Minimally invasive coronary artery bypass grafting (MIDCAB) procedures are purported to result in improvements in patient management over standard techniques. A comparative study was performed on risk-stratified patients treated with either technique. Following institutional review board approval, a retrospective random chart review was conducted on 27 MIDCAB and 37 standard coronary artery bypass grafting (CABG) patients who were operated on over a 12-month period at the University of Nebraska Medical Center. Risk stratification was accomplished by dividing the two patient populations, MIDCAB and 'standard', into one of four subgroups based on a preoperative risk score. Risk stratification was achieved by dividing the patient populations into one of four subgroups: good, fair, poor and high risk. Both groups received similar operations and surgical interventions, except for the inclusion of cardiopulmonary bypass (CPB). Approximately 200 parameters were collected and analyzed in the following categories: anthropometric, operative and postoperative outcomes. The MIDCAB group had a significantly lower number of vessels bypassed (2.0+/-0.7 vs 3.4+/-0.9, p < 0.0001). Total postoperative blood product transfusions trended higher in the standard group (6.1+/-12.6 U) when compared to the MIDCAB patients (2.3+/-5.5 U, p < 0.15), although not statistically significant. Postoperative inotrope use was significantly less in the MIDCAB group (19% vs 59%, p < 0.002). Ventilator time in the MIDCAB group was 10.5+/-5.4 h vs 15.0+/-12.3 h in the standard group (p < 0.07). The MIDCAB group had an overall greater length of stay, but was only statistically different within the poor-risk subgroup (12.2+/-10.7 vs 7.5+/-3.9, p < 0.04). The results of this study show that when CPB is not utilized in treating patients undergoing CABG procedures, the benefits in regards to patient outcomes are unclear. This necessitates the need for further work when comparing outcomes for risk-stratified patients.

The flow of fluids in extracorporeal circuits does not conform to conventional Poiseuille mechanics which confounds calculating cardioplegia (CP) flow distribution. The purpose of this study was to quantify CP flow dynamics in a model simulating coronary atherosclerosis across varying sized restrictions. An in vitro preparation was designed to assess hydraulic fluid movement across paired restrictions of 51, 81 and 98% lumen reductions. Volume data were obtained at variable flow, temperature, viscosity and pressure conditions. CP delivered through 14- and 18-gauge (GA) conduits at 8 degrees C and 100 mmHg infusion pressure revealed that both four to one and crystalloid CP solutions had significantly less total percentage flow through the 14-GA conduit, p < 0.0001 and p < 0.001, respectively. Overall, 4:1 CP exhibited the most favorable fluid dynamics at 8 degrees C in that it delivered the highest percentages of total CP flow through the smaller lumen conduit. At both 8 degrees C and 37 degrees C delivery, blood CP resulted in the least homogeneous fluid distribution at all delivery parameters. The results in relation to blood viscosity indicate that, although the 8 degrees C blood CP had a significantly greater viscosity than 37 degrees C blood CP, it did not produce an effect in fluid distribution. These data show that increasing the cardioplegic solution hematocrit causes an inhomogeneous fluid distribution regardless of delivery temperature or infusion pressure.

During cardiac surgery with cardiopulmonary bypass (CPB), fibrinolytic activity may be stimulated when blood exposed to pleural surfaces is suctioned into the extracorporeal circuit (ECC). The purpose of this study was to determine the effect of reinfused blood exposed to pleural surfaces on systemic fibrinolytic activity. Following Institutional Animal Care Utilization Committee approval, 120 ml of blood was drawn from the femoral artery of 4 pigs and placed in both pleural cavities, where it remained for 120 min during CPB. After this time, the exposed blood was suctioned back into the ECC. Blood samples were drawn at the following times: 40 min prior to median sternotomy, 30 and 90 min during CPB, and 30 min post-suction. Tests performed on the samples included thromboelastography (TEG), D-dimer (DD), fibrin degradation products (FDP), fibrinogen concentration, activated clotting time (ACT), hematocrit, and platelet count. TEG index decreased significantly in the circuit following suction (5.28 ± 0.45 vs. 0.98 ± 1.86, p < 0.0007), while fibrinolytic activity increased (6.25 ± 1.50%) in the ECC when compared to pleural blood (2.17 ± 1.04%, p < 0.01). The DD and FDP were both elevated in the systemic circulation following suction of the pleural blood, although statistical significance was not achieved. The ACT was significantly elevated in the pleural fluid during CPB (707 ± 213) compared with the ECC (378 ± 32, p < .003), which may indicate an accelerated consumption of coagulation factors. In conclusion, blood exposed to pleural surfaces may have increased fibrinolytic activity, but systemic hyperfibrinolysis was not seen.

The optimum model for hemostasis monitoring during cardiopulmonary bypass (CPB) is the evaluation of physiologic changes in the intact organism. This is often logistically difficult and expensive. The purpose of this study was to design an in vitro model of blood coagulation for use in simulated CPB. Human expired blood components within 4 days of outdating were reconstitituted as follows: 4 units of packed red blood cells, 4 units of platelets, and 3 units of fresh frozen plasma. The mixture was circulated in a simulated extracorporeal circuit. Blood samples were drawn every 30 minutes over a 2 hour period, recalcified, and analyzed for platelet count (PL T), fibrinogen concentration (FIB), prothrombin time (PT), activated partial thromboplastin time (aPTT), celite and kaolin activated clotting times (ACT), and thrombelastography (TEG). In the four different coagulation monitors utilized, there were no significant changes in celite or kaolin ACTs. PT increased from 15.8 ± 1.1 sec to 25.2 ± 7.8 sec and aPTT from 62.1 ± 15.9 sec to 78.9 ± 36.5 sec (p = NS). There were no changes in either PL T count or FIB concentration. Both celite and tissue factor activated TEG values trended towards hypocoagulability. In conclusion, the results show that the in vitro model is stable over 120 min of recirculation time within a simulated cardiopulmonary bypass circuit in regards to platelet count, hematocrit, total protein, PT, aPTT, and ACT. Further examination will be necessary to establish the effects of the model in regard to platelet function.