Cardiopulmonary bypass and dual antiplatelet therapy: a strategy to minimise transfusions and blood loss.

BACKGROUND: Patients with preoperative dual antiplatelet therapy prior to coronary artery bypass surgery are at risk of bleeding and blood component transfusion. We hypothesise that an optimised cardiopulmonary bypass strategy reduces postoperative blood loss and transfusions. METHODS: In total, 60 patients admitted for coronary artery bypass grafting with ticagrelor and aspirin medication withdrawn <96 hours before surgery were prospectively randomised into two equal sized groups. Cardiopulmonary bypass combined a closed Cortiva® heparin-coated circuit with low systemic heparinisation (activated clotting time < 250 seconds) and intraoperative cell salvage in the study group, whereas the control group used a Balance® coated open circuit, full systemic heparinisation (activated clotting time > 480 seconds) and conventional cardiotomy suction. This perfusion strategy was evaluated by the chest drain volume after 24 hours, perioperative haemoglobin and platelet loss accompanied by global coagulation assessments. RESULTS: Patients in the study group demonstrated significantly better outcomes signified by lower blood loss 554 ± 224 versus 1,100 ± 989 mL (p < 0.001), reduced packed red cell transfusion 7% versus 53% (p < 0.001), reduced haemoglobin -28 ± 15 versus -40 ± 14 g/L (p = 0.004) and platelet loss -35 ± 36 versus -82 ± 67 × 109/L (p = 0.001). Indices of rotational thromboelastometry indicated shorter clotting times within the internal and external pathways. Adenosine diphosphate activated platelet function was within normal range based on Multiplate® aggregometry, while ROTEM® platelet analyses indicated inhibited function both preoperatively and post-bypass. Platelet inhibition by aspirin was verified throughout the perioperative period. Platelet function showed no intergroup differences. CONCLUSION: A stringent perfusion strategy reduced blood loss and transfusions in dual antiplatelet therapy patients requiring urgent surgery.

The scientific evidence of arterial line filtration in cardiopulmonary bypass.

BACKGROUND: The indication for arterial line filtration (ALF) is to inhibit embolisation during cardiopulmonary bypass. Filtration methods have developed from depth filters to screen filters and from a stand-alone component to an integral part of the oxygenator. For many years, ALF has been a standard adopted by a majority of cardiac centres worldwide. The following review aims to summarize the available evidence in support for ALF and report on its current practice in Europe. METHOD: The principles and application of ALF in Europe was investigated using a survey conducted in 2014. The scientific evidence for ALF was examined by performing a systematic literature search in six different databases, using the following search terms: "Cardiopulmonary bypass AND filters AND arterial". The primary endpoint was protection against cerebral injury verified by the degree of cerebral embolisation or cognitive tests. The secondary endpoint was improvement of the clinical outcome verified elsewise. Only randomised clinical trials were considered. RESULTS: The response rate was 31% (n=112). The great majority (88.5%) of respondents were using ALF, following more than 10 years of experience. Integrated arterial filtration was used by 55%. Of respondents not using ALF, fifty-four percent considered starting using integrated arterial filtration. The systematic literature database search returned 180 unique publications where 82 were specifically addressing ALF in cardiopulmonary bypass. Only four out of the 82 identified publications fulfilled our inclusion criteria. Of these, three were more than 20 years old and based on the use of bubble oxygenation. CONCLUSION: ALF is a standard implemented in a majority of cardiopulmonary bypass procedures in Europe. The level of scientific evidence available in support of current arterial line filtration methods in cardiopulmonary bypass is, however, poor. Large, well-designed, randomised trials are warranted.

Reversal of heparin after cardiac surgery: protamine titration using a statistical model.

OBJECTIVE: To establish a statistical model for determination of protamine dose in conjunction with cardiopulmonary bypass. DESIGN: Prospective. SETTING: University hospital. PARTICIPANTS: Ninety consecutive cardiac surgical patients. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A series of clinically oriented variables were introduced into a statistical model for projection of the protamine dose after cardiopulmonary bypass. The following significant predictors were identified using multivariable regression analysis: The patient's body surface area, the administered dose of heparin, heparin clearance, and the preoperative platelet count. The statistical model projected the protamine dose within 3±23 mg of the point-of-care test used as reference. CONCLUSION: Protamine dosing based on statistical modeling represents an alternative to point-of-care tests.

Can the oxygenator screen filter reduce gaseous microemboli?

Gaseous microemboli (GME) define small bubbles as < 200 microm in size. GME are reported to increase morbidity after cardiopulmonary bypass (CPB) and cardiac surgery. To prevent intrusion of GME into the systemic circulation during CPB, arterial line filtration is generally recommended. New trends in oxygenator design promote location of arterial filtration as an integral part of the oxygenator housing. The present experimental study aimed to evaluate the GME removal properties of an integrated arterial screen filter in a standard microporous oxygenator. The GME properties of Terumo Capiox FX25 with an integrated arterial screen filter was assessed in an experimental setup and compared with Capiox RX25, in which no arterial screen filter is present. A blood analog prime solution was recirculated using a roller pump at 4 and 6 L per minute flow rate, respectively, through a customized CPB circuit comprising oxygenator, reservoir, and connecting tubing. A controlled volume of air was introduced into the circuit. The GME activity was measured and computed using a Gampt BCC200 ultrasonic device placing one probe at the venous inlet and one other at the arterial outlet of the oxygenator. Transmembrane delta values of GME activity were used to calculate the removal efficacy based on counts and volume of GME. Use of screen filtration reduced the GME volume by 99.1% +/- .1% compared with 98.0% +/- .1% for controls at 4 L/min flow rate (p < .001). At 6 L/min, the reduction was 97.9% +/- .1% compared with 97.0% +/- .1% (p < .001). In contrast, the reduction of GME counts was less effective after screen filtration compared with controls: 89.6 +/- .6% versus 91.4 +/- .4% at 4 L/min and 55.6% +/- 1.6% versus 76.0% +/- 1.4% at 6 L/min, respectively (p < .001). The tested oxygenator with incorporated arterial screen filter reduced GME activity based on the calculated volume at the same time as counts of GME increased.

A microscopic view of gaseous microbubbles passing a filter screen.

PURPOSE: The aim of this study was to investigate the filtration efficacy of a 38-µm 1-layer screen filter based on Doppler registrations and video recordings of gaseous microbubbles (GME) observed in a microscope. METHODS: The relative filtration efficacy (RFE) was calculated from 20 (n = 20) sequential bursts of air introduced into the Plasmodex® primed test circuit. RESULTS: The main findings indicate that the RFE decreased (p = 0.00), with increasing flow rates (100-300 mL/min) through the filter screen. This reaction was most accentuated for GME below the size of 100 µm, where counts of GME paradoxically increased after filtration, indicating GME fragmentation. For GME sized between 100-250 µm, the RFE was constantly >60%, independently of the flow rate level. The video recording documenting the GME interactions with the screen filter confirmed the experimental findings. CONCLUSIONS: The 38-µm 1-layer screen filter investigated in this experimental setup was unable to trap gaseous microbubbles effectively, especially for GME below 100 µm in size and in conjunction with high flow rates.