An institutional-based prospective cohort study was employed from January 1 to April 30, 2019 in Mahatma Gandhi and Empress Zewditu Memorial Hospitals, the public hospitals in Addis Ababa, capital of Ethiopia. Ethical clearance was obtained from the Addis Ababa university institutional review board before the start of the study. Official support letter was written to the Hospitals and permission for data collection was sought from the responsible authorities. Verbal as well as written informed consent was obtained from each participant. All ASA I and II parturients who underwent elective caesarean delivery under spinal anaesthesia were included in this study. Parturients with preeclampsia, eclampsia, history of medical illness, history of chronic opioid use, diabetes mellitus, use of other adjuvant, use of adjuvants for spinal anesthesia, bleeding abnormality and patients with BMI > 30 kg/m2 were excluded from the study.
The protocol and routine procedures before, during and after CS at the study site were as follows:
On arrival of the patients to the operative theater, and after application of the routine hospital monitoring protocol, HR, noninvasive blood pressure, and SPO2 has been recorded before institution of spinal anesthesia, then all patient received spinal anesthesia with 2–3 ml of 0.5% bupivacaine (according to the height of the patient) using 25 or 26-Gauge spinal needle based on the responsible anesthetists preference. After this, all patients were repositioned in supine position and level of sensory and degree of motor block was assessed. Then, the necessary Intraoperative data was recorded. We the investigators did not participate in the perioperative patient management and post-operative pain management option.
In study hospital postoperative pain management for CS are done by either bilateral TAP block with bupivacaine alone (40 ml (20 ml each side), 0.25%), with IV dexamethasone (8 mg) or perineural dexamethasone (8 mg) depending the decision of anesthetist in charge. The block was performed by using a standard land mark technique immediately after skin closure.
Since randomized control trial (RCT) was not yet allowed in our university, the patients were not randomized, rather patients were classified as TAP-alone (n = 29), TAP-IVD (n = 29) and TAP-PD (n = 29) based on the responsible anesthetists decision at the end of skin closure. TAP-alone group were considered as control group
Under aseptic technique, after identifying lumbar triangle of Petit as an access point to the neurofascial plane, TAP block has been performed by Msc anesthesia trainee or staff Msc on duty with the patient lying in supine position. Following aseptic preparation of the skin, 22G blunted needle was advanced perpendicular to skin 2 cm above anterior superior iliac spine in triangle of petit, as the external oblique muscle is pierced a characteristic ‘click’ or ‘pop’ was felt and as the needle was advanced further a second ‘click’ was felt as the internal oblique muscle is pierced then after care full aspiration 20 ml of 0.25% bupivacaine (for one side) was injected in the facial plane (TAP-Alone).
Eight (8) mg Dexamethasone was given either mixed with bupivacaine or IV immediately when the block is performed (for TAP-PD and TAP-IVD respectively).
The same procedure has been performed at the contra lateral side and the patients were transferred to the obstetric recovery ward after the procedure
Postoperative pain was assessed in all groups using a NRS score. The scale consists of horizontal lines ranging from 0 (no pain) to 10 (worst imaginable pain). Patients were asked to report their pain based on 11 point NRS score. The pain intensity was rated as no pain (NRS: 0), mild (NRS: 1–3), moderate (NRS: 4–6), and severe (NRS: 7–10). The first NRS score was recorded at 4th hr of the procedure and then at 6th, 8th, 12th and 24th hr. The pain score was assessed during a quiet breathing period or at rest (static NRS) and after voluntary cough/ movement (dynamic NRS). The time to the first request and total analgesic consumption of each patient was recorded from the chart. At the times of pain evaluation, the heart rate, the mean arterial blood pressure, respiratory rate and SPO2 was assessed. Any postoperative adverse events such as nausea, vomiting and shivering were recorded and informed to the clinicians on duty for treatment
For the purpose of this study, the following definitions were used:
Time to first analgesia request
a time in minutes (hour) from the end of surgery to a first time analgesia (Diclofenac or tramadol or both) were given.
Total post-operative analgesia consumption
total dose and type of analgesic medication given in mg within the first 24 hour starting from admission to recovery room.
Post-operative nausea and vomiting
when a patients experience at least one episode of either nausea or vomiting within 24 hours
in voluntary repetitive activity of skeletal muscle
Failed TAP block
when the NRS score is ≥ 4 at 4th hour post procedure.
Lost follow up
any follow up followed for less than 24 hour for any reason.
Sample size and sampling technique
The sample size was calculated from the data of the primary outcome in a preceding pilot study using all outcome variables. Time to first analgesic request was used to estimate the sample size because it gave us the largest sample size .A priori power analysis for a one-way ANOVA with 3 groups was conducted in G*Power (using version 184.108.40.206) to determine sample size using an alpha = 0.05, a power of 0.80. In order to ensure a minimum of 78 patients needed, an additional 9 patients (≈ 10%) were added as attrition rate.
From situational analysis about 130 patients are estimated to take TAP block with dexamethasone or alone during the study period in the two hospitals. Proportional allocation to size (PAS) were determined from these 130 patients, 87 participants were recruited with the probability of about 66%. By considering the consecutive TAP block with dexamethasone or alone, data collection was made on 2 patients for every 3 patients who underwent elective CS under spinal anesthesia and took TAP block with dexamethasone and alone. From number 1 to 3, one number was selected by lottery method which was used for exclusion for consecutive patient in all groups until the required sample size is reached.
Data processing and analysis
Data were entered and analyzed by SPSS Version 20. The data were tested for normality using histogram and Shapiro–Wilk normality test and homogeneity of variance by Levene’s test. Normally distributed and continuous data were analyzed using one way analysis of variance (ANOVA) with post hoc analysis for multiple tests and non-normally distributed data were analyzed using kuruska-walih H rank test with pairwise comparison. Time to first analgesic request was analyzed using Life table, log rank Kaplan–Meier survival curves.
The comparison of categorical variable was analyzed using Pearson chi-square test. Data were presented as mean ± SD for normally distributed, median ± IQR (25th–75th percentile) and mean rank for non normally distributed data (decision was made by visual inspection of box plot) and categorical data were presented as numbers and frequencies (percentages). P-values < 0.05 were considered statistically significant.