Microaggregates in frozen and saline washed red blood cells

Factors affecting the formation of white particulate matter in red blood cell components

BACKGROUND

Recently white particulate matter (WPM) in red blood cell (RBC) components has received increased attention. The nature and causes of WPM formation were investigated.

STUDY DESIGN AND METHODS

Whole-blood units were collected from 18 healthy subjects with three different types of collection sets. Six units were collected into each type. Units were divided into four equal parts and stored for 4 hours: two parts at room temperature and two at 4 degrees C. RBCs were prepared from each quarter-unit: two by heavy centrifugation (5000 x g) and two by light centrifugation (2000 x g). Whole blood was inspected for WPM over 4 hours and RBCs over 1 hour.

RESULTS

No WPM was detected in whole blood, but WPM was detected in at least one RBC component from 9 of the 18 donations. The 36 components prepared by heavy centrifugation were more likely to contain WPM than the 36 prepared by light centrifugation (50% vs. 19%; p < 0.02). The incidence of WPM was similar among RBCs stored at room temperature and 4 degrees C. Donors of RBCs with WPM had higher total cholesterol levels than donors of components without WPM (191 +/- 20 mg/dL vs. 163 +/- 32 mg/dL; p < 0.04), but there was no difference in triglyceride levels between the two groups.

CONCLUSIONS

WPM is an expected consequence of standard RBC manufacturing methods, but it is more frequent in RBCs prepared by heavy centrifugation and from donors with higher cholesterol levels.

White particulate matter found in blood collection bags consist of platelets and leukocytes

BACKGROUND

In late January 2003, some blood centers and hospitals throughout the US voluntarily sus-pended the use of some RBC and plasma units for trans-fusion due to the presence of unknown white particulate matter (WPM) in these units. To better understand the WPM phenomena, a number of technologies were used to establish the nature of the particulates observed in Terumo Collection sets.

STUDY DESIGN AND METHODS

All AS-5 nonleuko-reduced RBCs and plasma units were visually inspected for WPM by placing the bags on a flat counter, undisturbed, for approximately 10 minutes and then perform-ing a visual examination for particles. Particles were isolated and placed on microscope slides or in plastic tubes for further analysis. Electron microscopy, bright field microscopy, differential interference contrast microscopy, infrared spectroscopy, and flow cytometry procedures were performed to establish the nature of the particulate matter. In addition, leukoreduction filters and blood transfusion sets were used on RBCs units with WPM.

RESULTS

The particles were mostly composed of PLTs and WBCs, and fragments of these cells. All macroscopic WPM was removed from RBCs with leukoeduction and transfusion filters.

CONCLUSIONS

WPM originated from PLTs and WBCs. Foreign matter (e.g., plastic) was not observed in any of the units. Leukoreduction and transfusion filters can be used to remove macroscopic WPM.

Cardiopulmonary function following transfusion of three red blood cell products in elective abdominal aortic aneurysmectomy

In order to evaluate the importance of red cell O(2) affinity of transfused blood on cardiac performance and adverse effects of transfusion on lung function, a prospective double-blind protocol was used in 27 patients undergoing abdominal aortic aneurysmectomy. Three types of blood were administered: packed red cells (PC), washed red cells (WC) and high 2,3 DPG red cells (2,3 DPG). An average of 4.5 units of blood was used per patient. Transfusion of 2,3 DPG blood resulted in maintenance of in vivo P(50) during surgery and an increase to 31.2 torr after operation (p < 0.001). An intraoperative fall in in vivo P(50) to 23.2 +/- 2.0 torr was observed in patients who were transfused with PC (p < 0.001) and to 25.1 +/- 2.6 torr with WC (p < 0.005). A fall in body temperature averaging 2.2 C intraoperatively was noticed in all three groups. After operation, in vitro P(50) decreased in patients transfused with PC (p < 0.005) and WC (p < 0.005) while it remained unchanged in the high 2,3 DPG group. This was consistent with the decrease of red cell 2,3 DPG in the PC (p < 0.001) and WC groups (p < 0.01) and maintenance in the 2,3 DPG group. Left ventricular stroke work and volume loading Starling type myocardial performance curves were similar for the three groups. Microaggregates measured by Coulter counting and screen filtration pressure were the same for all three products in samples drawn on both sides of the 40 microm transfusion filter. There was no relationship of transfusion volumes or type of blood product to changes in lung function (physiologic shunting, dynamic compliance and pulmonary arterial pressure) in the three groups of patients. The false negative, beta, error of missing a true 25% difference was less than 10%. It is concluded that 2,3 DPG enriched red cells improved oxygen availability, but that a 4.5 unit transfusion of any of the three blood products did not influence lung function or myocardial performance following aneurysmectomy.

Blood microfiltration. A review

The factors which contribute to the formation of microaggregates in stored blood for transfusion have been discussed and their significance assessed. The history of the development of blood microfiltration is described. The advantages and disadvantages of screen microfilters in comparison with depth filters are considered. Screen filters with a pore diameter of about 40 micron would appear to have definite advantages.

Use and analysis of saline washed red blood cells

Data collected from 50 saline washed units of red blood cells shows that units washed with one liter of 0.9 per cent NaCl on an IBM cell processor have an average hematocrit of 72.2 per cent, with 84.7 per cent of the white blood cells removed, and only 0.6 per cent of the original total protein remaining. The red blood cell recovery is 85.5 per cent. Other advantages include low extracellular potassium and reduction in supernatant hemoglobin, metabolic waste products, debris, and nonviable cells. Over 1500 washed units have been transfused, with an average of 150 per month. The clinical response has been very favorable with only one suspected reaction reported since the use of washed cells, and no reported cases of hepatitis.

The occurence and significance of microaggregates in stored blood

During storage whole blood progressively forms microaggregates by adhesion of platelets and leucocytes. This occurs from the second day of storage and the presence of such potential microemboli can be demonstrated by light microscopy of smears of blood samples. They cause an increase in the viscosity of the blood as measurable by the screen filtration pressure method. If infused into a patient they, by causing microvascular occlusion, result in multiple organ dysfunction, primarily of the lung. It is recommended that, if whole blood greater than 4 days in storage is to be infused, an in-line microfilter be used to remove the microaggregates from the transfusion. Alternatively, early separation, or the use of fresh blood is recommended.