Causes of Higher Blood Loss during General Anesthesia Compared to Spinal Anesthesia in Total Hip Replacement – a Retrospective Analysis of Data Collected Online

Abstract

Objective: The purpose of this study was to evaluate indicators of intraoperative blood loss in patients undergoing total hip replacement under general or spinal anesthesia using data collected by an anesthesia information management system (AIMS). Furthermore, we wanted to investigate whether data collected with an AIMS are suitable for other comparable clinical investigations. Material and Methods: From January 1, 1997 until July 31, 1999, parameters of 681 elective hip replacements were collected with the AIMS NarkoData and stored in a relational database. The effects of possible influences on blood loss were analyzed for the entire collective. These influential factors were then studied for differences between both methods of anesthesia. Results: The duration of surgery (r = +0.50) and the mean body temperature (r = –0.36) correlated with blood loss. There was a significant difference in blood loss between the 478 hip replacements under spinal anesthesia (604 ??404 ml) and the 203 under general anesthesia (751 ??552 ml). Differences in duration of surgery, transfusion of packed red cells and fluid infusion were noticed. Mean arterial blood pressure was lower in the regional-anesthesia group than in the general-anesthesia group (82.8 ??10.8 vs. 88.1 ??11.4 mm Hg). However, an influential effect was not observed. Conclusions: In this study, duration of surgical procedure under general anesthesia as compared to spinal anesthesia was evaluated as being a cause for increased blood loss. The effects of differences in blood pressure, as described by other authors, could not be verified. The role of body temperature has yet to be investigated. Although retrospective analysis of routinely gathered online data is less comprehensive and coherent when compared to prospective data gathering, it is still useful in forming hypotheses for prospective studies.