Non-Heart-Beating Organ Donation in Patients with Amyotrophic Lateral Sclerosis: Why Is General Anaesthesia Necessary?

To the Editor:

Smith and colleagues reported controlled non-heart-beating (NHB) organ donation from two patients with amyotrophic lateral sclerosis (ALS). ¹ They alluded to the challenges of titrating medication to relieve distress in anticipation of terminal withdrawal of life support and multi-organ procurement in ALS patients. We elaborate on (1) the method to assess distress and (2) the medication to alleviate this distress.

The neural pathways and interrelationship of the two components of consciousness– (1) level of consciousness (i.e., wakefulness) and (2) content of consciousness (i.e., subjective awareness)– are poorly characterized. ² Experimental evidence suggests that subjective awareness of external and internal sensory stimuli may be independent of wakefulness. ² Furthermore, electroencephalography (EEG) can detect awareness that may not be discernible from bedside clinical examination. ³ ALS is a neurodegenerative disease of the peripheral and central motor nervous system. ALS donors generally have normal peripheral and central sensory nervous system and intact higher brain structures. Higher brain structures can retain their neural reactivity for several minutes after circulatory arrest and can be detected by electric surges on EEG. ⁴ Non-heart-beating donors with catastrophic brain injuries also display acute surges on EEG. ⁵

In NHB protocols, death is declared after two to five minutes of circulatory arrest. ⁶ Interventions for in-situ organ preservation include but are not limited to (1) administration of heparin for systemic anticoagulation prior to circulatory arrest, (2) resumption of artificial circulation with extracorporeal cardiopulmonary bypass (i.e., heart-lung machine); and (3) in-situ exchange-transfusion with hypothermic preservative fluids after circulatory arrest.^6,7 These perimortem interventions also preserve brain viability after circulatory arrest. Since the duration of circulatory arrest is not long enough for the central and peripheral neural pathways to cease functioning irreversibly, nociception and awareness in donors becomes a real concern. ⁸ Weakness and paralysis in ALS donors can conceal motor signs of distress. We and others have urged that NHB donors should be routinely monitored with continuous EEG.^5,8

Auyong and colleagues ⁵ have demonstrated that administering benzodiazepines and opioids may be inadequate to mitigate distress in donors. Additional administration of intravenous and inhalational anaesthetic medication have been advocated.^5,9 The titration of anaesthetic medication without EEG monitoring is difficult in the operating room, since bedside assessment of distress can be unreliable.

In conclusion, we urge the use of EEG monitoring and appropriate titration of anaesthetic medication and opioids to ensure optimal relief of distress in ALS donors.