Quantification of perioperative changes in von Willebrand factor and factor VIII during elective orthopaedic surgery in normal individuals

A Generative and Causal Pharmacokinetic Model for Factor VIII in Hemophilia A: A Machine Learning Framework for Continuous Model Refinement

In rare diseases, such as hemophilia A, the development of accurate population pharmacokinetic (PK) models is often hindered by the limited availability of data. Most PK models are specific to a single recombinant factor VIII (rFVIII) concentrate or measurement assay, and are generally unsuited for answering counterfactual ("what-if") queries. Ideally, data from multiple hemophilia treatment centers are combined but this is generally difficult as patient data are kept private. In this work, we utilize causal inference techniques to produce a hybrid machine learning (ML) PK model that corrects for differences between rFVIII concentrates and measurement assays. Next, we augment this model with a generative model that can simulate realistic virtual patients as well as impute missing data. This model can be shared instead of actual patient data, resolving privacy issues. The hybrid ML-PK model was trained on chromogenic assay data of lonoctocog alfa and predictive performance was then evaluated on an external data set of patients who received octocog alfa with FVIII levels measured using the one-stage assay. The model presented higher accuracy compared with three previous PK models developed on data similar to the external data set (root mean squared error = 14.6 IU/dL vs. mean of 17.7 IU/dL). Finally, we show that the generative model can be used to accurately impute missing data (< 18% error). In conclusion, the proposed approach introduces interesting new possibilities for model development. In the context of rare disease, the introduction of generative models facilitates sharing of synthetic data, enabling the iterative improvement of population PK models.

Tachyphylaxis and reproducibility of desmopressin response in perioperative persons with nonsevere hemophilia A: implications for clinical practice

Background

Desmopressin is frequently used perioperatively in persons with nonsevere hemophilia A. However, increase in factor (F)VIII:C after desmopressin use is interindividually highly variable. Tachyphylaxis has only been reported in test setting for persons with hemophilia A, with a remaining response of approximately 70% after a second dose compared with that after a first dose.

Objectives

To study tachyphylaxis of FVIII:C response after multiple administration(s) of desmopressin in perioperative persons with nonsevere hemophilia A.

Methods

We studied FVIII:C levels after desmopressin before (day 0 [D0]) and on days 1 (D1) and 2 (D2) after surgery in 26 patients of the DAVID and Little DAVID studies. We studied tachyphylaxis by comparing the responses at D1 and D2 with that at D0. We also assessed the reproducibility of the D0 response in comparison to an earlier performed desmopressin test.

Results

The median absolute FVIII:C increase was 0.50 IU/mL (0.35-0.74; n = 23) at D0, 0.21 IU/mL (0.14-0.28; n = 17) at D1, and 0.23 IU/mL (0.16-0.30; n = 11) at D2. The median percentage of FVIII increase after the second administration (D1) compared with the first (D0) was 42.9% (29.2%-52.5%; n = 17) and that of the third (D2) compared with the first (D0) was 36.4% (23.7%-46.9%; n = 11). The FVIII:C desmopressin response at D0 was comparable with the desmopressin test response in 74% of the patients.

Conclusion

Tachyphylaxis in the surgical setting was considerably more pronounced than previously reported, with FVIII:C at D1 and D2 of 36% to 43% of the initial response. Our results may have important implications for monitoring repeated desmopressin treatment when used perioperatively.

Continuous Infusion of Factor VIII and von Willebrand Factor in Surgery: Trials with pdFVIII LFB or pdVWF LFB in Patients with Bleeding Disorders

INTRODUCTION

A plasma-derived factor VIII product (pdFVIII, Factane 100 or 200 IU/mL) and a plasma-derived von Willebrand factor product (pdVWF, Wilfactin 100 IU/mL) are approved for replacement therapy by intravenous bolus injections in haemophilia A (HA) and von Willebrand disease (VWD), respectively. However, in situations requiring intensive treatment, continuous infusion (CI) may be desirable to better control target plasma factor levels.

AIM

To evaluate the perioperative haemostatic efficacy and safety of these concentrates administered by CI.

METHODS

Three phase III trials were conducted. Adults with HA (FVIII:C <1%) (Studies 1 and 2) or VWD (VWF:RCo <20%) (Study 3) received a preoperative bolus followed by CI of undiluted concentrate for at least 6 days. Bolus doses and CI rates were based on individual recovery and clearance, respectively. Initial infusion rate had to be higher for 48 hours for HA and 24 hours for VWD patients to anticipate potential fluctuations of factor concentrations during major surgery. Target levels of FVIII:C in HA and VWF:RCo in VWD were 80 and 70 IU/dL, respectively. Efficacy was assessed using a global haemostatic efficacy score.

RESULTS

Studies 1, 2, and 3 included 12, 4 and 6 patients, respectively. Efficacy outcomes were excellent/good in all 22 major surgeries including 18 orthopaedic procedures. Most daily measured FVIII and VWF levels (92%) were on target. No safety concerns, thrombotic events or inhibitors were identified.

CONCLUSION

pdFVIII and pdVWF administered by CI represent an effective and safe alternative to bolus injections in patients with severe HA or VWD undergoing surgery.

The heparin-von Willebrand factor interaction and conventional tests of haemostasis - the challenges in predicting bleeding in cardiopulmonary bypass

Bleeding is a significant complication of cardiopulmonary bypass (CPB), despite routine anticoagulation monitoring. This is likely to be multifactorial. In this prospective, single-centre cohort study of 30 patients undergoing CPB surgery, our aim was to characterise the changes in von Willebrand factor (VWF) function, platelet interaction and the global coagulation changes during and after CPB surgery and to determine whether bleeding can be predicted. Samples were taken at six time points before, during and after CPB surgery. We observed a significant rise in VWF antigen (VWF:Ag) throughout surgery, which continued postoperatively. The absolute VWF collagen-binding assays (VWF:CB) and VWF ristocetin cofactor (VWF:RCo) rose significantly but the VWF:CB/VWF:Ag and VWF:Ag/VWF:RCo fell significantly (P = 0·0015 and P = 0·0143), suggesting loss of large multimers. We detected a non-significant trend to loss of VWF:RCo after heparinisation and a significant recovery after protamine reversal which could reflect a direct heparin effect. There was a significant increase in the R and K times with a fall in alpha angle and maximum amplitude after heparin administration, using heparinase-thromboelastography (TEG). The parameters both significantly improved following protamine (P = 0·007 and P = 0·0054). The activated clotting time (ACT) and heparin anti-Xa level correlated poorly; neither predicted clinically significant bleeding. None of these parameters had a relationship with intraoperative blood loss or requirement for blood product replacement.

Bleeding assessment tools to predict von Willebrand disease: Utility of individual bleeding symptoms

BACKGROUND

Bleeding assessment is part of the diagnostic workup of von Willebrand disease (VWD). Bleeding assessment tools (BATs) have standardized obtaining this information but have been criticized because they are time consuming.

OBJECTIVE

To use our legacy data to determine which questions from BATs are the strongest predictors of a VWD diagnosis.

PATIENTS/METHODS

Bleeding score data from 3 different BATs were used. Patients aged <12 years were excluded. Questions on BATs relate to different bleeding symptoms, and each symptom is scored by severity. Scores for each symptom were sorted based on whether they indicated clinically significant bleeding, and nonsignificant scores were set as the reference category. Multivariable logistic regression was used to determine the symptoms that were the strongest predictors of a laboratory-confirmed VWD diagnosis.

RESULTS

A total of 927 participants were included; 144 (16%) were patients with VWD, and 783 (84%) were healthy controls. The top 3 symptoms for which a clinically significant positive response increased the likelihood of VWD were hemarthrosis (odds ratio [OR], 19.2; 95% confidence interval [CI], 3.7-100.4), postsurgical bleeding (OR, 15.2; 95% CI, 5.9-38.9), and menorrhagia (OR, 10.3; 95% CI, 4.9-21.9). With each increase in number of bleeding symptom categories with clinically significant scores, subjects had a stepwise increase in odds of a VWD diagnosis.

CONCLUSIONS

Our results suggest that most of the bleeding symptoms on BATs are significant predictors of VWD, and there is value in assessing multiple bleeding symptoms when eliciting a bleeding history. Certain bleeding symptoms are more useful predictors than others. Future BAT revisions may consider adding a relative weighting to each symptom.

Long-lasting prothrombotic state implied by changes of plasma von Willebrand factor parameters after radical prostatectomy for prostate malignancy

OBJECTIVES

Thromboembolic complications are present in 0.8%-16.8% of the cases after radical prostatectomy (RP). Association between elevated plasma von Willebrand factor (VWF) levels-as an endothelial activation marker-and increased risk of thrombotic events has been evidenced. We aimed to elicit new data on the VWF after RP in prostate cancer patients and explore the role of it as a thrombotic risk factor. Upon perioperative plasma VWF levels (VWF:Ag) its collagen-binding (CB) activity (VWF:CB), multimerization, and cleaving enzyme (ADAMTS13 [a disintegrin and metalloprotease with thrombospondin type repeats, motif 1, type 13]) of the VWF multimers were quantitated along with Factor VIII and routine laboratory parameters in this observational pilot study.

METHODS

Plasma samples of 24 prostate cancer patients were collected before (-1 day; D-1) and after RP (1 hour, 6 days, 1 month, and 10 months; H1, D6, M1, and M10). VWF:Ag, VWF:CB, ADAMTS13:Ag were measured by ELISA, and the multimer distribution by electrophoresis and quantitative densitometry. Factor VIII, fibrinogen, D-dimer, and other routine laboratory parameters were determined as well. Preoperative values served as baselines which were compared to controls (24 healthy individuals).

RESULTS

VWF:Ag and CB elevated by 122% and 143% respectively at H1 after RP then plateaued at D6 compared to baseline values. ADAMTS13/VWF:Ag ratio reduced by 41% at H1, and by 46% at D6, meanwhile the ratio of high molecular weight multimers increased as well. Values returned to baseline at M1 and further reduced to the levels of the controls at M10. All of the 24 patients at H1 and D6 and 14 at M10 were in potential prothombotic state according ROC analysis of the VWF parameters as indicators.

CONCLUSIONS

Prostate malignancy and then surgical stress, and inflammatory reactions induced release of VWF from the endothelial cells, along with an increasing amount of large multimers and relative reduction of ADAMTS13 level. Because these changes mark a prothrombotic state even at M1 after RP, more than 1 month follow-up and prophylactic targeting through the thrombotic and inflammatory activity of the VWF is proposed. Evaluation of VWF parameters provides new information about the long-term disturbances of primary hemostasis after radical pelvic oncologic surgery like RP and might improve the understanding the physiological and pathological recovery.

Current dosing practices for perioperative factor VIII concentrate treatment in mild haemophilia A patients result in FVIII levels above target

BACKGROUND

In patients with haemophilia A (HA) perioperative dosing of factor VIII (FVIII) concentrate is based on body weight, historical FVIII level, in vivo recovery and FVIII level target values. In moderate and severe HA patients, this dosing regimen frequently leads to perioperative FVIII levels below and above target. This has not yet been evaluated in mild HA patients.

OBJECTIVES

To evaluate perioperative FVIII concentrate treatment in mild HA patients and to assess the frequency of FVIII levels below or above target.

PATIENTS/METHODS

This retrospective single-centre study collected data from medical files of mild HA patients undergoing surgery and treated with FVIII concentrate. FVIII levels were compared to their target ranges and predictive factors for levels outside the target ranges were determined by logistic regression.

RESULTS

Fifty surgeries performed in 34 patients were evaluated. Median age was 47 years and median historical FVIII level was 0.14 IU/mL. Preoperative peak FVIII level was above or below the target range in 80% and 6.7% of surgeries, respectively. Postoperatively, the percentages above and below target trough ranges were 55.8% and 12.8%. Patients with blood group 0 had the highest risk on the preoperative peak FVIII level being above target. In addition, patients who had a preoperative baseline FVIII level of >0.10 IU/mL higher than their historical FVIII level had a higher preoperative peak FVIII level than patients without this increase.

CONCLUSIONS

Dosing above FVIII target ranges with FVIII concentrates occurs frequently during perioperative treatment of mild HA patients. These results underline the necessity for better patient-tailored treatment.

Management of von Willebrand disease in patients undergoing total hip and knee arthroplasty

Von Willebrand disease is the commonest bleeding disorder encountered in the medical and surgical field. As a result of the repetitive bleeding into the joints many patients suffer from arthropathy that can cause a significant amount of pain and functional limitation. Total joint arthroplasty is being utilised as the last resort in managing these patients; however, the presence of von Willebrand disease raises a number of dilemmas. In this review, we look at the effects of von Willebrand disease on joints and the perioperative management of von Willebrand disease patients undergoing total joint arthroplasty.

Impact of Arterial Procedures on Coagulation and Fibrinolysis - A Pilot Study

Objective

The main goal of our study was to assess the impact of vascular procedures on the activity of hemostatic and fibrinolytic pathways.

Methods

We enrolled 38 patients with ≥ 45 years old undergoing surgery for abdominal aortic aneurysm or peripheral artery disease under general or regional anesthesia and who were hospitalized at least one night after the procedure. Patients undergoing carotid artery surgery and those who had acute bypass graft thrombosis, cancer, renal failure defined as estimated glomerular filtration rate < 30 ml/min/1.73m2, venous thromboembolism three months prior to surgery, or acute infection were excluded from the study. We measured levels of markers of hemostasis (factor VIII, von Willebrand factor:ristocetin cofactor [vWF:CoR], antithrombin), fibrinolysis (D-dimer, tissue plasminogen activator [tPA], plasmin-antiplasmin complexes), and soluble cluster of differentiation 40 ligand (sCD40L) before and 6-12h after vascular procedure.

Results

Significant differences between preoperative and postoperative levels of factor VIII (158.0 vs. 103.3, P<0.001), antithrombin (92.1 vs. 74.8, P<0.001), D-dimer (938.0 vs. 2406.0, P=0.005), tPA (10.1 vs. 12.8, P=0.002), and sCD40L (9092.9 vs. 1249.6, P<0.001) were observed. There were no significant differences between pre- and postoperative levels of vWF:CoR (140.6 vs. 162.8, P=0.17) and plasmin-antiplasmin complexes (749.6 vs. 863.7, P=0.21).

Conclusion

Vascular surgery leads to significant alterations in hemostatic and fibrinolytic systems. However, the direction of these changes in both pathways remains unclear and seems to be different depending on the type of surgery. A study utilizing dynamic methods of coagulation and fibrinolysis assessment performed on a larger population is warranted.

Prevention of relapse in patients with acquired thrombotic thrombocytopenic purpura undergoing elective surgery: a case series

Essentials Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disease. Surgery is a possible trigger of acute TTP episodes and no guidelines are available. Six patients with severe ADAMTS-13 deficiency during remission underwent elective surgery. Patients were prophylactically treated to restore ADAMTS-13 activity and no relapses occurred. SUMMARY: Background Severe ADAMTS-13 deficiency has been recognized as the main risk factor for recurrence of thrombotic thrombocytopenic purpura (TTP). Several conditions, including surgery, may influence the levels of ultra-large von Willebrand factor and ADAMTS-13, acting as a trigger for an acute TTP event. Objectives To report our experience of management of six patients with acquired TTP who underwent elective surgery after prophylactic treatment to restore ADAMTS-13 activity levels. Patients Six patients followed for acquired TTP with severe ADAMTS-13 deficiency during remission were candidates for seven elective surgeries (inguinal hernioplasty, cholecystectomy, laparoscopic hysterectomy, oophorectomy, parotidectomy and two total hip arthroplasties). Results Four patients were treated with prophylactic plasma exchange (PEX) therapy immediately before surgery. One patient was treated with PEX therapy before her first surgery and with preemptive rituximab once her second surgery was scheduled. Because rituximab increased ADAMTS-13 levels only partially, she required one PEX procedure the day before her second surgery. One patient was treated with azathioprine after rituximab failure, obtaining a progressive increase of ADAMTS-13 activity to more than 40%. This level allowed her to undergo total hip arthroplasty without additional treatment. All surgeries were successful and no complications or relapses occurred. Conclusions Six patients with acquired TTP underwent seven successful surgical procedures using prophylaxis to restore ADAMTS-13 activity. Further observational studies or randomized clinical trials are needed to confirm whether prophylactic PEX could be the key factor in preventing relapse.

Analysis of current perioperative management with Haemate® P/Humate P® in von Willebrand disease: Identifying the need for personalized treatment

INTRODUCTION

Patients with Von Willebrand disease (VWD) are regularly treated with VWF-containing concentrates in case of acute bleeding, trauma and dental or surgical procedures.

AIM

In this multicentre retrospective study, current perioperative management with a von Willebrand factor (VWF)/Factor VIII (FVIII) concentrate (Haemate^® P) in patients with VWD was evaluated.

PATIENTS/METHODS

Patients with VWD undergoing minor or major surgery between 2000 and 2015, requiring treatment with a VWF/FVIII concentrate (Haemate^® P), were included. Achieved VWF activity (VWF:Act) and FVIII during FVIII-based treatment regimens were compared to predefined target levels in national guidelines.

RESULTS

In total, 103 patients with VWD (148 surgeries) were included: 54 type 1 (73 surgeries), 43 type 2 (67 surgeries) and 6 type 3 (8 surgeries). Overall, treatment resulted in high VWF:Act and FVIII levels, defined as ≥0.20 IU/mL above predefined levels. In patients with type 1 VWD, respectively, 65% and 91% of trough VWF:Act and FVIII levels were higher than target levels. In patients with type 2 and type 3 VWD, respectively, 53% and 57% of trough VWF:Act and 72% and 73% of trough FVIII levels were higher than target level. Furthermore, FVIII accumulation over time was observed, while VWF:Act showed a declining trend, leading to significantly higher levels of FVIII than VWF:Act.

CONCLUSION

High VWF:Act and accumulation of FVIII were observed after perioperative FVIII-based replacement therapy in patients with VWD, both underlining the necessity of personalization of dosing regimens to optimize perioperative treatment.

Setting the stage for individualized therapy in hemophilia: What role can pharmacokinetics play?

Replacement therapy with clotting factor concentrates (CFC) is the mainstay of treatment in hemophilia. Its widespread application has led to a dramatic decrease in morbidity and mortality in patients, with concomitant improvement of quality of life. However, dosing is challenging and costs are high. This review discusses benefits and limitations of pharmacokinetic (PK)-guided dosing of replacement therapy as an alternative for current dosing regimens. Dosing of CFC is now primarily based on body weight and based on its in vivo recovery (IVR). Benefits of PK-guided dosing include individualization of treatment with better targeting, more flexible blood sampling, increased insight into association of coagulation factor levels and bleeding, and potential overall lowering of overall costs. Limitations include a slight burden for the patient, and availability of closely collaborating, experienced clinical pharmacologists.

Thrombogenicity evaluation in 221 patients with haemophilia B treated with nonacog alfa

Risk for thrombotic events with factor IX replacement therapy in patients with haemophilia B remains a concern for patients, those who treat them, and regulatory agencies, based on experience with early use of prothrombin complex concentrates. The current post hoc analysis assessed the incidence of thrombotic events and changes in prothrombin fragment 1 + 2, thrombin–antithrombin complex, and d-dimer in 221 patients with haemophilia B who received nonacog alfa in clinical studies. Thrombotic event and coagulation marker data were collected from 8 interventional studies utilizing on-demand, prophylactic, and preventive regimens in patients with haemophilia B. Mean age was 25 years (min–max, 0–69), with 51 (23%) patients aged less than 12 years and 15 (7%) aged less than 2 years. None tested positive for inhibitors. Mean time on study was 60.9 ± 32 weeks and mean number of exposure days was 69.3 (min–max, 1–496). Sixty-nine (31%) patients regularly received infusions that were approximately 100 IU/kg as part of a routine prophylaxis regimen, and 29 (13%) patients underwent surgical procedures. No clinical thrombotic events were reported, and no patient experienced clinically significant changes in coagulation markers between baseline and end-of-study testing. These collective data support the low thrombotic risk associated with nonacog alfa in paediatric, adult, and surgical patients with haemophilia B receiving different treatment regimens, including doses of approximately 100 IU/kg. Although careful thrombotic clinical evaluation is important, regular coagulation marker monitoring does not appear to be warranted in patients with haemophilia B.

Pharmacokinetic-guided dosing of factor VIII concentrate in a patient with haemophilia during renal transplantation

A 29-year-old man with severe haemophilia A and end-stage renal disease underwent a renal transplantation. To prevent bleeding, patient was treated with replacement therapy using factor VIII (FVIII) concentrate, according to National guidelines. Bayesian analysis was performed by combining observed FVIII concentrations with a population pharmacokinetic (PK) model for patients with severe haemophilia A in a perioperative setting. Application of Bayesian analysis led to accurate prediction of observed concentrations after prescribing dosing advice. We believe that PK-guided dosing of factor concentrates is a valuable step towards further individualisation of treatment in patients with bleeding disorders, especially in those patients requiring precise targeting of coagulation factor levels due to high risk of either bleeding or thrombosis, as illustrated by this patient undergoing a major surgical procedure.

A single-centre study of haemostatic outcomes of joint replacement in von Willebrand disease and control patients and an analysis of the literature

INTRODUCTION

Haemostatic assessments of patients with von Willebrand disease (VWD) who undergo total knee arthroplasty (TKA) and total hip arthroplasty (THA) have mainly relied on subjective parameters.

AIMS

To compare objective haemostatic outcomes of TKA/THA in VWD patients and controls without bleeding disorders.

METHODS

We retrospectively analysed haemostatic outcomes in VWD patients undergoing TKA/THA from 1993 to 2011 and compared them with two matched controls per operation. Using one-way analysis of variance, we tested the effect of VWD on bleeding risk after TKA and THA.

RESULTS

Twelve VWD patients (6 type 1, 3 type 2M, 1 each of types 2A/2B/3) undergoing 19 operations (12 TKA, 7 THA) were matched to 38 controls. One (5%) of 19 operations in VWD patients and none of the control operations met clinical criteria for major bleeding. Baseline and postoperative day 1 haemoglobin levels, postoperative blood loss, transfused red blood cells (RBCs) and mean hospitalization days were not significantly different. More VWD patients than controls received RBC transfusions [12 (63%) vs. 12 (32%)]. Only 9 (47%) VWD patients vs. 38 (100%) controls received pharmacologic VTE prophylaxis. No postoperative symptomatic VTE occurred in either group.

CONCLUSION

In this largest, single-institutional study, von Willebrand factor replacement based on daily levels resulted in low frequency of major bleeding in VWD patients after TKA/THA. RBC transfusion was more frequent compared with matched controls, but other objective measures of haemostasis were similar. Lack of sufficient details in published reports precluded comparison of haemostatic outcomes.

A population pharmacokinetic model for perioperative dosing of factor VIII in hemophilia A patients

The role of pharmacokinetic-guided dosing of factor concentrates in hemophilia is currently a subject of debate and focuses on long-term prophylactic treatment. Few data are available on its impact in the perioperative period. In this study, a population pharmacokinetic model for currently registered factor VIII concentrates was developed for severe and moderate adult and pediatric hemophilia A patients (FVIII levels <0.05 IUmL^-1) undergoing elective, minor or major surgery. Retrospective data were collected on FVIII treatment, including timing and dosing, time point of FVIII sampling and all FVIII plasma concentrations achieved (trough, peak and steady state), brand of concentrate, as well as patients' and surgical characteristics. Population pharmacokinetic modeling was performed using non-linear mixed-effects modeling. Population pharmacokinetic parameters were estimated in 75 adults undergoing 140 surgeries (median age: 48 years; median weight: 80 kg) and 44 children undergoing 58 surgeries (median age: 4.3 years; median weight: 18.5 kg). Pharmacokinetic profiles were best described by a two-compartment model. Typical values for clearance, intercompartment clearance, central and peripheral volume were 0.15 L/h/68 kg, 0.16 L/h/68 kg, 2.81 L/68 kg and 1.90 L/68 kg. Interpatient variability in clearance and central volume was 37% and 27%. Clearance decreased with increasing age (P<0.01) and increased in cases with blood group O (26%; P<0.01). In addition, a minor decrease in clearance was observed when a major surgical procedure was performed (7%; P<0.01). The developed population model describes the perioperative pharmacokinetics of various FVIII concentrates, allowing individualization of perioperative FVIII therapy for severe and moderate hemophilia A patients by Bayesian adaptive dosing.

Practical aspects of factor concentrate use in patients with von Willebrand disease undergoing invasive procedures: a European survey

INTRODUCTION

The bleeding propensity in von Willebrand disease (VWD) is usually moderate or mild and patients with VWD do not need continuous treatment, but do require extra increased haemostatic cover when undergoing dental or surgical procedures. Desmopressin can be effective in certain patient groups and this has been considered in a previous publication.

AIM

This paper now seeks to evaluate current knowledge and practice in the use of factor concentrate in the management of VWD patients undergoing invasive procedures.

METHODS

A literature search was performed on the use of factor concentrates to cover invasive procedures and a survey of current practice in a number of specialist haematology centres across Europe represented by the European Haemophilia Strategy Board was conducted.

RESULTS

Our review of the literature and the results of the survey showed considerable heterogeneity in treatment regimens, and a lack of consistency in reporting of the variables that determine factor concentrate dosing and monitoring.

CONCLUSION

By analysing the literature, examining guidelines and using consensus deliberation, this survey allowed the group to develop recommendations for management of VWD patients undergoing invasive procedures.

Perioperative treatment of hemophilia A patients: blood group O patients are at risk of bleeding complications

ESSENTIALS: Targeting of factor VIII values is a challenge during perioperative replacement therapy in hemophilia. This study aims to identify the extent and predictors of factor VIII underdosing and overdosing. Blood group O predicts underdosing and is associated with perioperative bleeding. To increase quality of care and cost-effectiveness of treatment, refining of dosing is obligatory.

SUMMARY

BACKGROUND

Perioperative administration of factor VIII (FVIII) concentrate in hemophilia A may result in both underdosing and overdosing, leading to respectively a risk of bleeding complications and unnecessary costs.

OBJECTIVES

This retrospective observational study aims to identify the extent and predictors of underdosing and overdosing in perioperative hemophilia A patients (FVIII levels < 0.05 IU mL(-1)).

PATIENTS AND METHODS

One hundred nineteen patients undergoing 198 elective, minor, or major surgical procedures were included (median age 40 years, median body weight 75 kg). Perioperative management was evaluated by quantification of perioperative infusion of FVIII concentrate and achieved FVIII levels. Predictors of underdosing and (excessive) overdosing were analyzed by logistic regression analysis. Excessive overdosing was defined as upper target level plus ≥ 0.20 IU mL(-1).

RESULTS

Depending on postoperative day, 7-45% of achieved FVIII levels were under and 33-75% were above predefined target ranges as stated by national guidelines. A potential reduction of FVIII consumption of 44% would have been attained if FVIII levels had been maintained within target ranges. Blood group O and major surgery were predictive of underdosing (odds ratio [OR] 6.3, 95% confidence interval [CI] 2.7-14.9; OR 3.3, 95% CI 1.4-7.9). Blood group O patients had more bleeding complications in comparison to patients with blood group non-O (OR 2.02, 95% CI 1.00-4.09). Patients with blood group non-O were at higher risk of overdosing (OR 1.5, 95% CI 1.1-1.9). Additionally, patients treated with bolus infusions were at higher risk of excessive overdosing (OR 1.8, 95% CI 1.3-2.4).

CONCLUSION

Quality of care and cost-effectiveness can be improved by refining of dosing strategies based on individual patient characteristics such as blood group and mode of infusion.