Mollison’s Blood Transfusion in Clinical Medicine - part 10 pot

collection of blood from children is difficult. Children weighing between 28 and 50 kg can be bled of 250 ml into paedipaks, which contain 35 ml of CPD-A1. If these packs are not available, a standard-sized pack can be used with a satellite pack attached so that excess anticoagulant can be removed while retaining a closed system. The amount of blood to be taken should not exceed 12% of the blood volume and is calculated as: [weight (kg)/50] × 450 ml, and the volume of anticoagulant to be used as: [volume of donation (ml)/450] × 63 ml. It is prudent to perform the same tests on autologous blood as on blood donated by routine blood donors. The main reasons for this recommendation are: (1) to address the possibility that a mistake in identification may be made, leading to the transfusion of blood of the wrong ABO group or of blood contaminated with an infectious agent and (2) to discover whether the patient is already infected with a virus that he or she fears might be acquired by transfusion with allogeneic blood. UK collection and transfusion centres will not store autologous units found positive for HBsAg or for anti-HIV, -HCV or -HTLV. In any case, autologous donations should be clearly labelled and stored separ- ately from routine blood donations (Lee et al. 1993). Although the use of platelets is rarely indicated in elective surgery, except perhaps in complicated cardiac or vascular surgery, the collection of platelets with cell separators taken either 1–2 days or immediately before surgery has been reported (Giordano et al. 1988, 1989). The practice of collecting blood from healthy subjects for long-term frozen storage in case they should require future transfusion is expensive, wasteful and impractical. On the other hand, long-term storage of autologous blood is indicated for: (1) subjects with rare blood groups or with multiple red cell antibodies, for whom compatible blood may be difficult to find and (2) those rare patients who have had more than one unexplained haemolytic transfusion reaction. Even then, these frozen units often remain unused in storage and even the patient may forget that they exist (Depalma et al. 1990). In the UK, blood taken for autologous transfusion should not, if unused, be put into the general stocks of allogeneic blood (‘crossover’). The main reasons for this recommendation are that: (1) as, at the time of withdrawal, the donation was not intended for allogeneic transfusion, the criteria for donor acceptance could have been less stringent (e.g. the patient might have been taking medications or might have been transfused within the last year); (2) the labelling will be inappropriate; (3) most autologous blood is collected in hospitals, using different documentation from that used at transfusion centres; (4) the risk of errors increases as donation details transfer from one database to another; (5) the donor may have an increased chance of being positive for markers of infectious disease (Grossman et al. 1988; Starkey et al. 1989); and (6) a considerable proportion of the autologous units will be near expiry date before it is determined that they will not be needed for the patient donor. In any case, if programmes of autologous transfusion are properly planned, the volume of blood left unused after surgery should be small. In fact, in well-conducted programmes not less than 3% and at the most 9% of autologous units would be available for allogeneic blood transfusion. The complexities of record keeping in order to transfer such small numbers of units to the voluntary donor pool argue against the practice of ‘crossover’ (Silvergleid 1991). Intraoperative haemodilution Details of the haemodilution procedure are discussed in Chapter 2. Mathematical modelling indicates that deep acute normovolaemic haemodilution must be performed and substantial blood loss must occur before a practical red cell mass of autologous blood is ‘saved’ (Cohen and Brecher 1995). Put a different way, acute haemodilution appears to be as effective as pre-donation, and the same caveats regarding patient selection apply (Ness et al. 1992; Monk et al. 1999). Although most patients tolerate the reduced red cell mass that accompanies haemodilution and surgical bleeding without problems, cardiac ischaemia remains a concern and the procedure is best left to experienced practitioners (Carvalho et al. 2003). Red cell salvage: harvesting the operative field Intraoperative red cell salvage It was once a fairly common practice to collect blood shed into the peritoneal cavity, particularly when operating on patients with a ruptured ectopic gesta- tion or ruptured spleen, and to re-inject the blood immediately, or after filtration and citration, into the CHAPTER 18 812 patient’s circulation (for details, see eighth edition). Nowadays, when blood is salvaged at operation, special devices are used for the purpose. At least two types are available: (1) The simpler, less expensive, lightweight, canister type in which salvaged blood is anticoagulated and aspirated, using a vacuum supply, into a disposable liner bag contained in a reusable rigid canister. The liner bag has a capacity of 1900 ml and an integral filter. Once the liner is full, the red cells can be concentrated and washed in the blood bank or re-infused directly through the filter. (2) The more automated type, based on centrifuge-assisted, semi-continuous-flow technology and requiring some technical expertise, anticoagulates, washes and concentrates the red cells before re-infusion. Automated, microprocessor-controlled devices use disposable bowls, bags and tubing and can produce processed blood within 3–5 min, depending on the PCV of the aspirated red cells (Leach 1991; Williamson and Taswell 1991). As the simpler system has the potential for the transfusion of activated clotting factors, pro- coagulants, complement components, haemolysed blood, excess anticoagulant, particulate matter and tissue fluids, as well as for producing air embolism, large volumes of blood salvaged in this way cannot be used unless it is washed (Pineda 1990; Williamson and Taswell 1991). However, there is little risk of systemic complement activation or disseminated intravascular coagulation if less than 500 ml of unwashed salvaged blood is re-infused (Dzik and Sherburne 1990; Tawes et al. 1994). Cell salvage instruments of all types induce mechanical injury to the red cells collected, resulting in a fall in the Hb level, although the 2,3-DPG levels and red cell survival are satisfactory (Pineda 1990). Salvaged red cells are ordinarily not used if the blood is contaminated by microorganisms, tumour cells or substances such as topical disinfectants or bovine collagen (AuBuchon 1989; Williamson and Taswell 1991). However data to support these pro- hibitions are limited and the contraindications should not be considered absolute. For example, malignant cells can be found in the circulation prior to surgery and many more enter the circulation as soon as the surgeon manipulates the tumour. No randomized, controlled studies have been performed in the setting of malignancy and it is unlikely that any will be contemplated. However, uncontrolled studies do not suggest that intraoperative blood salvage increases the risk of tumour spread or shortens the life of the cancer patient (Osawa et al. 1992; Thomas 1999). For patients who decline transfusion for religious reasons, intraoperative salvage can enable major surgical procedures such as hepatic resection for the cancer patient (Nieder et al. 2004). Favourable results associated with the transfusion of significant volumes of salvaged washed red cells during operation have been reported in various type of patients, i.e. those with trauma or ruptured ectopic pregnancy or those receiving liver transplants or undergoing cardiovascular, vascular or orthopaedic surgery. However, despite the apparent value of cell salvage in procedures such as vascular surgery, there are as yet surprisingly few controlled data to support its use (Alvarez et al. 2004). When very large volumes of salvaged red cells are transfused, sup- plementary transfusions of platelets and fresh-frozen plasma (FFP) are likely to be needed. More than 7000 cases of red cell salvage with no major untoward effects have been reported from the Mayo Clinic over a period of 5 years, using both types of technology, the choice depending on the indications, cost and required speed of return of blood. Automated cell savers are used when blood loss is expected to be rapid and large. Processing blood collected with canisters takes not less than 45 min; hence, the use of this method is suitable only for prolonged collection periods, and then only if the red cells are washed (Williamson and Taswell 1991). In a multiyear community autologous blood pro- gramme, efficacy of blood salvage was measured by both reduction in allogeneic transfusion and the volumes salvaged and re-transfused (Giordano et al. 1993). An analysis of 9918 consecutive procedures in various surgical specialties revealed that the average return of autologous blood salvaged was equivalent to 2.61 units of erythrocytes. Cardiac operation had the great- est average number of units recovered (4.65), whereas orthopaedic operation had the least (1.05). Postoperative red cell salvage Several devices are available for the collection and re-infusion of blood from thoracic, mediastinal and orthopaedic drainages after surgery. Extensive experience has been reported with postoperative collection of both washed and unwashed wound drainage from patients who have undergone orthopaedic or cardiac surgery. The results are conflicting (Schaff et al. 1979; Eng et al. 1990; Martin et al. 1992; Ward et al. 1993; ALTERNATIVES TO ALLOGENEIC TRANSFUSION 813 Ritter et al. 1994). As with the other methods of autologous collection and transfusion, patient selection is the key to effective use of these procedures (Goodnough et al. 1995). Febrile reactions are not uncommon with infusion of unwashed collections. Concerns about transfusion of activated plasma proteins and wound detritus, especially after orthopaedic procedures, has led to the recommendation that the red cells should be washed prior to re-infusion and infused through a microaggregate filter within 6 h of starting the collection (Leach 1991; Tawes et al. 1994). Pharmacological alternatives Haematopoietic growth factors Haemopoietic growth factors produced by recombinant technology have enjoyed increasing use in clinical medicine, and in many instances their administration has either complemented or replaced transfusion therapy. The use of G-CSF and GM-CSF for mobilizing marrow progenitor cells and the effectiveness of G- CSF for granulocyte mobilization have been discussed in Chapter 14. Use of recombinant human erythropoietin (rhEPO) as an adjunct to autologous transfusions has been discussed previously in this chapter. Erythropoietin Erythropoietin (EPO) is a 36-kDa glycoprotein that is the primary regulator of erythropoiesis. EPO is produced primarily by the peritubular cells in the kidney in response to hypoxia. A small amount is made in the liver in adults. Administration of rhEPO results in egress of immature reticulocytes from the bone marrow and gradual elevation of the haematocrit (Spivak 1993, 2001). The EPO gene was cloned in 1985. Clinical-grade rhEPO became available and became a standard treatment for anaemic patients with end-stage renal disease by 1989 (Fisher 2003). The drug is now administered in a variety of settings in addition to uraemia where it may replace the use of allogeneic blood (Cazzola et al. 1997). Treatment of patients with renal failure. The major cause of anaemia in patients with end-stage renal disease is a lack of production of erythropoietin, and recombinant human erythropoietin (rhEPO) is now used successfully to treat the anaemia in these patients (Winearls et al. 1986; Eschbach et al. 1989). The approved dose of rhEPO in renal failure is 50–150 U/kg intravenously or subcutaneously three times a week until the haematocrit reaches 0.30–0.34 (Eschbach 2002). The clinical response to rhEPO will probably not improve at doses above 500 U/kg intravenously three times weekly. On average, subcutaneous (s.c.) administration is more effectivethan i.v., as the drug is released more slowly from the tissues, which results in a longer circulating half-life and lower but more sustained plasma levels (Sisk et al. 1991). Pharmacokinetic studies indicate that rhEPO has a half-life of 4–9 h after i.v. administration, but > 24 h afters.c. injection. Treatment with rhEPO leads to functional iron deficiency as red cell production outstrips the mobilization of iron stores, and patients must be monitored appropriately (Brugnara et al. 1993). A randomized, open label study comparing intravenous iron with oral iron supplementation and controls in 157 cancer patients with chemotherapy-related anaemia sug- gested that intravenous iron raises haematocrit more effectively than does ferrous sulphate (Auerbach et al. 2004). Although patient randomization was not stratified for a variety of clinical factors, the study supports the notion that iron is necessary for at least a portion of patients treated with rhEPO. The major side-effects of treatment with rhEPO are hypertension and thrombotic episodes, originally thought to be related primarily to excessive doses and too rapid correction of anaemia (Johnson et al. 1990; Spivak 2001). However, rhEPO appears to have haematocrit-independent, vasoconstrictive activity that can result in hypertension (Bode-Boger et al. 1996; Banerjee et al. 2000). EPO-related pure red cell aplasia has been reported in association with the appearance of circulating EPO-neutralizing antibodies (Casadevall et al. 2002; Bennett et al. 2004). Incidence is 10-fold higher when the Eprex ® formulation is administered (Cournoyer et al. 2004). Discontinuation of drug and immunosuppressive therapy are associated with haematological recovery, and a majority (56%) regain responsiveness to rhEPO therapy, 89% of those without evidence of antibody at the time of re-exposure (Bennett et al. 2005). A novel erythropoiesis-stimulating recombinant cytokine (darbepoetin) has been synthesized, which has a higher carbohydrate content resulting in a longer plasma half-life and an amino acid sequence different from that of native human EPO. Darbopoietin reportedly is as effective as rhEPO at CHAPTER 18 814 maintaining haemoglobin level but with less frequent dosing (Locatelli et al. 2001). In the USA, the use of EPO almost immediately decreased consumption of red cells by 0.5 million units per year (Adamson 1991a,b). Treatment of patients without renal disease. Those patients with AIDS and zidovudine-induced anaemia, whose levels of erythropietin are decreased (< 500 mu/ ml), respond to treatment with rHuEPO (100 U/kg three times a week) (Spivak et al. 1989). Good results have also been obtained in anaemia related to chemotherapy in patients with cancer whose EPO level is < 200 mu/ml (Abels 1991). The dose advised is 100– 150 U/kg three times weekly (Miller et al. 1990). In a randomized, double-blind, placebo-controlled study of 375 patients with anaemia receiving nonplatin chemotherapy with solid or non-myeloid haematological malignancies, decreased transfusion requirements and increased haematocrit followed rhEPO treatment of 150–300 IU/kg three times per week subcutaneously for 12–24 weeks (Littlewood et al. 2001). rhuEPO has been used for bone marrow transplantation (Steegmann et al. 1992), myelodysplastic syndrome (Di Raimondo et al. 1996), rheumatoid arthritis (Pincus et al. 1990) and the anaemia of prematurity (Bader et al. 1996; Maier et al. 2002). All require further study. Colony-stimulating factors Myeloid growth factors For use as mobilizing agents for granulocyte and progenitor cell collection, see Chapter 14. Febrile neutropenia with cancer chemotherapy. More than a dozen studies have evaluated the benefit of administering myeloid cytokines (granulocyte colony- stimulating factor, G-CSF; granulocyte–macrophage colony-stimulating factor, GM-CSF) to febrile neutro- penic patients with malignancies. Although such therapy is more convenient than granulocyte transfusion, the results are no more satisfying. A Cochrane analysis found that overall mortality was not influenced by the use of colony-stimulating factor (CSF) (Clark et al. 2003). The benefit in reducing infection- related mortality is marginal, and even this result was highly influenced by one study. The prophylactic use of these cytokines for patients with febrile neutropenia due to cancer chemotherapy did not reduce the number of hospital days or the neutrophil recovery period. Although primary prophylaxis with a myeloid growth factor can reduce the incidence of febrile neutropenia by as much as 50%, such use is hard to justify if there is no improvement in response or survival (Ozer et al. 2000). The collective results of eight treatment trials provide consistent support for the recommendation that cytokines should not be used routinely as adjunct therapy for the treatment ofuncom- plicated fever and neutropenia (Ozer et al. 2000). Chronic neutropenia. Severe chronic neutropenia, an absolute neutrophil count of less than 0.5 × 10 9 /l lasting from months to years, was one of the original indications for G-CSF treatment. Congenital, cyclic and idiopathic neutropenia fall into this category. A sustained increase of the neutrophil count, a reduction of the number of infections and reduced requirement for antibiotics was obtained in 40 out of 44 children with congenital neutropenia. Treatment for 4–6 years was well tolerated in the majority of patients and resulted in a long-term improvement of the clinical condition (Bonilla et al. 1989). More than 850 patients, most treated with daily or alternate-day recombinant human G-CSF (or filgrastim), have been followed on the Chronic Neutropenia Registry (Dale et al. 2003). G- CSF treatment increased the ANC 10-fold during the first year of treatment. For most patients, the responses were durable and patients remained on the same dose of G-CSF for years. Most patients remained free of bacterial infection. Thrombocytopenia developed in 4% of patients and myelodysplasia or acute myelo- cytic leukaemia has occurred in 35 out of 387 patients with congenital neutropenia with a cumulative risk of 13% after 8 years of G-CSF treatment. These events occurred without a predictable relationship to the duration or dose of G-CSF treatment. It is not clear whether the drug had any causative role in these disorders. No patient with cyclic or idiopathic neutropenia developed myelodysplasia or leukaemia. Growth and development and the outcome of pregnancy appeared to be unaffected by G-CSF treatment (Dale et al. 2003). Neonatal neutropenia. In infants of very low birth- weight, GM-CSF has been found to produce a significant increase in the neutrophil and platelet counts and in the bone marrow neutrophil storage pool (Cairo et al. 1995). ALTERNATIVES TO ALLOGENEIC TRANSFUSION 815 Thrombopoietin For almost 50 years scientists have looked for ‘thrombopoietin’, a humoral factor that regulates platelet production and might be used to treat patients with thrombocytopenia (Kelemen et al. 1958). Clinical trials with cytokines such as interleukin 6 (IL-6) and IL-11 showed that these proteins stimulate platelet production, and IL-11 has been given to reduce the need for platelettransfusions in patients with chemotherapy- induced thrombocytopenia (D’Hondt et al. 1995; Gordon et al. 1996). However, IL-11 is not a true thrombopoietin. Although its administration can reduce the need for platelet transfusions by one-third in selected patients with severe thrombocytopenia, it is accompanied by significant side-effects such as fever, fatigue, chills, dyspnoea, hypotension, peripheral oedema, atrial arrhythmias and syncope (Gordon et al. 1996; Vredenburgh et al. 1998). In contrast with IL-11, thrombopoietin (TPO), also called c-Mpl ligand, is a 95-kDa, 332-amino-acid, lineage-specific glycoprotein with considerable homo- logy to erythropoietin, which stimulates megakaryocyte growth and maturation (De Sauvage et al. 1994; Foster 1994; Lok et al. 1994). TPO is synthesized primarily in the liver (Peck-Radosavljevic et al. 2000). Various recombinant preparations of TPO have been developed including recombinant human thrombopoietin (rhTPO) and pegylated recombinant human megakaryocyte growth and development factor (PEG- rHuMGDF). TPO levels usually increase as platelet mass declines, and remain elevated during the course of thrombocytopenia. Platelet transfusions ordinarily decrease the plasma TPO levels, as TPO binds to the c-Mpl receptor on platelets and is removed from the circulation (Scheding et al. 2002). Chemotherapy-induced thrombocytopenia. Of the two recombinant thrombopoietins, PEG-rHuMGDF, the most widely studied, produces dose-dependent increases in platelet counts in patients with advanced malignancies and chemotherapy-induced thrombocytopenia (Basser et al. 1997; Fanucchi et al. 1997). When administered before chemotherapy as a daily subcutaneous injection, PEG-rHuMGDF produced a dose dependent increase in peripheral blood platelet count. No evidence of platelet activation or altered platelet function has been observed. In a randomized, dose-escalation study, the platelet nadir in 53 patients with lung cancer treated with PEG-rHuMGDF after chemotherapy was higher than that of control subjects, but the need for platelet transfusions was unchanged because few patients developed severe thrombocytopenia (Basser et al. 1997). Similar results have been reported in other studies of chemotherapy for non- myeloid malignancies. Some reduction in the need for platelet transfusion may be found, but the effect is usually limited to the early cycles of chemotherapy. Similar experience has been reported with recombinant human thrombopoietin. When administered as a single intravenous dose before chemotherapy, rhTPO was associated with a dose-dependent increase in platelets that began about day 4 and peaked about day 12 (Vadhan-Raj et al. 1997). rhTPO administered subcutaneously to previously treated patients with gynae- cological malignancies before and after chemotherapy produced a modest dose-dependent rise in circulating platelet count. The need for platelet transfusions decreased by 75% (Vadhan-Raj et al. 1997). PEG- rHuMGDF and rhTPO have not improved thrombocytopenia significantly when administered to patients receiving intensive chemotherapy for acute leukaemia or stem cell transplantation, and failed to reduce the requirement for platelet transfusion (Nash et al. 2000; Schiffer et al. 2000). Immune thrombocytopenia. TPO administration may have a role in management of ITP. Six HIV-infected patients with ITP and normal or slightly elevated endogenous TPO levels experienced a 10-fold rise in platelet count within 14 days of the start of PEG- rHuMGDF (Harker et al. 1998). A similar response has been reported in patients with non-HIV-related ITP treated with intravenous PEG-rHuMGDF. One patient with ITP has been successfully treated twice weekly with subcutaneous PEG-rHuMGDF for more than 3 years (Kuter and Begley 2002). These patients appear to have a suboptimal endogenous TPO response to thrombocytopenia, possibly as a result of their megakaryocyte mass, and appear to be able to increase the rate of effective platelet production when recombinant drug is administered. Thrombapheresis. Healthy thrombapheresis donors increase their platelet count at 10–14 days after a single injection of PEG-rHuMGDF (Goodnough et al. 2001; Kuter et al. 2001). The rise in platelet count is dose CHAPTER 18 816 dependent and effects a significant increase in the apheresis platelet yield (Fig. 18.1). The platelets appear to aggregate normally and retain normal function after transfusion intothrombocytopenic recipients. The corrected count increment was significantly higher in patients transfused with cells mobilized by PEG- rHuMGDF than in those whose platelets came from control donors. No serious adverse events were seen in these donors. Safety of recombinant thrombopoietin. Administra- tion of multiple doses of PEG-rHuMGDF to some cancer patients and healthy volunteers was associated with the development of neutralizing antibodies and thrombocytopenia (Li et al. 2001).Thrombocytopenia occurred in 4 out of 665 cancer/stem cell transplantation/leukaemia patients given multiple doses, in 2 of 210 healthy volunteers who received two doses and in 11 out of 124 healthy volunteers given three doses of PEG-rHuMGDF (Li et al. 2001). No subject developed neutralizing antibodies or thrombocytopenia after a single injection. Evaluationof these thrombocytopenic subjects showed that the thrombocytopeniawas due to the formation of an IgG antibody to PEG-rHuMGDF that crossreacted with endogenous TPO (Li et al. 2001). Neutralizing antibodies have not appeared in patients treated with intravenous rhTPO, although one non-neutralizing antibody was detected after subcutaneous injectionof rhTPO (Vadhan-Raj et al. 2000). Naturally occurring antibodies have been discovered in some patients with thrombocytopenia, and one would expect that platelet transfusion, not rhTPO, would be the treatment of choice should such patients require haemostasis support (Aledort et al. 2004). Adjuncts to haemostasis Pharmaceutical and biological agents occasionally replace transfusion therapy, but are more commonly used as adjuncts in the treatment of patients with haemostatic disorders (Counts et al. 1979; Mannucci 1998). A wide range of agents is available. Recombinant factor VIIa has emerged not as a replacement therapy, although it is licensed for this purpose in Europe, but as a treatment for bleeding haemophiliacs with inhibitors (Chapter 14), and as both prophylaxis and therapy for patients with surgically induced massive bleeding. A synthetic analogue of l-vasopressin, DDAVP, has been used to minimize haemorrhage for most mild forms of haemophilia A and VWD, and is increasingly recog- nized to have multiple less well-defined haemostatic effects when administered empirically in other circumstances. Lysine analogues that inhibit fibrinolysis are used both systemically and locally for acquired and inherited defects in haemostasis and thrombocytopenia. Aprotinin, a bovine-derived serine protease inhibitor with potent antifibrinolytic activity, is widely employed to enhance surgical haemostasis after cardiopulmonary ALTERNATIVES TO ALLOGENEIC TRANSFUSION 817 0 9 6 3 18 Placebo (n = 65) MGDF 1 µg/kg (n = 23) MGDF 3 µg/kg (n = 20) 15 12 0 800600400 Pre-apheresis platelet count, 10 9 /l 200 Yield of platelets, 10 11 Fig 18.1 PEG-rHuMGDF increases the yield of platelet apheresis. Administration of a single dose of PEG-rHuMGDF produced a dose-dependent increase in platelet count and apheresis yield 15 days later. Reprinted from Kuter and colleagues (2001) with permission. bypass. Vitamin preparations in the naphthoquinone family (vitamin K) are used to prevent neonatal bleeding syndromes as well as to reverse warfarin anticoagulation or to treat ingestion of warfarin-like rodenticides. Still other agents such as oestrogens and protamine sulphate have proved valuable adjuncts to transfusion therapy. Recombinant factor VIIa The effectiveness of plasma fractions containing activated clotting factors in treating factor VII-deficient patients as well as other haemophiliacs with coagulation factor inhibitors led to the appreciation of the singular role of factor VII and the development of recombinant factor VIIa (rFVIIa) for human use (see also Chapter 14) (Hedner and Kisiel 1983). Recombinant factor VIIa, a two-chain procoagulant enzyme of approximately 50 000 molecular weight, becomes active when complexed with tissue factor in the extrinsic clotting cascade (Butenas et al. 2003). The circulating half-life is between 2 and 3 h, although it appears to be somewhat shorter in children than in adults (Villar et al. 2004). Dosage remains con- tentious. Most studies have used a dose of 90 µg/kg repeated every 2 h; however, doses as low as 30 µg/kg and as high as 120 µg/kg have been administered. The mechanism of action remains controversial. Preclinical studies in dogs indicate that functional platelets are critical to achieve normal haemostasis, although FVIIa can induce localized fibrin deposition on the surface of platelets with defective aggregation and induce platelet aggregates (Lisman et al. 2004). At pharmacological doses, rFVIIa binds directly to activated platelets and may generate a burst of thrombin that is localized to the site of bleeding (Lisman et al. 2004). For this reason, administration of rFVIIa has not been recom- mended for thrombocytopenic patients, although anec- dotal reports suggest that even with severe, refractory thrombocytopenia, haemostasis may be improved (Vidarsson and Onundarson 2000; Gerotziafas et al. 2002; Tranholm et al. 2003). Whether the absolute platelet count or the mechanism of thrombocytopenia is important has yet to be determined. Additional indications. Recombinant VIIa has been administered for a wide range of bleeding problems in addition to replacement therapy and management of haemophiliacs with inhibitors. The drug reduces the prothrombin time and controls bleeding in patients who require rapid reversal of warfarin anticoagulation (Deveras and Kessler 2002; Freeman et al. 2004). Changes in the laboratory test do not correlate with cessation of bleeding. There is no assay suitable for monitoring drug efficacy. rFVIIa infusion may provide one option for reversing treatment with newer anti- coagulants such as those that target factor Xa– or tissue factor, but as yet little experience has been reported in this setting (Levi et al. 2004). rVIIa has reportedly controlled bleeding in a variety of inherited and acquired disorders of platelet function, such as Glanzmann thrombasthenia, Hermansky–Pudlak syndrome, Bernard–Soulier syndrome, VWD and uraemia (Monroe et al. 2000; Pozo Pozo et al. 2002; Poon et al. 2004). Patients with liver disease and profuse variceal bleeding have responded promptly to bolus infusions and the drug has been used prophylactically for patients undergoing liver biopsy (Bosch et al. 2004; Caldwell et al. 2004; Romero-Castro et al. 2004). Although bleeding has been well controlled in a sub- group of patients with variceal haemorrhage, reduction in mortality has not yet been seen. rFVIIa is reportedly effective and well tolerated as an option for managing central nervous system bleeding in patients with VII deficiency, anticoagulation, haemophilia with inhibitors and possibly other conditions such as aneurysms and trauma (Schmidt et al. 1994; Freeman et al. 2004; Huang et al. 2004). In a proof-of-concept study, rVIIa (160 µg/kg) administered within 4 h of symptoms reduced haematoma expansion at 24 h in patients who sustained intracerebral haemorrhage (Mayer et al. 2005). Each of three treatment groups realized improvements in functional scores when compared to a placebo control group at 3 months. However, arterial and venous thromboembolic events were more than three times as common in the treatment groups (7% vs. 2%) than in the control group. Trauma and surgery. The earliest and perhaps most promising applications for rVIIa seemed to be in the settings of trauma and surgery with profuse bleeding. The observation that after a bolus of rVIIa, bleeding may cease virtually instantaneously in patients with desperate wounds or profuse bleeding at operation has produced many advocates but few controlled trials (Kenet et al. 1999; Martinowitz et al. 2001). In the largest series of trauma patients, coagulopathy was reversed in 61 out of 81 cases, with an associated reduction in prothrombin time from 19.6 to 10.8 s. CHAPTER 18 818 However, these findings did not translate into improved mortality compared to historical controls (Dutton et al. 2004). The same dramatic improvements in haemostasis have been reported with cardiac surgery and surgery for extensive, disfiguring facial haemangiomas (Tanaka et al. 2003; Waner 2004). In a controlled trial of rVIIa during retropubic prostatec- tomy, the patients who received drug sustained less blood loss and required on the average 2 units fewer red cell transfusion. Seven out of twelve placebo- treated patients were transfused, whereas no patients who received 40 µg/kg of rVIIa needed transfusion (Friederich et al. 2003). One surprise has been the apparent lack of side- effects related to the administration of an activated clotting factor even in patients, who may be pre- disposed to thrombosis. In several hundred thousand administrations to patients with haemophilia, only a 1% incidence of serious adverse reactions has been reported (Abshire and Kenet 2004). Although experience in non-haemophilic patients is much less extensive, the concern about excessive thrombosis with resultant stroke and myocardial infarction has not been realized. It is still too early to conclude that the concern is unwarranted. DDAVP (1-deamino-8-D-arginine vasopressin or desmopressin) DDAVP is a synthetic analogue of the antidiuretic hormone l-vasopressin that has been used to control bleeding in patients with mild congenital or acquired bleeding disorders for more than 25 years (Richardson and Robinson 1985; Mannucci 1986; Lee et al. 1999). The drug has been used to reduce blood loss in a variety of surgical settings; however, with the possible exceptions of patients who have ingested aspirin or have other disorders of platelet function, benefit appears to be minimal (Dilthey et al. 1993; Despotis et al. 1999b; Carless et al. 2004). Mechanisms of action and tachyphylaxis. DDAVP administration raises circulating FVIII and VWF levels, which account in part for the drug’s haemostatic effect (Edelson et al. 1974; Richardson and Robinson 1985). Compared with vasopressin, DDAVP has increased affinity for V-1 receptors, which results in rapid release of FVIII and VWF from preformed cellular stores, and markedly decreased affinity for V-2 receptors that mediate vasoconstriction (Richardson and Robinson 1985; Mannucci 1986). In normal subjects, DDAVP increases FVIII and VWF levels within 30 min after infusion. Levels peak at 300–400% of baseline in 1– 2 h, and persist for 6–12 h (Mannucci et al. 1981). Response is faster with intravenous infusion than with intranasal administration. Both red blood cell (RBC) and platelet adhesion to endothelial cells are increased by DDAVP when studied in vitro (Tsai et al. 1990; Rosse and Nishimura 2003). These effects might be produced by direct action on the vessel wall (Rosse and Nishimura 2003) or by release of high-molecular-weight VWF at the endothelial cell surface (Barnhart et al. 1983; Takeuchi et al. 1988). DDAVP also increases procoagulant platelet microparticle formation (Horstman et al. 1995), expression of tissue factor on endothelial cells (Galvez et al. 1997) and expression of p-selectin and the adhesive glycoprotein Ib on platelet membranes (Sloand et al. 1994; Wun et al. 1995). One or more of these or other unidentified effects may explain the observation that DDAVP shortens the bleeding time in patients with severe VWD who have already received cryoprecipitate infusions (Cattaneo et al. 1989), and in qualitative platelet disorders such as uraemia (Mannucci et al. 1983), liver disease (Mannucci et al. 1986) or other acquired or congenital conditions (Kentro et al. 1987) in which levels of FVIII and VWF are usually normal. DDAVP infusion for haemophilia A and VWD produces short-term increases of circulating FVIII and VWF as preformed cell stores are released (Mannucci 1997). DDAVP alone has been used to control bleeding associated with minor surgical procedures or dental work, but is inadequate for procedures that require prolonged haemostasis. Repeat administration of DDAVP at intervals shorter than 24 h or repeatedly for several days is associated with decreased laboratory and clinical response (tachyphylaxis) (Mannucci et al. 1992; Mannucci 2004). The blunted response appar- ently results from depletion of intracytoplasmic stores of FVIII and VWF. The pattern of tachyphylaxis is not predictable. Patients with VWD are less likely to respond poorly or fail to respond after repeated doses. Although the haemostatic response to initial administration of DDAVP varies among patients, it is usually reproducible on each occasion for a given patient (Mannucci et al. 1992). If management with DDAVP is planned, patients should receive a test infusion to ALTERNATIVES TO ALLOGENEIC TRANSFUSION 819 establish response several days prior to any planned invasive procedure. Dose and administration. DDAVP may be administered by intravenous, subcutaneous and intranasal routes. The intravenous dose is 0.3 µg/kg, administered over 30 min in 50 ml of normal saline for adults (in 10 ml for children weighing less than 10 kg). The maximum response, factor elevations of three to five times baseline levels, occur within 30 to 60 min at intravenous doses of 0.3 µg/kg (Mannucci et al. 1981, 1992). The subcutaneous dose is 0.3–0.4 µg/kg, with peak responses approximately 230% above baseline at 60 min after administration, slightly lower and later than the peak dose after intravenous administration. The intranasal dose is an order of magnitude higher than the intravenous or subcutaneous dose, 300 µg for adults. Higher doses do not enhance efficacy, but may be associated with increased toxicity. A concentrated nasal spray formulation is available in both the USA and Europe. However, a concentrated pre- paration for subcutaneous use is not available in the USA, and the substantial volume (7 ml) required for subcutaneous treatment of a 70-kg individual may be uncomfortable. DDAVP is cleared by the liver and kidneys and has a plasma half-life of 124 min (Mannucci 1997). Indications. As the bleeding tendency in haemophilia A, and to a lesser degree in VWD, correlates with measured blood levels of the deficient factor, the ability of DDAVP to transiently raise FVIII and VWF has resulted in its approval for use in these disorders. Experience has confirmed its usefulness and DDAVP is now the treatment of choice for minor and even moderately invasive procedures in patients with these disorders who respond to a test infusion (Mannucci 1997; Porte and Leebeek 2002; Mannucci 2004). Response is estimated from prospective studies at about 28% for VWD type I, 18% for type IIA, 14% for type IIM and 75% for type IIN (Federici et al. 2004). Genotype predicts response better than does phenotype for type IIA and IIN. The use of DDAVP in type IIB VWD remains controversial, but is generally contraindicated because these patients develop mild thrombocytopenia related to the affinity of the VWF for the platelets. Infusion of DDAVP and release of endogenous VWF stores into circulation may worsen thrombocytopenia (Mannucci 2004). Nevertheless improved haemostasis in type IIB VWD after infusion of DDAVP associated with little or only mild thrombocytopenia has been reported (McKeown et al. 1996). In patients with severe haemophilia A, FVIII levels do not increase after DDAVP infusion; however, DDAVP may still provide potential benefit by increasing VWF levels, with an associated increased response in activity of infused FVIII concentrates (Deitcher et al. 1999). DDAVP has been found to augment haemostasis in a variety of acquired and congenital conditions with impaired haemostasis in which other treatment options are limited. In a double-blind placebo-controlled study of patients with congenital platelet defects, DDAVP lowered the bleeding time most effectively in subjects with normal platelet-dense granule stores (Rao et al. 1995). In other studies, DDAVP has been shown to improve the bleeding time or be associated with ade- quate surgical haemostasis in patients with storage pool defect (Schulman et al. 1987; Kobrinsky et al. 1991), Bernard Soulier disease (Noris et al. 1998), aspirin ingestion (Flordal and Sahlin 1993; Reiter et al. 2003) and other defects in platelet hemostasis. DDAVP shortens the bleeding time in some haemor- rhagic diseases of multifactorial origin such as cirrhosis and uraemia. Extrapolation of the utility of DDAVP in these conditions should be done with caution. Most studies have determined the efficacy of DDAVP by observing a shortening of the bleeding time, a notori- ously poor predictor of haemostasis in most settings, or by assessing surgical haemostasis in uncontrolled studies of small numbers of patients. Initial reports that DDAVP decreased blood loss and transfusion requirements after cardiac and spinal surgery have not been confirmed in follow-up studies (Mannucci 1997; Porte and Leebeek 2002). One large meta-analysis revealed no reduction in bleeding after the use of DDAVP in cardiac surgery, in contrast with comparative studies with lysine analogue antifibrinolytics and aprotinin (Levi et al. 1999). DDAVP had no effect on mortality or need for repeat thoracotomy, but was associated with a two- to four-fold increased risk of coronary thrombosis. A Cochrane analysis arrived at a similar conclusion (Carless et al. 2004). The subset of patients with preoperative platelet defects, including those that have ingested aspirin, appears to benefit from administration of DDAVP prior to surgery. Blood loss was markedly reduced in patients with preoperative CHAPTER 18 820 defects in platelet function (identified by point-of-care testing) who received DDAVP compared with those who received placebo (Despotis et al. 1999b). Three randomized double-blind placebo-controlled trials have shown clinically significant reductions in blood loss and transfusion requirements after the use of DDAVP in patients who have ingested aspirin before cardiac surgery (Gratz et al. 1992; Dilthey et al. 1993; Sheridan et al. 1994). DDAVP also reduced bleeding in an unblinded comparison with placebo in patients who ingested aspirin before cholecystectomy (Gratz et al. 1992). In addition, DDAVP has been demonstrated to shorten the bleeding time in normal volunteers after aspirin ingestion, perhaps due to direct effects on platelets or increases in VWF (Lethagen et al. 2000). Whereas some studies have indicated that DDAVP is not effective in patients with thrombocytopenia or Glanzman disease, other patients with Glanzman disease or thrombocytopenia have been reported to respond (Mannucci et al. 1986; DiMichele and Hathaway 1990). Toxicity. Most side-effects of DDAVP are minor. Facial flushing, often marked, and minimal elevation in pulse rate or blood pressure are observed, more frequently with the intravenous than with the subcutaneous or intranasal routes. The most common, clinically significant adverse event is hyponatraemia, which results from the antidiuretic effect of this vasopressin analogue. Hyponatraemic seizures have been reported in children aged 1 month to 8 years, especially when hypotonic intravenous fluids and multiple doses of DDAVP are administered concurrently in the surgical setting (Sutor 2000). Less severe but significant symptoms of headache, nausea or lethargy have been reported in adults after intranasal or repeated intravenous and subcutaneous administration (Dunn et al. 2000). Careful monitoring of i.v. fluids, urine output and electrolytes is therefore important, especially for children who receive DDAVP perioperatively, and in older patients when mild renal insufficiency decreases their ability to excrete free water. Patients should be instructed to restrict fluid intake for 24 h. Isolated cases of thrombosis such as myocardial infarction, cerebral thrombosis and unstable angina have been reported after use of DDAVP in patients at risk for thrombotic events. In the surgical setting, one randomized, placebo-controlled study specifically designed to detect deep venous thrombosis in 50 patients undergoing hip surgery did not detect an increased incidence of thrombosis following DDAVP therapy (Flordal et al. 1992). However, meta-analysis has found a two- to four-fold increased risk of myocardial infarction in cardiac surgery patients who received DDAVP (Levi et al. 1999). It therefore seems prudent to evaluate patients receiving DDAVP for possible occult coronary artery disease and to avoid the con- current use of antifibrinolytic agents in these patients under most circumstances. Lysine analogue antifibrinolytic agents Fibrinolysis occurs when plasmin generated from the proenzyme plasminogen by plasminogen activators digests fibrin clots (Collen 1999). Both plasmin and plasminogen bind to fibrin through specific lysine binding sites. The synthetic lysine analogues, tran- examic acid (AMCA) and epsilon-aminocaproic acid (EACA), delay fibrinolysis by reducing the binding of plasminogen to fibrin that is required for activation by plasminogen activators (Mannucci 1998). These agents have been available for more than 30 years to inhibit fibrinolysis and ensure clot stability (Dunn and Goa 1999). AMCA was developed within a few years of EACA. AMCA is 10-fold more potent on a molar basis, and tends to cause less gastrointestinal dis- comfort at equivalent antifibrinolytic doses in healthy volunteers (Verstraete 1985). Much of the early use of antifibrinolytics in the USA involved EACA, whereas AMCA was used relatively more frequently in Europe. Although AMCA and EACA have been considered equivalent agents, optimal dosing regimens have not been determined for either agent and reported toxicities vary (Bluemle 1965; Porte and Leebeek 2002). Lysine analogue antifibrinolytic drugs are effective and clearly indicated in rare inherited conditions associated with excessive fibrinolysis such as congenital α2-antiplasmin deficiency (Aoki et al. 1979). How- ever, much of the enthusiasm for these drugs has focused on acquired disorders with evidence of excessive systemic fibrinolysis, especially cardiac bypass surgery and, to a lesser degree, orthopaedic surgery performed with the use of tourniquets. Both agents are useful when administered topically in areas with excessive local fibrinolysis such as the oral cavity and ALTERNATIVES TO ALLOGENEIC TRANSFUSION 821 [...]... hydroquinone required for carboxylation However, a second, warfarin-insensitive reductase can reduce vitamin K to the active hydroquinone in the presence of high tissue concentrations of vitamin K Thus, exogenous vitamin K can produce additional active vitamin K hydroquinone via this warfarin-insensitive step, bypassing the warfarininduced inhibition of vitamin K epoxide reductase and reversing excessive... Haemost 74: 107 1 107 8 Rapaport SI, Zivelin A, Minow RA et al (1992) Clinical significance of antibodies to bovine and human thrombin and factor V after surgical use of bovine thrombin Am J Clin Pathol 97: 84–91 Ray MJ, Marsh NA (1997) Aprotinin reduces blood loss after cardiopulmonary bypass by direct inhibition of plasmin J Thromb Haemost 78: 102 1 102 6 Reddy P, Song J (2003) Cost comparisons in open-heart... Low-molecular-weight heparin contains a protamine-resistant ultra-low-molecular-weight fraction with low sulphate charge density (Crowther et al 2002) Protamine sulphate reverses only about 60% of the anti-factor Xa activity of low-molecular-weight heparin, has negligible effects on danaparoid, a mixture of anticoagulant glycosaminoglycans used to treat heparin-induced thrombocytopenia, and fondaparinux,... injection, aprotinin distributes into the extracellular space, leading to a rapid decrease in plasma concentration The drug is eliminated in a biphasic pattern: a rapid-phase half-life of approximately 40 min and a slower phase half-life of 7 h (Porte and Leebeek 2002) Indications During trials of aprotinin designed to reduce neutrophil activation in patients undergoing repeat open heart surgery, investigators... factor-alpha (TNF-α), IL-6 and IL-8 and inhibits endogenous cytokine-induced nitric oxide synthase induction (Mahdy and Webster 2004) Dosage and clearance As was the case with the other antifibrinolytic agents, aprotinin has been used in different doses and regimens; the most common regimen involves a loading dose of 2 million KIU followed by continuous infusion of 500 000 KIU/h (Royston et al 1987) In. .. the red cell, haemoglobin is vulnerable to oxidative inactivation and its chains dissociate into dimers The oxygen affinity of human haemoglobin in solution is much higher than that of intracellular haemoglobin, in part because of the absence of 2,3-diphosphoglycerate within the red cell stroma, and in part because of the relatively alkaline pH of plasma in comparison with the interior of the red cell... On the use of Ringer-Locke solutions containing hemoglobin as a substitute for normal blood in animals J Cell Comp Physiol 5: 359 Amberson WR, Jennings JJ, Rhode CM (1949) Clinical experience with hemoglobin-saline solutions J Appl Physiol I: 469 Ambrus JL, Schimert G, Lajos TZ et al (1971) Effect of antifibrinolytic agents and estrogens on blood loss and blood coagulation factors during open heart... synthetic antithrombin-binding pentasaccharide 827 CHAPTER 18 with exclusive anti-factor Xa activity used for antithrombotic prophylaxis following orthopaedic surgery (Warkentin and Crowther 2002) Protamine possesses additional intrinsic anticoagulant activities, including platelet clumping, thrombocytopenia and interference with the formation of fibrin by thrombin so that doses in excess of those calculated... Surreptitious ingestion of a long-acting vitamin K antagonist/rodenticide, brodifacoum: clinical and metabolic studies of three cases Blood 76: 2555–2559 Williams EC (1989) Plasma alpha 2-antiplasmin activity Role in the evaluation and management of fibrinolytic states and other bleeding disorders Arch Intern Med 149: 1769–1772 Williamson KR, Taswell HF (1991) Intraoperative blood salvage In: Autologous Transfusion. .. platelets, with a leucocyte count in the concentrate of 13 ± 7 × 106 ; blood is taken into the collecting bag of a quadruple blood bag system (e.g Terumo, Baxter, NPBI) with CPD as an anticoagulant The bag is then stored in such a way in a ‘cooling unit’ containing butane-1,4-diol that the collecting bag is in contact with the unit The temperature of the blood is reduced to 22°C in 2 h After a variable period . recombinant technology have enjoyed increasing use in clinical medicine, and in many instances their administration has either complemented or replaced transfusion therapy. The use of G-CSF. al. 1998). In contrast with IL-11, thrombopoietin (TPO), also called c-Mpl ligand, is a 95-kDa, 332-amino-acid, lineage-specific glycoprotein with considerable homo- logy to erythropoietin, which. been successful for control of intract- able urinary bleeding localized to the bladder (Singh and Laungani 1992). Aprotinin. Aprotinin is a bovine lung-derived 5 8- residue polypeptide with broad

Định dạng
Số trang	92
Dung lượng	0,96 MB