Effects of nitrous oxide on memory for instructions in dental patients

Abstract

Outpatients attending for conservative dental treatment were presented with eight instructions which they were asked to remember. The instructions were either written or spoken, and were in a positive or negative form. Patients treated with nitrous oxide remembered fewer instructions than those treated with local analgesia alone, and this effect of nitrous oxide was particularly marked for written instructions. Patients receiving local analgesia alone were more likely to remember positive than negative instructions in their original syntactical form, but this bias was not evident in the nitrous oxide group. In a second experiment both normal and dentally phobic patients were read dental and general instructions both before and during inhalation of 30 per cent nitrous oxide. Both groups showed a nitrous oxide-induced reduction in partially recalled instructions. There was interesting evidence for a different attentional bias in our two patient groups. The normal group remembered more general than dental instructions, whereas the phobic group showed the opposite pattern, yielding a significant patient group x type of instruction interaction.KEY woms-Nitrous oxide, memory, attention, syntax, cognitive bias. INTRODUCTIONThere have been several reports of impairments in memory for lists of digits and nouns following inhalation of 30 per cent nitrous oxide (Steinberg, 1954;Kortilla et a/., 1981), the impairments being in acquisition (Steinberg and Summerfield, 1957;Block et al., 1988;Mewaldt et al., 1988). Impairments are not restricted to artificial material, but have also been found in recognition of faces (Norton et al., 1984) and memory for dental events (File et al., 1991).Task difficulty seems to determine whether or not memory impairments are detected after nitrous oxide. Thus. no impairments were found in an easy recall task (Norton et al., 1984) or in a recognition task made easier by repetitions (Block et al., 1988). The purpose of Experiment 1 was to investigate whether clinically used concentrations of nitrous oxide reduced memory for dental instructions and if any such reduction was dependent on the syntax of the instructions and whether they were written or spoken. Mehler (1963) found better recall of active, affirmative instructions than of passive or negative ones, and File and Jew (1973) also found * Author to whom correspondence should be addressed.better recall of airline safety instructions when these were positive, rather than negative, and when passengers heard them rather than read them.In Experiment 2 we investigated whether there was an interaction between the effects of nitrous oxide and the patient group. In Experiment 1 and the File et al. (1992) study the patients receiving nitrous oxide were dental phobics and their memory was compared with a control group receiving similar dental treatment under local analgesia alone. In Experiment 2 we therefore examined the effects of nitrous oxide on memory for instructions in a group of normal and a group of dentally phobic patients. There is some evi...

The subjective, behavioral and cognitive effects of subanesthetic concentrations of isoflurane and nitrous oxide in healthy volunteers

“…These results are somewhat consistent with other studies which have also documented the amnestic properties of these agents (Adam 1973;Dwyer et al 1992;File et al 1992). However, in the Dwyer et al (1992) study, isoflurane impaired memory to a greater extent than did NaO (at equianesthetic concentrations).…”

“…There appear to be some differences in how subjects react to N20, with some subjects reporting liking the effects and other subjects, within the same study and using the same procedures, reporting the effects to be unpleasant (Steinberg 1956;Rosenberg 1974;Timsit-Bertheier et al 1987;Dohrn et al 1992). In terms of the psychomotor/cognitive effects of N20, extended inhalation of concentrations of 15% and higher impairs such functions as reaction time, eye-hand coordination, divided attention, and memory (Jarvis et al 1970;Trieger et al 1971 ;Korttila et al 1981;Dohrn et al 1992;File et al 1992;Tiplady et al 1992).…”

Cognitive properties of sedation agents: comparison of the effects of nitrous oxide and midazolam on memory and mood

“…[4][5] In clinical groups, it has also been shown that nitrous oxide administration impairs the recall of written instructions given to dental patients. 6 However, the effects of this compound appear to be more widespread and diffuse than those of the benzodiazepines, as it may act through a mechanism that does not involve direct binding to receptor sites. 7 It might thus be expected that the behavioural and functional effects of nitrous oxide and midazolam would differ.…”

Contrasting effects of midazolam and nitrous oxide on memory and cognitive bias in dentally phobic patients

“…It is possible that the 'remembering' component is more open to the conscious process of cognitive avoidance than the 'knowing' component. Anterograde amnesia with midazolam is well documented in normal volunteers, dental and medical patients (Curran and Birch, 1991;File et al, 1992;Birch and Curran, 1990) and in this experiment was clearly demonstrated for both superficial and deeper levels of coding. Curran er af.…”

“…No bias was found in anxious patients using a recognition memory test (Mogg et al 1987(Mogg et al , 1989, and in dentally phobic patients using recall of instructions. However, non-phobic dental patients did show significant cognitive avoidance of dental instructions (File et a)., 1992). It is possible that in anxious patients the two processes of an attentional bias rowarcis threat-related items and a conscious avoidance strategy lead to no overall bias when the task involves memory.…”