Joseph Rinehart

Technical communication: respiratory variation in pulse pressure and plethysmographic waveforms: intraoperative applicability in a North American academic center.

Dynamic variables are the best predictors of fluid responsiveness in patients under general anesthesia and mechanical ventilation; namely, respiratory variations in pulse pressure and in the plethysmographic waveform. However, these variables have potential limitations. Our aim was to evaluate their intraoperative applicability. We extracted clinical data from all anesthesia procedures performed at our institution in 2009 and identified the number of cases that presented predetermined conditions of application. Among the 12,308 procedures, 39% met the criteria for the noninvasive monitoring of variations in the plethysmographic waveform of which 23% had arterial lines and met the criteria for the invasive monitoring of variations in pulse pressure.

Accuracy and Precision of Continuous Noninvasive Arterial Pressure Monitoring Compared with Invasive Arterial Pressure: A Systematic Review and Meta-analysis

Background: Continuous noninvasive arterial pressure monitoring devices are available for bedside use, but the accuracy and precision of these devices have not been evaluated in a systematic review and meta-analysis. Methods: The authors performed a systematic review and meta-analysis of studies comparing continuous noninvasive arterial pressure monitoring with invasive arterial pressure monitoring. Random-effects pooled bias and SD of bias for systolic arterial pressure, diastolic arterial pressure, and mean arterial pressure were calculated. Continuous noninvasive arterial pressure monitoring was considered acceptable if pooled estimates of bias and SD were not greater than 5 and 8 mmHg, respectively, as recommended by the Association for the Advancement of Medical Instrumentation. Results: Twenty-eight studies (919 patients) were included. The overall random-effect pooled bias and SD were −1.6 ± 12.2 mmHg (95% limits of agreement −25.5 to 22.2 mmHg) for systolic arterial pressure, 5.3 ± 8.3 mmHg (−11.0 to 21.6 mmHg) for diastolic arterial pressure, and 3.2 ± 8.4 mmHg (−13.4 to 19.7 mmHg) for mean arterial pressure. In 14 studies focusing on currently commercially available devices, bias and SD were −1.8 ± 12.4 mmHg (−26.2 to 22.5 mmHg) for systolic arterial pressure, 6.0 ± 8.6 mmHg (−10.9 to 22.9 mmHg) for diastolic arterial pressure, and 3.9 ± 8.7 mmHg (−13.1 to 21.0 mmHg) for mean arterial pressure. Conclusions: The results from this meta-analysis found that inaccuracy and imprecision of continuous noninvasive arterial pressure monitoring devices are larger than what was defined as acceptable. This may have implications for clinical situations where continuous noninvasive arterial pressure is being used for patient care decisions.

Variability in practice and factors predictive of total crystalloid administration during abdominal surgery: retrospective two-centre analysis

BACKGROUND Variation in clinical practice in the perioperative environment and intensive care unit is a major challenge facing modern medicine. The objective of the present study was to analyse intraoperative crystalloid administration practices at two academic medical centres in the USA. METHODS We extracted clinical data from patients undergoing intra-abdominal procedures performed at UC Irvine (UCI) and Vanderbilt University (VU) Medical Centres. Limiting data to uncomplicated elective surgery with minimal blood loss, we quantified variability in fluid administration within individual providers, between providers, and between types of procedures using a corrected coefficient of variation (cCOV). Regression was performed using a general linear model to determine factors most predictive of fluid administration. RESULTS For provider analysis and model building, 1327 UCI and 4585 VU patients were used. The average corrected crystalloid infusion rate across all providers at both institutions was 7.1 (sd 4.9) ml kg(-1) h(-1), an overall cCOV of 70%. Individual providers ranged from 2.3 (sd 3.7) to 14 (sd 10) ml kg(-1) h(-1). The final regression model strongly favoured personnel as predictors over other patient predictors. CONCLUSIONS Wide variability in crystalloid administration was observed both within and between individual anaesthesia providers, which might contribute to variability in surgical outcomes.

Impact Assessment of Perioperative Point-of-Care Ultrasound Training on Anesthesiology Residents

Background:The perioperative surgical home model highlights the need for trainees to include modalities that are focused on the entire perioperative experience. The focus of this study was to design, introduce, and evaluate the integration of a whole-body point-of-care (POC) ultrasound curriculum (Focused periOperative Risk Evaluation Sonography Involving Gastroabdominal Hemodynamic and Transthoracic ultrasound) into residency training. Methods:For 2 yr, anesthesiology residents (n = 42) received lectures using a model/simulation design and half were also randomly assigned to receive pathology assessment training. Posttraining performance was assessed through Kirkpatrick levels 1 to 4 outcomes based on the resident satisfaction surveys, multiple-choice tests, pathologic image evaluation, human model testing, and assessment of clinical impact via review of clinical examination data. Results:Evaluation of the curriculum demonstrated high satisfaction scores (n = 30), improved content test scores (n = 37) for all tested categories (48 ± 16 to 69 ± 17%, P < 0.002), and improvement on human model examinations. Residents randomized to receive pathology training (n = 18) also showed higher scores compared with those who did not (n = 19) (9.1 ± 2.5 vs. 17.4 ± 3.1, P < 0.05). Clinical examinations performed in the organization after the study (n = 224) showed that POC ultrasound affected clinical management at a rate of 76% and detected new pathology at a rate of 31%. Conclusions:Results suggest that a whole-body POC ultrasound curriculum can be effectively taught to anesthesiology residents and that this training may provide clinical benefit. These results should be evaluated within the context of the perioperative surgical home.

Accuracy of continuous noninvasive hemoglobin monitoring: a systematic review and meta-analysis.

BACKGROUND:Noninvasive hemoglobin (Hb) monitoring devices are available in the clinical setting, but their accuracy and precision against central laboratory Hb measurements have not been evaluated in a systematic review and meta-analysis. METHODS:We conducted a comprehensive search of the literature (2005 to August 2013) with PubMed, Web of Science and the Cochrane Library, reviewed references of retrieved articles, and contacted manufactures to identify studies assessing the accuracy of noninvasive Hb monitoring against central laboratory Hb measurements. Two independent reviewers assessed the quality of studies using recommendations for reporting guidelines and quality criteria for method comparison studies. Pooled mean difference and standard deviation (SD) (95% limits of agreement) across studies were calculated using the random-effects model. Heterogeneity was assessed using the I2 statistic. RESULTS:A total of 32 studies (4425 subjects, median sample size of 44, ranged from 10 to 569 patients per study) were included in this meta-analysis. The overall pooled random-effects mean difference (noninvasive—central laboratory) and SD were 0.10 ± 1.37 g/dL (−2.59 to 2.80 g/dL, I2 = 95.9% for mean difference and 95.0% for SD). In subgroup analysis, pooled mean difference and SD were 0.39 ± 1.32 g/dL (−2.21 to 2.98 g/dL, I2 = 93.0%, 71.4%) in 13 studies conducted in the perioperative setting and were −0.51 ± 1.59 g/dL (−3.63 to 2.62 g/dL, I2 = 83.7%, 96.4%) in 5 studies performed in the intensive care unit setting. CONCLUSIONS:Although the mean difference between noninvasive Hb and central laboratory measurements was small, the wide limits of agreement mean clinicians should be cautious when making clinical decisions based on these devices.

Closed-loop fluid administration compared to anesthesiologist management for hemodynamic optimization and resuscitation during surgery: an in vivo study.

BACKGROUND: Closed-loop systems have been designed to assist practitioners in maintaining stability of various physiologic variables in the clinical setting. In this context, we recently performed in silico testing of a novel closed-loop fluid management system that is designed for cardiac output and pulse pressure variation monitoring and optimization. The goal of the present study was to assess the effectiveness of this newly developed system in optimizing hemodynamic variables in an in vivo surgical setting. METHODS: Sixteen Yorkshire pigs underwent a 2-phase hemorrhage protocol and were resuscitated by either the Learning Intravenous Resuscitator closed-loop system or an anesthesiologist. Median hemodynamic values and variation of hemodynamics were compared between groups. RESULTS: Cardiac index (in liters per minute per square meter) and stroke volume index (in milliliters per square meter) were higher in the closed-loop group compared with the anesthesiologist group over the protocol (3.7 [3.4–4.1] vs 3.5 [3.2–3.9]; 95% Wald confidence interval, −0.5 to −0.23; P < 0.0005 and 40 [34–45] vs 36 [31–38]; 95% Wald confidence interval, −5.9 to −3.1; P < 0.0005, respectively). There was no significant difference in total fluid administration between the closed-loop and anesthesiologist groups (3685 [3230–4418] vs 3253 [2735–3926] mL; 95% confidence interval, −1651 to 431; P = 0.28). Closed-loop group animals also had lower coefficients of variance of cardiac index and stroke volume index during the protocol (11% [10%–16%] vs 22% [18%–23%]; confidence interval, 0.8%–12.3%; P = 0.02 and 11% [8%–16%] vs 17% [13%–21%]; confidence interval, 0.2%–11.4%; P = 0.04, respectively). CONCLUSION: This in vivo study building on previous simulation work demonstrates that the closed-loop fluid management system used in this experiment can perform fluid resuscitation during mild and severe hemorrhages and is able to maintain high cardiac output and stroke volume while reducing hemodynamic variability.

Intraoperative Stroke Volume Optimization Using Stroke Volume, Arterial Pressure, and Heart Rate: Closed-Loop (Learning Intravenous Resuscitator) Versus Anesthesiologists

OBJECTIVE The authors compared the performance of a group of anesthesia providers to closed-loop (Learning Intravenous Resuscitator [LIR]) management in a simulated hemorrhage scenario using cardiac output monitoring. DESIGN A prospective cohort study. SETTING In silico simulation. PARTICIPANTS University hospital anesthesiologists and the LIR closed-loop fluid administration system. INTERVENTIONS Using a patient simulator, a 90-minute simulated hemorrhage protocol was run, which included a 1,200-mL blood loss over 30 minutes. Twenty practicing anesthesiology providers were asked to manage this scenario by providing fluids and vasopressor medication at their discretion. The simulation program was also run 20 times with the LIR closed-loop algorithm managing fluids and an additional 20 times with no intervention. MEASUREMENTS AND MAIN RESULTS Simulated patient weight, height, heart rate, mean arterial pressure, and cardiac output (CO) were similar at baseline. The mean stroke volume, the mean arterial pressure, CO, and the final CO were higher in the closed-loop group than in the practitioners group, and the coefficient of variance was lower. The closed-loop group received slightly more fluid (2.1 v 1.9 L, p < 0.05) than the anesthesiologist group. CONCLUSIONS Despite the roughly similar volumes of fluid given, the closed-loop maintained more stable hemodynamics than the practitioners primarily because the fluid was given earlier in the protocol and CO optimized before the hemorrhage began, whereas practitioners tended to resuscitate well but only after significant hemodynamic change indicated the need. Overall, these data support the potential usefulness of this closed-loop algorithm in clinical settings in which dynamic predictors are not available or applicable.

Goal-Directed fluid therapy with closed-loop assistance during moderate risk surgery using noninvasive cardiac output monitoring: A pilot study

BACKGROUND Goal directed fluid therapy (GDFT) has been shown to improve outcomes in moderate to high-risk surgery. However, most of the present GDFT protocols based on cardiac output optimization use invasive devices and the protocols may require significant practitioner attention and intervention to apply them accurately. The aim of this prospective pilot study was to evaluate the clinical feasibility of GDFT using a closed-loop fluid administration system with a non-invasive cardiac output monitoring device (Nexfin™, BMEYE, Amsterdam, Netherlands). METHODS Patients scheduled for elective moderate risk surgery under general anaesthesia were enrolled. The primary anaesthesia team managing the case selected GDFT targets using the controller interface and all patients received a baseline 3 ml kg(-1) h(-1) crystalloid infusion. Colloid solutions were delivered by the closed-loop system for intravascular volume expansion using data from the Nexfin™ monitor. Compliance with GDFT management was defined as acceptable when a patient spent more than 85% of the surgery time in a preload independent state (defined as pulse pressure variation <13%) or when average cardiac index during surgery was >2.5 litre min(-1) m(-2). RESULTS A total of 13 patients were included in the study group. All patients met the established criteria for delivery of GDFT for greater than 85% of case time. The median length of stay in the hospital was 5 [3-6] days. CONCLUSION In this pilot study, GDFT management using the closed-loop fluid administration system with a non-invasive CO monitoring device was feasible and maintained a high rate of protocol compliance. CLINICAL TRIAL REGISTRATION NCT02020863.

Auscultation versus Point-of-care Ultrasound to Determine Endotracheal versus Bronchial Intubation: A Diagnostic Accuracy Study.

Background:Unrecognized malposition of the endotracheal tube (ETT) can lead to severe complications in patients under general anesthesia. The focus of this double-blinded randomized study was to assess the accuracy of point-of-care ultrasound in verifying the correct position of the ETT and to compare it with the accuracy of auscultation. Methods:Forty-two adult patients requiring general anesthesia with ETT were consented. Patients were randomized to right main bronchus, left main bronchus, or tracheal intubation. After randomization, the ETT was placed via fiber-optic visualization. Next, the location of the ETT was assessed using auscultation by a separate blinded anesthesiologist, followed by an ultrasound performed by a third blinded anesthesiologist. Ultrasound examination included assessment of tracheal dilation via cuff inflation with air and evaluation of pleural lung sliding. Statistical analysis included sensitivity, specificity, positive predictive value, negative predictive value, and interobserver agreement for the ultrasound examination (95% CI). Results:In differentiating tracheal versus bronchial intubations, auscultation showed a sensitivity of 66% (0.39 to 0.87) and a specificity of 59% (0.39 to 0.77), whereas ultrasound showed a sensitivity of 93% (0.66 to 0.99) and specificity of 96% (0.79 to 1). Identification of tracheal versus bronchial intubation was 62% (26 of 42) in the auscultation group and 95% (40 of 42) in the ultrasound group (P = 0.0005) (CI for difference, 0.15 to 0.52), and the McNemar comparison showed statistically significant improvement with ultrasound (P < 0.0001). Interobserver agreement of ultrasound findings was 100%. Conclusion:Assessment of trachea and pleura via point-of-care ultrasound is superior to auscultation in determining the location of ETT.

Closed-loop fluid resuscitation: robustness against weight and cardiac contractility variations.

BACKGROUND: Surgical patients present with a wide variety of body sizes and blood volumes, have large differences in baseline volume status, and may exhibit significant differences in cardiac function. Any closed-loop fluid administration system must be robust against these differences. In the current study, we tested the stability and robustness of the closed-loop fluid administration system against the confounders of body size, starting volume status, and cardiac contractility using control engineering methodology. METHODS: Using an independently developed previously published hemodynamic simulation model that includes blood volumes and cardiac contractility, we ran a Monte-Carlo simulation series with variation in starting blood volume and body weight (phase 1, weight 35–100 kg), and starting blood volume and cardiac contractility (phase 2, contractility from 1500 [severe heart failure] to 6000 [hyperdynamic]). The performance of the controller in resuscitating to the target set point was evaluated in terms of milliliters of blood volume error from optimal, with <250 mL of error defined as “successful.” RESULTS: One thousand simulations were run for each of the 2 phases of the study. The phase 1 mean blood volume error ± SD from optimal was 25 ± 59 mL. The phase 2 mean blood volume error from optimal was −60 ± 89 mL. The lower 95% Clopper-Pearson binomial confidence interval for resuscitation to within 250 mL of optimal blood volume for phase 1 and 2 was 99.6% and 97.1%, respectively. CONCLUSION: The results indicate that the controller is highly effective in targeting optimal blood and stroke volumes, regardless of weight, contractility or starting blood volume.