eComment. Perfusion strategies in type A acute aortic dissection

This interesting paper raises many questions that could not be answered only by experience of the surgeon and of the anaesthesiologist [1]. It does not describe the modality of selective antegrade cerebral perfusion (SACP), and in particular, the pressures and pH strategies during SACP. This is a very important issue as we know that some degree of auto-regulation is lost at temperatures (<18°C) as low as that used by these Authors. This phenomenon may increase the cerebral vessel pressure and potentially cause excess perfusion and neurological damage by overflow [2]. During hypothermic circulatory arrest, direct cerebral perfusion was used in 55.3% with central cannulation and in 45.8% with femoral cannulation. We do not know the reasons for this choice in the non-SACP-perfused group. Regardless of the arterial inflow method, we believe, as do many other Authors, that if a supra-aortic vessel is not to be perfused during SACP, it should be clamped to prevent steal and subsequent neurological injury [2]. This technical aspect has not been described in this paper. There is no mention of the occurrence of visceral malperfusion, which is a major complication in these patients [3, 4]. The site of cannulation may not only affect neurological outcome but may also cause malperfusion of visceral arteries and retrograde emboli to the kidneys [3]. This event, along with a longer bypass time could be the cause of the borderline significant difference in the need for dialysis in the ICU with 40% in the femoral artery group compared with 28% in the central cannulation group (P = 0.073). The dialysis figures are quite high. Another very important issue is the evolving pattern during extracorporeal circulation. It is mandatory to keep checking the blood flow status both by transoesophageal echocardiography (TOE) [5] and by near infrared spectrography (NIRS). This has to be done also at the end of repair in order to diagnose any residual false lumen. All these tips could help in decreasing complications during surgery of AADA and achieve clear conclusions about the choice of cannulation site. Conflict of interest: none declared.