A Hospital-based prospective follow up study was conducted from mid, February to April 20, 2019, in University of Gondar Comprehensive Specialized Hospital (UoGCSH). The Hospital is located in Gondar town, Northwest Ethiopia. Cesarean section (CS) is the commonly performed surgical operation with an average of 120–160 operation per month in two functional operation theatres that are dedicated for CS only.
The source population was all parturients who gave birth by CS under anesthesia and study population was all parturients who gave birth by CS under anesthesia at UoGCSH during the study period were the study. All volunteer adult (18+) parturients that underwent CS under both spinal and general anesthesia were included in this study. Parturients who had pre-existing cognitive dysfunction and those who had an ongoing treatment for chronic pain were excluded.
The dependent variable was postoperative pain after CS which was measured with numerical rating scale (NRS). The independent variables were socio-demographic factors (age, body mass index, religion, educational status, marital status and ethnicity), clinical factors (preoperative visit by anesthetists, preoperative anxiety, history of previous CS, preoperative use of analgesics, ASA status, and parity), intraoperative factors (type of surgery, type of incision, length of incision, type of anesthesia, the status of the newborn, surgical time, anesthesia time, regional nerve blocks and intraoperative analgesics) and postoperative factors (types of analgesics given at the postoperative period).
Numerical rating scale with 11 points (NRS-11) is a valid and reliable pain assessment tool in which the number assigned from 0–10 to represent the severity of pain: 0 = no pain, 1–3 = mild pain, 4–6 = moderate pain, 7–10 = severe pain . In this study, NRS-11 was preferred to use due to its simplicity to understand by the parturients. Tolerable pain threshold is defined as a treatment threshold of pain score with a cut of point of NRS-11 ≥ 4, which was considered to identify patients with pain of moderate to severe intensity [15, 16]. Full return of consciousness is defined as a state of consciousness of an individual when he/she is awake or easily arousable and aware of his surroundings and identity after general anesthesia . Spinal anesthesia wear-off is defined as a period of time the spinal anesthetic ends up and patients will gradually start to be able to feel and move their legs and may experience tingling or pins and needles in their legs .
To determine sample size, single population proportion formula was used. A study done in South Africa reported that the incidence of moderate to severe pain during the first 24 postoperative hours and in the immediate postoperative period after cesarean section was (87%) . By assuming 95% of confidence interval with 4% margin of error, the sample size for the study was calculated as so based on this data sample size of this study was calculated by using a single population αproportion formula as:
We have p = 0.87, ℇ = 0.04, Zα/2 at 95% CI = 1.96
n = (1.96)²(0.87x0.13) / (0.04)²
n = 271.6≈ 272, then when we added 10% of the non-response rate, the sample size was n = 299.
All eligible consecutive parturients who underwent cesarean section were included in the study till the calculated sample size reached.
Data was collected by using a pre-tested structured questionnaire. The questionnaire was primarily prepared in English language and translated to Amharic language. Training for data collectors and supervisors was provided by the principal investigator. A pilot was conducted on 30 (10%) patients who were not included in the main study. Then necessary corrections were made accordingly to the questionnaire for the main study. The data collectors and supervisors were closely mentored by the principal investigator throughout the study period. Study participants were provided with adequate information regarding assessment tool (NRS-11). The data collectors took informed consent; reviewed the charts and document pain severity at rest and on movement by using NRS-11 at 2, 12, 24 postoperative hours. The type, doses and time of administered analgesics were also documented. The collected data was checked for the completeness and clarity
After completion of data collection, the variables were coded and cleaned. The data was entered into the Epi-data software (version 4.2) for cleaning for errors and was analyzed by SPSS version 20 (IBM Corporate). The normality of the data was tested by using Shapiro-Wilk normality test. Descriptive statistic was done and presented with frequency, percentage, mean, standard deviation, median and inter-quartile range (IQR). The relationships of nominal data with postoperative pain were analyzed by using cross-tabulations. Hosmer and Lemeshow test was used to assess the goodness of fit. The associations between the independent variables and outcome variable were determined at 95% confidence interval with chi-squared test, bivariate and multivariate binary logistic regression. The cut-point of statistical significance was P < 0.2 for bivariate and 0.05 for multivariate regression. Crude and adjusted Odds Ratio were used to see the strength of the association for bivariate and multivariate logistic regression respectively.