Intensivist Bedside Ultrasound (INBU) for Volume Assessment in the Intensive Care Unit: A Pilot Study

The Effect of Fluid Pre-loading on Vital Signs and Hemodynamic Parameters in a Porcine Model of Lipopolysaccharide-Induced Endotoxemia

Background Animal models of distributive hypotension and resuscitation allow the assessment of hemodynamic monitoring modalities and resuscitation strategies. The fluid-first paradigm for resuscitation is currently being challenged with clinical trials. In this investigation, venous return and perfusion are assessed, and full hemodynamics are characterized, in a porcine model of endotoxemic hypotension with and without fluid pre-loading. Methods Two groups of six pigs had the induction of standardized endotoxemic hypotension ("critical hypotension"). Group 1 underwent four 10 cc/kg crystalloid boluses, and Group 2 was not fluid pre-resuscitated. Both groups underwent progressive norepinephrine (NE) up-titration to 0.25 mcg/kg/minute over 30 minutes. Vital signs, central parameters, and laboratory values were obtained at baseline, "critical hypotension," after each bolus and during NE administration. Results Endotoxemia decreased the systemic vascular resistance (SVR) in Group 1 (1031±106 dyn/s/cm-5 versus 738±258 dyn/s/cm-5; P=0.03) and Group 2 (1121±196 dyn/s/cm-5 versus 759±342 dyn/s/cm-5; P=0.003). In Group 1, the four fluid boluses decreased heart rate (HR), pulmonary capillary wedge pressure (PCWP), and central venous pressure (CVP) (P<0.05). No changes were observed in blood pressure, cardiac output (CO), or lactate. NE up-titration increased HR in Group 1 and decreased CVP in both groups. Higher final CVP (11 {3} versus 4 {4} mmHg; P=0.01) and PCWP (5 {1} versus 2 {2} mmHg; P=0.005) values were observed in Group 1 relative to Group 2, reflecting increased venous return. Conclusions Porcine endotoxemic hypotension and resuscitation were robustly characterized. In this model, fluid loading improved venous return with NE, though perfusion (CO) was preserved by increased NE-induced chronotropy.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Sonographic Estimation Rather Than Quantification of Fluid Status Using Inferior Vena Cava and Other Major Vessel Parameters in a Non-Bleeding Fluid Loss and Centralization Model

Objective

A well-accepted step in emergency sonography is the estimation of a fluid deficit through Inferior Vena Cava (IVC) diameter variability with known cut-offs especially in bleeding. We sought to answer, whether a non-bleeding fluid deficit can be quantified through sonographic assessment of IVC diameter variability and related aortic parameters. Sport divers were used as human hypovolemic vasoconstriction models since immersion is known to cause relevant volume depletion through vasoconstriction and induced diuresis.

Materials and Methods

Forty-one sport divers performed 342 single and repetitive dives to account for intra- and interindividual variability and were assessed for inferior Vena Cava and neighboring aortic diameters as well as their cardiac/respiratory variations. Dive-related weight loss was measured together with sonographic vessel diameter changes inferior to the right atrium.

Results

Highest correlation with dive-related weight loss of max. 2.9 kg per an average 47 minutes dive was found with r=0.34 for the difference of IVC maximum diameter related to minimum Aortic diameter. Single or combined parameters, as well as Collapsibility Index, showed lower or no correlations. Vascular parameters were able to explain 7.5% of the variance of fluid losses, whereas interindividual effects explained 10%. The remaining 82.5% is of mixed intraindividual counterregulatory effects.

Conclusion

IVC diameter changes in immersion-induced hypovolemic centralization provides qualitative information on relevant fluid loss only. Confounding factors like inter and intraindividual variability prevent a sufficient correlation for useful quantification of the experienced non-bleeding fluid deficit in the clinical setting.

Correlation of internal jugular and subclavian vein diameter variation on bedside ultrasound with invasive right heart catheterization

Introduction

Accurate estimation of fluid status is paramount in patients with heart failure. We hypothesized that bedside ultrasound assessment of the internal jugular vein (IJV) and subclavian vein (SCV) could reliably estimate right atrial pressure (RAP).

Methods

Prospectively enrolled patients were positioned supine. IJV was imaged at the apex of the right sternocleidomastoid muscle and SCV was imaged at the lateral third of the right clavicle. Using M-mode on a portable ultrasound machine, the maximum (D_max) and minimum (D_min) anteroposterior diameters were noted during normal breathing. Respiratory variation in diameter (RVD) was calculated as [(D_max – D_min)/D_max] and expressed as percent. Collapsibility was assessed with sniff maneuver. Patients then underwent right heart catheterization and their findings were correlated with above.

Results

Total of 72 patients were enrolled with mean age 61 years, mean BSA 1.9 m², and left ventricular ejection fraction 45 ± 20%. Elevated RAP≥ 10 mmHg was associated with dilated IJV D_max(1.0 vs. 0.7cm, p = 0.001), less RVD with resting respiration (14% vs. 40% for IJV, p = 0.001 and 24% vs. 45% for SCV, p = 0.001), and reduced likelihood of total collapsibility with sniff (16% vs. 66% patients for IJV, p = 0.001 and 25% vs. 57% patients for SCV, p = 0.01). For RAP ≥10 mmHg, lack of IJV complete collapsibility with sniff had a sensitivity of 84% while IJV D_max > 1cm and RVD <50% had a specificity of 80%.

Conclusion

The IJV and SCV diameters and their respiratory variation are reliable in estimating RA pressure.

Pre-anaesthesia ultrasonography of the subclavian/infraclavicular axillary vein for predicting hypotension after inducing general anaesthesia: A prospective observational study

BACKGROUND

Bedside sonography of the inferior vena cava has been demonstrated to be a reliable tool for assessing intravascular volume status. Subclavian vein (SCV) assessment was proposed as a reasonable adjunct for measuring the inferior vena cava.

OBJECTIVE

We examined whether the preoperative diameter and collapsibility index of the SCV or the infraclavicular axillary vein could predict the incidence of hypotension after induction of general anaesthesia in patients undergoing laparoscopic cholecystectomy.

DESIGN

Prospective, observational study.

SETTING

Tertiary university hospital.

PATIENTS

Adults scheduled for laparoscopic cholecystectomy.

INTERVENTION

Sonographic evaluation of the SCV or the axillary vein (SCV-AV) before induction of anaesthesia.

MAIN OUTCOME MEASURES

The main outcome was the association between the SCV-AV measurements (diameter an collapsibility index) and intra-operative hypotension (IOH) after induction of anaesthesia.

RESULTS

Patients who developed IOH had a higher collapsibility index of the SCV-AV during spontaneous breathing (P = 0.009) and deep inspiration (P = 0.002). After adjusting for confounding variables, the collapsibility index of the SCV-AV during spontaneous breathing was not a significant predictor of a decrease in mean arterial blood pressure (MAP) after inducing anaesthesia (P = 0.127), whereas the collapsibility index of the SCV-AV during deep inspiration was a significant predictor (P < 0.001).

CONCLUSION

The collapsibility index of the SCV-AV during deep inspiration was a significant predictor of IOH occurrence and the percentage decrease in MAP after inducing anaesthesia. Further studies in patients with higher collapsibility index are needed to confirm our findings, before the collapsibility index of the SCV-AV can be recommended unequivocally for clinical use.

TRIAL REGISTRATION

This trial was registered on 8 September 2017 at the Clinical Trial Registry of Korea (https://cris.nih.go.kr/cris/index.jsp; Identifier: KCT0001078KCT0002457), and the first patient was enrolled on 14 October 2017.

Clinical correlates of hand-held ultrasound-guided assessments of the inferior vena cava in patients with acute decompensated heart failure

BACKGROUND

Accurately assessing volume status in acutely decompensated heart failure (ADHF) can be challenging. Inferior vena cava (IVC) dynamics by echocardiography allow indirect assessment of volume status in these patients. Recently introduced hand-held ultrasound devices are promising. We aimed to describe the clinical correlates of volume status assessment using a hand-held ultrasound device in ADHF.

METHODS

In this prospective study, we evaluated 106 patients admitted with ADHF. First scan was performed within 24 hours of admission and timed in reference to first dose of intravenous diuretic. Daily resting and inspiratory (sniff) IVC diameters were measured according to standard echocardiography methods during hospitalization including the day of discharge. IVC collapsibility index (IVC-CI = Maximum IVC diameter-Inspiratory IVC diameter/maximum diameter; <0.5 representing hypervolemia) was calculated. Primary study endpoint was 30-day readmission. Research activities were independent of clinical decision-making.

RESULTS

Data for 106 patients was analyzed. Mean age was 66.7 ± 13.8 years, of which 53.8% were females, and a mean ejection fraction was 39 ± 18%. Initial scan of the IVC was obtained at an average time of 5.2 ± 8.04 hours from first diuretic dose. 81.2% of patients at admission had an IVC-CI <0.5. 63.2% patients had an IVC-CI <0.5 at discharge. There were no significant differences in age, length of stay, diuretic dose, or 30-day readmissions between patients with a discharge IVC-CI <0.5 vs ≥ 0.5.

CONCLUSION

Hand-held ultrasound assessment of IVC-CI in ADHF patients, although a feasible concept, is unable to predict 30-day readmissions in our study. Further prospective studies are necessary.

Non-Invasive Venous waveform Analysis (NIVA) for monitoring blood loss in human blood donors and validation in a porcine hemorrhage model

STUDY OBJECTIVE

There is an unmet need for a non-invasive approach to diagnose hemorrhage early, before changes in vital signs occur. Non-Invasive Venous waveform Analysis (NIVA) uses a unique physiological signal (the peripheral venous waveform) to assess intravascular volume. We hypothesized changes in the venous waveform would be observed with blood loss in healthy adult blood donors and characterized hemorrhage using invasive monitoring in a porcine model.

DESIGN

Prospective observational study.

SETTING

American Red Cross donation center.

PATIENTS

50 human blood donors and 12 non-donating controls; 7 Yorkshire pigs.

INTERVENTIONS

A venous waveform capturing prototype (NIVA device) was secured to the volar aspect of the wrist in human subjects. A central venous catheter was used to obtain hemodynamic indices and venous waveforms were obtained using the prototype NIVA device over the saphenous vein during 400 mL of graded hemorrhage in a porcine model.

MEASUREMENTS

Venous waveforms were transformed from the time to the frequency domain. The ratiometric power contributions of the cardiac frequencies were used to calculate a NIVA value representative of volume status.

MAIN RESULTS

A significant decrease in NIVA value was observed after 500 mL of whole blood donation (p < .05). A ROC curve for the ability of the NIVA to detect 500 mL of blood loss demonstrated an area under the curve (AUC) of 0.94. In the porcine model, change in NIVA value correlated linearly with blood loss and with changes in hemodynamic indices.

CONCLUSIONS

This study provides proof-of-concept for a potential application of NIVA in detection of blood loss. NIVA represents a novel physiologic signal for detection of early blood loss that may be useful in early triage and perioperative management.

Ultrasound as First Line Step in Anaemia Diagnostics

This review covers the role of ultrasonography as an essential non-invasive diagnostic approach when facing patients with anaemia, a common clinical problem. Abdomen ultrasound is well recognised as a first-line examination in the setting of blood loss, both acute and chronic. Less is clear about the additional opportunities, given by ultrasound in anaemia, due to the many other possible causes. Here we provide information on the utility of ultrasound in different contexts and a practical guide for clinicians facing anaemic patients.

Review of bedside surgeon-performed ultrasound in pediatric patients

PURPOSE

Pediatric surgeon performed bedside ultrasound (PSPBUS) is a targeted examination that is diagnostic or therapeutic. The aim of this paper is to review literature involving PSPBUS.

METHODS

PSPBUS practices reviewed in this paper include central venous catheter placement, physiologic assessment (volume status and echocardiography), hypertrophic pyloric stenosis diagnosis, appendicitis diagnosis, the Focused Assessment with Sonography for Trauma (FAST), thoracic evaluation, and soft tissue infection evaluation.

RESULTS

There are no standards for the practice of PSPBUS.

CONCLUSIONS

As the role of the pediatric surgeon continues to evolve, PSPBUS will influence practice patterns, disease diagnosis, and patient management.

TYPE OF STUDY

Review Article.

LEVEL OF EVIDENCE

Level III.

Ultrasound for Volume Assessment in Patients with Shock: Effectiveness of an Educational Intervention for Fourth-year Medical Students

Objective

Shock is a common emergency condition with high morbidity and mortality, and judicious fluid resuscitation can significantly affect outcomes. The use of a bedside echocardiogram and evaluation of the inferior vena cava (IVC) via ultrasound (US) for collapsibility can predict volume status. Additionally, the Association of American Medical Colleges (AAMC) Entrustable Professional Activities (EPA) 10 states that residents need to be able to address a patient with a critical illness, including hypotension, on Day 1 of residency. Existing literature revealed no published curriculum to teach medical students these skills. We aimed to determine the effectiveness of an educational intervention to teach fourth-year medical students how to utilize IVC US measurement and echocardiography to assist in volume assessment of patients presenting with shock.

Methods

Students participated in an hour session on the first day of the emergency medicine (EM) clerkship. Didactic effectiveness was evaluated by comparing results on a pre-test and post-test. The test was administered to residents and attendings during the first week of the academic year to gain evidence for content validity. Students also responded to a survey to evaluate learner satisfaction.

Results

The average score on the validation test was 68.4% (standard deviation (SD): 21.6%, number (n) = 38) for residents and attendings, and 47.4% (SD: 19.4, n = 13) for interns. Students scored an average of 45.6% (SD: 23.6, n = 83) on the pre-test and 66.4% (SD: 22.1 n = 72) on the post-test, p < 0.01 (degrees of freedom (df) = 153, t = 5.7), Cohen's d = 0.92. The satisfaction survey showed 97.6% of students felt the session was worthwhile, 96.4% would recommend it to other students, and 83.1% felt it taught new information.

Conclusion

These results show that the educational intervention provides a significant increase in knowledge regarding volume assessment and the use of echocardiogram and IVC US. Additionally, students rated the course highly and felt that it provided information not otherwise taught in medical school. This curriculum addresses the AAMC EPA 10, as it increases students’ readiness to address hypotension and could add significant value to the medical school curriculum.

Curriculum Development and Evaluation of a Hemodynamic Critical Care Ultrasound: A Systematic Review of the Literature

OBJECTIVE

The application of ultrasound to assess a patient's cardiac function and volume status is becoming commonplace in the practice of critical care. These skills have been taught through varying curricula; however, no consensus on the optimal curriculum has been established. The purpose of this systematic review is to evaluate the literature regarding critical care ultrasound curriculum development and evaluation.

DATA SOURCES

Studies were identified using MEDLINE, Embase, CINAHL, PsycInfo, the Cochrane Center Register of Controlled Trials, and ERIC according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines through June 2014.

STUDY SELECTION

Included studies were limited to those that described adult (age, > 16 yr) cardiac or hemodynamic critical care ultrasound curricula for physicians. Two reviewers independently screened studies based on predetermined exclusion criteria, and disagreements were resolved by a third reviewer.

DATA EXTRACTION

Data were abstracted, and quality was assessed by two reviewers using the Newcastle-Ottawa Scale. Data abstracted from the studies included the learner population, examination type, duration, composition, and setting of the curriculum, means of evaluation, and outcomes.

DATA SYNTHESIS

The search yielded 654 studies; of which, 15 met inclusion criteria. All curricula used a combination of didactic and hands-on components. The highest agreement between novice and experts, coupled with the most time-efficient application, was achieved when the study was limited to a basic qualitative approach for the assessment of global function or contractility and assessment of inferior vena cava collapsibility. The mode of delivery seemed most efficient when a hybrid method was used, including online instruction. Minimum scanning competency may be achieved with 30 scans although more rigorous study on this element is necessary.

CONCLUSIONS

Assessment of cardiac function and volume assessment is becoming an essential skill in critical care medicine. Physicians can be taught bedside echocardiography in a time-effective manner with positive benefit to patients by applying a concise curriculum with limited content.

Predicting Central Venous Pressure by Measuring Femoral Venous Diameter Using Ultrasonography

Objectives

The objective of this exploratory study was to find out the correlation of femoral vein diameter (FVD) to central venous pressure (CVP) measurements and to derive a prediction equation to help ascertain the fluid volume status in a critical patient.

Patients and methods

This was a single-centered prospective cohort study designed and conducted by the critical care department of Shifa International hospital in Islamabad, Pakistan. Patients were enrolled from the medical and surgical intensive care units. The inclusion criteria consisted of patients > 18 years of age, and an intrathoracic central venous catheterization (CVC) in place for producing CVP waveform through the transducer. Patients having contraindications to CVP placement and those unable to lie supine were excluded from the study. Critical Care fellows with sufficient training in performing venous ultrasonography measured the FVD. They were blinded to the CVP values of the same patients.

Results

The study included 108 patients. Among these 70/108 (64.8%) were males. Mean age was 53.85 (SD=16.74). The CVP and femoral vein diameter were measured in all patients. Mean CVP was 9.89 cmH2O (SD=3.46) and mean femoral vein diameter was 0.92 cm (SD=0.27). Multiple regression was used to generate a prediction model. FVD, age and sex of the patient were used as predictor variables to predict CVP diameter. The model was statistically significant with a p-value of < 0.000 and an F-value of 104.806. R-squared value for this model came out to be 0.744, thus the model was able to explain about 74.4% of the variance in the values observed for CVP. When controlled for age and sex, FVD was found highly correlated with CVP diameter with a p-value of < 0.000. A regression equation was derived that can be used to generate predicted values of CVP in millimeters of mercury with an R-square of 0.745 if FVD in centimeters is provided; CVP (cmH2O) = -0.039 + 10.718* FVD.

Conclusions

FVD was found highly correlated to CVP measurements and it suggests an alternate non-invasive method of ascertaining the volume status in the critically ill.

Image-based resuscitation of the hypotensive patient with cardiac ultrasound: An evidence-based review

This article is a detailed review of the literature regarding the use of cardiac ultrasound for the resuscitation of hypotensive patients. In addition, figures regarding windows and description of how to perform the test are included.

Point-of-Care Ultrasound Assessment of Tropical Infectious Diseases--A Review of Applications and Perspectives

The development of good quality and affordable ultrasound machines has led to the establishment and implementation of numerous point-of-care ultrasound (POCUS) protocols in various medical disciplines. POCUS for major infectious diseases endemic in tropical regions has received less attention, despite its likely even more pronounced benefit for populations with limited access to imaging infrastructure. Focused assessment with sonography for HIV-associated TB (FASH) and echinococcosis (FASE) are the only two POCUS protocols for tropical infectious diseases, which have been formally investigated and which have been implemented in routine patient care today. This review collates the available evidence for FASH and FASE, and discusses sonographic experiences reported for urinary and intestinal schistosomiasis, lymphatic filariasis, viral hemorrhagic fevers, amebic liver abscess, and visceral leishmaniasis. Potential POCUS protocols are suggested and technical as well as training aspects in the context of resource-limited settings are reviewed. Using the focused approach for tropical infectious diseases will make ultrasound diagnosis available to patients who would otherwise have very limited or no access to medical imaging.

Surgeon-performed bedside ultrasound to assess volume status: a feasibility study

PURPOSE

Rapid assessment of volume status in children is often difficult. The purpose of this study was to evaluate the feasibility of surgeon-performed ultrasound to assess volume status in patients with hypertrophic pyloric stenosis.

METHODS

Ultrasounds were performed on admission and before operation. The diameters of the inferior vena cava (IVC) and aorta (Ao) were measured and IVC/Ao ratios were calculated. Electrolytes were measured on admission and repeated if warranted. Logistic regression was used to associate the clinical outcome, defined as CO2 ≤30 mEq/L, with IVC/Ao ratios. Predictive capacity was estimated from the logistic regression for IVC/Ao ratios. Linear regression was used to estimate associations between CO2 values and IVC/Ao ratios.

RESULTS

Thirty-one patients were enrolled. The IVC/Ao ratio is highly associated with actual CO2 values (P < 0.001) and the clinical outcome (P = 0.004). For every 0.05 unit increase in IVC/Ao ratio, predicted CO2 decreased 1.1 units. For every 0.05 unit increase in the IVC/Ao ratio, the odds of having a CO2 ≤30 mEq/L increased 48% [OR = 1.48, 95% CI (1.13,1.94)]. Predictive capacity is maximized at an IVC/Ao ratio of 0.75 as 83.9 % of subjects were correctly classified and specificity and PPV = 100%.

CONCLUSIONS

Surgeon-performed ultrasound to determine IVC/Ao ratio is feasible. An IVC/Ao ratio of 0.75 predicted adequate resuscitation.

Inferior vena cava diameters and collapsibility index reveal early volume depletion in a blood donor model

BACKGROUND

Changes of volume status can be readily inferred from variations in diameter of the inferior vena cava (IVC) measured by ultrasound. However the effect of IVC changes following acute blood loss are not fully established. In this study, three different approaches to measuring IVC variables were compared in healthy blood donors, as a model of acute volume depletion, in order to establish their relative ability to detect acute blood loss.

METHODS

Inspiratory and expiratory IVC diameters were measured before and after blood donation in hepatic long axis, hepatic short axis and renal short axis views using a 2-5 MHz curvilinear probe. All measurements were recorded and examined in real-time and post-processing sessions.

RESULTS

All windows performed satisfactorily but the renal window approach was feasible in only 30 out of 47 subjects. After blood donation, IVC diameters decreased in hepatic long axis, hepatic short axis and renal short axis (expiratory: -19.9, -18.0, -26.5 %; CI 95 %: 14.5-24.1; 13.1-22.9; 16.0-35.9, respectively) (inspiratory: -31.1, -31.6, -36.5 %; CI 95 %: 21.3-40.1; 18.8-45.2; 23.4-46.0, respectively), whereas the IVC collapsibility index increased by 21.6, 22.6 and 19.3 % (CI 95 %: 11.6-42.9; 18.5-39.5; 7.7-30.0). IVC diameters appeared to return to pre-donation values within 20 min but this was only detected by the hepatic long axis view.

CONCLUSIONS

IVC diameter and collapsibility index variations, as measured in M mode, consistently detect volume changes after blood donation. The longitudinal mid-hepatic approach performed better by allowing a panoramic view, avoiding anatomical aberrancies at fixed points and permitting to identify the best possible perpendicular plane to the IVC. In addition, it was able to detect time-dependent physiological volume replacement. In contrast, in our hands, the renal window could not be visualized consistently well.

Dynamic behavior of venous collapsibility and central venous pressure during standardized crystalloid bolus: A prospective, observational, pilot study

INTRODUCTION

Measurement of intravascular volume status is an ongoing challenge for physicians in the surgical intensive care unit (SICU). Most surrogates for volume status, including central venous pressure (CVP) and pulmonary artery wedge pressure, require invasive lines associated with a number of potential complications. Sonographic assessment of the collapsibility of the inferior vena cava (IVC) has been described as a noninvasive method for determining volume status. The purpose of this study was to analyze the dynamic response in IVC collapsibility index (IVC-CI) to changes in CVP in SICU patients receiving fluid boluses for volume resuscitation.

MATERIALS AND METHODS

A prospective pilot study was conducted on a sample of SICU patients who met clinical indications for intravenous (IV) fluid bolus and who had preexisting central venous access. Boluses were standardized to crystalloid administration of either 500 mL over 30 min or 1,000 mL over 60 min, as clinically indicated. Concurrent measurements of venous CI (VCI) and CVP were conducted right before initiation of IV bolus (i.e. time 0) and then at 30 and 60 min (as applicable) after bolus initiation. Patient demographics, ventilatory parameters, and vital sign assessments were recorded, with descriptive outcomes reported due to the limited sample size.

RESULTS

Twenty patients received a total of 24 IV fluid boluses. There were five recorded 500 mL boluses given over 30 min and 19 recorded 1,000 mL boluses given over 60 min. Mean (median) CVP measured at 0, 30, and 60 minutes post-bolus were 6.04 ± 3.32 (6.5), 9.00 ± 3.41 (8.0), and 11.1 ± 3.91 (12.0) mmHg, respectively. Mean (median) IVC-CI values at 0, 30, and 60 min were 44.4 ± 25.2 (36.5), 26.5 ± 22.8 (15.6), and 25.2 ± 21.2 (14.8), respectively.

CONCLUSIONS

Observable changes in both VCI and CVP are apparent during an infusion of a standardized fluid bolus. Dynamic changes in VCI as a measurement of responsiveness to fluid bolus are inversely related to changes seen in CVP. Moreover, an IV bolus tends to produce an early response in VCI, while the CVP response is more gradual. Given the noninvasive nature of the measurement technique, VCI shows promise as a method of dynamically measuring patient response to fluid resuscitation. Further studies with larger sample sizes are warranted.

Optimal fluid resuscitation in trauma: type, timing, and total

PURPOSE OF REVIEW

This review article explores the recent literature regarding the optimal type and amount of intravenous fluids for the trauma patient from the time of injury through their ICU stay. It discusses damage control principles as well as targeted resuscitation utilizing new technology.

RECENT FINDINGS

In the prehospital arena, intravenous fluids have been associated with worse patient outcomes due to increased coagulopathy and time to definitive care. Once in the trauma bay, damage control resuscitation principles apply to the severely injured patient. Large volume crystalloid infusion increases mortality. The best patient outcomes have been found with transfusion of blood products in a ratio that closely mimics whole blood. Thrombelastography is a useful adjunct in resuscitation and can help guide the judicious use of blood products. New technology can help providers ascertain when a patient is appropriately resuscitated by determining adequate global and regional perfusion.

SUMMARY

During the resuscitation of the acutely injured patient, crystalloids should be limited in favor of blood components. Damage control principles apply until definitive hemostasis is obtained, at which point the focus should change to targeted resuscitation using traditional global endpoints of resuscitation in conjunction with determinants of regional perfusion.

International evidence-based recommendations for focused cardiac ultrasound

BACKGROUND

Focused cardiac ultrasound (FoCUS) is a simplified, clinician-performed application of echocardiography that is rapidly expanding in use, especially in emergency and critical care medicine. Performed by appropriately trained clinicians, typically not cardiologists, FoCUS ascertains the essential information needed in critical scenarios for time-sensitive clinical decision making. A need exists for quality evidence-based review and clinical recommendations on its use.

METHODS

The World Interactive Network Focused on Critical UltraSound conducted an international, multispecialty, evidence-based, methodologically rigorous consensus process on FoCUS. Thirty-three experts from 16 countries were involved. A systematic multiple-database, double-track literature search (January 1980 to September 2013) was performed. The Grading of Recommendation, Assessment, Development and Evaluation method was used to determine the quality of available evidence and subsequent development of the recommendations. Evidence-based panel judgment and consensus was collected and analyzed by means of the RAND appropriateness method.

RESULTS

During four conferences (in New Delhi, Milan, Boston, and Barcelona), 108 statements were elaborated and discussed. Face-to-face debates were held in two rounds using the modified Delphi technique. Disagreement occurred for 10 statements. Weak or conditional recommendations were made for two statements and strong or very strong recommendations for 96. These recommendations delineate the nature, applications, technique, potential benefits, clinical integration, education, and certification principles for FoCUS, both for adults and pediatric patients.

CONCLUSIONS

This document presents the results of the first International Conference on FoCUS. For the first time, evidence-based clinical recommendations comprehensively address this branch of point-of-care ultrasound, providing a framework for FoCUS to standardize its application in different clinical settings around the world.

Development and preliminary assessment of a critical care ultrasound course in an adult pulmonary and critical care fellowship program

BACKGROUND

The focused ultrasound examination has become increasingly recognized as a safe and valuable diagnostic tool for the bedside assessment of the critically ill patient. We implemented a dedicated on-site critical care ultrasonography curriculum with the goal of developing a model for teaching ultrasound skills to pulmonary and critical care medicine fellows.

METHODS

The program was comprised of blended didactic and bedside sessions in the following topic domains: fundamentals; vascular access and diagnosis; and abdominal, thoracic, and cardiac ultrasonography. Formal knowledge and image acquisition assessments were performed before and after the program to assess success in meeting predefined learning objectives. Participants completed surveys (on Likert scale 1-5) before and after the program to assess their confidence in ultrasonography knowledge and skills as well as their perception as to training effectiveness.

RESULTS

The preintervention knowledge and bedside image acquisition scores were 71 and 32%, respectively. The global preintervention score was 51%. All postintervention measures demonstrated significant improvement: 89% (P < 0.01), 86% (P < 0.0001), and 87% (P < 0.0001). Preintervention participant confidence in their ultrasound knowledge and skill was 2.9/5, which improved to 4.3/5 (P = 0.007) after intervention. Participants rated the curriculum as meeting course objectives at a mean of 4.8/5.

CONCLUSIONS

At one academic medical center, the knowledge of eight adult pulmonary and critical care fellowship trainees regarding critical care ultrasound was high at baseline; however, bedside image acquisition skills were poor. A dedicated 6-week educational intervention resulted in highly significant improvements in subject knowledge and image acquisition skills. These preliminary results warrant validation studies at other medical centers.

Clinician-performed ultrasound in hemodynamic and cardiac assessment: a synopsis of current indications and limitations

Accurate hemodynamic and intravascular volume status assessment is essential in the diagnostic and therapeutic management of critically ill patients. Over the last two decades, a number of technological advances were translated into a variety of minimally invasive or non-invasive hemodynamic monitoring modalities. Despite the promise of less invasive technologies, the quality, reliability, reproducibility, and generalizability of resultant hemodynamic and intravascular volume status data have been lacking. Since its formal introduction, ultrasound technology has provided the medical community with a more standardized, higher quality, broadly applicable, and reproducible method of accomplishing the above-mentioned objectives. With the advent of portable, hand-carried devices, the importance of sonography in hemodynamic and volume status assessment became clear. From basic venous collapsibility and global cardiac assessment to more complex tasks such as the assessment of cardiac flow and tissue Doppler signals, the number of real-life indications for sonology continues to increase. This review will provide an outline of the essential ultrasound applications in hemodynamic and volume status assessment, focusing on evidence-based uses and indications.

Sonographic evaluation of intravascular volume status: Can internal jugular or femoral vein collapsibility be used in the absence of IVC visualization?

INTRODUCTION

Inferior vena cava collapsibility index (IVC-CI) has been shown to correlate with both clinical and invasive assessment of intravascular volume status, but has important limitations such as the requirement for advanced sonographic skills, the degree of difficulty in obtaining those skills, and often challenging visualization of the IVC in the postoperative patient. The current study aims to explore the potential for using femoral (FV) or internal jugular (IJV) vein collapsibility as alternative sonographic options in the absence of adequate IVC visualization.

METHODS

A prospective, observational study comparing IVC-CI and Fem- and/or IJV-CI was performed in two intensive care units (ICU) between January 2012 and April 2014. Concurrent M-mode measurements of IVC-CI and FV- and/or IJV-CI were collected during each sonographic session. Measurements of IVC were obtained using standard technique. IJV-CI and FV-CI were measured using high-frequency, linear array ultrasound probe placed in the corresponding anatomic areas. Paired data were analyzed using coefficient of correlation/determination and Bland-Altman determination of measurement bias.

RESULTS

We performed paired ultrasound examination of IVC-IJV (n = 39) and IVC-FV (n = 22), in 40 patients (mean age 54.1; 40% women). Both FV-CI and IJV-CI scans took less time to complete than IVC-CI scans (both, P < 0.02). Correlations between IVC-CI/FV-CI (R(2) = 0.41) and IVC-CI/IJV-CI (R(2) = 0.38) were weak. There was a mean -3.5% measurement bias between IVC-CI and IJV-CI, with trend toward overestimation for IJV-CI with increasing collapsibility. In contrast, FV-CI underestimated collapsibility by approximately 3.8% across the measured collapsibility range.

CONCLUSION

Despite small measurement biases, correlations between IVC-CI and FV-/IJV-CI are weak. These results indicate that IJ-CI and FV-CI should not be used as a primary intravascular volume assessment tool for clinical decision support in the ICU. The authors propose that IJV-CI and FV-CI be reserved for clinical scenarios where sonographic acquisition of both IVC-CI or subclavian collapsibility are not feasible, especially when trended over time. Sonographers should be aware that IJV-CI tends to overestimate collapsibility when compared to IVC-CI, and FV-CI tends to underestimates collapsibility relative to IVC-CI.

Early management of patients with acute heart failure: state of the art and future directions. A consensus document from the society for academic emergency medicine/heart failure society of America acute heart failure working group

Heart failure (HF) afflicts nearly 6 million Americans, resulting in one million emergency department (ED) visits and over one million annual hospital discharges. An aging population and improved survival from cardiovascular diseases is expected to further increase HF prevalence. Emergency providers play a significant role in the management of patients with acute heart failure (AHF). It is crucial that emergency physicians and other providers involved in early management understand the latest developments in diagnostic testing, therapeutics and alternatives to hospitalization. Further, clinical trials must be conducted in the ED in order to improve the evidence base and drive optimal initial therapy for AHF. Should ongoing and future studies suggest early phenotype-driven therapy improves in-hospital and post-discharge outcomes, ED treatment decisions will need to evolve accordingly. The potential impact of future studies which incorporate risk-stratification into ED disposition decisions cannot be underestimated. Predictive instruments that identify a cohort of patients safe for ED discharge, while simultaneously addressing barriers to successful outpatient management, have the potential to significantly impact quality of life and resource expenditures.

Early management of patients with acute heart failure: state of the art and future directions--a consensus document from the SAEM/HFSA acute heart failure working group

Heart failure (HF) afflicts nearly 6 million Americans, resulting in 1 million emergency department (ED) visits and over 1 million annual hospital discharges. The majority of inpatient admissions originate in the ED; thus, it is crucial that emergency physicians and other providers involved in early management understand the latest developments in diagnostic testing, therapeutics, and alternatives to hospitalization. This article discusses contemporary ED management as well as the necessary next steps for ED-based acute HF research.

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

BACKGROUND

Noninvasive evaluation of central venous pressure (CVP) can be achieved by assessing the Jugular Venous Pressure (JVP), Peripheral Venous Collapse (PVC), and ultrasound visualization of the inferior vena cava. The relative accuracy of these techniques compared to one another and their application by trainees of varying experience remains uncertain. We compare the application and utility of the JVP, PVC, and handheld Mini Echo amongst trainees of varying experience including a medical student, internal medicine resident, and cardiology fellow. We also introduce and validate a new physical exam technique to assess central venous pressures, the Anthem sign.

METHODS

Patients presenting for their regularly scheduled echocardiograms at the hospital echo department had clinical evaluations of their CVP using these non-invasive bedside techniques. The examiners were blinded to the echo results, each other's assessments, and patient history; their CVP estimates were compared to the gold standard level 3 echo-cardiographer's estimates at the completion of the study.

RESULTS

325 patients combined were examined (mean age 65, s.d. 16 years). When compared to the gold standard of central venous pressure by a level 3 echocardiographer, the JVP was the most sensitive at 86%, improving with clinical experience (p<0.01). The classic PVC technique and Anthem sign had better specificity compared to the JVP. Mini Echo estimates were comparable to physical exam assessments.

CONCLUSIONS

JVP evaluation is the most sensitive physical examination technique in CVP assessments. The PVC techniques along with the newly described Anthem sign may be of value for the early learner who still has not mastered the art of JVP assessment and in obese patients in whom JVP evaluation is problematic. Mini Echo estimates of CVPs are comparable to physical examination by trained clinicians and require less instruction. The use of Mini Echo in medical training should be further evaluated and encouraged.

Bedside US imaging in multiple trauma patients. Part 1: US findings and techniques

OBJECTIVES

The aim of this review article is to present the current views and visions of the role of ultrasound (US) in the management of patients with multiple trauma. The article is divided into two parts. Part 1 (US findings and techniques) will mainly deal with the technical aspects of US imaging in trauma patients and is written also for educational purposes. Part 2 (pathophysiology and US imaging in trauma patients) will deal with integration of US in the clinical and pathophysiological management of multiple trauma patients.

METHODS

A non-systematic review of the literature through PubMed search (restricted to the last 10 years) of original articles and review articles.

RESULTS

80 publications were selected for Part 1. Of these 80 articles, the author selected 50 according to personal criteria on the basis of their innovative or original contents (48 original articles and 2 literature review articles); 19 articles were furthermore extracted from the references of the selected publications. The information extracted from these 69 publications was organized into sections dealing with different fields of applications of US imaging in multiple trauma patients.

CONCLUSIONS

US imaging in trauma has evolved from the initial use, i.e., early diagnosis of peritoneal effusion (focused abdominal sonography for trauma), to a wider use known as resuscitative ultrasonography, and is today considered as an extension of physical examination to implement a more effective approach to clinical problems and increase the timeliness and safety of interventions.

Introduction of an Echocardiography Service to a General Intensive Care Unit

Studies have suggested that significant undiagnosed pathology exists in the intensive care unit (ICU) population, and that bedside transthoracic echocardiography (TTE) can aid prompt diagnosis with potential outcome benefits. This study assesses the introduction of a bedside echocardiography service on patient care in a tertiary university intensive care unit (ICU). Data were collected from 101 TTEs, of which 58 were full studies and 43 were screening TTEs with a limited dataset. Seventy-five scans (74%) revealed previously undiagnosed pathology, which was considered serious in 30 (30%) cases. The most commonly diagnosed pathologies were: severe ventricular dysfunction (n=19), severe valvular dysfunction (n=9) and severe pulmonary hypertension (n=4). Full studies were more likely than screening studies to reveal previously undiagnosed pathology (47/58 vs 28/43 studies, p=0.035). However, the number of patients whose management was changed as a result of TTE was not significantly different between the two groups. Overall, patient management was altered as a result of the TTE in 51 cases (50%), and 11 patients (11%) were subsequently referred for cardiology consultation. In keeping with previous work, we have found that TTE uncovered a high percentage of unsuspected cardiac abnormalities, which impacted management in half of the patients who were scanned.

Sonographic evaluation of intravascular volume status in the surgical intensive care unit: a prospective comparison of subclavian vein and inferior vena cava collapsibility index

BACKGROUND

Traditional methods for intravascular volume status assessment are invasive and are associated significant complications. While focused bedside sonography of the inferior vena cava (IVC) has been shown to be useful in estimating intravascular volume status, it may be technically difficult and limited by patient factors such as obesity, bowel gas, or postoperative surgical dressings. The goal of this investigation is to determine the feasibility of subclavian vein (SCV) collapsibility as an adjunct to IVC collapsibility in intravascular volume status assessment.

METHODS

A prospective study was conducted on a convenience sample of surgical intensive care unit patients to evaluate interchangeability of IVC collapsibility index (IVC-CI) and SCV-CI. After demographic and acuity of illness information was collected, all patients underwent serial, paired assessments of IVC-CI and SCV-CI using portable ultrasound device (M-Turbo; Sonosite, Bothell, WA). Vein collapsibility was calculated using the formula [collapsibility (%) = (max diameter - min diameter)/max diameter × 100%]. Paired measurements from each method were compared using correlation coefficient and Bland-Altman measurement bias analysis.

RESULTS

Thirty-four patients (mean age 56 y, 38% female) underwent a total of 94 paired SCV-CI and IVC-CI sonographic measurements. Mean acute physiology and chronic health evaluation II score was 12. Paired SCV- and IVC-CI showed acceptable correlation (R(2) = 0.61, P < 0.01) with acceptable overall measurement bias [Bland-Altman mean collapsibility difference (IVC-CI minus SCV-CI) of -3.2%]. In addition, time needed to acquire and measure venous diameters was shorter for the SCV-CI (70 s) when compared to IVC-CI (99 s, P < 0.02).

CONCLUSIONS

SCV collapsibility assessment appears to be a reasonable adjunct to IVC-CI in the surgical intensive care unit patient population. The correlation between the two techniques is acceptable and the overall measurement bias is low. In addition, SCV-CI measurements took less time to acquire than IVC-CI measurements, although the clinical relevance of the measured time difference is unclear.

Focused Transthoracic Echocardiography Performed and Interpreted by Medical Residents in the Critically Ill

Purpose. Intensivist-performed focused echocardiography (FE) is accepted practice. Whether medical residents can perform and interpret quality FE in the critically ill is unknown. Methods. Novice residents trained in an 8-hour module in FE, evaluating ejection fraction (EF), pericardial effusion, right ventricular (RV) strain, valvular pathology, wall motion abnormalities (WMAs), and inferior vena cava collapsibility in patients awaiting comprehensive echocardiograms. The Fleiss kappa (κ), sensitivity, specificity, positive predictive values, and negative predictive values were calculated against the comprehensive echocardiogram. Results. Seven residents performed 102 FE, demonstrating substantial agreement with cardiologists for EF as decreased versus normal or hyperdynamic (κ = .67, P < .001, sensitivity = 94%, specificity = 93%) and pericardial effusion (κ = .60, P < .001, sensitivity = 85%, specificity = 93%); moderate agreement for aortic stenosis (κ = .54, P < .001, sensitivity = 56%, specificity = 98%), aortic insufficiency (κ = .50, P < .001, sensitivity = 47%, specificity = 97%), mitral regurgitation (κ = 0.51, P < .001, sensitivity = 65%, specificity = 90%), and WMAs (κ = .49, P < .001, sensitivity = 71%, specificity = 88%) and fair agreement for RV strain (κ = .38, P < .001, sensitivity = 41%, specificity = 95%). Conclusions. After an 8-hour course, resident FE demonstrated substantial agreement with comprehensive echocardiography for EF and pericardial effusion, moderate agreement for valvulopathy and WMAs and fair agreement for RV strain. Sensitivity and specificity were high for systolic dysfunction and pericardial effusion. Whereas sensitivity was lower for RV strain, valvular abnormalities, and WMAs, residents demonstrated excellent specificity for all parameters studied. Clinical implications. FE can be taught to residents to hasten diagnosis of key pathologies while awaiting comprehensive echocardiography.

Point of care cardiac ultrasound applications in the emergency department and intensive care unit--a review

The use of point of care echocardiography by non-cardiologist in acute care settings such as the emergency department (ED) or the intensive care unit (ICU) is very common. Unlike diagnostic echocardiography, the scope of such point of care exams is often restricted to address the clinical questions raised by the patient's differential diagnosis or chief complaint in order to inform immediate management decisions. In this article, an overview of the most common applications of this focused echocardiography in the ED and ICU is provided. This includes but is not limited to the evaluation of patients experiencing hypotension, cardiac arrest, cardiac trauma, chest pain and patients after cardiac surgery.

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.

Core review: physician-performed ultrasound: the time has come for routine use in acute care medicine

The use of ultrasound in the acute care specialties of anesthesiology, intensive care, emergency medicine, and surgery has evolved from discrete, office-based echocardiographic examinations to the real-time or point-of-care clinical assessment and interventions. "Goal-focused" transthoracic echocardiography is a limited scope (as compared with comprehensive examination) echocardiographic examination, performed by the treating clinician in acute care medical practice, and is aimed at addressing specific clinical concerns. In the future, the practice of surface ultrasound will be integrated into the everyday clinical practice as ultrasound-assisted examination and ultrasound-guided procedures. This evolution should start at the medical student level and be reinforced throughout specialist training. The key to making ultrasound available to every physician is through education programs designed to facilitate uptake, rather than to prevent access to this technology and education by specialist craft groups. There is evidence that diagnosis is improved with ultrasound examination, yet data showing change in management and improvement in patient outcome are few and an important area for future research.

The effect of weight-based volume loading on the inferior vena cava in fasting subjects: a prospective randomized double-blinded trial

OBJECTIVES

Inferior vena cava ultrasound (IVC-US) assessment has been proposed as a noninvasive method of assessing volume status. Current literature is divided on its ability to do so. The primary objective was to compare IVC-US changes in healthy fasting subjects randomized to either 10 or 30 mL/kg of intravenous (IV) fluid administration versus a control group that received only 2 mL/kg.

METHODS

This was a prospective randomized double-blinded trial set in emergency department (ED) clinical care rooms. Volunteer subjects with no history of cardiac disease or hypertension fasted for 12 hours. Subjects were randomly assigned to receive IV 0.9% saline bolus of 2 (control group), 10, or 30 mL/kg over 30 minutes. IVC-US was performed before and 15 minutes after each fluid bolus.

RESULTS

Forty-two fasting subjects were enrolled. Analysis of variance (ANOVA) comparison showed that IVC-US was unable to detect any significant difference between the control group and those given either 10 or 30 mL/kg fluid, whether using maximum or minimum IVC diameter or caval index (IVC-CI). The groups receiving 10 and 30 mL/kg each had a statistically significant change in IVC-CI; however, the 30 mL/kg group had no significant change in either of the mean IVC diameters.

CONCLUSIONS

Overall, there were statistically significant differences in mean IVC-US measurements before and after fluid loading, but not between groups. Fasting asymptomatic subjects had a wide intersubject variation in both baseline IVC-US measurements and fluid-related changes. The degree of IVC-US change in association with graded acute volume loading was not predictably proportional between our subjects.

Caval Aorta Index and Central Venous Pressure Correlation in Assessing Fluid Status! “Ultrasound Bridging the Gap”

Accurate body fluid assessment and estimation of fluid status are essential in guiding fluid therapy in emergency setup. This prospective cross-sectional descriptive study conducted to ascertain the effectiveness of inferior vena cava and aorta (IVC/Aorta) index in assessing the fluid status by comparing it with the central venous pressure (CVP). Results showed the mean IVC/Aorta index in patients who had normal CVP range was 1.2 ± 0.12 SD, while in patients with low CVP, the mean index was 0.7 ± 0.09 SD, and, patients with high CVP, the mean index was 1.6 ± 0.05 SD. In conclusion, the sonographic IVC/Aorta index assessment seems to be a quick, simple, noninvasive, and reliable method to access the fluid status in a busy setup like an emergency room.

Qualitative Assessment of the Inferior Vena Cava: Useful Tool for the Evaluation of Fluid Status in Critically Ill Patients

Inferior vena cava (IVC) diameter change on limited transthoracic echocardiogram (LTTE) can provide a useful guide of fluid status evaluation in critically ill patients. Institutional review board approval was obtained. Prospective evaluation of hemodynamic status was performed in hypotensive patients via LTTE. Images were obtained using an ultrasound machine without M-mode capability. Qualitative assessment of the IVC was obtained via subxyphoid window. FLAT IVC was defined as diameter less than 2 cm and FAT IVC when the vein was equal or larger than 2 cm. Collapsibility was assessed by observing respiratory variation of the vessel. Lactate was measured before and after therapy was initiated. A follow-up LTTE was obtained after fluid challenge. A total of 108 LTTE were performed. Patients’ age ranged from 18 to 89 years with an average of 53. Admission diagnosis was blunt trauma in 66 patients, penetrating trauma in 17, whereas 25 had nontraumatic intra-abdominal emergency. Sixty-nine patients were receiving mechanical ventilation at time of LTTE. Seventy-three patients had a FLAT IVC, and received fluid challenge as therapy. All patients had a change in IVC volume from “FLAT” to “FAT” after the fluid challenge. Seventy-one patients (97%) had resolution of hypotension after the first fluid challenge. Two patients had persistent hypotension and received a second fluid challenge. Follow-up LTTE demonstrated a FAT IVC and lack of collapsibility. Lactate decreased in all 73 patients after therapy guided by LTTE ( P < 0.00001) Evaluation of the IVC diameter via LTTE offers a rapid, non invasive way to evaluate fluid status in critically ill patients.

Battlefield applications for handheld ultrasound

Combat medical care provides unique challenges and opportunities for military medical teams. The austerity of the environment severely limits access to many diagnostic and therapeutic tools. Because of their compact size, handheld ultrasound (US) machines are increasingly being used in these constrained environments. A growing body of literature documents the diagnostic utility of handheld US for trauma encountered in the battlefield. Furthermore, US guidance may assist in the performance of some procedures performed in battlefield medical care. This review will provide an overview of the history, current status, limitations and potential future of US utility for the battlefield.

Focused bedside echocardiography in the surgical intensive care unit: comparison of 3 methods to estimate cardiac index

We sought to determine which of 3 methods used to evaluate cardiac index (CI) is the most accurate using focused bedside echocardiography (ECHO). We hypothesized that the fractional shortening (FS) method would provide a more accurate estimate of CI than the left ventricular outflow tract/velocity-time integral (LVOT/VTI) or Simpson's methods. This was a prospective observational cohort study conducted in the surgical ICU of an urban level 1 trauma center utilizing all patients with a pulmonary artery catheter (PAC) in place. Three surgical intensive care unit (SICU) faculty and 3 fellows underwent focused cardiac ultrasound training. Focused ECHO exams-bedside echocardiographic assessment in trauma/critical care (BEAT)- were performed using the Sonosite portable ultrasound device (Bothall, Washington). Stroke volume (SV) measurements were prospectively obtained on all trauma/SICU patients, with a PAC in place, using FS, LVOT/VTI, and Simpson's methods. The investigators were blinded to the PAC data. From each measurement, CI was calculated and categorized as low, normal, or high, based on a normal range of 2.4 to 4.0 L/min per m(2). Each CI obtained from the PAC was similarly categorized. The association between the BEAT and PAC estimates of CI was evaluated for each method using chi-square goodness of fit. Eighty five BEAT exams were performed on consecutive SICU patients, 56% were on trauma and 44% on emergency general surgery patients. There was a statistically significant association between the CI estimate using the FS method (P = .012), but not the LVOT/VTI (P = .33) or Simpson's method (P = .74). Our data showed a significant association between the PAC estimate of CI and our estimate using the FS method. The other methods were difficult to obtain, subjective, and inaccurate. Fractional shortening was the method of choice to estimate CI for the BEAT exam performed by intensivists in SICU patients.

The sensitivity and specificity of ultrasound estimation of central venous pressure using the internal jugular vein

PURPOSE

The fluid volume status of a patient is difficult to assess clinically. The aim of this study was to compare the ultrasound estimation of the height of the right internal jugular vein (CVP(IJV)) with direct estimation of central venous pressure (CVP) (CVP(CVC)).

MATERIALS AND METHODS

A portable ultrasound machine defined the "top" of the right internal jugular vein in 44 patients from a single tertiary hospital. The vertical height from this point to the sternal angle was used to estimate CVP(IJV). A central venous catheter was then inserted and direct measurement of CVP was made with a pressure transducer. A normal CVP was defined as 3 to 6 mm Hg.

RESULTS

For overloaded patients, CVP(IJV) correlated well with CVP(CVC), P = .004, sensitivity of 64.3%, specificity of 81.3%, and positive predictive value of 85.7%. The area under the curve for the receiver operating characteristic curve was 0.73 (95% confidence interval, 0.59-0.86). For undervolumed patients, the correlation remained statistically significant, P < .001, sensitivity of 88.9%, specificity of 77.1%, and negative predictive value of 96.4%. The area under the curve was 0.83 (95% confidence interval, 0.70-0.96).

CONCLUSION

Ultrasound estimation of CVP using a portable ultrasound machine and the internal jugular vein is simple, noninvasive, and accurate.

My patient has no blood pressure: are they empty or full? Point-of-care ultrasound of the inferior vena cava in the hypotensive emergency department patient

Bedside, focused or point-of-care ultrasound (PoCUS) is becoming an established technique within emergency and critical care medicine to answer time-dependent, focused clinical questions. Bedside sonography is not a complete radiological investigation, rather an extension of the clinical examination to rule in or rule out key diagnoses in specific clinical settings. PoCUS is geared to addressing highly time-dependent and focused questions, and in general most focused scans become more obviously positive as the patient becomes increasingly unwell. In the hypotensive patient, one of the first questions a clinician must address is whether the patient requires emergency fluid resuscitation. That is, is the patient under-filled or overloaded? So, how can we use ultrasound to add value to our clinical assessment of filling in the hypotensive patient?

Correlation between IVC dimensions and volume status on CT scan

BACKGROUND

End points of resuscitation in trauma patients are difficult to define. The size of the inferior vena cava (IVC) on CT scan may accurately indicate volume status and guide resuscitation efforts. Our hypothesis was that IVC "flatness" on CT scan reflects volume status in hemodynamically normal trauma patients.

METHODS

The study population was drawn from a database of trauma patients who had abdominal CT scans and lactate levels drawn on arrival. Lactate was chosen as a marker of volume status since hypotensive patients were unlikely to undergo CT. Anteroposterior (AP) and transverse (TV) diameters of the IVC were measured at the suprarenal and infrarenal locations. A flatness index was calculated for each location (TV ÷ AP) and this value was correlated with heart rate, blood pressure, and lactate.

RESULTS

There was no difference in IVC flatness at the suprarenal or infrarenal position for patients with an elevated lactate compared with those with a normal lactate: 1.54 ± 0.18 versus 1.43 ± 0.08 (P = 0.2) suprarenal and 1.54 ± 0.46 versus 1.68 ± 0.58 (P = 0.4) infrarenal. IVC flatness at the suprarenal location weakly correlated with blood pressure (r = -0.29). IVC flatness did not correlate with blood pressure at the infrarenal location (r = -0.1). IVC flatness did not correlate with heart rate (P > 0.3) or age (P > 0.2).

CONCLUSION

These results did not demonstrate a correlation between IVC flatness and the markers of intravascular volume of heart rate, blood pressure, or lactate. IVC flatness on CT scan is not a valid indicator of volume status in hemodynamically normal trauma patients.

Ultrasound does not detect early blood loss in healthy volunteers donating blood

BACKGROUND

Ultrasound has been suggested as a useful non-invasive tool for the detection of early blood loss. Two possible sonographic markers for hypovolemia are the diameter of the inferior vena cava (IVC) and the thickness of the left ventricle (LV).

STUDY OBJECTIVES

The goal of the study was to evaluate the utility of ultrasound to detect signs of early hemorrhagic shock in healthy volunteers, compared with changes in vital signs.

METHODS

In the current study, healthy volunteers from blood donation drives were used as models for early hemorrhage. Changes in vital signs, IVC diameter, and LV wall thickness were recorded after approximately 500 cc of blood loss.

RESULTS

Thirty-eight subjects were enrolled and completed the study. After blood donation, there was a 7-mm Hg (8%) decrease in mean arterial pressure without a significant change in heart rate. There was a decrease in maximum IVC diameter (IVCmax) (12% decrease [95% confidence interval (CI) -6 to -19] in short axis and 20% decrease [95% CI -12 to -27] in long axis), but no change was seen in the respiratory caval index ((IVCmax - IVCmin)/IVCmax) × 100). There was no change in LV wall thickness.

CONCLUSION

In this study, serial changes in vital signs, IVC diameter, and LV wall thickness were clinically insignificant after approximately 500 cc of blood loss in healthy volunteers.

The interrater reliability of inferior vena cava ultrasound by bedside clinician sonographers in emergency department patients

OBJECTIVES

Inferior vena cava ultrasound (IVC-US) is a noninvasive bedside tool to assess intravascular volume status. This study set out to investigate the interrater reliability of IVC-US by bedside clinician sonographers and determine whether alternative methods of IVC-US such as B-mode and visual estimation are equally reliable to traditional M-mode.

METHODS

A convenience sample of adult emergency department (ED) patients was prospectively enrolled. Each patient underwent IVC-US by two different emergency physicians (EPs), each of whom first performed visual estimation of IVC percent collapse and of volume status, followed by caliper measurements in M-mode and B-mode. EPs were blinded to patient data and to the other sonographer's results. For each technique, interrater reliability was determined between the two EPs' assessments using intraclass correlation coefficients (ICC) for continuous data and Cohen's weighted kappa for categorical data. In addition, analysis was performed on M-mode diameter measurements to determine the relationship between sonographer and patient characteristics on interrater reliability.

RESULTS

Five EPs performed 92 US exams on 46 patients. Using M-mode, the ICC for maximum IVC diameter was 0.81 (95% confidence interval [CI]=0.67 to 0.89), and for minimum diameter was 0.77 (95% CI=0.62 to 0.87). There were no statistically significant differences between the caliper methods used for IVC measurements (M-mode diameter, B-mode diameter, or B-mode area). Agreement for visually estimated IVC collapse (0.60, 95% CI=0.36 to 0.76) was similar to agreement for calculated M-mode IVC collapse index (0.52, 95% CI=0.27 to 0.71). Cohen's weighted kappa for volume status based on visual estimation of IVC filling (size, shape, and collapse) was 0.64 (95% CI=0.53 to 0.73). ICC values for M-mode diameter measurements were significantly higher in studies involving patients who were noneuvolemic and studies in which sonographers had each performed at least five prior IVC-US.

CONCLUSIONS

Emergency physicians' US measurements of IVC diameter have a high degree of interrater reliability. IVC percent collapse by visual estimation or based on caliper measurements have lower, but still moderate to good reliability. The use of the visual estimation technique should be considered by clinicians who have learned to obtain measured parameters of IVC filling because it is equally reliable to traditional M-mode and can be performed more rapidly.