Study design, period and setting
A cross-sectional study was conducted at hospitals in the South Gondar Zone, Ethiopia, from January 1st to November 30th, 2023. The South Gondar Zone is one of the ten administrative zones in the Amhara Regional State. According to Ethiopia’s 2021 statistical report, the South Gondar Zone has a total population of 2,631,566, with 1,331,888 males and 1,299,678 females27. The zone is served by eight government hospitals, including seven primary hospitals and one comprehensive specialized hospital. These hospitals are Nefas Mewucha Primary Hospital (NMPH) in Lay Gaynt Woreda, Wogeda Primary Hospital (WPH) in Simada Woreda, Ebinat Primary Hospital (EPH) in Ebinat Woreda, Mekane Eyesus Primary Hospital (MEPH) in Estie Woreda, Andabet Primary Hospital (APH) in Andabet Woreda, Debre Tabor Comprehensive Specialized Hospital (DTCSH) in Debre Tabor, Dr. Ambachew Memorial Hospital (Dr. AMH) in Tach Gaynt Woreda, and Addis Zemen Primary Hospital (AZPH) in Libokemkem Woreda.
For this study, three institutions (DTCSH, AZPH, and NMPH) were selected, and an average of 57 elderly patients underwent surgery (Fig. 1). After collecting the data, the study was registered with the title on Research Registry, using the unique registration number researchregistry10049.
Schematic presentation for the incidence and risk factors of postoperative delirium in elderly surgical patients in South Gondar Zone hospitals, 2023 (n = 424).
Inclusion/exclusion criteria
Patients above the age of 65 years and who were scheduled for elective surgery9,28 were included in the study. However, elderly patients with severe pulmonary disease or severe cardiac disease, as well as those who were unable to perform cognitive and psychometric tests due to reasons such as sensory impairment, language disorders, or a previous diagnosis of dementia9,28 were excluded from the study.
Sampling size and technique
Since there were no similar studies conducted in Ethiopia, the proportion of postoperative delirium was taken as 50%, with a 95% confidence interval and a margin of error of 0.05. The sample size was determined using the following formula for a single population proportion.
$$n=z2\left(p\right)(1-p)/d2$$
Whereas n represents the sample size, Z represents the confidence interval (1.96), P represents the prevalence (0.5), and d represents the margin of sampling error to be tolerated (0.05), the goal is to determine the sample size with a confidence interval of 95% and a margin of error of 5%.
n= (1.96)2 * 0.5(1- 0.5)/ (0.05)2 = 385, and by adding a 10% non-response rate the final sample size was 424. Consecutive sampling technique was used in which every study participant meeting the inclusion criteria was selected until the required sample size was achieved. The daily operation schedule list in each hospital was used as a sampling frame. The situational analysis showed that an average of 40, 10, and 7 elderly patients who meet the inclusion criteria were operated on Debre Tabor Comprehensive Specialized Hospital, Addis Zemen Primary Hospital, and Nefas Mewucha Primary Hospital respectively per month. According to this data, the calculated sample size was proportionally allocated for each hospital (DTCSH = 298, AZPH = 74, NMPH = 52) during the study period.
Dependent variable
Postoperative delirium (Yes/No).
Independent variables
Demographic variables: Age, sex, BMI, history of smoking and alcohol consumption, presence of comorbid disease (medical conditions that are simultaneously present with the surgical condition they already present with in the patient), activities of daily living, presence of preoperative cognitive impairment using Short Portable Mental Status Questionnaire (SPMSQ) score, preoperative anxiety.
Preoperative variables: Premedication (benzodiazepines, hypnotics, narcotic drugs), ASA status, serum electrolytes, creatinine, glycaemia, etc.
Intraoperative and postoperative variables: Surgical specialty, duration of surgery, type of anesthesia, induction agent, use of anticholinergic, IV opioids used, duration of anesthesia, presence of hypotension, intraoperative blood loss, perioperative blood transfusions, postoperative analgesics used, stay duration in PACU, duration of hospital stay, and admission to ICU.
Operational definitions
Elderly: A chronological age of 65 years old or older, while those from 65 to 74 years old are referred to as “early elderly” and those over 75 years old as “late elderly”29.
Activities of Daily Living: The Katz Index of Independence in Activities of Daily Living is the most appropriate instrument to assess the functional status of the elderly. The Index ranks adequacy of performance in functions of bathing, dressing, toileting, transferring, continence, and feeding. Each function is scored as yes/no for independence functions. A score of 6 indicates full function, 4 indicates moderate impairment, and 2 or less indicates severe functional impairment30.
Preoperative dementia: The Short Portable Mental Status Questionnaire (SPMSQ) Scoring of > 2 errors suggests cognitive impairment31. The Short Portable Mental Status Questionnaire (SPMSQ) asks for the following information: date of birth, age in years, and time to the nearest hour, year, name of the hospital or home address, and the ability to recognize two people. What the year before will be: Enter the patient’s grandfather’s name and count backwards from 20 to 1 (no errors or suggestions permitted). On a scale of 1 to 10, a score less than 7 indicates’ cognitive impairment.
Preoperative anxiety: Preoperative anxiety was assessed using the six-item State-Trait Anxiety Inventory measure. The total of all six scores was multiplied by 20/6. Patients with a score of 20 have no anxiety, while those with a score of 80 have a significant level of worry. A score of 44 and above was considered to indicate clinically severe anxiety32.
The State-Trait Anxiety Inventory consists of negative items (I feel tense, I feel upset, I feel worried), and positive items (I feel calm, I feel relaxed, I feel content). Each item was scored as follows: 1 = Not at all, 2 = Somewhat, 3 = Moderately, 4 = Very much32 .
Postoperative delirium: In our research, we utilized the NU-DESC scale to assess delirium in postoperative patients. The NU-DESC scale comprises five parameters: disorientation, inappropriate behavior, inappropriate communication, illusions/hallucinations, and psychomotor retardation. Each parameter is assigned a sub-score ranging from 0 to 2 points, where 0 indicates the absence of symptoms, 1 represents mild symptoms, and 2 corresponds to severe symptoms. A total score of ≥ 2 points is indicative of postoperative delirium33.
Data collection procedure
The questionnaire consists of two sections: Section 1 consists of demographic and patient-related preoperative data, and Section 2 consists of anesthesia and surgery-related intraoperative data. Section 3 consists of post-operative data such as the duration of surgery/anesthesia, stay duration in the PACU, and length of hospital stay.
Patient history was taken to document pertinent patient demographics and health habits. Functional autonomy was assessed using the basic Activities of Daily Living34. Data for Activities of Daily Living were obtained from the patient or from a close relative or caregiver. Cognitive status was measured using the ten-item Short Portable Mental Status Questionnaire (SPMSQ), which is a brief, easy-to-administer tool that does not require specific training for administration and scoring31, It is a reliable and valid tool35. Consecutive patients in the PACU were prospectively evaluated for the presence of delirium. The nursing staff of the PACU will record the Nu-DESC. The presence of delirium was determined using the Nursing Delirium Scale score36. PACU delirium was assessed by obtaining a Nu-DESC score during transfer to the inpatient ward at the end of their PACU stay when deemed ready to be transferred to the surgical inpatient ward. Content validity and reliability have been established33,37,38.
Data quality assurance
A pretest was conducted on 5% of the study participants (21 patients) at Felege Hiwot Comprehensive Specialized Hospital. Nurses working in the Post-Anesthesia Care Unit (PACU) were trained on both the Nu-DESC tool and the clinical significance of delirium before conducting delirium screenings on the patients. Throughout the data collection period, repeated PACU visits were made to provide assistance with any questions related to the delirium assessments.
Data analysis and interpretation
The data was coded and entered into STATA version 17 after being cleaned and checked for completeness. Descriptive statistics, including percentages, frequency distributions, and measures of central tendency, were calculated. Independent variables were initially analyzed using binary logistic regression, with postoperative delirium as the dependent variable. Variables with a p-value of ≤ 0.2 from the bivariate analysis were then included in a multivariable logistic regression model to assess their association with postoperative delirium. Odds ratios with 95% confidence intervals and p-values were computed to identify factors associated with postoperative delirium. A p-value of < 0.05 was considered statistically significant.
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