Perioperative changes in complement associated with cardiopulmonary bypass

Blood - Artificial Surface Interactions during Cardiopulmonary Bypass

Evaluation of the biocompatibility of four different types of oxygenator (bubble, membrane, hollow fibre and ‘hybrid’) was performed on 26 patients undergoing cardiopulmonary bypass during elective coronary surgery. More platelet derangement and an increased degree of hemolysis, revealed by higher plasmatic concentration of beta-thromboglobulin, platelet factor 4 and plasmatic free hemoglobin (p < 0.05), was seen when using the bubble oxygenator. Damage to blood cells was minimal with the membrane oxygenator while the ‘hybrid’ and the hollow fibre oxygenators proved to rank at an intermediate level. Complement activation at the beginning of the cardiopulmonary bypass occurred via the alternative pathway as demonstrated by C3adesarg increase (up to nine times) without a concomitant elevation of C4adesarg. Cardiopulmonary bypass complement activation was quantitatively similar with all the oxygenators. A further activation via the classical pathway occured in all the patients after protamine injection. Consistent differences as far as clinical and biological effects exist among the various commercially available cardiopulmonary bypass apparatus; our study provides guidelines for the evaluation and selection of devices which might reduce postoperative sequelae.

Complement activation by different cardiopulmonary bypass priming solutions

Similarities between the known biological activities of complement derived factors and the clinical findings observed in the 'post-pump syndrome' suggest that complement may play a role in the pathogenesis of this syndrome.

Mixing of blood with autologous or homologous blood revealed no significant reduction in C3 and C4 concentration, whereas mixing with plasma showed a lower C3 value without differences in C4. Mixing of blood with albumin, Normosol, D5 water and normal saline solution revealed a progressive reduction both in C3 and C4 concentration; mixing with Emagel showed C4 reduction, without reduction in C3 concentration.

Our findings suggest that crystalloid solutions used for priming the pump oxygenator circuit are an additional C3 and C4 activating factor. Such activation should be regarded as a 'pre-pump complement activation'.

The effects of methylprednisolone on complement, immunoglobulins and pulmonary neutrophil sequestration during cardiopulmonary bypass

In this study, the authors administered high dose (30 mg/kg body weight i.v.) methylprednisolone before cardiopulmonary bypass to observe the effects on complement, immunoglobulins and pulmonary neutrophil sequestration. Fifty patients undergoing valve replacements were included in this study. Patients were divided into two groups: group I (20 patients) served as control and did not receive methylprednisolone, group II (30 patients) received methylprednisolone. Blood samples for complements (C3c and C4) were taken, before cardiopulmonary bypass, at 5, 10 and 30 min intervals from the end of cardiopulmonary bypass, after reversal of heparin with protamine infusion, and after skin closure. Blood samples for immunoglobulins were taken before cardiopulmonary bypass, 30 min after onset of cardiopulmonary bypass and after skin closure. After onset of cardiopulmonary bypass, all C3c and C4 levels decreased in both groups. There was a significant decrease in C4 levels at end of cardiopulmonary bypass and after protamine infusion in group I compared with group II (P < 0.05). C3c levels in group I decreased significantly compared with group II after 30 min of cardiopulmonary bypass and after protamine infusion (P < 0.05). All immunoglobulin (IgG, IgM, IgA) levels were decreased in both groups, but the decrease in IgG was statistically significant after skin closure in group I compared with group II (P < 0.05). Pulmonary neutrophil sequestration was higher in the control group compared with the methyl-prednisolone group (P < 0.05). In conclusion, methylprednisolone administration before cardiopulmonary bypass may prevent the harmful effects of complement activation, immunoglobulin denaturation and neutrophil sequestration in the pulmonary capillary system.

The inflammatory response to cardiopulmonary bypass

The inflammatory response to cardiopulmonary bypass is the product of a complex interplay of humoral and cellular components. Contact activation cascades, the complement system, and cytokines comprise the humoral elements and interact in such a way as to propagate their own cascades and to activate the cellular elements. Neutrophils and endothelial cells are the cellular components and become involved after their "activation" by the humoral mediators. Neutrophil-endothelial cell adherence is the initial step of the cellular inflammatory response and is promoted by the expression of specific adhesion molecules on the surfaces of both of these cells leading to the emigration of neutrophils into the extravascular space where they release toxins that damage surrounding tissues. The resulting organ dysfunction produces the clinical picture referred to as the "postperfusion syndrome." Strategies to attenuate this response include the administration of corticosteroids, aprotinin, and anticytokine monoclonal antibodies, as well as various modifications of the bypass circuit. The existence of multiple pathways to trigger this inflammatory response hampers efforts at its attenuation and leaves much investigation to be done as the quest to understand the body's inflammatory response to cardiopulmonary bypass continues.

Diagnostic significance of hypocomplementemia

Hypocomplementemia is an important marker for the presence of IC-mediated disease and can be used to assess disease activity. However, in interpreting the clinical significance of hypocomplementemia, the following must be kept in mind: 1) There are numerous non-immunologic conditions that also can cause hypocomplementemia. Furthermore, some of these conditions can cause a multisystem disease that, along with the hypocomplementemia, can closely resemble an IC-mediated systemic vasculitis. Furthermore, these nonimmunologic conditions that lower serum complement levels can complicate the course of patients with inactive IC-mediated disease, spuriously indicating that the disease is active. The most relevant of these differential diagnostic problems are listed in Table 2. 2) There are a few conditions (for example, pregnancy) that can raise serum complement levels, thereby possibly obscuring the presence of a disorder (such as, active SLE) that is lowering complement levels. 3) There are some conditions that might be expected to lower serum complement levels, because of their effect on protein metabolism, but do not. Nephrotic syndrome, and moderately poor nutrition are examples. All of these factors should be considered when interpreting results of serum complement levels in a given patient.

Complement activation in cardiopulmonary bypass, with special reference to anaphylatoxin production in membrane and bubble oxygenators

Complement activation by cardiopulmonary bypass (CPB) was studied in 82 patients divided into membrane (MOG) and bubble oxygenator groups (BOG). The influence of primed homologous to circulating autologous blood volume (H/A) ratio was also evaluated. C4a increased very slowly during CPB in both groups, maintaining slightly higher levels in the BOG than in the MOG, with the exception of a marked initial rise in the BOG with a high H/A ratio (greater than or equal to 20%). Anaphylatoxin C3a levels increased more steeply in the BOG than in the MOG. An obvious rise in anaphylatoxin C5a production was observed in the BOG alone. The influence of high H/A ratio perfusion on complement activation was milder in the MOG than in the BOG. In 20 monkeys (Macaca fascicularis), continuous intraaortic infusion with bubbled autologous blood increased C4a and C3a levels, while autologous blood extracorporeally contacted with nylon increased C3a levels alone. In vitro studies revealed that human immunoglobulin fractions denatured by oxygen bubbling produced C4a, C3a, and C5a in a dose-dependent manner, although human albumin treated identically as human immunoglobulin did not produce these complements. It was thus inferred that (1) during CPB, complement is predominantly activated via the classical pathway in the BOG and via the alternative pathway in the MOG; (2) higher anaphylatoxin levels in the BOG than in the MOG are related to mode and grade of blood trauma; (3) anaphylatoxin level differences in both groups tend to increase with high H/A perfusion; and (4) immunoglobulin-free sera may reduced classical pathway activation.

Complement and leukocytes during cardiopulmonary bypass: Effects on plasma cad and C5a, leukocyte countr Release of granulocyte elastase and granulocyte chemotaxis

In an effort to further elucidate the complex changes in the complement-leukocyte system during cardiopulmonary bypass (CPB), plasma levels of C3d, C5a, and granulocyte elastase bound to alpha1-proteinase inhibitor (E-alpha1 PI) were followed prior to, during, and after CPB. Leukocyte and differential cell counts and granulocyte migration were also determined. Complement activation was documented during CPB by an increase in plasma C3d corrected for hemodilution. Significant amounts of C5a were not revealed. Cell counts decreased during CPB but, if corrected for hemodilution, remained unchanged apart from a slight decrease in lymphocyte count after 60 minutes. Eighteen hours after CPB, neutrocytosis and lymphopenia occurred. Plasma E-alpha1 PI increased during CPB, reflecting release of granulocyte lysosomal enzymes. Granulocyte migration was transitorily depressed during CPB, and it was shown that this was due to the appearance of an intrinsic cellular defect. CPB is associated with acute changes in cells and plasma, resembling an acute whole-body inflammatory response, with transitory impairment of granulocyte migration. The clinical significance of these observations remains to be determined.

Total parental nutrition using conventional and medium chain triglycerides: effect on liver function tests, complement, and nitrogen balance

Conventional long chain triglyceride (LCT) was compared with a new emulsion containing 50% medium chain triglyceride (5% MCT/5% LCT) in a randomized cross-over trial of 10 days duration. Plasma concentrations of albumin, prealbumin, the complement components C3 and C4, and prothrombin times measured daily at 8 am, before lipid infusion, showed no progressive change during the 10 days of the trial, nor in each separate 5-day period when LCT or MCT/LCT was infused. Aspartate transaminase and alkaline phosphatase activities were similar over the two periods. There was a significant increase (compared with preinfusion levels) in C3 and C4 levels after 5 hr of either lipid infusion. Nitrogen balance was improved, and plasma bilirubin levels were lower on the regimen containing MCT/LCT.

Paroxysmal nocturnal haemoglobinuria. Peri-operative management of a patient with Budd-Chiari syndrome

The peri-operative management of a patient with paroxysmal nocturnal haemoglobinuria and associated hypoplastic anaemia, who underwent successful elective surgery for the complication of Budd-Chiari syndrome, is described. Anaesthesia in patients with paroxysmal nocturnal haemoglobinuria should be based on drugs and materials least likely to cause complement activation. The reasons for use of a technique based on benzodiazepines, opioids, isoflurane and the avoidance of nitrous oxide are discussed.

Neutrophil lysosomal enzyme release and complement activation during cardiopulmonary bypass

Complement activation and neutrophil degranulation were concomitantly studied during uncomplicated cardiopulmonary bypass (CPB). Plasma concentrations of complement factor C4, complement split product C3d, the neutrophil lysosomal enzyme elastase complexed with alpha 1-proteinase inhibitor (PI) and fibronectin were measured in 12 patients, C3d and elastase/PI increased significantly during CPB (volume-corrected results). The C3d rise was almost linear, whereas elastase/PI showed exponential increase. Mean elastase/PI and mean C3d concentrations at different times during CPB covaried closely. The study showed that during CPB neutrophil lysosomal enzyme release is intimately related to complement activation, although activation of the two systems may be caused by a common third activator within the extracorporeal circuit.

[A new case of bronchospasm under extracorporeal circulation]

A case of bronchospasm occurring after the termination of cardiopulmonary bypass is reported. The complement fractions C3a, C4a and C5a were measured before and right after CPB. Complement activation is not specific to CPB but may occur in any thoracotomy. The statistically significant increase in complement C3a without any pulmonary symptomatology has been reported by several authors. Complement activation cannot therefore be considered as the explanation of this bronchospasm.

Complement and clinical intervention

The nine major components of the complement protein system are normally activated in sequence by antigen-antibody complexes, initiating the inflammatory response. The clinical manifestations arise mainly from the release of histamine, mediated by anaphylatoxin action on mast cells. In rampant infection, this classical pathway is enhanced by further activation of complement C3 through a specific enzyme loop, the alternative pathway. Unfortunately the complexity of the complement system makes it vulnerable to external interference, particularly to man's intervention both through the administration of intravenous "drugs" and by certain surgical procedures. This results in gross systemic activation of complement, particularly C3 giving rise to anaphylactoid shock. More recently, direct activation of complement C5 has been reported, particularly as a result of polytrauma. This has consequences on polymorphonuclear leucocyte behaviour and is likely to be involved in adult respiratory distress syndrome (ARDS). Similarly, excessive activation of C3 may stimulate disseminated intravascular coagulation (DIC) rather than immediate anaphylactoid response. The clinical outcome of complement activation appears to depend upon the rate of activation and its extent, as well as upon the particular component involved. In immediate reactions, complement may be involved in both immune and non-immune activations. Bias to certain pathways is revealed by certain drugs or procedures, and practical methods of evaluating reaction mechanisms are discussed. Despite the high incidence of complement involvement in immediate reactions, there are no useful screening pointers to the patient "at risk". Delayed effects have received little attention. Although C3 conversion is certainly associated with DIC, its predictive value in a clinical trial was not very great.(ABSTRACT TRUNCATED AT 250 WORDS)

Pathways to complement activation during cardiopulmonary bypass

Complement activation was assessed in 34 patients undergoing cardiopulmonary bypass. Arterial concentrations of complement fragments Ba and C3d rose in all patients, the increase in Ba preceding that of C3d. At the same time as complement fragments were being generated the arterial neutrophil count fell. These findings suggest (a) that complement activation is initiated by the alternative pathway during cardiopulmonary bypass and (b) that complement activation mediates loss of neutrophils during bypass. Complement mediated loss of neutrophils during the analogous setting of haemodialysis is the result of leucosequestration in the pulmonary vasculature. During cardiopulmonary bypass the lungs are out of circuit, so that activated leucocytes may sequester in other target organs. This may be an aetiological factor in the multi-organ failure occasionally seen after uneventful cardiopulmonary bypass.

Complement activation during cardiopulmonary bypass: quantitative study of effects of methylprednisolone and pulsatile flow

Forty four patients undergoing open heart surgery were divided into three groups. Group 1 (17 patients) underwent routine anaesthesia and surgery; group 2 (17 patients) received two doses of methylprednisolone (30 mg/kg), one during induction of anaesthesia and the other immediately before induction of cardiopulmonary bypass; and group 3 (10 patients) received pulsatile flow while undergoing pulsatile perfusion by the heart-lung machine. A modification of the previously described technique was used to detect and measure complement activation in plasma before and during the bypass period using crossed immunoelectrophoresis. About 45% of all patients showed measurable complement activation (greater than 4.5%) during cardiopulmonary bypass and the mean activation in this group was 6.4%. There was no significant difference between the three groups in complement activation. In group 2, however, women showed significantly more complement activation than men (p less than 0.05). It is suggested that neither corticosteroids nor pulsatile flow affect complement activation, but caution should be exercised in women receiving methylprednisolone.