Filtration Characteristics of Polyester Mesh (Pall) Micropore Blood Transfusion Filter John Barrett, MB; Edith Miller, MS; Martin S. Litwin, MD
\s=b\ Stored
human blood of varying age
was
turn to normal after filtration. On the basis of this research, we conclude that polyester mesh micropore blood transfusion filters are not as effective as Dacron wool (Swank) transfusion filters in removal of microaggregates from stored human blood. If a polyester mesh filter must be used, it is recommended that once occlusion of the filter has occurred, the filter should then be discarded and another in-
serted.
(Arch Surg 111:56-59, 1976)
of microaggregates in blood stored under standard blood bank conditions is now a well recog¬ nized occurrence.19 The presence of microaggregates is in¬ dicated by an increase in screen filtration pressure (SFP) of the blood.3·5·812 Transfusion of blood containing microaggregates has been implicated in the development in hu¬ mans of posttraumatic pulmonary insufficiency.2-41216 The simplest method for removal of microaggregates from blood transfusions containing such particles is by ad¬ ministration of the blood to patients through micropore blood transfusion filters. The two types of micropore fil¬ ters most widely used are Dacron wool (Swank) filters and pleated polyester mesh (Pall) filters. Filtration character¬ istics of the Dacron wool filter for multiple transfusions of human blood have been previously described.17 This study determines in similar fashion the filtration characteristics of the polyester mesh filter.
Development
METHODS AND RESULTS
Twenty-five units (1 unit approximately 500 ml) of human blood that had been stored in citrate-phosphate-dextrose (CPD) solution under standard blood bank conditions at 4 C for varying periods of time were used in this research. All were filtered through pleated polyester mesh micropore blood transfusion fil¬ ters, and various indexes were measured before and after filtra¬ tion. =
for publication June 19, 1975. From the Department of Surgery, Tulane University School of Medicine, New Orleans. Dr Barrett was an Ainsworth Scholar from University College, Cork, Ireland, and a Surgical Research Fellow. Reprint requests to Tulane University School of Medicine, 1430 Tulane Ave, New Orleans, LA 70112 (Dr Litwin).
Accepted
Outdated Human Blood
passed through
polyester mesh (Pall) micropore blood transfusion (pore size, 40\g=m\).Passage through the filter resulted in decreased screen filtration pressure (SFP) of the blood and increased filter weight. Numerous microaggregates were removed, but SFP did not re-
1. One unit of blood (average age, 34 days) was filtered through each of five polyester mesh filters. Before filtration, average SFP was 256 mm Hg; after filtration, average SFP decreased to 18 mm Hg (P < .0025) [Fig 1]). Slight differences in average platelet and white blood cell counts and average plasma hemoglobin levels be¬ fore and after filtration were not of statistical significance. There were no changes after filtration in average hematocrit readings, serum protein concentrations, or whole blood viscosities at 23 in¬ verse seconds (23 sec"' [Table]). Prior to blood filtration, each filter was saturated with normal saline solution and then weighed. After the unit of blood had passed through the filter, it was weighed again. Average wet weight of the material removed from each unit of blood was 4.2 gm. 2. Seven units of blood (average age, 25 days) were passed through a single polyester mesh filter. The SFP of each unit was elevated prior to filtration (Fig 2). After passage of five units, the filter became occluded and no further blood could be passed under gravity pressure. When a pressure cuff was applied, the remain¬ ing two units were pumped through. Screen filtration pressure of each of the units was lowered by passage through the filter (Fig 2). After filtration, there were no statistically significant changes in hematocrit readings, platelet or white blood cell counts, or plasma hemoglobin levels. Prior to nitration, the filter was saturated with normal saline solution and then weighed. After filtration of the seven units of blood, the filter was again weighed. Total wet weight of the mate¬ rial removed from all seven units of blood was 23.2 gm. 3. Three units of grossly outdated human blood (more than 90 days old) were filtered through a single polyester mesh filter. Prior to filtration, each of the units had a markedly elevated SFP (Fig 3), but no gross blood clots were present. The filter became oc¬ cluded after gravity passage of only one half of the first unit of blood, and the remaining two and one half units were pushed through under pressure. Filtration of the second unit led to a marked increase in SFP after filtration. After filtration of the third unit, SFP rose still further.
Unexpired
Human Blood
1. One of each of five units of seven-day-old blood was passed of five polyester mesh filters. Average SFP prior to filtration was 172 mm Hg, and after passage through the filters, average SFP was 17 mm Hg (P < .0125) [Fig 4]). No statistically significant changes occurred after filtration in average platelet or white blood cell counts or average plasma hemoglobin levels. Average hematocrit readings, plasma protein concentrations, and whole blood viscosities at 23 sec- ' were also not altered by filtra¬ tion (Table). Prior to filtration, each filter was saturated with normal saline
through each
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Iowa User on 06/21/2015
Fig 1.—Average changes in expired human blood af¬ ter passage through polyester mesh (Pall) transfu¬ sion filters. Even though large numbers of microaggregates were removed, many passed filter, and screen filtration pressure (SFP) did not return to normal. Other cellular elements were not damaged. WBC indicates white blood cell count; plasma Hgb,
-
JJxilii
SFP(mmHg) Before G After
plasma hemoglobin level.
34 DAYS OtD
SINGtE PAU
25 DAY OLD BLOOD
PAU FILTER
-
(%)
Hematocrit
25
Before D After
jmmniM
00
Platelet Count
(thousands/mm3) A Before
VAfter 50
WBC( hundreds) • Before
OArter 0
1000
Hgb (mg%)
Plasma
• Before
OAfter
After
Before SINGtE
PALI- >90 DAYS OtD
SFP (mmHg) -/
Unit Number 2.—Seven units of expired human blood were passed through single poly¬ ester mesh (Pall) filter. Many microaggregates were removed without damage to remaining cellular elements. SFP indicates screen filtration pressure; WBC, white blood cell count; plasma Hgb, plasma hemoglobin level.
Fig
BEFORE after
Average Changes Occurring in Five Units of Banked Blood After Polyester Mesh (Pall) Filtration
_
Expired Blood* Hematocrit reading, % Plasma proteins Albumin, gm/100 ml Globulin, gm/100 ml
Unir Number
Fig 3.—Outdated human blood with markedly ele¬ vated screen filtration pressure (SFP) was forced through single polyester mesh (Pall) filter. Large numbers of microaggregates passed through filter in progressively increasing numbers, and SFP after filtration of blood increased in progressive fashion.
Fibrinogen, mg/100 ml Blood viscosity, centipoises at 23 inverse sec
(23 sec-i)_ *
Blood
t Blood solution and then weighed. After the unit of blood had been fil¬ tered, the filter was weighed again. Average wet weight of the material removed by each filter from each unit of blood was 3.8 gm. 2. Five units of
seven-day-old human blood were passed through a single polyester mesh filter. Average SFP of four of the five units was markedly elevated prior to filtration, and SFP of each of the units was lowered by passage through the filter (Fig 5). There were no significant changes after filtration in average platelet or white blood cell counts, or plasma hemoglobin levels. Prior to filtration, the filter was saturated with normal saline solution and then weighed. After filtration of the five units of blood, the filter was again weighed. Total wet weight of the mate¬ rial removed from all five units of blood
was
8.0 gm.
was was
Human
Unexpired
Blood i
Before 42
After 41
Before 42
After 43
3.25 1.97 339
3.12 1.97 331
2.88 1.68 304
2.80 1.68 293
8.1
8.1
8.0
8.0
34 days old. 7 days old.
COMMENT That microaggregates accumulate in banked blood has been well established.19 Transfusion to animals through standard transfusion filters of blood containing such par¬ ticles has been demonstrated to be associated with devel¬ opment of detrimental pulmonary changes.1018 For this reason, it seems reasonable that microaggregates should be removed before blood is transfused. Filtration through micropore blood transfusion filters ap¬ pears to be the simplest method for removal of this amorphous debris. The polyester mesh micropore blood transfusion filter consists of a polyester mesh filter screen arranged in a
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Iowa User on 06/21/2015
5 PAU FILTERS- AVERAGE OF 5 UNITS 200
7 DAY OLD BLOOD
PALL FILTER 300
r
-
SFP(mmHg) SFP
(mmHg)
Before After 100
50
Hematocrit
WBC( hundreds) .O
30
h Before After
Platelets
(thousands/mm3)
ig
k-«7
(%)
0
II fill
111
250
Free Plasma Hgb
(mgVo)
110
200
Platelet Count
(thousands/mm5)
Before
After
Fig 4.—Average changes in seven-day-old human blood after passage through polyester mesh (Pall)
A Before V After
1 50
WBC (hundreds) • Before OAfter
100
transfusion filters. As occurred with outdated blood (Fig 1), large numbers of microaggregates were re¬ moved. However, other microaggregates passed fil¬ ter and screen filtration pressure (SFP) after filtra¬ tion did not return to normal. Other cellular elements were not damaged. WBC indicates white blood cell count; free plasma Hgb, free plasma hemoglobin level.
200
Fig 5.—Five units of seven-day-old human blood passed through single polyester mesh (Pall) fil¬ ter. As occurred with outdated blood (Fig 2), many microaggregates were removed without damage to remaining cellular elements. SFP indicates screen
were
Plasma
Hgb
(mg·/.)
loo
•Before OAfter 0
filtration pressure; WBC, white blood cell count; plasma Hgb, plasma hemoglobin level.
pleated, accordion-like fashion (Fig 6). Its total filtering area is 160 sq cm. The strands of the filter are arranged in a lock-weave manner so that they are mechanically bound to each other at each
crossover. The uniform-size pores formed by this arrangement are 40> square. The filtering element is supported by a larger mesh screen (pore size, 1.25 mm) immediately preceding and in juxtaposition to it. The entire apparatus is enclosed in an outer rigid poly¬ propylene housing. The unit requires no priming and is designed to be interposed between the transfusion con¬ tainer and a standard intravenous set. It adds 6 cm to the length of the overall intravenous set. In the present experiments, the polyester mesh filter caused no detrimental changes in the formed elements of the blood. This was true for outdated as well as for unexpired seven-day-old blood. The filter did not cause changes in plasma protein concentrations. Satisfactory flow rates were achieved by gravity flow for up to five units of hu¬ man blood through a single filter. In one experiment, the filter became occluded with debris at that point, but an ad¬ ditional two units could be pumped through.
As evidenced by a reduction in the SFP of all filtered blood, the polyester mesh filters also removed large quan¬ tities of microaggregates. Greater quantities of blood could be passed through polyester mesh filters than through Dacron wool filters before filter occlusion oc¬ curred, but this increased passage was at the expense of
allowing microaggregates to pass. The experiment illustrated in Fig
3 was conducted to determine whether aggregates would pass the 40µ pores when pressure was used to force blood through an oc¬ cluded polyester mesh filter. Obstruction of the filter oc¬ curred after filtration of only 250 ml of this microaggregate-rich blood. When pressure was then applied to force passage of the remaining blood, SFP after filtration rose progressively. Blood of this advanced age would cer¬ tainly not be used clinically for transfusion; nevertheless, this experiment demonstrates that once microaggregate occlusion of the polyester mesh filter has occurred, the danger then exists that particles may be forced through the filter if pressure is applied. For this reason it appears that once occlusion of the polyester mesh filter has oc-
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Iowa User on 06/21/2015
does not effectively remove all microaggregates. As yet there is no evidence that detrimental pulmonary effects occur in the human after infusion of blood contain¬ ing microaggregates between 20µ and 40µ in diameter. In recent animal experiments, however, microaggregate-rich blood was transfused through polyester mesh filters to dogs.19 Average SFP of the transfused blood after filtra¬ tion was 26 mm Hg. The animals developed an increase in pulmonary arteriovenous shunting of blood and a decrease in pulmonary diffusing capacity for oxygen. When a sim¬ ilar group of dogs was transfused through Dacron wool filters, average SFP of the blood after filtration was only 4 mm Hg, and they did not develop similar-detrimental pul¬ monary changes.
This investigation was supported by Contract No. DADA 17-67-C-7049, Surgical Directorate, US Army Medical Research and Development Com¬ mand.
References
Fig 6.—Polyester mesh (Pall) micropore blood transfusion filter. Polyester mesh screen with uniform-size pores 40µ square is ar¬ ranged in pleated, accordion-like fashion (A). Total filtering area is 160 sq cm and is enclosed in rigid polypropylene housing (B). Entire apparatus is 6 cm long. Upper spike is inserted into trans¬ fusion container and standard intravenous set fits into lower out¬ let port.
curred, the filter should then be discarded and
a new one
inserted.
Using a 40µ filter, Solis and Gibbs8 showed that microag¬ gregates in the 40µ range are not all removed by this filter. In his research, it appeared that aggregates smaller than 40µ and indeed, others up to 50µ in diameter passed
through the filter. He further suggested that even though the filter may disrupt the "binding" forces of other larger aggregates, such disruption may only be temporary and
the aggregates may reform distal to the filter. In this research great numbers of microaggregates were removed by the polyester mesh filter. This was dem¬ onstrated by the increase in filter weight after the blood had passed through it and the decrease in SFP of the fil¬ tered blood. Certainly, larger amounts of blood can be ad¬ ministered through this filter than through standard transfusion filters before detrimental pulmonary changes are induced. However, SFP of the blood after filtration was higher than that of blood passed through Dacron wool filters.17 These data indicate that the polyester mesh filter
1. Arrington PJ, McNamara JJ: Effect of agitation on platelet aggregation and microaggregate formation in banked blood. Ann Surg 181:243-244, 1975. 2. Connell RS, Swank RL: Pulmonary microembolism after blood transfusions: An electron microscopic study. Ann Surg 177:40-50, 1973. 3. Dhall DP, Matheson NA: Platelet aggregates filtration pressure: A method of measuring platelet aggregation in whole blood. Cardiovasc Res 3:155-160, 1969. 4. Jenevein EP, Weiss DL: Platelet microemboli associated with massive blood transfusions. Am J Pathol 45:313-321, 1964. 5. McNamara JJ, Boatright D, Burran EL, et al: Changes in some physical properties of stored blood. Ann Surg 174:58-60, 1971. 6. Moseley RV, Doty DB: Changes in filtration characteristics of stored blood. Ann Surg 171:329-335, 1970. 7. Shields CE: Evaluation of undefined material present in stored blood. Milit Med 136:351-353, 1971. 8. Solis RT, Gibbs MB: Filtration of microaggregates in stored blood. Transfusion 12:245-250, 1972. 9. Swank RL, Roth JC, Jansen J: Screen filtration pressure method and adhesiveness and aggregation of blood cells. J Appl Physiol 19:340-346, 1964. 10. Dawidson I, Barrett JA, Miller E, et al: Pulmonary microembolism associated with massive transfusion: I. Physiologic effects and comparison in vivo of standard and Dacron wool (Swank) blood transfusion filters in its prevention. Ann Surg 181:51-57, 1975. 11. Dhall DP, Engeset J, McKenzie FN, et al: Screen filtration pressure of blood: An evaluation. Cardiovasc Res 3:147-154, 1969. 12. McNamara JJ, Molot MD, Stremple JM: Screen filtration pressure in combat casualties. Ann Surg 172:334-341, 1970. 13. Bennet SH, Geelhoed GW, Aaron RK, et al: Pulmonary injury resulting from perfusion with stored bank blood in the baboon and dog. J Surg Res 13:295-306, 1972. 14. Martin AM, Simmons RL, Heisterkamp CA: Respiratory insufficiency in combat casualties: Pathologic changes in the lungs of patients dying of wounds. Ann Surg 170:30-38, 1969. 15. Moseley RV, Doty DB: Death associated with multiple pulmonary emboli soon after battle injury. Ann Surg 171:336-346, 1970. 16. Reul G J, Greenberg SD, Lefrak EA, et al: Prevention of post-traumatic pulmonary insufficiency: Fine screen filtration of blood. Arch Surg 106:386-393, 1973. 17. Litwin MS, Relihan M, Sillin L: Filtration characteristics of Dacron wool (Swank) blood transfusion filters. South Med J 68:694-698, 1975. 18. Barrett J, Dawidson I, Dhurandhar HN, et al: Pulmonary microembolism associated with massive transfusion: II. The basic pathophysiology of its pulmonary effects. Ann Surg 182:56-61, 1975. 19. Barrett J, Dhurandar HN, Miller E, et al: 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. Ann Surg, to be published.
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Iowa User on 06/21/2015
\s=b\ Stored
human blood of varying age
was
turn to normal after filtration. On the basis of this research, we conclude that polyester mesh micropore blood transfusion filters are not as effective as Dacron wool (Swank) transfusion filters in removal of microaggregates from stored human blood. If a polyester mesh filter must be used, it is recommended that once occlusion of the filter has occurred, the filter should then be discarded and another in-
serted.
(Arch Surg 111:56-59, 1976)
of microaggregates in blood stored under standard blood bank conditions is now a well recog¬ nized occurrence.19 The presence of microaggregates is in¬ dicated by an increase in screen filtration pressure (SFP) of the blood.3·5·812 Transfusion of blood containing microaggregates has been implicated in the development in hu¬ mans of posttraumatic pulmonary insufficiency.2-41216 The simplest method for removal of microaggregates from blood transfusions containing such particles is by ad¬ ministration of the blood to patients through micropore blood transfusion filters. The two types of micropore fil¬ ters most widely used are Dacron wool (Swank) filters and pleated polyester mesh (Pall) filters. Filtration character¬ istics of the Dacron wool filter for multiple transfusions of human blood have been previously described.17 This study determines in similar fashion the filtration characteristics of the polyester mesh filter.
Development
METHODS AND RESULTS
Twenty-five units (1 unit approximately 500 ml) of human blood that had been stored in citrate-phosphate-dextrose (CPD) solution under standard blood bank conditions at 4 C for varying periods of time were used in this research. All were filtered through pleated polyester mesh micropore blood transfusion fil¬ ters, and various indexes were measured before and after filtra¬ tion. =
for publication June 19, 1975. From the Department of Surgery, Tulane University School of Medicine, New Orleans. Dr Barrett was an Ainsworth Scholar from University College, Cork, Ireland, and a Surgical Research Fellow. Reprint requests to Tulane University School of Medicine, 1430 Tulane Ave, New Orleans, LA 70112 (Dr Litwin).
Accepted
Outdated Human Blood
passed through
polyester mesh (Pall) micropore blood transfusion (pore size, 40\g=m\).Passage through the filter resulted in decreased screen filtration pressure (SFP) of the blood and increased filter weight. Numerous microaggregates were removed, but SFP did not re-
1. One unit of blood (average age, 34 days) was filtered through each of five polyester mesh filters. Before filtration, average SFP was 256 mm Hg; after filtration, average SFP decreased to 18 mm Hg (P < .0025) [Fig 1]). Slight differences in average platelet and white blood cell counts and average plasma hemoglobin levels be¬ fore and after filtration were not of statistical significance. There were no changes after filtration in average hematocrit readings, serum protein concentrations, or whole blood viscosities at 23 in¬ verse seconds (23 sec"' [Table]). Prior to blood filtration, each filter was saturated with normal saline solution and then weighed. After the unit of blood had passed through the filter, it was weighed again. Average wet weight of the material removed from each unit of blood was 4.2 gm. 2. Seven units of blood (average age, 25 days) were passed through a single polyester mesh filter. The SFP of each unit was elevated prior to filtration (Fig 2). After passage of five units, the filter became occluded and no further blood could be passed under gravity pressure. When a pressure cuff was applied, the remain¬ ing two units were pumped through. Screen filtration pressure of each of the units was lowered by passage through the filter (Fig 2). After filtration, there were no statistically significant changes in hematocrit readings, platelet or white blood cell counts, or plasma hemoglobin levels. Prior to nitration, the filter was saturated with normal saline solution and then weighed. After filtration of the seven units of blood, the filter was again weighed. Total wet weight of the mate¬ rial removed from all seven units of blood was 23.2 gm. 3. Three units of grossly outdated human blood (more than 90 days old) were filtered through a single polyester mesh filter. Prior to filtration, each of the units had a markedly elevated SFP (Fig 3), but no gross blood clots were present. The filter became oc¬ cluded after gravity passage of only one half of the first unit of blood, and the remaining two and one half units were pushed through under pressure. Filtration of the second unit led to a marked increase in SFP after filtration. After filtration of the third unit, SFP rose still further.
Unexpired
Human Blood
1. One of each of five units of seven-day-old blood was passed of five polyester mesh filters. Average SFP prior to filtration was 172 mm Hg, and after passage through the filters, average SFP was 17 mm Hg (P < .0125) [Fig 4]). No statistically significant changes occurred after filtration in average platelet or white blood cell counts or average plasma hemoglobin levels. Average hematocrit readings, plasma protein concentrations, and whole blood viscosities at 23 sec- ' were also not altered by filtra¬ tion (Table). Prior to filtration, each filter was saturated with normal saline
through each
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Iowa User on 06/21/2015
Fig 1.—Average changes in expired human blood af¬ ter passage through polyester mesh (Pall) transfu¬ sion filters. Even though large numbers of microaggregates were removed, many passed filter, and screen filtration pressure (SFP) did not return to normal. Other cellular elements were not damaged. WBC indicates white blood cell count; plasma Hgb,
-
JJxilii
SFP(mmHg) Before G After
plasma hemoglobin level.
34 DAYS OtD
SINGtE PAU
25 DAY OLD BLOOD
PAU FILTER
-
(%)
Hematocrit
25
Before D After
jmmniM
00
Platelet Count
(thousands/mm3) A Before
VAfter 50
WBC( hundreds) • Before
OArter 0
1000
Hgb (mg%)
Plasma
• Before
OAfter
After
Before SINGtE
PALI- >90 DAYS OtD
SFP (mmHg) -/
Unit Number 2.—Seven units of expired human blood were passed through single poly¬ ester mesh (Pall) filter. Many microaggregates were removed without damage to remaining cellular elements. SFP indicates screen filtration pressure; WBC, white blood cell count; plasma Hgb, plasma hemoglobin level.
Fig
BEFORE after
Average Changes Occurring in Five Units of Banked Blood After Polyester Mesh (Pall) Filtration
_
Expired Blood* Hematocrit reading, % Plasma proteins Albumin, gm/100 ml Globulin, gm/100 ml
Unir Number
Fig 3.—Outdated human blood with markedly ele¬ vated screen filtration pressure (SFP) was forced through single polyester mesh (Pall) filter. Large numbers of microaggregates passed through filter in progressively increasing numbers, and SFP after filtration of blood increased in progressive fashion.
Fibrinogen, mg/100 ml Blood viscosity, centipoises at 23 inverse sec
(23 sec-i)_ *
Blood
t Blood solution and then weighed. After the unit of blood had been fil¬ tered, the filter was weighed again. Average wet weight of the material removed by each filter from each unit of blood was 3.8 gm. 2. Five units of
seven-day-old human blood were passed through a single polyester mesh filter. Average SFP of four of the five units was markedly elevated prior to filtration, and SFP of each of the units was lowered by passage through the filter (Fig 5). There were no significant changes after filtration in average platelet or white blood cell counts, or plasma hemoglobin levels. Prior to filtration, the filter was saturated with normal saline solution and then weighed. After filtration of the five units of blood, the filter was again weighed. Total wet weight of the mate¬ rial removed from all five units of blood
was
8.0 gm.
was was
Human
Unexpired
Blood i
Before 42
After 41
Before 42
After 43
3.25 1.97 339
3.12 1.97 331
2.88 1.68 304
2.80 1.68 293
8.1
8.1
8.0
8.0
34 days old. 7 days old.
COMMENT That microaggregates accumulate in banked blood has been well established.19 Transfusion to animals through standard transfusion filters of blood containing such par¬ ticles has been demonstrated to be associated with devel¬ opment of detrimental pulmonary changes.1018 For this reason, it seems reasonable that microaggregates should be removed before blood is transfused. Filtration through micropore blood transfusion filters ap¬ pears to be the simplest method for removal of this amorphous debris. The polyester mesh micropore blood transfusion filter consists of a polyester mesh filter screen arranged in a
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Iowa User on 06/21/2015
5 PAU FILTERS- AVERAGE OF 5 UNITS 200
7 DAY OLD BLOOD
PALL FILTER 300
r
-
SFP(mmHg) SFP
(mmHg)
Before After 100
50
Hematocrit
WBC( hundreds) .O
30
h Before After
Platelets
(thousands/mm3)
ig
k-«7
(%)
0
II fill
111
250
Free Plasma Hgb
(mgVo)
110
200
Platelet Count
(thousands/mm5)
Before
After
Fig 4.—Average changes in seven-day-old human blood after passage through polyester mesh (Pall)
A Before V After
1 50
WBC (hundreds) • Before OAfter
100
transfusion filters. As occurred with outdated blood (Fig 1), large numbers of microaggregates were re¬ moved. However, other microaggregates passed fil¬ ter and screen filtration pressure (SFP) after filtra¬ tion did not return to normal. Other cellular elements were not damaged. WBC indicates white blood cell count; free plasma Hgb, free plasma hemoglobin level.
200
Fig 5.—Five units of seven-day-old human blood passed through single polyester mesh (Pall) fil¬ ter. As occurred with outdated blood (Fig 2), many microaggregates were removed without damage to remaining cellular elements. SFP indicates screen
were
Plasma
Hgb
(mg·/.)
loo
•Before OAfter 0
filtration pressure; WBC, white blood cell count; plasma Hgb, plasma hemoglobin level.
pleated, accordion-like fashion (Fig 6). Its total filtering area is 160 sq cm. The strands of the filter are arranged in a lock-weave manner so that they are mechanically bound to each other at each
crossover. The uniform-size pores formed by this arrangement are 40> square. The filtering element is supported by a larger mesh screen (pore size, 1.25 mm) immediately preceding and in juxtaposition to it. The entire apparatus is enclosed in an outer rigid poly¬ propylene housing. The unit requires no priming and is designed to be interposed between the transfusion con¬ tainer and a standard intravenous set. It adds 6 cm to the length of the overall intravenous set. In the present experiments, the polyester mesh filter caused no detrimental changes in the formed elements of the blood. This was true for outdated as well as for unexpired seven-day-old blood. The filter did not cause changes in plasma protein concentrations. Satisfactory flow rates were achieved by gravity flow for up to five units of hu¬ man blood through a single filter. In one experiment, the filter became occluded with debris at that point, but an ad¬ ditional two units could be pumped through.
As evidenced by a reduction in the SFP of all filtered blood, the polyester mesh filters also removed large quan¬ tities of microaggregates. Greater quantities of blood could be passed through polyester mesh filters than through Dacron wool filters before filter occlusion oc¬ curred, but this increased passage was at the expense of
allowing microaggregates to pass. The experiment illustrated in Fig
3 was conducted to determine whether aggregates would pass the 40µ pores when pressure was used to force blood through an oc¬ cluded polyester mesh filter. Obstruction of the filter oc¬ curred after filtration of only 250 ml of this microaggregate-rich blood. When pressure was then applied to force passage of the remaining blood, SFP after filtration rose progressively. Blood of this advanced age would cer¬ tainly not be used clinically for transfusion; nevertheless, this experiment demonstrates that once microaggregate occlusion of the polyester mesh filter has occurred, the danger then exists that particles may be forced through the filter if pressure is applied. For this reason it appears that once occlusion of the polyester mesh filter has oc-
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Iowa User on 06/21/2015
does not effectively remove all microaggregates. As yet there is no evidence that detrimental pulmonary effects occur in the human after infusion of blood contain¬ ing microaggregates between 20µ and 40µ in diameter. In recent animal experiments, however, microaggregate-rich blood was transfused through polyester mesh filters to dogs.19 Average SFP of the transfused blood after filtra¬ tion was 26 mm Hg. The animals developed an increase in pulmonary arteriovenous shunting of blood and a decrease in pulmonary diffusing capacity for oxygen. When a sim¬ ilar group of dogs was transfused through Dacron wool filters, average SFP of the blood after filtration was only 4 mm Hg, and they did not develop similar-detrimental pul¬ monary changes.
This investigation was supported by Contract No. DADA 17-67-C-7049, Surgical Directorate, US Army Medical Research and Development Com¬ mand.
References
Fig 6.—Polyester mesh (Pall) micropore blood transfusion filter. Polyester mesh screen with uniform-size pores 40µ square is ar¬ ranged in pleated, accordion-like fashion (A). Total filtering area is 160 sq cm and is enclosed in rigid polypropylene housing (B). Entire apparatus is 6 cm long. Upper spike is inserted into trans¬ fusion container and standard intravenous set fits into lower out¬ let port.
curred, the filter should then be discarded and
a new one
inserted.
Using a 40µ filter, Solis and Gibbs8 showed that microag¬ gregates in the 40µ range are not all removed by this filter. In his research, it appeared that aggregates smaller than 40µ and indeed, others up to 50µ in diameter passed
through the filter. He further suggested that even though the filter may disrupt the "binding" forces of other larger aggregates, such disruption may only be temporary and
the aggregates may reform distal to the filter. In this research great numbers of microaggregates were removed by the polyester mesh filter. This was dem¬ onstrated by the increase in filter weight after the blood had passed through it and the decrease in SFP of the fil¬ tered blood. Certainly, larger amounts of blood can be ad¬ ministered through this filter than through standard transfusion filters before detrimental pulmonary changes are induced. However, SFP of the blood after filtration was higher than that of blood passed through Dacron wool filters.17 These data indicate that the polyester mesh filter
1. Arrington PJ, McNamara JJ: Effect of agitation on platelet aggregation and microaggregate formation in banked blood. Ann Surg 181:243-244, 1975. 2. Connell RS, Swank RL: Pulmonary microembolism after blood transfusions: An electron microscopic study. Ann Surg 177:40-50, 1973. 3. Dhall DP, Matheson NA: Platelet aggregates filtration pressure: A method of measuring platelet aggregation in whole blood. Cardiovasc Res 3:155-160, 1969. 4. Jenevein EP, Weiss DL: Platelet microemboli associated with massive blood transfusions. Am J Pathol 45:313-321, 1964. 5. McNamara JJ, Boatright D, Burran EL, et al: Changes in some physical properties of stored blood. Ann Surg 174:58-60, 1971. 6. Moseley RV, Doty DB: Changes in filtration characteristics of stored blood. Ann Surg 171:329-335, 1970. 7. Shields CE: Evaluation of undefined material present in stored blood. Milit Med 136:351-353, 1971. 8. Solis RT, Gibbs MB: Filtration of microaggregates in stored blood. Transfusion 12:245-250, 1972. 9. Swank RL, Roth JC, Jansen J: Screen filtration pressure method and adhesiveness and aggregation of blood cells. J Appl Physiol 19:340-346, 1964. 10. Dawidson I, Barrett JA, Miller E, et al: Pulmonary microembolism associated with massive transfusion: I. Physiologic effects and comparison in vivo of standard and Dacron wool (Swank) blood transfusion filters in its prevention. Ann Surg 181:51-57, 1975. 11. Dhall DP, Engeset J, McKenzie FN, et al: Screen filtration pressure of blood: An evaluation. Cardiovasc Res 3:147-154, 1969. 12. McNamara JJ, Molot MD, Stremple JM: Screen filtration pressure in combat casualties. Ann Surg 172:334-341, 1970. 13. Bennet SH, Geelhoed GW, Aaron RK, et al: Pulmonary injury resulting from perfusion with stored bank blood in the baboon and dog. J Surg Res 13:295-306, 1972. 14. Martin AM, Simmons RL, Heisterkamp CA: Respiratory insufficiency in combat casualties: Pathologic changes in the lungs of patients dying of wounds. Ann Surg 170:30-38, 1969. 15. Moseley RV, Doty DB: Death associated with multiple pulmonary emboli soon after battle injury. Ann Surg 171:336-346, 1970. 16. Reul G J, Greenberg SD, Lefrak EA, et al: Prevention of post-traumatic pulmonary insufficiency: Fine screen filtration of blood. Arch Surg 106:386-393, 1973. 17. Litwin MS, Relihan M, Sillin L: Filtration characteristics of Dacron wool (Swank) blood transfusion filters. South Med J 68:694-698, 1975. 18. Barrett J, Dawidson I, Dhurandhar HN, et al: Pulmonary microembolism associated with massive transfusion: II. The basic pathophysiology of its pulmonary effects. Ann Surg 182:56-61, 1975. 19. Barrett J, Dhurandar HN, Miller E, et al: 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. Ann Surg, to be published.
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