Lower segment cesarean section (LSCS) is the most common surgery performed worldwide today. Comfortable and pain-free mother during and after surgery is the crucial aspect of maternal care as she has to take care of the baby also. Effective anaesthesia and postoperative analgesia play key role in achieving this goal. Unfortunately optimum postoperative pain relief is commonly neglected. Inadequately relieved postoperative pain leads to prolonged recovery, increased physical and psychological morbidity, delayed mobilization leading to complications like deep vein thrombosis and embolization, increased medical costs, prolonged use of opioids and analgesics, and the worst is development of chronic pain. It negatively affects the maternal -neonatal bonding and breast feeding [1]. Acute postoperative pain after cesarean section is maximum for first 48 hours and is moderate to severe type of pain. The basic principle of successful postoperative analgesia is multimodal analgesia [2,3]. The recent guideline recommends multimodal analgesia with neuraxial opioids, NSAIDs, local wound infiltration and regional blocks for optimum pre, intra and postoperative analgesia [2,3].

Pain after LSCS has two components - somatic pain arising from the abdominal surgical wound. It has cutaneous and deep components. The visceral pain is from the uterus and abdominal organs. The anterior abdominal wall is supplied by anterior rami of T6 - T12 and L1spinal segmental nerves. The lateral cutaneous nerve supplies the lateral abdominal wall. The visceral pain is dull, diffuse and poorly localized pain transmitted by the autonomic nervous system via the sympathetic fibres [4-6]. Intrathecal opioids can take care of the visceral pain and the abdominal blocks take care of the somatic pain. But transversus abdominis plane block (TAP), quadratus lumborum block and transversalis fascia plane (TFP) block can take care of the visceral pain to some extent because of the spread of the local anaesthetic to the sympathetic chain in the paravertebral space [4,7].

Regional anaesthesia techniques including nerve blocks with intrathecal opioid is a very effective multimodal analgesia combination for post LSCS pain. This can be used alone or combined with systemic analgesics to provide several benefits. Regional anaesthesia with effective pain relief can minimize complications like stress response, nausea, vomiting and reduce the opioid requirements postoperatively, this leads to enhanced recovery facilitating early mobilization and faster recovery [8,9]. A significant component of pain experienced after abdominal surgery is related to incision of the abdominal wall and adequate analgesia can be a challenge. Regional blocks of the anterior abdominal wall can significantly help with intraoperative and postoperative analgesia. Abdominal field blocks are simple techniques that can provide excellent postoperative analgesia and decrease the opioids requirement. This allows patients to breathe and cough more comfortably and facilitates early mobilization and discharge [8].

Dexamethasone is a synthetic glucocorticoid with anti-inflammatory, antiemetic and immunomodulator properties. The perineural dexamethasone prolongs analgesia because of both - its local as well as systemic actions. It causes local vasoconstriction prolonging the absorption of the local anaesthetic and by suppressing the C pain fibres transmission reducing neural discharge. Perineural dexamethasone prolongs analgesia duration by mean period of 6-8 hours when combined with local anesthetics, reduces postoperative nausea and vomiting. The systemic action is because of its anti-inflammatory property [10-13].

Buprenorphine is a centrally acting synthetic opioid having high binding affinity for µ and kappa opiate receptors. Buprenorphine has slow receptor dissociation kinetics, a biphasic (‘bell’ or ‘inverted U’shaped) dose–response relation and a ceiling effect on respiratory depression, but not analgesia in humans [14,15]. Buprenorphine is a mixed agonist - antagonist opioid and an effective analgesic. It has got high lipophilicity and affinity for opiate receptors limiting its cephalad spread and chances of delayed respiratory depression. Nausea, vomiting, pruritus, drowsiness and respiratory depression are some of the side effects. Buprenorphine is a long acting analgesic by epidural and intrathecal route. When used intrathecally with local anesthetic it enhances the sensory blockade without affecting the sympathetic activity [16-18].

This study was undertaken to evaluate and compare the open surgical linea semilunaris block with dexamethasone and without dexamethasone– for post LSCS pain management. All LSCS were done under spinal anaesthesia with intrathecal buprenorphine. The duration of analgesia, mobility score and requirement of other analgesics were monitored in the postoperative period.

1. Trial design and setting

This single center prospective randomized comparative study was conducted in K E M Hospital, Pune. India between August 2021 to December 2022.

The inclusion Criteria for this study were -

1) ASA Grade 2 and 3 patients between 20-40 years of age undergoing LSCS,

2) patients who agreed to participate and gave consent,

The exclusion Criteria for this study were -

1) Body mass index > 35,

2) history of major systemic disease (ASA 3 OR MORE),

3) history of chronic pain,

4) history of drug abuse or alcohol,

5) history of allergies to any study medications.

6) patients having active infection at the site of the block

2. Ethics approaval

This study was approved by the Internal Institutional Review Board constituted and functioning as per ICH-GCP, Indian GCP, ICMR guidelines and local regulatory guidelines. All the study treatments and procedures were done according to the ethical standards. Written informed consent was taken from all the patients.

3. Trial methods

American Society of Anaesthesiologists (ASA) physical status 2 and 3 pregnant woman aged 20-40 years requiring elective/emergency LSCS under spinal anaesthesia were included in the study. After explaining the procedure to the patient and her relatives informed consent was taken prior to surgery while doing pre anaesthetic evaluation. Admitted patients were advised fasting 6 hours for solids, 2 hours for clear liquids for elective LSCS. Patients were randomly allocated to one of the two groups by a computer-generated randomization number. Spinal anaesthesia was given under all aseptic precaution using 27 G Quincke’s spinal needle, 2 ml (10 mg) of 0.5% hyperbaric bupivacaine plus 60 mcg of buprenorphine was injected intrathecally in all the patients. All LSCS were done with Pfannenstiel incision. Intra operatively linea semilunaris block was given by anterior approach after the closure of uterine incision and achieving hemostasis.

4. Linea semilunaris block

The anterior rectus sheath was retracted cranially by the surgeon and block was given by the anaesthesiologist using 22 G hypodermic needle. The needle was inserted in linea semilunaris below the arcuate line above rectus muscle at 10 to 20 degree angulation posterior to horizontal plane, directing towards Petit’s triangle at 3 o’clock on one side and 9 o’clock position on other side of the anterior abdominal wall. The other hand was kept below the rectus muscle and peritoneum to avoid bowel injury. A needle was inserted at linea semilunaris, from medial to lateral direction to place the tip below the anterior rectus sheath, in a myofascial plane between the aponeurosis of anterior abdominal muscles above and fascia transversalis and peritoneum below (Fig. 1, 2).

Figure 1. Linea semilunaris.

Figure 2. Linea semilunaris block.

Group 1 received bilateral open surgical linea semilunaris block with injection 0.2% ropivacaine 20 ml with 1 ml normal saline on either side and Group 2 received bilateral open surgical linea semilunaris block with injection 0.2% ropivacaine 20 ml with dexamethasone 4 mg on either side of the abdomen. After closure of the surgical wound diclofenac suppository 100 mg was inserted rectally in all patients.

5. Rescue analgesia and efficacy outcomes

Postoperatively the patients were evaluated for hemodynamic parameters, pain, requirement of other analgesic drugs, complications like nausea, vomiting, pruritis. Arrival at the post anaesthesia care unit was taken as time 0, patients were subsequently assessed at 2 hours interval for 24 hrs. The pain was quantified on visual analogue scale (VAS). At the onset of pain (VAS > 3, 4) rescue analgesia was given. Inj diclofenac 75 mg IV in 100 ml normal saline was given and repeated every 8 hourly thereafter. Inj tramadol 50 mg and inj paracetamol 1 gm IV were given for breakthrough pain. The time for the first analgesic request and supplemental analgesic requirements over 24 hours were recorded. Johns Hopkins High Level Mobility score was used to mark postoperative mobilization. Twenty four hours after surgery patients were asked to rate their satisfaction with pain management 1 – highly satisfied, 2 – satisfied, 3 – dis-satisfied (Table 1).

Table 1 . Inter group comparison of level of satisfaction.

Level of satisfaction	Group 1	Group 2
Highly satisfied	24	30
Satisfied	6	0
Dissatisfied	0	0

All patients in group 2 were highly satisfied with the pain relief. Twenty four out of thirty in group 1 were highly satisfied and 6 were satisfied with pain relief..

6. Statistical analysis of the patients data

The sample size calculation was done by using the effect sizes from the previously published study (Panpan Zhang et al., Reg Anesthesia Pain Med 2019) and with the help of:

$$n\left(PerGroup\right)=2{\left[\frac{\left(\frac{Z_a}{2}+Z_{\beta }\right)\sigma }{\Delta }\right]}^2$$

For 95% confidence (i.e. = 0.05) and 5% level of significance (z = 1.96), cut-off value for Power 0.8416 [80% power] was taken. The inter-group difference of more than 0.720 standard deviations was treated as clinically significant, even if the results were not statistically significant. Thus, sample size of 30.28 ^≅ 30 (Minimum Per Group) i.e. Total 60 (minimum in two groups) was calculated. The data was presented as Mean ± Standard deviation (SD) across study groups. The significance of difference of distribution of categorical variables across two study groups was tested using Chi-Square test with Bonferroni’s post-Hoc test as a correction for two group comparison. One-way analysis of variance (ANOVA) with Bonferroni’s post-Hoc test as a correction for the two group comparisons was used to test the statistical significance of inter-group difference in the average of continuous variables across two study groups. In the absence of normality, appropriate non-parametric tests for testing the statistical significance of inter-group differences was used. P-values less than 0.05 was considered to be statistically significant. All the hypotheses was formulated using two tailed alternatives against each null hypothesis (hypothesis of no difference). The entire data was statistically analyzed using Statistical Package for Social Sciences (SPSS ver 22.0, IBM Corporation) for MS Windows.

The demographic parameters like age, BMI, duration of surgery were comparable in both the groups. The mean heart rate at 4.5 to 7.0 hours among the cases studied was significantly higher in Group B compared to Group A (P-value < 0.05 for all). The mean systolic BP at 5.0 to 6.0 hours was significantly higher in Group B compared to Group A (P-value < 0.05 for all). The mean diastolic BP at 5.0 and 5.5 hours was significantly higher in Group B compared to Group A (P-value < 0.05 for all). Distribution of mean respiratory rate and SPO2 at baseline and in 24 hours did not differ significantly between the two study groups (P-value > 0.05 for all).

Distribution of mean post-operative pain score (VAS) at 6, 14, 16 and 22 hours is significantly higher in Group 1 compared to Group 2 (P-value < 0.05 for all). Distribution of mean post-operative pain score (VAS) at 2, 4, 8, 10, 12, 18, 20 and 24 hours did not differ significantly between two study groups. All patients in Group 1 required rescue analgesia around 17th postoperative hour and that might be the reason for higher pain scores between 14th to 18th postoperative hours and had pain scores comparable to Group 2 after rescue analgesic (Fig. 3).

Figure 3. Inter-group comparison of mean post-operative pain score (VAS).

The mean ± SD of time to first rescue analgesia in Group 1 was 17.70 ± 8.70 hours and in Group 2 was 24.43 ± 5.52 hours. The minimum – maximum time to first rescue analgesia in Group 1 was 3-36 hours and in Group 2 was 12-36 hours. Distribution of mean time to first rescue analgesia is significantly higher in Group 2 compared to Group 1 (P-value < 0.05 for all) (Fig. 4).

Figure 4. Inter-group comparison of mean time to first rescue analgesia.

In Group 1 almost 70% patients required diclofenac for analgesia compared to only 27% in Group 2. In Group 1 twenty percent patients required paracetamol and 10% required tramadol in addition whereas only 3-4% in Group 2 required tramadol for analgesia. The requirement of analgesic was significantly less in group 2 compared to group 1 (P-value < 0.05 for all) (Fig. 5).

Figure 5. Inter-group distribution of incidence of requirement of other analgesics in first 24 hrs.

The post-operative mobilization time for in bed mobilization in Group 1 was 14.20 ± 5.61 hours and in Group 2 was 6.57 ± 2.31 hours. The post-operative mobilization time for seating in bed in Group 1 was 20.77 ± 7.33 hours and in Group 2 was 9.43 ± 1.92 hours. The post-operative mobilization time for walking in Group 1 was 37.64 ± 10.87 hours and in Group 2 was 20.90 ± 4.07 hours. Group 1 patients were specifically monitored till they started walking. The post-operative mobilization time for mobilization in the bed, seating in the bed and walking is significantly lower in Group 2 compared to Group 1 (P-value < 0.05 for all) (Fig. 6).

Figure 6. Inter-group comparisons of mean post-operative mobilization time.

Ropivacaine is a long acting amide local anaesthetic. It is less lipophilic than bupivacaine. Motor blockade, central nervous system toxicity and cardiotoxicity are less compared to bupivacaine and levobupivacaine. These properties make it the perfect drug for regional anaesthesia, nerve blocks, postoperative analgesia and labour analgesia. The anterior abdominal field blocks are high volume bilateral blocks. Systemic absorption of local anaesthetic is high because of large surface area and good vascularity of the abdominal wall. To avoid overdosing and drug toxicity 0.2 % ropivacaine is the ideal choice. For field block 2-200 mg that is 1-100 ml 0.2% ropivacaine can be used safely [4,19].

Rafi in 2001 introduced transversus abdominis plane (TAP) block first as a blind technique using the lumbar traingle of petit as a landmark [19]. Mc Donnell developed ultrasonography guided TAP block [20]. Spinal or epidural anaesthesia with neuraxial opioids remains a popular technique for post LSCS analgesia. Regional anaesthesia techniques with nerve blocks have been used effectively for pain management in the perioperative period [19-21].

The proposed mechanism of action of linea semilunaris block is - spread of the analgesic drug in the inter-fascial plane between internal oblique and transversus abdominis muscle involving ilio-hypogastric and ilio-inguinal nerve, or spread along fascia transversalis posteriorly towards quadratus lumborum muscle. It was seen in three cadaveric dye study. Blockade of A delta and C fibers in fascia, the muscle and the parietal peritoneum are responsible for intense nature of analgesia [8,22].

In the literature review we came across 2 studies similar to our study.

1. Akhade et al.’s study (prospective observational study) - 120 ASA II patients undergoing emergency/planned lower segment LSCS with Pfannenstiel incision, were given spinal anesthesia using 2.2 ml of 0.5% of bupivacaine. Intraoperative abdominal field block by anterior approach was performed after the closure of uterine incision and achieving hemostasis. In all patients 20 ml of 0.25% of bupivacaine was given on either side of abdomen. In all patients diclofenac suppository 100 mg was inserted at the end of the surgery. Postoperative pain was assessed by using the NRS score at 2 hourly interval for 24 hours. Rescue analgesia requirement were noted for 24 hours. All patients reported adequate analgesia, reduced pain scores, reduced analgesic requirement and were ambulated early. Around 96% of patients experienced no pain in the immediate post-operative hours after the effect of spinal anesthesia wore off. Only 3.3% had mild pain with NRS between 1 and 3. No patient in the study group had severe pain and required opioid supplementation. Patient satisfaction was high and postoperative ambulation was early. There were no block related complications. They concluded that there is considerable potential for anterior approach of anterior abdominal field block (linea semilunaris block) as a component of multimodal regimen for post LSCS analgesia and is easy to perform, simple and safe [22]. In our study we have used additives - intrathecal buprenorphine and 0.2% ropivacaine with dexamethasone in linea semilunaris block. Our patients had lower pain scores with prolonged postoperative analgesia almost 17 to 24 hours. The analgesic requirements were low, sparing opioids and no complications. They were mobilized fast, walking few steps by 20 hours and highly satisfied in dexamethasone group. Group 1 patients started moving in the bed by 14 hours. sitting in the bed by 21 hours and walking 37 hours postoperatively. Group 2 patients were moving in the bed after 7 hours, sitting in the bed after 10 hours and walking around 20 hours postoperatively. Addition of dexamethasone to the block fastens mobilization, prolongs analgesia, reduces postoperative requirements of analgesics (Table 2).

Table 2 . Comparison of our study with similar studies.

Reference no	Intrathecal additive	LS block additive	LS block drug	Rescue analgesia time	Pain score	Ambulation	Analgesic consumption
22	None	None	0.25% bupivacaine	Prolonged	Low	Early	Reduced
23	None	Adrenaline	0.35% ropivacaine	Prolonged	Low	Early	Reduced
Our study	Buprenorphine	Dexamethasone	0.2% ropivacaine	17 to 24 hours	Low	Walking by 24 hours	Reduced

2. Singh et al.’s study (prospective randomized study) - eighty ASA II term pregnant patients posted for elective LSCS under spinal anaesthesia were divided into two groups of 40 patients each. Group B surgically assisted linea semilunaris block was given after closure of the uterine incision bilaterally with 20 ml ropivacaine 0.35% with 1:200000 adrenaline. In group C patients conventional analgesia protocol was followed. Intravenous inj paracetamol 1 gm was given 8 hourly to all patients and for breakthrough pain inj tramadol 1 mg/kg was given. Mean time to first rescue analgesia was significantly longer, mean consumption of rescue analgesics was significantly low with no opioid requirement, patient satisfaction and quality of sleep was better, nausea and vomiting was significantly low in the study group. They concluded that linea semilunaris block has good potential as a component of multimodal analgesia for post cesarean section pain. It is easy to perform, simple, given under vision, effective with high patient satisfaction, opioid sparing and effective [23]. In our study we have used 0.2% ropivacaine and dexamethasone for linea semilunaris block and intrathecal buprenorphine with prolonged analgesia 17-24 hours, lower analgesic requirements and fast mobilisation (Table 2).

In our study 40 ml ropivacaine 0.2% was used for linea semilunaris block. Lower concentration and high volume of local anaesthetic reduced the chances of cardio and neurotoxicity in pregnant patients. Addition of dexamethasone to ropivacaine prolonged the postoperative analgesia and fastened the ambulation reducing nausea and vomiting. Intrathecal buprenorphine 60 mcg prolongs the postoperative analgesia without much complications. This multimodal combination of intrathecal buprenorphine, dexamethasone and ropivacaine for linea semilunaris block is very effective analgesia technique.

In a systematic review and meta-analysis of studies on dexamethasone added to local anesthetics in ultrasound guided transversus abdominis plane block (TAP block) for analgesia after abdominal surgery the time request to the first rescue analgesia was prolonged. The opioid consumption over 24 hours after surgery and incidence of postoperative nausea and vomiting was significantly decreased in dexamethasone group. No complications were reported in all the included studies. They concluded that dexamethasone added to local anesthetics in ultrasound guided TAP block was a safe and effective strategy for postoperative analgesia [12].

In a systemic review and meta-analysis the analgesic effect of dexmedetomidine in transversus abdominis plane block for abdominal surgery was evaluated. Pain scores, opioid consumption, duration of TAP block and the common adverse effect were analyzed. The conclusions were - addition of dexmedetomidine significantly reduced the pain scores postoperatively at rest and on movement, reduced post-operative analgesic requirements and prolonged the duration of TAP block [24].

Lacunae of our study: sample size of our study was small. More studies on linea semilunaris block for post cesarean section analgesia done in multiple centers with large sample size, long term follow up of postoperative pain management with requirement of other analgesics will prove efficacy of this multimodal analgesia technique. The analgesia is for a limited time period. Continuous block with catheters may be tried but it may increase the chances of wound infection.

We recommend linea semilunaris block with intrathecal opioid as an effective multimodal analgesia combination for post LSCS and lower abdominal surgeries. It is an open surgical technique, easy and safe to perform under vision. It does not require costly gadgets, is very cost effective, opioid sparing and reduces consumption of postoperative analgesics. Recovery is fast with early mobilization and high patient satisfaction.

No potential conflict of interest relevant to this article was reported.