Inhibition of kinin formation by a kallikrein inhibitor during extracorporeal circulation in open-heart surgery

Human plasma kallikrein: roles in coagulation, fibrinolysis, inflammation pathways, and beyond

Human plasma kallikrein (PKa) is obtained by activating its precursor, prekallikrein (PK), historically named the Fletcher factor. Human PKa and tissue kallikreins are serine proteases from the same family, having high- and low-molecular weight kininogens (HKs and LKs) as substrates, releasing bradykinin (Bk) and Lys-bradykinin (Lys-Bk), respectively. This review presents a brief history of human PKa with details and recent observations of its evolution among the vertebrate coagulation proteins, including the relations with Factor XI. We explored the role of Factor XII in activating the plasma kallikrein-kinin system (KKS), the mechanism of activity and control in the KKS, and the function of HK on contact activation proteins on cell membranes. The role of human PKa in cell biology regarding the contact system and KSS, particularly the endothelial cells, and neutrophils, in inflammatory processes and infectious diseases, was also approached. We examined the natural plasma protein inhibitors, including a detailed survey of human PKa inhibitors' development and their potential market.

Inaccuracies in plasma oxytocin extraction and enzyme immunoassay techniques

Numerous studies have reported extensive associations between plasma oxytocin (OXT) concentrations and various human physiological and neurobehavioral processes. Measurement of OXT is fraught with difficulty due to its low molecular weight and plasma concentrations, with no consensus as to the optimal conditions for pre-analytical sample extraction, standards for immunoassay validation or the ideal protease inhibitors to prevent OXT degradation. Previous attempts at determining the efficacy of various purification techniques such as solid phase extraction (SPE) or ultrafiltration have only utilized human plasma samples, making it difficult to dissect out whether the effect of interference comes from the extraction process itself or cross-reactivity with other proteins. By testing these on pure OXT solutions, we demonstrate poor recovery efficacy and reliability of reversed phase SPE (maximum 58.1%) and ultrafiltration (<1%) techniques, and the potential for the former to introduce interference into enzyme immunoassay (EIA) measurements. The clonality of antibodies used in EIA kits also potentially contributes to the differences in the readings obtained, and we validate an EIA kit which did not require pre-analytical sample extraction with low cross-reactivity and high reliability (intraclass correlation coefficient 0.980 (95% CI 0.896-0.999). Biochemical techniques used for measuring plasma OXT concentrations must therefore be internally validated prior to translation into clinical studies.

Fluid Status After Cardiac Surgery Assessed by Bioelectrical Impedance Vector Analysis and the Effects of Extracorporeal Circulation

OBJECTIVE

Hydration status after cardiac surgery can be difficult to assess, often requiring invasive measurements. Bioelectrical impedance vector analysis (BIVA) is based on patterns of resistance (R) and reactance (Xc), corrected by height, and has been used in various clinical scenarios to determine body composition and monitor its changes over time. The purpose of the present study was to apply this method in cardiac surgery patients to assess the variation in hydration status and to compare its changes according to the use of extracorporeal circulation.

DESIGN

Single-center, observational, prospective study including patients older than 18 years undergoing elective or urgent cardiac surgery.

SETTING

Intensive cardiac care unit of a tertiary center in a metropolitan area.

PARTICIPANTS

The study comprised 76 patients with a median age of 60 years and mostly undergoing coronary artery bypass grafting (CABG) (n = 47 [61.8%]) with extracorporeal circulation (n = 54 [73%]).

INTERVENTIONS

Bioimpedance was measured with a standard tetrapolar single-frequency bioimpedance meter using a standardized procedure and plotted in an R-Xc graph.

MEASUREMENTS AND MAIN RESULTS

The study demonstrated an increase in total body water immediately after surgery that was sustained until producing hyperhydration 24 hours later. Off-pump CABG was associated with a normal hydration status after surgery, whereas on-pump CABG produced a significant increase in total body water.

CONCLUSIONS

Fluid status assessment with BIVA in cardiac surgery showed an increase in total body water up to 24 hours after surgery. Off-pump surgery prevented overhydration, which partially could explain the reduction in some of the postoperative complications. BIVA could serve as a useful method for monitoring fluid status in the setting of goal-directed therapy to assist in maintaining euvolemia in cardiac surgical patients.

Bleeding Following Deep Hypothermia and Circulatory Arrest in Children

Deep hypothermic circulatory arrest (DHCA) is a technique of extracorporeal circulation commonly used in children with complex congenital heart defects undergoing surgical repairs. The use of profound cooling (20°C) and complete cessation of circulation allow adequate exposure and correction of these complex lesions, with enhanced cerebral protection. However, the profound physiologic state of DHCA results in significant derangement of the coagulation system and a high incidence of postoperative bleeding. This review examines the impact of DHCA on bleeding and transfusion requirements in children and the pathophysiology of DHCA-induced platelet dysfunction. It also focuses on possible pharmacologic interventions to decrease bleeding following DHCA in children.

The Effect of Aprotinin on Brain Ischemic-Reperfusion Injury After Hemorrhagic Shock in Rats: An Experimental Study

BACKGROUND

We aimed to demonstrate the positive effects of the serine protease inhibitor aprotinin on neural ischemia-reperfusion injury and apoptosis in a rat model.

METHODS

There were 18 rats divided into 3 groups: group A (sham, n = 6), group B (ischemia-reperfusion, n = 6), and group C (ischemia-reperfusion + aprotinin, n = 6). The systolic blood pressure of the group B and C rats was decreased to 40% to 50% of the normal level by taking blood from the femoral vein to develop hemorrhagic shock. The blood was retained and given to the remaining group B and C rats for reperfusion 20 minutes after the procedure. In group B, isotonic solution and, in group C, aprotinin was administered to the rats 5 minutes before reperfusion. After the rats were killed, the brain tissue samples were fixed for histopathologic examination. Brain tissue superoxide dismutase, malondialdehyde, and tissue myeloperoxidase level and apoptotic cell analyses were performed in all groups.

RESULTS

Superoxide dismutase level decreased from group A to group B and increased from group B to group C (p < 0.05). Malondialdehyde and myeloperoxidase levels and apoptotic cells increased from group A to group B and decreased from group B to group C (p < 0.05).

CONCLUSION

The results suggest that the systemic use of aprotinin in ischemic neural tissue prevents reperfusion injury and also protects the morphologic, functional, and biochemical integrity of the neural tissue.

Systemic inflammatory response to coronary artery bypass graft surgery

PURPOSE

Several aspects of the systemic inflammatory response to coronary artery bypass graft surgery are described.

SUMMARY

The inflammatory response is a fundamental biological protective mechanism that gathers together the body's cellular and chemical defense mechanisms at the local site of tissue injury. The systemic inflammatory response syndrome refers to a systemic, whole body, non-localized response. This response, which occurs to some degree in most patients undergoing coronary artery bypass graft surgery, has the potential to affect all tissues and vital organs. When blood interacts with the cardiopulmonary bypass machine, several cellular and humoral pathways are activated including the complement system, the coagulation system, and the fibrinolytic system. These, in turn, activate inflammatory response cells, such as leukocytes and platelets. Together these molecular pathways and activated cells mediate the frequently observed clinical sequelae such as edema, tissue and organ damage, and hyperfibrinolysis. In order for a molecule drug to attenuate effectively this response, it would need to have a broad enough spectrum of activity to inhibit multiple pathways and to limit their cross-amplification. Aprotinin, a nonspecific serine protease, is an important attenuator of this response as it inhibits several important serine proteases, including kallikrein, plasmin, thrombin, and elastase, which are involved in fibrinolysis and cell transmigration and degranulation into soft tissues.

CONCLUSION

Treatment with aprotinin during coronary artery bypass graft surgery should be considered as a way to attenuate bleeding and systemic inflammatory responses.

Bradykinin and histamine generation with generalized enhancement of microvascular permeability in neonates, infants, and children undergoing cardiopulmonary bypass surgery

OBJECTIVE

To investigate whether generation and liberation of bradykinin and histamine contribute to generalized edema formation in pediatric cardiopulmonary bypass surgery.

DESIGN

Prospective observational study.

SETTING

Pediatric heart surgery of a university hospital.

PATIENTS

Forty-one neonates, infants, and children undergoing cardiopulmonary bypass to correct congenital cardiac anomalies.

INTERVENTIONS

Plasma concentrations of bradykinin and histamine were determined before, during, and after cardiopulmonary bypass. Fluid balance was evaluated by control of fluid intake and output.

MEASUREMENTS AND MAIN RESULTS

The susceptibility to generalized edema formation increased significantly (r = -.457; p <.005) with decreasing age. Approximately three times higher plasma concentrations of bradykinin (p <.001) were found at the onset of anesthesia and during the total observation period in patients with a fluid retention of >6% of body weight compared with patients with a lower retention rate. Plasma bradykinin reached significantly (p <.01) higher peak concentrations of 237.9 +/- 58.6 fmol/mL during cardiopulmonary bypass and of 227.5 +/- 90.7 fmol/mL during the early postoperative period in patients with severe edema formation in contrast to only 86.6 +/- 10.9 and 65.5 +/- 26.8 fmol/mL in patients with minor fluid retention. A tendency (p =.06) to slightly increasing histamine concentrations from 2.07 +/- 0.13 nmol/L at baseline to 3.32 +/- 1.41 nmol/L during 90 mins of cardiopulmonary bypass was only observed in patients with high fluid retention.

CONCLUSIONS

Bradykinin seems to be essentially involved in the enhancement of microvascular permeability in pediatric cardiopulmonary bypass surgery, although a dominant causal role cannot be claimed by this study. Histamine, however, doesn't appear to play a major role and may only contribute as a cofactor. To what extent an increased expression of bradykinin-1 and bradykinin-2 receptors or a reduced potential of bradykinin-degrading enzymes is involved is the object of a further clinical study.

Increase of bradykinin in plasma of patients undergoing cardiopulmonary bypass: the importance of lung exclusion

STUDY OBJECTIVES

Hemodynamic complications including hypotensive episodes are frequently associated with cardiopulmonary bypass (CPB) and can be attributed to a generalized inflammatory response in which bradykinin may be a mediator. The purpose of this study was to determine the plasma levels of bradykinin-(1-9)nonapeptide in patients during CPB and the physiologic elimination of bradykinin by the lungs.

DESIGN

Prospective, observational study.

SETTING

University hospital, cardiac surgery unit.

PATIENTS AND METHODS

Intra-arterial BP was monitored and serial blood samples were obtained from 27 patients undergoing CPB for cardiac surgery. We measured plasma bradykinin and parameters of coagulation, fibrinolysis, complement, contact system, and the cytokine tumor necrosis factor (TNF).

RESULTS

Mean arterial pressure fell progressively until the end of CPB (- 18 mm Hg, p = 0.001) but returned to baseline by the end of surgery. The venous bradykinin level, normal in basal conditions (median, 1.90 fmol/mL), was increased (p = 0.001) from 15 min after the beginning of CPB (5.71 fmol/mL) to the end of the operation (7.07 fmol/mL), with a peak at the end of CPB (9.81 fmol/mL; p = 0.0001); it was normal at recovery 24 h later (2.81 fmol/mL). Bradykinin plasma levels fell 60% across the lung when the pulmonary circulation was fully restored while the patients were still receiving CPB. Activated-factor XII, thrombin-antithrombin complexes, prothrombin fragment F1 + 2, plasmin-antiplasmin complexes, C(3)a, and TNF increased significantly after the beginning of the surgical procedure, rising further during CPB, and remained elevated until the end of surgery, but they all returned to normal within 24 h. Changes in plasma bradykinin levels were not correlated with any of the other variables.

CONCLUSIONS

During CPB, there is a progressive increase of plasma bradykinin that is at least partially due to reduced catabolism as a consequence of shunting the lungs. The increase in bradykinin may contribute to the fall in BP.

Electric impedance for evaluation of body fluid balance in cardiac surgical patients

OBJECTIVE

To evaluate whether electric impedance can be used to monitor body fluid balance and fluid distribution in cardiac surgical patients.

DESIGN

Prospective clinical study.

SETTING

Heart Center, Rigshospital, Copenhagen.

PARTICIPANTS

Sixteen consecutive patients scheduled for cardiac surgery.

MEASUREMENTS AND MAIN RESULTS

Body weight, fluid balance, central hemodynamics, and total and segmental body impedance were examined perioperatively. During semisupine rest before surgery, changes in impedance indicated relocation of fluid from the legs to the thorax, mostly in the extracellular space. After surgery, weight and fluid balance increased by 3.87 +/- 0.35 kg and 1.86 +/- 0.16 L (mean +/- SE, p < 0.01) and remained elevated through the next 2 days. Impedance decreased by 30% over the thorax, by 24% over the abdomen, by 2% over the leg, and by 4% over the entire body. Changes in total and thoracoabdominal impedances had the highest correlation to the fluid balance (r = -0.86 and r = -0.87). After correction of impedance values by the constant from the regression model, the mean difference in estimation of fluid changes obtained by electric impedance and by fluid balance was 0 +/- 0.1 L at the range of changes of 4.6 L.

CONCLUSION

Alterations in electric impedance closely follow changes in fluid balance during the perioperative period. This method can be used in clinical practice to control postoperative body fluid balance in cardiac surgical patients.

Aprotinin and the systemic inflammatory response after cardiopulmonary bypass

Cardiopulmonary bypass is associated with a systemic inflammatory response, a spectrum of pathophysiologic changes ranging from mild organ dysfunction to multisystem organ failure. Complications include coagulation disorders (bleeding diathesis, hyperfibrinolysis) from platelet defects and plasmin activation, as well as pulmonary dysfunction from neutrophil sequestration and degranulation. Diverse injuries are a consequence of multiple inflammatory mediators (complement, kinins, kallikrein, cytokines). Both plasmin and kallikrein amplify the inflammatory response by activating components of the contact activation system. The full-Hammersmith (high dose) of aprotinin, a serine protease inhibitor approved for reducing blood loss and transfusion requirements in cardiopulmonary bypass, inhibits kallikrein and plasmin, resulting in suppression of multiple systems involved in the inflammatory response. Specifically, inhibition of factor XII, bradykinin, C5a, neutrophil integrin expression, elastase activity, and airway nitric oxide production are observed. Clinical correlates include reduced capillary leak, preserved systemic vascular resistance and blood pressure, and improved myocardial recovery following ischemia. Overall, evidence indicates that aprotinin attenuates the systemic inflammatory response associated with cardiopulmonary bypass.

Aprotinin in deep hypothermic circulatory arrest

Early experience with aprotinin in deep hypothermic circulatory arrest (DHCA) raised alarm about hazards associated with its use. Based on what little is known about possible mechanistic interactions between hypothermia, stasis, and aprotinin, there is no evidence that aprotinin becomes unusually hazardous in DHCA. Excessive mortality and complication rates have only been reported in clinical series in which the adequacy of heparinization is questionable. Benefits associated with use of aprotinin in DHCA have been inconsistently demonstrated. The only prospective, randomized series showed significant reduction in blood loss and transfusion requirements. Use of aprotinin in DHCA should be based on the same considerations applied in other cardiothoracic procedures.

Operations on the thoracic aorta and hypothermic circulatory arrest: is aprotinin safe?

INTRODUCTION

The safety of aprotinin, especially when used with profound hypothermic circulatory arrest, is still a matter of intense debate despite its presumed salutary effects on blood loss. Many investigators have reported toxic renal effects of high-dose aprotinin in such patients, but no prospective, randomized study has been conducted. To assess the potential detrimental effect of aprotinin on renal function and its putative reduction of blood loss, 50 patients undergoing thoracic aortic operations with the use of profound hypothermic circulatory arrest were randomly assigned to receive either low-dose aprotinin (1 x 10(6) kallikrein activation units) or placebo.

METHODS

The specific renal tubular markers beta-2-microglobulin and beta-N-acetyl-D-glucosaminidase, as well as serum creatinine and blood urea nitrogen, creatinine clearance, sodium excretion, and potassium excretion, were measured to evaluate renal function preoperatively, immediately after the procedure, and 24 hours and 48 hours later.

RESULTS

No statistically significant difference was found in any measured renal parameter between the two groups (analysis of variance). Renal dysfunction, defined as an elevation of serum creatinine early postoperatively (> or = 1.5 times the preoperative value), occurred in two patients who received aprotinin and in one patient in the control group. Temporary dialysis (hemodialysis or continuous venovenous hemofiltration) was needed in two patients in the aprotinin group versus one in the control group. Furthermore, patients treated with aprotinin had significantly less total postoperative blood loss (718 +/- 340 ml vs 920 +/- 387 ml, p = 0.04). The aprotinin recipients also had a significantly lower transfusion requirement (p < 0.05).

CONCLUSION

This controlled trial of low-dose aprotinin in patients undergoing thoracic aortic operations using profound hypothermic circulatory arrest demonstrated no detectable deleterious effects on renal function; moreover, the use of aprotinin was associated with significantly lower need for transfusion.

Aprotinin effects related to oxidative stress in cardiosurgery with mechanical cardiorespiratory support (CMCS)

There is evidence to support a relationship between oxidative stress and protease release in "ischemia-reperfusion damage." We have proposed that aprotinin may exert an antioxidant effect. A double blind clinical trial was performed with a control (G-1) and treated (G-2) groups, both submitted to CMCS. Blood samples were taken 5 times. Biochemical indicators were measured spectrophotometrically. Aprotinin was supplied by Bayer. Malonildialdehyde levels were greater in G-1 (7.2 +/- 3.6 nmoles/ml) than in G-2 (4 +/- 1.65) at the time of reperfusion. Phospholipase A2 exhibited a tendency of higher activity in G-1 than in G-2. Uric acid levels were higher in G-2 (431 +/- 274 mumoles/1) than in G-1 (224 +/- 188) at 5 minutes after aortic clamping, and catalase activity was greater in G-2 (294 +/- 55 KU/1) than in G-1 (118 +/- 47) at time of reperfusion. Low cardiac output was 10% in G-2 and 30% in G-1. Arrythmias appeared in 30% of G-2 and in 60% of G-1. These results suggest an antioxidant effect of aprotinin under ischemia-reperfusion conditions.

Pathogenic mechanisms induced by microbial proteases in microbial infections

Most bacterial and fungal proteases excreted into infected hosts exhibit a wide range of pathogenic potentials ranging from pain, edema or even shock to translocation of bacteria from the site of infection into systemic circulation, thus resulting in septicemia. The basic mechanism or principle common to all these phenomena is explained by kinin generation, either directly from high- and/or low-molecular weight kininogens or indirectly via activation of the bradykinin generating cascade: i.e. Hageman factor-->activated Hageman factor-->prekallikrein-->kallikrein-->high-molecular weight kininogen-->bradykinin. Some bacterial proteases are also involved in activation of other host protease zymogens such as plasminogen, procollagenase (matrix metallo proteases) and proenzymes of the clotting system. Furthermore, most bacterial proteases are not only resistant to plasma protease inhibitors of the hosts, most of which belong to a group of serine protease inhibitors called serpins (serine protease inhibitors), but they also quickly inactivate serpins. Some bacterial proteases may also activate bacterial toxins thus rendering toxigenic pathogenesis. They are also capable of degrading immunoglobulins and components of the complement system and facilitate propagation of micro organisms. All in all, microbial proteases are very critical in enhancing pathogenesis of severe diseases. It is also noteworthy that bacterial cell wall components themselves, i.e. endotoxin (or lipopolysaccharide) of gram negative bacteria and teichoic/lipoteichoic acid of gram positive bacteria, are also able to activate the bradykinin generating cascade-involving activation of Hageman factor as mentioned above.

Comparison of responses of canine pulmonary artery and vein to angiotensin II, bradykinin and vasopressin

Responses to angiotensin II, bradykinin and arginine vasopressin were compared in helical strips of canine pulmonary arteries and veins. Angiotensin II contracted the artery but relaxed the vein strip. The artery contraction was augmented by indomethacin and aspirin and was abolished by losartan. The vein relaxation was not affected by endothelium denudation but was abolished by the cyclooxygenase inhibitors, a prostaglandin I2 synthase inhibitor and losartan. The bradykinin-induced artery relaxation was inhibited by endothelium denudation, NG-nitro-L-arginine (L-NA) or indomethacin and abolished by their combined treatment. The vein relaxation produced by bradykinin was endothelium-independent and was abolished by indomethacin. Vasopressin produced a slight relaxation in the arteries, which was abolished by endothelium denudation and L-NA. The vein relaxation produced by vasopressin was abolished by endothelium denudation and combined treatment with L-NA and indomethacin. It may be concluded that (1) activation of angiotensin AT1 receptor subtype in smooth muscle produces contraction and also relaxation due to prostaglandin I2 release; the former predominates over the latter in the artery, whereas only the latter is operative in the vein, (2) the bradykinin-induced relaxation is due to nitric oxide (NO) from the endothelium and prostaglandin I2 from subendothelial tissues in the artery and solely to prostaglandin I2 in the veins, and (3) the vasopressin-induced relaxation is mediated by endothelial NO in the artery, and NO and prostaglandin I2 in the vein.

Effects of aprotinin on acute recovery of cerebral metabolism in piglets after hypothermic circulatory arrest

Brain protection during cardiopulmonary bypass and hypothermic circulatory arrest is incomplete. Activation of blood protease cascades may contribute to cellular injury under these conditions. To test this hypothesis, effects of the protease inhibitor aprotinin on recovery of brain energy metabolism after hypothermic circulatory arrest were studied in the piglet. Twenty-four 4-week-old piglets (10 aprotinin-treated and 14 control) underwent core cooling, 1 hour of circulatory arrest at 15 degrees C, reperfusion and rewarming (45 minutes), and normothermic perfusion (3 hours) on cardiopulmonary bypass. Cerebral high-energy phosphate concentration and intracellular pH were studied by phosphorus-31 magnetic resonance spectroscopy in 12 animals. In the remaining animals cerebral and regional blood flow were measured with radioactive microspheres and carotid artery blood flow was measured with an electromagnetic flowmeter. Cerebral oxygen and glucose extraction were measured, and vascular resistance responses to endothelium-dependent (acetylcholine) and -independent (nitroglycerin) vasodilators were calculated. Recovery of cerebral adenosine triphosphate (p = 0.02) and intracellular pH (p = 0.04) in the initial 30 minutes of reperfusion was accelerated in the aprotinin-treated piglets. These piglets showed a greater in vivo cerebral and systemic endothelium-mediated vasodilation (acetylcholine response: cerebral p < 0.01, systemic p = 0.04) after reperfusion. The response to endothelium-independent vasodilation (nitroglycerin) was the same in both groups. Carotid blood flow tended to be greater at 20 minutes of reperfusion and less during 45 to 80 minutes after reperfusion in the aprotinin-treated animals. Brain water content postoperatively was 0.8077 in the aprotinin group and 0.8122 in control animals (p = 0.06).(ABSTRACT TRUNCATED AT 250 WORDS)

Preservation of pancreatic beta cell function with pulsatile cardiopulmonary bypass

Pancreatic islet cell function and tissue metabolism were studied during and after cardiopulmonary bypass in 38 patients undergoing an open heart operation. Twenty patients were operated on with pulsatile cardiopulmonary bypass (group I) and 18, with nonpulsatile cardiopulmonary bypass (group II). Hyperglycemia was observed during and early after operation in both groups. In group I during cardiopulmonary bypass, the immunoreactive insulin and c-peptide levels and the insulin to glucagon molar ratio increased significantly compared with the preoperative values, but in group II, these variables did not alter significantly. An hour postoperatively, the immunoreactive insulin (71 +/- 34 muIU/mL) and c-peptide (8.3 +/- 3.0 ng/mL) levels and the insulin to glucagon molar ratio (11.0 +/- 5.2) in group I were significantly higher than those in group II (immunoreactive insulin, 29 +/- 20 muIU/mL; c-peptide, 4.8 +/- 1.8 ng/mL; insulin to glucagon molar ratio, 3.4 +/- 2.6). The blood lactate level in group I (41 +/- 22 mg/dL) was significantly lower than that in group II (78 +/- 30 mg/dL) an hour postoperatively. In conclusion, pulsatile cardiopulmonary bypass is quite effective in preserving pancreatic beta cell function and tissue metabolism during and early after open heart procedures.

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.

Hematologic effects of cardiac and noncardiac surgery

The intraoperative and postoperative changes in number and type of WBCs in patients undergoing cardiac surgery were studied. These changes were then compared with those that occurred in patients undergoing four noncardiac surgical procedures (abdominal vascular reconstruction, thoracotomy, cholecystectomy, and carotid thromboendarterectomy). Both cardiac surgery and abdominal vascular surgery resulted in a marked increase in bands and decrease in lymphocytes. Thoracotomy and cholecystectomy resulted in similar but smaller changes. Carotid thromboendarterectomy did not produce hematologic changes. We conclude that the hematologic changes that occur with cardiac surgery are primarily a result of the stress and trauma of major surgery rather than a result of cardiopulmonary bypass itself.

Enzymatic assessment of myocardial necrosis after cardiac surgery: differentiation from skeletal muscle damage, hemolysis, and liver injury

Plasma activities of various (iso)enzymes were measured in patients after cardiac surgery (n = 114) and after acute myocardial infarction (n = 40). From these activities, the cumulative release of enzymes in plasma was calculated with a two-compartment circulatory model. This model was adapted to transient postoperative changes in plasma volume and similar changes in the transcapillary escape rate of proteins, observed after cardiac surgery and verified in dogs after cardiopulmonary bypass (CPB). Comparison of cumulative release of enzymes with the enzyme content of myocardium, skeletal muscle, and blood cells allows identification of the various sources of enzyme release. Cardiac injury after uncomplicated bypass surgery is only 1.5 +/- 1.5 (mean +/- SD) gram equivalents (gmEq) of myocardium, compared to a loss of 31 +/- 13 gmEq of myocardium after AMI. Peroperative hemolysis is estimated at 68 +/- 15 ml of blood. Total loss of skeletal muscle amounts to 13 +/- 10 gmEq. Some hepatic enzyme release is observed after AMI but not after surgery. Large differences in time course exist between the release of enzymes from myocardium and skeletal muscle and also between myocardial release in the surgery group and in the AMI group. The accuracy of estimations is discussed and indicated as a function of the extent of cardiac injury.

Bradykinin, plasma protein fraction, and hypotension

A directive from the Food and Drug Administration indicates that the use of plasma protein fraction (PPF) is contraindicated during cardiopulmonary bypass because of possible hypotension. Bradykinin has been implicated as the cause of this hypotension. Bradykinin levels were measured by radioimmunoassay in PPF and in 5% albumin and were found to be consistently elevated in the former and occasionally in the latter. The addition of PPF to pump primes resulted in significantly elevated levels of bradykinin, which rapidly cleared, indicating that extrapulmonary sites of bradykinin inactivation were efficient. The potential hypotensive effect of PPF was observed by determining the change in mean perfusion pressure in two groups of patients: one group with a 3,000 ml crystalloid prime and the other with a prime of 2,000 ml of crystalloid and 1,000 ml of PPF. There was no significant difference in the perfusion pressure between the two groups at any point, and the hypotensive effects seen in both groups were readily treated, suggesting that the directive against the use of PPF during cardiopulmonary bypass may be unnecessarily restrictive.