Present status of apheresis technologies: part 4. Leukocyte filter

This article is the fourth of a 4 part series describing the currently available apheresis devices and technologies. The sections include the following: Part 1, Membrane Plasma Separator (published in Vol. 1, No. 1); Part 2, Membrane Plasma Fractionator (published in Vol. 1, No. 2); Part 3, Adsorbent (published in Vol. 1, No. 3); and Part 4, Leukocyte Filter.

Leukocytapheresis therapy by extracorporeal circulation using a leukocyte removal filter

Leukocytapheresis therapy has been used to try to treat such intractable diseases as autoimmune and neurologic diseases, achieving good results. However, a number of problems have been identified in leukocyte removal by thoracic duct drainage or continuous centrifugal separation; namely the high risk, expensive cost, and complicated operation. Asahi Medical Co. has developed an innovative solution for such conventional problems. Its new leukocyte removal filter (Cellsorba) is capable of removing white blood cells by perfusion of whole blood by means of simple extracorporeal circulation. Leukocytapheresis therapy using the Cellsorba column is being confirmed as extremely effective for many inflammatory diseases, as well as in autoimmune and neurologic diseases. This paper outlines information about the Cellsorba column and introduces several reports on therapeutic results.

Clinical evaluation of the new Pall leucocyte-depleting blood cardioplegia filter (BC1)

It is now widely acknowledged that autologous leucocytes are inappropriately activated during cardiopulmonary bypass (CPB). Removal of these activated leucocytes has been proposed as a clinical intervention. Several papers have recently reported benefits of systemic leucocyte depletion during CPB. There is also evidence that leucocyte-depleted blood cardioplegia is advantageous in the globally ischaemic human heart transplant setting. Recently, a new leucocyte-depleting filter for blood cardioplegia has been developed (Pall, BC1). In this paper, we report on the safety and efficiency of this device in the clinical situation. Fourteen patients undergoing routine cardiac surgery were recruited into this study. The BC1 blood cardioplegia filter was found to be an efficient leucocyte-depleting device, removing in excess of 70% (p = 0.001) of white blood cells, on average, from up to 5.3 litres of blood cardioplegia. The filter removed a small proportion of platelets (typically 11.3%), however, this was not statistically significant and no bleeding problems were encountered. Red cell removal was negligible and was not statistically significant, and no evidence of haemolysis was noted. The filter offered a very low resistance to flow with a mean pressure drop (deltaP) of 10.8 mmHg at a mean flow rate of 315 ml/min. We conclude that the Pall BC1 filter is a safe and efficient device for use with blood cardioplegia.

The protective effect of a leucocyte removal filter on the lung in open-heart surgery for ventricular septal defect

We elucidated the protective effect of a leucocyte removal filter on cardiopulmonary bypass (CPB)-induced lung dysfunction during open-heart surgery for ventricular septal defect (VSD). Forty-six VSD patients were divided into two groups: (a) a control group of 22 patients in whom the banked blood was used to prime the CPB circuit, and (b) a leucocyte removal group of 24 patients in whom a leucocyte removal filter was used for priming and every supplement of banked blood during and after the operation. The respiratory index immediately after the CPB was significantly lower in the leucocyte removal group than in the control group (2.23 +/- 0.22 vs 3.90 +/- 0.68; p < 0.05). The duration of stay in the intensive care unit was significantly shorter in the leucocyte removal group (3.0 +/- 0.4 vs 4.1 +/- 0.4 days; p < 0.05). These data suggest that the use of a leucocyte removal filter for blood added to the CPB prime or administered after CPB may have protective effects on lung function after open heart surgery for VSD patients.

Pediatric peripheral blood progenitor cell collection: haemonetics MCS 3P versus COBE Spectra versus Fresenius AS104

BACKGROUND

An increasing number of apheresis machines are becoming available for peripheral blood progenitor cell (PBPC) collection in children.

STUDY DESIGN AND METHODS

At the Children's Hospital of Florence (Italy), three apheresis machines were evaluated: MCS 3P (Haemonetics) (10 procedures in 4 patients, aged 10-12 years, weight 23.5-64 kg), Spectra, (COBE) (8 procedures in 3 patients, aged 4-17 years, weight 19-59 kg), and AS104 (Fresenius) (24 procedures in 9 patients, aged 2-16 years, weight 13.6-60 kg). For PBPC quantitative analysis, CD34 cytofluorimetry was employed. Relevant variables analyzed included efficiency of CD34+ cell extraction and enrichment, mononuclear cell purity and red cell contamination of the apheresis components, and platelet count decreases after leukapheresis.

RESULTS

No significant differences in CD34+ cell-extraction abilities were found. However, the AS104 provided consistently purer leukapheresis components in terms of mononuclear cell and CD34+ cell enrichment (441 +/- 59%, vs. 240 +/- 35% and 290 +/- 42% for MCS 3P and Spectra, respectively). Postapheresis platelet counts dropped the least with the AS104. The smallest patient who underwent apheresis with MCS 3P (the only machine working on discontinuous flow and hence with greater volume shifts) weighed 23.5 kg and tolerated the procedure well, with no signs of hemodynamic instability. No significant complications were observed.

CONCLUSION

All machines seem to have comparable PBPC extraction efficiency, but the AS104 seems to give the component with the greatest PBPC enrichment. This feature might be relevant for further ex vivo cell processing (CD34+ cell selection, expansion, and so on).

A comparison of different filters for white cell reduction

Removal of white blood cells (WBCs) from blood components before transfusion by filters with at least 3 log10 depletion may prevent or delay leukocyte-associated transfusion reactions such as HLA alloimmunization, non-hemolytic febrile reactions, transmitted infections (e.g., CMV, HTLV-1), and immunomodulation. The aim of this study was to compare the leukocyte removal efficiency (LRE) of six commercial bedside filters that are said to achieve 3 log10 (Bio R-01), Leucostop 4LT-1, Pall RC 50) and 4 log10 (Bio R-01 Plus, Pall RC 400, Pall RC XL-1) WBC depletion. A total of 430 units of whole blood ranging from 32 to 92 for each filter type were analyzed by an automated counter before and after filtration. Postfiltration blood samples were also evaluated for WBCs by Nageotte chamber. All the filters demonstrated leukocyte removal about 1 log10 less than the manufacturer's claim. The fourth generation filters showed a better performance than the third generation filters. Of them, Pall RC XL-1 showed the best efficacy with 99.93 percent leukocyte removal and a median residual WBCs of 1.6 x 10(6) per unit. These results indicate that the fourth generation filters, which are designed for the filtration of packed red cells, in particular Pall RC XL-1, are also able to reduce WBCs from whole blood below the critical antigenic leukocyte load (5 x 10(6)), and can be efficiently used for polytransfused patients to prevent alloimmunization.

Comparison of COBE white cell-reduction and standard plateletpheresis protocols in the same donors

BACKGROUND

It is necessary to protect patients from white cell (WBC)-caused side effects of platelet transfusion by reducing the WBC contamination in single-donor platelets.

STUDY DESIGN AND METHODS

A new COBE Spectra WBC (leuko)-reduction system (LRS) was compared to the COBE standard plateletpheresis (standard) procedure. Each of 62 donors underwent plateletpheresis under the two protocols (LRS and standard). The collection efficiency and WBC contamination in the components collected using the techniques were compared. Platelets were counted in a cell counter and WBCs were counted using two full grids of a Nageotte chamber.

RESULTS

The preseparation and postseparation numbers for red cells, WBCs, and platelets as well as the number of collected platelets were not different in the two techniques. Collection efficiency in the LRS procedures was 96.2 +/- 13.0 percent of that in the standard procedures. Median WBC contamination in the platelet components was 10,160 per LRS procedure and 56,500 per standard procedure. The purity of the LRS components was significantly improved (p = 0.001), as seen in a comparison of the WBC numbers in components per procedure after log10 transformation (LRS: 0.096 +/- 0.195 x 10(6); standard: 0.390 +/- 1.075 x 10(6)).

CONCLUSION

These data suggest that the LRS procedure produces platelet concentrates with a collection efficiency that is comparable to that obtained with the standard technique and with a residual WBC content that satisfies even the most stringent criteria for filtered platelets. As this purity can be achieved without platelet loss or alteration, conventional fiber filtration no longer seems necessary or useful in this type of single-donor platelet component.

Leukocytapheresis with leukocyte removal filter as new therapy for ulcerative colitis

Leukocytapheresis (LCAP) with a leukocyte removal filter column was administered for 45 patients with ulcerative colitis (UC). We evaluated changes in the leukocyte count and the differential percentages during LCAP. Cytokine production was assessed from each patient's peripheral mononuclear cells or monocytes. Flow cytometry was performed to assess the removal rates of activated cells and adhesion molecule positive cells by LCAP. Clinical improvement was recognized in 35 of 45 patients during intensive LCAP therapy, and it continued throughout maintenance therapy in 32 patients (71.1%). The leukocyte count was decreased to about 40% during the first 30 min, but it increased to approximately 170% at 20 min after the completion of LCAP. The concentration of tumor necrosis factor (TNF)alpha before LCAP in the effective group was higher than it was in either the ineffective group or the control group. Its level decreased to near normal range after LCAP. In the effective group, the concentrations of interleukin (IL)-1beta, IL-2, interferon (IFN)gamma, and IL-8 were near the normal upper limits before LCAP; however, they had decreased after LCAP. The concentration of IL-4 increased after LCAP. In the ineffective group, in contrast, the concentrations had been at or near normal before the initial LCAP treatment. Flow cytometry study revealed that LCAP could remove the activated cells and adhesion molecule positive cells more effectively. The clinical improvement and the changes observed before and after LCAP therapy suggest that LCAP is able to intervene in the causal mechanism(s) of UC.

Non-tunneled catheters for the collection and transplantation of peripheral blood stem cells in children

We analyzed the use of non-tunneled (polyurethane, double lumen) central venous catheters (CVCs) for the collection, conditioning, transplantation and immediate post-transplantation periods in 56 children with various malignant diseases. A total of 71 leukaphereses were performed, with a mean of 1.2 apheresis per patient, following administration of granulocyte colony-stimulating factor (G-CSF) using a continuous flow blood cell separator (Cobe Spectra). The mean TBV (total blood volume) processed was 4.5 +/- 1.2 s.d. (range 2.4-7). The mean flow rate was 30.6 ml/min and the duration of a single apheresis was 327 +/- 84 s.d. (range 175-511 min). The mean purities and efficacies of collections were 77.38 +/- s.d. (range 42-100) and 42.78 +/- s.d. (range 24-80), respectively. The mean numbers of mononuclear cells (MNC) and CD34+ cells collected were 9.3 +/- 6.9 s.d. x 10(8)/kg (range 2-49) and 6.2 +/- 7.2 s.d. x 10(6)/kg (range 1-42), respectively. We observed the following complications during catheter insertion for collection: pneumothorax (1.7%), mechanical dysfunction (3.5%) that resolved with thrombolytic therapy. Complications during conditioning, transplantation and immediate post-transplantation periods were entry site infection in five patients (8.92%), catheter-related infection in two (3.57%) and catheter-related sepsis in three (5.35%). Our results indicate that the collection of PBSC with non-tunneled catheters is safe, effective and dis associated with a low incidence of complications.

[The efficiency of a new porous type leukocyte removal filter for red cell blood components, Terumo Imuguard III-RC, in the rapid transfusion conditions]

We evaluated the efficiency of a new porous type leukocyte removal filter for red cell blood components, Terumo Imuguard III-RC, in the rapid transfusion conditions. One leukocyte removal filter was used for 2 units of RC-M.A.P (red cell mannitol-adenine-phosphate). Filtration methods employed were gravity infusion, high pressure infusion (300 mmHg), pumping infusion and 20 ml.min-1 infusion under high pressure (300 mmHg). Blood samples were taken before and after the filtration to measure white blood cell (WBC), red blood cell (RBC) and platelet content. Blood samples before filtration and after filtration with WBC excluded, were examined by automated hematology analyzer (Coulter counter STKS-Retic). WBC after filtration was counted by the hemacytometer method using Nageotte Chamber. The removal rate of WBC was found to be more than 99.99% and residual WBC content was less than 4 x 10(4) with every method. The recovery rate of RBC was not significantly decreased in all filtration methods. The removal rate of platelet was equal in all filtration methods. In conclusion, Imuguard III-RC could be useful for effective homologous blood transfusion.

Activation of the contact system by filtration of platelet concentrates with a negatively charged white cell-removal filter and measurement of venous blood bradykinin level in patients who received filtered platelets

BACKGROUND

Several recent reports have described hypotensive transfusion reactions in patients receiving platelet concentrates (PCs) filtered through white cell-reduction filters. It is well known that a negatively charged surface activates the contact system, consisting of factor XII, prekallikrein, and high-molecular-weight kininogen.

STUDY DESIGN AND METHODS

To clarify the mechanisms of these hypotensive reactions, the possibility that white cell-reduction filtration activates the contact system was examined. Venous blood plasma bradykinin levels were also measured in patients receiving PC transfusions through filters.

RESULTS

None of the measured values were changed by filtration through a positively charged filter. However, filtration through a negatively charged filter resulted in a decrease in the amounts of prekallikrein and an increase in the amount of bradykinin generated, which indicated the activation of the contact system. The bradykinin level was inversely related to the activity of angiotensin-converting enzyme (ACE) in the PCs and was elevated by addition of an ACE inhibitor. Although the venous blood plasma bradykinin level did not change in two patients with a normal ACE activity during PC transfusion through the negatively charged filter, two patients who had decreased ACE activity, showed a significant increase in bradykinin during the transfusion.

CONCLUSION

These results suggest that the generation of a large amount of bradykinin by filtration of PCs through a negatively charged filter might cause hypotensive reactions in patients with decreased ACE activity. The clinical significance of bradykinin generation requires further study.

Complications associated with central venous catheters used for the collection of peripheral blood progenitor cells to support high-dose chemotherapy and autologous stem cell rescue

The purpose of this study was to review the incidence and type of complications associated with the insertion and use of central venous catheters for leukapheresis and high-dose chemotherapy with stem cell rescue. One hundred sixty-seven central venous catheters placed either at the transplant center or by various community surgeons were studied for insertion complications, inability to perform leukapheresis and incidence of infection. The overall incidence of hemo- or pneumothorax was 3.6%. Inability to pherese occurred in 13% of catheters placed by outside surgeons and 6.5% of catheters inserted at the transplant institution. Most often, these were due to malposition of the catheter too high in the superior vena cava or in other veins. Deep venous thrombosis was often related to this malposition and occurred in 4.8% of all patients. Pulmonary embolism was not seen in these patients despite the fact the catheters were often left in place during the thrombotic episode. Early or late-onset infections occurred in 6.5% of patients and were most often exit site infections. The incidence of complications of pheresis catheters is high but might be reduced by more attention to proper placement of the catheter closer to the right atrial/superior vena cava junction, and limiting insertion to a cadre of surgeons familiar with leukapheresis requirements.

A new tool in white blood cell reduction for packed red cells: 5 log depletion

The recent development of new filters used for leucocyte reduction aims at restricting the number of leucocytes to a threshold where their undesirable effects can be minimized or excluded. In this paper we describe the performance of a new filter named BIO R01 MAX and claimed by the manufacturer to perform 5 Log10 depletion. The results show that the efficiency of the filter reached 5 Log10 depletion and the absolute number of white blood cells in the post-filtration units is always less than 2 x 10(4) with considerable safety in the prevention of transfusion reactions.

Large-scale isolation of CD34+ cells using the Amgen cell selection device results in high levels of purity and recovery

The Amgen Cell Selection Device (ACSD) is a fully automated system based on the research scale magnetic-activated cell separation (MACS) system (Miltenyi Biotech GmbH, Bergisch Gladbach, Germany) for the selection of CD34+ cells. Leukapheresis products (LP) (n = 30) from normal donors mobilized with recombinant human granulocyte colony-stimulating factor (rhG-CSF) were selected with the ACSD to evaluate the performance of this system. The starting LP contained a median of 0.51% CD34+ cells (range 0.21%-1.54%) and a median WBC count of 3.0 x 10(10) (range 1-4.7 x 10(10) cells). After selection on the ACSD a mean purity of 91.5% +/- 0.6% CD34+ cells was obtained, with a median purity of 95.5% CD34+ cells. A median of 98 x 10(6) total CD34+ cells were recovered postselection, with a range of 31-323 x 10(6) cells collected from the LP. This represented a mean recovery of 81.7% +/- 6% of CD34+ cells and a median of 78% compared with starting CD34+ cell numbers in the LP. FACS analysis of the selected products demonstrated a 4-5 log depletion of T cell subsets, including CD3, CD4, CD8, and CD56 subsets. These data demonstrate the high performance obtained with the ACSD resulting in a final product of greater than 90% purity of CD34+ cells. CD34+ cells selected with the ACSD represent an ideal product for clinical applications, such as tumor cell purging, T cell depletion for allogeneic transplant, ex vivo expansion, and gene therapy.

Strategy of leukocyte filtration for immunomodulation: development of stainless steel leukocyte filter

Commercially available leukocyte filters are frequently used to prepare leukocyte depleted blood products for prevention of transfusion reactions. Recently, immunomodulation by using leukocyte filtration was evaluated. At this time, a new leukocyte filter was fabricated with a 4 microm diameter stainless steel fiber. The goal of this study was to assess the efficiency of the stainless steel filter for leukocyte and platelet removal by comparison with the polyester filter that is commercially available. The production of humoral factors, including interleukin-1 beta, tumor necrosis factor-alpha, and interleukin-1 receptor antagonist (IL-1 Ra), was also evaluated. The results show that the stainless steel filter has more than 2 times greater efficiency in leukocyte removal than the polyester filter. Furthermore, the cytokine studies indicate good biocompatibility of the filter, and the stainless steel filter has a possibility of inhibiting inflammatory cytokines by inducing interleukin-1 receptor.

Evaluation of a new prestorage leukoreduction filter for red blood cell units

BACKGROUND AND OBJECTIVES

Prestorage leukoreduction offers a variety of potential benefits and is becoming more commonly practiced. The LeukoNet prestorage leukoreduction filtration system is intended for leukoreduction of red blood cells and uses a vent to allow automatic drainage of red cells from the filter.

MATERIALS AND METHODS

We studied the functional characteristics and the in-vivo and in-vitro properties of leukoreduced AS-1 Red Blood Cells prepared with this new system. Units of AS-1 Red Blood Cells were filtered at 4 degrees C through the LeukoNet filter 24-48 h after collection and stored under usual conditions for 42 days. Residual leukocytes were enumerated using a Nageotte chamber or with a polymerase chain reaction (PCR) technique. In the clinical trial (phase one), 21 donors had units stored with and without leukoreduction for 42 days; biochemical assays were done before and after storage, and 51Cr/99mTc red cell recovery studies at the end of the storage period.

RESULTS

Leukocyte content after filtration was 3.2 +/- 2.6 x 10(4)/unit (n = 21), and all units had < 1 x 10(5) leukocytes (median: 3.8 x 10(4)). In-vivo paired studies showed no difference in 24-hour recovery (control: 82.1 +/- 5.8%; test: 82.9 +/- 6.0%). Hemolysis was halved with leuko-reduction (0.59 +/- 0.30 vs. 0.29 +/- 0.11%; p < 0.05), and glucose consumption was reduced by 5% compared to control units (p = < 0.05). Other biochemical parameters showed no differences. In the practical trial (phase two), filtration time was 41 +/- 23 min. With a residual leukocyte content of 6.6 +/- 4.9 x 10(4)/unit and 14 +/- 3% red cell loss (n = 84). Six additional units underwent leukocyte enumeration by PCR and had 2.6 +/- 1.1 x 10(4) residual leukocytes.

CONCLUSIONS

Under the conditions studied, the LeukoNet leukoreduction filtration system produces about 4-5 log10 leukocyte content reduction.

Leukocyte filtration of single-donor platelet units through an integrated filter system for the Fresenius AS 104 blood cell separator

BACKGROUND AND OBJECTIVES

White cell depletion of platelet concentrates is widely applied to reduce the incidence of transfusion complications. We investigated a new plateletpheresis kit with an integrated filter for leukocyte depletion of platelets.

MATERIALS AND METHODS

Parameters of product quality were investigated before and after in-line filtration of 70 single-donor platelet (SDP) units obtained by apheresis. We studied three different filter batches manufactured for the Fresenius AS 104 blood cell separator, and evaluated different softwares and interface positions with respect to platelet (PLT) yield and white blood cell (WBC) contamination.

RESULTS

PLT yields before and after filtration was not statistically different in the protocols studied. WBC contamination after WBC depletion was in the range of 10(4)/SDP unit. Glucose, lactate dehydrogenase, and the morphology score were not statistically different before and after filtration.

CONCLUSIONS

In-line WBC filtration of SDP units sufficiently reduced WBC below 5 x 10(6)/unit. The study allowed definition of the filter composition and apheresis parameters to optimize PLT yield and minimize WBC contamination.

Quinton-Mahurkar catheter as short-term central venous access for PBSC collection: single-center experience of 370 aphereses in 110 patients

We retrospectively analyzed our experience with the Quinton-Mahurkar dual-lumen hemodialysis catheter as short-term central venous access for harvesting peripheral blood stem cells (PBSC) for autologous transplantation. For intensification therapy for various malignancies 370 leukaphereses were performed in 110 candidates. The catheter was placed percutaneously under local anesthesia only for the time of blood collection and in no case was it used for the PBSC transplant. No systemic antithrombotic prophylaxis was administered. PBSC were collected using a continuous flow cell separator, COBE Spectra, after mobilization with chemotherapy followed by cytokine: rhGM-CSF and rhG-CSF s.c. (35 patients) or rhG-CSF s.c. alone (75 patients). The median number of aphereses was two (1-13). Eighty-nine patients (81.3%) required three or fewer sessions to collect the minimum mononuclear cell target number of 6 x 10(8) MNC/kg. The volume of blood per kg body weight processed for each apheresis was 240 ml (range 150-560 ml) equivalent to 13 l (6-30 l) and the median flow rate was 61 ml/min (range 30-90 ml/min). The total CD34+ cell yield per patient was 3.55 x 10(6)/kg (0.26-34.8) and the MNC yield was 6.1 x 10(8)/kg (2.96-12.6). We observed the following complications: local infection in four cases (3.6%), catheter occlusion for local thrombosis in two cases (1.8%) and pneumothorax in one case (0.97%). In our experience the Mahurkar-Quinton catheter, when placed specifically for apheresis sessions, was very effective and safe for PBSC harvesting with a low incidence of complications.

Cytokine production and protein adsorption in a stainless steel filter used for leukocyte reduction

A new metallic filter made from a stainless steel fiber has been under development. To evaluate biocompatibility of this filter, the authors compared cytokine production with that of stainless steel fibers and polyester fibers by using a mononuclear cell culture. Furthermore, adsorbed proteins on each fiber were identified by using sodium-dodecyl sulfate (SDS)-polyacrlyamide gel electrophoresis (PAGE). The levels of tumor necrosis factor (TNF)-alpha in the cultured supernatant without fibers as the control, with polyester fibers, and with stainless steel fibers were 28.1 +/- 8.1, 39.3 +/- 2.6, and 29.1 +/- 6.7 pg/ml, respectively. The levels of interleukin (IL)-1 beta were 7.6 +/- 3.2, 8.9 +/- 1.5, and 8.9 +/- 2.1 pg/ml, respectively. The IL-4 levels were less than 0.25 pg/ml, and the interferon-tau levels were less than 7.8 pg/ml in all three conditions. The amount of adsorbed proteins was 3.39 +/- 0.27 microgram/cm2 for the polyester fibers and 2.72 +/- 0.23 microgram/ cm2 for the stainless steel fibers. The protein bands adsorbed to the polyester fibers by SDS-PAGE analysis were observed at approximately 180, 120, 90, 76, 67, 59, 56, and 28 kd molecular weight. In contrast, the protein bands adsorbed to the stainless steel fibers were observed at 90, 76, 67, 62, 56, 28, and 12 kd molecular weight. Thus, the proteins adsorbed to the stainless steel fibers differed from those on the polyester fibers. By western blot analysis, the amounts of albumin, IgG tau chain, and fibronectin adsorbed on the stainless steel fibers were smaller than those on the polyester fibers. The results of this study suggest that the stainless steel fibers do not stimulate monocytes, Th1, and Th2 cells. In addition, lesser adsorption of IgG tau chain and fibronectin may indicate that the stainless steel is a superior material for anti thrombogenicity compared to polyester.

Influence of the red blood cell preparation method on the efficacy of a leukocyte reduction filter

The performance of a leukocyte reduction bedside filter with different types of RBC concentrates was analyzed. Three types of RBCs were prepared: buffycoat-depleted RBCs suspended in saline-adenine-glucose-mannitol (SAGM)-additive solution (BC-RBCs; n = 20), RBCs suspended in SAGM-additive solution without buffy coat removal (SAGM-RBCs; n = 20), and RBCs drawn in CPDA-I conservative solution and processed for component preparation by the platelet-rich plasma method (CPDA-RBCs; n = 20). The units were filtered within 8 h of collection. One filter was used for every 2 units. High numbers of residual WBCs were found even in the units filtered first. Filtration of CPDA-RBCs resulted in a higher residual WBC content than SAGM-RBCs or BC-RBCs (p = 0.0032 and p = 0.0002, respectively). The filter performance strikingly decreased when the WBC load per filter exceeded 4 x 10(9) or the platelet load was less than 100 x 10(9). We conclude that filter performance varies with the WBC and platelet content of the RBC concentrates. Under the experimental conditions assayed in this study CPDA-RBCs are the least appropriate ones to be used for bedside leukocyte reduction.

Peripheral blood stem cell (PBSC) collection in extremely low-weight infants

While PBSC collection has become a safe procedure for adults, only a few reports exist about its efficacy, safety and feasibility in paediatric patients, especially extremely low-weight infants. We describe successful PBSC collection in three infants of less than 10 kg body weight (BW; range: 6.92-9.4 kg) suffering from stage IV neuroblastoma. Harvest of PBSC started after mobilisation with high-dose chemotherapy and G-CSF, as soon as 1.0% CD34+ cells were detected. Collections were performed using a Baxter CS-3000 Plus separator primed with a mixture of irradiated, white cell-depleted and CMV-negative packed red cells resuspended in 5% human albumin and diluted with saline to match the patient's haematocrit. Performing a median of four, (4-7, median, range) procedures we collected at least 4 x 10(8)/kg BW nucleated cells (NC) from all three patients. The infants were not sedated and showed no serious side-effects. All three children were successfully transplanted with myeloid engraftment in 8 (7-9) days, independence from red cell support was achieved in 15 (10-20) days and from platelet transfusions in 25 (14-29) days after PBSC infusion. We conclude that PBSC harvesting using continuous flow cell separators is safe, even in low-weight infants of less than 7 kg BW.

Allogeneic peripheral blood progenitor cell transplantation: analysis of short-term engraftment and acute GVHD incidence in 33 cases. allo-PBPCT Spanish Group

The results of 33 allogeneic peripheral blood progenitor cells transplants (allo-PBPCT) in adult patients with hematologic malignancies were analyzed in a retrospective and multicenter study. In 21 of 33 cases (63%) the disease was refractory or in advanced stage and eight of the 33 cases (24%) were second transplants after relapse. Donors were treated with a median of 10 (4-16) micrograms/kg/day of rhG-CSF subcutaneously for 5-7 days. Three required a central venous line for harvesting. Peripheral blood leukapheresis product contained a median of 5.9 (1.8-13) 10(6)/kg CD34+ cells and a median of 309.5 (153-690) 10(6)/kg CD3+ cells. After a myeloablative regimen, all patients received PBPC from HLA-identical donors as the sole source of progenitor cells. Cyclosporin A (CsA) alone (n = 2), CsA and steroids (n = 9), and CsA and methotrexate (MTX) (n = 22) were used for GVHD prophylaxis. Growth factors post-transplant were given to 11 patients (33%). The median follow-up of the patients was 3 months. Actuarial median day for hemopoietic recovery was: neutrophils to >0.5 (>1) x 10(9)/l, day 14 (15); platelets to >20 (>50) x 10(9)/l, day 14 (21). The quantity of CD34+ cells infused did not significantly affect the engraftment kinetics, from a starting cutoff of 2.5 x 10(6)/kg. The speed of neutrophil recovery seemed to be influenced strongly by using rhG-CSF post-transplant and marginally by the type of GVHD prophylaxis. Actuarial probability for grade II-IV acute GVHD of the whole group was 37% (95% Cl, 20-54%).

Leukocyte-reduced blood components: patient benefits and practical applications

PURPOSE/OBJECTIVES

To review the various types of filters used for red blood cell and platelet transfusions and to explain the trend in the use of leukocyte removal filters, practical information about their use, considerations in the selection of a filtration method, and cost-effectiveness issues.

DATA SOURCES

Published articles, books, and the author's experience.

DATA SYNTHESIS

Leukocyte removal filters are used to reduce complications associated with transfused white blood cells that are contained in units of red blood cells and platelets. These complications include nonhemolytic febrile transfusion reactions (NHFTRs), alloimmunization and refractoriness to platelet transfusion, transfusion-transmitted cytomegalovirus (CMV), and immunomodulation. Leukocyte removal filters may be used at the bedside, in a hospital blood bank, or in a blood collection center. Factors that affect the flow rate of these filters include the variations in the blood component, the equipment used, and filter priming. Studies on the cost-effectiveness of using leukocyte-reduced blood components demonstrate savings based on the reduction of NHFTRs, reduction in the number of blood components used, and the use of filtered blood components as the equivalent of CMV seronegative-screened products.

CONCLUSIONS

The use of leukocyte-reduced blood components significantly diminishes or prevents many of the adverse transfusion reactions associated with donor white blood cells. Leukocyte removal filters are cost-effective, and filters should be selected based on their ability to consistently achieve low leukocyte residual levels as well as their ease of use.

IMPLICATIONS FOR NURSING PRACTICE

Physicians may order leukocyte-reduced blood components for specific patients, or the components may be used because of an established institutional transfusion policy. Nurses often participate in deciding on a filtration method, primarily based on ease of use. Understanding the considerations in selecting a filtration method will help nurses make appropriate decisions to ensure quality patient care.