The Impact of Surgery and Stored Red Blood Cell Transfusions on Nitric Oxide Homeostasis.

BACKGROUND: Cell-free hemoglobin (Hb) forms in stored red blood cells (RBCs) as a result of hemolysis. Studies suggest that this cell-free Hb may decrease nitric oxide (NO) bioavailability, potentially leading to endothelial dysfunction, vascular injury, and multiorgan dysfunction after transfusion. We tested the hypothesis that moderate doses of stored RBC transfusions increase cell-free Hb and decrease NO availability in postoperative surgical patients. METHODS: Twenty-six patients undergoing multilevel spine fusion surgery were studied. We compared those who received no stored RBCs (n = 9) with those who received moderate amounts (6.1 ± 3.0 units) of stored RBCs over 3 perioperative days (n = 17). Percent hemolysis (cell-free Hb), RBC-NO (heme-NO), and plasma nitrite and nitrate were measured in samples from the stored RBC bags and from patients' blood, before and after surgery. RESULTS: Posttransfusion hemolysis was increased approximately 3.5-fold over preoperative levels (P = 0.0002) in blood samples collected immediately after surgery but not on postoperative days 1 to 3. Decreases in both heme-NO (by approximately 50%) and plasma nitrite (by approximately 40%) occurred postoperatively, both in nontransfused patients (P = 0.036 and P = 0.026, respectively) and transfused patients (P = 0.0068 and P = 0.003, respectively) and returned to preoperative baseline levels by postoperative day 2 or 3. Postoperative plasma nitrite and nitrate were decreased significantly in both groups, and this change was slower to return to baseline in the transfused patients, suggesting that blood loss and hemodilution from crystalloid administration contribute to this finding. CONCLUSIONS: The decrease in NO metabolites occurred irrespective of stored RBC transfusions, suggesting this decrease may be related to blood loss during surgery and hemodilution rather than to scavenging of NO or inhibition of NO synthesis by stored RBC transfusions.

2,3-Diphosphoglycerate Concentrations in Autologous Salvaged Versus Stored Red Blood Cells and in Surgical Patients After Transfusion.

BACKGROUND: Stored red blood cells (RBCs) are deficient in 2,3-diphosphoglycerate (2,3-DPG), but it is unclear how autologous salvaged blood (ASB) compares with stored blood and how rapidly 2,3-DPG levels return to normal after transfusion. Therefore, we compared levels of 2,3-DPG in stored versus ASB RBCs and in patients' blood after transfusion. METHODS: Twenty-four patients undergoing multilevel spine fusion surgery were enrolled. We measured 2,3-DPG and the oxyhemoglobin dissociation curve (P50) in samples taken from the ASB and stored blood bags before transfusion and in blood samples drawn from patients before and after transfusion. RESULTS: The mean storage duration for stored RBCs was 24 ± 8 days. Compared with fresh RBCs, stored RBCs had decreased 2,3-DPG levels (by approximately 90%; P < 0.0001) and a decreased P50 (by approximately 30%; P < 0.0001). However, ASB RBCs did not exhibit these changes. The mean 2,3-DPG concentration decreased by approximately 20% (P < 0.05) in postoperative blood sampled from patients who received 1 to 3 stored RBC units and by approximately 30% (P < 0.01) in those who received ≥4 stored RBC units. 2,3-DPG was unchanged in patients who received no stored blood or ASB alone. After surgery, 2,3-DPG levels recovered gradually over 3 postoperative days in patients who received stored RBCs. CONCLUSIONS: Stored RBCs, but not ASB RBCs, have decreased levels of 2,3-DPG and a left-shift in the oxyhemoglobin dissociation curve. Postoperatively, 2,3-DPG levels remain below preoperative baseline levels for up to 3 postoperative days in patients who receive stored RBCs but are unchanged in those who receive only ASB RBCs.

Oxidative stress and rheologic properties of stored red blood cells before and after transfusion to surgical patients.

BACKGROUND: The loss of structural and functional integrity of red blood cells (RBCs) during storage, collectively referred to as "storage lesion," has been implicated in reduced oxygen delivery after transfusion. RBCs are highly susceptible to oxidative damage from generation of reactive oxygen species by autoxidation of hemoglobin. Therefore, we examined whether increased oxidative stress (OS) in stored RBCs is associated with impaired cell membrane deformability before or after transfusion. STUDY DESIGN AND METHODS: Thirty-four patients undergoing multilevel spine fusion surgery were enrolled. OS in RBCs was assessed by the presence of fluorescent heme degradation products and methemoglobin, which were measured with fluorimetric and spectrophotometric methods, respectively. Deformability and aggregation were determined by ektacytometry in stored RBCs, autologous salvaged RBCs, and posttransfusion blood samples. RESULTS: OS in stored RBCs was significantly increased with longer storage (R = 0.54, p = 0.032) and significantly higher than that in fresh RBCs (9.1 ± 1.3 fluorescent arbitrary units vs. 7.7 ± 0.9 fluorescent arbitrary units, p < 0.001). Deformability decreased (R = -0.60, p = 0.009) with increasing storage duration. OS was elevated (p < 0.05) and deformability was decreased (p < 0.05) in postoperative blood from patients who had undergone moderate (≥4 RBC units) but not minimal or no transfusion. Neither the decrease in deformability of RBCs nor the aggregation changes were correlated with OS. CONCLUSIONS: Although stored RBCs show signs of increased OS and loss of cell membrane deformability, these changes were not directly correlated and were only evident after moderate but not lower dose transfusion in postoperative surgical patients. These findings suggest that factors other than OS may contribute to impaired rheology with stored RBCs in the clinical setting.