Intraoperative Washing of Long-Stored Packed Red Blood Cells by Using an Autotransfusion Device Prevents Hyperkalemia

We report the first use of an autotransfusion device to wash packed red blood cells (PRBCs) to reduce the amount of potassium infused in a patient with end-stage renal failure requiring multiple transfusions.

Case Report

A 73-yr-old man was to undergo an elective nephrectomy under combined general and epidural anesthesia. The underlying kidney tumor further caused a vena caval tumor thrombus, which was to be removed as well. Unfortunately, this patient had a rare blood type (type B, Rh negative), and only eight compatible units of PRBCs (28–32 days old) were available.

The patient’s preoperative hematocrit (Hct) was 31%. When his Hct decreased to 20%, we transfused 2 U of these PRBCs. Subsequently, the potassium increased from 5.4 to 6.7 mmol/L. Further transfusion of PRBCs would have resulted in a further and potentially fatal increase in potassium. However, the patient continued to bleed, and transfusion was absolutely mandatory. Therefore, we decided to wash these PRBCs before transfusion by using a continuous autotransfusion device (CATS; Fresenius AG, Bad Homburg, Germany). This device was operated in the “high-quality mode,” in which 1 mL of blood is washed with 2 mL of normal saline. The patient received four more units of PRBCs; each was processed before transfusion by using the CATS. Each unit of PRBCs was processed separately. Processing these 4 U of PRBCs took 35 min. We measured the hemoglobin, Hct, and potassium levels of each unit before and after processing with the CATS (Table 1). The CATS allowed for a mean potassium elimination rate of 97.3%. The Hct increased to 33%, whereas the plasma potassium level decreased from 6.7 to 5.9 mmol/L during transfusion of the washed PRBCs. No other therapy to decrease the potassium level was initiated.

Table 1: Hemoglobin (Hb), Hematocrit (Hct), and Potassium Measured Before Processing 4 U of Packed Red Blood Cells (PRBCs) with a CATS Autotransfusion Device

Discussion

This case report shows that autotransfusion devices not only serve to wash and hemoconcentrate salvaged shed blood, but may also be extremely useful in terms of potassium elimination in patients with end-stage renal failure who are in need of a homologous blood transfusion. We previously studied the potassium elimination rate of autotransfusion devices in vitro by using outdated PRBCs ^(1,2). Given these in vitro results, we advocated the use of autotransfusion devices for patients with end-stage renal failure and patients requiring a massive transfusion ⁽³⁾. This technique has never been reported in a clinical setting.

In our case, we had only 8 U of compatible blood available; the newest had a storage time of four weeks. During storage time, the potassium levels may increase to extremely high values. Therefore, in such patients, the PRBCs ideally should be characterized by a rather short storage time. However, in cases of rare blood type, this may or may not be achievable. In our case, we had to use relatively old units of PRBCs with a mean potassium level of 39.6 mmol/L (Table 1). The infusion of two such units caused a marked increase in the patient’s serum potassium level. We doubted that the transfusion of four more units would have been tolerated by the patient. Therefore, we decided to process the PRBCs with the CATS. The blood-processing procedure is based on the principle of centrifugation, in which denser particles (i.e., red blood cells) are separated from the lighter blood components and fluids (including free hemoglobin and potassium), which are removed to a waste bag. The processed blood had a mean potassium level of 2.3 mmol/L and was well tolerated by the patient. After the operation, the patient was transferred to our intensive care unit for one night and was then discharged to an intermediate care unit. He recovered uneventfully and was shortly thereafter discharged from the hospital.

Alternatively, the PRBCs could have been washed by the blood bank. However, this is much more time consuming. Autotransfusion devices are readily available in the operating room and are so user-friendly nowadays that we preferred to operate such a device ourselves rather than waiting for PRBCs to be washed by the blood bank. Especially in bleeding patients with low Hct, it is reassuring for the anesthesiologist to have PRBCs readily available in the operating room rather than to have them processed in a blood bank outside the operating room. The CATS, like other modern autotransfusion devices, is characterized by an extremely fast red blood cell recovery rate ⁽¹⁾, so that nearly no red blood cells are wasted during the washing procedure.

Autotransfusion of shed blood in cancer surgery is controversial. Although some advocate the retransfusion of shed blood after radiation, it is not our policy to retransfuse such blood. Therefore, in our patient the autotransfusion system was not hooked up in the first place. However, the additional costs (approximately 70 Euros) for one disposable autotransfusion set seem to be well spent when compared with the costs of washing PRBCs in a blood bank, because countless units of PRBCs can be washed with one set. Furthermore, bedside washing of PRBCs is so time effective that only those units are washed that are definitely going to be transfused. Washing PRBCs in a blood bank, however, mostly ends up in washing more units than are really needed, simply because the anesthesiologist compensates for the prolonged waiting time for washed PRBCs from the blood bank by ordering more PRBCs at a time.