Quantitative evaluation of heparin-coated versus non-heparin-coated bypass circuits during cardiopulmonary bypass.

The extracorporealization of blood activates various elements of the fibrinolytic, coagulation, and complement systems. It is theorized that advancements in biocompatibility ameliorate many of the changes leading to improved patient management. The purpose of this study was to determine if heparin-coated circuit (HCC) utilization during cardiopulmonary bypass enhances patient outcomes in a cost-effective manner. A search of the English medical literature was completed to identify all clinical, prospective, randomized trials comparing HCC and non-HCC in patients undergoing coronary artery bypass grafting or valvular surgery. Twenty-six papers consisting of a sample size of 1515 patients were identified and included in the study parameters. The study distinguished between Duraflo II and Carmeda coating techniques and matched papers with different heparin loading doses, as well as use of a heparin-coated cardiotomy. Study parameters were matched for all papers and analyzed according to the availability of data. Statistically significant benefits of HCC were found in postoperative blood loss, time in the ICU, end bypass C3a, time to extubation, end bypass lactoferrin, and end platelet count, but not with respect to postoperative chest tube drainage, red blood cell transfusions, and end bypass TAT complex, D-dimers, and BTG. Data comparing the use of coated or uncoated cardiotomy utilization failed to demonstrate a benefit to heparin coating. Several immunological variables were ameliorated when Carmeda HCC was utilized, although data were insufficient to establish a cost-benefit analysis. In conclusion, heparin-coated circuitry provided statistically better results when compared to noncoated circuitry.

Hematological abnormalities in neonatal patients treated with extracorporeal membrane oxygenation (ECMO).

The physical process of extracorporeal membrane oxygenation (ECMO) results in derangement of the hemostatic mechanism, which may lead to increased morbidity, secondary to the disease process. The purpose of this study was to evaluate the hematological status of neonates undergoing ECMO therapy, and to evaluate coagulation tests in predicting hemorrhagic risk. Following Institutional Review Board approval, 30 patients undergoing ECMO treatment were retrospectively entered into this study. Medical records were reviewed and indicators of hemostasis, transfusion, morbidity, and outcomes recorded. Assessment of coagulation was determined through serial analysis of platelet count, fibrinogen concentration, prothrombin time (PT), activated partial thromboplastin time (aPTT), antithrombin III, fibrin split products, D-dimers, plasma free hemoglobin, activated clotting time, ionized calcium, and thrombelastography (TEG). Median total transfusion requirements for all patients were 1.79 ml/kg/ECMO hr. Fifty-seven percent of the 30 patients were diagnosed as coagulopathic according to Extracorporeal Life Support Organization standards. Patients were separated into either a hemorrhagic group (HEM, > 2.0 ml/kg/ECMO hr, n = 13) or a nonhemorrhagic group (N-HEM, n = 17), with HEM patients requiring twice the transfusion volume of N-HEM (p < 0.0001). Hemorrhagic complications were reported in 53.8% of the HEM patients vs. 35.3% in the N-HEM group. HEM patients were transfused with significantly greater quantities of platelets on days 1, 3, 5, and 8 and packed red blood cells on day 7 when compared to N-HEM (p < 0.05). TEG determination showed significant differences between groups on days 3 and 6 (p < 0.005), and 8 (p < 0.05). Derangements in hemostasis resulting from ECMO are profound, with methods of assessing coagulation complicated by both the variability in patient condition and lack of specificity of laboratory tests. Interpretation of TEG data has shown to be a valuable supplement for managing this challenging patient population.

Evaluation of a new generation cardioplegia administration system.

The delivery of cardioplegia has traditionally been constrained by the physical limitations of the mechanical devices in use, yet myocardial protective strategies may vary both according to patient condition and operative requirements. The need for a cardioplegia administration device that allows flexibility and safety is evident. The purpose of this study was to evaluate the performance of the Quest Myocardial Protection System (MPS) during clinically simulated conditions. The MPS was evaluated in an in vitro setting under the following conditions: blood to crystalloid ratios (1:1, 4:1, 8:1, all blood), potassium concentrations ([K+]) of 10 and 25 mmol/L, calcium concentrations ([Ca++]) of 1.4 and 2.8 mmol/L, and at flow rates of 100 and 300 ml/min. Predicted values from the MPS were compared with measured values, with statistically significance accepted at p < .05 level. Significant differences were seen between measured and MPS cardioplegia delivery volumes at the 4:1, 8:1 and all blood ratios with a flow rate of 300 ml/min. There were no significant differences seen between measured and expected [K+] and [Ca++] delivery values across all combination of flow rates and ratios. Differences between delivery pressures of the MPS and measured values for flow rates of 100, 250 and 500 ml/min were 0.4, 1.2 and 7.6 mmHg respectively. The mean cardioplegia cooling time from 37 degrees C to 9 degrees C was 37 +/- 4.5 seconds, while rewarming from 7 degrees C to 37 degrees C, took 53 +/- 10.4 seconds. In conclusion, the Myocardial Protection System performance characteristics were precise in ratio delivery, concentrations of potassium agents, additive agent concentration, temperature, and pressure across all experimental conditions, with the exception of delivery volume.

Coagulopathic-induced membrane dysfunction during extracorporeal membrane oxygenation: a case report.

This paper describes an unusual complication of membrane dysfunction during extracorporeal membrane oxygenation (ECMO) for treatment of neonatal respiratory distress. A 2.8-kg term infant presented to our facility in severe respiratory distress and was diagnosed with primary pulmonary hypertension. After routine priming of the extracorporeal circuit, the patient was placed on veno-arterial ECMO with 8 F arterial and 12 F venous cannulae. Transfusion criteria were established which included trigger values of the following: platelet count 100,000/microliters, fibrinogen 150 mg/dl, haematocrit 40%. The ECMO course was uneventful until approximately the 132nd hour on support when the patient developed a consumptive coagulopathy, as evidenced by 55-60% reductions in both platelet count and fibrinogen concentrations, despite transfusion therapy. Total autogeneic blood product transfusion during the first 120 h of ECMO averaged 4.4 +/- 2.2 ml/h, while the transfusion rate for the final 35 h was 7.8 +/- 3.5 ml/h. Coinciding with this rise in transfusion requirements was an increase in transmembrane pressure from 0.29 to 1.52 mmHg/ml blood flow. The patient was separated from ECMO after 175 h due to a continuing coagulopathy and haemothorax. The patient was then treated with nitric oxide therapy before succumbing on the twelfth postoperative day due to refractory respiratory failure. The circuit was dissected and significant clots found in both the venous bladder and oxygenator. In addition, approximately one-third of the membrane compartment had a 'fused' circumferential pattern of dessicated clot which interrupted blood path continuity. In conclusion, this report describes an unusual complication of the ECMO oxygenator that occurred during long-term extracorporeal life support which most likely resulted from a coagulopathy.

Evaluation of a variable ratio cardioplegia system.

Gish Biomedical has designed a blood cardioplegia delivery system (MyoManager) which is purported to provide rapid control of blood and crystalloid solution ratios for myocardial preservation. The present study was designed to evaluate the ability of this device to provide cardioplegia solutions of specific hematocrit and potassium ion concentrations ([K+]). An in vitro circuit was designed whereby a blood perfusate with a [K+] of 5 mEq/L was mixed with a base crystalloid solution containing 210 mEq/L of K+. Data was collected at several blood to crystalloid ratios (1:1, 4:1, 8:1, 16:1, 25:1), and at four delivery rates (100, 150, 200, 250 ml/min). Predicted and observed values of total cardioplegia volume, hematocrit, crystalloid volume, and [K+] were statistically (ANOVA) analyzed, and statistical significance accepted at p 0.05. There were no statistically significant differences observed at any flows or ratios in hematocrit. However, at 100 ml/min flow rates, the crystalloid delivery volume difference of 2.4 +/- 2.0 ml was significantly higher than that observed at 250 ml/min, 1.5 +/- 1.5 ml (p < 0.02) and at 200 ml/min flow rates, 1.5 +/- 1.6 ml (p < 0.02). There was no statistical significance in [K+] difference between flows across all ratios. However, within ratios, a significant difference in [K+] at 100 ml/min, 1:1 blood to crystalloid ratio, was observed (p < 0.0001) versus all other ratios and flows. The only statistically significant difference that was shown in total cardioplegia delivery volume was observed between 100 and 200 ml/min (p < 0.04) when analyzed across all ratios. The data suggests that the MyoManager effectively provides precise control of [K+] and hematocrit at cardioplegia flows greater than 100 ml/min.

Ultrafiltration of the waste plasma effluent from cardiopulmonary bypass circuit contents processed with a cell-washing device.

Blood conservation methods are commonly practiced throughout most hospitals that conduct cardiothoracic surgery. In an effort to reduce patients' exposure to homologous blood products and due to cost effectiveness of blood conservation techniques, this present study combines autotransfusion of the remaining blood in the extracorporeal circuit and ultrafiltration of the plasma effluent, and describes the resulting product. Seven patients, greater than 19 years of age, requiring cardiopulmonary bypass (CPB) were incorporated into this study. Exclusion criteria included age limitation. At termination of CPB, the remaining blood in the circuit was transferred to an autotransfusion machine and processed. Plasma (1054 +/- 206 ml) effluent was collected directly from the centrifugal bowl and processed through a ultrafiltrator, with a constant flow rate and negative pressure, until the plasma effluent concentrated down to an end processed volume of approximately 150 ml. The following variables were either measured or calculated: plasma-concentrate volumes per three minute interval, inlet/outlet pressures of an ultrafiltrator, transmembrane pressure (TMP), plasma free hemoglobin, fibrinogen, total protein, and colloid osmotic pressure. The average ultrafiltrate volume taken off from the plasma effluent was 828 +/- 237 ml, with an average ultrafiltrate volume of 115 ml in every three minute interval. The TMP did not change over the first 15 minutes of processing but became significantly elevated at the 18th minute interval and continued to increase and reach a maximum TMP of 286.5 +/- 2.1 mmHg at the end of concentration. Fibrinogen levels increased from pre-concentration values of 118.2 +/- 64 to 317 +/- 177 mg/dl (p = .03) along with increases in plasma free hemoglobin from 97.7 +/- 46 to 402.1 +/- 180 mg/dl (p = .0002). The total protein concentration increased by over 330% from baseline values. Ultrafiltrating plasma effluent from autotransfused cell salvaged CPB circuit contents could prove beneficial, but further study is required to discover ways to separate unfavorable products, such as activated platelet-leukocyte products and reduced plasma free hemoglobin, and to lower heparin concentrations of the plasma-concentrate.