Sustained Absence of Perfusion to the Brain Must Be Ensured During Thoracoabdominal Normothermic Regional Perfusion

We have read with interest the “Consensus Statement: Technical Standards for Thoracoabdominal Normothermic Regional Perfusion,” and applaud Hoffman et al1 for providing detailed guidance for the conduction of thoracoabdominal normothermic regional perfusion (TA-NRP) in donation after the circulatory determination of death (DCDD). However, we draw attention on 2 specific aspects of the guidance that may require reformulation. Our concerns relate to the most important limitation to the expansion of normothermic regional perfusion (NRP)—its consistency with the dead donor rule. The unified concept of death reconciles NRP with the diagnosis of death in the donor but requires the sustained absence of perfusion to the brain.2 Conceptually and in practice, this must be accomplished. Hoffman et al1 provide different options for excluding the brain during TA-NRP that are displayed in Figure 1 of their article. However, we only deem options 1a and 1b ethically appropriate since options 1c and 1d do not incorporate measures to deviate any potential collateral circulation from the brain. Manara et al3 were the first to warn that the simple clamping or ligation of the supra-aortic arch vessels might not be sufficient to exclude the brain during TA-NRP. In a series of 3 TA-NRP cases, where the arch vessels were clamped and the cephalad ends either vented to the atmosphere or drained to negative pressure, these authors described continuous flow from the cephalad ends, suggesting diversion of collateral flow from the brain. Although the estimated flow (up to 50 mL/min) was likely insufficient to support neuronal activity, their observation inspired the Spanish protocol for the practice of TA-NRP. According to our national standard, the supra-aortic arch vessels must be clamped and then cut and vented to the atmosphere.4 The flow from the vented vessels is then aspirated from the surgical field and returned to the NRP circuit. When applying this specific technique, we were able to confirm the absence of brain perfusion by the invasive monitoring of the intracranial blood pressure in 2 TA-NRP procedures.5 The authors also state that there is no evidence that adjunctive cerebral monitoring is needed during TA-NRP.1 To the contrary, we strongly recommend that neuromonitoring is incorporated into any TA-NRP protocol. This is the case in Spain where multimodal neuromonitoring is mandatory, to gain evidence of the appropriate isolation of the brain by the application of the above-mentioned technical procedures and to identify any potential technical error that would lead to immediately halting the procedure.4 In practice, when TA-NRP is used, DCDD donors are monitored with bispectral index and transcranial Doppler ultrasound, which can be replaced by intracranial arterial pressure monitoring in centers conducting the previously mentioned research project.5 NRP is a groundbreaking preservation strategy, but it must be applied based on an ethically robust protocol that includes the 2 elements that we have highlighted in this correspondence—deviation of collateral circulation from the brain and neuromonitoring. This is fundamental for the safe expansion of this technically complex in situ preservation strategy able to increase organ utilization and achieve optimal posttransplant outcomes of DCDD organs.