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

Pharmacology of spinal interventions: review of agents used in spine pain procedures

Spine procedures are commonly performed to diagnose and treat various spinal conditions, ranging from degenerative disc disease to vertebral fractures. These procedures often involve the use of pharmaceutical agents to enhance the efficacy of the intervention and improve patient outcomes. This review provides an overview of the pharmaceuticals commonly utilized in spine procedures, including corticosteroids, anesthetics, antibiotics, radiographic contrast, neurolytic agents, and materials used in kyphoplasty and vertebroplasty. This review summarizes the utilization of these pharmaceutical agents in spine procedures in an effort to optimize patient outcomes. Understanding the pharmacological properties and appropriate uses of these pharmaceuticals is essential for interventionalist and healthcare providers involved in the care of patients undergoing spinal interventions.

End-Site-Specific Conjugation of Enoxaparin and Tetradeoxycholic Acid Using Nonenzymatic Glycosylation for Oral Delivery

Heparin and low molecular weight heparins (LMWHs) have been the drug of choice for the treatment or the prevention of thromboembolic disease. Different methods are employed to prepare the LMWHs that are clinically approved for the market currently. In particular, enoxaparin, which has a reducing sugar moiety at the end-site of polysaccharide, is prepared by alkaline depolymerization. Focusing on this end-site-specific activity of LMWHs, we conjugated the tetraoligomer of deoxycholic acid (TetraDOCA; TD) at the end-site of enoxaparin via nonenzymatic glycosylation reaction. The end-site-specific conjugation is important for polysaccharide drug development because of the heterogeneity of polysaccharides. This study also showed that orally active enoxaparin and tetraDOCA conjugate (EnoxaTD) had therapeutic effect on deep vein thrombosis (DVT) without bleeding in animal models. Considering the importance of end-specific conjugation, these results suggest that EnoxaTD could be a drug candidate for oral heparin development.

Thromboelastography for the monitoring of the antithrombotic effect of low-molecular-weight heparin after major orthopedic surgery

Objective:

Low-molecular-weight heparins (LMWHs) are commonly used to prevent and manage postoperative thromboembolism. In general, monitoring of anticoagulant activity by anti-Xa testing is not done properly. Thromboelastography (TEG) evaluates the viscoelastic properties of blood during coagulation. The clinical application of TEG variables in monitoring LMWH treatment is not yet well defined.

Methods:

This prospective study was designed to systematically examine the correlation between anti-Xa and basic TEG parameters in monitoring LMWH treatment. We furthermore evaluated for the first time the usefulness of a composite TEG parameter, coagulation index (CI). Thirty patients undergoing unilateral or bilateral total knee replacement, admitted to the intensive care unit on a therapeutic dosage of subcutaneous enoxaparin (30-mg injections administered twice daily), were included into the study. TEG parameters and anti-Xa levels were measures at baseline and 4, 12, and 24 hours after the injection.

Results:

This study demonstrates a significant correlation between CI and plasma anti-Xa activity in surgical patients treated with enoxaparin. Although the correlation was significant between r time and anti-Xa level only at Hour 4, CI was significant for each time interval (p<0.05). CI increased immediately after T0, peaking at Hour 4, and remained elevated (relative to baseline) at Hour 24 but still did not return to admission levels.

Conclusion:

The current study may be an important first step in order to use CI to measure LMWH activity. Meanwhile, the value and usefulness of TEG in predicting bleeding or thrombotic complications following major orthopedic surgery merit further investigation.

Resveratrol Reduces the Incidence of Portal Vein System Thrombosis after Splenectomy in a Rat Fibrosis Model

Purpose. To investigate the preventive effect of resveratrol (RES) on the formation of portal vein system thrombosis (PVST) in a rat fibrosis model. Methods. A total of 64 male SD rats, weighing 200–300 g, were divided into five groups: Sham operation, Splenectomy I, Splenectomy II, RES, and low molecular weight heparin (LMWH), with the former two groups as nonfibrosis controls. Blood samples were subjected to biochemical assays. Platelet apoptosis was measured by flow cytometry. All rats were euthanized for PVST detection one week after operation. Results. No PVST occurred in nonfibrosis controls. Compared to Splenectomy II, the incidences of PVST in RES and LMWH groups were significantly decreased (both p < 0.05). Two rats in LMWH group died before euthanasia due to intra-abdominal hemorrhage. In RES group, significant decreases in platelet aggregation, platelet radical oxygen species (ROS) production, and increase in platelet nitric oxide (NO) synthesis and platelet apoptosis were observed when compared with Splenectomy II (all p < 0.001), while in LMWH group only significant decrease in platelet aggregation was observed. Conclusion. Prophylactic application of RES could safely reduce the incidence of PVST after splenectomy in cirrhotic rat. Regulation of platelet function and induction of platelet apoptosis might be the underlying mechanisms.

A systematic review on the accumulation of prophylactic dosages of low-molecular-weight heparins (LMWHs) in patients with renal insufficiency

PURPOSE

Although therapeutic dosages of most low-molecular-weight heparins (LMWHs) are known to accumulate in patients with renal insufficiency, for the lower prophylactic dosages this has not been clearly proven. Nevertheless, dose reduction is often recommended. We conducted a systematic review to investigate whether prophylactic dosages of LMWH accumulate in renal insufficient patients.

METHODS

A comprehensive search was conducted on 17 February 2015 using Embase, Medline, Web of Science, Scopus, Cochrane, PubMed publisher, and Google scholar. The syntax emphasized for LMWHs, impaired renal function, and pharmacokinetics. The search yielded 674 publications. After exclusion by reading the titles, abstracts, and if necessary the full paper, 11 publications remained.

RESULTS

For dalteparin and tinzaparin, no accumulation was observed. Enoxaparin, on the other hand, did lead to accumulation in patients with renal insufficiency, although not in patients undergoing renal replacement therapy. Bemiparin and certoparin also did show accumulation. No data were available for nadroparin.

CONCLUSIONS

In this systematic review, we show that prophylactic dosages of tinzaparin and dalteparin are likely to be safe in patients with renal insufficiency and do not need dose reduction based on the absence of accumulation. However, prophylactic dosages of enoxaparin, bemiparin, and certoparin did show accumulation in patients with a creatinine clearance (CrCl) below 30 ml/min, and therefore, dose reduction is required. The differences in occurrence of accumulation seem to depend on the mean molecular weight of LMWHs.

Cauda equina syndrome after repeated spinal attempts: A case report and review of the literature

Spinal and epidural blocks are widely used for cesarean section. Spinal hematoma causing cauda equina syndrome is a rare complication after spinal anesthesia (SA), but can lead to severe neurological deficit. It is usually associated with difficult SA and requires surgical decompression in most of the cases.

Significantly inhibitory effects of low molecular weight heparin (Fraxiparine) on the motility of lung cancer cells and its related mechanism

Low molecular weight heparin (LMWH) improving the cancer survival has been attracting attention for many years. Our previous study found that LMWH (Fraxiparine) strongly downregulated the invasive, migratory, and adhesive ability of human lung adenocarcinoma A549 cells. Here, we aimed to further identify the antitumor effects and possible mechanisms of Fraxiparine on A549 cells and human highly metastatic lung cancer 95D cells. The ability of cell invasion, migration, and adhesion were measured by Transwell, Millicell, and MTT assays. FITC-labeled phalloidin was used to detect F-actin bundles in cells. Chemotactic migration was analyzed in a modified Transwell assay. Measurement of protein expression and phosphorylation activity of PI3K, Akt, and mTOR was performed with Western blot. Our studies found that Fraxiparine significantly inhibited the invasive, migratory, and adhesive characteristics of A549 and 95D cells after 24 h incubation and showed a dose-dependent manner. Fraxiparine influenced the actin cytoskeleton rearrangement of A549 and 95D cells by preventing F-actin polymerization. Moreover, Fraxiparine could significantly inhibit CXCL12-mediated chemotactic migration of A549 and 95D cells in a concentration-dependent manner. Furthermore, Fraxiparine might destroy the interaction between CXCL12-CXCR4 axis, then suppress the PI3K-Akt-mTOR signaling pathway in lung cancer cells. For the first time, our data indicated that Fraxiparine could significantly inhibit the motility of lung cancer cells by restraining the actin cytoskeleton reorganization, and its related mechanism might be through inhibiting PI3K-Akt-mTOR signaling pathway mediated by CXCL12-CXCR4 axis. Therefore, Fraxiparine would be a potential drug for lung cancer metastasis therapy.

A comparative study of varying doses of enoxaparin for thromboprophylaxis in critically ill patients: a double-blinded, randomised controlled trial

Introduction

Critically ill patients are predisposed to venous thromboembolism. We hypothesized that higher doses of enoxaparin would improve thromboprophylaxis without increasing the risk of bleeding. Peak anti-factor Xa (anti-Xa) levels of 0.1 to 0.4 IU/ml reflect adequate thromboprophylaxis for general ward patients. Studies conducted in orthopaedic patients demonstrated a statistically significant relationship between anti-Xa levels and wound haematoma and thrombosis. Corresponding levels for critically ill patients may well be higher, but have never been validated in large studies.

Methods

Eighty critically ill patients weighing 50 to 90 kilograms were randomised in a double-blinded study to receive subcutaneous (sc) enoxaparin: 40 mg once daily (QD), 30 mg twice daily (BID), 40 mg BID, or 1 mg/kg QD, each administered for three days. Anti-Xa activity was measured at baseline, and daily at 4, 12, 16 and 24 hours post administration. Antithrombin, fibrinogen, and platelets were measured at baseline and twice daily thereafter.

Results

Two patients were transferred prior to participation. On day 1, doses of 40 mg QD (n = 20) and 40 mg BID (n = 19) yielded mean peak anti-Xa of 0.20 IU/ml and 0.17 IU/ml respectively. A dose of 30 mg BID (n = 20) resulted in much lower levels (0.08 IU/ml). Patients receiving 1 mg/kg QD (n = 19) achieved near steady-state mean peak anti-Xa levels from day 1 (0.34 IU/ml). At steady state (day 3), mean peak anti-Xa levels of 0.13 IU/ml and 0.15 IU/ml were achieved with doses of 40 mg QD and 30 mg BID respectively. This increased significantly to 0.33 IU/ml and 0.40 IU/ml for doses of 40 mg BID and 1 mg/kg QD respectively. Thus anti-Xa response profiles differed significantly over the three days between enoxaparin treatment groups (P <0.0001). Doses of 40 mg BID and1 mg/kg QD enoxaparin yielded target anti-Xa levels for over 80% of the study period. There were no adverse effects.

Conclusions

Doses of 40 mg QD enoxaparin (Europe) or 30 mg BID (North America) yield levels of anti-Xa which may be inadequate for critically ill patients. A weight-based dose yielded the best anti-Xa levels without bioaccumulation, and allowed the establishment of near steady-state levels from the first day of enoxaparin administration.

Trial registration

Current Controlled Trials ISRCTN91570009.

Deep vein thrombosis and pulmonary embolism - Prevention, management, and anaesthetic considerations

There is high incidence of venous thromboembolism, comprising of deep vein thrombosis and pulmonary embolism, in hospitalized patients. The need for systemic thromboprophylaxis is essential, especially in patients with inherited or acquired patient-specific risk factors or in patients undergoing surgeries associated with high incidence of postoperative deep vein thrombosis and pulmonary embolism. These patients, on prophylactic or therapeutic doses of anticoagulants, may present for surgery. General or regional anaesthesia may be considered depending on the type and urgency of surgery and degree of anticoagulation as judged by investigations. The dilemma regarding the type of anaesthesia can be solved if the anaesthesiologist is aware of the pharmacokinetics of drugs affecting haemostasis. The anaesthesiologist must keep abreast with the latest developments of methods and drugs used in the prevention and management of venous thromboembolism and their implications in the conduct of anaesthesia.

Epidural haematoma: Rare complication after spinal while intending epidural anaesthesia with long-term follow-up after conservative treatment

Epidural anaesthesia (EA) is an extensively used procedure for many surgeries. Increase incidence of bleeding in the epidural space [epidural haematoma (EH)] is reportedly more common in patients with altered coagulation and patients on anticoagulation treatment. EH secondary to spinal while intending EA for caesarean section (C-section) in a healthy individual leading to transient or persistent neurological problems is very rare. We report a case of EH after spinal while intending EA for C-section in a healthy young female along with 5-yrs follow-up after conservative treatment.

Spinal epidural hematoma after epidural anesthesia in a patient receiving enoxaparin -A case report-

Spinal epidural hematoma is a rare but serious neurological complication of neuraxial anesthesia. Enoxaparin sodium is a low molecular weight heparin (LMWH) for use in preventing deep venous thrombosis in patients undergoing total hip arthroplasty and total knee arthroplasty. Hemorrhage is an uncommon but documented adverse reaction when using LMWH. We report a case of epidural hematoma after lumbar epidural anesthesia in a patient who administered enoxaparin in perioperative period.

Enoxaparin, effective dosage for intensive care patients: double-blinded, randomised clinical trial

Introduction

Intensive care unit (ICU) patients are predisposed to thromboembolism. Routine prophylactic anticoagulation is widely recommended. Low-molecular-weight heparins, such as enoxaparin, are increasingly used because of predictable pharmacokinetics. This study aims to determine the subcutaneous (SC) dose of enoxaparin that would give the best anti-factor Xa levels in ICU patients.

Methods

The 72 patients admitted to a mixed ICU at Odense University Hospital (OUH) in Denmark were randomised into four groups to receive 40, 50, 60, or 70 mg SC enoxaparin for a period of 24 hours. Anti-factor Xa activity (aFXa) was measured before, and at 4, 12, and 24 hours after administration. An AFXa level between 0.1 to 0.3 IU/ml was considered evidence of effective antithrombotic activity.

Results

Median peak (4 hours after administration), aFXa levels increased significantly with an increase in enoxaparin dose, from 0.13 IU/ml at 40 mg, to 0.14 IU/ml at 50 mg, 0.27 IU/ml at 60 mg, and 0.29 IU/ml at 70 mg (P = 0.002). At 12 hours after administration, median aFXa levels were still within therapeutic range for those patients who received 60 mg (P = 0.02).

Conclusions

Our study confirmed that a standard dose of 40 mg enoxaparin yielded subtherapeutic levels of aFXa in critically ill patients. Higher doses resulted in better peak aFXa levels, with a ceiling effect observed at 60 mg. The present study seems to suggest inadequate dosage as one of the possible mechanisms for the higher failure rate of enoxaparin in ICU patients.

Trial Registration

ISRCTN03037804

Nordic guidelines for neuraxial blocks in disturbed haemostasis from the Scandinavian Society of Anaesthesiology and Intensive Care Medicine

BACKGROUND

Central neuraxial blocks (CNBs) for surgery and analgesia are an important part of anaesthesia practice in the Nordic countries. More active thromboprophylaxis with potent antihaemostatic drugs has increased the risk of bleeding into the spinal canal. National guidelines for minimizing this risk in patients who benefit from such blocks vary in their recommendations for safe practice.

METHODS

The Scandinavian Society of Anaesthesiology and Intensive Care Medicine (SSAI) appointed a task force of experts to establish a Nordic consensus on recommendations for best clinical practice in providing effective and safe CNBs in patients with an increased risk of bleeding. We performed a literature search and expert evaluation of evidence for (1) the possible benefits of CNBs on the outcome of anaesthesia and surgery, for (2) risks of spinal bleeding from hereditary and acquired bleeding disorders and antihaemostatic drugs used in surgical patients for thromboprophylaxis, for (3) risk evaluation in published case reports, and for (4) recommendations in published national guidelines. Proposals from the taskforce were available for feedback on the SSAI web-page during the summer of 2008.

RESULTS

Neuraxial blocks can improve comfort and reduce morbidity (strong evidence) and mortality (moderate evidence) after surgical procedures. Haemostatic disorders, antihaemostatic drugs, anatomical abnormalities of the spine and spinal blood vessels, elderly patients, and renal and hepatic impairment are risk factors for spinal bleeding (strong evidence). Published national guidelines are mainly based on experts' opinions (weak evidence). The task force reached a consensus on Nordic guidelines, mainly based on our experts' opinions, but we acknowledge different practices in heparinization during vascular surgery and peri-operative administration of non-steroidal anti-inflammatory drugs during neuraxial blocks.

CONCLUSIONS

Experts from the five Nordic countries offer consensus recommendations for safe clinical practice of neuraxial blocks and how to minimize the risks of serious complications from spinal bleeding. A brief version of the recommendations is available on http://www.ssai.info.

Risks and complications of neuraxial anesthesia and the use of anticoagulation in the surgical patient

Recognition of the risk of thromboembolic phenomena to patients in the postsurgical period has resulted in the practice of administering prophylactic anticoagulant agents to those patients who are at high risk for this complication. Institution of a perioperative anticoagulant or antithrombotic protocol needs to be considered when a regional anesthetic is proposed as part of, or as the total, anesthetic management of the patient. This article reviews current data on the risks involved in the use of neuraxial regional anesthesia in the care of surgical patients in whom prophylactic thromboembolic anticoagulant therapy is planned. Guidelines are established to help the physician minimize the risks of a neuraxial hematoma forming, monitor the patient for this complication, and optimally treat him or her if a hematoma were to occur.

Preoperative use of enoxaparin increases the risk of postoperative bleeding and re-exploration in cardiac surgery patients

OBJECTIVE

The purpose of this study was to investigate if the preoperative use of new platelet inhibitors and low-molecular-weight heparins may contribute to bleeding after cardiac surgery.

DESIGN

Retrospective data review.

SETTING

University teaching hospital.

PARTICIPANTS

One hundred eleven patients divided in 5 groups.

INTERVENTIONS

Patients were grouped according to preoperative antithrombotic regimen: group 1, control, no agents (n=55); group 2, clopidogrel (n=9); group 3, enoxaparin (n=17); group 4, any GP IIb/IIIa inhibitor (n=14); and group 5, any drug combination (n=15). Data included cumulative mediastinal chest tube drainage, allogeneic blood transfusions, total blood donor exposures, and re-exploration.

MEASUREMENTS AND MAIN RESULTS

Use of any drug (groups 2-5) resulted in greater total blood transfusions and donor exposure (p=0.0003) than control, especially red cells (p=0.002) and platelets (p=0.006). A greater percentage of patients on enoxaparin required mediastinal re-exploration for nonsurgical bleeding versus control (3/17 v 0/55, p=0.001). The use of enoxaparin was associated with significantly higher chest tube output after the first 24 hours postoperatively (p=0.048).

CONCLUSION

Newer antithrombotic agents were associated with greater transfusion rates and total donor exposures. Enoxaparin use was associated with greater overall blood loss and with higher incidence of mediastinal re-exploration. The relative risk-benefit ratio of reduced periprocedure morbidity versus increased bleeding complications has yet to be determined.

Spinal epidural hematoma following central neuraxial blockade and subcutaneous enoxaparin: A case report

An elderly patient developed a spinal epidural hematoma 3 days after lumbar puncture resulting in paraplegia. Concurrent administration of enoxaparin, aspirin, ketorolac, and a traumatic tap were implicated in causation.

High thoracic epidural anesthesia for off-pump coronary artery bypass surgery

OBJECTIVE

To assess the feasibility of high thoracic epidural anesthesia combined with sevoflurane for off-pump coronary artery bypass surgery and to evaluate the postoperative pain control, side effects, and perioperative hemodynamics.

DESIGN

Retrospective review of prospectively collected data.

SETTING

A university teaching hospital.

PARTICIPANTS

One hundred six consecutive patients receiving thoracic epidural combined with sevoflurane.

INTERVENTION

From November 1999, the patients undergoing off-pump coronary artery bypass grafting were offered the epidural-inhalation anesthetic approach.

MEASUREMENTS AND MAIN RESULTS

Insertion of the epidural catheter was successful in all but 2 patients; 1 bloody tap occurred and the dura was never punctured, although 1 patient presented with postoperative paraplegia. An emergency spinal cord nuclear magnetic resonance excluded signs of medullary compression caused by epidural or spinal hematoma. Visual analog scale scores for pain during the first 24-hour period were < 2 in all patients. Mean time to extubation was 4.6 +/- 2.9 hours. The average intensive care unit stay was 1.5 +/- 0.8 days. Incidences of perioperative myocardial infarction, myocardial ischemia, and atrial fibrillation were 2.8%, 7.5%, and 10.6%, respectively. Two patients died: 1 from multiorgan failure and the other from myocardial infarction. Heart rate, mean arterial pressure, cardiac index, and systemic vascular resistance were not affected by thoracic epidural alone. Mean arterial pressure and cardiac index decreased (p < 0.05) when general anesthesia was induced and remained stable thereafter. Neither heart rate nor systemic vascular resistance changed from baseline during operation.

CONCLUSIONS

Thoracic epidural as an adjunct to general anesthesia is a feasible technique in off-pump coronary artery bypass surgery. It induces intense postoperative analgesia and does not compromise central hemodynamics.

Heparin pentasaccharide

Fondaparinux (a synthetic heparin analogue) (Sanofi-Synthelabo; Paris, France and Organon Research; Oss, The Netherlands) is the subject of intense recent clinical evaluation for the prevention and treatment of venous and arterial thromboembolism. The drug replicates the sulphated antithrombin-binding pentasaccharide sequence in heparin and induces potent and specific antithrombin-mediated anti-Xa activity with excellent bioavailability and a long circulating half-life of 18 hours that makes it ideal for once-daily subcutaneous dosing. Its very short chain length ensures this heparin pentasaccharide (PS) is devoid of anti-factor IIa activity. No need for laboratory monitoring is anticipated. Fondaparinux does not cross-react ex vivo with the anti-platelet antibodies responsible for heparin-induced thrombocytopenia. Fondaparinux was evaluated in four large, randomized, placebo-controlled, double-blind phase III trials of deep vein thrombosis prevention after major joint surgery where the PS given after surgery was compared with a low molecular weight heparin (LMWH). LMWH was started before surgery in two comparisons and soon after surgery in the others. The trials shared the same blindly adjudicated efficacy and safety endpoints: efficacy was measured by recording subclinical deep vein thrombosis detected by screening with bilateral venography, plus clinically suspected and confirmed symptomatic thrombosis and embolism; safety was indicated by the rate of major bleeding. Bleeding was considered major if it caused death or reoperation, affected an internal organ, or was overt and associated with a bleeding index of 2 or more. By comparison with LMWH, 2.5 mg/d of the PS beginning 4 to 8 hours after wound closure reduced venous thromboembolism rates by 56% and 26% after elective hip replacement, 63% after knee replacement, and 62% after hip fracture surgery. In three studies and overall, the effect was statistically very significant and included similarly reduced rates of proximal deep vein thrombosis. In absolute terms, the DVT rates with PS are the lowest yet seen after major joint surgery. Trends toward more major bleeding with PS in three studies were statistically significant in one trial. PS did not increase risks from reoperation, internal bleeding, or death because of bleeding, because between-group differences were caused entirely by an excess of patients with a raised bleeding index. Post hoc analysis suggests this excess can be explained by too-early postoperative drug administration and may be avoided without loss of efficacy by giving the first PS injection 6 to 8 hours after surgery. Results of phase III treatment trials for DVT/PE will soon be available, but studies in coronary artery disease are less advanced.

Anaesthesia for non-scheduled caesarean delivery

In many countries there has been an increase in the number of women who deliver by caesarean section. This article reviews anaesthetic management of non-scheduled caesarean section. The choice of anaesthetic technique (regional anaesthesia versus general anaesthesia) is discussed and highlighted particularly from the viewpoint of urgency of operative delivery. A multidisciplinary approach is mandatory especially in emergency cases to prevent morbidity and mortality in mothers and neonates.

Low molecular weight heparins: a guide to their optimum use in pregnancy

The incidence of pulmonary embolism (PE) and venous thromboembolism (VTE) is higher in pregnant patients than in non-pregnant patients. The incidence of thrombosis in all pregnancies is reported to be between 0.05 and 1%, and an incidence as high as 3% may be present in women after caesarean section. Anticoagulant medication is prescribed during pregnancy in patients presenting with VTE, thrombophilia abnormalities, or a history of PE or VTE. Since unfractionated heparin (UH) does not cross the placental barrier, it has become the gold standard anticoagulant therapy during pregnancy. Oral anticoagulants may also be prescribed during the second trimester but they cross the placental barrier. Low molecular weight heparins (LMWH) are effective, easy to use and have good safety profiles. The practical conditions of use have yet to be validated for pregnancy settings. In the absence of an approved indication, LMWH use during pregnancy is therefore the responsibility of the practitioner. However, several studies on LMWH as prophylaxis for PE or VTE have shown that such products are effective with good safety. Moreover, LMWH use is associated with reduced frequencies of thrombocytopenia and osteoporosis compared with UH use. Very few studies on LMWH use for the treatment of PE or VTE during pregnancy have been published, but the safety of LMWH use in this setting appears to be good. The review of the use of LMWH in pregnancy settings includes recommendations on the practical conditions of use. In the absence of large-scale, randomised, double-blind trials in such settings (which are needed), we propose the use of LMWH as prophylaxis for PE and VTE during pregnancy, but not for the treatment of these conditions. In prophylaxis settings, dalteparin sodium and enoxaparin sodium have been the most widely studied LMWH and we believe that priority should therefore be given to those products. Pending approval of LMWH for use in pregnancy, the use of LMWH off-label is the practitioner's responsibility.

Spinal anesthesia for endoluminal abdominal aortic aneurysm repair

STUDY OBJECTIVE

To determine whether spinal anesthesia can be safely used for patients under endoluminal abdominal aortic aneurysm (AAA) repair.

DESIGN

Retrospective chart review.

SETTING

University hospital.

PARTICIPANTS

38 patients who underwent endoluminal AAA repair from 1999 to 2000.

MEASUREMENTS AND MAIN RESULTS

The charts of 38 patients who underwent endoluminal AAA repair from 1999 to 2000 were reviewed for variables known to be associated with AAA repair. Twenty-four patients had spinal anesthesia (63%), 13 patients had general anesthesia (35%), 1 patient had epidural anesthesia (2%). Eight patients (33%) in the spinal group eventually had to have general anesthesia. Reasons included prolonged procedure in six cases and patient intolerance and anxiety in two cases.

CONCLUSION

Endoluminal AAA repair can be safely performed with spinal anesthesia. The major disadvantage of spinal anesthesia is limited duration of anesthesia. The anesthesia team must be prepared to induce general anesthesia at any time. The decision regarding anesthetic technique should focus on patient and physician needs and preferences.

A potentially expanded role for enoxaparin in preventing venous thromboembolism in high risk blunt trauma patients

BACKGROUND

Venous thromboembolism (VTE) is a frequent and potentially life-threatening complication after trauma. The purpose of this study is to investigate the effectiveness of enoxaparin in preventing deep venous thrombosis (DVT) and pulmonary embolism (PE) after injury in patients who are at high risk for developing VTE.

STUDY DESIGN

A prospective single-cohort observational study was initiated for seriously injured blunt trauma patients admitted to a Level I trauma center during a 7-month period. Patients were eligible for the study if time hospitalized was > or = 72 hours, Injury Severity Score (ISS) was > or = 9, enoxaparin was started within 24 hours after admission, and one or more of the following high risk criteria were met: age > 50 years, ISS > or = 16, presence of a femoral vein catheter, Abbreviated Injury Score (AIS) > or = 3 for any body region, Glasgow Coma Scale (GCS) Score < or = 8, presence of major pelvic, femur, or tibia fracture, and presence of direct blunt mechanism venous injury. Patients with closed head injuries and nonoperatively treated solid abdominal organ injuries were also potential participants. The primary outcomes measured were thromboembolic events--either a documented lower extremity DVT by duplex color-flow doppler ultrasonography or a PE documented by rapid infusion CT pulmonary angiography or conventional pulmonary angiography.

RESULTS

There were 118 patients enrolled in the study. Two patients (2%) developed DVT, one of which was proximal to the calf (95% confidence interval, 0% to 6%). Two of 12 patients (17%) with splenic injuries who received enoxaparin failed initial nonoperative management. There were no other bleeding complications, and no clinical evidence or documented episodes of PE. One patient died from multiple system organ failure.

CONCLUSIONS

Enoxaparin is a practical and effective method for reducing the incidence of VTE in high risk, seriously injured patients. This study supports further investigation into the safety of enoxaparin prophylaxis in patients with closed head injuries and nonoperatively treated solid abdominal organ injuries.

Regional anesthesia and anticoagulation

The perioperative use of neuraxial techniques in the presence of anticoagulation is a controversial issue. There are significant pharmacokinetic differences between anticoagulants that will affect the timing of neuraxial needle insertion or catheter removal. The pharmacologic profiles of commonly used anticoagulants in the perioperative period are reviewed. Studies examining the use of neuraxial techniques in the presence of various anticoagulants are reviewed and evaluated in the context of the American Society of Regional Anesthesia consensus statements.

Is anticoagulation and central neural blockade a safe combination?

The indiscriminate insertion of epidural or subarachnoidal needles or catheters in patients who are anticoagulated or are about to be anticoagulated carries the inherent risk of the potential development of a compressing vertebral canal haematoma, which may severely jeopardize the patient's (quality of) life. Although the isolated use of aspirin or non-steroidal anti-inflammatory drugs in general is no longer considered a problem, its combination with any form of heparin therapy is. Intraoperative heparinization during cardiac or vascular surgery can be safely performed provided a minimum time interval between the regional anaesthetic block and the subsequent heparinization is respected and indwelling catheters are removed after the disappearance of any remaining heparin effect. Similarly, central neural blockade in combination with the thromboprophylactic use of standard unfractionated heparin or low-molecular-weight heparins is possible if: (1) only thromboprophylactic heparin doses are used; and (2) a specific minimum time interval between the previous or the next dose of the anticoagulant and the initiation of the block or the removal of the indwelling catheter is observed.

Low molecular weight heparin use during pregnancy: issues of safety and practicality

Low molecular weight heparin is an important agent for the treatment and prophylaxis against venous thromboembolism during pregnancy. It offers several distinct advantages over unfractionated heparin. A systematic search was performed of the literature review of low molecular weight heparin use in pregnancy and presents a practical approach to its use by obstetricians and internists.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader will be able to understand the pharmacology and the elimination of low molecular weight heparin, the potential side effects and how to appropriately monitor the drug, and the indications and management of the low molecular weight heparins during pregnancy.

Treatment and prevention of venous thromboembolic disease in pregnancy

Pulmonary embolism is a major, but potentially preventable, cause of maternal mortality in North America and Europe. Because venous thromboembolism is an infrequent cause of maternal morbidity, there are few randomized clinical trials to guide clinical decision-making with respect to treatment, prevention, and evaluation of innovative management modalities such as low molecular weight heparin. This article focuses on the evidence supporting the current guidelines for the pharmacologic management of venous thromboembolic disease in pregnancy.

Anaesthetists as pain management consultants

Anaesthetists who manage acute and chronic pain need to be familiar with current research and practice guidelines in these areas. New local anaesthetics and new routes of administration for opioids and adjuvants may further improve our management of acute pain. The safety of epidural analgesia in combination with low molecular weight heparins and the role of the anaesthetist on the acute pain service are reviewed. Chronic pain disability is increasing, necessitating a re-evaluation of our approach to chronic pain. The limitations of nerve blocks are acknowledged and guidelines for managing chronic pain and opioids are available. Anaesthetists must recognize psychological difficulties as a significant perpetuating factor in chronic pain.