Fat contamination of pericardial suction blood and its influence on in vitro capillary-pore flow properties in patients undergoing routine coronary artery bypass grafting

Do lipid microemboli induce acute kidney injury during cardiopulmonary bypass?

BACKGROUND

Acute kidney injury (AKI) following cardiopulmonary bypass affects 5% of patients, representing significant postoperative morbidity and mortality. Animal models have shown an increased uptake of lipid microemboli (LME) into the renal vasculature, potentially indicating ischaemic causation. This study tested a new lipid filtration system (RemoweLL) against a conventional system with no lipid-depleting capacity to determine the efficacy of the filtration system and its effects on renal function.

METHODS

Thirty consecutive patients underwent coronary artery bypass graft surgery using either the RemoweLL filtration system (15 patients) or a conventional cardiopulmonary bypass circuit (15 patients). Renal function was assessed using cystatin C concentrations as a surrogate marker of glomerular injury, as well as perioperative glomerular filtration rate (GFR) and serum creatinine concentrations. Patients were defined as having acute renal injury if there was an increase in absolute serum creatinine ⩾3 mg/dL (26.4 µmol/L) or 1.5-fold increase from baseline as categorised using the AKIN criteria.

RESULTS

Postoperative differences in LME count between the two groups were highly significant [p<0.001]. Analysis of peak cystatin C concentrations showed significantly lower levels in the LME filtration group on the 2^nd postoperative morning [p=0.04]. Two-factor ANOVA revealed a trend towards interaction, but this failed to reach significance [p=0.06]. There were no differences throughout the study period in serum creatinine or GFR [p>0.05]. There were no differences in any of the serum or urinary electrolytes.

CONCLUSIONS

This study has shown a trend towards improved cystatin C removal with LME filtration; with significantly lower peak concentrations, although no further evidence of renoprotection could be demonstrated. Further research is warranted to establish possible renal benefits of LME filtration in patients undergoing cardiac surgery.

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

Efficacy of the RemoweLL cardiotomy reservoir for fat and leucocyte removal from shed mediastinal blood: a randomized controlled trial

Introduction:

Re-transfusion of lipid particles and activated leucocytes with shed mediastinal blood (SMB) can aggravate cardiopulmonary bypass-associated inflammation and increase the embolic load. This study evaluated the fat and leucocyte removal capacity of the RemoweLL cardiotomy reservoir.

Methods:

Forty-five patients undergoing elective on-pump cardiac surgery were randomly allocated to filtration of SMB using the RemoweLL or the Admiral cardiotomy reservoir. The primary outcome was a drop in leucocytes and lipid particles obtained with the two filters. The effect of the filters on other blood cells and inflammatory mediators, such as myeloperoxidase (MPO), was also assessed.

Results:

The RemoweLL cardiotomy filter removed 16.5% of the leucocytes (p<0.001) while no significant removal of leucocytes was observed with the Admiral (p=0.48). The percentage reductions in lipid particles were similar in the two groups (26% vs 23%, p=0.2). Both filters similarly affected the level of MPO (p=0.71).

Conclusion:

The RemoweLL filter more effectively removed leucocytes from SMB than the Admiral. It offered no advantage in terms of lipid particle clearance.

Pathophysiological Basis of CNS Injury in Cardiac Surgical Patients: Detection and Prevention

The current understanding of adverse central nervous system (CNS) events following cardiac surgery involves several identifiable, evidence-based mechanisms: athero-sclerotic emboli, microgaseous and microparticulate emboli, and hypoperfusion.1 Secondary factors, including patient co-morbidities and inherent genetic susceptibilities, as well as systemic inflammatory processes and a suboptimal metabolic milieu may interact to potentiate the extent of injury.2 In this review a number of these factors and their potential interactions will be explored with a view towards developing a comprehensive management strategy to minimize CNS injury.

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.

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.

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.

Effects of poly-2-methoxyethylacrylate (PMEA)-coating on CPB circuits

OBJECTIVES

In this study, the immuno- and neuroprotective effect of a novel cardiopulmonary bypass coating was investigated.

DESIGN

Thirty nine patients scheduled for elective coronary artery bypass grafting were randomly assigned to either PMEA-coated (n = 19) or non-coated CPB circuits (n = 20). Pericardial suction blood was separated and retransfused only if needed at the end of operation. Neurocognitive functions were examined preoperatively and 7-10 days postoperatively using a standard neuropsychological test battery. Assuming an inflammatory etiology, the most cogent inflammatory markers were perioperatively analyzed.

RESULTS

Postoperatively, patients of the PMEA-coated group performed better in Go/NoGo and Mini-Mental-test than patients of the non-coated group (p < 0.04). Other neurocognitive testing did not reveal significant differences between the groups. Although most inflammatory parameters showed a significant intraindividual increase during or shortly after CPB, there was no difference in inflammatory alteration between the groups.

CONCLUSIONS

PMEA-coating of cardiopulmonary bypass surfaces revealed some minor benefits in preservation of neurocognitive functions after surgery. The immediate inflammatory response remained mostly unaffected. Suction blood separation may additionally contribute to proper postoperative outcome.

The kinetics of lipid micro-emboli during cardiac surgery studied in a porcine model

OBJECTIVE

To study the kinetics of lipid micro-emboli during cardiac surgery.

DESIGN

Eleven pigs were studied. Seven of these were put on extracorporeal circulation. A shed blood phantom consisted of blood, saline and radioactive triolein was added to the circuit. Both venous and arterial blood samples were taken at short intervals. Four animals were used to study renal kinetics without extracorporeal circulation. The same kind of shed blood phantom was infused into the ascending aorta. Samples were taken from the renal artery and vein. All samples were analyzed for radioactivity by scintillation counting.

RESULTS

A median 130-fold increase in radioactivity was seen in the blood and was quickly eliminated. Systemic first-pass wedging was found to be 62%. The first-pass elimination in the kidney was 77%. No radioactivity was found in urine.

CONCLUSIONS

This study shows that the turnover of lipid micro-emboli is fast, and that the majority of the emboli are trapped on their first passage through the capillary system. No evidence was found of a renal excretion of these lipid emboli.

A comparison of intra-operative cell-saving strategies upon immediate post-operative outcomes after CPB-assisted cardiac procedures

Cardiotomy suction has been associated with adverse outcomes under routine conditions in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). We hypothesized that the routine use of a cell saver (CS) in place of the cardiotomy sucker would have no negative impact on transfusion rate (TR), chest tube drainage (CTD), ventilation time (VT) or intensive care unit length of stay (ICULOS) while avoiding the detrimental effects of cardiotomy suction. Retrospective data were collected from 69 patients where a cell saver was not used (NCS). Prospective data were collected from 219 patients who were followed after the implementation of an intra-operative cell saver. No significant increase in transfusion rate, chest tube drainage or ventilation time was found between the NCS group and the CS group. However, post-operative hemoglobin concentrations were significantly higher in the CS group (0.0001) and the CS group spent significantly less time in the ICU (p=0.018).

Coronary artery surgery: cardiotomy suction or cell salvage?

Coronary artery bypass grafting (CABG) today results in what may be regarded as acceptable levels of blood loss with many institutions avoiding allogeneic red cell transfusion in over 60% of their patients. The majority of cardiac surgeons employ cardiotomy suction to preserve autologous blood during on-pump coronary artery bypass surgery; however the use of cardiotomy suction is associated with a more pronounced systemic inflammatory response and a resulting coagulopathy as well as exacerbating the microembolic load. This leads to a tendency to increased blood loss, transfusion requirement and organ dysfunction. Conversely, the avoidance of cardiotomy suction in coronary artery bypass surgery is not associated with an increased transfusion requirement. There is therefore no indication for the routine use of cardiotomy suction in on-pump coronary artery surgery.

Fat content in pericardial suction blood and the efficacy of spontaneous density separation and surface adsorption in a prototype system for fat reduction

OBJECTIVE

Fat embolization to the brain is a potential problem in cardiac surgery, assumed to originate from retransfused pericardial suction blood. Our aim was to measure the fat content in pericardial suction blood and to determine how it can be reduced by simple spontaneous density separation and surface absorption.

METHODS

Pericardial suction blood was collected during routine coronary bypass procedures and analyzed for blood-suspended fat and plastic surface binding. A single-chamber bag (n = 10) was compared with a fat-reducing system having a stacked 2-chamber design (n = 10). The fat-reducing system was also tested experimentally (n = 12) with heat-extracted liquid wound fat (1.25%) mixed with mediastinal drain blood.

RESULTS

Pericardial suction blood contained 1.5 mL (0.63/2.19) of fat suspended in 418 mL (269/631) of blood (median and quartiles). Surface-bound fat accounted for 24% (12/35). Experimental analysis of the new system revealed an 83% (71/92) fat-reduction rate (P < .001). This rate was confirmed under clinical conditions, suggesting 80% reduction (72/86; P = .001). The fat-reducing system also gave a small but significant red blood cell concentrating effect (P = .001).

CONCLUSIONS

It was confirmed that pericardial suction blood contains fat, possibly having an embolic potential. The new system allowed fat to separate by density while pericardial suction blood was temporally retained and incubated. A significant portion of fat adheres to the plastic surface, which added to the reduction. The method appeared efficient. It is proposed that pericardial suction blood should be collected during surgery to evaluate the need for retransfusion and to allow fat reduction.

Perioperative blood transfusion and blood conservation in cardiac surgery: the Society of Thoracic Surgeons and The Society of Cardiovascular Anesthesiologists clinical practice guideline

BACKGROUND

A minority of patients having cardiac procedures (15% to 20%) consume more than 80% of the blood products transfused at operation. Blood must be viewed as a scarce resource that carries risks and benefits. A careful review of available evidence can provide guidelines to allocate this valuable resource and improve patient outcomes.

METHODS

We reviewed all available published evidence related to blood conservation during cardiac operations, including randomized controlled trials, published observational information, and case reports. Conventional methods identified the level of evidence available for each of the blood conservation interventions. After considering the level of evidence, recommendations were made regarding each intervention using the American Heart Association/American College of Cardiology classification scheme.

RESULTS

Review of published reports identified a high-risk profile associated with increased postoperative blood transfusion. Six variables stand out as important indicators of risk: (1) advanced age, (2) low preoperative red blood cell volume (preoperative anemia or small body size), (3) preoperative antiplatelet or antithrombotic drugs, (4) reoperative or complex procedures, (5) emergency operations, and (6) noncardiac patient comorbidities. Careful review revealed preoperative and perioperative interventions that are likely to reduce bleeding and postoperative blood transfusion. Preoperative interventions that are likely to reduce blood transfusion include identification of high-risk patients who should receive all available preoperative and perioperative blood conservation interventions and limitation of antithrombotic drugs. Perioperative blood conservation interventions include use of antifibrinolytic drugs, selective use of off-pump coronary artery bypass graft surgery, routine use of a cell-saving device, and implementation of appropriate transfusion indications. An important intervention is application of a multimodality blood conservation program that is institution based, accepted by all health care providers, and that involves well thought out transfusion algorithms to guide transfusion decisions.

CONCLUSIONS

Based on available evidence, institution-specific protocols should screen for high-risk patients, as blood conservation interventions are likely to be most productive for this high-risk subset. Available evidence-based blood conservation techniques include (1) drugs that increase preoperative blood volume (eg, erythropoietin) or decrease postoperative bleeding (eg, antifibrinolytics), (2) devices that conserve blood (eg, intraoperative blood salvage and blood sparing interventions), (3) interventions that protect the patient's own blood from the stress of operation (eg, autologous predonation and normovolemic hemodilution), (4) consensus, institution-specific blood transfusion algorithms supplemented with point-of-care testing, and most importantly, (5) a multimodality approach to blood conservation combining all of the above.

Early results of a comprehensive operative and perfusion strategy to attenuate the incidence of adverse neurological outcomes in on-pump coronary artery bypass grafting (CABG) patients

Adverse neurological events, both focal (Type I) and non-focal (Type II), have been appreciated in postoperative on-pump coronary artery bypass grafting (CABG) patients for many years. Advanced age is a significant risk factor for adverse neurological events following CABG surgery. With full knowledge that our elderly population of patients was at high risk for these untoward neurological events, we adopted a comprehensive operative and perfusion strategy in an attempt to attenuate the incidence of these complications. Our strategy included efforts to minimise the number of emboli generated during the operation, avoid cerebral hypoperfusion, and attenuate the systemic inflammatory response. From 15 August 2002 to 31 December 2005, we performed 355 on-pump CABG operations. The incidence of Type I focal injury was 0/355 (0%), the incidence of Type II non-focal injury was 9/355 (2.5%), and postoperative mortality was 2/355 (0.6%). These results compared favorably to the results predicted by the Society of Thoracic Surgeons' (STS) model, and may suggest efficacy.

Differential Distribution of Lipid Microemboli After Cardiac Surgery

BACKGROUND

Lipid microemboli found in shed blood during cardiac surgery have been shown to block capillaries of the brain postoperatively. In this study, the distribution of lipid microemboli in different regions of the brain and other organs was examined. A novel porcine model using radioactive lipid particles was used.

METHODS

Ten animals (2 controls and 8 cases) were anesthetized and put on cardiopulmonary bypass. A shed-blood phantom was produced from arterial blood, saline, and tritium-labeled triolein. The phantom was infused into the cardiopulmonary bypass circuit. Tissue samples were taken postmortem from examined organs and prepared for scintillation counting. Levels of radioactivity were used as a measure of the uptake of lipid microemboli.

RESULTS

High levels of radioactivity were found in kidney and spleen (5 to 10 times higher than in the other organs investigated). In the brain, radioactivity was found in all regions examined. The gray matter of cerebrum showed the highest level of the regions examined.

CONCLUSIONS

This study shows that embolization of lipids is not a phenomenon restricted to the brain, but affected all the organs examined. The high levels found in the kidneys, and the relatively high levels in the gray matter of the cerebrum further legitimize the debate on the impact lipid microemboli has on postoperative kidney and cognitive dysfunction.

Miniaturized Cardiopulmonary Bypass in Coronary Artery Bypass Surgery: Marginal Impact on Inflammation and Coagulation but Loss of Safety Margins

PURPOSE

Inflammation and coagulation disturbances are common consequences of cardiopulmonary bypass (CPB). Recently, miniaturized closed CPB circuits without cardiotomy suction and venous reservoir have been proposed to reduce complication rates. We compared outcomes with conventional (CCPB) and miniaturized cardiopulmonary bypass (MCPB) after coronary artery bypass operations (CABG) with respect to inflammation and coagulation.

DESCRIPTION

Thirty patients (23% female; aged 67.9 +/- 9.0 years) were prospectively randomly assigned to undergo isolated CABG with CCPB or MCPB. Conventional CPB had a pump prime of 1, 600 mL. Miniaturized CPB consisted of a centrifugal pump, arterial filter, heparinized tubing, and oxygenator with a priming volume of 800 mL. Shed blood was removed by a cell-saving device and reinfused. Measurements included interleukin (IL)-2 receptor, IL-6, IL-10, tumor necrosis factor receptor 55 and 75, C reactive protein, leukocyte differentiation, d-dimers, fibrinogen, and thrombocytes at six time points.

EVALUATION

In both groups no major complication occurred. However, two dangerous air leaks occurred in the closed MCPB circuit, demonstrating the narrow safety margins. Operative handling was also more difficult owing to limitations in venting and fluid management. International normalized ratio (p = 0.03) and antithrombin III (p = 0.04) levels were elevated during CPB in the CCPB group, most likely owing to differences of the intraoperative anticoagulation management. Repeated measures analysis revealed that not a single parameter of inflammation or clinical outcome showed significant differences among groups.

CONCLUSIONS

Use of a MCPB affected inflammation and coagulation variables only marginally and did not lead to clinical relevant changes as assessed by blood loss, need for blood products, and intensive care unit and clinical stays. However, safety margins for volume loss, air emboli, and weaning from CPB decrease, because of the closed MCPB circuit.

Side differences in cerebrovascular accidents after cardiac surgery: a statistical analysis of neurologic symptoms and possible implications for anatomic mechanisms of aortic particle embolization

BACKGROUND

Aortic manipulation and particle embolization have been identified to cause cerebrovascular accidents in cardiac surgery. Recent data suggest that left-hemispheric cerebrovascular accident (right-sided symptoms) is more common, and this has been interpreted as being caused by aortic cannula stream jets. Our aim was to evaluate symptoms of cerebrovascular accident and side differences from a retrospective statistical analysis.

METHODS

During a 2-year period, 2641 consecutive cardiac surgery cases were analyzed. Patients positive for cerebrovascular accident were extracted from a database designed to monitor clinical symptoms. A protocol was used to confirm symptom data with the correct diagnosis in patient records. Patients were subdivided into 3 groups: control, immediate cerebrovascular accident, and delayed cerebrovascular accident.

RESULTS

Among pooled patients, immediate and delayed cerebrovascular accidents were 3.0% and 0.9%, respectively. The expected predisposing factors behind immediate cerebrovascular accidents were significant, although the type of operation affected this search. Aortic quality was a strong predictor ( P < .001). The rate of delayed cerebrovascular accident was unaffected by surgery group. Left-sided symptoms of immediate cerebrovascular accident were approximately twice as frequent ( P = .016) as on the contralateral side. This phenomenon was observed for pooled patients and for isolated coronary bypass procedures (n = 1882; P = .025).

CONCLUSIONS

Immediate cerebrovascular accident and aortic calcifications are linked. The predominance of left-sided symptoms may suggest that aortic manipulation and anatomic mechanisms in the aortic arch are more likely to cause cerebrovascular accidents than effects from cannula stream jets.

Embolic material generated by multiple aortic crossclamping: a perfusion model with human cadaveric aorta

BACKGROUND

Atherosclerosis of the ascending aorta and use of aortic crossclamping are risk factors for neurologic injury during cardiac surgery.

OBJECTIVES

Repeated aortic manipulation is part of the surgical approach to most cardiac operations. The aim of this study was to assess the amount and size of particulate matter that is dislodged from the aortic wall as a function of repeated aortic crossclamping.

METHODS

In 10 subjects undergoing autopsy the aorta was dissected and mounted in a perfusion model. The ascending aorta was crossclamped and washed out 10 times, with the perfusate collected in aliquots (1 to 10). The aliquots were examined by computerized image processing, both macroscopically and under the microscope for calcified and cellular material.

RESULTS

Aortic crossclamping produced substantial output of particulate matter. After repeated aortic crossclamping the number of particles decreased (P =.012) and approached the baseline for aliquots 6 to 10. The average particle diameter was 0.63 +/- 0.03 mm, with a maximum of 4.74 mm. Similar variability in particle outputs were recorded microscopically, with findings of both calcified and cellular material. Nine of 10 aortas had calcifications seen during simple visual inspection.

CONCLUSIONS

The washouts of dislodge material at aortic crossclamping had embolic potential. During the initial aortic crossclamping procedures the amount of particles was substantial, both macroscopically and microscopically. On the microscopic scale noncalcified cellular debris represents a significant pool of embolic material. Repeated aortic crossclamping reduced the amount of particles. These findings question surgical techniques associated with repeated aortic crossclamping.

The inflammatory response to recycled pericardial suction blood and the influence of cell-saving

OBJECTIVE

To investigate the inflammatory and cellular response attributed to conventional cardiotomy suction vs cell-saver during cardiac surgery.

DESIGN

Thirty-three (n = 33) low-risk patients admitted for routine coronary artery bypass grafting were randomly assigned to two groups: cardiotomy suction or cell-saver for salvage of pericardial blood. The groups were compared with reference to proinflammatory cytokines, complement activation, leukocyte pattern, and haemolysis during and after cardiopulmonary bypass.

RESULTS

Pericardial suction blood contained significantly increased concentrations of free plasma haemoglobin, C3a, IL-6, IL-8, TNF-alpha, eosinophils and basophils compared with the systemic circulation. No differences were found for the terminal complement complex and lymphocytes, whereas overall concentrations of leukocytes, platelets and haemoglobin were decreased. Recycling of pericardial suction blood gave no systemic effects except from that of free plasma haemoglobin, which increased significantly. The cell-saver eliminated plasma haemoglobin, but no other effects could be demonstrated.

CONCLUSION

Cardiotomy suction is a major cause of haemolysis, but contributes insignificantly to the systemic inflammatory response. Treatment of shed mediastinal blood with a cell-saver reduces haemolysis and may lower the dose load of inflammatory components.

The embolic potential of liquid fat in pericardial suction blood, and its elimination

Diffuse brain damage is a complex problem in cardiac surgery postoperatively. Liquid fat from recycled pericardial suction blood (PSB) is an embolic source. PSB can be discarded, but the recycling can be life saving, and methods have been developed to remove the fat. Blood washing by centrifugation is suggested to be the most effective method. In retained PSB, fat also separates without centrifugation, which is a novel and simple approach. Alternatively, inline fat filtration is easily accomplished but its effectiveness has been questioned. The present study aimed to investigate this phenomenon. Fat was heat extracted from retrieved pericardial fat tissue of coronary artery bypass graft (CABG) patients (n = 6), and was mixed, 1.25%, with postoperative mediastinal-shed blood. The mixture was filtered using a LipiGuard SB at constant flow rate. The filtration was scaled down to 3 mL and performed under temperature control, 37 degrees C, 20 degrees C and 10 degrees C. At these temperatures fat removal was 46.9 +/- 6.1%, 61.5 +/- 7.0% and 76.8 +/- 5.0%, respectively, with a statistical difference of P = 0.001. The improved fat removal at low temperature dramatically increased filtration pressures (P < 0.001) and caused haemolysis (P = 0.018). It is concluded that fat filtration is technically difficult. Cooling of blood increases fat extraction, but with negative side effects due to filter occlusion.

Fat reduction in pericardial suction blood by spontaneous density separation: an experimental model on human liquid fat versus soya oil

Pericardial suction blood (PSB) contains mediastinal liquid wound fat with an embolic potential to cause brain damage after cardiopulmonary bypass (CPB). The aims were to measure how fat separates spontaneously from blood by density and how temperature and fat surface adhesion affect the results under experimental conditions. Human liquid fat was heat-extracted from retrieved pericardial fat tissue of coronary artery bypass graft (CABG) patients (n = 10). Human fat or soya oil, 5% and 10%, respectively, were mixed with postoperatively shed mediastinal blood (n = 20). The mixture was loaded into a temperature-controlled (37 degrees C, 20 degrees C, 10 degrees C) vertical separation column. At 1, 2.5, 5 and 10 minutes, the blood was collected in five fractions, representing layers of density separation, followed by centrifugation. Human fat solidified at 8 degrees C. Soya oil remained liquid below 0 degrees C. Soya oil separated fast in water, but was slower in blood. At 10 minutes and 37 degrees C 73 +/- 6% of added soya oil was found in the top 20% fraction. Human fat at 37 degrees C behaved similarly to soya oil, with 58 +/- 2% separation at 10 minutes. However, at lower temperatures the density separation became less efficient (p < 0.001), whereas human fat more effectively adhered to the walls of the column, which added to the removal. In total, 66%-78% of the human fat was removed, depending on temperature. In conclusion, fat in PSB can be reduced by simple density separation and surface adhesion while it is temporarily retained from the CPB circuit.