Ultrasound Dilution Research Articles

Investigation of the Effect of Variations in the Puncture Site of the Arteriovenous Fistula on Access Blood Flow Measurement by Ultrasound Dilution Method

Investigation of the Effect of Variations in the Puncture Site of the Arteriovenous Fistula on Access Blood Flow Measurement by Ultrasound Dilution Method

Hemodynamic effects of low versus high dialysate bicarbonate concentration in hemodialysis patients.

Hemodialysis treatment using standard dialysate bicarbonate concentrations cause transient metabolic alkalosis possibly associated with hemodynamic instability. The aim of this study was to perform a detailed comparison of high and low dialysate bicarbonate in terms of blood pressure, intradialytic hemodynamic parameters, orthostatic blood pressure, and electrolytes. Fifteen hemodialysis patients were examined in a single-blind, randomized, controlled, crossover study. Participants underwent a 4-h hemodialysis session with dialysate bicarbonate concentration of 30 or 38 mmol/L with 1 week between interventions. Blood pressure was monitored throughout hemodialysis, while cardiac output, total peripheral resistance, stroke volume, and central blood volume were assessed with ultrasound dilution technique (Transonic). Orthostatic blood pressure was measured pre- and post-hemodialysis. With similar ultrafiltration (UF) volume (2.6 L), systolic blood pressure (SBP) tended to decrease more during high dialysate bicarbonate compared to low dialysate bicarbonate; the mean (95% confidence interval) between treatment differences in SBP were: 8 (-4; 20) mmHg (end of hemodialysis) and 7 (0; 15) mmHg (post-hemodialysis). Stroke volume decreased whereas total peripheral resistance increased significantly more during high dialysate bicarbonate compared to low dialysate bicarbonate with mean between treatment differences: Stroke volume: 12 (1; 23) mL; Total peripheral resistance: -2.9 (-5.3; -0.5) mmHg/(L/min). Cardiac output tended to decrease more with high dialysate bicarbonate compared to low dialysate bicarbonate with mean between treatment difference 0.7 (0.0; 1.4) L/min. High dialysate bicarbonate caused alkalosis, hypocalcemia, and lower plasma potassium, whereas patients remained normocalcemic with normal pH during low dialysate bicarbonate. Orthostatic blood pressure response after dialysis did not differ significantly. The use of high dialysate bicarbonate compared to low dialysate bicarbonate was associated with hypocalcemia, alkalosis, and a more pronounced hypokalemia. During hemodialysis with UF, a better preservation of blood pressure, stroke volume, and cardiac output may be achieved with low dialysate bicarbonate compared to high dialysate bicarbonate.

#2722 Hemodialysis vascular access flow assessment by ultrasound dilution method (NephroFlow™) and ultrafiltration method with NIKKISO DBB-EXA™

Abstract Background and Aims A functioning vascular access (VA) is needed to ensure optimal dialysis. Reduced or falling levels of VA flow volume (Qa) indicate VA dysfunction and predict thrombosis. Qa can be measured by a number of different techniques, most of all using dilution techniques such as ultrasound dilution to measure the amount of recirculation induced by reversal of blood lines. The NephroFlow™ hemodialysis monitor estimates Qa using ultrasound velocity measurements of flowing blood and their dilution with 0.9% NaCl. Nikisso DBB-EXATM dialysis machine has the capacity to measure the VA recirculation rate by photometry performing a controlled rise on ultrafiltration rate; Qa is subsequently estimated using the Krivitski formula. There is little literature on the comparison of the different methodologies, but it was described that the DBB-EXATM method underestimates Qa compared to others techniques [1]. Our study aims to compare the Qa between the NephroFlow™ ultrasound dilution technique and the Nikisso DBB-EXATM ultrafiltration method. Method We performed an observational study that included 45 hemodialysis patients followed at our unit. Measurements of VA flow using the NephroFlow® device and the Nikisso-EXATM Ultrafiltration method were performed in patients with a native arteriovenous fistula or a graft. They were hemodynamically stable without acute clinical conditions. Both studies were undertaken during the first 90 minutes of a mid-week dialysis session, under a constant dialysis blood pump flow with the ultrafiltration interrupted during the procedure after having reversed the dialysis lines. For each patient we calculated the average of two Qa evaluations conducted at Nikisso-EXATM, spaced 15 days apart, with an additional evaluation using NephroFlow® conducted between these assessments. Results Forty-five patients (male: 71.1%) with a mean age of 73.2 ± 8 years were selected. The main CKD causes were diabetic kidney disease (n = 13, 28.9%) and uncertain etiology (n = 13, 28.9%). The dialysis vintage of these patients was 142.6 months (minimum 19, maximum 168). An arteriovenous fistula was present in 38 patients (84.4%) and an arteriovenous graft in 7 patients (15.6%). In the entire group, the mean flow with NephroFlow™ was 986.9 ± 515 ml/min and with DBB-EXATM 859.7 ± 522 ml/min. The measured values of the two methods presented a significant positive correlation (by Pearson) (R = 0.822, P < 0.01) (Fig. 1). In the group of patients with arteriovenous fistula (n = 38, 84.4%), the mean flow with NephroFlow™ was 961.8 ± 395 ml/min and with DBB-EXATM 839.1 ± 577 ml/min. The measured values of the two methods presented a significant positive correlation (by Pearson) (R = 0.844, P < 0.01). In the group of patients with arteriovenous graft (n = 7, 15.6%), the mean flow with NephroFlow™ was 1017.3 ± 401 ml/min and with DBB-EXATM 909.2 ± 604 ml/min. The measured values of the two methods presented a significant positive correlation (by Pearson) (R = 0.906, P < 0.01). Conclusion We found a significantly positive correlation between the Qa measurements obtained using both methods. The measurement of Qa using the ultrafiltration method on Nikisso DBB-EXATM seems to be a valuable and easily implementable tool for VA surveillance in both arteriovenous fistula and grafts. However, a bigger number of studies are required in this field in order to clarify this correlation with an additional comparative analysis to assess the reproducibility of measurements.

#1328 Haemodynamic effects of low versus high dialysate bicarbonate concentration in haemodialysis patients

Abstract Background and Aims Haemodialysis (HD) treatment using standard dialysate bicarbonate concentrations cause transient metabolic alkalosis possibly associated with haemodynamic instability. We performed a detailed comparison of blood pressure (BP), haemodynamic parameters, electrolytes and orthostatic BP response with low (LDB) versus high dialysate bicarbonate concentration (HDB). Method Fifteen HD patients were examined in a single-blind, randomised, controlled, crossover study. Participants underwent a 4-hour HD session with dialysate bicarbonate concentration of 30 mmol/l (LDB) or 38 mmol/l (HDB) with one week between interventions. During HD, cardiac output (CO), total peripheral resistance (TPR), stroke volume (SV) and central blood volume were measured with ultrasound dilution technique (Transonic). Throughout dialysis, blood samples were obtained from the arterial cannula. Orthostatic BP was measured pre and post HD. Results With similar ultrafiltration volume (2.6 litres), systolic BP tended to decrease more during HDB compared to LDB (Fig. 1 and Table 1); the mean (95% confidence interval) between treatment differences in systolic BP were: 8 (-4;20) mmHg (end of HD) and 7 (0;15) mmHg (post HD). SV decreased (Fig. 2) whereas TPR increased significantly more during HDB compared to LDB with mean between treatment differences: SV: 12 (1;23) ml; TPR: -2.9 (-5.3;-0.5) mmHg/(L/min). CO tended to decrease more with HDB compared to LDB with mean between treatment difference 0.7 (0.0;1.4) L/min. HDB caused alkalosis, hypocalcaemia and lower plasma potassium, whereas patients remained normocalcaemic with normal pH during LDB (Table 1). Orthostatic BP response after dialysis did not differ significantly. Conclusion HDB compared to LDB was associated with hypocalcaemia and alkalosis and a more pronounced hypokalaemia which may impair preservation of BP, SV and CO during HD.

#2464 Association of vascular access flow and volume status on fistula arm by bio-impedance analysis

Abstract Background and Aims Multi-frequency bio-impedance is a tool of body composition measure and can monitor changes in extracellular volume during dialysis. Arterio-venous fistulae (AVF) could potentially affect fluid retention in the arm. We investigated whether multi-frequency bio-impedance could defect AVF stenosis or association of AVF with fluid retention in the AVF arm. Method We measured the extracellular water (ECF) and total body water (TBW) in AVF arm following hemodialysis by multi-frequency bio-impedance (Inbody S10®) using an eight-electrode contact technique. We measured AVF or AVG flow by transonic ultrasonography using an ultrasound dilution technology (HD 03®) in hemodialysis. Results Total 82 patients (male 38 patients : female 44 patients) were enrolled. The causes of ESRD were DM : non-DM = 38 : 44. The mean age of patients was 54.89 ± 13.21 years. The ECW/TBW ration of fistula arm was a significantly higher than the ECW/TBW ration of non-fistula arm (0.389 ± 0.010 vs. 0.382 ± 0.001; p<0.05). The ECW/TBW ration of fistula arm was a significantly negative correlation with access flow level (mL/min) on fistula (p<0.05). The 5kHz reactance of fistula arm was a significantly positive correlation with access flow level (mL/min) on fistula (p<0.05). The 5kHz Phase Angle of fistula arm was a significantly positive correlation with access flow level (mL/min) on fistula (p<0.05). Conclusion Absolute and also relative extracellular fluid volumes are increased in the fistula arm of hemodialysis. We thought that extracellular fluid volumes in the fistula arm were associated with access flow level (mL/min) and/or relative fistula stenosis. We suggest that multi-frequency bio-impedance can be a useful assistant tool of vascular access flow measure.

#540 Investigation of vascular sound visualization system using electronic stethoscope

Abstract Background and Aims The routine evaluation of VA involves visual, palpatory, and auscultatory examinations, as well as monitoring of venous pressure and other parameters. Surveillance indices include Flow Volume (FV) and Resistance Index (RI) obtained by Doppler ultrasound (DU) and Access Blood Flow (Qa) obtained by the Ultrasound Dilution Method (UDM) are well known. On the other hand, the MSS-U11C electronic stethoscope (Fig. 1) and dedicated application (Fig. 2) developed by Pioneer Inc. converts vascular sound into digital data and calculates the INDEX value obtained from the sound intensity (dB) analyzed by the vascular sound visualization system. In this study, we examined the correlation between INDEX values and conventional surveillance indices. Method 1. Eighty-three cases in which INDEX, FV, RI, and Qa were simultaneously measured in hemodialysis patients with AVF at the Artificial Kidney Department of Osaka Metropolitan University Hospital were included. 2. The measurement site for INDEX was just above the anastomosis of the AVF. 3. FV and RI were measured using a KONICA MINOLTA SONIMAGE HS2 diagnostic ultrasound system with the brachial artery as the measurement site. 4. Measurements were expressed in Median [IQR], and for statistical examination, Pearson's correlation coefficient was used for the correlation of each measurement, transformed to the natural logarithm to satisfy the assumption of normality of the residuals. The significance level for all hypothesis tests was 5%. For statistical analysis, R version 4.2.1 (https://www.r-project.org/foundation/) with the “rms” and “RcmdrPlugin.EZR ” packages were used. 5. This study protocol was conducted in accordance with the Principles of the Declaration of Helsinki. The ethics review boards of Osaka Metropolitan University approved the study (No. 2021-243). Opt-out consent was obtained instead of written informed consent. Results INDEX showed a significant positive correlation with Qa and FV (R = 0.449, P = 0.002 / R = 0.484, P < 0.001, respectively), INDEX showed a significant negative correlation with RI (R = −0.336, P = 0.002). Conclusion INDEX measurement using an electronic stethoscope is a monitoring index and showed a positive correlation with FV and Qa, which are established surveillance indices, and a weak negative correlation with RI. In Japan, FV and RI are commonly used as surveillance indices, but it has been reported that these indices can be underestimated or overestimated depending on the skill of the examiner, and that Qa requires specialized equipment and cannot be measured depending on the puncture site. We believe that monitoring by stethoscope is influenced by subjective factors of staff members, which may lead to differences in evaluation, but INDEX could become a more quantitative and standardized indicator. In addition, the electronic stethoscope could be used without any difference compared to the stethoscope currently in clinical use.

Early access flow rate predicts vascular access patency-related intervention in the first year: A retrospective cohort study.

Arteriovenous fistulas and grafts are lifelines for most hemodialysis patients, and a low access flow rate often requires patency-related intervention, such as angioplasty or thrombectomy, to prevent access failure. We examined whether early access flow rate, measured after initial fistula/graft cannulation, predicts vascular access patency-related intervention within 1 year. This was a single-center retrospective cohort study. Among 172 patients undergoing surgical creation of a fistula/graft, 52 (30.2%) had documented access flow rates measurement by the Transonic™ ultrasound dilution technique, performed within an average of 48 days from initial access cannulation. The need for a patency-related intervention, defined as undergoing a fistulogram, angioplasty, thrombectomy, or surgical revision, was ascertained within 1 year. A receiver-operating characteristic curve (ROC) was generated to evaluate the diagnostic performance of first and average access flow rates for predicting patency-related intervention within 1 year. Twenty-eight (53.8%) of the 52 study subjects required a patency-related intervention within 1 year. Their characteristics were not significantly different from those who did not require patency-related interventions. However, first access flow rates were significantly lower in patients requiring patency-related intervention compared to those who did not (898 vs. 1471 mL/min; p = 0.003), as were average access flow rates (841 vs. 1506 mL/min; p < 0.001). The ROC analyses revealed that first access flow rates and average access flow rates predicted the need for patency-related intervention within 1 year, with an area under-the-ROC curve of 0.743 (95% confidence interval [CI] 0.608, 0.877) and 0.775 (95% CI 0.648, 0.903), respectively, demonstrating acceptable discrimination. In adults undergoing hemodialysis, early access flow rate measurement can predict patency-related intervention within 1 year after initial vascular access cannulation. Additional studies are required to confirm these findings and identify optimal access flow rate cut-off values to predict vascular accesses at higher risk of stenosis.

DeepVAQ : an adaptive deep learning for prediction of vascular access quality in hemodialysis patients

BackgroundChronic kidney disease is a prevalent global health issue, particularly in advanced stages requiring dialysis. Vascular access (VA) quality is crucial for the well-being of hemodialysis (HD) patients, ensuring optimal blood transfer through a dialyzer machine. The ultrasound dilution technique (UDT) is used as the gold standard for assessing VA quality; however, its limited availability due to high costs impedes its widespread adoption. We aimed to develop a novel deep learning model specifically designed to predict VA quality from Photoplethysmography (PPG) sensors.MethodsClinical data were retrospectively gathered from 398 HD patients, spanning from February 2021 to February 2022. The DeepVAQ model leverages a convolutional neural network (CNN) to process PPG sensor data, pinpointing specific frequencies and patterns that are indicative of VA quality. Meticulous training and fine-tuning were applied to ensure the model’s accuracy and reliability. Validation of the DeepVAQ model was carried out against established diagnostic standards using key performance metrics, including accuracy, specificity, precision, F-score, and area under the receiver operating characteristic curve (AUC).ResultDeepVAQ demonstrated superior performance, achieving an accuracy of 0.9213 and a specificity of 0.9614. Its precision and F-score stood at 0.8762 and 0.8364, respectively, with an AUC of 0.8605. In contrast, traditional models like Decision Tree, Naive Bayes, and kNN demonstrated significantly lower performance across these metrics. This comparison underscores DeepVAQ's enhanced capability in accurately predicting VA quality compared to existing methodologies.ConclusionExemplifying the potential of artificial intelligence in healthcare, particularly in the realm of deep learning, DeepVAQ represents a significant advancement in non-invasive diagnostics. Its precise multi-class classification ability for VA quality in hemodialysis patients holds substantial promise for improving patient outcomes, potentially leading to a reduction in mortality rates.

Impact of monthly arteriovenous fistula flow surveillance on hemodialysis access thrombosis and loss

Arteriovenous fistula flow dysfunction is the leading cause of vascular access thrombosis and loss in patients undergoing hemodialysis. However, data regarding the influence of access flow rate measurements on the long-term outcomes of access are limited. This study aims to identify accesses at a high risk of thrombosis and loss among patients undergoing hemodialysis by measuring the access flow rate and exploring an optimal threshold value for predicting future access thrombosis. We enrolled 220 patients with arteriovenous fistula undergoing hemodialysis. The primary outcome was the occurrence of access thrombosis. Access flow rates were measured monthly using the ultrasound dilution method and were averaged using all measurements from patients with patent access. In patients experienced access thrombosis, those immediately before the thrombosis were selected. Using these data, we calculated the access flow rate threshold for thrombosis occurrence by analyzing the receiver operating characteristic curve, and the patients were divided into two groups according to whether access flow rates were higher or lower than 400 mL/min. During a median follow-up period of 3.1 years, 4,510 access flows were measured (median measurements per patient, 33 times; interquartile range, 11-54). A total of 65 access thromboses and 19 abandonments were observed. Access thrombosis and loss were higher in the lowflow group than in the high-flow group. This study revealed that low access flow rates are strongly associated with access thrombosis occurrence and subsequent loss of arteriovenous fistulas in patients undergoing hemodialysis.

#2543 NEPHROFLOW FOR ESTIMATION OF VASCULAR ACCESS FLOW FOR HEMODIALYSIS: WHEN TO MEASURE?

Abstract Background and Aims Current guidelines emphasize the need for surveillance of vascular access (VA) for hemodialysis (HD), especially arteriovenous fistulas (AVF). Detecting a reduction in VA flow is auseful tool to anticipate the complications of VA as thrombosis. The DMed NephroFlow(NIPRO®) system, based on ultrasound dilution (UD) methods, has been shown tobe comparable to the classic Transonic® measurement system for estimating VA flow and canbe applied for VA surveillance. Our objetctive is to determine if there are significant differences when performing flow measurements with NephroFlow® between the first hour and the second hour of the HD session, as well as between any of the three days in which the patient attends HD. Method For two consecutive weeks, patients with AVF or graft (gAVF) on HD in our unit underwent VA flow measurements using the NephroFlow® system at the first and second hour of HD, on the 3 days that they attended HD sessions. Interspersing the first hour with the second each week to avoid significant loss in HD quality. For the study, we proceeded according to the usual recommendations of stable flow at 250 ml/min, corresponding ultrafiltration rate, needles in the same vein, without change in dry weight, with the same nurse staff, and transferring all patients to conventional HD. Results Twenty-one patients have been included, 13 male and 8 female, mean age 68±12.3 years. The mean time on HD was 36±23 months. The type of VA was: 10 patients presented a radiocephalic AVF, 5 brachiocephalic AVF, 2 patients a brachiobasilic AVF, and 4 patients a gAVF. The estimated mean flow obtained by NephroFlow ® in the first hour of all sessions and in the second hour was 1056 ± 754 and 1130.16 ± 769 ml/min, respectively; intraclass correlation index was 0.737 and K-W Test H 0.349 (p≤0.05). The mean flow on the first day was 1129±794.5ml/min, ICC = 0.662; second day 1027.5±729ml/min, ICC = 0.812; third day 1121.5±±ml/min, ICC = 0.774. In all cases p&amp;lt;0.05. Conclusion No significant differences have been observed in the VA flow estimated with the NephroFlow® ultrasound dilution system, neither at measurement time (the first or the second hour of HD session) nor day of performance (first, second or third day of HD session of the week). NephroFlow® UD system may be a useful tool for VA surveillance and could be applied when is necessary.

Hemodialysis access flow measurement: Comparison of ultrasound dilution and ultrafiltration method on NIKKISO DBB-EXA™ dialysis machine.

The methods of estimating vascular access (VA) flow rates are usually based on the indicator dilution theory by measuring recirculation during dialysis sessions. This is an observational study comparing the VA flow rates measured by NIKKISO DBB-EXA™ and Transonic®. Sixty-five patients (38 M/27 F, mean age 72 ± 10 years) participated in the study. We measured the VA flow rates during dialysis twice with each method and repeated the procedure 7 days later. In 130 double measurements for each method on the same day, mean flow with Transonic® was 1413±715 ml/min and with DBB-EXA™ 1297 ± 664 ml/min. In Bland-Altman analysis, the mean difference between the two methods was 159 ± 211 ml/min (limits of agreement: -274 and 572 ml/min). Eighty-one out of the 130 DBB-EXA™ measurements were within 25% of the Transonic® measurements (62% accuracy). Regarding reproducibility of each method on different days, mean difference in the Bland-Altman analysis was 29 ± 620 ml/min (limits of agreement: -1186 and 1244 ml/min) for the Transonic® measurements and 132 ± 625 ml/min (limits of agreement: -1092 and 1356 ml/min) for the DBB-EXA™ measurements. The measurements on two different days were within 25% of each other for 52 of the 65 patients (80%) with the Transonic® method, and for 35 of the 65 patients (54%) with the DBB-EXA™ method. In conclusion, the DBB-EXA™ method underestimates VA flow rates compared to the Transonic® technique, resulting in a limited accuracy of 62%. There was poor reproducibility for both methods in different day measurements with better performance of the Transonic® technique. The DBB-EXA™ method could be used as a simple tool for a rough estimate of VA flow rates but cannot replace the Transonic® reference method.

Ultrasound dilution cardiac output and echocardiography findings in anesthetized mature alpacas (Vicugna pacos) during normotension, hypotension and hypertension.

Alpacas (Vicugna pacos) have physiologic adaptations to live at high altitude. These adaptations may result in unexpected responses to changes in cardiac performance and blood pressure during general anesthesia. There are few studies evaluating cardiovascular variables in anesthetized alpacas. The purpose of this study was to report cardiovascular performance in anesthetized mature alpacas during normotension, hypotension, and hypertension using ultrasound dilution and echocardiography. Six adult alpacas, 3 females and 3 castrated males, weighing 62.6 to 88.7 kg were anesthetized and maintained with isoflurane and placed in right lateral recumbency. Each alpaca underwent ultrasound dilution and echocardiography measurements during three cardiovascular phases, normotension, hypotension via increased isoflurane concentration, and hypertension via phenylephrine infusion. Variables were analyzed with a Friedman test and a post hoc Dunn's test when significant. A p < 0.05 was used for significance. Cardiac output, cardiac index, systemic vascular resistance, stroke volume, total ejection fraction, left ventricular internal diameter during diastole, and total stroke volume indexed to body weight were greater for hypertension compared to hypotension. Total ejection fraction, stroke volume, and left ventricular ejection time were greater for hypertions compared to normotension. There was no difference between ultrasound dilution and echocardiography determined cardiac output measurements within each cardiovascular phase. Phenylephrine appeared to have increased ventricular performance and/or increased preload in anesthetized, mature alpacas. For detecting change in cardiovascular status in anesthetized alpacas, ultrasound dilution and echocardiography may be useful.

Impact of intravenous fluid administration on cardiac output and oxygenation during cardiopulmonary resuscitation

BackgroundThe effect of intravenous fluid (IVF) administration during cardiopulmonary resuscitation (CPR) is an unexplored factor that may improve cardiac output (CO) during CPR. The aim of this study was to determine the effect of IVF administration on CO and oxygenation during CPR.MethodsThis experimental animal study was performed in a critical care animal laboratory. Twenty-two Landrace-Yorkshire female piglets weighing 27–37 kg were anesthetized, intubated, and placed on positive pressure ventilation. Irreversible cardiac arrest was induced with bupivacaine. CPR was performed with a LUCAS 3 mechanical compression device. Pigs were randomized into IVF or no-IVF groups. Pigs in the IVF group were given 20 mL/kg of Plasma-Lyte (Baxter International, Deerfield, IL USA), infused from 15 to 35 min of CPR. CPR was maintained for 50 min with serial measurements of CO obtained using ultrasound dilution technology and partial pressure of oxygen (PaO2).ResultsA mixed-effects repeated measures analysis of variance was used to compare within-group, and between-group mean changes in CO and PaO2 over time. CO and PaO2 for the piglets were measured at 10-min intervals during the 50 min of CPR. CO was greater in the IVF compared with the control group at all time points during and after the infusion of the IVF. Mean PaO2 decreased with time; however, at no time was there a significant difference in PaO2 between the IVF and control groups.ConclusionsAdministration of IVF during CPR resulted in a significant increase in CO during CPR both during and after the IVF infusion. There was no statistically significant decrease in PaO2 between the IVF and control groups.

The Impact of Recirculation on Extracorporeal Gas Exchange and Patient Oxygenation during Veno-Venous Extracorporeal Membrane Oxygenation-Results of an Observational Clinical Trial.

Recirculation during veno-venous extracorporeal membrane oxygenation reduces extracorporeal oxygen exchange and patient oxygenation. To minimize recirculation and maximize oxygen delivery (DO2) the interaction of cannulation, ECMO flow and cardiac output requires careful consideration. We investigated this interaction in an observational trial. In 19 patients with acute respiratory distress syndrome and ECMO, we measured recirculation with the ultrasound dilution technique and calculated extracorporeal oxygen transfer (VO2), extracorporeal oxygen delivery (DO2) and patient oxygenation. To assess the impact of cardiac output (CO), we included CO measurement through pulse contour analysis. In all patients, there was a median recirculation rate of approximately 14-16%, with a maximum rate of 58%. Recirculation rates &gt;35% occurred in 13-14% of all cases. In contrast to decreasing extracorporeal gas exchange with increasing ECMO flow and recirculation, patient oxygenation increased with greater ECMO flows. High CO diminished recirculation by between 5-20%. Extracorporeal gas exchange masks the importance of DO2 and its effects on patients. We assume that increasing DO2 is more important than reduced VO2. A negative correlation of recirculation to CO adds to the complexity of this phenomenon. Patient oxygenation may be optimized with the direct measurement of recirculation.

Evaluation of transpulmonary ultrasound dilution cardiac output in piglets: accuracy, precision and trending ability with room temperature injectate

ObjectiveTranspulmonary ultrasound dilution (TPUD) is a minimally invasive technique to measure cardiac output (CO) using a 1 mL kg–1 isotonic 37 °C saline injectate indicator. The objective was to evaluate the performance of TPUD using a room temperature saline injectate. Study designProspective experimental trial. AnimalsA total of seven anesthetized male Yorkshire piglets. MethodsPiglets aged 1 month and weighing 7.7–9.0 kg were anesthetized with detomidine–ketamine–hydromorphone–isoflurane and a pulmonary artery flow probe (PAFP) placed via a median sternotomy. The thoracic cavity remained open during measurement of CO by PAFP and TPUD. The TPUD indicators of 1 mL kg–1 0.9% saline at 37 °C and 20 °C were compared during infusions of phenylephrine and dobutamine, blood withdrawal and replacement. Bias, limits of agreement (LoAs) and percentage error (PE) between each iteration of PAFP and TPUD were measured with Bland–Altman plots. Trending ability via concordance, angular bias and radial LoA were compared. ResultsBland–Altman plots showed negligible bias with varying LoAs. PEs of 22% and 38% were found for 37 °C and 20 °C saline injectates, respectively. In the four-quadrant plots, the concordance rate was 94% and 100% for measurements obtained with 37 °C and 20 °C saline injectates, respectively. Angular bias for both were < ±5 °, with radial LoA < ±7 °. ConclusionsTPUD was accurate when using 1 mL kg–1 of isotonic saline at 37 °C in a range of CO within 0.2–0.8 L minute–1, and it reliably tracked positive and negative changes in CO. Room temperature (20 °C) indicator was less accurate but equally able to track direction of changes in CO. Clinical relevanceThe use of room temperature injectates allows an easy, readily available clinical application of TPUD CO monitoring while preserving the trending ability of the monitor.

Comparing non-invasive diagnostic methods for arteriovenous fistula stenosis: a prospective study.

International guidelines recommend screening for arteriovenous fistula (AVF) stenosis using various non-invasive methods. We evaluate different non-invasive AVF flow measurements for detecting AVF stenosis. Twenty-three haemodialysis patients with suspected AVF stenosis are enrolled based on abnormal physical signs or high venous pressure during dialysis. Ultrasound dilution, urea dilution, Doppler ultrasonography, and fistulography are performed on all patients. The accuracy of three non-invasive methods is compared. Fistulography reveals AVF stenosis in 18 patients, 12 of whom have severe stenosis (greater than 50% stenosis in diameter). Concerning the location of the stenosis lesions, eight are at the inflow site, six at the outflow site, and four on both sites. Receiver operating characteristic curve analysis shows that Doppler ultrasonography has a high discriminative ability and the averaged areas under the curves are 0.933 (95% confidence interval [CI]; 0.81 to 0.99) for stenosis and 0.929 (95% CI 0.82-0.99) for severe stenosis. The sensitivity of each method for the prediction of access stenosis using ultrasound dilution, urea dilution, and Doppler ultrasonography is 73%, 73%, and 80%, respectively. The respective specificity of each method is 40%, 80%, and 100%, respectively. Physical examination (PE) shows an 80% sensitivity and 80% specificity in the detection of AVF stenosis. The combination of Doppler ultrasound with PE produces the highest sensitivity (93%) for detecting AVF stenosis. Doppler ultrasound combined with physical examination is more accurate than other non-invasive methods for detecting AVF stenosis.

Recirculation in single lumen cannula venovenous extracorporeal membrane oxygenation: A non-randomized bi-centric trial.

BackgroundRecirculation is a common problem in venovenous (VV) extracorporeal membrane oxygenation (ECMO). The aims of this study were to compare recirculation fraction (Rf) between femoro-jugular and jugulo-femoral VV ECMO configurations, to identify risk factors for recirculation and to assess the impact on hemolysis.MethodsPatients in the medical intensive care unit (ICU) at the University Medical Center Regensburg, Germany receiving VV ECMO with femoro-jugular, and jugulo-femoral configuration at the ECMO Center Karolinska, Sweden, were included in this non-randomized prospective study. Total ECMO flow (QEC), recirculated flow (QREC), and recirculation fraction Rf = QREC/QEC were determined using ultrasound dilution technology. Effective ECMO flow (QEFF) was defined as QEFF = QEC * (1–Rf). Demographics, cannula specifics, and markers of hemolysis were assessed. Survival was evaluated at discharge from ICU.ResultsThirty-seven patients with femoro-jugular configuration underwent 595 single-point measurements and 18 patients with jugulo-femoral configuration 231 measurements. Rf was lower with femoro-jugular compared to jugulo-femoral configuration [5 (0, 11) vs. 19 (13, 28) %, respectively (p < 0.001)], resulting in similar QEFF [2.80 (2.21, 3.39) vs. 2.79 (2.39, 3.08) L/min (p = 0.225)] despite lower QEC with femoro-jugular configuration compared to jugulo-femoral [3.01 (2.40, 3.70) vs. 3.57 (3.05, 4.06) L/min, respectively (p < 0.001)]. In multivariate regression analysis, the type of configuration, distance between the two cannula tips, ECMO flow, and heart rate were significantly associated with Rf [B (95% CI): 25.8 (17.6, 33.8), p < 0.001; 960.4 (960.7, 960.1), p = 0.009; 4.2 (2.5, 5.9), p < 0.001; 960.1 (960.2, 0.0), p = 0.027]. Hemolysis was similar in subjects with Rf > 8 vs. ≤ 8%. Explorative data on survival showed comparable results in the femoro-jugular and the jugulo-femoral group (81 vs. 72%, p = 0.455).ConclusionVV ECMO with femoro-jugular configuration caused less recirculation. Further risk factors for higher Rf were shorter distance between the two cannula tips, higher ECMO flow, and lower heart rate. Rf did not affect hemolysis.

Transpulmonary ultrasound dilution is an acceptable technique for cardiac output measurement in anesthetized pigs

To evaluate cardiac output (CO) measurements using transpulmonary ultrasound (TPUD) technology and compare results with those of the gold standard, pulmonary arterial catheter thermodilution (PACTD), in 6 healthy anesthetized pigs during acute hemodynamic changes caused by manipulation of the blood volume. 6 healthy male Landrace pigs. Over a period of 1 week, pigs were anesthetized with isoflurane, mechanically ventilated, and underwent instrumentation in dorsal recumbency. They were subjected to sequential experimental states during which the blood volume was manipulated so that the animals transitioned from normovolemia to hypovolemia (20% and 40% of blood volume depletion), back to normovolemia (autologous blood transfusion), and then to hypervolemia (following colloid bolus). During each volume state, CO measurements were compared between TPUD and PACTD. The mean ± SD relative bias between TPUD and PACTD was 7.71% ± 21.2% with limits of agreement -33.9% to 49.3%, indicating TPUD slightly underestimated CO values, compared with values obtained with PACTD. The mean ± SD of the bias between the 2 methods was 0.13 ± 0.5 L/min. Only 5 of 36 (13.9%) TPUD CO measurements had an absolute value of relative bias > 30%. The percentage error calculated for TPUD was 29.4%. Results suggested that TPUD measurements have acceptable agreement with PACTD measurements. Moreover, TPUD exhibits promising potential in being used interchangeably with PACTD for future hemodynamic research involving swine as species of interest.

MO771: Haemodialysis Access Flow Measurement: Comparison of Ultrasound Dilution and Ultrafiltration Method on Nikisso DBB-EXA™ Dialysis Machine

Abstract BACKGROUND AND AIMS The regular measurement of the haemodialysis vascular access (VA) flow demonstrates a protective effect over thrombotic complications [1]. Transonic® Ultrasound dilution technique was first introduced in 1995 and progressively became a method of reference for recirculation and blood flow measurement on haemodialysis VA [2]. It is based on the technique of haemodilution with a certain volume of 0.9% NaCl and the measure of recirculation with inversed lines using the ultrasound technique. Consecutively the VA flow is estimated with a certain formula. Nikisso DBB-EXA™ dialysis machine has the capacity to measure the VA recirculation rate by photometry performing a controlled rise on ultrafiltration rate. The aim of the present study is to compare the VA flow rate between the Transonic® Ultrasound dilution technique and the Nikisso DBB-EXA™ Ultrafiltration method. METHOD The primary outcome of the study is the association of VA flow measured by Transonic® and the Nikisso DBB-EXA™. During the first half of the same dialysis session, we measured the VA recirculation and flow rate twice with the two methods under a constant dialysis blood pump flow of 250–300 mL/min with the ultrafiltration and haemodiafiltration interrupted during the procedure after having reversed the dialysis lines. RESULTS The values are represented as mean ± SD. A total of 18 chronic haemodialysis patients (13 male: 5 female, mean age: 70 ± 14 years) participated in the study. They were haemodynamically stable without acute clinical conditions and were dialysed with a well-functioning arteriovenous fistula for at least 6 months. The mean value of recirculation with inverted dialysis lines for the Transonic® method was 20.79 ± 7.58% and for the Nikisso DBB-EXA™ was 24.43 ± 7.77. The mean values of VA blood flow with the Transonic® method were 1229 ± 588 mL/min and for the Nikisso DBB-EXA™ 1096 ± 490 mL/min. The measured values of the two methods presented a significant positive correlation (by Pearson) (R = 0.920, P &amp;lt; 0.001) (Figure). CONCLUSION There is a significantly positive correlation concerning the VA flow measurement between the reference method of Transonic® and the Ultrafiltration method offered by the Nikisso DBB-EXA™. Larger studies are needed to confirm this correlation with an additional comparative analysis of the reproducibility of measurements.

Study of Anti-C1q Antibodies in Egyptian Systemic Lupus Erythematosus Patients.

Autoantibodies to complement are associated with various diseases. Anti-C1q antibodies are present in all patients with hypocomplementemic urticarial vasculitis, but also with varying prevalence in other conditions. Anti-C1q may interfere with the clearance of apoptotic cells, so influencing induction and expression of autoimmunity. The aim of this work is to study the relation between anti-C1q antibodies and systemic lupus erythematosus (SLE) and its manifestations including renal affection. The presence and levels of anti-C1q antibodies were investigated using enzyme-linked immunosorbent assay technique. The study included 70 Egyptian patients suffering from SLE and 18 healthy controls. They were 65 females and five males. Their age ranged from 12 to 48.5 years with a mean value of 27.4 ± 8.4. Anti-C1q antibodies were statistically significantly elevated in cases compared with controls being positive in 37.2% (mean 18.3 ± 27.1) in patients versus 11.1% (mean value 4.1 ± 3.5) in controls (P = 0. 03). Anti-C1q antibody-positive patients (n = 226) had significantly higher SLE Disease Activity Index (SLEDAI) (16.1 ± 9.9) compared to negative patients (n = 44) (SLEDAI = 8.1 ± 7.7) P = 0.000. Regarding renal affection, the presence of anti-C1q-positive antibodies was associated with proteinuria, P = 0.002. In conclusion, anti-C1q was more common in patients with SLE and disease activity. We confirmed a significant association of anti-C1q with renal involvement, independent of demographics and other serologies.