The activated clotting time in cardiac surgery: should Celite or kaolin be used?

Objectives: Both kaolin- and Celite-activated clotting times (ACT) are used to guide anticoagulation during cardiopulmonary bypass. It is unknown whether these methods lead to similar management procedures for anticoagulation in patients and are thus interchangeable in terms of bias, precision and variability. Methods: We randomized 97 patients undergoing coronary artery bypass grafting or aortic valve replacement to either kaolin- or Celite-guided anticoagulation. The ACT was measured simultaneously with the other method. We administered 300 IU/kg heparin to obtain initial ACT values greater than 400 s and additional heparin in each group using the minimum value of duplicate measurements according to a predefined protocol. The primary end point was the total heparin dose and the number of heparin supplements. Results: The total heparin dose per patient in the 48 Celite-guided patients was 35 271 ± 12 406 IU with 51 supplements and in the 49 kaolin-guided patients, 35 997 ± 11 540 IU ( P = 0.77) with 56 supplements ( P = 0.53). Postoperative thrombin generation time, fibrinolytic response time, chest tube loss and transfusion requirements were not different between the two groups. However, the methods differed in individual patients with regard to supplemental heparin ( P = 0.002). Bias between methods at baseline was +10.3%, Celite being higher, and changed to a value of -12.9% at 2 h bypass. The coefficient of variation at baseline for individual patients was 2.6 times larger with kaolin than with Celite ( P < 0.001). Correlation between ACT values at baseline was only 45%. Conclusions: Kaolin- and Celite-guided management of anticoagulation is clinically not different, but the methods are not interchangeable. Clinical registration number: www.trialregister.nl identifier 1738.

Platelet function in stored heparinised autologous blood is not superior to in patient platelet function during routine cardiopulmonary bypass.

BACKGROUND: In cardiac surgery, cardiopulmonary bypass (CPB) and unfractionated heparin have negative effects on blood platelet function. In acute normovolemic haemodilution autologous unfractionated heparinised blood is stored ex-vivo and retransfused at the end of the procedure to reduce (allogeneic) transfusion requirements. In this observational study we assessed whether platelet function is better preserved in ex vivo stored autologous blood compared to platelet function in the patient during CPB. METHODOLOGY/PRINCIPAL FINDING: We measured platelet aggregation responses pre-CPB, 5 min after the start of CPB, at the end of CPB, and after unfractionated heparin reversal, using multiple electrode aggregometry (Multiplate®) with adenosine diphosphate (ADP), thrombin receptor activating peptide (TRAP) and ristocetin activated test cells. We compared blood samples taken from the patient with samples taken from 100 ml ex-vivo stored blood, which we took to mimick blood storage during normovolemic haemodilution. Platelet function declined both in ex-vivo stored blood as well as in blood taken from the patient. At the end of CPB there were no differences in platelet aggregation responses between samples from the ex vivo stored blood and the patient. CONCLUSION/SIGNIFICANCE: Ex vivo preservation of autologous blood in unfractionated heparin does not seem to be profitable to preserve platelet function.

Bivalirudin is inferior to heparin in preservation of intraoperative autologous blood.

INTRODUCTION: Bivalirudin is used as an alternative to heparin in cardiac surgery, and may be superior to heparin with regard to platelet function. Bivalirudin however, is prone to cleavage by thrombin resulting in coagulation in areas of stasis. MATERIAL AND METHODS: We compared the preservation of platelet function and the quality of anticoagulation in autologous blood of 26 cardiac surgical patients collected intraoperatively and anticoagulated ex vivo with either bivalirudin or heparin, with supplementation of bivalirudin over time and prevention of stasis. RESULTS: We found in both preservatives a reduction in ADP-induced platelet aggregation response over a period of 105 minutes (median, IQR: 73-141) as measured by Multiplate®. Supplementation of additional bivalirudin (23 ± 1.1 µg/ml/hr) and prevention of stasis was not able to prevent thrombin generation. We found a 5-fold increase in levels of prothrombin fragment 1+2 in bivalirudin preserved autologous blood as compared to heparin preserved blood (F(1+2) levels median 8.9 nM [quartile percentiles 4.2-12.4] vs 1.3 nM [0.6-2.1], P=0.001 Mann-Whitney, n=10). CONCLUSIONS: Our study suggests that preservation of platelet function in autologous blood anticoagulated with bivalirudin is not a suitable alternative to heparin.

An assessment of clinical interchangeability of TEG and RoTEM thromboelastographic variables in cardiac surgical patients.

BACKGROUND: Bedside thromboelastography is increasingly used, but an assessment of the clinical interchangeability of the 2 major systems, TEG (Hemoscope) and RoTEM (Pentapharm), has not been performed. METHODS: We measured blood samples from 46 cardiac surgical patients after induction of anesthesia with kaolin TEG(R) (kaoTEG), native TEG(R) (natTEG), intrinsic RoTEM (inTEM), and extrinsic RoTEM (exTEM). Each measurement consisted of reaction time (R), coagulation time (K), maximum amplitude (MA), and angle (alpha). Bland-Altman plots and mixed-model analysis were used. To assess repeatability, we made 7 replicated measurements in rapid succession in 2 volunteers. RESULTS: One hundred sixty-six measurements were available for analysis. The R time of the kaoTEG (345 + or - 102 seconds, mean + or - sd) was longer than that of the inTEM (179 + or - 74 seconds, P < 0.001) and the exTEM (55 + or - 28 seconds, P < 0.001). The K time of the kaoTEG (78 + or - 18s) was not different from that of the inTEM (75 + or - 52 seconds, P = 0.60) but was longer than the K time of the exTEM (61 + or - 24 seconds, P < 0.003). The MA of the kaoTEG (71 + or - 6.5 mm) was larger than the MA of the inTEM (67 + or - 5.2 mm, P < 0.02) and almost similar to that of the exTEM (69 + or - 6.3 mm). The alpha of the kaoTEG (72 degrees + or - 4.1 degrees ) was not significantly different from that of both the inTEM (76 degrees + or - 7 degrees ) and the exTEM (79 degrees + or - 4.5 degrees ). The variability for MA and alpha was <10%. The repeatability of the R and K times was poor in both devices, whereas the repeatability of the MA and alpha was sufficient for clinical purposes. CONCLUSIONS: The TEG and RoTEM measurements demonstrated a close correlation for the MA, but the alpha did not for the R and K variables. The kaoTEG had the best agreement with the exTEM measurement. Therefore TEG and RoTEM measurements are not completely interchangeable, and the clinical interpretation of thromboelastograhic data should be used with caution.

Effects of preemptive enoximone on left ventricular diastolic function after valve replacement for aortic stenosis.

OBJECTIVE: Left ventricular (LV) hypertrophy is associated with increased diastolic chamber stiffness early after aortic valve replacement for valve stenosis. Enoximone, a phosphodiesterase III inhibitor, has been shown to improve myocardial contractility and relaxation when administered as a single dose after cardiac surgery. The present study investigated, by analysis of transmitral flow velocity patterns and end-diastolic pressure-area relations, whether enoximone administered before aortic valve surgery has an effect on LV diastolic properties. DESIGN: Prospective, randomized study. SETTING: Referral center for cardiothoracic surgery at a university hospital. PARTICIPANTS: Thirty-four patients undergoing aortic valve replacement for aortic stenosis. INTERVENTIONS: Patients in the enoximone group (n = 17) received a bolus dose of 0.35 mg/kg (0.15 mg/kg before aortic cross-clamping and 0.2 mg/kg added to the cardioplegic solution). Individual pressure-area relations (pulmonary capillary wedge pressure v left ventricular end-diastolic area) were obtained by using volume loading by leg elevation before and after surgery with closed chest. MEASUREMENTS AND MAIN RESULTS: The pressure-area relation on the pressure-area plot was shifted to the left after surgery, indicating decreased LV diastolic distensibility in the enoximone and control groups and providing evidence of decreased LV diastolic function. Indices of LV diastolic chamber stiffness, LV operating stiffness (K(LV)) derived from the deceleration time of early ventricular filling, and the constant of chamber stiffness (beta) derived from pressure-area relations were not different after enoximone treatment. Systolic LV function was unaltered after cardiac surgery in both groups. Analysis of changes in transmitral flow patterns identified an increased atrial filling fraction in enoximone-treated patients, suggesting increased atrial systolic function. The unaltered systolic pulmonary venous flow velocity compared with the decrease in the control group after volume loading further supports preservation of left atrial reservoir function with enoximone in the absence of evidence for decreased LV stiffness. CONCLUSION: Preemptive enoximone did not change LV diastolic function based on diastolic filling patterns or LV stiffness indices (K(LV) and beta) derived from Doppler early filling deceleration time and pressure-area relations. Doppler data suggested improvement of left atrial systolic function and preservation of left atrial reservoir function with enoximone.

Red blood cell aggregation during cardiopulmonary bypass: a pathogenic cofactor in endothelial cell activation?

OBJECTIVE: The bio-incompatibility of the cardiopulmonary bypass (CPB) circuit and the use of artificial colloids trigger massive defense reaction that involves endothelial cells and several blood cells: platelets, neutrophils, monocytes, red blood cells (RBC) and lymphocytes. Investigating the effects on RBC aggregation and endothelial cells activation, the present study addresses two different prime solutions commonly used in the clinical practice. METHODS: RBC aggregation was measured by means of Laser-assisted Optical Rotation Cell Analyzer, in an in vitro study designed to mimic the human blood-material interactions during extracorporeal circulation. A clinical study investigating endothelial activation was conducted in 20 patients undergoing elective coronary bypass surgery, randomly assigned for CPB using two different priming solutions: HAES-steril 6% (HES 200/0.5) and Voluven 6% (HES 130/0.4). RESULTS: Circulation trough a Chandler loop of HES-blood mixes altered significantly RBC aggregability. The use of HES 130/0.4 resulted in marked decrease in RBC aggregation (aggregation index (AI) before and after circulation was 23.5+/-3.8 and 18+/-2.9, respectively), no significant differences being found when compared with Ringer's lactate group. The use of HES 200/0.5 resulted in better maintained RBC aggregation (AI 39.7+/-5.9 and 29.7+/-4.7 before and after circulation, respectively). The AI measured for the whole blood (control) sample was 61.9+/-4.9 before circulation, and 58.1+/-4 after. Markers of endothelial activation (von Willebrand factor (vWF), thrombomodulin (TM), tissue plasminogen activator (tPA) and E-selectin) significantly increased during CPB. Differences between HES treatment groups were evident post-bypass. While the markers of endothelial activation returned to baseline in HES 200/0.5 group, HES 130/0.4 was associated on the first post-operative day with further increase of vWF and tPA. CONCLUSION: RBC aggregation significantly drooped as consequence of blood dilution and blood-material interaction. We reason that low RBC aggregation added to plasma viscosity reduction and non-physiologic flow conditions during extracorporeal circulation are important factors contributing to loss of shear stress at the venous endothelial wall. The loss of shear stress triggers complex signaling leading to endothelial activation. Additional fundamental research is needed in order to verify the hypothesis introduced by the present study. Characterizing the impact of rheologic parameters on endothelial function could prove to be valuable in patients undergoing CPB.

Sinus node function after cardiac surgery: is impairment specific for the maze procedure?

BACKGROUND: Maze surgery is a final solution for intractable atrial fibrillation (AF), but an adverse effect on postoperative sinus node function has been reported. Whether this also applies to other types of cardiac surgery is unclear. METHODS: We assessed postoperative rhythm by means of repeated exercise tolerance testing, ambulatory electrocardiography, and non-invasive testing of autonomic function between 1 and 12 months after four types of cardiac surgery. Fourteen patients without structural cardiac disease and medically refractory AF underwent the maze III procedure, 11 patients with mitral valve disease and preoperative AF underwent valvar surgery combined with a (simplified) maze III procedure, and 8 patients with mitral valve disease in sinus rhythm (SR) underwent isolated valvar surgery. The control group consisted of eight patients with sinus rhythm who underwent coronary artery bypass surgery (CABG). RESULTS: One month after surgery, the chronotropic response to exercise was depressed, mean heart rate was high, and heart rate variability (HRV) was low, especially after maze III, combined surgery, and isolated valvar surgery. Twelve months after surgery, moderate improvements were observed. After CABG, considerably fewer abnormalities were observed, and HRV parameters recovered to a large extent. Non-invasive testing of autonomic function indicated disturbed vagal modulation of heart rate in all three groups with atrial incision. CONCLUSION: Thus, attenuation of HRV and vagal modulation of sinus node function are not confined to maze surgery but also apply to isolated mitral valve surgery. Atrial incision therefore appears to be crucial and presumably produces autonomic nervous damage followed by partial reinnervation. Nevertheless, cardiac surgery in general seems initially to impair sinus node function with partial recovery in the consecutive 12 months.