Dexmedetomidine versus magnesium sulphate as adjuvants to ropivacaine in ilioinguinal–iliohypogastric nerve block for inguinal hernia repair: A randomised controlled trial

Abstract

Background and Aims:

Ultrasound-guided ilioinguinal–iliohypogastric nerve block (II–IHNB) provides effective analgesia for inguinal hernia surgery; however, the duration of analgesia with local anaesthetic alone is limited. This study compared dexmedetomidine and magnesium sulphate as adjuvants to ropivacaine for II–IHNB.

Methods:

In this randomised controlled trial, 120 patients were allocated into three groups (n = 40 each). Group A received 0.5% ropivacaine, group B received ropivacaine with magnesium sulphate (5 mg/kg), and group C received ropivacaine with dexmedetomidine (1 µg/kg). The primary outcome was time to first rescue analgesia. Secondary outcomes included visual analogue scale (VAS) scores, 24-hour opioid consumption, sedation, haemodynamic parameters, and adverse events.

Results:

The time to first rescue analgesia was significantly longer in group C than in group A, with a median difference of 1080 min [95% confidence interval (CI): 923–1125 min; P < 0.001]. The total 24-hour opioid consumption was significantly lower in group C than in group A, with a median difference of − 10 morphine milligram equivalents (95% CI: −15 to − 5; P < 0.001). VAS scores at rest and movement were significantly lower in group C at multiple postoperative time points (P < 0.001). Sedation scores were higher in group C in the immediate postoperative period (P < 0.001), but no clinically significant respiratory depression occurred. Haemodynamic parameters and the incidence of adverse events remained comparable across groups (P > 0.05).

Conclusion:

Dexmedetomidine is superior to magnesium sulphate as an adjuvant to ropivacaine in II–IHNB, providing prolonged analgesia, reduced opioid consumption, and stable haemodynamics with an acceptable sedation profile.

INTRODUCTION

Effective postoperative analgesia is a cornerstone of perioperative care, particularly in lower abdominal surgeries such as open inguinal hernia repair.[1] Despite advances in surgical techniques and multimodal analgesia strategies, postoperative pain following hernioplasty remains clinically significant due to surgical manipulation of the ilioinguinal and iliohypogastric nerves.[2] Inadequate analgesia may delay mobilisation, increase opioid consumption, prolong hospital stay, and contribute to post-herniorrhaphy groin pain (PHGP).[3] Consequently, regional anaesthesia (RA) techniques that provide targeted analgesia while minimising systemic drug exposure are increasingly emphasised in enhanced recovery after surgery (ERAS) pathways.[4]

Ultrasound-guided ilioinguinal–iliohypogastric nerve block (II-IHNB) has emerged as a reliable RA technique for inguinal surgeries.[3] Ropivacaine, a long-acting amide local anaesthetic (LA) with favourable sensory-motor differentiation and reduced cardiotoxicity, is commonly employed for II-IHNB.[5] However, when used alone, it provides postoperative analgesia of limited duration.[6]

Various adjuncts have been explored to improve the efficacy and duration of regional blocks. Dexmedetomidine, a highly specific α_₂-adrenergic agonist, offers analgesic and sedative effects through modulation of nociceptive transmission and has been shown to prolong peripheral nerve block (PNB) duration while reducing opioid requirements.[7] Magnesium sulphate (MgSO₄), an N-methyl-D-aspartate (NMDA) receptor antagonist and physiological calcium channel blocker, attenuates central sensitisation and enhances analgesic efficacy when used with LA.[8] Dexmedetomidine and MgSO₄ have individually demonstrated analgesic benefits as adjuvants to LA in a variety of peripheral nerve and fascial plane blocks. However, direct comparative evidence between these pharmacologically distinct agents in ultrasound-guided II-IHNB for inguinal hernia repair remains scarce. Furthermore, their relative effects on postoperative analgesia, opioid consumption, sedation profile, and haemodynamic stability in this specific surgical setting have not been adequately characterised. Addressing this knowledge gap is clinically important because the choice of adjuvant may significantly influence analgesic quality, recovery characteristics, and opioid-sparing outcomes following inguinal hernia surgery.

To our knowledge, no adequately powered randomised controlled trial has directly compared dexmedetomidine and MgSO₄ as adjuvants to ropivacaine in ultrasound-guided II-IHNB for unilateral open inguinal hernia repair. Therefore, this trial was designed with the primary objective of evaluating postoperative analgesic duration, with secondary assessment of pain scores, opioid consumption, haemodynamic parameters, sedation, and safety outcomes. We hypothesised that dexmedetomidine would prolong postoperative analgesia more effectively than MgSO₄.

METHODS

The study was approved by our institutional ethics committee (approval No. KIIT/KIMS/IEC/1582/2024; dated 06/02/2024) and prospectively registered with the Clinical Trials Registry–India (CTRI/2024/04/066048; dated 22/04/2024, https://www.ctri.nic.in). The protocol complied with the 2013 Helsinki Declaration and the Good Clinical Practice guidelines. Informed written consent was obtained from each participant to participate in the study and use patient data for research and educational purposes.

A total of 120 patients aged 18–75 years with American Society of Anesthesiologists (ASA) physical status I-III, planned for unilateral open inguinal hernia repair under spinal anaesthesia (SA), were recruited. The subjects with contraindications to SA or PNB, usage of opioids for persistent pain, a body mass index (BMI) ≥35 kg/m², significant coagulopathy, and cognitive impairment were excluded.

Patients were chosen at random for three groups in a 1:1:1 proportion utilising a programmable randomisation algorithm. Allocation concealment was accomplished by the adoption of consecutively arranged, opaque, sealed boxes created by an unbiased investigator not participating in the study. After enroling, the next envelope was opened in sequence to determine group allocation. The study was conducted in a double-blind manner. Postoperative data were gathered by a different anaesthesiologist who was unaware of group allocation and study interventions. The anaesthesiologist performing the block, the patients, and the postoperative outcome assessor were blinded to group allocation. An independent anaesthesia technician prepared the study drugs in identical syringes with equal final injectate volumes for all groups.

All groups received a final injectate volume of 10 mL. Group A received 8 mL of 0.5% ropivacaine (40 mg) +2 mL normal saline. Group B received 8 mL of 0.5% ropivacaine + MgSO₄ (5 mg/kg) diluted with normal saline to a final volume of 10 mL. Group C received 8 mL of 0.5% ropivacaine + dexmedetomidine (1 μg/kg) diluted with normal saline to a final volume of 10 mL. Thus, the final concentration of ropivacaine was maintained at 0.4% (40 mg in 10 mL) in all three groups.

After establishing intravenous (IV) access and doing standard monitoring, a seasoned anaesthesiologist performed all blocks under real-time ultrasound guidance (M Turbo, FUJIFORM Sonosite Edge II, Inc., USA) with a linear high-frequency (6–13 MHz) transducer. The needle was placed medially to laterally using an in-plane technique, aiming for the fascial plane across the internal oblique and transversus abdominis muscles, where the ilioinguinal-iliohypogastric nerves traverse [Figure 1].[9] The II-IHNB was followed by SA with 3 ml of 0.5% hyperbaric bupivacaine. Towards the end of surgery, IV diclofenac 75 mg and IV paracetamol 1 g were administered.

Figure 1.

Ultrasound-guided ilioinguinal–iliohypogastric nerve block. (a) Sono-anatomy demonstrating the fascial plane between the internal oblique (IO) and transversus abdominis (TA) muscles where the ilioinguinal and iliohypogastric nerves traverse (white arrow). (b) Ultrasound image showing spread of local anaesthetic (LA) around the nerves within the fascial plane (white arrow). ASIS = anterior superior iliac spine; EO = external oblique; IO = internal oblique; TA = transversus abdominis

All patients were evaluated for sedation using the modified Ramsay Sedation Scale (mRSS) and for pain using the visual analogue scale (VAS) (0–10) at specified time intervals of 0, 3, 6, 12, and 24 hours post-surgery. Rescue analgesia was administered with IV tramadol 50 mg when the VAS score was ≥4. If pain persisted (VAS ≥4) after 1 hour, a repeat dose of tramadol 50 mg was given slowly intravenously.

The principal outcome was the time required to receive the initial dose of the rescue analgesic. The secondary outcomes were the total 24 h opioid consumption (in ‘morphine milligram equivalents’); postoperative VAS score at 0, 3^rd, 6^th, 12^th, and 24^th hours during rest and movement; postoperative mRSS score at 0, 3^rd, 6^th, 12^th, and 24^th hours; intraoperative parameters like heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and peripheral oxygen saturation (SpO₂) every 5 minutes for the initial 15 minutes of surgery, followed by every 30 minutes until the procedure concludes; and the occurrence of nausea, vomiting, hypotension, and bradycardia.

The sample size was determined based on the time until the need for the initial rescue analgesic, which reported a clinically meaningful difference between dexmedetomidine and MgSO₄ when used as adjuvants to LA.[10] Assuming a two-sided significance level (α) of 0.05 and a statistical power of 95% (β =0.05), the minimum total sample size required for a three-group comparison was 51 patients (17 per group). However, considering the three-arm parallel-group design, requirement for multiple pairwise comparisons, interindividual variability in postoperative pain perception, and the need to ensure adequate power for secondary outcome analyses, the sample size was increased to 40 patients in each group (total n = 120). This larger sample also improved the precision and robustness of outcome estimates and compensated for possible perioperative exclusions or protocol deviations. The sample size was obtained using Open-Source Epidemiologic Statistics for Public Health, produced by Emory University’s Rollins School of Public Health (www.OpenEpi.com).

The Statistical Package for the Social Sciences (SPSS) version 29.0 [International Business Machines Corporation (IBM Corp.), Armonk, NY, USA] was used for statistical data analysis. The Shapiro–Wilk test was employed to assess the normality of the data distribution. Continuous variables such as BMI and surgery duration were normally distributed and analysed using one-way analysis of variance (ANOVA), with Tukey’s post-hoc testing for pairwise analyses. The non-normally distributed data (e.g., age, VAS scores, mRSS score, time to rescue analgesia, opioid consumption) were presented as median and interquartile range and assessed using the Kruskal–Wallis test followed by Dunn’s post-hoc analysis. Categorical variables like gender, ASA status, and surgical side were compared using Chi-square tests. Haemodynamic parameters were compared across groups at each time point using one-way ANOVA. A P value < 0.05 was defined as statistically significant.

RESULTS

A total of 140 subjects were examined for eligibility; 120 were randomised equally across three groups (n = 40 each). All allocated patients received the assigned intervention and were included in the final analysis. There were no losses to follow-up [Figure 2].

Figure 2.

A CONSORT flow diagram for enrolment, group allocation, follow-up, and analysis. CONSORT = Consolidated Standards of Reporting Trials; Group A = Ropivacaine; Group B = Ropivacaine + MgSO₄; Group C = Ropivacaine + Dexmedetomidine; MgSO₄: Magnesium sulphate; GA:General anaesthesia; II-IH:Ilioinguinal-iliohypogastric

The three groups were equivalent with respect to demographic and perioperative variables [Table 1]. Postoperative VAS scores at rest and with movement differed significantly among the three groups at multiple time points [Tables 2 and 3]. Patients in group C consistently displayed lower pain scores than those in groups A and B, particularly from 3 hours onward. Pairwise analysis demonstrated significant differences between group C and the other groups at most postoperative intervals, whereas differences between groups A and B were less consistent. Sedation scores were significantly higher in group C during the immediate postoperative period (P < 0.0001); however, the scores were comparable among groups from 3 h onward, and no patient developed excessive sedation requiring intervention.

Table 1.

Baseline demographic and perioperative characteristics

Variable		Group A (n=40)		Group B (n=40)		Group C (n=40)		P
Age (years)		52.48±16.76		55.75±12.80		50.98±16.11		0.449
Gender (Male/Female)		39/1 (97.5/2.5)		40/0 (100/0)		38/2 (95/5)		0.359
BMI (kg/m²)		23.44±1.96		23.20±1.54		23.70±2.28		0.520
ASA physical status (I/II/III)		28/10/2 (70/25/5)		23/16/1 (57.5/40/2.5)		25/13/2 (62.5/32.5/5)		0.684
Surgical site (Right/Left)		22/18 (55/45)		21/19 (52.5/47.5)		27/13 (67.5/32.5)		0.346
Duration of surgery (min)		120.4±16.36		122.6±14.94		121.3±15.56		0.814

Data expressed as mean (SD) and number of patients. Group A=ropivacaine; Group B=ropivacaine + magnesium sulphate; Group C=ropivacaine + dexmedetomidine; BMI=Body mass index; ASA=American Society of Anesthesiologists; SD=Standard deviation

Table 2.

Comparison of postoperative VAS scores at rest among the study groups

Time point		Group A (n=40)		Group B (n=40)		Group C (n=40)		Overall P		Post-hoc (A–B/A–C/B–C)		HL median difference (95% CI) A–B/A–C/B–C
Baseline		0 (0–0)		0 (0–0)		0 (0–0)		—		—		0 (0 to 0)/0 (0 to 0)/0 (0 to 0)
PACU		0 (0–0)		0 (0–0)		0 (0–0)		—		—		0 (0 to 0)/0 (0 to 0)/0 (0 to 0)
3 h		1 (0–2)		0 (0–0)		0 (0–0)		<0.0001		0.0003/<0.0001/0.2108		0 (0 to 2)/1 (0 to 2)/0 (0 to 0)
6 h		3 (2–3)		2 (2–2)		0 (0–0)		<0.0001		0.0259/<0.0001/<0.0001		1 (0 to 1)/3 (2 to 3)/2 (2 to 2)
12 h		2 (2–3)		3 (2–3)		0 (0–0.75)		<0.0001		0.2811/<0.0001/<0.0001		0 (−1 to 0)/2 (2 to 2)/2 (2 to 3)
24 h		2 (2–3)		2 (1–2)		2 (0–2)		<0.0001		0.0021/<0.0001/0.5597		1 (0 to 1)/1 (0 to 1)/0 (0 to 1)

Values are expressed as median (interquartile range). VAS=Visual analogue scale; PACU=Post-anaesthesia care unit; HL=Hodges–Lehmann; CI=Confidence interval. Overall comparisons were performed using the Kruskal–Wallis test followed by Dunn’s post-hoc analysis. HL median differences with 95% CIs are expressed as A–B, A–C, and B–C; positive values indicate a higher VAS score in the first group. Group A=Ropivacaine; Group B=Ropivacaine + magnesium sulphate; Group C=Ropivacaine + dexmedetomidine

Table 3.

Comparison of postoperative VAS scores at movement among the study groups

Time point		Group A (n=40)		Group B (n=40)		Group C (n=40)		Overall P		Post-hoc (A–B/A–C/B–C)		HL median difference (95% CI) A–B/A–C/B–C
Baseline		2 (2–3)		2 (2–2)		2 (2–2)		0.0733		NS		0 (0 to 0)/0 (0 to 0)/0 (0 to 0)
PACU		0 (0–0)		0 (0–2)		0 (0–0)		0.0093		0.1003/0.0091/>0.9999		0 (0 to 0)/0 (0 to 0)/0 (0 to 0)
3 h		3 (2–3)		2 (2–3)		0 (0–0)		<0.0001		0.1042/<0.0001/<0.0001		0 (0 to 1)/2 (2 to 3)/2 (2 to 2)
6 h		4 (4–5)		3 (3–4)		2 (0–2)		<0.0001		0.0040/<0.0001/<0.0001		1 (1 to 1)/3 (2 to 3)/2 (1 to 3)
12 h		4 (3–4)		4 (4–5)		2 (2–3)		<0.0001		0.2879/<0.0001/<0.0001		0 (−1 to 0)/1 (1 to 2)/2 (1 to 2)
24 h		4 (3–4)		3 (3–3)		3 (2–3)		<0.0001		0.0032/<0.0001/0.4883		0 (0 to 1)/1 (0 to 1)/0 (0 to 1)

Values are expressed as median (interquartile range). VAS=Visual analogue scale; PACU=Post-anaesthesia care unit; NS=Not significant; HL=Hodges–Lehmann; CI=Confidence interval. Overall comparisons were performed using the Kruskal–Wallis test followed by Dunn’s post-hoc analysis. HL median differences with 95% CIs are expressed as A–B, A–C, and B–C; positive values indicate a higher VAS score in the first group. Group A=Ropivacaine; Group B=Ropivacaine + magnesium sulphate; Group C=Ropivacaine + dexmedetomidine

The time to first rescue analgesia was significantly prolonged in groups B and C, particularly in group C. Compared with group A, group C demonstrated a Hodges–Lehmann median increase of 1080 min [95% confidence interval (CI): 923–1125 min; P < 0.001]. The overall difference was highly significant (Kruskal–Wallis, P = 0.0001; Dunn’s post-hoc A-B, P < 0.001; A-C, P < 0.001; B-C, P < 0.001), with group C demonstrating the longest duration of analgesia, followed by group B and group A. Similarly, the 24-hour opioid consumption was significantly reduced in group C compared with group A, with a Hodges–Lehmann median difference of − 10 morphine milligram equivalents (95% CI: −15 to − 5; P < 0.001). The differences were highly significant (Kruskal–Wallis, P < 0.001), with all post hoc comparisons (A-B, 0.0004; A-C, 0.0001; B-C, 0.0001) indicating reduced opioid requirement in groups B and C [Table 4]. Intraoperative HR, SBP, DBP, and SpO2 remained clinically stable throughout the study. A transient difference in HR was observed between groups B and C at 10 and 15 minutes, whereas all other haemodynamic comparisons were comparable (P > 0.05). The occurrence of adverse events was minimal and similar among the three groups [Table 4]. No patient developed respiratory depression, LA systemic toxicity, or excessive sedation that required intervention.

Table 4.

Analgesic outcomes and adverse events among the study groups

Variable		Group A (n=40)		Group B (n=40)		Group C (n=40)		Overall P		Post-hoc (A–B/A–C/B–C)		HL median difference (95% CI) A–B/A–C/B–C
Time to first rescue analgesia (min)		360 (345–375)		720 (692.5–750)		1440 (1440–1440)		<0.0001		<0.0001/<0.0001/<0.0001		−360 (−380 to −355)/−1080 (−1080 to −1065)/−705 (−720 to −690)
24-h opioid consumption (MME)		10 (10–10)		5 (5–10)		0 (0–0)		<0.0001		0.0004/<0.0001/<0.0001		5 (5 to 5)/10 (10 to 10)/5 (5 to 5)
Nausea, n (%)		2 (5.0)		1 (2.5)		1 (2.5)		0.81		—		—
Vomiting, n (%)		1 (2.5)		1 (2.5)		0 (0)		0.60		—		—
Hypotension, n (%)		0 (0)		1 (2.5)		1 (2.5)		0.60		—		—
Bradycardia, n (%)		0 (0)		0 (0)		1 (2.5)		0.36		—		—
Respiratory depression, n (%)		0 (0)		0 (0)		0 (0)		—		—		—
Excessive sedation, n (%)		0 (0)		0 (0)		0 (0)		—		—		—
Local anaesthetic toxicity, n (%)		0 (0)		0 (0)		0 (0)		—		—		—

Values are expressed as median (interquartile range) or number (%). MME=Morphine milligram equivalents; HL=Hodges–Lehmann; CI=Confidence interval. Continuous variables were analysed using the Kruskal–Wallis test followed by Dunn’s post-hoc analysis; categorical variables were analysed using Chi-square or Fisher’s exact test as appropriate. HL median differences with 95% CIs are expressed as A–B, A–C, and B–C. Group A=Ropivacaine; Group B=Ropivacaine + magnesium sulphate; Group C=Ropivacaine + dexmedetomidine

DISCUSSION

The present trial directly compared ropivacaine alone, ropivacaine with dexmedetomidine, and ropivacaine with MgSO₄ for ultrasound-guided II-IHNB during unilateral open inguinal hernia repair under SA. The key finding is that dexmedetomidine, in combination with ropivacaine, provides markedly superior and more consistent postoperative analgesia than the MgSO₄ and ropivacaine combination. Ropivacaine alone offers the shortest duration of pain relief.

These findings align with previous studies evaluating α_₂-agonists in PNB and fascial plane blocks.[10,11,12] Evidence from non-II-IHNBs like supraclavicular brachial plexus block and abdominal wall blocks supports our observations.[7,10,11,13,14,15] The marked reduction in opioid consumption in the dexmedetomidine group is clinically relevant and aligns with previous studies evaluating dexmedetomidine as a perineural adjuvant in peripheral and fascial plane blocks.[7,11,12,14] In an ultrasound-guided transversus abdominis plane (TAP) block study, Reddy et al. reported that dexmedetomidine prolonged time to first rescue analgesia more effectively than MgSO₄, which parallels the pattern observed in our II–IHNB study.[10] Similarly, Elyazed and Mogahed, in infraclavicular brachial plexus block, and Shukla et al., in supraclavicular brachial plexus block, found that dexmedetomidine produced longer analgesic duration and lower rescue analgesic requirement than MgSO₄ when used with ropivacaine.[13,16] Severe early postoperative pain is a strong predictor of PHGP, highlighting the importance of effective postoperative pain relief. By providing near 24 h analgesia and markedly reducing opioid exposure, the dexmedetomidine-ropivacaine II-IHNB regimen directly addresses these risks.[2,17]

Although the direction of effect was consistent across studies, direct comparison should be interpreted cautiously because previous investigations differed in block type, LA concentration, adjuvant dose, and surgical population. These methodological differences may partly explain variations in the magnitude of analgesic prolongation reported across studies.

In contrast, studies evaluating MgSO₄ as an adjuvant have also shown improvement in postoperative analgesia compared with LA alone, although the magnitude of prolongation is generally less than that achieved with dexmedetomidine. Abo-Zeid and El Mansy reported that adding MgSO₄ to bupivacaine in II–IHNB reduced acute post-herniorrhaphy pain and analgesic consumption.[18] Ahmed et al. also demonstrated that MgSO₄ improved block characteristics in II–IHNB compared with control.[11] These observations are consistent with our finding that MgSO₄ improved analgesic duration compared with ropivacaine alone but was less effective than dexmedetomidine.

The NMDA-antagonist and calcium-channel blocking properties of magnesium confer additional central antihyperalgesic effects on it, and several studies of TAP and plexus blocks have shown reductions in early opioid consumption when magnesium is added to LA, although with a shorter duration than steroid or α₂-agonist adjuvants. However, our findings suggest that dexmedetomidine outperforms MgSO₄ as an adjuvant to ropivacaine in the II-IHNB concerning 24 h opioid consumption.[8,10,11,12]

The observed differences in analgesic duration may be explained by the distinct pharmacological mechanisms of the two adjuvants. Dexmedetomidine has combined peripheral and central antinociceptive actions, including inhibition of norepinephrine release, hyperpolarisation of nerve membranes, and local vasoconstrictive effects that prolong LA action.[7,14] In contrast, MgSO₄ primarily acts through NMDA receptor antagonism and attenuation of central sensitisation, which may provide comparatively less prolongation of PNB.[8,19] However, interpretation of the analgesic superiority should be made cautiously as concomitant SA and administration of systemic analgesics (diclofenac and paracetamol) may have influenced postoperative pain scores and opioid consumption. Nevertheless, because these co-interventions were standardised across all study groups, the observed between-group differences are likely attributable to the study adjuvants rather than differences in background analgesia. This is consistent with comparative clinical studies of abdominal wall and upper limb blocks, in which dexmedetomidine produced more profound and sustained analgesic prolongation than MgSO₄ at doses comparable to those used in our trial.[8,10,11,13,15]

A potential concern with α_₂-agonists is the risk of bradycardia, hypotension, and excessive sedation. In the present study, perineural dexmedetomidine at 1 μg/kg did not produce clinically significant haemodynamic instability, and the SpO₂ remained comparable among the three groups. Sedation scores were modestly higher during the immediate postoperative period without respiratory depression or delayed recovery. These findings are consistent with previous reports and systematic reviews evaluating perineural dexmedetomidine.[7,10,11,12,14,16,20,21] Likewise, MgSO₄ at 5 mg/kg administered perineurally was well tolerated in our cohort, with no neurologic deficits or serious systemic adverse effects, consistent with earlier II-IHNB and TAP block data, in which magnesium doses in the 100–250 mg range did not increase perioperative complications.[10,12,18,22]

The results of this study have important implications for day-care surgery and enhanced recovery after surgery (ERAS) protocols. A single-shot ultrasound-guided II-IHNB using ropivacaine with dexmedetomidine can provide nearly 24 h of analgesia, markedly reduce opioid consumption, and enhance patient comfort without impairing motor function. Given that II-IHNBs are purely sensory, the prolonged analgesia achieved with dexmedetomidine supports early ambulation and timely discharge after open inguinal hernia repair. These results endorse the utilisation of dexmedetomidine as an efficacious adjuvant in ultrasound-guided II–IHNB within ERAS protocols for inguinal hernia surgery.

The limitations include the single-centre design and the absence of long-term follow-up for PHGP. Another limitation is that the doses of dexmedetomidine and MgSO₄ were selected from clinically used doses reported in previous PNB studies rather than from an established equianalgesic conversion model. Since these adjuvants act through different pharmacological pathways, a direct dose-equivalence relationship cannot be assumed. Future studies with multicentre designs and extended follow-up are warranted to assess the long-term benefits and safety of dexmedetomidine as a perineural adjuvant.

CONCLUSION

This study demonstrated that dexmedetomidine is a superior adjuvant for ultrasound-guided II-IHNB during unilateral open inguinal hernia repair under SA. Compared with MgSO₄ and ropivacaine alone, dexmedetomidine significantly prolongs postoperative analgesia, provides a marked opioid-sparing effect, and ensures more consistent pain control without compromising haemodynamic stability or safety.

Author contributions

LKS: Concepts, design of the study, literature review, data acquisition, manuscript preparation, manuscript review. RGB: Data collection, literature review, manuscript preparation. AMP: Study design, manuscript preparation, manuscript review, and editing. RKS: Concepts, study design, literature review, manuscript review, and editing. PS: Concepts, data analysis, manuscript editing, and manuscript review. We declare that the manuscript has been read and approved by all the authors, and the authors alone are responsible for the contents and writing of the manuscript.

Presentation at conferences/CMEs and abstract publication

None.

Study data availability

De-identified data may be requested with reasonable justification from the authors (email to the corresponding author) and shall be shared after approval as per the authors’ Institution policy.

Disclosure of use of artificial intelligence (AI)-assistive or generative tools

No artificial intelligence was used for manuscript preparation except for Grammarly for academic language editing.

Declaration of use of permitted tools

None

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.