Perfusion

Background . To date, there is no quality assurance program that correlates patient outcome to perfusion service provided during cardiopulmonary bypass (CPB). A score was devised, incorporating objective parameters that would reflect the likelihood to influence patient outcome. The purpose was to create a new method for evaluating the quality of care the perfusionist provides during CPB procedures and to deduce whether it predicts patient morbidity and mortality. Methods. We analysed 295 consecutive elective patients. We chose 10 parameters: fluid balance, blood transfused, Hct, ACT, PaO₂, PaCO₂, pH, BE, potassium and CPB time. Distribution analysis was performed using the Shapiro-Wilcoxon test. This made up the PerfSCORE and we tried to find a correlation to mortality rate, patient stay in the ICU and length of mechanical ventilation. Univariate analysis (UA) using linear regression was established for each parameter. Statistical significance was established when p < 0.05. Multivariate analysis (MA) was performed with the same parameters. Results. The mean age was 63.8 ± 12.6 years with 70% males. There were 180 CABG, 88 valves, and 27 combined CABG/valve procedures. The PerfSCORE of 6.6 ± 2.4 (0—20), mortality of 2.7% (8/295), CPB time 100 ± 41 min (19—313), ICU stay 52 ± 62hrs (7—564) and mechanical ventilation of 10.5 ± 14,8hrs (0—564) was calculated. CPB time, fluid balance, PaO₂, PerfSCORE and blood transfused were significantly correlated to mortality (UA, p < 0.05). Also, CPB time, blood transfused and PaO₂ were parameters predicting mortality (MA, p < 0.01). Only pH was significantly correlated for predicting ICU stay (UA). Ultrafiltration (UF) and CPB time were significantly correlated (UA, p < 0.01) while UF (p < 0.05) was the only parameter predicting mechanical ventilation duration (MA). Conclusions. CPB time, blood transfused and PaO ₂ are independent risk factors of mortality. Fluid balance, blood transfusion, PaO₂, PerfSCORE and CPB time are independent parameters for predicting morbidity. PerfSCORE is a quality of perfusion measure that objectively quantifies perfusion performance. Perfusion (2007) 22, 311—316.

Background. Given that there is an association between the degree of hemodilution during cardiopulmonary bypass (CPB) and postoperative complications, patients-outcome might be improved if the nadir hematocrit concentration is kept within an optimal range. Smaller patients are more likely to have a low hematocrit during CPB: this phenomenon may be related, at least partially, to the extreme hemodilution induced by a large fixed CPB priming volume. Methods. Forty patients with a body surface area (BSA) < 1.7 m² undergoing open heart operations were randomized to either standard CPB with full prime volume (control group) or reduced prime extracorporeal circuit and vacuum-assisted venous drainage (VAVD) (study group). Results. There were no significant differences between the groups with respect to baseline characteristics, body surface area, hematologic profile and operative data. Clinical outcomes were similar. Nadir hematocrit and hemoglobin on bypass were significantly lower in the control group (22 ± 2.3 vs 24 ± 2.5%, p < 0.02 and 7.4 ± 0.7 vs 8 ± 0.9g/dl, p < 0.04, respectively).

Postoperative chest tube drainage was significantly higher in the control group (272 ± 253vs 139 ± 84ml, p < 0.04). There was no difference in blood transfusion in the two groups (0.5 ± 1.14 v 1.0 ± 1.77 units of packed red blood cells (PRBC), p = 0.29). Conclusions. Lowering CPB priming volume by means of using a small oxygenator and vacuum-assisted venous drainage (VAVD) resulted in a significant decrease of intraoperative hemodilution. This technique should be strongly considered for patients with a small BSA (<1.7 m²) undergoing open heart surgery. Perfusion (2007) 22, 317—322.

Objective : Two extracorporeal membrane oxygenation (ECMO) circuits for children under 10 kg were evaluated and compared for plasma leakage, hemolysis, blood transfusions, and durability. Methods: Group A (n = 20) was supported by ECMO circuits with the Minimax oxygenator and the Biomedicus centrifugal pump. Group B (n = 10) was supported by ECMO circuits with the Lilliput 2 ECMO oxygenator and the Rotaflow centrifugal pump. Results: ECMO circuit durability, as measured by oxygenator lifespan, was significantly better in Group B than in Group A (p = 0.04). There was significantly lower hemolysis, measured by plasma free hemoglobin, in Group B (p = 0.019), and patients in Group B had significantly less need for antithrombin III transfusion (p = 0.004). No plasma leakage was observed in Group B oxygenators, but plasma leakage was observed in all Group A oxygenators. Conclusion: The combination of a Rotaflow centrifugal pump and Lilliput 2 ECMO oxygenator in pediatric ECMO circuits improved durability and reduced circuit-induced hemolysis. This improvement may be due to the low priming volume, the oxygenator's plasma leakage resistance, the suspended rotor of the centrifugal pump, or a combination of these factors. Perfusion (2007) 22, 323—326.

Objective . To determine the efficacy of decreasing cardiopulmonary bypass (CPB) prime volume for neonates and small infants by using low prime oxygenators, small diameter polyvinyl chloride (PVC) tubing and removing the arterial line filter (ALF) in an effort to reduce intraoperative exposure to multiple units of packed red blood cells (PRBC). Methods. Two retrospective database studies comparing neonatal CPB prime volume were undertaken: Study 1 — A CPB circuit consisting of a 1/8 inch arterial line, a 3/16 inch venous line and a low prime oxygenator with 172 ml total circuit prime (n = 74) was compared to a circuit with a 3/16 inch arterial line, a 1/4 inch venous line and a higher prime oxygenator with a 350 ml total circuit prime ( n = 74). Study 2 — The 172 ml circuit (n = 389) was compared to a circuit that included an ALF and had a total circuit prime volume of 218 ml (n = 389). Results. Study 1— of the 74 neonates and small infants whose CPB prime volume was 350 ml, 19 were exposed to two or more intraoperative exogenous PRBC units while only 3 neonates and small infants in the 172 ml prime group (n = 74) received two or more units (p = 0.0002). Study 2 — of the 389 neonates and small infants where an ALF was used (prime volume 218 ml), 54 were exposed to two or more exogenous PRBC units while only 36 of the 389 patients where an ALF was not used (prime volume 172 ml) received two or more units of intraoperative PRBCs (p = 0.0436). Conclusion. Decreasing the neonatal and small infant extracorporeal circuit prime volume by as little as 46 ml resulted in significantly fewer multiple exposures to exogenous PRBC units. Perfusion (2007) 22, 327—331.

Background: Non-protein plasma expanders carry a risk of potentially severe allergic reactions. As prime for cardiopulmonary bypass, we routinely use a gelatin plasma expander. Plasma expanding during anesthesia is achieved with high molecular starch (200/0.5 kDalton) in combination with Ringer Lactate solution (RL) and in the Intensive Care Unit (ICU) with a low molecular starch (130/0.4 kDalton). We evaluated the feasibility of low molecular starch in combination with RL (group LMSRL) versus gelatin plasma expanding (group GPE) for priming CPB circuits in patients undergoing cardiac surgery in a randomized prospective trial. Methods: One hundred and eighty adults who underwent primary valve or coronary artery bypass graft (CABG) surgery were equally stratified into 3 series of 60 patients with the routinely used oxygenators; Capiox RX-25, CML Duo and Quadrox-D. Then they were randomised by drawing lots and allocated into the LMSRL or GPE groups. We compared hematocrit, hemoglobin, platelet count, activated clotting time (ACT), lactate and colloid osmotic pressure (COP), blood loss, transfusion need, urine production and ICU stay. In addition, we monitored the average trans-oxygenator fluid resistance (AFR) for each type of oxygenator. Results: The COP is significantly lower in the LMSRL group (20 mmHg ± 0.2 versus 18 mmHg ± 0.2, p < 0.0001); as was the total use of plasma expanders (3846ml ± 98 versus 3059ml ± 77, p < 0.001). All other parameters were not significantly different. When comparing the observed AFR for the three types of oxygenators, a lower AFR in the LMSRL group (p < 0.02) was noted for the Capiox RX-25^®. Conclusions: This study shows a lower need for plasma expanders in patients who receive only starch plasma expanders. Further, we noted a lower COP in the LMSRL group, but since the mean COP was >17 ± 0.2 mmHg, this cannot be considered of clinical importance. In conclusion, our study result supports the use of low molecular starch as a good alternative choice for priming CPB. Perfusion (2007) 22, 333—337.

The abnormal conditions to which blood is subjected during cardiopulmonary bypass (CPB) trigger an activation of the inflammatory response and cause pulmonary dysfunction. It has been suggested that high-volume, zero-balanced ultrafiltration (ZBUF) facilitates clearance of inflammatory mediators and improves post-operative pulmonary function. Procalcitonin, a newly discovered inflammatory mediator, has been found to be increased after CPB and has been proven to be an appropriate parameter for predicting pulmonary dysfunction secondary to CPB. The aim of this study was to investigate the effects of zero-balanced ultrafiltration (ZBUF) on procalcitonin (PCT) and respiratory function of infants with Tetralogy of Fallot (TOF) after CPB. Twenty infants with TOF undergoing open-heart total surgical correction were randomly assigned to two groups. The trial group was given ZBUF (50 ml/kg) and conventional ultrafiltration (CUF), while the control group was given CUF only. Plasma PCT and pulmonary function were monitored and compared between the two groups before the operation (T1), before rewarming (T2), at the end of the operation (T3), and at 12 h, 24 h and 48 h after the operation (T4-T6). PCT was decreased in the trial group between 12 h and 48 h post-operatively, but the differences did not reach statistical significance. The trial group's pulmonary compliance was higher at 12 h post-operatively (p < 0.05). Oxygenation index was increased in the trial group at the end of the operation and 12 h post-operatively (p > 0.05). Intubation time was shorter in the trial group (P < 0.01). A positive correlation was found between peak PCT concentration and intubation time. ZBUF appeared to improve ventilation and shorten intubation time. The improved respiratory function may be due to the lower plasma PCT. Perfusion (2007) 22, 339—343.

Various strategies have been proposed to decrease allogeneic blood transfusion requirements after cardiac surgery. The aim of the study was to evaluate the efficacy of collected and re-infused autologous shed mediastinal blood on a patient's postoperative course.

Ninety patients who underwent heart surgery with cardiopulmonary bypass (CPB) were studied. The patients were divided into two groups: Group 1 (n = 41) received the centrifuged autologous shed mediastinal blood collected from the cardiotomy reservoir 4 hours after surgery; in Group 2 (n = 49) all shed mediastinal blood was discarded (control group). Haemoglobin (Hb), haematocrit (Hct), C-reactive protein values, and leucocyte count were compared before surgery, at 4 h and 20 h after surgery, and on the fifth postoperative day. We have measured serum procalcitonin (PCT) concentration at 4 h and 20 h after CPB. We assessed drained blood loss within 20 postoperative hours.

Leucocyte count, Hb, Hct values, C-reactive protein, and procalcitonin concentration did not differ between the groups before and at 4 h after surgery. Hb, Hct level, and leucocyte count were similar at 20 hours and on the fifth day after surgery. At 20 hours after surgery, an increase of serum PCT concentration (>0.5—2 ng/mL) was more frequent in Group 2 (58.3% vs. 33.3%; p = 0.03). On the fifth postoperative day, C-reactive protein concentration was lower in Group 1 (71.74 ± 15.23; p < 0.01) compared to Group 2 (93.53 ± 20.3). Postoperative blood loss did not differ between the groups. Requirement for allogeneic blood transfusion was significantly lower in Group 1 (14.6% vs. 38.8%; p < 0.02). Patients in Group 1 developed less infective complications compared with Group 2 (2.4% and 16.3%, respectively; p < 0.05). The length of postoperative in-hospital stay was shorter in Group 1 compared with Group 2 (9.32 ± 2.55 and 16.45 ± 6.5, respectively; p < 0.05).

We conclude that postoperative re-infusion of autologous red blood cells processed from shed mediastinal blood did not increase bleeding tendency and systemic inflammatory response and was effective in reducing the requirement for allogeneic transfusion, the rate of infective complications and the length of postoperative in-hospital stay. Perfusion (2007) 22, 345—352.

Objective. Buffers added to myocardial preservation solutions are considered to be critical for resisting myocardium pH changes from the accumulation of protons (H ⁺ ). Our hypothesis is that mathematical modeling of three clinically used buffers will define their individual buffering capacities under simulated clinical conditions. Methods. The buffers, tromethamine (THAM), sodium bicarbonate (HCO₃ ^-), and L-histidine, were compared in terms of their buffering capacity (β) under specific temperatures and concentrations, using a mathematical model. Results. At 37°C, the maximal beta (β _max) occurred at pH 7.75 for THAM, pH 6.10 for HCO₃ ^-, and pH 5.89 for L-histidine at equimolar concentrations. A decrease in temperature moved β _max to a higher pH value for each buffer. At clinical concentrations, L-histidine provided the greatest buffering capacity followed by HCO ₃ ^- and THAM, respectively. Discussion. This model permitted comparison of the above buffers under simulated clinical conditions. The assumption was that the magnitude of β _max at a given temperature determines which buffer(s) could be most effective for myocardial preservation. Also, the assumption was taken that these buffers are used in a closed system — where there is no continuous blood flow — and that the buffering ability of THAM and L-histidine were not influenced by the accumulation of CO₂ as is HCO₃ ^-. THAM and L-histidine were more effective at hypothermic temperatures compared with HCO₃ ^-; however, HCO₃ ^- provided buffering at normothermic temperatures. Through the theoretical considerations of this study, we propose that combining HCO₃ ^- with THAM or L-histidine could be most efficacious for myocardial preservation during open heart surgery or organ transplantation. Perfusion (2007) 22, 353—362.

Thoraco-abdominal aneurysm repair usually necessitates blood or blood product transfusion which is prohibited in Jehovah's Witnesses. We report the blood conservation strategy used during thoraco-abdominal aneurysm repair in a Jehovah's Witness. This included pre-operative recombinant erythropoietin, per-operative acute normovolaemic haemodilution, cell salvage, aprotinin, restricted heparinisation, left atrial-distal bypass and recombinant factor VIIa. Post-operative haemoglobin levels were maintained, but a left haemothorax necessitated re-thoracotomy on post-operative day 4. Following re-thoracotomy, Hb was 12.0 g.dL^—1 and platelet count 49 × 10⁹.L^—1. Recombinant erythropoietin was recommenced. At discharge (day 12), Hb was 10.1 g.dL^—1. The patient remains well at one year. A thoroughly, pre-planned multi-disciplinary blood conservation strategy can be used to undertake high-risk procedures. Perfusion (2007) 22, 363—364.

This case report describes the successful repair of an acute dissection of the ascending aorta in a 16-year-old girl. The dissection appeared to be related to the presence of an aortic coarctation. Furthermore, a bicuspid aortic valve was found. Echocardiography was helpful for quick pre-operative diagnosis. A computed tomography (CT) scan was used post-operatively to confirm these results. At the onset of extracorporeal circulation, active drainage was applied at the femoral vein by means of a routinely built-in shunt bypassing the venous reservoir. The practical implementation of this shunt is described in this report. One femoral artery and one femoral vein were cannulated, resulting in a blood flow index of 2.2l.min ^{- 1}.m ^{- 2} which proved to be sufficient for blood supply to both the lower and the upper parts of the body. Successful percutaneous dilatation of the coarctation was performed five months after the first operation. Perfusion (2007) 22, 365—367.