No difference in factual and delusional memories between delirious and non-delirious ICU patients 3 months post-ICU discharge
N.R.A.Versaevel
FNWI, Universiteit van Amsterdam
5102PBWS0Y: Bachelorproject Psychobiologie-Wetenschappelijke Stage Prof. Dr. A.J.C. Slooter
Abstract
Aims and objectives. This study investigates the effect of delirium on factual and delusional memories of Intensive Care Unit (ICU) patients with a minimum ICU stay of 12 hours 3 months post-ICU discharge.
Background. Delirium prevalence in the ICU may reach as high as 31%. Additionally, delirium could be contributing to delusional memories. Previous findings on the effect of delirium on factual and delusional memories are contradictory, however they never investigated the extent to which these memories occurred. Furthermore, they have not yet investigated patients with an ICU stay of ≥ 12 hours.
Design. An observational design with telephone interviews 3 months post-ICU discharge was conducted.
Methods. Patients were telephonically interviewed using the Intensive Care Unit Memory Tool (ICU-MT), Telephone Interview for Cognitive Status Modified (TICS-M), and the Cognitive Failure Questionnaire (CFQ-14).
Results. 129 patients were included and delirium was detected in 10.9% of the patients. Analysis showed no significant difference in the ratios of factual (U=735.50, z= -.54, p=.294), delusional (U=798.00, .35, p=.364), and factual & delusional memories (U=752.50, z=-.63, p=.264) between delirious and non-delirious patients. However, when both factual and delusional memories were present, delirium affected the ratios in elective patients (β=.281, p<.05).
Conclusions. Delirium did not influence the extent of memories present as there was no significant difference between delirious and non-delirious patients regarding factual, delusional, and factual & delusional memories. However, delirium affected the factual & delusional memories in elective patients. Future studies should include patients with delirium in the ward to determine whether this interferes with ICU memories.
Introduction
Patients in the Intensive Care Unit (ICU) frequently have little or no recall of their ICU admission and stay ICU discharge. Having no recall of the ICU, also called post-ICU amnesia, could depend on several factors such as the use of sedatives (Jones, Griffiths, & Humphris, 2000). However, when memories are present ICU patients regularly describe memories of ICU experiences that did not occur, so-called delusional memories. These unreal experiences could occur in severely ill patients during their ICU stay as hallucinations,
nightmares, dreams, and delusions (Löf, Berggren & Ahlström, 2006). A possible
contributing factor to these delusional memories could be delirium. Delirium is defined by The Diagnostic and Statistical Manual of Mental Disorders (DSM- V) as a disturbance of consciousness combined with inattention, changes in cognition, or perceptual disturbances. Delirium prevalence may reach as high as 31% in ICU patients and can cause patients to suffer from amnesia for the period of confusion (Krewulak et al., 2018; Jones et al., 2000). Risk factors for ICU delirium include hypertension, alcoholism, and severity of illness. Furthermore, administration of sedatives and analgesics increases the risk of delirium when inducing coma (Ouimet et al., 2006). Additionally, delirious patients have a longer ICU and hospital stay than non-delirious patients (Klouwenberg et al., 2014; Ouimet et al., 2006). It has also been shown that a longer duration of delirium is associated with global-long term cognitive impairments and that delirium is also correlated with higher PTSS-14 scores, which are suggestive of Post-Traumatic Stress Disorder (PTSD) (Pandharipande et al., 2013; Bashar et al., 2018). Moreover, it is suggested that having factual memories provide a protective factor against PTSD-related symptoms when delusional memories are present. Namely, having factual memories will aid patients to assign delusional memories as unreal experiences and therefore protect against PTSD-related symptoms (Jones et al., 2000).
Previous research has shown that delirium is associated with memory impairment and decreased memory quality six months post-ICU discharge (Bashar et al., 2018). Delirium duration was determined by the number of days with a positive delirium screening according to the Confusion Assessment Method for the ICU (CAM-ICU) in patients with an ICU-stay with more than 75 days. Furthermore, memories were assessed using the ICU Memory Tool (ICU-MT) and showed that 49% of the patients had factual memories while 47% had
delusional memories of their ICU-stay. Thus, the results demonstrate that the factual recall of the ICU in patients with delirium is impaired. Moreover, less factual memories and more delusional memories are associated with delirium six months post-ICU discharge
(Svenningsen et al., 2013). Similarly, as Bashar et al., (2018) the CAM-ICU and ICU-MT were used and showed that delirious patients had significantly less factual, but more
delusional memories than non-delirious patients six months post-ICU discharge. Additionally, delirious patients have significantly less factual memories of the ICU than non-delirious patients two years post-ICU discharge (Roberts et al., 2005). Instead of using the ICU-MT to assess factual memories, interviews with ICU patients were conducted. Furthermore, they used the Intensive Care Delirium Screening Checklist (ICDSC) to assess delirium and found that factual memories were significantly less in delirious patients than non-delirious patients two years post-ICU discharge. Therefore, previous studies show that delirious patients have less factual and more delusional memories of the ICU than non-delirious patients six months and two years post-ICU discharge. However, another study has found no association between delusional memories and delirium up to three months post-ICU discharge (Burry et al., 2015). Delirium and memories were again assessed using the ICDSC and ICU-MT in ICU patients. Contrary to the studies above, they found no difference in the occurrence of delusional memories in delirious and non-delirious patients. Thus, previous findings of the association between memories and delirium are contradictory.
Therefore, this study will investigate the association between the presence of delirium with factual and delusional memories in order to come to a conclusive answer. Furthermore, previous research never looked at the extent to which memories occurred and did not include patients with an ICU-stay of less than 36 hours. Hence this study will include patients with a minimum ICU stay of 12 hours to include elective surgery patients. Accordingly, this study aims to investigate the effect of delirium on factual and delusional memories of ICU patients with a minimum ICU stay of 12 hours three months post-ICU discharge. According to previous studies, it is expected that the presence of delirium is associated with more delusional and less factual memories. To test this hypothesis, the ICU-MT is conducted telephonically by patients three months post-ICU discharge to assess different subscales of memories: factual memories, memories of feelings, and delusional memories. Delirium was detected in ICU patients by using the CAM-ICU during their ICU stay. It is expected that delirious patients score lower on the subscale for factual memories, but higher on the subscale for delusional memories three months post-ICU discharge than non-delirious patients.
Furthermore, the Telephone Interview for Cognitive Status Modified (TICS-M) and the Cognitive Failure Questionnaire (CFQ-14) were conducted to control for impaired cognitive functioning. Lower scores on the TICS-M and CFQ indicate a mild cognitive impairment.
Material & Methods Participants
Patients of Radboudumc Nijmegen and UMC Utrecht were included three months post-ICU discharge. As this study was approved by the Medical Ethical Commission (METC) as research not subjected to the WMO (nWMO) an informed consent was not needed. In this study participated 129 former ICU-patients from the age of 20 to 85 years. Patients were eligible if they were ≥18 years, had a sufficient understanding of Dutch, and a minimum ICU stay of 12 hours. Patients were excluded if their admission was due to neurotrauma or
neurosurgery and if they had a form of a neurodegenerative disorder or a mental disorder. Furthermore, patients were excluded when they had a readmission to the ICU within three months post-ICU discharge.
Procedure
Patients were acquired using the database of the ICU. Access to the database was obtained via MetaVision (MetaVision Suite Version 5.46.44 (Hotfix-42)) for UMC Utrecht and EPIC (EPIC Hyperface Augustus 2019) for RadboudUmc. Furthermore, for patients from the UMC Utrecht the program HIX (HIX version 6.1 HF 112) was also used to verify and secure telephone numbers of the patients. In order to anonymize patients, patient numbers were differently modified for UMC Utrecht and RadboudUmc. After patients were included, they were telephonically interviewed using the questionnaires below in the following order: ICU memory tool, TICS-M, and CFQ. Due to the Monitor-IC study of the RadboudUmc which already includes the CFQ, only the ICU memory tool and TICS-M were telephonically assessed (Geense et al., 2017). Lastly, if telephone conversation showed that patients were still experiencing traumatic ICU memories or experiences related to the ICU, they were offered aftercare.
Measurements Delirium assessment.
During their ICU stay, the Confusion Assessment for the ICU (CAM-ICU) was assessed by nurses for diagnosing patients with delirium according to the DSM-V (Ely et al., 2001). The English version of the CAM-ICU was validated and showed a high sensitivity (85%) and specificity (95%) for detecting delirium (Ho et al., 2020). Furthermore, the CAM-ICU was translated into Dutch and validated by Vreeswijk et al., (2008) and correlated well with the English version. The CAM-ICU measures acute onset of mental status changes, inattention, disorganized thinking, and an altered level of consciousness. Acute onset of mental status changes was assessed by using the Richmond Agitation-Sedation Scale (RASS) over 24 hours to examine the behaviour fluctuation. Inattention was measured by estimating the ability to maintain and shift attention. To acquire the degree of inattention Attention Screening Examinations (ASE) were conducted. During the ASE patients had to squeeze the nurse’s hand by hearing the letter A in the letter list SAVEAHAART. Disorganized thinking was measured by assessing rambling or irrelevant conversation, unclear or illogical flow of ideas. Furthermore, patients were examined to see whether they were able to follow questions and simple commands. Lastly, the level of consciousness was assessed by scoring the level of consciousness (any level of consciousness other than alert, alert, vigilant, lethargic, stupor, and coma). Delirium was diagnosed when an acute onset of mental status changes and inattention were present along with either disorganized thinking or an altered level of consciousness.
Memory assessment.
Memories were assessed using the Intensive Care Unit Memory Tool (ICU-MT) developed by Jones, Humphris & Griffiths (2000) and which was translated into Dutch in the EuRIDICE trial (Smit et al., 2020). The questionnaire had a Cronbach’s alpha of .86 and the test-retest reliability over 4 months for factual memories was shown to be .84 and for
delusional memories .91. Therefore, the internal consistency and test-retest reliability of the ICU-MT were favourable (Jones et al., 2000). The ICU-MT consists of 14 items and
differentiates between factual memories, memories of feelings and delusional memories. Factual memories consisted of 11 items, memories of feelings of 6 items, and lastly delusional memories of 4 items. Patients were told to recall and describe their ICU memories and each item was scored when a key-word was present in the memory of the patient. Therefore, the scores of factual memories range between 0-11 (family, alarms, voices, lights, faces, breathing tube, suctioning, darkness, clock, tube in nose and visits), memories of feelings between 0-6 (being uncomfortable, feeling confused, feeling down, feeling anxious, panic and pain) and delusional memories between 0-4 (hallucinations, nightmares, dreams and the feeling of someone trying to hurt them). Additionally, the questionnaire contained additional explanatory questions if key-words of delusional memories were present.
Cognitive functioning.
To ascertain that memory recall was not due to impaired cognitive functioning, cognitive performances were compared between the delirious and non-delirious patients. The Telephone Interview for Cognitive Status Modified (TICS-M) developed by Brandt, Spencer and
Folstein (1988) was administered to assess cognitive functioning. The TICS-M has a high sensitivity (83%) and specificity (100%) for classifying patients with Dementia or no Dementia (Crooks et al., 2005). Moreover, the TICS-M has a high sensitivity (82.4%) and
specificity (87%) for classifying Mild Cognitive Impairment (MCI) in patients (Cook, Marsiske & McCoy, 2009). The Dutch version of the TICS-M was validated by Kempen et al., (2007). It was shown to be an acceptable screening instrument as the correlation between the TICS- M and the Mini-Mental State Examination (MMSE) were good (ρ=.77, p<.05). The TICS-M consists of 12 items that assess different aspects of cognitive functioning with
questions focused on the domains orientation, language, memory, and attention. Points can be assigned per question or task and the total score can vary between 0 and 50. Scores ≤ 34 are an indication for an MCI and scores ≤ 28 are an indication for Dementia (Cook et al., 2009; Crooks et al., 2005).
Daily cognitive functioning.
Daily cognitive performance was assessed using the Dutch version of the abbreviated Cognitive Failure Questionnaire (CFQ-14) to investigate whether patients suffer from
impaired cognitive functioning in daily life. The CFQ-14 was developed and validated by Wassenaar et al., (2018) and is a qualified abbreviated substitute with similar performance as the CFQ-25 due to their high correlation (ρ=.99, p<.0001). The CFQ-14 consists of 14 statements in order to assess memory, attention, and concentration performance. The statements are scored on a 5-point Likert-scale, ranging from 1 (‘’never’’) to 5 (‘’very often’’). The total CFQ-14 score is the sum score of the 14 rated statements and can vary between 14 and 70 points whereby higher scores indicate more cognitive mistakes. Scores ≥ 43 are seen as above average (Ponds, Boxtel & Jolles, 2006).
Statistical analysis
Data was collected into Castor (Castor v2020.2.25) and analysed using IBM SPSS for Windows, version 25.0 (IBM Corp., Armonk, N.Y., USA). Descriptive statistics were used to
summarize patient characteristics (e.g. age, sex, admission type). The presence of delirium, the independent variable, was obtained by a positive CAM-ICU score. Firstly, the ratio of the different types of memories, the dependent variables, were calculated by dividing the present items of factual, delusional, and factual & delusional memories by the total items of the specific type of memories on the ICU-MT. When no memories of the ICU were present the ratio for post-ICU amnesia was equal to 0. All tests were performed using a confidence interval of 95%. Then, a χ2-test was conducted after testing the assumptions for expected frequencies in order to investigate of the presence of delirium is associated with having recall of the ICU or not. Thereafter, the assumption for normality was assessed for the ratios of memories, TICS-M and CFQ-14 scores using the Shapiro-Wilk test. Equality of variances were assessed using Levene’s test. Ratios of memories were compared between delirious and non-delirious patients using a Mann-Whitney U test to investigate whether delirium affected the ratios of memories. After checking for Multicollinearity and Homoscedasticity six Multiple linear regressions were conducted to investigate whether delirium could predict the ratios of memories in elective and non-elective patients. The regressions were adjusted for coma days. Furthermore, an Independent T-test was used to investigate if the TICS-M scores differed between delirious and non-delirious patients. Lastly, a Spearman’s correlation test was used after checking for linearity to investigate whether there was a correlation between the TICS-M and CFQ-14.
Results Participants
A total of 183 ICU patients were excluded due to neurosurgery (n=56), an age ≤18 years (n=4), passing away (n=28), an ICU stay of ≤ 12 hours (n=45), a language barrier (n=8), and readmission to the ICU (n=6). Additionally, patients were excluded due to speech problems (n=10), not wanting to recall their ICU experiences (n=3), and not being
telephonically reachable (n=22). After excluding 183 ICU patients a total of 129 patients were included in the statistical analysis, of whom 14 were delirious (10.9%) and 115 were non-delirious (89.1%). Patient demographics and clinical features are presented in Table 1. This population consisted of 71.3% men (n=92), had a mean age of 62.8 (SD 14.22) years with a mean ICU length of stay (LOS) of 3 days (SD 5.32). Furthermore, 7% of the patients were readmitted to the ICU (n=9). 20.2% were admitted due to medical emergencies (n=26), 75.2% due to elective surgeries (n=97), and 4.7% due to emergency surgeries (n=6). 1.6% were COVID-19 positive on the ICU (n=2) and 48.8% were in a coma (n=63) with a mean length of 1.73 (SD 1.99) days during their ICU stay. Moreover, 10.9% of the patients experienced delirium with a mean duration of 3 days (SD 2.72) and 41.1% were sedated during their ICU stay (n=53) with a mean duration of 1.97 days (SD 2.54). Lastly, 10.1% received
Table 1.
Patient Demographics and Clinical Features
Percentages are given for Sex, Intensive Care Unit (ICU) readmission, Admission type, COVID-19, Coma, Delirium and Sedation. Means with Standard Deviations (SD) are given for ICU Length Of Stay (LOS), Coma
ICU patients (n=129) Sex Female Male 28.7% 71.3% Age (years) Median (Q1-Q3) Mean ± SD 65 (57-73) 62.8 (14.22)
ICU LOS ± SD (days) 3.0 (5.32)
ICU readmission (%) 7.0% Admission type Medical Elective surgery Emergency surgery 20.2% 75.2% 4.7% COVID-19 (%) 1.6% Coma (%) Median length (Q1-Q3) Mean length ± SD 48.8% 1 (1-2) 1.73 (1.99) Delirium (%)
Median duration (days) (Q1-Q3) Mean duration (days) ± SD
10.9%
2.0 (1-4.25) 3.0 (2.72) Sedation (%)
Median duration (days) (Q1-Q3) Mean duration (days) ± SD
41.1%
1 (1.00-1.25) 1.97 (2.54)
length, Delirium, and Sedation duration. Furthermore, Medians with first through third interquartile range (Q1-Q3) are given for Age, Coma length, Delirium, and Sedation duration.
Recall of ICU
According to the ICU-MT, 14.3% of the delirious (n=2) and 19.1% of the
non-delirious patients (n=22) had no recall of the ICU. Furthermore, when memories were present 64.3% of the delirious (n=9) and 63.5% of the non-delirious patients (n=73) had factual memories of their ICU-stay. Only 0.9% of the non-delirious patients (n=1) had only delusional memories of their ICU-stay, while there were no delirious patients with only delusional memories. However, 21.4% of the delirious (n=3) and 14.8% of the non-delirious patients (n=17) had factual and delusional memories of their ICU-stay. Percentages of the ICU-MT for delirious and non-delirious patients are displayed in Table 2. As the assumptions for expected frequencies were not met, the Bayes factor was also calculated. There was no significant association between the presence of delirium and having recall of the ICU or not (χ2 (1)=.19, p=.330). Moreover, the Bayes factor strongly supported the null hypothesis, BF00=3.70.
Table 2.
Percentages on the ICU-MT, Mean TICS-M and CFQ Scores for Delirious and Non-delirious Patients
Questionnaire Delirious patients
(n=14) Non-delirious patients (n=115) ICU-MT Factual memories Delusional memories
Factual & Delusional . memories Post-ICU amnesia 64.3% - 21.4% 14.3% 63.5% 0.9% 14.8% 19.1%
TICS-M Mean ± SD score Mild Cognitive …Impairment score <34 (%) Dementia score <28 (%) 32,5± 9.52* 42.9% - 38.2 ± 4.13* 18.3% 1.7% CFQ mean ± SD score 43.4± 9.37 44.3± 7.48
No significant difference was found between delirious and non-delirious patients for factual, delusional, factual & delusional memories and Post-ICU amnesia on the Intensive Care Unit Memory Tool (ICU-MT). Mean scores with Standard Deviations (SD) are presented for the Telephone Interview for Cognitive Status (TICS-M) for delirious and non-delirious patients. A significant difference was found between the mean TICS-M for delirious and non-delirious patients (p<.05). Furthermore, percentages are given for patients, who scored <34 and 28 points on the TICS-M. Cognitive Failure Questionnaire (CFQ) scores are given for both groups.
Factual, delusional, and factual & delusional memories
The ratios for factual, delusional, and factual & delusional memories were not normally distributed in delirious and non-delirious patients (all Shapiro-Wilk<.86, p<.05). The variances between delirious and non-delirious patients however, were equal for
delusional (F(1,127)=0.49, p=.484), factual (F(1,127)=0.59, p=.443), and delusional & factual memories (F(1,127)=1.00, p=.318). Medians of the ratios of factual, delusional, and factual & delusional memories are shown in Table 3. Factual memories in delirious patients (Mdn=.37) did not significantly differ from non-delirious patients (Mdn=.37) (U=735.50, z= -.54,
p=.294). There was also no significant difference in delusional memories between delirious (Mdn=.00) and non-delirious (Mdn=.00) patients (U=798.00, z=-.35, p=.364). Furthermore, there was no significant difference between delirious (Mdn=.00) and non-delirious patients (Mdn=.00) in terms of having factual as well as delusional memories (U=752.50, z=-.63, p=.264).
Table 3.
Median of the Ratio of Factual, Delusional, and Factual & Delusional Memories within Delirious and Non-delirious Patients
Factual memories Delusional memories Factual & Delusional memories Delirious patients .37 .00 .00 Non-delirious patients .37 .00 .00
Factual, delusional, and factual & delusional memories did not significantly differ between delirious and non-delirious patients.
Additionally, multiple linear regressions were conducted after log-transformations to investigate whether delirium was associated with the ratios of memories for elective and non-elective patients. The regressions were adjusted for the number of coma days. The results for the elective patients indicated that the variance was explained by the model for 2.0% and that there was no statistically significant association with the ratio of factual memories
(F(2,64)=0.651, p=.525). The presence of delirium (β=-.119, p=.382) did not significantly contribute to the model. As for non-elective patients, the variance was explained by the model for 0.2% and there was also no significant association with the ratio of factual memories (F(2,14)=0.01, p=.987). Furthermore, the presence of delirium (β=.041, p=.907) did not contribute to the model. A multiple linear regression has also been conducted for the ratio of delusional memories for elective patients. The variance was explained by the model for 0.1% and there was also no significant association with the ratio of delusional memories
(F(2,64)=0.041, p=.960). The presence of delirium (β=-.038, p=.781) did again not contribute to the model. No multiple linear regression was conducted for the ratio of delusional
memories. Lastly, multiple regressions were conducted for the ratio of factual and delusional memories for elective and non-elective patients. The results for the elective patients indicated that the variance was explained by the model for 6.7% and that there was again no statistically significant association with the ratio of factual and delusional memories (F(2,64)=2.307, p=.108). The presence of delirium (β=.281, p<.05), however, did significantly contribute to the model. As for non-elective patients, the model explained for 8.7% the variance and again there was no significant association with the ratio of factual and delusional memories (F(2, 14)=0.668, p=.528). The presence of delirium (β=-.372, p=.286) did not contribute to the model.
Cognitive functioning
Mean TICS-M scores and CFQ scores for delirious and non-delirious patients are shown in Table 2. The TICS-M scores were normally distributed for delirious (Shapiro-Wilk=.96, p=.795) and non-delirious patients (Shapiro-Wilk=.98, p=.151). Moreover, the variances between delirious and non-delirious patients were equal for the TICS-M scores (F(1, 127)=1.95, p=.165). Thereafter, a significant difference in the TICS-M scores between delirious (M=34.93) and non-delirious (M=38.22) was found (t(127)=-2.89, p<0.05).
Furthermore, a significant positive correlation between the TICS-M (Mdn= 38) and the CFQ (Mdn=45) scores was found using Spearman’s correlation as the assumption for linearity was not met (ρs=.20, p<.05).
Discussion
This study on the effect of delirium on memories 3 months post-ICU has shown that delirium prevalence in this population was 10.9%, which was lower than the prevalence of 31% found in the systematic review of Krewulak et al., (2018). Moreover, it has been shown that there was no difference between delirious and non-delirious patients in having recall of the ICU or having post-ICU amnesia. The hypothesis stated that delirious patients should have more delusional memories and less factual memories than non-delirious patients. However, contrary to the stated hypothesis no difference in having factual, delusional, and factual & delusional memories was found between delirious and non-delirious patients. Additionally, no effect of delirium on factual or delusional memories was found in elective and non-elective patients. However, when both factual and delusional memories were present, delirium affected the factual and delusional memories in elective patients. Cognitive
performances were compared between delirious and non-delirious patients and showed that non-delirious patients had better cognitive performance than delirious patients. Lastly, results showed that patients with better cognitive performances also perform better at daily cognitive functioning.
A possible alternative explanation for not finding a difference in factual, delusional, and factual & delusional memories between delirious and non-delirious patients is that there is no direct effect of delirium on memories. It is however possible that delirium interacts with sedation. Namely, other studies have found that heavily sedated ICU patients had more delusional memories than patients who were lightly sedated (Samualson, Lundberg &
Fridlund, 2008; da Costa et al., 2014). This is suggestive of sedation being a predictive factor for the different types of memories present in patients post-ICU discharge. Furthermore, it appears that delirium has an association with admission type, because delirium only affected factual & delusional memories in elective patients. Elective patients may be less prone to
develop delirium, whereby when they do develop delirium, it has an effect on their memory. Previous research found subsequently a significantly higher postoperative delirium incidence after emergency surgery in comparison to elective surgery (Ansaloni et al., 2010). Therefore, it is suggested that delirium is less common in elective admissions to the ICU and when present also shows an effect on memory. Another reason for not finding a difference between delirious and non-delirious patients could be due to the unequal sample sizes and the low number of delirium patients, whereby chances of finding statistical differences are low.
Another unexpected finding was that non-delirious patients had better cognitive
performance than delirious patients. Due to not manipulating both the presence of delirium and cognitive functioning in patients, it is not possible to determine their association. Therefore, it could be possible that delirious patients are more likely to develop cognitive impairments than non-delirious patients. This explanation is consistent with research findings that a longer duration of delirium is associated with global long-term cognitive impairments (Pandharipande et al., 2013). However, another possible explanation could be that patients with lower cognitive performances are more prone to develop delirium. This explanation is also consistent with other research as they found a strong and linear association between the cognitive performance in elderly elective presurgical patients and the risk of delirium (Jones et al., 2016).
As stated in the introduction, previous findings of the association between factual and delusional memories concerning delirium are contradictory. The results in this study are inconsistent with the findings that delirious patients have less factual and more delusional memories six months post-ICU discharge (Svenningsen et al., 2013). Additionally, the results are also inconsistent with the finding that delirious patients have less factual memories than non-delirious patients two years post-ICU discharge (Roberts et al., 2005). A reason for these contradictory results could be due to looking at memories three months post-ICU discharge in
this study instead of six months or two years. However, the findings in this study align with previous research stating that there is no difference in the occurrence of delusional memories between delirious and non-delirious ICU patients up to three months post-ICU discharge (Burry et al., 2015). Furthermore, they also found no difference in delirious and non-delirious patients regarding having no recall of their ICU stay. Therefore, the current study is in line with previous research about the effect of delirium on memories three months post-ICU discharge.
Furthermore, during the telephonic interviews, it became clear that some delirious as well as non-delirious patients experienced PTSD-related symptoms post-ICU discharge. Because there was no measurement tool to accurately measure PTSD-symptoms in this study, no definitive conclusions can be made about delirium and PTSD-related symptoms. Additionally, as there were no delirious patients with only delusional memories no comparisons could be made between delirious patients with only factual memories and both factual and delusional memories. Consequently, no conclusions can be made about the protective factor of factual memories against PTSD-related symptoms. (Jones et al., 2000). Therefore, future research could include a measurement tool such as the Impact of Event Scale-Revised (IES-R) to investigate the relation of delirium with PTSD.
By conducting the questionnaires telephonic instead of self-report, patients were able to ask questions about the interpretation of the statements and could clarify their responses. Due to having two investigators the inter-rater variation could not be avoided. However, due to reviewing each conversation together, the inter-rater variation was minimalized. Furthermore, some non-delirious ICU patients did develop delirium in the ward, however only delirium in the ICU and ICU memories were included in the analysis. Therefore, future research could include patients with delirium post-ICU to increase the sample size and investigate if delirium in the ward post-ICU discharge interferes with ICU memories. Ultimately, future studies
could explore the relation between sedation and delirium more regarding memories post-ICU discharge.
In conclusion, this study has shown that delirium does not affect post-ICU amnesia as there was no significant association between the presence of delirium and having recall of the ICU or not in ICU-patients 3 months post-discharge. Moreover, it has been shown that delirium does not influence the type of memories present as there was no significant difference between delirious and non-delirious patients regarding factual, delusional, and factual & delusional memories. However, delirium seems to influence the factual and delusional memories in elective patients.
Relevance to clinical practice
It is recommended to contact ICU-patients post-ICU discharge to offer them an opportunity to discuss their ICU memories and experiences. Especially patients who have been emotional, experienced delusions, or delirium during their ICU stay will greatly benefit from this.
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