Tönz M

The warm versus cold perfusion controversy: a clinical comparative study

To evaluate the effects of temperature on myocardial and total body protection, we analyzed 129 consecutive patients who underwent coronary artery bypass grafting, valve replacement, or both, with continuous cardioplegia (Cp). The patients were assigned to three groups: group I (n = 37) normothermic cardiopulmonary bypass (CPB) (37 degrees C) and warm (37 degrees C) Cp, group II (n = 49) normothermic CPB and cold (4 degrees C) Cp and group III (n = 43) hypothermic (28 degrees C) CPB and cold Cp. Comparison of groups I and II showed similar serum levels of creatine kinase (CK) and its myocardial-specific isoenzyme on the first postoperative day, a similar rate of perioperative myocardial infarction, postoperative need for intra-aortic balloon pump, postoperative need for inotropic support and mortality. Comparison of groups I and III showed similar serum levels of CK, amylase, lactate dehydrogenase and creatinine on the first postoperative day, a similar complication rate and mortality rate. However, normothermic CPB resulted in a shorter bypass time (83 +/- 4 vs 98 +/- 7 min, P < 0.05) and interval until extubation (25.0 +/- 3.8 vs 40.3 +/- 7.4 h, P < 0.05). In conclusion, there are no differences concerning myocardial protection, however, warm CPB shortens the perfusion time and postoperative course.

Evaluation of phospholipidic surface coatings ex-vivo.

To evaluate the thromboresistant properties of phospholipidic surface coatings mimicking the lipid surface of blood cells, we studied four different types of phospholipids bound onto PVC tubings in comparison to uncoated as well as heparin bonded controls. The samples analyzed included diacetylenic phospholipid coated as a monomeric treatment (A), diacetylenic phospholipid polymerised prior to being coated (B), and two types of polymeric phospholipids made using methacrylate containing monomers (C and D). A bovine (bodyweight 67 ± 3 kg) left heart bypass model (pump flow 3.2 ±0.1 l/min) was selected and the surfaces were exposed to the blood stream up to 360 min without systemic heparinization. Thereafter another set of samples was exposed to stagnant blood over 20 min. Besides hemodynamic, hematologic and biochemical analyses, the macroscopic appearance of 119 blood exposed surface samples was graded semiquantitatively on a scale of 0 to 10: no macroscopic deposits = grade 0, 1 spot (1 mm diameter) = grade 1, 2 spots = grade 2, 5 or more spots = grade 5, up to 10% of the surface covered with clots = grade 6, 100% covered = grade 10 (p<0.05=∗): mean grade of deposits was 0.0 ± 0.0 for segments perfused and 0.0 ± 0.0 for segments exposed to stagnant blood with surfaces exposing to the blood either heparin, phopholipid A, or phospholipid B (NS). Phospholipids C and D were graded 0.0 ± 0.0 if perfused and 0.7 ± 1.2 if exposed to stagnant blood. Uncoated PVC control tubings however were graded 0.2 ± 0.8 for segments perfused and 2.7 ± 3.0 for segments exposed to stagnat blood (p<0.05 in comparison to all surfaces coated with phospholipids or heparin if perfused and if exposed to stagnant blood). Hence phospholipidic surface coatings expose significant antithrombotic properties which out perform todays standard for tubings in clinical perfusion (uncoated PVC).

Heparin surface coated hard shell venous reservoirs: experimental evaluation ex vivo.

The present study was designed for ex vivo evaluation of a heparin coated hard shell venous reservoir in comparison to uncoated control reservoirs. An open chest bovine right heart bypass model (n=9, bodyweight 72 ± 6 kg) with passive blood drainage from the right atrium into the venous reservoir and active retransfusion into the pulmonary artery (roller pump) was selected for this purpose. Clear priming was used for the open perfusion circuit. No heparin was given before or during the evaluation period which was scheduled for 6 hours. Reservoir blood flow was at the beginning 3.5 ± 0.6 I/min for coated versus 3.4 ± 0.3 l/min for uncoated (NS). After 6 hours, blood flow was 3.3 ± 0.1 I/min for coated versus 2.7 ± 0.4 l/min for uncoated (p<0.05). Hematocrit moved from a baseline level of 30 ± 2% for coated versus 28 ± 3% for uncoated (NS) to 28 ± 3% for coated versus 27 ± 5% for uncoated (NS) after 6 hours. Prebypass platelet levels of 100% in both groups moved to 84 ± 3% for coated versus 78± 23% for uncoated (NS) after 6 hours. Activated coagulation time (ACT) before bypass was 148 ± 12 s for coated and 153 ± 6 s for uncoated (NS). After 6 hours, ACT was 160 ± 9 s for coated versus 152 ± 5 s for uncoated (NS). Thrombin time before bypass was 15 ± 2 s for coated versus 16 ± 2 s for uncoated (NS). After 6 hours, thrombin time was 17 ± 2 s for coated versus 18 ± 4 s for uncoated (NS). Baseline antithrombin III levels were 91 ± 25% for coated versus 96 ± 17% for uncoated (NS). After 6 hours antithrombin III levels were 95 ± 23% for coated versus 93 ± 19% for uncoated (NS). Baseline fibrinopeptide A levels were 2.6 ± 0.4 ng/ml for coated versus 2.6 ± 0.8 ng/ml for uncoated (NS). After 10 minutes of perfusion fibrinopeptide A moved to 4.8 ± 0.9 ng/ml for coated versus 8.8 ± 3.2 ng/ml for uncoated and reached 10.7 ± 2.6 ng/ml after 2 hours for coated versus 15.3 ± 0.1 for uncoated (p<0.01). We conclude, that despite the open perfusion mode, the tested heparin surface coated venous hard shell reservoirs have improved thromboresistance. Heparin surface coating increases the reservoir flows and reduces fibrinopeptide A production.