Sonographic assessment of abdominal vein dimensional and hemodynamic changes induced in human volunteers by a model of abdominal hypertension*:

Use of POCUS for the assessment of dehydration in pediatric patients-a narrative review

In pediatric practice, POCUS (point-of-care ultrasound) has been mostly implemented to recognize lung conditions and pleural and pericardial effusions, but less to evaluate fluid depletion. The main aim of this review is to analyze the current literature on the assessment of dehydration in pediatric patients by using POCUS. The size of the inferior vena cava (IVC) and its change in diameter in response to respiration have been investigated as a tool to screen for hypovolemia. A dilated IVC with decreased collapsibility (< 50%) is a sign of increased right atrial pressure. On the contrary, a collapsed IVC may be indicative of hypovolemia. The IVC collapsibility index (cIVC) reflects the decrease in the diameter upon inspiration. Altogether the IVC diameter and collapsibility index can be easily determined, but their role in children has not been fully demonstrated, and an estimation of volume status solely by assessing the IVC should thus be interpreted with caution. The inferior vena cava/abdominal aorta (IVC/AO) ratio may be a suitable parameter to assess the volume status in pediatric patients even though there is a need to define age-based thresholds. A combination of vascular, lung, and cardiac POCUS could be a valuable supplementary tool in the assessment of dehydration in several clinical scenarios, enabling rapid identification of life-threatening primary etiologies and helping physicians avoid inappropriate therapeutic interventions.   Conclusion: POCUS can provide important information in the assessment of intravascular fluid status in emergency scenarios, but measurements may be confounded by a number of other clinical variables. The inclusion of lung and cardiac views may assist in better understanding the patient's physiology and etiology regarding volume status. What is Known: • In pediatric practice, POCUS (point-of-care ultrasound) has been mostly implemented to recognize lung conditions (like pneumonia and bronchiolitis) and pleural and pericardial effusions, but less to evaluate fluid depletion. • The size of the IVC (inferior vena cava) and its change in diameter in response to respiration have been studied as a possible screening tool to assess the volume status, predict fluid responsiveness, and assess potential intolerance to fluid loading. What is New: • The IVC diameter and collapsibility index can be easily assessed, but their role in predicting dehydration in pediatric age has not been fully demonstrated, and an estimation of volume status only by assessing the IVC should be interpreted carefully. • The IVC /AO(inferior vena cava/abdominal aorta) ratio may be a suitable parameter to assess the volume status in pediatric patients even though there is a need to define age-based thresholds. A combination of vascular, lung, and cardiac POCUS can be a valuable supplementary tool in the assessment of intravascular volume in several clinical scenarios.

Evaluation of caudal vena cava size using computed tomography in dogs under general anesthesia

This study investigated the association between caudal vena cava (CVC) size and circulatory dynamics in dogs using computed tomography (CT) under general anesthesia. The subjects were 104 dogs who had undergone CT under general anesthesia in the past. The ratio of short diameter of the CVC to aortic diameter (CVC_S/Ao) and the ratio of long to short diameter of the CVC (CVC_L/CVC_S) in the thorax and abdomen, respectively, were calculated using factors such as mean blood pressure (MBP), shock index (SI), anemia, hypoproteinemia, presence of intra-abdominal mass, and cardiac disease. There was a significant but negligible negative correlation between CVC_S/Ao and MBP. In contrast, no significant correlation was found between CVC size and SI. The low MBP group had significantly higher CVC_S/Ao of the thorax than the normal MBP group. The group with intra-abdominal mass had significantly lower CVC_S/Ao of the abdomen than the group without intra-abdominal mass. The group with cardiac disease had significantly lower CVC_L/CVC_S of the thorax than the group without cardiac disease. In multiple regression analysis, low MBP, cardiac disease, intra-abdominal mass, and anemia were significant factors for CVC_S/Ao of the thorax, CVC_L/CVC_S of the thorax, CVC_S/Ao of the abdomen, and CVC_L/CVC_S of the abdomen, respectively. In conclusion, CVC size assessment using CT in dogs under general anesthesia is influenced by various factors.

Systematic Review of Diagnostic Sensors for Intra-Abdominal Pressure Monitoring

Intra-abdominal pressure (IAP) is defined as the steady-state pressure within the abdominal cavity. Elevated IAP has been implicated in many medical complications. This article reviews the current state-of-the-art in innovative sensors for the measurement of IAP. A systematic review was conducted on studies on the development and application of IAP sensors. Publications from 2010 to 2021 were identified by performing structured searches in databases, review articles, and major textbooks. Sixteen studies were eligible for the final systematic review. Of the 16 articles that describe the measurement of IAP, there were 5 in vitro studies (31.3%), 7 in vivo studies (43.7%), and 4 human trials (25.0%). In addition, with the advancement of wireless communication technology, an increasing number of wireless sensing systems have been developed. Among the studies in this review, five presented wireless sensing systems (31.3%) to monitor IAP. In this systematic review, we present recent developments in different types of intra-abdominal pressure sensors and discuss their inherent advantages due to their small size, remote monitoring, and multiplexing.

In situ Evidence of Collagen V and Interleukin-6/Interleukin-17 Activation in Vascular Remodeling of Experimental Pulmonary Hypertension

Several studies have reported the pathophysiologic and molecular mechanisms responsible for pulmonary arterial hypertension (PAH). However, the in situ evidence of collagen V (Col V) and interleukin-17 (IL-17)/interleukin-6 (IL-6) activation in PAH has not been fully elucidated. We analyzed the effects of collagen I (Col I), Col V, IL-6, and IL-17 on vascular remodeling and hemodynamics and its possible mechanisms of action in monocrotaline (MCT)-induced PAH. Twenty male Wistar rats were randomly divided into two groups. In the PAH group, animals received MCT 60 mg/kg intraperitoneally, whereas the control group (CTRL) received saline. On day 21, the pulmonary blood pressure (PAP) and right ventricular systolic pressure (RVSP) were determined. Lung histology (smooth muscle cell proliferation [α-smooth muscle actin; α-SMA] and periadventitial fibrosis), immunofluorescence (Col I, Col V, and α-SMA), immunohistochemistry (IL-6, IL-17, and transforming growth factor-beta [TGF-β]), and transmission electron microscopy to detect fibronexus were evaluated. The RVSP (40 ± 2 vs. 24 ± 1 mm Hg, respectively; p < 0.0001), right ventricle hypertrophy index (65 ± 9 and 25 ± 5%, respectively; p < 0.0001), vascular periadventitial Col I and Col V, smooth muscle cell α-SMA+, fibronexus, IL-6, IL-17, and TGF-β were higher in the MCT group than in the CTRL group. In conclusion, our findings indicate in situ evidence of Col V and IL-6/IL-17 activation in vascular remodeling and suggest that increase of Col V may yield potential therapeutic targets for treating patients with PAH.

The Correlation of Intraabdominal Pressure With Renal Resistive Index

BACKGROUND

To evaluate the correlation between intraabdominal pressure (IAP) measured via the bladder and renal resistive index (RRI) measured by Doppler ultrasonography (USG).

METHODS

Eighty consecutive surgical patients were included into this study. Before Doppler USG evaluation, IAP was measured by a Foley catheter via the bladder. The left and right RRI, the diameters of the inferior vena cava and portal vein were measured by colored Doppler USG. Spearman correlation analysis was used to evaluate the correlation between different measurements. Intraabdominal hypertension (IAH) was defined as of IAP ≥ 12 mmHg. Significantly different variables from the univariate analysis between patients with and without IAH were entered into backward stepwise binary logistic regression analysis of IAH as the dependent variable. P values < 0.05 were accepted as statistically significant.

RESULTS

In total, 80 patients were included into study. In 27 patients (34%) IAP was normal and in 53 patients (66%) IAH was diagnosed. The Spearman correlation analysis of IAP and the ultrasonographic measurements revealed a strong correlation between RRI and IAP (P < 0.001). Patients with IAH were more likely to be diabetic and had abdominal incisional hernia compared with patients with normal IAP (P < 0.05). The results of the multivariate logistic regression analysis revealed right RRI as the only independent predictor of IAH (B: 57.04, S. E.: 13.7, P < 0.001).

CONCLUSIONS

There is a strong correlation between IAP and RRI. RRI can be an alternative, noninvasive technique for the diagnosis and follow-up of IAH after further evaluations in different patient groups.

Inpatient Evaluation of Intra-abdominal Pressure Completed With a Urinary Catheter as Compared With Ultrasonographic Vessel Measurements

Background:

The purpose of this study was to evaluate the diagnostic value of ultrasonography as compared with intra-abdominal pressure (IAP) measured with a urinary catheter.

Methods:

This was a cross-sectional study. The participants consisted of 146 patients hospitalized in the emergency wards of two hospitals in Isfahan (2017-2018). Following measurement of IAP through a urinary catheter, ultrasonographic measurement of the inferior vena cava (IVC) diameter, internal jugular vein diameter, common femoral vein (CFV) diameter, and ratio between the IVC and abdominal aortic diameters was completed. Correlation between these methods of measurements for IAP was investigated.

Results:

There was a significant positive correlation between intrabladder pressure and the right internal jugular vein (RIJV) and CFV ( P < .001, R > 0). There was also a reverse significant correlation between intrabladder pressure and RIJV, IVC, IVC:aorta diameter, systolic blood pressure, and tricuspid annular plane systolic excursion ( P < .001, r < 0). RIJV, CFV, and tricuspid annular plane systolic excursion were suitable predictors for the estimation of intrabladder pressure or IAP ( P < .05), but IVC, IVC:aorta, and systolic blood pressure were not suitable factors for estimating IAP ( P > .05).

Conclusion:

Ultrasonographic measurement is a noninvasive method for determining IAP.

Respiratory variations of inferior vena cava fail to predict fluid responsiveness in mechanically ventilated patients with isolated left ventricular dysfunction

Background

Respiratory variation of inferior vena cava is problematic in predicting fluid responsiveness in patients with right ventricular dysfunction. However, its effectiveness in patients with isolated left ventricular systolic dysfunction (ILVD) has not been reported. We aimed to explore whether inferior vena cava diameter distensibility index (dIVC) can predict fluid responsiveness in mechanically ventilated ILVD patients.

Methods

Patients admitted to the intensive care unit who were on controlled mechanical ventilation and in need of a fluid responsiveness assessment were screened for enrolment. Several echocardiographic parameters, including dIVC, tricuspid annular plane systolic excursion (TAPSE), left ventricular ejection fraction (LVEF), and LV outflow tract velocity–time integral (VTI) before and after passive leg raising (PLR) were collected. Patients with LV systolic dysfunction only (TAPSE ≥ 16 mm, LVEF < 50%) were considered to have isolated left ventricular systolic dysfunction (ILVD).

Results

One hundred and twenty-nine subjects were enrolled in this study, among them, 28 were labelled ILVD patients, and the remaining 101 were patients with normal LV function (NLVF). The value of dIVC in ILVD patients was as high as that in NLVF patients, (20% vs. 16%, p = 0.211). The ILVD group contained a much lower proportion of PLR responders than NLVF patients did (17.9% vs. 53.2%, p < 0.001). No correlation was detected between dIVC and ΔVTI in ILVD patients (r = 0.196, p = 0.309). dIVC was correlated with ΔVTI in NLVF patients (r = 0.722, p < 0.001), and the correlation was strengthened compared with that derived from all patients (p = 0.020). A receiver-operating characteristic (ROC) analysis showed that the area-under-the-curve (AUC) of dIVC for determining fluid responsiveness from ILVD patients was not statistically significant (p = 0.251). In NLVF patients, ROC analysis revealed an AUC of 0.918 (95% CI 0.858–0.978; p < 0.001), which was higher than the AUC derived from all patients (p = 0.033). Patients with LVEF below 40% had a lower ΔVTI and fewer PLR responders than those with LVEF 40–50% and LVEF above 50% (p < 0.001).

Conclusion

dIVC should be used with caution when critically ill patients on controlled mechanical ventilation display normal right ventricular function in combination with abnormal left ventricular systolic function.

Size and shape of the inferior vena cava before and after a fluid challenge: a pilot study

BACKGROUND

Recent meta-analyses failed to support the reliability of ultrasound assessment of the inferior vena cava (IVC) to predict fluid responsiveness. However, the techniques utilized were heterogeneous. We hypothesized that the variability of the elliptic section and caliber of the IVC along its course may influence ultrasound evaluation. Therefore, we investigated IVC size and shape at four levels, before and after a fluid challenge.

METHODS

Twenty mechanically-ventilated adult patients who received a fluid challenge after cardiac surgery were enrolled. They were regarded as responders if the cardiac index increased more than 15%. Before and after the fluid challenge, IVC anteroposterior (AP) and lateral (LA) diameters, the flat ratio, and the distensibility index were assessed by ultrasound just above the iliac veins, at the confluence of the renal veins, before the confluence of the hepatic veins (where blood flow velocity was also measured), and after it.

RESULTS

At all levels, IVC section was elliptical, so that IVC diameters varied between a minimum and a maximum according to the measurement angle. Such interval increased in correspondence of the renal veins, where IVC section was more eccentric. The distensibility index was higher when assessed on AP diameters. After the fluid challenge, non-responders showed a diffuse increase of AP diameters, whereas responders showed an increase of blood velocity before the confluence of the hepatic veins.

CONCLUSIONS

The elliptic section should be considered when assessing IVC size. AP diameters are shorter and more affected by the respiratory cycle. After a fluid challenge, an increase of blood velocity associated with unchanged AP diameters may suggest fluid responsiveness.

Abdominal Compartment Syndrome as a Multidisciplinary Challenge. A Literature Review

Abdominal Compartment Syndrome (ACS), despite recent advances in medical and surgical care, is a significant cause of mortality. The purpose of this review is to present the main diagnostic and therapeutic aspects from the anesthetical and surgical points of view. Intra-abdominal hypertension may be diagnosed by measuring intra-abdominal pressure and indirectly by imaging and radiological means. Early detection of ACS is a key element in the ACS therapy. Without treatment, more than 90% of cases lead to death and according with the last reports, despite all treatment measures, the mortality rate is reported as being between 25 and 75%. There are conflicting reports as to the importance of a conservative therapy approach, although such an approach is the central to treatment guidelines of the World Society of Abdominal Compartment Syndrome, Decompressive laparotomy, although a backup solution in ACS therapy, reduces mortality by 16-37%. The open abdomen management has several variants, but negative pressure wound therapy represents the gold standard of surgical treatment.

Bladder Pressure Measurements in Patients Admitted to a Medical Intensive Care Unit

BACKGROUND

Intra-abdominal hypertension is identified as an independent risk factor for death. However, this pathophysiological state is not always considered in patients in medical intensive care units and is frequently underdiagnosed.

METHODS

Serial bladder pressure measurements were recorded in patients admitted to the medical intensive care units to determine the frequency of intra-abdominal hypertension.

RESULTS

This study included 53 patients with a mean age of 59.0 ± 17.7 years. The average admission intra-abdominal pressure was 10.0 ± 5.4 mm Hg with a range of 0 to 28 mm Hg. Eleven patients (21%) had an initial pressure reading above normal (>12 mm Hg). Peak airway pressures were higher, and PaO2/FiO2 ratios were lower in patients with an initial pressure >12 mm Hg.

CONCLUSIONS

Bladder pressure measurements provide an easy method to estimate intra-abdominal pressures and provide an additional tool for the physiologic assessment of critically ill patients.

Acute abdominal compartment syndrome: current diagnostic and therapeutic options

BACKGROUND

If untreated, the abdominal compartment syndrome (ACS) has a mortality of nearly 100 %. Thus, its early recognition is of major importance for daily rounds on surgical intensive care units. Intraabdominal hypertension (IAH) is a poorly recognized entity, which occurs if intraabdominal pressure arises >12 mmHg. Measurement of the intravesical pressure is the gold standard to diagnose IAH, which can be detected in about one fourth of surgical intensive care patients.

PURPOSE

The aim of this manuscript is to outline the current diagnostic and therapeutic options for IAH and ACS. While diagnosis of IAH and ACS strongly depends on clinical experience, new diagnostic markers could play an important role in the future. Therapy of IAH/ACS consists of five treatment "columns": intraluminal evacuation, intraabdominal evacuation, improvement of abdominal wall compliance, fluid management, and improved organ perfusion. If conservative therapy fails, emergency laparotomy is the most effective therapeutic approach to achieve abdominal decompression. Thereafter, patients with an open abdomen require intensive care and are permanently threatened by the quadrangle of fluid loss, muscle proteolysis, heat loss, and an impaired immune function. As a consequence, complication rate dramatically increases after 8 days of open abdomen therapy.

CONCLUSION

Despite many efforts, the mortality of patients with ACS remains unacceptably high. Permanent clinical education and surgical trials will be necessary to improve the outcome of our critically ill surgical patients.

Influence of reverse Trendelenburg position on aortocaval compression in obese pregnant women

INTRODUCTION

Obese pregnant women are at risk of aortocaval compression and associated hypotension with neuraxial anaesthesia. We hypothesised that addition of reverse Trendelenburg tilt to the standard practice of pelvic tilt may attenuate aortocaval compression.

METHODS

After ethical approval and consent, six women with a singleton pregnancy and booking body mass index of 30-35kg/m(2) underwent magnetic resonance imaging scanning in six different positions: right lateral decubitus; left lateral decubitus; supine with pelvic tilt; and reverse Trendelenburg positions of 5°, 10° and 15°. Dimensions of the inferior vena cava and abdominal aorta at the L2-3 intervertebral disc level were obtained from axial images using medical imaging software OsiriX™.

RESULTS

Inferior vena cava dimensions were higher in left lateral decubitus position compared to supine with pelvic tilt (P=0.002). Inferior vena cava compression was noted in all participants (59±33%, 95% CI 32 to 86). Addition of 15° reverse Trendelenburg tilt to standard pelvic tilt produced a non-statistically significant increase in inferior vena cava area (10.54±9.91cm(2), 95% CI 2.61 to 18.47, P=0.06).

CONCLUSION

A non-statistically significant improvement of aortocaval compression was noted with the addition of 15° reverse Trendelenburg tilt to the supine with pelvic tilt position in obese pregnant women.

Inferior Vena Cava Assessment: Correlation with CVP and Plethora in Tamponade

Bedside assessment of intravascular volume status plays an important role in the management of critically ill patients, guiding fluid replacement therapy and the use of vasopressor agents. Despite controversy in the existing evidence, many clinicians advocate the use of inferior vena cava ultrasound (IVC-US) in the assessment of intravascular volume status in critically ill patients. Respirophasic variation in IVC diameter may provide useful information regarding intravascular volume status, particularly in patients with high and low caval indices. However, due to conflicting results of small-scale clinical trials of divergent sample populations, there is insufficient evidence to support routine US assessment of the IVC to determine fluid responsiveness in spontaneous breathing with circulatory compromise. Additional large-scale clinical trials are required to determine the accuracy of IVC-US measurements in diverse populations and to ascertain the effects on IVC dimensions that result from cardiac dysfunction and intra-abdominal hypertension.

Multimodal monitoring for hemodynamic categorization and management of pediatric septic shock: a pilot observational study*

OBJECTIVES

To evaluate the cardiovascular aberrations using multimodal monitoring in fluid refractory pediatric septic shock and describe the clinical characteristics of septic myocardial dysfunction.

DESIGN

Prospective observational study of patients with unresolved septic shock after infusion of 40 mL/kg fluid in the first hour.

SETTING

Two tertiary care referral Indian PICUs.

PATIENTS

Patients aged 1 month to 16 years who had fluid refractory septic shock.

INTERVENTIONS

Changes in therapy were based on findings of clinical assessment, bedside echocardiography, and invasive blood pressure monitoring within 6 hours of recognition of septic shock.

MEASUREMENTS AND MAIN RESULTS

Over a 4-year period, 48 patients remained in septic shock despite at least 40 mL/kg fluid infusion. On clinical examination, 21 patients had cold shock and 27 had warm shock. Forty-one patients (85.5%) had vasodilatory shock on invasive blood pressure; these included 14 patients who initially presented with cold shock. The commonest echocardiography findings were impaired left ± right ventricular function in 19 patients (39.6%) and hypovolemia in 16 patients (33%). Three patients who had normal myocardial function on day 1 developed secondary septic myocardial dysfunction on day 3. Echocardio graphy, along with invasive arterial pressure monitoring, allowed fluid, inotropy, and pressors to be titrated more precisely in 87.5% of patients. Shock resolved in 46 of 48 patients (96%) and 44 patients (91.6%) survived to discharge.

CONCLUSION

Bedside echocardiography provided crucial information leading to the recognition of septic myocardial dysfunction and uncorrected hypovolemia that was not apparent on clinical assessment. With invasive blood pressure monitoring, echocardiography affords a simple noninvasive tool to determine the cause of low cardiac output and the physiological basis for adjustment of therapy in patients who remain in shock despite 40 mL/kg fluid.

Compression of the inferior vena cava in bowel obstruction

INTRODUCTION

We investigated whether (a) the inferior vena cava (IVC) is compressed in bowel obstruction and (b) some tracts are more compressed than others.

METHODS

Two groups of abdominal computed tomography (CT) examinations were collected retrospectively. Group O (N = 69) scans were positive for bowel obstruction, group C (N = 50) scans were negative for diseases. IVC anteroposterior and lateral diameters (APD, LAD) were assessed at seven levels.

RESULTS

In group C, IVC section had an elliptic shape (APD/LAD: .76 ± .14), the area of which increased gradually from 1.9 (confluence of the iliac veins) to 3.1 cm²/m² of BSA (confluence of the hepatic veins) with a significant narrowing in the hepatic section. In group O, bowel obstruction caused a compression of IVC (APD/LAD: .54 ± .17). Along its course, IVC section area increased from 1.3 to 2.5 cm²/m². At ROC curve analysis, an APD/LAD ratio lower than 0.63 above the confluence of the iliac veins discriminated between O and C groups with sensitivity of 74% and specificity of 96%.

CONCLUSIONS

Bowel obstruction caused a compression of IVC, which involved its entire course except for the terminal section. APD/LAD ratio may be useful to monitor the degree of compression.