Processing scavenged blood with a cell saver reduces cerebral lipid microembolization

Perioperative hemostatic management of patients with type A aortic dissection

Coagulopathy is common in patients undergoing thoracic aortic repair for Stanford type A aortic dissection. Non-critical administration of blood products may adversely affect the outcome. It is therefore important to be familiar with the pathologic conditions that lead to coagulopathy in complex cardiac surgery. Adequate care of these patients includes the collection of the medical history regarding the use of antithrombotic and anticoagulant drugs, and a sophisticated diagnosis of the coagulopathy with viscoelastic testing and subsequently adapted coagulation therapy with labile and stable blood products. In addition to the above-mentioned measures, intraoperative blood conservation measures as well as good interdisciplinary coordination and communication contribute to a successful hemostatic management strategy.

Neurologic complications after cardiopulmonary bypass - A narrative review

Neurologic complications, associated with cardiac surgery and cardiopulmonary bypass (CPB) in adults, are common and can be devastating in some cases. This comprehensive review will not only consider the broad categories of stroke and neurocognitive dysfunction, but it also summarises other neurological complications associated with CPB, and it provides an update about risks, prevention and treatment. Where appropriate, we consider the impact of off-pump techniques upon our understanding of the contribution of CPB to adverse outcomes.

Turbulence in surgical suction heads as detected by MRI

BACKGROUND

Blood loss is common during surgical procedures, especially in open cardiac surgery. Allogenic blood transfusion is associated with increased morbidity and mortality. Blood conservation programs in cardiac surgery recommend re-transfusion of shed blood directly or after processing, as this decreases transfusion rates of allogenic blood. But aspiration of blood from the wound area is often associated with increased hemolysis, due to flow induced forces, mainly through development of turbulence.

METHODS

We evaluated magnetic resonance imaging (MRI) as a qualitative tool for detection of turbulence. MRI is sensitive to flow; this study uses velocity-compensated T1-weighted 3D MRI for turbulence detection in four geometrically different cardiotomy suction heads under comparable flow conditions (0-1250 mL/min).

RESULTS

Our standard control suction head Model A showed pronounced signs of turbulence at all flow rates measured, while turbulence was only detectable in our modified Models 1-3 at higher flow rates (Models 1 and 3) or not at all (Model 2).

CONCLUSIONS

The comparison of flow performance of surgical suction heads with different geometries via acceleration-sensitized 3D MRI revealed significant differences in turbulence development between our standard control Model A and the modified alternatives (Models 1-3). As flow conditions during measurement have been comparable, the specific geometry of the respective suction heads must have been the main factor responsible. The underlying mechanisms and causative factors can only be speculated about, but as other investigations have shown, hemolytic activity is positively associated with degree of turbulence. The turbulence data measured in this study correlate with data from other investigations about hemolysis induced by surgical suction heads. The experimental MRI technique used showed added value for further elucidating the underlying physical phenomena causing blood damage due to non-physiological flow.

Leukoreduction in ex vivo perfusion circuits: comparison of leukocyte depletion efficiency with leukocyte filters

BACKGROUND

Leukodepletion of whole blood-based perfusates remains a challenge in experimental models of ex vivo perfusion. This study investigated the leukoreduction efficacy of the commonly used LeukoGuard LG Arterial and BC2 Cardioplegia filters.

METHODS

Eleven liters of washed porcine blood was used to evaluate the filtration efficiency of LG (n = 6) and BC2 (n = 5) filters. Filter efficacy was tested by passing 1 L of washed blood through each filter. Complete blood count was performed to detect a reduction of white blood cells, red blood cells, and hemoglobin concentration.

RESULTS

The BC2 Cardioplegia filter showed a significant reduction in white blood cell count (13.16 ± 4.2 × 10³ cells/μL pre-filtration, 0.62 ± 0.61 cells/μL post-filtration, p = 0.005), red blood cell count (9.18 ± 0.16 × 10⁶ cells/μL pre-filtration, 9.02 ± 0.16 × 10⁶ cells/μL post-filtration, p = 0.012) and hemoglobin concentration (15.89 ± 0.66 g/dL pre-filtration, 15.67 ± 0.83 g/dL post-filtration, p = 0.017). Platelet reduction in the LG filter group was statistically significant (13.23 ± 13.98 × 10³ cells/μL pre-filtration, 7.15 ± 3.31 × 10³ cells/μL post-filtration, p = 0.029), but no difference was seen in the BC2 group. There was no significant difference in white blood cell count in the LG filter group (10.12 ± 3.0 × 10³ cells/μL pre-filtration, 10.32 ± 2.44 × 10³ cells/μL post-filtration, p = 0.861).

CONCLUSION

Our results suggest that the LG filter should not be used in ex vivo perfusion circuits for the purpose of leukodepletion. The BC2 filter can be used in EVP circuits with flow rates of less than 350 mL/min. Alternatively, perfusate may be leukodepleted before perfusion.

[Cell salvage : Scientific evidence, clinical practice and legal framework]

Cell salvage is an efficient method to reduce the transfusion of homologous banked blood, as documented by several meta-analyses detected in a systematic literature search. Cell salvage is widely used in orthopedics, trauma surgery, cardiovascular and abdominal transplantation surgery. The retransfusion of unwashed shed blood from wounds or drainage is not permitted according to German regulations. Following irradiation of wound blood, salvaged blood can also be used in tumor surgery. Cell salvage makes a valuable contribution to providing sufficient compatible blood for transfusions in cases of massive blood loss. Certain surgical procedures for Jehovah's Witnesses are only possible with the use of cell salvage. Another possible use is the washing of homologous banked blood, e. g. to prevent potassium-induced arrhythmia or sequestration of autologous platelets. Other advantages besides a good compatibility are the high vitality and functionality of the unstored autologous red blood cells. These have been declared a pharmaceutical product by the German transfusion task force in 2014, so that the autologous red blood cells are now under the control of the Pharmaceutical Products Act (AMG). The new hemotherapy guidelines, however, tolerate cell salvage only under strict rules, whereby the production of autologous blood during or after surgery is still possible without additional special permits. The new guidelines now require the introduction of a quality management system for cell salvage and regular quality controls. These quality controls include a control of the product hematocrit for every application, monthly controls of the protein and albumin elimination rates and the erythrocyte recovery rate for each cell salvage device. Testing for infection markers is not required. The application of cell salvage has to be reported to the appropriate authorities.

Additional filtering of blood from a cell salvage device is not likely to show important additional benefits in outcome in cardiac surgery

BACKGROUND

Several authors and manufacturers of cell salvage devices recommend additional filtering of processed blood before transfusion. There is no evidence to support this practice. Therefore, we compared the clinical outcome and biochemical effects of cell salvage with or without additional filtering.

STUDY DESIGN AND METHODS

The patients, scheduled for coronary artery bypass grafting, valve replacement, or combined procedures were part of our randomized multicenter factorial study of cell salvage and filter use on transfusion requirements (ISRCTN 58333401). They were randomized to intraoperative cell salvage or cell salvage plus additional WBC depletion filter. We compared the occurrence of major adverse events (combined death/stroke/myocardial infarction) as primary outcome and minor adverse events (renal function disturbances, infections, delirium), ventilation time, and length of stay in the intensive care unit and hospital. We also measured biochemical markers of organ injury and inflammation.

RESULTS

One hundred eighty-nine patients had cell salvage, and 175 patients had cell salvage plus filter and completed the study. Demographic data, surgical procedures, and amount of salvaged blood were not different between the groups. There was no difference in the primary outcome with a risk of 6.3% (95% confidence interval [CI], 3.34-11.25) in the cell salvage plus filter group versus 5.8% (95% CI, 3.09-10.45) in the cell salvage group, a relative risk of 1.08 (95% CI, 0.48- 2.43]. There were no differences in minor adverse events and biochemical markers between the groups.

CONCLUSION

The routine use of an additional filter for transfusion of salvaged blood is unlikely to show important additional benefits.

The use of RemoweLL oxygenator-integrated device in the prevention of the complications related to aortic valve surgery in the elderly patient: Preliminary results

Background The effects of fat microembolization due to cardiopulmonary bypass are well known in cardiac surgery. Our aim is to evaluate the use of the RemoweLL device (Eurosets, Medolla, Italy) during elective aortic valve replacement in elderly patients (>70 years old) to rate its biochemical and clinical effects. The RemoweLL device is an oxygenator-integrated reservoir which combines two strategies for fat emboli and leucocytes removal: filtration and supernatant elimination. Methods Forty-four elderly patients were enrolled and assigned randomly to a Group A (standard device) and a Group B (RemoweLL). Biochemical effects were evaluated by blood samples, which were tested for white blood cells, neutrophils, protein SP-100 and interleukin 6 besides standard lab tests. Our clinical endpoints were any type of neurological, cardiac, respiratory, gastrointestinal or renal complications, and length of stay in the intensive care unit. Statistical analysis was carried out with chi square test for non-parametric data; t test and analysis of variance for repeated measures were used for parametric data. Results Group B showed lower levels of white blood cells, neutrophils, interleukin 6 and protein SP-100 immediately and 24 hours after the operation. Group B also showed a lower amount of neurocognitive type II dysfunction even if the length of stay in the ICU did not change. Conclusions The RemoweLL system is safe and effective in reducing inflammatory response to cardiopulmonary bypass and it could be a useful tool in minimizing negative effects of cardiopulmonary bypass; however, it does not seem to have any effect on elderly patients' hospital stay.

A Novel Macroscale Acoustic Device for Blood Filtration

Retransfusion of a patient's own shed blood during cardiac surgery is attractive since it reduces the need for allogeneic transfusion, minimizes cost, and decreases transfusion related morbidity. Evidence suggests that lipid micro-emboli associated with the retransfusion of the shed blood are the predominant causes of the neurocognitive disorders. We have developed a novel acoustophoretic filtration system that can remove lipids from blood at clinically relevant flow rates. Unlike other acoustophoretic separation systems, this ultrasound technology works at the macroscale, and is therefore able to process larger flow rates than typical micro-electromechanical system (MEMS) scale acoustophoretic separation devices. In this work, we have first demonstrated the systematic design of the acoustic device and its optimization, followed by examining the feasibility of the device to filter lipids from the system. Then, we demonstrate the effects of the acoustic waves on the shed blood; examining hemolysis using both haptoglobin formation and lactate dehydrogenase release, as well as the potential of platelet aggregation or inflammatory cascade activation. Finally, in a porcine surgical model, we determined the potential viability of acoustic trapping as a blood filtration technology, as the animal responded to redelivered blood by increasing both systemic and mean arterial blood pressure.

A new approach for fat removal in a discontinuous autotransfusion device-concept and evaluation

BACKGROUND

Fat present during blood salvage in orthopaedic or cardiac surgery can pose a risk of fat embolism and should be eliminated before transfusion. Based on observations of central fat accumulation at the bottom of Latham bowls, a fat reduction program was developed using two volume displacements, where blood temporarily is removed and respun in the bowl to force the fat through the RBC sediment.

MATERIALS AND METHODS

Pooled ABO-matched RBC and FFP were adjusted to a haematocrit of 10%, and human fat tissue added to a concentration of 1·25 vol%. In six experiments, blood was processed with the new-generation cell salvage device CS Elite in a newly developed fat reduction program in bowls of three sizes. Volumetric quantification of fat was performed after centrifugation of blood samples in Pasteur pipettes. From volumes, haematocrits and the concentrations of fat, RBC recovery and fat elimination rates were calculated.

RESULTS

Fat removal rates of 93·2 ± 2·8, 97·0 ± 2·1 and 99·6 ± 0·3% were observed with a 70-ml, 125-ml and 225-ml bowl, respectively, and even higher rates when removal rates were calculated one cycle. At the same time, high RBC recovery and plasma elimination rates were maintained, not significantly different to the default program mode.

CONCLUSION

Modifications in process parameters and sequence led to a fat reduction program that significantly improves fat removal with the Cell Saver Elite from 77·4 ± 5·1% in the default mode to an average of 98·6 ± 1·1%, yielding results equivalent to the continuous cell salvage system (C.A.T.S).

Cerebral Oximetry for Cardiac and Vascular Surgery

The technology of transcranial near-infrared spectroscopy (NIRS) for the measurement of cerebral oxygen balance was introduced 25 years ago. Until very recently, there has been only occasional interest in its use during surgical monitoring. Now, however, substantial technologic advances and numerous clinical studies have, at least partly, succeeded in overcoming long-standing and widespread misunderstanding and skepticism regarding its value. Our goals are to clarify common misconceptions about near-infrared spectroscopy and acquaint the reader with the substantial literature that now supports cerebral oximetric monitoring in cardiac and major vascular surgery.

Performance of a new-generation continuous autotransfusion device including fat removal and consequences for quality controls

BACKGROUND AND OBJECTIVES

Cell salvage plays a key role in blood conservation. To maintain high performance, quality management is recommended. Accordingly, a new-generation autotransfusion device was tested for its performance and compared with its predecessor. Two different calculations of quality parameters were applied.

MATERIALS AND METHODS

In an experimental study, the continuous autotransfusion devices CATSmart and Continuous Autotransfusion System (C.A.T.S) plus were tested using banked blood adjusted to a haematocrit of 20% and anticoagulated with heparin 5 U/L. Test blood was processed using an emergency programme, a high-quality programme/smart wash programme and a low-volume wash programme. Samples were taken after the production of 200 mL of red blood cells (RBC) and after the final emptying of the separation chamber. In an additional set of tests, blood containing 1·25% fat was processed with both devices to examine fat removal.

RESULTS

Both devices demonstrated an equally high performance with regards to product hematocrit (Hct); RBC recovery; and elimination rates of protein, heparin and fat. The high fat elimination rate (>99·8%) reported for C.A.T.S plus was confirmed for CATSmart, regardless of the used programme. Samples taken during the ongoing process show a higher haematocrit and RBC recovery rate than samples taken after the final emptying of the separation chamber. Interface sensors were not affected by fat in the blood.

CONCLUSIONS

The new-generation autotransfusion device CATSmart is not inferior to its predecessor and shows high performance with regards to RBC recovery, plasma and fat elimination in all programme modes. Samples for quality controls should be taken during blood processing.

Contaminating fat in pericardial suction blood: a clinical, technical and scientific challenge

Stroke and diffuse brain damage after cardiac surgery are too common. It is important to find means to reduce the incidence in view of future competition to surgery from less invasive procedures. Stroke is fairly well defined in clinical terms and with several identified mechanisms. Diffuse brain damage is less well defined and more complex in nature. One suggested mechanism is from cerebral fat microembolization of retrieved pericardial suction blood (PSB). The present study aimed to describe a simple method to measure fat content of PSB, how experimental artefacts interfere with the results, and how the unstable character of a fat-blood suspension can be used to design a simple fat-separation system. The quantity of small amounts of fat can be amplified by centrifugation to the tapered tip of a standard glass pipette. The coefficient of variation after repeated experiments was 9.5%. PSB after coronary bypass surgery contained 0.22±0.04% fat of which 15±3% was bound to the surface of the plastic collecting bag. Experimentation requires standardized routines. Static incubation, blood-fat mixing routines, and transfer steps of blood samples between syringes induce substantial artefacts from spontaneous density separation and surface-adhesion of fat. Soya oil is a common reference substance replacing human fat in technical laboratory science, but is associated with artefacts of its own. These artefacts cause problems during experimentation but the oil is a good resource in the design of a simple fat-separation system

Reducing Cerebral Emboli During Cardiopulmonary Bypass

Neurologic injury is a common complication of cardiac surgery and is associated with significant morbidity, mortality, and resource utilization. The incidence varies widely according to the definition used, patient age, and complexity of surgery. The manifestations of neurologic injury are broad, ranging from subtle neurocognitive dysfunction to frank stroke. An increasing amount of evidence points to cerebral embolization during cardiopulmonary bypass (CPB) as the principal etiologic factor of these neurologic complications. Cerebral emboli may be composed of atherosclerotic debris, calcium, air, fat, platelet thrombi, or CPB tubing. Advancements in perfusion technology, CPB techniques and surgical strategies may lead to a reduction in neurologic injury during cardiac surgery. In the current paper, we discuss the pathophysiology of neurologic injury after cardiac surgery and methods of reducing cerebral embolization. Reducing emboli and neurologic injury during CPB requires a multidisciplinary approach that includes several simple diagnostic and therapeutic strategies. Reducing cerebral emboli should be a major goal for future research in the fields of cardiac anesthesia, surgery and perfusion.

The Great Britain and Ireland perspective: current perfusion safety issues, preparing for the future

The Great Britain and Ireland (GBI) recommendations for standards of monitoring and alarms during cardio-pulmonary bypass (CPB) came into force in January 2004. While perfusion departments in Great Britain and Ireland should now have a good baseline level of safety, it is important that department-specific safety is also considered. Patient safety is paramount, but safety within our speciality must also take into account the protection of the perfusionists’ health and the protection of their careers. These different aspects of safety are fundamentally interrelated.

This paper focuses on the importance of careful assessment, implementation and documentation when a new component or technique is being introduced to the CPB circuit, even when the aim is to increase safety.

Knowledge of the civil justice system and the trends in medical negligence claims are an integral part of perfusionist safety. Perfusion in Great Britain and Ireland is rightly striving for professional recognition from the Health Professions Council (HPC). As we raise the profile of perfusion, we educate more people about the importance of our role and level of responsibility within the cardiac operating team. This will increase the potential for medical negligence claims to be directed specifically at our speciality. All these issues are discussed in detail.

Influence of pericardial suction blood retransfusion on memory function and release of protein S100B

Background: To study the influence of pericardial suction blood (PSB) on postoperative memory disturbances and release patterns of protein S100B during and after cardiopulmonary bypass (CPB).

Methods: Sixty male patients admitted for coronary artery bypass surgery were prospectively randomized to receive PSB either by using conventional cardiotomy suction retransfusion or after cell-saver processing.

Results: The concentration of S100B rose during the period of CPB from 0.065±0.004 to 0.24±0.001 mg/L (p<0.001). PSB contained 18.0±1.7 mg/L of S100B. Direct retransfusion from the cardiotomy reservoir made the systemic level increase to 1.42±0.19 mg/L compared to 0.25±0.02 mg/L using a cell-saver. Signs of postoperative memory dysfunction (> 1 SD) were discovered in one of three tests, but were unrelated to technique of retransfusion. No associations were found between serum concentrations of S100B and memory function.

Conclusion: In this study, retransfusion of PSB during cardiac surgery appeared not to cause memory disturbances. PSB contained high concentrations of protein S100B making its use as a marker of cerebral injury unsuitable.

Use of the Reamer/Irrigator/Aspirator Decreases Carotid and Cranial Embolic Events in a Canine Model

BACKGROUND

Approximately 2 million patients in the United States annually undergo total joint arthroplasty with reaming and placement of intramedullary nails, resulting in extravasation of bone marrow and fat into the circulatory system and potentially causing fat embolism syndrome. Acute and chronic changes in mental status documented after these procedures may be related to embolic events. The Reamer/Irrigator/Aspirator (RIA) device has been shown to decrease intramedullary pressure during reaming. We hypothesized that the use of the RIA in a canine model would reduce the number of microemboli detected in the carotid artery and brain compared with nailing either with or without reaming.

METHODS

Twenty-four large canines underwent unreamed nailing (UR), sequentially reamed nailing (SR), or RIA-reamed nailing (RIA) of bilateral femora (eight dogs per group). During reaming and nailing, the number and size of microemboli transiting the carotid artery were recorded. After euthanasia, the brain was harvested for immunostaining and measurement of microinfarction volumes.

RESULTS

Total embolic load passing through the carotid artery was 0.049 cc (UR), 0.045 cc (SR), and 0.013 cc (RIA). The number and size of microemboli in the UR and SR groups were similar; however, the RIA group had significantly fewer larger-sized (>200-μm) emboli (p = 0.03). Pathologic examination of the brain confirmed particulate emboli, and histologic analyses demonstrated upregulation of stress-related proteins in all groups, with fewer emboli and less evidence of stress for RIA reaming.

CONCLUSIONS

RIA reaming decreased microemboli compared with traditional reaming and unreamed nailing, suggesting that intramedullary pressure and heat are important variables. The documented embolic events and brain stress may help to explain subtle neurobehavioral symptoms commonly seen in patients after undergoing long-bone reaming procedures.

CLINICAL RELEVANCE

RIA reaming decreased cranial embolic events and may have an ameliorating effect on postoperative neurologic sequelae.

Fat removal during cell salvage: an optimized program for a discontinuous autotransfusion device

BACKGROUND

Fat in wound blood observed in orthopedic or cardiac surgery might pose a risk for fat embolism during blood salvage. Fat removal was optimized in the washing process.

STUDY DESIGN AND METHODS

In an experimental study blood from fresh donations was adjusted to a hematocrit (Hct) of 25% and an admixture of 1.25% human tissue fat. This blood was processed with the cell salvage device XTRA in a modified program mode. Volumetric quantification of fat was performed after centrifugation of blood samples in Pasteur pipettes. From the volumes, the Hct levels and the concentrations of fat and other variables elimination rates and RBC recovery were calculated.

RESULTS

Pretests showed wash volume, wash flow, and process interruptions affecting fat elimination. With the new optimized fat elimination program Pfat removal rate of fat increased to 98.5 ± 0.9% for the 225-mL bowl. The product had a mean Hct of 48.7 ± 1.2% and a RBC recovery rate of 93.5 ± 2.3%. The program conserved the high elimination rates for albumin, heparin, potassium, and free plasma hemoglobin (98.8, 99.3, 95.3, and 94.9%, respectively). Similar high fat removal was also observed with bowls of smaller size, namely, 98.1% for the 175-mL bowl and 98.2% for the 125- and the 55-mL bowls. With test blood of Hct 10% a mean fat elimination of 99.6 ± 01% was observed.

CONCLUSIONS

A special program modification Pfat involving extra washing and RBC concentration steps significantly improves fat removal by the Latham bowl-based autotransfusion device XTRA, thus yielding results equivalent to the continuous cell salvage system.

Fat removal during cell salvage: a comparison of four different cell salvage devices

BACKGROUND

Fat embolism is a possible risk factor for pulmonic and cerebral dysfunction after orthopedic and heart surgery. It is unknown whether fat occasionally observed during cell salvage adds to the risk of fat embolism after retransfusion. We have examined the fat removal capacities of different cell salvage devices including discontinuous and a continuous system under various conditions.

STUDY DESIGN AND METHODS

In an experimental study ABO-matched banked blood was adjusted to a hematocrit of 20%, and 1.25% of human fat was added. This blood was processed with the cell salvage devices XTRA and Electa, CATS, or Cell Saver 5 plus. Fat in the blood samples was quantified by volumetric measurement after centrifugation in Pasteur pipettes and by gravimetric measurement after extraction of fat in organic solvents and phase partition. Performance in fat removal was tested with different programs, bowl sizes, and additional filtration.

RESULTS

The continuous system consistently showed a high fat removal rate of 99.8 ± 0.2%. Fat accumulated in the wash disposal, but not in the product. In the Latham bowl-based discontinuous systems, fat removal varied from 69.2 to 92.8 ± 4.4% depending on the program mode, but not on the bowl size. Additional filtration increased fat removal to 96.7 ± 2.2%, but also increased red blood cell loss.

CONCLUSIONS

Fat contamination of wound blood can be detected by volumetric and gravimetric measurements. Continuous salvage systems remove fat to a higher extent than discontinuous systems. The fat removal capacities of discontinuous systems depend on the program mode and can be improved by filtration.

Pathophysiology of Cardiopulmonary Bypass

The techniques and equipment of cardiopulmonary bypass (CPB) have evolved over the past 60 years, and numerous numbers of cardiac surgical procedures are conducted around the world using CPB. Despite more widespread applications of percutaneous coronary and valvular interventions, the need for cardiac surgery using CPB remains the standard approach for certain cardiac pathologies because some patients are ineligible for percutaneous procedures, or such procedures are unsuccessful in some. The ageing patient population for cardiac surgery poses a number of clinical challenges, including anemia, decreased cardiopulmonary reserve, chronic antithrombotic therapy, neurocognitive dysfunction, and renal insufficiency. The use of CPB is associated with inductions of systemic inflammatory responses involving both cellular and humoral interactions. Inflammatory pathways are complex and redundant, and thus, the reactions can be profoundly amplified to produce a multiorgan dysfunction that can manifest as capillary leak syndrome, coagulopathy, respiratory failure, myocardial dysfunction, renal insufficiency, and neurocognitive decline. In this review, pathophysiological aspects of CPB are considered from a practical point of view, and preventive strategies for hemodilutional anemia, coagulopathy, inflammation, metabolic derangement, and neurocognitive and renal dysfunction are discussed.

Cognitive impairment before and six months after cardiac surgery increase mortality risk at median 11 year follow-up: a cohort study

BACKGROUND

The additive effects of cognitive impairment and depression on mortality risk after cardiac surgery are unknown.

METHODS

Patients were assessed on a battery of six neurocognitive measures before cardiac surgery (N = 521) and at six month follow up (N = 377/521, 72.4%). Cognitive impairment classification was based on cognitive test scores 1 SD below age and sex matched normative data, and classified according to amnestic, non-amnestic and mixed cognitive impairment subtypes. Survival analyses entered cognitive impairment subtypes and depression interactions terms adjusted for 12 common risk factors.

RESULTS

There were 5407 person years for analysis (median 11.1 year survival, interquartile range of 7.9 to 13.1) and 176 deaths (33.8%) by the census date. Before cardiac surgery, patients with a mixed-cognitive impairment (adjusted hazard ratio (HR) = 2.53; 95% confidence interval (CI), 1.57-4.06, p<.001) and non-amnestic cognitive impairment (adjusted HR = 1.51; 95%, 1.00-2.32, p = .05) were at greater mortality risk. Six month analyses corroborated that the mixed-cognitive impairment group were at higher mortality risk (adjusted HR = 2.35; 95% CI, 1.30-4.25, p = .005). When change in neurocognitive functioning over time was analyzed, a higher mortality risk was evident only amongst patients with cognitive impairment evident at baseline and six months (adjusted HR = 1.83; 95% CI, 1.08-3.10, p = .03). No cognition by depression interaction term was significant.

CONCLUSIONS

These data suggest that a mixed cognitive impairment subtype, and continuing cognitive impairment before and six months after cardiac surgery, is associated with long term mortality, independent of depression and common risk factors.

Lipid emboli distribution in cardiac surgery is dependent on the state of emulsification

OBJECTIVE

Lipid embolizations from retransfused shed blood during cardiac surgery have been shown to enter the circulation and end up in different organs. The purpose of this investigation was to evaluate differences in the kinetics and deposition between emulsified and non-emulsified lipid emboli in a porcine model.

DESIGN

Twelve animals were anesthetized and put on cardiopulmonary bypass. A shed-blood phantom (6 animals given emulsified and 6 given non-emulsified lipids) was produced from arterial blood, saline, and tritium-labeled triolein. The phantom was infused into the cardiopulmonary bypass circuit. Arterial and venous blood samples were taken at short intervals. Tissue samples were taken post-mortem from examined organs and prepared for scintillation counting. Levels of radioactivity were used to measure lipid emboli content in blood and tissue.

RESULTS

Emulsified lipid emboli generated a 5-fold higher embolic load in the arterial and a 12-fold higher in the venous circulation, compared with non-emulsified lipid emboli. Emulsified lipid micro emboli resulted in a 2-15-fold higher tissue deposition in investigated organs compared with non-emulsified lipid micro emboli.

CONCLUSIONS

This study shows that the state of emulsion significantly alter the kinetics and tissue deposition of lipid emboli. Emulsified lipid emboli give higher embolic load in the arterial and venous circulation, and higher tissue deposition versus non-emulsified lipid emboli. In both groups, the embolic load was higher in the arterial circulation than on the venous side.

Comparison between transcranial Doppler and Coulter counter for detection of lipid micro embolization from mediastinal shed blood reinfusion during cardiac surgery

INTRODUCTION

Lipid micro embolization (LME) from re-transfused shed blood has been postulated to be a potential reason for short- and long-term cognitive dysfunction after cardiac surgery. The purpose of this investigation was to evaluate if transcranial Doppler (TCD) has the capacity to detect LME.

METHODS

Thirteen patients undergoing cardiopulmonary bypass surgery were investigated. Each patient's cerebral circulation was monitored with transcranial Doppler during the first two minutes after re-transfusion of shed blood and blood was simultaneously sampled and characterised by a Coulter counter.

RESULTS

Strong correlation was found between embolic loads, as measured by transcranial Doppler and Coulter counter (r=0.79, P<0.005).

CONCLUSIONS

This pilot study shows that non-invasive monitoring by transcranial Doppler could be a potential tool to monitor LME during cardiopulmonary bypass surgery.

The coagulopathy of cardiopulmonary bypass

There have been numerous publications on the coagulopathy of cardiopulmonary bypass (CPB). This review provides an introduction to the history and main components of current CPB circuits and summarizes the current knowledge of pathogenesis, prevention, and treatment of the CPB coagulopathy. It encompasses an overview of intra- and postoperative monitoring of coagulation with special emphasis on the near-patient testing, its main complications, and the transfusion support, while taking into account the major changes in the technology used and supportive care provided since its inception.

Comparison of the use of minimized cardiopulmonary bypass with conventional techniques on the incidence of retinal microemboli during aortic valve replacement surgery

OBJECTIVES

Minimized cardiopulmonary bypass (MCPB) circuits have been shown to reduce cerebral and retinal microembolisation during coronary artery bypass graft (CABG) surgery compared to conventional CPB (CCPB) circuits. Our aim was to evaluate whether the reduction of microembolisation is sustained in aortic valve surgery, as well as to evaluate the effects of MCPB on inflammatory, endothelial, and platelet activation markers.

MATERIAL AND METHODS

Patients were randomized to undergo aortic valve replacement (AVR), with or without CABG, with MPCB (n=20) or CCPB (n=20). After anaesthesia induction and termination of CPB, standardized digital retinal fluorescein angiography images were obtained on both eyes and analyzed in a blinded fashion. Blood samples were collected at eight time points until the third postoperative day.

RESULTS

Fewer patients in the MCPB group showed evidence of microembolic perfusion defects on postperfusion retinal fluorescein angiographs compared to the CCPB group (37% vs. 63%, absolute difference 26%, 95% CI -5% -51%, P = 0.194). Polymorphonuclear leukocyte (PMN) elastase and von Willebrand factor release were statistically significantly reduced in the MCPB group, but there were no significant differences in other markers of inflammation, coagulation or endothelial activation. A significantly higher three-fold increase in the amount of shed blood was collected to the cell saver with a higher rate of intraoperative platelet transfusion in the MCPB group compared to CCPB.

CONCLUSIONS

The use of MCPB was associated statistically insignificantly with less retinal microemboli compared to CCPB. MCPB was complicated by excess bleeding and need for transfusion. The feasibility of MCPB techniques in valve surgery requires further studies.

Increased cerebral blood flow velocities assessed by transcranial Doppler examination is associated with complement activation after cardiopulmonary bypass

The role of complement activation on the cerebral vasculature after cardiopulmonary bypass (CPB) is unclear. The goal of the study was to assess whether heparin-coated CPB reduces complement activation, and influences cerebral blood flow velocities (CBFV). Twenty-four patients undergoing coronary surgery were randomly allocated to non-coated (NC-group) or heparin-coated (HC-group) CPB. Complement activation was assessed by measuring sC5b-9. Transcranial Doppler (TCD) was performed on middle cerebral arteries before and after CPB. Systolic (SV), diastolic (DV) and mean (MV) CBFV were measured. Significant increase of sC5b-9 (p=0.003) was observed in the NC-group and CBFV increased after CPB (SV by 27%, p=0.05; DV by 40%, p=0.06; MV by 33%, p=0.04) whereas no changes were detected in the HC-group. TCD values were higher in the NC-group than in the HC-group (SV, p=0.04; DV, p=0.03; MV, p=0.03) although cardiac index, systemic vascular resistance, haematocrit and pCO2 were similar. Postoperative SV, DV and MV were significantly correlated with sC5b-9 (r=0.583, p=0.009; r=0.581, p=0.009; r=0.598, p=0.007, respectively). Increased CBFV after CPB are correlated to the level of complement activation and may be controlled by heparin-coated circuits.

Efficacy of a New Oxygenator-Integrated Fat and Leukocyte Removal Device

We evaluated the effectiveness of a new oxygenator-integrated device for removing lipid particles and leukocytes from shed mediastinal blood in 20 patients undergoing elective cardiac surgery under cardiopulmonary bypass. Another 20 patients undergoing cardiac surgery without the device served as controls. After filtration with the RemoveLL device, lipid particles, leukocytes, and fats were significantly reduced compared to preoperative levels. In the control group, blood fats and lipid particles at the end of cardiopulmonary bypass were significantly increased compared to preoperative levels. Leukocyte counts at the end of bypass were significantly lower in patients who had the filtration device compared to the control group. Platelets counts and hematocrit changes were not significantly different between the 2 groups.

Cell salvage as part of a blood conservation strategy in anaesthesia

The use of intraoperative cell salvage and autologous blood transfusion has become an important method of blood conservation. The main aim of autologous transfusion is to reduce the need for allogeneic blood transfusion and its associated complications. Allogeneic blood transfusion has been associated with increased risk of tumour recurrence, postoperative infection, acute lung injury, perioperative myocardial infarction, postoperative low-output cardiac failure, and increased mortality. We have reviewed the current evidence for cell salvage in modern surgical practice and examined the controversial issues, such as the use of cell salvage in obstetrics, and in patients with malignancy, or intra-abdominal or systemic sepsis. Cell salvage has been demonstrated to be safe and effective at reducing allogeneic blood transfusion requirements in adult elective surgery, with stronger evidence in cardiac and orthopaedic surgery. Prolonged use of cell salvage with large-volume autotransfusion may be associated with dilution of clotting factors and thrombocytopenia, and regular laboratory or near-patient monitoring is required, along with appropriate blood product use. Cell salvage should be considered in all cases where significant blood loss (>1000 ml) is expected or possible, where patients refuse allogeneic blood products or they are anaemic. The use of cell salvage in combination with a leucocyte depletion filter appears to be safe in obstetrics and cases of malignancy; however, further trials are required before definitive guidance may be provided. The only absolute contraindication to the use of cell salvage and autologous blood transfusion is patient refusal.

Pathophysiological aspects of cardiotomy suction usage

Cardiotomy suction is used for preservation of autologous blood during on-pump cardiac surgery at present. Controversially, the exclusion of cardiotomy suction in some types of operations (coronary artery bypass surgery) is not necessarily associated with an increased transfusion requirement. On the other hand, the use of cardiotomy suction causes an amplification of systemic inflammatory response and a resulting coagulopathy, as well as exacerbation of the microembolic load and hemolysis. This leads to a tendency towards increased blood loss, transfusion requirement and organ dysfunction. On the basis of these facts, it is appropriate to reconsider routine use of cardiotomy suction in on-pump coronary artery surgery.

Role of surgical factors in strokes after cardiac surgery

Deficient neurological disorders after heart surgery are destructive and affect vital prognosis. They concern between 3% to 9% of patients and are related mainly to embolic episodes or brain perfusion defects. The causes of these mechanisms are numerous, but surgical procedures and cardiopulmonary bypass optimization reduce their occurrence significantly.

The efficacy of an intraoperative cell saver during cardiac surgery: a meta-analysis of randomized trials

BACKGROUND

Cell salvage may be used during cardiac surgery to avoid allogeneic blood transfusion. It has also been claimed to improve patient outcomes by removing debris from shed blood, which may increase the risk of stroke or neurocognitive dysfunction. In this study, we sought to determine the overall safety and efficacy of cell salvage in cardiac surgery by performing a systematic review and meta-analysis of published randomized controlled trials.

METHODS

A comprehensive search was undertaken to identify all randomized trials of cell saver use during cardiac surgery. MEDLINE, Cochrane Library, EMBASE, and abstract databases were searched up to November 2008. All randomized trials comparing cell saver use and no cell saver use in cardiac surgery and reporting at least one predefined clinical outcome were included. The random effects model was used to calculate the odds ratios (OR, 95% confidence intervals [CI]) and the weighted mean differences (WMD, 95% CI) for dichotomous and continuous variables, respectively.

RESULTS

Thirty-one randomized trials involving 2282 patients were included in the meta-analysis. During cardiac surgery, the use of an intraoperative cell saver reduced the rate of exposure to any allogeneic blood product (OR 0.63, 95% CI: 0.43-0.94, P = 0.02) and red blood cells (OR 0.60, 95% CI: 0.39-0.92, P = 0.02) and decreased the mean volume of total allogeneic blood products transfused per patient (WMD -256 mL, 95% CI: -416 to -95 mL, P = 0.002). There was no difference in hospital mortality (OR 0.65, 95% CI: 0.25-1.68, P = 0.37), postoperative stroke or transient ischemia attack (OR 0.59, 95% CI: 0.20-1.76, P = 0.34), atrial fibrillation (OR 0.92, 95% CI: 0.69-1.23, P = 0.56), renal dysfunction (OR 0.86, 95% CI: 0.41-1.80, P = 0.70), infection (OR 1.25, 95% CI: 0.75-2.10, P = 0.39), patients requiring fresh frozen plasma (OR 1.16, 95% CI: 0.82-1.66, P = 0.40), and patients requiring platelet transfusions (OR 0.90, 95% CI: 0.63-1.28, P = 0.55) between cell saver and noncell saver groups.

CONCLUSIONS

Current evidence suggests that the use of a cell saver reduces exposure to allogeneic blood products or red blood cell transfusion for patients undergoing cardiac surgery. Subanalyses suggest that a cell saver may be beneficial only when it is used for shed blood and/or residual blood or during the entire operative period. Processing cardiotomy suction blood with a cell saver only during cardiopulmonary bypass has no significant effect on blood conservation and increases fresh frozen plasma transfusion.

Suction, salvage, sutures, and potions: blood management post-aprotinin

Hemostasis management of the cardiac surgical patient has changed following the withdrawal of aprotinin for use in cardiac surgical patients. The challenge to minimize blood loss and reduce exposure of cardiac surgical patients to blood products continues to grow with patients presenting being older and sicker and more complex procedures being performed. The cardiac surgery team has many options available for it to consider; although current recommendations strongly support the use of cell salvage as one process to assist in this challenge, other options need to be equally critically evaluated.

Optimal Versus Suboptimal Perfusion During Cardiopulmonary Bypass and the Inflammatory Response

Despite major improvements in perfusion techniques over the past 50 years, it is still not possible to formulate a clear definition of what is meant by optimal perfusion. In part this is due to the lack of sufficient evidence-based data and in part because of the complex pathophysiology that takes place during cardiac surgery with cardiopulmonary bypass. To find an answer we need to understand the exact mechanism of the inflammatory reaction triggered by the cardiopulmonary bypass. However, it is clear that further improvement of the cardiopulmonary bypass components alone will be sufficient. Only a combined strategy can further improve cardiopulmonary bypass—related morbidity and mortality. Such a combined strategy will embrace perfusion techniques as well as a pharmacological approach. It will also require a continuous monitoring of the microcirculation. The latter will not only allow to rapidly sense changes in the quality of perfusion but, even more important, also make it possible to intervene at the moment of deterioration. Recent research shows that such an approach has positive an impact on cardiopulmonary bypass—related morbidity postoperatively.

Pericardial suction blood separation attenuates inflammatory response and hemolysis after cardiopulmonary bypass

OBJECTIVES

Retransfusion of pericardial suction blood (PSB) is critically considered under the aspect of the biocompatibility of the cardiopulmonary bypass (CPB). We investigated various indicators of inflammation and blood cell activation associated with CPB and re-transfusion of PSB during cardiac surgery.

DESIGN

Thirty-five patients undergoing elective coronary artery bypass grafting were prospectively randomized into two groups. In group A (n = 15, retransfusion group) the pericardial suction blood was continuously retransfused during CPB, in group B (n = 20, no-retransfusion group) the suction blood was separated. Parameters indicating the status of the inflammation and blood cell activation were analyzed before and at the end of CPB, latest after 90 minutes on CPB.

RESULTS

Patients' perioperative data did not differ between groups. The inflammatory markers C-reactive protein, PMN-Elastase and Interleukin-6 increased in both groups after CPB (p < 0.04) with significantly lower values in the no-retransfusion group (p < 0.02). Leukocytes and platelet activation markers beta-Thromboglobulin and soluble P-Selectin also experienced a significant elevation during observation time (p < 0.02) without any difference between the groups. Free hemoglobin and LDH tremendously increased during CPB with lower values in the no-retransfusion group.

CONCLUSIONS

Cardiotomy suction is a major cause of hemolysis and contributes significantly to the systemic inflammatory response.

Detection and Elimination of Microemboli Related to Cardiopulmonary Bypass

Background— Neurobehavioral impairment is a common complication of coronary bypass surgery. Cerebral microemboli during cardiopulmonary bypass (CPB) are a principal mechanism of cognitive injury. The aim of this work was to study the occurrence of cerebral embolism during CPB and to evaluate the effectiveness of evidence-based CPB circuit component and process changes on the exposure of the patient to emboli.

Methods and Results— M-Mode Doppler was used to detect emboli in the inflow and outflow of cardiopulmonary circuit and in the right and left middle cerebral arteries. Doppler signals were merged into a single display to allow real-time associations between discrete clinical techniques and emboli detection. One hundred sixty-nine isolated coronary artery bypass grafting (CABG) patients were studied between 2002 and 2008. There was no statistical difference in median microemboli detected in the inflow of the CPB circuit, (Phase I, 931; Phase II, 1214; Phase III, 1253; Phase IV, 1125; F [3,158]=0.8, P =0.96). Significant changes occurred in median microemboli detected in the outflow of the CPB circuit across phases, (Phase I, 702; Phase II, 572; Phase III, 596; Phase IV, 85; F [3,157]=13.1, P <0.001). Significant changes also occurred in median microemboli detected in the brain across phases, (Phase I, 604; Phase II, 429; Phase III, 407; Phase IV, 138; F [3,153]=14.4, P <0.001). Changes in the cardiopulmonary bypass circuit were associated with an 87.9% (702 versus 85) reduction in median microemboli in the outflow of the CPB circuit ( P <0.001), and a 77.2% (604 versus 146) reduction in microemboli in the brain ( P <0.001).

Conclusions— Changes in CPB techniques and circuit components, including filter size and type of pump, resulted in a reduction in more than 75% of cerebral microemboli.

Avecor Trillium oxygenator versus noncoated Monolyth oxygenator: a prospective randomized controlled study

OBJECTIVES

The surface coating of a synthetic surface is currently investigated to decrease the harmful effects of cardiopulmonary bypass (CPB). This study was designed to study the effects of the surface coating of a hollow fiber membrane oxygenator on coagulation, inflammation markers, and clinical outcomes. The biomaterials used to coat the membrane include heparin, polyethylene oxide chains (PEO), and sulfate/sulfonate groups. The coated membrane was compared to an uncoated oxygenator made of polypropylene.

METHODS

Two hundred patients who were scheduled to undergo valve repair and/or replacement surgery with or without coronary surgery were enrolled in the study. The patients were randomized to undergo CPB with either the Avecor oxygenator with Trillium (Medtronic, Minneapolis, MN, USA), a biopassive surface, or the Monolyth (Sorin, Irvine, CA, USA) oxygenator without coating. The primary and secondary endpoints were the differences between these oxygenators in regard to patients' biochemistry, coagulation profiles, inflammatory mediators, and clinical outcomes, including blood loss and neurological events.

RESULTS

There were no differences between the two groups in terms of biochemistry, coagulation profile, inflammatory mediator release, and blood loss. Five patients in the Avecor group showed clinical evidence of a stroke confirmed with computerized tomography (CT) scan imaging, and none in the noncoated oxygenator group.

CONCLUSION

The oxygenator Avecor offers similar results in terms of inflammation and coagulation profiles and blood loss during valvular surgery compared to a standard uncoated control oxygenator. The rate of neurological events was unusually elevated in the former group of patients, with only speculative explanation at this point. Further studies are warranted to clarify this aspect.

Microbubbles detection during cardiopulmonary bypass with transoesophageal echocardiography: a case report

INTRODUCTION

Microembolic signals are usually detected with transcranial doppler during cardiac surgery.This report focuses on suggesting the transesophageal echocardiography as a different diagnostic approach to detect microemboli during cardiopulmonary bypass.

CASE PRESENTATION

A 58 year old male patient, caucasian race, was operated on video assisted minimally invasive mitral valve repair using right minithoracotomy approach. His past medical history included an uncontrolled hypertension, dyslipidemia, insulin dependent diabetes mellitus, carotid arteries stenosis. The extracorporeal circulation was performed with femoral-femoral artery and venous approach. Negative pressure for vacuum assist venous drainage was applied in order to facilitate venous blood return. The patient had a brain monitoring with bilateral transcranial doppler of middle cerebral arteries and a double channels electroencephalogram. A three dimensional transesophageal echocardiography to evaluate the mitral valve repair was performed.During the cardiopulmonary bypass a significant microembolic activity was detected in the middle cerebral arteries spectrum velocities due to gas embolism from venous return. Simultaneous recording of microbubbles was also observed on the descending thoracic aorta transesophageal echo views.

CONCLUSION

During the aortic cross-clamping time the transesophageal echocardiography can be useful as an alternative method to assess the amount of gas embolism coming from cardiopulmonary bypass. These informations can promote immediate interaction between perfusionist, surgeon and anesthesiologist to perform adequate manoeuvres in order to reduce the microembolism during extracorporeal circulation.