The aim of this study was to assess the analgesic effect of RSB block after emergency midline laparatomy in terms of VAS score; time to 1st analgesic request and total post operative analgesic consumption in 24 hours period.
Study design and period study area
Institutional based prospective observational cohort study was done from February 1 to May 10, 2018 in University of Gondar comprehensive specialized Hospital.
University of Gondar comprehensive specialized Hospital is located in Amhara region, North Gondar zone, which is about 738km away from Addis Ababa in Northwest of Ethiopia.
The non- exposed group of all patients who had emergency midline laparatomy, patient’s age≥18 years old, American Society of Anesthesiologist (ASA) physical status I–II, patients who were induced with standard dose of ketamine anesthesia (2mg/kg), maintained with halothane anesthesia and on standard dose of intraoperative morphine analgesia (0.1mg/kg) were included in this study. The exposed group of all patients that contented the information listed at the non exposed group plus patients who received 32 ml of 0.25% bupivacaine for the RSB group at the end of surgery were included in this study. On the other hand, patients who were managed with combined TAP and RSB, who had lateral side abdominal wound, BMI>35kg/m2, elective procedures, who were not keen to give consent to contribute in this study and uncooperative patients were our exclusion criteria.
In this study the dependant variables were postoperative pain which were assessed using VAS score at rest and on movement, total postoperative analgesics consumption and first analgesic request time. The independent variables were duration of surgery, duration of anesthesia, size of incision, ASA physical status, weight, height, BMI, age and sex of the patients (Table 1).
Sample size determination
The sample size was designed using mean± standard deviation of the VAS score(1.06 ± 0.82 VS 0.63 ± 0.61) in rectus sheath block group and control group respectively. With a mean comparison formula of: n (in each group) = (S12 + S22) f (α, β)/ (M1–M2)2 ,where β=20% and α=5%.M1, S1 and M2, S2 are the mean and standard deviation of the RSB group and non exposed group respectively. n (in each group) = (0.822+0.612) (1.96+0.85)2/ (0.43)2=44.N (total) =88. Then finally we added 5% non response rate with considering of loss of follow up and our sample size came up with 93 patients.
Patients were categorized as exposed and none exposed group based on the responsible anesthetists' independent decision to use RSB at the end of the surgery. Participants were consecutively selected from each group till the required samples were achieved.
Data collection procedure
Structured questionnaires were prepared for all patients who fulfilled the inclusion criteria. After skin closure RSB was done by the responsible anesthetists using blunted needle on supine position at four places on each side of the umbilicus. The space was identified by moving the needle from side to side to felt the scratching of the sheath and advancing until the resistance of posterior layer of the rectus sheath wall felt. The drug was deposited at a potential space that exists between the rectus muscles and posterior rectus sheath. The first data collector coded patient group and recorded intraoperative information like patient’s age, sex, ASA status, height, weight, BMI, incision size, duration of surgery and duration of anesthesia. The second data collector recorded postoperative information within the first 24 hours period in terms of total analgesic consumption, the first analgesic request time and VAS score at 1hour,2 hours,4 hours,6 hours,8 hours,10 hours, 12 hours and 24 hours. The VAS score was determined by patient marking of their pain intensity on a line which is 10 cm long at rest and on movement. The data collection process was supervised by principal investigator.
Data quality management
Data was ensured with pre-test on 5% of the sample and collected data were checked out for the accuracy, clarity and completeness by principal investigator. After pre-test the questionnaires were modified appropriately. Training was given to data collectors for one day on inclusion and exclusion criteria, how to approach the study participants and how to use data collection tools. Finally data clean up and cross-checking was done before analysis.
Data processing and analysis procedures
Data were entered, coded, cleaned and cross checked with SPSS software version 20.Shapiro Wilk normality test was used to identify distribution of data. Normally distributed demographic data were analyzed with independent student t-test. There was normal distribution of data for VAS score at rest and on movement, first analgesic request time and 24 hours total tramadol consumption. Therefore an independent student t-test was performed on these data with a 95% confidence interval and homogeneity of variance was assessed using the Levene's test for equality of variances. There was no normal distribution of data for 24 hours total diclofenac consumption, so Mann-Whitney U test was performed on the data with a 95% confidence interval to analyze the total diclofenac consumption. Normally distributed data was presented as mean±SD, whereas not normally distributed data was presented with median (IQR). Categorical variables were analyzed with chi-square test and presented as frequency (percentage). A P value<0.05 was considered as statistically significant.
Ethical clearance was obtained from University of Gondar ethical Committee.Confidentiality was insured by avoiding personal identifications and keeping questionnaires block. The aim of the research was explained to the patients and informed consent was obtained. None willing participants in the study were guaranteed to refuse at any time.The responsible nurses were informed whenever patients feel pain during data collection time by the second data collector.