Hemodilution on microvascular oxygen delivery potential of the blood during coronary bypass surgery.

PURPOSE: The hematocrit-to-whole blood viscosity ratio (Hct/WBV) reflects the blood O2 delivery potential (O2-DP). WBV is variable to the dynamic vascular shear rate (SR), 1-5/s at microcirculation and 300/s at larger vessels. To estimate the impact of hemodilution on the blood O2-DP to the myocardium, we analyzed the hemodilution-induced change of Hct/WBV at SR 5/s (Hct/WBV5) during off-pump coronary bypass (OPCAB) surgery. METHODS: During OPCAB surgery (n = 21), 10% acute normovolemic hemodilution (HD 10%) was applied. Arterial blood samples were taken: one before and two after HD 10%. One of which after HD 10% underwent an additional 33% in vitro hemodilution (reaching 40% hemodilution in total, HD 40%). WBV of all blood samples was determined using a scan-capillary tube viscometer (Hemovister™). The changes of Hct/WBV5 were analyzed as a primary measure of the study and compared with those of Hct/WBV at SR 300/s (Hct/WBV300). RESULTS: Median[IQR] of Hct/WBV5 [3.5 (2.8-4.2)%/cPoise] was significantly increased by HD 10 and HD 40% [3.6 (3.2-4.6)%/cPoise and 4.2 (3.3-5.2)%/cPoise, respectively, all P < 0.001], but the degrees of changes after HD 10 and HD 40% were not different. Median[IQR] of Hct/WBV300 [10.3(8.6‒10.8)%/cPoise] was not changed by HD 10% [10.3(9.1-11.1)%/cPoise], but it was significantly decreased by HD 40% [8.4(7.4‒9.2)%/cPoise, P < 0.001]. CONCLUSION: The increased Hct/WBV5 suggests that 10-40% hemodilution improves the blood O2-DP to the myocardium during OPCAB surgery. The SR-specific discrepancy in Hct/WBV changes advocates using microvascular WBV and Hct/WBV to evaluate the blood O2-DP changes to the myocardium. Further study is warranted to assess the actual changes in myocardial O2 delivery.

Correction: Comparing Classroom Instruction to Individual Instruction as an Approach to Teach Avatar-Based Patient Monitoring With Visual Patient: Simulation Study.

[This corrects the article DOI: 10.2196/17922.].

Situation Awareness-Oriented Patient Monitoring with Visual Patient Technology: A Qualitative Review of the Primary Research.

Visual Patient technology is a situation awareness-oriented visualization technology that translates numerical and waveform patient monitoring data into a new user-centered visual language. Vital sign values are converted into colors, shapes, and rhythmic movements-a language humans can easily perceive and interpret-on a patient avatar model in real time. In this review, we summarize the current state of the research on the Visual Patient, including the technology, its history, and its scientific context. We also provide a summary of our primary research and a brief overview of research work on similar user-centered visualizations in medicine. In several computer-based studies under various experimental conditions, Visual Patient transferred more information per unit time, increased perceived diagnostic certainty, and lowered perceived workload. Eye tracking showed the technology worked because of the way it synthesizes and transforms vital sign information into new and logical forms corresponding to the real phenomena. The technology could be particularly useful for improving situation awareness in settings with high cognitive demand or when users must make quick decisions. This comprehensive review of Visual Patient research is the foundation for an evaluation of the technology in clinical applications, starting with a high-fidelity simulation study in early 2020.

Comparing Classroom Instruction to Individual Instruction as an Approach to Teach Avatar-Based Patient Monitoring With Visual Patient: Simulation Study.

BACKGROUND: Visual Patient is an avatar-based alternative to standard patient monitor displays that significantly improves the perception of vital signs. Implementation of this technology in larger organizations would require it to be teachable by brief class instruction to large groups of professionals. Therefore, our study aimed to investigate the efficacy of such a large-scale introduction to Visual Patient. OBJECTIVE: In this study, we aimed to compare 2 different educational methods, one-on-one instruction and class instruction, for training anesthesia providers in avatar-based patient monitoring. METHODS: We presented 42 anesthesia providers with 30 minutes of class instruction on Visual Patient (class instruction group). We further selected a historical sample of 16 participants from a previous study who each received individual instruction (individual instruction group). After the instruction, the participants were shown monitors with either conventional displays or Visual Patient displays and were asked to interpret vital signs. In the class instruction group, the participants were shown scenarios for either 3 or 10 seconds, and the numbers of correct perceptions with each technology were compared. Then, the teaching efficacy of the class instruction was compared with that of the individual instruction in the historical sample by 2-way mixed analysis of variance and mixed regression. RESULTS: In the class instruction group, when participants were presented with the 3-second scenario, there was a statistically significant median increase in the number of perceived vital signs when the participants were shown the Visual Patient compared to when they were shown the conventional display (3 vital signs, P<.001; effect size -0.55). No significant difference was found for the 10-second scenarios. There was a statistically significant interaction between the teaching intervention and display technology in the number of perceived vital signs (P=.04; partial η2=.076). The mixed logistic regression model for correct vital sign perception yielded an odds ratio (OR) of 1.88 (95% CI 1.41-2.52; P<.001) for individual instruction compared to class instruction as well as an OR of 3.03 (95% CI 2.50-3.70; P<.001) for the Visual Patient compared to conventional monitoring. CONCLUSIONS: Although individual instruction on Visual Patient is slightly more effective, class instruction is a viable teaching method; thus, large-scale introduction of health care providers to this novel technology is feasible.

Rotation thromboelastometry (ROTEM) stability and reproducibility over time.

BACKGROUND: Thromboelastometry is a whole blood assay performed to evaluate the viscoelastic properties during blood clot formation and lysis. Rotation thromboelastography (ROTEM), Pentapharm GmbH, Munich, Germany) has overcome some of the limitations of classic thromboelastography. So far, no clinical validation on reproducibility (inter- and intra-assay variability) and sample stability over time has been published. METHODS: To evaluate the pre-analytic aspects, sample stability over time was assessed in 48 patients in eight age groups. Citrated blood was stored at room temperature. Tests measured every 30 min from T 0 min up to T 120 min on two ROTEM devices were INTEM (ellagic acid activated intrinsic pathway), EXTEM (tissue factor-triggered extrinsic pathway) and FIBTEM (with platelet inhibitor (cytochalasin D) evaluating the contribution of fibrinogen to clot formation). Precision by intra- and inter-assay variability was evaluated at two points of time in 10 volunteers. Finally, reference intervals and effect of age and sex were evaluated. RESULTS: Blood was stable over 120 min and no significant differences in ROTEM results were found. Maximum clot firmness measurements had a coefficient of variation of <3% for EXTEM, <5% for INTEM and <6% for FIBTEM. For clot formation time, the coefficient of variation was <4% for EXTEM and <3% for INTEM. Coefficient of variation for angle alpha was <3% for EXTEM and <6% for INTEM. The coefficient of variation for clotting time was <15% for both EXTEM and INTEM. Small but significant differences between ROTEM devices were found for maximum clot firmness in FIBTEM and INTEM as well as clot formation time and alpha angle in INTEM. CONCLUSIONS: ROTEM yields stable results over 120 min with a minimal variability on the same ROTEM device. However, small but significant differences between ROTEM devices were observed. Analysis should be performed on the same ROTEM device if small differences are of importance for treatment.