Low molecular weight heparin : Biochemistry, pharmacology, perioperative prophylaxis regimens, and guidelines for regional anesthetic management

TLDR: In this paper, the authors provided guidelines for minimizing the risk of spinal hematoma in patients undergoing regional anesthesia while receiving perioperative anticoagulant-based prophylaxis.

Abstract: M ultiple randomized clinical trials have established the efficacy of standard heparin (SH) anticoagulation for venous thromboembolism prophylaxis. However, for high-risk populations, such as patients undergoing total hip or knee replacement, SH is relatively ineffective and may be associated with significant bleeding complications (1). Initial animal model studies suggested that low molecular weight fractions of heparin, when administered at equivalent antithrombotic doses, caused less bleeding than SH (2). These early studies raised the exciting possibility of separating the antithrombotic from the bleeding effects of heparin. The efficacy and safety of low molecular weight heparins (LMWH) as postoperative venous thromboembolism prophylaxis subsequently has been demonstrated in more than 60 clinical trials including more than 20,000 patients (3). However, reports of spinal hematoma occurring spontaneously and in association with regional anesthesia (4,5) have generated concern regarding the safety of spinal or epidural anesthesia in patients receiving LMWH. In this review, we focus on the biochemistry and pharmacology of LMWH compared with SH, current LMWH prophylaxis regimens, and the implications of perioperative LMWH prophylaxis for anesthesia, particularly among patients receiving regional anesthesia and analgesia. Guidelines will be provided for minimizing the risk of spinal hematoma in patients undergoing regional anesthesia while receiving perioperative anticoagulant-based prophylaxis.