Utilization of a new strength citrate anticoagulant during centrifugal plateletpheresis. I. Assessment of donor effects

Apheresis techniques for collection of peripheral blood progenitor cells

The combination of effective mobilisation protocols and efficient use of apheresis machines has caused peripheral blood progenitor cells (PBPC) transplantation to grow rapidly. The development of apheresis technology has improved over the years. Today PBSC procedures have changed towards systems to minimise operator interaction and to reduce the collection of undesired cells such as polymorphonuclear cells and platelets using functionally closed, sterile environments for PBSC collection in keeping with Good Manufacturing Practice guidelines. Blood cell separators with continuous flow technique allow the processing of more blood than intermittent flow devices resulting in higher PBSC yields. Large volume leukapheresis with the processing of 3-4-fold donor's/patient's blood volume can increase the number of collected progenitor cells. Therefore, intermittent flow cell separators are indicated if only single vein access is available. Anticoagulant induced hypocalcaemia is an often observed side effect in long lasting PBPC harvesting and monitoring of electrolytes should be performed especially at the end of the apheresis procedure to supplement low levels of potassium, calcium or magnesium. Refinement and improvement of collection techniques continue to add to the armamentarium of current approaches for cancer and non-malignant conditions and will enable future strategies.

Randomized placebo-controlled study of oral calcium carbonate supplementation in plateletpheresis: II. Metabolic effects

BACKGROUND

The metabolic effects of oral calcium (Ca) supplementation during plateletpheresis were evaluated in a randomized, placebo-controlled trial.

STUDY DESIGN AND METHODS

Twenty-three donors underwent four plateletpheresis procedures each, receiving in random order, elemental Ca (Ca) 1 or 2 g orally, or a corresponding placebo, 30 minutes before donation. Ten of these donors underwent a fifth procedure using a 4-g Ca dose. All procedures were performed at a fixed citrate infusion rate of 1.5 mg per kg per minute.

RESULTS

Oral Ca induced dose-sensitive changes in parathyroid hormone (iPTH), total (tCa), and ionized (iCa) calcium levels. Compared to placebo, the greatest improvement in tCa and iCa levels occurred after the 2-g Ca dose (tCa of 73, 89, and 25% above placebo levels at 60 min, using 1, 2, and 4 g of oral Ca, respectively). Twenty-four hours after apheresis, serum tCa and iCa levels were higher, and iPTH levels lower, in donors who received oral Ca rather than placebo. Marked increases in urinary Ca and magnesium (Mg) excretion occurred at the completion of apheresis, were unaffected by Ca dose, and returned to baseline within 24 hours. Plateletpheresis also induced significant changes in serum alkaline phosphatase, 1,25-dihydroxyvitamin D, and osteocalcin levels immediately and at 24 hours after apheresis.

CONCLUSION

Plateletpheresis induces marked acute metabolic effects, with sustained changes evident up to 24 hours after the completion of apheresis. Oral Ca supplementation exerts a significant but clinically modest impact on selected laboratory variables associated with these effects. Further studies are indicated to examine the long-term impact of plateletpheresis, with or without Ca supplementation, on donor Ca balance and bone density.

Comprehensive analysis of citrate effects during plateletpheresis in normal donors

BACKGROUND

Although plateletpheresis procedures are generally well tolerated, the clinical and metabolic consequences associated with rapid infusion of up to 10 g of citrate are underappreciated, and a comprehensive description of these events is not available.

STUDY DESIGN AND METHODS

Clinical and laboratory changes were studied in seven healthy donors undergoing three 90-minute plateletpheresis procedures each, at continuous, fixed citrate infusion rates of 1.1, 1.4, and 1.6 mg per kg per minute.

RESULTS

Serum citrate levels increased markedly with increasing citrate infusion rates and did not achieve a stable plateau. As citrate infusion rates increased, the total volume processed and platelet yields also increased, but donor symptoms became more severe. Ionized calcium (iCa) and ionized magnesium (iMg) concentrations decreased markedly, by 33 and 39 percent below baseline, respectively, at a citrate rate of 1.6 mg per kg per minute. Intact parathyroid hormone levels were higher at 30 minutes than at later time points, despite progressive decreases in iCa and iMg. Urine citrate, calcium, magnesium, sodium, and potassium concentrations and urine pH values increased markedly during all procedures.

CONCLUSION

Marked, progressive increases in serum citrate levels occur during plateletpheresis, accompanied by symptomatic decreases in iCa and iMg, with significantly increased renal excretion of calcium, magnesium, and citrate.

Mechanisms of adverse effects during hemapheresis

For over 20 years blood components have been collected from normal donors by automated hemapheresis. Cell separators have become increasingly sophisticated, and relatively pure component "concentrates" can be obtained quite safely. Cytapheresis donors are monitored carefully, and serious reactions are very rare. In contrast, therapeutic apheresis procedures may be technically demanding and frequently are performed on very sick patients. Large volumes of blood are rapidly removed from the patient, anticoagulated, and separated into components by the automated cell separator. The blood component containing the pathogenetic factor (e.g., plasma containing an antibody) is retained outside of the body, and the remaining components (e.g., red cells, white cells, and platelets) plus the replacement fluid are reinfused. Complications can occur in normal cytapheresis donors because of the technical challenges of the procedure (e.g., extracorporeal circuit to be filled, use of citrate anticoagulant, need for large bore intravascular access, and rapid blood flow rates). All of these factors apply also to therapeutic patients plus the additional requirement for replacement fluids, and the clinical features of the underlying illness for which each patient is being treated. Fortunately, even with therapeutic patients, most complications are of modest severity and are easily managed with only temporary slowing or interruption of the hemapheresis procedure.

Plasma separation for artificial liver support

A bioartificial liver (BAL) support system, using plasma separation, has been developed to support acute liver failure patients. This study examined 14 consecutive BAL treatments in nine patients with severe acute liver failure. We report methods to achieve and manage plasma separation for an extended period of time. The mean duration of a BAL treatment was 435 minutes, with 26-59 liters of blood processed. Ionized hypocalcemia resulting in muscle twitching was a side effect of the therapy. Ionized calcium levels decreased significantly (P < .02) after BAL treatment; however, total calcium levels increased (P < .05). No significant changes were noted in heart rate, electrocardiogram [Q-T (Q-Tc) interval], blood pressure, prothrombin time, partial thromboplastin time, hematocrit, platelet count and serum phosphorous, magnesium, glucose, and pH. Plasma fibrinogen levels decreased significantly (P < .002). Ionized hypocalcemia due to the chelating effect of sodium citrate was controlled by calcium chloride administration, adjustment of blood separation rates, and reduction of the blood-to-citrate ratio. This report demonstrates that intensive, large-volume plasma separation for long periods of time can be achieved safely in critically ill patients without serious adverse effects.

[Safety of donors, quality of products, how much to reduce the quantity of citrate]

We examined 1,053 blood samples from 48 donors, for the effect of gradual reduction of citrate. We observed that: 1--Platelet count does not show any significant variation between 1/8 to 1/18 ratio. 2--In 13.3% of the cases, platelet clumping starts at 1/18 ratio. 3--There was no significant variation of the thrombin plasma level between 1/8 to 1/16 ratio (by measuring thrombin/ATIII complex). Our results show clearly that we can reduce the citrate ratio to 1/14 without expecting any adverse effect. Therefore we designated 1/14 as the security ratio. Parallel to this we also found that the average level +/- SD of ionized calcium is 100 +/- 10 muMol at 1/14 ratio.

Optimal hematologic variables for oxygen transport, including P50, hemoglobin cooperativity, hematocrit, acid-base status, and cardiac function

The two important blood properties that affect O2 delivery are the O2 equilibrium curve (OEC) and blood viscosity with its subsequent effect on flow (cardiac output). To quantitate these properties blood OEC's were analyzed in terms of the Adair 4-step oxygenation model and the resulting parameters were used to construct a computer nomogram to reproduce the OEC at any combination of effectors that regulate P50 (pH, PCO2, and 2,3-DPG). In this way, the P50 could be changed systematically and the effects on overall O2 transport could be studied. Hematocrit-viscosity-cardiac output relationships were taken from the literature and validated using data from human subjects with various pathological states and high-altitude natives. A model was then developed, using the Bohr integration, to predict the O2 transport function of blood under a variety of conditions including exercise and hypoxia. The results indicate that the optimal hematocrit is about 43-45%, even in hypoxia. The optimal P50, however, depends on the availability of O2: a high P50 is not necessarily beneficial in hypoxia and high cardiac output states. This model and general approach should prove useful in the design of blood substitutes.

Studies on the procurement of blood coagulation factor VIII in vitro studies on blood components prepared in half-strength citrate anticoagulant

The effect of replacing a standard citrate anticoagulant with one containing half the amount of citrate on the in vitro properties of components prepared from blood donations was investigated. This resulted in a significant improvement in factor VIII stability such that there was little loss during overnight storage, and this was reflected in the factor VIII yield in cryoprecipitate. The quality of cellular components in red cell units stored up to 35 days or platelet concentrates stored up to 7 days was not adversely affected. Although initial levels were similar to those in standard anticoagulant, the extent of fibrinopeptide A generation and complement C3 breakdown in red cell units stored for 35 days in half-strength citrate was somewhat increased.

Regional anticoagulation: hemodialysis with hypertonic trisodium citrate

We have developed a simplified method for performing regional citrate anticoagulation during hemodialysis. High ultrafiltration rates and specialized equipment were obviated by the use of a 1.6-mol/L trisodium citrate solution and a standard calcium-containing dialysate. Thirty-six dialyses were performed with this technique on 14 stable and 22 high bleeding risk patients. There was no significant decline in plasma-ionized calcium during citrate dialysis, ie, 3.85 +/- 0.34 mg/dL (mean +/- SE) predialysis, to 3.31 +/- 0.26 postdialysis; furthermore, no patient developed neuromuscular symptoms or evidence of cardiovascular instability from hypocalcemia. Serum sodium rose with this procedure, but not to hypernatremic levels. This method of citrate dialysis is safe and effective during continuous blood flow (double-needle) hemodialysis, and is no more difficult to perform than conventional heparin dialysis. Single-needle (reciprocating blood flow) hemodialysis was successfully performed by the additional use of a calcium-free dialysate and separate calcium chloride infusion (10% calcium chloride), but risks the production of unexpected hypercalcemia.

Controlling Anticoagulation in Extracorporeal Blood Circuits (hemoperfusion)

The study demonstrates that different individuals (monkeys) need different heparin doses so as to avoid either clotting or bleeding when an extracorporeal blood system is involved. The linear correlation between PT and WBPTT values enables to utilize the latter for monitoring the heparin level in the blood. One procedure is based on the application of the Gotch and Keen intravenous heparinization model in its steady state limit by utilizing the pre-treatment evaluation of k/S, the ratio of the elimination rate constant to the individual's sensitivity to heparin. A second procedure involves the direct heparinization of the extracorporeal system. The heparin infusion rate is monitored through the arterial WBPTT values after relating the individual's PT or WBPTT values to the in vitro heparin concentration in the blood.

In vitro and in vivo study of the effect of hemoperfusion through a column containing anion exchange particles on the amount and rate of heparin administration indicates that only the in vivo results are meaningful. The sharp response of WBPTT to relatively small changes of citrate concentration in the blood precludes individual monitoring by WBPTT. Work on the advantage of utilizing heparin together with citrate is required.

Adverse reactions to whole blood donation and plasmapheresis

Whole blood donation is recognized to be extremely safe, yet there have been reports of serious problems stemming from whole blood donation, and so-called "donor reactions" are regularly seen. While the physiologic causes of the common donor reactions are not completely understood, some effects of whole blood donation (such as transient iron deficiency) are understood but probably not significant. In order to avoid accepting any volunteer donor who might be at risk of a serious reaction, we may have been overly cautious in exclusion of potential donors. The pheresis donor is subjected to potential depletion of the protein or cellular elements being removed, problems caused by the device used for automated pheresis, or problems related to the infusion of potentially toxic substances. Documented benefit to the patient must balance these additional risks.

Citrate induced hypocalcaemia during cell separation

The value of calcium addition during cell-separation by the Haemonetics Model 30 has been investigated in two patient groups. Where citrated plasma was used as the replacement fluid the addition of calcium abolished clinical symptoms and reduced the degree of citrate induced hypocalcaemia. When Plasma Protein Fraction was used as the replacement fluid, calcium addition was not necessary as clinical symptoms and significant hypocalcaemia did not occur.

Plateletpheresis with the IBM model 2997. I. Effects of ACD, NIH formula B on selected donor indices

9 healthy subjects dosed with acid-citrate-dextrose, NIH formula B (ACD-B) while undergoing plateletpheresis with the continuous-flow IBM Model 2997 centrifuge, received on average 59.5 +/- (SD) 3.2 mg Na3 citrate.kg-1.h-1. This rate of infusion of Na3 citrate resulted in a maximum 12-fold rise in the concentration of citrate in serum (plasma) following the processing of 10 litres of whole blood, and subsequently reduced the level of total calcium in serum (plasma) by 9%. This dose of Na3 citrate produced no clinical symptoms suggestive of hypocalcaemia in these subjects, even though the use of acid-citrate-dextrose, NIH formula A (ACD-A) under identical conditions has been reported to reduce significantly the level of total calcium in serum, and concomitantly increase the number or reactions occurring in donors. From previous studies employing the intermittent-flow centrifugation system of plateletpheresis, a rate of infusion of Na3 citrate below 65 mg.kg-1.h-1 can insure maximum donor safety and this rate can be achieved with the IBM Model 2997 by the utilisation of ACD-B.

The utilisation of a new strength citrate anticoagulant during centrifugal plateletpheresis. III. Assessment of in vitro platelet metabolism

Employing the Haemonetics Blood Processor (IFC), a relatively pure platelet concentrate can be prepared by collecting only the first portion of the PRP leaving the centrifuge bowl (Fraction I). A subsequent fraction containing RBC and WBC contaminants (Fraction II) can be purified by means of a second centrifugation, using a conventional blood bank centrifuge (Fraction II), if transfusion of these contaminants would be detrimental to the recipient. Utilising the new 1.4% Na3-citrate anticoagulant, platelet metabolic parameters (ATP, ADP, AMP, lactate and pyruvate) as well as O2-uptake, were determined in Fraction I and II prepared from 10 normal healthy subjects. In contrast to previous studies reporting marked dysfunction in platelets contained in Fraction II when standard ACD-A was used during IFC, we observed no significant difference (Student's t test) in the present study between Fractions I and II, in regard to platelet metabolism, when using the new anticoagulant. It is further concluded that the second centrifugal manipulation does not exert a detrimental effect on platelet metabolism.

Leukapheresis and granulocyte transfusion

Granulocyte transfusion is becoming widely used in the treatment of infections in granulocytopenic patients. Several techniques are available for granulocyte collection. Some involve centrifugation of the whole blood and one removes granulocytes from whole blood by reversible adhesion to nylon fibers. The risks to the donor from leukapheresis do not appear to be greater than from whole blood donation. Granulocytes collected by centrifuge techniques function normally in vitro and have normal intravascular recovery and disappearance following transfusion. Granulocytes collected by filtration leukapheresis function almost normally in vitro but have a reduced intravascular recovery and abnormal kinetics as they leave the circulation. The role of leukocyte typing and compatibility testing for granulocyte transfusion is controversial. When the recipient has circulating antibody against donor leukocytes, transfused leukocytes do not circulate or migrate to sites of infection but are sequestered in the liver and spleen. Clinical studies have not defined whether patients benefit equally well clinically from transfusion of compatible or incompatible granulocytes. Initial reports of clinical trials of granulocyte transfusion were promising. However, similar patients who did not receive granulocytes were not studied. Most subsequent controlled trials showed a clear benefit from granulocyte transfusion while others did not. Differences in antibiotic therapy, chemotherapy, use of laminar flow rooms, and grouping of patients make it difficult to compare these clinical trials. Some, but not all, infected granulocytopenic patients benefit from transfusion. Granulocyte transfusions improve survival of granulocytopenic patients with gram negative sepsis and prolonged bone marrow aplasia. Studies are now attempting to identify other patients who should receive granulocytes, the optimum dose and schedule of transfusions, the optimum time to begin transfusion, and the value, if any, of prophylactic transfusions.

Plateletpheresis by discontinuous centrifugation: effect of collecting methods on the in vitro function of platelets

The in vitro function of platelets collected by two different methods during centrifugal plateletpheresis was compared. The RBC method involves collecting platelets with red cells followed by a supplementary spin to remove them, whereas the no-RBC method requires collecting platelets only from the buffy coat without red cells. Platelet response to adenosine diphosphate (ADP), epinephrine and collagen was slightly reduced in platelet-rich plasma (PRP) prepared by no-RBC technique and was markedly decreased in samples obtained by the RBC technique when compared to prepheresis controls. The decrease in platelet response to ADP, epinephrine and collagen was apparent in three testing systems: aggregation, release of serotonin and reptilase clot retraction. Both plasma and platelets appeared to be affected by the pheresis procedure. Platelet preparations obtained by both RBC and no-RBC techniques showed an increase of platelet factor 3 activity and an enhancement of aggregation, release of serotonin and clot retraction induced by thrombin as compared to prepheresis controls. Postpheresis platelet-poor plasma contains platelet membrane fragments which exhibit a high platelet factor 3 activity. The results showed that the RBC method, although providing a higher platelet yield, caused more qualitative alterations in platelets than in those obtained by no-RBC method, and that both methods of collecting platelets activated the procoagulant activity of platelets.

Whole blood storage in citrate and phosphate solutions containing half-strength trisodium citrate: cellular and biochemical studies

The efficacy of whole blood preservation in acid citrate dextrose (ACD-A) and citrate-phosphate dextrose (CPD) anticoagulants containing half-strength trisodium citrate concentrations, was determined by biochemical and cellular assessment during 28 day storage at 4 degrees--6 degrees. Erythrocyte 2,3-DPG and ATP concentrations, serum potassium, plasma haemoglobin, and blood pH values were similar between the standard and half-strength citrate counterpart in both ACD-A and CPD series, throughout the entire storage period. Erythrocyte indices (MCV, MCH, MCHC, and osmotic fragility) and the red cell, platelet, and leucocyte counts, were also similar regardless of the final citrate concentration in both ACD-A and CPD series during the 28 day storage period. Tests of coagulation (PT, KCCT, TT, and ethanol gel) and fibrinogen levels were also similar, except for a lower quantity of clottable fibrinogen at day 28 in half-strength CPD. The formation of platelet and leucocyte aggregates during storage, as measured by changes in the SFP, were similar in magnitude whether or not the half-strength citrate formulation was used in ACD-A or CPD. Phagocytic and bactericidal capacity against Staph. aureus was normal following 24-hr storage at 4 degrees--6 degrees, in both ACD-A and CPD preserved blood, regardless of the final citrate concentration. It may now be concluded from this evaluation and those of others, that a reasonable argument can be made for reducing the citrate quantity presently used during blood storage, in order to provide a safe and effective transfusion product for routine use.

The utilization of a new strength citrate anticoagulant during centrifugal plateletpheresis. II. Assessment of in vitro platelet function

Platelets contained in concentrates prepared by intermittent flow centrifugation utilizing 5.0 g total ionized citrate, function normally as assessed by tests for adhesion, spreading, and ADP and collagen-induced aggregation. The ability of platelets to adhere and to aggregate following incubation with ADP is significantly reduced, in samples taken immediately after the collection procedure. Total platelet collection and platelet collection efficiency, is not compromised by use of the above citrate concentration.