A Comparative Study to Evaluate the Efficacy of Adding Ultrasound-guided Bilateral Erector Spinae Block to Standard Anaesthesia Care Versus General Anaesthesia in Patients Undergoing Single-level Transforaminal Lumbar Interbody Fusion Surgery: A Double-blinded Randomised Controlled Study

Abstract

Introduction:

The erector spinae plane (ESP) block, introduced in 2016, is a fascial plane block gaining popularity for its analgesic efficacy in multiple cardiac, thoracic and abdominal surgeries. It involves injecting local anaesthetic deep into the erector spinae muscles. Multiple large retrospective and prospective studies have shown the efficacy of ESP blocks in various surgeries, and we determined to evaluate them in Spinal surgeries.

Methods:

This study evaluated the efficacy of erector spinae block in single-level lumbar fusion surgery. Pain scores, surgical field, opioid use and adverse effects were compared in a double-blind randomised controlled trial (RCT). The block group received 20 mL of 0.375% ropivacaine on each side and the control group received 20 mL of 0.9% normal saline.

Results:

The ESP block group showed lower pain scores in the post anaesthesia care unit (PACU) and up to eight hours postoperatively, with 82.4% requiring no additional analgesia, unlike the control group, where all patients needed supplements like tramadol or buprenorphine. Surgical field conditions, assessed using Boezaart’s grading scale, were significantly better up to 30 minutes after incision. Although blood loss differences were statistically significant (P = .048), correlation was weak. Adverse effects, including constipation, nausea and drowsiness, were higher in the control group due to greater opioid use.

Conclusion:

The ultrasound-guided ESP block is a practical, feasible analgesic modality for lumbar spine surgeries, suitable for multimodal and opioid-sparing analgesia.

Keywords

7Erector spinae plane block regional analgesia multimodal analgesia spinal surgeries lumbar surgery

Introduction

India is one of the advancing aging societies of the world and with the aging, the demographic structure of the country also changes. An aging society characterises an increased number of spinal disorders and an increased number of spinal surgeries.

In one of the largest prospective cohort studies done in 2013 to compare standardised pain scores between different surgical procedures, spinal procedures were ranked as the second most painful procedure with a median pain score of 6 to 7.^[1]

Transforaminal lumbar interbody fusion (TLIF) is one of the standard established modalities for treating multiple spinal disorders which can be degenerative, traumatic, infectious or neoplastic.^[2]

The erector spinae plane (ESP) block is a comparatively newer fascial plane block. Since its first description in the year 2016, it has gained wide popularity for its analgesic efficacy in multiple cardiac and thoracic procedures. Anatomically, the erector spinae muscle is a complex of muscles formed by the muscles spinalis, Longissimus thoracis and iliocostalis that run in a vertical fashion in the dorsum.^[3] The ESP block involves the deposition of local anaesthetic deep to the erector spinae muscles where the tip of the transverse process of the vertebra is present.

Need of the Study

With the advent of regional anaesthesia and the recent advances in this domain, supplementing standard anaesthesia care of spinal surgeries with a regional analgesia technique seems only plausible. Multiple studies show the efficacy of this block in various surgeries, but the evidence is limited in spinal surgeries and more so in the Indian population. Hence, in this study, we focus on determining the same. The use of this block pertaining to spine surgeries is limited in terms of studies done and the concern of it being near the surgical site. We aim at studying the effect of the block on the blood loss and the field as well which was a part of the secondary objectives.

Materials and Methods

The study aims to find the efficacy of erector spinae block in patients undergoing single-level lumbar spinal fusion surgery. The primary objective is to compare pain scores using the visual analogue score (VAS)/numeric rating scale (NRS) at different time points between the groups. The secondary objectives are to compare the intraoperative surgical field (Boezaart’s grading scale), intraoperative and postoperative opioid requirements and adverse effects and complications. This is a double-blinded prospective randomised controlled study conducted between May 2022 and May 2023 after approval of all the study protocols by the ethical committee.

Sample Size Calculation

In the Teng-Jiao Zhang trial (2020),^[4] the primary outcome was the VAS of 24 hours. The mean VAS score at movement in the erector spine block is 2.9 (1.4) and in control it is 3.7 (1.9) Keeping this as our background information, with two-tailed distribution, effect size of 0.7, level of significance at 5%, power of 80% and allocation ratio of 1:1, the required sample size is 34 cases in each group. This sample size calculation is done using G*Power 3.1.9.2 software. Hence, there is no manual calculation required.

For the randomisation, a block randomisation technique was adopted. The random sequence was generated using a computer. Thirty-four sequences with a block size of two were generated and all the generated sequences were put into a sealed envelope. The blocks were selected randomly. Based on the selected envelope by the observer, either erector spinae block or 0.9% normal saline was administered.

The patients who belonged to American Society of Anesthesiologists (ASA) grade I/ II/ III, age group of 18–85 years and patients undergoing single-level TLIF were included in this study and any patient with known allergy to local anaesthetics, two or multiple-level surgeries and revision surgeries were excluded.

Methodology

After a detailed preoperative assessment, patients who satisfied inclusion criteria were explained regarding anaesthesia procedure in their vernacular language and a written consent was obtained in each case. Standard monitors were attached and after securing intravenous access, balanced anaesthesia was induced and maintained using an oxygen and nitrous oxide mixture and propofol infusion titrated according to the bispectral index (BIS).

A third party (other than the anaesthetist giving the block and the observer) was given the randomisation envelope and was asked to prepare the block syringe (drug/sham), label it as ‘BLOCK’ and was given it to the managing anaesthetist. The patient was placed in the prone position, and a low-frequency convex array ultrasound transducer covered in a sterile sleeve was placed in a transverse orientation at a level to identify the tip of the T12 transverse process [Figure 1]. The T12 transverse process was identified by the twelfth rib. All the procedures were lumbar spine surgeries. The dermatomes involved from skin incision to bone range from T10 to L3/L4. This block can cover up to three levels cranial and caudal from the site of deposition and hence T12 was used. The tip of the transverse process was centred on the ultrasound screen, and the probe was then rotated into a longitudinal orientation to produce a parasagittal view. An echogenic 23-gauge block needle was inserted in-plane to the ultrasound beam in a cephalocaudal direction until contact was made with the T12 transverse process. The drug was injected and repeated contralateral side.

Figure 1.

Ultrasound image showing erector spinae muscle and transverse process

Any additional opioid requirement intraoperative was met by fentanyl at 1 μg/kg bolus dose, and if required it was supplemented by morphine at the discretion of the managing anaesthetist with the hemodynamic goal of maintaining systolic blood pressure within 20% of the baseline.

Pain was assessed using the VAS [Figure 2],^[4] the surgical field was assessed using Boezaart’s scale [Figure 3],^[5] blood loss was assessed using VAS [Figure 4],^[6] and sedation using The University of Michigan Sedation Scale (UMSS) [Figure 5].^[7]

Figure 2.

Visual analogue scale (VAS) for pain^[4]

Figure 3.

Boezaart’s surgical field score^[5]

Figure 4.

Visual analogue for estimating blood loss^[6]

Figure 5.

The University of Michigan Sedation Scale (UMSS)^[7]

Ethical Issues

No patient was harmed during the study. All procedures were done in compliance with standardised protocols and ensuring standard patient care. Informed consent was obtained before enrolment into the study. Participants had the right to withdraw from the study. Privacy and confidentiality were maintained. Approval of the Institutional Ethical Committee and Scientific Committee has been obtained.

Statistical Analysis

Descriptive statistics were presented with frequency (percentage) and mean (standard deviation [SD]) for the categorical and continuous factors respectively. Median (interquartile range [IQR]) was presented for the skewed data. The normality of the data was checked by using the Shapiro–Wilk test. Student’s t-test/Mann–Whitney U test was used to determine the significant difference between block and control. Chi-squared/Fisher’s exact test was used to determine the association between two independent categorical factors. A paired sample t-test/Wilcoxon Sign rank test was used to determine the significant changes between baseline and last visits. P value < .05 is considered as statistical significance. All the analyses was carried out by using SPSS (IBM, 28.0).

Results

This study included 68 eligible patients satisfying both inclusion and exclusion criteria, who underwent elective single-level TLIF surgery during the defined study period. These patients were equally divided into a block and control group, and received 20 mL of 0.375% ropivacaine or 20 mL of 0.9% normal saline respectively in a double-blinded fashion.

Confounding factors were compared between the two groups, as demonstrated statistically by a P value > .05 when age, sex, ASA grading and lumbar level of surgery were analysed [Table 1]. Table 2 and Figure 6 show the pain score trend between the two groups at different time intervals. Surgical fields were compared using the Boezaart’s scale which is shown in Table 3. Table 4 shows the comparison of blood loss, amount of opioids used, adverse effects and additional analgesia requirement.

Table 1.

Comparison of demographic factors

Parameters	Group, n (%)		Overall (n = 68)	P Value
Parameters	Block (n = 34)	Control (n = 34)	Overall (n = 68)	P Value
Age (in years) Mean ± SD Range	51 ± 12.1 23–74	56.9 ± 13.8 22–75	53.9 ± 13.2 22–75	.083^a
Gender Male Female	21 (61.8) 13 (38.2)	26 (76.5) 8 (23.5)	47 (69.1) 21 (30.9)	.294^b
ASA 1 2 3	18 (52.9) 13 (38.2) 3 (8.8)	16 (47.1) 15 (44.1) 3 (8.8)	34 (50) 28 (41.2) 6 (8.8)	.878^b
Diagnosis L2 L3 L3 L4 L4 L5 L5 S1	4 (11.8) 14 (41.2) 13 (38.2) 3 (8.8)	2 (5.9) 9 (26.5) 15 (44.1) 8 (23.5)	6 (8.8) 23 (33.8) 28 (41.2) 11 (16.2)	.244^b

Note: ^aStudent’s t-test/Mann–Whitney U test; ^bChi-squared/Fisher’s exact test.

Table 2.

VAS score

VAS score	Group, n (%)		P Valuea
VAS score	Block (n = 34)	Control (n = 34)	P Valuea
Immediate post-oP Median (IQR)	2 (1–2)	3.5 (3–4)	<.001
Post-op 1 hour Median (IQR)	1.5 (1–2)	3.5 (3–5)	<.001
Post-op 2 hours Median (IQR)	2 (1–2)	3 (2–5)	<.001
Post-op 3 hours Median (IQR)	1 (1–2)	3 (2–4)	<.001
Post-op 4 hours Median (IQR)	1 (1–1)	3 (3–4)	<.001
Post-op 8 hours Median (IQR)	1 (0–2)	2 (2–3)	<.001
Post-op 12 hours Median (IQR)	2 (0–3)	2 (2–3)	.024
Post-op 16 hours Median (IQR)	2 (1–4)	2 (1–3)	.429
Post-op 20 hours Median (IQR)	2 (1–3)	2 (1–3)	.602
Post-op 24 hours Median (IQR)	2 (1–3)	2 (1–3)	.718

Note: ^aStudent’s t-test/Mann–Whitney U test; Boldface indicates statistical significance.

Discussion

Our study showed that the group that received the ESP block had lower pain scores in the immediate post anaesthesia care unit (PACU) and the postoperative period of up to eight hours. After this period, there was not any significant difference in pain scores between the two groups until 24 hours postoperatively [Table 2 and Figure 6]. These were in accordance with the results of the meta-analysis done by Cui et al.^[8]

Figure 6.

Bar graph to compare pain score

Our study also showed that all patients in the ‘control’ group required additional analgesia supplementation either in the form of intravenous tramadol 50 mg or transdermal buprenorphine patch or both. However, in the ‘block’ group 82.4% of patients did not require any additional analgesic supplementation [Table 4].

When assessing the conditions of the surgical field using Boezaart’s surgical field grading scale during the intraoperative period at regular time intervals, a statistical significance was found between the two groups up to 30 minutes after incision. Though similar results were seen at 60 and 75 minutes, it did not show significance at 45 minutes post-incision [Table 3].

Table 3.

Surgical field

Field	Group, n (%)		Overall, (n = 68)	P Value^a
Field	Block, (n = 34)	Control, (n = 34)	Overall, (n = 68)	P Value^a
5 mins 1 2 3 4	– 30 (88.2) 4 (11.8) –	1 (2.9) 14 (41.2) 17 (50) 2 (5.9)	1 (1.5) 44 (64.7) 21 (30.9) 2 (2.9)	<.001
15 mins 2 3 4	29 (85.3) 5 (14.7) –	11 (32.4) 19 (55.9) 4 (11.8)	40 (58.8) 24 (35.3) 4 (5.9)	<.001
30 mins 1 2 3 4	7 (20.6) 18 (52.9) 9 (26.5) -	– 18 (52.9) 11 (32.4) 5 (14.7)	7 (10.3) 36 (52.9) 20 (29.4) 5 (7.4)	.007
45 mins 1 2 3 4	6 (17.6) 22 (64.7) 6 (17.6) –	2 (5.9) 17 (50) 13 (38.2) 2 (5.9)	8 (11.8) 39 (57.4) 19 (27.9) 2 (2.9)	.065
60 mins 1 2 3 4	8 (23.5) 14 (41.2) 8 (23.5) 4 (11.8)	– 18 (58.1) 11 (35.5) 2 (6.5)	8 (12.3) 32 (49.2) 19 (29.2) 6 (9.2)	.023
75 mins 1 2 3	3 (27.3) 4 (36.4) 4 (36.4)	– 9 (90) 1 (10)	3 (14.3) 13 (61.9) 5 (23.8)	.035
90 mins 2 3	– 1 (100)	3 (100) –	3 (75) 1 (25)	–

Notes: ^aChi-squared/Fisher’s exact test.

Boldface indicates statistical significance.

On quantifying and comparing the blood loss between the two groups, though it was significant statistically, a strong correlation could not be established (P = .048) [Table 4]. These findings are similar to those in the study done by Patel et al.^[9] although that study showed a more statistical correlation. Informally, the level of surgeon satisfaction was high in the ‘block’ group patients with respect to the operating conditions and surgical field, assessed subjectively.

Table 4.

Amount of blood loss, opioid usage, adverse effects and additional analgesia

Parameters	Group, n (%)		Overall, (n = 68)	P value
Parameters	Block, (n = 34)	Control, (n = 34)	Overall, (n = 68)	P value
Blood loss Mean ± SD Range	73.7 ± 14.1 50–100	80.6 ± 13.9 60–120	77.2 ± 14.3 50–120	.048 ^a
Total fentanyl Mean ± SD Range	366.5 ± 40.1 250–450	592.9 ± 129.6 200–870	479.7 ± 148.6 200–870	<.001 ^a
Total morphine Median (IQR)	0 (0–0)	6 (3.8–10)	0 (0–6)	<.001 ^a
Adverse effects No Constipation NV Drowsiness Const Plus NV Const NV Dep	33 (97.1) 1 (2.9) – – – –	23 (67.6) 4 (11.8) 4 (11.8) 1 (2.9) 1 (2.9) 1 (2.9)	56 (82.4) 5 (7.4) 4 (5.9) 1 (1.5) 1 (1.5) 1 (1.5)	.060^b
Analgesia No Tramadol 50 Buprenorphine Patch Both	28 (82.4) 1 (2.9) 4 (11.8) 1 (2.9)	– 4 (11.8) 11 (32.4) 19 (55.9)	28 (41.2) 5 (7.4) 15 (22.1) 20 (29.4)	<.001 ^b

Note: ^aStudent’s t-test/Mann–Whitney U test; ^bChi squared/Fisher’s exact test; Boldface indicates statistical significance.

On comparing the hemodynamic parameters intraoperatively between the two groups, it was observed that the response in heart rate and systolic blood pressure on skin incision was more pronounced in the ‘control’ group than the ‘block’ group. This was also observed statistically with a significant P value and was demonstrated in Figures 7 and 8 respectively.

Figure 7.

Line chart for heart rate

Figure 8.

Line chart for systolic blood pressure

A total of six patients required morphine and all six patients belonged to the ‘control’ group [Table 4].

The total amount of fentanyl required was significantly higher in the ‘control’ group. The mean amount in the ‘block’ group was approximately 366 mg whereas in the ‘control’ group, it was approximately 593 mg [Table 4].

On comparing the occurrence of adverse effects between the two groups, it was found that 97.1% of patients in the ‘block’ group and 67.6% of patients in the ‘control’ group had no adverse effects [Table 4]. The occurrence of adverse effects like constipation, nausea, vomiting and drowsiness was more in the ‘control’ group probably due to the requirement of more opioids and other analgesics. These findings are similar to those concluded in the meta-analysis done by Duan et al.^[10]

Conclusion

Our study was aimed at finding the efficacy of a newer analgesic modality in patients undergoing lumbar spine surgery. We used 0.375% ropivacaine in a total 40 mL volume and was observed that this novel technique does provide satisfactory analgesia in the postoperative period, statistically significant up to eight hours, though multiple studies have observed that the analgesic effect was present till 24 hours. Similarly, it reduced the total amount of opioids used (fentanyl, morphine, tramadol, buprenorphine) and was associated with lesser side effects most probably due to the opioid-sparing effect. Statistically, there was less blood loss in patients whom this block was given and was also subjectively reassured by the surgeon. But this was not a strong observation and is not backed by evidence from the literature review. Hence, this novel ultrasound-guided ESP block is a practical and feasible modality for analgesia in patients undergoing lumbar spine surgeries and can be included as a part of multimodal analgesia and opioid sparing analgesia.

Footnotes

Acknowledgements

Thanks to Dr Shivashankari—research assistant and Mr. Logesh—Biostatistician, Research Department, Apollo Hospital Chennai.

Credit author statement

SV participated in data acquisition, literature search, investigations, data analysis and manuscript preparation.

VR participated in conceptualisation, investigation, supervision, data analysis and manuscript editing.

Both the authors have reviewed and approved the manuscript.

Data availability

Data presenting the study’s findings is available with the corresponding author.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article.

Funding

The authors received no financial support for the research, authorship and/or publication of this article.

Institutional ethical committee approval number

Ethical approval was obtained from Institutional Ethics Committee- Bio Medical Research, Apollo Hospitals, Chennai. Application no- AMH-DNB-034/06-22.

Informed consent

Informed consent has been obtained from all the patients who met the eligibility criteria.

Use of artificial intelligence

Nil.

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