Letters to the Editor 1411
Low incidence of venographically detected deep vein thrombosis after knee arthroscopy without thromboprophylaxis: a prospective cohort study H . B . E T T E M A , * M . R . H O P P E N E R , N . J . G . M . V E E G E R , à H . R . B U¨ L L E R and J . V A N D E R M E E R à *Department of Orthopaedic Surgery and Traumatology, Isala Clinics (De Weezenlanden Hospital), Zwolle; Department of Vascular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam; and àDivision of Haemostasis and Thrombosis, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
To cite this article: Ettema HB, Hoppener MR, Veeger NJGM, Bu¨ller HR, van der Meer J. Low incidence of venographically detected deep vein thrombosis after knee arthroscopy without thromboprophylaxis: a prospective cohort study. J Thromb Haemost 2006; 4: 1411–3.
Venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism (PE), is a serious complication of major orthopedic surgery. Without prophylaxis, the risk of venographically detected DVT ranges from 40% to 70% following major orthopedic procedures [1]. It is current practice to use pharmacological thromboprophylaxis in these patients. Knee arthroscopy is the most commonly performed orthopedic operation, with over 3 million procedures each year worldwide. Despite the frequency of this procedure, there are little data on the incidence of DVT in patients undergoing knee arthroscopy in daycare and thromboprophylaxis is not routinely applied. A recent study of > 300 patients using compression ultrasonography as the detection method for DVT showed a low incidence of symptomatic as well as asymptomatic VTE (0.9% and 5.1%) [2]. However, contrast venography remains the standard screening method for detecting DVT postoperatively. The main aim of the present study was to assess the incidence of venous thromboembolic complications after arthroscopy of the knee, as detected by mandatory venography in the absence of pharmacological thromboprophylaxis. During the period between September 1997 and February 1999, 242 consecutive patients undergoing knee arthroscopy were potentially eligible for the study. Patients were included if they were older than 18 years, were planned for knee arthroscopy and had given written informed consent. Exclusion criteria were: known inherited thrombophilic disorders; thrombocytopenia; severe liver and/or renal diseases; pregnancy; previous DVT; previous surgery of the ipsilateral lower extremity; anticoagulant drug therapy; and allergy to iodine or contrast media. The study was approved by the institutional review board.
Correspondence: H. B. Ettema, Department of Orthopaedic Surgery and Traumatology, Isala clinics (De Weezenlanden Hospital), PO Box 10500, 8000 GM Zwolle, the Netherlands. Tel.: +31 384242203; fax: +31 384243220; e-mail:
[email protected] Received 24 July 2005, accepted 23 February 2006 2006 International Society on Thrombosis and Haemostasis
During arthroscopy a pneumatic thigh tourniquet inflated to a pressure of 350 mmHg was used. Six to 8 h after surgery, the patients went home using elbow-crutches; full weight bearing was allowed and encouraged. None of the patients received thromboprophylaxis. Patients were scheduled for venography 9 ± 2 days postoperatively, restricted to the site of operation. Clinical data including age, sex, race, weight and height were recorded. Preoperative assessment also included the patient’s medical history and use of medication. Operation details, including side of the arthroscopy, type of anesthesia, preoperative blood pressure, duration of arthroscopy and tourniquettime were also recorded. The outcomes were DVT and (non-)fatal PE, established by objective test. Ipsilateral antegrade contrast venography was scheduled for all patients 9 ± 2 days after the procedure. Patients who experienced symptoms or signs of VTE (pain, swelling or discoloration of the leg, dyspnea, pleuritic chest pain, cough or hemoptysis) before their follow-up contact were instructed to contact the study center. A B-mode ultrasonography or perfusion/ventilation lung scanning would then be made. DVT was diagnosed when an intraluminal filling defect was seen on at least two views at venography. It was classified as proximal if it involved the iliac, superficial femoral, or popliteal veins, and distal if it involved the posterior tibial, anterior tibial, or peroneal veins. Perfusion/ventilation lung scanning was performed if patients had symptoms of PE. If not conclusive it was followed by pulmonary angiography. PE was diagnosed if the perfusion/ventilation lung scintigraphy showed a defect with a high probability or an abnormal pulmonary angiography. All venograms were assessed by one experienced radiologist. The rates of VTE and 95% confidence intervals (95% CI) were calculated. Patients with and without VTE were compared with respect to baseline characteristics. Categorical data were compared using the chi-squared test or, with small sample size, Fisher’s exact test, continuous data using Student’s t-test for equality of means, or in case of an abnormal distribution by the Mann–Whitney U-test. A difference was considered significant at P < 0.05. Of the 242 consecutive patients who had knee arthroscopy, 104 patients entered the study. Reasons for exclusion were: age
1412 Letters to the Editor Table 1 Baseline demographic, operative and medication characteristics of the 69 study patients Age in years (mean ± SD) BMI (mean ± SD) Sex (n) (%) Male Female Ethnicity (n) (%) White Black Asian/pacific Mixed Side (n) (%) Left Right Anesthesia (n) (%) Spinal General Operation type (n) (%) Diagnostic Therapeutic Duration (min) (mean ± SD) Arthroscopy Tourniquet Preoperative blood pressure (mmHg, mean ± SD) Systolic Diastolic Aspirin (n) (%) NSAID (n) (%) Oral contraceptive* (n) (%)
38 ± 11 24 ± 3 46 (67) 23 (33) 58 (84) 3 (4) 3 (4) 5 (7) 26 (38) 43 (62) 37 (54) 32 (46) 17 (25) 52 (75) 28 ± 12 30 ± 13 128 ± 12 83 ± 9 0 (0.0) 4 (6.2) 3 (14)
BMI, body mass index; NSAID, non-steroidal anti-inflammatory drug; SD, standard deviation.
younger than 18 years (n ¼ 4); previous surgery (n ¼ 62); allergy to contrast medium (n ¼ 4); previous ipsilateral DVT (n ¼ 6); contralateral DVT within 3 months (n ¼ 4); anticoagulant therapy at the time of operation (n ¼ 2); and pregnancy at the time of operation (n ¼ 2). Fifty-four patients could not be scheduled for venography (inability to get informed consent or inability to be followed up). Of the 104 patients that entered the study, 35 patients could not be evaluated for the following reasons: withdrawal of consent (n ¼ 22); inaccessible veins (n ¼ 2); and inadequate venograms (n ¼ 11). One patient experienced a PE before venography according to the protocol was performed. Therefore, 68 venograms were evaluated and 69 patients were included for analysis of the primary outcome. The group of evaluated patients was not statistically different from the excluded patients regarding their characteristics at baseline and the details of the procedure. Baseline and operation characteristics of the 69 study patients are listed in Table 1. DVT was demonstrated by venography in three asymptomatic male patients (4.4%; 95% CI 0.9– 12.2%). Two patients had proximal and one had distal DVT. They had no period of immobilization prior to surgery. One patient, a 43-year-old woman who used oral contraceptives and had a body mass index of 29.1, had a symptomatic non-fatal PE confirmed by perfusion/ventilation scanning. Thus, the overall risk of VTE was 5.8% (95% CI 1.6–14.2%). Perioperative tourniquet cuff
pressure (350 mmHg) was always above systolic blood pressure. Operative characteristics did not differ for the groups with and without VTE. Only two patients were immobilized after the procedure, neither developed VTE. Our study reveals a rate of DVT and PE of 5.8% (95% CI 1.6–14.2%) after knee arthroscopy without the use of pharmacological thromboprophylaxis. Most of these patients were asymptomatic (4.4%), although two (2.9%) had proximal DVT and one patient developed a symptomatic non-fatal PE (1.4%). Our findings are in line with a recent review in which all studies concerning arthroscopic surgery of the knee were included [3]. The pooled overall estimate of the incidence of all VTE (symptomatic and asymptomatic), without the use of thromboprophylaxis, was 10.5% (95% CI: 8.2–13%). The rates regarding symptomatic and asymptomatic VTE were 4.9% (95% CI: 3.3–7%) and 5.8% (95% CI: 4.1–8%), respectively. Another recent study using an improved technique of complete compression ultrasound showed a similar relatively low incidence of symptomatic and asymptomatic VTE (0.9% and 5.1%) [2]. These findings are in contrast with a study in which venography was used as the diagnostic modality, which showed a surprisingly high incidence of DVT (17.9%, 95% CI: 12.7–24.3%), although mostly calf vein thrombosis [4]. Despite advances in ultrasonography for the detection of DVT in asymptomatic patients [5] and its proven sensitivity and specificity in symptomatic patients, venography remains the gold standard for the diagnosis of VTE. The discrepancy between the studies may be explained by differences in patientsÕ characteristics and in surgical procedures. In our study, 62 patients were excluded mainly because of previous major surgery of the ipsilateral leg. This was carried out to avoid the inclusion of patients with a previous thromboembolism in whom venographic assessment might not be reliable. Excluded patients were comparable with the patients that were included regarding baseline and arthroscopy characteristics. Thus, selection bias apparently remained limited to the mentioned exclusion criteria. Nevertheless, the incidence of DVT may have been underestimated, because a history of DVT is considered a risk factor for the development of VTE. In addition, the patients were relatively young (mean age 38 years) and the mean operation time (28 min) as well as tourniquet time (30 min) were short compared with other studies. The procedure yielded a relatively small trauma because we included a relatively high number of diagnostic procedures, possibly contributing to the observed low incidence rate of VTE. A limitation of this study is the small population size, which is due mainly to our strict inclusion and exclusion criteria. However, we find the incidence rate of 5.8% a reliable estimate as no selection bias could be detected between the included and excluded patients. The relatively small patient group that developed VTE did not differ in patient characteristics from the group that did not. Therefore it was not possible to determine a group at higher risk in the present study. 2006 International Society on Thrombosis and Haemostasis
Letters to the Editor 1413
In conclusion, in this group, representing the common population of knee arthroscopy patients without a history of VTE, VTE was demonstrated in 5.8% of patients with a rate of 1.4% symptomatic VTE. These findings are in line with current literature. The incidence of VTE after arthroscopy of the knee is low. As we could not identify a specific high-risk group for the development of VTE, it appears to be justified to withhold thromboprophylaxis after routine arthroscopy of the knee. References
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Conference on Antithrombotic and Thrombolytic Therapy. Chest 2004; 126: (Suppl. 3) 338S–400S. Hoppener MR, Ettema HB, Henny CP, Verheyen CC, Buller HB. Incidence of deep vein thrombosis after knee arthroscopy without thromboprophylaxis. Acta Orthop 2006; in press. Hoppener MR, Ettema HB, Kraaijenhagen RA, Verheyen CC, Henny PC. Day-care or short-stay surgery and venous thromboembolism. J Thromb Haemost 2003; 1: 863–5. Demers C, Marcoux S, Ginsberg JS, Laroche F, Cloutier R, Poulin J. Incidence of venographically proved deep vein thrombosis after knee arthroscopy. Arch Intern Med 1998; 158: 47–50. Schellong SM. Complete compression ultrasound for the diagnosis of venous thromboembolism. Curr Opin Pulm Med 2004; 5: 350–5.
1 Geerts WH, Pineo GF, Heit JA, Bergqvist D, Lassen MR, Colwell CW, Ray JG. Prevention of venous thromboembolism: the Seventh ACCP
b-Thalassemia intermedia and pregnancy: should we anticoagulate? A . H . N A S S A R , * I . M . U S T A * and A . M . T A H E R Departments of *Obstetrics and Gynecology and Internal Medicine, American University of Beirut Medical Center, Beirut, Lebanon
To cite this article: Nassar AH, Usta IM, Taher AM. b-Thalassemia intermedia and pregnancy: should we anticoagulate?. J Thromb Haemost 2006; 4: 1413–4.
There is now compelling evidence that thalassemia intermedia (TI) is a predisposing risk factor for thromboembolic events [1,2]. Our patient was a 30-year-old G6P4A1L3, a known case of TI (Table 1), who presented at 22 weeks and one day gestation with right thigh pain of a few days duration. A venous duplex scan revealed partial recanalization of the right common and superficial femoral veins with thrombosis of branches of the long saphenous veins bilaterally. During this pregnancy, she was maintained on a prophylactic dose of low-molecular weight heparin (LMWH). Laboratory studies revealed hemoglobin (Hb) ¼ 7 g dL)1, platelets ¼ 1 071 000 lL)1 with normal connective tissue studies. A thrombophilia profile was negative for factor V Leiden (FVL) and prothrombin mutations, heterozygote for MTHFR mutation with normal Protein C, Protein S, and antithrombin III levels. No evidence of dysfibrinogenemia was found. Prior to pregnancy, she was investigated for her poor obstetrical history with negative lupus anticoagulant and anticardiolipin antibodies. Hb electrophoresis revealed an elevated HbF (49.2%). The patient was transfused with packed red blood cells (RBCs) and discharged on therapeutic LMWH, baby aspirin, and high-dose folic acid Correspondence: A. H. Nassar, Department of Obstetrics and Gynecology, American University of Beirut Medical Center, PO Box 113-6044/B36, Beirut, Lebanon. Tel.: +961 1 350000; fax: +961 1 370829; e-mail:
[email protected] Received 20 December 2005, accepted 13 February 2006 2006 International Society on Thrombosis and Haemostasis
to present at 26 weeksÕ gestation with profuse vaginal bleeding. A Cesarean delivery was performed for suspected placental abruption and a live male infant was delivered who died of prematurity-related complications. The risk of thrombosis associated with TI might reach as high as 29% [3], especially in splenectomized and nontransfused patients [1]. Splenectomized patients are at a particularly increased risk of thrombosis, partly due to the procoagulant activity of damaged circulating RBCs as it is thought that RBC remnants expose negatively charged phosphatidyl-serine through the ÔFlip-FlopÕ phenomenon and subsequently initiate thrombosis [2]. It has been suggested that TI patients receiving regular transfusions have a lower incidence of thromboembolic events compared with those not Table 1 Characteristics of our patient Description Transfusions Splenectomy Molecular studies Family history of thrombosis Obstetrical history
Not transfused prior to pregnancy At age of 8 years b mutations: IVS I-6/CD39 a mutations: )a3.7/aa3.7 Negative Postpartum left ileo-femoral deep vein thrombosis 5 years ago Intrauterine fetal death (severe pre-eclampsia and abruption) Spontaneous early second trimester abortion Two intrauterine growth-restricted fetuses
