The clinical role of central venous pressure measurements

Can central venous pressure help identify acute right ventricular dysfunction in mechanically ventilated critically ill patients?

OBJECTIVE

To investigate the relationship between central venous pressure (CVP) and acute right ventricular (RV) dysfunction in critically ill patients on mechanical ventilation.

METHODS

This retrospective study enrolled mechanically ventilated critically ill who underwent transthoracic echocardiographic examination and CVP monitoring. Echocardiographic indices including tricuspid annular plane systolic excursion (TAPSE), fractional area change (FAC), and tricuspid lateral annular systolic velocity wave (S') were collected to assess RV function. Patients were then classified into three groups based on their RV function and presence of systemic venous congestion as assessed by inferior vena cava diameter (IVCD) and hepatic vein (HV) Doppler: normal RV function (TAPSE ≥ 17 mm, FAC ≥ 35% and S' ≥9.5 cm/sec), isolated RV dysfunction (TAPSE < 17 mm or FAC < 35% or S' <9.5 cm/sec with IVCD ≤ 20 mm or HV S ≥ D), and RV dysfunction with congestion (TAPSE < 17 mm or FAC < 35% or S' <9.5 cm/sec with IVCD > 20 mm and HV S < D).

RESULTS

A total of 518 patients were enrolled in the study, of whom 301 were categorized in normal RV function group, 164 in isolated RV dysfunction group and 53 in RV dysfunction with congestion group. Receiver operating characteristic analysis revealed a good discriminative ability of CVP for identifying patients with RV dysfunction and congestion(AUC 0.839; 95% CI: 0.795-0.883; p < 0.001). The optimal CVP cutoff was 10 mm Hg, with sensitivity of 79.2%, specificity of 69.4%, negative predictive value of 96.7%, and positive predictive value of 22.8%. A large gray zone existed between 9 mm Hg and 12 mm Hg, encompassing 95 patients (18.3%). For identifying all patients with RV dysfunction, CVP demonstrated a lower discriminative ability (AUC 0.616; 95% CI: 0.567-0.665; p < 0.001). Additionally, the gray zone was even larger, ranging from 5 mm Hg to 12 mm Hg, and included 349 patients (67.4%).

CONCLUSIONS

CVP may be a helpful indicator of acute RV dysfunction patients with systemic venous congestion in mechanically ventilated critically ill, but its accuracy is limited. A CVP less than10 mm Hg can almost rule out RV dysfunction with congestion. In contrast, CVP should not be used to identify general RV dysfunction.

Simultaneous Venous-Arterial Doppler Ultrasound During Early Fluid Resuscitation to Characterize a Novel Doppler Starling Curve: A Prospective Observational Pilot Study

Background: The likelihood of a patient being preload responsive-a state where the cardiac output or stroke volume (SV) increases significantly in response to preload-depends on both cardiac filling and function. This relationship is described by the canonical Frank-Starling curve. Research Question: We hypothesize that a novel method for phenotyping hypoperfused patients (ie, the "Doppler Starling curve") using synchronously measured jugular venous Doppler as a marker of central venous pressure (CVP) and corrected flow time of the carotid artery (ccFT) as a surrogate for SV will refine the pretest probability of preload responsiveness/unresponsiveness. Study Design and Methods: We retrospectively analyzed a prospectively collected convenience sample of hypoperfused adult emergency department (ED) patients. Doppler measurements were obtained before and during a preload challenge using a wireless, wearable Doppler ultrasound system. Based on internal jugular and carotid artery Doppler surrogates of CVP and SV, respectively, we placed hemodynamic assessments into quadrants (Qx) prior to preload augmentation: low CVP with normal SV (Q1), high CVP and normal SV (Q2), low CVP and low SV (Q3) and high CVP and low SV (Q4). The proportion of preload responsive and unresponsive assessments in each quadrant was calculated based on the maximal change in ccFT (ccFTΔ) during either a passive leg raise or rapid fluid challenge. Results: We analyzed 41 patients (68 hemodynamic assessments) between February and April 2021. The prevalence of each phenotype was: 15 (22%) in Q1, 8 (12%) in Q2, 39 (57%) in Q3, and 6 (9%) in Q4. Preload unresponsiveness rates were: Q1, 20%; Q2, 50%; Q3, 33%, and Q4, 67%. Interpretation: Even fluid naïve ED patients with sonographic estimates of low CVP have high rates of fluid unresponsiveness, making dynamic testing valuable to prevent ineffective IVF administration.

Pulse Pressure Variation-Based Intraoperative Fluid Management Versus Traditional Fluid Management for Colon Cancer Patients Undergoing Open Mass Resection and Anastomosis: A Randomized Controlled Trial

Background

Bowel edema leads to decreased perfusion and oxygenation of the intestine at the anastomotic site after colonic mass resection with failure of healing and leakage. Additionally, dehydration causes bowel hypoperfusion and difficulty healing with more complications. Fluid therapy guided by dynamic monitoring of fluid response can help avoid bowel dehydration and edema with fewer complications.

Objectives

The main goal of this study was to compare the effects of intraoperative fluid therapy based on pulse pressure variation (PPV) to traditional fluid therapy to maintain adequate hydration without intraoperative instability of hemodynamics and postoperative complications.

Methods

This randomized controlled study was conducted on 90 adult patients (age range: 18-70 years) undergoing elective open colonic mass resection and anastomosis at Eldemerdash Hospital, Ain Shams University, Cairo, Egypt. There were two groups of patients, namely group A (n = 45; conventional fluid management [CFM] group) and group B (n = 45; goal-guided fluid management [GGFM] group based on PPV), using randomly generated data from a computer. Intraoperative fluids and vasopressors were given using GGFM or routine care. The key tool for directing hemodynamic management in the GGFM algorithm was the fluid protocol and PPV. As a result, the outcomes were measured to include the volume of intraoperative fluid, water fraction, and postoperative complications.

Results

In this study, 90 patients underwent analysis. Both groups' demographics were similar (P > 0.05). Baseline characteristics and surgical procedures did not differ significantly between the two groups (P > 0.05). Both the amount of urine output and the intraoperative administration of crystalloids were statistically significantly higher in group A (P < 0.05). The two groups' heart rate, mean arterial pressure and intraoperative usage of colloids and ephedrine were not statistically different (P > 0.05). Water fraction, bowel recovery, anastomotic leak, and length of hospital stay were significantly higher in the CFM group (P < 0.05).

Conclusions

For patients with the American Society of Anesthesiologists physical status I - II undergoing elective open resection of colonic mass and anastomosis, PPV-based GGFM, a less invasive tool for intraoperative fluid management, might be a better option than CFM.

Simultaneous venous-arterial Doppler during preload augmentation: illustrating the Doppler Starling curve

Providing intravenous (IV) fluids to a patient with signs or symptoms of hypoperfusion is common. However, evaluating the IV fluid 'dose-response' curve of the heart is elusive. Two patients were studied in the emergency department with a wireless, wearable Doppler ultrasound system. Change in the common carotid arterial and internal jugular Doppler spectrograms were simultaneously obtained as surrogates of left ventricular stroke volume (SV) and central venous pressure (CVP), respectively. Both patients initially had low CVP jugular venous Doppler spectrograms. With preload augmentation, only one patient had arterial Doppler measures indicative of significant SV augmentation (i.e., 'fluid responsive'). The other patient manifested diminishing arterial response, suggesting depressed SV (i.e., 'fluid unresponsive') with evidence of ventricular asynchrony. In this short communication, we describe how a wireless, wearable Doppler ultrasound simultaneously tracks surrogates of cardiac preload and output within a 'Doppler Starling curve' framework; implications for IV fluid dosing are discussed.

The effect of gravity-induced preload change on the venous excess ultrasound (VExUS) score and internal jugular vein Doppler in healthy volunteers

BACKGROUND

The venous excess ultrasound (VExUS) score is a multi-organ Doppler approach to assess venous congestion. Despite growing use of VExUS in research and clinical practice, other veins can be visualized to assess for venous hypertension, which may overcome acquisition barriers of the VExUS exam. In this pilot, observational study, we used a wearable Doppler ultrasound to assess the relationship between jugular venous Doppler and the VExUS score under different preload conditions. We hypothesized that jugular Doppler morphology would accurately distinguish preload conditions, that it would most closely relate to the hepatic venous Doppler morphology in the fully supine position and that the VExUS score would be influenced by preload condition.

RESULTS

We recruited 15 healthy volunteers with no cardiovascular history. Preload change was achieved using a tilt-table with three positions: supine, fully upright, and 30-degree head-down tilt. In each position, a VExUS score was performed; furthermore, inferior vena collapsibility and sphericity index were calculated. At the same time, jugular venous Doppler was captured by a novel, wireless, wearable ultrasound system. A continuous jugular venous Doppler morphology was 96% accurate for detecting the low preload condition. The jugular venous Doppler morphology was highly correlated with the hepatic vein, but only in the supine position. Gravitational position did not significantly affect the sphericity index or the VExUS score.

CONCLUSIONS

The jugular vein Doppler morphology was able to accurately distinguish low from high preload conditions in healthy volunteers. Comparisons between VExUS Doppler morphologies and other veins should occur in the supine position when gravitational pressure gradients are minimized; finally, different preload conditions in healthy subjects did not affect the VExUS score.

Right Ventricular Limitation: A Tale of Two Elastances

Right ventricular (RV) dysfunction is a commonly considered cause of low cardiac output in critically ill patients. Its management can be difficult and requires an understanding of how the RV limits cardiac output. We explain that RV stroke output is caught between the passive elastance of the RV walls during diastolic filling and the active elastance produced by the RV in systole. These two elastances limit RV filling and stroke volume and consequently limit left ventricular stroke volume. We emphasize the use of the term "RV limitation" and argue that limitation of RV filling is the primary pathophysiological process by which the RV causes hemodynamic instability. Importantly, RV limitation can be present even when RV function is normal. We use the term "RV dysfunction" to indicate that RV end-systolic elastance is depressed or diastolic elastance is increased. When RV dysfunction is present, RV limitation occurs at lowerpulmonary valve opening pressures and lower stroke volume, but stroke volume and cardiac output still can be maintained until RV filling is limited. We use the term "RV failure" to indicate the condition in which RV output is insufficient for tissue needs. We discuss the physiological underpinnings of these terms and implications for clinical management.

The magnitude, but not the duration of elevated central venous pressure is associated with mortality in sepsis patients: An analysis of the MIMIC-IV database

BACKGROUND

It is unclear whether the magnitude and duration of elevated central venous pressure (ECVP) greater than ten mmHg has the same impact on mortality in sepsis patients.

METHODS

Critically ill patients with sepsis were identified from the Medical Information Mart for Intensive Care (MIMIC)-IV database. The duration and the magnitude of ECVP were calculated. Normalized ECVP load was defined as the ECVP load (the sum of ECVP value times its duration) divided by the total duration of ECVP. The primary endpoint was 28-day mortality. Kaplan-Meier survival analysis was used to compare survival between patients with high or low normalized ECVP load.

RESULTS

A total of 1071 sepsis patients were included. Higher normalized ECVP load was associated with higher mortality rate; in contrast, the duration of ECVP was not associated with mortality. A linear relationship between normalized ECVP load and mortality was identified. Patients with higher normalized ECVP load had less urine output and more positive fluid balance.

CONCLUSION

The magnitude, but not the duration of ECVP, is associated with mortality in sepsis patients. ECVP should be considered as a valuable and easily accessible safety parameter during fluid resuscitation.

Central venous pressure estimation with force-coupled ultrasound of the internal jugular vein

We estimate central venous pressure (CVP) with force-coupled ultrasound imaging of the internal jugular vein (IJV). We acquire ultrasound images while measuring force applied over the IJV by the ultrasound probe imaging surface. We record collapse force, the force required to completely occlude the vein, in 27 healthy subjects. We find supine collapse force and jugular venous pulsation height (JVP), the clinical noninvasive standard, have a linear correlation coefficient of r² = 0.89 and an average absolute difference of 0.23 mmHg when estimating CVP. We perturb our estimate negatively by tilting 16 degrees above supine and observe decreases in collapse force for every subject which are predictable from our CVP estimates. We perturb venous pressure positively to values experienced in decompensated heart failure by having subjects perform the Valsalva maneuver while the IJV is being collapsed and observe an increase in collapse force for every subject. Finally, we derive a CVP waveform with an inverse three-dimensional finite element optimization that uses supine collapse force and segmented force-coupled ultrasound data at approximately constant force.

Correlation of internal jugular vein, common carotid artery, femoral artery and femoral vein diameters with central venous pressure

BACKGROUND

This study aimed to detect the correlation of central venous pressure (CVP) with the internal jugular vein (IJV), common carotid artery (CCA), femoral vein (FV), and femoral artery (FA) diameters measured with ultrasound (USG) in patients under mechanical ventilation to evaluate whether they are suitable to be used as an alternative low-cost and noninvasive method for the detection of CVP.

METHODS

A total of 40 patients aged from 18 to 90 who had been receiving therapy in the intensive care unit (ICU) were included in the study. Central venous catheter was placed into the patients through right IJV or subclavian vein in their first 24-hour of hospitalization and the right atrium pressure (RAP) was measured from the catheter, the tip of which was confirmed to reach right atrium. In the same session, CCA, IJV, FA, and FV diameters were measured with USG and their correlations with CVP were calculated. In addition, correlations of the measured venous and artery diameters between each other were detected as well.

RESULTS

There was a significantly high correlation between CVP and CCA diameter (R = 0.603, P < .000). There was a significantly low correlation between CVP and IJV diameter (R = 0.352, P = .026), a significantly low correlation between FA and FV diameters (R = 0.317, P = .047), a significantly low correlation between FA and CCA diameters (R = 0.330, P = .038), and a significantly low correlation between IJV and CCA diameters (R = 0.364, P = .020).

CONCLUSION

CVP and CCA diameters exhibited a high correlation. For detection of CVP, the ultrasonographic CCA diameter measurement can be used as an alternative noninvasive method which is easy to use and minimally affected by measurement errors of individuals and which has low learning curve compared with the other measurement methods.

Assessing Fluid Intolerance with Doppler Ultrasonography: A Physiological Framework

Ultrasonography is becoming the favored hemodynamic monitoring utensil of emergentologists, anesthesiologists and intensivists. While the roles of ultrasound grow and evolve, many clinical applications of ultrasound stem from qualitative, image-based protocols, especially for diagnosing and managing circulatory failure. Often, these algorithms imply or suggest treatment. For example, intravenous fluids are opted for or against based upon ultrasonographic signs of preload and estimation of the left ventricular ejection fraction. Though appealing, image-based algorithms skirt some foundational tenets of cardiac physiology; namely, (1) the relationship between cardiac filling and stroke volume varies considerably in the critically ill, (2) the correlation between cardiac filling and total vascular volume is poor and (3) the ejection fraction is not purely an appraisal of cardiac function but rather a measure of coupling between the ventricle and the arterial load. Therefore, management decisions could be enhanced by quantitative approaches, enabled by Doppler ultrasonography. Both fluid ‘responsiveness’ and ‘tolerance’ are evaluated by Doppler ultrasound, but the physiological relationship between these constructs is nebulous. Accordingly, it is argued that the link between them is founded upon the Frank–Starling–Sarnoff relationship and that this framework helps direct future ultrasound protocols, explains seemingly discordant findings and steers new routes of enquiry.

Inferring the Frank-Starling Curve From Simultaneous Venous and Arterial Doppler: Measurements From a Wireless, Wearable Ultrasound Patch

The Frank–Starling relationship is a fundamental concept in cardiovascular physiology, relating change in cardiac filling to its output. Historically, this relationship has been measured by physiologists and clinicians using invasive monitoring tools, relating right atrial pressure (P_ra) to stroke volume (SV) because the P_ra-SV slope has therapeutic implications. For example, a critically ill patient with a flattened P_ra-SV slope may have low P_ra yet fail to increase SV following additional cardiac filling (e.g., intravenous fluids). Provocative maneuvers such as the passive leg raise (PLR) have been proposed to identify these “fluid non-responders”; however, simultaneously measuring cardiac filling and output via non-invasive methods like ultrasound is cumbersome during a PLR. In this Hypothesis and Theory submission, we suggest that a wearable Doppler ultrasound can infer the P_ra-SV relationship by simultaneously capturing jugular venous and carotid arterial Doppler in real time. We propose that this method would confirm that low cardiac filling may associate with poor response to additional volume. Additionally, simultaneous assessment of venous filling and arterial output could help interpret and compare provocative maneuvers like the PLR because change in cardiac filling can be confirmed. If our hypothesis is confirmed with future investigation, wearable monitors capable of monitoring both variables of the Frank–Starling relation could be helpful in the ICU and other less acute patient settings.

Association Between the Central Venous Pressure and All-Cause Mortality in Critically Ill Patients with Acute Kidney Injury

Purpose

Elevated central venous pressure (CVP) plays an important role in the occurrence of acute kidney injury (AKI) and it is also independently associated with the prognosis of critically ill patients. However, the effect of CVP on critically ill AKI patients remains unclear. In this study, we analyzed the relationship between CVP and all-cause mortality of critically ill patients with AKI.

Patients and Methods

The clinical data of patients in intensive care unit (ICU) were retrieved from the Medical Information Mart for Intensive Care III (MIMIC-III) database and retrospectively analyzed. The all-cause mortality for up to 90 days was the main observed outcome. We used the minimum CVP value obtained during the first 72 hours after ICU admission for our analysis and patients were grouped according to this parameter. Patients were also analyzed after being further divided according to stages 1, 2 and 3 of AKI. Multiple Cox regression and Kaplan–Meier analyses were used to explore the association between CVP measurements and death of ICU patients with AKI.

Results

A total of 1986 ICU patients with AKI were studied. A total of 527 (26.5%) patients died by day 90. The high CVP group (patients with ≥10 mmHg) had the lowest 90-day survival rate (P =0.001 by log rank test) when according to Kaplan–Meier analysis. By using Cox regression analysis, high CVP was found to be linked to an increase in mortality (CVP ≥10 mmHg versus ≤5 mmHg, HR, 1.336, 95% CI, 1.064 to 1.677, P trend=0.014). Furthermore, when using in a multivariate Cox regression analysis with CVP as a continuous variable, the higher CVP levels were still an independent risk factor for 90-day all-cause mortality (per 1 mmHg increase, HR, 1.031, 95% CI, 1.013–1.049, P=0.001). In subgroup analysis, a similar trend was observed in patients with AKI stages 2 and 3.

Conclusion

The minimum CVP level during the first 72h after ICU admission was positively associated with mortality in critically ill patients with AKI and this more marked in cases with severe AKI.

[The use of diuretics in chronic heart failure. Position paper of the Russian Heart Failure Society]

The document focuses on key issues of diuretic therapy in CHF from the standpoint of current views on the pathogenesis of edema syndrome, its diagnosis, and characteristics of using diuretics in various clinical situations.

Central Venous Pressure Estimation by Ultrasound Measurement of Inferior Vena Cava and Aorta Diameters in Pediatric Critical Patients: An Observational Study

OBJECTIVES

To evaluate the ability to predict central venous pressure by ultrasound measured inferior vena cava and aortic diameters in a PICU population and to assess interoperator concordance.

DESIGN

Noninterventional observational study.

SETTING

PICU of a tertiary-care academic center.

PATIENTS

Eighty-eight pediatric patients (0-16 yr old) with a central venous catheter in place were studied. Sixty-nine percent of the patients received positive-pressure ventilation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

An experienced and a nonexperienced operator used ultrasound to measure the maximal diameter of inferior vena cava and minimal diameter of the inferior vena cava and the maximum diameter of the abdominal aorta from the subxiphoid window. The inferior vena cava collapsibility index and the ratio of maximal diameter of inferior vena cava/maximum diameter of the abdominal aorta were then derived. The central venous pressure was measured using a central venous catheter and recorded. Twenty-three patients had low central venous pressure values (≤ 4 mm Hg), 35 patients a value in the range of 5-9 mm Hg, and 30 patients high values (≥ 10 mm Hg). Both inferior vena cava collapsibility index and ratio of maximal diameter of inferior vena cava/maximum diameter of the abdominal aorta were predictive of high (≥ 10 mm Hg) or low (≤ 4 mm Hg) central venous pressure. The test accuracy showed the best results in predicting low central venous pressure with an inferior vena cava collapsibility index greater than or equal to 35% and ratio of maximal diameter of inferior vena cava/maximum diameter of the abdominal aorta less than or equal to 0.8, and in predicting high central venous pressure with an inferior vena cava collapsibility index less than or equal to 20% and ratio of maximal diameter of inferior vena cava/maximum diameter of the abdominal aorta greater than or equal to 1.3. Inferior vena cava collapsibility index returned generally higher accuracy values than ratio of maximal diameter of inferior vena cava/maximum diameter of the abdominal aorta. Lin's coefficient of concordance between the operators was 0.78 for inferior vena cava collapsibility index and 0.86 for ratio of maximal diameter of inferior vena cava/maximum diameter of the abdominal aorta.

CONCLUSIONS

Inferior vena cava collapsibility index and ratio of maximal diameter of inferior vena cava/maximum diameter of the abdominal aorta correlate well with central venous pressure measurements in this PICU population, and specific inferior vena cava collapsibility index or ratio of maximal diameter of inferior vena cava/maximum diameter of the abdominal aorta thresholds appear to be able to differentiate children with high or low central venous pressure. However, the actual clinical application of these statistically significant results remains limited, especially by the intrinsic flaws of the procedure.

Recommendations for hemodynamic monitoring for critically ill children-expert consensus statement issued by the cardiovascular dynamics section of the European Society of Paediatric and Neonatal Intensive Care (ESPNIC)

BACKGROUND

Cardiovascular instability is common in critically ill children. There is a scarcity of published high-quality studies to develop meaningful evidence-based hemodynamic monitoring guidelines and hence, with the exception of management of shock, currently there are no published guidelines for hemodynamic monitoring in children. The European Society of Paediatric and Neonatal Intensive Care (ESPNIC) Cardiovascular Dynamics section aimed to provide expert consensus recommendations on hemodynamic monitoring in critically ill children.

METHODS

Creation of a panel of experts in cardiovascular hemodynamic assessment and hemodynamic monitoring and review of relevant literature-a literature search was performed, and recommendations were developed through discussions managed following a Quaker-based consensus technique and evaluating appropriateness using a modified blind RAND/UCLA voting method. The AGREE statement was followed to prepare this document.

RESULTS

Of 100 suggested recommendations across 12 subgroups concerning hemodynamic monitoring in critically ill children, 72 reached "strong agreement," 20 "weak agreement," and 2 had "no agreement." Six statements were considered as redundant after rephrasing of statements following the first round of voting. The agreed 72 recommendations were then coalesced into 36 detailing four key areas of hemodynamic monitoring in the main manuscript. Due to a lack of published evidence to develop evidence-based guidelines, most of the recommendations are based upon expert consensus.

CONCLUSIONS

These expert consensus-based recommendations may be used to guide clinical practice for hemodynamic monitoring in critically ill children, and they may serve as a basis for highlighting gaps in the knowledge base to guide further research in hemodynamic monitoring.

Pulmonary hypertension with adult respiratory distress syndrome: prevalence, clinical impact, and association with central venous pressure

Pulmonary hypertension (PH) occurs in patients with acute respiratory distress syndrome (ARDS); the most severe form comprises acute cor pulmonale (ACP). Here, we investigated the prevalence of PH in patients with ARDS to evaluate its correlation with ACP risk, ARDS severity and central venous pressure (CVP). We conducted a secondary analysis using data from the MIMIC-III open-source clinical database. The prevalence of PH associated with new-onset ARDS during the first 72 h after intensive care unit admission was investigated; moreover, the association between ACP risk score and PH was validated. We also evaluated the association between elevated CVP (mean CVP > 10 mmHg) and PH and other clinical outcomes. Among 2434 patients who met the ARDS Berlin criteria and underwent echocardiography or pulmonary artery catheterization evaluation, a total of 583 (24.0%) patients were diagnosed with moderate or severe PH, of which 418 had low and 165 had high ACP risk. After adjustment for disease/ARDS severity, ACP risk score, and other demographic variables, elevated CVP was independently associated with the occurrence of PH (odds ratio, 2.239 (1.674, 2.993), p < 0.005). Among patients with PH, higher mean CVP was associated with prolonged hospital stay (13.4 vs. 15.2 days, p = 0.041) and duration of ventilation (116.5 vs. 150.5 h, p = 0.023). Incidence of PH was 24.0% in patients with new-onset ARDS in this retrospective study. Elevated CVP is relevant with higher incidence of PH and worse clinical outcome; these highlighted the importance of hemodynamic monitoring in the management of ARDS.

Understanding basic vein physiology and venous blood pressure through simple physical assessments

An understanding of the complexity of the cardiovascular system is incomplete without a knowledge of the venous system. It is important for students to understand that, in a closed system, like the circulatory system, changes to the venous side of the circulation have a knock-on effect on heart function and the arterial system and vice versa. Veins are capacitance vessels feeding blood to the right side of the heart. Changes in venous compliance have large effects on the volume of blood entering the heart and hence cardiac output by the Frank-Starling Law. In healthy steady-state conditions, venous return has to equal cardiac output, i.e., the heart cannot pump more blood than is delivered to it. A sound understanding of the venous system is essential in understanding how changes in cardiac output occur with changes in right atrial pressure or central venous pressure, and the effect these changes have on arterial blood pressure regulation. The aim of this paper is to detail simple hands-on physiological assessments that can be easily undertaken in the practical laboratory setting and that illustrate some key functions of veins. Specifically, we illustrate that venous valves prevent the backflow of blood, that venous blood pressure increases from the heart to the feet, that the skeletal muscle pump facilitates venous return, and we investigate the physiological and clinical significance of central venous pressure and how it may be assessed.

Prediction of the central venous pressure in trauma patients on the basis of non-invasive parameters using artificial neural network

Background:

Generally, in traumatic patients, uncontrolled bleeding leads to shock and ultimately death. So, any early detection of shock can reduce the likelihood of a patient’s death. At present, the precise method for estimating the body’s need for fluids is to measure central venous pressure (CVP). However, this method is invasive and time consuming.

Objective:

This study aimed to predict the central venous pressure value and range of trauma patients through non-invasive parameters such as caval index, lactate clearance, base excess and shock index.

Methods:

A prospective observational study was performed in 100 trauma patients. Written informed consent was obtained from patient(s) or relatives for their anonymized information to be published in any article.

Results:

It indicated that parameters such as caval index (at a proposed cutoff point of 35%), lactate clearance (at a cutoff point of 6%) and base excess (at a proposed cutoff point of 6 mmol/L) are approximately of the same level of accuracy for estimating the central venous pressure range, while parameter shock index (at a cutoff point of 1.25) is of the least level of accuracy to predict the central venous pressure range. Results also showed that among all proposed predictive models for estimating the central venous pressure value, which were on the basis of either non-linear regression or artificial neural network, the most accurate model was the one on the basis of the artificial neural network. Among parameters lactate clearance, base excess and shock index used to form the artificial neural network-based model, parameters base excess and lactate clearance were of the highest and lowest level of importance, respectively.

Conclusion:

Among all proposed models and non-invasive parameters to predict the central venous pressure range, CVPLC model (at a cutoff point of 9), which is a non-linear regression model and is in terms of parameter lactate clearance, was the most accurate model.

Role of Internal Jugular Vein Ultrasound Measurements in the Assessment of Central Venous Pressure in Spontaneously Breathing Patients: A Systematic Review

BACKGROUND

Few studies have tested the role of the internal jugular vein (IJV) ultrasonographic (US) diameters in the assessment of central venous pressure (CVP) in spontaneously breathing patients. No review or meta-analysis is currently available on the role of IJV assessment in this setting. The aim of this systematic review is to check the reliability and accuracy of IJV US diameters in predicting CVP and to evaluate its correlation with CVP in spontaneously breathing patients.

METHODS

This systematic review was based on the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines. We included studies on the accuracy and reliability of the IJV ultrasound measures and studies exploring its correlation with CVP in adult spontaneously breathing patients. The studies' report quality was assessed by Standards for Reporting of Diagnostic Accuracy (STARD) and Quality Assessment of Diagnostic Accuracy Studies (QUADAS)-2 scales.

RESULTS

A total of five studies was eligible for final analysis. The studies on IJV ultrasound measures showed a good quality in reporting. The anterior-posterior diameter maximum of IJV (AP-IJV Dmax) showed the best correlation with the CVP with a good inter-rater reliability and validity in predicting CVP. All measures showed good inter-rater reliability and validity in predicting CVP, but only the AP-IJV Dmax showed good correlation with CVP.

CONCLUSIONS

The AP-IJV Dmax could be a potential surrogate of CVP because of its good reliability and validity in predicting CVP value and its fair-moderate correlation with CVP. Anyway, further research should confi rm these conclusions.

Noninvasive estimation of intravascular volume status in cirrhosis by dynamic size and collapsibility indices of the inferior vena cava using bedside echocardiography

Background and Aim

Echocardiographic assessment of the inferior vena cava diameter (IVCD) and collapsibility index (IVCCI) is a noninvasive estimate of intravascular volume status (IVS) but requires validation for cirrhosis. We evaluated IVC dynamics in cirrhosis and correlated it with conventional tools such as central venous pressure (CVP), pulmonary capillary wedge pressure (PCWP), and right atrial pressure (RAP).

Methods

A total of 673 consecutive cirrhotic patients were screened by echocardiography, and 125 patients underwent right heart catheterization with recording of hepatic venous pressure gradient (HVPG), RAP, pulmonary artery (PA) pressure, and PCWP. CVP data were available for 80 (64%) patients, and finally, 76 patients (84% male, 50% ethanol related, mean age 52.1 years, 57.8% with ascites) with complete data were enrolled.

Results

The mean CVP measured was 12.8 ± 4.8 mmHg, and IVCCI was 29.5 ± 10.9%. The IVCD ranged from 0.97 to 2.26 cm and from 0.76 to 1.84 cm during expiration and inspiration, respectively, with a mean of 1.8 ± 0.9 cm. The mean IVCD correlated with RAP (r = 0.633, P = 0.043) but not with HVPG (r = 0.344, P = 0.755), PCWP (r = 0.562, P = 0.072), or PA pressure (r = 0.563, P = 0.588). A negative linear correlation was observed between the CVP and the IVCCI (r = −0.827, P = 0.023) in all patients and substratified for those with (r = −0.748, P = 0.039) and without ascites (r = −0.761, P = 0.047). A positive correlation was observed between CVP and IVCD_max (r = 0.671, P = 0.037) and IVCD_min (r = 0.612, P = 0.040).

Conclusions

IVCD and collapsibility index provides noninvasive IVS assessment, independent of HVPG or ascites, with the potential for calculating fluid requirements in cirrhosis.

Renal failure in critically ill patients, beware of applying (central venous) pressure on the kidney

The central venous pressure (CVP) is traditionally used as a surrogate of intravascular volume. CVP measurements therefore are often applied at the bedside to guide fluid administration in postoperative and critically ill patients. Pursuing high CVP levels has recently been challenged. A high CVP might impede venous return to the heart and disturb microcirculatory blood flow which may cause tissue congestion and organ failure. By imposing an increased "afterload" on the kidney, an elevated CVP will particularly harm kidney hemodynamics and promote acute kidney injury (AKI) even in the absence of volume overload. Maintaining the lowest possible CVP should become routine to prevent and treat AKI, especially when associated with septic shock, cardiac surgery, mechanical ventilation, and intra-abdominal hypertension.

High central venous pressure is associated with acute kidney injury and mortality in patients underwent cardiopulmonary bypass surgery

PURPOSE

We sought to investigate the relationship between high CVP, AKI, and mortality in patients undergoing cardiac surgery with cardiopulmonary bypass.

MATERIALS

All patients aged 18 years or older who underwent cardiac surgery with CPB were prospectively reviewed. Patients were excluded when renal artery were involved before and during surgery. Patients were dichotomized into high CVP group(>10 mmHg) and low CVP group(<10 mmHg). All patients were followed by telephone.

RESULTS

A total of 1941 patients were included in observed study. In high CVP group, three hundred forty-seven patients (43.32%) developed AKI, while eighty-six (7.543%) in low CVP group(P <0.0001). Furthermore, in every KDIGO stage, patients of AKI in high CVP group were more than those in low CVP group(P <0.0001). The incidence of AKI increased as CVP increased, especially when CVP was higher than 10cmH2O. In a median follow-up time of 9.2 months, Crude mortality is 8.365% in the high CVP group compared to 1.929% in the low CVP group (p<0.0001). In multivariate analysis, CVP remained the independent predictor of survival.

CONCLUSIONS

High CVP is associated with AKI , and it is independently related to all-cause mortality in patients underwent cardiovascular surgery with cardiopulmonary bypass.

A Comparison between the Bedside Sonographic Measurements of the Inferior Vena Cava Indices and the Central Venous Pressure While Assessing the Decreased Intravascular Volume in Children

Background:

Hemodynamic monitoring is an essential part in the treatment of critically ill patients. Establishment of intravascular volume and creation of a normal systemic perfusion are the most important part to reduce the risk of organ failure and mortality. This study aimed to determine the correlation between the inferior vena cava (IVC) sonographic indices and the central venous pressure (CVP) to provide a useful guide for noninvasive intravascular volume status assessment in children.

Materials and Methods:

Target sample of children who were admitted to the pediatric critical care unit and required CVP monitoring were enrolled in this study. The collapsibility index (CI) and IVC/aorta (AO) ratio, from bedside ultrasonography measurement of the IVC, were calculated.

Results:

Of the 70 participants, 22 patients (31.4%) revealed a CVP of 8 mm/Hg or less and 48 patients (68.6%) revealed a CVP >8 mm/Hg. Fifty-six patients (80%) had an IVC-CI of 0.5 or greater and 17 patients (24.3%) had an IVC/AO of 0.8 or less. IVC-CI index is 45.5% sensitive and 91.7% specific with positive predictive value of 71.4 and negative predictive value of 78.6 to predict CVP <8, and the IVC/AO index is 50.8% sensitive and 87.5% specific with a positive predictive value of 64.7 and a negative predictive value of 79.2 to predict CVP <8.

Conclusion:

Based on the present finding, the IVC sonographic indices provide a useful guide for noninvasive intravascular volume status assessment in children.

Comparison of conventional fluid management with PVI-based goal-directed fluid management in elective colorectal surgery

Intraoperative fluid management is quite important in terms of postoperative organ perfusion and complications. Different fluid management protocols are in use for this purpose. Our primary goal was to compare the effects of conventional fluid management (CFM) with the Pleth Variability Index (PVI) guided goal-directed fluid management (GDFM) protocols on the amount of crystalloids administered, blood lactate, and serum creatinine levels during the intraoperative period. The length of hospital stay was our secondary goal. Seventy ASA I–II elective colorectal surgery patients were randomly assigned to CFM or GDFM for fluid management. The hemodynamic data and the data obtained from ABG were recorded at the end of induction and during the follow-up period at 1 h intervals. In the preoperative period and at 24 h postoperatively, blood samples were taken for the measurement of hemoglobin, Na, K, Cl, serum creatinine, albumin and blood lactate. In the first 24 h after surgery, oliguria and the time of first bowel movement were recorded. Length of hospital stay was also recorded. Intraoperative crystalloid administration and urine output were statistically significantly higher in CFM group (p < 0.001, p: 0.018). The end-surgery fluid balance was significantly lower in Group GDFM. Preoperative and postoperative Na, K, Cl, serum albumin, serum creatinine, lactate and hemoglobin values were similar between the groups. The time to passage of stool was significantly short in Group-GDFM compared to Group-CFM (p = 0.016). The length of hospital stay was found to be similar in both group. PVI-guided GDFM might be an alternative to CFM in ASA I–II patients undergoing elective colorectal surgery. However, further studies need to be carried out to search the efficiency and safety of PVI.

Elevated central venous pressure is associated with increased mortality in pediatric septic shock patients

BACKGROUND

Central venous pressure (CVP) is an important factor affecting capillary blood flow, and it is associated with poor outcomes in adult septic shock patients. However, whether a similar association exists in pediatric patients remains unclear.

METHODS

We retrospectively analyzed data from patients admitted to our pediatric intensive care unit (PICU) between February 2009 and July 2015. Patients were divided into two groups-survivors and nonsurvivors-according to 28-day mortality. The associations between (a) mortality and CVP at 6, 24, 48, and 72 h after initiating treatment for established septic shock was analyzed and (b) initial serum lactic acid levels and 6-h CVP.

RESULTS

Two hundred twenty-six patients were included in this study, and the mortality rate was 29.6% (67 deaths, nonsurvivor group). Initial serum lactic acid levels, Pediatric Risk of Mortality (PRISM) III score, and Vasoactive-Inotropic Score (VIS) within 24 h after PICU admission were significantly higher in the nonsurvivors than in survivors (1.3 [0.9, 2.4] vs. 3.9 [1.6, 8.0] mmol/l, 11.0 [7.0, 15.0] vs. 17.0 [10.0, 21.5], 12.0 [7.0, 25.0] vs. 22.5 [8.0, 55.0], respectively with p-values < 0.001, < 0.001, and 0.009, respectively). In addition, compared to survivors, a greater percentage of nonsurvivors required mechanical ventilation (92.5% vs. 51.6%, p <  0.001) and showed a greater extent of fluid overload at 48 h after admission (3.9% vs. 1.9%, p = 0.006), along with higher 6-h CVP (10.0 [7.0, 16.0] vs. 8.0 [5.0, 11.0] mmHg, p <  0.001). Patient survival according to levels of CVP (CVP < 8 mmHg, CVP 8-12 mmHg, or CVP > 12 mmHg) showed that the CVP > 12-mmHg group had significantly greater mortality rates (50.0%, p = 0.002) than the other groups (21.3% and 27.5%). Furthermore, multivariate analysis identified significant associations of CVP > 12 mmHg, serum lactic acid levels, and the need for mechanical ventilation with mortality (OR: 2.74, 1.30, and 12.51, respectively; 95% CI: 1.11-6.72, 1.12-1.50, and 4.12-37.96, respectively).

CONCLUSIONS

Elevated CVP is an independent risk factor for mortality in pediatric septic shock patients.

Association between elevated central venous pressure and outcomes in critically ill patients

Background

Some prior studies have shown that elevated mean central venous pressure in certain patient populations and disease processes may lead to poor prognosis. However, these studies failed to generalize the concept of elevated central venous pressure (ECVP) load to all patients in critical care settings because of the limited cases and exclusive cohorts. The aim of the study was to investigate the association between elevated central venous pressure and outcomes in critical care.

Methods

We performed a retrospective analysis on a single-center public database (MIMIC) of more than 9000 patients and more than 500,000 records of central venous pressure measurement. We evaluated the association between mean central venous pressure level and 28-day mortality after intensive care unit admission. The secondary outcomes were duration of mechanical ventilation, vasoactive drug use, laboratory results related to organ dysfunction and length of intensive care unit hospitalization. Accordingly, we proposed the concept of ECVP₁₀ (the time sum of CVP above 10 mmHg) and investigated its association with outcome.

Results

There were 1645 deaths at 28 days after admission. Compared with the lowest quartile of mean central venous pressure [mean (SD) 7.4 (1.9) mmHg], the highest quartile [17.4 (4.1) mmHg] was associated with a 33.6% (95% CI 1.117–1.599) higher adjusted risk of death. Poor secondary outcomes were also associated with higher quartiles of elevated mean central venous pressure. After stratification by mean central venous pressure, elevated duration of central venous pressure above 10 mmHg was significantly higher in the non-survival group than in the survival group.

Conclusions

Elevated central venous pressure level correlated with poor outcomes and prolonged treatment in critical care settings. Level and duration of elevated central venous pressure should be both evaluated to establish its cause and apply appropriate treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s13613-017-0306-1) contains supplementary material, which is available to authorized users.

Impact of restrictive fluid protocol on hypoxemia after aneurysmal subarachnoid hemorrhage

PURPOSE

In patients with aneurysmal subarachnoid hemorrhage (aSAH), acute cardiac dysfunction and triple-H-therapy, can lead to hypoxemia. Our aim was to assess impact of a protocoled fluid restrictive approach on hypoxemia in these patients.

METHODS

We included prospectively ICU patients with aSAH admitted within 24h after the bleed. The study was divided into 2 phases. The first phase, from January to December 2012, was designated as control group (group C). The second phase, from February 2014 to January 2015, was designated as study group (group S). Between these periods, a protocoled fluid intake approach was implemented to maintain as low as possible the cumulative fluid balances.

RESULTS

Effective fluid restriction was obtained: at day 3 cumulative fluid balances were respectively for group C and group S, 1559±2402ml and 759±1855ml (p=0.04); and 2211±4918ml vs 529±2806ml (p=0.04) at day 7. We observed reduction in proportion of hypoxemic patient in group S compared to group C, at day 3 (22% vs 40%, p=0.047) and at day 7 (28% vs 57%, p=0.007).

CONCLUSIONS

Fluid restrictive management of patients with aSAH decreases number of hypoxemic patients at day 3 and day 7.

Right Atrial Pressure in the Critically Ill: How to Measure, What Is the Value, What Are the Limitations?

Right atrial pressure (P_ra) is determined by the interaction of the function of the heart as a pump, which is called cardiac function, and the factors that determine the return of blood to the heart, which is called return function. Thus, monitoring P_ra or its surrogate, central venous pressure (CVP), can give important insights into mechanisms behind changes in hemodynamic status, responses to interventions, and the likelihood of diagnoses. Examination of the components of the P_ra tracing, especially during the ventilator cycle, can also give information about right-sided cardiac diastolic function, the status of the tricuspid valve, volume responsiveness, and the cardiac rhythm. Importantly, the pressure difference from the large venous reservoir to the heart is small, and thus great care must be taken with technical factors that affect the measurement.

Initial central venous pressure could be a prognostic marker for hemodynamic improvement of polymyxin B direct hemoperfusion: a retrospective cohort study

BACKGROUND

Direct hemoperfusion with polymyxin B-immobilized fiber column (PMX-DHP) could improve the hemodynamic status of septic shock patients. As PMX-DHP is an invasive and costly procedure, it is desirable to estimate the therapeutic effect before performing the therapy. However, it is still unclear when this therapy should be started and what type of sepsis it should be employed for. In this study, we retrospectively examined the clinical effect of patients treated with PMX-DHP by using central venous pressure (CVP).

METHODS

Seventy patients who received PMX-DHP for septic shock during the study period were recruited and divided into a low CVP group (n = 33, CVP < 12 mmHg) and a high CVP group (n = 37, CVP≧12 mmHg). The primary endpoint was vasopressor dependency index at 24 hours after starting PMX-DHP, and the secondary endpoint was the 28-day survival rate. Additionally, we performed a multivariate linear regression analysis on the difference in the vasopressor dependency index.

RESULTS

The vasopressor dependency index significantly improved at 24 h in the low CVP group (0.33 to 0.16 mmHg^-1; p < 0.01) but not in the high CVP group (0.43 to 0.34 mmHg^-1; p = 0.41), and there was a significant difference between the two groups in the index at 24 h (p = 0.02). The 28-day survival rate was higher in the low CVP group (79 vs. 43 %; p < 0.01). Multivariate linear regression analysis showed that CVP (p = 0.04) was independently associated with the difference in the vasopressor dependency index.

CONCLUSIONS

Our study indicates that the clinical effect of PMX-DHP for septic shock patients with higher CVP (≧12 mmHg) might be limited and that the initial CVP when performing PMX-DHP could function as an independent prognostic marker for the hemodynamic improvement.

Identifying the position of the right atrium to align pressure transducer for CVP : Spirit level or 3D electromagnetic positioning?

The central venous pressure, CVP, is an important variable in the management of selected perioperative and intensive care cases and in clinical decision support systems, CDSS. In current routine, when measuring CVP the health care provider may use anatomical landmarks and a spirit level, SL, to adjust the pressure transducer to the level of the tricuspid valve, i.e. the phlebostatic axis. The aim of the study was to assess the agreement in the postoperative setting between the SL method and electromagnetic 3D positioning (EM). CVP was measured with patients in positions dictated by nursing routines. The staff members measured CVP using SL to position the transducer at the perceived phlebostatic level. This position was compared to coordinates based on an electromagnetic field with external sensors at anatomical landmarks and an internal sensor in the CV catheter for 3D determination of the phlebostatic axis. An electronic survey took bearing on the accepted error in measurement among colleagues at the department. There was a clinically relevant difference between the CVP measured by the staff members and the CVP based on the 3D EM positioning. The limits of agreement extended in excess of ±8 mmHg and half of the measurements had deviations outside an accepted error range of ±2.5 mmHg. There was a large variation in CVP measurements when assessing the agreement with the current method. This may indicate the need for improvement in accuracy, e.g. using the electromagnetic field positioning system, in association with routine monitoring and clinical decision support systems.

The Use of Internal Jugular Vein Ultrasonography to Anticipate Low or High Central Venous Pressure During Mechanical Ventilation

BACKGROUND

Critically low or high central venous pressure (CVP) values, together with systemic hypotension, can indicate hypovolemia or acute heart failure. However, measuring CVP requires the insertion of a central venous catheter, a time-consuming procedure that can be associated with severe complications.

OBJECTIVE

We sought to evaluate the use of ultrasonography of the internal jugular vein (IJV) to estimate low or high CVP values in patients who were on ventilation.

METHODS

Ultrasonography of IJV dimensions and the collection of hemodynamic data was performed in 47 patients, and the ratio between IJV diameter in the 30° and 0° position was calculated (ratio(30/0)). The predictive value of ratio(30/0) for estimating low and high CVP levels was analyzed using receiver operating characteristic curves.

RESULTS

The median IJV diameter ratio(30/0) was 0.49. CVP ranged from 1 to 13 mm Hg (median 7 mm Hg). Seventeen patients had a CVP ≤ 5 mm Hg or lower (defined as "low"), and in 11 patients, values of ≥ 10 mm Hg were measured (defined as "high"). The corresponding IJV diameter ratios increased significantly from 0.34 (in the low CVP group) to 0.9 (in the high CVP group). Receiver operating characteristic analysis revealed a good predictive value of the ratio(30/0) for the prediction of low or high CVP values, respectively. A ratio(30/0) of < 0.45 optimally indicated a low CVP, while > 0.65 was the cutoff value to detect a CVP ≥ 10 mm Hg.

CONCLUSION

The estimation of low or high CVP values by IJV ultrasonography in different patient positions can be a helpful instrument for the rapid hemodynamic assessment of the critically ill patient.

Invasive hemodynamic monitoring

Although invasive hemodynamic monitoring requires considerable skill, studies have shown a striking lack of knowledge of the measurements obtained with the pulmonary artery catheter (PAC). This article reviews monitoring using a PAC. Issues addressed include basic physiology that determines cardiac output and blood pressure; methodology in the measurement of data obtained from a PAC; use of the PAC in making a diagnosis and for patient management, with emphasis on a responsive approach to management; and uses of the PAC that are not indications by themselves for placing the catheter, but can provide useful information when a PAC is in place.

Inverted U-Shaped Relationship between Central Venous Pressure and Intra-Abdominal Pressure in the Early Phase of Severe Acute Pancreatitis: A Retrospective Study

OBJECTIVE

Many studies have indicated that intra-abdominal pressure (IAP) is positively correlated with central venous pressure (CVP) in severe cases. However, although elevated IAP is common in patients with severe acute pancreatitis (SAP), its relationship with CVP remains unclear. Our study aimed to investigate the association of IAP with CVP in early-phase SAP patients.

METHODS

In total, 116 SAP patients were included in this retrospective study. On the first day of hospitalization, blood samples were collected for biochemical examination and cytokine concentration monitoring. Additionally, a urinary catheter and right subclavian vein catheter were inserted for IAP and CVP measurement, respectively. Other routine clinical data were also recorded.

RESULTS

Within 24 hours after hospitalization, CVP fluctuated and increased with increasing IAP up to 15.7 mmHg (P = 0.054) but decreased with increasing IAP when the IAP was > 15.7 mmHg (P < 0.001). After adjusting for abdominal perfusion pressure (APP) and mean arterial pressure (MAP), a similar distribution was observed. An inverted U-shaped trend between IAP and CVP was also present in the groups classified according to the patient's sex, local complications, ascites, and serum amylase levels.

CONCLUSIONS

CVP and IAP have an inverted U-shaped relationship, with a peak at an IAP of 15.7 mmHg in the early phase of SAP. After this peak, CVP decreases as IAP increases. These results have crucial implications for clinical fluid resuscitation in SAP patients. In particular, because one CVP value might be correlated with different IAP values in patients with the same CVP, the volume of fluid needed might be different.

Current tools for assessing heart function and perfusion adequacy

PURPOSE OF REVIEW

Many devices are currently available for measuring cardiac output and function. Understanding the utility of these devices requires an understanding of the determinants of cardiac output and cardiac function, and the use of these parameters in the management of critically ill patients. This review stresses the meaning of the physiological measures that are obtained with these devices and how these values can be used.

RECENT FINDINGS

Evaluation of devices for haemodynamic monitoring can include just measurement of cardiac output, the potential to track spontaneous changes in cardiac output or changes produced by volume infusions or vasoactive drugs, or the ability to assess cardiac function. Each of these puts different demands on the need for accuracy, precision, and reliability of the devices, and thus devices must be evaluated based on the clinical need.

SUMMARY

Evaluation of cardiac function is useful when first dealing with an unstable patient, but for ongoing management measurement of cardiac output itself is key and even more so the trend in relationship to the patient's overall condition. This evaluation would be greatly benefited by the addition of objective measures of tissue perfusion.

Increased fluid administration in the first three hours of sepsis resuscitation is associated with reduced mortality: a retrospective cohort study

BACKGROUND

The surviving sepsis guidelines recommend early aggressive fluid resuscitation within 6 h of sepsis onset. Although rapid fluid administration may offer benefit, studies on the timing of resuscitation are lacking. We hypothesized that there is an association between quicker, adequate fluid resuscitation and patient outcome from sepsis onset time.

METHODS

This is a retrospective cohort study of consecutive adults with severe sepsis and septic shock admitted to a quaternary care medical ICU between January 2007 and December 2009. Data were collected from a previously validated electronic medical database. Multivariate regression modeling was performed, adjusting for age, admission weight, Sequential Organ Failure Assessment score, APACHE (Acute Physiology and Chronic Health Examination) III score, and total fluid administration within the first 6 h of sepsis onset time.

RESULTS

Of 651 patients with severe sepsis and septic shock screened, 594 had detailed fluid data. In a univariate analysis, the median amount of fluid within the first 3 h for survivors at discharge was 2,085 mL (940-4,080 mL) and for nonsurvivors, 1,600 mL (600-3,010 mL; P = .007). In comparison, during the latter 3 h, the median amount was 660 mL (290-1,485 mL) vs 800 mL (360-1,680 mL; P = .09), respectively. After adjusting for confounders, the higher proportion of total fluid received within the first 3 h was associated with decreased hospital mortality (OR, 0.34; 95% CI, 0.15-0.75; P = .008).

CONCLUSIONS

Earlier fluid resuscitation (within the first 3 h) is associated with a greater number of survivors with severe sepsis and septic shock.

Hemodynamic performance of the Fontan circulation compared with a normal biventricular circulation: a computational model study

The physiological limitations of the Fontan circulation have been extensively addressed in the literature. Many studies emphasized the importance of pulmonary vascular resistance in determining cardiac output (CO) but gave little attention to other cardiovascular properties that may play considerable roles as well. The present study was aimed to systemically investigate the effects of various cardiovascular properties on clinically relevant hemodynamic variables (e.g., CO and central venous pressure). To this aim, a computational modeling method was employed. The constructed models provided a useful tool for quantifying the hemodynamic effects of any cardiovascular property of interest by varying the corresponding model parameters in model-based simulations. Herein, the Fontan circulation was studied compared with a normal biventricular circulation so as to highlight the unique characteristics of the Fontan circulation. Based on a series of numerical experiments, it was found that 1) pulmonary vascular resistance, ventricular diastolic function, and systemic vascular compliance play a major role, while heart rate, ventricular contractility, and systemic vascular resistance play a secondary role in the regulation of CO in the Fontan circulation; 2) CO is nonlinearly related to any single cardiovascular property, with their relationship being simultaneously influenced by other cardiovascular properties; and 3) the stability of central venous pressure is significantly reduced in the Fontan circulation. The findings suggest that the hemodynamic performance of the Fontan circulation is codetermined by various cardiovascular properties and hence a full understanding of patient-specific cardiovascular conditions is necessary to optimize the treatment of Fontan patients.

Does the central venous pressure predict fluid responsiveness? An updated meta-analysis and a plea for some common sense

BACKGROUND

Despite a previous meta-analysis that concluded that central venous pressure should not be used to make clinical decisions regarding fluid management, central venous pressure continues to be recommended for this purpose.

AIM

To perform an updated meta-analysis incorporating recent studies that investigated indices predictive of fluid responsiveness. A priori subgroup analysis was planned according to the location where the study was performed (ICU or operating room).

DATA SOURCES

MEDLINE, EMBASE, Cochrane Register of Controlled Trials, and citation review of relevant primary and review articles.

STUDY SELECTION

Clinical trials that reported the correlation coefficient or area under the receiver operating characteristic curve (AUC) between the central venous pressure and change in cardiac performance following an intervention that altered cardiac preload. From 191 articles screened, 43 studies met our inclusion criteria and were included for data extraction. The studies included human adult subjects, and included healthy controls (n = 1) and ICU (n = 22) and operating room (n = 20) patients.

DATA EXTRACTION

Data were abstracted on study characteristics, patient population, baseline central venous pressure, the correlation coefficient, and/or the AUC between central venous pressure and change in stroke volume index/cardiac index and the percentage of fluid responders. Meta-analytic techniques were used to summarize the data.

DATA SYNTHESIS

Overall 57% ± 13% of patients were fluid responders. The summary AUC was 0.56 (95% CI, 0.54-0.58) with no heterogenicity between studies. The summary AUC was 0.56 (95% CI, 0.52-0.60) for those studies done in the ICU and 0.56 (95% CI, 0.54-0.58) for those done in the operating room. The summary correlation coefficient between the baseline central venous pressure and change in stroke volume index/cardiac index was 0.18 (95% CI, 0.1-0.25), being 0.28 (95% CI, 0.16-0.40) in the ICU patients, and 0.11 (95% CI, 0.02-0.21) in the operating room patients.

CONCLUSIONS

There are no data to support the widespread practice of using central venous pressure to guide fluid therapy. This approach to fluid resuscitation should be abandoned.

Does bedside sonographic measurement of the inferior vena cava diameter correlate with central venous pressure in the assessment of intravascular volume in children?

OBJECTIVES

Previous studies demonstrated that the collapsibility index (percent decrease in inferior vena cava [IVC] diameter with inspiration) of 50% or greater and an IVC/aorta ratio of 0.8 or less correlated with a low intravascular volume. Our study sought to determine if bedside ultrasound (BUS) measurements of the IVC diameter correlate with central venous pressure (CVP) measurements as an indicator of intravascular volume status in acutely ill children.

METHODS

A convenience sample of children younger than 21 years who were admitted to the pediatric critical care unit and required CVP monitoring had BUS measurements of both IVC and aortic diameters with simultaneous CVP measurement. The collapsibility index (sagittal view) and IVC/aorta ratio (transverse view) were calculated from these measurements. A CVP of 8 mm Hg or less was considered as a marker for decreased intravascular volume.

RESULTS

Of the 51 participants, 21 (43%) had a CVP of 8 mm Hg or less. Eight (16%) of 51 children had a collapsibility index 50% or greater, and 8 (18%) of 43 had an IVC/aorta ratio of 0.8 or less. The sensitivity of a collapsibility index 0.5 or greater to predict a CVP of 8 mm Hg or less was 14%, the specificity was 83%, the positive predictive value was 38%, and the negative predictive value was 57%. Neither collapsibility index (r = -0.23, P = 0.11) nor IVC/aorta (r = -0.19, P = 0.22) correlated with CVP in assessing intravascular volume in our study population.

CONCLUSIONS

Based on these data, the IVC and aortic measurements by BUS are not reliable indicators of intravascular volume (as determined by CVP) in acutely ill children.

Bench-to-bedside review: An approach to hemodynamic monitoring--Guyton at the bedside

Hemodynamic monitoring is used to identify deviations from hemodynamic goals and to assess responses to therapy. To accomplish these goals one must understand how the circulation is regulated. In this review I begin with an historical review of the work of Arthur Guyton and his conceptual understanding of the circulation and then present an approach by which Guyton's concepts can be applied at the bedside. Guyton argued that cardiac output and central venous pressure are determined by the interaction of two functions: cardiac function, which is determined by cardiac performance; and a return function, which is determined by the return of blood to the heart. This means that changes in cardiac output are dependent upon changes of one of these two functions or of both. I start with an approach based on the approximation that blood pressure is determined by the product of cardiac output and systemic vascular resistance and that cardiac output is determined by cardiac function and venous return. A fall in blood pressure with no change in or a rise in cardiac output indicates that a decrease in vascular resistance is the dominant factor. If the fall in blood pressure is due to a fall in cardiac output then the role of a change in the return function and cardiac function can be separated by the patterns of changes in central venous pressure and cardiac output. Measurement of cardiac output is a central component to this approach but until recently it was not easy to obtain and was estimated from surrogates. However, there are now a number of non-invasive devices that can give measures of cardiac output and permit the use of physiological principles to more rapidly appreciate the primary pathophysiology behind hemodynamic abnormalities and to provide directed therapy.

Central venous pressure and shock index predict lack of hemodynamic response to volume expansion in septic shock: a prospective, observational study

PURPOSE

Volume expansion is a common therapeutic intervention in septic shock, although patient response to the intervention is difficult to predict. Central venous pressure (CVP) and shock index have been used independently to guide volume expansion, although their use is questionable. We hypothesize that a combination of these measurements will be useful.

METHODS

In a prospective, observational study, patients with early septic shock received 10-mL/kg volume expansion at their treating physician's discretion after brief initial resuscitation in the emergency department. Central venous pressure and shock index were measured before volume expansion interventions. Cardiac index was measured immediately before and after the volume expansion using transthoracic echocardiography. Hemodynamic response was defined as an increase in a cardiac index of 15% or greater.

RESULTS

Thirty-four volume expansions were observed in 25 patients. A CVP of 8 mm Hg or greater and a shock index of 1 beat min(-1) mm Hg(-1) or less individually had a good negative predictive value (83% and 88%, respectively). Of 34 volume expansions, the combination of both a high CVP and a low shock index was extremely unlikely to elicit hemodynamic response (negative predictive value, 93%; P = .02).

CONCLUSIONS

Volume expansion in patients with early septic shock with a CVP of 8 mm Hg or greater and a shock index of 1 beat min(-1) mm Hg(-1) or less is unlikely to lead to an increase in cardiac index.