The experience of complete neuromuscular blockade in awake humans

To describe the subjective experience and the physiologic effects of endotracheal intubation and complete neuromuscular block in unsedated humans.

Metropolitan V.A. Hospital.

4 healthy, unsedated volunteers.

Subjects' tracheas were intubated using topical anesthesia, then subjects were completely paralyzed with vecuronium and mechanically ventilated at various end-tidal partial pressure of carbon dioxide (PETCO2) levels, all without sedation.

Heart rate (HR), blood pressure, oxygen saturation by pulse oximeter (SpO2), and PETCO2 were measured. Subjects' verbatim descriptions of their experiences and answers to systematic questions were recorded after the experiments. All subjects reported that tracheal intubation was a very unpleasant experience. None of the subjects found paralysis itself to be distressing, and it did not affect mentation. Subjects felt breathless when PETCO2 was even slightly elevated. HR was increased by intubation, but not by paralysis. All subjects reported sore throat, muscle aches, fever, and fatigue lasting up to 24 hours after the experiment. One subject experienced nausea and vomiting. Another subject experienced a sore throat that persisted for weeks due to a vocal cord ulcer, which resolved spontaneously. All subjects' SpO2 levels after the experiment were below their pre-experiment baselines.

Our findings suggest that paralysis of healthy, knowledgeable, and psychologically well-prepared subjects for experimental purposes is feasible but may result in unpleasant, self-limiting after effects. Further, we conclude that, in any case of awake paralysis, close attention should be paid to arterial PCO2, adequate sedation and analgesia, minimization of pain during procedures, psychological support, and maintenance of communication when possible.