Feasibility of Fluid Responsiveness Assessment in Patients at Risk for Increased Intracranial Pressure.

Background: Effective fluid management is important for patients at risk of increased intracranial pressure (ICP). Maintaining constant cerebral perfusion represents a challenge, as both hypovolemia and fluid overload can severely impact patient outcomes. Fluid responsiveness tests, commonly used in critical care settings, are often deemed potentially hazardous for these patients due to the risk of disrupting cerebral perfusion. Methods: This single-center, prospective, clinical observational study enrolled 40 patients at risk for increased ICP, including those with acute brain injury. Informed consent was obtained from each participant or their legal guardians before inclusion. The study focused on the dynamics of ICP and cerebral perfusion pressure (CPP) changes during the Passive Leg Raise Test (PLRT) and the End-Expiratory Occlusion Test (EEOT). Results: The results demonstrated that PLRT and EEOT caused minor and transient increases in ICP, while consistently maintaining stable CPP. EEOT induced significantly lower ICP elevations, making it particularly suitable for use in high-risk situations. Conclusions: PLRT and EEOT can be considered feasible and safe for assessing fluid responsiveness in patients at risk for increased ICP. Notably, EEOT stands out as a preferred method for high-risk patients, offering a dependable strategy for fluid management without compromising cerebral hemodynamics.

Inferior vena cava ultrasound and other techniques for assessment of intravascular and extravascular volume: an update.

Goals of volume management are to accurately assess intravascular and extravascular volume and predict response to volume administration, vasopressor support or volume removal. Data are reviewed that support the following: (i) Dynamic parameters reliably guide volume administration and may improve clinical outcomes compared with static parameters, but some are invasive or only validated with mechanical ventilation without spontaneous breathing. (ii) Ultrasound visualization of inferior vena cava (IVC) diameter variations with respiration reliably assesses intravascular volume and predicts volume responsiveness. (iii) Although physiology of IVC respiratory variations differs with mechanical ventilation and spontaneous breathing, the IVC collapsibility index (CI) and distensibility index are interconvertible. (iv) Prediction of volume responsiveness by IVC CI is comparable for mechanical ventilation and spontaneous breathing patients. (v) Respiratory variations of subclavian/proximal axillary and internal jugular veins by ultrasound are alternative sites, with comparable reliability. (vi) Data support clinical applicability of IVC CI to predict hypotension with anesthesia, guide ultrafiltration goals, predict dry weight, predict intra-dialytic hypotension and assess acute decompensated heart failure. (vii) IVC ultrasound may complement ultrasound of heart and lungs, and abdominal organs for venous congestion, for assessing and managing volume overload and deresuscitation, renal failure and shock. (viii) IVC ultrasound has limitations including inadequate visualization. Ultrasound data should always be interpreted in clinical context. Additional studies are required to further assess and validate the role of bedside ultrasonography in clinical care.

Volume responsiveness revisited: an observational multicenter study of continuous versus binary outcomes combining echocardiography and venous return physiology.

Echocardiography can assess cardiac preload when fluid administration is used to treat acute circulatory failure. Changes in stroke volume (SV) are inherently a continuous phenomenon relating to the pressure gradient for venous return (VRdP). However, most clinical studies have applied a binary definition based on a fractional change in SV. This study tested the hypothesis that calculating the analog mean systemic filling pressure (Pmsa) and VRdP would enhance echocardiography to describe SV responses to a preload challenge. We investigated 540 (379 males) patients during a standardized passive leg raising (PLR) maneuver. Patients were further categorized by the presence of impaired right ventricular function (impRV) or increased intra-abdominal hypertension (IAH). Multivariable linear regression identified VRdP (partial r = -0.26, P < 0.001), ventilatory-induced variations in superior vena cava diameter (partial r = 0.43, P < 0.001), and left ventricular outflow tract maximum-Doppler velocity (partial r = 0.13, P < 0.001) as independent variables associated with SV changes. The model explained 38% (P < 0.001) of the SV change in the whole cohort and 64% (P < 0.001) when excluding patients with impRV or IAH. The correlation between Pmsa or VRdP and SV changes lost statistical significance with increasing impRV or IAH. A binary definition of volume responsiveness (>10% increase in SV) generated an area under the curve of 0.79 (P < 0.001) in logistic regression but failed to identify Pmsa or VRdP as independent variables and overlooked the confounding influence of impRV and IAH. In conclusion, venous return physiology may enhance echocardiographic assessments of volume responsiveness, which should be based on continuous changes in stroke volume.NEW & NOTEWORTHY The analog mean systemic filling pressure and the pressure gradient for venous return combined with echocardiography predict continuous changes in stroke volume following a passive leg raising maneuver. The confounding effects of impaired right ventricular function and increased intra-abdominal pressure can be identified. Using a binary cutoff for the fractional change in stroke volume, common in previous clinical research, fails to identify the importance of variables relevant to venous return physiology and confounding conditions.

Cardiopulmonary interactions-which monitoring tools to use?

Heart-lung interactions occur due to the mechanical influence of intrathoracic pressure and lung volume changes on cardiac and circulatory function. These interactions manifest as respiratory fluctuations in venous, pulmonary, and arterial pressures, potentially affecting stroke volume. In the context of functional hemodynamic monitoring, pulse or stroke volume variation (pulse pressure variation or stroke volume variability) are commonly employed to assess volume or preload responsiveness. However, correct interpretation of these parameters requires a comprehensive understanding of the physiological factors that determine pulse pressure and stroke volume. These factors include pleural pressure, venous return, pulmonary vessel function, lung mechanics, gas exchange, and specific cardiac factors. A comprehensive knowledge of heart-lung physiology is vital to avoid clinical misjudgments, particularly in cases of right ventricular (RV) failure or diastolic dysfunction. Therefore, when selecting monitoring devices or technologies, these factors must be considered. Invasive arterial pressure measurements of variations in breath-to-breath pressure swings are commonly used to monitor heart-lung interactions. Echocardiography or pulmonary artery catheters are valuable tools for differentiating preload responsiveness from right ventricular failure, while changes in diastolic function should be assessed alongside alterations in airway or pleural pressure, which can be approximated by esophageal pressure. In complex clinical scenarios like ARDS, combined forms of shock or right heart failure, additional information on gas exchange and pulmonary mechanics aids in the interpretation of heart-lung interactions. This review aims to describe monitoring techniques that provide clinicians with an integrative understanding of a patient's condition, enabling accurate assessment and patient care.

An Assessment of Carotid Flow Time Using a Portable Handheld Ultrasound Device: The Ideal Tool for Guiding Intraoperative Fluid Management?

Volume resuscitation is a cornerstone of modern anesthesia care. Finding the right balance to avoid inadequate or excess volume administration is often difficult to clinically discern and can lead to negative consequences. Pulse pressure variation is often intraoperatively used to guide volume resuscitation; however, this requires an invasive arterial line and is generally only applicable to patients who are mechanically ventilated. Unfortunately, without a pulmonary artery catheter or another costly noninvasive device, performing serial measurements of cardiac output is challenging, time-consuming, and often impractical. Furthermore, noninvasive measures such as LVOT VTI require significant technical expertise as well as access to the chest, which may not be practical during and after surgery. Other noninvasive techniques such as bioreactance and esophageal Doppler require the use of costly single-use sensors. Here, we present a case report on the use of corrected carotid flow time (ccFT) from a portable, handheld ultrasound device as a practical, noninvasive, and technically straightforward method to assess fluid responsiveness in the perioperative period, as well as the inpatient and outpatient settings.

The diagnostic accuracy of inferior vena cava respiratory variation in predicting volume responsiveness in patients under different breathing status following abdominal surgery.

BACKGROUND: The validation of inferior vena cava (IVC) respiratory variation for predicting volume responsiveness is still under debate, especially in spontaneously breathing patients. The present study aims to verify the effectiveness and accuracy of IVC variability for volume assessment in the patients after abdominal surgery under artificially or spontaneously breathing. METHODS: A total of fifty-six patients after abdominal surgeries in the anesthesia intensive care unit ward were included. All patients received ultrasonographic examination before and after the fluid challenge of 5 ml/kg crystalloid within 15 min. The same measurements were performed when the patients were extubated. The IVC diameter, blood flow velocity-time integral of the left ventricular outflow tract, and cardiac output (CO) were recorded. Responders were defined as an increment in CO of 15% or more from baseline. RESULTS: There were 33 (58.9%) mechanically ventilated patients and 22 (39.3%) spontaneously breathing patients responding to fluid resuscitation, respectively. The area under the curve was 0.80 (95% CI: 0.68-0.90) for the IVC dimeter variation (cIVC1) in mechanically ventilated patients, 0.87 (95% CI: 0.75-0.94) for the collapsibility of IVC (cIVC2), and 0.85 (95% CI: 0.73-0.93) for the minimum IVC diameter (IVCmin) in spontaneously breathing patients. The optimal cutoff value was 15.32% for cIVC1, 30.25% for cIVC2, and 1.14 cm for IVCmin. Furthermore, the gray zone for cIVC2 was 30.72 to 38.32% and included 23.2% of spontaneously breathing patients, while 17.01 to 25.93% for cIVC1 comprising 44.6% of mechanically ventilated patients. Multivariable logistic regression analysis indicated that cIVC was an independent predictor of volume assessment for patients after surgery irrespective of breathing modes. CONCLUSION: IVC respiratory variation is validated in predicting patients' volume responsiveness after abdominal surgery irrespective of the respiratory modes. However, cIVC or IVCmin in spontaneously breathing patients was superior to cIVC in mechanically ventilated patients in terms of clinical utility, with few subjects in the gray zone for the volume responsiveness appraisal. TRIAL REGISTRATION: ChiCTR-INR-17013093 . Initial registration date was 24/10/2017.

Functional echocardiographic preload markers in neonatal septic shock.

BACKGROUND: There are no established clinical or laboratory markers of preload adequacy and fluid responsiveness in management of neonatal shock. Functional echocardiographic preload markers are evaluated in children and adults, but there is no data in neonatal septic shock. We evaluated five functional echocardiographic preload markers during intravenous volume resuscitation in neonatal septic shock. OBJECTIVE: (1) To compare baseline functional echocardiographic preload markers between neonates with septic shock and their "matched" healthy controls. (2) To compare echocardiographic preload markers before and after intravenous volume resuscitation. METHODS: In this cohort study, we enrolled neonates with septic shock (cases) and recorded five preload markers - inferior vena cava collapsibility index (IVC-CI), left ventricular end-diastolic (LVEDV) & end-systolic volume (LVESV) and their indices (LVEDVI, LVESVI) - before initiation of intravenous fluid resuscitation (baseline evaluation). An equal number of "matched hemodynamically stable" controls were recruited, who underwent functional echocardiographic assessment once. In neonates with shock, we recorded these markers again after volume resuscitation. RESULTS: We analyzed 46 neonates (23 cases and 23 controls). Neonates with shock had significantly elevated baseline IVC-CI as compared to controls [53% (21, 100) vs. 20% (15, 24) respectively, p-value = .01). Rest 4 echocardiographic markers (LVEDV, LVESV, LVEDVI, and LVESVI) were comparable between cases and controls. Sixteen neonates (70% of 23) received intravenous fluid resuscitation and rest 7 (30%) were started directly on vasoactive drugs. None of the preload markers changed significantly after volume resuscitation as compared to the baseline values including IVC-CI, which was almost significant [74% (33, 100) at baseline to 48% (13, 93) after 10 mL/kg and 50% (40, 69) after 20 mL/kg, (p = .05). All preload markers were comparable between survivors and non-survivors. CONCLUSION: Neonates with septic shock had significantly elevated IVC-CI at baseline as compared to hemodynamically stable neonates. None of the preload markers changed significantly after volume resuscitation as compared to the baseline values including IVC-CI, which was almost significant.

End-tidal carbon dioxide partial pressure to assess the value of passive leg-raising test in predicting volume responsiveness in patients with septic shock / 中华危重病急救医学

Objective:To investigate the value of partial pressure of end-tidal carbon dioxide (P ETCO 2) combined with passive leg raising test (PLR) in predicting volume responsiveness in patients with septic shock. Methods:A total of 43 patients with septic shock admitted to the second department of critical care medicine, People's Hospital of Xinjiang Uygur Autonomous Region from December 2019 to June 2021 were selected as the research subjects. P ETCO 2, cardiac index (CI), stroke volume variation (SVV), mean arterial pressure (MAP) and other hemodynamic indexes were monitored before and after PLR and volume stress test (VE). Subjects were grouped according to the CI variation rate (ΔCI) after VE test. Patients with ΔCI ≥ 15% were the responding group, and patients with ΔCI < 15% were the non-responding group. The receiver operator characteristic curve (ROC curve) was drawn to analyze the evaluation value of the change in P ETCO 2 after PLR on the evaluation value of fluid responsiveness. Results:Among the 43 patients, 22 cases were in the responding group, accounting for 51.2%; 21 cases were in the non-responding group, accounting for 48.8%. After the PLR test, the change values of MAP, SVV, CI and P ETCO 2 in the responding group were higher than those in the non-responding group, and the differences were statistically significant [MAP (mmHg): 3.8±2.1 vs. 1.4±2.0, SVV (%): -5.3±2.5 vs. 2.7±2.0, CI (mL·s -1·m -2): 0.48±0.13 vs. 0.14±0.18, P ETCO 2 (mmHg): 3.4±1.8 vs. 1.1±1.0, all P < 0.05, 1 mmHg≈0.133 kPa]. After the VE test, the changes of HR, MAP, SVV, CI and P ETCO 2 in the responding group were higher than those in the non-responding group [HR (times/min): -8.3±2.8 vs. -2.3±3.7, MAP (mmHg): 3.8±2.4 vs. 1.2±1.7, SVV (%): -6.3±3.1 vs. -3.3±2.0, CI (mL·s -1·m -2): 0.51±0.14 vs. 0.16±0.12, P ETCO 2 (mmHg): 3.3±1.2 vs. 1.3±1.1, all P < 0.05]. The area under the ROC curve (AUC) of the change in P ETCO 2 before and after the PLR test (ΔP ETCO 2 PLR) for evaluating fluid responsiveness was 0.881. When the critical value was 5.9%, the sensitivity was 76.7%, the specificity was 89.5%, and the correct index was 0.68; the AUC for SVV baseline assessment of fluid responsiveness was 0.835, and when the cut-off value was 12.8%, the sensitivity was 84.6%, the specificity was 80.0%, and the correct index was 0.65. The predictive value of ΔP ETCO 2 was not lower than the SVV baseline. Conclusion:After the PLR test, the change of P ETCO 2 can be used as a non-invasive, simple, safe and reliable indicator for predicting the volume responsiveness of patients with septic shock.

Clinical study of internal jugular vein dilatation index in predicting septic shock volume responsiveness / 中华急诊医学杂志

Objective:To explore the value of severe ultrasound measurement of internal jugular vein dilation index (ΔIJV) combined with passive leg raising (PLR) in predicting the volume responsiveness of septic shock.Methods:Patients diagnosed with septic shock under complete mechanical ventilation in the ICU of Jinshan Hospital Affiliated to Fudan University from January 2020 to March 2021 were prospectively selected as the research objects. After 500 mL crystals were injected within 30 min, the patients having the "gold standard" left stroke volume (SV) increased by 15% were allocated to the volume response positive group, and patient having an SV increased by less than 15% to the volume response negative group. First, the maximum anterior posterior diameter (IJV max) and the minimum anterior posterior diameter (IJV min) in the respiratory cycle of internal jugular vein were measured by ultrasound, then SV before and after PLR was measured, and finally SV, IJV max and IJV min were measured again after rapid infusion of 500 mL crystals, and ΔIJV=(IJV max-IJV min)/(IJV mean)×100%. The Wilcoxon rank-sum test was used to compare the hemodynamic indexes before and after capacity expansion and PLR. Spearman rank method was used to analyze the change rate of SV (ΔSV) after PLR and the correlation between ΔIJV and ΔSV of the "gold standard". The sensitivity, specificity and relevant cut-off values were obtained by drawing the subject function curve to evaluate the value of ΔIJV and PLR in predicting the volume responsiveness of patients with sepsis. Results:A total of 56 patients were enrolled in the study, and they were divided into two groups: 32 patients in the volume response positive group and 24 patients in the volume response negative group. There was a positive correlation between ΔIJV and ΔSV after capacity expansion ( r=0.778, P<0.01). Taking ΔIJV>17.3% as the threshold, the area under the curve (AUC) was 0.846 (95% CI: 0.716~0.977), the sensitivity was 84.4% and the specificity was 83.3%. PLR was also positively correlated with ΔSV ( r=0.698, P<0.01). Taking ΔSV>15.5% after PLR as the threshold, the AUC was 0.895 (95% CI: 0.796~0.993), the sensitivity was 96.9%, and the specificity was 79.2%. When ΔIJV combined with PLR predicted volume reactivity, the AUC was 0.944 (95% CI: 0.862~1.000), the sensitivity was 99.8% and the specificity was 87.5%. Conclusions:The measurement of internal jugular vein respiratory dilation index by bedside ultrasound is a reliable index to predict volume responsiveness in patients with sepsis. When combined with PLR, the sensitivity and specificity of prediction can be improved.

Assessing volume responsiveness using right ventricular dynamic indicators of preload.

PURPOSE: Dynamic indicators of preload currently only do reflect preload requirements of the left ventricle. To date, no dynamic indicators of right ventricular preload have been established. The aim of this study was to calculate dynamic indicators of right ventricular preload and assess their ability to predict ventricular volume responsiveness. MATERIALS AND METHODS: The study was designed as experimental trial in 20 anaesthetized pigs. Micro-tip catheters and ultrasonic flow probes were used as experimental reference to enable measurement of right ventricular stroke volume and pulse pressure. Hypovolemia was induced (withdrawal of blood 20 ml/kg) and thereafter three volume-loading steps were performed. ROC analysis was performed to assess the ability of dynamic right ventricular parameters to predict volume response. RESULTS: ROC analysis revealed an area under the curve (AUC) of 0.82 (CI 95% 0.73-0.89; p < 0.001) for right ventricular stroke volume variation (SVVRV), an AUC of 0.72 (CI 95% 0.53-0.85; p = 0.02) for pulmonary artery pulse pressure variation (PPVPA) and an AUC of 0.66 (CI 95% 0.51-0.79; p = 0.04) for pulmonary artery systolic pressure variation (SPVPA). CONCLUSIONS: In our experimental animal setting, calculating dynamic indicators of right ventricular preload is possible and appears promising in predicting volume responsiveness.

Collapsibility of caval vessels and right ventricular afterload: decoupling of stroke volume variation from preload during mechanical ventilation.

Collapsibility of caval vessels and stroke volume and pulse pressure variations (SVV, PPV) are used as indicators of volume responsiveness. Their behavior under increasing airway pressures and changing right ventricular afterload is incompletely understood. If the phenomena of SVV and PPV augmentation are manifestations of decreasing preload, they should be accompanied by decreasing transmural right atrial pressures. Eight healthy pigs equipped with ultrasonic flow probes on the pulmonary artery were exposed to positive end-expiratory pressure of 5 and 10 cmH2O and three volume states (Euvolemia, defined as SVV < 10%, Bleeding, and Retransfusion). SVV and PPV were calculated for the right and PPV for the left side of the circulation at increasing inspiratory airway pressures (15, 20, and 25 cmH2O). Right ventricular afterload was assessed by surrogate flow profile parameters. Transmural pressures in the right atrium and the inferior and superior caval vessels (IVC and SVC) were determined. Increasing airway pressure led to increases in ultrasonic surrogate parameters of right ventricular afterload, increasing transmural pressures in the right atrium and SVC, and a drop in transmural IVC pressure. SVV and PPV increased with increasing airway pressure, despite the increase in right atrial transmural pressure. Right ventricular stroke volume variation correlated with indicators of right ventricular afterload. This behavior was observed in both PEEP levels and all volume states. Stroke volume variation may reflect changes in right ventricular afterload rather than changes in preload.NEW & NOTEWORTHY Stroke volume variation and pulse pressure variation are used as indicators of preload or volume responsiveness of the heart. Our study shows that these variations are influenced by changes in right ventricular afterload and may therefore reflect right ventricular failure rather than pure volume responsiveness. A zone of collapse detaches the superior vena cava and its diameter variation from the right atrium.

Functional Hemodynamic Monitoring With a Wireless Ultrasound Patch.

In this Emerging Technology Review, a novel, wireless, wearable Doppler ultrasound patch is described as a tool for resuscitation. The device is designed, foremost, as a functional hemodynamic monitor-a simple, fast, and consistent method for measuring hemodynamic change with preload variation. More generally, functional hemodynamic monitoring is a paradigm that helps predict stroke volume response to additional intravenous volume. Because Doppler ultrasound of the left ventricular outflow tract noninvasively measures stroke volume in realtime, it increasingly is deployed for this purpose. Nevertheless, Doppler ultrasound in this manner is cumbersome, especially when repeat assessments are needed. Accordingly, peripheral arteries have been studied and various measures from the common carotid artery Doppler signal act as windows to the left ventricle. Yet, handheld Doppler ultrasound of a peripheral artery is susceptible to human measurement error and statistical limitations from inadequate beat sample size. Therefore, a wearable Doppler ultrasound capable of continuous assessment minimizes measurement inconsistencies and smooths inherent physiologic variation by sampling many more cardiac cycles. Reaffirming clinical studies, the ultrasound patch tracks immediate SV change with excellent accuracy in healthy volunteers when cardiac preload is altered by various maneuvers. The wearable ultrasound also follows jugular venous Doppler, which qualitatively trends right atrial pressure. With further clinical research and the application of artificial intelligence, the monitoring modalities with this new technology are manifold.

End-of-Procedure Volume Responsiveness Defined by the Passive Leg Raise Test Is Not Associated With Acute Kidney Injury After Cardiopulmonary Bypass.

OBJECTIVES: Renal hypoperfusion is a common mechanism of cardiac surgery-related acute kidney injury (CS-AKI). However, the optimal amount of volume resuscitation to correct systemic hypoperfusion and prevent the postoperative development of CS-AKI has been a subject of debate. The goal of this study was to assess the association of volume responsiveness determined by stroke volume variation using the passive leg raise test (PLRT) at chest closure, with the development of CS-AKI according to the Kidney Disease Improving Global Outcomes criteria. DESIGN: Single-center, prospective observational study. SETTING: Tertiary hospital. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A total of 131 patients were studied from January 2015 until May 2017. All patients underwent cardiac surgery that required cardiopulmonary bypass. Volume responsiveness was assessed at chest closure using the PRLT. Stroke volume variation from the sitting to the recumbent positions was measured by transesophageal echocardiography. Fluid responsiveness was defined as an increase of >12% of stroke volume from sitting to recumbent positions. A total of 82 (68.3%) patients were fluid-responsive versus 38 (31.6%) who were fluid-unresponsive. CS-AKI occurred in 30% of patients. There was no difference in CS-AKI between fluid-responsive and fluid-nonresponsive groups. However, CS-AKI was associated independently with an increases in body mass index and preoperative diastolic blood pressure. CS-AKI also was associated with prolonged intensive care unit length of stay. CONCLUSION: End-of-procedure volume responsiveness is not associated with a high risk for postoperative CS-AKI.

Clinical value of point of care ultrasound on cardiac output and volume responsiveness in patients with septic shock / 中华危重病急救医学

Objective:To assess the value of point of care ultrasound on cardiac output (CO) and volume responsiveness in patients with septic shock.Methods:A prospective investigation study was conducted. Twenty-four mechanical ventilation patients with septic shock who needed pulse-indicated continuous cardiac output (PiCCO) monitoring in the department of critical care medicine of Zhengzhou University People's Hospital, Henan Provincial People's Hospital from November 25, 2020 to April 30, 2021 were selected as the subjects, the patient's basic information and laboratory test results were recorded. PiCCO was used as standard to monitor CO and stroke volume variability (SVV) at 0, 2, 6, 12, 24 and 48 hours. At the same time, point of care transthoracic echocardiography (TTE) was used to measure velocity time integral (VTI) and inferior vena cava diameter (dIVC), the CO, VTI variation rate (△VTI) and dIVC variation rate (△dIVC) were calculated. Then, using the value monitored by PiCCO as the standard, the consistency and correlation analysis were carried out between point of care ultrasound with PiCCO.Results:Twenty-two out of 24 patients obtained satisfactory ultrasound Doppler images, the heart rate (HR), mean arterial pressure (MAP) and body temperature of the enrolled patients were consistent with the pathophysiological characteristics of septic shock. With the extension of treatment time, HR and CO both gradually decreased, and MAP gradually increased, reaching a peak or trough at 48 hours after admission. The difference were statistically significant compared with the time of admission [HR (bpm): 90.36±15.35 vs. 116.82±19.82, MAP (mmHg, 1 mmHg = 0.133 kPa): 87.82±11.06 vs. 58.82±9.85, CO (L/min): 4.80±0.56 vs. 6.78±1.31, all P < 0.05]. The CO obtained by PiCCO and point of care ultrasound had good agreement [5.36 (4.78, 6.33) L/min and 5.21 (4.88, 6.35) L/min, respectively], the average difference value at each time point was (-0.02±0.69) L/min, the 95% agreement limit range was -1.35-1.34, and there was a high degree of correlation ( rs = 0.800, P < 0.001); The SVV by PiCCO and the △dIVC by point of care ultrasound were in good agreement [18.00% (14.00%, 24.00%) and 21.00% (14.00%, 25.75%), respectively], the average difference value at the time point was (-3.16±6.89)%, the 95% agreement limit range was -16.89-10.54, and there was a moderate correlation ( rs = 0.702, P < 0.001); The SVV by PiCCO and the △VTI by point of care ultrasound were in good agreement [18.00% (14.00%, 24.00%) and 16.00% (11.25%, 20.75%), respectively], the average difference value at each time point was (13.03±14.75)%, and the 95% agreement limit range was 1.72-27.78, and there was a high correlation ( rs = 0.918, P < 0.001). Conclusion:Point of care ultrasound can accurately assess CO and volume responsiveness of patients with septic shock, and the △VTI is better than the △dIVC in assessing volume responsiveness.

Application progress of point-of-care ultrasound monitoring inferior vena cava in volume management of critically ill patients / 中华危重病急救医学

Determining whether patients have volume-responsiveness is one of the frequently asked questions in the intensive care unit, especially in shock patients. Evaluating the volume status and volume responsiveness can help clinical medical staff accurately grasp the patient's cardiac preload, guide reasonable volume management, and help improve patient prognosis. Therefore, many non-invasive and invasive methods have been proposed to evaluate volume responsiveness. Inferior vena cava ultrasound has been widely used to guide the fluid management of critically ill patients due to its simplicity, non-invasiveness, and good repeatability. This article reviews the clinical applications of inferior vena cava ultrasound in fluid management of critically ill patients, so as to provide a reference for circulatory management of critically ill patients.

Accuracy assessment of noninvasive cardiac output monitoring in the hemodynamic monitoring in critically ill patients.

BACKGROUND: The consistency of cardiac output (CO) measured by noninvasive cardiac output monitoring (NICOM), pulse index continuous cardiac output (PiCCO), and ultrasound in the hemodynamic monitoring of critically ill patients was studied. Using the NICOM built-in passive leg raising (PLR) test, stroke volume index variation (∆SVI) was calculated and was used to predict volume responsiveness in patients with circulatory shock (excluding cardiogenic shock). METHODS: Critically ill patients requiring hemodynamic monitoring were admitted during the study period. The CO of each included patient under hemodynamic monitoring was measured by NICOM plus PiCCO or ultrasound, and the consistency of the measured COs was analyzed. By the NICOM built-in PLR test, ∆SVI was calculated and was used to predict volume responsiveness. RESULTS: The CO of 58 patients was measured by NICOM and ultrasound, and the COs measured by these two methods were consistent. The CO of 40 patients was measured by NICOM and PiCCO, and the COs measured by these two methods were consistent. The volume responsiveness of all 98 patients was assessed by the NICOM built-in PLR test. A total of 60 patients had ∆SVI >10%, so they underwent the fluid challenge. Among them, 43 patients were positive by both the NICOM built-in PLR and fluid challenge. When using ∆SVI to predict volume responsiveness in patients with circulatory shock (excluding cardiogenic shock), the area under the receiver operating characteristic curve was 0.754 (95% confidence interval, 0.626-0.856), and the cut-off value was 18% (sensitivity: 88.37%, specificity: 52.94%), indicating that ∆SVI has value in predicting the volume responsiveness of patients with noncardiogenic circulatory shock. CONCLUSIONS: NICOM had good consistency with ultrasound and PiCCO in the hemodynamic monitoring of critically ill patients and can be for hemodynamic monitoring and evaluation in critically ill patients. The ∆SVI obtained by the NICOM built-in PLR test has certain clinical value in predicting the volume responsiveness of patients with circulatory shock (excluding cardiac shock) and provides a method for evaluating the volume responsiveness of critically ill patients.

Super-Soft DNA/Dopamine-Grafted-Dextran Hydrogel as Dynamic Wire for Electric Circuits Switched by a Microbial Metabolism Process.

Engineering dynamic systems or materials to respond to biological process is one of the major tasks in synthetic biology and will enable wide promising applications, such as robotics and smart medicine. Herein, a super-soft and dynamic DNA/dopamine-grafted-dextran hydrogel, which shows super-fast volume-responsiveness with high sensitivity upon solvents with different polarities and enables creation of electric circuits in response to microbial metabolism is reported. Synergic permanent and dynamic double networks are integrated in this hydrogel. A serials of dynamic hydrogel-based electric circuits are fabricated: 1) triggered by using water as switch, 2) triggered by using water and petroleum ether as switch pair, 3) a self-healing electric circuit; 4) remarkably, a microbial metabolism process which produces ethanol triggering electric circuit is achieved successfully. It is envisioned that the work provides a new strategy for the construction of dynamic materials, particularly DNA-based biomaterials; and the electric circuits will be highly promising in applications, such as soft robotics and intelligent systems.

Carotid Flow as a Surrogate for Cardiac Output Measurement in Hemodynamically Stable Participants.

OBJECTIVE: Evaluation of common carotid artery (CCA) blood flow can provide valuable information regarding the hemodynamic status of a patient. Utilizing ultrasound, we aimed to evaluate the correlation between cardiac output and different hemodynamic parameters in the CCA, namely systolic carotid flow (SCF), corrected flow time (CFT), and total carotid flow (TCF). METHODS: We studied a pilot sample of 20 healthy volunteers. Hemodynamic parameters were collected in the right CCA and the heart at rest (baseline), 1-leg compression, 2-leg compression, and passive leg raise. Nonparametric Spearman correlation was calculated using STATA 13 software. RESULTS: This study demonstrated the feasibility and safety of the leg compression testing as a hemodynamic maneuver to simulate volume depletion status. We demonstrated a direct correlation between cardiac output and SCF of 0.67 with a P value < 0.001. Interestingly, TCF calculated based on volume-time integral (VTI) in the carotid artery showed positive correlation of only 0.41, with P < 0.06, and it did not reach statistical significance. We also found a positive correlation between CFT and cardiac output at baseline 0.57, with P < 0.001. CONCLUSION: Variations in cardiac preload and the subsequent alterations in cardiac output were directly translatable into variations in the carotid blood flow. This supports the potential for using carotid flow as a surrogate for cardiac output. The most promising parameters were SCF, CFT, and carotid systolic VTI. Further work is needed to validate these correlations and utilize these acquired carotid parameters to guide fluid management and predict fluid responsiveness.

Role of IVC collapsibility index to predict post spinal hypotension in pregnant women undergoing caesarean section. An observational trial.

BACKGROUND: Postspinal anesthesia hypotension (PSH) in pregnant women is common and may lead to poor maternal and fetal outcome. Fluid loading in pregnant women before spinal anesthesia to prevent hypotension is of limited ability. We hypothesized that those women who are hypovolemic before spinal anesthesia may be at risk of PSH and inferior vena cava collapsibility index (IVCCI) will be able to identify hypovolemic parturients. METHODS: In this prospective observational study, n = 45 women undergoing elective lower segment cesarean section with singleton pregnancy were recruited and IVCCI in left lateral tilt (with wedge) and supine position (without wedge) were noted by M-mode ultrasound (USG) before spinal anesthesia. After spinal anesthesia, changes in blood pressure were noted till 15 min after spinal anesthesia. RESULTS: USG measurements were obtained in 40 patients and 23 of 40 patients (57.5%) had at least one episode of hypotension. Area under the ROC curve of IVCCI with wedge to predict PSH was 0.46 (95% CI 0.27, 0.64) and best cut-of value was 25.64 with a sensitivity and specificity of 60.9% and 35.5%, respectively. Area under the ROC curve of IVCCI without wedge to predict PSH was 0.38 (95% CI 0.19, 0.56) and best cut-of value was 20.4 with a sensitivity and specificity of 69.6% and 23.5%, respectively. CONCLUSION: We conclude that IVCCI is not a predictor of PSH in pregnant women undergoing elective cesarean section.

Resuscitation Guided by Volume Responsiveness Does Not Reduce Mortality in Sepsis: A Meta-Analysis.

Resuscitation with IV fluids is a critical component in the management of sepsis. Although the optimal volume of IV fluid is unknown, there is evidence that excessive administration can be deleterious. Static measures of volume status have not proven to be meaningful resuscitative endpoints. Determination of volume responsiveness has putative benefits over static measures, but its effect on outcomes is unknown. The goal of this systematic review and meta-analysis was to determine if resuscitation with a volume responsiveness-guided approach leads to improved outcomes in septic patients. DATA SOURCES: We searched PubMed, EMBASE, CINAHL, Web of Science, Cochrane Library, and Google Scholar from inception until April 2018. STUDY SELECTION: Prospective studies of patients with sepsis, severe sepsis, or septic shock that compared volume responsiveness-guided fluid resuscitation to standard techniques and reported mortality data. DATA EXTRACTION: We extracted study details, patient characteristics, volume responsiveness assessment method, and mortality data. DATA SYNTHESIS: Of the 1,224 abstracts and 31 full-texts evaluated, four studies (total 365 patients) met inclusion criteria. Using random effects modeling, the pooled odds ratio for mortality at time of longest follow-up with a volume responsiveness-guided strategy was 0.87 (95% CI, 0.49-1.54). Pooling of clinical data was not possibly owing to heterogeneity of reporting in individual studies. CONCLUSIONS: We found no significant difference in mortality between septic patients resuscitated with a volume responsiveness-guided approach compared with standard resuscitative strategies. It remains unclear whether the findings are due to the small sample size or a true lack of efficacy of a volume responsiveness-guided approach.