Indocyanine green clearance as an outcome prediction tool in cardiac surgery: A prospective study

Purpose

To evaluate the role of plasma disappearance rate of indocyanine green (PDR-ICG) as an outcome prediction tool in cardiac surgery.

Patients and Methods

One hundred ninety patients undergoing coronary artery bypass grafting, valve surgery or combined procedures were enrolled. PDR-ICG measurements along with standard lab values were performed preoperative and on postoperative days 1, 2, and on discharge from the intensive care unit. Adverse outcomes were defined as prolonged length of stay in the intensive care unit and/or mortality. Two groups were defined according to length of stay in the intensive care unit (≤ 3 days vs > 3 days).

Results

PDR-ICG values differed significantly for all time points between the groups. In a multivariate model, in patients over 65 years with a EuroSCORE below 8.5, a preoperative PDR-ICG value below 12.85%/min was the strongest independent predictor for prolonged intensive care unit stay (> 3 days). A preoperative PDR-ICG value below 8.2%/min was the strongest independent predictor for mortality in a multivariate analysis including age, cardiac function, and EuroSCORE.

Conclusions

In addition to the established scores, PDR-ICG may provide valuable information for the assessment of perioperative morbidity and mortality in cardiac surgery. Pre- and early postoperative measurements may help to identify patients at risk for developing perioperative complications.     

Leukocyte mitochondrial alterations after cardiac surgery involving cardiopulmonary bypass: clinical correlations

Cardiac surgery with the use of cardiopulmonary bypass (CPB) is known to initiate systemic inflammatory responses that are associated with immune dysregulations, but the pathomechanisms underlying these changes remain elusive. Mitochondrial transmembrane potential (MTP) is an important determinant of leukocytic functions and viability, and may be altered as a part of the cellular responses to systemic inflammatory insults. Therefore, we examined MTP in three subsets of peripheral leukocytes in 18 patients receiving uncomplicated cardiac surgery involving CPB. The MTP of neutrophils and lymphocytes significantly increased, whereas that of monocytes significantly declined, after the surgery. The alterations in leukocytic MTP were transient, normalizing 3 days to 1 week after the surgery, and were accompanied by transient overproduction of intracellular oxidants, including nitric oxide and superoxide. Despite these perturbations, the viability status of leukocytes remained unaltered. Positive correlations were found between the changes of leukocyte MTP and various clinical parameters, implying that leukocyte mitochondrial alterations are parts of the systemic immune perturbations induced by the bypass surgery.     

Inhaled prostacyclin and platelet function after cardiac surgery and cardiopulmonary bypass

Objective: To study the effects of 6 h inhalation of aerosolized prostacyclin (PGI₂) on platelet function.¶Design: In a prospective, double-blind, randomized study, 28 patients scheduled for elective cardiac surgery requiring cardiopulmonary bypass (CPB), received either 0.9 % sodium chloride (n = 8), PGI₂ 5 μg × ml^–1 (n = 10) or PGI₂ 10 μg × ml^–1 (n = 10) as an aerosol for 6 h postoperatively.¶Setting: Cardiothoracic intensive care unit at a university hospital.¶Interventions: All patients were studied immediately after surgery during mechanical ventilation and sedation. The PGI₂ solutions or saline were administered with a jet nebulizer.¶Measurements and results: Bleeding time and chest tube drainage were measured. Blood samples for platelet aggregation, thrombelastography (TEG) and analysis of coagulation parameters and the stable prostacyclin metabolite 6-keto-PGF₁α were obtained immediately before inhalation and after 2, 4 and 6 h of inhalation. After 6 h of PGI₂ inhalation, regardless of administered dose, there was a lower rate of platelet aggregation and a lower maximal increase in light transmission in response to adenosine diphosphate (ADP) than in the control group. The TEG variable reaction time (R) was prolonged after 4 and 6 h of inhalation in the PGI₂ group receiving 10 μg × ml^–1. There were no differences between groups with respect to bleeding time and chest tube drainage or any of the other variables examined.¶Conclusion: Inhalation of PGI₂ for 6 h in patients after cardiac surgery is associated with impaired platelet aggregation detected by in vitro techniques, with no in vivo signs of platelet dysfunction.     

Pulse contour analysis after normothermic cardiopulmonary bypass in cardiac surgery patients

Introduction  

Monitoring of the cardiac output by continuous arterial pulse contour (CO_PiCCOpulse) analysis is a clinically validated procedure proved to be an alternative to the pulmonary artery catheter thermodilution cardiac output (CO_PACtherm) in cardiac surgical patients. There is ongoing debate, however, of whether the CO_PiCCOpulse is accurate after profound hemodynamic changes. The aim of this study was therefore to compare the CO_PiCCOpulse after cardiopulmonary bypass (CPB) with a simultaneous measurement of the CO_PACtherm.     

Atrial natriuretic factor after cardiac surgery with cardiopulmonary bypass in children.

OBJECTIVE: To determine circulating atrial natriuretic factor (ANF) concentrations in the postoperative state and to define potential hemodynamic determinants of regional plasma ANF concentrations. DESIGN: Cohort study. SETTING: Pediatric ICU in a university hospital. PATIENTS: Twenty-two children, mean age 4.2 yrs (range 0.9 to 13.5), were studied 18 hrs after corrective surgery on cardiopulmonary bypass. The underlying cardiac malformations were ventricular septum defect (n = 5), transposition of great arteries (n = 5), tetralogy of Fallot (n = 4), pulmonary stenosis (n = 3), and miscellaneous (n = 5). INTERVENTIONS: In addition to the commonly monitored variables in postoperative cardiac patients, blood volume was estimated by the 125I albumin method, and plasma samples for radioimmunoassay determination of ANF concentrations were taken simultaneously from indwelling catheters. MEASUREMENTS AND MAIN RESULTS: Compared with normal age-matched values, plasma ANF concentrations were increased in all patients, with values tending to be highest in the left atrium, followed by systemic artery, superior vena cava, and pulmonary artery (345 +/- 158, 333 +/- 169, 311 +/- 154, and 272 +/- 160 pg/mL, respectively [mean +/- SD; NS]). Simple regression analysis demonstrated a moderate correlation between blood volume and the concentration of ANF in the superior vena cava (p less than .05). Stepwise multivariate analysis showed no significant independent predictor of plasma ANF concentrations. CONCLUSIONS: Plasma ANF concentrations are increased after open-heart surgery in children, with moderate direct correlation to blood volume. The wide scatter of increased hormone concentrations may be explained by the many factors known to influence circulating ANF concentrations, such as age, underlying disease, cardiovascular state, and drugs.     

Time-course of impairment of respiratory mechanics after cardiac surgery and cardiopulmonary bypass.

OBJECTIVE: Cardiopulmonary bypass (CPB) is associated with abnormalities of lung function characterized by an increase in static elastance of the respiratory system. We examined the following: a) the effects of CPB on the total inspiratory volume-pressure (V-P) relationship of the respiratory system; b) the relative contribution of the chest wall and lung to the impairment of respiratory system mechanics; and c) the time-course of such impairment. DESIGN: Prospective, interventional study. SETTING: Surgical and medical intensive care units in a teaching hospital. PATIENTS: Eight adult patients scheduled for elective open heart surgery to correct valvular dysfunction. INTERVENTIONS: V-P curves (interrupter technique) of the respiratory system were partitioned between the chest wall and lung by measurements of esophageal pressure. Measurements were obtained before sternotomy (control), immediately after, 4 hrs after, and 7 hrs after separation from CPB. MEASUREMENTS AND MAIN RESULTS: Control V-P relationships of the respiratory system and lung showed lower inflection points (Pflex) at pressure values of 5.9+/-2.3 and 4.3+/-2.5 cm H2O, respectively. Immediately after and 4 hrs after separation from CPB, both curves had sigmoid shapes because of lower Pflex and formation of upper inflection (UIP) points. The pressures corresponding to the Pflex increased significantly (p < .001) by 56%+/-3% and 78%+/-4%, whereas the UIP corresponded to a pressure value of 42.34+/-8.5 and 35.6+/-7.8 cm H2O in the respiratory system and lung, respectively. A linear V-P relationship of the chest wall was observed during the control condition and after separation from CPB. Four hours later, no further increases in the pressure values corresponding to Pflex were observed on the inspiratory V-P curves of the respiratory system and lung, whereas the UIP occurred at a pressure of 35.6+/-9.1 and 29.7+/-8.4 cm H2O, respectively. A UIP was present on the V-P curve of the chest wall at a volume of 0.77+/-0.02 L. Seven hours after separation from CPB, the inspiratory V-P curves of the respiratory system, chest wall, and lung returned to normal. CONCLUSIONS: Sternotomy and CPB produced immediate changes in lung mechanics. Chest wall mechanics were affected only 4 hrs after sternotomy. Seven hours after disconnection from CPB, all mechanics had returned to normal.     

Plasma fibronectin depletion after cardiac surgery in children with or without cardiopulmonary bypass

Plasma fibronectin depletion decreases resistance to sepsis. After cardiac surgery, septic complications occur more frequently when the surgical procedure is managed with a cardio-pulmonary bypass than when it is not. To determine whether cardio-pulmonary bypass produces a greater decrease in plasma fibronectin than surgery without cardio-pulmonary bypass, we studied plasma fibronectin concentrations in two groups of children operated for congenital heart diseases. Group I: 10 children undergoing surgery with cardio-pulmonary bypass. Group II: 11 children undergoing surgery without cardio-pulmonary bypass. Plasma fibronectin was monitored pre-operatively (t 1) and post-operatively at the 6th hour (t 2), 1st (t 3) and 7th (t 4) days. In both groups, plasma fibronectin concentration dropped at (t 2) and (t 3) and rose again at (t 4). There was no significant difference in plasma fibronectin levels between the two groups at any time. We conclude that the plasma fibronectin decline alone cannot explain why septic complications after surgery are more frequent with cardio-pulmonary bypass than without.     

Miniaturized cardiopulmonary bypass in adult cardiac surgery: a clinical update

Introduction: Cardiopulmonary bypass has undoubtedly been the cornerstone in the rapid development of cardiac surgery, allowing even the performance of procedures beyond the scope of cardiothoracic surgery. Its use however, is associated with significant complications that arise from the mechanical effects of the circuit on circulating blood components as well as the contact of blood with non-endothelial surfaces. Miniature cardiopulmonary bypass systems have been developed in an attempt to minimize these complications.

Areas covered: Herein clinical outcomes from the most recent studies in adult cardiac surgery are discussed. The main benefits of miniaturisation as well as potential areas of further application are described.

Expert commentary: Data is critically appraised in the context of current guidelines. Finally the need for further basic science in addition to large multi-centre randomized controlled trial data is highlighted.     

Inflammatory response of neutrophil granulocytes and monocytes after cardiopulmonary bypass in pediatric cardiac surgery

OBJECTIVE: To determine whether the activation state of polymorphonuclear neutrophils (PMNs) and monocytes contributes to the inflammatory response after cardiopulmonary bypass (CPB) in pediatric cardiac surgery. DESIGN: Observational prospective clinical study. SETTING: Pediatric intensive care unit of a university hospital. PATIENTS: Twenty pediatric patients before and after open heart surgery with CPB. MEASUREMENTS: Cell counts of circulating PMNs and monocytes as well as phenotypic and functional analysis of these cells, and plasma levels of myeloperoxidase. RESULTS: Levels of myeloperoxidase (a marker of PMN degranulation) were significantly elevated after CPB (2.9+/-1.6 ng/ml before CPB versus 13.7+/-6.5 ng/ml after CPB, p=0.0001). However, PMN function, as measured by surface expression of CD11b/CD18 and phagocytic respiratory burst, was reduced. In contrast, the phagocytic respiratory burst of circulating monocytes was increased in some patients and there was a correlation with the increase of monocyte cell count after CPB (r=0.63, p=0.015). CONCLUSIONS: After the end of CPB, there was an ongoing inflammatory process. In particular, there was an activation of monocytes after the end of CPB.     

Effects of cardiac surgery with cardiopulmonary bypass on lidocaine disposition

We investigated lidocaine kinetics after cardiac surgery to elucidate the effects of cardiopulmonary bypass (CPB) and major surgery on its disposition. In five patients lidocaine kinetics were unchanged 15 min and 1 day after CPB, but lidocaine clearance decreased 42% and volume of distribution was reduced by 40% in eight patients 3 days after surgery. Seven days after surgery lidocaine kinetics had returned to baseline in five patients. These changes correlated with a doubling of the alpha 1-acid glycoprotein concentration and a 46% decrease in lidocaine free fraction on day 3, effects that persisted on day 7. Our results suggest that the use of lidocaine need not be altered in the first day after uncomplicated coronary artery surgery, but, in light of our findings the use of lidocaine and the interpretation of measured total lidocaine concentrations 3 to 7 days thereafter should be reexamined.     

体外循环术后室性心律失常应用胺碘酮与利多卡因后血液动力学及临床疗效观察

目的 观察胺碘酮与利多卡因对体外循环术后室性心律失常的疗效及对血流动力学的影响.方法 体外循环术后并发室性心律失常患者87例,分为胺碘酮组(A组)42例和利多卡因组(L组)45例,分别予以胺碘酮及利多卡因治疗,持续心电监护,观察用药前后有创平均动脉压(MAP)、心率(HR)和中心静脉压(CVP)变化,比较临床疗效.结果 胺碘酮组总有效率92.86%,利多卡因组总有效率78.78%,差异有显著性意义(χ2=3.89,P<0.05);两组MAP、HR、CVP值比较,差异均无显著性意义(P>0.05).结论 胺碘酮治疗体外循环术后并发室性心律失常的有效率高于利多卡因,二者对血流动力学的影响差异小.     

Utstein style study of cardiopulmonary bypass after cardiac arrest

Objective

The aim of this study is to describe the effect emergency cardiopulmonary bypass (CPB) for resuscitation on the survival rate of patients.

Methods

The study population was composed of persons 16 years or older who had out-of-hospital cardiac arrest and were transferred to the Sapporo Medical University Hospital from the scene between January 1, 2000, and September 30, 2004. Children younger than 16 years and persons who were dead were excluded. Data were collected according to the Utstein style. Survival rates and cerebral performance category were analyzed using χ² analysis for the patients with presumed cardiac etiology. Cardiopulmonary bypass was applied to patients who showed no response with standard advanced cardiac life support. The interval from collapse and other noncardiac etiologies were considered criteria for exclusion.

Results

Of the 919 patient medical records reviewed, CPB was performed in 92 patients. Of the 919 patients, 398 were of presumed cardiac etiology (n = 66 for CPB), 48 patients survived, and 24 patients (n = 7 for CPB) had a good cerebral outcome (cerebral performance category score 1). With CPB, the rate of survival at 3 months increased significantly (22.7% vs 9.9%, P < .05), but the rate of good cerebral outcome (10.6% vs 5.1%, P = .087) showed a positive trend.

Conclusion

The use of CPB for arrest patients was associated with reduced mortality. It did not increase good neurologic outcome significantly. Still, 7 cases with intact central nervous system would have been lost without CPB.     

Influence of residual blood autotransfused from cardiopulmonary bypass circuit on clinical outcome after cardiac surgery

Autotransfusion of the residual blood from the cardiopulmonary bypass (CPB) circuit is considered to be one of the methods enabling reduction in the need for transfusion, the possible adverse effects of which are well known and documented. The aim of the study was to evaluate the effectiveness of the autologous autotransfusion of centrifuged red blood cells from the residual blood of the CPB circuit in patients following heart surgery. Three groups of patients who underwent heart surgery were examined. The first group (Group 1) consisted of 37 patients who received all of the residual blood in the bypass circuit after CPB (collected into sterile plastic bags) during the early postoperative period. The second group (Group 2) consisted of 45 patients who did not receive the residual blood following CPB. The third group (Group 3) consisted of 42 patients who underwent reinfusion of centrifuged red blood cells from the residual blood remaining in the CPB circuit during the early postoperative period. Hematocrit (Hct) values 12 hours after the operation were found to be higher in Group 3 compared with those of the first and the second groups (by 13.2% and 11.1%, respectively). Blood loss during the first 12 hours after the operation and during the time spent in the intensive care unit did not differ between the groups. The number of transfusions was significantly lower in Group 3 (28.57%) in comparison with that of Groups 1 and 2 (37.83% and 38.10%, respectively). The rate of infective complications in Group 3 was lower in comparison with both Group 1 and Group 2 (9.2% and 18.1%, respectively). The duration of in-hospital stay in Group 3 was 25.8% shorter than Group 1. We conclude that autotransfusion of centrifuged red blood cells processed from the residual blood of the CPB circuit after CPB was effective in increasing Hct values 12 hours postoperatively, reducing the need for donor blood product transfusions, the rate of infective complications and lenght of stay in hospital.     

Pancreatic cellular injury after cardiac surgery with cardiopulmonary bypass: frequency, time course and risk factors

Although often clinically silent, pancreatic cellular injury (PCI) is relatively frequent after cardiac surgery with cardiopulmonary bypass; and its etiology and time course are largely unknown. We defined PCI as the simultaneous presence of abnormal values of pancreatic isoamylase and immunoreactive trypsin (IRT). The frequency and time evolution of PCI were assessed in this condition using assays for specific exocrine pancreatic enzymes. Correlations with inflammatory markers were searched for preoperative risk factors. One hundred ninety-three patients submitted to cardiac surgery were enrolled prospectively. Blood IRT, amylase, pancreatic isoamylase, lipase, and markers of inflammation (alpha1-protease inhibitor, alpha2-macroglobulin, myeloperoxidase) were measured preoperatively and postoperatively until day 8. The postoperative increase in plasma levels of pancreatic enzymes and urinary IRT was biphasic in all patients: early after surgery and later (from day 4 to 8 after surgery). One hundred thirty-three patients (69%) experienced PCI, with mean IRT, isoamylase, and alpha1-protease inhibitor values higher for each sample than that in patients without PCI. By multiple regression analysis, we found preoperative values of plasma IRT >or=40 ng/mL, amylase >or=42 IU/mL, and pancreatic isoamylase >or=20 IU/L associated with a higher incidence of postsurgery PCI (P < 0.005). In the PCI patients, a significant correlation was found between the 4 pancreatic enzymes and urinary IRT, total calcium, myeloperoxidase, alpha1-protease inhibitor, and alpha2-macroglobulin. These data support a high prevalence of postoperative PCI after cardiac surgery with cardiopulmonary bypass, typically biphasic and clinically silent, especially when pancreatic enzymes were elevated preoperatively.     

体外循环心脏手术术后并发症的影响因素研究

目的：探讨体外循环心脏手术术后并发症的影响因素。方法回顾性分析2009年5月至2013年3月行体外循环心脏手术的203例成年患者的临床资料,分析术后并发症发生情况;根据是否发生术后并发症,将患者分为并发症组和无并发症组,对可能的危险因素进行单因素分析和Logistic多因素回归分析。结果203例患者中,发生术后并发症31例,并发症发生率为15．3％。单因素分析结果显示,年龄大于或等于55岁、体外循环时间大于或等于2 h、主动脉阻断时间大于或等于100 min、心脏功能Ⅳ级以及术前合并原发性高血压、糖尿病、慢性阻塞性肺疾病是诱发术后并发症的相关因素（P＜0．05）。Logistic多因素回归分析结果显示,年龄大于或等于55岁、体外循环时间大于或等于2 h、主动脉阻断时间大于或等于100 min及心脏功能Ⅳ级是导致术后并发症的危险因素（P＜0．05）。结论对于行体外循环心脏手术的患者,应通过术前评估,及时干预可诱发术后并发症的危险因素,从而提高手术安全性和疗效。     

Anesthesia with ciprofol in cardiac surgery with cardiopulmonary bypass: A case report

BACKGROUNDCiprofol is a novel agent for intravenous general anesthesia. In February 2022, it was approved by the National Medical Products Administration for general anesthesia induction and maintenance. It has the advantages of fast onset, fast elimination, stable circulation, and few adverse reactions. However, the efficacy and safety of ciprofol in cardiac surgery with cardiopulmonary bypass have not been reported. Here we describe a case where ciprofol was successfully used for anesthesia in cardiac surgery with cardiopulmonary bypass.CASE SUMMARYA 72-year-old man (height 176 cm; weight 70 kg) was diagnosed with coronary atherosclerotic cardiomyopathy requiring coronary artery bypass grafting and left ventricular aneurysmectomy. Ciprofol was administered for induction (0.4 mg/kg) and maintenance (0.6-1.0 mg/kg/h) of general anesthesia. During the entire operation, the bispectral index, hemodynamics, and blood oxygen saturation were maintained at normal levels. The patient recovered well after surgery, with no serious adverse events related to ciprofol.CONCLUSIONCiprofol is safe and effective for anesthesia in cardiac surgery with cardiopulmonary bypass.     

Aprotinin: antifibrinolytic and anti-inflammatory mechanisms of action in cardiac surgery with cardiopulmonary bypass

Cardiopulmonary bypass results in activation of the coagulation, fibrinolytic, inflammatory, and complement cascades. These activated cascades result in a decrease in the number of circulating coagulation factors, hyperfibrinolysis, thrombocytopenia, platelet defects, coagulopathies, and an acute inflammatory response. Patients experiencing cardiac surgery with cardiopulmonary bypass are at risk for many potential problems. The use of aprotinin, an antifibrinolytic agent, has multiple effects that tend to reduce hematological defects and blunts the inflammatory response that is associated with cardiac surgery. The pathophysiological consequences of cellular activation associated with cardiopulmonary bypass, basic mechanisms of action of aprotinin, pharmacodynamic and pharmacokinetic properties, dosing, adverse reactions, and cost/benefit ratio are discussed in this article. Critical care nurses need to know about aprotinin to understand its role in reducing blood loss and transfusions during and after cardiac surgery.     

Plasminogen activator inhibitor activity is associated with raised lactate levels after cardiac surgery with cardiopulmonary bypass

OBJECTIVE: To investigate the pathophysiology underlying raised lactate levels after cardiac surgery with cardiopulmonary bypass (CPB). DESIGN: Prospective observational study. SETTING: Medical and surgical intensive care unit of a tertiary hospital. PATIENTS: A total of 40 patients undergoing first-time coronary artery bypass grafting with CPB. INTERVENTIONS: The prothrombotic response to cardiac surgery with CPB was assessed by measuring plasma levels of prothrombin fragment 1 + 2 and plasminogen activator inhibitor (PAI) activity. The hemodynamic responses to cardiac surgery with CPB were also measured using standard techniques. MEASUREMENTS AND MAIN RESULTS: After cardiac surgery, prothrombin fragment 1 + 2 levels increased 6-fold and PAI activity increase 2- to 3-fold (p <.0001). Lactate levels were not associated with prothrombin fragment 1 + 2 and PAI activity levels after CPB. Lactate levels were associated with baseline PAI activity (p =.006), a history of hypertension (p =.02), raised baseline lactate levels (p =.02), an early increase in body temperature after CPB (p =.05), a late increase in oxygen consumption after CPB (p =.03), and a raised white cell count after CPB (p =.06). Lactate levels were inversely associated with the maximum activated clotting time level reached during CPB (p =.02). Multivariate linear regression demonstrated lactate levels were independently associated with baseline PAI activity. CONCLUSION: We found cardiac surgery with CPB was associated with a marked prothrombotic response. Lactate levels were associated with elevated baseline PAI activity and evidence of an amplified inflammatory response to cardiac surgery with CPB. Our findings implicate aspects of the inflammatory response, including microvascular thrombosis, in the development of raised lactate levels after cardiac surgery with CPB.     

Efficiency and safety of leukocyte filtration during cardiopulmonary bypass for cardiac surgery

BACKGROUND: Leukocyte filtration of systemic blood during cardiopulmonary bypass surgery to reduce post-operative morbidity has not yet been established because of the enormous leukocyte release from the third space. This study was designed to examine the efficiency and safety of leukocyte filtration by a new prototype large capacity leukocyte filter. PATIENTS AND METHODS: Patients undergoing cardiopulmonary bypass surgery were prospectively divided into two groups: a leukocyte removal group (n = 11) receiving leukocyte filtration during cardiopulmonary bypass and a control group (n = 20) with no filtration. The filtration efficiency was indicated by electronic leukocyte counts before and after filtration and the clinical efficiency to reduce post-operative morbidity was indicated by PaO2. Safety was indicated by monitoring the filtration pressure and leukocyte release products across the filter, as well as by examining the post-filtration filter by light and electron microscopy. RESULTS: On an average, 75% of all entering leukocytes were removed by the filter. The post-operative PaO2 showed a tendency to improve after filtration. During filtration, the pressure across the filter material increased in five cases, accompanied by an increase in post-filter plasma hemoglobin and beta-glucoronidase. Within these filters accumulations of fibrin network with many trapped leukocytes were discovered microscopically. CONCLUSIONS: The filter was efficient in filtering leukocytes, but the filtration efficiency slowed at the end of filtration. Furthermore, the patients' post-operative parameters showed a tendency to improve after filtration. However, flow obstruction by means of clotting seems to be an important issue of safety involved in the filtration of large numbers of leukocytes for cardiopulmonary surgical patients.