Yoeri Bemelmans

Tranexamic acid in hip and knee arthroplasty 39 3 When looking closely to the pharmacokinetics and pharmacodynamics of TXA, oral uptake is rapid, which makes oral TXA eligible. Bioavailability of TXA is approximately 45% in a healthy population, therefore a preoperative high dose of oral TXA can be considered to maximise the intraoperative blood sparing effect. T-max of TXA was estimated to be around 3 hours, inwhich the oral dosewould almost bemaximumat time of incision. Equal timeframe is stated for the elimination half-life of TXA. Therefore, the IV administration at the end of the surgery provides coverage for the first postoperative hours. These first 4 hours postoperative were stated by Jung et al. [16] to bemost crucial in postoperative blood loss after knee arthroplasty. A topical dose was not considered due to the use of local infiltration analgesia in TKA patients. Thereby, an addition of TXA would result in a high fluid volume which would be infiltrated in the surrounding knee tissue. Various IV doses are used, with similar blood transfusion results [21,27,29,30]. Doses above 20mg/kg are considered to be a ‘high dose’. Thus, in the presented study, a low dose oral and IV TXA was used which led to low blood transfusion rates. These results are in line with previous studies and would support a low dose TXA usage to prevent for drug side effects [11]. The BT group consisted of significant more females. Other studies report female gender to be a risk factor for perioperative blood transfusion [12,25]. The exact mechanism remains unclear, but several hypotheses (e.g. lower preoperative haematocrit level and smaller body habitus) exists [23]. BT patients were significantly older and had a higher ASA classification, in line with previous findings [12,23]. This could be explained by the fact that in this group, blood transfusion was consideredmore often due to comorbidity status. On the other hand, the decision for blood transfusion was not only based on ASA classification, but also strongly dependent on postoperative Hb levels and the clinical well-being of the patient. Since different thresholds for Hb levels were used, the transfusion rate could be biased. Nevertheless, BT patients had significant lower Hb levels preoperatively which can be seen as a risk factor for transfusion. Basora et al.[4] reported similar results regarding preoperative Hb level (7.7 mmol/L) and ASA classification (III-IV) in transfused TKA patients. A cut-off value for preoperative optimisation was not given, but based on these and our results, preoperative Hb level seems to play a role in postoperative blood transfusion and should therefore be monitored preoperatively which was also found by other studies [4,25]. Unsurprisingly the BT group consisted of more THA patients, since blood loss in THA is higher and therefore significant higher risk for blood transfusion [23,24].