A Comparison In Vivo of Dacron Wool (Swank) and Polyester Mesh (Pall) Micropore Blood Transfusion Filters in the Prevention of Pulmonary Microembolism Associated with Massive Transfusion JOHN BARRETT, M.B.,* H. N. DHURANDHAR, M.B.B.S., D.C.P. (LOND),t EDITH MILLER, M.S., MARTIN S. LITWIN, M.D.4
Experiments were performed to compare the effectiveness in vivo of the two most widely used micropore blood transfusion filters in preventing detrimental physiologic changes associated with transfusion of microaggregate-containing blood. Exchange transfusion with stored bloodhaving an elevated screen filtration pressure (SFP) through polyester mesh (Pall) filters (Group PM) was followed by decreases in arterial blood pH and 02 consumption, increases in arterial blood pyruvate and lactate concentrations, and a decrease in pulmonary D02. The lungs of 5 of 6 animals revealed emboli far out in the pulmonary microcirculation. These changes did not occur in animals transfused through dacron wool (Swank) filters (Group DW). Even though an increase after transfusion in pulmonary Qs/Qt in Group PM did not achieve statistical significance when compared to pretransfusion Qs/Qt, it was significantly higher than that in animals in Group DW. Both filters removed considerable quantities of microaggregates; however, the polyester mesh (Pall) filters permitted passage of small microaggregates and development of detrimental physiologic changes. Dacron wool (Swank) filters completely removed measurable microaggregates and detrimental changes did not occur. T HE FORMATION of microaggregates consisting mainly
of platelets and white blood cells in human blood stored under standard blood bank conditions is a wellrecognized phenomenon.1 8'11'13"7"9'26'28'30 Their presence is indicated by an elevation in screen filtration pressure (SFP) of the blood.9-1'17'8' 27'29 Transfusion of banked blood containing such microaggregates through standard blood transfusion filters may be a cause of post-traumatic pulmonary insufficiency.8'13'15'18'20'22 Submitted for publication June 9, 1975. *Ainswoorth Scholar from University College, Cork, Ireland; and Surgical Research Fellow. tAssistant Professor of Pathology. tProfessor of Surgery. Supported by Contract No. DADA 17-67-C-7049, Surgical Directorate, U.S. Army Medical Research and Development Command
From the Departments of Surgery and Pathology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, La. 70112
Previous research in these laboratories has demonstrated that when blood with an elevated SFP is transfused to dogs, pulmonary artery pressure rises; arterial blood pH and 02 consumption drop; blood pyruvate and lactate concentrations increase; pulmonary shunting of blood away from the pulmonary alveoli (Qs/Qt) increases; and diffusing capacity of the pulmonary membrane for oxygen (DO2) decreases.2'9 These changes are caused by embolization of transfused microaggregates to the pulmonary arterioles and capillaries and later damage to their endothelial lining may result.2'8 At present two principal types of micropore blood transfusion filters for removal of 'microaggregates from stored blood are in general use. The first contains dacron wool as its main filtering element and removes particles larger than 15 microns in diameter (Swank filter, IL 200, Extracorporeal Medical Specialties, Inc., King of Prussia, Pennsylvania). The second is a polyester mesh filter with a fixed pore size of 40 microns (Pall "Ultipore" Filter, Pall Corporation, Glen Cove, New York). It was the purpose of this study to compare the effectiveness of dacron wool (Swank) and polyester mesh (Pall) micropore blood transfusion filters in preventing the physiologic changes associated with transfusion of microaggregate-containing blood. Materials and Methods
Using techniques previously described, blood from donor animals was collected and stored at 4 C.9 After 5
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days SFP of each unit of blood was determined. If the SFP was elevated, the unit was then used in the study. Mongrel dogs (average weight 15 kgs) were anesthesized with intravenous sodium pentobarbital, 25 mg/kg. Animals were ventilated on room air using a Harvard respirator at a rate of 12-14 cyles per minute and a tidal volume of 25 + 5 cc/kg. Tidal volume was monitored using a spirometer (Wright's Respirometer Mark 12). Pancuronium bromide, 1 mg, was injected intravenously to achieve muscle relaxation and was repeated as necessary during the course of the experiment to maintain complete relaxation. Under fluoroscopic control two catheters were passed through a right jugular venous cut-down, one into the pulmonary artery and the other into the right atrium. Using widebore catheters, the right femoral artery and vein were cannulated through a right femoral cut-down. Each animal was allowed to stabilize and the respiratory rate and tidal volume were adjusted until femoral arterial blood studies gave stable reproducible readings for pH, Pco2, and P02. Mixed venous P02 was then determined on blood from the right atrium. Per cent saturations of arterial and mixed venous blood were determined using an oximeter (American Optical Co.). 02 consumption on room air was determined using an 02 consumption meter (Oxford Instrument Co., Jackson, Mississippi). Blood pyruvate and lactate concentrations were determined by enzymatic procedures.21'25 Femoral artery, pulmonary artery and right atrial pressures were recorded continuously. Percent pulmonary arteriovenous shunt (Qs/Qt) was calculated by Berggren's method.4 Pulmonary diffusing capacity for 02 (DO2) was calculated by a modification of Bohr's method.5'7'23 Ventilation: perfusion ratio (Va/Qb) was determined from the 02-CO2 diagram of Rahn and
Fenn.7'24 Animals were then divided into two groups:
L. Group DW: Dacron Wool (Swank) Filter. The blood volume of each of 7 animals was assumed to be 10%o of its body weight. Each underwent an exchange transfusion of twice its calculated blood volume using the previously stored blood. Immediately prior to infusion each blood bag was warmed to 37 C in a water bath. Blood was infused in 50 cc aliquots into the femoral vein, and at the same time 50 cc aliquots were withdrawn from the femoral artery. Blood removed for the various sampling procedures was replaced during this period. All transfused blood was passed through a dacron wool (Swank) blood transfusion filter. SFP, hematocrit and white blood cell and platelet counts were determined on each unit of blood both before and after filtration. Each blood transfusion filter was replaced after three units
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(1500 cc) of blood had passed through it. The average time needed to complete each exchange transfusion was 90 minutes. Once transfusion had been completed Qs/Qt, DO2 and Va/Qb were again determined. At the conclusion of the experiment 5 animals were sacrificed and the positions of the pulmonary artery and right atrial catheters were confirmed. The remaining two animals served as followup models. Indicated determinations were repeated 6 hours after transfusion had been completed and these latter two animals were then sacrificed. A sample of lung tissue was obtained from 6 of the 7 animals for microscopic pathological examination. Sections of representative pieces of lung tissue were routinely stained with hematoxylin and eosin (H&E) and with periodic-acid-Schiff (PAS) and Verhoeff-Van Gieson (VVG) stains as the need arose. II. Group PM: Polyester Mesh (Pall) Filter. Seven animals were included in this group. Each underwent the same protocol as those in Group DW except that a polyester mesh (Pall) filter (pore size 40 microns) was used in place of the dacron wool (Swank) filter.
Results Pretransfusion arterial blood pH, Pco2 and Po2 did not differ significantly between the two groups (Table 1). After transfusion pH decreased in both groups. This change was of statistical significance only in Group PM (P
Experiments were performed to compare the effectiveness in vivo of the two most widely used micropore blood transfusion filters in preventing detrimental physiologic changes associated with transfusion of microaggregate-containing blood. Exchange transfusion with stored bloodhaving an elevated screen filtration pressure (SFP) through polyester mesh (Pall) filters (Group PM) was followed by decreases in arterial blood pH and 02 consumption, increases in arterial blood pyruvate and lactate concentrations, and a decrease in pulmonary D02. The lungs of 5 of 6 animals revealed emboli far out in the pulmonary microcirculation. These changes did not occur in animals transfused through dacron wool (Swank) filters (Group DW). Even though an increase after transfusion in pulmonary Qs/Qt in Group PM did not achieve statistical significance when compared to pretransfusion Qs/Qt, it was significantly higher than that in animals in Group DW. Both filters removed considerable quantities of microaggregates; however, the polyester mesh (Pall) filters permitted passage of small microaggregates and development of detrimental physiologic changes. Dacron wool (Swank) filters completely removed measurable microaggregates and detrimental changes did not occur. T HE FORMATION of microaggregates consisting mainly
of platelets and white blood cells in human blood stored under standard blood bank conditions is a wellrecognized phenomenon.1 8'11'13"7"9'26'28'30 Their presence is indicated by an elevation in screen filtration pressure (SFP) of the blood.9-1'17'8' 27'29 Transfusion of banked blood containing such microaggregates through standard blood transfusion filters may be a cause of post-traumatic pulmonary insufficiency.8'13'15'18'20'22 Submitted for publication June 9, 1975. *Ainswoorth Scholar from University College, Cork, Ireland; and Surgical Research Fellow. tAssistant Professor of Pathology. tProfessor of Surgery. Supported by Contract No. DADA 17-67-C-7049, Surgical Directorate, U.S. Army Medical Research and Development Command
From the Departments of Surgery and Pathology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, La. 70112
Previous research in these laboratories has demonstrated that when blood with an elevated SFP is transfused to dogs, pulmonary artery pressure rises; arterial blood pH and 02 consumption drop; blood pyruvate and lactate concentrations increase; pulmonary shunting of blood away from the pulmonary alveoli (Qs/Qt) increases; and diffusing capacity of the pulmonary membrane for oxygen (DO2) decreases.2'9 These changes are caused by embolization of transfused microaggregates to the pulmonary arterioles and capillaries and later damage to their endothelial lining may result.2'8 At present two principal types of micropore blood transfusion filters for removal of 'microaggregates from stored blood are in general use. The first contains dacron wool as its main filtering element and removes particles larger than 15 microns in diameter (Swank filter, IL 200, Extracorporeal Medical Specialties, Inc., King of Prussia, Pennsylvania). The second is a polyester mesh filter with a fixed pore size of 40 microns (Pall "Ultipore" Filter, Pall Corporation, Glen Cove, New York). It was the purpose of this study to compare the effectiveness of dacron wool (Swank) and polyester mesh (Pall) micropore blood transfusion filters in preventing the physiologic changes associated with transfusion of microaggregate-containing blood. Materials and Methods
Using techniques previously described, blood from donor animals was collected and stored at 4 C.9 After 5
690
Vol. 182
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No. 6
MICROPORE BLOOD TRANSFUSION FILTERS
days SFP of each unit of blood was determined. If the SFP was elevated, the unit was then used in the study. Mongrel dogs (average weight 15 kgs) were anesthesized with intravenous sodium pentobarbital, 25 mg/kg. Animals were ventilated on room air using a Harvard respirator at a rate of 12-14 cyles per minute and a tidal volume of 25 + 5 cc/kg. Tidal volume was monitored using a spirometer (Wright's Respirometer Mark 12). Pancuronium bromide, 1 mg, was injected intravenously to achieve muscle relaxation and was repeated as necessary during the course of the experiment to maintain complete relaxation. Under fluoroscopic control two catheters were passed through a right jugular venous cut-down, one into the pulmonary artery and the other into the right atrium. Using widebore catheters, the right femoral artery and vein were cannulated through a right femoral cut-down. Each animal was allowed to stabilize and the respiratory rate and tidal volume were adjusted until femoral arterial blood studies gave stable reproducible readings for pH, Pco2, and P02. Mixed venous P02 was then determined on blood from the right atrium. Per cent saturations of arterial and mixed venous blood were determined using an oximeter (American Optical Co.). 02 consumption on room air was determined using an 02 consumption meter (Oxford Instrument Co., Jackson, Mississippi). Blood pyruvate and lactate concentrations were determined by enzymatic procedures.21'25 Femoral artery, pulmonary artery and right atrial pressures were recorded continuously. Percent pulmonary arteriovenous shunt (Qs/Qt) was calculated by Berggren's method.4 Pulmonary diffusing capacity for 02 (DO2) was calculated by a modification of Bohr's method.5'7'23 Ventilation: perfusion ratio (Va/Qb) was determined from the 02-CO2 diagram of Rahn and
Fenn.7'24 Animals were then divided into two groups:
L. Group DW: Dacron Wool (Swank) Filter. The blood volume of each of 7 animals was assumed to be 10%o of its body weight. Each underwent an exchange transfusion of twice its calculated blood volume using the previously stored blood. Immediately prior to infusion each blood bag was warmed to 37 C in a water bath. Blood was infused in 50 cc aliquots into the femoral vein, and at the same time 50 cc aliquots were withdrawn from the femoral artery. Blood removed for the various sampling procedures was replaced during this period. All transfused blood was passed through a dacron wool (Swank) blood transfusion filter. SFP, hematocrit and white blood cell and platelet counts were determined on each unit of blood both before and after filtration. Each blood transfusion filter was replaced after three units
691
(1500 cc) of blood had passed through it. The average time needed to complete each exchange transfusion was 90 minutes. Once transfusion had been completed Qs/Qt, DO2 and Va/Qb were again determined. At the conclusion of the experiment 5 animals were sacrificed and the positions of the pulmonary artery and right atrial catheters were confirmed. The remaining two animals served as followup models. Indicated determinations were repeated 6 hours after transfusion had been completed and these latter two animals were then sacrificed. A sample of lung tissue was obtained from 6 of the 7 animals for microscopic pathological examination. Sections of representative pieces of lung tissue were routinely stained with hematoxylin and eosin (H&E) and with periodic-acid-Schiff (PAS) and Verhoeff-Van Gieson (VVG) stains as the need arose. II. Group PM: Polyester Mesh (Pall) Filter. Seven animals were included in this group. Each underwent the same protocol as those in Group DW except that a polyester mesh (Pall) filter (pore size 40 microns) was used in place of the dacron wool (Swank) filter.
Results Pretransfusion arterial blood pH, Pco2 and Po2 did not differ significantly between the two groups (Table 1). After transfusion pH decreased in both groups. This change was of statistical significance only in Group PM (P
