Neuropsychologic impairment after coronary bypass surgery: effect of gaseous microemboli during perfusionist interventions

OBJECTIVE: Neuropsychologic impairment is a common complication of coronary bypass surgery. Cerebral microemboli during cardiopulmonary bypass are the principal cause of cognitive deficits after coronary bypass grafting. We have previously demonstrated that the majority of cerebral emboli occur during perfusionist interventions (ie, during the injection of air into the venous side of the cardiopulmonary bypass circuit). The purpose of this study was to determine whether an increase in perfusionist interventions is associated with an increased risk of postoperative cognitive impairment. METHODS: Patients undergoing elective coronary artery bypass grafting (n = 83) underwent a battery of neuropsychologic tests preoperatively and 3 months postoperatively. Patients were divided into 2 groups according to the median value of perfusionist interventions during cardiopulmonary bypass. Group 1 patients (n = 42) had fewer than 10 perfusionist interventions, and group 2 patients (n = 41) had 10 or more interventions. RESULTS: The 2 groups of patients were similar for all preoperative, intraoperative, and postoperative variables, with the exception of longer cardiopulmonary bypass times in group 2 patients (P <.001). Group 2 patients had lower mean scores on 9 of 10 neuropsychologic tests, with 3 (Rey Auditory Verbal Learning, Digit Span, and Visual Span) being statistically significant. Group 2 patients had worse cognitive test scores, even when controlling for increased bypass times. Group 2 patients had a nonsignificant trend toward an increased prevalence of neuropsychologic impairment 3 months postoperatively. CONCLUSIONS: Introduction of air into the cardiopulmonary bypass circuit by perfusionists, resulting in cerebral microembolization, may contribute to postoperative cognitive impairment.     

Events related to microembolism during extracorporeal perfusion in man: effectiveness of in-line filtration recorded by ultrasound.

Microparticle generation during cardiopulmonary bypass was monitored continuously in 60 adult patients who underwent open-heart operations. Echo-ultrasound transducers of 5 mHz frequency were interposed in a bubble oxygenator arterial line proximal and distal to a commercially available micropore filter. Ordinary perfusion events correlated with an increase in embolic counts and were recorded graphically. Calculation of filter efficiency revealed that all filters decreased measurable embolic counts. Platelet and leukocyte determinations and plasma hemoglobin values were not altered beyond limits ordinarily encountered during perfusion without filters. No patient in any filter group experienced postoperative respiratory distress, diffuse pulmonary infiltrate, or low PaO2. The 20 mu woven nylon mesh filter and the Dacron-wool filter showed greater than 90% effectiveness in removing recorded particles. Insertion of a cardiotomy filter did not appreciably alter recorded embolic counts distal to the arterial line filter.     

Venous air in the bypass circuit: a source of arterial line emboli exacerbated by vacuum-assisted drainage.

BACKGROUND: Arterial emboli cause neurocognitive deficits in cardiac surgical patients. Carotid artery emboli, detected ultrasonically, have been observed after venous air entrainment into the cardiopulmonary bypass circuit. We investigated in vitro the extent to which venous air affected emboli detected in the arterial line downstream from a 40-microm filter. METHODS: Using salvaged clinical cardiopulmonary bypass circuits, fixed volumes of air were introduced into the venous return line at unrestricted rates and at fixed rates using gravity venous drainage and vacuum-assisted venous drainage. Emboli counts were recorded distal to the arterial line filter using a 2-MHz pulsed-wave Doppler monitor. Emboli counts were similarly recorded after the introduction of carbon dioxide into the venous return line instead of air. RESULTS: The number of emboli rose with increasing volumes of entrained venous air (p < 0.001), and there was an almost tenfold increase with vacuum-assisted venous drainage (p < 0.0001) compared with gravity venous drainage. Venous air was entrained at a significantly faster rate under vacuum-assisted venous drainage (p < 0.0001). When the entrainment rate of venous air was fixed, the difference in emboli numbers recorded for gravity and assisted venous drainage was not significant. There was a significant reduction in arterial line emboli when carbon dioxide rather than air was entrained under both vacuum-assisted and gravity drainage (p < 0.001). CONCLUSIONS: Entrained venous air during cardiopulmonary bypass is a potential hazard, particularly during vacuum-assisted venous drainage. Every effort should be made to avoid venous air entrainment.     

Clinical evaluation of the Sorin Synthesis oxygenator with integrated arterial filter

The use of arterial line filters has long been a standard of practice in the field of cardiopulmonary bypass. Sorin Biomedica has designed an adult hollow-fiber oxygenator that not only incorporates their Mimesys biomimicry coating technology but also has a 40-micron arterial filter as an integrated component of this unique membrane oxygenator. We did a prospective, randomized clinical trial of 54 Synthesis coated oxygenators and compared them with 54 uncoated Monolyth Pro oxygenators, the latter of which incorporated an external arterial line filter with a standard bypass loop There were few statistically significant differences found between the Synthesis group and the Monolyth group with regard to pressure differentials, hemodynamic resistance, and platelet drop. The Synthesis oxygenator did require less priming volume, but the amount was not significant. Platelet counts with the Phosphorylcholine coated Synthesis oxygenators, using crystalloid perfusates, was similar to our previously published data on platelet protection and Albumin perfusates. We conclude that the Sorin Synthesis oxygenator appears to have better flow characteristics than the Monolyth oxygenator, with the potential for lower priming volumes. The most clinically significant benefit comes from the elimination of the arterial filter bypass loop and the avoidance of inverting the arterial filter during priming.     

Reduction of heparin dose is not beneficial to platelet function

BACKGROUND: To clarify the effects of the reduction of heparin dose on platelets, we conducted a prospective trial on patients undergoing cardiopulmonary bypass. METHODS: Twenty-three patients undergoing coronary artery bypass grafting were studied. The systemic heparin dose was 300 IU/kg in the control group (n = 11) and 200 IU/kg in the low-dose group (n = 12). Heparin-coated cardiopulmonary bypass equipment was used for both the groups. Platelet counts, beta-thromboglobulin (beta-TG) and platelet factor 4 (PF4) concentrations were measured and the arterial filters in the circuits were observed by electron microscopy. RESULTS: Platelet counts were higher in the low-dose group than in the control group (p < 0.01). No significant differences were found in the platelet release reaction (beta-TG and PF4). Electron microscopy demonstrated that cell adhesion on the arterial filters in the control group was significantly more marked than in the low-dose group (p < 0.01) and that most of the cells on the filters were neutrophils. CONCLUSIONS: We conclude that the reduction of heparin dose with the use of heparin-coated equipment reduces platelet loss, but does not suppress the platelet release reaction. Furthermore, the reduction of heparin dose reduces adherence of leukocytes to the filter surface.     

Evaluation of leukocyte-reducing arterial line filter (LG6) for postoperative lung function, using cardiopulmonary bypass.

OBJECTIVE: To prevent postoperative pulmonary dysfunction, we have investigated the effect of the Leuko-Guard 6 leukocyte-reducing arterial line filter (LG6) on postoperative lung function. METHODS: Twenty-six cases of adult valvular heart disease were included in this study. Thirteen cases were operated upon using the LG6 (Group LG), and 13 cases were operated upon using a conventional arterial line filter (Group C). Neutrophil, polymorphonuclear leukocyte elastase and lipoperoxide were measured for this study, and the lung function was evaluated using the Oxygenation Index (PaO2/FiO2). RESULTS: Statistically significant differences were observed in neutrophil counts between Group LG and Group C (LG = 2225 +/- 572/mm3, C = 3157 +/- 1413/mm3, p = 0.04) at 5 minutes after the onset of cardiopulmonary bypass. In simultaneous blood sampling from the pulmonary artery and the pulmonary vein, the sequestration of neutrophil in the lung decreased in Group LG after the discontinuation of cardiopulmonary bypass. Release of polymorphonuclear leukocyte elastase from the lungs was significantly decreased (p = 0.04) in the Group LG at 1 hour post-bypass. Significant differences were observed in the Oxygenation Index between Group LG and Group C (LG = 398 +/- 72, C = 326 +/- 71, p = 0.019) at 3 hours post-bypass. CONCLUSION: We concluded that LG6 improved the postoperative lung function, and its mechanism might be derived from the prevention of leukosequestration in the lungs that occurs during the rewarming phase due to selective absorption of activated leukocyte by the LG6.     

Centrifugal versus roller head pumps for cardiopulmonary bypass: effect on early neuropsychologic outcomes after coronary artery surgery

OBJECTIVE: To test the hypothesis that routine use of a centrifugal pump in the cardiopulmonary bypass circuit would result in a lower incidence of early neuropsychologic deficit when compared with conventional roller pumps. DESIGN: Prospective, randomized, double-blind. SETTING: University teaching hospital. PARTICIPANTS: Patients (n = 103) scheduled for elective coronary artery surgery. INTERVENTIONS: Patients were randomized into group C (centrifugal pump for cardiopulmonary bypass; n = 54) and group R (roller pump for cardiopulmonary bypass; n = 49). MEASUREMENTS AND MAIN RESULTS: A neuropsychologic test battery of 6 standard tests was administered before surgery and 5 days after surgery. An abnormal test result was defined as deterioration by >1 group SD from an individual's preoperative test performance. There were no significant differences between groups in preoperative or surgical parameters, intensive care unit stay, or hospital stay. There were no significant differences in the incidence of neuropsychologic deficit for patients with a deficit in at least 1 test (group C, 33%; group R, 51%; odds ratio, 0.48; 95% confidence interval, 0.22 to 1.06) or patients with a deficit in >/=2 tests (group C, 6%; group R, 18%; odds ratio, 0.26; 95% confidence interval, 0.07 to 1.03). In group R, there were more individual test deficits per patient than in group C (p = 0.04). CONCLUSION: There was no significant difference in the incidence of neuropsychologic deficit postoperatively with routine use of centrifugal pumps. The larger number of individual test deficits in the roller pump group suggest that further studies to assess the potential neuropsychologic benefits of the use of centrifugal pumps are warranted.     

Effects of pulsatile cardiopulmonary bypass on the renin-angiotensin-aldosterone system following open heart surgery

The effects of pulsatile cardiopulmonary bypass on the renin-angiotensin-aldosterone system and tissue metabolism, especially those which occur soon after surgery, were studied in 26 patients who required total cardiopulmonary bypass for longer than 60 minutes. These patients comprised 11 who underwent open heart surgery utilizing nonpulsatile cardiopulmonary bypass (Group I) and 15 who underwent open heart surgery utilizing pulsatile cardiopulmonary bypass (Group II). Plasma angiotensin II and serum aldosterone levels were significantly increased one and 5 hours postoperatively in Group I when compared with the preoperative values, whereas no significant elevations were observed in Group II. Plasma angiotensin II and serum aldosterone levels one hour postoperatively in Group II were significantly lower than those in Group I. Lactate levels in the arterial blood were significantly elevated, one and 5 hours postoperatively in both Groups I and II. Moreover, no significant difference was observed in the lactate levels between Groups I and II, one hour postoperatively. In the nonpulsatile group (Group I), plasma angiotensin II levels one hour postoperatively were correlated significantly with the duration of total cardiopulmonary bypass. In conclusion, pulsatile cardiopulmonary bypass offers significant advantages in terms of lower plasma angiotensin II and serum aldosterone levels, when compared with nonpulsatile cardiopulmonary bypass soon after open heart surgery requiring total cardiopulmonary bypass for longer than 60 minutes, however, it does not offer a definite advantage for tissue metabolism.     

Effects of pulsatile cardiopulmonary bypass on the renin-angiotensin-aldosterone system following open heart surgery

The effects of pulsatile cardiopulmonary bypass on the renin-angiotensin-aldosterone system and tissue metabolism, especially those which occur soon after surgery, were studied in 26 patients who required total cardiopulmonary bypass for longer than 60 minutes. These patients comprised 11 who underwent open heart surgery utilizing nonpulsatile cardiopulmonary bypass (Group I) and 15 who underwent open heart surgery utilizing pulsatile cardiopulmonary bypass (Group II). Plasma angiotensin II and serum aldosterene levels were significantly increased one and 5 hours postoperatively in Group I when compared with the preoperative values, whereas no significant elevations were observed in Group II. Plasma angiotensin II and serum aldosterone levels one hour postoperatively in Group II were significantly lower than those in Group I. Lactate levels in the arterial blood were significantly elevated, one and 5 hours postoperatively in both Groups I and II. Moreover, no significant difference was observed in the lactate levels between Groups I and II, one hour postoperatively. In the nonpulsatile group (Group I), plasma angiotensin II levels one hour postoperatively were correlated significantly with the duration of total cardiopulmonary bypass. In conclusion, pulsatile cardiopulmonary bypass offers significant advantages in terms of lower plasma angiotensin II and serum aldosterone levels, when compared with nonpulsatile cardiopulmonary bypass soon after open heart surgery requiring total cardiopulmonary bypass for longer than 60 minutes, however, it does not offer a definite advantage for tissue metabolism.     

Evidence-based used, yet still controversial: the arterial filter

Arterial line filters are considered by many as an essential safety measure inside a cardiopulmonary bypass circuit. There is no doubt that this was true during the bubble oxygenator era, but we can question whether the existing arterial line filter design and positioning of the filter are still optimal seeing the tremendous progress in cardiopulmonary bypass circuit components. This overview gives a critical overview of existing arterial line filter design.     

Activation of neutrophils and monocytes by a leukocyte-depleting filter used throughout cardiopulmonary bypass

OBJECTIVE: Cardiopulmonary bypass elicits systemic inflammation. Depletion of circulating leukocytes might alleviate inflammatory response. We studied the effects of a leukocyte-depleting filter on phagocyte activation during cardiopulmonary bypass. METHODS: Fifty patients undergoing coronary artery bypass grafting were randomly allocated into an arterial line leukocyte filter group (n = 25) with a Pall LeukoGuard 6 leukocyte-depleting filter (LG6; Pall Biomedical, Portsmouth, United Kingdom) and a control group without any filter (n = 25). Blood sampling took place from arterial line at predetermined time points. In the filter group, the sample was taken immediately before the filter; to evaluate activation at the site, an additional sample was taken immediately after the filter. CD11b/CD18 and L-selectin expressions and basal production of hydrogen peroxide were determined with whole-blood flow cytometry, and plasma lactoferrin level was determined with enzyme-linked immunosorbent assay. RESULTS: Neutrophil CD11b expression was higher in the filter group than in the control group (P < .001). Likewise, monocyte CD11b expression, neutrophil hydrogen peroxide production, and lactoferrin plasma levels were all significantly higher, whereas neutrophil and monocyte counts and neutrophil L-selectin expression were all significantly lower in the filter group (all P < .001). At 5 minutes of CPB, CD11b expression increased across the filter on neutrophils (median difference 197 relative fluorescence units, range 45-431 relative fluorescence units, P < .001) and monocytes (median difference 26 relative fluorescence units, range -68-111 relative fluorescence units, P < .001). CONCLUSION: The LG6 arterial line leukocyte filter is ineffective in its principal task of diminishing phagocyte activation during cardiopulmonary bypass.     

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 a leucocyte depleting arterial line filter on perioperative proteolytic enzyme and oxygen free radical release in patients undergoing aortocoronary bypass surgery

BACKGROUND: Proteolytic enzymes and oxygen free radicals released from activated leucocytes contribute significantly to the organ dysfunction associated with cardiopulmonary bypass. Leucocyte depletion during extracorporeal circulation should reduce the release of these toxic compounds and thereby improve postbypass myocardial and pulmonary function. Recently, a leucocyte-specific arterial line filter to achieve leucocyte depletion during clinical perfusion has become commercially available. The aim of this study, therefore, was to evaluate the influence of the leucocyte depleting arterial line filter on proteolytic enzyme release, oxygen free radical release and postbypass pulmonary and myocardial function in patients undergoing bypass surgery. METHODS: Forty patients undergoing elective aortocoronary bypass surgery were included into this prospective, randomized clinical study, 20 in the leucocyte depletion (LG-6 group, leucocyte-specific arterial line filter) and 20 in the control group (AV-6 group, standard arterial line filter). White cell count, differential white cell count, plasma elastase concentration, plasma malondialdehyde concentration and C-reactive protein were determined before, twice during and immediately after cardiopulmonary bypass, at the end of surgery and 6 and 20 h thereafter. RESULTS: White cell count, differential white cell count, malondialdehyde and C-reactive protein were not significantly different between LG-6 and control patients. Plasma elastase concentrations were significantly (P < or = 0.03) higher during and immediately after extracorporeal circulation in LG-6 group patients. Need for inotropic support, arterial pO2 after extracorporeal circulation and perioperative CK MB mass and troponin I release were not different between the two groups of patients. CONCLUSION: The use of a leucocyte depleting arterial line filter is associated with an increased release of the proteolytic enzyme elastase, but does not reliably and consistently achieve effective leucocyte depletion during clinical perfusion. In contrast to previous studies, we could not demonstrate any significant difference in postbypass pulmonary or myocardial function between patients perfused with the leucocyte-specific arterial line filter and control patients. Our data do not support the routine use of a leucocyte depleting arterial line filter during clinical perfusion in patients undergoing elective aortocoronary bypass surgery.     

A prospective,double-blind study on the efficacy of the bioline surface-heparinized extracorporeal perfusion circuit

BACKGROUND: We evaluated the newly introduced Bioline heparin coating and tested the hypothesis that surface heparinization limited to the oxygenator and the arterial filter will ameliorate systemic inflammation and preserve platelets during cardiopulmonary bypass (CPB). METHODS: In a prospective double-blind study, 159 patients underwent coronary revascularization using closed-system CPB with systemic heparinization, mild hypothermia (33 degrees C), a hollow-fiber oxygenator, and an arterial filter. The patients were randomly divided in three groups. In group A (controls, n = 51), surface heparinization was not used. In group B (n = 52), the extracorporeal circuits were totally surface-heparinized with Bioline coating. In group C (n = 56), surface heparinization was limited to oxygenator and arterial filter. RESULTS: No significant difference was noted in patient characteristics and operative data between groups. Operative (30-day) mortality was zero. Platelet counts dropped by 12.3% of pre-CPB value among controls at 15 minutes of CPB, but were preserved in groups B and C throughout perfusion (p = 0.0127). Platelet factor 4, plasmin-antiplasmin levels, and tumor necrosis factor-alpha increased more in controls during CPB than in groups B or C (p = 0.0443, p = 0.0238 and p = 0.0154 respectively). Beta-thromboglobulin, fibrinopeptide-A, prothrombin fragments 1 + 2, factor XIIa levels, bleeding times, blood loss, and transfusion requirements were similar between groups. Intensive care unit stay was shorter in groups B and C than in controls (p = 0.037). CONCLUSIONS: Surface heparinization with Bioline coating preserves platelets, ameliorates the inflammatory response and is associated with a reduced fibrinolytic activity during CPB. Surface heparinization limited to the oxygenator and the arterial filter had similar results as totally surface-heparinized circuits.     

A randomized study of carbon dioxide management during hypothermic cardiopulmonary bypass

Eighty-six patients undergoing coronary artery bypass graft (n = 63) or intracardiac (n = 23) surgery were randomly assigned with respect to the target value for PaCO2 during cardiopulmonary bypass. In 44 patients the target PaCO2 was 40 mmHg, measured at the standard electrode temperature of 37 degrees C, while in 42 patients the target PaCO2 was 40 mmHg, corrected to the patient's rectal temperature (lowest value reached: mean 30.1, SD 1.9 degrees C). Other salient features of bypass management include use of bubble oxygenators without arterial filtration, flows of 1.8-2.4 l.min-1.m-2, mean hematocrit of 23%, and mean arterial blood pressure of approximately 70 mmHg, achieved by infusion of phenylephrine or sodium nitroprusside. Neuropsychologic function was assessed with series of tests administered on the day prior to surgery, just before discharge from the hospital (mean 8.0, SD 5.8 days postoperatively, n = 82), and again 7 months later (mean 220.7, SD 54.4 days postoperatively, n = 75). The scores at 8 days showed wide variability and generalized impairment unrelated to the PaCO2 group or to hypotension during cardiopulmonary bypass. At 7 months no significant difference was observed in neuropsychologic performance between the PaCO2 groups. Regarding cardiac outcome, there were no significant differences between groups in the appearance of new Q-waves on the electrocardiogram, the postoperative creatine kinase-MB fraction, the need for inotropic or intraaortic balloon pump support, or the length of postoperative ventilation or intensive care unit stay. These findings support the hypothesis that CO2 management during cardiopulmonary bypass at moderate hypothermia has no clinically significant effect on either neurobehavioral or cardiac outcome.     

Neuropsychological dysfunction after cardiopulmonary bypass: a comparison of two institutions.

The authors compared perioperative neuropsychologic dysfunction in patients participating in two studies conducted in institutions using different strategies to manage cardiopulmonary bypass. These differences included hypothermia versus normothermia, presence versus absence of arterial microfilters, and the presence versus absence of glucose-containing solution in the pump prime. Other differences between the two institutions included the type of surgery (intracardiac v extracardiac), the mean duration of cardiopulmonary bypass, and degree of low perfusion pressure during bypass. Despite these major differences, perioperative neuropsychologic dysfunction measured by the two-part Trail-Making psychometric test was similar in the two institutions. Several factors were analyzed for their possible contribution to development of dysfunction, including institution, anesthetic management, age, sex, degree of low perfusion pressure during bypass, and duration of bypass; only age was significant. These results suggest that differences in surgical procedure and management of cardiopulmonary bypass previously thought to contribute to the development of subtle cognitive deficits after cardiac surgery may have been overemphasized.     

Assisted venous drainage, venous air, and gaseous microemboli transmission into the arterial line: an in-vitro study.

The objective of this study was to examine the interaction of cardiopulmonary bypass venous air with assisted venous drainage, focusing on its production of gaseous microemboli in the arterial line. An in-vitro recirculating cardiopulmonary bypass circuit containing fresh whole bovine blood was monitored with a pulsed-doppler microbubble detector. Air of specific amounts was injected into the venous line and gaseous microemboli counts were obtained distal to the arterial filter. Data was recorded for unassisted drainage, vacuum-assisted drainage, and centrifugal pump-assisted drainage. Centrifugal pump-assisted drainage produced over 300 microbubbles in one minute distal to the arterial filter when venous air was introduced into the circuit. Of these, 220 were greater than 80 microns in size. Vacuum-assisted drainage produced no microbubbles when the same amount of venous air was introduced into the circuit. However, vacuum-assisted drainage did produce some microbubbles in the arterial line when a stopcock was left open on the venous line for 30 seconds. Unassisted drainage produced no microbubbles at all levels of venous air entrainment. Air becomes entrained in the venous line from a variety of sources. In a typical gravity-drained situation, the air remains whole and is dissipated in the venous reservoir by buoyancy and filtration. In an assisted-drainage situation, the air is subjected to additional forces. The air is subjected to a greater degree of negative pressure and, with centrifugal pump assisted drainage, is subjected to kinetic energy imparted by the cones or vanes of the pump. The kinetic energy from the centrifugal pump appears to break the air into small bubbles which become suspended in the blood, passing through the reservoir, oxygenator, and arterial filter. In a clinical setting, these bubbles would be passed into a patient's arterial system.     

Magnetic resonance imaging of the brain before and after open heart operations.

Magnetic resonance imaging of the brain was performed in 29 adult male patients before and 1 week after elective coronary artery bypass grafting to study the cerebral effect of cardiopulmonary bypass. The mean age of the patients was 60 years (range, 45 to 69 years). During cardiopulmonary bypass, either a bubble oxygenator without an arterial line filter (n = 9), a bubble oxygenator with a depth adsorption filter (n = 10), or a flat-sheet membrane oxygenator without a filter (n = 10) was used. The mean bypass time was 88 minutes (standard deviation, 31 minutes) and did not differ significantly between the three groups. Preoperative magnetic resonance imaging revealed high signal intensity foci on T2-weighted images (white matter abnormalities) in 17 (59%; 95% confidence limits, 39% to 76%) of the 29 patients, all of which were nonspecific and of the common type considered to be related to aging, and all were unchanged at the postoperative examination. Preoperative and postoperative frontal horn indices, bicaudate diameters, and third ventricle widths did not differ significantly regardless of oxygenator type or whether or not an arterial line filter was used during cardiopulmonary bypass. Two patients (7%; 95% confidence limits, 1% to 23%), both receiving bubble oxygenation (1 without a filter and 1 with an arterial line filter) sustained a cerebral infarction during cardiopulmonary bypass.     

Does leukodepletion during elective cardiac surgery really influence the overall clinical outcome?

AIM: We examined the impact of leukocyte filtration during the entire bypass time on postoperative leukocytosis, perioperative hemorrhage and overall clinical outcome in patients undergoing elective cardiac surgery. METHODS: Eighty patients who electively underwent cardiac surgery were randomly allocated to a leukocyte depletion group (n=40) or a control group (n=40). In patients of the leukocyte depletion group an arterial line filter with leukocyte depleting capacity (Pall LG6) was applied instead of a standard arterial line filter. White blood cells and platelet count were estimated preoperatively and at various times postoperatively. Postoperative clinical outcomes were also recorded. RESULTS: Repeated measure analysis of variance between groups showed that leukocyte counts were significantly lower in the depletion group postoperatively (p=0.005) whereas no difference was found in the platelet counts (p=0.37). The catecholamine dose required at the time of weaning from cardiopulmonary bypass and during the first 12 postoperative hours was found to be lower in the leukodepletion group (p=0.027 and p=0.021, respectively). Furthermore leukodepleted patients showed a transient improvement in the oxygenation index (p=0.029) and a shorter period of mechanical ventilation (p<0.001). The incidences of postoperative complications were similar between the groups. No difference was observed in regard to postoperative blood loss (p=0.821) and amount of packed red blood cells required for transfusion during the first 24 hours (p=0.846). The duration of intensive care unit stay and of hospitalization were similar between the groups. CONCLUSION: Leukocyte depletion contributes to early postoperative improvement in heart and lung function but does not influence significantly the overall clinical outcome of patients undergoing elective cardiac surgery.     

Antiinflammatory effect of heparin-coated circuits with leukocyte-depleting filters in coronary bypass surgery

Cardiac surgery with cardiopulmonary bypass is associated with a systemic inflammatory response. We examined combined use of heparin coating of the cardiopulmonary bypass circuit and a leukocyte-depleting arterial line filter to reduce this response. Thirty patients were allocated randomly to equal groups with a conventional circuit and arterial line filter (C group), a heparin-coated circuit with a conventional filter (H group), or a heparin-coated circuit with a leukocyte-depleting arterial line filter (HF group). Cytokines and respiratory function were repeatedly measured perioperatively. Plasma interleukin (IL)-6 concentrations in the HF group were lower than in the C group immediately following bypass and operation, at 4 h, and 12 h (p < 0.05). Plasma IL-8 was lower in the HF group than in the C group at 4 h (p < 0.05). The respiratory index was lower immediately after bypass in the HF group than the C group (0.61 +/- 0.2 versus 1.05 +/- 0.4, p < 0.05). Heparin-coated circuits with leukocyte-depleting filters decrease inflammatory responses and improve pulmonary function during operation.