New Design of an Oxygenation Cannula with a Comprehensive Set of Blood Pump

To compare insulin dose adjustments made by physicians to those made by an artificial intelligence-based decision support system, the Advisor Pro, in people with type 1 diabetes (T1D) using an insulin pump and self-monitoring blood glucose (SMBG). This was a multinational, non-interventional study surveying 17 physicians from 11 countries. Each physician was asked to provide insulin dose adjustments for the settings of the pump including basal rate, carbohydrate-to-insulin ratios (CRs), and correction factors (CFs) for 15 data sets of pumps and SMBG of people with T1D (mean age 18.4 ± 4.8 years; eight females; mean glycated hemoglobin 8.2% ± 1.4% [66 ± 11mmol/mol]). The recommendations were compared among the physicians and between the physicians and the Advisor Pro. The study endpoint was the percentage of comparison points for which there was an agreement on the direction of insulin dose adjustments. The percentage (mean ± SD) of agreement among the physicians on the direction of insulin pump dose adjustments was 51.8% ± 9.2%, 54.2% ± 6.4%, and 49.8% ± 11.6% for the basal, CR, and CF, respectively. The automated recommendations of the Advisor Pro on the direction of insulin dose adjustments were comparable )49.5% ± 6.4%, 55.3% ± 8.7%, and 47.6% ± 14.4% for the basal rate, CR, and CF, respectively( and noninferior to those provided by physicians. The mean absolute difference in magnitude of change between physicians was 17.1% ± 13.1%, 14.6% ± 8.4%, and 23.9% ± 18.6% for the basal, CR, and CF, respectively, and comparable to the Advisor Pro 11.7% ± 9.7%, 10.1% ± 4.5%, and 25.5% ± 19.5%, respectively, significant for basal and CR. Considerable differences in the recommendations for changes in insulin dosing were observed among physicians. Since automated recommendations by the Advisor Pro were similar to those given by physicians, it could be considered a useful tool to manage T1D.

Preliminary In Vivo Testing of a Novel Pump for Short-Term Extracorporeal Life Support

Pulsatile perfusion during extracorporeal circulation is a promising concept to improve perfusion of critical organs. Clinical benefits are limited by the amount of pulsatile energy provided by standard pumps. The present study investigated the properties of a novel positive displacement blood pump in a mock circulation. The pump was attached to an aortic model with a human-like geometry and compliance as a pseudo patient. Hemodynamic data were recorded while the pump settings were adjusted systematically. Using a regular oxygenator, maximum flow was 2.6L/min at a pressure of 27 mm Hg and a frequency (F) of 90 bpm. Pulse pressure (PP; 28.9 mm Hg) and surplus hemodynamic energy (SHE; 26.1% of mean arterial pressure) were highest at F=40 bpm. Flow and pressure profiles appeared sinusoid. Using a low-resistance membrane ventilator to assess the impact of back pressure, maximum flow was 4.0L/min at a pressure of 58.6 mm Hg and F=40 bpm. At F=40 bpm, PP was 58.7 mm Hg with an SHE of 33.4%. SHE decreased with increasing flow, heart rate, and systolic percentage but surpassed 10% with reasonable settings. The present prototype achieved sufficient flow and pressure ranges only in the presence of a low-resistance membrane ventilator. It delivered supraphysiologic levels of pulse pressure and SHE. Further modifications are planned to establish this concept for adult pulsatile perfusion.

Objective: to analyze the inflow cannula of an implantable axial-flow blood pump for a long-term left ventricular assist system in order to minimize thromboembolic complications. Materials and methods. Hemodynamics was considered for 4 different designs of the inflow cannula, from 0 mm to 25 mm long. Areas at the base of the cannula received the most attention. Analysis was performed using the OpenFOAM software. Results. It was revealed that sizes of stagnation and recirculation zones directly depended on the length of the cannula when placed in the left ventricle. Accordingly, longer cannula increases the risk of thrombosis. Conclusion. The design of an inflow cannula determines the likelihood of thrombosis in the cannula. Longer inflow cannula increases stagnation and recirculation zones. This provides a basis for a search for other possible modifications.

IntroductionThe application of extracorporeal circulation (ECC) systems is known to be associated with several implications regarding hemolysis, inflammation, and coagulation. In the last years, systems with pulsatile blood flow are increasingly used with the intention to improve hemodynamics in reperfusion. However, their implications on the aforementioned aspects remain largely unknown. To investigate the effects of pulsatility, this ex-vivo study was initiated.MethodsTest circuits (primed with human whole blood) were set up in accordance with the recommendations of international standards for in-vitro evaluation of new components and systems of ECC. Diagonal pumps were either set up with non-pulsatile (n = 5, NPG) or pulsatile (n = 5, PG) pump settings and evaluated for 6 h. All analyses were conducted with human whole blood. Blood samples were repeatedly drawn from the test circuits and analyzed regarding free hemoglobin, interleukin 8 (IL-8), platelet aggregation and acquired von Willebrand syndrome (AVWS).ResultsAfter 1 h of circulation, a significant coagulation impairment (impaired platelet function and AVWS) was observed in both groups. After 6 h of circulation, increased IL-8 concentrations were measured in both groups (NPG: 0.05 ± 0.03 pg./mL, PG: 0.03 ± 0.01 pg./mL, p = 0.48). Pulsatile pump flow resulted in significantly increased hemolysis after 6 h of circulation (NPG: 37.3 ± 12.4 mg/100 L; PG: 59.6 ± 14.5 mg/100 L; p < 0.05).ConclusionOur results indicate that the coagulative impairment takes place in the early phase of ECC. Pulsatility did not affect the occurrence of AVWS ex-vivo. Prolonged durations of pulsatile pump flow led to increased hemolysis and therefore, its prolonged use should be employed cautiously in clinical practice with appropriate monitoring.

Introduction The maintenance of cerebral functions strongly depends on the sustained supply of blood and the ability to adapt cerebral blood flow (CBF) to its metabolic demands. Occlusion of afferent vessels bears a risk for ischemic stroke and permanent cerebral damage. Arterial spin labeling (ASL) technique [1] can be used to quantify CBF. However, the CBF measure extracted by this technique may contain artifacts [2] and moreover may be affected by large within-subject, between-subject and regional variability [3]. An unambiguous and reliable description of physiological features by this method may therefore represent a “mission impossible”. It is therefore mandatory to validate and optimize the CBF measure by independent methods. Validation via a perfusion phantom is the aim of the present study. Methods A perfusion phantom was constructed with 125cm3 volume filled with SiO2 spheres of different diameters [e.g. 0.01 mm 0.05 mm and 0.1 mm]. Due to this set of diameters an average pore size of 0.0138 mm was achieved. With this average pore size, we are a factor 2 larger than average diameter of capillaries of ~ 6 m. A pump (Harvard Apparatus Pulsatile Blood pump for hemodynamic studies) provides a circular flow into the phantom via the input- and output tubes. The pump allows exact setting of flow volume and flow rate. MR imaging was conducted in a 3T Siemens Prisma Scanner. The pseudo CASL sequence [1] were set with the following paramerters: TE = 30 ms, TR = 2 s, 3 mm  3 mm  3 mm voxel dimension, 64  64 matrix size, FOV 192 mm, 38 slices, and slice thickness = 3 mm. In order to assess variability and precision of CBF measure estimate we systematically changed the following ASL parameters [4]: Post-labeling delay [100 ms:200:ms:1500ms], Bolus duration # RF [ 20, 60, 80]; and the following pump parameters: flow ratio [0.5, 1, 1.5] and Flow volume*Flow rate [20:20:200]. Results The perfusion phantom is operating (Fig 1.A and B). Due to the large amount of different sequence and pump settings we present a limited set only. Setting the pump Flow volume*Flow rate at 200 [ml/min], a flow ratio of 1, post labeling delay of 500 ms revealed an extraordinary high precision of CBF estimation by the perfusion phantom: 198.3029 ± 0.76 [ml/100g/min] (Fig 1.C and Fig. 2). The signal to noise ratio (SNR) was 4.2. The 0expected value of CBF was therefore underestimated by 1.7 [ml/100g/min]. The error in CBF estimation is 0.5 % which is at same level as the accuracy of the pulsatile pump. Conclusion The perfusion phantom with the pulsatile pump showed high accuracy of CBF estimation that were reliable and reproducible. The observed CBF values showed high precision (i.e. low standard deviation) that allows to draw conclusion about the variance of the CBF measure originated by the ASL sequence only. Uncertainty in CBF estimation by ASL technique may therefore be assessed. This novel approach will finally allow clinicians, physicians and researchers to unambiguously estimate disease-related CBF effects. Therefore, it is relevant for patients as well as for socioeconomic aspects. The perfusion phantom will be generalized to be used within other institutions to enable quality controls on different scanners with different ASL sequences and different field strengths: since the phantom is stable and easy to send.

Ventricular assist devices (VADs) are increasingly being used in pediatric patients to support cardiac failure. As more centers adopt this technology, there may be a need to transport these patients over long distances to facilitate patient care and organ transplantation. Food and Drug Administration indications for use state only that the patient must be a candidate for transplantation and does not place restrictions on the transplant capabilities of the implanting medical center. Nontransplanting institutions are able to use this technology with a predetermined agreement to transfer the patient to a partnering transplant center. We report the first two cases of interhospital air and ground transport of nonambulatory or intubated pediatric (<13 kg) patients supported by Berlin Heart EXCOR pediatric VADs and Ikus stationary drivers. We present our protocol for transporting this delicate patient population. In addition, we discuss important challenges encountered on these operations regarding vehicle transfers and the management of vehicle power supply. These two cases demonstrate that the transportation of pediatric patients on Berlin Heart VADs is feasible and safe and should be considered a treatment option in certain situations.

When writing "Cannulation Camp" back in 1995, I never imagined the article would have such lasting impact on the nephrology community. I first want to thank the people who made the article happen. Joseph Herman was the editor of D&T at the time, and he decided the article should be the first-ever full-color article published in the journal. The color was necessary due to the amazing illustrations created from my very crude drawings. The concept for the article was conceived thanks to Mitchell Henry, MD and the Ohio State's "Vascular Access for Hemodialysis IV" symposium in 1994. Dr. Henry chose me to present "Hemodialysis: A Nursing Perspective" to a mainly surgeon audience symposium. Susan Boothe, RN, MS, is the product specialist for vascular access at W.L. Gore & Associates, who published the symposium book, and she coordinated the creation of the illustrations by the Gore medical illustrator. The illustrations where initially used to create slides for the presentation, and subsequently used in the black-and-white format for the symposium book. Joe Herman saw the need to spread the cannulation information from the symposium to the wider dialysis community, and thus "Cannulation Camp" was written. Once the article was published, my hands-on training course and lecture presentations for dialysis professionals was termed "Cannulation Camp." I have lost track of the number of professional educational programs that have resulted from "Cannulation Camp," but it has traveled to many small and large towns within the U.S., as well as to countries around the globe. The publication of "Cannulation Camp" also led to one of the most rewarding volunteer efforts I could ever have imaged—I served as a Work Group member for the KDOQI Vascular Access Guidelines for the 1997, 2000, and 2006 versions. Thanks to Steve Schwab, MD, and Anatole Besarab, MD, for selecting me as one of the two nurses honored to represent our profession and, even more importantly, the hemodialysis patients in the original Work Group. I have been truly honored to remain on the 2000 and 2006 Work Groups to update the guidelines. The guidelines led to the Centers for Medicare and Medicaid Services creation of the National Vascular Access Improvement Initiative. Thanks once again to the publication of "Cannulation Camp," I was selected to be one of the original Work Group Members that formed the initial Change Concepts, now widely accepted, and the Fistula First Breakthrough Initiative (FFBI). It is fair to say my work as a nephrology nurse volunteer to help improve the vascular access options for all chronic kidney disease patients began with the publication of a simple "how to" cannulation guide! AVF maturation for needle cannulation—how, why, and when an AVF matures; The best method for new AVF cannulation—buttonhole or self cannulation for all HD modalities (not just for home HD); and Needle-placement direction and bloodflow rates—whether they impact the formation of aneurysms or create vessel damage. An important correction to "Cannulation Camp" was discovered when I was reviewing one of the many KDOQI 2006 reference articles. The theory of recirculation based solely on needle distance was disproven by Basile and colleagues in 2003.1 This study found that the recirculation was not related to needle distance, but to bloodflow (access flow) within the body of the fistula in relationship to the blood pump flow rate. For example: AVF access flow of 800 mL/min and the HD blood pump set at 500 mL/min = no recirculation regardless of the needle distances (2, 5 or 11 cm). But, if the AVF access flow is low at 400 mL/min and the HD blood pump set at 500 mL/min = recirculation. The venous blood pulls dialyzer blood backward into the arterial needle due to the lack of adequate flow to meet the demand of the blood pump on the arterial needle. For the most current recommendation on the proper techniques for AVF cannulation, please use the many outstanding references found on the Fistula First website (www.fistulafirst.org). I want to personally thank several of the key cannulation educators who have helped me over the past 28 years in nephrology nursing: Susan Boothe, Patt Peterson Ryder, Janet Holland, and Kay Bregel. I also want to thank D&T for the amazing opportunity to use simple words and simple illustrations to help teach so many nephrology professionals about the importance of hemodialysis vascular access cannulation, and for the many years of providing a journal that reaches the frontline care givers in dialysis units around the globe. D&T has supported the dissemination of updated nephrology information to people who can use the information to improve the care and lives of chronic kidney disease patients. The journal will be missed. Thanks for 40 years of service to the nephrology community!

To the Editor: Recently, we provided anesthetic care for a 6-mo-old, 8-kg child during craniofacial reconstruction. Because of the 10 degrees head-up position used intraoperatively, a precordial Doppler probe was placed over the right atrium and checked for appropriate position by rapid infusion of intravenous fluid (rapid infusion resulting in a change in the quality of Doppler tones). The intraoperative course was smooth except for blood loss during the scalp incision and dissection of the skull flap; approximately one blood volume was lost intraoperatively. As blood was lost during the dissection, it was replaced with packed red blood cells reconstituted with saline, infused via a Y-type blood pump set connected to a Hotline Trademark fluid warmer (Level I Technologies, Rockland, MA). Occasionally, a change in quality of Doppler tones was noted intraoperatively--a change different from that related to rapid intravenous infusion alone. This short-lived change in Doppler tones was not associated with any change in vital signs or end-tidal CO2; the Doppler tone changes rapidly disappeared when fluid was not being infused. Close inspection revealed that visible air bubbles were forming in the tubing just distal to the Hotline Trademark Figure 1. The bubbles were so small that they could barely be noted unless a fluid bolus was being infused, at which time bubbles seem to coalesce into larger bubbles Figure 2. The entire system was reexamined to ensure appropriate assembly; no air was being entrained from the Y-type pump system hooked into the Hotline Trademark.Figure 1: Note bubbles within the intravenous tubing of the child described (arrows).Figure 2: Note coalescence of bubbles into larger bubbles within the intravenous tubing of the child described (arrows).We were able to replicate this bubble phenomenon at a later time (without a patient!) using infusion of cold fluids through the Hotline Trademark system. Presumably, these bubbles form because of the decreasing solubility of gases in liquid as they are warmed. Owing to their small size, these bubbles are unlikely to be of clinical hemodynamic significance, although they might pose a hazard of paradoxical embolization in patients with a potential for right-to-left intracardiac shunting. In addition, if a precordial Doppler is being used to detect early signs of operative air embolus, these bubbles are, at least, an annoyance and possibly the source of ill-advised therapeutic interventions for treatment of suspected air entry from the surgical field. A Hotline Trademark gas eliminator, L10 Model (Level I Technologies), is available as an optional addition of the Hotline Trademark fluid warmer system. This optional piece of equipment was not being used during the case described, since it comes with the warning "DO NOT USE WTTH HAND PUMPS," a component of our standard intravenous fluid administration set. Clinicians should be aware of this potential problem, especially if a precordial Doppler is being used during anesthesia for pediatric patients in whom an air embolus from the surgical field might occur. G. W. Stevenson, MD Michael Tobin, MD Steven C. Hall, MD Department of Anesthesia, Children's Memorial Hospital, Northwestern University Medical School, Chicago, IL 60614

Optimization of high-efficiency hemodialysis by detection and correction of fistula dysfunction

Introduction: The use of mechanical circulatory support (MCS) in patients with end-stage dilated cardiomyopathy (DCM) reportedly allows myocyte recovery and improves left ventricular (LV) function. The slope, Emax, of the end-systolic pressure-volume relationship (ESPVR) can give a preload- and afterload-independent estimate of LV contractility and recovery. Methods: A 53 year-old woman with idiopathic DCM and LVEF<20% received the Jarvik 2000 LVAD through a left thoracotomy. The LV and aortic pressures were recorded simultaneously with TEE measurements of LV dimensions in 2 and 4-chamber views. Modified Simpson's rule was used to calculate LV volumes at 33-msec intervals during a single cardiac cycle at pump settings of 0; 9,000; and 11,000 rpm. Measurements were taken at the time of LVAD implantation and immediately prior to its explantation for cardiac transplantation. Stroke work (SW) was calculated from the area enclosed by the PV loops. LV stiffness was calculated by the slope, Sed, of LV end-diastolic P-V relationship (EDPVR). Results: During the 14-day MCS, Emax increased from 0.28 mmHg/ml at implant to 1.4 mmHg/ml at explant while Sed remained unchanged at 0.16 mmHg/ml. SW decreased with increasing pump speeds from 38.8 gm.m at 0 rpm to 19.8 gm.m at 11,000 rpm. When the pump was on, PV loops were observed to slant to the left during simultaneous closure of aortic and mitral valves. The pt tolerated the operations well and recovered uneventfully. Conclusions: Low values of Emax and SW in this isolated case were consistent with profound cardiac failure and the associated degree of ventricular dilatation at admission. The substantial increase in Emax over the 14-day support period was suggestive of myocardial recovery despite unchanged diastolic function. Although susceptible to observer-dependent measurement errors, the method accurately reflected the non-pulsatile, continuous flow characteristics of this intraventricular blood pump. In a large sample of patients with longer durations of MCS, the method may prove useful in estimating the extent of LV recovery during LV unloading.

To the Editor: Recently, we provided anesthetic care for a 6-mo-old, 8-kg child during craniofacial reconstruction. Because of the 10 degrees head-up position used intraoperatively, a precordial Doppler probe was placed over the right atrium and checked for appropriate position by rapid infusion of intravenous fluid (rapid infusion resulting in a change in the quality of Doppler tones). The intraoperative course was smooth except for blood loss during the scalp incision and dissection of the skull flap; approximately one blood volume was lost intraoperatively. As blood was lost during the dissection, it was replaced with packed red blood cells reconstituted with saline, infused via a Y-type blood pump set connected to a Hotline Trademark fluid warmer (Level I Technologies, Rockland, MA). Occasionally, a change in quality of Doppler tones was noted intraoperatively--a change different from that related to rapid intravenous infusion alone. This short-lived change in Doppler tones was not associated with any change in vital signs or end-tidal CO2; the Doppler tone changes rapidly disappeared when fluid was not being infused. Close inspection revealed that visible air bubbles were forming in the tubing just distal to the Hotline Trademark Figure 1. The bubbles were so small that they could barely be noted unless a fluid bolus was being infused, at which time bubbles seem to coalesce into larger bubbles Figure 2. The entire system was reexamined to ensure appropriate assembly; no air was being entrained from the Y-type pump system hooked into the Hotline Trademark.Figure 1: Note bubbles within the intravenous tubing of the child described (arrows).Figure 2: Note coalescence of bubbles into larger bubbles within the intravenous tubing of the child described (arrows).We were able to replicate this bubble phenomenon at a later time (without a patient!) using infusion of cold fluids through the Hotline Trademark system. Presumably, these bubbles form because of the decreasing solubility of gases in liquid as they are warmed. Owing to their small size, these bubbles are unlikely to be of clinical hemodynamic significance, although they might pose a hazard of paradoxical embolization in patients with a potential for right-to-left intracardiac shunting. In addition, if a precordial Doppler is being used to detect early signs of operative air embolus, these bubbles are, at least, an annoyance and possibly the source of ill-advised therapeutic interventions for treatment of suspected air entry from the surgical field. A Hotline Trademark gas eliminator, L10 Model (Level I Technologies), is available as an optional addition of the Hotline Trademark fluid warmer system. This optional piece of equipment was not being used during the case described, since it comes with the warning "DO NOT USE WTTH HAND PUMPS," a component of our standard intravenous fluid administration set. Clinicians should be aware of this potential problem, especially if a precordial Doppler is being used during anesthesia for pediatric patients in whom an air embolus from the surgical field might occur. G. W. Stevenson, MD Michael Tobin, MD Steven C. Hall, MD Department of Anesthesia, Children's Memorial Hospital, Northwestern University Medical School, Chicago, IL 60614

Blood flow in peripheral arteriovenous fistulae and grafts as used for hemodialysis access can be derived from simultaneous measurements of 1) the amount of access recirculation (AR) induced by reversing the dialysis blood lines, and 2) the dialyzer blood flow rate (Qb). The hemodynamic monitor (HDM) uses magnetic principles to measure AR. The measurement is based on differential conductivity between arterial (A) and venous (V) blood flows in the dialysis blood tubing sets after the injection of hypertonic saline into the V line as a conductivity tracer. Access blood flow rates (Qa) derived from AR measurements by the HDM are predictive of access outcome. The measurement of AR is traditionally done from the comparison of urea levels simultaneously taken from the A and V blood lines and from the systemic circulation. Thus, the urea method can also be used to estimate access blood flow rates. The purpose of this study was to determine whether urea based Qa values are also predictive of outcome. Forty-one patients with arteriovenous fistulae (n = 25) or Gore-Tex grafts (n = 16) were studied by a standard protocol. The protocol involved temporarily reversing the A and V lines, taking three blood samples for urea estimation, performing an HDM recirculation test, and recording Qb as per the machine blood pump setting. The data allowed calculation of Qa by the HDM (Qa [HDM]) and urea (Qa [urea]) methods. Qa (HDM) was 1,177 +/- 887 ml/min (mean +/- standard deviation) and Qa (urea) 964 +/- 793 ml/min, a statistically significant difference (paired t-test p < 0.001). There was a significant linear correlation between the results (r = 0.94, p < 0.0001), but the regression equation also showed that Qa (urea) values were less than Qa (HDM). The influence of the Qa value on access outcome was determined after an 8 month follow-up. Nine of the 41 accesses were lost to clotting. Chi-square and discriminate analyses showed that Qa (HDM) significantly (p = 0.005) predicted access outcome, whereas Qa (urea) did not (p = 0.164). The specificity of a low Qa (HDM) in predicting access clotting was 0.78, compared with 0.62 for Qa (urea). The data show that although Qa can be estimated by the urea method, the finding of a low Qa (urea) is a poor predictor of access outcome and may lead to cost ineffective investigations.

Hemodialysis access blood flow rates can be measured by a differential conductivity technique and are predictive of access clotting

ObjectiveTo evaluate the in vivo and in vitro performance of a China-made dialysis machine (SWS-4000).MethodsThis was a multi-center prospective controlled study consisting of both long-term in vitro evaluations and cross-over in vivo tests in 132 patients. The China-made SWS-4000 dialysis machine was compared with a German-made dialysis machine (Fresenius 4008) with regard to Kt/V values, URR values, and dialysis-related adverse reactions in patients on maintenance hemodialysis, as well as the ultrafiltration rate, the concentration of electrolytes in the proportioned dialysate, the rate of heparin injection, the flow rate of the blood pump, and the rate of malfunction.ResultsThe Kt/V and URR values at the 1st and 4th weeks of dialysis as well as the incidence of adverse effects did not differ between the two groups in cross-over in vivo tests (P > 0.05). There were no significant differences between the two groups in the error values of the ultrafiltration rate, the rate of heparin injection or the concentrations of electrolytes in the proportioned dialysate at different time points under different parameter settings. At weeks 2 and 24, with the flow rate of the blood pump set at 300 mL/min, the actual error of the SWS-4000 dialysis machine was significantly higher than that of the Fresenius 4008 dialysis machine (P < 0.05), but there was no significant difference at other time points or under other settings (P > 0.05). The malfunction rate was higher in the SWS-4000 group than in the Fresenius 4008 group (P < 0.05).ConclusionsThe in vivo performance of the SWS-4000 dialysis machine is roughly comparable to that of the Fresenius 4008 dialysis machine; however, the malfunction rate of the former is higher than that of the latter in in vitro tests. The stability and long-term accuracy of the SWS-4000 dialysis machine remain to be improved.