Alexandre Joosten

Accuracy and precision of non-invasive cardiac output monitoring devices in perioperative medicine: a systematic review and meta-analysis†

Cardiac output (CO) measurement is crucial for the guidance of therapeutic decisions in critically ill and high-risk surgical patients. Newly developed completely non-invasive CO technologies are commercially available; however, their accuracy and precision have not recently been evaluated in a meta-analysis. We conducted a systematic search using PubMed, Cochrane Library of Clinical Trials, Scopus, and Web of Science to review published data comparing CO measured by bolus thermodilution with commercially available non-invasive technologies including pulse wave transit time, non-invasive pulse contour analysis, thoracic electrical bioimpedance/bioreactance, and CO2 rebreathing. The non-invasive CO technology was considered acceptable if the pooled estimate of percentage error was <30%, as previously recommended. Using a random-effects model, sd, pooled mean bias, and mean percentage error were calculated. An I2 statistic was also used to evaluate the inter-study heterogeneity. A total of 37 studies (1543 patients) were included. Mean CO of both methods was 4.78 litres min−1. Bias was presented as the reference method minus the tested methods in 15 studies. Only six studies assessed the random error (repeatability) of the tested device. The overall random-effects pooled bias (limits of agreement) and the percentage error were −0,13 [−2.38 , 2.12] litres min−1 and 47%, respectively. Inter-study sensitivity heterogeneity was high (I2=83%, P<0.001). With a wide percentage error, completely non-invasive CO devices are not interchangeable with bolus thermodilution. Additional studies are warranted to demonstrate their role in improving the quality of care.

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.

Guiding Goal-Directed Therapy

Several studies have demonstrated that perioperative hemodynamic optimization (or “goal directed therapy”) using minimally invasive hemodynamic monitoring technologies has the ability to improve postoperative patients’ outcome with lower complication rates, shorter hospital lengths of stay, and lower cost of surgery. This specific concept of goal-directed therapy (GDT) uses perioperative cardiac output monitoring and manipulation of physiologic parameters (dynamic parameters of fluid responsiveness) to guide intravenous fluids and inotropic therapy with the goal of ensuring adequate tissue perfusion. Recently, the evidence related to the implementation of GDT strategies has been considered strong enough to allow for the creation of national recommendations in the UK, in France, and by the European Society of Anaesthesiology. The aims of the programs are to apply best practices to high-risk surgical patients and requires the participation of all clinicians involved in patients’ care. Considering the potential clinical and economic benefits of GDT protocols and the positive recommendations from influential scientific societies, more and more hospitals around the world have become interested in implementing hemodynamic optimization in their departments. This review provides the information about the evolution of hemodynamic monitoring from invasive to the more recent noninvasive devices, and how these devices can be used in the operating rooms through well-defined algorithms of GDT.

Crystalloid versus Colloid for Intraoperative Goal-directed Fluid Therapy Using a Closed-loop System: A Randomized, Double-blinded, Controlled Trial in Major Abdominal Surgery

Background: The type of fluid and volume regimen given intraoperatively both can impact patient outcome after major surgery. This two-arm, parallel, randomized controlled, double-blind, bi-center superiority study tested the hypothesis that when using closed-loop assisted goal-directed fluid therapy, balanced colloids are associated with fewer postoperative complications compared to balanced crystalloids in patients having major elective abdominal surgery. Methods: One hundred and sixty patients were enrolled in the protocol. All patients had maintenance-balanced crystalloid administration of 3 ml · kg–1 · h–1. A closed-loop system delivered additional 100-ml fluid boluses (patients were randomized to receive either a balanced-crystalloid or colloid solution) according to a predefined goal-directed strategy, using a stroke volume and stroke volume variation monitor. All patients were included in the analysis. The primary outcome was the Post-Operative Morbidity Survey score, a nine-domain scale, at day 2 postsurgery. Secondary outcomes included all postoperative complications. Results: Patients randomized in the colloid group had a lower Post-Operative Morbidity Survey score (median [interquartile range] of 2 [1 to 3] vs. 3 [1 to 4], difference –1 [95% CI, –1 to 0]; P < 0.001) and a lower incidence of postoperative complications. Total volume of fluid administered intraoperatively and net fluid balance were significantly lower in the colloid group. Conclusions: Under our study conditions, a colloid-based goal-directed fluid therapy was associated with fewer postoperative complications than a crystalloid one. This beneficial effect may be related to a lower intraoperative fluid balance when a balanced colloid was used. However, given the study design, the mechanism for the difference cannot be determined with certainty.

Continuous noninvasive hemoglobin monitoring: ready for prime time?

Purpose of reviewDetermination of hemoglobin (Hb) concentration is essential for the detection of anemia and hemorrhage and is widely used to evaluate a patient for a possible blood transfusion. Although commonly accepted as intrinsic to the process, traditional laboratory measurements of Hb are invasive, intermittent, and time-consuming. Noninvasive Hb (NIHb)-monitoring devices have recently become available and promise the potential for detecting sudden changes in a patients Hb level. In addition to reduced delays in clinical intervention, these devices also allow for a reduction in patient discomfort, infection risk, required personnel, and long-term costs. Unfortunately, it has been shown that many clinical factors can influence their accuracy. Recent findingsMany studies have been published on the accuracy and precision of NIHb-monitoring devices in various clinical settings. A recent meta-analysis has shown a small mean difference but wide limits of agreement between NIHb and laboratory measurements, indicating that caution should be used by physicians when making clinical decisions based on this device. SummaryNIHb measurements may currently be considered to be a supplemental tool for monitoring trends in Hb concentration, but are not currently developed enough to replace an invasive approach. Moreover, further studies are still required before implementing NIHb in the clinical decision-making process. Specifically, no studies have demonstrated that this technology improves clinical outcomes or patient safety.

A Novel Mobile Phone Application for Pulse Pressure Variation Monitoring Based on Feature Extraction Technology: A Method Comparison Study in a Simulated Environment

BACKGROUND:Pulse pressure variation (PPV) can be used to assess fluid status in the operating room. This measurement, however, is time consuming when done manually and unreliable through visual assessment. Moreover, its continuous monitoring requires the use of expensive devices. Capstesia™ is a novel Android™/iOS™ application, which calculates PPV from a digital picture of the arterial pressure waveform obtained from any monitor. The application identifies the peaks and troughs of the arterial curve, determines maximum and minimum pulse pressures, and computes PPV. In this study, we compared the accuracy of PPV generated with the smartphone application Capstesia (PPVapp) against the reference method that is the manual determination of PPV (PPVman). METHODS:The Capstesia application was loaded onto a Samsung Galaxy S4TM phone. A physiologic simulator including PPV was used to display arterial waveforms on a computer screen. Data were obtained with different sweep speeds (6 and 12 mm/s) and randomly generated PPV values (from 2% to 24%), pulse pressure (30, 45, and 60 mm Hg), heart rates (60–80 bpm), and respiratory rates (10–15 breaths/min) on the simulator. Each metric was recorded 5 times at an arterial height scale X1 (PPV5appX1) and 5 times at an arterial height scale X3 (PPV5appX3). Reproducibility of PPVapp and PPVman was determined from the 5 pictures of the same hemodynamic profile. The effect of sweep speed, arterial waveform scale (X1 or X3), and number of images captured was assessed by a Bland-Altman analysis. The measurement error (ME) was calculated for each pair of data. A receiver operating characteristic curve analysis determined the ability of PPVapp to discriminate a PPVman > 13%. RESULTS:Four hundred eight pairs of PPVapp and PPVman were analyzed. The reproducibility of PPVapp and PPVman was 10% (interquartile range, 7%–14%) and 6% (interquartile range, 3%–10%), respectively, allowing a threshold ME of 12%. The overall mean bias for PPVappX1 was 1.1% within limits of −1.4% (95% confidence interval [CI], −1.7 to −1.1) to +3.5% (95% CI, +3.2 to +3.8). Averaging 5 values of PPVappX1 with a sweep speed of 12 mm/s resulted in the smallest bias (+0.6%) and the best limits of agreement (±1.3%). ME of PPVapp was <12% whenever 3, 4, or 5 pictures were taken to average PPVapp. The best predictive value for PPVapp to detect a PPVman > 13% was obtained for PPVappX1 by averaging 5 pictures showing a PPVapp threshold of 13.5% (95% CI, 12.9–15.2) and a receiver operating characteristic curve area of 0.989 (95% CI, 0.963–0.998) with a sensitivity of 97% and a specificity of 94%. CONCLUSIONS:Our findings show that the Capstesia PPV calculation is a dependable substitute for standard manual PPV determination in a highly controlled environment (simulator study). Further studies are warranted to validate this mobile feature extraction technology to predict fluid responsiveness in real conditions.

Impact of balanced tetrastarch raw material on perioperative blood loss: a randomized double blind controlled trial

BACKGROUND As 6% hydroxyethyl starch (HES) 130/0.40 or 130/0.42 can originate from different vegetable sources, they might have different clinical effects. The purpose of this prospective, randomized, double-blind controlled trial was to compare two balanced tetrastarch solutions, one maize-derived and one potato-derived, on perioperative blood loss in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). METHODS We randomly assigned 118 patients undergoing elective cardiac surgery into two groups, to receive either a maize- or a potato-derived HES solution. Study fluids were administered perioperatively (including priming of CPB) until the second postoperative day (POD#2) using a goal directed algorithm. The primary outcome was calculated postoperative blood loss up to POD#2. Secondary outcomes included short-term incidence of acute kidney injury (AKI), and long-term effect (up to one yr) on renal function. RESULTS Preoperative and intraoperative characteristics of the subjects were similar between groups. Similar volumes of HES were administered (1950 ml [1250-2325] for maize-HES and 2000 ml [1500-2700] for potato-HES; P=0.204). Calculated blood loss (504 ml [413-672] for maize-HES vs 530 ml [468-705] for potato-HES; P=0.107) and the need for blood components were not different between groups. The incidence of AKI was similar in both groups (P=0.111). Plasma creatinine concentration and glomerular filtration rates did vary over time, although changes were minimal. CONCLUSIONS Under our study conditions, HES 130/0.4 or 130/0.42 raw material did not have a significant influence on perioperative blood loss. Moreover, we did not find any effect of tetrastarch raw material composition on short and long-term renal function. CLINICAL TRIAL REGISTRATION EudraCT number: 2011-005920-16.

Perioperative goal directed therapy: Evidence and compliance are two sides of the same coin

Goal directed therapy (GDT) based on the optimization of cardiac output (CO) or dynamic parameters of fluid responsiveness have been shown to improve clinical outcome and to decrease the overall cost related to major surgery. This concept has recently been recommended by professional societies in the UK, in France, and in Europe. The most significant implementation has been made in the UK where the National Institute of Health and Clinical Excellence has endorsed the use of CO monitoring and optimization for highrisk surgical patients and financial incentives have even been created by the National Health Service to ensure that hospitals are adopting this strategy as standard of care for at least 80% of eligible patients. Despite the overwhelming support for its use, there remains significant variability in practice with a low adoption of GDT protocols among clinicians. One possible reason may be that protocols are timeand attention-consuming; even under optimal study conditions, ‘‘complete’’ adherence to protocol is often not greater than 50%. Another explanation may be the learning curve which is expected for applying such protocols correctly in clinical practice. This learning curve and the difficulty to adhere consistently to the protocol may thus be one of the major weaknesses of this approach, a fact highlighted by

Comparison of the ability of esCCO and Volume View to measure trends in cardiac output in patients undergoing cardiac surgery

BACKGROUND Cardiac output (CO) is a physiological variable that should be monitored during cardiac surgery. The purpose of this study was to assess the trending ability of two CO monitors, esCCO (Nihon Kohden™, Tokyo, Japan) and Volume View (VV) (Edwards Lifesciences, Irvine, USA). METHODS A total of 19 patients were included in the study. Before cardiopulmonary bypass (CPB), CO was measured simultaneously using both esCCO and VV devices before and after three CO-modifying manoeuvres (passive leg raise [PLR], the end expiratory occlusion test [EEOT] and positive end expiratory pressure [PEEP] at 10 cm H₂O). Five CO values for esCCO and three for VV were averaged and compared during a one-minute period of time before and after each manoeuvre. RESULTS A total of 114 paired readings were collected. Median CO values were 4.3 L min⁻¹ (IQR: 3.8; 5.2) and 3.8 L min⁻¹ (IQR: 3.5; 4.5) for esCCO and VV, respectively. The precision error was 1.4% (95% CI:1.0-1.7) for esCCO and 2.2% (95% CI: 1.8-2.7) for VV. The bias between esCCO and VV values was normally distributed (P = 0.0596). Between esCCO and VV, the mean bias was +0.6 L min⁻¹ with a Limit of Agreement (LOA) of -1.8 L min⁻¹ and +3.0 L min⁻¹. The concordance rate was 43% (95% CI: 29-58) between esCCO and VV. CONCLUSION Both single and trended measurements of CO using esCCO and VV were not in agreement. This large discrepancy leads one to the conclusion that any outcome study conducted with one of these devices cannot be applied to the other.

Next Generation of Method-Comparison Studies: Standardization of Data Presentation and Clinical Application Are a Goal to Reach.

e468 www.ccmjournal.org October 2015 • Volume 43 • Number 10 O’Brien et al (1) looked for additional signs supporting the diagnosis of vasospasm, based on intracranial pressure, brain tissue oxygenation, or brain perfusion imaging. Among 19 patients with a diagnosis of vasospasm, supportive signs suggestive of this diagnosis were absent in 10, among which eight had an LR between 3 and 3.6. Hyperemia has been reported in 42% of children in the first 8 days after TBI, with concomitant impaired cerebral autoregulation in most cases (4). Hyperemia and impaired autoregulation are associated with poor outcome (4). Hyperemia is probably involved in the frequently observed combination of intracranial hypertension and increased brain tissue oxygenation, also associated with poor outcome (5). In the present study, there is no doubt that several of the 19 children identified with vasospasm really had a vasospasm. However, there is insufficient evidence to confirm this diagnosis based on the criteria used. In light of the high prevalence of hyperemia and impaired cerebral autoregulation, and the low discriminative value of an LR ratio above 3, it is probable that several patients had hyperemia rather than vasospasm, especially those with an LR closer to 3. This limitation is of major importance, as the treatment strategy for each condition is quite different. We completely agree with O’Brien et al (1) that screening for vasospasm should be encouraged when caring for children with TBI and that TCD monitoring should be undertaken. However, although challenging, the distinction between hyperemia and vasospasm is important to make. In patients in whom TCD findings are not obvious, the use of additional modalities, such as brain tissue oxygen monitoring or imaging perfusion studies, is essential to ascertain the diagnosis of vasospasm and appropriately orientate the treatment. Dr. Emeriaud’s institution received grant support from Fonds de Recherche du Québec–Santé (Dr. Emeriaud’s research program is supported by a clinical research scholarship from Fonds de Recherche du Québec–Santé). The remaining authors have disclosed that they do not have any potential conflicts of interest.