Maximum Inferior Vena Cava Diameter Research Articles

Change of Serum BNP Between Admission and Discharge After Acute Decompensated Heart Failure Is a Better Predictor of 6-Month All-Cause Mortality Than the Single BNP Value Determined at Admission.

BackgroundB-type natriuretic peptide (BNP) is regarded as a reliable predictor of outcome in patients with acute decompensated heart failure (ADHF). However, according to some scholars, a single isolated measurement of serum BNP at the time of hospital admission would not be sufficient to provide reliable prognostic information.MethodsA retrospective study was carried out on patients hospitalized for ADHF, who had then undergone follow-up of at least 6 months, in order to see if there was any difference in midterm mortality among patients with rising BNP at discharge as compared to those with decreasing BNP at discharge. Medical records had to be carefully examined to divide the case records into two groups, the former characterized by an increase in BNP during hospitalization, and the latter showing a decrease in BNP from the time of admission to the time of discharge.ResultsUltimately, 177 patients were enrolled in a retrospective study. Among them, 53 patients (29.94%) had increased BNPs at the time of discharge relative to admission, whereas 124 (70.06%) exhibited decreases in serum BNP during their hospital stay. The group with patients who exhibited BNP increases at the time of discharge had higher degree of congestion evident in the higher frequency of persistent jugular venous distention (odds ratio: 3.72; P = 0.0001) and persistent orthopnea at discharge (odds ratio: 2.93; P = 0.0016). Moreover, patients with increased BNP at the time of discharge had a lower reduction in inferior vena cava maximum diameter (1.58 ± 2.2 mm vs. 6.32 ± 1.82 mm; P = 0.001 (one-way ANOVA)). In contrast, there was no significant difference in weight loss when patients with increased BNP at discharge were compared to those with no such increase. A total of 14 patients (7.9%) died during the 6-month follow-up period. Cox proportional hazard analysis revealed that BNP increase at the time of discharge was an independent predictor of 6-month all-cause mortality after adjustment for age, sodium at discharge, creatinine at discharge and New York Heart Association (NYHA) class at discharge (hazard ratio 34.49; 95% confidence intervals: 4.55 - 261.06; P = 0.001).ConclusionsAmong patients with recent ADHF, increased BNP at the time of discharge from the hospital entailed a higher grade of congestion and higher 6-month mortality.

Correlation between Central Venous Pressure and Inferior Vena Cava Sonographic Diameter; Determining the Best Anatomic Location.

The correlation of central venous pressure (CVP) with inferior vena cava (IVC) sonographic diameter has been reported in several studies. However, few studies have attempted to find the best anatomic location of measurement. Therefore, the purpose of this study was determining the best anatomic location to find precise correlation between CVP and IVC diameter using transesophageal echocardiography (TEE). In the present diagnostic accuracy study, patients in need of central venous catheterization and TEE were enrolled. Maximum diameter of IVC were measured during expiratory phase of respiratory cycle at the level of diaphragm, 2cm above the diaphragm and at the point of entry into the right atrium using SonoSite TEE device. CVP was measured using an electronic transducer connected to the central venous line. The best location for sonography was determined via calculating and comparing area under the receiver operating characteristics (ROC) curve (AUC). 39 patients were enrolled (53.8% female). Mean CVP was 6.8 ± 1.4 mmHg and 25 (64.1%) patients had normal CVP, while 14 (35.9%) showed elevated CVP (> 6 mmHg). Evaluating AUC showed that IVC diameter (p = 0.01), aorta diameter (p = 0.01) and IVC / aorta ratio (p = 0.004) had acceptable correlation with CVP. Point of entry of IVC into the right atrium with AUC of 0.98 (95% CI: 0.95 - 1.00) was the location of highest correlation with CVP. Based on the present findings, the IVC sonographic diameter and IVC / aorta ratio had acceptable correlation with CVP at the level of IVC entry into the right atrium.

Inferior vena cava collapsibility loses correlation with internal jugular vein collapsibility during increased thoracic or intra-abdominal pressure.

Point-of-care ultrasound evaluates inferior vena cava (IVC) and internal jugular vein (IJV) measurements to estimate intravascular volume status. The reliability of the IVC and IJV collapsibility index during increased thoracic or intra-abdominal pressure remains unclear. Three phases of sonographic scanning were performed: spontaneous breathing phase, increased thoracic pressure phase via positive pressure ventilation (PPV) phase, and increased intra-abdominal pressure (IAP) phase via laparoscopic insufflation to 15mmHg. IVC measurements were done at 1-2cm below the diaphragm and IJV measurements were done at the level of the cricoid cartilage during a complete respiratory cycle. Collapsibility index was calculated by (max diameter-min diameter)/max diameter×100%. Chi square, t test, correlation procedure (CORR) and Fisher's exact analyses were completed. A total of 144 scans of the IVC and IJV were completed in 16 patients who underwent laparoscopic surgery. Mean age was 46±15years, with 75% female and 69% African-American. IVC and IJV collapsibility correlated in the setting of spontaneous breathing (r (2)=0.86, p<0.01). IVC collapsibility had no correlation with the IJV in the setting of PPV (r (2)=0.21, p=0.52) or IAP (r (2)=0.26, p=0.42). Maximal IVC diameter was significantly smaller during increased IAP (16.5mm±4.9) compared to spontaneous breathing (20.6mm±4.8, p=0.04) and PPV (21.8mm±5.6, p=0.01). IJV and IVC collapsibility correlated during spontaneous breathing but there was no statistically significant correlation during increased thoracic or intra-abdominal pressure. Increased intra-abdominal pressure was associated with a significant smaller maximal IVC diameter and cautions the reliability of IVC diameter in clinical settings that are associated with intra-abdominal hypertension or abdominal compartment syndrome.

Impact of Body Size on Inferior Vena Cava Parameters for Estimating Right Atrial Pressure: A Need for Standardization?

Inferior vena cava (IVC) diameter and its respiratory change, as determined using echocardiography, are commonly used to assess right atrial pressure (RAP). Despite the widespread use of the IVC approach for RAP assessment, the relations among body surface area (BSA), IVC diameter, and respirophasic change remain unclear. The aim of this study was to investigate the impact of BSA on IVC parameters for predicting elevated RAP. Ninety consecutive patients undergoing right-heart catheterization or central venous catheter insertion were prospectively included. To investigate the impact of BSA on IVC parameters, patients were divided into higher and lower BSA groups by comparing individual BSA measurements with the median value. Optimal cutoff points of IVC parameters for detecting RAP of ≥ 10 mm Hg were defined using receiver operating characteristic curves. The median RAP and BSA were 8 mm Hg (range, 1-25 mm Hg) and 1.61 m(2) (range, 1.23-2.22 m(2)), respectively. In all patients, the optimal cutoff point for maximal IVC diameter (IVCDmax) and IVC collapsibility for the detection of RAP ≥ 10 mm Hg were 20 mm and 49.0%, respectively. The optimal cutoff point of IVCDmax for predicting RAP of ≥ 10 mm Hg was significantly larger in patients with higher BSAs than in those with lower BSAs (21 vs 17 mm, P = .0342). No differences in collapsibility indices were detected between the two groups. IVCDmax was larger in men (19 ± 5 vs 17 ± 5 mm in women, P = .0347) and weakly correlated with BSA (r = 0.35, P = .0007), whereas no relation was found between IVCDmax and age. However, the partial correlation coefficient of the entire cohort demonstrated that only BSA was still associated with IVCDmax after adjusting for age and gender (partial correlation coefficient = 0.32, P = .0020). Body size, measured as BSA, is important to consider when IVC diameter is used to assess RAP. The optimal cutoff point of IVCDmax was 21 mm for patients with larger BSAs and 17 mm for those with smaller BSAs. However, the cutoff point of IVC collapsibility was not influenced by the difference of BSA.

Impact of individual characteristics on sonographic IVC diameter and the IVC diameter/aorta diameter index

BackgroundThe inferior vena cava (IVC) parameters, including its diameter and collapsibility index have been evaluated for fluid status for over 30 years, but little is known about the impacts of patient characteristics on IVC parameters. The purpose of this study was to explore the relationships between individual patient characteristics and IVC parameters in healthy Chinese adult volunteers. MethodsFrom February 2012 to May 2012, 216 healthy volunteers older than the age of 18 years were consecutively enrolled in our study. The individual characteristics and presence or absence of hypertension of each participant were recorded. Sonographic measurements of IVC and abdominal aorta diameter (Ao) were performed (DP-6900; Mindray, Shenzhen, China). ResultsVolunteers ranged in age from 18 to 84 years (43.7 ± 7.8 years), and 50.5% were males. In univariate analyses, maximum IVC diameter (IVCmax) was negatively correlated with age (years) (r = −0.171, P = .012) and positively correlated with sex (men) (r = 0.174, P = .01), height (centimeters) (r = 0.281, P < .001), and body surface area (square meters) (r = 0.173, P = .011). The IVC/Ao index was negatively correlated with age (years) (r = −0.326, P < .001), waist circumference (centimeters) (r = −0.176, P = .01), body mass index (r = −0.173, P = .011), and hypertension (r = −0.186, P = .006). None of the patient characteristics were significantly correlated with percentage collapse of the IVC. Height (centimeters) was the sole significant predictor of IVCmax (R2 = 0.079, P < .001). Age (years) and body mass index (kilogram/square meter) were independent predictors of the IVC/Ao index (R2 = 0.123; P < .001 and P = .046, respectively). ConclusionsThe percentage collapse of IVC and the IVCmax are not substantially influenced by patient characteristics. In contrast, the IVC/Ao index is more susceptible to patient characteristics than IVC.

Echocardiographic characteristics of patients with acute heart failure requiring tolvaptan: a retrospective study

BackgroundNo study has investigated the admission echocardiographic characteristics of acute heart failure (AHF) patients who are resistant to conventional diuretics and require tolvaptan.MethodsWe retrospectively analyzed the echocardiographic characteristics of AHF patients who were resistant to conventional diuretics and took tolvaptan (tolvaptan group: 26 patients), and compared them to those who were sensitive to conventional diuretics (conventional group: 180 patients).ResultsThe tolvaptan group had a higher left atrial volume index (96.0 ± 85.0 mL/m2 vs. 45.8 ± 25.9 mL/m2, p < 0.0001), maximum inferior vena cava diameter (20.7 ± 6.9 mm vs. 18.1 ± 4.2 mm, p < 0.01), and higher tricuspid regurgitation grade (1.1 ± 0.8 vs. 0.8 ± 0.6, p < 0.05) than the conventional group. However, the left ventricular ejection fraction and end diastolic diameter were similar between the groups. Responders of tolvaptan had no significant echocardiographic differences compared to the non-responders.ConclusionsThe admission echocardiographic characteristics of AHF patients requiring tolvaptan included a larger left atrium, inferior vena cava, and more severe tricuspid regurgitation. Echocardiography may provide useful information for the early and appropriate initiation of tolvaptan.

The baseline diameter of the inferior vena cava measured by sonography increases with age in normovolemic children.

To evaluate normative sonographic measurements of the inferior vena cava (IVC) diameter in healthy pediatric patients. We performed a prospective observational study of a convenience sample of healthy patients between the ages of 0 and 22 years presenting to a pediatric emergency department. Exclusion criteria included abnormal vital signs, pregnancy, or illnesses thought to influence volume status. During quiet respiration, the maximum and minimum IVC diameters were measured in the sagittal plane distal to the hepatic vein-IVC junction. As second measurements, the maximum diameters of the IVC and aorta were measured in the transverse plane distal to the insertion of the left renal vein into the IVC. From February 2013 through April 2014, 63 children (51% female; mean age, 11 years) were enrolled. There were 20 children in each age group of 2 to 7, 7 to 12, and 12 to 22 years. The correlations between IVC and aortic diameters as a function of age were calculated using the Spearman rank correlation coefficient. The correlation coefficients were all statistically significant (P < .001): sagittal maximum IVC diameter (0.81), sagittal minimum IVC diameter (0.79), transverse maximum IVC diameter (0.79), and transverse maximum aortic diameter (0.81). This pilot study of sonographic measurements of the IVC diameter in normovolemic children suggests a statistically significant positive correlation between age and IVC diameter. Future studies should focus on multicenter enrollment, children in the youngest age group, and the development of normative growth curves for the IVC by age, sex, and body mass index.

Agreement between inferior vena cava diameter measurements by subxiphoid versus transhepatic views.

Context:Correcting hypovolemia is extremely important. Central venous pressure measurement is often done to assess volume status. Measurement of inferior vena cava (IVC) is conventionally done in the subcostal view using ultrasonography. It may not be possible to obtain this view in all patients.Aims:We therefore evaluated the limits of agreement between the IVC diameter measurement and variation in subcostal and that by the lateral transhepatic view.Settings and Design:Prospective study in a tertiary care referral hospital intensive care unit.Subjects and Methods:After Institutional Ethics Committee approval and informed consent, we obtained 175 paired measurements of the IVC diameter and variation in both the views in adult mechanically ventilated patients. The measurements were carried out by experienced researchers. We then obtained the limits of agreement for minimum, maximum diameter, percentage variation of IVC in relation to respiration.Statistical Analysis Used:Bland–Altman's limits of agreement to get precision and bias.Results:The limits of agreement were wide for minimum and maximum IVC diameter with variation of as much as 4 mm in both directions. However, the limits of agreement were much narrower when the percentage variation in relation to respiration was plotted on the Bland–Altman plot.Conclusions:We conclude that when it is not possible to obtain the subcostal view, it is possible to use the lateral transhepatic view. However, using the percentage variation in IVC size is likely to be more reliable than the absolute diameter alone. It is possible to use both views interchangeably.

Inferior Vena Cava and Hemodynamic Congestion.

Background:Among the indices able to replace invasive central venous pressure (CVP) measurement for patients with acute decompensated heart failure (ADHF) the diameters of the inferior vena cava (IVC) and their respiratory fluctuations, so-called IVC collapsibility index (IVCCI), measured by echocardiography, have recently gained ground as a quite reliable proxy of CVP.Objectives:The aims of our study were to compare three different ways of evaluating cardiac overload by using the IVC diameters and/or respiratory fluctuations and by calculating the inter-method agreementPatients and Methods:Medical records of patients hospitalized for right or bi-ventricular acute decompensated heart failure from January to December 2013 were retrospectively evaluated. The predictive significance of the IVC expiratory diameter and IVC collapsibility index (IVCCI) was analyzed using three different methods, namely a) the criteria for the indirect estimate of right atrial pressure by Rudski et al. (J Am Soc Echocardiogr. 2010); b) the categorization into three IVCCI classes by Stawicki et al. (J Am Coll Surg. 2009); and c) the subdivision based on the value of the maximum IVC diameter by Pellicori et al. (JACC Cardiovasc Imaging. 2013).Results:Among forty-seven enrolled patients, those classified as affected by persistent congestion were 22 (46.8%) using Rudski’s criteria, or 16 (34%) using Stawicki’s criteria, or 13 (27.6%) using Pellicori’s criteria. The inter-rater agreement was rather poor by comparing Rudski’s criteria with those of Stawicki (Cohen’s kappa = 0.369; 95% CI 0.197 to 0.54), as well as by comparing Rudski’s criteria with those of Pellicori (Cohen’s kappa = 0.299; 95% CI 0.135 to 0.462). Further, a substantially unsatisfactory concordance was also found for Stawicki’s criteria compared to those of Pellicori (Cohen’s kappa= 0.468; 95% CI 0.187 to 0.75).Conclusions:The abovementioned IVC ultrasonographic criteria for hemodynamic congestion appear clearly inconsistent. Alternatively, a sequential or simultaneous combination of clinical scores of congestion, IVC ultrasonographic indices, and circulating levels of natriuretic peptides could be warranted.

Bedside ultrasonographic measurement of the inferior vena cava fails to predict fluid responsiveness in the first 6 hours after cardiac surgery: a prospective case series observational study.

To assess validity of respiratory variation of inferior vena cava (IVC) diameter to predict fluid responsiveness and guide fluid therapy in mechanically ventilated patients during the first 6 hours after elective cardiac surgery. Prospective observational case series study. Single-center hospital. 50 consecutive patients undergoing elective cardiac surgery. Transthoracic bedside echocardiography. Parameters derived from ultrasonographic assessment of the IVC diameter (collapsibility index [CI], distensibility index [DI], and IVC/aorta index). In the whole study group, change in fluid balance correlated with change in IVC maximum diameter (p = 0.034, r = 0.176). IVC-CI and IVC-DI correlated with IVC/aorta index. A weak correlation between central venous pressure (CVP) and IVC-derived parameters (IVC-CI and IVC-DI) was noticed. Despite statistical significance (p<0.05), all observed correlations expressed low statistical power (r<0.21). There were no statistically significant differences between fluid responders and nonresponders in relation to clinical parameters, CVP, ultrasound IVC measurement, and IVC-derived indices. Dynamic IVC-derived parameters (IVC-CI, IVC-DI, and IVC/aorta index) and CVP are not reliable predictors of fluid responsiveness in the first 6 hours after cardiac surgery. Complexity of physiologic factors modulating cardiac performance in this group may be responsible for the difficulty in finding a plausible monitoring tool for fluid guidance. Bedside ultrasonographic measurement of IVC is unable to predict fluid responsiveness in the first 6 hours after cardiac surgery.

153 What are the Sonographic Baseline Measurements of the Inferior Vena Cava Diameter in Normovolemic Children?

Children who present with dehydration or sepsis account for a significant number of pediatric emergency department visits. Accurate and rapid assessment of intravascular volume status is vital to providing appropriate management. Adult studies have demonstrated that point-of-care ultrasound of the inferior vena cava (IVC) can provide a rapid and objective measurement of a patient’s intravascular volume status. However, there is a lack of reference values for IVC diameter measurements in pediatric patients. Previous studies report the patient’s dry weight, IVC/body surface area ratio, IVC/aorta ratio, or collapsibility index as reference standards for pediatric IVC measurements. There are no definitive studies to date evaluating baseline IVC diameters in healthy children with presumed normal intravascular volume. To evaluate normative baseline sonographic measurements of the IVC diameter in healthy pediatric patients. This was a prospective observational study of a convenience sample of healthy patients between ages 0 and 22 presenting to a single institution pediatric emergency department. Exclusion criteria included abnormal vital signs, pregnancy, or illnesses thought to influence volume status (eg, diarrhea, vomiting, and asthma). Point-of-care ultrasound was performed on supine patients in the subxiphoid area using the phased array transducer of a SonoSite Edge machine. During quiet respiration, the maximal and minimal IVC diameters were measured in the sagittal plane distal to where the hepatic vein joins the IVC. As a second measurement, the maximal diameters of the IVC and aorta were measured in the transverse plane distal to the insertion of the left renal vein into the IVC. The institutional review board approved this study. From February 2013 through April 2014, sixty-three children (50.8% female, mean age 10.5 years) were enrolled. There were twenty children in each age group 2-7 years, 7-12 years, and 12-22 years. Children less than two years old had difficulty tolerating the examination and commonly presented with chief complaints and/or vital signs which met exclusion criteria. Consequently, fewer patients were enrolled in the less-than-two-years age group. The correlation between IVC and aorta diameters as a function of age were calculated using the Spearman’s rank correlation coefficient. The correlation coefficients were all statistically significant (P<.001): maximum IVC diameter sagittal plane (0.81), minimum IVC diameter sagittal plane (0.79), maximum IVC diameter transverse plane (0.79), maximum aorta diameter transverse plane (0.81). We present a pilot study of the sonographic measurements of the IVC diameter in normovolemic children. A statistically significant positive correlation was found between age and IVC diameter. Future studies should focus on multi-center enrollment, children in the youngest age group, and the development of normative growth curves of the IVC by age, sex, and body mass index.

Estimation of Right Atrial Pressure on Inferior Vena Cava Ultrasound in Asian Patients

Right atrial pressure (RAP) is commonly estimated using inferior vena cava (IVC) diameter and its respirophasic variations. Although a guideline has been provided for estimation of RAP due to variation in IVC dimensions based on studies in Western subjects, echocardiographic values in Asian subjects are unknown. We studied 369 patients who underwent IVC ultrasound within 24h of right heart catheterization (RHC). The maximum and minimum IVC diameter during a respiratory cycle and the percent collapse after a sniff test were measured. These IVC parameters were compared with mean RAP measured on RHC. Receiver operating characteristic curves were generated for each IVC parameter to determine the optimal cut-off to detect RAP >10mmHg. The IVC maximum diameter cut-off for detecting RAP >10mmHg was 19mm (sensitivity, 75%; specificity, 78%) and the percent collapse cut-off was 30% (sensitivity, 75%; specificity, 83%). Both cut-offs were smaller than those previously reported in patients from Western countries. When the cut-off values from the existing guideline were applied to the present cohort, the sensitivity and specificity for normal RAP (0-5mmHg) were 38.6% and 74.2%, respectively, and 60.0% and 92.0% for elevated RAP (>10mmHg). The optimal IVC maximum diameter and percent collapse cut-offs to detect elevated RAP were smaller in Asian subjects than in a previously reported Western cohort.

Hospitalists' ability to use hand‐carried ultrasound for central venous pressure estimation after a brief training intervention: A pilot study

Access to hand-carried ultrasound technology for noncardiologists has increased significantly, yet development and evaluation of training programs are limited. We studied a focused program to teach hospitalists image acquisition of inferior vena cava (IVC) diameter and IVC collapsibility index with interpretation of estimated central venous pressure (CVP). Ten hospitalists completed an online educational module prior to attending a 1-day in-person training session that included directly supervised IVC imaging on volunteer subjects. In addition to making quantitative assessments, hospitalists were also asked to visually assess whether the IVC collapsed more than 50% during rapid inspiration or a sniff maneuver. Skills in image acquisition and interpretation were assessed immediately after training on volunteer patients and prerecorded images, and again on volunteer patients at least 6 weeks later. Eight of 10 hospitalists acquired adequate IVC images and interpreted them correctly on 5 of the 5 volunteer subjects and interpreted all 10 prerecorded images correctly at the end of the 1-day training session. At 7.4 ± 0.7 weeks (range, 6.9-8.6 weeks) follow-up, 9 of 10 hospitalists accurately acquired and interpreted all IVC images in 5 of 5 volunteers. Hospitalists were also able to accurately determine whether the IVC collapsibility index was more than 50% by visual assessment in 180 of 198 attempts (91% of the time). After a brief training program, hospitalists acquired adequate skills to perform and interpret hand-carried ultrasound IVC images and retained these skills in the near term. Though calculation of the IVC collapsibility index is more accurate, coupling a qualitative assessment with the IVC maximum diameter measurement may be acceptable in aiding bedside estimation of CVP.

The interrater reliability of ultrasound imaging of the inferior vena cava performed by emergency residents

ObjectiveUltrasonography (US) has gained popularity in the emergency medicine to assess intravascular volume status in critically ill patients. However, there are a limited number of studies on the interrater reliability of US examination of the inferior vena cava (IVC) by emergency residents. MethodOne hundred eighty US examinations were performed on 90 emergency critical care unit patients by 6 emergency medicine residents. Minimum and maximum IVC diameters during normal passive inspiration were measured, and the IVC index was calculated. The interrater reliability of the measurable data was analyzed using intraclass correlation coefficients. ResultsThe measurements of minimum and maximum IVC diameters were moderately reliable by emergency residents (κ = 0.60 [95% confidence interval {CI}, 0.45-0.72] and κ = 0.56 [95% CI, 0.41-0.69], respectively). In the patients with moderate IVC depth (8.5-12.5 cm), the interrater reliabilities of sonographers were κ = 0.51 (95% CI, 0.30-0.67) for maximum diameter and κ = 0.43 (95% CI, 0.21-0.61) for minimum diameter. In patients with superficial (≤8.5 cm) and profound located (≥12.5 cm) IVC, the interrater reliabilities of sonographers for maximum and minimum diameters were κ = 0.69 (95% CI, 0.29-0.89) and κ = 0.75 (95% CI, 0.4-0.91), and κ = 0.58 (95% CI, 0.09-0.85) and κ = 0.76 (95% CI, 0.39-0.92), respectively. ConclusionThe measurement of the IVC is moderately reliable by emergency residents. The interrater reliability of measurements in patients with profound and superficial located IVC is higher than that of measurements in patients with moderate-depth located IVC.

Trauma Resuscitation Using Echocardiography in a Deployed Military Intensive Care Unit

Casualties with severe traumatic injury frequently suffer haemodynamic instability. There is interest in the use of transthoracic echocardiography (TTE) to assess haemodynamic status in intensive care resuscitation. We describe a feasibility study of focused TTE (fTTE) echocardiography in trauma resuscitation in a deployed military setting. fTTE was performed on patients admitted to ICU following severe injury. Data were collected on TTE view availability, LV function, volume status, and inferior vena cava (IVC) dimensions. Doppler of the LV outflow tract was performed to provide a velocity time integer (LVOT VTi) as an indicator of preload. Twenty-three patients were recruited, and 48 individual studies performed. TTE windows available were: parasternal long axis-68%, parasternal short axis-66%, apical 4-chamber-64%, subcostal-66%. IVC imaging was possible in 85%, and LVOT VTi Doppler in 37%. The mean maximal IVC diameter in volume-optimised patients (Group 1, n=19) was 2.07 cm (±0.07), compared with 1.47 (±0.06) in the hypovolaemic cohort (Group 2, n=23). The mean minimum IVC diameter in Group 1 was 1.93(±0.07) vs 1.03(±0.08) in Group 2. IVC collapsibility was 3.16% (±1.61%) in Group 1 vs 30.81%(±1.62) in Group 2. In 12%, profound hypovolaemia with systolic LV cavity obliteration was noted. fTTE suggested hypovolaemia in 69% of patients on admission to the study. Of patients arriving on the ICU following damage-control resuscitation only 31% were volume-optimised. fTTE led to a change in volume management strategy in 47% of cases. This study demonstrates, for the first time in a deployed military setting, that intensivist-delivered fTTE is feasible and changes resuscitation strategy in almost half of patients admitted to a deployed ICU.

Point-of-Care Ultrasound to Estimate Central Venous Pressure

To determine the most accurate predictor of central venous pressure among three point-of-care venous ultrasound techniques. Cross-sectional study. Medical ICU in an academic medical center. Convenience sample of 67 spontaneously breathing patients who had an intrathoracic central venous catheter to allow measurement of central venous pressure. Measurement of the internal jugular vein height to width ratio (aspect ratio), the inferior vena cava diameter, and the percent collapse of the inferior vena cava with inspiration (collapsibility index) by ultrasound. Complete data for analysis were available in 65 patients, as the inferior vena cava could not be visualized in two patients. A central venous pressure of 10 mm Hg was chosen a priori as a clinically significant cutoff. The range of central venous pressure values was 1-23 mm Hg with a median value of 7 mm Hg. The maximal inferior vena cava diameter correlated moderately with central venous pressure (R = 0.58), whereas the inferior vena cava collapsibility index and the internal jugular vein aspect ratio showed poor correlation (R = 0.16 and 0.21, respectively). The area under the receiver operating characteristics curve (area under the curve) to discriminate a low central venous pressure (< 10 mm Hg) was 0.91 for inferior vena cava diameter (95% confidence interval 0.84-0.98), which was significantly higher than the internal jugular vein aspect ratio (area under the curve 0.76; 95% confidence interval 0.65-0.89) or the inferior vena cava collapsibility index (area under the curve 0.66; 95% confidence interval 0.51-0.80) (p = 0.0001). An inferior vena cava diameter < 2 cm predicted a central venous pressure < 10 mm Hg with a sensitivity of 85% (95% confidence interval 69% to 94%), specificity of 81% (95% confidence interval 60% to 93%), and positive predictive value of 87% (95% confidence interval 71% to 95%). Inferior vena cava collapsibility index was not an independent predictor of central venous pressure after adjusting for inferior vena cava diameter in a multiple linear regression model. Among spontaneously breathing patients largely without vasopressor support, the maximal inferior vena cava diameter is a more robust estimate of central venous pressure than the inferior vena cava collapsibility index or the internal jugular vein aspect ratio.

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Introduction: Point of care ultrasound evaluates inferior vena cava (IVC) collapsibility and internal jugular vein (IJV) collapsibility to estimate intravascular volume status at the bedside. The reliability of the IVC and IJV collapsibility index in the setting of increased thoracic or intra-abdominal pressure remains unclear. Hypothesis: IVC and IJV collapsibility index correlate irrespective of changes in thoracic or intra-abdominal pressure for patients undergoing laparoscopic surgery. Methods: IRB approved prospective, observational study in an urban, academic tertiary care center for patients undergoing laparoscopic surgery. Three phases of sonographic scanning were performed: the pre-operative spontaneous ventilation (SV) phase, the intubated positive pressure ventilation (PPV) phase, and the increased intra-abdominal pressure (IAP) phase via laparoscopic insufflation to 15mmHg. IVC measurements were done at 1-2cm below the diaphragm in the anterior axillary line and IJV measurements were done at the level of the cricoid cartilage (IJV) during a complete respiratory cycle. Collapsibility index was calculated by max diameter-min diameter/max diameter x 100%. Chi-square, Fisher exact, t-test analysis and CORR procedure analysis were completed. Results: 16 patients were enrolled and 3 excluded for inability to obtain adequate ultrasound images. Mean age was 46 ± 15 years, BMI 29.5 ± 6.7kg/m2, 75% female and 69% African-American. Maximal IVC diameter was significantly smaller during increased IAP (16.5mm ±4.9) compared to SV (20.6mm ±4.8, p=0.04) and PPV (21.8mm ±5.6 p=0.01). Maximal diameter of IJV had no significant variability in the three phases. IVC and IJV collapsibility correlated in the setting of SV (r2= 0.86, p<0.01). IVC collapsibility had no correlation with IJV collapsibility in the setting of PPV (r2= 0.21, p=0.52) or increased IAP (r2= 0.26, p=0.42). Conclusions: Maximal IVC diameter is significantly smaller in the setting of increased intra-abdominal pressure. During laparoscopic surgery, the IJV and IVC collapsibility correlated only with spontaneous ventilation and not in the setting of increased thoracic or intra-abdominal pressure.

Resuscitation of the pregnant patient: What is the effect of patient positioning on inferior vena cava diameter?

Study objectivePatients in the third trimester of pregnancy presenting to the emergency department (ED) with hypotension are routinely placed in the left lateral tilt (LLT) position to relieve inferior vena cava (IVC) compression from the gravid uterus thereby increasing venous return. However, the relationship between patient position and proximal intrahepatic IVC filling has never assessed directly. This study set out to determine the effect of LLT position on intrahepatic IVC diameter in third trimester patients under real-time visualization with ultrasound. MethodsThis prospective observational study on the labor and delivery floor of a large urban academic teaching hospital enrolled patients between 30 and 42 weeks estimated gestational age from August 2011 to March 2012. Patients were placed in three different positions: supine, LLT, and right lateral tilt (RLT). After the patient was in each position for at least 3min, IVC ultrasound using the intercostal window was performed by one of three study sonologists. Maternal and fetal hemodynamics were also monitored and recorded in each position. ResultsA total of 26 patients were enrolled with one excluded from data analysis due to inability to obtain IVC measurements. The median IVC maximum diameter was 1.26cm (95% confidence interval [CI] 1.13–1.55) in LLT compared to 1.13cm (95% CI 0.89–1.41) in supine, p=0.01. When comparing each individual patient's LLT to supine measurement, LLT lead to an increase in maximum IVC diameter in 76% (19/25) of patients with the average LLT measurement 29% (95% confidence interval 10–48%) larger. Six patients had the largest maximum IVC measurement in the supine position. No patients experienced any hemodynamic instability or distress during the study. ConclusionIVC ultrasound is feasible in late pregnancy and demonstrates an increase in diameter with LLT positioning. However, a quarter of patients had a decrease in IVC diameter with tilting and, instead, had the largest IVC diameter in the supine position suggesting that uterine compression of the IVC may not occur universally. IVC assessment at the bedside may be a useful adjunct in determining optimal positioning for resuscitation of third trimester patients.

Role of inferior vena cava diameter in assessment of volume status: a meta-analysis

Background and ObjectiveHypovolemic shock is an important cause of death in the emergency department (ED). We sought to conduct a meta-analysis to quantify existing evidence on sonographic measurement of inferior vena cava (IVC) diameter in assessing of volume status adult ED patients. MethodsA search of 5 major databases of biomedical publication, EMBASE, Ovid Medline, evidence-based medicine (EBM) Reviews, Scopus, and Web of Knowledge, was performed in first week of March 2011. Studies meeting the following criteria were included: (1) prospectively conducted, (2) measured IVC diameter using ultrasonography, (3) inpatients under spontaneous ventilation, and (4) reported IVC diameter measurement with volume status or shock. Article search, study quality assessment, and data extraction were done independently and in duplicate. Mean difference in IVC diameter was calculated using RevMan version 5.5 (Cochrane collaboration). ResultsA total of 5 studies qualified for study eligibility from 4 different countries, 3 being case-control and 2 before-and-after design, studying 86 cases and 189 controls. Maximal IVC diameter was significantly lower in hypovolemic status compared with euvolemic status; mean difference (95% confidence interval) was 6.3 mm (6.0-6.5 mm). None of the studies blinded interpreters for volume status of participants. ConclusionModerate level of evidence suggests that the IVC diameter is consistently low in hypovolemic status when compared with euvolemic. Further blinded studies are needed before it could be used in the ED with confidence.

Inferior vena cava assessment in the bedside diagnosis of acute heart failure

ObjectivesThe objective of this study was to determine the test characteristics of the caval index and caval-aortic ratio in predicting the diagnosis of acute heart failure in patients with undifferentiated dyspnea in the emergency department (ED). MethodsThis prospective observational study was performed at an urban ED that enrolled patients, 50 years or older, with acute dyspnea. A sonographic caval index was calculated as the percentage decrease in the inferior vena cava (IVC) diameter during respiration. A caval-aortic ratio was defined by the maximum IVC diameter divided by the aortic diameter. The sensitivity, specificity, and likelihood ratios of these measurements associated with heart failure were estimated. ResultsEighty-nine patients were enrolled in the study with a mean age of 68 years. A caval index of less than 33% had 80% sensitivity (95% confidence interval [CI], 63%-91%) and 81% specificity (95% CI, 68%-90%) in diagnosing acute heart failure, whereas an index of less than 15% had a 37% sensitivity (95% CI, 22%-55%) and 96% specificity (95% CI, 86%-99%). The sensitivity of a caval-aortic ratio of more than 1.2 was 33% (95% CI, 18%-52%) and the specificity was 96% (95% CI, 86%-99%). Positive likelihood ratios were 10 for a caval index of less than 15%, 4.3 for an index of less than 33%, and 8.3 for a caval-aortic ratio of more than 1.2. ConclusionBedside assessments of the caval index or caval-aortic ratio may be useful clinical adjuncts in establishing the diagnosis of acute heart failure in patients with undifferentiated dyspnea.