Extracorporeal Circulation Procedures Research Articles

BIO2: Microcirculation Perfusion is Impaired up to 24 Hours after Veno-arterial Extracorporeal Circulation.

Extracorporeal circulation (ECC) procedures, such as extracorporeal membrane oxygenation (ECMO) and cardiopulmonary bypass (CPB), are used to replace the function of the heart and lung, but they induce complications in the form of acute kidney failure, bleeding, heart arrhythmias or thromboembolic complications. This study aimed to quantify the changes in microvascular perfusion and oxygenation that occur after veno-arterial ECC (VA-ECC). Male Golden Syrian hamsters were instrumented with a dorsal window chamber to study their microcirculation and an exteriorized carotid artery catheter for blood pressure and blood gas measurements. After baseline (BL) measurements were taken, the hamster underwent surgery under isoflurane to insert a drainage catheter into the jugular vein. A heparin bolus (0.05 IU/g) was then provided, and the animal was connected to the VA-ECC circuit, which consists of a peristaltic pump and bubble trap. The VA-ECC circuit was primed with either lactated ringers (LR) or 5% human serum albumin in saline (HSA). Blood flow was ramped up over 15 minutes, maintained at 15% of the animal’s cardiac output for 60 minutes, then ramped down over 15 minutes. Sham animals underwent cannulation surgery and heparinization but were not connected to the VA-ECC circuit. The animals were surgically closed, placed on a heating pad, and allowed at least 30 minutes to wake up from the anesthetic plane before taking measurements at 1, 2, and 24 hours after VA-ECC. Results show that flow in arterioles and venules (Figure 1) at all post-ECC timepoints statistically decreased in LR and HSA groups compared to Sham. LR and HSA failed to recover flow in arterioles and venules back to BL levels post-ECC. Interestingly, venule perfusion statistically increased at 1 and 2 hrs in the HSA group compared to the LR group. Functional capillary density (FCD, Figure 2) showed a statistical reduction in capillary perfusion for both ECC groups, with the HSA group maintaining higher levels compared to the LR group. Microvascular hemoglobin (Hb) oxygen (O2) saturation (Figure 3), in venules was statistically reduced post-ECC for both LR and HSA compared to Sham and BL. The microvascular perfusion results, combined with the consistent drop in hematocrit (Hct) post-ECC suggest an imbalance in oncotic pressure that slowly rectifies after ECC. Via Starling’s law of filtration, the priming volume dilutes protein content within the blood, causing the intravascular oncotic pressure to drop, resulting in ultrafiltration at the capillary level. Additionally, the drop in venule Hb O2 saturation and the reduced microvascular perfusion suggest a reduced O2 delivery and potentially a repayment of an O2 debt post-ECC. This study shows that microvascular sequelae could potentially cause ischemic injury in ECC procedures, which can lead to organ damage and inflammation.Figure 1. Microcirculatory hemodynamics. Diameter, velocity, and volumetric blood flow are shown from top to bottom, while arterioles (Sham: n = 38, LR: n = 33; HSA: n = 33) and venules (Sham: n = 38, LR: n = 30, HSA: n = 33) are shown from the left to right columns. All values are normalized to baseline (BL, before ECC) measurements for each vessel. * P < 0.05, ** P < 0.01, *** P < 0.001, **** P < 0.0001 between groups at each timepoint. † P<0.05 compared to BL, within each group.Figure 2. Functional capillary density (FCD). * P < 0.05, ** P < 0.01, *** P < 0.001, **** P < 0.0001 between groups. † P<0.05 compared to baseline (BL). N = 6 for all groups.Figure 3. Microvascular Hemoglobin Oxygen Saturation Changes. The top row shows arterioles (Sham: n = 19, LR: n = 13, HSA: n = 16), while the bottom row shows venules (Sham: n = 21, LR: n = 19, HSA: n = 22). * P < 0.05, ** P < 0.01, *** P < 0.001, **** P < 0.0001 between groups. † P<0.05 compared to baseline (BL).

BIO18: Hemoglobin and Heme Scavenger Proteins Reduce Free Hemoglobin During Venovenous Extracorporeal Circulation and Preserves Microvascular Function.

Extracorporeal circulation procedures often utilize a blood pump to drive flow through an external circuit, which can cause hemolysis due to high shear conditions and foreign surface contact. The purpose of this study was to determine whether priming fluids containing proteins to sequester hemoglobin (Hb) and heme could be used in venovenous extracorporeal circulation (VV-ECC) to reduce their toxicity. A day prior to the experiment, male Golden Syrian hamsters were instrumented with a dorsal window chamber to monitor the microcirculation. The day of the experiment, both jugular veins were then cannulated under isoflurane anesthesia. Baseline (BL) microvascular oxygenation was measured using a hyperspectral camera. The animals were then heparinized (2.5 IU/g) and connected to the VV-ECC circuit, consisting of a peristaltic pump and bubble trap. The ECC circuit was primed with either 5% human serum albumin (HSA), ApoHb-Hp (62.01 mg/mL), or a protein solution containing hemopexin, transferrin, and Hp (protein cocktail, 84.50 mg/mL). Haptoglobin (Hp), hemopexin, and transferrin are native proteins that bind to Hb, heme, and iron respectively. Apohemoglobin (apoHb) is a synthetic scavenger produced by removing heme from Hb. ApoHb binds to haptoglobin (Hp) forming the apoHb-Hp complex that retains its ability to bind heme and scavenge free Hb. The experiment lasted a total of 2 hrs (Table 1), in which first the animals were hemodiluted, and the flow rate through the circuit was ramped up to 50% of the animal’s cardiac output. This max flow rate was then maintained for 35 minutes before being ramped down to 0.2 mLPM. The circuit was maintained at this flow rate for 15 minutes, allowing the animal and the circuit to equilibrate before the circuit flow was stopped. While mean arterial pressure (MAP, Figure 1a) showed differences at baseline (BL) between HSA and both other groups, there was no significance observed after hemodilution and the ramp up phase of the experiment. This difference in MAP between HSA and the two other solutions returned at all timepoints after the ramp up phase. Hb oxygen saturation (sO2, Figure 2) within the microvasculature showed a drop for both arterioles and venules in both the protein cocktail and ApoHb-Hp groups at the full VV-ECC timepoint. The plasma Hb (Figure 3) for the protein cocktail and ApoHb-Hp groups were significantly lower than the HSA control from the start of VV-ECC to the equilibration stage when compared to the HSA control. These results confirm that the ApoHb and protein cocktail solutions have the capability to bind and sequester free Hb, which has the potential to reduce the extravasation of Hb from the circulatory compartment into tissues, preserves the vascular nitric oxide (NO) signaling pathway, and reduce Hb and heme toxicity. Future work is needed to determine impact on organs, especially the kidneys, and to quantify the binding efficiency of these proteins to free hemoglobin.Figure 1. Hemodynamic parameters measured via the carotid artery: a) Mean arterial pressure (MAP) and b) heart rate (HR). bl = baseline, dil = hemodilution, up = ramp up, ecc = VV-ECC at max flow rate (50% of cardiac output), down = ramp down, equ = equilibration, off = off pump. * P < 0.05, ** P < 0.01, *** P < 0.001 between groups. N = 6 for all groups.Figure 2. Changes in microvascular hemoglobin oxygen saturation. The top row shows arterioles, while the bottom row shows venules. Arterioles and venules were analyzed for 4 hamsters per group. bl = baseline, dil = hemodilution, up = ramp up, ecc = VV-ECC at max flow rate (50% of cardiac output), down = ramp down, equ = equilibration, off = off pump. * P < 0.05, ** P < 0.01, *** P < 0.001, **** P < 0.0001 between groups. † P<0.05 compared to baseline (BL).Figure 3. a) Hematocrit (Hct) and b) plasma hemoglobin (pHb). 0 = baseline (BL), 25 = hemodilution, 45 = VV-ECC (start), 75 = VV-ECC (end), 105 = equilibrate, 120 = off pump. * P < 0.05, ** P < 0.01, *** P < 0.001, **** P < 0.0001 between groups. † P<0.05 compared to BL. Table 1. - Experimental timeline highlight the blood flow through the circuit. Baseline Hemodilution Ramp Up VV-ECC Ramp Down Equilibrate Off Pump Duration 15 min 15 min 15 min 35 min 15 min 15 min 10 min Blood Flow 0 mLPM 0.2 mLPM 0.2 mLPM → 50% CO 50% CO 50% CO → 0.2 mLPM 0.2 mLPM 0 mLPM Hyperspectral images were taken every 5 minutes. mLPM = milliliters per minute, CO = cardiac output, VV-ECC = full venovenous extracorporeal circulation.

BIO9: The Addition of High Molecular Weight Linear Polymers Improves Microvascular Perfusion in an Animal Model of Veno-arterial Extracorporeal Circulation.

High molecular weight linear polymers have been used in turbulent flow applications such as crude oil transfer to reduce drag. These polymers have branched into bioengineering applications to improve pressure changes within the macrocirculation and improve RBC distribution within the microcirculation. The current study aims to determine whether the addition of these polymers to priming fluids used for veno-arterial extracorporeal circulation (VA-ECC) procedures improve microvascular flow and tissue oxygenation. To assess the microcirculation, male Golden Syrian hamsters were instrumented with a dorsal skinfold window chamber, and an exteriorized carotid artery catheter was implanted for arterial blood and blood pressure access. After baseline (BL) measurements were taken, the hamster underwent surgery under isoflurane to insert a drainage catheter into the jugular vein. A heparin bolus (0.05 IU/g) was then provided, and the animal was connected to the VA-ECC circuit. The circuit, consisting of a peristaltic pump and bubble trap, was primed with lactated ringers (LR, control), LR with 5 ppm of 500 kDa polyethylene glycol (PEG500k) or LR with 5 ppm of 3500kDa polyethylene glycol (PEG3500k). Blood flow was ramped up over 15 minutes, maintained at 15% of the animal’s cardiac output for 60 minutes, then ramped down over 15 minutes. The animal was then surgically closed and placed on a heating pad and allowed at least 30 minutes to wake up from the anesthetic plane before taking measurements at 1, 2, and 24 hours after VA-ECC. Capillary perfusion (Figure 1) within the skinfold preparation showed a significant decrease immediately post-ECC for all three groups. However, the PEG3500k group consistently showed significant increase in functional capillary density (FCD) as compared to both other groups after ECC. 24 hrs after ECC, FCD was recovered close to BL levels for both PEG groups, while the LR control did not. Arteriole and venule velocity (Figure 2) was significantly elevated at both 1 and 2 hrs post-ECC for the PEG3500k group when compared to the other two groups. Arteriole flow for the PEG3500k was significantly improved over the LR control at 24 hrs post-ECC, and was significantly higher than BL levels. Hemoglobin saturation within arterioles and venules (Figure 3) revealed that PEG3500k had higher venule saturation at 1 and 2 hrs post-ECC compared to both other groups. The results indicate that the use of PEG3500k improved microvascular perfusion acutely post-ECC, and continued to up to 24 hrs afterwards. The most important changes were in arteriole perfusion and FCD, since that directly impacts oxygen delivery and metabolic washout respectively. Ultimately, this aids in maintaining organ function and preventing the development of ischemic injury and inflammatory cascades. Future studies could optimize the molecular weight, concentration, and type of polymer, along with testing in a clinical ECC circuit to determine hemodynamic changes.Figure 1. Functional capillary density (FCD), normalized to baseline (BL, represented by the dotted line). † P < 0.05 as compared to BL, within each group. * P < 0.05; ** P < 0.01; *** P < 0.001 between groups, at each timepoint.Figure 2. Perfusion within the microcirculation. From top to bottom: diameter, velocity, blood flow. Arterioles are on the left, while venules are on the right. Note that all values were normalized to baseline (BL, represented by the dashed line) and that blood flow was calculated from the diameter and velocity measurements of each vessel. Bar plots represent mean and standard deviation. † P < 0.05 as compared to BL, within each group. * P < 0.05; ** P < 0.01; *** P < 0.001; **** P < 0.0001 between groups, at each timepoint.Figure 3. Hemoglobin oxygen saturation within the microcirculation. Top = arterioles, bottom = venules. Bar plots show mean and standard deviation. † P < 0.05 as compared to BL, within each group. * P < 0.05; ** P < 0.01; *** P < 0.001; **** P < 0.0001 between groups, at each timepoint.

Effects of rapid fluid infusion on hemoglobin concentration: a systematic review and meta-analysis

BackgroundRapid fluid administration may decrease hemoglobin concentration (Hb) by a diluting effect, which could limit the increase in oxygen delivery (DO2) expected with a positive response to fluid challenge in critically ill patients. Our aim was to quantify the decrease in Hb after rapid fluid administration.MethodsOur protocol was registered in PROSPERO (CRD42020165146). We searched PubMed, the Cochrane Database, and Embase from inception until February 15, 2022. We selected studies that reported Hb before and after rapid fluid administration (bolus fluid given over less than 120 min) with crystalloids and/or colloids in adults. Exclusion criteria were studies that included bleeding patients, or used transfusions or extracorporeal circulation procedures. Studies were divided according to whether they involved non-acutely ill or acutely ill (surgical/trauma, sepsis, circulatory shock or severe hypovolemia, and mixed conditions) subjects. The mean Hb difference and, where reported, the DO2 difference before and after fluid administration were extracted. Meta-analyses were conducted to assess differences in Hb before and after rapid fluid administration in all subjects and across subgroups. Random-effect models, meta-regressions and subgroup analyses were performed for meta-analyses. Risk of bias was assessed using the Cochrane Risk of Bias Assessment Tool. Inconsistency among trial results was assessed using the I2 statistic.ResultsSixty-five studies met our inclusion criteria (40 in non-acutely ill and 25 in acutely ill subjects), with a total of 2794 participants. Risk of bias was assessed as “low” for randomized controlled trials (RCTs) and ‘low to moderate’ for non-RCTs. Across 63 studies suitable for meta-analysis, the Hb decreased significantly by a mean of 1.33 g/dL [95% CI − 1.45 to − 1.12; p < 0.001; I2 = 96.88] after fluid administration: in non-acutely ill subjects, the mean decrease was 1.56 g/dL [95% CI − 1.69 to − 1.42; p < 0.001; I2 = 96.71] and in acutely ill patients 0.84 g/dL [95% CI − 1.03 to − 0.64; p = 0.033; I2 = 92.91]. The decrease in Hb was less marked in patients with sepsis than in other acutely ill patients. The DO2 decreased significantly in fluid non-responders with a significant decrease in Hb.ConclusionsHb decreased consistently after rapid fluid administration with moderate certainty of evidence. This effect may limit the positive effects of fluid challenges on DO2 and thus on tissue oxygenation.

Drag Reducing Polymers Improves Microvascular Perfusion After Extracorporeal Circulation

Drag reducing polymers (DRPs) have been used in various engineering applications, such as the transfer of crude oil or seawater in pipelines. The use of DRPs has crossed into the bioengineering sphere, with previous ex‐vivo and in‐vivo studies suggesting that the addition of DRPs decreases the erythrocyte cell free layer (CFL) or cell depleted layer near the vessel wall and increases microvascular blood flow. The objective of this study was to investigate whether the addition of DRPs would improve microvascular perfusion in a rodent model of extracorporeal circulation (ECC).Male Golden Syrian hamsters were instrumented with a dorsal skinfold window chamber, along with an arterial catheter into the right carotid artery to monitor blood pressure and heart rate. During ECC, animals were anesthetized with isoflurane, and a drainage cannula was inserted through the left jugular. The animal was connected to the circuit, primed with either lactate ringers (LR group) or 5 PPM 500 kDa polyethylene glycol in lactate ringers (DRP group). Blood was drained from the jugular cannula, run through a peristaltic pump and bubble trap, before entering the carotid catheter for reinfusion. The circuit was run for 90 minutes in total, with 60 minutes at a flowrate equivalent to 15% of the animal’s cardiac output. Measurements were taken before ECC (baseline, BL) and after 1, 2, and 24 hrs post‐ECC. At each timepoint, microvessel (arterioles and venules) diameter, red blood cell velocity and functional capillary density (FCD) were measured using intravital microscopy.Arteriole and venule hemodynamics are displayed in Figure 1. The arteriole results showed an interesting contrast between effects at 1 hr and 24 hrs post‐ECC. At 1 hr post‐ECC, the DRP group displayed a statistically lower arteriole diameter compared to the LR group, but no statistical difference in blood flow between the two groups. At 24 hrs post‐ECC, no difference in arteriole diameter was observed between groups, while arteriole blood flow was statistically higher in the DRP group compared to the LR group. In venules, no changes were observed between groups at 1 hr post‐ECC. However, at 2 and 24 hrs post‐ECC, the DRP group had a statistically significant higher diameter compared to the LR group. Venular blood flow was statistically elevated in the DRP group at 24 hrs post‐ECC compared to the LR group. Figure 2 shows the changes in FCD. FCD was lower for both DRP and LR groups at 1 and 2 hrs post‐ECC when compared to BL levels. The DRP group displayed a higher FCD at 2 hrs post‐ECC compared to the LR group. At 24 hrs however, while the DRP group was able to recover back to BL levels, the LR group was statistically lower than BL.From these results we conclude that the addition of DRPs to priming fluids for ECC procedures may be beneficial in preserving microvascular perfusion 24 hrs post‐ECC. This may help reduce the risk of ischemic injury, production of pro‐inflammatory markers, and development of multiorgan dysfunction. Further research is warranted to optimize the DRPs parameters, such as concentration and molecular weight.

The Disconnect Between Extracorporeal Circulation and the Microcirculation: A Review.

Extracorporeal circulation (ECC) procedures, such as cardiopulmonary bypass (CPB) and extracorporeal membrane oxygenation (ECMO), take over the function of one or more organs, providing clinicians time to treat underlying pathophysiological conditions. ECMO and CPB carry significant mortality rates for patients, despite prior decades of research focused on the resulting failure of critical organs. Since the focus of these procedures is to support blood flow and provide oxygen-rich blood to tissues, a shift in research toward the effects of ECMO and CPB on the microcirculation is warranted. Along with provoking systemic responses, both procedures disrupt the integrity of red blood cells, causing release of hemoglobin (Hb) from excessive foreign surface contact and mechanical stresses. The effects of hemolysis are especially pronounced in the microcirculation, where plasma Hb leads to nitric oxide scavenging, oxidization, formation of reactive oxygen species, and inflammatory responses. A limited number of studies have investigated the implications of ECMO in the microcirculation, but more work is needed to minimize ECMO-induced reduction of microcirculatory perfusion and consequently oxygenation. The following review presents existing information on the implications of ECMO and CPB on microvascular function and proposes future studies to understand and leverage key mechanisms to improve patient outcomes.

Continuous ultrafiltration during extracorporeal circulation and its effect on lactatemia: A randomized controlled trial.

Hyperlactatemia occurs during or after extracorporeal circulation in the form of lactic acidosis, increasing the risk of postoperative complications and the mortality rate. The aim of this study was to evaluate whether continuous high-volume hemofiltration with volume replacement through a polyethersulfone filter during the extracorporeal circulation procedure decreases postoperative lactatemia and its consequences. This was a randomized controlled trial. Patients were randomly divided into two groups of 32: with or without continuous high-volume hemofiltration through a polyethersulfone membrane. Five patients were excluded from each group during the study period. The sociodemographic characteristics, filter effects, and blood lactate levels at different times during the procedure were evaluated. Secondary endpoints were studied, such as the reduction in the intubation time and time spent in ICU. Lactatemia measurements performed during the preoperative and intraoperative phases were not significantly different between the two groups. However, the blood lactate levels in the postoperative period and at 24 hours in the intensive care unit showed a significant reduction and a possible clinical benefit in the hemofiltered group. Following extracorporeal circulation, the mean lactate level was higher (difference: 0.77 mmol/L; CI 0.95: 0.01-1.53) in the nonhemofiltered group than in the hemofiltered group (p<0.05). This effect was greater at 24 hours (p = 0.019) in the nonhemofiltered group (difference: 1.06 mmol/L; CI 0.95: 0.18-1.93) than in the hemofiltered group. The reduction of lactatemia is associated with a reduction of inflammatory mediators and intubation time, with an improvement in liver function. The use and control of continuous high-volume hemofiltration through a polyethersulfone membrane during heart-lung surgery could potencially prevent postoperative complications. The reduction of lactatemia implied a reduction in intubation time, a decrease in morbidity and mortality in the intensive care unit and a shorter hospital stay.

Blood heparin sensor made from a paste electrode of graphite particles grafted with molecularly imprinted polymer

A real-time heparin monitor could be used to optimize the dosage of heparin during extracorporeal circulation procedures. This report describes the development of a graphite-paste (GP) electrode with molecularly imprinted polymer (MIP) grafted onto it. Heparin-imprinted poly (methacryloxyethyltriammonium chloride -co- acrylamide -co- methylenebisacrylamide) was grafted directly onto graphite particles. The grafted particles were thoroughly mixed with oil to fabricate the MIP-GP electrode. Traditional cyclic voltammetry was performed with the electrode in physiological saline or bovine whole blood containing 5 mM ferrocyanide and 0–8 units/mL heparin. The current intensity increased with heparin concentration, due to expansion of the effective surface area resulting from heparin-promoted mobility of the oil in the MIP-GP electrode. No significant difference was found in the sensitivity of the current to unfractionated heparin among the electrodes fabricated because of the electrode homogenization resulting from thorough mixing of the MIP-grafted particles and oil. (A previous MIP-grafted indium tin oxide electrode exhibited lower sensitivity in blood than in saline.) Only 60 s were needed to stabilize the current. The current at the MIP-GP electrode was also sensitive to low-molecular-weight heparin in blood, but insensitive to chondroitin sulfate C (CSC), which is a heparin analog. The non-imprinted polymer (NIP)-grafted electrode was insensitive to heparin. Thus, the MIP-GP electrode, which operated through a new heparin-sensing mechanism, is an excellent candidate for application as a disposable sensor to monitor heparin levels in blood.

Abstract TP138: Carotid Endarterectomy for Complicated Carotid Artery Disease∼ Application of Extracorporeal Circulation Technique

Intorduction: In performing carotid endarterectomy (CEA), indwelling shunt tube placement is necessary in some cases with poor collateral flow. Particularly, in patients with critical hemodynamic insufficiency like contralateral internal carotid artery (ICA) occlusion, shorter cross-clamping duration is preferable. Furthermore, in patients who have common carotid artery (CCA) ulceration, shunt placement can be dangerous because of the risk of embolic complication through the indwelling shunt tube. For such cases, we introduced extracorporeal circulation technique for cerebral perfusion during CEA. Methods: In 309 consecutive CEA cases, 16 cases (5.2%) were performed CEA under extracorporeal circulation. Using roller pump, arterial blood was supplied from brachial or femoral artery to the distal portion of the cervical ICA. In cases with contralateral ICA occlusion, distal ICA cannulation was performed without any cross clamping by using Seldinger technique. Other cases with CCA ulceration, distal ICA cannulation was performed with conventional indwelling shunt tube insertion technique. Results: In 6 cases with contralateral ICA occlusion and 9 cases with ipsilateral CCA ulceration concomitant with ICA stenosis, and in one case had both contralateral ICA occlusion and ipsilateral CCA ulceration, we successfully performed CEA under extracorporeal circulation. No ischemic event was observed in all the cases. Conclusions: This extracorporeal circulation procedure is very useful in patients with carotid artery disease who have extremely poor collateral flow or have severe CCA lesions.

Stabilized sensing of heparin in whole blood using the ‘gate effect’ of heparin-imprinted polymer grafted onto an electrode

AbstractA real-time heparin monitor is required to optimize the dosage of heparin and its antidote, protamine sulfate, during extracorporeal circulation procedures. The gate effect of molecularly imprinted polymer (MIP) is a potential tool for the rapid and selective sensing of heparin. We here present a method to stabilize the measurement of heparin concentration in whole blood using an MIP-grafted electrode. An initiator of radical polymerization, the diethyldithiocarbamicbenzyl group, was introduced onto the surface of an indium-tin oxide (ITO) electrode. Heparin sodium, methacryloxethyltrimethoxysilane, and acrylamide were dissolved in water, and methylenebisacrylamide was dissolved in dimethylformamide. A mixture of the two solutions was introduced into the 50 μm gap between the surfaces of a quartz crystal plate and the treated ITO electrode. Ultraviolet light was irradiated onto the surface of the ITO to graft the copolymer of the monomers, then the ITO was washed with a 1 M sodium chloride aqueous solution to remove the heparin template and obtain the MIP-grafted electrode. Cyclic voltammetry was performed with the MIP-grafted electrode in physiological saline or bovine whole blood containing 0-8 units/ mL heparin and 5 mM ferrocyanide as a redox marker, and the relationship between the current intensity and the heparin concentration was analyzed. The current intensity decreased as the heparin concentration in either saline or whole blood increased, and the sensitivity of the electrode to heparin in blood was approximately 52% of its sensitivity to heparin in saline. The grafted-electrode was washed with a protease-containing detergent (Sterizyme® S, Maruishi Pharmaceutical) between measurements in blood. The heparin-sensitivity of the washed electrode in blood was 77% of that in saline. No sensitivity to chondroitin sulfate C was observed but sensitivity to low molecular weight heparin was demonstrated. We thus conclude that selective and stable sensing of heparin can be achieved using an electrode grafted with heparinimprinted polymer.

Heparin-coated cardiopulmonary bypass circuits selectively deplete the pattern recognition molecule ficolin-2 of the lectin complement pathway in vivo.

The complement system can be activated via the lectin pathway by the recognition molecules mannose-binding lectin (MBL) and the ficolins. Ficolin-2 exhibits binding against a broad range of ligands, including biomaterials in vitro, and low ficolin-2 levels are associated with increased risk of infections. Thus, we investigated the biocompatibility of the recognition molecules of the lectin pathway in two different types of cardiopulmonary bypass circuits. Bloods were drawn at five time-points before, during and postoperatively from 30 patients undergoing elective cardiac surgery. Patients were randomized into two groups using different coatings of cardiopulmonary bypass circuits, Phisio® (phosphorylcholine polymer coating) and Bioline® (albumin-heparin coating). Concentrations of MBL, ficolin-1, -2 and -3 and soluble C3a and terminal complement complex (TCC) in plasma samples were measured. Ficolin-3-mediated complement activation potential was evaluated with C4, C3 and TCC as output. There was no significant difference between the two circuit materials regarding MBL, ficolin-1 and -3. In the Bioline® group the ficolin-2 levels decreased significantly after initiation of surgery (P < 0.0001) and remained reduced throughout the sampling period. This was not seen for Phisio®-coated circuits. Ficolin-3-mediated complement activation potential was reduced significantly in both groups after start of operation (P < 0.0001), whereas soluble C3a and TCC in the samples were increased (P < 0.0001). Ficolin-2 was depleted from plasma during cardiac surgery when using heparin-coated bypass circuits and did not reach baseline level 24 h postoperation. These findings may have implications for the postoperative susceptibility to infections in patients undergoing extracorporeal circulation procedures.

Pharmacokinetic Assessment of Sufentanil in Cardiac Surgery

Plasma monitoring and pharmacokinetic assessment are important tools used in therapeutic control. Sufentanil is responsible for the hemodynamic stabilization of patients, providing better suppression of the neuroendocrine response compared to its analogue fentanyl. This study aims to use the plasma monitoring of sufentanil in patients undergoing cardiac surgery with extracorporeal circulation (ECC, group 1) or without ECC (group 2) to assess the pharmacokinetics of the compound.The 42 patients in this study received 0.5 μg/kg of sufentanil through bolus injection followed by a maintenance infusion of 0.5 μg/kg.h. Serial blood samples were collected during the post induction intraoperative period and during the postoperative period until 36 h after sufentanil administration. The plasma concentrations were determined by a validated method utilizing liquid chromatography coupled to mass spectrometry. The pharmacokinetic modeling was performed using a 3-compartment model fit.The surgical patients included in the protocol were adults of both genders, with 30 patients in the ECC group and 12 in the group without ECC. The plasma concentrations obtained were significantly different between the 2 groups. During the extracorporeal circulation procedure, intense fluctuations were observed in the sufentanil plasma concentrations. Compared with the results of group 2, the ECC procedure reduced the terminal or gamma half-life from 36.35 ± 6.37 h to 23.25 ± 2.75 h in group 1. In addition, the ECC procedure promoted higher fluctuations in the sufentanil plasma concentrations without causing alterations in the area under the curve, distribution volume, clearance or the distributional (alpha) and rapid elimination (beta) half-lives (t1/2α and t1/2β, respectively).

Platelet aggregation monitoring with a newly developed quartz crystal microbalance system as an alternative to optical platelet aggregometry

The objective of this study was to establish a new test system for the monitoring of platelet aggregation during extracorporeal circulation (ECC) procedures. Even though extensive progress has been made in improving the haemocompatibility of extracorporeal circulation devices, activation of blood coagulation, blood platelets and inflammatory responses are still undesired outcomes of cardiopulmonary bypass. This study deals with an approach towards a platelet aggregation measuring system using a newly developed quartz crystal microbalance (QCM) system. Since QCM is a rarely used technique in the field of blood analytics, the challenge was to transfer the well established methods of aggregometry to the new test system. In a QCM system, either bare gold or fibrinogen-coated sensors were incubated with ADP or arachidonic acid (AA) stimulated platelet rich plasma. For negative controls the GPIIb/IIIa inhibitory antibody abciximab (Reopro®) was used as an inhibitor of platelet aggregation. During incubation, the frequency shifts of the sensors were recorded. The results gained from the QCM system were compared to results gained by optical platelet aggregometry (born aggregometry). For additional visualization of platelet adhesion to the sensor surfaces, fluorescent microscopy and scanning electron microscopy were used. The QCM sensor was able to detect platelet aggregation in both uncoated and fibrinogen coated sensors. The measuring curves of aggregation measurements and controls were clearly distinguishable from each other in terms of frequency shifts and kinetics. For aggregation measurements and inhibited controls the therapeutic diagnosis of platelet function is identical between aggregometer and QCM data. In future, QCM based measuring devices may become an alternative to established point of care methods for rapid bedside testing of platelet aggregation.

Minimal Extracorporeal Circulation: An Alternative for On-Pump and Off-Pump Coronary Revascularization

Coronary artery bypass surgery employing minimal extracorporeal circulation (MECC) was compared with standard extracorporeal circulation (ECC) and off-pump coronary artery bypass graft surgery (OPCABG) with regard to the perioperative course. From January 2004 to December 2007, 1,674 patients (n = 558 MECC, n = 558 ECC, n = 558 OPCABG) who underwent coronary bypass surgery were studied. The primary end point was in-hospital mortality; secondary end points were perioperative variables, intensive care, and in-hospital course. Demographic data, comorbidity, and the European System for Cardiac Operative Risk Evaluation score (MECC 3.0%, ECC 3.5%, OPCABG 3.2%) were similar among the groups, but in-hospital mortality for elective and urgent/emergent patients was lower in the MECC and OPCABG groups (MECC 3.2%, OPCABG 3.7%, ECC 6.9%; p < 0.05). The number of distal anastomoses was lowest in the OPCABG group, but comparable for MECC and ECC patients. Postoperative ventilation time, release of creatinine kinase, catecholamine therapy, drainage loss, and transfusion requirements were lower in the MECC and OPCABG groups, whereas stay in the intensive care unit was shorter only in the latter (p < 0.05). Minimal extracorporeal circulation is an easy and safe procedure for coronary artery bypass graft surgery. In selected patients, the advantages of MECC equal those of OPCABG. MECC should be considered as an alternative to OPCABG and standard ECC procedures.

CD41 Western blotting: a new method to detect platelet adhesion to artificial surfaces used in extracorporeal circulation procedures

Cardiopulmonary bypass (CPB) surgery is associated with platelet activation and reduced platelet counts due to artificial surface activation of blood elements and non-physiological flow-patterns. As shown in former studies, coating of medical devices can improve hemocompatibility in extracorporeal circulation systems. In this study, we demonstrate a new method to determine platelet adhesion on 18 coated and non-coated membrane oxygenators in a simulated CPB model with CD41 Western blot. Platelet loss and the release of beta-TG (platelet activation marker) were determined during a 120 min recirculation phase. At the end of the run the membrane oxygenators (with tubing system) were rinsed and the amount of adsorbed proteins on the surface was analyzed by using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting technique. Uncoated devices showed significantly higher concentrations of CD41 and of fibrinogen adsorption compared to the coated membrane oxygenators. These results correspond with the release of beta-TG and platelet loss indicating less platelet adhesion on the coated oxygenators compared with the uncoated group. This new method may be useful in choosing less platelet activating materials for all kind of blood contacting devices to improve thrombogenicity including platelet functionality.

Intracaval and intracardiac extension of Wilms' tumor: the influence of preoperative chemotherapy on surgical morbidity

The aim of this retrospective study is to compare surgical complications and long-term survival in children with Wilms' tumor (WT) and tumor thrombus receiving or not preoperative chemotherapy. Review of the charts of 155 children with WT treated between 1983 and 2005, and analysis of 16/155 (10.3%) children with WT who presented cavoatrial tumor extension, being 8/16 IVC and 8/16 atrial thrombus. Median age was 54 months. 2/16 had cardiac failure as the first symptom. 11/16(7 IVC and 4 atrial extension) (67%) were submitted to preoperative chemotherapy with vincristine plus actinomycin D, and 5/16(1 IVC and 4 atrial) (33%) underwent initial nephrectomy and thrombus resection. So, 11 patients were submitted to preoperative VCR/ACTD and 2/11 (18.1%) had complete regression of the thrombus, 6/11(54.5%) partial regression and 3/11 (27%) had no response. Among the partial responders, nephrectomy with thrombus removal was performed in all, including one patient with previous intracardiac involvement, without extracorporeal circulation procedures. In two of the three non-responders, cardiopulmonary bypass was necessary for thrombus removal. There were no surgical related deaths. Long-term survival is 91% in the group submitted to preoperative chemotherapy and 100% in the group who had surgery as first approach. Preoperative chemotherapy was able to reduce thrombus extension in 8/11 (73%) treated patients and cardiopulmonary bypass was avoided in 2 patients with atrial thrombus. Surgical resection of tumor and thrombus was successful in all cases, receiving or not preoperative chemotherapy and overall survival was similar in both groups.

Non-cardiac surgery applications of extracorporeal circulation

Although the efficacy of extracorporeal circulation (ECC) is well established for open-heart surgery, application of ECC in other surgical areas has not been given much attention. Advances in the related surgical technique and anesthetic management combined with refinements in the ECC procedure itself have encouraged several institutions to use ECC for complex non-cardiac surgeries. ECC is beginning to be used for circulatory support or tissue oxygenation during surgery on the lung, brain, liver, and kidney as well as in emergency situations. With ECC, difficult and complex surgeries can be performed more safely, and the success rate of certain surgeries has been positively affected. It is important that the surgeon, anesthesiologist, and perfusionist are trained in non-cardiac surgery applications of ECC. Thus, we review here non-cardiac uses that have emerged and summarize the related procedures.

Effect of biopassive and bioactive surface‐coatings on the hemocompatibility of membrane oxygenators

Postoperative complications associated with cardiopulmonary bypass (CPB) surgery and extracorporeal circulation (ECC) procedures are still a major clinical issue. Improving the hemocompatibility of blood contacting devices used for ECC procedures may ameliorate various postpump syndromes. In a simulated CPB model using human blood, we investigated the hemocompatibility, fibrinogen adsorption, and platelet receptor (GPIIb-IIIa) binding capacity of surface-modified membrane oxygenators (Jostra Quadrox). Three groups were compared: (i) biopassive protein coatings (SafeLine), (ii) bioactive heparin coatings (BioLine), and (iii) noncoated controls. During the 2 h recirculation period, plasma concentrations of activation markers for platelets (beta-thromboglobulin), inflammation (elastase), complement (C5a), and coagulation (prothrombin fragment 1+2, thrombin-antithrombin III) were lower in the groups with biopassive and bioactive coatings compared to the noncoated group (p < 0.01). These parameters did not significantly differ between the two surface-coated groups, except for complement activation: C5a levels were higher in the biopassive group compared to the bioactive group (p < 0.01). Moreover, surface-coated oxygenators showed less fibrinogen adsorption, GPIIb-IIIa binding, and platelet/leukocyte adhesion (p < 0.01). We assume that fewer fibrinogen and platelet receptor molecules bound to the surface-coated oxygenator surfaces results in fewer platelet adhesion and activation, which will significantly contribute to the improved hemocompatibility of the biopassive and bioactive oxygenators. Our results suggest that the application of bioactive oxygenators (BioLine) during CPB surgery may reduce postoperative complications for the patient more effectively than biopassive oxygenators (SafeLine).

Strategies for improving the functionality of an affinity bioreactor

Heparin employed in extracorporeal blood circulation (ECBC) procedures (e.g. open heart operations) often leads to a high incidence of bleeding complications. Protamine employed in heparin neutralization, on the other hand, can cause severe adverse reactions. We previously developed an approach that could prevent both heparin- and protamine-induced toxic side effects concomitantly. This approach consisted of placing a hollow fiber-based bioreactor device containing immobilized protamine (termed a “protamine bioreactor”) at the distal end of the ECBC procedure. This protamine bioreactor would remove heparin after heparin served its anticoagulant purpose in the ECBC device, thereby eliminating heparin-induced bleeding risks. In addition, this protamine bioreactor would prevent protamine from entering the patients, thereby aborting any protamine-induced toxic effects. Both in vitro and in vivo studies have successfully demonstrated the feasibility of this approach. Despite promises, early findings also revealed two shortcomings that must be overcome for the protamine bioreactor to be applied clinically. The first drawback was that the cyanate ester linkages, involved in conjugating protamine to the bioreactor device, were unstable and prone to hydrolysis, resulting in the leakage of a significant amount of protamine into circulation during application of the protamine bioreactor. The second deficiency was that the capacity of the protamine bioreactor in heparin removal was rather low, owing to the limited surface area of the hollow fibers for protamine immobilization and subsequently heparin adsorption. In this paper, we present novel strategies to overcome these two limitations. A new conjugation method based on the use of 4-(oxyacetyl)phenoxyacetic acid (OAPA) as the activating reagent was employed to yield stable linkages, via the abundant arginine residues of protamine, onto the hollow fibers. Results showed that while the amount of protamine immobilized on each gram of fibers was relatively comparable between the OAPA and the previous CNBr activation methods (7.45 mg/g versus 7.69 mg/g fibers), there was virtually no detectable leaching of immobilized protamine from the bioreactor by the OAPA method, comparing to 35% leaching of protamine by the previous CNBr method following 72 h of storage of the bioreactor in PBS buffer at 37 °C. To improve the capacity and functionality of the protamine bioreactor, two novel approaches were adopted. Long chain and high molecular weight poly-lysine was linked to the hollow fibers, prior to protamine coupling, to create multiple layers of immobilized protamine for subsequent heparin adsorption. In addition, a poly(ethylene glycol) (PEG) chain was inserted between protamine and the hollow fibers to yield a three-dimensional, free dynamic motion for immobilized protamine. Preliminary observations indicated that a four- to five-fold enhancement in heparin adsorption was attained by utilizing each of these new approaches. Aside from their current use, these new strategies can also be employed generically to improve the functionality of any affinity-type bioreactor. Indeed, efforts have been made recently in utilizing these approaches to develop a clinically usable GPIIb/IIIa bioreactor for the treatment of immune thrombocytopenic purpura (ITP)—an autoimmune disease.

Sepsis-associated coagulation disorders

Coagulation activation with intravascular fibrin formation is a general finding in patients with sepsis. Low coagulation factors may be caused by disseminated intravascular coagulation, as well as by loss of plasma and impaired hepatic synthesis in the course of sepsis. The leading clinical symptom in consumption coagulopathy is bleeding. Therefore, treatment mainly consists of substitution of coagulation factors and platelets. Meningococcal and pneumococcal, as well as some other infections may lead to sepsis-induced purpura fulminans, a condition associated with microvascular thrombosis, necrosis, and haemorrhage. A typical laboratory sign is a very low plasma protein C level. Treatment with protein C concentrate or recombinant activated protein C (Drotrecogin alfa, activated) has been shown to be beneficial in sepsis-induced purpura fulminans. Unfractionated heparin or low molecular weight heparin has been recommended for prophylaxis of venous thrombosis, but there are no clinical studies specifically on patients with sepsis. Antithrombin concentrate is used in patients with antithrombin deficiency treated with heparin for acute venous thrombosis or embolism, extracorporeal circulation procedures or other invasive procedures. There is no indication for general use of antithrombin concentrate in patients with sepsis even in patients with low plasma antithrombin levels. Drotrecogin alfa, activated, is used for treatment of patients with severe sepsis. Its use is not limited to patients with sepsis-induced disseminated intravascular coagulation, although these patients appear to benefit especially from this therapy.