Circulation of red blood cells having high levels of 2,3-bisphosphoglycerate protects rat brain from ischemic metabolic changes during hemodilution

Unexplored Roles of Erythrocytes in Atherothrombotic Stroke

Stroke constitutes the second highest cause of morbidity and mortality worldwide while also impacting the world economy, triggering substantial financial burden in national health systems. High levels of blood glucose, homocysteine, and cholesterol are causative factors for atherothrombosis. These molecules induce erythrocyte dysfunction, which can culminate in atherosclerosis, thrombosis, thrombus stabilization, and post-stroke hypoxia. Glucose, toxic lipids, and homocysteine result in erythrocyte oxidative stress. This leads to phosphatidylserine exposure, promoting phagocytosis. Phagocytosis by endothelial cells, intraplaque macrophages, and vascular smooth muscle cells contribute to the expansion of the atherosclerotic plaque. In addition, oxidative stress-induced erythrocytes and endothelial cell arginase upregulation limit the pool for nitric oxide synthesis, leading to endothelial activation. Increased arginase activity may also lead to the formation of polyamines, which limit the deformability of red blood cells, hence facilitating erythrophagocytosis. Erythrocytes can also participate in the activation of platelets through the release of ADP and ATP and the activation of death receptors and pro-thrombin. Damaged erythrocytes can also associate with neutrophil extracellular traps and subsequently activate T lymphocytes. In addition, reduced levels of CD47 protein in the surface of red blood cells can also lead to erythrophagocytosis and a reduced association with fibrinogen. In the ischemic tissue, impaired erythrocyte 2,3 biphosphoglycerate, because of obesity or aging, can also favor hypoxic brain inflammation, while the release of damage molecules can lead to further erythrocyte dysfunction and death.

Remote ischemic conditioning enhances oxygen supply to ischemic brain tissue in a mouse model of stroke: Role of elevated 2,3-biphosphoglycerate in erythrocytes

Oxygen supply for ischemic brain tissue during stroke is critical to neuroprotection. Remote ischemic conditioning (RIC) treatment is effective for stroke. However, it is not known whether RIC can improve brain tissue oxygen supply. In current study, we employed a mouse model of stroke created by middle cerebral artery occlusion (MCAO) to investigate the effect of RIC on oxygen supply to the ischemic brain tissue using a hypoxyprobe system. Erythrocyte oxygen-carrying capacity and tissue oxygen exchange were assessed by measuring oxygenated hemoglobin and oxygen dissociation curve. We found that RIC significantly mitigated hypoxic signals and decreased neural cell death, thereby preserving neurological functions. The tissue oxygen exchange was markedly enhanced, along with the elevated hemoglobin P50 and right-shifted oxygen dissociation curve. Intriguingly, RIC markedly elevated 2,3-biphosphoglycerate (2,3-BPG) levels in erythrocyte, and the erythrocyte 2,3-BPG levels were highly negatively correlated with the hypoxia in the ischemic brain tissue. Further, adoptive transfusion of 2,3-BPG-rich erythrocytes prepared from RIC-treated mice significantly enhanced the oxygen supply to the ischemic tissue in MCAO mouse model. Collectively, RIC protects against ischemic stroke through improving oxygen supply to the ischemic brain tissue where the enhanced tissue oxygen delivery and exchange by RIC-induced 2,3-BPG-rich erythrocytes may play a role.

Oxygen tension-mediated erythrocyte membrane interactions regulate cerebral capillary hyperemia

The tight coupling between cerebral blood flow and neural activity is a key feature of normal brain function and forms the basis of functional hyperemia. The mechanisms coupling neural activity to vascular responses, however, remain elusive despite decades of research. Recent studies have shown that cerebral functional hyperemia begins in capillaries, and red blood cells (RBCs) act as autonomous regulators of brain capillary perfusion. RBCs then respond to local changes of oxygen tension (PO₂) and regulate their capillary velocity. Using ex vivo microfluidics and in vivo two-photon microscopy, we examined RBC capillary velocity as a function of PO₂ and showed that deoxygenated hemoglobin and band 3 interactions on RBC membrane are the molecular switch that responds to local PO₂ changes and controls RBC capillary velocity. Capillary hyperemia can be controlled by manipulating RBC properties independent of the neurovascular unit, providing an effective strategy to treat or prevent impaired functional hyperemia.

Purinergic control of red blood cell metabolism: novel strategies to improve red cell storage quality

Transfusion of stored blood is regarded as one of the great advances in modern medicine. However, during storage in the blood bank, red blood cells (RBCs) undergo a series of biochemical and biomechanical changes that affect cell morphology and physiology and potentially impair transfusion safety and efficacy. Despite reassuring evidence from clinical trials, it is universally accepted that the storage lesion(s) results in the altered physiology of long-stored RBCs and helps explain the rapid clearance of up to one-fourth of long-stored RBCs from the recipient's bloodstream at 24 hours after administration. These considerations explain the importance of understanding and mitigating the storage lesion. With the emergence of new technologies that have enabled large-scale and in-depth screening of the RBC metabolome and proteome, recent studies have provided novel insights into the molecule-level metabolic changes underpinning the accumulation of storage lesions to RBCs in the blood bank and alternative storage strategies to mitigate such lesion(s). These approaches borrow from recent insights on the biochemistry of RBC adaptation to high altitude hypoxia. We recently conducted investigations in genetically modified mice and revealed novel insights into the role of adenosine signalling in response to hypoxia as a previously unrecognised cascade regulating RBC glucose metabolism and increasing O₂ release, while decreasing inflammation and tissue injuries in animal models. Here, we will discuss the molecular mechanisms underlying the role of purinergic molecules, including adenosine and adenosine triphosphate in manipulating RBCs and blood vessels in response to hypoxia. We will also speculate about new therapeutic possibilities to improve the quality of stored RBCs and the prognosis after transfusion.

Impact of carbon dioxide tension during cardiopulmonary bypass on tissue perfusion in neonates undergoing cardiac surgery using autologous umbilical cord blood

Objective:

Previously, we reported that the oxyhemoglobin dissociation curve is shifted leftward in patients who receive autologous umbilical cord blood (UCB) during neonatal open heart surgery. In this study, we assessed whether allowing the pCO2 to rise during hypothermic cardiopulmonary perfusion would shift the curve back to the right and improve tissue oxygenation.

Methods:

The study population included prenatally diagnosed patients with transposition of the great arteries. The study cohort was divided into two groups and consisted of early patients originally managed with lower pCO2 levels (Group I, n=42, 2009-12) and later patients subsequently managed with higher pCO2 levels (Group II, n=38, 2012-14).

Results:

Patients received similar volumes of collected autologous UCB (Group I, 80 ml; Group II, 75ml, p=0.207) with a similar mean level of HbF during CPB (Group I, 90±8%; Group II, 87±9%, p=0.310). Higher levels of pCO2 during CPB (Group I, 31 mmHg; Group II, 37 mmHg, p=0.011) resulted in a rightward shift of the oxyhemoglobin dissociation curve (increased p50O2) (Group I, 19.5±3.4 mmHg; Group II, 22.5±2.2 mmHg, p=0.011). The use of a higher pCO2 strategy was associated with decreased serum lactate during CPB (Group I, 4.7±2 mmol/l; Group II, 2.8±1.4 mmol/l, p=0.001), decreased duration of mechanical ventilation (Group I, 46h; Group II, 22h, p<0.001) and decreased of length of intensive care unit (ICU) stay (Group I, 7.6±2.6, Group II, 5.6±2.2, p=0.003)

Conclusions:

A higher pCO2 during CPB in neonates who underwent open heart surgery using UCB resulted in a rightward shift of the oxyhemoglobin dissociation curve and was associated with improved serum lactate levels.

The effect of storing whole blood at 22 degrees C for up to 24 hours with and without rapid cooling on the quality of red cell concentrates and fresh-frozen plasma

BACKGROUND

Storage of whole blood (WB) for less than 24 hours at ambient temperature is permitted in Europe, but data directly comparing storage with and without active cooling are lacking, which was investigated and compared to current standard methods.

STUDY DESIGN AND METHODS

WB was stored in one of four different ways for 24 hours after donation before processing on Day 1 to red cell concentrates (RCCs) in saline-adenine-glucose-mannitol and fresh-frozen plasma (FFP; n = 20 each): 1) at 22 degrees C in plastic trays, 2) in cooling devices (Compocool II, NPBI), 3) at 4 degrees C, or 4) processed from WB without storage less than 8 hours from donation (Day 0).

RESULTS

2,3-Diphosphoglycerate (2,3-DPG) in RCCs were lower after ambient storage compared with those processed on Day 0 or after 4 degrees C storage. Rapid cooling slowed the loss of 2,3-DPG but levels were undetectable by Day 21 with any method. On Day 42 of RCC storage, there was no significant difference between storage methods in levels of adenosine triphosphate or hemolysis. Potassium levels were lower in RCCs from WB stored at ambient compared with those produced on Day 0, regardless of the use of cooling plates. FFP produced from WB on Day 0 or after storage at ambient with or without active cooling met UK specifications (>75% of units >0.70 IU/mL Factor VIII).

CONCLUSION

These data suggest that RCCs and FFP produced from WB that has been stored at ambient temperature with or without active cooling are of acceptable quality compared with those produced using current standard methods in the United Kingdom.

Prolonged maintenance of 2,3-diphosphoglycerate acid and adenosine triphosphate in red blood cells during storage

BACKGROUND

Current additive solutions (ASs) for red cells (RBCs) do not maintain a constant level of critical metabolites such as adenosine triphosphate (ATP) and 2,3-diphosphoglycerate acid (2,3-DPG) during cold storage. From the literature it is known that the intracellular pH is an important determinant of RBC metabolism. Therefore, a new, alkaline, AS was developed with the aim to allow cold storage of RBCs with stable product characteristics.

STUDY DESIGN AND METHODS

Whole blood-derived RBCs (leukoreduced) were resuspended in experimental medium phosphate-adenine-guanosine-glucose-gluconate-mannitol (PAGGG-M; pH 8.2) with and without washing in the same medium. During cold storage several in vitro variables, such as intracellular pH, 2,3-DPG, ATP, and hemolysis, were analyzed.

RESULTS

During cold storage, RBCs resuspended in PAGGG-M showed a constant ATP level (approx. 6 mumol/g Hb) and a very limited hemolysis (<0.2%). The 2,3-DPG content showed an increase until Day 21 (150% of initial level), followed by a slow decrease, with at Day 35 still 100 percent of the initial level. RBCs washed in PAGGG-M even showed a continuous increase of 2,3-DPG during 35 days, with a maximum level of 200 percent of the initial value. The effect of PAGGG-M appears to be related to long-lasting effects of the initial intracellular pH shortly after production.

CONCLUSION

Resuspension of RBCs in our alkaline medium PAGGG-M resulted in a RBC unit of high quality during storage for up to at least 35 days, with 2,3-DPG levels of higher than 10 mumol per g Hb, hemolysis of less than 0.2 percent, and ATP levels of higher than 5 mumol per g Hb.

Hemodilution with liposome-encapsulated low-oxygen-affinity hemoglobin does not attenuate hypothermic cerebral ischemia in rats

Hypothermia decreases cerebral metabolism and increases hemoglobin oxygen affinity. A hypothesis that the reversal of increased oxygen affinity would further attenuate hypothermic cerebral ischemia was tested by evaluating the effects of liposome-encapsulated hemoglobin (LipoHb) with low oxygen affinity (P50 = 40-50 mmHg) on hypothermic incomplete cerebral ischemia. Wistar rats were randomly assigned to one of the following two groups: (A) exchange transfusion with LipoHb solution (Hb = 6 g/dl) (LipoHb, n = 5), (B) no exchange transfusion (control, n = 5). After surface cooling to 22 degrees C, forebrain ischemia was induced for 15 min by bilateral carotid artery occlusion combined with a decrease in the mean arterial pressure (MAP) to 40 mmHg. (31)P-magnetic resonance spectroscopy was performed during ischemia and 45 min of reperfusion. After reperfusion, MAP was significantly higher in the control group than in the LipoHb group (P < 0.01), although there were no significant differences during ischemia. Intracellular pH and phosphocreatine (PCr) levels decreased during ischemia and returned to the preischemic level in both groups following reperfusion. The LipoHb group had a significantly larger decrease and smaller recovery in PCr than the control group (P < 0.0001). Althouth beta-adenosine triphosphate decreased during ischemia in the LipoHb group, it increased in the control group (P < 0.0001). Inorganic phosphate (Pi) increased during ischemia and decreased to the normal value after reperfusion. The LipoHb group experienced a significantly larger production of Pi than the control group (P = 0.02). Hemodilution with high-P50 LipoHb does not reduce ischemic energy depletion induced by hypothermic incomplete forebrain ischemia in rats.

Red blood cells intended for transfusion: quality criteria revisited

Great variation exists with respect to viability and function of fresh and stored red blood cells (RBCs) as well as of the contents of RBC hemoglobin (Hb) in individual units. Improved technology is available for the preparation as well as the storage of RBCs. The authors raise the question whether it may be time to revise current standards for RBC units. The establishment of a standard unit of blood based on Hb content should be a high-priority goal. It is recommended that a standard RBC unit should contain 50 g of Hb. Major organizations concerned with the collection and distribution of blood components should agree on the criteria for a standard unit of RBCs based on Hb content and for the collection of double units. Manufacturers of blood collection equipment should provide suitable technology for collecting a standard unit with defined contents of RBC Hb. Efforts should be directed at the design of storage solutions acceptable for transfusion that maximize the maintenance of both RBC viability and function during storage. The ideal storage protocol would require sterile, high-pH solutions containing both glucose and electrolytes.

Physiologic aspects of anemia

The most important adaptive responses from a physiological stance involved the cardiovascular system, consisting in particular of elevation of the cardiac output and its redistribution to favor the coronary and cerebral circulations, at the expense of the splanchnic vascular beds. The evidence regarding these physiological responses, especially in experimental studies that permit the control of many variables, is particularly powerful and convincing. On the other hand, there is a remarkable lack, in quality and quantity, of clinical studies addressing how normal physiological adaptive responses may be affected by a variety of diseases and conditions that often accompany and may complicate anemia, and interactions with other such compounding variables as age and different patient populations. For these reasons, it is not possible to offer guidelines on how to increase, maintain, or even to determine optimal DO2 in high-risk patients and how best transfusion strategies might be used under these conditions. From the brief review of physiological principles and the strong consensus in the literature, it is evident that cardiac function must be a central consideration in decisions regarding transfusion in anemia, because of the critical role it plays in assuring adequate oxygen supply of all vital tissues. Particular attention should be paid to the possible presence of CAD or incipient or cardiac failure, as these conditions may require careful transfusions to improve DO2 at levels that may not necessitate such interventions when cardiac disease is absent. Although the cerebral circulation also serves an obligate aerobic organ unable to tolerate significant hypoxia, there is little convincing evidence to support the notion that cerebral ischemia is aggravated by anemia and that this can be prevented by improved DO2 through rapid correction of anemia. Consequently, the arguments favoring transfusions in the presence of ischemic heart disease do not appear to apply to occlusive cerebrovascular disease. Because firm evidence is lacking on the interactions of concurrent diseases and anemia in various patient populations, understanding of the physiological consequences of anemia, and of the diseases concerned, is useful but not fully sufficient to provide firm and rational guidance to transfusion practice in specific complex clinical instances. A good deal of clinical and experimental investigation is required to support fully rational and comprehensive guidelines. In the meantime, prudent and conservative management, based on awareness of risks and sound understanding of the normal and pathological physiology, must remain the guiding principle.

Why is VO2 max after altitude acclimatization still reduced despite normalization of arterial O2 content?

Acute hypoxia (AH) reduces maximal O2 consumption (VO2 max), but after acclimatization, and despite increases in both hemoglobin concentration and arterial O2 saturation that can normalize arterial O2 concentration ([O2]), VO2 max remains low. To determine why, seven lowlanders were studied at VO2 max (cycle ergometry) at sea level (SL), after 9-10 wk at 5,260 m [chronic hypoxia (CH)], and 6 mo later at SL in AH (FiO2 = 0.105) equivalent to 5,260 m. Pulmonary and leg indexes of O2 transport were measured in each condition. Both cardiac output and leg blood flow were reduced by approximately 15% in both AH and CH (P < 0.05). At maximal exercise, arterial [O2] in AH was 31% lower than at SL (P < 0.05), whereas in CH it was the same as at SL due to both polycythemia and hyperventilation. O2 extraction by the legs, however, remained at SL values in both AH and CH. Although at both SL and in AH, 76% of the cardiac output perfused the legs, in CH the legs received only 67%. Pulmonary VO2 max (4.1 +/- 0.3 l/min at SL) fell to 2.2 +/- 0.1 l/min in AH (P < 0.05) and was only 2.4 +/- 0.2 l/min in CH (P < 0.05). These data suggest that the failure to recover VO2 max after acclimatization despite normalization of arterial [O2] is explained by two circulatory effects of altitude: 1) failure of cardiac output to normalize and 2) preferential redistribution of cardiac output to nonexercising tissues. Oxygen transport from blood to muscle mitochondria, on the other hand, appears unaffected by CH.

Increasing P(50) does not improve DO(2CRIT) or systemic VO(2) in severe anemia

Reducing the hemolobin (Hb)-O(2) binding affinity facilitates O(2) unloading from Hb, potentially increasing tissue mitochondrial O(2) availability. We hypothesized that a reduction of Hb-O(2) affinity would increase O(2) extraction when tissues are O(2) supply dependent, reducing the threshold of critical O(2) delivery (DO(2 CRIT)). We investigated the effects of increased O(2) tension at which Hb is 50% saturated (P(50)) on systemic O(2) uptake (VO(2) (SYS)), DO(2 CRIT), lactate production, and acid-base balance during isovolemic hemodilution in conscious rats. After infusion of RSR13, an allosteric modifier of Hb, P(50) increased from 36.6 +/- 0.3 to 48.3 +/- 0.6 but remained unchanged at 35.4 +/- 0.8 mmHg after saline (control, CON). Arterial O(2) saturations were equivalent between RSR13 and saline groups, but venous PO(2) was higher and venous O(2) saturation was lower after RSR13. Convective O(2) delivery progressively declined during hemodilution reaching the DO(2 CRIT) at 3.4 +/- 0.8 ml x min(-1) x 100 g(-1) (CON) and 3.6 +/- 0.6 ml x min(-1) x 100 g(-1) (RSR13). At Hb of 8.1 g/l VO(2) (SYS) started to decrease (CON: 1.9 +/- 0.1; RSR13: 1.8 +/- 0.2 ml x min(-1) x 100 g(-1)) and fell to 0.8 +/- 0.2 (CON) and 0.7 +/- 0.2 ml x min(-1). 100 g(-1) (RSR13). Arterial lactate was lower in RSR13-treated than in control animals when animals were O(2) supply dependent. The decrease in base excess, arterial pH, and bicarbonate during O(2) supply dependence was significantly less after RSR13 than after saline. These findings demonstrate that during O(2) supply dependence caused by severe anemia, reducing Hb-O(2) binding affinity does not affect VO(2) (SYS) or DO(2 CRIT) but appears to have beneficial effects on oxidative metabolism and acid base balance.

Post-ischemic RSR13 amplifies the effect of dizocilpine on outcome from transient focal cerebral ischemia in the rat

In a recent study of focal cerebral ischemia in rats, pre-ischemic administration of the synthetic allosteric hemoglobin modifier RSR13 (2-[4-[[3,5-dimethylanilino) carbonyl] methyl] phenoxy]-2-methylproprionic acid) reduced cerebral infarct size when combined with the NMDA receptor antagonist dizocilpine (MK-801) but not when given alone. We hypothesized that post-ischemic RSR13 administration would enhance neuroprotection afforded by NMDA receptor antagonism in a rat model of transient middle cerebral artery occlusion (MCAO). Fasted normothermic Wistar rats underwent 75 min of temporary MCAO. At onset of reperfusion, rats randomly received: (1) 0.9% NaCl (vehicle) i.v. alone (n=16); (2) 0.9% NaCl+dizocilpine (0.25 mg/kg) i.v. (n=16); or (3) RSR13 (150 mg/kg)+dizocilpine (0.25 mg/kg) i.v. (n=17). Seven days later, neurologic deficit and cerebral infarct size were determined. Dizocilpine alone compared to vehicle reduced mean+/-S.D. subcortical (52+/-24 mm(3) vs. 122+/-64 mm(3), P=0.003) and cortical (35+/-35 mm(3) vs. 125+/-72 mm(3), P=0.00074) infarct volumes. When compared to dizocilpine alone, the combination of RSR13+dizocilpine further reduced subcortical (37+/-14 mm(3) vs. 52+/-24 mm(3), P=0. 034) and cortical (8+/-19 mm(3) vs. 35+/-35 mm(3), P=0.018) infarct size. RSR13+dizocilpine improved neurologic scores vs. either dizocilpine alone (P=0.0014) or vehicle (P=10(-7)). The combination of NMDA receptor antagonism and a RSR13 mediated rightward shift of the oxy-hemoglobin dissociation curve improved outcome from MCAO. Because this occurred after reperfusion, our results suggest that the post-ischemic brain continues to suffer from hypoperfusion defects, which are amenable to therapy by enhanced O(2) delivery. The results also support the concept that neuroprotective strategies, which combine drugs with different mechanisms of action, may yield cumulative benefits.

Storage of blood components

Recent studies have shown that a restrictive transfusion policy results in lower mortality in patients undergoing surgery. The negative effects of red cell transfusion are associated with the presence of contaminating leukocytes, leukocyte products, and probably also with effects of nonviable and poorly functioning red cells. By relatively simple means it is possible to improve the quality of red cells in these respects. The removal of leukocytes from platelet concentrates (PCs) is even more important because of high immunogenicity and capacity to produce cytokines under the storage conditions applied. Prestorage leukocyte removal has clear advantages. Bacterial contamination of PCs is common, but fatal bacterial complications are rare because most contaminating microorganisms grow slowly and do not produce toxins, which are frequent causes of death. Suitable methods for routine bacterial culture of PCs are available and used in some countries.

Pre-separation storage of whole blood: the effect of temperature on red cell 2,3-diphosphoglycerate and myeloperoxidase in plasma

BACKGROUND

Although whole blood intended for component preparation is commonly left to cool at ambient temperature, knowledge is insufficient concerning what effects this may have on red blood cell (RBC) quality, in particular after a prolonged hold.

STUDY DESIGN AND METHODS

Whole blood collected in CPD was incubated at 20 degrees C and 28 degrees C for 6 h designed as a paired study. Blood components were prepared and the red blood cell concentrates (RBCs) were stored for 28 days at 4 degrees C +/- 2 degrees C. Blood gases, pH, glucose, lactate, adenosine triphosphate (ATP), 2,3-diphosphoglycerate (2,3-DPG) and plasma myeloperoxidase (MPO) were investigated.

RESULTS

After 6 h the 2,3-DPG concentrations had lowered to 88% (20 degrees C) and 54% (28 degrees C) of initial levels, respectively. The difference was significant and was maintained for 28 days, although, at low levels from day 7 (28 degrees C) and day 14 (20 degrees C) of storage. ATP was maintained at the initial level in both groups during the first 6 h of storage but after component separation the levels were significantly higher in the 28 degrees C group during the first 5 days. The release of myeloperoxidase (MPO) was significantly higher in the non-cooled group than in the cooled group.

CONCLUSIONS

Pre-separation holding for 6 h of whole blood at temperatures of 28 degrees C causes a great and rapid loss of 2,3-DPG and considerable formation of acid metabolites resulting in clearly subnormal 2,3-DPG levels even on day 1. Active pre-separation cooling to 20 degrees C is to be recommended.

Effects of RSR13, a synthetic allosteric modifier of hemoglobin, alone and in combination with dizocilpine, on outcome from transient focal cerebral ischemia in the rat

This study examined the effect of a pharmacologically induced rightward shift in the partial pressure of oxygen at which 50% of hemoglobin is saturated (P50) on outcome from transient focal cerebral ischemia in the rat. Halothane anesthetized rats (n=20 per group) were given saline or a single 15-min infusion of 150 mg/kg RSR13 (2-[4-[[3,5-dimethylanilino) carbonyl]methyl]phenoxy]-2-methylproprionic acid) intravenously before or 30 min after onset of 75 min of middle cerebral artery filament occlusion (MCAO). Seven days later, severity of hemiparesis and cerebral infarct size were examined. RSR13 alone did not significantly improve outcome. Conscious normothermic rats (n=12 per group) were also given RSR13 (150 mg/kg) or 0.9% NaCl intravenously and subjected to 75 min of MCAO with 7 days of recovery. Again, RSR13 alone did not significantly reduce infarct size or improve neurologic score. A dose-response curve for dizocilpine (MK-801) was then constructed in conscious normothermic rats subjected to 75 min of MCAO. Dizocilpine (0.5 mg/kg i.v.) caused a 90% reduction in mean infarct size while 0.25 mg/kg reduced infarct size by 48%. Other rats were then subjected to 75 min of MCAO after being given dizocilpine (0.25 mg/kg i.v.; n=18) or RSR13 (150 mg/kg i.v. )+dizocilpine (0.25 mg/kg i.v.; n=15). RSR13+dizocilpine resulted in smaller cortical infarct volume (8+/-14 mm3 vs. 34+/-37 mm3, p<0.02) and total cerebral infarct volume (46+/-28 mm3 vs. 81+/-60 mm3, p<0. 05) compared to dizocilpine alone, respectively. We conclude that a pre-ischemic peak increase in P50 of approximately 25 mmHg alone is insufficient to reduce focal ischemic injury, but may be advantageous when used in conjunction with other neuroprotective agents.

Storage of whole blood before separation: the effect of temperature on red cell 2,3 DPG and the accumulation of lactate

BACKGROUND

Although whole blood intended for component preparation is commonly left to cool at ambient temperature, knowledge is insufficient as to the effects this may have on red cell quality, in particular after a prolonged hold.

STUDY DESIGN AND METHODS

Whole blood collected in ACD-A (7% wt/wt) and CPD (12% wt/wt) was incubated at 4, 10, 15, 20, 25, and 30 degrees C for 24 hours. Blood gases, pH, bicarbonate, glucose, lactate, and red cell 2,3 DPG were investigated.

RESULTS

When the blood was stored at 30 degrees C, the 2,3 DPG concentration decreased within 4 hours from 858 +/- 106 to 316 +/- 172 mmol per mol of hemoglobin (a 63% decrease); 99 percent was lost within 18 hours. At 25 degrees C, 46 percent was lost within 4 hours and 94 percent within 18 hours; at 20 degrees C, the decrease at 18 hours was 62 percent and that at 15 degrees C was 24 percent. No loss of 2,3 DPG was observed at 4 degrees C and 10 degrees C storage. No difference was attributable to the anticoagulant used. After 24 hours, the lactate concentration at 15 degrees C was 2.9 times the original, that at 20 degrees C was 3.8 times the original, that at 25 degrees C was 7.0 times, and that at 30 degrees C was 9.2 times.

CONCLUSIONS

With current anticoagulants, storage of whole blood at temperatures of 25 to 30 degrees C before separation causes a great and rapid loss of 2,3 DPG and an accumulation of acid metabolites. In a hold of blood for >4 hours, rapid cooling is desirable to avoid initial loss of 2,3 DPG.

Preparation and preservation of red cells

BACKGROUND

The production of blood components has undergone several changes during the last decades.

METHODS

Red blood cells will have slightly different properties depending on the way of preparation: whether a hard or soft spin has been used, whether platelets and/or leukocytes have been removed or not, and whether the red cells have been suspended in part of the original plasma or in an additive solution. Automated techniques are now often used for the separation of buffy coats, red cells and plasma. Recently, apheresis techniques have been applied for the preparation of red cells, mostly in combination with plasma or platelets. Continuous addition of the anticoagulant during collection reduces the delay between collection and separation, but the cost is higher and donor time longer.

RESULTS

Most of the methods for the preparation and storage of red cells allow 35-42 days of storage with a mean in vivo recovery of > 75%. However, the content of erythrocyte 2,3-DPG is commonly lost within 1-2 weeks, caused by the accumulation of acid metabolites, but can be maintained longer with new systems of storage. Leukodepletion of red cells by filtration is used increasingly, but its importance in the majority of transfusions is still unclear.

CONCLUSION

New options for the preparation and storage of red blood cells are available and undergo continuous evaluation.

Clinical and laboratory experience with erythrocyte and platelet preparations from a 0.5CPD Erythro-Sol opti system

BACKGROUND

Red blood cells stored as concentrates or suspensions in additive solutions change rapidly their oxygen affinity mainly due to the loss of 2,3-diphosphoglycerate (2,3-DPG). When collected in CPD with half of the normal concentration of citrate and citric acid (0.5CPD) and stored in a new additive solution (Erythro-Sol), 2,3-DPG is better maintained. No studies of the oxygen affinity of red cells stored under these conditions have been published. In Erythro-Sol, red cells have a satisfactory in vivo recovery for 49 days but the conditions after 28 days, within which time most red cell units are transfused, have not been investigated. Of importance is also to be able to make platelet concentrates (PCs) from 0.5CPD blood. Little data are available concerning the clinical usefulness of platelets prepared from 0.5CPD buffy coats (BCs).

METHODS

Blood was collected in 0.5CPD, held at 20 degrees C for 3-4 h, then separated with the bottom-and-top technique into red cells, plasma and BC. In a storage experiment with 6 U the 2,3-DPG and P50 values were determined weekly and a number of in vitro parameters were tested on day 28. In 6 donors the in vivo recovery and survival of red cells were determined using a single-chromium technique. Transfusions of 212 0.5CPD-Erythro-Sol red cell units were given to hematological patients under supervision. PCs derived from pools of 0.5CPD BCs suspended in PAS2 (T-Sol) were transfused to 20 thrombocytopenic patients and compared with CPD-BC-PCs suspended in PASI. Corrected count increments (CCI) were determined.

RESULTS

The erythrocyte 2,3-DPG and P50 values were normal or slightly subnormal initially but increased to supernormal levels during the 1 week, and remained at these levels for a further 1-3 weeks; the 2,3-DPG was two thirds of normal after 28 days, the P50 was 3.72 +/- 0.28 kPa after 14 days and 2.84 +/- 0.41 after 28 days (mean +/- SD). The P50 values corresponded closely (r2 = 0.903) to 2,3-DPG. The in vivo recovery of 4-week-stored red cells was 89.6 +/- 5.5% and the T50 was 32.2 +/- 2.0 days. No adverse effects were observed in the transfusions. The CCI values did not differ between test and control groups; in both, 3- to 5-day-stored PCs gave lower CCI than fresh (0-2 days) PCs. Patients with acute myeloid leukemia AML (n = 11) had significantly lower CCI values than patients with myelodysplastic syndrome, myeloma and lymphoma (n = 9; CCI 1 h: p = 0.001; CCI 24 h: p = 0.006).

CONCLUSIONS

Red cells stored in Erythro-Sol sustain a normal or slightly lowered oxygen affinity for 2-4 weeks, their viability is excellent, and they are well tolerated in clinical transfusions. Platelets prepared from 0.5CPD-BCs cause CCI, of the same magnitude as CPD-BCs.

Phosphoenolpyruvate prevents the decline in hepatic ATP and energy charge after ischemia and reperfusion injury in rats

BACKGROUND

Phosphoenolpyruvate (PEP) is a high-energy metabolite in the final step of glycolysis. PEP is converted into pyruvate by pyruvate kinase. One molecule of adenosine triphosphate (ATP) is generated from one molecule of PEP. The aim of this study was to examine the effects of PEP on hepatic energy metabolism at an early phase after ischemia and reperfusion were examined in rats.

MATERIALS AND METHODS

Male Wistar rats (250-350 g) were divided into two groups; after two 15-min periods of ischemia with 2 min reperfusion in between, either PEP or glucose solution (400 mmol/liter, pH 7.4) was infused into the portal vein (2.5 ml/300 g body wt/5 min). Before and 0, 5, 10, and 30 min after ischemia, arterial blood and liver tissue were collected for analyses.

RESULTS

During the two ischemic periods, ATP and total adenine nucleotide (TAN) of the liver decreased from 9.10 +/- 0.50 and 14.06 +/- 0.29 to 0.99 +/- 0.50 and 10.86 +/- 0.42 mmole/g liver, respectively (P < 0.05), while adenosine monophosphate (AMP) increased from 1.18 +/- 0.15 to 8.47 +/- 0.66 mmole/g liver (P < 0. 05). Hepatic energy charge (EC) significantly decreased from 0.78 +/- 0.02 to 0.16 +/- 0.03 (P < 0.05). Serum concentrations of pyruvate and lactate were elevated from 1.18 +/- 0.15 and 18.4 +/- 0. 52 to 3.29 +/- 0.52 and 72.6 +/- 4.8 mg/dl, respectively (P < 0.05). After a 5-min infusion of PEP or glucose solution, the ATP concentration was significantly higher in the PEP group than in the glucose group (4.08 +/- 0.58 micromole/g liver vs 2.20 +/- 0.45 micromole/g liver, P < 0.01), whereas AMP concentration was significantly lower in the PEP group than in the glucose group (4.26 +/- 0.66 micromole/g liver vs 7.02 +/- 0.71 micromole/g liver, P < 0. 01). EC in the PEP group was significantly higher than that in the glucose group (0.493 +/- 0.051 vs 0.293 +/- 0.042, P < 0.01). Ten minutes after ischemia, the ATP, TAN, and EC levels were still higher in the PEP group than in the glucose group, but the difference did not reach statistical significance. At 30 min after ischemia, these values became similar in both groups. At 5, 10, and 30 min after ischemia, serum pyruvate concentrations were higher in the PEP group than in the glucose group.

CONCLUSION

These findings suggest that PEP recovers hepatic energy from liver cell damage at an early phase after ischemia and reperfusion by prompt ATP production through the degradation of PEP into pyruvate in the liver.

Time-course and treatment response with SNX-111, an N-type calcium channel blocker, in a rodent model of focal cerebral ischemia using diffusion-weighted MRI

Diffusion-weighted magnetic resonance imaging (DWI) is capable of noninvasively imaging acute cerebral ischemia. We demonstrate the utility of this technique by evaluating SNX-111, a novel N-type calcium channel blocker with potential neuroprotective properties, in a rodent model of transient focal ischemia. Twenty-four Sprague-Dawley rats weighing between 310-350 g underwent occlusion of the middle cerebral artery (MCAO) for 105 min followed by 22.5 h of reperfusion. Thirty minutes following MCAO, animals were randomized to receive SNX-111 5 mg/kg intravenously over 1 h vs. placebo. DWI and T2-weighted MRIs (T2W) were performed at 0.5, 1.5 and 24 h after the onset of ischemia. Area fractions of increased signal intensity on the DWI and T2W images were measured. DWI area fractions at 1.5 and 24 h were also normalized to the initial, pre-treatment scans. Apparent diffusion coefficients (ADC) were calculated from fitted maps. Tri-phenyl tetrazolium chloride (TTC) staining was performed on brains at 24 h and infarct area fractions were measured. SNX-111 treated animals showed significantly improved 1.5-h DWI scan ratios compared to controls (ratios of 1.06 +/- 0.25 vs. 2.98 +/- 0.78 SNX vs. controls respectively, P < 0.05). A trend toward improved DWI ratios was seen by 24 h in the SNX-111 group (2.5 +/- 0.75 vs. 4.12 +/- 1.6, N.S.) DWI, T2W and TTC area fractions at 24 h also showed trends favoring a neuroprotective effect of SNX-111. Bright areas on DWI corresponded to ADC decreases of about 30% compared to the non-ischemic hemisphere. These decreases were the same in both treatment groups and at each time point. DWI, T2W and TTC area fractions at 24 h were strongly correlated (r = 0.98, DWI and TTC; r = 0.99, T2W and TTC; r = 0.97, T2W and DWI, P < 0.0001). We conclude that in this ischemic model, SNX-111 provides early neuroprotection and that serial DWI is a useful way of demonstrating this.