In Reply:-First, we would like to thank Drs. Hill and Whitten for their constructive and relevant criticism, in which they note three important points:(1) lack of control group not receiving red cell concentrates;(2) influence of anesthetic techniques; and (3) lack of control of blood storage length for the autologous and allogeneic red cell concentrates. We will discuss these points respectively.
Regarding their first point, we agree that it would be most interesting with a true control group receiving no blood products. However, total hip joint replacement surgery is associated with large intra- and postoperative blood loss. A total blood loss of at least 1,500–2,000 ml is common. Most patients require some kind of blood transfusion. In the discussed study, 2 of 56 patients did not receive any blood transfusion. In a randomized clinical study, it is more or less impossible to include a randomized control group not receiving any blood transfusions because there simply are not enough patients and because it is impossible to ethically randomize patients to not receive blood transfusions when they are expected to need blood.
Surgical trauma leads to release of cytokines, which was also noted in the discussion. The majority of IL-6 and IL-8 release is probably a result of the surgical trauma (an indication of this is the mentioned post hoc study of six patients not receiving blood products, in whom we found concentrations similar to those found in the allogeneic and the autologous group), but the difference between the groups cannot possibly be explained by the surgery.
Regarding their second point, it is true that local anesthetics may influence cytokine release. However, this has been shown in vitro and in concentrations of 0.00125–0.125% of bupivacaine, which is at least 25 times a higher concentration than what is found after administration of 20 mg of bupivacaine in an adult (weight. 70 kg). Both groups were treated identically. No patients were converted to general anesthesia.
Regarding their third point, the blood storage time for both groups is given in table 1 in our article. No significant differences appeared between the groups.
Anders Avall, M.D.
Department of Anaesthesiology and Intensive Care; Institute of Surgical Sciences; Sahlgrenska University Hospital; Goteborg, Sweden
(Accepted for publication December 18, 1997.)