Fluid responsiveness predicted by noninvasive Bioreactance-based passive leg raise test

Are We Always Right? Evaluation of the Performance and Knowledge of the Passive Leg Raise Test in Detecting Volume Responsiveness in Critical Care Patients: A National German Survey

Background: In hemodynamically unstable patients, the passive leg raise (PLR) test is recommended for use as a self-fluid challenge for predicting preload responsiveness. However, to interpret the hemodynamic effects and reliability of the PLR, the method of performing it is of the utmost importance. Our aim was to determine the current practice of the correct application and interpretation of the PLR in intensive care patients. Methods: After ethical approval, we designed a cross-sectional online survey with a short user-friendly online questionnaire. Using a random sample of 1903 hospitals in Germany, 182 hospitals with different levels of care were invited via an email containing a link to the questionnaire. The online survey was conducted between December 2021 and January 2022. All critical care physicians from different medical disciplines were surveyed. We evaluated the correct points of concern for the PLR, including indication, contraindication, choice of initial position, how to interpret and apply the changes in cardiac output, and the limitations of the PLR. Results: A total of 292 respondents participated in the online survey, and 283/292 (97%) of the respondents completed the full survey. In addition, 132/283 (47%) were consultants and 119/283 (42%) worked at a university medical center. The question about the performance of the PLR was answered correctly by 72/283 (25%) of the participants. The limitations of the PLR, such as intra-abdominal hypertension, were correctly selected by 150/283 (53%) of the participants. The correct effect size (increase in stroke volume ≥ 10%) was correctly identified by 217/283 (77%) of the participants. Conclusions: Our results suggest a considerable disparity between the contemporary practice of the correct application and interpretation of the PLR and the practice recommendations from recently published data at German ICUs.

Dynamic monitoring tools for patients admitted to the emergency department with circulatory failure: narrative review with panel-based recommendations

Intravenous fluid therapy is commonly administered in the emergency department (ED). Despite the deleterious potential of over- and under-resuscitation, professional society guidelines continue to recommend administering a fixed volume of fluid in initial resuscitation. Predicting whether a specific patient will respond to fluid therapy remains one of the most important, but challenging questions that ED clinicians face in clinical practice. Surrogate parameters (i.e. blood pressure and heart rate), are widely used in usual care to estimate changes in stroke volume (SV). Due to their inadequacy in estimating SV, noninvasive techniques (e.g. bioreactance, echocardiography, noninvasive finger cuff technology), have been proposed as a more accurate and readily deployable method for assessing flow and preload responsiveness. Dynamic monitoring systems based on cardiac preload challenge and assessment of SV, by using noninvasive and continuous methods, provide more accurate, feasible, efficient, and reasonably accurate strategy for prediction of fluid responsiveness than static measurements. In this article, we aimed to analyze the different methods currently available for dynamic monitoring of preload responsiveness.

Manually Controlled, Continuous Infusion of Phenylephrine or Norepinephrine for Maintenance of Blood Pressure and Cardiac Output During Spinal Anesthesia for Cesarean Delivery: A Double-Blinded Randomized Study

BACKGROUND

To counteract the vasoplegia induced by spinal anesthesia (SA) and maintain blood pressure (BP) during cesarean delivery, phenylephrine is currently recommended, but norepinephrine might offer superior preservation of cardiac output. We aimed to compare the hemodynamic effects of phenylephrine and norepinephrine administered by manually adjusted continuous infusion during elective cesarean delivery.

METHODS

In this pragmatic, parallel-group, double-blind randomized controlled trial, 124 parturients scheduled for elective cesarean delivery under SA in a tertiary maternity in France, between February 2019 and December 2020, were randomized to receive norepinephrine at a starting rate of 0.05 μg·kg -1 ·min -1 (n = 62) or phenylephrine at a starting rate of 0.5 μg·kg -1 ·min -1 (n = 62). In both groups, the vasopressor infusion rate was then manually adjusted to maintain maternal systolic BP above 90% of the baseline value. The primary outcome, the change in cardiac index (CI) measured by thoracic bioreactance from SA to umbilical cord clamping, was analyzed through repeated measures analysis of variance and post hoc t tests. Secondary outcomes included maternal BP and neonatal outcomes.

RESULTS

In the norepinephrine group, cardiac index was maintained between 90% and 100% of baseline from SA to umbilical cord clamping, whereas it was maintained at significantly lower values (81%-88%) in the phenylephrine group ( P = .001). The percentage of elapsed time with a mean maternal BP <65 mm Hg and with systolic BP <80% of the baseline value was higher in the phenylephrine group: 2.9% (7.3) vs 0.5% (1.8) (absolute risk difference [ARD], -2.4%; 95% confidence interval, -4.4 to -0.5; P = .012) and 8.5% (16.6) vs 2.3% (5.2) (ARD, -6.2%; 95% confidence interval, -10.6 to -1.8; P = .006). Excluding parturients with gestational diabetes, severe neonatal hypoglycemia was more common in the phenylephrine group at 19.6% (9/46) vs 4.1% (2/49) ( P = .02). The other neonatal outcomes did not differ significantly between the groups.

CONCLUSIONS

When administered by manually adjusted infusion during SA for cesarean delivery, norepinephrine was associated with a higher CI; both infusions were effective for maintaining BP.

Can passive leg raise predict the response to fluid resuscitation in ED?

Objective

Passive leg raise (PLR) can be used as a reversible preload challenge to stratify patients according to preload response. We aim to evaluate the accuracy of PLR, monitored by a non-invasive cardiac output monitor in predicting to response to fluid resuscitation in emergency department (ED).

Methods

We recruited adult patients planned to receive a resuscitation fluid bolus. Patients were monitored using a thoracic electrical bioimpedance (TEB) cardiac output monitor (Niccomo, Medis, Germany). A 3-min PLR was carried out before and after fluid infusion. Stroke volume changes (ΔSV) were calculated and a positive response was defined as ≥ 15% increase.

Results

We recruited 39 patients, of which 37 were included into the analysis. The median age was 63 (50–77) years and 19 patients were females. 17 patients (46%) were fluid responders compared to 11 (30%) with positive response to PLR1. ΔSV with PLR1 and fluid bolus showed moderate correlation (r = 0.47, 95% confidence interval, CI 0.17–0.69) and 62% concordance rate. For the prediction of the response to a fluid bolus the PLR test had a sensitivity of 41% (95% CI 22–64) and specificity of 80% (95% CI 58–92) with an area under the curve of 0.59 (95% CI 0.41–0.78). None of the standard parameters showed a better predictive ability compared to PLR.

Conclusion

Using TEB, ΔSV with PLR showed a moderate correlation with fluid bolus, with a limited accuracy to predict fluid responsiveness. The PLR test was a better predictor of fluid responsiveness than the parameters commonly used in emergency care (such as heart rate and blood pressure). These data suggest the potential for a clinical trial in sepsis comparing TEB monitored, PLR directed fluid management with standard care.

Noninvasive Bioreactance-Based Fluid Management Monitoring: A Review of Literature

Body fluid balance is an independent predictor of mortality. For each liter of fluid over and above 5 L, risk-adjusted excess mortality is seen. Mortality increased by 2.3% for each 1 L of fluid and hospital costs increased by $999. Accordingly, most recent guidelines have endorsed dynamic modeling. Passive leg raising-induced increase of aortic blood flow ≥ 10% predicts fluid responsiveness with a sensitivity of 97% and a specificity of 94%. Thus, passive leg raising is often used as gold standard for validation of other procedures (though it's usefulness to assess respiratory variation in vena cava is not conclusive). STARLING, a device based on bioreactance, works on phase shift or time delay while bioimpedance works on the amplitude of the thoracic impedance. Unlike bioimpedance, bioreactance is not affected by the size of the patient, thoracic fluids, or position of sensors.

STARLING is equipped with four sensor pads. Each pad contains two sensors, the outer sensor is a transmitting electrode and the inner sensor is a receiving electrode. The STARLING monitor induces a 75-KHz AC current. It then measures the time delay/phase shift.

STARLING system, a bioreactance-based dynamic assessment system for fluid responsiveness, predicts it accurately, precisely, and noninvasively. It reduces invasive risks and is independently validated against pulmonary artery catheter. It is not affected by vasopressors or shock and has wide range of application.

Shock Management Without Formal Fluid Responsiveness Assessment: A Retrospective Analysis of Fluid Responsiveness and Its Outcomes

BACKGROUND

In order to quantify fluid administration and evaluate the clinical consequences of conservative fluid management without hemodynamic monitoring in undifferentiated shock, we analyzed previously collected data from a study of carotid Doppler monitoring as a predictor of fluid responsiveness (FR).

METHODS

This study was a retrospective analysis of data collected from a single tertiary academic center from a previous study. Seventy-four patients were included for post-hoc analysis, and 52 of them were identified as fluid responsive (cardiac output increase > 10% with passive leg raise) according to NICOMTM bioreactance monitoring (Cheetah Medical, Newton Center, MA, USA). Treating teams provided standard of care conservative fluid resuscitation but were blinded to independently performed FR testing results. Outcomes were compared between fluid responsive and fluid non-responsive patients. Primary outcome measures were volume fluids administered and net fluid balance 24- and 72-hour post-FR assessment. Secondary outcome measures included change in vasopressor requirements, mean peak lactate levels, length of hospital/intensive care unit stay, acute respiratory failure, hemodialysis requirement, and durations of vasopressors and mechanical ventilation.

RESULTS

Mean fluids administered within 72 hours were similar between fluid non-responsive and fluid responsive patients (139 mL/kg [95% confidence interval [CI]: 102.00-175.00] vs. 136 mL/kg [95% CI: 113.00-158.00], p = 0.92, respectively). We observed an insignificant trend toward higher 28-day mortality among fluid non-responsive patients (36% vs. 19%, p = 0.14). Volume of fluids administered significantly correlated with adverse outcomes such as increased hemodialysis requirements (32 patients, 43%), (odds ratio [OR] = 1.7200, p = 0.0018). Subgroup analysis suggested administering ≥ 30 mL/kg fluids to fluid responsive patients had a trend toward increased mortality (25% vs. 0%, p = 0.09) and a significant increase in hemodialysis (55% vs. 17%, p = 0.024).

CONCLUSIONS

Without formal FR assessment, similar amounts of total fluids were administered in both fluid responsive and non-responsive patients. As greater volumes of intravenous fluids administered were associated with adverse outcomes, we suggest that dedicated FR assessment may be a beneficial utility in early shock resuscitation.

Application of perioperative hemodynamics today and potentials for tomorrow

Hemodynamic (HD) monitoring remains integral to the assessment and management of perioperative and critical care patients. This review article seeks to provide an update on the different types of flow-guided HD monitoring technologies available, highlight their limitations, and review the therapies associated with the application of these technologies. Additionally, we will also comment on the expanding roles of HD monitoring in the future.

Agreement of Bioreactance Cardiac Output Monitoring With Thermodilution in Healthy Standing Horses

Bioreactance is the continuous analysis of transthoracic voltage variation in response to an applied high frequency transthoracic current and was recently introduced for non-invasive cardiac output measurement (NICOM). We evaluated NICOM compared to thermodilution (TD) in adult horses. Six healthy horses were used for this prospective, blinded, experimental study. Cardiac output (CO) measurements were performed simultaneously using TD and the bioreactance method. Different cardiac output scenarios were established using xylazine (0.5 mg/kg IV) and dobutamine (1.5–3 mcg/kg/min). Statistical analysis was performed by calculating the concordance rate, performing a regression analysis, Pearson correlation, and Bland Altman. The TD-based CO and NICOM values were highly correlated for low, normal and high CO values with an overall correlation coefficient. A 4-quadrant plot showed an 89% rate of concordance. The linear regression calculated a relationship between NICOM and TDCO of Y = 0.4874 · X + 0.5936. For the corrected Bland Altman agreement, the mean bias and lower/upper limits of agreement were −0.26 and −3.88 to 3.41 L/min, respectively. Compared to TD, bioreactance- based NICOM showed good accuracy at induced low, normal, and high CO states in normal horses. Future studies performed under more clinical conditions will show if this monitor can help to assess hemodynamic status and guide therapy in horses in ICU settings and under general anesthesia.

Effects on cerebral blood flow of position changes, hyperoxia, CO2 partial pressure variations and the Valsalva manoeuvre: A study in healthy volunteers

BACKGROUND

Maintaining adequate blood pressure to ensure proper cerebral blood flow (CBF) during surgery is challenging. Induced mild hypotension, sitting position or unavoidable intra-operative circumstances such as haemorrhage, added to variations in carbon dioxide and oxygen tensions, may influence perfusion. Several of these circumstances may coincide and it is unclear how these may affect CBF.

OBJECTIVE

To describe the variation in transcranial Doppler and regional cerebral oxygen saturation (rSO2), as a surrogate of CBF, after cardiac preload and gravitational positional changes.

DESIGN

Observational study.

SETTING

Operating room at Hospital Clínic de Barcelona.

VOLUNTEERS

Ten healthy volunteers, white, both sexes.

INTERVENTIONS

Measurements were performed in the supine, sitting and standing positions during hyperoxia, hypocapnia and hypercapnia protocols and after a Valsalva manoeuvre.

MAIN OUTCOME MEASURES

Cardiac index (CI), haemodynamic and respiratory variables, maximal and mean velocities (Vmax, Vmean) (transcranial Doppler) and rSO2 were acquired. Results were analysed using a generalised estimating equation technique.

RESULTS

CI increases more than 16% after a preload challenge were not accompanied by differences in rSO2 or Vmax - Vmean. With positional changes, Vmean decreased more than 7% (P = 0.042) from the supine to the seated position. Hyperoxia induced a cerebral rSO2 increase more than 6% (P = 0.0001) with decreases in Vmax, Vmean and CI values more than 3% (P = 0.001, 0.022 and 0.001) in the supine and standing position. During hypocapnia, CI rose more than 20% from supine to seated and standing (P = 0.0001) with a 4.5% decrease in cerebral rSO2 (P = 0.001) and a decrease of Vmax - Vmean more than 24% in all positions (P = 0.001). Hypercapnia increased cerebral rSO2 more than 17% (P = 0.001), Vmax - Vmean more than 30% (P = 0.001) with no changes in CI. After a Valsalva manoeuvre, rSO2 decreased more than 3% in the right hemisphere in the upright position (P = 0.001). Vmax - Vmean decreased more than 10% (P = 0.001) with no changes in CI.

CONCLUSION

CBF changes in response to cerebral vasoconstriction and vasodilatation were detected with rSO2 and transcranial Doppler in healthy volunteers during cardiac preload and in different body positions. Acute hypercapnia had a greater effect on recorded brain parameters than hypocapnia.

Bioimpedance analysis as a tool for hemodynamic monitoring: overview, methods and challenges

Recent advances in hemodynamic monitoring have seen the advent of non-invasive methods which offer ease of application and improve patient comfort. Bioimpedance Analysis or BIA is one of the currently employed non-invasive techniques for hemodynamic monitoring. Impedance Cardiography (ICG), one of the implementations of BIA, is widely used as a non-invasive procedure for estimating hemodynamic parameters such as stroke volume (SV) and cardiac output (CO). Even though BIA is not a new diagnostic technique, it has failed to gain consensus as a reliable measure of hemodynamic parameters. Several devices have emerged for estimating CO using ICG which are based on evolving methodologies and techniques to calculate SV. However, the calculations are generally dependent on the electrode configurations (whole body, segmental or localised) as well as the accuracy of different techniques in tracking blood flow changes. Blood volume changes, concentration of red blood cells, pulsatile velocity profile and ambient temperature contribute to the overall conductivity of blood and hence its impedance response during flow. There is a growing interest in investigating limbs for localised BIA to estimate hemodynamic parameters such as pulse wave velocity. As such, this paper summarises the current state of hemodynamic monitoring through BIA in terms of different configurations and devices in the market. The conductivity of blood flow has been emphasized with contributions from both volume and velocity changes during flow. Recommendations for using BIA in hemodynamic monitoring have been mentioned highlighting the suitable range of frequencies (1 kHz-1 MHz) as well as safety considerations for a BIA setup. Finally, current challenges in using BIA such as geometry assumption and inaccuracies have been discussed while mentioning potential advantages of a multi-frequency analysis to cover all the major contributors to blood's impedance response during flow.

Early hemodynamic assessment using NICOM in patients at risk of developing Sepsis immediately after emergency department triage

Background

One factor leading to the high mortality rate seen in sepsis is the subtle, dynamic nature of the disease, which can lead to delayed detection and under-resuscitation. This study investigated whether serial hemodynamic parameters obtained from a non-invasive cardiac output monitor (NICOM) predicts disease severity in patients at risk for sepsis.

Methods

Prospective clinical trial of the NICOM device in a convenience sample of adult ED patients at risk for sepsis who did not have obvious organ dysfunction at the time of triage. Hemodynamic data were collected immediately following triage and 2 hours after initial measurement and compared in two outcome groupings: (1) admitted vs. dehydrated, febrile, hypovolemicdischarged patients; (2) infectious vs. non-infectious sources. Receiver operator characteristic (ROC) curves were calculated to determine whether the NICOM values predict hospital admission better than a serum lactate.

Results

50 patients were enrolled, 32 (64 %) were admitted to the hospital. Mean age was 49.5 (± 16.5) years and 62 % were female. There were no significant associations between changes in hemodynamic variables and patient disposition from the ED or diagnosis of infection. Lactate was significantly higher in admitted patients and those with infection (p = 0.01, p = 0.01 respectively). The area under the ROC [95 % Confidence Intervals] for lactate was 0.83 [0.64–0.92] compared to 0.59 [0.41–0.73] for cardiac output (CO), 0.68 [0.49–0.80] for cardiac index (CI), and 0.63 [0.36–0.80] for heart rate (HR) for predicting hospital admission.

Conclusions

CO and CI, obtained at two separate time points, do not help with early disease severity differentiation of patients at risk for severe sepsis. Although mean HR was higher in those patients who were admitted, a serum lactate still served as a better predictor of patient admission from the ED.

Fluid Responsiveness in the Critically Ill Patient

Accurate assessment of intravascular volume status in critically ill patients remains a very challenging task. Recent data have shown adverse outcomes in critically ill patients with either inadequate or overaggressive fluid therapy. Understanding the tools and techniques available for accurate volume assessment is imperative. This article discusses the concept of fluid responsiveness and reviews methods for assessing fluid responsiveness in critically ill patients.

Bioreactance-Based Noninvasive Fluid Responsiveness and Cardiac Output Monitoring: A Pilot Study in Patients with Aneurysmal Subarachnoid Hemorrhage and Literature Review

Management of volume status, arterial blood pressure, and cardiac output are core elements in approaching the patients with aneurysmal subarachnoid hemorrhage (SAH). For the prevention and treatment of delayed cerebral ischemia (DCI), euvolemia is advocated and caution is made towards the avoidance of hypervolemia. Induced hypertension and cardiac output augmentation are the mainstays of medical management during active DCI, whereas the older triple-H paradigm has fallen out of favor due to lack of demonstrable physiological or clinical benefits and serious concern for adverse effects such as pulmonary edema and multiorgan system dysfunction. Furthermore, insight into clinical hemodynamics of patients with SAH becomes salient when one considers the frequently associated cardiac and pulmonary manifestations of the disease such as SAH-associated cardiomyopathy and neurogenic pulmonary edema. In terms of fluid and volume targets, less attention has been paid to dynamic markers of fluid responsiveness despite the well-established, in the general critical care literature, superiority of these as compared to traditionally used static markers such as central venous pressure (CVP). Based on this literature and sound pathophysiologic reasoning, reliance on static markers (such as CVP) is unjustified when one attempts to assess strategies augmenting stroke volume (SV), arterial blood pressure, and oxygen delivery. There are several options for continuous bedside cardiorespiratory monitoring and optimization of SAH patients. We, here, review a noninvasive monitoring technique based on thoracic bioreactance and focusing on continuous cardiac output and fluid responsiveness markers.

Precision and consistency of the passive leg raising maneuver for determining fluid responsiveness with bioreactance non-invasive cardiac output monitoring in critically ill patients and healthy volunteers

Objective

The passive leg raising (PLR) maneuver has become standard practice in fluid resuscitation. We aim to investigate the precision and consistency of the PLR for determining fluid responsiveness in critically ill patients and healthy volunteers using bioreactance non-invasive cardiac output monitoring (NiCOM™, Cheetah Medical, Inc., Newton Center, Massachusetts, USA).

Methods

This study is prospective, single-center, observational cohort with repeated measures in critically ill patients admitted to the medical intensive care unit and healthy volunteers at a tertiary academic medical center. Three cycles of PLR were performed, each at 20–30 minutes apart. Fluid responsiveness was defined as a change in stroke volume index (ΔSVI) > 10% with each PLR as determined by NiCOM™. Precision was the variability in ΔSVI after the 3 PLR’s, and determined by range, average deviation and standard deviation. Consistency was the same fluid responsiveness determination of “Yes” (ΔSVI > 10%) or “No” (ΔSVI ≤ 10%) for all 3 PLR’s.

Results

Seventy-five patients and 25 volunteers were enrolled. In patients, the precision was range of 17.2±13.3%, average deviation 6.5±4.0% and standard deviation 9.0±5.2%; and for volunteers, 17.4±10.3%, 6.6±3.8% and 9.0±6.7%, respectively. There was no statistical difference in the precision measurements between patients and volunteers. Forty-nine (65.3%) patients vs. twenty-four (96.0%) volunteers had consistent results, p < 0.01. Among those with consistent results, twenty-four (49.0%) patients and 24 (100%) volunteers were fluid responsive.

Conclusions

The precision and consistency of determining ΔSVI with NiCOM™ after PLR may have clinical implication if ΔSVI > 10% is the absolute cutoff to determine fluid responsiveness.

Ultrasound Assessment of the Change in Carotid Corrected Flow Time in Fluid Responsiveness in Undifferentiated Shock

OBJECTIVES

Adequate assessment of fluid responsiveness in shock necessitates correct interpretation of hemodynamic changes induced by preload challenge. This study evaluates the accuracy of point-of-care Doppler ultrasound assessment of the change in carotid corrected flow time induced by a passive leg raise maneuver as a predictor of fluid responsiveness. Noninvasive cardiac output monitoring (NICOM, Cheetah Medical, Newton Center, MA) system based on a bioreactance method was used.

DESIGN

Prospective, noninterventional study.

SETTING

ICU at a large academic center.

PATIENTS

Patients with new, undifferentiated shock, and vasopressor requirements despite fluid resuscitation were included. Patients with significant cardiac disease and conditions that precluded adequate passive leg raising were excluded.

INTERVENTIONS

Carotid corrected flow time was measured via ultrasound before and after a passive leg raise maneuver. Predicted fluid responsiveness was defined as greater than 10% increase in stroke volume on noninvasive cardiac output monitoring following passive leg raise. Images and measurements were reanalyzed by a second, blinded physician. The accuracy of change in carotid corrected flow time to predict fluid responsiveness was evaluated using receiver operating characteristic analysis.

MEASUREMENTS AND MAIN RESULTS

Seventy-seven subjects were enrolled with 54 (70.1%) classified as fluid responders by noninvasive cardiac output monitoring. The average change in carotid corrected flow time after passive leg raise for fluid responders was 14.1 ± 18.7 ms versus -4.0 ± 8 ms for nonresponders (p < 0.001). Receiver operating characteristic analysis demonstrated that change in carotid corrected flow time is an accurate predictor of fluid responsiveness status (area under the curve, 0.88; 95% CI, 0.80-0.96) and a 7 ms increase in carotid corrected flow time post passive leg raise was shown to have a 97% positive predictive value and 82% accuracy in detecting fluid responsiveness using noninvasive cardiac output monitoring as a reference standard. Mechanical ventilation, respiratory rate, and high positive end-expiratory pressure had no significant impact on test performance. Post hoc blinded evaluation of bedside acquired measurements demonstrated agreement between evaluators.

CONCLUSIONS

Change in carotid corrected flow time can predict fluid responsiveness status after a passive leg raise maneuver. Using point-of-care ultrasound to assess change in carotid corrected flow time is an acceptable and reproducible method for noninvasive identification of fluid responsiveness in critically ill patients with undifferentiated shock.

Renal Angina Is a Sensitive, but Nonspecific Identifier of Postcardiac Surgery Acute Kidney Injury

OBJECTIVES

Acute kidney injury (AKI) is a common complication of cardiac surgery, and early detection is difficult. This study was performed to determine the sensitivity, specificity, positive predictive value, negative predictive value, and statistical performance of renal angina (RA) as an early predictor of AKI in an adult cardiac surgical patient population.

DESIGN

Retrospective, nonrandomized, observational study.

SETTING

A single, university-affiliated, quaternary medical center.

PARTICIPANTS

The study comprised 324 consecutive patients undergoing coronary artery bypass grafting or cardiac valvular surgery from February 1 through July 30, 2014.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

One hundred-seven patients at moderate or high risk of developing postoperative renal injury were identified, 82 of whom met criteria for RA. The occurrence of RA was found to have an 80.9% sensitivity and 30.8% specificity for the prediction of AKI using Acute Kidney Injury Network criteria and 89.3% sensitivity and 27.8% specificity when paired with the Risk, Injury, Failure, Loss, End Stage Renal Disease criteria. A receiver operating characteristic area under the curve analysis revealed a nonsignificant predictive ability of 55.8% (95% confidence interval 0.47-0.65) when RA was paired with Acute Kidney Injury Network criteria; however, the receiver operating characteristic area under the curve was significant when paired with Risk, Injury, Failure, Loss, End Stage Renal Disease criteria, with a predictive ability of 0.586 (0.509-0.662).

CONCLUSIONS

RA is a sensitive, but nonspecific, predictor of postcardiac surgery AKI, with clinical utility most suited as a screening tool.

Estimating the rapid haemodynamic effects of passive leg raising in critically ill patients using bioreactance

BACKGROUND

Rapid detection of changes in cardiac index (CI) in real time using minimally invasive monitors may be of clinical benefit. We tested whether the Starling-SV bioreactance device, which averages CI over a short 8 s period, could assess the effects of passive leg raising (PLR), a clinical test that is recommended to assess fluid responsiveness during septic shock.

METHODS

In 32 critically ill patients, we measured CI by transpulmonary thermodilution (PiCCO2, CI_td), pulse contour analysis (PiCCO2, CI_Pulse), and the Starling-SV device (CI_Starling) at baseline. CI_Pulse and CI_Starling were measured again at the end of a PLR test. In the 13 patients with a positive PLR test, CI_td, CI_Pulse, and CI_Starling were measured before and after a 500 ml saline infusion. The primary outcome was relative changes from baseline measurements in CI_td, CI_Pulse, and CI_Starling. Secondary outcomes compared absolute values measured by each method.

RESULTS

Relative changes in CI_Pulse and CI_td were significantly correlated (r=0.82; n=45; P<0.001), with an 89% concordance rate (n=45 paired measurements). Relative changes in CI_Starling and CI_td were also significantly correlated (r=0.59; n=45; P<0.001) with a 78% concordance rate. For absolute measures of CI (n=77 paired measurements), the bias between CI_Pulse and CI_td was 0.01 L min^-1 m^-2 (limits of agreement, -0.49 and 0.51 L min^-1 m^-2; 15% percentage error). Bias between CI_Starling and CI_td was 0.03 L min^-1 m^-2 (limits of agreement, -1.61 and 1.67 L min^-1 m^-2; 48% percentage error).

CONCLUSIONS

In critically ill patients, a non-invasive bioreactance device with a shorter averaging period assessed a passive leg raising test with reasonable accuracy.

Reliability of Passive Leg Raising, Stroke Volume Variation and Pulse Pressure Variation to Predict Fluid Responsiveness During Weaning From Mechanical Ventilation After Cardiac Surgery: A Prospective, Observational Study

Objective

During assisted ventilation and spontaneous breathing, functional haemodynamic parameters, including stroke volume variation (SVV) and pulse pressure variation (PPV), are of limited value to predict fluid responsiveness, and the passive leg raising (PLR) manoeuvre has been advocated as a surrogate method. We aimed to study the predictive value of SVV, PPV and PLR for fluid responsiveness during weaning from mechanical ventilation after cardiac surgery.

Methods

Haemodynamic variables and fluid responsiveness were assessed in 34 patients. Upon arrival at the intensive care unit, measurements were performed during continuous mandatory ventilation (CMV) and spontaneous breathing with pressure support (PSV) and after extubation (SPONT). The prediction of a positive fluid responsiveness (defined as stroke volume increase >15% after fluid administration) was tested by calculating the specific receiver operating characteristic (ROC) curves.

Results

A significant increase in stroke volumes was observed during CMV, PSV and SPONT after fluid administration. There were 19 fluid responders (55.9%) during CMV, with 22 (64.7%) and 13 (40.6%) during PSV and SPONT, respectively. The predictive value for a positive fluid responsiveness (area under the ROC curve) for SVV was 0.88, 0.70 and 0.56; was 0.83, 0.69 and 0.48 for PPV; was 0.72, 0.74 and 0.70 for PLR during CMV, PSV and SPONT, respectively.

Conclusion

During mechanical ventilation, adequate prediction of fluid responsiveness using SVV and PPV was observed. However, during spontaneous breathing, the reliability of SVV and PPV was poor. In this period, PLR as a surrogate was able to predict fluid responsiveness better than SVV or PPV but was less reliable than previously reported.

Right ventricular fractional area of change is predictive of ventilator support days in trauma and burn patients

Echocardiography has contributed to the care of critically ill patients but there remains a need for more publications about its association with outcomes to confirm its role. We conducted a retrospective review of trauma and burn patients that were admitted to our intensive care unit between 2015 and 2017 that underwent hemodynamic transesophageal echocardiography. Data collected included demographics, clinical and laboratory data. Right ventricle fractional area of change (RVFAC) measurements were performed on still mages obtained from mid-esophageal four-chamber-view clips. There were 74 patients, mean age was 51 years, and were predominantly white and male. Linear regression was used to test for the association between RVFAC and clinical outcomes. Adjusting for age, injury mechanism and injury severity, higher RVFAC was significantly associated with lower ventilator days (p = 0.03). Conclusion, higher right ventricle systolic function is associated with a lower number of ventilator support days in critically injured trauma and burn patients.

Passive Leg-Raising and Prediction of Fluid Responsiveness: Systematic Review

Fluid boluses are often administered with the aim of improving tissue hypoperfusion in shock. However, only approximately 50% of patients respond to fluid administration with a clinically significant increase in stroke volume. Fluid overload can exacerbate pulmonary edema, precipitate respiratory failure, and prolong mechanical ventilation. Therefore, it is important to predict which hemodynamically unstable patients will increase their stroke volume in response to fluid administration, thereby avoiding deleterious effects. Passive leg-raising (lowering the head and upper torso from a 45° angle to lying supine [flat] while simultaneously raising the legs to a 45° angle) is a transient, reversible autotransfusion that simulates a fluid bolus and is performed to predict a response to fluid administration. The article reviews the accuracy, physiological effects, and factors affecting the response to passive-leg raising to predict fluid responsiveness in critically ill patients.

Stroke volume guided resuscitation in severe sepsis and septic shock improves outcomes

To determine whether stroke volume (SV) guided fluid resuscitation in patients with severe sepsis and septic shock alters Intensive Care Unit (ICU) fluid balance and secondary outcomes, this retrospective cohort study evaluated consecutive patients admitted to an ICU with the primary diagnosis of severe sepsis or septic shock. Cohorts were based on fluid resuscitation guided by changes in SV or by usual care (UC). The SV group comprised 100 patients, with 91 patients in the UC group. Net fluid balance for the ICU stay was lower in the SV group (1.77L) than in the UC group (5.36L) (p=0.022). ICU length of stay was 2.89days shorter (p=0.03) and duration of vasopressors was 32.8h less (p=0.001) in the SV group. SV group required less mechanical ventilation (RR, 0.51; p=0.0001). The SV group was less likely to require acute hemodialysis (6.25%) compared with the UC group (19.5%) (RR, 0.32; p=0.01). In multivariable analysis, SV was an independent predictor of lower fluid balance, LOS, time on vasopressors, and not needing mechanical ventilation. This study demonstrated that SV guided fluid resuscitation in patients with severe sepsis and septic shock was associated with reduced fluid balance and improved secondary outcomes.

Comparison of bioreactance non-invasive cardiac output measurements with cardiac magnetic resonance imaging

Impedance cardiography measurement of cardiac output gained wide interest due to its ease of use and non-invasiveness. However, validation studies of different algorithms yielded diverging results. Bioreactance (BR) as a recent adaption differs fundamentally as the flow signal is derived from phase shifts. Our aim was to assess the accuracy and reproducibility of BR, as compared to the non-invasive gold standard--cardiac magnetic resonance imaging (CMR). We prospectively included 32 stable patients. BR was performed twice in the supine position and averaged over 30 seconds. Mean bias was 0.2 ± 1.8 l/minute (1 ± 28%, percentage error 55%) with limits of agreement ranging from  -3.4 to 3.7 l/minute. Reproducibility was acceptable with a mean bias of 0.1 ± 0.9 l/minute (1 ± 14%, 27%). Low cardiac output was significantly overestimated (-1.1 ± 1.5 l/minute), while high cardiac output was underestimated (1.5 ± 1.7 l/minute), (P=0.001), although reproducibility was unaffected. Bias and weight were moderately correlated in men (r = 0.50, P=0.02). No differences for accuracy were found in nine patients who had an arrhythmia (0.3 ± 1.4 versus 0.1 ± 2.0 l/minute, P=0.76), while clinically relevant differences were found in patients with mild aortic valve disease (1.9 ± 2.2 versus -0.3 ± 1.7 l/minute, P=0.02). Overall, BR showed insufficient agreement with CMR, overestimating low and underestimating high cardiac output states. Reproducibility was acceptable and not negatively affected by the circulatory condition. Consequently, absolute values acquired with BR should be interpreted with caution and must not be used interchangeably in clinical practice.

Fluid responsiveness predicted by transcutaneous partial pressure of oxygen in patients with circulatory failure: a prospective study

BACKGROUND

Significant effort has been devoted to defining parameters for predicting fluid responsiveness. Our goal was to study the feasibility of predicting fluid responsiveness by transcutaneous partial pressure of oxygen (PtcO₂) in the critically ill patients.

METHODS

This was a single-center prospective study conducted in the intensive care unit of a tertiary care teaching hospital. Shock patients who presented with at least one clinical sign of inadequate tissue perfusion, defined as systolic blood pressure <90 mmHg or a decrease >40 mmHg in previously hypertensive patients or the need for vasopressive drugs; urine output <0.5 ml/kg/h for 2 h; tachycardia; lactate >4 mmol/l, for less than 24 h in the absence of a contraindication for fluids were eligible to participate in the study. PtcO₂ was continuously recorded before and during a passive leg raising (PLR) test, and then before and after a 250 ml rapid saline infusion in 10 min. Fluid responsiveness is defined as a change in the stroke volume ≥10% after 250 ml of volume infusion.

RESULTS

Thirty-four patients were included, and 14 responded to volume expansion. In the responders, the mean arterial pressure, central venous pressure, cardiac output, stroke volume and PtcO₂ increased significantly, while the heart rate decreased significantly by both PLR and volume expansion. Changes in the stroke volume induced either by PLR or volume expansion were significantly greater in responders than in non-responders. The correlation between the changes in PtcO₂ and stroke volume induced by volume expansion was significant. Volume expansion induced an increase in the PtcO₂ of 14% and PLR induced an increase in PtcO₂ of 13% predicted fluid responsiveness.

CONCLUSIONS

This study suggested the changes in PtcO₂ induced by volume expansion and a PLR test predicted fluid responsiveness in critically ill patients. Trial registration NCT02083757.

Inferior vena cava collapsibility detects fluid responsiveness among spontaneously breathing critically-ill patients

PURPOSE

Measurement of inferior vena cava collapsibility (cIVC) by point-of-care ultrasound (POCUS) has been proposed as a viable, non-invasive means of assessing fluid responsiveness. We aimed to determine the ability of cIVC to identify patients who will respond to additional intravenous fluid (IVF) administration among spontaneously breathing critically-ill patients.

METHODS

Prospective observational trial of spontaneously breathing critically-ill patients. cIVC was obtained 3cm caudal from the right atrium and IVC junction using POCUS. Fluid responsiveness was defined as a≥10% increase in cardiac index following a 500ml IVF bolus; measured using bioreactance (NICOM™, Cheetah Medical). cIVC was compared with fluid responsiveness and a cIVC optimal value was identified.

RESULTS

Of the 124 participants, 49% were fluid responders. cIVC was able to detect fluid responsiveness: AUC=0.84 [0.76, 0.91]. The optimum cutoff point for cIVC was identified as 25% (LR+ 4.56 [2.72, 7.66], LR- 0.16 [0.08, 0.31]). A cIVC of 25% produced a lower misclassification rate (16.1%) for determining fluid responsiveness than the previous suggested cutoff values of 40% (34.7%).

CONCLUSION

IVC collapsibility, as measured by POCUS, performs well in distinguishing fluid responders from non-responders, and may be used to guide IVF resuscitation among spontaneously breathing critically-ill patients.

Correlation of carotid blood flow and corrected carotid flow time with invasive cardiac output measurements

Background

Non-invasive measures that can accurately estimate cardiac output may help identify volume-responsive patients. This study seeks to compare two non-invasive measures (corrected carotid flow time and carotid blood flow) and their correlations with invasive reference measurements of cardiac output. Consenting adult patients (n = 51) at Massachusetts General Hospital cardiac catheterization laboratory undergoing right heart catheterization between February and April 2016 were included. Carotid ultrasound images were obtained concurrently with cardiac output measurements, obtained by the thermodilution method in the absence of severe tricuspid regurgitation and by the Fick oxygen method otherwise. Corrected carotid flow time was calculated as systole time/√cycle time. Carotid blood flow was calculated as π × (carotid diameter)²/4 × velocity time integral × heart rate. Measurements were obtained using a single carotid waveform and an average of three carotid waveforms for both measures.

Results

Single waveform measurements of corrected flow time did not correlate with cardiac output (ρ = 0.25, 95% CI −0.03 to 0.49, p = 0.08), but an average of three waveforms correlated significantly, although weakly (ρ = 0.29, 95% CI 0.02–0.53, p = 0.046). Carotid blood flow measurements correlated moderately with cardiac output regardless of if single waveform or an average of three waveforms were used: ρ = 0.44, 95% CI 0.18–0.63, p = 0.004, and ρ = 0.41, 95% CI 0.16–0.62, p = 0.004, respectively.

Conclusions

Carotid blood flow may be a better marker of cardiac output and less subject to measurements issues than corrected carotid flow time.

Electronic supplementary material

The online version of this article (doi:10.1186/s13089-017-0065-0) contains supplementary material, which is available to authorized users.

A review of hemodynamic monitoring techniques, methods and devices for the emergency physician

The emergency department (ED) is frequently the doorway to the intensive care unit (ICU) for a significant number of critically ill patients presenting to the hospital. Hemodynamic monitoring (HDM) which is a key component in the effective management of the critically ill patient presenting to the ED, is primarily concerned with assessing the performance of the cardiovascular system and determining the correct therapeutic intervention to optimise end-organ oxygen delivery. The spectrum of hemodynamic monitoring ranges from simple clinical assessment and routine bedside monitoring to point of care ultrasonography and various invasive monitoring devices. The clinician must be aware of the range of available techniques, methods, interventions and technological advances as well as possess a sound approach to basic hemodynamic monitoring prior to selecting the optimal modality. This article comprises an in depth discussion of an approach to hemodynamic monitoring techniques and principles as well as methods of predicting fluid responsiveness as it applies to the ED clinician. We review the role, applicability and validity of various methods and techniques that include; clinical assessment, passive leg raising, blood pressure, finger based monitoring devices, the mini-fluid challenge, the end-expiratory occlusion test, central venous pressure monitoring, the pulmonary artery catheter, ultrasonography, bioreactance and other modern invasive hemodynamic monitoring devices.

Ultrasound and NICOM in the assessment of fluid responsiveness in patients with mild sepsis in the emergency department: a pilot study

OBJECTIVE

We investigated whether combining the caval index, assessment of the global contractility of the heart and measurement of stroke volume with Noninvasive Cardiac Output Monitoring (NICOM) can aid in fluid management in the emergency department (ED) in patients with sepsis.

SETTING

A prospective observational single-centre pilot study in a tertiary care centre.

PRIMARY AND SECONDARY OUTCOMES

Ultrasound was used to assess the caval index, heart contractility and presence of B-lines in the lungs. Cardiac output and stroke volume were monitored with NICOM. Primary outcome was increase in stroke volume after a fluid bolus of 500 mL, while secondary outcome included signs of fluid overload.

RESULTS

We included 37 patients with sepsis who received fluid resuscitation of at least 500 mL saline. The population was divided into patients with a high (>36.5%, n=24) and a low caval index (<36.5%, n=13). We observed a significant increase (p=0.022) in stroke volume after 1000 mL fluid in the high caval index group in contrast to the low caval index group but not after 500 mL of fluid. We did not find a significant association between global contractility of the left ventricle and the response on fluid therapy (p=0.086). No patient showed signs of fluid overload.

CONCLUSIONS

Our small pilot study suggests that at least 1000 mL saline is needed to induce a significant response in stroke volume in patients with sepsis and a high caval index. This amount seems to be safe, not leading to the development of fluid overload. Therefore, combining ultrasound and NICOM is feasible and may be valuable tools in the treatment of patients with sepsis in the ED. A larger trial is needed to confirm these results.

Fluid responsiveness prediction using Vigileo FloTrac measured cardiac output changes during passive leg raise test

Background

Passive leg raising (PLR) is a so called self-volume challenge used to test for fluid responsiveness. Changes in cardiac output (CO) or stroke volume (SV) measured during PLR are used to predict the need for subsequent fluid loading. This requires a device that can measure CO changes rapidly. The Vigileo™ monitor, using third-generation software, allows continuous CO monitoring. The aim of this study was to compare changes in CO (measured with the Vigileo device) during a PLR manoeuvre to calculate the accuracy for predicting fluid responsiveness.

Methods

This is a prospective study in a 20-bedded mixed general critical care unit in a large non-university regional referral hospital. Fluid responders were defined as having an increase in CO of greater than 15 % following a fluid challenge. Patients meeting the criteria for circulatory shock with a Vigileo™ monitor (Vigileo™; FloTrac; Edwards™; Lifesciences, Irvine, CA, USA) already in situ, and assessed as requiring volume expansion by the clinical team based on clinical criteria, were included. All patients underwent a PLR manoeuvre followed by a fluid challenge.

Results

Data was collected and analysed on stroke volume variation (SVV) at baseline and CO and SVV changes during the PLR manoeuvre and following a subsequent fluid challenge in 33 patients. The majority had septic shock. Patient characteristics, baseline haemodynamic variables and baseline vasoactive infusion requirements were similar between fluid responders (10 patients) and non-responders (23 patients). Peak increase in CO occurred within 120 s during the PLR in all cases. Using an optimal cut point of 9 % increase in CO during the PLR produced an area under the receiver operating characteristic curve of 0.85 (95 % CI 0.63 to 1.00) with a sensitivity of 80 % (95 % CI 44 to 96 %) and a specificity of 91 % (95 % CI 70 to 98 %).

Conclusions

CO changes measured by the Vigileo™ monitor using third-generation software during a PLR test predict fluid responsiveness in mixed medical and surgical patients with vasopressor-dependent circulatory shock.

Electronic supplementary material

The online version of this article (doi:10.1186/s40560-016-0188-6) contains supplementary material, which is available to authorized users.

Predicting cardiorespiratory instability

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency medicine 2016. Other selected articles can be found online at http://www.biomedcentral.com/collections/annualupdate2016. Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901.

Major Upper Abdominal Surgery Alters the Calibration of Bioreactance Cardiac Output Readings, the NICOM, When Comparisons Are Made Against Suprasternal and Esophageal Doppler Intraoperatively

BACKGROUND

Minimally invasive continuous cardiac output measurements are recommended for use during anesthesia to guide fluid therapy, but such measurements must trend changes reliably. The NICOM Cheetah, a BioReactance monitor, is being recommended for intraoperative use. To validate its use, Doppler methods, suprasternal USCOM and esophageal CardioQ, were used in tandem to provide reliable estimates of changing trends in cardiac output. Preliminary comparisons showed that upper abdominal surgical interventions caused shifts in the calibration of the NICOM. The purpose of this study was to confirm and measure these calibration shifts.

METHODS

Major surgery patients, aged 58 (32-78) years, 12 males and 15 females, were divided into 4 study groups: (a) controls-lower abdominal or peripheral surgery (n = 9); (b) laparoscopy with abdominal insufflation (n = 6); (c) open upper abdominal surgery with large multiblade retractor placement (n = 6) and (d) head-down robotic surgery (n = 6). Simultaneous NICOM and Doppler readings were taken every 15 to 30 minutes. Within-individual time plots were drawn, and regression analysis between NICOM-USCOM and CardioQ-USCOM readings was performed. Bland-Altman and trend (concordance) analyses were also performed.

RESULTS

Three hundred ninety NICOM comparisons were collected. Duration of surgeries was 4 (1½ to 11) hours, with 7 to 22 sets of readings per case. Mean (SD) cardiac index from USCOM readings was 3.5(1.0) L/min/m. Individual time plots showed shifts in NICOM calibration relative to Doppler (USCOM) in cardiac index of ±0.9 (0.6-1.4) L/min/m during the surgical interventions. In 13 of 18 patients (72%), the shift was downward, but upward shifts did occur. Within-individual correlations between CardioQ-USCOM showed good trending R = 0.87 (range, 0.60-0.97). In the control group, NICOM-USCOM also showed good trending R = 0.89 (0.69-0.97). However, trending was poor in the intervention groups, R = 0.43 (0.03-0.71; P < 0.0001). The Bland-Altman percentage error between NICOM-USCOM (57 [54-60]%) was greater than that between CardioQ-USCOM (42 [40-44]%) (P < 0.0001). Concordance rates were 82 (77-88)% from 101 data pairs and 95 (90-99)% from 72 data pairs, respectively.

CONCLUSIONS

Doppler monitoring used in tandem provided valid trend lines of cardiac output changes against which NICOM readings could be compared. Intraoperatively, the NICOM was shown to track changes in cardiac output reliably in most circumstances. However, surgical interventions to the upper abdomen caused shifts in readings by >1 L/min/m, and the direction of the shifts was unpredictable. Anesthesiologists need to be aware of these calibration shifts and anticipate their occurrence, whenever the NICOM is used intraoperatively.

Emergency Department Management of Sepsis Patients: A Randomized, Goal-Oriented, Noninvasive Sepsis Trial

STUDY OBJECTIVE

The noninvasive cardiac output monitor and passive leg-raising maneuver has been shown to be reasonably accurate in predicting fluid responsiveness in critically ill patients. We examine whether using a noninvasive protocol would result in more rapid lactate clearance after 3 hours in patients with severe sepsis and septic shock in the emergency department.

METHODS

In this open-label randomized controlled trial, 122 adult patients with sepsis and serum lactate concentration of greater than or equal to 3.0 mmol/L were randomized to receive usual care or intravenous fluid bolus administration guided by measurements of change of stroke volume index, using the noninvasive cardiac output monitor after passive leg-raising maneuver. The primary outcome was lactate clearance of more than 20% at 3 hours. Secondary outcomes included mortality, length of hospital and ICU stay, and total hospital cost. Analysis was intention to treat.

RESULTS

Similar proportions of patients in the randomized intervention group (70.5%; N=61) versus control group (73.8%; N=61) achieved the primary outcome, with a relative risk of 0.96 (95% confidence interval [CI] 0.77 to 1.19). Secondary outcomes were similar in both groups (P>.05 for all comparisons). Hospital mortality occurred in 6 patients (9.8%) each in the intervention and control groups on or before 28 days (relative risk=1.00; 95% CI 0.34 to 2.93). Among a subgroup of patients with underlying fluid overload states, those in the intervention group tended to receive clinically significantly more intravenous fluids at 3 hours (difference=975 mL; 95% CI -450 to 1,725 mL) and attained better lactate clearance (difference=19.7%; 95% CI -34.6% to 60.2%) compared with the control group, with shorter hospital lengths of stay (difference=-4.5 days; 95% CI -9.5 to 2.5 days).

CONCLUSION

Protocol-based fluid resuscitation of patients with severe sepsis and septic shock with the noninvasive cardiac output monitor and passive leg-raising maneuver did not result in better outcomes compared with usual care. Future studies to demonstrate the use of the noninvasive protocol-based care in patients with preexisting fluid overload states may be warranted.

The passive leg raise test to predict fluid responsiveness in children--preliminary observations

OBJECTIVE

To assess whether the passive leg raising (PLR) test can predict fluid responsiveness in pediatric patients.

METHODS

This was a prospective observational study in a tertiary care pediatric center. Hemodynamic parameters including heart rate, stroke volume and cardiac output were assessed at baseline, after passive leg raising (PLR), at second baseline, and after volume loading (10 mL/kg normal saline in 10 min). Cutoff values of 7.5 and 10 % increase in cardiac index (CI) with passive leg raising were explored as predictors of volume loading response.

RESULTS

Overall, the changes in CI with passive leg raising varied widely and was a poor predictor of response to volume loading in children under 5 years of age. Of 40 patients, 23 had greater than 10 % increase in CI with PLR which predicted fluid responsiveness with a sensitivity of 94 % (95 % confidence interval 71,100) and specificity of 26 % (95 % confidence interval 10,48). Sensitivity was higher (100 % vs. 91 %) and specificity similar (27 % vs. 25 %) in predicting CI for those over 5 as compared to under 5 y, respectively. In patients over 5 y, simple linear regression revealed a positive correlation (R(2) = 21) while R(2) values were much lower (0-0.07) for those under 5 y.

CONCLUSIONS

Cardiac index changes after PLR varies widely in children and may be a poor predictor to volume loading in children under 5-y-old. However, in those over 5 y, PLR may be helpful in predicting fluid responsiveness in pediatric patients.

Functional hemodynamic monitoring

Functional hemodynamic monitoring is the assessment of the dynamic interactions of hemodynamic variables in response to a defined perturbation. Recent interest in functional hemodynamic monitoring for the bedside assessment of cardiovascular insufficiency has heightened with the documentation of its accuracy in predicting volume responsiveness using a wide variety of monitoring devices, both invasive and noninvasive, and across multiple patient groups and clinical conditions. However, volume responsiveness, though important, reflects only part of the overall spectrum of functional physiologic variables that can be measured to define the physiologic state and monitor response to therapy.

Correlation of cardiac output measured by non-invasive continuous cardiac output monitoring (NICOM) and thermodilution in patients undergoing off-pump coronary artery bypass surgery

Purpose

This observational study was designed to evaluate the clinical value of cardiac output (CO) obtained via bioreactance (NICOM™) as compared with values of CO obtained via thermodilution (using pulmonary artery catheter, Vigilance™) and the thoracic bioimpedance (BioZ.com™), in patients undergoing off-pump coronary artery bypass surgery.

Methods

Fifty American Society of Anesthesiologists physical status I–III patients, aged 38–81 years, scheduled for off-pump coronary artery bypass surgery were enrolled in this study. CO data (NCO, BCO, PCO) were recorded during the operative period at ten time points after stable hemodynamic conditions were achieved.

Results

The equation of the relationship between the PCO and NCO is PCO = 0.945 × NCO + 0.328 (r = 0.77), and that of PCO and BCO is PCO = 0.965 × BCO + 0.729 (r = 0.63). Furthermore, no statistical difference was found between PCO versus NCO (mean (SD): 4.4 (1.1) versus 4.4 (0.9), p = 0.431). A significant correlation was found between PCO and NCO (r = 0.77, p < 0.001). Correlation was also found between PCO and BCO (r = 0.63, p < 0.001).

Conclusions

The NICOM device is a safe, convenient, and reliable device for measuring continuous non-invasive cardiac output and cardiac index, and the trends of change in CO during the surgery are similar between NICOM and PAC.

Stroke volume variation and indexed stroke volume measured using bioreactance predict fluid responsiveness in postoperative children

BACKGROUND

Postoperative fluid management can be challenging in children after haemorrhagic surgery. The goal of this study was to assess the ability of dynamic cardiovascular variables measured using bioreactance (NICOM®, Cheetah Medical, Tel Aviv, Israel) to predict fluid responsiveness in postoperative children.

METHODS

Children sedated and mechanically ventilated, who require volume expansion (VE) during the immediate postoperative period, were included. Indexed stroke volume (SVi), cardiac index, and stroke volume variation (SVV) were measured using the NICOM® device. Responders (Rs) to VE were patients showing an increase in SV measured using transthoracic echocardiography of at least 15% after VE. Data are median [95% confidence interval (CI)].

RESULTS

Thirty-one patients were included, but one patient was excluded because of the lack of calibration of the NICOM® device. Before VE, SVi [33 (95% CI 31-36) vs 24 (95% CI 21-28) ml m(-2); P=0.006] and SVV [8 (95% CI 4-11) vs 13 (95% CI 11-15)%; P=0.004] were significantly different between non-responders and Rs. The areas under the receiver operating characteristic curves of SVi and SVV for predicting fluid responsiveness were 0.88 (95% CI 0.71-0.97) and 0.81 (95% CI 0.66-0.96), for a cut-off value of 29 ml m(-2) (grey zone 27-29 ml m(-2)) and 10% (grey zone 9-15%), respectively.

CONCLUSIONS

The results of this study show that SVi and SVV non-invasively measured by bioreactance are predictive of fluid responsiveness in sedated and mechanically ventilated children after surgery.