through algorithmic quantification of changes in the waveform that occur at different volume states. A noninvasive method to capture peripheral venous signals is described (Non-Invasive Venous waveform Analysis, NIVA). The objective of this proof-of-concept study was to characterize changes in NIVA signal with dialysis. We hypothesized that there would be a change in signal after dialysis and that the rate of intradialytic change in signal would be predictive of IDH. METHODS: Fifty subjects undergoing inpatient hemodialysis were enrolled. A 10-mm piezoelectric sensor was secured to the middle volar aspect of the wrist on the extremity opposite to the access site. Signals were obtained fifteen minutes before, throughout, and up to fifteen minutes after hemodialysis. Waveforms were analyzed after a fast Fourier transformation and identification of the frequencies corresponding to the cardiac rate, with a NIVA value generated based on the weighted powers of these frequencies. RESULTS: Adequate quality (signal to noise ratio > 20) signals pre- and post- dialysis were obtained in 38 patients (76%). NIVA values were significantly lower at the end of dialysis compared to pre-dialysis levels (1.203 vs 0.868, p < 0.05, n = 38). Only 16 patients had adequate signals for analysis throughout dialysis, but in this small cohort the rate of change in NIVA value was predictive of IDH with a sensitivity of 80% and specificity of 100%. CONCLUSIONS: This observational, proof-of-concept study using a NIVA prototype device suggests that NIVA represents a novel and non-invasive technique that with further development and improvements in signal quality may provide static and continuous measures of volume status to assist with volume directed dialysis and prevent intradialytic hypotension.

Observational Study of Clinician Attentional Reserves (OSCAR): Acuity-Based Rounds Help Preserve Clinicians' Attention.

OBJECTIVES: Team rounding in the ICU can tax clinicians' finite attentional resources. We hypothesized that a novel approach to rounding, where patients are seen in a decreasing order of acuity, would decrease attentional attrition. DESIGN: Prospective interventional internal-control cohort study in which stop signal task testing was used as a proxy for attentional reserves. Stop signal task is a measure of cognitive control and response inhibition in addition to performance monitoring, all reflective of executive control abilities, and our surrogate for attentional reserves. SETTING: The ICUs of Vanderbilt University Medical Center (site 1) and the University of Pennsylvania (site 2) from November 2014 to August 2017. SUBJECTS: Thirty-three clinicians at site 1, and 24 clinicians at site 2. INTERVENTIONS: Acuity-based rounding, in which clinicians round from highest to lowest acuity as determined by Sequential Organ Failure Assessment score or an equivalent acuity score. MEASUREMENTS AND MAIN RESULTS: The stop signal task results of ICU staff at two sites were compared for conventional (in room order) versus novel (in decreasing order of acuity) rounding order. At site 1, the difference in stop signal reaction time change between two rounding types was -39.0 ms (95% CI, -50.6 to -27.4 ms; p < 0.001), and at site 2, the performance stop signal reaction time was -15.6 ms (95% CI, -29.1 to -2.1 ms; p = 0.023). These sub-second changes, while small, are significant in the neuroscience domain. CONCLUSIONS: Rounding in decreasing order of patient acuity mitigated attrition in attentional reserves when compared with the traditional rounding method.

Non-Invasive Venous waveform Analysis (NIVA) for monitoring blood loss in human blood donors and validation in a porcine hemorrhage model.

STUDY OBJECTIVE: There is an unmet need for a non-invasive approach to diagnose hemorrhage early, before changes in vital signs occur. Non-Invasive Venous waveform Analysis (NIVA) uses a unique physiological signal (the peripheral venous waveform) to assess intravascular volume. We hypothesized changes in the venous waveform would be observed with blood loss in healthy adult blood donors and characterized hemorrhage using invasive monitoring in a porcine model. DESIGN: Prospective observational study. SETTING: American Red Cross donation center. PATIENTS: 50 human blood donors and 12 non-donating controls; 7 Yorkshire pigs. INTERVENTIONS: A venous waveform capturing prototype (NIVA device) was secured to the volar aspect of the wrist in human subjects. A central venous catheter was used to obtain hemodynamic indices and venous waveforms were obtained using the prototype NIVA device over the saphenous vein during 400 mL of graded hemorrhage in a porcine model. MEASUREMENTS: Venous waveforms were transformed from the time to the frequency domain. The ratiometric power contributions of the cardiac frequencies were used to calculate a NIVA value representative of volume status. MAIN RESULTS: A significant decrease in NIVA value was observed after 500 mL of whole blood donation (p < .05). A ROC curve for the ability of the NIVA to detect 500 mL of blood loss demonstrated an area under the curve (AUC) of 0.94. In the porcine model, change in NIVA value correlated linearly with blood loss and with changes in hemodynamic indices. CONCLUSIONS: This study provides proof-of-concept for a potential application of NIVA in detection of blood loss. NIVA represents a novel physiologic signal for detection of early blood loss that may be useful in early triage and perioperative management.

Peripheral Intravenous Volume Analysis (PIVA) for Quantitating Volume Overload in Patients Hospitalized With Acute Decompensated Heart Failure-A Pilot Study.

BACKGROUND: To determine the feasibility of peripheral intravenous volume analysis (PIVA) of venous waveforms for assessing volume overload in patients admitted to the hospital with acute decompensated heart failure (ADHF). METHODS: Venous waveforms were captured from a peripheral intravenous catheter in subjects admitted for ADHF and healthy age-matched controls. Admission PIVA signal, brain natriuretic peptide, and chest radiographic measurements were related to the net volume removed during diuresis. RESULTS: ADHF patients had a significantly greater PIVA signal on admission compared with the control group (P = .0013, n = 18). At discharge, ADHF patients had a PIVA signal similar to the control group. PIVA signal, not brain natriuretic peptide or chest radiographic measures, accurately predicted the amount of volume removed during diuresis (R2 = 0.781, n = 14). PIVA signal at time of discharge greater than 0.20, demonstrated 83.3% 120-day readmission rate. CONCLUSIONS: This study demonstrates the feasibility of PIVA for assessment of volume overload in patients admitted to the hospital with ADHF.

Recent advances in perioperative glucose monitoring.

PURPOSE OF REVIEW: There is ongoing controversy surrounding the use of glucose monitoring in the perioperative setting. It is an important aspect of patient care, but the best way to go about monitoring this parameter is still up for debate. This article will review previously established data and new developments in this field. RECENT FINDINGS: Several different methods exist to measure blood glucose levels in the perioperative setting, including central laboratory devices, blood gas analyzers, and point-of-care devices. However, it has been recommended that point-of-care devices not be used on 'critically ill' patients, which throws into question the common use of these devices perioperatively. Recently, the Centers for Medicare and Medicaid placed a moratorium on this recommendation, and these devices continue to be a staple in the perioperative setting, but there are other methods of glucose monitoring that can be employed. SUMMARY: The monitoring of blood glucose levels in the perioperative patient remains an important part of patient care; however, debate still exist on how best to reliably measure blood glucose levels in the most effective manner.