Effects of the Memo - Concentrator on Blood

___________ _ A high flux, non-traumatic ultrafilter (UF) can be useful for co;Jtrolling the volume in the cardiopulmonary bypass circuit. Recently three such devices have been made available. It is the purpose of this work to describe the direct effects of ultrafiltration with one of these devices, the HemoConcentrator, on blood. The effects were determined by calculating the net changes in blood components due to hemoconcentration of pump blood at the end of bypass. The net changes were calculated from measurements taken before and after the concentration process. Samples taken pre and post-transfusion of the concentrated blood to the patient were also compared. The blood volume left in the circuit, 2050 ± 136 cc was concentrated by circulation through the UF and a total of I 083 ± 74 cc of plasma water extracted at a rate of 87 ± 3 cc/min. The % net change for glucose, chloride, C02 , potassium, sodium, BUN, creatinine, and phosphorous approximated the net loss of the plasma water. There were no losses in hemoglobin, albumin, and fibrinogen and only 2.5% losses in white blood cells* and 15.3% losses in platelets.* There were no changes in the total amount of free plasma hemoglobin or lactate dehydrogenase. This work was supported in part by NIH Grant #S08-RR09128-03 and by a Grantin-Aid from the American Heart Association. Nassau and Suffolk County Chapters. Direct communications to: Yehuda Tamari, Division of Cardiovascular Surgery, North Shore University Hospital, Manhasset, NY 11030. Presented at AmSECT's 21st International Conference, April 19-21, 1983, New Orleans, LA. Volume 16, Number 3, Fall 1984 There was a decrease towards normal in prothrombin time from 48 to 34 sec* and thrombin time from 7.4 to 2.8 sec.* Following transfusion of the ultrafiltered blood there were increases in albumin from 3.5 to 4.2 gr/dl, * WBC from 11.4 to 12.9 x 10/ul,* RBC from 2.6 to 3.3 x 10/ul,* platelets from 150 to 182 x 10 /ul, * and fibrinogen from 161 to 216 mg/dl *. The RBC indices were not altered by the UF or transfusion. Conclusion: The Hemo-Concentrator is an efficient atraumatic UF device. Introduction ____________ _ Ultrafiltration in association with cardiopulmonary bypass (CPB) permits artificial diuresis during bypass as well as concentration of the blood left in the extracorporeal circuit at the end of bypass. 'The technique utilizes a simple, disposable devise to extract plasma water in order to concentrate and salvage all blood components with a molecular weight greater than 20,000 daltons. 6 Previous work from this laboratory has shown that a Tri Ex-3 hollow fiber dialyzera used in the ultrafiltration mode effectively concentrated blood after CPB. 3 However, the low water extraction rate (29 ml!min), the hematological changes associated with the use of the device as well as the recent availability of new devices prompted evaluations of other units. It is the purpose of this communication to report on the clinical use of the Hemo-Concentrator. *Paired t-test p < 0.05 "Tri Ex-3. Extracorporeal, Inc., King of Prussia, PA 19406 The Journal of Extra-Corporeal Technology 89 Materials and Methods _______ _ Fourteen patients undergoing coronary artery bypass surgery were studied as previously described. 3 Pre-bypass, the Hemo-Concentratorh was rinsed by a single pass of I ,000 ml of normal saline. At the end of CPB, aL the lines were emptied into the oxygenator and a blood sample (Pre-Cone) was taken from the arterial port of the oxygenator (Harvey H-I OOO)h. The blood was then pumped from the coronary perfusion port of the oxygenator through the ultrafilter (UF). The first 100 ml of the crystalloid priming solution to exit the ultrafilter were discarded and the outlet port of the UF was then connected to the arterial reservoir sampling port of the oxygenator. The blood was then recirculated at 275 ml!min through the ultrafilter and returned to the arterial side of the oxygenator. The ultrafiltration port was connected to a vacuum source (460 to -480 torr). The mean blood pressure in the ultrafilter was 50 to 80 torr, resulting in a mean transmembrane pressure of 530 torr. Recirculation through the ultrafilter continued until the initial volume in the oxygenator was reduced by about 50%. Suction was then discontinued and the blood flow was stopped. The outlet port of the ultrafilter was connected to a transfusion bag, the pump was restarted and the oxygenator and ultrafilter circuit were emptied into the bag. During the collection the ultrafilter was positioned with the blood outlet facing down, thereby facilitating the emptying of the device. The bag was weighed, mixed well and another blood sample obtained (Post -Cone). Within 30 minutes after the patient arrived in the surgical intensive care unit, a blood sample was taken from the patient (Pt-Cont) and the transfusion of the concentrated pump blood begun. During transfusion of the pump blood, protamine was administered to counteract the heparin. The transfusion was completed within 90 minutes. Thirty minutes after the transfusion another sample was taken (Pt-30). A final sample was taken the morning after surgery (Pt-AM). To determine the effect of the UF on the blood (Pre-Cone vs. Post-Cone) as well as the effect of the transfusion of this blood on the patient (Pt-Cont vs. Pt-30) the following tests were performed on bCR Bard, Santa Ana. CA 92705 90 The Journal of Extra-Corporeal Technology each sample: complete routine blood chemistries: glucose, chloride, C02 , potassium, sodium, blood urea nitrogen, creatinine, uric acid, calcium, phosphorous, osmolality, total protein, albumin, cholesterol, total bilirubin, direct bilirubin, alkaline phosphatase, lactate dehydrogenase (LDH), serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT) and creatinine phosphokinase (CPK); complete blood cell count; prothrombin time (normal 10-13 sec.), activated partial thromboplastin time (normal 25-35 sec.) thrombin time (normal 3.5 ± 0.5 sec), fibrinogen, heparin and plasma hemoglobin as previously described. 3 Complete routine chemistry tests and a sensitive total protein test, the accuracy being in mg% rather than gr% 7 were performed in the ultrafiltrate. To determine the effects of the ultrafiltration process on blood, the blood concentration of each component after ultrafiltration process, Cf, was calculated in terms of its concentration before the ultrafiltration process, Ci. For each blood component this normalized concentration, Cf/Ci x 100%, called the Measured Final Concentration, was compared to the Measured Final Concentration of hemoglobin (Hb). 3 Total hemoglobin was chosen as a marker because it does not cross the UF membrane and is not lost. Thus, the relative change in total hemoglobin concentration due to the ultrafiltration should be accompanied by identical changes in other components that are not lost. The comparison of the Cf/Ci ratios allows the determination of the effect of the UF on the blood independent of any inaccuracies in volume determinations. For any component, if Cf/Ci was greater than that for Hb, then the UF caused a net gain. Conversely, if the Cf/Ci was lower than that for Hb then the Uf caused a net loss. In contrast to the Measured Final Concentration, the Expected Final Concentration is defined as Ci times the ratio of initial blood volume, Vi, divided by the final blood volume, Vf. Thus if the initial blood volume is reduced by half, then the concentrations of components that do not cross the ultrafiltration membrane and are not lost or formed by the process are expected to double. Cf(expected) = Ci x Vi!Vf For any component, if the Measured Final Concentration is greater than the Expected Final ConVolume 16, Number 3, Fall 1984