Critically ill patients with respiratory failure on mechanical ventilation may have prolonged unconsciousness days to weeks following sedation withdrawal yet still achieve functional neurological recovery. This prolonged recovery cannot be attributed solely to the kinetics of drug elimination, even when accounting for delays due to concurrent metabolic derangements. In a series of over 1200 critically ill COVID patients, the time to recovery of consciousness (RoC) was correlated with the degree of hypoxaemia, even among patients without evidence of structural brain injury A similar phenomenon has also been observed in a small cohort of comatose patients suffering from out-of-hospital anoxic cardiac arrest. It has been hypothesised that a shared neuroprotective mechanism underlies both phenomena. The case report presented here offers evidence in favour of this hypothesis.
The post-arrest patients who achieved independent outcomes after prolonged unresponsiveness exhibited burst-suppression on electroencephalography (EEG), and an increasing intra-burst theta (~4-7 Hz) peak frequency over time. RoC occurred long after EEG activity was slowly restored, and patients ultimately achieved functionally independent neurologic recovery. Here we provide evidence that links only brief hypoxaemic insults to similarly prolonged unresponsiveness but with good late behavioural recovery, and documents similar EEG features.
We present a patient recovering from COVID critical illness who experienced two short (i.e., two- and six-minute) witnessed cardiac arrests while on mechanical ventilation. Continuous EEG monitoring for 26 days revealed similar features to recordings in the aforementioned patients with out-of-hospital arrests: specifically, the emergence of a similar intra-burst theta range activity. These features followed GABA-mediated sedation, instituted after the two cardiac arrests. A prolonged period of unresponsiveness (44 days following sedation withdrawal) ensued, far outlasting conservative estimates of sedation washout times before the recovery of a conversant conscious state.