Pulsatile Cardiopulmonary Bypass Research Articles

Ocular surface microcirculation is better preserved with pulsatile versus continuous flow during cardiopulmonary bypass-An experimental pilot.

Non-pulsatile cardiopulmonary bypass (CPB) may induce microvascular dysregulation. In piglets, we compared ocular surface microcirculation during pulsatile versus continuous flow (CF) bypass. Ocular surface microcirculation in small tissue volumes (~0.1 mm3 ) at limbus (high metabolic rate) and bulbar conjunctiva (low metabolic rate) was examined in a porcine model using computer assisted video microscopy and diffuse reflectance spectroscopy, before and after 3 and 6h of pulsatile (n=5 piglets) or CF (n=3 piglets) CPB. Functional capillary density, capillary flow velocity and microvascular oxygen saturation were quantified. At limbus, velocities improved with pulsatility (p < 0.01) and deteriorated with CF (p < 0.01). In bulbar conjunctiva, velocities were severely reduced with CF (p < 0.01), accompanied by an increase in capillary density (p < 0.01). Microvascular oxygen saturation decreased in both groups. Ocular surface capillary densities and flow patterns are better preserved with pulsatile versus CF during 6h of CPB in sleeping piglets.

Changes in intraocular pressure during coronary artery bypass graft surgery: an observational study

BackgroundIn this study, the effects of pulsatile and non-pulsatile on-pump Coronary Artery Bypass Graft surgery (CABG) and off-pump CABG techniques on the intraocular pressure were investigated. MethodsForty-five patients who planned to elective coronary artery bypass surgery with on-pump pulsatile (n=15), non-pulsatile (n=15), or off-pump (n=15) were included. Intraocular Pressure (IOP) measurements were performed on both eyes at nine time-points: 1) Before the operation, 2) After anesthesia induction, 3) 3 minutes after heparin administration Left Internal Mammary Artery (LIMA) harvesting, 4) End of the first anastomosis, 5) End of LIMA anastomosis, 6) 3 minutes after protamine administration, 7) End of the operation, and 8) Second hour in Intensive Care Unit (ICU), 9) Fifth hour in ICU. Mean Arterial Pressure (MAP) and Central Venous Pressure (CVP) were also recorded at the same time points as IOP. ResultsIn Cardiopulmonary Bypass (CPB) groups (pulsatile or non-pulsatile CPB) with the beginning of CPB, there were significant decreases in IOP values when compared to baseline (p=0.012). This decrease was more prominent in the non-pulsatile group when compared to the pulsatile group (T4 IOP values: pulsatile, 9.7±2.6; non-pulsatile, 6.8±1.9; p=0.002; T5 IOP values: pulsatile, 9.5±1.9; non-pulsatile, 6.7±2.1; p=0.004). At the end of the surgery (T7), IOP values returned to the baseline and stayed stable at the remaining time-points. In-off pump group, IOP values significantly increased with a head-down position (T4 IOP values: off-pump surgery, 19.7±5.2; p=0.015). IOP values remained high until the normalization of head-down position (T6) and stayed stable through the rest of all remaining time-points. ConclusionDuring cardiac surgery regardless of the technique (on-pump CABG, off-pump CABG), intraocular pressures remain in the normal ranges. It should be kept in mind that patients should be avoided from long and extreme Trendelenburg position, low CVP, and MAP levels during cardiac surgery to prevent eye-related complications.

Validation of transcutaneous carbon dioxide monitoring using an artificial lung during adult pulsatile cardiopulmonary bypass.

Measurements of transcutaneous carbon dioxide (tcCO2) have been used in multiple venues, such as during procedures utilizing jet ventilation, hyperbaric oxygen therapy, as well as both the adult and neo-natal ICUs. However, tcCO2 measurements have not been validated under conditions which utilize an artificial lung, such cardiopulmonary bypass (CPB). The purpose of this study was to (1) validate the use of tcCO2 using an artificial lung during CPB and (2) identify a location for the sensor that would optimize estimation of PaCO2 when compared to the gold standard of blood gas analysis.tcCO2 measurements (N = 185) were collected every 30 min during 54 pulsatile CPB procedures. The agreement/differences between the tcCO2 and the PaCO2 were compared by three sensor locations. Compared to the earlobe or the forehead, the submandibular PtcCO2 values agreed best with the PaCO2 and with a median difference of -.03 mmHg (IQR = 5.4, p < 0.001). The small median difference and acceptable IQR support the validity of the tcCO2 measurement. The multiple linear regression model for predicting the agreement between the submandibular tcCO2 and PaCO2 included the SvO2, the oxygenator gas to blood flow ratio, and the native perfusion index (R2 = 0.699, df = 1, 60; F = 19.1, p < 0.001).Our experience in utilizing tcCO2 during CPB has demonstrated accuracy in estimating PaCO2 when compared to the gold standard arterial blood gas analysis, even during CO2 flooding of the surgical field.

Sleep Quality after Coronary Artery Bypass Graft Surgery: Comparing Pulsatile and Nonpulsatile Pump Flow.

Poor postoperative sleep quality is a common problem in patients undergoing coronary artery bypass graft surgery (CABG). The purpose of this study was to compare the effect of pulsatile and nonpulsatile pump flow on sleep quality of these patients. In this clinical trial, 52 patients undergoing on pump CABG surgery with the roller pump were randomly divided into two equal groups of 26 patients: group 1 using pulsatile pump flow and group 2 nonpulsatile pump flow while the heart was arrested. Sleep score of both groups was evaluated by Pittsburgh Sleep Quality Index questionnaire 2 days before operation and 1 month after operation, and they were compared with each other. Analysis was performed with SPSS software version 22 (SPSS for Windows Inc., Chicago, IL) using the independent t-test, chi-square test, and Fisher exact test. Both groups were the same in demographic characteristics and risk factors such as age, gender, diabetes mellitus, hypertension, hyperlipidemia, smoking, body mass index, and preoperative ejection fraction. Operation data showed no difference between two groups considering cardiopulmonary bypass time and cardiac arrest time. Preoperative sleep quality score of both groups had no significant difference (p = .84). One month postoperative sleep quality score of the pulsatile group was significantly better than that of the nonpulsatile group (p = .04). Using pulsatile flow cardiopulmonary bypass can effectively decrease postoperative sleep disorders in comparison to nonpulsatile flow.

Effect of Pulsatile Cardiopulmonary Bypass in Adult Heart Surgery.

This study aimed to examine the effect of pulsatile flow pattern on tissue perfusion, particularly cerebral tissue perfusion, at pre-determined intervals during CPB, as well as its effects on postoperative morbidity and mortality. This retrospective study included 134 adult patients, who underwent cardiac surgery with cardiopulmonary bypass (CPB). Patients were grouped based on the flow pattern used during CPB: non-pulsatile CPB group (N = 82) and pulsatile CPB group (N = 52). Cerebral oxygen saturation, arterial pH and arterial lactate levels were measured at four time points, during the operation and the 2 groups were compared with regard to changes over time as well as differences in postoperative outcomes. The 2 groups were similar, in terms of mean values and intraoperative changes in cerebral oxygen saturation and arterial pH. Non-pulsatile CABG group had significantly higher arterial lactate levels over the measurement period, which was not affected by the timing of the measurements. Postoperative drainage, duration of ventilation and duration of hospital stay significantly were higher and postoperative blood urea nitrogen significantly was lower in the non-pulsatile CPB group. Other postoperative outcomes were similar across the groups. Findings of this study do not support the superiority of pulsatile flow pattern during CPB, in terms of cerebral oxygen saturation or postoperative mortality/morbidity. Further and larger comparative studies are warranted before pulsatile blood flow pattern can be established as a routine clinical method.

Pulsatil ve Nonpulsatil Kardiyopulmoner Baypas ile Koroner Baypas Cerrahisi Uygulanan Hastalarda Nörokognitif Değişikliklerin Elektroensefalografi ve Minimental Test Kullanılarak Değerlendirilmesi

Introduction: The aim of this study was to compare the neurocognitive effects of pulsatile and non-pulsatile perfusion using electroencephalography and the Mini-Mental State Examination (MMSE) in patients undergoing coronary bypass surgery. Patients and Methods: We created two groups, each containing 11 consecutive randomized patients, who were candidates for coronary bypass surgery. Pulsatile cardiopulmonary bypass (CPB) was conducted in Group I, and non-pulsatile CPB was conducted in Group II. An electroencephalogram (EEG) was performed preoperatively, intraoperatively, 15 minutes after placement of the cross-clamp, and seven days postoperatively. The MMSE was performed preoperatively and on postoperative day seven. Results: In both groups, pathological EEG waves were detected intraoperatively. However, no statistically significant difference was found between the groups (p> 0.05). Urine output was significantly higher at postoperative day1 in Group I. Overall urine drainage was higher in Group I, but the difference was not statistically significant. Diabetes mellitus, hypercholesterolemia, hypertension, cross-clamp, and perfusion time did not have a significant impact on the formation of pathological EEG waves. The difference between pre- and postoperative MMSE scores was not statistically significant (p> 0.05). Conclusion: No remarkable superiority was shown between CPB pulsatile and non-pulsatile perfusion in our study. Improving physiology of perfusion techniques during CPB and performing further studies on patients at high risk for organ perfusion would suggest more comprehensive perfusion flow strategies.

Pulsatile Versus Nonpulsatile Flow During Cardiopulmonary Bypass: Extent of Hemolysis and Clinical Significance.

Pulsatile flow has been used during cardiopulmonary bypass (CPB) for decades and its use is increasing with advancing extracorporeal technology. Pulsatile flow generates higher circuit pressures and shear forces than nonpulsatile flow at comparable pump flow and patient mean arterial pressure. Very little is known about the effect this has on erythrocytes. We included 62 adult patients (32 in the pulsatile group and 30 in the nonpulsatile group) undergoing elective coronary artery bypass grafting in this prospective observational study. Blood samples were collected at routine sampling times throughout surgery and were analyzed for the presence of free heme and globin using mass spectroscopy. Patient characteristics, CPB, and aortic cross-clamp times, pump flow as well as patient mean arterial pressure were similar in both groups. Maximum circuit pressure in the pulsatile flow group was statistically significantly higher than that in the nonpulsatile flow group (257.12 vs. 190.64 mmHg, p < 0.0001). Both heme and globin levels were higher in the pulsatile flow group. This reached statistical significance with globin at 30 minutes of CPB and with heme after aortic unclamping. We conclude that pulsatile CPB using roller pumps results in a greater extent of hemolysis. The clinical significance, however, is not yet known.

Monitoring and optimization of the microcirculation during CPB.

In this review the impact of cardiopulmonary bypass (CPB) on the microcirculation is discussed. The impact of conventional non-pulsatile perfusion is contrasted with the microcirculatory impact of pulsatile CPB which is associated with better preservation of microcirculatory function. Evidence that alterations in microcirculatory function that persist following cardiac surgery are associated with adverse clinical outcomes is reviewed. Recent studies using novel techniques employing near infrared reflectance spectroscopy (NIRS) and sublingual microscopy to explore alterations in microcirculatory function during CPB are reviewed and the implications of these observations for studies investigating minimally invasive extracorporeal circulation (MiECC) are discussed.

The Association Between Pulsatile Cardiopulmonary Bypass and Acute Kidney Injury After Cardiac Surgery: A Before-and-After Study

To investigate the association between pulsatile perfusion and cardiac surgery-associated acute kidney injury. An uncontrolled, retrospective before-and-after study. Single tertiary hospital. A total of 2,489 patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). Pulsatile versus nonpulsatile perfusion. Data for nonpulsatile perfusion was collected from April 1, 2016, to March 31, 2017 (n = 1,223). A practice change to universal pulsatile CPB occurred on April 3, 2017. Data for pulsatile perfusion was collected from May 1, 2017, to June 30, 2018 (n = 1,266). The primary outcome was the incidence of acute kidney injury (AKI) after cardiac surgery. Multivariable analysis was carried out to adjust for known confounders. Secondary outcomes included AKI stage, stroke, length of stay, and mortality. Subgroup analyses were carried out using prolonged CPB and chronic kidney disease. The primary outcome, incidence of AKI, did not differ between the nonpulsatile control group and the pulsatile group (23.9% v 25.4%, p = 0.392). The pulsatile group was not associated with AKI in the multivariable analysis (Odds ratio 1.09, p = 0.413). There were no differences in stages of AKI in the nonpulsatile group v pulsatile group (13.6% v 14.9%, 2.9% v 4.3%, and 7.4% v 6.1% for stages 1, 2, and 3, respectively, p = 0.12). There were no differences in subgroup analyses or secondary outcomes. There was no association found between kidney injury and pulsatile perfusion. It is likely that there is either no association between pulsatile perfusion and reduced kidney injury or that the difference is extremely small.

Comparison of intestinal ischemia after on-pump versus off-pump coronary artery bypass grafting surgery

Background/aim Acute mesenteric ischemia (AMI), one of the gastrointestinal system complications, which occurs following cardiac surgery, is challenged in the literature with a diminished incidence of AMI by heart surgery without cardiopulmonary bypass (CPB) or with pulsatile CPB. This study aims to compare the incidence and mortality rate of mesenteric ischemia in a series of consecutive patients undergoing coronary artery bypass grafting (CABG) through on-pump and off-pump techniques.Materials and methods This study included patients who underwent CABG between 1 January 2010 and 31 June 2016. All patients were divided into two groups: Group 1 comprised 6396 CABG patients operated on with the off-pump technique. Group 2 included 1210 patients who received CABG with the on-pump technique. Preoperative data were collected on the studied variables. Postoperative data included the development of intestinal ischemia and in-hospital mortality.Results Of 7606 consecutive CABG patients, a total of 31 (0.4%) developed intestinal ischemia. The incidence of postoperative mesenteric ischemia was 0.28% in Group 1 and 1.07% in Group 2 (P = 0.000). The survival rates after AMI were 61.1% in Group 1 (off-pump) and 7.7% in Group 2 (on-pump) (P = 0.003). Time from the first occurrence of nonspecific GI complaints to laparotomy was similar in the off-pump and on-pump groups and had no effect on mortality.Conclusions: With regard to the incidence of mesenteric ischemia and survival after laparotomy, off-pump CABG patients revealed significant improvement compared with those operated on with the on-pump technique.

The outcome of pediatric patients undergoing congenital cardiac surgery under pulsatile cardiopulmonary bypass in different frequencies.

PurposeTo investigate the influence and possible pathophysiological mechanism of pulsatile cardiopulmonary bypass (CPB) in various frequencies in pediatric patients undergoing congenital cardiac surgery.Patients and methodsClinical data and hemodynamic parameters were collected in 80 patients who underwent congenital cardiac surgeries and were perfused in different settings: pulsatile perfusion (PP) in frequencies of 30 beats/min, PP 60 beats/min, PP 100 beats/min and non-pulsatile perfusion (NP). Serum proteins, plasma-free hemoglobin (PFH), endothelin-1 (ET-1) and nitric oxide (NO) were collected to study possible pathophysiological changes, possible hematological injury and oxidative status under different perfusing conditions.ResultsPatients in all groups had similar baseline characteristics, aortic cross-clamping time and CPB duration. More effective pulse gradient (PG), energy-equivalent pressure (EEP) and surplus hemodynamic energy (SHE) were observed in pulsatility with lower frequency setting, under which more patients achieved physiologically normal mean arterial pressure (MAP), without the support of inotropic agents during bypass. Significant between-group differences of serum proteins and PFH were absent the whole time during and after bypass, while a relatively lower percentage of perioperative requirement of diuretics was observed in the low frequency pulsatile group. A better performance to oxidative stress was seen in the low frequency group with higher levels of NO and lower concentration of ET-1, and both intergroup differences were found (P<0.01). Satisfactory clinical outcome was obtained on post procedure course in all groups.ConclusionPulsatile perfusion with low frequency setting in pediatric patients undergoing congenital cardiac surgery showed better hemodynamic profiles, potential protective effects on vital organs, better oxidative status and satisfactory clinical outcome.

Pulsed-Doppler evaluation of renal perfusion during pulsatile extracorporeal circulation. A pilot study

Abstract Introduction Acute renal failure (ARF) after cardiac surgery is a risk factor associated with mortality and use of resources. Some studies have reported beneficial effects of pulsatile flow on cardiopulmonary bypass (CPB) on renal function. The aim of this study is to describe the echographic morphology of the renal arterial wave modifying the parameters of pulsatile CPB. Material and method Descriptive study was performed on 10 patients without previous AFR and undergoing cardiac surgery with CPB. Pre-, intra- and post-surgery renal ultrasound was performed. During pulsatile CPB, the amplitude and the baseline flow were modified. Recordings of pulsed Doppler in intrarenal arteries were obtained by measuring maximum systolic velocity, minimum diastolic velocity, resistance index (RI) and acceleration time (AT). Results Statistical differences were found in ultrasounds pre-CPB between A50F50 modality (p = 0.013), A50F30 (p = 0.013) and A60F50 (p = 0.003). No statistically significance was found with A30F30 modality (p = 0.125). Conclusions The decrease in the amplitude and the baseline flow of pulsatility during CPB shows a renal ultrasound morphology that is more similar to the physiological one. Subsequent studies using these characteristics during pulsatile CPB could thus show perfusion over the ARF that occurs after cardiac surgery.

P05-1 - Doppler evaluation of renal perfusion during pulsatile extracorporeal circulation. Pilot study

Acute renal failure (ARF) after cardiopulmonary bypass (CPB) cardiac surgery is a complication associated with healthcare resource consumption and mortality. Since some studies have reported that pulsatile flow on CPB may have beneficial effects on renal function, we decided to describe the renal artery wave morphology modifying pulsatile CPB parameters.

Impact of Distinct Oxygenators on Pulsatile Energy Indicators in an Adult Cardiopulmonary Bypass Model.

The quantification of pulse energy during cardiopulmonary bypass (CPB) post-oxygenator is required prior to the evaluation of the possible beneficial effects of pulsatile flow on patient outcome. We therefore, evaluated the impact of three distinctive oxygenators on the energy indicators energy equivalent pressure (EEP) and surplus hemodynamic energy (SHE) in an adult CPB model under both pulsatile and laminar flow conditions. The pre- and post-oxygenator pressure and flow were measured at room temperature using a 40% glycerin-water mixture at flow rates of 1, 2, 3, 4, 5, and 6 L/min. The pulse settings at frequencies of 40, 50, 60, 70, and 80 beats per minute were according to the internal algorithm of the Sorin CP5 centrifugal pump. The EEP is equal to the mean pressure, hence no SHE is present under laminar flow conditions. The Quadrox-i Adult oxygenator was associated with the highest preservation of pulsatile energy irrespective of flow rates. The low pressure drop-high compliant Quadrox-i Adult oxygenator shows the best SHE performance at flow rates of 5 and 6 L/min, while the intermediate pressure drop-low compliant Fusion oxygenator and the high pressure drop-low compliant Inspire 8F oxygenator behave optimally at flow rates of 5 L/min and up to 4 L/min, respectively. In conclusion, our findings contributed to studies focusing on SHE values post-oxygenator as well as post-cannula in clinical practice. In addition, our findings may give guidance to the clinical perfusionist for oxygenator selection prior to pulsatile CPB based on the calculated flow rate for the individual patient.

Changes in intraocular pressure during cardiopulmonary bypass.

The aim of the present study was to investigate the changes in intraocular pressures (IOP) in patients who underwent pulsatile and non-pulsatile cardiopulmonary bypass (CPB). A total of 42 patients operated for elective coronary bypass surgery (CABG) on CPB were randomly allocated to pulsatile (Group P) and non-pulsatile (Group N) groups. Pulsatile flow was applied to Group P patients during crops-clamp period. The IOP measurements were made before and after the induction of anesthesia, before the onset of CPB, on the 5th, 15th, 30th, 45th, and 60thmin of CPB, after CPB and at the end of the operation. The results of repetitive measurements were analyzed at different intervals and in two groups. The second IOP measurements of right and left eyes displayed statistically significant decreases from the baseline level [11.9±2.9 (p=0.0001) and 12.5±3.2 (p=0.0001), respectively]. The significant decrease in the IOP values persisted in the repeated measurements except for the 5thmin of CPB values [17.0±3.5 (p=0.346) and 16.7±3.6 (p=0.399)]. Comparison of two groups demonstrated significant differences at pre-CPB (right 12.8±2.3 vs. 10.8±2.4; p=0.013 and left 13.3±2.4 vs. 11.5±2.5; p=0.023), and 5thmin of CPB measurements (right 18.5±3.1 vs. 15.9±3.4; p=0.015; left 18.2±3.0 vs. 15.7±3.6; p=0.019). We noted a steady decrease in repeated IOP measurements except for the transient increase in CPB values on 5thmin. The IOP values were higher in pulsatile CPB group in pre-CPB and 5thmin of CPB measurements; however, the difference was not significant in the repeated measurements.

Invited Commentary

I would like to congratulate Elvevoll and colleagues [1Elvevoll B. Lundemoen S. Svendsen O.S. et al.Does roller pump-induced pulsatile CPB perfusion affect microvascular fluid shifts and tissue perfusion?.Ann Thorac Surg. 2016; 102: 564-572Abstract Full Text Full Text PDF PubMed Scopus (3) Google Scholar] for this well thought out trial. Although the size of the aortic cannula does restrict the pulsatile wave form, I think it is still a valid model. The use of microspheres also adds validity to the model and to its results: no difference in pulsatile versus nonpulsatile flow. Pulsatile flow is the most efficient means for our body to power the cardiovascular system, but it is not necessary. This is shown clinically by the success of second-generation mechanical assist devices. The most energy demanding of patients, the pediatric population, grow and thrive on both pulsatile and nonpulsative devices. Hopefully the “golden calf” of pulsatility will soon be slain with device companies focusing on smaller devices and research dollars funneled toward better understanding the nuances of an individuals’ coagulation cascade. Does Roller Pump–Induced Pulsatile CPB Perfusion Affect Microvascular Fluid Shifts and Tissue Perfusion?The Annals of Thoracic SurgeryVol. 102Issue 2PreviewPulsatile versus nonpulsatile cardiopulmonary bypass (CPB) perfusion remains debated. Beneficial effects on tissue perfusion, inflammation, and microvascular fluid exchange have been linked to pulsatile perfusion by some investigators and denied by others. This study evaluated fluid extravasation and tissue perfusion during nonpulsatile or pulsatile roller pump–induced CPB perfusion. Full-Text PDF

The effect of pulsatile cardiopulmonary bypass on the need for haemofiltration in patients with renal dysfunction undergoing cardiac surgery.

The aim of our study was to investigate the effects of pulsatile cardiopulmonary bypass (CPB) on renal function and the need for haemofiltration in patients with preoperative renal impairment undergoing cardiac surgery. Clinical data were collected prospectively for patients undergoing cardiac surgery with pulsatile CPB (Group A, n=66) and compared to matched patients with standard non-pulsatile CPB (Group B, n=66). Patients included in the study had mild renal impairment and at least moderate risk from surgery as defined by logistic EuroSCORE. Emergency operations were excluded. Patients in Groups A and B had similar age (71 ± 10 versus 70 ± 10 years), sex distribution, mean preoperative renal function (creatinine clearance 63.9 ± 28 versus 67.7 ± 27.3 ml/min) and overall risk profile as predicted by the logistic EuroSCORE (8 ± 8.3 versus 11.05±13.3, p=0.122). Intraoperative variables were comparable with respect to bypass and cross-clamp times (96 ± 37 minutes and 64 ± 28 minutes versus 103 ± 40 minutes and 70 ± 33 minutes in Groups A and B, respectively). A smaller proportion of patients in Group A (4.5% versus 15%, p=0.076) required haemofiltration in the postoperative period. Postoperative mortality was low in both groups (Group A 1.54% versus Group B 3.03%, p=1.00). Within the limitations imposed by retrospective analyses, our study demonstrates that pulsatile CPB may confer a reno-protective effect in higher-risk patients with pre-existing mild renal dysfunction undergoing cardiac surgery.

Does Roller Pump–Induced Pulsatile CPB Perfusion Affect Microvascular Fluid Shifts and Tissue Perfusion?

Pulsatile versus nonpulsatile cardiopulmonary bypass (CPB) perfusion remains debated. Beneficial effects on tissue perfusion, inflammation, and microvascular fluid exchange have been linked to pulsatile perfusion by some investigators and denied by others. This study evaluated fluid extravasation and tissue perfusion during nonpulsatile or pulsatile roller pump-induced CPB perfusion. Fourteen pigs underwent roller pump-induced pulsatile (n= 7) or nonpulsatile CPB perfusion (n= 7) for 90 minutes. Fluid input/losses, colloid osmotic pressures (plasma/interstitium), hematocrit, serum electrolytes, serum proteins, tissue perfusion, and total tissue water content were measured, and plasma volume and fluid extravasation were calculated. Fluid additions/losses, plasma volume, and fluid extravasation changed similarly in both groups during CPB with no between-group differences. Neither was between-group differences observed for tissue perfusion and total tissue water content, with one exception. Total tissue water content of the right (3.92 ± 0.26 versus 4.32 ± 0.28 g/g dry weight) and left ventricle (4.02 ± 0.25 versus 4.33 ± 0.24 g/g dry weight) was lowered in the pulsatile group. No important differences were found between pulsatile and nonpulsatile CPB perfusion for microvascular fluid balance and tissue perfusion.

Vascular Occlusion Test to Dynamically Assess Microcirculation During Normothermic Pulsatile Cardiopulmonary Bypass.

To evaluate parameters of the vascular occlusion test (VOT) before, during, and after pulsatile cardiopulmonary bypass (CPB). Prospective, observational study. Single-center university hospital. Adult patients undergoing elective cardiac surgery with pulsatile CPB. An oximeter sensor and adult-sized pneumatic tourniquet were positioned at the right forearm. A VOT with a predefined ischemic time of 3 minutes was performed before, during, and after CPB. Changes in tissue oxygen saturation were recorded. Thirty-four patients who underwent cardiac surgery were enrolled in the study. The lowest tissue oxygen saturation measured during the ischemic challenge differed among all 3 stages of surgery, with median values of 62.9% before, 57.5% during, and 59.3% after perfusion (p<0.05). Both occlusion (p<0.001) and reperfusion (p<0.05) slopes were steeper after bypass compared with before initiating bypass, whereas the reperfusion time remained constant among the different time points. The microcirculatory function as demonstrated by changes in VOT parameters was enhanced during and after normothermic pulsatile CPB. Clinical relevance, however, needs to be further explored.

Investigation of hemodynamics during cardiopulmonary bypass: A multiscale multiphysics fluid–structure-interaction study

Neurological complications often occur during cardiopulmonary bypass (CPB). Hypoperfusion of brain tissue due to diminished cerebral autoregulation (CA) and thromboembolism from atherosclerotic plaque reduce the cerebral oxygen supply and increase the risk of perioperative stroke. To improve the outcome of cardiac surgeries, patient-specific computational fluid dynamic (CFD) models can be used to investigate the blood flow during CPB.In this study, we establish a computational model of CPB which includes cerebral autoregulation and movement of aortic walls on the basis of in vivo measurements. First, the Baroreflex mechanism, which plays a leading role in CA, is represented with a 0-D control circuit and coupled to the 3-D domain with differential equations as boundary conditions. Additionally a two-way coupled fluid–structure interaction (FSI) model with CA is set up. The wall shear stress (WSS) distribution is computed for the whole FSI domain and a comparison to rigid wall CFD is made. Constant flow and pulsatile flow CPB is considered.Rigid wall CFD delivers higher wall shear stress values than FSI simulations, especially during pulsatile perfusion. The flow rates through the supraaortic vessels are almost not affected, if considered as percentages of total cannula output. The developed multiphysic multiscale framework allows deeper insights into the underlying mechanisms during CPB on a patient-specific basis.