Non-invasive bedside assessment of central venous pressure: scanning into the future

Noninvasive Quantitative Compression Ultrasound Central Venous Pressure: A Clinical Pilot Study

Objective: This is an initial study to validate central venous pressure (CVP) measurements derived from quantitative compression ultrasound (QCU). Impact Statement: This study is the first gold standard invasive validation of CVP estimation from QCU. Introduction: QCU finds the collapse force-the force required for complete occlusion-of the short axis of the internal jugular vein (IJV) to estimate CVP. Methods: We captured QCU data as well as the noninvasive clinical standard jugular venous pulsation height (JVP) on cardiac intensive care unit (CICU) patients at Massachusetts General Hospital (MGH). We compared these data to ground truth invasive CVP data from the MGH CICU. Results: Using linear regression, we correlated invasive CVP with collapse force (r 2: 0.82, error: 1.08 mmHg) and with JVP (r 2: 0.45, error: 1.39 mmHg). To directly compare our method to JVP, we measured the percentage of patients whose uncertainty estimates for QCU methods and for JVP overlapped with their invasive CVP counterparts. We found that the CVP overlap accuracy of collapse force (77.8%) and of collapse force and hydrostatic offset (88.9%) are higher than that of JVP (12.5%). Finally, we input QCU image segmentation data of the short-axis cross-sections of the IJV and carotid artery into an inverse finite element model to predict the invasive CVP waveform. Conclusion: These results validate the noninvasive technique for estimating CVP, namely, QCU, indicating that it may provide a desirable, middle-ground alternative to invasive catheterization and to visual inspection of the JVP.

Volume Status: A Preload Assessment by Ultrasound of the Inferior Vena Cava and Jugular Venous Pulsation

An accurate assessment of intracardiac pressure and etiology of its pathologic change is crucial in assessing volume status and cardiac hemodynamics. The assessment for abnormal central venous pressure in heart failure has driven the development of noninvasive assessment of the central veins: the inferior vena cava and, more recently, ultrasound assessment of the jugular venous pressure. This article discusses the evidence, techniques, and limitations of estimating central venous pressure by ultrasound assessment of the inferior vena cava and internal jugular vein.

The Role of The Hospitalist in the Clinical Education of Medical Students

Hospitalist clinician-educators frequently work with medical students at the clinical level, but many early career educators may lack an understanding of how to effectively promote student learning and growth. We explore the role of hospitalists working with medical students in the clinical environment as it pertains to three overarching domains - clinical skills, systems-based healthcare, and career mentorship.

Inappropriate therapy of euvolemic hyponatremia, the most frequent type of hyponatremia in SARS-CoV-2 infection, is associated with increased mortality in COVID-19 patients

Introduction

Admission hyponatremia, frequent in patients hospitalized for COVID-19, has been associated with increased mortality. However, although euvolemic hyponatremia secondary to the Syndrome of Inappropriate Antidiuresis (SIAD) is the single most common cause of hyponatremia in community-acquired pneumonia (CAP), a thorough and rigorous assessment of the volemia of hyponatremic COVID-19 subjects has yet to be described. We sought to identify factors contributing to mortality and hospital length-of-stay (LOS) in hospitalized COVID-19 patients admitted with hyponatremia, taking volemia into account.

Method

Retrospective study of 247 patients admitted with COVID-19 to a tertiary hospital in Madrid, Spain from March 1st through March 30th, 2020, with a glycemia-corrected serum sodium level (SNa) < 135 mmol/L. Variables were collected at admission, at 2nd-3rd day of hospitalization, and ensuing days when hyponatremia persisted. Admission volemia (based on both physical and analytical parameters), therapy, and its adequacy as a function of volemia, were determined.

Results

Age: 68 years [56-81]; 39.9% were female. Median admission SNa was 133 mmol/L [131- 134]. Hyponatremia was mild (SNa 131-134 mmol/L) in 188/247 (76%). Volemia was available in 208/247 patients; 57.2% were euvolemic and the rest (42.8%) hypovolemic. Hyponatremia was left untreated in 154/247 (62.3%) patients. Admission therapy was not concordant with volemia in 43/84 (51.2%). In fact, the majority of treated euvolemic patients received incorrect therapy with isotonic saline (37/41, 90.2%), whereas hypovolemics did not (p=0.001). The latter showed higher mortality rates than those receiving adequate or no therapy (36.7% vs. 19% respectively, p=0.023). The administration of isotonic saline to euvolemic hyponatremic subjects was independently associated with an elevation of in-hospital mortality (Odds Ratio: 3.877, 95%; Confidence Interval: 1.25-12.03).

Conclusion

Hyponatremia in COVID-19 is predominantly euvolemic. Isotonic saline infusion therapy in euvolemic hyponatremic COVID-19 patients can lead to an increased mortality rate. Thus, an exhaustive and precise volemic assessment of the hyponatremic patient with CAP, particularly when due to COVID-19, is mandatory before instauration of therapy, even when hyponatremia is mild.

Brief training in ultrasound equips novice clinicians to accurately and reliably measure jugular venous pressure in obese patients

Introduction/Purpose

Measurement of jugular venous pressure (JVP) by novice clinicians can be unreliable, particularly when evaluating obese patients. Measurement of JVP using ultrasound (uJVP) is simple to perform and provides accurate measurements. This study evaluated whether students and residents inexperienced with ultrasound could rapidly be taught to measure JVP using ultrasound in obese patients with the same accuracy as cardiologists measuring JVP via physical examination. Additionally, this study also evaluated the correlation between qualitative and quantitative JVP assessment.

Methods

This prospective, blinded study compared uJVP measurements performed by novice clinicians after brief training to JVP measurements performed by cardiologists (cJVP) on physical examination. Association between uJVP and cJVP was assessed using linear correlation, agreement and bias were assessed using the Bland-Altman analysis and inter-rater reliability of uJVP was assessed using intraclass correlation coefficient (ICC). The association between qualitative and quantitative JVP assessment was assessed using linear correlation.

Results

Novice clinicians (n = 16) obtained 34 measurements from 26 patients (mean BMI 35.5) and reported moderate-to-high confidence in all measurements. uJVP correlated well with cJVP (r = 0.73) with an average error of 0.06 cm. The estimated uJVP ICC was 0.83 (95% CI = 0.44, 0.96). Qualitative uJVP had only a moderate correlation (r = 0.63) to quantitative uJVP.

Discussion

Novice clinicians often have difficulty assessing JVP on physical examination, particularly in obese patients. Our findings show a high degree of correlation between JVP measurements performed by novice clinicians using ultrasound compared with JVP measurements made by experienced cardiologists on physical examination. Furthermore, novice clinicians were able to be trained quickly, their measurements were determined to be accurate and precise and they expressed moderate-to-high confidence in their results.

Conclusions

After brief training, novice clinicians were able to accurately assess JVP in obese patients as compared to measurements made by experienced cardiologists on physical examination. Results suggest that ultrasound may greatly improve novice clinicians' JVP assessment accuracy, particularly in obese patients.

Assessing jugular venous compliance with optical hemodynamic imaging by modulating intrathoracic pressure

SIGNIFICANCE

The internal jugular veins (IJV) are critical cerebral venous drainage pathways that are affected by right heart function. Cardiovascular disease and microgravity can alter central venous pressure (CVP) and venous return, which may contribute to increased intracranial pressure and decreased cardiac output. Assessing jugular venous compliance may provide insight into cerebral drainage and right heart function, but monitoring changes in vessel volume is challenging.

AIM

We investigated the feasibility of quantifying jugular venous compliance from jugular venous attenuation (JVA), a noncontact optical measurement of blood volume, along with CVP from antecubital vein cannulation.

APPROACH

CVP was progressively increased through a guided graded Valsalva maneuver, increasing mouth pressure by 2 mmHg every 2 s until a maximum expiratory pressure of 20 mmHg. JVA was extracted from a 1-cm segment between the clavicle and midneck. The contralateral IJV cross-sectional area (CSA) was measured with ultrasound to validate changes in the vessel size. Compliance was calculated using both JVA and CSA between four-beat averages over the duration of the maneuver.

RESULTS

JVA and CSA were strongly correlated (median and interquartile range) over the Valsalva maneuver across participants (r = 0.986, [0.983, 0.987]). CVP more than doubled on average between baseline and peak strain (10.7 ± 4.4 vs. 25.8 ± 5.4 cmH2O; p < 0.01). JVA and CSA increased nonlinearly with CVP, and both JVA- and CSA-derived compliance decreased progressively from baseline to peak strain (49% and 56% median reduction, respectively), with no significant difference in compliance reduction between the two measures (Z = - 1.24, p = 0.21). Pressure-volume curves showed a logarithmic relationship in both CSA and JVA.

CONCLUSIONS

Optical jugular vein assessment may provide new ways to assess jugular distention and cardiac function.

Automated Force-Coupled Ultrasound Method for Calibration-Free Carotid Artery Blood Pressure Estimation

We develop, automate and evaluate a calibration-free technique to estimate human carotid artery blood pressure from force-coupled ultrasound images. After acquiring images and force, we use peak detection to align the raw force signal with an optical flow signal derived from the images. A trained convolutional neural network selects a seed point within the carotid in a single image. We then employ a region-growing algorithm to segment and track the carotid in subsequent images. A finite-element deformation model is fit to the observed segmentation and force via a two-stage iterative non-linear optimization. The first-stage optimization estimates carotid artery wall stiffness parameters along with systolic and diastolic carotid pressures. The second-stage optimization takes the output parameters from the first optimization and estimates the carotid blood pressure waveform. Diastolic and systolic measurements are compared with those of an oscillometric brachial blood pressure cuff. In 20 participants, average absolute diastolic and systolic errors are 6.2 and 5.6 mm Hg, respectively, and correlation coefficients are r = 0.7 and r = 0.8, respectively. Force-coupled ultrasound imaging represents an automated, standalone ultrasound-based technique for carotid blood pressure estimation, which motivates its further development and expansion of its applications.

Changes in Serum Creatinine Levels Can Help Distinguish Hypovolemic from Euvolemic Hyponatremia

Background and Objectives: Differentiating between hypovolemic (HH) and euvolemic hyponatremia (EH) is crucial for correct diagnosis and therapy, but can be a challenge. We aim to ascertain whether changes in serum creatinine (SC) can be helpful in distinguishing HH from EH. Materials and Methods: Retrospective analysis of patients followed in a monographic hyponatremia outpatient clinic of a tertiary hospital during 1 January 2014−30 November 2019. SC changes during HH and EH from eunatremia were studied. The diagnostic accuracy of the SC change from eunatremia to hyponatremia (∆SC) was analyzed. Results: A total of 122 hyponatremic patients, median age 79 years (70−85), 46.7% women. In total, 70/122 patients had EH, 52/122 HH. During hyponatremia, median SC levels increased in the HH group: +0.18 mg/dL [0.09−0.39, p < 0.001], but decreased in the EH group: −0.07 mg/dL (−0.15−0.02, p < 0.001), as compared to SC in eunatremia. HH subjects presented a higher rate of a positive ∆SC than EH (90.4% vs. 25.7%, p < 0.001). EH subjects presented a higher rate of a negative/null ∆SC than HH (74.3% vs. 9.6%, p < 0.001). ROC curve analysis found an AUC of 0.908 (95%CI: 0.853 to 0.962, p < 0.001) for ∆SC%. A ∆SC% ≥ 10% had an OR of 29.0 (95%CI: 10.3 to 81.7, p < 0.001) for HH. A ∆SC% ≤ 3% had an OR of 68.3 (95%CI: 13.0 to 262.2, p < 0.001) for EH. Conclusions: The assessment of SC changes from eunatremia to hyponatremia can be useful in distinguishing between HH and EH.

Accuracy of Ultrasound Jugular Venous Pressure Height in Predicting Central Venous Congestion

BACKGROUND

Assessment of volume status through the estimation of central venous pressure (CVP) is integral in the care of heart failure (HF). Bedside assessment is limited by obesity, variation in physical examination skills, and expertise in ultrasonography.

OBJECTIVE

To validate the accuracy of quantitative and qualitative point-of-care ultrasonography assessment of jugular venous pressure (JVP) in predicting elevated CVP.

DESIGN

Prospective observational study using convenience sampling.

SETTING

2 U.S. academic hospitals.

PATIENTS

Adult patients undergoing right heart catheterization between 5 February 2019 and 1 March 2021.

MEASUREMENTS

Estimation of the JVP height by handheld ultrasound device (uJVP), JVP by traditional physical examination, and qualitative presence of a distended uJVP in the upright position (upright-uJVP) was done before invasive measurements. Receiver-operating characteristic analysis of the uJVP was compared with invasive hemodynamics.

RESULTS

In 100 participants undergoing right heart catheterization for HF indications (mean age, 59.6 years; 44% with preserved ejection fraction), the uJVP in a reclined position accurately predicted elevated right atrial pressure (RAP) (>10 mm Hg), with an area under the curve of 0.84. A positive uJVP in the upright position was 94.6% specific for predicting elevated RAP.

LIMITATION

Limited examiners, only 2 centers, and convenience sampling.

CONCLUSION

Point-of-care ultrasonography assessment of the uJVP is feasible, reproducible, and accurately predictive of elevated CVPs in patients undergoing right heart catheterization. Further investigation of clinical application of ultrasound-measured JVP seems warranted.

PRIMARY FUNDING SOURCE

None.

Cardiovascular examination using hand-held cardiac ultrasound

Echocardiography is the first-line imaging modality for assessing cardiac function and morphology. The miniaturisation of ultrasound technology has led to the development of hand-held cardiac ultrasound (HCU) devices. The increasing sophistication of available HCU devices enables clinicians to more comprehensively examine patients at the bedside. HCU can augment clinical exam findings by offering a rapid screening assessment of cardiac dysfunction in both the Emergency Department and in cardiology clinics. Possible implications of implementing HCU into clinical practice are discussed in this review paper.

A Novel Non-Invasive Device for the Assessment of Central Venous Pressure in Hospital, Office and Home

Background

Venous congestion can be quantified by central venous pressure (CVP) and its monitoring is crucial to understand and follow the hemodynamic status of patients with cardio-respiratory diseases. The standard technique for CVP measurement is invasive, requiring the insertion of a catheter into a jugular vein, with potential complications. On the other hand, the current non-invasive methods, mainly based on ultrasounds, remain operator-dependent and are unsuitable for use in the home environment. In this paper, we will introduce a novel, non-invasive device for the hospital, office and home assessment of CVP.

Methods

After describing the measurement concept, we will report a preliminary experimental study enrolling 5 voluntary healthy subjects to evaluate the VenCoM measurements’ repeatability, and the system’s capability in measuring small elicited venous pressure variations (2 mmHg), as well as an induced venous hypertension within a pathological range (12÷20 mmHg).

Results

The experimental measurements showed a repeatability of ±1mmHg. The VenCoM device was able to reliably detect the elicited venous pressure variations and the simulated congestive status.

Discussion and Conclusion

The proposed non-invasive VenCoM device is able to provide a fast and repeatable CVP estimate, having a wide spectrum of potential clinical applications, including the monitoring of venous congestion in heart failure patients and in subjects with renal and hepatic dysfunction, as well as pulmonary hypertension (PH) that can be extended to pneumonia COVID-19 patients even after recovery. The device needs to be tested further on a large sample size of both healthy and pathological subjects, to systematically validate its reliability and impact in clinical setting.

Use of point-of-care ultrasound for the assessment of intravascular volume in five rural New Zealand hospitals

Introduction

Measuring the diameter of the inferior vena cava (IVC) or the height of the jugular venous pressure (JVP) with point-of-care ultrasound (POCUS) is a practical alternative method for estimating a patient's intravascular volume in the rural setting. This study aims to determine whether or not POCUS of the IVC or JVP generates additional useful clinical information over and above routine physical examination in this context.

Methods

Twenty generalist physicians, working in five New Zealand rural hospitals, recorded their estimation of a patient's intravascular volume based on physical examination and then again after performing POCUS of the IVC or JVP, using a visual scale from 1 to 11.

Results

Data were available for 150 assessments. There was an only moderate agreement between the pre- and post-test findings (Spearman's correlation coefficient = 0.46). In 28% (42/150) of cases, the difference was four or more points on the scale, and therefore, had the potential to be clinically significant.

Conclusion

In the rural context, POCUS provides new information that frequently alters the clinician's estimation of a patient's intravascular volume.

Objective Assessment of Venous Pulse Wave Velocity in Healthy Humans

Central venous pressure and volume status are relevant parameters for characterization of a patient's hemodynamic condition; however, their invasive assessment is affected by various risks while non-invasive approaches provide limited and subjective indications. Here we explore the possibility of assessing venous pulse wave velocity (vPWV), a potential indicator of venous pressure changes. In eight healthy patients, pressure pulses were generated artificially in the leg veins by rapid compression of the foot, and their propagation was detected at the level of the superficial femoral vein with Doppler ultrasound. Changes in leg venous pressure were obtained by raising the trunk from the initial supine position by 30° and 60°. vPWV increased from 1.78 ± 0.06 m/s (supine) to 2.26 ± 0.19 m/s (60°) (p < 0.01) and exhibited an overall linear relationship with venous pressure. These results indicate that vPWV can be easily assessed, and is a non-invasive indicator of venous pressure changes.

The Master Clinician's Elective: Integrating Evidence-Based Physical Examination and Point of Care Ultrasonography in Modern Clinical Medicine

Background: Many internal medicine residency programs have incorporated ultrasonography into their curriculum; however, its integration with physical examination skills teaching at a graduate medical level is scarce. The program's aim is to create a reproducible elective that combines physical exam and bedside ultrasound as a method for augmenting residents' knowledge and competence in these techniques with the ultimate goal of improving patient care. Methods: We designed and implemented a two-week elective rotation for senior internal medicine residents, combining evidence-based physical examination with diagnostic bedside ultrasonography. The rotation took place in an inpatient setting at Denver Health Hospital. Program evaluation data was collected data between February 2016 to March 2019. IRB approval was waived. Results: Since its inception in 2016, 19 residents completed the rotation. Residents performed a pre-test and a post-test under direct observation by course faculty. Each resident was measured on the ability to perform pre-determined physical exam and point-of-care ultrasound (POCUS) skills. In the pre-test, participants correctly performed an average of 40% of expected physical exam maneuvers and 32% of expected POCUS skills. At elective conclusion, all participants were effectively able to demonstrate the highest yield physical exam and ultrasound maneuvers. Discussion and Conclusion: An elective designed specifically to integrate POCUS and physical exam modalities improves the ability of resident physicians to utilize both diagnostic modalities.

Bedside hand vein inspection for noninvasive central venous pressure assessment

Rapid estimates of the central venous pressure (CVP) can be helpful to administer early fluid therapy or to manage cardiac preload in intensive care units, operating rooms or emergency rooms in order to start and monitor an adequate medical therapy. Invasive CVP measurements have inherent and non-negligible complication rates as well as great expenditures. Several noninvasive methods of CVP measurements, like ultrasound-guided techniques, are available, but require trained skills and special equipment which might not be at hand in all situations. Our purpose was to evaluate the feasibility and accuracy of CVP estimates assessed upon the height of hand veins collapse (HVC) using invasively measured CVP as the gold standard. The HVC was determined by slowly lifting the patient's hand while watching the dorsal hand veins to collapse. The vertical distance from the dorsal hand to a transducer air zero port was noted and converted to mmHg. The observer was blinded to the simultaneously measured CVP values, which were categorized as low (<7 mmHg), normal (7-12 mmHg) and high (>12 mmHg). Measurements were performed in 82 patients who had a median [IQR] age of 67 [60;74]. Median CVP was 12 [8;15] mmHg and the median absolute difference between the measured HVC and CVP was 4 [2;7] mmHg. The Spearman correlation coefficient between CVP and HVC was 0.55, 95%-CI [0.35;0.69]. Overall CVP categorization was correct in 45% of the cases. HVC had a sensitivity of 92% for a low CVP with a negative predictive value of 98%. A high HVC had a sensitivity of 29% but a high specificity of 94% for a high CVP. The overall performance of observing the hand vein collapse to estimate CVP was only moderate in the intensive care setting. However, the median difference to the CVP was low and HVC identifies a low CVP with a high sensitivity and excellent negative predictive value.

Management of hyponatremia: causes, clinical aspects, differential diagnosis and treatment

INTRODUCTION

Hyponatremia is the most frequent electrolyte disorder in hospitalised patients. Acute and severe hyponatremia may be a life-threatening situation. However, also mild and chronic hyponatremia may negatively affect the health status (i.e. gait disturbances, attention deficits, falls and fractures, and bone loss) and may increase the risk of death. Therefore, it is of paramount importance for clinicians to have an in-depth knowledge on this topic, in order to appropriately manage patients affected by hyponatremia.

AREAS COVERED

This review will cover different areas related to this electrolyte disorder. Because many pathologic conditions may be associated with hyponatremia, thorough investigations have to be performed in order to establish the underlying etiology. To establish the cause of hyponatremia is of great importance, because an appropriate therapeutic strategy is strictly dependent on a correct diagnosis. A description of the different available therapeutic approaches for the correction of hyponatremia, including vaptans, will follow.

EXPERT COMMENTARY

Undoubtedly, the studies that have been published in recent years and the introduction of vaptans in clinical practice have contributed to increase the awareness on hyponatremia among clinicians. Nevertheless, additional studies are needed in order to clarify some partially uncovered areas.

Evaluation of right atrial volumes and functions by real-time three-dimensional echocardiography in patients after acute inferior myocardial infarction

BACKGROUND

Right ventricle (RV) involvement causes acute systolic and diastolic functional alterations in the RV in patients after inferior myocardial infarction (IMI), which may result in an increase in left ventricle (LV) end-diastolic and right atrial (RA) pressure. In our study, we sought to evaluate RA volumes and mechanical functions using real-time three-dimensional echocardiography (RT3DE) in IMI patients with or without RV involvement.

METHODS

Ninety-six consecutive patients with IMI (mean age: 59.7 ± 10.2 years, 60 female) were included. RV myocardial involvement (RVMI) was defined as the presence of a culprit lesion at the proximal portion of the first RV marginal branch in coronary angiography. The study population was divided into two groups: IMI (58.3%) and IMI + RVMI (41.7%). Patients were evaluated using conventional two-dimensional echocardiography (2DE) and RT3DE.

RESULTS

In RT3DE measurements, IMI + RVMI patients had significantly higher RA phasic volumes and worse conduit mechanical function. A receiver operating characteristic (ROC) curve analysis revealed that an RT3DE RA maximum volume (Vmax) index > 27.9 mL/m² was an independent predictor of RV involvement in patients after acute IMI, with a sensitivity of 80.0% and a specificity of 89.3%.

CONCLUSIONS

Right ventricle involvement may cause an increase in RA phasic volumes and deterioration of conduit function in patients with acute IMI.

Noninvasive Assessment of Jugular Venous Pressure via Force-Coupled Single Crystal Ultrasound

OBJECTIVE

we have developed a handheld device for noninvasive quantitative assessment of jugular venous pressure (JVP).

METHODS

we used a single crystal ultrasound coupled to a force-sensing load cell to measure JVP based on the force necessary to collapse the internal jugular vein (IJV) walls. We used a gelatin-based model system of the IJV to test the ability of single crystal ultrasound to identify the IJV and verified the cross-sectional position and diameter of the vessels with conventional imaging ultrasound. We also tested our prototype device on healthy human volunteers.

RESULTS

experiments on model system demonstrated that vessel diameters determined with single crystal ultrasound were in close agreement with the diameters derived from conventional 2-D ultrasound. Proof-of-concept human experiments demonstrate that single crystal ultrasound can detect the IJV in basal and collapsed states, as compared to gold-standard sonography (insert stats). Assessment of JVP in human volunteers was physiologically consistent with and sensitive to postural changes (supine JVP 6.6 ± 2.4 mmHg; standing JVP 4.2 ± 1.9 mmHg (p < 0.0001).

CONCLUSION

noninvasive assessment of JVP could prove valuable in informing rapid clinical decision-making across various pathologies and conditions leading to derangements in intravascular volume status.

The Role of Technology in the Bedside Encounter

Technology has the potential to both distract and reconnect providers with their patients. The widespread adoption of electronic medical records in recent years pulls physicians away from time at the bedside. However, when used in conjunction with patients, technology has the potential to bring patients and physicians together. The increasing use of point-of-care ultrasound by physicians is changing the bedside encounter by allowing for real-time diagnosis with the treating physician. It is a powerful example of the way technology can be a force for refocusing on the bedside encounter.

Comparison between noninvasive measurement of central venous pressure using near infrared spectroscopy with an invasive central venous pressure monitoring in cardiac surgical Intensive Care Unit

Introduction:

Central venous pressure (CVP) measurement is essential in the management of certain clinical situations, including cardiac failure, volume overload and sepsis. CVP measurement requires catheterization of the central vein which is invasive and may lead to complications. The aim of this study was to evaluate the accuracy of measurement of CVP using a new noninvasive method based on near infrared spectroscopy (NIRS) in a group of cardiac surgical Intensive Care Unit (ICU) patients.

Methodology:

Thirty patients in cardiac surgical ICU were enrolled in the study who had an in situ central venous catheter (CVC). Sixty measurements were recorded in 1 h for each patient. A total of 1800 values were compared between noninvasive CVP (CVPn) obtained from Mespere VENUS 2000 CVP system and invasive CVP (CVPi) obtained from CVC.

Results:

Strong positive correlation was found between CVPi and CVPn (R = 0.9272, P < 0.0001). Linear regression equation - CVPi = 0.5404 + 0.8875 × CVPn (r² = 0.86, P < 0.001), Bland–Altman bias plots showed mean difference ± standard deviation and limits of agreement: −0.31 ± 1.36 and − 2.99 to + 2.37 (CVPi–CVPn).

Conclusion:

Noninvasive assessment of the CVP based on NIRS yields readings consistently close to those measured invasively. CVPn may be a clinically useful substitute for CVPi measurements with an advantage of being simple and continuous. It is a promising tool for early management of acute state wherein knowledge of CVP is helpful.

Assessment of central venous physiology of Fontan circulation using peripheral venous pressure

OBJECTIVE

Elevated central venous pressure is a major cause of morbidity and mortality after the Fontan operation. The difference between mean circulatory filling pressure and central venous pressure, a driving force of venous return, is important in determining dynamic changes in central venous pressure in response to changes in ventricular properties or loading conditions. Thus, noninvasive central venous pressure and mean circulatory filling pressure estimation may contribute to optimal management in patients undergoing the Fontan operation. We tested the hypothesis that central venous pressure and mean circulatory filling pressure in those undergoing the Fontan operation can be simply estimated using peripheral venous pressure and arm equilibrium pressure, respectively.

METHODS

This study included 30 patients after the Fontan operation who underwent cardiac catheterization (median 8.6, 3.4-42 years). Peripheral venous pressure was measured at the peripheral vein in the upper extremities. Mean circulatory filling pressure was calculated by the changes of arterial pressure and central venous pressure during the Valsalva maneuver. Arm equilibrium pressure was measured as equilibrated venous pressure by rapidly inflating a blood pressure cuff to 200 mm Hg.

RESULTS

Central venous pressure and peripheral venous pressure were highly correlated (central venous pressure = 1.6 + 0.68 × peripheral venous pressure, R = 0.86, P < .0001). Stepwise multivariable regression analysis showed that only peripheral venous pressure was a significant determinant of central venous pressure. Central venous pressure was accurately estimated using regression after volume loading by contrast injection (R = 0.82, P < .0001). In addition, arm equilibrium pressure measurements were highly reproducible and robustly reflected invasively measured mean circulatory filling pressure (mean circulatory filling pressure = 9.1 + 0.63 × arm equilibrium pressure, R = 0.88, P < .0001).

CONCLUSIONS

Central venous pressure and mean circulatory filling pressure can be noninvasively estimated by peripheral venous pressure and arm equilibrium pressure, respectively. This should help clarify unidentified Fontan pathophysiology and the mechanisms of Fontan failure progression, thereby helping construct effective tailor-made approaches to prevent Fontan failure.