Authors: Pandit JJ
Anesthesia & Analgesia. September 05, 2025. doi: 10.1213/ANE.0000000000007722
This perspective connects findings from NAP5 and decades of isolated forearm technique (IFT) research to a unifying neurophysiology: the efference copy / reafference network. NAP5 showed AAGA is concentrated in cases using neuromuscular blockade (NMB) and that paralysis—not pain—is the dominant driver of psychological trauma. IFT consistently demonstrates that under light anesthesia with partial/“regional” paralysis, patients typically do not move spontaneously to surgical stimulus yet can move to verbal command, whereas under similarly light anesthesia without NMB, patients may show spontaneous movements to stimulus but do not obey verbal commands.
Pandit argues these patterns are best explained if NMB heightens cortical arousal by creating a mismatch between intended motor output (efference copy) and absent reafferent feedback (because movement is blocked). With full NMB at light planes, this mismatch can escalate arousal toward awareness and distress (AAGA). With no NMB, small movements “satisfy” the loop and blunt arousal. In IFT, the ability to respond to command via an isolated, unparalyzed forearm provides just enough reafference to prevent escalating arousal, even at light planes. The article contends that NMB intensity and anesthetic depth interact to shape arousal; depth mitigates NMB-induced arousal, while NMB shifts the system toward awareness risk if hypnosis/analgesia are inadequate.
What You Should Know
• NAP5: AAGA risk and psychological trauma are overwhelmingly linked to use of NMB.
• IFT shows a dissociation: with NMB (isolated forearm free), patients can follow commands; without NMB, patients may move to stimulus but not to command.
• Pandit frames this via efference copy: blocked movement under NMB creates a reafferent mismatch that drives cortical arousal.
• Depth monitors (e.g., processed EEG) can mislead; movement patterns under NMB vs no NMB carry different implications for arousal/awareness risk.
• The piece invites rethinking MAC-centric interpretations at light planes: identical anesthetic concentrations can yield divergent behaviors depending on NMB.
Practice Implication
Maintain adequate hypnosis/analgesia before intensifying NMB when movement occurs; be cautious interpreting “no movement” under deep NMB as safety. During cases using NMB, pair depth-of-anesthesia assessment with active strategies (e.g., structured verbal checks when appropriate contexts allow, careful hemodynamic and anesthetic titration) to reduce AAGA risk and avoid relying on paralysis to mask inadequate anesthesia.
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