Analgesic Efficacy of Ultrasound Guided Transversus Abdominis Plane Block after Cesarean Delivery Analgesic Efficacy of Ultrasound Guided Transversus Abdominis Plane Block after Cesarean Delivery

Women having a cesarean delivery present a unique set of challenges to the anesthesiologists after operation. Adequate pain relief after cesarean is more compelling than any other surgery. The goals include minimizing maternal sedation to facilitate interaction with the newborn, improve mobility to reduce the risk of puerperal thromboembolic events, minimize transfer of analgesics in the breast milk and quicken expected discharge to home after delivery.1

Analgesic Efficacy of Ultrasound Guided Transversus Abdominis Plane Block after Cesarean Delivery the thoracolumbar nerves T10 to L1. The introduction of local anaesthetic in this plane blocks these nerves (T10 to L1). We hypothesized that ultrasonography (USG)-guided TAP block reduces requirement of opioids and provides effective and adequate analgesia. 2

METHODS
After receiving ethical approval from the institutional review board of National Academy of Medical Science(NAMS), 74 patients in Paropakar Maternity and Women's Hospital of ASA grade II undergoing either elective or emergency section by Pfannenstiel incision were included in a prospective, interventional studywhich was completed over a period of November 2016 to January 2017.
Sample size was calculated by using formula n= {2(Zα +Zβ) 2 × SD2)} / d2 Where n = the number of patients in each group,Zα = constant at given alpha error, Zβ = constant at given beta error,SD = standard deviation, d = difference between two means, or effect size with Type I or Alpha error = 1.96 (P value <0.05), Type II or Beta error = 0.842 (80% power), Confidence Interval of 95% corresponding to 1.96 or P<0.05.
Patients were excluded from the study if they refused, had contraindications to spinal anaesthesia, required general anaesthesia for the surgery, had local anaesthetic sensitivity or were morbidly obese and those who were using opioids regularly.
The patients enrolled into the study was randomly allocated to one of the two study groups (B/N, n=37 each). Lottery method was used for randomization, where total 74 small pieces of papers, among which was an equal number (n=37 each) of papers with code name either B or N written in it, were kept inside a container. Patients were asked to pick one of the paper from the bottle and were assigned to the respective group as per written on it and the patients were unaware of the drug coding. Patients were randomized to undergo USG guided TAP block with 0.25% Bupivacine (n = 37) 15 ml on bothside-Group B and noTAP block (n = 37) -Group N. We used 0.25% Bupivacaine 15 ml and also took care not to exceed the toxic dose that is, 3 mg/kg. All patients pre-loaded with Ringer Lactate or normal saline amounting 10ml/kg over 15 to 20 minutes as per standard hospital practice and received spinal anesthesia with 2.2 ml of 0.5% heavy bupivacaine. Surgery was conducted after adequate sensory level block achieved. USG-guided TAP block was given to patients after skin closure. TAP block was administered by the posterior approach using the Sonosite ultrasound machine with high frequency with 13 to 6 MHZ a linear transducer probe.Patients were then transferred to the post-operative recovery room.
Injection paracetamol 1gm was given 6 hourly. Pain severity was assessed by an investigator to the allotment every 0, 2, 4, 6, 8, 12, 18 and 24 hours It was measured using numeric pain rating scale. At any point of time if numerical pain rating scale was 4, injection pethidine 50 mg and injection Phenergan 25 mg was given via intramuscular route.
The parameters studied and compared in both the groups were time to first request for analgesic, total pethidine requirement in 24 hours and numerical pain rating scale at 0, 2, 4, 6, 8, 12, 18, 24 hours.
Data entry and statistical analysis was performed using SPSS version 20 for windows. Age, weight, height, and duration of surgery were compared between two groups by independent Student's t test. The numeric pain rating score for pain and the time to first analgesic rescue and postoperative pethidine requirement were compared in groups by the Mann-Whitney U-test.

RESULTS
A total of 74 patients meeting the inclusion criteria were enrolled in the study. Each group included equal number of patients (n=37). Result of randomization was revealed after the completion of the study and it revealed that the Group B patients had received 0.25% bupivacaine15 ml and no TAP block was in Group N. Demographic data of patients were comparable in both groups (Table1).

NMJ | VOL 4 | No 1 | ISSUE 6 | Jan-Jun 2021
Analgesic Efficacy of Ultrasound Guided Transversus Abdominis Plane Block after Cesarean Delivery The mean time to first rescue analgesia among the two groups was comparable.  The mean total pethidine consumption in first 24 hours in bupivacaine group(group B) was 59.45 ± 19.85 mg and in no TAP group(group N) was 140.54 ± 23.08 mg which was significant statistically (p<0.05).

DISCUSSION
The results of our study showed that TAP block when used as part of analgesic regimen after caesarean delivery delayed time for rescue analgesia, reduced requirement of opioid analgesic and decreased numerical pain rating scale.The prolonged duration of analgesia following TAP block may be because of its poor vascularity thereby causing delayed absorption of bupivacaine and may be due to prolonged action of the amide local anesthetic drug (bupivacaine). Multimodal analgesia is an established technique for controlling postoperative pain. Multimodal analgesia provides better results by combining various drugs with different duration, and onset of action also reduces the side effects of individual drugs. 3 Various other drugs can also be used for improving post-operative analgesia. Opioids have been effectively used to provide postoperative analgesia after caesarean section. Various studies have been conducted in which opioids have been used however; opioids are associated with complications such as respiratory depression, pruritus, sedation, nausea and vomiting. 4 Unfortunately, NSAIDs alone are insufficient to effectively treat post-cesarean delivery pain. 5 The disadvantages of NSAIDs include their gastrointestinal side effects and platelet dysfunction. 6 Ibuprofen and the COX-2 inhibitor, rofecoxib, may even be used antepartum as tocolytic drugs. 7 There are case reports of uterine atony after the use of ketorolac and diclofenac in postpartum women. 8 Analgesic Efficacy of Ultrasound Guided Transversus Abdominis Plane Block after Cesarean Delivery TAP block was introduced by Rafi in 2001. 9 He described it as block delivering local anaesthetics in the TAP using the anatomical landmarks (iliac crest) by first identifying the lumbar triangle of Petit. In 2007, Hebbard etal. introduced the USG-guided approach for TAP block. 10 The USG probe was placed transverse to the abdominal wall which made the three muscle layers distinctly visible after which the probe was moved to the mid-axillary line just above the iliac crest (i.e., over the triangle of Petit). The needle was then advanced medially by in-plane approach. This is referred to as the posterior approach. This approach is used in our study.  12 Paracetamol was needed only after 440 minutes when VAS was more than 3.The most important finding from their study was the significant reduction in the consumption of other analgesics.
Bhattacharjee et al reported duration of postoperative analgesia was 290 minutes following TAP block with bupivacaine, which is similar to this study (416.75 minutes following TAP block with bupivacaine). 13 Baaj J et alfound that total morphine consumption was reduced by more than 60% in the bupivacaine group i.e. total morphine requirements in the first postoperative 24 hours were reduced in the bupivacaine group as compared to the placebo group (25.89 ± 5.13 mg versus 62 ± 4.78, p <0.05) and the bupivacaine group also reported improved satisfaction with their pain relief over 24 hours after surgery and reduced morphine consumption. 14 Like these two studies, in our study, pethidine requirements was reduced by 50% in TAP block with bupivacaine group i.e. the duration of postoperative analgesia with TAP block in bupivacaine group lasted for 416.75 (mean) minutes in comparison to normal saline group. In our study, we used USG guided technique for TAP block to avoid the complications of blind technique. We used pethidine instead of morphine to avoid its complications such as respiratory depression. 17 We used 0.25% Bupivacaine 15 ml and also took care not to exceed the toxic dose that is, 3 mg/kg. Also patients were excluded from the studies if they regularly used opioids. Inadequate analgesia even after TAP block may be either due to technical failure or due to visceral pain component, which is not addressed by TAP block. As such, till now, all local anesthetic techniques carry an inherent failure rate of 5-20%, depending on the skill of the individual. Multiple studies have demonstrated its superiority over standard medical therapy for postoperative pain control. There were no complications attributable to the TAP block.
Obese patients were excluded as the block was difficult to perform, and assessment was limited to only 24 hours post-operatively (but pain severity reduced even in control group by this time). This may be considered as a limitation to our study.

CONCLUSIONS
The conclusion of this study is that USG-guided bilateral TAP block with 0.25% bupivacaine (15mL bilaterally) reduces the postoperative opioid NMJ | VOL 4 | No 1 | ISSUE 6 | Jan-Jun 2021  Table 1.

fIGURES
Duration of first rescue analgesia distribution in two groupsfigure 1.
Numeric pain rating scale in two groups at different time interval figure 2.
Total opioids consumption in first 24 hours figure 3.