TABLE 1.

Summary of anesthesia-related criticality literature.

Study	Study population	Modality	Analysis	Main findings
Alonso et al., 2014	3 adult subjects with intractable epilepsy undergoing surgical removal of an epileptic focus	ECoG under propofol anesthesia	Vector auto-regressive (VAR) model; critical eigenvalues	• Eigenvalues of VAR matrices change significantly as anesthesia is induced. This finding is robust to changes in how data is normalized and could be used as a metric for depth of anesthesia. • As anesthesia is induced, high frequency modes are damped, suggesting that cognitive processes associated with higher frequencies are being tuned out while lower frequency processes are associated with maintaining the patient alive during anesthesia. • Self-organized criticality (SOC) could be result of synaptic adaptation. Disrupting synaptic adaptation should lead to loss of SOC.
Liu et al., 2014	8 healthy adults receiving propofol infusion; 5 adults with unresponsive wakefulness syndrome (UWS)	fMRI	Power-law estimation	• Node degree distribution was power-law distributed for healthy participants throughout all phases of anesthesia, but was never power-law distributed for patients with UWS, regardless of spatial scale. Node size distribution was power-law distributed for both. Study did not meet (Clauset et al., 2009)criteria for power law. • Criticality would not be needed for wakefulness alone but would underlie the brain’s ability to recover from anesthesia or deep sleep. Future research should investigate whether power laws or other markers of SOC are helpful predictors of recovery from coma or other minimally conscious states
Thiery et al., 2018	7 adults receiving sevoflurane anesthesia	EEG	DFA	• Unconsciousness under sevoflurane was associated with increases in LRTC in beta amplitude over frontocentral channels and decrease in alpha amplitude over occipito-parietal channels. • LRTC and oscillation amplitude may reflect different properties of the brain that are impacted during anesthesia.

ECoG, electrocorticogram; fMRI, functional magnetic resonance imaging; EEG, electroencephalogram.