Blood management issues: getting clots together when you want them.

Coagulation is a complex process that allows whole blood to form clots at tissue and vessel sites where damage has occurred. Activation of the hemostasis system causes platelets and fibrin-containing clot to stop the bleeding. Perfusionists must find ways to preserve the coagulation system if we are to avoid bleeding in the cardiopulmonary bypass patient. It is still unclear what techniques are best to continue maintaining hemostasis and avoiding transfusion in patients requiring cardiopulmonary bypass (CPB). There are numerous factors that come into play with the use of CPB including deactivating the coagulation system with anticoagulants, hemodilution of the circulating blood volume, inflammatory response, and a possible pro-coagulant response from protamine with heparin reversal once the surgical procedure has been completed and CPB terminated. All these factors make achieving hemostasis post CPB extremely difficult. This review attempts to assess what is currently being discussed in the literature, which may improve hemostasis with cardiopulmonary bypass. There is still no one technique that will improve hemostasis post CPB. Perhaps the answer may lie in a combination of reported techniques that may in some way lead to the preserving of coagulation factors during CPB.

Getting it right: optimizing transfusion management during the procedure.

There is little doubt that blood transfusions have saved many lives in cases of acute hypovolemia and anemia, but both the literature and practitioners still do not agree as to what the appropriate indicators for transfusion are in a cardiac surgical patient. Furthermore, there are those who claim that the benefit of blood transfusions has never been conclusively demonstrated, and evidence of transfusion related harm continues to accumulate. Cardiac surgical patients may be transfused not only because of bleeding but also due to hemodilution from preoperative and intraoperative intravenous fluids and pump primes in conjunction with a possible preoperative anemia. Getting transfusion right to improve our practice has to be approached multifactorially. The use of prophylactic dosing of blood products has been suggested to be ineffective in reducing blood loss. There are many factors that impact transfusion rates including determining the optimal hematocrit where it is highly unlikely that one figure will be applicable to all patients. The formulation of transfusion guidelines and algorithms that have been agreed upon by all practitioners involved in the care of cardiac surgical patients may have a positive effect-if everyone agrees to transfuse patients via the formulated guidelines or algorithms. Importantly, no one individual should be able make the decision on whether a patient requires a blood transfusion-it must at all times be a team decision, whether in the operating room or intensive care unit.

Transfusion and bleeding in coronary artery bypass grafting: an on-pump versus off-pump comparison.

Blood transfusion rates in coronary artery bypass grafting (CABG) surgery using cardiopulmonary bypass (CPB) are typically higher compared with off-pump CABG (OPCAB). However, few studies have specifically examined intraoperative hemodilution as a contributing factor. The aim of this retrospective review was to compare the effect of using CPB or OPCAB on red blood cell (RBC) transfusion and postoperative bleeding. The lowest intraoperative hematocrit (Hct) was used as marker of intraoperative hemodilution. We reviewed the perioperative data of all isolated CABG patients at a metropolitan hospital from January 2003 to June 2005. Stepwise regression analyses were performed to determine whether CPB was an independent predictor of RBC transfusion, reoperation for bleeding, or postoperative chest drainage. Of a total of 1043 patients, there were 433 CPB and 610 off-pump cases. CPB use was not significantly related to increased RBC transfusions (odds ratio [OR], 0.98; 95% confidence interval [CI], 0.63-1.52; p = .921) and was associated with a lower incidence of reoperations for bleeding (OR, 0.4; 95% CI, 0.2-0.8; p = .009). There was less chest drainage over the first 12 hours in patients undergoing CPB (p < .0001); however, total postoperative chest drainage was not significantly related to operative procedure (p = .122). The lowest documented intraoperative Hct was a significant factor in RBC transfusions (OR, 0.89; p < .0001), an increased reoperation rate for bleeding (OR, 0.9; p = .001) and more postoperative chest drainage (log10-transformed: at 12 hours, b = -0.009, p < .0001; total, b = -0.006, p < .0001). CPB is not an independent risk factor in the incidence of RBC transfusions and is not associated with increased postoperative bleeding for isolated CABG. However, intraoperative hemodilution is an independent risk factor, with a lower intraoperative Hct associated with more RBC transfusions, increased reoperations for bleeding, and increased postoperative chest drainage. Addressing intraoperative hemodilution is important in minimizing CPB-associated morbidities.

Membrane oxygenator exhaust capnography for continuously estimating arterial carbon dioxide tension during cardiopulmonary bypass.

Typically, the standard practice for measuring the arterial blood carbon dioxide tension (PaCO2) during cardiopulmonary bypass (CPB) is to take intermittent blood samples for analysis by a bench blood gas analyzer. Continuous inline blood gas monitors are available but are expensive. A potential solution is the capnograph, which was evaluated by determining how accurately the carbon dioxide tension in the oxygenator exhaust gases (PECO2) predicts PaCO2. A standard capnograph monitoring line was attached to the exhaust port of the membrane oxygenator. During CPB, the capnograph reading and arterial blood temperature were recorded at the same time as routine arterial blood gases were taken. One hundred fifty-seven blood samples were collected from 78 patients. A good correlation was found between the PECO2 and the temperature corrected PaCO2 (r2 = 0.833, P < .001). There was also a reasonable degree of agreement between the PECO2 and the temperature corrected PaCO2 during all phases of CPB: accuracy (bias or mean difference between PaCO2 and PECO2) of -1.2 mmHg; precision (95% limits of agreement) of +/- 4.7 mmHg. These results suggest that oxygenator exhaust capnography may be a simple and inexpensive adjunct to the bench blood gas analyzer in continuously estimating PaCO2 of a clinically useful degree of accuracy during CPB.

Coronary artery bypass grafting: an off-pump versus on-pump review.

There has been a proliferation in the number of coronary artery bypass grafts (CABG) being performed without the use of cardiopulmonary bypass (CPB). However, the benefits of off-pump coronary artery grafting (OPCAB) are still being determined. The aim of this retrospective review was to compare the perioperative outcomes of CPB patients with OPCAB patients and to identify the patients most likely to benefit from the off-pump procedure. We reviewed the perioperative data of all isolated CABG patients at two metropolitan hospitals for the period of August 2000 to September 2001. The two groups (OPCAB vs. CPB) were further divided into subgroups identifying patients by their predicted mortality (higher-risk and lower-risk) and the number of distal graft anastomoses received (1, 2, 3, 4, or 5). A p value less than .05 was considered significant. Out of the total of 882 patients, 46.2% were OPCAB cases. Both CPB and OPCAB groups were similar in terms of demographics and predicted risk of mortality. Intraoperatively, OPCAB patients had fewer distal graft anastomoses (2.4 +/- 1.0 vs. 3.2 +/- 1.0, p < .001). Postoperatively, patients in the OPCAB group had less chest drainage (889 +/- 588 vs. 989 +/- 662 mls, p < .001), sustained fewer strokes (0.2 vs. 1.9%, p < .05), were transfused less (15.4 vs. 32.5%, p < .001) and were discharged earlier (7.3 +/- 5.6 vs. 8.5 +/- 9.1 days, p < .05). For higher-risk patients, OPCAB was associated with fewer reoperations for bleeding (1.3 vs. 6.4%, p < .05), a lower stroke rate (0 vs. 3.2%, p < .05), and a trend toward lower mortality (7.1 vs. 15.1%, p = .08). However, lower-risk OPCAB patients' stroke incidences (0.5% OPCAB group vs. 1.4% CPB group), and mortality rates (0.5 vs. 0.5%) were similar. Comparisons by number of grafts performed revealed that only the single-grafted OPCAB patients had statistically fewer postoperative complications, reduced chest drainage, and a shorter intensive care stay. Differences between either operation groups in transfusion rates were only statistically significant for the one to three grafted patients, while postoperative stays were similar for patients having four grafts. These results suggest that OPCAB is associated with a reduction in mortality and morbidity, particularly within the higher-risk patients. However, the benefits of OPCAB diminished with an increasing number of distal anastomoses performed.