Anticoagulation and Anticoagulation Reversal With Cardiac Surgery Involving Cardiopulmonary Bypass: An Update

Anti-inflammatory effect of colchicine on organ damage during the perioperative period of cardiac surgery: a study protocol for a multicentre, randomised, double-blind, placebo-controlled clinical trial

INTRODUCTION

The systemic inflammatory response syndrome during the perioperative period of cardiac surgery can lead to serious postoperative complications and significantly increase the hospital mortality rate. Colchicine, a widely used traditional anti-inflammatory drug, has good clinical value in cardiovascular anti-inflammatory therapy. Our preliminary single-centre study had confirmed the protective value of colchicine in patients undergoing cardiac surgery with cardiopulmonary bypass. For this multicentre investigation, we aim to further validate the anti-inflammatory and organ-protective effects of low-dose colchicine during the perioperative period in a low-risk population.

METHODS AND ANALYSIS

This study is a multicentre, randomised, double-blind, placebo-controlled clinical trial. A total of 768 patients undergoing elective cardiac surgery will be enrolled from eight heart centres in China. The participants will be randomly assigned to two groups: the colchicine group will receive low-dose colchicine (0.5 mg once-a-day dosing regimen (QD) orally for 3 days before the surgery and 0.5 mg dosing frequency of every other day (QOD) continuously for 10 days after the surgery), whereas the placebo group will be given starch tablets for the same time and dosage. Primary endpoints are the occurrence of postoperative inflammatory diseases, including postoperative atrial fibrillation, acute respiratory distress syndrome, preoperative myocardial injury and post-pericardiotomy syndrome. Secondary endpoints included laboratory tests on postoperative days 1, 3, 5, 7 and 10, intensive care unit data, APACHE II score, Murray lung injury score, medication-related gastrointestinal reactions, 30-day and 90-day all-cause mortality, surgical data, chest radiograph on postoperative days 1, 2 and 3, and chest CT within 14 days after surgery.

ETHICS AND DISSEMINATION

This research has received approval from the Medical Ethics Committee of Affiliated Nanjing Drum Tower Hospital, Nanjing University Medical College (approval number 2023-366-01). The study findings will be made available by publishing them in an open access journal.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov (NCT06118034).

Factors Influencing Unfractionated Heparin Pharmacokinetics and Pharmacodynamics During a Cardiopulmonary Bypass

BACKGROUND

Unfractionated heparin (UFH) is commonly used during cardiac surgery with a cardiopulmonary bypass to prevent blood clotting. However, empirical administration of UFH leads to variable responses. Pharmacokinetic and pharmacodynamic modeling can be used to optimize UFH dosing and perform real-time individualization. In previous studies, many factors that could influence UFH pharmacokinetics/pharmacodynamics had not been taken into account such as hemodilution or the type of UFH. Few covariates were identified probably owing to a lack of statistical power. This study aims to address these limitations through a meta-analysis of individual data from two studies.

METHODS

An individual patient data meta-analysis was conducted using data from two single-center prospective observational studies, where different UFH types were used for anticoagulation. A pharmacodynamic/pharmacodynamic model of UFH was developed using a non-linear mixed-effects approach. Time-varying covariates such as hemodilution and fluid infusions during a cardiopulmonary bypass were considered.

RESULTS

Activities of UFH's anti-activated factor/anti-thrombin were best described by a two-compartment model. Unfractionated heparin clearance was influenced by body weight and the specific UFH type. Volume of distribution was influenced by body weight and pre-operative fibrinogen levels. Pharmacodynamic data followed a log-linear model, accounting for the effect of hemodilution and the pre-operative fibrinogen level. Equations were derived from the model to personalize UFH dosing based on the targeted activated clotting time level and patient covariates.

CONCLUSIONS

The population model effectively characterized UFH's pharmacokinetics/pharmacodynamics in cardiopulmonary bypass patients. This meta-analysis incorporated new covariates related to UFH's pharmacokinetics/pharmacodynamics, enabling personalized dosing regimens. The proposed model holds potential for individualization using a Bayesian estimation.

Adjusted calculation model of heparin management during cardiopulmonary bypass in obese patients: A randomised controlled trial

BACKGROUND

Anticoagulation during cardiopulmonary bypass (CPB) is usually adapted to total body weight (TBW). This may be inaccurate in obese patients and lead to heparin overdose with a risk of bleeding.

OBJECTIVES

To validate the efficacy and safety of an adjusted calculation model of heparin dosing based on ideal body weight (IBW) rather than TBW in obese CPB patients, with an expected target mean plasma heparin concentration of 4.5 IU ml after onset of CPB in the experimental group.

DESIGN

Randomised controlled study.

SETTING

University hospital.

PATIENTS

Sixty obese patients (BMI ≥ 30 kg m) scheduled for CPB were included from January to June 2016.

INTERVENTIONS

Patients received a bolus dose of unfractionated heparin of either 300 IU kg of TBW or 340 IU kg of IBW before onset of CPB. Additional adjusted boluses were injected to maintain an activated clotting time (ACT) of at least 400 s.

MAIN OUTCOME MEASURES

Plasma heparin concentration and ACT were measured at different time points. Total heparin doses and transfusion requirements were recorded.

RESULTS

The target heparin concentration of 4.5 IU ml was reached in the IBW group at the onset of CPB and maintained at all time points during CPB. Heparin concentrations were significantly higher in the TBW group after the bolus (6.52 ± 0.97 vs. 4.54 ± 1.13 IU ml, P < 0.001) and after cardioplegia (5.10 ± 1.03 vs. 4.31 ± 1.00 IU ml, P = 0.02). Total heparin doses were significantly higher in the TBW group. Mean ACT was significantly lower in the IBW group but remained over 400 s during CPB. The correlation between heparin and ACT was poor. Peri-operative bleeding and transfusion requirements were comparable. No thrombotic event occurred in the CPB circuit.

CONCLUSION

The current IBW-adjusted regimen of heparin administration may be used efficiently in obese CPB patients, thereby avoiding overdose which cannot be accurately assessed by ACT monitoring alone.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02675647.

Sutureless Perceval Aortic Valve Versus Conventional Stented Bioprostheses: Meta-Analysis of Postoperative and Midterm Results in Isolated Aortic Valve Replacement

Background

Aortic stenosis is the most common valvular disease and has a dismal prognosis without surgical treatment. The aim of this meta‐analysis was to quantitatively assess the comparative effectiveness of the Perceval (LivaNova) valve versus conventional aortic bioprostheses.

Methods and Results

A total of 6 comparative studies were identified, including 639 and 760 patients who underwent, respectively, aortic valve replacement with the Perceval sutureless valve (P group) and with a conventional bioprosthesis (C group). Aortic cross‐clamping and cardiopulmonary bypass duration were significantly lower in the P group. No difference in postoperative mortality was shown for the P and C groups (2.8% versus 2.7%, respectively; odds ratio [OR]: 0.99 [95% confidence interval (CI), 0.52–1.88]; P=0.98). Incidence of postoperative renal failure was lower in the P group compared with the C group (2.7% versus 5.5%; OR: 0.45 [95% CI, 0.25–0.80]; P=0.007). Incidence of stroke (2.3% versus 1.7%; OR: 1.34 [95% CI, 0.56–3.21]; P=0.51) and paravalvular leak (3.1% versus 1.6%; OR: 2.52 [95% CI, 0.60–1.06]; P=0.21) was similar, whereas P group patients received fewer blood transfusions than C group patients (1.16±1.2 versus 2.13±2.2; mean difference: 0.99 [95% CI, −1.22 to −0.75]; P=0.001). The incidence of pacemaker implantation was higher in the P than the C group (7.9% versus 3.1%; OR: 2.45 [95% CI, 1.44–4.17]; P=0.001), whereas hemodynamic Perceval performance was better (transvalvular gradient 23.42±1.73 versus 22.8±1.86; mean difference: 0.90 [95% CI, 0.62–1.18]; P=0.001), even during follow‐up (10.98±5.7 versus 13.06±6.2; mean difference: −2.08 [95% CI, −3.96 to −0.21]; P=0.030). We found no difference in 1‐year mortality.

Conclusions

The Perceval bioprosthesis improves the postoperative course compared with conventional bioprostheses and is an option for high‐risk patients.

Engineering the Surface of Therapeutic "Living" Cells

Biological cells are complex living machines that have garnered significant attention for their potential to serve as a new generation of therapeutic and delivery agents. Because of their secretion, differentiation, and homing activities, therapeutic cells have tremendous potential to treat or even cure various diseases and injuries that have defied conventional therapeutic strategies. Therapeutic cells can be systemically or locally transplanted. In addition, with their ability to express receptors that bind specific tissue markers, cells are being studied as nano- or microsized drug carriers capable of targeted transport. Depending on the therapeutic targets, these cells may be clustered to promote intercellular adhesion. Despite some impressive results with preclinical studies, there remain several obstacles to their broader development, such as a limited ability to control their transport, engraftment, secretion and to track them in vivo. Additionally, creating a particular spatial organization of therapeutic cells remains difficult. Efforts have recently emerged to resolve these challenges by engineering cell surfaces with a myriad of bioactive molecules, nanoparticles, and microparticles that, in turn, improve the therapeutic efficacy of cells. This review article assesses the various technologies developed to engineer the cell surfaces. The review ends with future considerations that should be taken into account to further advance the quality of cell surface engineering.

Optimal Management of Bleeding Complications After Cardiac Surgery

Patients undergoing cardiac surgery with cardiopulmo nary bypass (CPB) are at increased risk for excessive perioperative blood loss requiring transfusion of blood products. Point-of-care evaluation of platelets, coagu lation factors, and fibrinogen can enable physicians to assess bleeding abnormalities rapidly. They also can facilitate the optimal administration of pharmacologic and transfusion-based therapy and allow physicians to identify patients with surgical bleeding. The ability to reduce the unnecessary use of blood products in this setting has important implications for emerging issues in blood inventory and blood costs. The ability to de crease operative time along with re-exploration rates has important consequences for health care costs in an increasingly managed health care environment. Copyright© 2001 by W.B. Saunders Company.

Comparison of ACT point-of-care measurements: repeatability and agreement

Background: Accurate control of heparin anticoagulation is necessary during all stages of cardiopulmonary bypass (CPB). The activated clotting time, first described by Hattersley in 1966, is mostly used for determination of anticoagulation. Either celite or kaolin are used as activators. An ACT value of 480 sec is proposed to be the safe minimum level for anticoagulation during CPB. This study was designed to determine if the activated coagulation time (ACT) values of each analyser separately are repeatable, and to determine whether there exists a significant difference in ACT values measured by three different analysers: the GEM PCL (Instrumentation Laboratory), the Hemochron 801 (International Techni-dyne Corporation) and the ACT II Automated Coagulation Timer (Medtronic).

Methods: All patients underwent cardiovascular surgical procedures requiring heparinisation (200 - 300 IU/kg). Blood samples for the measurement of the ACT were taken from all patients before and after heparinisation, during CPB, and after protamine administration. All samples were measured in duplicate with the three different analysers. To compare the activated clotting time data, the method described by Bland and Altman was used. The Pearson correlation coefficient was used to determine whether the differences were related to the average ACTs. p-Values < 0.05 were considered statistically significant.

Results: The results showed that the three tested ACT analysers met the requirements of repeatability. The mean differences and standard deviations of the ACT values measured with the GEM PCL, the Hemochron 801, and the ACT II analyser were, respectively, -8.789 ± 37.61, -19.779±68.82, and -6.239±39.21, with p-values=0.177, 0.081 and 0.384, respectively. The Pearson correlation coefficients were too low (-0.012, -0.221 and -0.241, respectively) to show any correlation between the differences and the means. The ACT values measured with the Hemochron 801 were not significantly different from the ACT values measured with the ACT II analyser: ΔACT=-34.09 ± 146.68, with p=0.132. However, the GEM PCL did not agree with the Hemochron 801: ΔACT=-80.29 ± 143.06, with p=0.001, or the ACT II analyser: ΔACT=-119.139 ± 138.51, with p<0.001. A rather strong correlation was evident between the differences and the means measured with the GEM PCL compared with the Hemochron 801 (r=0.68) and the ACT II analyser (r=0.76).

Conclusions: All analysers used celite or kaolin as activator. However, it was evident that the ACT measurements depended also on the analyser that had been chosen. A precaution that ACT values could not always be interpreted in the same way seems to be necessary.

Activated Clotting Time during Cardiopulmonary Bypass: Is Repetition Necessary during Open Heart Surgery?

We evaluated the need of activated clotting time monitoring and efficacy of heparinization protocol in 100 patients undergoing open heart surgery. Patients were anticoagulated with 300 or 400 units·kg−1 heparin, based on their heparin sensitivity assessed at 5 min by activated clotting time. One-third of the initial dose was repeated at 90 min and thereafter hourly until completion of cardiopulmonary bypass. Patients who attained an activated clotting time of > 350 seconds at 5 min were included. Activated clotting time was repeated every 30 min. A time of < 350 seconds or presence of clot in the surgical field/extracorporeal circuit was considered failure of the protocol. Cardiopulmonary bypass was performed using a membrane oxygenator, non-pulsatile flow, hypothermia and crystalloid/blood priming solution. At 5 min, 94 patients had activated clotting time of > 350 seconds, 6 were < 350 seconds. At predetermined time intervals of 30 min, up to 210 min, 406 activated clotting time measurements were above 400 seconds and 40 were between 350 and 400 seconds. No clot was observed in the surgical field or extracorporeal circuit. This anticoagulation protocol ensures adequate anticoagulation during hypothermic cardiopulmonary bypass. With this protocol, only one activated clotting time at 5 min after heparin administration is required and essential; subsequent monitoring is not necessary.

Routine transfusion of platelet concentrates effectively reduces reoperation rate for bleeding and pericardial effusion after elective operations for ascending aortic aneurysm

Patients with ascending aortic aneurysm undergoing complex surgical procedures are at increased risk of early postoperative excessive blood loss. The aim of this study was to analyze safety and efficacy of routine transfusions of platelet (PLT) concentrates in reduction of hemorrhagic postoperative complications. The study involved 396 consecutive patients (289 males and 107 females) with the mean age of 55.9 ± 13.6 years who underwent elective operations for aortic aneurysms. They were divided retrospectively into two groups, without (group A; n = 123) or with the routine use of PLTs (group B; n = 273). PLTs were transfused intraoperatively just after completion of cardiopulmonary bypass. Twelve patients in group A (9.8%) and 10 (3.7%) in group B required re-thoracotomy due to hemorrhage (p = 0.027). Routine transfusions of PLT concentrates reduced postoperative incidence of excessive pericardial effusion from 24.1% in group A to 2.1% in group B (p = 0.002). In a consequence, significantly less units (p < 0.0001) of red blood concentrates and fresh frozen plasma were transfused in group B than in group A. The rates of other adverse events in the early postoperative period did not differ between groups. Patients with pericardial effusion required 6.3 ± 2.7 additional days of hospitalization due to surgical re-intervention. Neither blood transfusion-related infections nor adverse reactions were noted. In conclusion, routine intraoperative transfusions of PLT concentrates in patients with ascending aortic aneurysms significantly reduced a need for re-intervention due to both early bleeding and late cardiac tamponade.

Accelerated activation of the coagulation pathway during cardiopulmonary bypass in aortic replacement surgery: a prospective observational study

Background

Any form of surgery or tissue damage causes release of tissue factor into the circulation. This may lead to the accelerated consumption of coagulation factors, resulting in severe consumptive coagulopathy. In this study, we compared the molecular markers involved in coagulation activation during cardiopulmonary bypass (CPB) between patients who underwent aortic replacement surgery and those who underwent valve surgery.

Methods

This prospective observational study was performed in each 14 patients who underwent aortic replacement surgery or valve surgery. We evaluated the differences in the levels of fibrinogen, activated factor VII (FVIIa), thrombin–antithrombin complex (TAT), and soluble fibrin monomer complex (SFMC) during surgery between these two groups.

Results

The change in fibrinogen levels showed no difference between the groups. The magnitude of increase in TAT was much larger in patients who underwent aortic replacement surgery than in those who underwent valve surgery (173.6 vs. 49.4 ng/mL; p = 0.0001). More importantly, the elevation of FVIIa was significantly higher in patients who underwent aortic replacement (28.5 vs. 19.0 mU/mL; p = 0.0122). The magnitude of increase in SFMC was also larger in the aortic replacement surgery.

Conclusions

The activation of coagulation during CPB was dramatically higher in the aortic replacement surgery compared with the valve surgery, probably owing to the activation of the extrinsic coagulation pathway in the former. This could potentially exacerbate consumptive coagulopathy after CPB termination in patients who underwent aortic replacement, possibly resulting in massive hemorrhage due to impaired hemostasis.

Chemically modified poly(2-hydroxyethyl methacrylate) cryogel for the adsorption of heparin

Various clinical procedures, such as cardiovascular surgery or extracorporeal blood purification, involve systemic anticoagulation using heparin. High concentrations of circulating heparin require neutralization due to possible serious bleeding complications. The intravenous administration of the heparin antagonist protamine sulfate is routinely clinically performed, but is frequently associated with adverse reactions. Therefore, there is a need for a valid and safe alternative to achieve extracorporeal heparin removal from blood or plasma, such as a filter, a matrix, or an adsorbent. Here, we describe the development of a macroporous poly(2-hydroxyethyl methacrylate)-based monolithic cryogel functionalized with l-lysine (pHEMA-lys) and the characterization of its selective heparin adsorption. The maximum binding capacity was quantified in vitro using aqueous and serum solutions under static and dynamic conditions, and fresh human plasma under static conditions. The pHEMA-lys bound 40,500 IU and 32,500 IU heparin/g cryogel at the equilibrium in aqueous solution and 50% serum, respectively. In human plasma spiked with 100 IU/mL of heparin, the binding was still highly efficient (4330 IU/g cryogel after 30 min, i.e., 87% of the initial concentration). The cryogels showed good blood compatibility, as indicated by negligible adsorption of albumin, antithrombin III, and total protein, and may thus be suitable for extracorporeal heparin removal.

Impact of protamine dose on activated clotting time and thromboelastography in infants and small children undergoing cardiopulmonary bypass

OBJECTIVES

To study the effect of two protamine-dosing strategies on activated clotting time (ACT) and thromboelastography (TEG).

BACKGROUND

Protamine dosage based on neutralizing heparin present in the combined estimated blood volumes (EBVs) of the patient and cardiopulmonary bypass (CPB) pump may result in excess protamine and contributes toward a coagulopathy that can be detected by ACT and TEG in pediatric patients.

METHODS

A total of 100 pediatric patients 1 month to ≤5 years of age undergoing CPB were included in this retrospective before/after design study. Combined-EBV group consisted of 50 consecutive patients whose protamine dose was calculated to neutralize heparin in the combined EBVs of the patient and the pump. Pt-EBV group consisted of the next 50 consecutive patients whose protamine dose was calculated to neutralize heparin in the patient's EBV.

RESULTS

Baseline and postprotamine ACTs were similar between groups. Postprotamine heparin assay (Hepcon) showed the absence of residual heparin in both groups. Postprotamine kaolin-heparinase TEG showed that R was prolonged by 7.5 min in the Combined-EBV group compared with the Pt-EBV group (mean R of 20.17 vs. 12.4 min, respectively, P < 0.001). Increasing doses of protamine were associated with a corresponding, but nonlinear increase in R. There was no significant difference in the changes for K, alpha, and MA between the groups.

CONCLUSION

Automated protamine titration with a protamine dosage based on Pt-EBV can adequately neutralize heparin as assessed by ACT while minimizing prolonging clot initiation time as measured by TEG.

The heparin recall of 2008

Heparin is one of the oldest drugs still in widespread clinical use. Its discovery in 1916 predates the establishment of the Food and Drug Administration. Since 1935, over 15,000 research papers have been published on the effects of heparin. Because the exact chemical formula of heparin is unknown, synthetic manufacturing has proven difficult. In 2008, a worldwide recall of heparin occurred. Scientists determined that a contaminant known as oversulfated chondroitin sulfate was responsible for the numerous deaths and adverse events. This contaminant was first traced to a chemical plant in Changzou, China. This article will review the discovery of heparin and the adulteration process that jeopardized the world's heparin supply.

Hypercoagulable state after off-pump coronary artery bypass grafting: evidence, mechanisms and implications

During the past decade, there has been a dramatic resurgence in the adoption of off-pump technology in coronary artery bypass surgery. This has inspired remarkable advances in the techniques of localized tissue stabilization and a greater understanding of the physiology of beating-heart mobilization and exposure. An avalanche of reports in the literature has demonstrated the early safety and efficacy of the procedure. However, despite abundant evidence validating the safety and efficacy of off-pump coronary artery bypass surgery, considerable controversy still persists regarding the long-term outcomes of this approach to myocardial revascularization. One area of concern, and even greater uncertainty, surrounds the issue of the existence of a hypercoagulable state after off-pump coronary artery bypass surgery. This article evaluates the current best evidence available from randomized controlled trials to assess the impact of off-pump coronary artery bypass surgery on coagulation, fibrinolysis and platelet activation, discusses the issue of hypercoagulability with emphasis on the mechanisms responsible for this actual or potential hypercoagulability, and explores the implications of this issue for clinical practice.

Antithrombin-heparin covalent complex reduces microemboli during cardiopulmonary bypass in a pig model

Transcranial Doppler-detected high-intensity transient signals (HITS) during cardiopulmonary bypass (CPB) surgery have been associated with postoperative neurocognitive dysfunction, suggesting microemboli in the brain could be a contributing factor. HITS occur despite administration of unfractionated heparin (UFH). This study was done to determine whether antithrombin-heparin covalent complex (ATH), a more potent anticoagulant than heparin, can reduce HITS during CPB. In a pig CPB model, ATH, UFH, or UFH + antithrombin (AT) was intravenously administered to female Yorkshire pigs after sternotomy. Twenty minutes later, hypothermic CPB was initiated and continued for 1.25 hours, then normothermia was re-established for 45 minutes. Protamine sulfate was given to neutralize the anticoagulants, and pigs were allowed to recover. HITS were monitored using an arterial flow probe placed over the carotid artery. Compared with UFH (300 or 1000 U/kg), ATH reduced the number of HITS during CPB in a dose-dependent manner. AT (3 mg/kg) + UFH (300 U/kg) resulted in an intermediate HITS rate between UFH and ATH (2 mg/kg in terms of AT). Examination of brain sections for emboli formation confirmed that, similar to HITS, number of thrombi decreased in direct proportion to ATH dosage. These results support the hypotheses that the majority of HITS represent thromboemboli and that ATH reduces emboli formation during CPB.

Biological and pharmacological aspects of perioperative hemorrhagic complications associated with oral platelet-directed antithrombotic agents. Focus on isolated coronary artery bypass grafting and oral irreversible P2Y(12) receptor antagonists

Coronary arterial bypass grafting (CABG)-the most common heart surgery performed worldwide-is an effective procedure for treating patients with advanced, obstructive atherothrombotic coronary artery disease, prolonging survival in selected high-risk patients. However, CABG is also associated with hemorrhagic complications, which can impact outcome measures such as perioperative morbidity, mortality, length of hospital stay, and health care expenditures. Recent observations have expanded our understanding of the complex process of hemostasis, fostering a more informed view of CABG-associated bleeding complications. Additional research is warranted to determine whether new antithrombotic drug treatment options, such as reversible P2Y12 receptor antagonists among patients with acute coronary syndromes, will favorably impact these clinically relevant complications.

Aprotinin during coronary-artery bypass grafting and risk of death

BACKGROUND

Aprotinin (Trasylol) is used to mitigate bleeding during coronary-artery bypass grafting (CABG). Accumulating evidence suggests that this practice increases mortality.

METHODS

Using electronic administrative records of the Premier Perspective Comparative Database, we studied hospitalized patients with operating-room charges for the use of aprotinin (33,517 patients) or aminocaproic acid (44,682 patients) on the day CABG was performed. We tabulated the numbers of patients with a hospital-discharge status of death and performed three types of analyses: a multivariable logistic-regression analysis (primary analysis); propensity-score matching in the highly selected subcohort of patients who received full amounts of the study drug, who underwent CABG by surgeons who performed 50 or more CABG surgeries during the study period, and for whom information on 10 additional covariates was available because the surgery occurred on hospital day 3 or later; and an instrumental-variable analysis of data from patients whose surgeons showed a strong preference for one of the two study drugs.

RESULTS

In all, 1512 of the 33,517 aprotinin recipients (4.5%) and 1101 of the 44,682 aminocaproic acid recipients (2.5%) died. After adjustment for 41 characteristics of patients and hospitals, the estimated risk of death was 64% higher in the aprotinin group than in the aminocaproic acid group (relative risk, 1.64; 95% confidence interval [CI], 1.50 to 1.78). In the first 7 days after surgery, the adjusted relative risk of in-hospital death in the aprotinin group was 1.78 (95% CI, 1.56 to 2.02). The relative risk in a propensity-score-matched analysis was 1.32 (95% CI, 1.08 to 1.63). In the instrumental-variable analysis, the use of aprotinin was found to be associated with an excess risk of death of 1.59 per 100 patients (95% CI, 0.14 to 3.04). Postoperative revascularization and dialysis were more frequent among recipients of aprotinin than among recipients of aminocaproic acid.

CONCLUSIONS

Patients who received aprotinin alone on the day of CABG surgery had a higher mortality than patients who received aminocaproic acid alone. Characteristics of neither the patients nor the surgeons explain the difference, which persisted through several approaches to control confounding.

Coagulation and fibrinolytic protein kinetics in cardiopulmonary bypass

The development of Cardiopulmonary Bypass (CPB) catopulted the field of cardiothoracic surgery into a new dimension--one that changed the lives of individuals with congenital and acquired heart disease worldwide. Despite its contributions, CPB has clear limitations and creates unique challenges for clinicians and patients alike, stemming from profound hemostatic pertubations and accompanying risk for bleeding and possibly thrombotic complications.

Aprotinin does not prolong the Sonoclot aprotinin-insensitive activated clotting time

STUDY OBJECTIVE

To determine whether a new Sonoclot-based, aprotinin-insensitive activated clotting time (aiACT) assay yields stable results over a broad range of aprotinin concentrations.

DESIGN

Prospective trial conducted on in vitro blood samples.

SETTING

Tertiary-care teaching medical center.

PARTICIPANTS

19 healthy adult volunteers.

INTERVENTIONS

Whole blood samples were collected from volunteers. Heparin (2 U/mL) and escalating concentrations of aprotinin of 160 to 500 kallikrein inhibitory units (KIU)/mL were added in vitro.

MEASUREMENTS AND MAIN RESULTS

Celite ACT, kaolin ACT, and aiACT assays were completed. The aiACT showed stable activated clotting time (ACT) results on heparinized, noncitrated blood with added aprotinin (P = nonsignificant). In contrast, celite ACT and kaolin ACT were greatly prolonged when aprotinin was added to heparinized, noncitrated, and citrated blood (P < 0.05). The aiACT had consistent results at all aprotinin concentrations (P = nonsignificant).

CONCLUSIONS

Aprotinin (160, 320, and 500 KIU/mL) significantly prolongs the ACT value with celite and kaolin activators but not with the aprotinin-insensitive activator.

Coronary Artery Bypass Grafting Ameliorates the Decreased Plasma Adiponectin Level in Atherosclerotic Patients

Adiponectin functions as an anti-inflammatory and anti-atherogenic factor, and the decreased plasma adiponectin is a risk factor for coronary disease. The aim of this study was to determine the changes in plasma levels of adiponectin, a potential parameter for atherosclerosis, in patients underwent surgical revascularization. We included forty patients with atherosclerosis (age, 58 +/- 9 years; body mass index [BMI] 26.93 +/- 2.3 kg/m(2)) undergoing coronary artery bypass grafting (CABG). Control group consisted of 40 healthy volunteers, matched for age, gender and BMI (age, 56 +/- 6 years; BMI, 26.78 +/- 2.3 kg/m(2)). We measured various parameters, including high sensitive C-reactive protein (hsCRP), homeostasis model assessment-insulin resistance (HOMA-IR) indexes, and adiponectin. The baseline profile of the patients before CABG showed higher levels of serum hsCRP (13.15 +/- 2.40 mg/l vs 3.97 +/- 1.07 mg/l) and HOMA-IR (1.86 +/- 0.30 vs 1.26 +/- 0.33) and lower plasma adiponectin levels (7.02 +/- 2.01 microg/ml vs 25.46 +/- 3.9 microg/ml), compared to controls (p < 0.001 for each parameter). Plasma adiponectin level was increased one month after CABG from the baseline level to 8.67 +/- 2.05 microg/ml(p < 0.001), although the level was still lower than the control value. Thus, postoperative adiponectin level might be helpful for evaluating the progression of atherosclerosis. Moreover, CABG significantly decreased hsCRP to 7.25 +/- 1.89 mg/l and HOMA-IR to 1.59 +/- 0.33, although these levels were higher than the controls. These results suggest that CABG decreases the cardiac risk factors in atherosclerotic patients.

The effects of high-dose heparin on inflammatory and coagulation parameters following cardiopulmonary bypass

Systemic inflammation and the activation of the coagulation system following cardiopulmonary bypass (CPB) may contribute to postoperative complications. In vitro studies have demonstrated that heparin possesses anti-inflammatory properties. To ascertain the relative benefits of high versus low heparin doses, we studied the impact of varying heparin doses on the inflammatory response and coagulation system during and following CPB. Forty patients scheduled for elective coronary artery bypass surgery requiring CPB were randomized to either a low dose (300 U/kg) (Group L) or a high dose of unfractionated heparin (600 U/kg) (Group H). To evaluate the inflammatory response, proinflammatory cytokines [tumor necrosis factor-alpha and interleukin-6 (IL-6)] were measured at four different times: before CPB (T0), 30 min after the institution of CPB (T1), 30 min after cross-clamp release (T2), and 4 h after the end of CPB (T3). Thrombin-antithrombin complex, platelet factor 4 and anti-activated factor X heparin concentrations were also measured. Patients in Group H received greater heparin (44.934 U versus 27.741 U, P<0.001) and protamine (P=0.003) doses. Postoperative blood loss and blood products transfusions were not significantly different in the groups. At T1, mean heparin plasma concentration was higher in Group H (P<0.001). IL-6 was significantly lower in Group H compared with Group L (P=0.01) only at T1. Using a mixed-effects statistical model, tumor necrosis factor-alpha and IL-6 levels were comparable regardless of the heparin dose. Thrombin-antithrombin complex levels were lower in Group H (P=0.04) and platelet factor 4 levels were significantly lower in Group H at T2 (P=0.04). Higher heparin doses were associated with higher heparin concentrations during CPB. A high heparin dose achieved a better preservation of the coagulation system with less thrombin formation and platelet activation. The heparin dose had small influence on proinflammatory cytokines release.

Antithrombotic therapy in cardiac surgery

PURPOSE

To review the perioperative management of antithrombotic therapy in cardiac surgery, including the management of cardiopulmonary bypass (CPB) and off-pump surgery.

METHODS

A review of the relevant English literature over the period 1975-2005 was undertaken, in addition to a review of international practices in antithrombotic therapy in cardiac surgery.

PRINCIPAL FINDINGS

Cardiopulmonary bypass is required in most procedures and makes anticoagulation mandatory. Anticoagulation is, usually, achieved with unfractionnated heparin (UFH). Unfractionated heparin is monitored by point-of-care (POC) testing, such as the activated clotting time or the determination of heparin concentration. The target values of both tests remain empirical, with no clearly validated thresholds. The target value needs to be adjusted according to the POC test, given significant variations between devices and activators. After CABG, the need for antiplatelet therapy is well demonstrated, in order to limit the risk of postoperative death or ischemic events, and improve venous graft patency. Immediately after valvular surgery, antithrombotic therapy should take into account the specific risk carried by each patient and by each prosthetic device. The risk of venous thromboembolism, though poorly defined, is also present in the postoperative period and may require additional attention. Given the frequent exposure to UFH, occurrence of heparin-induced thrombocytopenia is not infrequent in these patients and requires careful individual management.

CONCLUSIONS

Antithrombotic therapy is an essential component of cardiac surgery. Yet, with the exception of antiplatelet agents in CABG patients, antithrombotic therapy is often based on the clinical experience of medical teams more than on an evidence-based assessment of the literature.

Postoperative treatment with low molecular weight heparin after right heart assist for coronary artery bypass grafting

Right heart assist (RHA) was used for coronary artery bypass grafting (CABG). We explored the affection of the coagulation system during surgery and evaluated two different antithrombotic treatments postoperatively. The pilot study comprised 14 patients. During surgery activated clotting time (ACT) was kept > 200 sec. By random the patients were selected to different postoperative treatments. The control group received acetyl salicylic acid (ASA) 150 mg daily, the intervention group received ASA 150 mg daily and Low Molecular Weight Heparin (LMWH) 5000 IU x2 for three days. Serum levels of prothrombin fragment 1 and 2 (F 1 + 2), plasmin-antiplasmin product (PAP), anti-Xa activity and functional antithrombin (ATIII) were measured. During surgery there was no increase of F 1 + 2 or PAP. After protamin was administered there was a significant increase of F 1 + 2 but not in PAP during the next 6 hours. Postoperative antithrombotic treatment with LMWH seems to normalise F1 + 2 while ASA does not. ACT level > 200 sec. seems sufficient for RHA-CABG surgery. Fibrinolytic agents are not necessary. It seems that postoperative LMWH treatment prevents increased thrombin formation. General recommendations with respect to antithrombotic treatment beyond ASA can not be made based on study.

The effect of haemodilution on antithrombin concentration during cardiac surgery

The effect of haemodilution on antithrombin concentration was investigated in 73 patients undergoing elective cardiac surgery with and without cardiopulmonary bypass. In patients who required cardiopulmonary bypass (n = 45), the antithrombin concentration fell to 52% of baseline during surgery (24.2 mg.dl(-1) to 12.6 mg.dl(-1)), and the haemoglobin level fell to 55% (136 g.l(-1) to 75 g.l(-1)). In patients who did not require cardiopulmonary bypass (n = 28), the antithrombin concentration fell to 82% of baseline (23.7 mg.dl(-1) to 19.5 mg.dl(-1)), and the haemoglobin concentration fell to 78% (141 g.l(-1) to 109 g.l(-1)). The overall correlation coefficient (r) for changes in antithrombin and haemoglobin concentrations was 0.76. The results indicate that most of the decrease in concentration of antithrombin during cardiac surgery is a consequence of cardiopulmonary bypass and is due to haemodilution. This data demonstrates that the percentage decrease in haemoglobin concentration can be used to estimate the percentage decrease in antithrombin concentration that occurs during cardiac surgery, if blood products that might effect the results are not administered between measurements.

Direct thrombin inhibitors: pharmacology and clinical relevance

Although heparin has been a cornerstone of treatment for the prevention of thrombosis, it is limited by its adverse effects and unpredictable bioavailability. Direct thrombin inhibitors are a novel class of drugs that have been developed as an effective alternative mode of anticoagulation in patients who suffer from heparin-induced thrombocytopaenia, and for the management of thromboembolic disorders and acute coronary syndromes. The main disadvantages of the direct thrombin inhibitors are the lack of an antidote or readily available clinical monitoring. The mechanism of action, the properties of direct thrombin inhibitors and their potential to replace currently available anticoagulants are reviewed.

Bleeding in Cardiac Surgery: Its Prevention and Treatment—an Evidence-Based Review

Expected and unexpected bleeding occur frequently in patients undergoing cardiac surgery. Bleeding after cardiac surgery can be broadly divided into two groups: surgical (unrecognized bleeding vessel, anastomosis, or other suture line) or nonsurgical bleeding (caused by coagulopathy). Factors influencing both surgical and nonsurgical bleeding can be further broken down into those occurring preoperatively and those that occur intraoperatively and postoperatively. A thorough understanding of these factors is necessary to reduce bleeding. This is a desirable clinical goal, because excessive bleeding is associated with adverse outcomes.

Bidirectional Glenn Shunt Surgery Using Lepirudin Anticoagulation in an Infant with Heparin-Induced Thrombocytopenia with Thrombosis

There are few reports of the management of pediatric patients with heparin-induced thrombocytopenia (HIT) requiring cardiac surgery using currently available anticoagulants. We report a case of an infant with HIT requiring a bidirectional Glenn shunt who was successfully managed using lepirudin (r-hirudin, Refludan; Aventis, Bridgewater, NJ). Dosing and monitoring of anticoagulation were difficult, and we suggest caution in the use of lepirudin for cardiac surgery unless reliable monitoring of the degree of anticoagulation becomes available.

Monitoring anticoagulation and hemostasis in cardiac surgery

The need to monitor anticoagulation and hemostasis during and after cardiac surgery has led to recognition of the importance of evaluation and use of hemostasis monitors in this setting. Consequently, rapid and accurate identification of abnormal hemostasis has been the major impetus for the development of point-of-care tests and their use in transfusion algorithms for cardiac surgical and other critically ill patients.

Antithrombin-heparin covalent complex: a possible alternative to heparin for arterial thrombosis prevention

BACKGROUND

The anticoagulant effect of heparinoids is attributed to their cofactor activity for antithrombin (AT) and heparin cofactor II. In patients with thrombosis, however, thrombin is often protected from AT-dependent, heparin-mediated inactivation. The purpose of this study was to compare the properties of unfractionated/standard heparin (UFH/SH) and those of a novel covalent AT-heparin complex (ATH) in a rabbit arterial thrombosis prevention and bleeding model.

METHODS AND RESULTS

Thrombosis in the distal aorta was triggered by vessel wall injury and critical stenosis. Blood flow in the damaged arterial segment was monitored with a flow probe placed distal to the constrictor. Rabbits were given doses of SH (62.5 to 187.5 IU x kg(-1) x 90 min(-1)) or ATH (16 to 65 IU x kg(-1) x 90 min(-1)). Cumulative blood loss from skin incisions was used to assess drug safety. The antithrombotic effects of ATH were greater than those of SH as measured by clot weight, blood flow, and vessel patency; eg, complete thrombus resolution was achieved with ATH (33 to 65 IU/kg), but not SH (125.0 to 187.5 IU/kg). At doses that produced equivalent vessel patency (50% to 60%), blood loss induced by ATH (60.2 microL) was 2.6-fold lower (P<0.05) than that induced by SH (154.6 microL).

CONCLUSIONS

In our experimental system, ATH was able to control arterial thrombosis more effectively than its SH precursor, without pronounced bleeding.

The plasma supplemented modified activated clotting time for monitoring of heparinization during cardiopulmonary bypass: a pilot investigation

The standard celite or kaolin activated clotting time (ACT) correlates poorly with heparin levels during cardiopulmonary bypass (CPB). We compared a modified kaolin ACT, in which plasma was supplemented, to a standard undiluted kaolin ACT for monitoring heparin levels during CPB. Fifteen patients undergoing normothermic CPB were enrolled in this prospective study. Heparin management was performed according to the Hepcon HMS results (Medtronic, Minneapolis, MN). The ACTs were performed with the ACT II device (Medtronic). Hepcon HMS calculations, standard kaolin ACTs, and plasma supplemented modified ACTs (mACTs), prepared by diluting blood samples 1:1 with human plasma (Behring, Marburg, Germany), were measured every 30 min during CPB. The data obtained were correlated to the plasma chromogenic anti-Xa activity as a reference assay for heparin levels. A total of 64 samples were evaluated. The chromogenic anti-Xa activity ranged from 0.2 to 5.5 IU/mL. The Hepcon HMS calculations ranged from 2.7-8.2 IU/mL of heparin, the standard ACT ranged from 424 to >999 s, and the mACT ranged from 210 to 801 s. The correlation to the chromogenic anti-Xa method was r = 0.43 for the standard kaolin ACT and r = 0.69 for the plasma mACT. The plasma mACT provided an improved correlation to chromogenically measured levels of anti-Xa activity during CPB. The improved correlation most likely results from a correction of the effects of the impairment of the coagulation system caused by hemodilution and consumption of procoagulants on extracorporeal surfaces.

IMPLICATIONS

During cardiopulmonary bypass, the plasma modified kaolin activated clotting time (ACT) provides a better correlation with heparin levels than the standard kaolin ACT.