Leukocyte activation with increased expression of CR3 receptors during cardiopulmonary bypass

Ex Vivo Testing of Heparin-Coated Extracorporeal Circuits: Bovine Experiments

In this study the intrinsic thrombogenicity of the extracorporeal circuits and the benefit of heparin-bonded circuits in an extracorporeal life support system without full systemic heparinization and with minimal interference of the so called material-independent factors was tested in four calves. In two circuits (group A) all blood-contacting surfaces were coated with end-point-attached heparin and the other two were non-coated (group B). Under standardized conditions the calves were perfused at a blood flow rate of 2 L/min. After only one bolus injection of heparin (250 IU/kg body weight) before cannulation, plasma heparin activity rapidly decreased in both groups: half life of about 55 minutes. This decrease of the heparin activity was accompanied by a fall of the activated clotting time (ACT) level to baseline values. The experiments using a heparin-coated circuit, had a runtime of more than 360 minutes, whereas the experiments using a non-coated circuit had to be terminated after a runtime of 255 minutes, because massive fibrin formation was noticed in the circuit. This formation was accompanied by a rapid increase in the line pressure, measured just before the inlet of the oxygenator. The macroscopic inspections after terminating the experiments and rinsing the circuit showed a clean circuit in group A. The fibrinopeptide A (FPA) level increased faster during perfusion with the non-coated circuit than in the heparin coated circuit. Lung histopathological examinations of the lungs of the animals in group A showed no fibrin deposition, whereas most of the blood vessels of the lung preparations of the animals in group B were partially or completely occluded with fibrin. These results suggest that heparin-bonding greatly reduces the thrombogenicity of the extracorporeal circuit, and therefore it can reduce the need for systemic heparinization in an extracorporeal life support system.

Blood compatibility of two different types of membrane oxygenator during cardiopulmonary bypass in infants

The contact of blood with the artificial extracorporeal circuit causes a systemic inflammatory response due to blood activation. In this study, we compared two different paediatric membrane oxygenators used for extracorporeal circulation: a hollow fibre membrane oxygenator (Dideco Masterflo D-701, n=10), and a flat sheet silicone membrane oxygenator (Avecor Kolobow 800-2A, n=10). Blood compatibility was indicated by measuring complement activation as well as leukocyte and platelet activation. In patients perfused with a flat sheet membrane oxygenator, concentrations of complement split products C3a were significantly increased 30 minutes after the start of bypass (p<0.01), whereas only a mild increase of C3a was found in patients perfused with a hollow fibre membrane oxygenator. Leukocyte and platelet counts dropped uniformly in both groups after the start of bypass mainly due to hemodilution. Activation of leukocytes and platelets identified by both plasma β-glucuronidase and β-thromboglobulin was similar in both groups. Infants perfused with a flat sheet membrane oxygenator received significantly more donor blood than those perfused with a hollow fibre oxygenator (p<0.05). These results indicate that when used during paediatric cardiopulmonary bypass, a flat sheet membrane oxygenator has a higher complement activity than a hollow fibre membrane oxygenator, which is probably due to the relatively larger blood-surface contacting area of the oxygenator.

Longitudinal analysis of serum oxylipin profile as a novel descriptor of the inflammatory response to surgery

BACKGROUND

Oxylipins are potent lipid mediators demonstrated to initiate and regulate inflammation yet little is known regarding their involvement in the response to surgical trauma. As key modulators of the inflammatory response, oxylipins have the potential to provide novel insights into the physiological response to surgery and the pathophysiology of post-operative complications. We aimed to investigate the effects of major surgery on longitudinal oxylipin profile.

METHODS

Adults patients undergoing elective laparoscopic or open colorectal resections were included. Primary outcomes were serum oxylipin profile quantified by ultra high-performance liquid chromatography-mass spectrometry, serum white cell count and C-reactive protein concentration. Serum samples were taken at three time-points: pre-operative (day zero), early post-operative (day one) and late post-operative (day four/five).

RESULTS

Some 55 patients were included, of which 33 (60%) underwent surgery that was completed laparoscopically. Pre-operative oxylipin profiles were characterised by marked heterogeneity but surgery induced a common shift resulting in more homogeneity at the early post-operative time-point. By the late post-operative phase, oxylipin profiles were again highly variable. This evolution was driven by time-dependent changes in specific oxylipins. Notably, the levels of several oxylipins with anti-inflammatory properties (15-HETE and four regioisomers of DHET) were reduced at the early post-operative point before returning to baseline by the late post-operative period. In addition, levels of the pro-inflammatory 11-HETE rose in the early post-operative phase while levels of anti-thrombotic mediators (9-HODE and 13-HODE) fell; concentrations of all three oxylipins then remained fairly static from early to late post-operative phases. Compared to those undergoing laparoscopic surgery, patients undergoing open surgery had lower levels of some anti-inflammatory oxylipins (8,9-DHET and 17-HDoHE) in addition to reduced concentrations of anti-thrombotic mediators (9-HODE and 13-HODE) with increased concentration of their pro-thrombotic counterpart (TxB2).

CONCLUSIONS

Serum oxylipin profile is modified by surgical intervention and may even be sensitive to the degree of surgical trauma and therefore represents a novel descriptor of the surgical systemic inflammatory response.

Evaluation of a new condensed extra-corporeal circuit for cardiac surgery: a prospective randomized clinical pilot study

This prospective randomized clinical pilot study was conducted to evaluate a recently introduced reduced volume CPB system that is coated with the biopassive Xcoating™. Twenty-two patients undergoing coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB), either with a fully heparin-coated CPB circuit (control, n=11) or with an Xcoating™ coated condensed extra-corporeal circuit (CondECC, n=11), were included.

We examined activation of the complement system (C3bc and C4bc), activation of neutrophils (BPI), the acute phase response (interleukin (IL)-6, and acute phase proteins (LBP, AGP, and CRP)), myocardial tissue injury (troponin T), hemolysis (free hemoglobin (FHb)), and clinical outcome parameters. Preoperative risk profiles were identical for both patient groups. All patients went through the procedure without major complications and were discharged from the hospital. FHb and BPI levels at the end of pump support ( p <0.01) and at 15 min after the administration of protamine ( p <0.05) were significantly higher in the control group. In addition, FHb levels were still significantly elevated upon arrival on the cardiothoracic intensive care unit (CICU) in the control group ( p <0.05). C3bc and C4bc, acute phase proteins, IL-6, and troponin T concentrations, and clinical outcome variables were identical in both patient groups.

In conclusion, the evaluated condensed extracorporeal circuit is a flexible and multifunctional CPB sytem that offers safe procedures. Furthermore, the results indicate improved biocompatibility of this option for extracorporeal circulation.

Selective Recruitment Maneuvers for Lobar Atelectasis: Effects on Lung Function and Central Hemodynamics: An Experimental Study in Pigs

We investigated whether selective lung recruitment of a lobar collapse would improve oxygenation and lung volume as well as a general (global) lung recruitment maneuver, with fewer circulatory side effects. In 10 ventilated, anesthetized pigs, a bronchial blocker was inserted in the right lower lobe, which was selectively lavaged to create a dense lobar collapse. The pigs were randomized into two orders of lung recruitment maneuvers (40 cm H2O airway pressure for 30 s): either a selective lung recruitment maneuver (using the inner lumen of the bronchial blocker) followed by a general lung recruitment maneuver, or vice versa. Median end-expiratory lung volume and median Pao2 increased significantly by approximately 100 mL and 16 kPa, respectively, with no significant differences between the two recruitment methods. There were no circulatory changes during the selective lung recruitment maneuver, but during the general lung recruitment maneuver, mean arterial blood pressure decreased significantly by 36 (21, 41) mm Hg (median, 25th and 75th percentiles), cardiac output by 2.1 (1.6, 2.5) L/min and left ventricular end-diastolic area by 4.4 (3.5, 4.5) cm2. In conclusion, a selective recruitment maneuver improved lung function similar to a general lung recruitment maneuver but without any circulatory side effects.

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.

Leucocyte depletion during cardiac surgery: a comparison of different filtration strategies

The results of leucocyte filtration during cardiac surgery are conflicting. This may be due to timing and duration of the filtration procedure, and to flow and pressure conditions in the filter. Therefore, we prospectively compared three major leucocyte filtration strategies in cardiac surgical patients. Forty patients were randomly divided into four groups. Group I: leucofiltration of arterial blood throughout cardiopulmonary bypass (CPB) (associated with high-flow and pressure gradients), Group II: leucofiltration of a part of the venous return blood in the rewarming phase during CPB (associated with intermediate flow, but high pressure), Group III: leucofiltration of residual heart-lung machine blood during transfusion into the patient after CPB (associated with low flow and low pressure), Group IV: control group without leucofiltration. We measured circulating leucocyte counts, plasma elastase levels and arterial blood oxygenation. Filters were postoperatively examined using scanning electronmicroscopy (SEM). Leucocyte counts increased over time and oxygenation decreased in all groups, without significant differences between the groups. SEM demonstrated extensive protein deposits and damaged leucocytes in the deeper layers of the filters from Group I. This was not observed in the filters from Group III. The postoperative plasma elastase levels increased in Groups II and IV and decreased in Groups I and III. In conclusion, we could not demonstrate a clinical difference among the three leucocyte depletion strategies. However, our laboratory results suggest that leucocyte filtration at low flow and pressure conditions is associated with less leucocyte damage and less release of elastase.

Increased neutrophil priming and sensitization before commencing cardiopulmonary bypass in cardiac surgical patients

BACKGROUND

Neutrophil activation is implicated in postoperative complications in patients having cardiac surgery with cardiopulmonary bypass (CPB). This study was designed to determine the temporal fluctuations in the primability of neutrophils in the preoperative, intraoperative, and postoperative periods of CPB, and specifically whether CPB was a primary cause leading to increased neutrophil priming and elastase release.

METHODS

Twenty patients undergoing multiple coronary bypass grafting, valve replacement, or both of these procedures were included in this study. Blood samples were taken 1 day before the operation and at several time points during and after the operation. For each sample, blood was divided in vitro into four subgroups: control without priming, priming alone with cytochalasin B (CytoB), priming plus stimulation with platelet-activating factor (PAF), and priming plus stimulation with N-formyl-methionyl-leucyl-phenylalanine (fMLP). The elastase concentration of all these samples was determined using the enzyme immunoassay.

RESULTS

Compared with the controls, CytoB priming increased release of elastase more than 10-fold before CPB, 1.6-fold during CPB, and 1.5-fold at the end of CPB. Further stimulation with PAF or fMLP showed greater increase of elastase than priming alone, with peak values in both found before CPB. This increased neutrophil primability prior to CPB did not differ significantly among patients who had different preoperative disease profiles.

CONCLUSIONS

Our data suggest that neutrophil priming occurs early before commencing CPB in cardiac surgical patients, and that CPB is not the primary primer. Anesthesia, surgical trauma, and other events may have been involved in neutrophil priming and sensitization before CPB, which warrants further investigation.

Cardiopulmonary bypass for bilateral sequential lung transplantation in patients with chronic obstructive pulmonary disease without adverse effect on lung function or clinical outcome

OBJECTIVE

The use of cardiopulmonary bypass in lung transplantation remains controversial. Previous studies have concluded that cardiopulmonary bypass is deleterious, but these studies were confounded by the inclusion of patients with different diagnoses undergoing single- and double-lung transplantation with elective or emergency use of bypass. The goal of this study was to determine whether cardiopulmonary bypass has deleterious effects on lung function or clinical outcome by analyzing the cases of patients with a single disease entity and elective use of bypass for bilateral sequential lung transplantation.

METHODS

A retrospective review of 50 patients with chronic obstructive pulmonary disease who underwent bilateral sequential lung transplantation was performed. Fourteen patients who underwent elective cardiopulmonary bypass for 218.3 +/- 75.4 minutes were compared to 36 control patients.

RESULTS

After the operation, the bypass and nonbypass groups were not significantly different with respect to median duration of mechanical ventilation (1 day vs 1 day, P =.76), median stay in the intensive care unit (4 days vs 4 days, P =.44), median hospital stay (15.5 days vs 16 days, P =.74), mean increase in serum creatinine level (1.4 +/- 1.9 mg/dL vs 0.9 +/- 1.0 mg/dL, P =.33), and mean ratio of Pao(2) to fraction of inspired oxygen at 1 hour (376.6 +/- 123 vs 357.0 +/- 218, P =.75), at 24 hours (309.9 +/- 92 vs 350.6 +/- 122, P =.26), and at 48 hours (335.0 +/- 144 vs 316.2 +/- 120, P =.64). Late outcome markers compared between the bypass and nonbypass groups were the following: 1-year percentage predicted forced expiratory volume in 1 second (76.1% +/- 17.0% vs 85.3% +/- 21.7%, P =.24), 30-day mortality (7.1% vs 8.3%, P >.999), 1-year survival (85.7% vs 80.1%, P =.66), 3-year survival (64.3% vs 58.3%, P =.70), and the prevalence of bronchiolitis obliterans syndrome (0% vs 36.1%, P =.01).

CONCLUSION

Cardiopulmonary bypass appears to have no deleterious effect on early lung function or clinical outcome. We hope that this pilot study removes some of the unwarranted fear of the use of bypass in lung transplantation for chronic obstructive pulmonary disease.

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

OBJECTIVE

Neurologic dysfunction after cardiopulmonary bypass might be due to arterial microembolization. Pericardial suction blood is a possible source of embolic material. Our aim was to determine the capillary-pore flow ability of pericardial suction blood.

METHODS

Pericardial suction blood from patients undergoing coronary bypass was collected, and pericardial suction blood and venous blood were sampled at the end of cardiopulmonary bypass and before reinfusion of pericardial suction blood. Pericardial suction blood was (n = 10) or was not (n = 10) prefiltered through a 30-microm cardiotomy screen filter before capillary in vitro analysis. Additionally, in 8 patients the plasma viscosity was measured, and in 5 of these patients, pericardial suction blood capillary deposits were evaluated by using a microscopy-imprint method and fat staining. Capillary flow was tested through 5-microm pore membranes. Tested components were plasma, plasma-eliminated whole-blood resuspension, and leukocyte/plasma-eliminated erythrocyte resuspension. Initial filtration rate and clogging slope expressed the blood-to-capillary interaction.

RESULTS

The plasma-flow profile of pericardial suction blood was highly impaired, with a 47% reduction in initial filtration rate (P <.001) and a 142% steeper clogging slope flow deceleration (P <.01). This difference was not due to a change in pericardial suction blood viscosity, such as by free hemoglobin, which corresponded to 5.7% of the erythrocytes. There were no differences in resuspended whole blood or erythrocytes. The cardiotomy filter had no effect. Microscopy suggested the presence of capillary fat deposits in pericardial suction blood that were not seen with venous plasma (P <.05). The pericardial suction blood volume was 458 +/- 42 mL and contained 95.6 +/- 9.3 g/L hemoglobin.

CONCLUSIONS

The pericardial suction blood plasma capillary flow function was highly impaired by liquid fat. Pericardial suction blood hemoglobin appears worth recovering after fat removal, despite profound hemolysis.

Effects of lung recruitment maneuver and positive end-expiratory pressure on lung volume, respiratory mechanics and alveolar gas mixing in patients ventilated after cardiac surgery

BACKGROUND

It is unclear whether positive end-expiratory pressure (PEEP) is needed to maintain the improved oxygenation and lung volume achieved after a lung recruitment maneuver in patients ventilated after cardiac surgery performed in the cardiopulmonary bypass (CPB).

METHODS

A prospective, randomized, controlled study in a university hospital intensive care unit. Sixteen patients who had undergone cardiac surgery in CPB were studied during the recovery phase while still being mechanically ventilated with an inspired fraction of oxygen (FiO2) 1.0. Eight patients were randomized to lung recruitment (two 20-s inflations to 45 cmH2O), after which PEEP was set and kept for 2.5 h at 1 cmH2O above the pressure at the lower inflexion point (14+/-3 cmH2O, mean +/-SD) obtained from a static pressure-volume (PV) curve (PEEP group). The remaining eight patients were randomized to a recruitment maneuver only (ZEEP group). End-expiratory lung volume (EELV), series dead space, ventilation homogeneity, hemodynamics and PaO2 (oxygenation) were measured every 30 min during a 3-h period. PV curves were obtained at baseline, after 2.5 h, and in the PEEP group at 3 h.

RESULTS

In the ZEEP group all measures were unchanged. In the PEEP group the EELV increased with 1220+/-254 ml (P<0.001) and PaO2 with 16+/-16 kPa (P<0.05) after lung recruitment. When PEEP was discontinued EELV decreased but PaO2 was maintained. The PV curve at 2.5 h coincided with the curve obtained at 3 h, and both curves were both steeper than and located above the baseline curve.

CONCLUSIONS

Positive end-expiratory pressure is required after a lung recruitment maneuver in patients ventilated with high FiO2 after cardiac surgery to maintain lung volumes and the improved oxygenation.

No impact of a leucocyte depleting arterial line filter on patient recovery after cardiopulmonary bypass

BACKGROUND

Contact of blood with foreign surfaces in the cardiopulmonary bypass (CPB) circuit induces an inflammatory response and immunosuppression which are associated with several organ dysfunctions following cardiac surgery. The aim of the present study was to evaluate clinical patient recovery after coronary artery bypass surgery (CABG) using CPB with leucocyte filtration or no arterial line filter.

METHODS

Sixty patients scheduled for CABG were randomly assigned to undergo CPB with a leucocyte depleting arterial line filter (Pall LG6) or no filter. Total leucocyte count and platelet count were determined before and after CPB. Values for blood urea nitrogen, serum creatine, serum sodium and potassium, serum osmolality, urine creatine, urine sodium and potassium, and urine osmolality were recorded at baseline, at 6 h and 24 h after CPB, and on the 5th postoperative day. Complement status was evaluated by measuring the levels of C3 and C4 before surgery and 24 h after CPB. Need for postoperative inotropic support was recorded, as was oxygen index prior to and after tracheal extubation. Times to awakening and tracheal extubation were noted, as were length of stay at the intensive care unit (ICU) and the hospital. Amount of chest drainage until 24 h and need for red blood cell transfusions were recorded.

RESULTS

The level of C3 at 24 h was significantly lower in LG6-patients, but no further differences were detected between the groups in any of the laboratory or clinical parameters except for greater chest drainage in LG6-patients. However, need for red blood cell transfusions was similar in both groups.

CONCLUSION

Leucocyte filtration in our elective CABG patients did not have any impact on pulmonary gas exchange, need for postoperative inotropic support, length of postoperative mechanical ventilation, or length of ICU or hospital stay.

Low degree of activation of circulating neutrophils determined by flow cytometry during cardiac surgery with cardiopulmonary bypass

BACKGROUND

Enhanced expression of adhesion molecules LFA-1 (CD11a/CD18) and Mac-1 (CD11b/CD18) following cardiac surgery with cardiopulmonary bypass (CPB) is held responsible for postoperative complications. Surface expression of these molecules, intracellular pH (pH(i)), and oxidative burst capacity was analyzed to test for neutrophil activation during pediatric cardiac surgery.

METHODS

Blood samples were drawn from 36 patients (age: 3--16 years) 24 h preoperatively, after onset of anesthesia, after connection to CPB (CPB1, before and after passing CPB, n = 15), at reperfusion (CPB2), and up to 7 days postoperatively. Cells adhering to CPB filters were isolated (n = 11). Antigen expression, pH(i), and oxidative burst capacity on neutrophils was analyzed by flow cytometry.

RESULTS

During surgery, oxidative burst capacity was at low level with a mild increase only 1 day after surgery. pH(i) was decreased throughout the surgery. Surgery induced more than 36% decrease of LFA-1 and Mac-1 expression (P < 0.03). Up to postoperative day 7, no increase of antigen expression above baseline was found. Neutrophils isolated from filters of the CPB had increased LFA-1 and Mac-1 expression (all P < 0.05). Integrin expression on neutrophils passing the CPB at CPB1 was decreased (P < 0.05).

CONCLUSION

Reduced adhesion molecule expression on neutrophils may be due to selective filtration of highly adhesive cells. This, in combination with low-level oxidative burst capacity, induced by immunosuppressive cytokines (e.g., interleukin-10), reduced the neutrophil activity. Our data indicate that increased activity of circulating neutrophils cannot exclusively be held responsible for postoperative complications after surgery with CPB.

Filtration of activated granulocytes during cardiopulmonary bypass surgery: a morphologic and immunologic study to characterize the trapped leukocytes

Cardiopulmonary bypass surgery induces an inflammatory reaction among others by activation of granulocytes. Leukocyte filtration has been shown to reduce the postoperative morbidity mediated by activated granulocytes. However, little is known about the mechanism of filter-leukocyte interaction. This study examines whether a leukocyte filter removes activated granulocytes or a general leukocyte population. Eleven patients undergoing cardiopulmonary bypass surgery were included in this study. Leukocyte filtration was achieved before the reperfusion phase with a Pall non-woven polyester filter located at the venous side of the heart-lung machine. After filtration, the trapped granulocytes inside the filter were examined morphologically with light and scanning electron microscopy and immunologically by CD45RO antigen binding to the filter material. Furthermore, leukocyte release markers were measured to determine whether cells were activated during filtration. Microscopic evaluation revealed 84% granulocytes and 14% lymphocytes trapped in the filter, compared with 78% granulocytes and 22% lymphocytes in the blood before filtration. Granulocytes were trapped significantly more in the first blood contact layer of the filter material than in the middle layer and last layer, whereas lymphocytes trapped slightly more in the middle layer. The near maximum level of CD45RO expression was measured on granulocytes trapped inside the filter material, whereas CD2 and CD19 measured on lymphocytes were bound to a minor extent. Beta-glucuronidase concentration did not increase after filtration, suggesting the absence of activation of granulocytes by filtration. A leukocyte filter made of non-woven polyester material removes the activated granulocytes rather than leukocytes at random. This implies that this particular type of leukocyte removal filter is suitable for use in cardiopulmonary bypass patients whose granulocytes in the circulation are activated. Furthermore, measurement of activated granulocytes instead of total leukocyte count is likely preferable for functional assessment of leukocyte removal devices.

Pressure drop, shear stress, and activation of leukocytes during cardiopulmonary bypass: a comparison between hollow fiber and flat sheet membrane oxygenators

The membrane oxygenator is known to be superior to the bubble oxygenator, but little information is available about the difference between the hollow fiber and flat sheet membrane oxygenators with regard to pressure drop, shear stress, and leukocyte activation. In this study, we compared these 2 types of membrane oxygenators in patients undergoing cardiopulmonary bypass (CPB) surgery with special focus on leukocyte activation and pressure drop across the oxygenators. Plasma concentration of elastase, a marker indicating leukocyte activation, increased to 593+/-68% in the flat sheet oxygenator group versus 197+/-42% in the hollow fiber oxygenator group (p<0.01) at the end of CPB compared to their respective baseline concentrations before CPB. Pressure drop across the oxygenator was significantly higher in the flat sheet group than in the hollow fiber group throughout the entire period of CPB (p<0.01). High pressure drop across the oxygenator as well as the calculated shear stress was positively correlated with the release of elastase at the end of CPB (r = 0.760, p<0.01, r = 0.692, p<0.01). However, this positive correlation existed in the flat sheet oxygenator but not in the hollow fiber oxygenator. Clinically, both membrane oxygenators have satisfactory performance in O2 and CO2 transfer. These results suggest that a higher pressure drop across the flat sheet oxygenator is associated with more pronounced activation of leukocytes in patients undergoing cardiopulmonary bypass.

Differential expression of neutrophil adhesion molecules during coronary artery surgery with cardiopulmonary bypass

BACKGROUND

Activation of neutrophil adhesion molecules and subsequent neutrophil adhesion to vascular endothelium are key events initiating inflammatory organ dysfunction after cardiopulmonary bypass and ischemic reperfusion.

OBJECTIVES

We sought to characterize neutrophil integrin CD11b and L-selectin activation associated with coronary artery bypass graft surgery and to determine whether neutrophil activation contributes to their sequestration on postbypass reperfusion.

METHODS

Twenty patients undergoing routine coronary artery bypass were studied. Heparinized whole blood was simultaneously sampled from a central venous line, aorta, coronary sinus, and right and left atrium before, during, and up to 20 minutes after cardiopulmonary bypass. Neutrophil counts were obtained, and neutrophil CD11b and L-selectin expression was determined by flow cytometric analysis in whole blood.

RESULTS

CD11b expression on circulating neutrophils increased during cardiopulmonary bypass, peaking at 145% of baseline level after release of the aortic clamp and then declined by 20 minutes after bypass (analysis of variance, P =.003). No change in neutrophil L-selectin expression was observed during cardiopulmonary bypass. Neutrophils responded to ex vivo stimulation by C5a and leukotriene B(4) during cardiopulmonary bypass but not at 24 hours after the operation. After reperfusion, neutrophil loss, but not local activation, was demonstrated in the coronary and pulmonary circulations.

CONCLUSIONS

Upregulated CD11b expression on neutrophils is likely to contribute to neutrophil sequestration in the heart and lungs after bypass, but neutrophil activation may be limited by their reduced responsiveness to agonist stimulation. CD11b represents a potential therapeutic target for diminishing inflammation after cardiac operations.

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.

Fat emulsion administration in the early postoperative period in patients undergoing esophagectomy for carcinoma depresses arachidonic acid metabolism in neutrophils

The aim of this study was to evaluate the effect of fat emulsion administration on neutrophil arachidonic acid and leukotriene B4 (LTB4) generation in surgically stressed patients. Total parenteral nutrition was administered to 17 patients for 2 wk after esophagectomy for carcinoma. Eight patients received fat with glucose (fat group, 30% of total calories) and 9 patients received glucose (glucose group) as a non-protein calorie source from the day of the operation to the seventh postoperative day (POD), and they gradually were converted to enteral nutrition during the second postoperative week. The arachidonic acid in the fat group decreased in the serum from POD 4 to 14. and in neutrophils from 12 h after the beginning of surgery to POD 14, compared to preoperative levels. LTB4 production by A23187-stimulated neutrophils was highest 6 h after the beginning of surgery, when neutrophil arachidonic acid concentration was decreasing, and then fell below the preoperative value from POD 4 to 14 in both groups. LTB4 production on POD 14 was lower in the fat group than in the glucose group. Biosynthesis of arachidonic acid from linoleic acid is inhibited in surgically stressed patients receiving fat emulsion, resulting in the diminished synthesis of LTB4 by neutrophils. The decrease in LTB4 may diminish chemotactic and chemokinetic signals to other leukocytes.

Multiple sequential insults cause post-pump syndrome

BACKGROUND

We hypothesize that post-pump syndrome (PPS) following cardiopulmonary bypass (CPB) can be caused by multiple minor insults and that the mechanism of PPS is a priming and subsequent activation of polymorphonuclear (PMN) leukocytes. In this study extensive pathophysiologic and morphometric assessment was undertaken in a porcine model of sequential insult PPS.

METHODS

Pigs were anesthetized, placed on a ventilator, instrumented for measurements of hemodynamic function, and separated into five groups: (1) Control (n = 4)--surgery only, (2) CPB (n = 4)--placed on femoral-femoral hypothermic (28 degrees C) bypass for 1 h, (3) LPS (n = 6)--underwent sham CPB followed by infusion of low dose endotoxin [E. coli lipopolysaccharide (LPS-1 microg/kg)], (4) Heparin + protamine + LPS (HP + LPS, n = 4)--were heparinized without CPB for 1 h, following which protamine and LPS were infused and (5) CPB + LPS (n = 8)--subjected to both CPB and LPS.

RESULTS

Only CPB + LPS resulted in acute respiratory distress typical of PPS as indicated by a significant decrease in PaO2 and increase in intrapulmonary shunt fraction (p<0.05). CPB + LPS significantly increased tissue density and the number of sequestered monocytes and PMNs (p<0.05) above all other groups. Alveolar macrophages (AM) increased equally in all groups receiving LPS.

CONCLUSIONS

CPB primes the inflammatory system causing pulmonary PMN sequestration without lung injury. Exposure to an otherwise benign dose of endotoxin results in activation of the sequestered PMNs causing PPS. This study confirms that PPS can be caused by multiple minor insults.

The effects of extracorporeal whole body hyperthermia on the functional and phenotypic features of canine peripheral blood mononuclear cells (PBMC)

In this study the effect of transient 42.3 degrees C whole body hyperthermia (WBH) on the distribution of PBMC phenotypes and in vitro blastogenic responsiveness was determined in dogs. Hyperthermia (n = 6) was induced by heating venous blood during extracorporeal circulation (venous perfusion WBH); perfused non-heated dogs (n = 4) were used as controls. Both euthermic and hyperthermic perfusion produced transient lymphopenia which normalized in controls after perfusion but persisted in hyperthermic animals throughout the 8-day post-perfusion observation interval. The transient lymphopenia in control dogs was non-selective. In contrast, WBH-associated lymphopenia was selective, in that CD5+ T lymphocytes were more sensitive to hyperthermia than sIg+ B cells and, within the T cell compartment, suppressor (CD8+) cells were more sensitive to hyperthermic stress than helper (CD4+) lymphocytes. Functional analyses showed that WBH caused persistent suppression of PBMC blastogenesis in response to T cell phytomitogens. Increased plasma cortisol levels were correlated to peak lymphopenia and hyporesponsiveness to phytomitogens. Despite these alterations, high grade WBH was well tolerated and there was no evidence of opportunistic infection.

Acute and chronic effects of bilateral lung transplantation without cardiopulmonary bypass on the first transplanted lung

BACKGROUND

Bilateral lung transplantation (BLT) without cardiopulmonary bypass (CPB) may exacerbate reperfusion injury to the initially engrafted lung because of increases in pulmonary flow during implantation of the second graft.

METHODS

In a retrospective review of 23 BLT patients, we hypothesized that BLT without CPB injures the first transplanted lung measured by acute and late graft dysfunction compared to the second transplanted lung. Of the 23 BLT, 19 underwent transplantation without CPB while 4 patients were placed on CPB secondary to hemodynamic instability.

RESULTS

Acute graft function was assessed by radiographic scoring of lung quadrants (blinded radiologist; 0 = no infiltrate; 1 = infiltrate; maximum = 2 per lung) and by arterial/alveolar oxygen tension ratios (PaO2/ FiO2) ratios. Late graft function was evaluated by quantitative perfusion scan. Lung perfusion was graded as abnormal if less than 50% on the right or less than 45% on the left (Fisher's exact). Radiographic scores were not different between first and second implanted lungs at 1 and 24 hours, PaO2/FiO2 ratios at 1 and 24 hours were 273+/-26 and 312+/-23, respectively, and perfusion scans at 3 and 12 months revealed normal differential blood flow.

CONCLUSIONS

These findings suggest no acute or chronic differences occur between the first or second transplanted lung completed without CPB.

Cytokine release during long-term extracorporeal circulation in an experimental model

The objective of this study was to determine the degree of leukocyte activation, as measured by cytokine release, in circulating blood during experimental extracorporeal circulation. Complete in vitro extracorporeal membrane oxygenation (ECMO) circuits were used, and 9 experiments were performed. Whole blood stored at 37 degrees C was used as the control. Blood samples were withdrawn before the start of perfusion and at 24 h of perfusion. Statistically significant releases of interleukin (IL)-1beta, IL-8, and IL-1 receptor antagonist were observed in the perfusion circuits compared to both the control blood and baseline values. Also, increases in plasma tumor necrosis factor (TNF)alpha and IL-6 were seen after 24 h of perfusion although these changes did not reach statistical significance. These results indicate that extracorporeal circulation induced leukocyte activation and cytokine release. These reactions might, as an additional trauma, deteriorate the situation in an already severely ill patient. A search for methods to counteract this untoward activation seems warranted.

Systemic inflammation present in patients undergoing CABG without extracorporeal circulation

STUDY OBJECTIVES

This study was conducted to evaluate to what extent the cardiopulmonary bypass (CPB) procedure in patients undergoing coronary artery bypass grafting (CABG) contributes to the systemic inflammatory response. Therefore, we measured bactericidal permeability increasing protein (BPI) as an indicator of neutrophil activation, interleukin 6 as inducer of the acute phase response, and lipopolysaccharide binding protein and C-reactive protein as parameters of the acute phase response in patients undergoing CABG either with or without the use of CPB.

DESIGN

Prospective study.

SETTING

Cardiopulmonary surgery department in a university hospital.

PATIENTS

Sixteen patients undergoing elective CABG were included. Eight patients underwent surgery with CPB, and eight patients underwent surgery without CPB (non-CPB).

INTERVENTIONS

In the CPB group, blood samples were taken upon induction of anesthesia, at the start of aortic cross-clamping, at aortic unclamping, and 0.5, 4, 8, and 18 h thereafter. In the non-CPB group, blood samples were taken upon induction of anesthesia, and 0.5, 4, 8, and 18 h after completion of the bypass graft anastomoses.

MEASUREMENTS AND RESULTS

BPI release from neutrophil granules markedly increased during surgery in CPB patients but not in non-CPB patients. The increase in acute phase reactants, however, was the same in both patient groups.

CONCLUSIONS

These data indicate that the acute phase response in CABG patients, which has historically been ascribed to the CPB procedure, is predominantly caused by the surgical procedure per se. Early neutrophil activation, however, is seen only when extracorporeal circulation is used.

Intercellular adhesion molecule-1 regulation in the canine lung after cardiopulmonary bypass

OBJECTIVE(S)

Neutrophil sequestration in the lung after cardiopulmonary bypass has been shown to be dependent on the adhesion molecule CD18. Thus we sought to determine whether endothelial expression of intercellular adhesion molecule-1 (a ligand for CD18) in pulmonary capillaries mediates neutrophil adhesion in this setting.

METHODS

Seven adult mongrel dogs underwent 90 minutes of hypothermic cardiopulmonary bypass with 60 minutes of cardioplegic arrest. After warming, dogs were reperfused for up to 9 hours and lung biopsy specimens were obtained. Lung tissue was examined by Northern and Western blot analysis and by immunohistologic methods. Three sham-operated dogs served as time-matched controls.

RESULTS

Northern blots demonstrated increased expression of intercellular adhesion molecule-1 messenger ribonucleic acid within 5 minutes of cessation of bypass (or approximately 30 minutes after aortic crossclamp release), which persisted at 9 hours of recovery and was not present in controls. Western blots showed intercellular adhesion molecule-1 protein expression before bypass but a measurable increase in intercellular adhesion molecule-1 protein in four of seven dogs in the bypass group by the ninth hour of recovery. Pulmonary neutrophil accumulation 9 hours after cardiopulmonary bypass was greater in those dogs with an increased intercellular adhesion molecule-1 protein expression. Immunoelectron microscopy demonstrated the pulmonary capillary endothelium capable of increased intercellular adhesion molecule-1 protein expression at the 9-hour time point.

CONCLUSIONS

Cardiopulmonary bypass resulted in intercellular adhesion molecule-1 induction in the canine lung during recovery. An increased expression of intercellular adhesion molecule-1 protein in the lung was associated with an increased accumulation of neutrophils in affected animals. Thus intercellular adhesion molecule-1 expression may serve as a mechanism that predisposes the lungs to inflammatory cell-mediated injury postoperatively.

Phenotypic alterations in circulating monocytes induced by open heart surgery using heparinized and nonheparinized cardiopulmonary bypass systems

In this study of 31 patients with coronary bypass surgery, we used flow cytometry to compare heparin-coated and noncoated cardiopulmonary bypass systems on leukocyte activation. We found significant differences between the groups during bypass, with activation of the complement system, measured as elevated levels of C3a desArg, upregulation of granulocyte beta2 integrin (CD11b), and a loss of circulating monocytes when noncoated systems were used. In both groups an early increase in the monocyte cell surface CD62L expression was obvious while the percentage of human leukocyte antigen (HLA)-DR positive monocytes did not alter. The morning after the operation, leukocytosis was present, together with a highly significant reduction in the monocyte expression of CD11b and HLA-DR, indicating the recruitment to the peripheral blood of cells with altered phenotypes. This alteration in phenotype on potent inflammatory cells may be one part of the impaired function of the immunological system reported after major surgery.

Inflammatory response to cardiopulmonary bypass: mechanisms involved and possible therapeutic strategies

BACKGROUND

Recent study of the inflammatory reactions occurring during and after cardiopulmonary bypass (CPB) has improved our understanding of the involvement of the inflammatory cascade in perioperative injury. However, the exact mechanisms of this complex response remain to be fully determined.

METHODS

Literature on the inflammatory response to CPB was reviewed to define current knowledge on the possible pathways and mediators involved, and to discuss recent developments of therapeutic interventions aimed at attenuating the inflammatory response to CPB.

RESULTS

CPB has been shown to induce complement activation, endotoxin release, leukocyte activation, the expression of adhesion molecules, and the release of many inflammatory mediators including oxygen-free radicals, arachidonic acid metabolites, cytokines, platelet-activating factor, nitric oxide, and endothelins. Therapies aimed at interfering with the inflammatory response include the administration of pharmacologic agents such as corticosteroids, aprotinin, and antioxidants, as well as modification of techniques and equipment by the use of heparin-coated CPB circuits, intraoperative leukocyte depletion, and ultrafiltration.

CONCLUSIONS

Improved understanding of the inflammatory reactions to CPB can lead to improved patient outcome by enabling the development of novel therapies aimed at limiting this response.

Cardiac valve prostheses at autopsy: an analysis of 337 cases with clinicopathologic correlation

We evaluated the pathologic findings at autopsy in 337 patients who had undergone cardiac valve replacement over 10 years (1982 to 1991). Rheumatic heart disease was the most common indication for valve replacement (84% of cases). Among the 255 patients with short-term survival (<1 month), in 162 cases (63.5%), the cause of death was related to surgery and/or underlying cardiovascular conditions. Host-prosthetic valve interactions contributed to mortality in 14.9% cases. However, in longtime survivors (82 patients), a significant number (86.5%) showed evidence of prosthesis-related complications, such as infective endocarditis, thrombosis, anticoagulant-related hemorrhage, and bioprosthetic valve degeneration.

Prevention of remote organ injury in cardiopulmonary bypass: the impact of flow generation technique

The purpose of this study was to investigate the effects of 3 different types of flow generation for cardiopulmonary bypass on gastrointestinal permeability and on neutrophil expression of CD11b, a surface marker of neutrophil activation. Fourteen patients undergoing elective coronary revascularization were selected randomly to receive 1 of the 3 flow generation techniques (roller, pulsatile, or centrifugal). Intestinal permeability was assessed by the fraction of an oral dose of 51chromium-ethylenediaminetetraacetate (51Cr-EDTA) recovered in the urine over 24 h. Neutrophil activation was determined by expression of CD11b markers at 6 time points. Overall, the 14 patients showed significant increases in intestinal permeability. It was not possible to demonstrate statistically significant differences among the flow generation groups; however, when compared to both roller pump groups, the centrifugal pump group showed a 3.2% reduction in intestinal permeability. There was no change in the expression of CD11b receptors throughout the time points, nor was there a relationship of CD11b markers to the flow generation technique.

Immobilized heparin inhibits the increase in leukocyte surface expression of adhesion molecules

The effect of heparin coating of artificial materials on the surface expression of leukocyte surface molecules was assessed in blood from 9 donors in an experimental model of extracorporeal circulation. The leukocyte surface molecules CD11b, complement receptor type 3 (CR3), and CD45, leukocyte common antigen (LCA), on granulocytes and monocytes exposed to unmodified polyvinyl chloride tubes increased significantly compared with unmanipulated controls (p < 0.001) whereas a very modest and nonsignificant increase was observed in blood circulated in heparin-coated tubes. Accordingly, a highly significant reduction in expression of the 2 molecules was achieved by heparin coating (p < 0.001). The expression of CD11b and CD45 correlated with the degree of complement activation in plasma (rho = 0.6, p = 0.003). The expression of CD14 (endotoxin receptor) and CD16 (Fc gamma III receptor) was increased to the same extent in blood from unmodified and heparin-coated tubes (p < 0.02), and no correlation to complement activation was seen (rho = -0.275, p = 0.17 and rho = -0.004, p = 1, respectively). In conclusion, heparin coating of artificial surfaces has a substantial effect, reducing the expression of molecules involved in cellular adhesion and activation (CD11b and CD45), and the increase of these molecules by unmodified surfaces is complement dependent. In contrast, up-regulation of other surface molecules (CD14 and CD16) seems to be independent of heparin coating and complement activation and, thus, might be regulated by other mechanisms.

Release of lipopolysaccharide toxicity-modulating proteins in patients undergoing cardiopulmonary bypass using noncoated and heparin-coated extracorporeal circuits. A clinical pilot study

STUDY OBJECTIVE

Cardiopulmonary bypass (CPB) induces a generalized inflammatory response, including activation of leukocytes, contributing to postoperative morbidity. The inflammatory pathways leading to this systemic inflammatory response syndrome are considered identical to those involved in septic shock. Therefore, we studied the release of bactericidal/permeability-increasing protein (BPI), lipopolysaccharide binding protein (LBP), and soluble CD14 (sCD14)-all proteins that modulate the effects of lipopolysaccharide (LPS)-in patients undergoing CPB. In addition, the effect of heparin coating of the extracorporeal bypass circuit on the release of these parameters was assessed.

DESIGN

Prospective, randomized clinical pilot study.

SETTING

Cardiothoracic Surgery Department in a university hospital.

PATIENTS

Fourteen patients undergoing elective coronary artery bypass grafting were included. Seven patients underwent CPB using a standard, noncoated extracorporeal circuit, and seven patients had CPB using a heparin-coated extracorporeal circuit (Duraflo II).

INTERVENTIONS

Blood samples were taken after induction of anesthesia, just before aortic crossclamping, and 0, 0.5, 1.5, 3, 6, 12, and 24 h after declamping.

MEASUREMENTS AND RESULTS

CPB with a noncoated extracorporeal circuit induced a sharp increase in neutrophil-derived BPI, manifest directly after release of the aortic crossclamp, which was significantly attenuated using a heparin-coated system. Also, CPB induced a gradual increase of the acute-phase reactant LBP, which was identical in the noncoated and heparin-coated groups. Systemic release of sCD14 after crossclamp release was significantly higher in the noncoated group compared with the heparin-coated group, but did not rise above baseline levels.

CONCLUSIONS

These data confirm that CPB-induced leukocyte activation is attenuated using a heparin-treated extracorporeal circuit and point to the possible role of LPS toxicity-modulating proteins in the systemic inflammatory response after bypass surgery.

Coronary microvascular reactivity after ischemic cold storage and reperfusion

BACKGROUND

The coronary microvascular system is important in the regulation of myocardial perfusion. Preservation of microvascular reactivity may be important in those hearts undergoing ischemic storage for transplantation. Endothelium-dependent relaxation of right and left ventricular coronary microvessels was examined in a canine model of heart transplantation.

METHODS

Canine hearts underwent topical cooling, antegrade arrest, and 3 hours' ischemic cold storage at 4 degrees C using crystalloid cardioplegia (n = 8), Roe's solution (n = 8), and University of Wisconsin solution (n = 8). All groups underwent 1 hour of reperfusion in an isolated heart circuit. Noninstrumented canines were used as controls (n = 10). Coronary microvessels (100 to 200 microns in diameter) were examined in a pressurized, no-flow state with video microscopic imaging and electronic dimension analysis.

RESULTS

Endothelium-dependent microvascular relaxation was examined in response to the receptor-dependent acetylcholine and to the receptor-independent calcium ionophore. Microvascular relaxation to acetylcholine in Roe's solution and University of Wisconsin solution was preserved (p = not significant) in the left ventricle, whereas crystalloid cardioplegia failed to preserve (p < 0.05) microvascular relaxation when compared with the control groups. Right ventricular microvascular relaxation was always (p < 0.05) less than left ventricular microvascular relaxation. Endothelium-independent microvascular relaxation to nitroprusside was similar to that in controls, indicating normal smooth muscle responsiveness.

CONCLUSIONS

Ischemic cold storage with Roe's solution and University of Wisconsin solution preserved microvascular relaxation in the left ventricle, whereas crystalloid cardioplegia failed to preserve microvascular relaxation. Right ventricular microvascular relaxation was impaired in all groups, but University of Wisconsin solution was superior to crystalloid cardioplegia and Roe's solution. This suggests that microvascular dysfunction may be partially responsible for right ventricular dysfunction after heart transplantation. The choice of preservation solution may be important in preservation of the microvascular endothelium.

Leukocyte depletion results in improved lung function and reduced inflammatory response after cardiac surgery

Leukocyte depletion during cardiopulmonary bypass has been demonstrated in animal experiments to improve pulmonary function. Conflicting results have been reported, however, with clinical depletion by arterial line filter of leukocytes at the beginning of cardiopulmonary bypass. In this study, we examined whether leukocyte depletion from the residual heart-lung machine blood at the end of cardiopulmonary bypass would improve lung function and reduce the postoperative inflammatory response. Thirty patients undergoing elective heart operations were randomly allocated to a leukocyte-depletion group or a control group. In the leukocyte-depletion group (n = 20), all residual blood (1.2 to 2.1 L) was filtered by leukocyte-removal filters and reinfused after cardiopulmonary bypass, whereas in the control group an identical amount of residual blood after cardiopulmonary bypass was reinfused without filtration (n = 10). Leukocyte depletion removed more than 97% of leukocytes from the retransfused blood (p < 0.01) and significantly reduced circulating leukocytes (p < 0.05) and granulocytes (p < 0.05) compared with the control group. Levels of the inflammatory mediator thromboxane B2 determined at the end of operation (p < 0.05) were significantly lower in the depletion group than in the control group, whereas no statistical differences in interleukin-6 levels were found between the two groups. After operation, pulmonary gas exchange function (arterial oxygen tension at a fraction of inspired oxygen of 0.4) was significantly higher in the leukocyte-depletion group 1 hour after arrival to the intensive care unit (p < 0.05) and after extubation (p < 0.05). There were no statistical differences between the two groups with respect to postoperative circulating platelet levels and blood loss, and no infections were observed during the whole period of hospitalization. These results suggest that leukocyte depletion of the residual heart-lung machine blood improves postoperative lung gas exchange function and is safe for patients who are expected to have a severe inflammatory response after heart operations.

The routine use of fresh frozen plasma in operations with cardiopulmonary bypass is not justified

BACKGROUND

The negative influence of cardiopulmonary bypass on hemostasis has been documented. Although abnormalities in platelet function are reported as the major cause of postoperative blood loss related to this hemostasis defect, fresh frozen plasma is often used in operations with cardiopulmonary bypass because it is thought to contribute to the reduction of postoperative bleeding complications. This study was designed to evaluate the effect of the administration of fresh frozen plasma after cardiopulmonary bypass on blood loss, transfusion requirements, and a number of coagulation parameters.

METHODS

In a prospective, randomized, double-blind clinical trial 50 patients (mean age 63 years; 35 men/15 women) undergoing elective operation with cardiopulmonary bypass were randomly assigned to one of two groups: group I (n = 24) received 3 units of fresh frozen plasma after operation and group II (n = 26) received an equal amount of Gelofusine plasma substitute. At seven points before, during, and after operation hemoglobin concentration, hematocrit level, thrombocyte count, and coagulation parameters were analyzed. Study endpoints were the volume of blood loss and the transfusion requirement.

RESULTS

There were no significant differences between the two study groups in blood loss, transfusion requirement, coagulation parameters, or thrombocyte counts.

CONCLUSION

The routine use of fresh frozen plasma in operations with cardiopulmonary bypass cannot be recommended.

An investigation of the effects of heparin, low molecular weight heparin, protamine, and fentanyl on the balance of pro- and anti-inflammatory cytokines in in-vitro monocyte cultures

We report a study conducted to determine if drugs given peri-operatively during cardiac surgery could themselves modulate the balance of pro- and anti-inflammatory cytokines. We determined the cytokine response of 10 separate in vitro monocyte cultures to the administration of drugs at concentrations used during cardiac 'surgery:fentanyl (25 ng.ml-1), heparin 2.5 i.u.ml-1, heparin with an equal concentration of protamine, and enoxaparin 2.5 i.u.ml-1. Fentanyl, heparin and low molecular weight heparin (enoxaparin) led to increased tumour necrosis factor alpha but this did not reach statistical significance. Tumour necrosis factor soluble receptor 1 and 2 was not elevated. Interleukin-1 beta was increased by heparin (p < 0.05), whereas interleukin-1 receptor antagonist was increased by fentanyl (p < 0.05). Protamine blocked the heparin-induced increase in tumour necrosis factor alpha and interleukin-1 beta. These data raise the possibility that endogenous and exogenously administered opioids may be partly contributing to the interleukin-1 receptor antagonist response seen during major surgery.

Time course of beta 2-integrin CD11b/CD18 (Mac-1, alpha M beta 2) upregulation on neutrophils and monocytes after coronary artery bypass grafting. CD11b upregulation after CABG surgery

Although upregulation of CD11b/CD18 receptor, i.e. activation of neutrophils and monocytes, during cardiopulmonary bypass is well documented, the duration of the active state after uncomplicated operation is less understood. We therefore investigated CD11b expression of phagocytes in blood samples collected 2-4, 24, 48 and 72 h after coronary artery bypass grafting. CD11b expression on neutrophils was significantly elevated at 2-4 and 24 hours after operation as compared with baseline. On monocytes, expression peaked at 24 h and returned to baseline by 72 h. Because CD11b is a sensitive marker, effects of different sampling techniques on its expression were also studied. CD11b expression was similar in samples collected with a syringe from arterial or central venous catheter or with open technique from cubital vein. On neutrophils from healthy subjects, sampling with syringe caused small (10%) but statistically significant increase of expression. We conclude that activated neutrophils disappear from circulation within hours after CABG surgery while activated monocytes may continue circulating for 2-3 days, and that CD11b sampling can be done with a syringe.

Hypothermia during cardiopulmonary bypass delays but does not prevent neutrophil-endothelial cell adhesion. A clinical study

BACKGROUND

An accurate evaluation of warm heart surgery cannot be limited to the assessment of the myocardial effects of warm blood cardioplegia but should also address the effects of systemic normothermia on the inflammatory response to cardiopulmonary bypass. A major component of this response is the endothelial adhesion of neutrophils, because it is linked to the release of cytotoxic compounds. This study was designed (1) to characterize the bypass-induced changes in the expression of neutrophil adhesion molecules (L-selectin and beta 2-integrins) and (2) to assess the influence of bypass temperature on these changes.

METHODS AND RESULTS

Twenty case-matched patients undergoing open-heart procedures were divided into two equal groups according to the core temperature during cardiopulmonary bypass: warm (33.4 +/- 0.3 degrees C) or cold (27.1 +/- 0.4 degrees C, P < .0001 versus warm). Arterial blood samples were collected before, during, and 30 minutes after bypass and processed for the expression of L-selectin and beta 2-integrins (CD11a, CD11b, and CD11c) with flow cytometry. Warm bypass was associated with an early and sustained upregulation of CD11b. In contrast, hypothermia resulted in a strikingly less pronounced CD11b upregulation during bypass. However, CD11b expression sharply increased thereafter so that 30 minutes after bypass, it was no longer significantly different between the two groups. Changes in CD11c expression grossly paralleled those described for CD11b. Neither CD11a nor L-selectin changed significantly from baseline values in either group.

CONCLUSIONS

Clinical cardiopulmonary bypass is associated with a marked upregulation of the neutrophil CD11b and CD11c integrins. Hypothermia delays but does not prevent the increased expression of these adhesion molecules, which could consequently represent logical targets for interventions designed to blunt the neutrophil-mediated component of bypass-induced inflammatory tissue damage.

Clinical performance of a high-efficiency rapid flow leucocyte removal filter for leucocyte depletion of heparinized cardiopulmonary bypass perfusate

The method of leucocyte depletion has been recently introduced to the field of cardiopulmonary bypass to reduce leucocyte-mediated organ dysfunction. In this study, we evaluated the efficacy and biocompatibility of the Pall RC400 filters for leucocyte depletion of heparinized cardiopulmonary bypass (CPB) perfusate taken from the heart-lung machine during routine cardiac surgery. For each filter, 700 ml blood were used as filtrate. Filtration was divided into the following groups to study the effect of loading pressure on the efficacy of the filters: under gravity pressure as a control (n = 8), under 100 mmHg (n = 8), 200 mmHg (n = 8), and 300 mmHg loading pressure (n = 8) driven by a roller pump. In addition, heparinized predonation blood taken at the beginning of CPB (n = 8) was filtered under gravity in comparison with the perfusate taken at the end of CPB. The results showed that the average leucocyte removal rate by an RC400 filter for 700 ml of blood was 96.8%. There was no significant difference of leucocyte removal rate between filtration under gravity and under loading pressure up to 300 mmHg. This allows clinical filtration at a speed up to 500 ml/min. The platelet removal rate was significantly higher in blood taken at the beginning of CPB than in blood taken at the end of CPB. Complment split product, C5a, increased only slightly during filtration indicating that this filter, made from polyester, has a good blood compatible characteristic. We conclude that the Pall RC400 leucocyte removal filter is suitable and safe to be used for leucocyte filtration of heparinized CPB perfusate during cardiac surgery.

Influence of temperature on neutrophil trafficking during clinical cardiopulmonary bypass

BACKGROUND

The adhesion of neutrophils to endothelial cells and their subsequent transendothelial migration play a major role in inflammatory damage elicited by cardiopulmonary bypass (CPB) because these events are linked to the release of cytotoxic proteases and oxidants. However, the patterns of neutrophil trafficking in relation to systemic temperature during clinical CPB have not yet been characterized.

METHODS AND RESULTS

Twenty case-matched patients undergoing warm (31.8 +/- 0.4 degrees C) or cold (26.3 +/- 0.5 degrees C, P < .0001 versus warm) bypass were studied. Blood samples were simultaneously collected from the right and left atria before, at the end of, and 30 minutes after CPB. Plasma levels of C3a, P- and E-selectins, elastase, and interleukin-8 were determined by immunoassays. The results demonstrate: (1) a rise in C3a, reflecting complement activation, (2) a fall in soluble E-selectin consistent with an increased adhesiveness of activated neutrophils, (3) a rise in soluble P-selectin expected to enhance endothelial adhesion of these neutrophils, (4) a rise in elastase, suggesting an adhesion-triggered neutrophil degranulation, and finally (5) a rise in interleukin-8 that is likely to promote transendothelial migration of adherent neutrophils. All of these changes occurred in the two groups of patients and were significant compared with prebypass values. However, in none of the groups was there a significant difference between right and left atrial values for any of the markers. The single difference between cold and warm bypass patients was a significant reduction of elastase release in the cold group (P < .001 versus the warm group).

CONCLUSIONS

Clinical CPB is associated with biological changes suggesting the occurrence of neutrophil trafficking. Hypothermia provides only partial protection through a reduced release of elastase. Overall, these results reinforce the rationale for the development of therapeutic strategies targeted at blunting the neutrophil-mediated component of bypass-induced inflammatory damage.

The influence of leukocyte filtration during cardiopulmonary bypass on postoperative lung function. A clinical study

The accumulation of activated leukocytes in the pulmonary circulation plays an important role in the pathogenesis of lung dysfunction associated with cardiopulmonary bypass. Animal studies have demonstrated that the elimination of leukocytes from the circulation reduces postoperative lung injury and improves postoperative pulmonary function. We conducted a prospective randomized clinical study to evaluate whether postoperative lung function could be improved by use of a leukocyte filter during cardiopulmonary bypass. Elective coronary artery bypass grafting was done with a leukocyte-depleting arterial blood filter incorporated in the extracorporeal circuit (14 patients, leukocyte filter group) or without the filter (18 patients, control group). Blood samples collected at intervals before, during, and after operation were used for analysis of blood cell counts, elastase concentrations, and arterial blood gases. The use of the leukocyte filter caused no significant reduction in leukocyte count (p = 0.86). There were no differences in postoperative lung function between the groups, as assessed through (1) oxygenation index (290 for leukocyte filter group compared with 329 for control group, 95% confidence interval, 286 to 372, p = 0.21), (2) pulmonary vascular resistance (p = 0.10), and (3) intubation time (16.6 hours for leukocyte filter group versus 15.7 hours for control group, 95% confidence interval, 12.1 to 19.1 hours, p = 0.72). The levels of neutrophil elastase were significantly higher at the end of cardiopulmonary bypass in the leukocyte filter group (460 microgram/L in leukocyte filter group versus 230 microgram/L in control group, 95% confidence interval, 101 to 359 microgram/L, p = 0.003). We conclude that the clinical use of the present form of leukocyte-depleting filter did not improve any of the postoperative lung function parameters analyzed in this study.

Lung transplantation with cardiopulmonary bypass exaggerates pulmonary vasomotor dysfunction in the transplanted lung

Pulmonary vascular resistance is significantly increased in the transplanted lung. If cardiopulmonary bypass is required, the transplanted lung is reperfused with activated blood elements, which might exacerbate the reperfusion injury. The purpose of this study was to examine the influence of cardiopulmonary bypass on the following mechanisms of pulmonary vasomotor control in a dog model of autologous lung transplantation: (1) endothelium-dependent cyclic guanosine monophosphate-mediated relaxation (response to acetylcholine), (2) endothelium-independent cyclic guanosine monophosphate-mediated relaxation (response to nitroprusside), and (3) beta-adrenergic cyclic adenosine monophosphate-mediated relaxation (response to isoproterenol). Autologous right lung transplants were performed with (n = 4 dogs) and without (n = 5 dogs) bypass. Lungs were stored in cold saline solution (4 degrees C, 3 hours) before reimplantation. Pulmonary vasomotor control mechanisms were studied in isolated pulmonary arterial rings immediately after harvest and 1 hour after reimplantation. Ten rings were studied in each group at each time. Statistical analysis was by analysis of variance. Without bypass, endothelium-dependent cyclic guanosine monophosphate-mediated relaxation and beta-adrenergic cyclic adenosine monophosphate-mediated relaxation were significantly impaired, although endothelium-independent cyclic guanosine monophosphate-mediated relaxation was not. Use of bypass produced significantly greater impairment of both endothelium-dependent cyclic guanosine monophosphate-mediated relaxation and beta-adrenergic cyclic adenosine monophosphate-mediated relaxation. In addition, use of bypass produced significant dysfunction of endothelium-independent cyclic guanosine monophosphate-mediated relaxation as well. We conclude that using cardiopulmonary bypass to perform lung transplantation greatly exaggerates pulmonary vasomotor dysfunction in the transplanted lung. This dysfunction may contribute to significantly higher pulmonary vascular resistance in the transplanted lung if cardiopulmonary bypass is used.

Effect of cardiopulmonary bypass on the circulating level of soluble GMP-140

Soluble GMP-140 can prevent the adhesion of activated neutrophils to endothelium in vitro. Because cardiopulmonary bypass causes neutrophil-endothelial interaction, the plasma level of soluble GMP-140 was measured using an enzyme immunoassay system in 32 children undergoing intracardiac repair of congenital heart disease. They had either a high, low, or normal pulmonary blood flow (n = 13, 12, and 7 respectively). Because activated platelets are a source of GMP-140, the plasma beta-thromboglobulin level was also measured. Blood was sampled before, during, and for 24 hours after cardiopulmonary bypass. Plasma levels of both soluble GMP-140 and beta-thromboglobulin increased after the onset of cardiopulmonary bypass in all patients but for both substances the increase was greater in those with a low pulmonary blood flow (p < 0.05 for all comparisons). The sum total of soluble GMP-140 values during and after operation was correlated negatively with the preoperative mean pulmonary arterial pressure (p < 0.05 for all time intervals). GMP-140 level correlated with the plasma beta-thromboglobulin level (r = 0.5, p < 0.05). This work supports the contention that soluble GMP-140 is released from activated platelets during cardiopulmonary bypass, the level being particularly high in those who had intrinsically abnormal platelets preoperatively in association with a low pulmonary blood flow. Patients with a high pulmonary blood flow, who are more susceptible to endothelial cell injury, may be less well protected by soluble GMP-140.

Mechanisms of coronary vasomotor dysfunction in the transplanted heart

The transplanted heart sustains both cold ischemic and reperfusion injuries. These can produce coronary vascular endothelial or smooth muscle injury or both, which, in turn, can produce coronary vasomotor dysfunction. Using a canine model of autologous heart transplantation, we examined the following coronary vasomotor control mechanisms in isolated coronary artery rings: (1) endothelial-dependent cyclic guanosine monophosphate (cGMP)-mediated vasorelaxation (response to acetylcholine); (2) endothelial-independent cGMP-mediated vasorelaxation (response to sodium nitroprusside); and (3) beta-adrenergic cyclic adenosine monophosphate (cAMP)-mediated vasorelaxation (response to isoproterenol hydrochloride). Further, these mechanisms were related to 3 hours of cold ischemia alone and to 3 hours of cold ischemia plus 1 hour of reperfusion. Autologous heart transplantation was performed in dogs, and isolated distal left anterior descending coronary artery rings were studied in individual organ chambers. Cold ischemia alone produced significant dysfunction of beta-adrenergic cAMP-mediated vasorelaxation, which was exacerbated after reperfusion. Neither endothelial-dependent nor endothelial-independent cGMP-mediated vasorelaxation was dysfunctional after cold ischemia alone, but both were significantly impaired after reperfusion. We conclude that cold ischemia and reperfusion each produce coronary vasomotor dysfunction in the transplanted heart. Cumulatively, such coronary vasomotor dysfunction can acutely impair coronary vasodilatation and potentially jeopardize myocardial blood flow in the transplanted heart.

Effect of cardiopulmonary bypass on early graft dysfunction in clinical lung transplantation

The records of 100 lung transplant recipients (13 heart-lungs, 45 double-lungs, and 42 single-lungs) from September 1990 through April 1992 were reviewed to determine the role of cardiopulmonary bypass (CPB) in early graft dysfunction. Fifty-five patients requiring CPB (CPB group) for 186 +/- 54 minutes were compared with the 45 patients without CPB (no-CPB group). All of the heart-lung and en-bloc double-lung transplantations were performed under CPB, with pulmonary vascular lung disease the principal diagnosis, resulting in a significantly younger age population in the CPB group. All other donor- and recipient-related factors matched well in both groups. Of 38 bilateral single-lung transplantations, CPB was used in 18. In double-lung and heart-lung recipients gas exchange of the allografts was evaluated by the arterial/alveolar oxygen tension ratios at nine intervals during the first 72 hours. The mean arterial/alveolar oxygen tension ratio in the CPB group was 0.48 +/- 0.19, significantly lower than in the no-CPB group with 0.60 +/- 0.22 (p = 0.025). All patients had radiographic interpretation and scoring of pulmonary infiltrates from chest roentgenograms taken within 12 hours after reperfusion. The CPB group had more severe pulmonary infiltrates than the no-CPB group (p = 0.034). Prolonged intubation defined as 7 days or longer occurred significantly more often (29/55) in the CPB group than in the no-CPB group (8/45) (p = 0.003). Actuarial graft and patient survival at 1 month was better in the no-CPB group than in the CPB group (42/45 versus 44/55 [p = 0.05] and 43/45 versus 45/55 [p = 0.033], respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Complement and neutrophil activation during cardiopulmonary bypass: a study in the complement-deficient dog

Cardiopulmonary bypass (CPB) is known to cause complement and neutrophil activation, but the relative importance and interaction of these components in CPB-induced inflammation is unknown. In this study, a strain of dogs genetically deficient in the third component of complement (C3) was used to determine the contribution of C3 to neutrophil activation and pulmonary injury after CPB. Eleven dogs (5 C3-deficient and 6 controls) underwent 150 minutes of hypothermic CPB (28 degrees C) followed by 2 hours of observation. Before CPB, C3 levels were normal in controls and less than 1% of normal in C3-deficient dogs. In control dogs, functional activity of C3 decreased to 53.2% of baseline after 1 hour of CPB and there was immunohistochemical evidence of C3 deposition in lung after CPB; C3-deficient dogs had no C3 deposition in lung. Although similar degrees of neutropenia occurred during CPB in the two groups, expression of neutrophil adhesion molecule subunit CD18 was significantly lower in C3-deficient dogs than controls after 1 hour of CPB (45.9 +/- 3.7 versus 82.9 +/- 10.0 mean fluorescence units; p < 0.02). Postbypass lung tissue myeloperoxidase content was also less in C3-deficient dogs (43.8 +/- 4.6 versus 71.1 +/- 8.6 mumol x 10 mg-1 x min-1; p < 0.03). Cardiopulmonary bypass-associated lung injury (assessed by alveolar-arterial oxygen gradient, pulmonary vascular resistance, percent lung water, and light and electron microscopic appearance) was similar between groups. These results demonstrate that (1) C3 is deposited on pulmonary vascular endothelium during CPB and (2) C3 mediates increased expression of neutrophil CD18 and neutrophil sequestration in lung after CPB.(ABSTRACT TRUNCATED AT 250 WORDS)