Post-operative
Post-operative measures for Witness patients consists of standard post-operative cardiac care with additional considerations. From the literature, avoidance of hypertension and the maintenance of normothermia is key, as is the use of paediatric or low-volume blood bottles for sample collection26,52. Further to this, as can be expected, it is also important to continue the delivery of adjuncts such as IV iron and desmopressin as necessary to patients26,52. Tanaka et al. additionally suggests that Witness patients can be given haemodynamic support for longer in order to maximise systemic oxygen delivery26. Mechanical ventilation is one such example of these measures, however, it has been noted in the literature that this is not a measure untaken by all clinicians, as no difference was found in ventilation times in seven comparative studies between Witnesses vs controls2,44,47-51 (Table 2).
Six of the 11 comparative studies in table 2 which reported the outcome of blood loss did so differently, making direct comparison difficult2,20,47,49-51. However, within the studies themselves, two found that the Witness group experienced significantly less postoperative blood loss compared to the non-Witness control (Witness vs non-Witness: 466.8 vs 843ml, p=0.000144; 312±141 vs 721±619ml, p<0.0549). This may be explained by more careful surgery and the blood conserving strategies discussed in the studies. Binder et al. investigated different transcatheter aortic valve replacement (TAVR) techniques and concluded the use of transfemoral TAVR decreased blood loss when no transfusions were given42. Taken together, the results suggest that Witnesses do not have more postoperative blood loss than non-Witnesses, and may even have better outcomes due to strategies employed.