Higher Pump Flow Research Articles

Characterizing the Racial Discrepancy in Hypoxemia Detection in Venovenous Extracorporeal Membrane Oxygenation: An Extracorporeal Life Support Organization Registry Analysis.

Skin pigmentation influences peripheral oxygen saturation (SpO2) compared to arterial saturation of oxygen (SaO2). Occult hypoxemia (SaO2 ≤ 88% with SpO2 ≥ 92%) is associated with increased in-hospital mortality in venovenous-extracorporeal membrane oxygenation (VV-ECMO) patients. We hypothesized VV-ECMO cannulation, in addition to race/ethnicity, accentuates the SpO2-SaO2 discrepancy due to significant hemolysis. Adults (≥ 18years) supported with VV-ECMO with concurrently measured SpO2 and SaO2 measurements from over 500 centers in the Extracorporeal Life Support Organization Registry (1/2018-5/2023) were included. Multivariable logistic regressions were performed to examine whether race/ethnicity was associated with occult hypoxemia in pre-ECMO and on-ECMO SpO2-SaO2 calculations. Of 13,171 VV-ECMO patients, there were 7772 (59%) White, 2114 (16%) Hispanic, 1777 (14%) Black, and 1508 (11%) Asian patients. The frequency of on-ECMO occult hypoxemia was 2.0% (N = 233). Occult hypoxemia was more common in Black and Hispanicpatients versus White patients (3.1% versus 1.7%, P < 0.001 and 2.5% versus 1.7%, P = 0.025, respectively). In multivariable logistic regression, Black patients were at higher risk of pre-ECMO occult hypoxemia versus White patients (adjusted odds ratio [aOR] = 1.55, 95% confidence interval [CI] = 1.18-2.02, P = 0.001). For on-ECMO occult hypoxemia, Black patients (aOR = 1.79, 95% CI = 1.16-2.75, P = 0.008) and Hispanic patients (aOR = 1.71, 95% CI = 1.15-2.55, P = 0.008) had higher risk versus White patients. Higher pump flow rates (aOR = 1.29, 95% CI = 1.08-1.55, P = 0.005) and on-ECMO 24-h lactate (aOR = 1.06, 95% CI = 1.03-1.10, P < 0.001) significantly increased the risk of on-ECMO occult hypoxemia. SaO2 should be carefully monitored if using SpO2 during ECMO support for Black and Hispanic patients especially for those with high pump flow and lactate values at risk for occult hypoxemia.

Associations of cephalad drainage in neonatal veno-venous ECMO – A mixed-effects, propensity score adjusted retrospective analysis of 20 years of ELSO data

BackgroundNeurologic complications can occur during neonatal Veno-Venous (VV) ECMO. The addition of a cephalad drainage cannula (i.e., VVDL+V) to dual lumen cannulation (i.e., VVDL) has been advocated to reduce such complications, but previous studies have presented mixed results. MethodsData from the ECMO Registry of the Extracorporeal Life Support Organization was used to extract all neonates (≤28 days old) who underwent VV ECMO for respiratory support between 2000 and 2019. Primary outcomes were mortality, conversion to Veno-Arterial (VA) ECMO, pump flows, and complications. A mixed-effects, propensity score adjusted analysis was performed. Results4,275 neonates underwent VV ECMO, 581 (13.6%) via VVDL+V cannulation, and 3,694 (86.4%) via VVDL. On unadjusted analyses, VVDL+V patients had higher rates of mortality (25.5% vs 19.0%, p<0.001), conversion to VA ECMO (14.5% vs 4.1%, p<0.001), and higher pump flows at 4 h from ECMO initiation (112.7 vs 105.5 mL/Kg/min, p<0.001), but lower at 24 h (100.3 vs 104.0 mL/Kg/min, p = 0.004), and a higher proportion of them experienced hemorrhagic (29.3% vs 18.3%, p<0.001), cardiovascular (60.8% vs 45.8%, p<0.001), and mechanical (42.5% vs 32.6%, p<0.001) complications compared to VVDL patients. After adjusting for propensity scores and the multi-level nature of ELSO data, there were no differences in neurologic outcomes, pump flows, or mortality. Rather, VVDL+V cannulation was associated with higher rates of conversion to VA ECMO (adjusted odds ratio [AOR] 43.3, 95% CI 24.3 – 77.4, p<0.001), and increased mechanical (AOR 2.2, 95% CI 1.6 – 3.0, p<0.001) and hemorrhagic (AOR 2.0, 95% CI 1.4 – 3.0, p<0.001) complications. ConclusionsIn this analysis, VVDL+V cannulation was not associated with any improvement in neurologic outcomes, pump flows, or mortality, but was rather associated with higher rates of conversion to Veno-Arterial ECMO, mechanical, and hemorrhagic complications.

Risk factors for postoperative delirium on oxygen delivery-guided perfusion

BackgroundStudies have demonstrated the efficacy of oxygen delivery-guided perfusion (ODGP) in preventing postoperative acute kidney injury, but the benefit of ODGP for delirium has not been confirmed. We retrospectively investigated the risk factors for postoperative delirium in patients who underwent ODGP (with oxygen delivery index [DO2i] > 300 mL/min/m2).MethodsConsecutive patients who underwent on-pump cardiovascular surgery with ODGP from January 2018 to December 2020 were retrospectively analyzed. In addition to examining patients’ DO2i during cardiopulmonary bypass (CPB), we quantified the two primary DO2 components-hematocrit (Hct) and pump flow. Delirium was defined based on the Intensive Care Delirium Screening Checklist (ICDSC). Patients were divided into three groups: no delirium (ICDSC score = 0), subsyndromal delirium (ICDSC score = 1–3), and clinical delirium (ICDSC score ≥ 4).ResultsMultivariate analysis identified only the number of red blood cell (RBC) units transfused, intubation time, and the cumulative time below the Hct threshold of 25% as predictive factors of postoperative delirium. Although patients with higher ICDSC scores had greater hemodilution during CPB, ODGP resulted in a higher pump flow, and DO2i was maintained above 300 mL/min/m2, with no significant difference between the three groups.ConclusionsA low Hct level during CPB with ODGP, the number of RBC units transfused, and intubation time were associated with postoperative delirium. Further investigations are needed to determine the ability of ODGP to prevent low Hct during CPB.

Experimental investigation of the effect of hydrogen recirculation on the performance of a proton exchange membrane fuel cell

The hydrogen recirculation in proton exchange membrane fuel cell (PEMFC) is recommended for the hydrogen supply of PEMFC, and hydrogen ejectors are gradually being used in fuel cell vehicles due to low noise and low energy consumption. However, there is a lack of discussion about the influence of recirculation rate on the stack. Due to passive regulating mechanism of the ejectors, a miniature speed-adjustable peristaltic pump is used to simulate the hydrogen ejector in this study to investigate the effect of hydrogen recirculation on the performance of PEMFC stack. Experiments are conducted under different pump flow rates. The stack with hydrogen recirculation is proven to have better performance, but over high pump flow rate can lead to hydrogen shortage. It is interesting to find that the flow rate fluctuation of hydrogen inlet affects the stability of stack performance, and pressure drop and recovery time during purge process are proposed as effective indicators for performance analysis. Finally, pump flow rates between 60 ml/min and 105 ml/min are defined as “effective area”. Based on the analysis of effective indicators, keeping at “effective area” is further proved to improve the performance of the stack, which is also useful to design hydrogen recirculation.

Factors Determining Continuous Infusion Aerosol Delivery During Mechanical Ventilation.

Continuous nebulization of prostacyclins and albuterol by infusion pump during mechanical ventilation evolved as a popular off-label treatment for severe hypoxemic respiratory failure and asthma. Most institutions use a vibrating mesh nebulizer. A new breath-enhanced jet nebulizer is a potential alternative. This study was designed to compare these devices to better define factors influencing continuous infusion aerosol delivery. Device function, ventilator settings, and infusion pump flow were studied invitro. Using a bench model of adult mechanical ventilation, radiolabeled saline was infused at6 flows (1.5-12mL/h) into test nebulizers; 4 examples of each were used in rotation to test device reproducibility. Four breathing patterns with duty cycles (percentage of inspiratory time) ranging from0.13 to0.34 were tested. The vibrating mesh nebulizer was installed on the "dry" side of the heated humidifier (37°C). The breath-enhanced jet nebulizer, installed on the "wet" side, was powered by air at3.5L/min and50psi. Infusion time was1h. Inhaled mass of aerosol was collected on a filter at the airway opening. Inhaled mass was expressed as the percentage of the initial syringe radioactivity delivered per hour. Radioactivity deposited in the circuit was measured with a gamma camera. Data were analyzed with multiple linear regression. Variation in inhaled mass was significantly explained by pump flow and duty cycle (R20.92) and not by nebulizer technology. Duty cycle effects were more apparent at higher pump flow. Vibrating mesh nebulizers failed to nebulize completely in 20% of the test runs. Mass balance indicated that vibrating mesh nebulizers deposited 15.3% in the humidifier versus 0.2% for breath-enhanced jet nebulizer. Aerosol delivery was determined by infusion pump flow and ventilator settings with comparable aerosol delivery between devices. The breath-enhanced jet nebulizer was more reliable than the vibrating mesh nebulizer;10-12mL/h was the maximum infusion flow for both nebulizer technologies.

Hydration behavior of chia seed and spray drying of chia mucilage

Chia seeds (Salvia hispanica), rich in omega-3 fatty acids, were soaked in water with different seed to water ratios at 60°C for 10 hr. Mucilage was extracted using a stirrer at 2,000 rpm for 6 hr and centrifuged. Total soluble solids of collected gel was increased to 1% using maltodextrin and homogenized. Chia seed mucilage powder was produced by using laboratory-scale spray dryer at various temperatures, feed flow rates, and air flow rates. Effect of spray drying air temperature, feed flow rate, and air flow rate on chia mucilage powder cyclone recovery was studied to find the best combination of spray drying parameters to get high cyclone recovery. Seed to water ratio of 1:30 gave reasonable hydration yield with minimum water leftover. Combination of low drying air temperature, high pump flow, and high air flow (150°C, 475 ml/h, 54 m3/h) gave good cyclone recovery of chia seed mucilage powder. Practical applications Aim of this study is to produce chia mucilage powder using spray drying. Chia mucilage powder is made successfully through spray drying technique using very low quantity of maltodextrin even (to adjust mucilage to 1 °Brix only). However, maltodextrin does not give any merit to the resultant spray dried product, generally. Best combination of spray drying parameters were 150°C, 475 ml/h and 54 m3/h. They yielded chia seed mucilage powder cyclone recovery of 19.33%. With these spray drying process parameters, it is commercially viable to produce chia mucilage powder with low maltodextrin incorporated. The developed spray dried chia seed mucilage powder is white in color and suitable for all industrial applications in preparing food products, namely, bread, energy bars, tortilla chips, cake mixes, omega-3 enriched ready-to-eat cereal, chia flakes ready-to-eat cereal, omega-3 enriched pasta, chia pasta, muffins, cookies, snack bars, fabricated chips, energy drinks, etc.

Flow, turbulence and potential droplet break up mechanisms in an in-line Silverson 150/250 high shear mixer

Angle resolved 2-D PIV measurements were performed to characterise the flow and turbulence as well as indicate potential droplet break up mechanisms in an in-line Silverson 150/250 high shear mixer, using water as the working fluid in the turbulent regime (120,000 < Re < 420,000). Distributions of Reynolds stresses, turbulent kinetic energy (TKE), and energy dissipation rates (ε) were examined. The regions of interest (ROI) were: A – jet emanating from a stator hole and B – the rotor swept volume. The complex flow pattern can cause droplet break up under either laminar or turbulent conditions depending on the characteristic length and velocity in the ROI; break up due to turbulence in the inertial regime was identified as the dominant mechanism in this study. Evaluated energy dissipation rates obtained assuming either a fully resolved velocity field (DE) or using the Smagorinsky closure model (SGS) were found to depend on rotor speed e.g. ε∝Nb with b exponents of 1.59–1.90 (DE) and 2.42–2.84 (SGS), which are comparable to existing literature values. The influence on ε of the rotor speed, external pump flow rate and induced backpressure on the mixer outlet, were also investigated. Analysis revealed that the intensity and propensity of ε is dictated by the dominant flow in the mixing head e.g. radial flow at high pump flow rates, prominent in ROI A or tangential flow at high rotor speeds and when backpressure is induced, prominent in ROI B.

Flow Pulsatility of Heart Pump: State Space Modeling and Control

In this work, a physiological control strategy using full state feedback (FSF) control method is developed to drive mechanical circulatory support (MCS). This strategy is utilized a validated state space pump model to implement the controller and to track the desired reference flow. The developing strategy is assessed using a software model of the hemodynamical cardiovascular system interacted with left ventricular assist device in different physiological conditions ranging from rest to exercise scenarios. During these scenarios, heart failure disease simulates by changing the hemodynamical parameters of total blood volume, heart rate, cardiac contractility, and systemic peripheral resistance. The results are numerically observed during postural changes. The rate of change in physiological variables showed that the control method can track the reference pump flow with minimal error within acceptable clinical range to prevent suction with lower pump flow (3.35 L/min) and over perfusion with higher pump flow (5.2 L/min).

Conventional or minimized cardiopulmonary bypass support during coronary artery bypass grafting? - An analysis by means of perfusion and body mass index.

The use of minimized cardiopulmonary bypass support to reduce the side effects of extracorporeal circulation is still contradictorily discussed. This study compares perfusion operated by conventional (CCPB) and minimized (MCPB) cardiopulmonary bypass support during coronary artery bypass grafting (CABG). This study includes the data of 5164 patients treated at our department between 2004 and 2014. Tissue perfusion during cardiopulmonary bypass support and cardiac arrest was assessed by means of body mass index, hemodilution, blood pressure with corresponding pump flow and venous oxygen saturation, serum lactate, and serum pH. Hemodilution was more pronounced after CCPB: hemoglobin had dropped to 4.47±0.142g/dL after CCPB and to 2.77±0.148 g/dL after MCPB (P=0.0022). Despite the higher pump flow in conventional circuits (4.86-4.95L/min vs. 4.1-4.18L/min), mean blood pressure was higher during minimized bypass support (53±10 vs. 56±13mmHg [aortic clamping], 57±9 vs. 61±12mmHg [34°C], 55±9 vs.59±11mmHg [aortic clamp removal], P<0.0001) at all time points. Venous oxygen saturation remained on comparable levels of >70% during both conventional and minimized cardiopulmonary bypass support. The increase in serum lactate was more pronounced after CCPB (8.98±1.28 vs. 3.66±1.25mg/dL, P=0.0079), corresponding to a decrease in serum pH to acidotic levels (7.33±0.06 vs. 7.35±0.06, P<0.0001). These effects were evident in all BMI ranges. Minimized cardiopulmonary bypass support provides efficient perfusion in all BMI ranges and is thus equivalent to conventional circuits.

A Novel Pulse Damper for Endothelial Cell Flow Bioreactors.

Peristaltic pumps (PP) are favored in flow bioreactors for their non-contact sterile design. But they produce pulsatile flow, which is consequential for the cultured cells. A novel pulse damper (PD) is reported for pulsatility elimination. ThePD designwas implemented to target static pressure pulsatility and flow rate (velocity) pulsatility from a PP. Damping effectiveness was tested in a macro-scale, closed-loop recirculating bioreactor mimicking the aortic arch at flow rates up to (4L/min). Time-resolved particle image velocimetry was used to characterize the velocity field. Endothelial cells (EC) were grown in the bioreactor, and subjected to continuous flow for 15min with or without PD. The PD was found to be nearly 90% effective at reducing pulsatility. The EC exposed to low PP flow without PD exhibited distress signaling in the form of increased ERK1/2 phosphorylation (2.5 folds) when compared to those exposed to the same flow with PD. At high pump flow without PD, the cells detached and did not survive, while they were perfectly healthy with PD. Flow pulsatility from PP causes EC distress at low flow and cell detachment at high flow. Elevated temporal shear stress gradient combined with elevated shear stress magnitude at high flow are believed to be the cause of cell detachment and death. The proposed PD design was effective at minimizing the hemodynamic stressors in the pump's output, demonstrably reducing cell distress. Adoption of the proposed PD design in flow bioreactors should improve experimental protocols.

Haemolysis as a first sign of thromboembolic event and acute pump thrombosis in patients with the continuous-flow left ventricular assist device HeartMate II.

BackgroundDespite advances in pump technology, thromboembolic events/acute pump thrombosis remain potentially life-threatening complications in patients with continuous-flow left ventricular assist devices (CF-LVAD). We sought to determine early signs of thromboembolic event/pump thrombosis in patients with CF-LVAD, which could lead to earlier intervention.MethodsWe analysed all HeartMate II recipients (n = 40) in our centre between December 2006 and July 2013. Thromboembolic event/pump thrombosis was defined as a transient ischaemic attack (TIA), ischaemic cerebrovascular accident (CVA), or pump thrombosis.ResultsDuring median LVAD support of 336 days [IQR: 182–808], 8 (20 %) patients developed a thromboembolic event/pump thrombosis (six TIA/CVA, two pump thromboses). At the time of the thromboembolic event/pump thrombosis, significantly higher pump power was seen compared with the no-thrombosis group (8.2 ± 3.0 vs. 6.4 ± 1.4 W, p = 0.02), as well as a trend towards a lower pulse index (4.1 ± 1.5 vs. 5.0 ± 1.0, p = 0.05) and a trend towards higher pump flow (5.7 ± 1.0 vs. 4.9 ± 1.9 L m, p = 0.06).The thrombosis group had a more than fourfold higher lactate dehydrogenase (LDH) median 1548 [IQR: 754–2379] vs. 363 [IQR: 325–443] U/L, p = 0.0001). Bacterial (n = 4) or viral (n = 1) infection was present in 5 out of 8 patients. LDH > 735 U/L predicted thromboembolic events/pump thrombosis with a positive predictive value of 88 %.ConclusionsIn patients with a CF-LVAD (HeartMate II), thromboembolic events and/or pump thrombosis are associated with symptoms and signs of acute haemolysis as manifested by a high LDH, elevated pump power and decreased pulse index, especially in the context of an infection.

A facile method to functionalize engineering solid membrane supports for rapid and efficient oil–water separation

A facile and low-cost method is developed to functionalize engineering metal membrane supports, such as stainless steel (SS), with epoxy-containing polymer poly(glycidyl methacrylate) (PGMA) to produce a versatile and universal platform for subsequent surface modification. With a PGMA anchoring layer, we have demonstrated that hydrogel particles, such as polyacrylamide-co-poly(acrylic acid) (PAM-co-PAA), can be subsequently grafted to form functional polymer membranes for rapid and efficient oil–water separation. By contact angle and AFM measurement, we have confirmed that PAM-co-PAA hydrogel particle layer grafted on a PGMA-modified SS surface exhibits excellent selectivity as required for liquid–liquid separation, showing high affinity to water but not to oils as an ideal membrane for oil–water separation. To evaluate the separation efficiency, a simple flow-through device is employed to separate free-floating oil from water in the mixture of varied initial oil volume fraction and oil composition. Under substantially high pump flow rate up to 1.3 L/min, PAM-co-PAA hydrogel treated SS mesh can achieve excellent separation efficiency with less than 5% oil or water in the respective filtrate at the flux of as high as 540 m3/(m2·h) and retentate at the flux of 1.95 m3/(m2·h). This separation efficiency is better than, or comparable to, the maximal performance achieved using conventional gravity methods at much lower flow rate. Similar approach could be also adapted to graft superhydrophobic and superoleophilic polymer membranes with PGMA-treated engineering support to separate water from oil.

Unsuccessful Trans-catheter Aortic Valve Implantation (TAVI) for acquired native aortic valve insufficiency in an end-stage heart failure patient with Left Ventricular Assist Device (LVAD)

Introduction: Aortic valve insufficiency (AI) is associated with left ventricular assist device (LVAD) implantation. We report a patient with end-stage heart failure secondary to hypertrophic cardiomyopathy on LVAD support who developed severe AI. He was initially treated by TAVI, which was complicated by CoreValve migration into the left ventricular outflow tract (LVOT) post-procedure. He subsequently underwent emergency sternotomy with explantation of the CoreValve and aortic valve stitch closure. Case report description: A 49-year-old male patient with hypertrophic cardiomyopathy developed AI 10 months after Heartmate II LVAD implantation as a bridge to heart transplant. He presented with increasing dyspnea. A right heart study demonstrated a cardiac output of 2.9L/min with a corresponding high LVAD pump flow. Transesophageal echocardiogram confirmed severe AI. He was planned for open surgical aortic valve closure. Prior to surgery, he developed cardiac decompensation and pneumonia, which necessitated ICU care and rendered him high risk for surgery. In view of heart failure symptoms refractory to medical therapy, he underwent TAVI via the transfemoral approach. Post-deployment, transesophageal echocardiogram and fluoroscopy demonstrated satisfactory CoreValve position, and mild paravalvular AI. Two hours post procedure, the patient became hypotensive, and bedside echocardiogram showed severe AI and migration of the CoreValve towards the LVOT. He underwent emergency sternotomy with explantation of the CoreValve and suture closure of the aortic valve. Discussion: AI can occur in patients with long-standing LVAD. However, there is no consensus on the optimal management of AI in LVAD patients. Options include medical management, suture repair or closure of the native valve, prosthetic valve replacement, and patch closure of the LVOT. Case reports of successful percutaneous treatment of AI in LVAD patients using TAVI and Amplatzer devices have also been previously described. The use of TAVI in our patient was complicated by migration of the CoreValve into the LVOT shortly after the procedure. Likely contributory factors include suboptimal anchoring of the prosthesis due to absence of aortic root and valve calcification and the continuous suction by the continuous flow LVAD in the left ventricular apex. Conclusions: AI remains a significant complication of long term LVAD support. Surgical aortic valve closure remains the definitive treatment for this problem. While percutaneous therapy remains a potentially viable option, further studies on the feasibility of each of these methods in LVAD patients is required.

Transpulmonary thermodilution measurements are not affected by continuous veno-venous hemofiltration at high blood pump flow

To assess whether continuous veno-venous hemofiltration (CVVH) with high blood pump flow alters the measurements of cardiac index (CI), global end-diastolic volume indexed (GEDVI), and extravascular lung water indexed (EVLWI) performed by transpulmonary thermodilution. Sixty-nine patients were included if they were monitored by a PiCCO2 device and received CVVH through a femoral (n = 62) or an internal jugular (n = 7) dialysis catheter. The blood pump flow was set at 250 mL/min (n = 31) or 350 mL/min (n = 38) and the filtration flow at 6,000 mL/h. A first set of data was collected with a first transpulmonary thermodilution (TD(on)). The blood pump was stopped and the continuous CI derived from pulse contour analysis was recorded (PC(off)). A second data set (TD(off)) was collected before and a last one (TD(on-last)) after restarting the blood pump. [Formula: see text], [Formula: see text], [Formula: see text] , and [Formula: see text] were not significantly different in patients with a femoral dialysis catheter (3.49 ± 0.96, 3.51 ± 0.96, 3.51 ± 0.99, and 3.44 ± 1.00 L min(-1) m(-2), respectively). This was observed with a blood pump flow at 350 mL/min and at 250 mL/min. In these patients with a femoral dialysis catheter, GEDVI did not significantly change when the blood pump was stopped. EVLWI significantly decreased when the blood pump was stopped but to a non-clinically relevant extent (-0.3 ± 0.8 mL/kg). No significant changes in CI, GEDVI, and EVLWI were observed in patients with an internal jugular dialysis catheter over the study period. CVVH with a high blood flow pump does not alter the transpulmonary thermodilution measurements of CI, GEDVI, and EVLWI.

Resuscitation after prolonged cardiac arrest: effects of cardiopulmonary bypass and sodium–hydrogen exchange inhibition on myocardial and neurological recovery☆

To determine if cardiopulmonary bypass (CPB), together with inhibition of the sodium-hydrogen exchanger (NHE), limits myocardial and neurological injury and improves recovery after prolonged (unwitnessed) cardiac arrest (CA), as NHE inhibition improved recovery after deep hypothermic circulatory arrest. Twenty-seven pigs (31-39 kg) underwent 15 min of prolonged (no-flow) CA followed by 10 min of cardiopulmonary resuscitation-advanced life support (CPR-ALS). Subjects with restoration of spontaneous circulation (ROSC) during CPR-ALS received either no drug (n=6) or an inhibitor of the NHE (HOE-642; n=5). In the 16 unsuccessfully resuscitated animals, peripheral normothermic CPB was instituted, and either no drug (n=9) or similar HOE-642 (n=7) therapy started. Hemodynamic data, a species-specific neurological deficit score (0=normal to 500=brain death), and mortality were recorded at 24h, and biochemical variables of organ injury measured. CPR-ALS restored ROSC in 41% (11/27) of animals, but was unsuccessful in 59% (16/27) that required CPB. Without CPB, HOE-642 increased cardiac index and decreased vascular resistance; with CPB, HOE-642 caused higher pump flows (3.4±0.6 l min(-1)m(-2) vs 2.5±0.7 l min(-1)m(-2); p<0.001) and higher post-arrest cardiac index; but animals required more vasopressors (p=0.019) from drug-induced vasodilation. No differences between biochemical markers of oxidative and organ injury and overall 24-h mortality (20%) were found between groups. Neurological score was improved at 24h compared with 4h only after HOE-642 treatment with (150±34 vs 220±43; p=0.003) or without CPB (162±39 vs 238±48; p≤0.001), but failed to reach statistical difference with respect to the untreated group. CPB is an effective resuscitative tool to treat prolonged CA but there is limited improvement of neurological function. NHE inhibition augments cardiac and neurological function, but its effect was less pronounced than in other studies.

Effect of increased pump flow on hepatic blood flow and systemic inflammatory response following on-pump coronary artery bypass grafting

Reduced organ perfusion during cardiopulmonary bypass (CPB) is responsible for morbidity associated with cardiac surgery. Non-pulsatile flow and hypothermia during CPB have been shown to cause reduced perfusion. During CPB, cardiac output is directly proportional to the pump flow rate. Therefore, we hypothesised that increasing pump flow during hypothermic CPB would improve organ perfusion and reduce the inflammatory response in the post-operative period. Ethics committee approval was obtained. Twelve consecutive patients with good or moderate left ventricular function undergoing elective or inpatient coronary artery bypass grafting were included in the study after obtaining informed consent. Patients were randomised to receive either normal flow or higher pump flow (20% more than the usual flow during hypothermia). Hepatic blood flow, cytokines such as interleukins 1β, 6, 8, 10 and 12, tumour necrosis factor-α and complements C3a, C4a and C5a were measured during the peri-operative period. Data were analysed using SPSS (ver.15). Categorical data were compared using the chi-square test and trends in cytokines were compared using a repeated measures ANOVA test. Both the groups were similar in pre- and peri-operative variables. Hepatic blood flow almost doubled in the high-pump-flow group following an increase in the flow rate during hypothermia(p=0.026). The release of serum complement IL-6 and 8 appeared to be reduced in the high-flow group; however, the difference did not reach statistical significance. Higher pump flows during hypothermic CPB increase hepatic blood flow. There was a trend towards attenuation of post-operative inflammatory response; however, larger studies will be needed to confirm these findings.

Impact of the Postpump Resistance on Pressure-Flow Waveform and Hemodynamic Energy Level in a Neonatal Pulsatile Centrifugal Pump

This study tested the impact of different postpump resistances on pulsatile pressure-flow waveforms and hemodynamic energy output in a mock extracorporeal system. The circuit was primed with a 40% glycerin-water mixture, and a PediVAS centrifugal pump was used. The pre- and postpump pressures and flow rates were monitored via a data acquisition system. The postpump resistance was adjusted using a Hoffman clamp at the outlet of the pump. Five different postpump resistances and rotational speeds were tested with nonpulsatile (NP: 5000 RPM) and pulsatile (P: 4000 RPM) modes. No backflow was found when using pulsatile flow. With isoresistance, increased arterial resistances decreased pump flow rates (NP: from 1,912 ml/min to 373 ml/min; P: from 1,485 ml/min to 288 ml/min), increased postpump pressures (NP: from 333 mm Hg to 402 mm Hg; P: from 223 mm Hg to 274 mm Hg), and increased hemodynamic energy output with pulsatile mode. Pump flow rate correlated linearly with rotational speed (RPMs) of the pump, whereas postpump pressures and hemodynamic energy outputs showed curvilinear relationships with RPMs. The maximal pump flow rate also increased from 618 ml/min to 4,293 ml/min with pulsatile mode and from 581 ml/min to 5,665 ml/min with nonpulsatile mode. Results showed that higher postpump resistance reduced the pump flow range, and increased postpump pressure and surplus hemodynamic energy output with pulsatile mode. Higher rotational speeds also generated higher pump flow rates, postpump pressures, and increased pulsatility.

Methylene Blue-induced Methemoglobinemia during Cardiopulmonary Bypass? A Case Report and Literature Review

The guanylate cyclase (GC) and inducible nitric oxide (iNOS) inhibitor methylene blue (MB) has been used in cardiac surgery patients for the treatment of a variety of conditions. Methylene blue has been successfully used for the prevention and treatment of vasoplegia syndrome (VS) in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). Vasoplegia syndrome occurs in up to 10% of cardiac surgery patients and is associated with poor clinical outcomes. Vasoplegia syndrome is described along with the results of studies that have shown benefits of MB in the treatment of VS. These studies include the use of MB prior to CPB, when added to the CPB prime and when given into the CPB circuit during the operation. We report a case of emergency CPB on a 55-year-old male with bacterial endocarditis, scheduled for an AVR/MVR who arrested on arrival to the operating room. Once on CPB the patient developed a profound hypotension despite normal to high pump flows, with low systemic vascular resistance (SVR), which was refractory to vasopressors—consistent with a diagnosis of VS. Unbeknownst to the perfusionist, the patient was treated with MB which was immediately followed by an apparent sudden arterial desaturation, despite oxygenator ventilation with 100% oxygen (O2), and development of severe metabolic acidosis. Troubleshooting the cause of the apparent desaturation and eventual diagnosis of a false indication of arterial oxygen desaturation and methemoglobinemia (MHgb) due to MB injection is described. Methemoglobinemia is explained as well as its presentation and treatment with MB. The importance of intraoperating room communication and knowledge of drug effects are discussed.

A rat model of cardiopulmonary bypass with cardioplegic arrest and hemodynamic assessment by conductance catheter technique

Cardiopulmonary bypass (CPB) is known to induce systemic inflammation and cardiac dysfunction associated with a significant morbidity. Aim of the study was to develop an in vivo model of rat CPB with hypothermic cardiac arrest and the use of cardioplegia. The CPB circuit consisted of a venous reservoir, membrane oxygenator, heat exchanger, and roller pump. CPB was instituted in adult male Wistar rats (400-500 g) for 60 min at a flow rate of 120 ml x kg(-1) x min(-1), including 15 min cooling to 32 degrees C, 30 min cardiac arrest with the use of cold crystalloid cardioplegia after aortic cross clamping, and 15 min of reperfusion and rewarming to 37 degrees C. Arterial blood pressure (MAP) and heart rate (HR) were monitored, arterial blood samples were analyzed. Left ventricular (LV) function parameters were assessed by intraventricular conductance catheter. Important technical aspects are: ventilation is required during partial bypass; anticoagulation should be performed immediately prior to CPB to reduce blood loss; active suction on venous drainage allows higher pump flows; and the small priming volume of the extracorporeal circuit (8 ml) avoids the need for donor blood. MAP remained stable prior to and during CPB.MAP and HR were significantly decreased 60 min after weaning from bypass. Hct was significantly lowered after hemodilution, but remained stable during CPB and 60 min after weaning from bypass. BE and pH remained stable throughout the experiment.Without inotropic support diastolic and systolic LV function parameters were impaired after 30 min of cardioplegic arrest followed by 15 min of reperfusion. Myocardial TNF-alpha mRNA levels were slightly increased (1.28-fold, p = 0.71), and IL-6 mRNA was significantly increased in the cardioplegia group (90.3-fold, p = 0.001). Both IL-6 and TNF-alpha plasma levels were significantly elevated in the cardioplegia group (TNF-alpha: 4.6-fold increase,p < 0.05; IL-6: 426.8-fold increase, p < 0.001). We have developed a rat CPB with mild hypothermic cardioplegic arrest. This rodent model is suitable to study clinically relevant problems related to CPB,myocardial protection and systemic inflammation.

Completely pulsatile high flow circulatory support with a constant-speed centrifugal blood pump: mechanisms and early clinical observations

Various types of rotary blood pumps (axial flow, centrifugal) have been introduced into clinical use recently. These pumps have different pressure-flow characteristics, and some investigators have noted that a limited pump flow rate and less pulsatility are the problems with the axial flow devices. A new implantable centrifugal blood pump was developed that has an extremely flat pressure-flow curve and is able to produce a significantly high pump flow rate of 20 l/min at a low pressure of 10-30mmHg. When the pressure difference between the left ventricle and aorta decreases during systole, an instant high peak flow is achieved, which results in a higher peak pressure in the aorta (systolic pressure). During the diastolic phase, the left ventricle-aorta pressure difference increases to maximum, and the pump flow rate decreases to minimum. Thus, the pump flow rate becomes completely pulsatile, and the high peak flow provides a higher mean pump flow rate. This pump was applied to two end-stage heart failure patients (dilated cardiomyopathy, New York Heart Association (NYHA) class IV, inotrope-dependent). The pump was observed to provide completely pulsatile high flow assistance of 6-9 l/min with a constant pump speed. Both patients are currently in NYHA class I after 1 year on the device with no major adverse events. The new centrifugal blood pump provides completely pulsatile high-flow circulatory support with a constant pump speed, which solves the current clinical problems with rotary blood pumps.