CI-581, a derivative of phencyclidine, is an effective analgesic and anesthetic at doses of 1.0 to 2.0 mg per kilogram. Given intravenously, it acts within one minute and lasts 5 to 10 minutes depending on dose and individual variation. Repeat doses did not produce tachyphylaxis. Respiratory depression was slight and transient. Undesirable effects included hypertension, tachycardia, and psychic changes. Recovery from analgesia and coma typically occurred within 10 minutes, though electroencephalographic evidence indicated subjects were not fully normal for 1 to 2 hours. No liver or kidney toxicity was observed. The drug's effects resemble those of phencyclidine but are shorter-lasting, and it is proposed that the term 'dissociative anesthetic' describe the mental state it produces.
Consciousness—subjective experience—persists during sleep and anesthesia, as evidenced by dreaming. A defining feature of dreaming is disconnection from the environment. Anesthesia aims to prevent the experience of surgery (connected consciousness) by inducing either unconsciousness or disconnection. The isolated forearm technique reveals that consciousness, connectedness, and responsiveness can uncouple during anesthesia; under clinical conditions, a median 37% of patients demonstrate connected consciousness. Potential neurobiological constructs explain this: during light anesthesia, subcortical mechanisms for spontaneous behavioral responsiveness are disabled, but information integration within the corticothalamic network continues producing consciousness, while unperturbed norepinephrinergic signaling maintains connectedness. These concepts emphasize the need for anesthetic regimens and depth-of-anesthesia monitors targeting mechanisms of consciousness, connectedness, and responsiveness.