Comparison of analgesic efficacy of ropivacaine versus ropivacaine plus dexmedetomidine in modified thoracolumbar interfascial plane block in patients undergoing lumbar disc surgeries: A randomised controlled trial

Abstract

Background and Aims:

Inadequate pain control can cause a delay in recovery; hence, adequate analgesia is of much importance. The thoracolumbar interfascial plane (TLIP) block is a relatively newer block which has shown promising effects in pain control. In this study, we aim to determine the efficacy and safety of dexmedetomidine in enhancing the impact of local anaesthetic in TLIP block in patients undergoing lumbar surgeries.

Methods:

60 patients aged 18–70 years were randomised to Group Plain [modified TLIP block with 20 mL of 0.25% ropivacaine bilaterally with general anaesthesia (GA)] and Group Dexmed (modified TLIP block with 0.25% ropivacaine along with 0.5 µg/kg dexmedetomidine bilaterally with GA). The primary outcome was to assess the total perioperative opioid consumption in the first 24 h. The secondary outcomes were to assess pain score upon arriving in the post-anaesthesia care unit, time to first analgesic need after surgery, postoperative opioid consumption in 24 h, and incidence of adverse events, including nausea and vomiting. Continuous variables were analysed using an independent t-test. The variables which had a non-normal distribution were analysed using the Mann–Whitney U test. Paired continuous data following a normal distribution were analysed using the Paired T-test. Categorical variables were analysed using the Chi-square test. The statistical analysis was performed using Jamovi 2.4.

Results:

The total perioperative opioid consumption in Group Plain was 653.33 [standard deviation (SD): 250.4 µg] and that in Group Dexmed was 523.6 (SD: 258.6 µg), with a mean difference of 129.67 [95% confidence interval (CI): -1.89, 261.22] (P = 0.053). However, the first request for analgesia was significantly prolonged in the Group Dexmed with a median of 180 minutes [interquartile range (IQR): 97.50–232.50; range (Min–Max: 30–360) min] vs 90 minutes in Group Plain [(IQR):45–120; range (Min–Max: 15–360) min], P = 0.001. Postoperative pain scores were comparable between both groups at different time points in 24 hours, except at 0 h rest and movement, and 3h at movement. The median highest postoperative nausea and vomiting (PONV) scores within the 24 h postoperative period did not differ significantly between the groups (P = 0.073).

Conclusion:

TLIP block with dexmedetomidine as an adjuvant did not decrease cumulative fentanyl consumption as compared to TLIP block with ropivacaine alone. But the time to first request of analgesia was increased in the Group Dexmed.

INTRODUCTION

Perioperative pain management in spinal surgery demands a nuanced approach owing to the high prevalence of preexisting chronic pain, significant perioperative pain affecting early recovery and the substantial likelihood of progression to chronic postsurgical pain.[1,2]

Multimodal analgesia, including opioids, non-steroidal anti-inflammatory drugs (NSAIDs), and local infiltration analgesia, although has been the mainstay of perioperative analgesia, is limited by suboptimal efficacy, limited duration of action, and opioid associated adverse effects. Regional techniques form an important component of multimodal analgesia, and various methods, such as erector spinae plane (ESP) block and quadratus lumborum (QL) block, have been described. The thoracolumbar interfascial plane (TLIP) block is one such technique, first described by Hand et al. in 2015,[3] which targets the dorsal rami of the thoracolumbar nerves. A modification of this technique was proposed in 2017, where the injection is placed between the longissimus (LS) and iliocostalis (IC) muscles, further from the midline. TLIP block has been found to provide superior analgesia compared to conventional systemic analgesia alone in lumbar spine surgeries. In a meta-analysis of six randomised controlled trials (RCTs), Abdildin et al.[4] found significant reduction in pain scores, postoperative opioid consumption, and side effects in favour of TLIP block. Ekinci et al. demonstrated that the TLIP block is superior to local wound infiltration.[5]

Dexmedetomidine, a highly selective α2-adrenergic receptor (α2-AR) agonist, has demonstrated efficacy in prolonging sensory blockade when used as an adjuvant to local anaesthetics in various peripheral nerve blocks.[6,7] However, to the best of our knowledge, no published studies have evaluated the efficacy of dexmedetomidine as an adjuvant in TLIP blocks for patients undergoing lumbar disc surgeries. Therefore, in the present study, we aimed to compare the analgesic efficacy and opioid sparing effects of ropivacaine alone versus ropivacaine combined with dexmedetomidine in the modified TLIP block for lumbar disc surgery. We hypothesised that ropivacaine with dexmedetomidine would have superior perioperative analgesia than ropivacaine alone. The primary objective of this study was to compare 24 h perioperative fentanyl consumption. Secondary objectives included the evaluation of postoperative pain scores and fentanyl consumption, adverse effects, and intraoperative and postoperative haemodynamic stability.

METHODS

This was a randomised, interventional, double-blinded study conducted between December 2022 to July 2024, after obtaining approval from the Institutional Ethics Committee (vide approval number- IECPG-628/25.08.2022, RT-17/29.09.2022, dated 30/09/2022) and registered in the Clinical Trials Registry-India (vide registration number CTRI/2022/12/048350; accessible at https://www.ctri.nic.in). Written informed consent was obtained from all participants for participation in the study and the use of patient data for research and educational purposes. The research was conducted by the principles of the Declaration of Helsinki 2013 and Good Clinical Practice guidelines.

Accordingly, 30 patients in each group of American Society of Anesthesiologists (ASA) physical status I-III classification between 18 and 70 years of age who were undergoing elective lumbar disc surgeries at less than or equal to two levels were included in the study. The determinants of exclusion criteria were patient refusal, previous lumbar spine surgery, extensive lumbar spine surgeries like large tumour excisions, scoliosis correction or more than 2 level spine fixations, body mass index (BMI) >35 kg/m², history of opioid tolerance, contraindications to regional technique, for example, local infection (administration site), systemic infection, coagulopathy, allergy to any drugs used in the study, and pregnancy or lactation.

Patients were randomised using online randomisation software available at www.sealedenvelope.com, and allocation was concealed using the Sequentially Numbered Opaque Sealed Envelope (SNOSE) technique. The sealed envelopes were sequentially labelled from 1 to 60. Each envelope contained a folded slip mentioning Group Plain or Group Dexmed. Patients were informed about the patient controlled analgesia (PCA) device and were educated regarding the Visual Analogue Scale (VAS).

The intervention in both study groups was performed after the induction of general anaesthesia (GA). To ensure blinding, the patient was unaware of the group allocation. Study drug syringes were prepared by an independent anaesthesia technician not involved in the block administration or data collection. The syringes were identical in both groups to keep the administrator blinded. The anaesthesiologist performing the block was not involved in data collection. The investigator responsible for intraoperative data collection entered the operating room only after the regional block had been performed and had no access to the anaesthesia chart or any documentation indicating group allocation. Similarly, postoperative data collection was conducted by a separate investigator who was not involved in the preoperative assessment, block administration, or intraoperative management. This postoperative assessor was also blinded to group allocation and did not have access to the intraoperative anaesthesia records. These measures were implemented to minimise the risk of observer bias and ensure rigorous blinding throughout the study.

All selected patients underwent a routine preanaesthetic assessment, and adequate fasting was ensured. They were informed about the study protocol in a language that they understood with the help of the patient’s information sheet, and informed written consent was obtained from them.

In the operating room, after adequate preoxygenation, induction in both groups was achieved with intravenous (IV) fentanyl 1.5–2 µg/kg, followed by IV propofol 2–2.5 mg/kg, and atracurium (0.5mg/kg). The airway was secured by an appropriately sized cuffed endotracheal tube (ETT), and the position of the ETT was confirmed clinically by 5-point auscultation and capnography. After taking adequate precautions, all patients were turned into the prone position for placing a modified TLIP block and proceeding with lumbar disc surgeries. The third lumbar vertebra (L3) was identified by a counting-up approach after identification of the L4-5 interspace, which corresponds to the anterior superior iliac spine and was marked with a marker. A SonoSite S-Nerve USG machine (FUJIFILM SonoSite Inc., USA) with a (2–5 Hz) curved array ultrasound probe at a depth of 3–8 cm was used in transverse orientation in a midline position at the level of L3. Skin asepsis was achieved with 2% chlorhexidine. After identification of all structures [Figure 1], a 10 cm 21G Stimuplex needle was inserted in a medial-to-lateral orientation under real-time in-plane ultrasound guidance through the belly of the LS muscle towards the IC muscle with an approximate angle of 30 degrees to the skin. Once the needle tip reached the LS/IC muscle interface, a total volume of 20 mL of drug was administered with intermittently repeated negative aspiration. Anterior spread of local anaesthetic was viewed as favourable, as confirmed with ultrasound.

Figure 1.

Sonographic Anatomy of TLIP block. SP = Spinous process; MF = Multifidus; LS = Longissimus; IC = Iliocostalis; TLF = Thoracolumbar fascia; SAP = Superior articular process; TLIP = Thoracolumbar Interfascial Plane block

Group Plain patients received ultrasound guided modified TLIP block with bilateral administration of 20 mL of 0.25% ropivacaine under GA. In Group Dexmed, patients received a total volume of 20 mL ropivacaine 0.25%+0.5 µg/kg dexmedetomidine with intermittently repeated negative aspiration on each side.

In all patients, anaesthesia was maintained with isoflurane in oxygen and air (50:50) with a target minimum alveolar concentration (MAC) of 0.8–1.2. Intraoperative neuromuscular blockade was maintained by administration of boluses of atracurium 0.2 mg/kg. Intraoperative analgesia was maintained with boluses of IV fentanyl 0.5–1.0 µg/kg as required and intravenous acetaminophen 15 mg/kg 30 to 45 minutes before the end of surgery. At the end of surgery, reversal of neuromuscular blockade was done by IV neostigmine 50–70 µg/kg and IV glycopyrrolate 7–10 µg/kg. Tracheal extubation was performed once the patient was conscious, able to follow commands, and generated at least 5 mL/kg tidal volume. Then, patients were transferred to the post-anaesthesia care unit (PACU).

On arrival in the PACU, VAS scores at rest and on movement were noted at 0, 1, 3, 6, and 24 h. VAS scores were measured at 0, 1, 3, 6, and 24 h, corresponding to the immediate, early, and late postoperative phases, corresponding to the onset, peak effect, and delayed analgesia effect. If the VAS was >3, a bolus of IV fentanyl 0.5–1.0 µg/kg body weight was given to all patients as rescue analgesia. Then, patients were connected to an IV PCA pump containing fentanyl, which was programmed to deliver a 20 µg fentanyl bolus with a lockout interval of 15 minutes without continuous infusion, so that the maximum dose of fentanyl delivered in a 1 h dose was limited to 80 µg. Similarly, rescue analgesia was administered as a IV bolus of fentanyl 0.5–1.0 µg/kg body weight whenever VAS was > 3 in the postoperative period.

The time to the first bolus dose was recorded as the first analgesic requirement during the first 24 h. In addition to this, IV acetaminophen 15 mg/kg was given every 6 hours to all patients for the first 24 hours post-operatively and thereafter as and when required. Post-operative nausea and vomiting (PONV) was noted till 24 h and graded according to PONV score previously used,[8,9] and the highest median score was reported (PONV scoring was defined as 0 = no nausea or vomiting; 1 = nausea but no vomiting; 2 = vomiting once in 30 minutes; 3 = two or more episodes of vomiting in 30 minutes). IV ondansetron 4 mg was administered if the PONV score was two or more. In case of inadequate relief after ondansetron, IV metoclopramide 150 µg/kg was administered.

The primary outcome was to assess the total perioperative fentanyl consumption in the first 24 h defined as cumulative intraoperative and postoperative PCA opioid consumption from the onset of surgery. The secondary outcomes were to assess postoperative VAS scores at pre-defined time points mentioned above, time to first analgesic request after surgery, postoperative PCA fentanyl consumption in 24 h and at pre-defined time points, that is, 0, 1, 3, and 6 h, and rescue analgesia as defined and adverse events, including median scores of nausea and vomiting.

Data were collected at baseline and in the perioperative period, and a separate proforma was designated for every patient for intraoperative and postoperative monitoring. The sample size was calculated from https://clincalc.com/stats/samplesize.aspx. Based on the hypothesis that dexmedetomidine in modified TLIP block will result in a 20% decrease in total IV fentanyl consumption in the 24 h postoperative period, and also taking results of Chen K et al.,[10] who reported a mean of 26.7 [standard deviation (SD): 5.3)], for 80% power and an alpha error of 0.05, the sample size was calculated as 28 per group. We included 30 patients in each group to accommodate patient dropouts and other confounding factors.

The statistical analyses were performed using Jamovi statistical software (version 2.4), developed by The Jamovi Project, Sydney, New South Wales, Australia. Normality was assessed by the Shapiro–Wilk test and Q-Q plots. Continuous variables such as age, height, weight, heart rate (HR), blood pressure, saturation, respiratory rate, time for first PCA use, and patient satisfaction score were described as mean and variation of each observation from the mean value was represented as mean (SD) as they were normally distributed. They were analysed using an independent t-test. The variables which failed to follow a normal distribution, such as cumulative opioid consumption, VAS scores for pain, and time for first analgesia request, were analysed using the Mann–Whitney U test and were represented as median [interquartile range (IQR)]. Categorical variables such as gender and type of surgery were described by taking percentages and were analysed using the Chi-square test. Variables with P < 0.05 were considered statistically significant.

RESULTS

The eligibility of 68 patients was assessed to be enroled. Of them, four patients declined to participate, two did not meet the inclusion criteria, and two patients were excluded from the study due to surgical factors. The remaining 60 patients were divided into two equal groups and analysed [Figure 2]. Demographic characteristics were comparable between the two groups [Table 1].

Figure 2.

CONSORT flow chart. TLIP = Thoracolumbar Interfascial Plane block; GA = General anaesthesia; USG = Ultrasonography; PCA = Patient-controlled analgesia; CONSORT = Consolidated Standards of Reporting Trials; IV: Intravenous

Table 1.

Demographic characteristics and characteristics related to surgery

Characteristics	Group Plain (n=30)	Group Dexmed (n=30)
Age (years)	45.23 (12.66)	40.6 (12.22)
Height (cm)	158.30 (10.31)	161.00 (10.50)
Weight (kg)	63.37 (12.28)	65.67 (10.06)
ASA: I/II/II	14/15/1	20/10/0
Duration of anaesthesia	185.33 (36.83)	183.83 (34.95)
Duration of surgery	149.67 (35.1)	142.17 (39.4)
Gender: Male/Female	12/18	14/16
Surgery: TLIF/Discectomy	28/2	27/3

Data expressed in Mean (SD) or number. ASA=American Society of Anesthesiologists; TLIF=Transforaminal Lumbar Interbody Fusion; SD=Standard Deviation; n=number of patients

Intraoperative vitals such as HR, systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) were comparable between both groups at regular time intervals except at a few time points (as depicted in Figure 3). The intraoperative rescue fentanyl consumption was comparable (P = 0.289).

Figure 3.

Intraoperative Haemodynamic variables. *= Significant P values; SBP = Systolic Blood Pressure; DBP = Diastolic Blood Pressure; MAP = Mean Arterial Pressure

The total perioperative fentanyl requirement was lower in Group Dexmed [Group Plain vs Group Dexmed 653.33 µg (SD: 250.4) vs 523.6 µg (SD: 258.6); P = 0.053]; however, it did not attain statistical significance [Table 2]. The median time to first analgesic requirement was significantly prolonged in Group Dexmed [Group Plain vs Group Dexmed –90 minutes (IQR: 45–120) vs 180 minutes (IQR: 97.50–232.50); P = 0.001].

Table 2.

Post-operative fentanyl consumption

	Group Plain (n=30)	Group Dexmed (n=30)	Mean difference (95% CI)	P
PCA fentanyl consumption at different time points (μg)
0 h	0 (0-0); 0-50	0 (0-0); 0-50	0 (-6.50,4.72)	>0.99
1 h	20 (0-55); 0-120	0 (0-15); 0-110	0 (0,20)	0.041
3 h	120 (45-155); 0-220	40 (0-115); 0-220	40 (0,80)	0.021
6 h	250 (200-315); 20-480	190 (85-247.5); 20-480	58.67 (-0.4,117.75)	0.052
24 h	570 (408.80-802.50); 240-970	500 (290-660); 80-920	108.83 (-16.2, 233.890)	0.087
24 h PCA fentanyl consumption (μg)	590.83 (225.55)	482 (257.33)	108.83 (-16.2, 233.890)	0.087
Post-operative rescue fentanyl consumption (μg)	0 (0-0); 0-100	0 (0-0); 0-35	0 (0,0)	0.354
24 hours total fentanyl consumption (μg)	653.33 (250.4)	523.6 (258.6)	129.67 (-1.89, 261.23)	0.053
Time for the first analgesic requirement (minutes)	90 (45-120); 15-360	180 (97.50-232.50); 30-360	-90 (-120,-30)	0.001

Data expressed as Median (IQR); Range (Min-Max) or Mean (SD). PCA=Patient Controlled Analgesia; CI=Confidence Interval; IQR=Interquartile Range; SD=Standard Deviation; n: Number Of Patients

It was noted that Group Dexmed had significantly lower VAS scores at rest at 0 hours (P <0.001) and during movement at 0 hours (P <0.001) and 3 hours (P = 0.009) [Table 3, Figure 4a and b].

Table 3.

VAS scores at rest and movement

	Group Plain (n=30)	Group Dexmed (n=30)	P
VAS R0	3 (2-4.75); 0-7	1.5 (0-2); 0-4	<0.001
VAS R1	2 (2-3); 0-5	2 (1-3); 0-5	0.129
VAS R3	3 (2-4); 1-6	2 (2-3); 0-5	0.060
VAS R6	2 (2-3); 1-6	2 (2-3); 0-6	0.677
VAS R24	2 (1-2); 0-4	2 (1-2); 0-3	0.221
VAS M0	4 (3-5.75); 1-8	3 (2-4); 2-6	<0.001
VAS M1	4 (3-5); 2-7	3 (3-4); (2-7)	0.072
VAS M3	5 (4-6); 3-7	4 (3-5); 1-6	0.009
VAS M6	4 (3-5); 2-7	4 (3.25-5); 2-7	0.388
VAS M24	3 (3-4); 2-7	3 (2.25-4); 2-5	0.207

Data expressed as Median (IQR); Range (Min-Max). VAS R=Visual Analogue Scale at Rest; VAS M=Visual Analogue Scale at Movement ; IQR=Interquartile Range; n: Number Of Patients

Figure 4.

(a) VAS at rest; 1 = Group Plain, 2 = Group Dexmed, VAS = Visual Analogue Scale. (b) VAS at movement 1 = Group Plain; 2 = Group Dexmed,; VAS = Visual Analogue Scale

The median highest PONV scores within the 24 h postoperative period were 0 (IQR: 0–1) in Group Plain versus 0 (IQR: 0–0) in Group Dexmed (P = 0.073); thus, no significant difference was noted. There were four incidents of postoperative urinary retention requiring a Foley catheter insertion (two patients in each group). No incidents of respiratory depression or pruritus were recorded.

DISCUSSION

In this study, the addition of dexmedetomidine to ropivacaine increased the time to first analgesic request and decreased VAS scores in the TLIP block for lumbar spine surgery. There was a non-significant trend towards reduced fentanyl consumption in the first 24 h. However, the reduction of 130 µg fentanyl in 24 h in Group Dexmed may be considered clinically meaningful in enhanced recovery pathways, possibly underpowered due to sample size limitations.

Existing literature indicates that TLIP blocks outperform non-block procedures, resulting in reduced analgesic requirements (total opioid use and time to first analgesia) and improved pain relief throughout the hospital stay for patients undergoing spinal surgery.[11,12,13] Moreover, previous literature supports the efficacy of adjuvant dexmedetomidine in ESP and paravertebral blocks, with benefits including prolonged analgesia, lower opioid consumption, cardiovascular stability, and minimal respiratory depression.[14,15] The current study demonstrates its efficacy in the TLIP block as well.

Significant prolongation of time to first rescue analgesia in Group Dexmed reflects a substantial extension of the block duration and improved early post-operative pain control. This is reflected in significantly lower VAS scores at rest at 0 hours and at movement at 0 and 3 hours in Group Dexmed. These results strongly suggest that adding dexmedetomidine as an adjuvant to local anaesthetics provides a higher quality of analgesia for patients undergoing TLIF surgeries.

These early analgesic benefits observed in the current study align with previous studies using dexmedetomidine in peripheral nerve blocks or plane blocks.[14,15,16,17,18] Gao et al. (2021)[15] demonstrated that adding dexmedetomidine (0.5–1 µg/kg) to bilevel ESP block significantly improved analgesia and reduced opioid consumption without any safety concerns in video-assisted thoracic surgery. Hamed et al.[18] found significantly lower opioid consumption in the dexmedetomidine group in high thoracic erector spinae block for shoulder arthroscopic surgeries. We could not find any study using dexmedetomidine as an adjuvant in TLIP block.

The lack of a significant difference in cumulative fentanyl consumption may be multifactorial. The TLIP block primarily covers the dorsal rami, offering limited coverage for deeper visceral or anterior spinal nociception, unlike broader blocks such as ESP. A recent meta-analysis by the same authors also suggests that ESP blocks may offer superior analgesic coverage in spinal surgery compared to TLIP, potentially explaining the rescue opioid requirements in both groups.[19] Moreover, the relatively avascular fascial plane targeted in the TLIP block may limit systemic absorption and central effects of dexmedetomidine.

Dexmedetomidine did not contribute to added adverse events such as bradycardia, hypotension, excessive sedation, or nausea/vomiting. This confirms the favourable safety profile of dexmedetomidine at the studied dose (1 µg/kg) in the modified TLIP block, consistent with earlier findings of its application in other interfascial plane blocks.[16,17,18]

The strengths of the study lie in its robust design, adherence to standardised peri-operative protocols, and no loss of follow-up patient data. However, limitations include the relatively small sample size, single centre design, lack of continuous PCA basal infusion, and only 24-hour follow-up duration.

These findings suggest that dexmedetomidine enhances the quality of analgesia in the early post-operative period, warranting larger trials to evaluate further its impact on overall opioid use and long-term outcomes in lumbar disc surgeries.

CONCLUSION

Thoracolumbar interfascial plane block with dexmedetomidine as an adjuvant to ropivacaine did not decrease 24 h cumulative fentanyl consumption as compared to thoracolumbar interfascial plane block with ropivacaine alone. However, the time to first request for analgesia was increased, and patients reported lower pain scores in the dexmedetomidine group.

Presentation at conferences/CMEs and abstract publication

EUROANAESTHESIA-2024. Published in e-Supplement of the European Journal of Anaesthesiology* (Volume 41, e-Supplement 62).

Study data availability

De-identified data may be requested with reasonable justification from the authors (email to the corresponding author) and shall be shared upon request.

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

The AI tools or language models (LLM) have not been utilised in the manuscript, except that software has been used for grammar corrections.

Declaration of use of permitted tools

Postoperative Nausea and Vomiting score cited is freely available and not copyrighted.

Supplementary material

None.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.