Nonpulsatile Flow Research Articles

87 A Low-Cost Simulator for Ultrasound-Guided Retrograde Endovascular Balloon Occlusion of the Aorta

Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) is a technique used for obtaining emergent control of life-threatening, non-compressible thoracic, abdominal, or pelvic hemorrhage (1). This abstract will detail a low-cost, ultrasound-realistic simulator for performance of the REBOA procedure. A major hurdle to widespread implementation of the REBOA technique has been the difficulty in obtaining adequate training analogues for development of competency among physicians (2). Currently, there is a paucity of literature and few commercially available simulators for REBOA training. Commercial simulation models for REBOA include high-fidelity simulators developed by Keller et al. (2), Prytime Medical (3), and Medalus (4). A low-cost, low-fidelity simulator has been proposed by Walsh et al. (5), however it lacks ultrasound compatibility. Performance of the REBOA procedure involves several steps. First, the provider must prepare a sterile field and cannulate the femoral artery with an introducer sheath under ultrasound guidance. The REBOA device is then passed through the introducer sheath to one of three target zones. Once positioned, the REBOA balloon is inflated until occlusion is achieved (1). Our simulator is constructed from a gelatin thigh analog with silicon tubing vessels connected to a clear plastic reusable simulated aorta. To create the gelatin thigh analog, two 30-cm sections of 0.5-in diameter silicon tubing are secured within an aluminum mold and embedded into a gelatin mixture. To create the gelatin, 50g of commercially available psyllium husk powder and 120g of gelatin powder (Commercial Knox Gelatin Powder(R)) are mixed in 1L of water and refrigerated for 12 hours prior to use. One of the two 0.5-in silicon tubing segments is connected to a 40-cm length of 1-in diameter rigid clear plastic tubing, which constitutes the aortic segment of the model. The aortic segment is then connected to a length of latex tubing with an in-line unidirectional manual pressure bulb to simulate pulsatile arterial flow. The other 0.5-in tubing segment is connected to an unpressurized reservoir to simulate non-pulsatile venous flow. To test the simulator, a 30-minute simulation session was conducted among 24 current emergency medicine resident physicians. Participants were asked to describe their knowledge of and confidence performing the REBOA procedure on a 1-to-5 Likert Scale before and after the simulation session. Confidence improved after the training, with a median confidence score of 1.0 before the session and 4.0 after the session. The results were evaluated using a Mann-Whitney U test which yielded a p-value <0.0001. Regarding cost, our model can be constructed for a total cost of $24. It is ultrasound compatible, provides life-like aortic pulsatility, and maintains anatomic functional accuracy. This project details the construction of a low-cost, ultrasound-compatible simulator for training physicians in the REBOA procedure. Our simulation session and subsequent review of participant data demonstrate that such a simulation exercise yielded measurable benefits in procedural skills and medical knowledge for the participants.

Mitochondrial Oxygenation During Cardiopulmonary Bypass: A Pilot Study.

ObjectiveAdequate oxygenation is essential for the preservation of organ function during cardiac surgery and cardiopulmonary bypass (CPB). Both hypoxia and hyperoxia result in undesired outcomes, and a narrow window for optimal oxygenation exists. Current perioperative monitoring techniques are not always sufficient to monitor adequate oxygenation. The non-invasive COMET® monitor could be a tool to monitor oxygenation by measuring the cutaneous mitochondrial oxygen tension (mitoPO2). This pilot study examines the feasibility of cutaneous mitoPO2 measurements during cardiothoracic procedures. Cutaneous mitoPO2 will be compared to tissue oxygenation (StO2) as measured by near-infrared spectroscopy.Design and MethodThis single-center observational study examined 41 cardiac surgery patients requiring CPB. Preoperatively, patients received a 5-aminolevulinic acid plaster on the upper arm to enable mitoPO2 measurements. After induction of anesthesia, both cutaneous mitoPO2 and StO2 were measured throughout the procedure. The patients were observed until discharge for the development of acute kidney insufficiency (AKI).ResultsCutaneous mitoPO2 was successfully measured in all patients and was 63.5 [40.0–74.8] mmHg at the surgery start and decreased significantly (p < 0.01) to 36.4 [18.4–56.0] mmHg by the end of the CPB run. StO2 at the surgery start was 80.5 [76.8–84.3]% and did not change significantly. Cross-clamping of the aorta and the switch to non-pulsatile flow resulted in a median cutaneous mitoPO2 decrease of 7 mmHg (p < 0.01). The cessation of the aortic cross-clamping period resulted in an increase of 4 mmHg (p < 0.01). Totally, four patients developed AKI and had a lower preoperative eGFR of 52 vs. 81 ml/min in the non-AKI group. The AKI group spent 32% of the operation time with a cutaneous mitoPO2 value under 20 mmHg as compared to 8% in the non-AKI group.ConclusionThis pilot study illustrated the feasibility of measuring cutaneous mitoPO2 using the COMET® monitor during cardiothoracic procedures. Moreover, in contrast to StO2, mitoPO2 decreased significantly with the increasing CPB run time. Cutaneous mitoPO2 also significantly decreased during the aortic cross-clamping period and increased upon the release of the clamp, but StO2 did not. This emphasized the sensitivity of cutaneous mitoPO2 to detect circulatory and microvascular changes.

The Fontan Circulation: From Ideal to Failing Hemodynamics and Drug Therapies for Optimization.

Fontan palliation results in a hemodynamically complex circulation with multisystem consequences, which in the long term adversely affect many body processes. Systemic venous hypertension, nonpulsatilelow-shear pulmonary blood flow, and low cardiac output are the 3 main characteristics of a Fontan circulation, leading to unavoidableslowly progressive failure. An appreciation of how the hemodynamics of a Fontan circulation change with time and relate to the various modes of Fontan circulatory failure is important. Accurate hemodynamic assessment aid this understanding and may permit early identification of potentially treatable drivers of decline. While no evidence-based or guideline-directed pharmacologic management strategy has been established in Fontan patients, understanding the hemodynamics of Fontan circulation failure will assist in the rational selection of potentially helpful drug therapies for individual patients. In this review, we present hemodynamic concepts of the optimal Fontan physiology and Fontan circulatory failure, review practical aspects of invasive hemodynamic assessment, and discuss the role of drug therapies in increasing systemic venous blood flow return and decreasing ventricular filling pressures in Fontan circulation. Oftencomplementary to catheter-based or surgical interventions, pharmacologicmanagement aims at preserving patency of the circuit, adequate systolic and diastolic ventricular function, atrioventricular valve function, an unobstructed ventricular outflow tract, and pulmonary vascular integrity in order to maintain an acceptable cardiac output.

CARC13: Early Low Pulsatility in VA-ECMO is Associated with Acute Brain Injury

Background: Pulse pressure (or pulsatility) is a dynamic marker of cardiovascular function and is often decreased in patients on veno-arterial extracorporeal membrane oxygenation (VA-ECMO), which provides non-pulsatile flow. We explored the impact of pulse pressure on development of acute brain injury (ABI) in VA-ECMO patients. Methods: We retrospectively analyzed all adult (≥18 years old) patients receiving VA-ECMO at a single tertiary care center between 7/2016 and 1/2021. All patients received routine neurocritical care consultations with standardized neuromonitoring. ABI included intracranial hemorrhage, ischemic stroke, hypoxic ischemic brain injury, cerebral edema, seizure, and brain death. Blood pressure (BP) was recorded every 15 minutes during the first 24 hours after ECMO initiation. Pulse pressure (systolic minus diastolic pressure) was categorized as: very low (<10mmHg), low (1029mmHg), moderate (30-44mmHg), and high (≥45mmHg). Multivariable logistic regression, controlling for baseline illness severity, operative characteristics, and left ventricle (LV) venting strategy, was performed for the association of pulse pressure with ABI. LV venting strategies included intra-aortic balloon pump (IABP), percutaneous ventricular assist device, right superior pulmonary vein, and left ventricle apex vents. Results: We collected 9,179 pressure measurements from 123 VA-ECMO patients (median age=63, 63% male), of which 41 (33%) experienced ABI. Demographics, baseline clinical characteristics, and pre-ECMO arterial blood gases were not significantly different between those with and without ABI. Those with ABI had a lower median pulse pressure than those without (20 mmHg vs. 32, p=0.038). In a multivariable model controlling for cannulation site, preECMO lactate, and left ventricle venting strategy, low (adjusted odds ratio/aOR=7.04, 95%CI: 1.72-28.82, p=0.007) and very low pulse pressure (aOR=5.14, 95%CI: 1.18-22.34, p=0.029) were associated with ABI (Figure 1). In a model with the same covariates, every 10-mmHg decrease in pulse pressure was associated with a 1.29 increased adjusted odds of ABI (95%CI: 1.00-1.65, p=0.047) (Figure 2). In a sensitivity analysis, adjusting for systolic BP yielded similar associations between pulse pressure and ABI, suggesting pulse pressure acts independently of BP in mediating ABI. Conclusions: Decreased pulsatility in the first 24 hours of VA-ECMO was associated with ABI. Special attention should be given to management practices which sustain sufficient pulse pressure early during ECMO. Figure 1. Forest plot for multivariable model of pulse pressure and acute brain injury (ABI), with the covariates of central cannulation, lactate on ECMO day 1, and left ventricle venting strategy. Covariates are not shown in the figure. Dots represent adjusted odds ratios and brackets represent 95% confidence intervals. Low and very low pulse pressure were associated with increased odds of ABI. This model had a C-index of 0.76. Figure 2. Multivariable logistic regression model with pulse pressure treated as a continuous variable, with the covariates of central cannulation, lactate on ECMO day 1, and left ventricle venting strategy. The adjusted relative odds of acute brain injury decrease as pulse pressure increases.

B-13 | Impella Cardiac Perforation Events - A Report from FDA MAUDE Database

Impella® device (Abiomed Inc., Danvers, MA, USA) is a non-pulsatile microaxial flow pump that continuously propels blood from the left ventricle (LV) to the ascending aorta to provide short-term mechanical circulatory support, for example in patients with cardiogenic shock. Although bleeding and vascular complications have been reported data on cardiac perforation are limited. We analyzed data from the Food and Drug Administration (FDA) Manufacturer and User Facility Device Experience (MAUDE) database to investigate this complication.

Parametric Numerical Study of Turbulent Airflow in a Wavy Channel Under Pulsatile Conditions

In the present work, a parametric numerical study is performed for a converging–diverging channel under pulsatile flow conditions. The sinusoidal velocity at the channel entrance provides the pulsatile flow condition. Simulations are performed for transient flow in the range of 0.001 − 0.5 for the Strouhal numbers, 3400 − 6500 for the Reynolds numbers, and 0.025 − 0.5 for the nondimensionalized amplitude values. The thermal–hydraulic performance is reported to compare pulsatile flow conditions with non-pulsatile conditions. The numerical results showed that the Nusselt number decreased as the Strouhal number and nondimensionalized amplitude values increased. In addition, an improvement in heat transfer is observed in pulsatile conditions for the Reynolds number range 3400–5200. It is understood that turbulent pulsatile airflow in a converging–diverging duct has a limited potential for heat transfer improvement in a specific range. The maximum thermal–hydraulic performance coefficient is found to be 1.17 for the Reynolds number of 3412 and for the Strouhal number of 0.001. It is concluded that pulsatile flow provides satisfactory improvement at lower Reynolds numbers than non-pulsatile flow. Moreover, pulsatile airflow in a converging–diverging duct has a limited potential for the heat transfer improvement in a specific range.

Monitoring free flaps and replanted digits via perfusion index - A proof of concept study.

Early detection and treatment of vascular complications in replanted digits is essential for the survival. The perfusion index (PI) represents a marker of peripheral perfusion as it shows the ratio of pulsatile to non-pulsatile blood flow. To evaluate the feasibility and applicability of the PI as a monitoring tool for free flaps and replanted digits by measuring the inter- and intraindividual changes in PI. Five patients were postoperatively monitored according to intern standards by hourly clinical evaluation. Additionally, a pulse oximeter with SET-technology® (Masimo Radial 7, Masimo Corporation, Irvine, USA) was added with a LNCS® Red TFA-1 SpO2 sensor (Masimo Corporation, Irvine, USA) and respectively a LNCS® Neo-3 neonatal finger clip to evaluate the perfusion via PI and SpO2. All patients showed sufficient perfusion in clinical controls. There was no detectable vascular complication during follow-up. Mean perfusion index was 0.93 with a median of 0.44. The patients showed a mean SpO2 of 90.59%with a median of 89.21%. Our results show a great intra- and interindividual range of PI and SpO2. SpO2 provided an even greater range than PI. Trends in intraindividual PI changes may be a promising monitoring tool for free flaps and replanted digits.

Soft Robotic Dynamic Cardiomyoplasty with Electrically Contractile Artificial Muscle (AHM)

<h3>Purpose</h3> Ventricular assist devices (VADs) have clinically evolved as a promising alternative for the treatment of end-stage heart failure. The greatest challenges of these devices still remain infections, bleedings and thromboembolic events. Moreover, non-pulsatile blood flow has led to new complications such as formation of arteriovenous malformations with subsequent bleeding in the gastro-intestinal tract and aortic valve regurgitation. Aim of our experimental study was the development of soft electrically contractile artificial muscles wrapped around the heart. This enables a physiological pulsatile flow of the heart and does not require anticoagulation, the main cause of major adverse cardiac and cerebrovascular events in VAD therapy as there is no direct blood contact between the artificial muscle and blood. <h3>Methods</h3> Silver coated nylon (SCN) conductive actuator filaments were fabricated, aligned in a braided fashion and linked together with silicone akin to human striated muscle. Wrapped in layers around lamb hearts with closed mitral valve as a heart sleeve in-vitro, the aortic pressure and contraction rate during upon electrical stimulation of the AHM with 32.5 V electricity was monitored. <h3>Results</h3> After a series of modifications and improvements, in analogy to the human heart stable pressures of 120 mmHg in systole, 80 mmHg in diastole and a mean stimulation rate was 84 /minute could be achieved. <h3>Conclusion</h3> This represents the first successful study demonstrating that an electrically contractile artificial muscle/soft robot can generate pressures and contraction rates necessary to support the left ventricle of the heart.

Impact of Statins on the Incidence of Gastrointestinal Bleeding Events Among Patients with Continuous Flow Left Ventricular Assist Devices

<h3>Purpose</h3> Patients with continuous flow left ventricular assist devices (CF-LVADs) are at an increased risk of gastrointestinal bleeding (GIB) events due to von Willebrand factor degradation, enhanced angiogenesis and endothelial dysfunction resulting from non-pulsatile flows of the device. LVAD patients also commonly receive statins for the primary or secondary prevention of cardiovascular disease. However, the impact of such therapy on the incidence of GIB is controversial. Importantly, literature regarding the impact of statins on GIB in LVAD patients is lacking. <h3>Methods</h3> This was a single-center, retrospective review of adult patients that underwent CF-LVAD implantation between May 2016 and January 2020. Patients were categorized based on statin use throughout the study period. The primary outcome was the composite of arteriovenous malformation (AVM) confirmed GIB and other major GIB events for up to 1-year post-LVAD implantation. Secondary outcomes included each of the components of the primary outcome, non-clinically relevant GIB, time to GIB, and frequency of GIB. Multivariable Cox regression was utilized to assess association between confounding variables and major GIB. <h3>Results</h3> Of the 123 patients who met inclusion criteria, 66 (54%) received statin therapy during the study period. No difference was observed in the primary outcome of major GIB between the statin and non-statin groups (21.2% vs. 12.3%, p=0.20). Similarly, AVM confirmed GIB (12.1% vs. 5.3%, p=0.20), other major GIB (9.1% vs. 7.0%, p=0.75), and non-clinically relevant GIB (3.0% vs. 1.8%, p=0.68) were similar between the two groups. Using a competing risk modeling, we observed no difference in the development of a major GIB (32.4% vs. 18.7%, p=0.14) or in the frequency of major GIB [1.5 (interquartile range, 1-2) vs. 1 (1-1), p=0.12] within 12 months of device implantation. Multivariable Cox regression revealed that older age and higher baseline creatinine were associated with an increased risk of GIB within 1-year of LVAD implantation (p<0.05 for both). <h3>Conclusion</h3> Among patients with CF-LVADs, there was a non-significant increase in the incidence of major GIB events with the use of statin therapy. Further long-term studies are needed to determine if statin use has a significant impact on the incidence of GIB events among this patient population.

Bicuspidalization of the Native Tricuspid Aortic Valve: A Porcine in Vivo Model of Bicuspid Aortopathy.

Objective: To examine early histologic changes in the aorta exposed to bicuspid flow.Material and Methods: A porcine bicuspid aortopathy model was developed by suturing aortic cusps. Of nine pigs, eight underwent sham surgery (n=3) or bicuspidalization (n=5); one was used as an intact control. Wall shear stress (WSS) was assessed by computational fluid dynamics (CFD). Animals were exposed to normal or bicuspid flow for 48 h and were then euthanized for histologic examinations.Results: No animal died intraoperatively. One animal subjected to bicuspidalization died of respiratory failure during postoperative imaging studies. Echocardiography showed the aortic valve area decreased from 2.52±1.15 to 1.21±0.48 cm2 after bicuspidalization, CFD revealed increased maximum WSS (10.0±5.2 vs. 54.0±25.7 Pa; P=0.036) and percentage area of increased WSS (>5 Pa) in the ascending aorta (30.3%±24.1% vs. 81.3%±13.4%; P=0.015) after bicuspidalization. Hematoxylin–eosin staining and transmission electron microscopy showed subintimal edema and detached or degenerated endothelial cells following both sham surgery and bicuspidalization, regardless of WSS distribution.Conclusion: A bicuspid aortic valve appears to increase aortic WSS. The endothelial damage observed might have been related to non-pulsatile flow (cardiopulmonary bypass). Chronic experiments are needed to clarify the relationship between hemodynamic stress and development of bicuspid aortopathy.

Effects of Pulsatile Flow on Phosphorylcholine Coated Oxygenator and Arterial Filter

Objective: We aimed to compare the effects of pulsatile/nonpulsatile flow on phosphorylcholine coated (PC) oxygenator fibers, arterial filters by using scanning electron microscope (SEM). Methods: Eleven patients were randomly divided into two groups, as; nonpulsatile and pulsatile flow groups (NP and P groups) by using PC oxygenators. The oxygenator fiber samples were examined under SEM to compare the thickness of absorbed blood proteins and amount of blood cells on the surface of oxygenators. Arterial filters were also analysed by SEM regarding the captured blood elements or particles. Results: The mean fiber thickness from the axial images were calculated as 46.9 m and 47.6 m at group P and NP respectively which is statistically insignificant. Evaluation of the blood samples that were extracted from the arterial filter bring out higher amount of fibrin network and blood cells on fibers at group NP. Conclusion: We concluded that there is lesser amount of blood components on the fibers of arterial filter at pulsatile flow. Coating of oxygenators is beneficial in case of surface biocompatibility and pulsatile perfusion develops lower amount of blood elements on arterial filter.

Fontan-associated liver disease.

Fontan-associated liver disease.

Pulsatile Perfusion during Cardiopulmonary Bypass: A Literature Review.

The use of cardiopulmonary bypass (CPB) in cardiac surgery has often been associated with postoperative organ dysfunction. Roller and centrifugal pumps produce non-pulsatile flow (NPF) by default, and this still is the most widely used mode of perfusion. The development of pulsatile pumps has allowed comparisons to be made with NPF. Pulsatile flow (PF) mimics the arterial pulse generated by the heart and is thought to be more physiological by some. This review aims to examine the proposed mechanisms behind the potential physiological benefits of PF during CPB and to summarize the current clinical evidence. MEDLINE and EMBASE were used to identify articles published over a 25 year period from 1995 to 2020. A literature review was conducted to determine the effects of PF on organ functions. A total of 44 articles were considered. Most of the articles published on PF were randomized controlled trials (RCTs). However, there was a wide variation in study methodology, method of pulse generation and how pulsatility was measured. Most of the evidence in favor of PF showed a marginal improvement on renal and pulmonary outcomes. In these studies, pulsatility was generated by an intra-aortic balloon pump. In conclusion, there is a lack of good quality RCTs that can inform on the short- and long-term clinical outcomes of PF. Further research is required in order to draw a conclusion with regards to the benefits of PF on organ function.

Thermal analysis of simultaneously evolving laminar pulsatile flow through two large parallel plates with time-dependent heat flux boundary conditions

Understanding unsteady convective heat transfer (UCHT) behavior of simultaneously evolving laminar pulsatile flow between two large parallel plates exposed to time-dependent thermal boundary conditions is the goal of this research. The time-dependent sinusoidal velocity waveform is applied at the entrance of the two large parallel plates exposed to time-dependent sinusoidal heat flux boundary conditions (TSHBC). The finite volume technique is used in the present work. The current results have been compared to the literature data under the same operating conditions and found to be in good concurrence. The influence of various parameters, for instance, amplitude, frequency, phase difference, heat flux ratio, and the Reynolds number on the transient Nusselt number, is investigated. An improvement in energy transfer is observed when the pulsatile flow between two large parallel plates with TSHBC than the non-pulsatile flow with a fixed heat flux type boundary. Furthermore, the energy transfer improvement is observed once the velocity and heat flux waveform frequency is equal. The applicability of the present work could be found in the solar heating system, cooling of electronic devices, etc., whereby a more robust understanding of the unsteady convective heat transfer could facilitate the design and develop an efficient system.

Arterial Pulsatility Augments Microcirculatory Perfusion and Maintains the Endothelial Integrity during Extracorporeal Membrane Oxygenation via hsa_circ_0007367 Upregulation in a Canine Model with Cardiac Arrest.

Background The impairment of microcirculation is associated with the unfavorable outcome for extracorporeal membrane oxygenation (ECMO) patients. Studies revealed that pulsatile modification improves hemodynamics and attenuates inflammation during ECMO support. However, whether flow pattern impacts microcirculation and endothelial integrity is rarely documented. The objective of this work was to explore how pulsatility affects microcirculation during ECMO. Methods Canine animal models with cardiac arrest were supported by ECMO, with the i-Cor system used to generate nonpulsatile or pulsatile flow. The sublingual microcirculation parameters were examined using the CytoCam microscope system. The expression of hsa_circ_0007367, a circular RNA, was measured during ECMO support. In vitro validation was performed in pulmonary vascular endothelial cells (PMVECs) exposed to pulsatile or nonpulsatile flow, and the expressions of hsa_circ_0007367, endothelial tight junction markers, endothelial adhesive molecules, endothelial nitric oxide synthases (eNOS), and NF-κB signaling activity were analyzed. Results The pulsatile modification of ECMO enhanced microcirculatory perfusion, attenuated pulmonary inflammation, and stabilized endothelial integrity in animal models; meanwhile, the expression of hsa_circ_0007367 was significantly upregulated both in animals and PMVECs exposed to pulsatile flow. In particular, upregulation of hsa_circ_0007367 stabilized the expressions of endothelial tight junction markers zonula occludens- (ZO-) 1 and occludin, followed by modulating the endothelial nitric oxide synthases (eNOS) activity and inhibiting the NF-κB signaling pathway. Conclusion The modification of pulsatility contributes to microcirculatory perfusion and endothelial integrity during ECMO. The expression of hsa_circ_0007367 plays a pivotal role in this protective mechanism.

Pulsatile versus nonpulsatile blood flow during cardiopulmonary bypass.

Pulsatile versus nonpulsatile blood flow during cardiopulmonary bypass.

Efficacy of Pulsatile Flow Perfusion in Adult Cardiac Surgery: Hemodynamic Energy and Vascular Reactivity.

Background: The role of pulsatile (PP) versus non-pulsatile (NP) flow during a cardiopulmonary bypass (CPB) is still debated. This study’s aim was to analyze hemodynamic effects, endothelial reactivity and erythrocytes response during a CPB with PP or NP. Methods: Fifty-two patients undergoing an aortic valve replacement were prospectively randomized for surgery with either PP or NP flow. Pulsatility was evaluated in terms of energy equivalent pressure (EEP) and surplus hemodynamic energy (SHE). Systemic (SVRi) and pulmonary (PVRi) vascular resistances, endothelial markers levels and erythrocyte nitric-oxide synthase (eNOS) activity were collected at different perioperative time-points. Results: In the PP group, the resultant EEP was 7.3% higher than the mean arterial pressure (MAP), which corresponded to 5150 ± 2291 ergs/cm3 of SHE. In the NP group, the EEP and MAP were equal; no SHE was produced. The PP group showed lower SVRi during clamp-time (p = 0.06) and lower PVRi after protamine administration and during first postoperative hours (p = 0.02). Lower SVRi required a higher dosage of norepinephrine in the PP group (p = 0.02). Erythrocyte eNOS activity results were higher in the PP patients (p = 0.04). Renal function was better preserved in the PP group (p = 0.001), whereas other perioperative variables were comparable between the groups. Conclusions: A PP flow during a CPB results in significantly lower SVRi, PVRi and increased eNOS production. The clinical impact of increased perioperative vasopressor requirements in the PP group deserves further evaluation.

The effect of pulsatile versus non-pulsatile flow during cardiopulmonary bypass on cerebral oxygenation: A randomized trial.

The present study aims to compare regional oxygen supply determined by Near-Infrared Spectroscopy in the course of pulsatile perfusion with non-pulsatile perfusion during cardiopulmonary bypass in patients undergoing valvular heart surgery. In this prospective randomized single-blinded trial, we enrolled adult subjects aged 18-65 years scheduled for elective valvular heart repair/replacement surgery with non-stenotic carotid arteries, employing a consecutive sampling method. Eligible patients were then randomly assigned in a 1:1 ratio to pulsatile or non-pulsatile perfusion during aortic cross-clamp. The primary outcome was regional cerebral oxygenation monitored by Near-Infrared Spectroscopy in each group. Seventy patients were randomly assigned, and each group comprised 35 patients. Mean age was 46.8 and 46.5 years in pulsatile and non-pulsatile groups, respectively. There were no significant between-group differences in regional cerebral oxygen saturation at different time points of cardiopulmonary bypass (p-value for analysis of variance repeated measures: 0.923 and 0.223 for left and right hemispheres, respectively). Moreover, no significant differences in regional cerebral oxygen saturation levels from baseline between pulsatile and non-pulsatile groups at all desired time points for the left (p = 0.51) and right (p = 0.22) hemispheres of the brain were detected. Pulsatile perfusion during cardiopulmonary bypass does not offer superior regional cerebral oxygenation measured by Near-Infrared Spectroscopy than non-pulsatile perfusion during cardiopulmonary bypass. Nonetheless, the efficacy of pulsatile flow in the subgroup of patients in whom cerebral blood flow is impaired due to carotid artery stenosis needs to be explored and evaluated by this method in future studies.

Abstract 9064: The Increase of Tissue Echogenicity as the Pre-State of Steam Pops During Radiofrequency Catheter Ablation

Introduction: Steam pops (SPs) during radiofrequency catheter ablation (RFA) using force sensing catheters are infrequent but represent a potential severe complication such as embolic stroke, cardiac perforation. SPs remains unpredictable, and unclear in detailed phenomenon. Methods: In an ex vivo, we set the bovine myocardium to 36 °C in a constant temperature bath and performed an experiment in a water tank that generated a non-pulsatile flow. RFA using irrigation catheter was applied at catheter-tissue contact force (CF) 5, 10, 20g, 30g, 40g, and 50g for 30sec. The increase of tissue echogenicity (increased echo brightness) observed by intracardiac echocardiographic images using ViewFlex™ Xtra and impedance during RFA were evaluated with and without SPs. Results: SPs phenomenon appeared in 48 out of 137 sites (35%), and the increased echo brightness during RFA was observed in 89 lesions (65%). All lesions with SPs showed increased echo brightness before SPs (6.4±6.1sec before SPs). Sites with SPs showed stronger CF (30.8±14.8g vs. 22.9±15.9g, p=0.0047), higher initial impedance (78±12Ω vs. 73±9Ω, p=0.0063), greater impedance drops in 5 seconds after the beginning of RFA (13±7Ω, vs. 6±5Ω, p&lt;0.0001), and earlier appearance of increased echo brightness (9.7±6.2 vs 17.4±6.3 sec, p&lt;0.0001). Among 89 lesions with increased echo brightness, sites with SPs showed greater impedance drops in 5 seconds after the beginning of RFA (13±7Ω, vs. 7±6Ω, P&lt;0.0001). In ROC curve analysis of the impedance drops in 5 seconds after the beginning of RFA (AUC, 0.81; sensitivity, 85%; specificity, 71%), optimal cut-off value of SPs was 7.6Ω, and SPs were not observed in lesions with the impedance drops of 3Ω or less. (Figure) Conclusions: The increase of tissue echogenicity observed by ICE images show the pre-state of all steam pops during RFA. Steam pops could be avoided by checking the impedance drop at the initial stage of RFA under ICE monitoring.

MITOCHONDRIAL OXYGENATION DURING CARDIOPULMONARY BYPASS: A PILOT STUDY

Introduction Cardiopulmonary bypass (CPB) is used during cardiac-surgery and provides oxygenated blood to the tissues. Ensuring adequate oxygenation is essential for the preservation of organ function during CPB. Both hypoxia and hyperoxia result in undesired outcomes and a narrow window for optimal oxygenation exists. Current perioperative monitoring techniques are not always sufficient to monitor adequate oxygenation, especially in high-risk patients. Near-infrared spectroscopy (NIRS) tissue oxygen measurement (StO2) is widely used to monitor tissue oxygenation but responds slowly to change. However, the novel non-invasive COMET-monitor measures the mitochondrial oxygen tension (mitoPO2) in the epidermis using the enhanced mitochondrial Protoporphyrin IX Triplet State Lifetime Technique (PpIX-TSLT). The mitoPO2 reflects the local balance between oxygen supply and consumption and provides an insight into the microcirculatory system [1]. This pilot study investigates the correlation between mitoPO2 versus StO2 and varying hemodynamic conditions during CPB and the development of acute kidney injury (AKI). Methods This single center observational study examined 41 cardiac-surgery patients requiring CPB. Six-hours pre-operatively, patients received a 5-aminolevulinc acid plaster on the upper arm to facilitate the mitoPO2 measurements. After induction of anesthesia, both the COMET and INVOS measurements were executed in 5-minute intervals throughout the procedure. To compare mitoPO2 with StO2, NIRS probes were placed near the COMET probe. Post-operatively, both measurements were stopped simultaneously, and the patients were observed until discharge for the development of AKI. Results NIRS data was available for 31 of the 41 patients. The median mitoPO2 at the start of surgery was 63.5 [40.0 – 74.8] mmHg and significantly decreased (p Discussion In contrast to StO2, the mitoPO2 decreased significantly during CPB time. A hemodilution study in pigs also demonstrated that mitoPO¬2 is more likely to change than StO2, which reacted slowly to change. The mitoPO2 also significantly decreased during non-pulsatile flow and increased once pulsatile flow returned, whilst the StO2 did not. This highlights the sensitivity of mitoPO2 to detect circulatory and microvascular changes early through the analysis of oxygen delivery on a cellular level. Lastly, the association found between the AKI and the non-AKI group in time spent below a mitoPO2 of 20 mmHg must be further examined in a well powered study. However, it highlights the potential of this technique to be an early predictor of ischemia.