Joeky Senders

79 Thromboprophylaxis after craniotomy Two case series, 9,10 one retrospective cohort study, 6 and one randomized clinical trial 11 evaluated the effect of prolonged thromboprophylaxis on VTE rate in HGG patients. In the case series and trial performed by Perry et al., thromboprophylaxis was started up to four weeks and continued up to 12 months after surgery. 10,11 The trial closed early because of expiration of study medication and was effectively underpowered to assess the safety and effectiveness of long-term thromboprophylaxis. Additionally, the trial did not directly compare short versus long-term prophylaxis because the control group received placebo instead of short-term prophylaxis. Robins et al. started anticoagulation on the first day of radiotherapy and continued up to 24 months after surgery. 9 Smith et al. administered LMWH during the period of hospitalization postoperatively and prolonged prophylaxis in high-risk patients only. 6 However, the latter study was also underpowered since it only included 25 patients who received prophylactic anticoagulation. Previous studies have already found an association between the therapeutic use of anticoagulation and the incidence of ICH among HGG patients; 31,33,34 however, this has not been demonstrated yet for the prophylactic use of anticoagulation as well as the duration of this treatment. Lastly, immobility 2-4,17,18 and high BMI score 15 have already been identified as predictors of VTE in HGG patients. Several limitations of the current study should be mentioned. Patients were not randomized to a prophylactic regimen. The duration of thromboprophylaxis was, however, dependent on the timing of surgery and the surgeon’s preference. Retrospectively dividing the cohort based on prophylactic regimen can therefore introduce confounding by indication, and this can be a reason for the significant differences in baseline characteristics between the two groups (Table 1). We tried to reduce confounding by including all potential risk factors (p<0.20) in the multivariable regression analysis; however, confounders that have not been measured could still influence the results. Due to a low number of events our study can be underpowered, especially for the occurrence of VTE within 21 days after surgery and ICH (all < 5 events per variable in the multivariable analysis). Despite the low number of events, an association with the occurrence of ICH can still be observed, and the absolute VTE rates do not suggest a thromboprophylactic effect of continuing LMWH administration post-discharge. Since all ICHs occurred within 10 days after surgery, it is questionable whether prolongation of thromboprophylaxis is responsible for all these events. Classification into prophylactic subgroups was based on the neurosurgeon performing the operation and the intention-to-treat as described in the postoperative orders; however, some minor degree of discrepancy between these orders and the actual postoperative management cannot be excluded. Lastly, VTEs can be missed if they were asymptomatic or diagnosed in other hospitals and not corresponded back to our