Hypnotic analgesia: a constructivist framework.

Hypnotic analgesia remains an enigma. Recent neuroscience studies demonstrate that widespread distributed processing occurs in the brains of individuals experiencing pain. Emerging research and theory on the mechanisms of consciousness, along with this evidence, suggest that a constructivist framework may facilitate both pain research and the study of hypnosis. The authors propose that the brain constructs elements of pain experience (pain schemata) and embeds them in ongoing consciousness. The contents of immediate consciousness feed back to nonconscious, parallel distributed processes to help shape the character of future moments of consciousness. Hypnotic suggestion may interact with such processing through feedback mechanisms that prime associations and memories and thus shape the formation of future experience.

Evoked potentials as correlates of pain and pain relief in man.

This contribution reviews the practical applications of evoked potentials (EPs) in the evaluation of experimental studies on analgesic intervention in humans. It is also intended as an introduction to EP methodology, its possibilities, and its limitations, for all fellow researchers working in other fields.

New directions in the understanding and management of pain.

Control of pain and the suffering that it causes still eludes us. Despite impressive progress in the prevention and cure of disease and in care of the trauma victim, pain is still a frontier in medical research. It accompanies surgery, various diagnostic procedures and dental care as well as acute injury and disease. For a significant number of patients it persists after injury or illness into a chronic state. Chronic pain is recognized to be the most frequent cause of disability in the United States and many industrialized nations today, and is a major cost to society in both work hours lost and medical expenses. In addition to its social importance, pain is an intimate cause of personal concern for every human being throughout life. The progress, or lack of progress, achieved by medical research in pain control is of interest to us all. Pain disorders may be usefully classified in two categories: acute and chronic. The etiology, physiopathology, symptomatology, diagnosis and therapy of these two types of pain are quite different and require separate consideration. Acute pain is that which arises from an acute injury or disease process and persists only as long as the tissue pathology itself. If acute pain problems are not effectively treated, they may progress to chronic states. Chronic pain is that: (1) associated with chronic tissue pathology; or (2) which persists beyond the normal healing period for an acute injury or disease. There are unique challenges for health care providers associated with each of these two categories of problems, and failure to distinguish between these types of pain has led to a widespread, ongoing mismanagement of patients that can be prevented if strong efforts are made to better educate health care professionals about pain and its therapy. This paper presents an overview of current understanding about the nature of pain and its management. The physiology and psychology of pain are reviewed against a background of the concepts and information taught 25 years ago. Some common acute and chronic pain problems are reviewed and discussed. Finally, several new directions in pain control are described.

Effects of nitrous oxide, transcutaneous electrical stimulation, and their combination on brain potentials elicited by painful stimulation.

Combinations of transcutaneous electrical stimulation (TES) and inhalation of nitrous oxide with oxygen have been used for surgical pain control and this report explored the possible synergism of these two treatments. During painful dental stimulation, 18 subjects gave pain reports while event-related potentials were recorded at vertex. Electrical stimulation was delivered bilaterally at the LI-4 acupuncture points on the hands at 20 Hz, mean = 9.65 mA intensity. Inhalation treatment was nitrous oxide 33% with oxygen. Testing was done on two days to permit evaluation of each treatment alone and their combination. Treatment sequence was counterbalanced. Base-to-peak amplitude and peak latency scores were derived for the event-related potentials under each testing condition. Both stimulation and inhalation treatments altered event-related potential scores and pain report. The combination treatment was significantly more effective than stimulation alone but was not significantly more effective than nitrous oxide alone. Nitrous oxide with oxygen alone reduced peak amplitude at 250 ms and 350 ms, as well as pain report. It increased peak latency at 100 ms. Transcutaneous electrical stimulation alone decreased peak amplitude and latency at 150 ms and increased peak latency at 350 ms. Decreased peak amplitude at 250 ms and increased peak latency at 150 ms were observed when inhalation was added to stimulation, and there was also a significant reduction in pain report. Nine control subjects were studied to demonstrate that analgesic changes were not due to repeated testing. These outcomes demonstrated no synergism between the stimulation and inhalation treatments. The data suggest that nitrous oxide blocks the effects of electrical stimulation at LI-4.

Varying electrical acupuncture stimulation intensity: effects on dental pain-evoked potentials.

Electrical acupunctural stimulation (EAS) has repeatedly been shown in the laboratory to diminish human dental pain perception. This study compared the effects of low, medium, and high EAS levels on event-related potentials elicited by painful dental stimulation and on subjective pain report. Acupuncture was performed bilaterally at LI-4 on the hands, and each subject received all EAS levels, counterbalanced for order. Only the highest level of EAS was effective, and it reduced the pain report in addition to the amplitudes of the positive event-related potential deflections from base line at 100 and 250 msec. No dose-response effect was observed for EAS levels. The outcome suggests that the analgesic effect occurs abruptly when stimulation reaches a strong level and a subnoxious pounding sensation is elicited.

Effects of nitrous oxide inhalation on brain potentials evoked by auditory and noxious dental stimulation.

1. Effects of inhaling nitrous oxide in oxygen were observed in subjects undergoing noxious dental (N=10) or nonnoxious auditory (N=10) stimulation. Evoked potentials (EPs), 100-500 msec poststimulus, were recorded at vertex, and peak-to-peak amplitudes as well as peak latencies were quantified. 2. Both dental and auditory EPs were reduced by 33% nitrous oxide in oxygen concentration and a dose-related effect was seen in the auditory modality when the concentration was increased to 50%. 3. These observations demonstrate that nitrous oxide inhalation has a broad impact on neurophysiological function in addition to behaviorally determined analgesia.

[Modulation of experimental dental pain in man with acupuncture and by transcutaneous electric stimulation]. / Modulation de l'odontalgie expèrimentale chez l'homme par l'acupuncture et par la stimulation électrique transcutanée.

We have studied the effects of electrical acupuncture stimulation and transcutaneous electrical stimulation on the ability of human volunteers to perceive pain. Both psychophysical indices and measures of cerebral evoked responses to painful stimuli have been used to demonstrate that these treatments reduce pain perception. A recently completed study showed that the analgesic effects of transcutaneous electrical stimulation can be partly reversed when 0,4 mg of naloxone is injected. This observation suggests that endogenic morphine-like peptides are released in response to low frequency electrical stimulation of the skin.

Effects of intrasegmental electrical acupuncture on dental pain: evaluation by threshold estimation and sensory decision theory.

The effect of 80 min of low frequency (2 Hz) electric acupunctural stimulation at facial sites on the perception of induced dental pain was evaluated using both pain threshold and sensory decision theory (SDT) procedures. The demonstration of a 187% increase in threshold over a 20 min period of acupunctural stimulation replicated earlier work by Swedish investigators. SDT analyses indicated that the threshold increase reflected a relatively pure sensory change with no significant modification of response bias. However, subjects were able to perceive some of the stimuli presented below threshold level following acupuncture, thus indicating that the threshold concept has been an inadequate description of the phenomenon. This study demonstrated that intrasegmental analgesic stimulation is more efficacious than the extrasegmental meridian point stimulation used in our earlier studies. Possible mechanisms for the observed effect were discussed.

Acupuncture compared with 33 per cent nitrous oxide for dental analgesia: A sensory decision theory evaluation.

Responses to electrical stimulation of the tooth pulp were obtained in both baseline and test sessions for subjects receiving acupuncture, 33 per cent nitrous oxide, or control conditions. A signal-detection analysis across sessions showed that both treatment groups demonstrated reduced sensitivity to stimulation, and increases in bias against reporting strong stimuli as painful. (Key words: Acupuncture; Anesthetics, gases, nitrous oxide; Measurement techniques, sensory decision theory; Pain, sensory decision theory).