Can the use of thromboelastography predict and decrease bleeding and blood and blood product requirements in adult patients undergoing cardiac surgery?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether use of thromboelastography could predict and decrease bleeding and blood and blood product requirements in adult patients undergoing cardiac surgery. Altogether 170 papers were identified using the reported search strategy of which 14 represented the best evidence on the topic. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses were tabulated. We conclude that thromboelastography may be useful in predicting patients who are likely to bleed postoperatively but more importantly, it can guide transfusion therapy algorithms in the bleeding cardiac surgical patient resulting in significant decreases in blood and blood component transfusion requirements. However, the technique remains unvalidated in the eyes of many haematologists and further large studies involving them are required to fully validate its use and to define the 'ideal' treatment algorithm.     

Does use of aprotinin decrease the incidence of stroke and neurological complications in adult patients undergoing cardiac surgery?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether aprotinin use was associated with a lower incidence of stroke and neurological complications in adult patients undergoing cardiac surgery. Using the reported search 224 papers were identified on Medline, 722 on Embase and 12 by hand-searching reference lists. Eight papers represented the best evidence on the subject and the author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results and study comments and weaknesses were tabulated. We conclude that there is evidence from three meta-analyses and two more recent RCTs that the use of aprotinin is associated with a decreased incidence of stroke and neurological complications in some patients undergoing cardiac surgery. However, many single studies within these meta-analyses are small and designed to look at other outcomes so are underpowered for neurological outcome. In contrast, however, a recent cohort study has raised concerns about aprotinin, suggesting that its use is associated with a significant increased risk of stroke in uncomplicated CABG surgery. Ideally further large well-constructed RCTs are required to give a definitive answer to this question and determine the most appropriate dose but given recent concerns, data may have to be obtained from large better controlled cohort studies.     

Can ventilation while on cardiopulmonary bypass improve post-operative lung function for patients undergoing cardiac surgery?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether ventilation during cardiopulmonary bypass (CPB) improves post-operative lung function. Altogether 187 relevant papers were identified using the below mentioned search, 9 papers represented the best evidence to answer the question. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses were tabulated. We conclude that a wide range of ventilatory strategies, while on cardiopulmonary bypass, have been attempted including CPAP with positive airway pressures of 5-15 cm H(2)O, high frequency low volume ventilation (with 100 breaths per min), inspired oxygen concentrations from 21% to 100% and bilateral extra-corporeal circulation using the lungs to oxygenate the blood while on bypass. While some small and transient benefits for CPAP with 10 cm H(2)O have been demonstrated, no convincing clinical benefits for any of these strategies have been shown and thus ventilation while on cardiopulmonary bypass cannot be supported as a strategy to improve post-operative lung function.     

Does a hyperoncotic cardiopulmonary bypass prime affect extravascular lung water and cardiopulmonary function in patients undergoing coronary artery bypass surgery?

OBJECTIVE: Different types of colloidal priming for cardiopulmonary bypass (CPB) have been used to reduce fluid load and to avoid the fall of plasma colloid osmotic pressure (COP) that leads to edema formation and consequently can cause organ dysfunction. The discussion about the optimal priming composition, however, is still controversial. We investigated the effect of a hyperoncotic CPB-prime with hydroxyethyl starch (HES) 10% (200;0.5) on extravascular lung water (EVLW) and post-pump cardiac and pulmonary functions. METHODS: In 20 randomized patients undergoing elective coronary artery bypass graft surgery (CABG), a colloid prime (COP: 48 mmHg, HES-group, n = 10) and a crystalloid prime (Ringer's lactate, crystalloid group, n = 10) of equal volume were compared with respect to the effects on cardiopulmonary function. Cardiac index (CI), mean arterial pressure (MAP), pulmonary capillary wedge pressure (PCWP), systemic vascular resistance index (SVRI), pulmonary artery pressure (PAP), pulmonary vascular resistance index (PVRI), alveolo-arterial oxygen difference (AaDO(2)), pulmonary shunt fraction (Q(s)/Q(T)), EVLW (double-indicator dilution technique with ice-cold indocyanine green), COP, fluid balance and body weight were evaluated peri-operatively. RESULTS: Pre-operative demographic and clinical data, CPB-time, cross-clamp time and the number of anastomoses were comparable for both groups. During CPB, COP was reduced by 20% in the HES-group (18.9 +/- 3.7 vs. 23.7 +/- 2.2 mmHg, P < 0.05) while it was reduced by more than 50% of the pre-CPB value (9.8 +/- 2.0 vs. 21.4 +/- 2.1 mmHg, P < 0.05) in the crystalloid group (P < 0.05 HES- vs. crystalloid group). Post-CPB EVLW was unchanged in the HES-group but it was elevated by 22% in the crystalloid group (P < 0.05 HES- vs. crystalloid group), CI was higher in the HES-group (3.4 +/- 0.3 vs. 2.7 +/- 0.5l/min, P < 0.05). Fluid balance was less in the HES-group (813 +/- 619 vs. 2143 +/- 538, P < 0.05). Post-operative weight gain could be prevented in the HES-group but not in the crystalloid group (1.5 +/- 1.2 vs. -0.3 +/- 1.5, P < 0.05). No significant differences were seen for MAP, PAP, PCWP, SVRI, PVRI, AaDO(2) and (Q(s)/Q(T)) between the two groups at any time. CONCLUSIONS: Hyperoncotic CPB-prime using HES 10% improves CI and prevents EVLW accumulation in the early post-pump period, while pulmonary function is unchanged. This effect can be of benefit especially in patients with congestive heart failure.     

Platelet mapping as part of modified thromboelastography (TEG(®) ) in patients undergoing cardiac surgery and cardiopulmonary bypass

The platelet‐mapping assay of the thromboelastograph was used to measure platelet aggregation and to examine the effect of cardiopulmonary bypass on multiple platelet receptors and the role of altered receptor activity in postoperative bleeding. The percentage platelet aggregation for collagen, adenosine diphosphate and arachidonic acid was measured in 40 patients divided post‐hoc into high‐ or low‐bleeding groups depending on postoperative 24‐h chest tube output. Platelet aggregation was lower after cardiopulmonary bypass compared to before it using collagen (mean (SD) 45 (25) vs 19 (12) %, p < 0.001), adenosine diphosphate (76 (23) vs 35 (24) %, p < 0.001), and arachidonic acid (61 (33) vs 31 (35) %, p < 0.001). Only platelet aggregation as measured using collagen pre‐ and post‐cardiopulmonary bypass was significantly less in the high‐ compared to the low‐bleeding group. This finding was significantly correlated with the 24‐h chest tube drainage, and it predicted postoperative bleeding with a sensitivity of 83% and a specificity of 68%. Therefore, platelet aggregation is reduced following cardiopulmonary bypass, and this may play a role in predicting postoperative blood loss.     

Clopidogrel-related refractory bleeding after coronary artery bypass graft surgery: a rationale for the use of coagulation factor concentrates?

Clopidogrel, an irreversible ADP-receptor antagonist, inhibits platelet aggregation mediated by reduced activation of glycoprotein receptor IIb/IIIa. Clopidogrel in combination with aspirin has been shown to be superior to aspirin alone for treating unstable angina, but clopidogrel recipients have shown increases in blood loss, transfusion requirements, and rate of reoperation after cardiac surgery. We describe a patient who had taken clopidogrel 75 mg daily until the day prior to coronary artery bypass graft surgery. Severe postoperative bleeding developed and was refractory to conventional hemostatic therapy consisting of 19 units of packed red blood cell concentrates, 16 of fresh frozen plasma, 8 of platelet apheresis concentrates plus high-dose treatment with aprotinin (500.000 kallikrein-inhibiting units/h) and administration of 0.3 microg/kg 1-deamino-8-D-arginine vasopressin (DDAVP). Two reoperations were performed, but surgical hemostasis was not achieved, so 100 microg/kg recombinant activated factor VII was applied to generate sufficient thrombin to stop the bleeding. This treatment approach reduced the bleeding. Then, to promote clot formation and firmness, 2 g of fibrinogen and 1250 IU of factor XIII were administered, and the bleeding finally stopped. No further transfusions were required, and the patient was discharged from the hospital on day 10 after the operation. This case suggests that in clopidogrel-related bleeding refractory to conventional hemostatic therapy, hemostasis may be achieved by a stepwise administration of coagulation factor concentrates.