Laboratory testing in patients treated with direct oral anticoagulants: a practical guide for clinicians

Click to hear Dr Baglin's perspective on the role of the laboratory in treatment with new oral anticoagulants SUMMARY: One of the key benefits of the direct oral anticoagulants (DOACs) is that they do not require routine laboratory monitoring. Nevertheless, assessment of DOAC exposure and anticoagulant effects may become useful in various clinical scenarios. The five approved DOACs (apixaban, betrixaban, dabigatran etexilate, edoxaban and rivaroxaban) have different characteristics impacting assay selection and the interpretation of results. This article provides an updated overview on (i) which test to use (and their advantages and limitations), (ii) when to assay DOAC levels, (iii) how to interpret the results relating to bleeding risk, emergency situations and perioperative management, and (iv) what is the impact of DOACs on routine and specialized coagulation assays. Assays for anti-Xa or anti-IIa activity are the preferred methods when quantitative information is useful, although the situations in which to test for DOAC levels are still debated. Different reagent sensitivities and variabilities in laboratory calibrations impact assay results. International calibration standards for all specific tests for each DOAC are needed to reduce the inter-laboratory variability and allow inter-study comparisons. The impact of the DOACs on hemostasis testing may cause false-positive or false-negative results; however, these can be minimized by using specific assays and collecting blood samples at trough concentrations. Finally, prospective clinical trials are needed to validate the safety and efficacy of proposed laboratory thresholds in relation to clinical decisions. We offer recommendations on the tests to use for measuring DOACs and practical guidance on laboratory testing to help patient management and avoid diagnostic errors.

Multimodal assessment of non-specific hemostatic agents for apixaban reversal

BACKGROUND

Non-specific hemostatic agents, namely activated prothrombin complex concentrate (aPCC), PCC and recombinant activated factor (F) VII (rFVIIa), can be used, off-label, to reverse the effects of FXa inhibitors in the rare cases of severe hemorrhages, as no approved specific antidote is available. We have evaluated the ability of aPCC, PCC and rFVIIa to reverse apixaban.

METHODS

Healthy volunteer whole blood was spiked with therapeutic or supra-therapeutic apixaban concentrations and two doses of aPCC, PCC or rFVIIa. Tests performed included a turbidimetry assay for fibrin polymerization kinetics analysis, scanning electron microscopy for fibrin network structure observation, thrombin generation assay (TGA), thromboelastometry, prothrombin time and activated partial thromboplastin time.

RESULTS

aPCC generated a dense clot constituting thin and branched fibers similar to those of a control without apixaban, increased fibrin polymerization velocity and improved quantitative (endogenous thrombin potential and peak height) as well as latency (clotting and lag times) parameters. Adding PCC also improved the fibrin and increased quantitative parameters, but fibrin polymerization kinetics and latency parameters were not corrected. Finally, rFVIIa improved latency parameters but failed to restore the fibrin network structure, fibrin polymerization velocity and quantitative parameters.

CONCLUSION

aPCC was more effective than PCC or rFVIIa in reversing in vitro the effects of apixaban. aPCC rapidly triggered the development of an apparently normal fibrin network and corrected latency and quantitative parameters, whereas PCC or rFVIIa had only a partial effect.

[Efficacy and safety of tranexamic acid administration for the prevention and/or the treatment of post-partum haemorrhage: a systematic review with meta-analysis]

OBJECTIVE(S)

Assess the efficacy and safety of tranexamic acid administration for the prevention and/or the treatment of postpartum haemorrhage.

STUDY DESIGN

Systematic review with meta-analysis.

MATERIAL AND METHODS

Systematic review of the literature with the aim of identifying prospective, randomised, controlled trials that assessed the effect of tranexamic acid on peripartum blood loss and transfusion requirement in three clinical contexts: (i) prevention of post-partum haemorrhage in case of elective caesarean section, (ii) prevention of post-partum haemorrhage in case of vaginal delivery, (iii) treatment of post-partum haemorrhage.

RESULTS

Prophylactic administration of tranexamic acid reduced blood loss (mean difference for intraoperative blood loss: -177.9mL, IC 95%: -189.51 to -166.35, total blood loss: -183.94, IC 95%: -198.29 to -169.60), and the incidence of severe post-partum haemorrhage (OR: 0.49, IC 95%: 0.33 to 0.74). None of the published trials assessed the effect of tranexamic acid on blood products administration or transfusion requirement. Only one study assessed and reported the efficacy of tranexamic acid when administered as a treatment for postpartum haemorrhage. A significant reduction in blood loss was reported within 30 minutes after randomisation (P=0.03) and confirmed after 6 hours (median: 170mL (58-323) vs 221mL (110-543), P=0.04). None of the included studies adequately studied the incidence of side effects after tranexamic acid administration.

CONCLUSION

Although tranexamic acid administration seemed to significantly reduce blood loss and the incidence of severe post-partum haemorrhage, further prospective trials are needed to confirm the efficacy and safety of tranexamic administration in the treatment of postpartum haemorrhage. Those studies should assess the pharmacokinetic profile and the safety of this drug in pregnant women.

Comparison of fondaparinux with low molecular weight heparin for venous thromboembolism prevention in patients requiring rigid or semi-rigid immobilization for isolated non-surgical below-knee injury

BACKGROUND

In several small studies, anticoagulant therapy reduced the incidence of venous thromboembolism (VTE) in patients with isolated lower-limb injuries.

OBJECTIVES

To compare the efficacy and safety of fondaparinux 2.5 mg (1.5 mg in patients with a creatinine clearance between 30 and 50 mL min(-1) ) over nadroparin 2850 anti-factor Xa IU.

PATIENTS AND METHODS

In this international, multicenter, randomized, open-label study, patients with an isolated non-surgical unilateral below-knee injury having at least one additional major risk factor for VTE and requiring, in the Investigator's opinion, rigid or semi-rigid immobilization for 21-45 days with thromboprophylaxis up to complete mobilization received subcutaneously once-daily either fondaparinux or nadroparin. The primary efficacy outcome was the composite of VTE (symptomatic or ultrasonographically detected asymptomatic deep vein thrombosis of the lower limb or symptomatic pulmonary embolism) and death up to complete mobilization. The main safety outcome was major bleeding.

RESULTS

We randomized 1349 patients (mean age 46 years): 88.7% had a bone fracture, and 83.8% had a plaster cast fitted (mean duration of immobilization, 34 days). The primary efficacy outcome occurred in 15 of 584 patients (2.6%) in the fondaparinux group and 48 of 586 patients (8.2%) in the nadroparin group (odds ratio, 0.30; 95% confidence interval [CI], 0.15-0.54; P < 0.001). A single major bleed was experienced by fondaparinux-treated patients and none by nadroparin-treated patients. These results were maintained up to the end of follow-up.

CONCLUSIONS

Fondaparinux 2.5 mg day(-1) may be a valuable therapeutic option over nadroparin 2850 anti-FXa IU day(-1) for preventing VTE after below-knee injury requiring prolonged immobilization in patients with additional risk factors.

[Reversal for heparins and new anticoagulant treatments]

Even with unfractionated heparin or derivates, the reversal of pharmacologic anticoagulation is crucial in anticoagulated patients developing a life-threatening bleeding or scheduled for an emergency procedure. The antagonisation of unfractionated heparin is well codified: each milligram of protamine sulfate antagonizes 100 IU of heparin. Measurement of thrombin time reflects the anti-IIa effect of heparin and has to be monitored immediately and 1hour after the injection of protamine. The required dose of protamine sulfate depends on dosage and time of LMWH administration, although no clinical study supports these data. To date, there is no effective antidote for new anticoagulants (fondaparinux and other pentasaccharides, direct thrombin inhibitors, direct anti-Xa inhibitors). Some preliminary studies suggest the effectiveness of recombinant activated factor VII for pentasaccharides and activated or not Prothrombin Complex Concentrates and recombinant activated factor VII for oral anti-Xa and anti-IIa agents. Therefore, while the characteristics of these new anticoagulants could increase the comfort and improve the compliance, their development needs to ascertain the lack of increase in bleeding complications and the need for a safe and effective antidote.

Impact of preoperative maintenance or interruption of aspirin on thrombotic and bleeding events after elective non-cardiac surgery: the multicentre, randomized, blinded, placebo-controlled, STRATAGEM trial

BACKGROUND

Patients receiving anti-platelet agents for secondary cardiovascular prevention frequently require non-cardiac surgery. A substantial proportion of these patients have their anti-platelet drug discontinued before operation; however, there is uncertainty about the impact of this practice. The aim of this study was to compare the effect of maintenance or interruption of aspirin before surgery, in terms of major thrombotic and bleeding events.

METHODS

Patients treated with anti-platelet agents for secondary prevention and undergoing intermediate- or high-risk non-cardiac surgery were included in this multicentre, randomized, placebo-controlled, trial. We substituted non-aspirin anti-platelets with aspirin (75 mg daily) or placebo starting 10 days before surgery. The primary outcome was a composite score evaluating both major thrombotic and bleeding adverse events occurring within the first 30 postoperative days weighted by their severity (weights were established a priori using a Delphi consensus process). Analyses followed the intention-to-treat principle.

RESULTS

We randomized 291 patients (n=145, aspirin group, and n=146, placebo group). The most frequent surgical procedures were orthopaedic surgery (52.2%), abdominal surgery (20.6%), and urologic surgery (15.5%). No significant difference was observed neither in the primary outcome score [mean values (SD)=0.67 (2.05) in the aspirin group vs 0.65 (2.04) in the placebo group, P=0.94] nor at day 30 in the number of major complications between groups.

CONCLUSIONS

In these at-risk patients undergoing elective non-cardiac surgery, we did not find any difference in terms of occurrence of major thrombotic or bleeding events between preoperative maintenance or interruption of aspirin.

Maize- or potato-derived hydroxyethyl starches: is there any thromboelastometric difference?

BACKGROUND

Hydroxyethyl starches (HES) could differ with regard to the origin, and the influence on the coagulation of the raw material is unknown. This study compared the effects of a new potato-derived HES with a maize-derived HES and two crystalloid solutions.

METHODS

Whole blood from 10 healthy individuals was diluted by 20% and 40% using either non-balanced potato-derived HES 130/0.42/6:1, non-balanced maize-derived HES 130/0.4/9:1, isotonic saline or Ringer's lactate solution. Samples were analysed by thromboelastometry ROTEM(®) : Coagulation was initiated by acid ellagic [intrinsic thromboelastometry (INTEM)] or tissue factor (extrinsic thromboelastometry) with and without cytochalasin to determine the functional component of fibrinogen [cytochalasin-d-modified thromboelastometry (FIBTEM)]. Platelet count and fibrinogen activity were measured.

RESULTS

No effect of raw material was found as no difference was detected among the HES solutions. Whatever the solution, progressive haemodilution impaired haemostasis in a dose-dependant manner: For INTEM, the clot formation time was increased up to 308% and the maximum clot firmness (MCF) was decreased down to 49%. As dilution increased, initiation of coagulation was also impaired. Thromboelastometric alterations were more severe with HES than with crystalloids, especially regarding fibrin polymerization explorations: MCF of FIBTEM was considerably reduced from 12[10-14] to 2[2-3] mm (P<0.05). Fibrinogen activity and platelet count were reduced by dilution in a dose-dependant manner and decreased similarly in all groups.

CONCLUSION

Maize- and potato-derived HES have similar effects on coagulation. Both the starch preparations tested lead to more severe haemostatic defects than crystalloids, and impairment of fibrin polymerization appears to be a leading determinant of this coagulopathy.

[A new deal with new anticoagulants?]

The anticoagulant market has been very active recently with the development of new compounds including injectable anti-Xa such as fondaparinux, already available, and idraparinux, already replaced by its new biotynilateed form, and new oral drugs which can be divided into anti-IIa with dabigatran already available, and anti-Xa, such as the recently marketed rivaroxaban and apixaban still in the development stage. Others are coming forward. The competition is strong and the place for each drug remains to be determined. This review discusses these new anticoagulants in terms of efficacy and tolerance based on data in the literature. These recent reports mainly concern prophylaxis for orthopedic surgery but also consider treatment of deep venous thrombosis. The results of studies in heart patients have raised much curiosity since they will be determinant in the future use of innovating compounds, which could replace current oral anticoagulants. This will be upcoming but not yet for tomorrow.

Can oral vitamin K before elective surgery substitute for preoperative heparin bridging in patients on vitamin K antagonists?

BACKGROUND

After a vitamin K antagonist (VKA) overdose, 1-2 mg of oral vitamin K can lower the International Normalized Ratio (INR) to the therapeutic range.

OBJECTIVE

To establish whether oral vitamin K can substitute for heparin bridging and decrease the INR to < or = 1.5 before elective surgery.

METHODS

Patients on long-term VKAs were randomized either to heparin bridging after the last VKA dose on day -5 before surgery (group H) or to VKA treatment until day -2, followed by 1 mg of oral vitamin K on the day before surgery (group K). Blood clotting variables were assessed on days -5/-2, 1 and 0, and postoperatively. If the target INR was not achieved 2 h before incision, surgery was deferred or performed after injection of prothrombin complex concentrate (PCC).

RESULTS

In 30 of 94 included patients, baseline INR was outside the chosen range (18, INR < 2; 12, INR > 3.5), leaving 34 eligible patients in group H and 30 in group K. The groups were balanced in terms of body mass index, VKA treatment duration and indication, scheduled surgery, preoperative and postoperative hemoglobin, and blood loss. The INR was significantly higher in group K on days -1 and 0 than in group H. An INR < or = 1.5 was not achieved in 20 group K patients (66%). Surgery was postponed or performed after PCC injection in 12 of these 20 patients.

CONCLUSIONS

Oral vitamin K (1 mg) cannot substitute for heparin bridging before surgery. In addition, one-third of patients on VKAs were exposed to a risk of bleeding (overdose) or thrombosis (underdose), thus highlighting the need for new oral anticoagulants.

[Prevention of intraoperative venous thromboembolism: what are the American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th edition)?]

Extensive evidence related to thromboembolism risk and its prevention are available to guide health care providers. The 8th ACCP Evidence-Based Clinical Practice Guidelines were published in June 2008. The chapter on venous thromboembolism prophylaxis is the result of the collaboration of six senior authors with expertise in thrombosis, surgery, medicine, and critical appraisal. The methodology and the philosophy of these guidelines are explained in this paper and the major recommendations dealing with perioperative thromboprophylaxis are summarized.

[Perioperative venous thromboembolism prophylaxis: short review and recommendations]

The overall thromboembolic risk is the resultant of patient-related risk and surgical risk. The surgical risk is decreasing, especially with the introduction of new procedures (fast-track surgery). The value of prophylaxis has been firmly established. Mechanical prophylaxis is to be used as first-line prophylaxis when there is a risk of bleeding. Combining this with drugs increases the antithrombotic efficacy. However, the effectiveness of prophylaxis on pulmonary embolism and mortality has not been demonstrated. Renal function needs to be evaluated when low molecular weight heparins, fondaparinux, rivaroxaban or dabigatran are prescribed. An age of over 75 years and low body weight (<50 kg) have to be taken into account. There is a risk of spinal or epidural hematoma in patients receiving anticoagulants. Caution should be taken especially when administering the newer agents. Patients undergoing surgery that involves a moderate or high overall risk should receive prophylaxis until full mobilization. Patients who have undergone a total hip replacement, surgery for hip fracture, or major abdominal surgery should receive prophylaxis for about 5 weeks longer. The relevance of distal vein thromboses is debated. Surrogate venographic end-points should be gradually replaced by a combination of ultrasound and clinical criteria. The new antithrombotic agents will probably modify prevention in the years to come but currently there are very few long-term data for these products for which - it should be reminded - no antagonists are available.

Prothrombin complex concentrates: a brief review

Prothrombin complex concentrates are haemostatic blood products containing four vitamin K-dependent clotting factors (II, VII, IX and X). They are a useful, reliable and fast alternative to fresh frozen plasma for the reversal of the effects of oral anticoagulant treatments (vitamin K antagonists). They are sometimes used for factor II or factor X replacement in patients with congenital or acquired deficiencies. They are widely prescribed in Europe. Several retrospective and prospective studies have demonstrated their efficacy in normalizing coagulation and in helping to control life-threatening bleeding. Few side-effects, mainly thromboembolic events, have been reported. The link between these events and prothrombin complex concentrate infusion has, however, often been brought into question. The use of prothrombin complex concentrates in new promising indications such as the management of massive bleeding requires prospective studies providing a high level of evidence in a high-risk setting.

Epidemiology of venous thromboembolism after lower limb arthroplasty: the FOTO study

BACKGROUND

In view of recent substantial changes in the management of orthopedic surgery patients, a study was performed in order to update data on the epidemiology of venous thromboembolism (VTE) in patients undergoing lower limb arthroplasty according to contemporary practise.

METHODS

We performed a prospective observational study of a cohort of consecutive patients hospitalized for total hip or knee replacement in June 2003. The primary study outcome was the incidence of symptomatic VTE at 3 months. All events were adjudicated by an independent critical event committee.

RESULTS

Data from 1080 patients (mean age 68.0 years) were available; 63.2% were undergoing total hip replacement and 36.8% total knee replacement. Pharmacological thromboprophylaxis was administered for a mean time of 36 days. Injectable antithrombotics were used in more than 99% of patients, irrespective of the type of surgery. The incidence of the primary study outcome was 1.8% (20 events; 95% CI: 1.0-2.6%). The incidences were 1.3% and 2.8% in hip and knee surgery patients, respectively. There were two pulmonary embolisms, both in knee surgery patients; neither was fatal. Thirty-five per cent of VTEs occurred after hospital discharge. An age of at least 75 years and the absence of ambulation before hospital discharge were the only significant (P < 0.05) predictors of VTE. The rate of clinically significant bleeding was 1.0% and the rate of death was 0.9%.

CONCLUSIONS

The incidence of symptomatic VTE after lower limb arthroplasty is low, even if there is still a need to improve thromboprophylaxis, notably in patients undergoing knee arthroplasty.

Recombinant activated factor VII efficacy and safety in a model of bleeding and thrombosis in hypothermic rabbits: a blind study

BACKGROUND

Recombinant activated factor VII (rFVIIa) is increasingly used to secure hemostasis in hemorrhagic situations in trauma and surgical patients. Hypothermia is often observed in these clinical settings.

OBJECTIVE

To study the efficacy and safety of rFVIIa in hypothermia in a rabbit model of bleeding and thrombosis.

METHODS

Sixty-nine rabbits were anesthetized, ventilated and monitored for blood pressure, temperature and carotid flow. The Folts model was used: a stenosis (75%) and an injury were carried out on the carotid artery, inducing thrombosis. Blood flow decreased as thrombus size increased until the pressure gradient was such that the thrombus was released and local arterial blood flow was suddenly restored. This is known as a cyclic flow reduction (CFR). After counting baseline CFRs during a 20-min period (P1), rabbits were randomized blindly to one of four groups: normothermic (NT) placebo or rFVIIa (150 microg kg(-1)), hypothermic (HT) (34 degrees C) placebo or rFVIIa. Then CFRs were recorded over a second period (P2). At the end of the experiment, a hepato-splenic section was performed and the amount of blood loss was recorded. After each period, the following were measured: ear immersion bleeding time (BT), hemoglobin, platelet count, prothrombin time (PT), activated partial thromboplastin time (aPTT) and fibrinogen.

RESULTS

Hypothermia increased BT and blood loss. These effects were reversed by rFVIIa. In NT rabbits, rFVIIa shortened BT but did not reduce blood loss. rFVIIa-treated rabbits bled similarly regardless of temperature. The incidence of CFRs was higher in treated than placebo animals regardless of temperature. rFVIIa decreased PT and aPTT without modifying platelet count or fibrinogen level.

CONCLUSION

Hemostatic efficacy of rFVIIa was maintained in hypothermia. However, the number of CFRs was higher in the rFVIIa-treated group than in the placebo groups, whether for NT or HT rabbits.

Traitement médicamenteux et phytothérapie des patients adressés en consultation d'anesthésie: enquête multicentrique

OBJECTIVE

This study was undertaken to quantify the use of chronic medication and herbal remedies in the presurgical population.

STUDY DESIGN

Prospective multicenter survey.

PATIENTS AND METHODS

Adult patients presenting for anaesthesia were directly asked if they were currently using chronic medication or herbal remedies.

RESULTS

Among 1057 patients (age 54+/-17 yrs, woman 54%, ASA 2 [1-4], 74%) were taking one or more chronic medication. The most commonly used treatments were, in descending order angiotensin-converting enzyme inhibitors and angiotensin-II receptor blockers (15%), beta blockers (11%) and platelet inhibitors (10%). Also, 9% were taking one or more of the following herbal remedies known to interact with the perioperative period: valeriane, ginseng, ginkgo, St John's wort, echinacea and ephedra. Women and patients aged 40-70 yr were most likely to be taking a herbal product (p<0.001 and p<0.01 respectively).

CONCLUSION

Chronic medication and herbal remedies are common in patients presenting for anaesthesia. Because of the potential interactions between anaesthetic drugs or techniques and such medication it is important for anaesthetists to be aware of their use.

[Coronary stents and anaesthesia: it is time to have national data]

We report 13 cases of coronary stent patients, undergoing a non cardiac surgery. Despite an heterogenous perioperative management of antiplatelet agents, none of these patients developed any significant complications. Recently, several case reports of postoperative drug eluting stent thrombosis have been reported. However, the actual incidence of this dramatic event is not known. This confirms the need to perform prospective studies or registries of patients with coronary stents undergoing non cardiac surgery, in order to propose evidence-based recommendations on perioperative antiplatelet management in such patients.

A randomized study comparing the efficacy and safety of nadroparin 2850 IU (0.3 mL) vs. enoxaparin 4000 IU (40 mg) in the prevention of venous thromboembolism after colorectal surgery for cancer

BACKGROUND

The optimal thromboprophylactic dosage regimen of low-molecular-weight heparins in high-risk general surgery remains debatable.

OBJECTIVES

We performed a randomized, double-blind study to compare the efficacy and safety of nadroparin 2850 IU (0.3 mL) and enoxaparin 4000 IU (40 mg) in the prevention of venous thromboembolism (VTE) after colorectal surgery for cancer.

PATIENTS AND METHODS

Patients undergoing resection of colorectal adenocarcinoma were randomized to receive once daily either 2850 IU nadroparin or 4000 IU enoxaparin s.c. for 9 +/- 2 days. The primary efficacy outcome was the composite of deep vein thrombosis (DVT) detected by bilateral venography or documented symptomatic DVT or pulmonary embolism up to day 12. The main safety outcome was major bleeding. A blinded independent committee adjudicated all outcomes.

RESULTS

Out of 1288 patients analyzed, efficacy was evaluable in 950 (73.8%) patients. The VTE rate was 15.9% (74/464) in nadroparin-treated patients and 12.6% (61/486) in enoxaparin-treated patients, a relative risk of 1.27 (95% confidence interval; CI: 0.93-1.74) that did not met the criterion for non-inferiority of nadroparin. The rate of proximal DVT was comparable in the two groups (3.2% vs. 2.9%, respectively), but that of symptomatic VTE was lower in nadroparin-treated patients (0.2% vs. 1.4%). There was significantly (P = 0.012) less major bleeding in nadroparin- than in enoxaparin-treated patients (7.3% vs. 11.5%, respectively).

CONCLUSION

Compared with those receiving enoxaparin 4000 IU, patients treated with nadroparin 2850 IU showed a higher incidence of asymptomatic distal DVT, but a lower incidence of symptomatic VTE. Nadroparin treatment was safer in terms of bleeding risk.

Perioperative platelet transfusion. Recommendations of the French Health Products Safety Agency (AFSSAPS) 2003

The aim of this paper is to present the recommendations of the Agence Française de Sécurité Sanitaire des Produits de Santé (AFSSaPS; French Safety Agency for Health Products). A panel of experts reviewed and graded the literature on platelet transfusions; recommendations were formulated. Threshold platelet counts (PC) for transfusions in the perioperative context have not been clearly defined and should be determined by the existence of hemorrhagic risk factors. In the case of commonly practiced invasive procedures, the recommendation is to transfuse in order to achieve PC > 50,000 x microL-1. In the absence of platelet dysfunction, regardless of the type of surgery, the standard hemorrhagic risk threshold for surgery is 50,000 x microL-1. It has not been proven that the risk threshold is different according to the type of surgery. For neurosurgery and ophthalmologic surgery involving the posterior segment of the eye, a PC of 100,000 x microL-11 is required. For axial regional anesthesia, a PC of 50,000 x microL-11 is sufficient for spinal anesthesia; a PC of 80,000 x microL-11 has been proposed for epidurals. During massive transfusion, prophylactic platelet infusion cannot be recommended beyond a loss of two blood volumes in less than 24 h (Professional Consensus). As for the therapeutic transfusion of plasma and/or platelets, as much as possible, platelet deficit should be documented with test results (PC and fibrinogen) before transfusing. In the event of bleeding, platelet transfusion may precede plasma infusion. However, although this recommendation has been the subject of several professional consensus agreements, it is not based on any randomized studies. Threshold PC for perioperative transfusions have not been clearly defined and most recommendations are the result of a professional consensus.

Venous thromboembolism prevention in surgery and obstetrics

BACKGROUND AND OBJECTIVE

To produce up-to-date clinical practice guidelines on the prevention of venous thromboembolism in surgery and obstetrics.

METHODS

A Steering Committee defined the scope of the topic, the questions to be answered, and the assessment criteria. Eight multidisciplinary working groups (total of 70 experts) performed a critical appraisal of the literature in the following disciplines: pharmacology of antithrombotic agents, orthopaedics; general surgery (gastrointestinal (GI) and varicose vein surgery); urology; gynaecology and obstetrics; thoracic, cardiac and vascular surgery; surgery of the head, neck and spine; and surgery of burns patients. The resultant reports and guidelines were submitted for comment and completion of the Appraisal of Guidelines Research & Evaluation questionnaire to a total of 150 peer reviewers, before producing definite guidelines.

RESULTS

The report answers the following questions for each type of surgery: (i) What is the venous thromboembolism incidence according to clinical and/or paraclinical criteria in the absence of prophylaxis? (with stratification of venous thromboembolism risk into low, moderate and high categories); (ii) What is the efficacy and safety of the prophylactic measures used? (iii) When should prophylaxis be introduced and how long should it last? (iv) Does ambulatory surgery affect efficacy and safety of prophylaxis?

CONCLUSIONS

Apart from answering the above questions, the guidelines provide a summary table for each discipline. This table stratifies types of surgery into the three risk categories, specifies the recommended prophylaxis for venous thromboembolism (pharmacological and/or mechanical) and grades each recommendation. In addition, whenever appropriate, the recommended prophylaxis is adjusted to low- and high-risk patients.

The coagulopathy of massive transfusion

Recently, the Groupe d'Intérêt en Hémostase Périopératoire reviewed the pathophysiology of coagulopathy in massively transfused, adult and previously haemostatically competent patients in both elective surgical and trauma settings. In this article, we focus on our main observations. First, in most cases, the onset and severity of coagulopathy associated with massive transfusion differs depending on whether haemorrhage occurs as a result of trauma or elective surgery. In trauma patients, tissue trauma is uncontrolled, the interval between haemorrhage and treatment can vary widely, hypovolemia, shock and hypothermia are frequent, and coagulopathy is often related to the development of disseminated intravascular coagulation. Monitoring of haemostasis occurs late, when coagulopathy is installed, and treatment can be very difficult. In elective surgery patients, the situation remains controlled and, in most cases, a decrease in fibrinogen concentration is observed initially while thrombocytopenia is a late occurrence. Monitoring of haemostasis is ongoing and treatment is usually much simpler. Second, blood products have changed over time and this has affected the management of the bleeding patient. Contrary to the recommendations of studies published at a time when whole blood was readily available, the first line of treatment (at least in elective surgery patients) ought to be with fresh-frozen plasma to correct decreased levels of coagulation factors. The role of recombinant activated factor VII to treat bleeding that cannot be controlled by conventional measures remains to be clarified. Coagulopathy associated with massive transfusion remains an important clinical problem. Treatment strategies must be adapted to the context and to the blood products available. Nevertheless, the level of evidence supporting specific treatment options is low and more studies are required to guide our management of massively transfused patients.

Hémorragie massive après laminectomie dorsale décompressive

We describe a case of a massive haemorrhage after dorsal decompressive laminectomy. The biological syndrome was at first a disseminated intravascular coagulation (DIC), rapidly complicated by a secondary fibrinolysis. The usual treatment of DIC with plasma and platelet transfusion failed to control bleeding and the patient underwent four repeat operations for relapsing rapidly evolving paraplegia. Aprotinine treatment stopped the haemorrhage. The vertebral metastasis causing spinal compression proved to be of prostatic origin.

[Prevention of venous thromboembolism in surgery and obstetrics]

The French Society of anaesthesiology and intensive care has chosen a high level methodology to issue professional Recommendations on perioperative and obstetrical venous thromboembolism prophylaxis. In addition with a short review on mechanical and pharmacological prophylaxis, all surgical and obstetrical settings have been studied. The initiation and duration of prophylaxis have been particularly debated in close relation with the level of surgical risk. A large group of experts has been involved in this process. More than 150 other experts have participated in the reading process. Didactic tables have been added to help the prescription.

Postoperative residual neuromuscular block: a survey of management

BACKGROUND

To avoid postoperative residual neuromuscular block there is a need for a change in clinician's attitude towards monitoring and reversal. This study aims to evaluate changes of perioperative neuromuscular block management during the last decade in our institution and to quantify the incidence of postoperative residual neuromuscular block.

METHODS

Patients receiving intermediate-acting neuromuscular blocking agents for scheduled surgical procedures during 3-month periods in 1995 (n=435), 2000 (n=130), 2002 (n=101), and in 2004 (n=218) were prospectively and successively enrolled in our study. The management of neuromuscular block in the operating room and the adequacy of the recovery were at the discretion of the anaesthesiologist. An attempt was made between each study period to promote a change in the management of neuromuscular block. In the post-anaesthesia care unit, train-of-four (TOF) stimulations were used to assess the presence of a residual neuromuscular block.

RESULTS

Between 1995 and 2004 quantitative measurement and reversal of neuromuscular block in the operating room increased from 2 to 60% and from 6 to 42%, respectively (P<0.001). During the same time, the incidence of residual neuromuscular block defined as a TOF ratio less than 0.9 decreased from 62 to 3% (P<0.001). Use of objective neuromuscular monitoring and/or anticholinesterase drugs was less likely in patients with an inadequate recovery (P<0.001).

CONCLUSIONS

During the last decade the incidence of residual neuromuscular block strongly decreased in our institution. It confirms the positive impact of neuromuscular monitoring and reversal of neuromuscular block in routine anaesthetic practice.

Tracheal intubation in routine practice with and without muscular relaxation

BACKGROUND AND OBJECTIVE

The ease of endotracheal intubation has been recently shown to affect the incidence of laryngeal injury. There remains controversy as to whether or not a muscle relaxant is routinely required for tracheal intubation. This study examined conditions of intubation in our routine practice, which employs a relaxant-sparing approach.

METHODS

All adult patients scheduled for surgery with general anaesthesia were prospectively included. A muscle relaxant was used to facilitate intubation when it was required for the surgical procedure and/or otherwise regarded as necessary by the anaesthesiologist. In the remaining patients, a relaxant-free intubation was performed. Intubating conditions were evaluated in all the patients as well as the post-intubation laryngeal symptoms.

RESULTS

Between March and July 2003, 612 patients were consecutively included. A muscle relaxant was used in 32% of patients and no relaxant in the remaining patients (68%). Clinically acceptable intubating scores were observed in 98.4% overall with no significant difference between the two groups. Excellent conditions occurred more frequently in the relaxant group as compared to the relaxant-free group, 87% vs. 72%, P = 0.005. Laryngeal symptoms occurred in 184 (33%) patients with no difference between the two groups.

CONCLUSIONS

Our relaxant-sparing approach did not increase the incidence of poor conditions of intubation nor laryngeal symptoms. However, excellent conditions occurred more frequently in the relaxant group. A more flexible approach to the issue of the need for neuromuscular blockade prior to intubation is proposed.

Venous thromboembolism and mortality after hip fracture surgery: the ESCORTE study

BACKGROUND

Recent changes in the management of hip fracture surgery patients may have modified the epidemiology of postoperative complications.

OBJECTIVES

We performed an observational study of a cohort of patients undergoing hip fracture surgery to update the epidemiological data on this population. The primary study outcome was the incidence of confirmed symptomatic venous thromboembolism (VTE) [defined as deep vein thrombosis, pulmonary embolism (PE), or both] at 3 months. Overall mortality at 1, 3 and 6 months was also evaluated.

PATIENTS/METHODS

Consecutive patients aged at least 18 years hospitalized in French public or private hospitals (531 centers) undergoing hip fracture surgery were recruited prospectively during 2 months in 2002 and a follow-up at 6 months. Predictive factors for VTE at 3 months and for death at 6 months were also analyzed.

RESULTS

Data from 6860 (97.3%) of the 7019 recruited patients were included in the analysis. The median age was 82 years. Low molecular weight heparins were administered perioperatively in 97.6% of patients; 69.5% received this treatment for at least 4 weeks. The actuarial rate of confirmed symptomatic VTE at 3 months was 1.34% (85 events, 95% CI: 1.04-1.64). There were 16 PEs (actuarial rate: 0.25%), three of which were fatal. Overall, 1006 (14.7%) patients were dead at 6 months. Cardiovascular disease was the most frequent cause of death (270 patients; 26.8%).

CONCLUSIONS

The current rate of postoperative VTE is low, but overall mortality remains high. Indeed, hip fracture patients belong to a vulnerable group of old people with comorbid diseases and a high risk of postoperative morbidity and mortality. An interdisciplinary approach could be the challenge to improve short and long-term outcome.

Étude des effets directs et indirects de l’érythropoïétine dans un modèle expérimental de thrombose et de saignement chez le lapin

OBJECTIVES

To study direct and indirect effects of EPO on haemostasis.

STUDY DESIGN

Experimental, randomised.

ANIMALS

Forty-eight New Zealand rabbits.

METHOD

Animals were anaesthetised, ventilated and monitored continuously for blood pressure, heart rate, body temperature, and carotid blood flow variations and were randomised into four groups: control, EPO bolus 2400 IU kg(-1), fractionated EPO (one injection a week of 600 IU kg(-1) for 4 weeks), homologous red blood cell transfusion to reach the Ht level of the fractionated EPO group. A compression injury and a 75% stenosis of the carotid artery triggered a series of cyclic flow reductions (CFRs). CFRs were observed for a 20 min period in each group. Ear immersion bleeding time (BT) and hepato-splenic bleeding were performed at the end of the experiment. Biology was performed at the end of the thrombosis period: blood cells count, Hte, activated partial thromboplastin time, fibrinogen, arachidonic-induced platelet aggregation, EPO dosages.

RESULTS

No significant increase in thrombosis (CFRs) in the two EPO groups and in the transfused group. Increase in Hte in the fractionated EPO group versus control. Group EPO bolus: decrease in BT and hepato-splenic bleeding versus control; decrease in hepato-splenic bleeding versus fractionated EPO group, increase in platelet aggregation velocity versus control.

CONCLUSION

EPO did not increase the thrombotic risk in this rabbit model. EPO bolus decreased BT and hepato-splenic bleeding.

Near-patient testing of haemostasis in the operating theatre: an approach to appropriate use of blood in surgery

Several haemostasis point-of-care (POC) monitors are now available in the operating theatre. Two of these are widely used; the Coaguchek and the thromboelastograph (TEG), but they have been developed in very different ways. Bedside-activated partial thromboplastin time and prothrombin time performed with the Coaguchek monitor seem to be reliable and have been used to build algorithms for transfusion decision making. They have been developed in close collaboration with haemostasis groups and therefore gain a benefit from these links. Conversely, TEG provides very important information except it has never been validated. The number of collaborative studies with biologists has to increase in order to implement the use of TEG in the routine practice.

Anaphylaxis to rocuronium

Reports about anaphylactic and anaphylactoid reactions to rocuronium have increased recently. We report two new cases of documented grade III anaphylaxis, leading to death in one patient. The first case occurred in an 81-year-old ASA II woman scheduled for emergency abdominal surgery. Severe hypotension and tachycardia were observed after rocuronium, without bronchospasm. Neosynephrine allowed rapid resuscitation, and the patient recovered fully. The second patient was a 64-year-old ASA II man scheduled for abdominal surgery. Severe haemodynamic instability and bronchospasm occurred after rocuronium. Despite immediate life support, the postoperative period was complicated by persistent low systolic pressure, acute respiratory distress syndrome, acute renal failure, disseminated intravascular coagulation and pancreatitis, leading to the death of the patient.

Hemostatic Changes in Patients Receiving Hydroxyethyl Starch: The Influence of ABO Blood Group

Hydroxyethyl starches (HES) interfere with coagulation because of their molecular structure and the amount infused during surgery. Coagulation defects include platelet dysfunction and a decrease of the VIII/von Willebrand factor complex (VIII/vWF). We examined the effects of 6% HES 200/0.6 on hemostasis by using an in vitro platelet function analyzer, the usual coagulation tests, the VIII/vWF complex assessment, and TEG analysis in patients undergoing abdominal surgery. The influence of the blood group was investigated. HES infusion induced primary hemostasis alterations, assessed by a prolonged platelet function analyzer closure time in the presence of epinephrine and adenosine diphosphate, which was not correlated with the platelet count. The decrease in VIII/vWF complex was proportional to the volume of infused HES (20 and 30 mL/kg) and was more pronounced in patients of the O blood group. The preoperative hypercoagulability status assessed by TEG analysis was reversed 24 h after HES infusion. In conclusion, 6% HES 200/0.6 induced immediate hemostasis alterations. Patients of the O blood group were likely to develop a von Willebrand-like syndrome after HES infusion. We conclude that intraoperative use of 6% HES 200/0.6 should be restricted in patients of the O blood group undergoing surgical procedures with high risk for bleeding.