Search

We performed a prospective analysis of iron status in plateletpheresis donors, using whole blood donors as a control group, to assess the haematinic effects of regular anti-coagulated extracorporeal circulation and platelet collection.Ferritin levels were measured in samples from 31 regular male plateletpheresis donors and from 14 first time male whole blood donors, immediately before and immediately after donation, and immediately before the next donation. An additional 33 regular male plateletpheresis donors and 17 first time male whole blood donors had serum ferritin levels checked predonation.Male plateletpheresis donors had a statistically significant fall in serum ferritin after donation (P = 0.005)*. In addition, male platelet donors had significantly lower serum ferritin levels than first time male blood donors: ferritin20 µg/L was found in 6/64 (9%) of regular platelet donors and 1/31 (3%) of first time blood donors (P 0.001)*.Our studies support the value of serum ferritin measurement in apheresis donor management.

As stem cell technologies move from the developmental to the commercial stage strategies must be developed to monitor culture operations. These will ensure consistency of differentiation programs and maintenance of optimum cell viability during production runs. Due to the sensitivity of stem cells to their environment, and their variability in response to external stimuli, accurate monitoring of in vitro conditions will be crucial for effective large-scale culturing of therapeutic stem cells. Here we describe a simple method to monitor the expansion and maturation of adult human haematopoietic stem/progenitor cells into red blood cells in vitro by measuring the oxygen consumption rate of cultures. Cell cultures followed a characteristic pattern of oxygen consumption that is reflective of in vivo erythroid maturation. This method could be easily developed as an online system to map erythroid differentiation and maturation of cultured cells as effectively as the more time consuming process of flow cytometric analysis of surface marker expression patterns.

Men and women have different mean haemoglobin levels in health in venous blood - women have mean levels approximately 12% lower than men. A similar sex-related difference in haemoglobin levels in adult animals is found in many species of mammals, birds and reptiles, indicating that it is an important physiological phenomenon. It is probably a direct effect of sex hormones, both oestrogen and androgens, on erythropoiesis. However, since there is no difference in erythropoietin levels between the sexes, this effect most likely takes place in the kidney, rather than in the bone marrow. Oestrogens dilate and androgens constrict the renal microvasculature: dilation and vasoconstriction in vessels below 300 μm in diameter respectively increase and decrease the haematocrit in blood in arterioles, capillaries and venules, altering the oxygen delivery per unit red cell mass, and providing a mechanism for varying the red cell mass without compensatory changes in erythropoiesis.

By the time vCJD was first described in 1996, it was already far too late to offset further disaster from transmission of the disease by blood transfusion: almost all the humans who would be infected and infectious were already diseased. Nothing done by the blood transfusion services around that time, with the exception of excluding transfusion recipients as blood donors, would have made any useful contribution to containing the extent of the epidemic. The ability to spread emerging diseases before the problem is manifest or understood is a fixed and unavoidable feature of blood transfusion as it is practiced today. A second fixed property of blood transfusion is that the root cause of disaster is not within the control of the blood transfusion universe. Strategies that have emerged to cope with similar threat in other enterprises that also contain these properties comprise the components of robust design: surveillance, preparedness for action, engagement, herding together, evasion or avoidance, early adoption of potentially useful measures, engineered resilience, defence in depth, damage limitation including modularity and removal of feedback loops, and contingency, redundancy and failure management, and ultimately, individual escape. Early adoption of leucodepletion based on the possibility that it might work rather than any hard evidence was a good example of threat management. Exclusion of previously transfused donors is a robust mechanism for containing any future infection; optimal blood use structures that provide a national transfusion rate as low as possible also constitute an effective threat management strategy.

Bacteria in transfused platelets can cause serious morbidity and, rarely, death. Most contaminating bacteria enter the blood at the time of venepuncture. While many of these contaminants fail to grow in the platelet unit, storage of platelets at 20–24 °C facilitates growth of some organisms, and the cumulative risk of severe sepsis increases with the storage age of platelet components. Several methods have been developed or adapted to attempt to detect contaminating bacteria with high sensitivity and specificity, but the perfect test has yet to be found. Testing early in the platelet component’s shelf life, even using exquisitely sensitive culture-based tests, is compromised by major problems of sample error – there may be too few bacteria present at this stage to ensure that any practical sample volume contains even one of them. Culture techniques are too slow to be useful as a release test. On the other hand, available rapid tests are too insensitive to use early in the shelf life, and have yet to show convincingly that they are sensitive enough for testing close to the time of transfusion. Nevertheless testing for bacteria in platelet components represents a significant advance in blood transfusion safety, and prevents the transfusion of many hundreds of bacterially-contaminated platelet units each year.

The cultivation of erythroid cells at large scale would have to be performed in suitable bioreactors which would most likely employ some mode of agitation to ensure optimal mass and gas transfer and prevent culture inhomogeneity. The effect of low agitation at 15-20 rpm on ex vivo erythropoiesis of PB CD34+ derived cultures was investigated and found to have significant impact on erythroid development. Agitated cultures showed a reduced lag phase and increased cell expansion during the early stages of culture. Additionally, agitation accelerated erythroid differentiation as seen by the loss of early development markers, acquisition of late erythroid markers and premature cell cycle arrest, although not yielding higher fractions of terminally differentiated cells in comparison to stationary culture. However, agitation at 20 rpm led to significantly increased loss of cell viability after day 15 in culture, an effect that could be reduced by decreasing the agitation rate to 15 rpm. On the one hand these results imply that agitation may improve cell yields and reduce expensive cytokine-dependent early culture stages but on the other hand it might introduce the risk of increased cell death in large scale culture.

Microparticles (MP) derived from vascular endothelium or circulating blood cells circulate in the peripheral blood. They originate from blebbing and shedding from cell membrane surfaces in physiological and pathological conditions and are present in low concentrations in normal plasma. Increased levels are generated by a number of mechanisms including platelet activation, direct vascular endothelial damage, thrombin activity on the cell surface, C5b-9 activation, and PF4-heparin-antibody interaction. Several techniques are currently used to study the generation and nature of circulating microparticles. In particular, the genesis and role of microparticles, derived from platelets, endothelial cells and monocytes, in sepsis (especially meningococcal-induced), heparin-induced thrombocytopenia (HIT), thrombotic thrombocytopenic purpura (TTP), aplastic anaemia, paroxysmal nocturnal haemoglobinuria (PNH) and sickle cell disease (SCD) have been well studied, and provide important insights into the underlying diseases. A defect in the ability to form microparticles leads to the severe bleeding disorder of Scott syndrome, which in turn provides a revealing insight into the physiology of coagulation. In addition the complex role of microparticles in vascular and cardiovascular diseases is an area of immense interest, that promises to yield important advances into diagnosis and therapy.

Glycocalicin (GC) is the soluble portion of platelet membrane protein GP1b, and may be cleaved from the platelet surface during platelet activation. Previous study has indicated that plasma glycocalicin/platelet (GC/plt) levels are elevated in patients presenting with acute stroke. The present study was undertaken to determine the GC/plt levels in patients being treated for transient ischaemic episodes, to assess whether the elevated GC/plt level in acute stroke is due to a detectable, constitutive premorbid state of platelet activation. In sixteen consecutive patients attending a vascular surgery clinic, GC levels were measured on a citrated plasma sample, and corrected for circulating platelet count. Since 15 of 16 patients were taking aspirin when seen at clinic, a control study was undertaken to assess the effect of aspirin on sequential plasma GC/plt levels measured over 10 days--5 pre and post daily aspirin for 5 days, 4 acting as non-aspirinated controls. Plasma GC/plt levels in normal plasma were 21.6 +/- 8.0 fg; mean +/- SD. In the 16 patients the GC/plt levels were 13.1 fg/plt; SD 5.4, range 2.9-24.3. All platelet counts were in the normal range in all patients involved. While a masking effect due to aspirin cannot be completely ruled out, these studies indicate that plasma GC/plt level is not useful as a predictor of acute stroke in the premorbid population.

Objectives:To determine whether topical fibrin sealant reduced suture line bleeding during carotid endarterectomy with polytetrafluoroethylene (PTFE) patch closure.Design:Prospective randomised non-blinded control trial.Setting:Regional vascular surgery unit.Materials:Seventeen patients undergoing carotid endarterectomy were randomised either to receive fibrin sealant as a topical haemostatic agent at the arteriotomy suture line or to act as control.Outcome measures:Time taken to achieve haemostasis at the suture line. Intraoperative blood loss. Total operative time.Results:The median time to achieve haemostasis was 5.5 min (range 4–31 min) in the treatment group and 19 min (range 10–47 min) in the control group. This difference was statistically significant p < 0.005 by Mann-Whitney test. There was no statistical difference in total operative time. Operative blood loss was lower in the treatment group (median 420ml, range 300–500ml) than in the control group (median 550ml, range 350–1200ml) but this difference was not statistically significant. One patient in the control group suffered a perioperative thrombo-embolic event.Conclusion:Fibrin sealant is an effective topical haemostatic agent for arteriotomy suture lines involving PTFE material.

Between 1988 and 1993, 17 (3%) out of a total 654 patients underwent reoperation for control of haemorrhage following repair of abdominal aortic aneurysm in a vascular surgery unit. The first operation was performed for rupture in 12 cases and electively in five. The incidence of reoperation for postoperative bleeding was 1.7% following elective operation and 3.3% following emergency operation. Case-controls, matched for sex and primary operation, were identified. The mortality rate in those requiring reoperation was 58% compared with 23% in the control group (p = 0.037). Seven patients suffered progressive deterioration and died in the early postoperative period. Of the remaining ten patients, four suffered unexpected serious complications; two a fatal cerebro-vascular accident (CVA), one a fatal myocardial infarction (MI) and the fourth a non-fatal CVA. The patients requiring reoperation had greater blood loss (p0.05), greater transfusion requirements and lower core temperatures (p0.05) at the end of their first operation than the control group. All except one of the patients who bled had evidence of coagulopathy and had lower platelet counts than the control group both before and after the first operation. At reoperation there were multiple minor bleeding points in 11 patients, no active bleeding points in two patients and a discrete bleeding point in four patients. In conclusion, re-operation for control of postoperative haemorrhage is an uncommon complication which is strongly associated with coagulopathy, may predispose to "rebound" postoperative thrombotic episodes, and carries a poor prognosis.