<P>Background: The incidence of thromboembolic events following traditional open heart surgery has not been clinically significant. However, with beating heart surgery, for which cardiopulmonary bypass (CPB) is not required, the incidence of spontaneous intravascular thrombosis may be similar to that encountered after general surgeries. Compounding this risk is that many cases of off-pump coronary artery bypass (OPCAB) surgery are reserved for the elderly patient with multiple comorbidities. The few studies to date that have assessed the coagulation profile in OPCAB patients have been limited to the first 24 hours after surgery. </P><P>Methods: We prospectively studied 17 OPCAB and 6 on-pump patients over 4 days (hospital course) with daily thromboelastography. A coagulation index (CI) (reflecting R and K times, a angle, and maximum amplitude [MA]) was calculated for the patients, who served as their own controls. </P><P>Results: The OPCAB patients demonstrated 3 days postoperatively a 17% increase in coagulation compared with the baseline. Specifically, the CI consistently revealed an elevation in the a angle and the MA, both of which reflect increased fibrinogen and platelet activity. On the other hand, 3 days following surgery the CI of the CPB group was tightly clustered around their respective baseline CI values, which had recovered from a significant decrease immediately after surgery. </P><P>Conclusion: A state of hypercoagulability, as measured by thromboelastography, exists in the OPCAB patient beyond the first postoperative day, and this finding suggests that prophylactic postoperative anticoagulation therapy targeting fibrinogen and platelet activity may be indicated for these patients.</P>
The purpose of this study was to evaluate the oxygen transfer performance of two membrane oxygenators: Bentley Univox and the Bard HF 5000. This evaluation was based on the comparison between: (1) the oxygen transfer slope; (2) the gas phase-arterial oxygen gradients; (3) the degree of blood shunting; (4) the maximum oxygen transfer; and (5) the diffusing capacity calculated for each membrane. The data were examined at both absolute values and relative to each device's membrane surface area. In absolute terms, the HF 5000 performed better than the Univox in each category. However, when surface area was taken into account, the Univox was clearly more efficient with regard to oxygen transfer. We conclude from this evaluation that the Univox does not offer a satisfactory oxygen transfer 'buffer' for larger, more metabolically active patients (297 ml/min for the Univox and 447 ml/min for the HF 5000). The trade-offs that were made between design and performance features, with the Univox, were unacceptable.
The purpose of this study was to determine whether thrombelastography could detect hypercoagulability in the off-pump coronary artery bypass (OPCAB) patient. Seventeen OPCAB and six cardiopulmonary bypass (CPB) patients were studied pre- and postprocedure, as well as on each of the first three postoperative days (POD). In the OPCAB patients, there was a small reduction in the postprocedure coagulation index (CI). This was followed by an increase in the CI on each of the next three POD, reaching a level exceeding the mean preprocedure CI by 2.32 units, indicative of a state of relative hypercoagulability. The mean CI for the CPB patients decreased significantly in the postprocedure sample. Over the next 72 h, the CI increased to a level that nearly equaled the preprocedure 'baseline'. We concluded that our study identified a state of relative hypercoagulability in the OPCAB patient 72 h after surgery. The mechanism of this hypercoagulation, as well as the clinical significance of this finding, is yet to be determined.
The purpose of this investigation was to compare the oxygen transfer efficiency of three different membrane oxygenators, each utilizing microporous polypropylene as its gas transfer material. Gross oxygen transfer was compared for each membrane with their performance when differences in surface area were taken into account. It was found that when hollow fibres were used, with blood flow around the fibres, efficiency was maximized. Our study technique offers an additional objective approach in the evaluation of oxygen transfer for membrane oxygenators.
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