Dreaming during anaesthesia in children: incidence, nature and associations

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1 doi: /j x Dreaming during anaesthesia in children: incidence, nature and associations G. H. Huang, 1 A. J. Davidson 2 and R. Stargatt 3 1 Research Assistant, Murdoch Children s Research Institute, 2 FANZCA GradDipBiostat, Consultant Anaesthetist, Department of Anaesthesia and Pain Management, 3 Clinical Neuropsychologist, Department of Psychology, Royal Children s Hospital, Flemington Road, Parkville, Victoria 3052, Australia Summary In previous studies, the incidence of dreaming during anaesthesia in children was reported to be between 9.7% and 19%. These limited studies were performed over 15 years ago using outmoded anaesthetic techniques. No recent studies have examined the nature of dreaming or its impact on children. In this prospective cohort study of 864 children, we determined the incidence, nature, predictors and behavioural consequences of children who reported dreaming during anaesthesia. Children aged 5 12 years who had undergone general anaesthesia were interviewed for dreaming on three occasions. Dreaming was reported by 10.4% of children. The content of the dreams was mostly pleasant and unrelated to their hospital experiences. Dreaming was more common in younger children and in children who had also experienced awareness during anaesthesia. No association was found between dreaming and the anaesthetic drugs used. Dreaming was not associated with an increased risk of behavioural disturbances postoperatively. Anaesthetists should be reassured that dreaming is a common occurrence that does not appear to distress children.... Correspondence to: Andrew J. Davidson andrew.davidson@rch.org.au Accepted: 1 April 2005 Dreaming during sleep can be defined as a subjective experience that is solely accessible by the dreamer s recollection after awakening [1]. Although anaesthesia and sleep are different, a similar definition can be used for dreaming during anaesthesia. A dream during anaesthesia has been defined as any experience (excluding awareness) which a patient thought occurred between the induction of anaesthesia and the first moment of consciousness after anaesthesia [2]. Little is known about the nature and associations of intra-operative dreaming in children. The reported incidence of dreaming during anaesthesia in adults ranges from 1% to 44% [3 9]. In children the incidence varies between 9.7% and 19% [2, 10, 11]. Factors associated with increased dreaming during anaesthesia in adults have been reported. Dreaming is more frequently reported by women [9, 12] and in adults who receive propofol [13 15]. The effect of particular anaesthetic drugs on the incidence of dreaming during anaesthesia in children is less certain. Some studies have reported a greater incidence of dreaming in children who received a depolarising neuromuscular blocking agent [2, 10]. In adults, Hellwagner et al. [8] found that dreaming during anaesthesia did not influence patient satisfaction or anxiety after anaesthesia. In contrast, Leslie et al. [12] found dreamers to be more anxious and less satisfied with hospital care. In children the impact of dreaming during anaesthesia on their behaviour is not known. The aim of this study was to determine the incidence of dreaming during anaesthesia in children, its impact on behaviour and possible predictors of dreaming. Methods This study reports data collected within a broader study investigating the incidence of awareness during anaesthesia and predictors of postoperative behavioural disturbances [16]. This paper only presents the dreaming data. With hospital ethics committee approval and written informed consent, children aged 5 12 years old having general anaesthesia at the Royal Children s Hospital, Melbourne, were enrolled. The exclusion criteria were parents who could not understand English, children with previously diagnosed developmental delay, an anaesthetic 854 Ó 2005 Blackwell Publishing Ltd

2 G. H. Huang et al. Æ Dreaming during child anaesthesia in the previous month and children undergoing cardiac surgery or surgery with intended ICU admission postoperatively. Participants were selected using a randomised method as previously described [16]. Participants were recruited from October 2002 to March Anaesthetists were aware of the study, but did not know which children had been enrolled until after the anaesthetic. The anaesthesia technician rated the child s behaviour at induction and the anaesthetist was asked to give details about the anaesthetic only after the child was in the postanaesthesia recovery unit. Children were asked about dreaming and awareness using a modification of the Brice interview [3]. The questions were: What was the last thing you remember before the operation? What is the next thing you remember after the operation? Did you have any dreams or feel or hear anything while you were having the operation? These questions were incorporated into a conversation with other questions (Table 1). The interviews were conducted on the day of their anaesthetic (or the next day if the interview was not possible on the first day) by a trained research assistant, and at 3 and 30 days after anaesthesia by the child s parents. Parents were instructed to ask the set of questions and write their child s answer verbatim. Details about dreaming and awareness were recorded. For this study, dreaming was defined as any experience (excluding awareness) which a patient thought occurred between the induction of anaesthesia and the first moment of consciousness after anaesthesia [2]. Events that the child equated with a plausible real event were regarded as awareness (or possible awareness) rather than a dream. The child s behaviour was also assessed at baseline and at 3 and 30 days after anaesthesia. Behaviour change was Table 1 Post-anaesthesia questionnaire. Were you upset or worried or frightened about your operation? How upset worried frightened were you? What was the last thing you remember before the operation? How did the doctor make you go to sleep? What is the next thing you remember after the operation? Did you have any dreams or feel or hear anything while you were having the operation? Were you sore after the operation? How much did it hurt? What did you like best about having an operation? What did you like least about having an operation? Did someone talk to you about what the operation was going to be like? Was that about the same as what happened? How do you feel about the operation? Would you like to have known more? quantified using the Post-Hospitalisation Behaviour Questionnaire [17] (Appendix 1). Seven or more negative behaviour changes were regarded as having clinically significant behaviour disturbance. Other possible predictors or factors likely to be associated with dreaming were recorded. Parental and child anxiety were measured using the State-Trait Anxiety Inventory [18] and, at induction of anaesthesia, the Modified Yale Preoperative Anxiety Scale (mypas) [19]. Family demographics, child temperament, preoperative preparation, hospital admissions, anaesthetic data, medical history and pain scores were also recorded. The number of children enrolled was based on the desire to assess whether children were a high risk group for awareness [16]. Previous studies have suggested that the incidence of awareness in adults is approximately 0.15%. An exact binomial test, with a one-sided alpha of 0.05 showed that 750 children would be needed to give a power of 0.81 to detect an incidence greater than 0.75% (i.e. five times the incidence in adults). Some children aged between 3 and 5 years were also enrolled for assessment for behaviour change, but not for dreaming or awareness. It was expected that approximately 60% of all the children who were enrolled would be assessed for dreaming and awareness. Therefore 1250 children were enrolled. Data from the children aged between 3 and 5 years old is not included in any analysis in this paper. Analysis of the data was performed using the twosample Student t-test with equal variances for continuous data and Chi-squared tests for categorical data. Significant predictors of dreaming from the univariate analysis were entered into a multivariate logistic regression model. Behaviour change and dreaming were analysed using a multivariate logistic regression model. Age is known to be associated with behaviour change and was therefore entered into this model [20 22]. Data are presented as number (%), mean and standard deviation (SD). Results are expressed as an odds ratio (OR) with standard errors, 95% confidence intervals (95% CI) and p-values. All analysis was performed using STATA version 7.0 software (Stata Corporation, College Station, TX). Results Of the 1250 children enrolled in the wider cohort, 921 were eligible for the dreaming study. Of these, 57 were excluded from analysis: two had their procedures cancelled, two withdrew and 53 children could not be interviewed at any time. The remaining 864 children had at least one assessment of dreaming and were included in the analysis. Seven hundred and fifty-six children (88%) were interviewed within 1 day of the procedure, 704 (81%) at day 3 and 590 (68%) at day 30. The main reasons Ó 2005 Blackwell Publishing Ltd 855

3 G. H. Huang et al. Æ Dreaming during child anaesthesia Anaesthesia, 2005, 60, pages Table 2 Patient characteristics. Data are expressed as number (%) or mean (SD). Table 3 Anaesthetic data. Data are expressed as number (%) or mean (SD). Dreaming (n = 90) Non-dreaming (n = 774) Dreaming (n = 90) Non-dreaming (n = 774) Age; years* 7.7 (2.3) 8.7 (0.1) Sex; M : F 50 (56) : 40 (44) 443 (57) : 331 (43) ASA 1 67 (74) 569 (74) 2 19 (21) 156 (20) 3 4 (4) 48 (6) 4 0 (0) 1 (0.1) Duration of admission; days 1.5 (1.4) 1.5 (2.1) Hospital admission area Day surgery 69 (77) 602 (78) Pre-surgical Unit 14 (16) 105 (14) Emergency 1 (1) 10 (1) MRI scanner 1 (1) 6 (1) In-patient 5 (6) 51 (6) Temperament; easy difficult 30 (35) 56 (65) 231 (31) 522 (69) Behaviour, emotional, 19 (21) 71 (79) 123 (16) 640 (84) learning problems; Yes No Behaviour when seeing doctor No problems 67 (77) 627 (85) Occasional problems 18 (21) 102 (14) Frequent problems 2 (2) 10 (1) Previous admission; Yes No 56 (62) 34 (38) 548 (72) 215 (28) Previous anaesthetic; Yes No 51 (57) 39 (43) 489 (64) 274 (36) Preparation; Yes No No preparation 2 (2) 85 (98) 11 (1) 747 (99) Extended conversation** 41 (47) 46 (53) 443 (58) 315 (42) Role play** 7 (8) 80 (92) 27 (4) 731 (96) Read the book 6 (7) 81 (93) 44 (6) 714 (94) Time of preparation** More than a week ago 58 (66) 470 (62) Several days ago 12 (14) 192 (25) One day before admission 12 (14) 74 (10) On the day of admission 5 (6) 22 (3) Socio-economic status** 4.3 (1.1) 4.1 (1.0) Parental state anxiety 38.6 (12.6) 38.7 (12.6) Parental trait anxiety 36.9 (8.7) 34.4 (10.7) Child anxiety at induction 3.6 (0.4) 3.5 (0.4) Child anxiety judged by parent 2.8 (1.4) 2.9 (1.4) Postoperative pain 2.3 (1.3) 2.5 (1.3) The socio-economic status score is inversely proportional to prestige status. *p < 0.001, **p < 0.05, for dreaming vs. non-dreaming. for not completing an assessment of dreaming on the day of their anaesthetic were early discharge or the child being too distressed to undergo an interview. Dreaming on day 3 or 30 could not be assessed if questionnaires were not returned. Patient characteristics, anaesthetic details and types of procedures performed are shown in Tables 2 4. Ninety of the 864 children interviewed reported dreaming during anaesthesia. The incidence of dreaming was 10.4% (95% CI: %). Dreaming during anaesthesia was most frequently reported in the younger age group (age 5 7 years) (17.1% (95% CI: %)). The incidence decreased to 6.8% (95% CI: %) in children aged 7 9 years and 7.6% (95% CI: %) in Awareness; Yes No* 4 (4) 86 (96) 3 (0.4) 771 (99.6) Critical incidents 2 (2) 88 (98) 23 (3) 751 (97) Duration of procedure; min 40.0 (3.6) 42.9 (1.4) Sedative 19 (21) 71 (79) 117 (15) 657 (85) premedication; Yes No Induction agent; Yes No Propofol 46 (54) 39 (46) 388 (56) 306 (44) Sevoflurane 36 (46) 43 (54) 295 (45) 364 (55) Halothane 79 (100) 5 (0.8) 654 (99.2) Thiopentone 2 (2) 83 (98) 10 (1) 685 (99) Maintenance agent(s); Yes No Isoflurane 67 (83) 14 (17) 551 (86) 93 (14) Sevoflurane 8 (10) 73 (90) 49 (8) 595 (92) Halothane 9 (11) 72 (89) 65 (10) 579 (90) Nitrous Oxide 79 (93) 6 (7) 661 (95) 36 (5) Propofol 8 (9) 80 (91) 46 (6) 672 (94) Other drugs; Yes No Ketamine 2 (4) 46 (96) 14 (4) 325 (96) Opiates 36 (75) 12 (25) 253 (75) 86 (25) Midazolam 21 (44) 27 (56) 148 (44) 191 (56) Suxamethonium 1 (2) 47 (98) 2 (0.6) 337 (99.4) Neuromuscular 13 (14) 77 (86) 87 (11) 687 (89) blocking drugs Local blocks 37 (41) 53 (59) 324 (42) 450 (58) Use of propofol; Yes No 52 (58) 37 (42) 419 (57) 316 (43) *p < Table 4 Types of procedures. Data are expressed as number (%). Procedure Dreaming (n = 90) Non-dreaming (n = 774) Dental 8 (9) 35 (4) Dermatology 5 (6) 17 (2) ENT 24 (27) 160 (21) Gastroenterology 8 (9) 97 (13) General Surgery 20 (22) 167 (22) Gynaecology 1 (1) Neurosurgery 4 (<1) Oncology Haematology 4 (<1) Ophthalmology 4 (4) 49 (6) Orthopaedics 11 (12) 97 (13) Plastics 7 (8) 84 (11) Radiology 2 (2) 11 (1) Respiratory 3 (<1) Urology 29 (4) Other 17 (2) children aged 9 12 years. Children s recall of their dream decreased with time. Dreaming was reported by 8.1% of children on the day of their anaesthetic. Only 5.7% and 5.9%, respectively, of children recalled dreaming 3 and 30 days after anaesthesia. Some dreams were hospital-related but the majority of the dreams were unrelated to their hospital experience. 856 Ó 2005 Blackwell Publishing Ltd

4 G. H. Huang et al. Æ Dreaming during child anaesthesia Table 5 Content of dreams. Table 5 (Continued). Ages 5 7 Animals (24.5%) Black monster with six legs scaring me with a mask, saying giggle giggle*, Dream of butterflies Dream about a scary dinosaur Dream about spider on my back Dream about dinosaurs and cars Dream about teddy bears and toys Dream about Disneyland and Goofy Dream about a big ladybird Dream about a cat Dream that there were birds in the hospital and many animals came in* Self-representation (29%) Dream about going to sleep* Dream that I was falling into a hole Dream about going to Maccas with grandma Dream about zoids and I was driving the zoids Dream about saying hello to mummy Dream about if I was better* Dream of crying then I feel better* Dream that I was playing ball sports Dream about playing baseball In my dream, I saw my God talk to me and say you will get better* Dream about me going to hospital* Dream about mummy and me Characters (22%) Dream of queen and castle Dream of fairies, princes and angels Dream about family Dream about spy fox Dream about fairies Dream about Batman Dream about Batman in his car Dream about Wizard of Oz Dream about mum Others (24.5%) Dream that hospital was made of chocolate* Dream of chocolate Mars bar Dream about toy Dream about Playstation game Dream about Disneyland Dumb dream Bad dream Good dream Good dream Happy dream Ages 7 9 Animals (21%) Dream that a dragon came to eat my mum Dream about a pirate killing a pig Dream of a tortoise Self-representation (29%) Dream I was floating around Dream I was at school and there was a fire Dream I was going to Disneyland with my best friend Dream I was a fairy, went to a ball and was wearing a wonderful dress Characters (29%) Dream of brothers, sisters and next door neighbours Dream about an old teacher Dream that I saw mum and dad while sleeping Dream of Lord Mayor who gave her some money because she was poor and she paid the bills and had a good life Others (21%) Dream of Brisbane Nice dream Bad dream Ages 9 12 Animals (5%) Dream about fish on wall Self-representation (38%) Dream I was camping and had a grasshopper on me so I ran away Dream I was circumcised and they accidentally cut the whole thing off* Had a nightmare about my operation going wrong* Dream that my mum bought me Maccas Dream about being a Christmas tree Dream that dad got me a laptop Dream that I got a horse Dream that I saw a flash of colours and movement Characters (19%) Dream about a stuntman Dream about poppy, mummy, daddy, brothers and sisters Dream of my nana who died during my operation Dream of Harry Potter Others (38%) Dream of Nintendo Dream of cars Dream of footy Dream that bulldozer came and chopped down all the trees and blew up Dream about food Good dream Good dream Scary dream *Hospital or illness-related dreams. Bad dream. Ten children (11.1% of dreamers) dreamed about hospital related events. Twenty-five children (27.8% of dreamers) were unable to recall the details of their dream, of which seven children only described it as a good nice happy dumb dream and three reported having a bad scary dream. Only nine of the 90 children (10%) who reported dreaming were considered to have had a bad dream. The content of the dreams where details could be recalled is shown in Table 5. Details of the awareness data have been described elsewhere [16]. Twenty-eight children described events that were possible awareness. Seven of these children were thought to have described convincing episodes of awareness. Of these seven children, four children also Ó 2005 Blackwell Publishing Ltd 857

5 G. H. Huang et al. Æ Dreaming during child anaesthesia Anaesthesia, 2005, 60, pages described what the child equated to a dream distinctly separate to the awareness event. These dreams have been included in the analysis. Of the 21 children whose recollections were not convincingly awareness events, five also had distinct dreams that were included in the analysis. The remaining 16 children described intraoperative events that the child did not think were a dream, but were not clearly cases of awareness. These accounts were mostly auditory memories that may have occurred in the Post Anaesthesia Care Unit (e.g. beeping and talking ). Two children recounted visual imagery of seeing people in green, one child remembered feeling a scratch on the hand, and another child heard the surgeons talking and working. These 16 accounts were not analysed as dreams because these children did not consider these events to be dreams. A univariate analysis was performed to examine factors associated with dreaming. Children who also experienced a convincing awareness event were more likely to have dreamed during anaesthesia (p < 0.001). From the univariate analysis, children who dreamed were also younger (p = ), had more anxious parents (measured by trait anxiety) (p = 0.03) and had a lower socio-economic status (p = 0.04). Dreaming patients were also more likely to have been prepared several days before their anaesthetic with extended conversations (p = 0.04) or roleplay (p = 0.04). Co-variance between variables identified in the univariate analysis was assessed. There were very low correlations between parental trait anxiety and socio-economic status (Pearson s correlation coefficient = 0.1; p = 0.003) and between parental trait anxiety and later preparation of the child, closer to the date of admission (correlation coefficient = 0.1; p = 0.02). All significant factors identified in the univariate analysis were entered into a multivariate regression model (Table 6). From this logistic regression, the only factors that were associated with Table 6 Associations of dreaming using multivariate logistic regression. Variable Odds Ratio Standard error p-value Age; each year < Awareness; Yes no Parental trait anxiety; score from State-Trait Anxiety Inventory Extended conversation; Yes no Role play; Yes no Time of preparation; day of admission day before several days before >1 week before Socio-economic status; score All the above variables were entered into the regression model. dreaming were younger age (p < 0.001) and awareness during anaesthesia (p = 0.001). From the multivariate logistic regression (which included age), there was no association found between dreaming and behavioural disturbance at 3 days (OR = 0.9; 95% CI: ; p = 0.7) or at 30 days (OR = 1.3; 95% CI: ; p = 0.5) after anaesthesia. Discussion In our study, dreaming during anaesthesia was reported by 10.4% of children. In 1973, McKie and Thorp [11] reported 11% of children experienced intra-operative dreaming. Two more studies were conducted in O Sullivan et al. [10] investigated dreaming in 144 children who had day surgery and found an incidence of 9.7%. Hobbs et al. [2] interviewed 120 day surgery children and reported an incidence of 19%. These studies enrolled a small number of children. Foulkes studied dreaming in children across age groups [23, 24]. He reported that the incidence of dreaming during both rapid eye movement and non-rapid eye movement sleep increased with older age and was least frequent in the youngest group (aged 3 5 years). This is contrary to our findings that dreaming during anaesthesia is more common in the younger age groups. The difference in age profile could suggest that either dreaming during sleep and dreaming during anaesthesia are different phenomena, or that there are age-related differences in anaesthesia that influence frequency of dreaming. For example, if dreaming is associated with lighter anaesthesia, then this data could suggest younger children receive relatively lighter anaesthesia. Although the incidence of reporting decreased with time after the anaesthetic, children did not always report dreaming in their first interview. This finding is similar to delayed reports of awareness after anaesthesia in adults [6, 25]. Two studies interviewed children only once [2, 10] while McKie and Thorp interviewed children twice [11]. In our study, children were interviewed on three occasions, increasing the likelihood of detecting dreaming. All three past studies used the Liverpool technique [2, 10, 11], which involves induction with thiopental, use of neuromuscular blocking drugs to allow tracheal intubation and maintenance with oxygen nitrous oxide mixture and increments of neuromuscular blocking agents. No volatile agents were used. This lighter anaesthetic technique may explain the higher incidence of dreaming seen in the study by Hobbs and colleagues. The content of dreaming in children has not been previously studied in any detail. In our study, dreams could be related to a number of themes such as animals, selfrepresentation, characters, hospital-related experiences 858 Ó 2005 Blackwell Publishing Ltd

6 G. H. Huang et al. Æ Dreaming during child anaesthesia or others. It has been suggested that dream content is influenced by external stimuli or by events that occur immediately before sleep. Few children in our study reported hospital-related dreams. Hospital-related experiences featured less frequently, and the dreams were less threatening than reported in adult studies of dreaming during anaesthesia. Foulkes reported that dreams during rapid eye movement sleep in younger children (aged 3 7 years) were brief, dominated by animal themes, lacking in feeling experience and had few active self-characterisations [23, 24]. Dreams rarely had an unfavourable outcome. As children grew older (age 7 12) their dreams became longer, had an increase in self-representation, and animal themes became scarce. These themes have also been observed in children s dreams during anaesthesia in our study. Animal themes were most dominant (24.5%) in the youngest group (age 5 7 years) and decreased with older age (21% at age 7 9 and 5% at age 9 12). Like Foulkes findings, we found self-characterisation in dreams became more common with older age (29% at age 5 9 to 38% at age 9 12). Children appear to experience similar dream themes during sleep and during anaesthesia. Children dream according to their ages and level of development [26]. In a study by Catalano, children with emotional disturbances were more likely to have bizarre, violent and bad dreams [26]. Children in the normal group, however, had more realistic dreams associated with developmental issues. In our study, parents were asked to indicate if their child had pre-existing emotional disturbance. There were nine emotionally disturbed children. Two of these nine children reported bad dreams (22%). Amongst non-emotionally disturbed children only seven reported bad dreams (9%). As the numbers are small, the results did not reach significance (p = 0.2). However, like Catalano, we observed that children with emotional disturbance experienced bad dreams more frequently than children with normal development. These observations are limited by the small numbers of bad dreams (n = 9) and emotionally disturbed children (n = 9). The relationship between dreaming and awareness is complex. One reason for the paucity of research into awareness in children was the assumption that children would confuse awareness and dreaming [11]. Certainly, in some patients it is impossible to determine what was a dream and what was a recollection of a real event. However, in our study, the majority of children were able to describe recollections that they clearly thought to be a dream. The content of these dreams was usually fantastic, and often not hospital-related, making differentiation between dream and awareness easier. On seven occasions children described events that they equated with real events, and features of the memory were sufficient to conclude that the memory reflected true awareness. Some of these children also described a distinct and separate dream. Sixteen children, however, described memories that were not obviously dreams or awareness. In contrast to the visual and active nature of dreams, many of these recollections were auditory recollections of beeping and talking. They probably reflected events in the Post Anaesthesia Care Unit as the child awoke. Our study suggests that differentiating a dream from awareness may not be as difficult as previously assumed. Adult studies have found a link between dreaming and awareness [9, 12]. Although mentioned in a previous study of awareness in children [11], no other studies have specifically examined this relationship in children. In our study, dreaming was strongly associated with children who experienced awareness during anaesthesia (p = 0.001). It is possible that light anaesthesia is associated with both risks of dreaming and awareness. Dreaming during anaesthesia was more common in younger children (p < 0.001). This is consistent with adult studies, where younger patients dreamed more than older patients [9, 12]. The incidence of awareness reported in children (0.8 5%) [11, 16] is also higher than that reported in adults ( %) [5, 6, 9, 27, 28]. Some previously described predictors of dreaming during anaesthesia in adults were not identified in our study. In adults, women report dreaming more frequently than men [9, 12]. An association between dreaming and the use of propofol has been reported [13 15], but we did not find this association. As this is an observational cohort study, only associations between anaesthetic drugs and dreaming can be detected. We found no association between the incidence of dreaming and the type of anaesthetic drugs used. This is consistent with results by Hellwagner et al. [8]. The anaesthetic drugs that were examined were sevoflurane, isoflurane, halothane, nitrous oxide, propofol, thiopental, ketamine, opiates, midazolam and neuromuscular blocking drugs. Previous studies using the Liverpool technique found succinylcholine to be associated with a higher incidence of dreaming [2, 10]. Our study did not detect any increase in dreaming with the use of depolarising (p = 0.3) or non-depolarising neuromuscular blocking drugs (p = 0.4). The anaesthetic techniques and drugs used in the present study are very different from those of Hobbs et al. and our results may not be directly comparable. The small number of children who received a depolarising neuromuscular blocking agent (n = 3) also limits the power of these results. Dreaming was not associated with increased behavioural disturbances at 3 days and 30 days after anaesthesia. In our study most children who reported dreaming Ó 2005 Blackwell Publishing Ltd 859

7 G. H. Huang et al. Æ Dreaming during child anaesthesia Anaesthesia, 2005, 60, pages did not experience more distress post procedure. The lack of association between dreaming and negative behaviour is consistent with the non-threatening nature of the dreams reported by children in this study. One of the major limitations of this study is the reliability of children s memories and possible confabulation. As children are very suggestible, parents and researchers were instructed to only ask the set of questions, and write down the child s answer verbatim. Prompting or leading questions were avoided. If the child answered no when asked if they dreamt, felt or heard anything while they were having the operation, no further questions were asked. If the child answered yes, an open-ended question, what did you dream about? was asked. As the second and third assessment of dreaming was conducted at home, parents may have prompted the answers, leading to reporter bias. Suggestibility increases with each interview, so the first interview is the most reliable and accurate [29]. To reduce the emphasis on dreaming and awareness, the questions were nested inside a set of questions and incorporated into the conversation (Table 1). It is also possible that children who were distressed by their dreams may have chosen not to answer the question. The numerous comparisons made in the univariate analysis may lead to an inflated Type I error. The results from the univariate analysis with low p-values should therefore be interpreted with caution. It is important to note that after performing a multivariate logistic regression analysis to adjust for multiple variables, the only robust factors that were associated with dreaming were younger age and awareness during anaesthesia. In conclusion, the incidence of dreaming during anaesthesia in children from our study was 10.4%. The content of the dreams was usually pleasant and unrelated to their hospital experiences. Dreaming was more common in younger children and in those who also experienced awareness during anaesthesia. Children who reported dreaming did not display an increased risk of behavioural disturbances postoperatively. Intra-operative dreaming is a common occurrence that does not appear to distress children. Acknowledgements We are indebted to Caroline Czarnecki, Margie Gibson, Stephanie Stewart and Sarah Downie for their assistance with this study. We would like to thank the staff of the Royal Children s Hospital Department of Anaesthesia, Clinical Epidemiology and Biostatistics Unit and in particular statistician Kris Jamsen for assistance with statistical analysis. We would like to thank Associate Professor Kate Leslie and Michael Hong for assistance in the preparation of this manuscript. The study was supported by grants and funding from Australian Society of Anaesthetists, University of Melbourne and Murdoch Children s Research Institute. We declare no conflict of interest. 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Recollection of dreams after short general anaesthesia: influence on patient anxiety and satisfaction. European Journal of Anaesthesiology 2003; 20: Ranta SO, Laurila R, Saario J, Ali-Melkkila T, Hynynen M. Awareness with recall during general anesthesia: incidence and risk factors. Anesthesia and Analgesia 1998; 86: O Sullivan EP, Childs D, Bush GH. Peri-operative dreaming in paediatric patients who receive suxamethonium. Anaesthesia 1988; 43: McKie BD, Thorp EA. Awareness and dreaming during anaesthesia in a paediatric hospital. Anaesthesia and Intensive Care 1973; 1: Leslie K, Myles PS, Forbes A, Chan MT, Swallow SK, Short TG. Dreaming during anaesthesia in patients at high risk of awareness. Anaesthesia 2005; 60: Brandner B, Blagrove M, McCallum G, Bromley LM. Dreams, images and emotions associated with propofol anaesthesia. Anaesthesia 1997; 52: Marsch SC, Schaefer HG, Tschan C, Meier B. Dreaming and anaesthesia: total i.v. anaesthesia with propofol versus balanced volatile anaesthesia with enflurane. European Journal of Anaesthesiology 1992; 9: Kasmacher H, Petermeyer M, Decker C. Incidence and quality of dreaming during anesthesia with propofol in comparison with enflurane. Anaesthesist 1996; 45: Ó 2005 Blackwell Publishing Ltd

8 G. H. Huang et al. Æ Dreaming during child anaesthesia 16 Davidson AJ, Huang GH, Czarnecki C, et al. Awareness during anaesthesia in children: a prospective cohort study. Anesthesia and Analgesia 2005; 100: Vernon DT, Schulman JL, Foley JM. Changes in children s behavior after hospitalization. Some dimensions of response and their correlates. American Journal of Diseases of Children 1966; 111: Spielberger CD, Gorsuch RL, Lushene RE, Vagg PR, Jacobs GA. Manual for the State-Trait Anxiety Inventory. Palo Alto: Consulting Psychologists Press, Kain ZN, Mayes LC, Cicchetti DV, Bagnall AL, Finley JD, Hofstadter MB. The Yale Preoperative Anxiety Scale: how does it compare with a gold standard? Anesthesia and Analgesia 1997; 85: Bradford R, Spinks P. Child distress during hospitalization: implications for practice. Clinical Otolaryngology and Allied Sciences 1992; 17: McGraw T. Preparing children for the operating room: psychological issues. Canadian Journal of Anaesthesia 1994; 41: Kotiniemi LH, Ryhanen PT, Moilanen IK. Behavioural changes following routine ENT operations in twoto-ten-year-old children. Paediatric Anaesthesia 1996; 6: Foulkes D. Children s Dreams: Longitudinal Studies. New York: John Wiley & Sons, Foulkes D. Children s Dreaming and the Development of Consciousness. Cambridge, MA: Harvard University Press, Sandin RH, Enlund G, Samuelsson P, Lennmarken C. Awareness during anaesthesia: a prospective case study. Lancet 2000; 355: Catalano S. Children s Dreams in Clinical Practice. New York: Plenum Press, Wennervirta J, Ranta SO, Hynynen M. Awareness and recall in outpatient anesthesia. Anesthesia and Analgesia 2002; 95: Nordstrom O, Engstrom AM, Persson S, Sandin R. Incidence of awareness in total i.v. anaesthesia based on propofol, alfentanil and neuromuscular blockade. Acta Anaesthesiologica Scandinavica 1997; 41: Ceci SJ, Huffman ML. How suggestible are preschool children? Cognitive and social factors. Journal of the American Academy of Child and Adolescent Psychiatry 1997; 36: Appendix 1 The modified Vernon post hospitalisation behaviour questionnaire. Please indicate how often your child displayed these behaviours over the LAST 3 DAYS How often Not at all Seldom Sometimes Frequently Always N/A 1. Did your child make a fuss about going to bed at night? Did your child make a fuss about eating? Did your child spend time just sitting or lying and doing nothing? Did your child need a pacifier? Did your child seem to be afraid of leaving the house with you? Was your child disinterested in what was going on around them? Did your child wet the bed at night? Did your child bite his or her fingernails? Did your child get upset when you left them alone for a few minutes? Did your child need a lot of help doing things? Was it difficult to get your child interested in doing things (like playing games, with toys and so on)? 12. Did your child seem to avoid or be afraid of new things? Did your child have difficulty making up their mind? Did your child have a temper tantrum? Was it difficult to get your child to talk to you? Did your child seem to get upset when someone mentions doctors or hospitals? 17. Did your child follow you everywhere around the house? Did your child spend time trying to get or hold your attention Was your child afraid of the dark? Did your child have bad dreams at night or wake up and cry? Was your child irregular in their bowel movements? Did your child have trouble getting to sleep at night? Did your child seem to be shy or afraid around strangers? Did your child have a poor appetite? Did your child tend to disobey you? Did your child break toys or other objects? Did your child suck their fingers or thumbs? Ó 2005 Blackwell Publishing Ltd 861