The Effect of Ultrasound-Guided Multipoint Thoracic Paravertebral Nerve Block in Metabolic and Bariatric Surgery (MBS): A Prospective Randomized Controlled Trial

Abstract

Background

The study aims to compare the effects of multipoint thoracic paravertebral block combined with general anesthesia to general anesthesia alone in metabolic and bariatric surgery (MBS).

Methods

A total of 80 patients were randomly assigned in a 1:1 ratio to the Thoracic Paravertebral Block group (TPVB group) and the General Anesthesia group (GA group). The TPVB group received multipoint TPVB combined with GA bilaterally at the T6 and T9 levels, while the GA group received only GA. The primary outcome was the quality of recovery scores (QoR-15) at 24 h and 48 h postoperatively, while secondary outcomes included NRS scores at different time points postoperatively, intraoperative sufentanil consumption, cumulative consumption of postoperative rescue analgesics, postoperative hospital length of stay, postoperative extubation time, time to first flatus and urination, and complications related to the nerve block.

Results

The QoR-15 scores at 24 h and 48 h were significantly higher in TPVB group compared with GA group [24 h: 127.0(124.0,129.0) vs 113.0(109.0,115.0), 48 h: 139.0(137.0,141.0) vs 132.5(126.0,135.0) (P < 0.001)]. The NRS scores in the TPVB group were significantly lower than the GA group at different time points postoperatively (P < 0.05). The intraoperative sufentanil use was significantly less in the TPVB group and the TPVB group required less rescue analgesia (P < 0.05). The extubation time and first flatus time were significantly shorter in the TPVB group than in the GA group (P < 0.05).

Conclusion

Multipoint TPVB improves the quality of postoperative recovery in patients undergoing metabolic and bariatric surgery (MBS) and reduces postoperative pain and opioid use.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11695-025-08154-3.

Introduction

Over the past few decades, the global prevalence of obesity has been rapidly increasing with no signs of slowing down [1]. In 2022, an estimated 2.5 billion adults worldwide were overweight, with 890 million of them classified as obese [2]. Despite various efforts involving dietary control, physical exercise, and pharmacological treatments, the effectiveness in managing obesity remains inadequate. Metabolic and bariatric surgery (MBS) presents a viable option for individuals struggling with severe obesity enabling significant weight loss and improvement in metabolic health [3]. Approximately 600,000 patients undergo MBS annually; a much larger group has indications for it [4]. Patients with obesity are at a higher risk of respiratory failure, hypoxia, and central or obstructive sleep apnea (OSA). Studies have shown that patients with obesity undergoing MBS frequently experience decreases in oxygen saturation [5]. Individuals with obesity are also more sensitive to pain [6, 7]. It has been reported that nearly 75% of patients undergoing laparoscopic MBS may experience moderate and severe pain [8].

Opioids are the primary analgesics used during general anesthesia, with approximately 99% of patients in the United States receiving them in the perioperative period [9, 10]. While opioids are effective for pain relief, their use is associated with multiple adverse effects, including excessive sedation, respiratory depression, nausea, vomiting, and opioid-induced nociceptive hypersensitivity. In patients with obesity, the incidence of airway obstruction can increase not only during opioid administration but also after the opioids are discontinued [11]. Therefore, for safety reasons, analgesic regimens for patients with severe obesity need to be tailored to achieve optimal pain relief while minimizing or avoiding the use of opioids.

Paravertebral block has been successfully used in various surgical procedures, including cardiovascular, thoracic, breast, and hepatobiliary surgeries. They have demonstrated analgesic benefits comparable to those of epidural anesthesia while also lowering the risk of complications such as respiratory depression and urinary retention [12, 13]. However, its use in MBS is not well studied.

We hypothesized that paravertebral block may offer a safer and more effective option for intraoperative and postoperative pain management in patients undergoing MBS, potentially enhancing the quality of their recovery. To explore this, we conducted a prospective randomized controlled trial comparing multipoint paravertebral block combined with general anesthesia to general anesthesia alone, focusing on early recovery quality, postoperative pain levels, and opioid consumption in patients undergoing MBS.

Methods

Trial Design

This prospective, single center, randomized controlled trial was conducted at the Second Xiangya Hospital of Central South University. The trial was approved by the local ethics committee ( LYEC2024-K0023) and prospectively registered in the Chinese Clinical Trial Registry (www.chictr.org.cn) with the registration number of ChiCTR2400084190. Prior to the start of the experiment, we provided detailed information about the trial procedures and patient rights to all enrolled patients or their families, and obtained written informed consent.

Participants

From May 11 to September 27, 2024, we enrolled patients aged 18 to 55 years with an American Society of Anesthesiologists (ASA) physical status classification of II or III who were scheduled to undergo MBS. Eligible participants included individuals with a body mass index (BMI) > 32.5 kg/m², regardless of obesity-associated diseases, or those with a BMI between 27.5 and 32.5 kg/m² and obesity-associated conditions (e.g., type 2 diabetes or hypertension) that were inadequately controlled with pharmacological therapy [14, 15]. The exclusion criteria included: 1) patients with neuropsychiatric disorders; 2) patients with preoperative cognitive or language impairments preventing communication; 3) patients with a history of chronic pain syndrome or long-term opioid use (> 4 weeks); 4) patients with a history of allergies to ropivacaine; 5) site infections, tumors, severe anatomical variations causing difficulties to perform nerve blocks; 6) changes in surgical procedures; and 7) severe coagulation disorders.

Randomization and Blinding

After obtaining patient consent, patients were randomly assigned in a 1:1 ratio to either the General Anesthesia (GA) group or the Thoracic Paravertebral Block (TPVB) group using a computer-generated randomization table. The group assignments were securely stored in opaque envelopes. Upon the patient’s arrival in the operating room, a designated anesthesiologist responsible for performing the TPVB opened the envelope and informed the patient of their group assignment before proceeding with the procedure (for the GA group, only induction was performed). Subsequently, the anesthesia team, surgical team and postoperative follow-up personnel remained blinded to group assignments, ensuring unbiased clinical management.

All data were recorded using the electronic medical records system (EMR), with strict blinding procedures applied to both recorders and collectors. Access to the EMR was restricted to dedicated personnel responsible for data collection and analysis, ensuring confidentiality of the group assignments.

Ultrasound-Guided Nerve Blocks

Accurate identification of vertebral segments is essential in TPVB procedures, especially in patients with obesity, where surface anatomy alone may be insufficient for precise localization. Therefore, using ultrasound to count ribs offers a more reliable method for correctly locating the paravertebral space. The patient was positioned in the lateral decubitus position, and a 10–5 MHz probe (L38xi, Sonosite SII, FUJIFILM) was placed along the short axis of the ribs on the patient's back. We employed the 12-rib method for localization: first, the elliptical shadow of the rib was identified, and then the probe was moved along the midline of the ribs to locate the transverse processes at the level of T12. The probe was then moved cephalad to identify T9 and T6 in sequence.

Once the transverse processes were located, the probe was rotated 90° perpendicular to the spine to visualize the paravertebral space. This space was characterized by the pleura at the base and bordered by the transverse processes and costotransverse ligament, forming a triangular area suitable for puncture. Using an in-plane puncture technique with a 22G needle, a small amount of solution was cautiously injected near the costotransverse ligament to verify needle tip position. Then, slightly pierce through the ligament with the needle, quickly inject normal saline, and observe the fluid spreading in the paravertebral space with the pleura moving downward to confirm that the needle tip is accurately positioned in the paravertebral space. Aspiration was performed to confirm the absence of blood, gas, or cerebrospinal fluid before proceeding.

The pre-prepared local anesthetic solution was then injected, and real-time observation confirmed its diffusion locally. The anesthetic solution was a mixture of 22 ml saline, 2 ml dexamethasone (8 mg), and 16 ml of 1% ropivacaine (Naropin, AstraZeneca), yielding a total of 40 ml of 0.4% ropivacaine combined with steroids. Four puncture points bilaterally at T6 and T9 intercostal spaces were administered the anesthetic solution, with each point receiving 10 ml to ensure effective coverage of the surgical area. After administration, ultrasound scanning confirmed adequate infiltration of the anesthetic in the targeted surgical field as shown in Fig. 1.

Fig. 1.

The thoracic paravertebral block procedure. A), Locate the 12th rib. B), Ultrasound-guided identification of the paravertebral space. C), Subluxation of the pleura after injection of local anesthetic into the paravertebral space

Anesthesia Introduction and Maintenance

Anesthesia induction was performed based on Normalized Lean Weight (NLW), calculated using the formula: total body weight multiplied by the square root of BMI divided by 22 [16]. The dosages were as follows: propofol at 2.0–2.5 mg/kg, midazolam at 0.15–0.35 mg/kg, sufentanil at 0.3–0.5 μg/kg, and rocuronium bromide at 0.6–1.2 mg/kg. Following the loss of consciousness and the achievement of required muscle relaxation, endotracheal intubation was performed with the patient in a 25° head-up position, ensuring the external auditory meatus level with the sternal notch [17]. Mechanical ventilation began immediately after intubation, with tidal volume set based on Ideal Body Weight (IBW) using lung-protective ventilation strategies [16]. Patients in the GA group were routinely given 8 mg of dexamethasone intravenously before induction. The tidal volume was set at 6–8 ml/kg, and Positive End-Expiratory Pressure (PEEP) was maintained at moderate to low levels (5–10 cmH₂O). Lung recruitment maneuvers were performed intermittently, with an inspiratory-to-expiratory ratio of 1:2.5 and adjustments to oxygen concentration (> 50%) to maintain SpO2 above 92–95%. Intraoperative arterial blood gas measurements were conducted to guide adjustments in ventilator parameters, ensuring end-tidal carbon dioxide remained between 35–50 mmHg.

The formulas used were:

$$\begin{array}{c}NLW=TotalBodyWeight\times \sqrt{22/BMI}\\ IBW=TotalBodyWeight\times 22/BMI\end{array}$$

Anesthesia was maintained with propofol at 4–10 mg/(kg·h), intermittent bolus administration of sufentanil to maintain heart rate (HR) and blood pressure (BP) within 20% of preoperative values, and repeated bolus doses of 0.1–0.2 mg/kg rocuronium to keep the TOF count at 1–2, supplemented with intermittent inhalation of sevoflurane. Dose of sedative drugs were adjusted based on the Bispectral index(BIS™), aiming to keep BIS™ levels between 35–60. At the end of the procedure, extubation was performed after reversing rocuronium with a combination of 0.02 mg/kg IV atropine and 0.04 mg/kg IV neostigmine to achieve a TOF ratio > 0.9.

Surgical Management

The surgical approach was determined preoperatively by the surgeon and thoroughly explained to the patients. All patients underwent laparoscopic sleeve gastrectomy, which was performed by the same surgical team. The procedure involved the use of four laparoscopic trocar ports. The trocar positions included a 10 mm visual trocar for observation, placed 5 cm above the umbilicus along the left midclavicular line; a 5 mm main operating port, located 3 cm below the right costal margin along the midclavicular line; a 5 mm auxiliary port, placed 3 cm below the left anterior axillary line along the costal margin; and a 12 mm auxiliary port, positioned 5 cm above the umbilicus along the right midclavicular line for insertion of the gastric resection stapler. The patient was positioned at a 30°−50° head-up tilt and tilted horizontally 10° to 15°, with the left side higher than the right. After confirming the position of the pylorus, the surgeon dissected the greater omentum and mobilized the gastric fundus and posterior wall. The greater curvature of the stomach was transected, creating a sleeve-shaped stomach. The gastric staple line was reinforced, followed by the repositioning of the greater omentum. Specimen retrieval, irrigation, and closure of the trocar incisions were performed to conclude the procedure.

Analgesia Management

All postoperative patients received patient-controlled analgesia (PCA), which included sufentanil at a dose of 2 μg/kg (calculated based on NLW), 150 mg flurbiprofenolide, and 16 mg ondansetron, diluted with normal saline to a total volume of 100 ml. The PCA pump was set to deliver a continuous background infusion of 2 ml/h, and patients could self-administer an additional 1.5 ml dose as needed, with a 10-min lockout interval and a maximum hourly limit of 11 ml. Patients were instructed to activate the PCA pump whenever they experienced discomfort. For rescue analgesia (resting NRS score ≥ 4 lasting more than 20 min), 1 g intravenous paracetamol first was administered in the ward. If pain is not relieved or the NRS score remains ≥ 6, intramuscular tramadol 50 mg may be given as needed. If both measures fail to relieve pain, a cautious intramuscular injection of morphine 5 mg may be administered with close monitoring.

Outcome Measures

The primary outcomes focused on assessing patient recovery postoperatively, specifically by documenting QoR-15 scores at 24 h and 48-h after surgery.

We used the Chinese version of the questionnaire translated and validated by Zuo et al., which has demonstrated good reliability and validity. The intraclass correlation coefficient, split-half reliability coefficient, and Cronbach’s α were 0.99, 0.70, and 0.76, respectively. The details have been added in Supplementary File. Specifically, we noted that the questionnaire was administered through face-to-face interviews conducted by trained physicians within a predefined time frame, in order to ensure patients’ full comprehension of the items.

Secondary outcomes included monitoring NRS at rest and coughing at 2, 6, 12, 24 and 48 h postoperatively. Patients were actively instructed to perform deep coughing and verbally prompted to cough twice in succession. After coughing, they were asked to rate their NRS score. Based on the NRS results, pain was categorized as mild, moderate and severe pain. Of these, 1–3 were categorized as mild pain, 4–6 as moderate pain and 7–10 as severe pain. Additional measures included intraoperative fentanyl consumption and need for postoperative rescue analgesia. Other outcomes included extubation time, time to first flatus and first urination postoperatively, hospital length of stay and the incidence of complications such as bleeding, hematoma, and pneumothorax at the puncture site related to nerve blocks. Data were collected by trained researchers and recorded in the electronic medical record system (EMR), with strict blinding procedures applied to both recorders and collectors.

Sample Size Calculation and Statistical Analysis

Based on preliminary data, QoR-15 scores at 24 h postoperatively were 128.8 ± 13.2 for the TPVB group and 115.6 ± 23.1 for the GA group. A sample size calculation was performed using GPower software, with a power of 0.8 and a significance level of 0.05. This calculation indicated that a minimum of 35 participants per group would be required. To account for potential postoperative attrition and surgery-related complications, an additional 5 participants per group were included, bringing the total sample size to 80 participants. This sample size is expected to enhance the reliability and validity of the study outcomes.

Data analysis was performed using SPSS version 25.0 statistical software. The normality of sample data was assessed using the Kolmogorov–Smirnov test. For data following a normal distribution, comparisons were made using independent samples t-tests, and results were presented as mean ± standard deviation or mean ± 95% confidence interval. For non-normally distributed data, comparisons were made using the Mann–Whitney U test or Wilcoxon rank-sum test, with results reported as the median and interquartile range (Q1, Q3). Categorical data were analyzed using the chi-square test or Fisher's exact test, with results presented as ratios and percentages. For ordinal data, the rank-sum test was employed. A P-value of less than 0.05 was considered statistically significant. Graphs were generated using GraphPad Prism 9.5.0 software.

Results

Patient Demographics

From May 11, 2024, to September 27, 2024, 92 patients were screened for eligibility. Of these, 7 patients did not meet the inclusion criteria, and 5 patients declined participation, leaving 80 patients for the study. Consented patients were randomly assigned into two groups: 40 patients in each group. No patients were lost to follow-up in either group. The Consolidated Standards of Reporting Trials (CONSORT) diagram is shown in Fig. 2.

Fig. 2.

Consolidation standards of reporting trials

The patient demographics and surgical characteristics are presented in Table 1, which were comparable in the 2 groups. In general, the mean age of the included patients was 28.6 years old, the mean BMI was 40.8 kg/m², with 51.3% (41/80) female patients.

Table 1.

Comparison of patient characteristics between two groups

	GA group (n = 40)	TPVB group (n = 40)	P value
Age (years)	27.4 ± 6.3	29.9 ± 9.1	0.142
Gender, n (%)			0.823
Female	20(50.0%)	21 (52.5%)
Male	20(50.0%)	19(47.5%)
Height (cm)	168.9 ± 8.6	167.2 ± 8.7	0.382
Weight (kg)	117.7 ± 17.6	113.4 ± 23.7	0.363
BMI (kg/m2)	41.3 ± 5.9	40.4 ± 6.9	0.549
ASA grade, n (%)			0.648
II	25 (62.5%)	23 (57.5%)
III	15 (37.5%)	17 (42.5%)
Preoperative obesity-associated diseases, n (%)
Diabetes	19 (47.5%)	20 (50.0%)	0.823
Hypertension	11 (27.5%)	15 (37.5%)	0.340
OSAHS	10 (25.0%)	7 (17.5%)	0.412
Duration of surgery (min)	116.2 ± 29.8	118.6 ± 23.1	0.689

ASA, American Society of Anesthesiologists

OSHAS, Obstructive Sleep Apnea–Hypopnea Syndrome

BMI, body mass index

Primary Outcome

The TPVB group showed significantly higher QoR-15 scores at both 24 h and 48 h postoperatively compared to the GA group, with statistical significance (P < 0.001), as shown in Table 2. Specifically, at 24 h post-surgery, the median QoR-15 score for the TPVB group was 127.0 (Q1, Q3; 124.3,129.0) compared to 113.0 (Q1, Q3; 109.0, 115.0) for the C group. At 48 h post-surgery, the TPVB group's median QoR-15 score was 139.0  (Q1, Q3; 137.0,141.0) compared to 132.5 (Q1, Q3; 129.0, 135.0) for the GA group.

Table 2.

Comparison of QoR-15 scores between two groups

	GA group (n = 40)	TPVB group (n = 40)	P value
Baseline	141.0(139.0, 142.0)	139.5 (137.0, 143.0)	0.664
QoR-15 scores at 24 h
1.Able to breathe easily	8.0(8.0,9.0)	9.0(9.0,10.0)	< 0.001
2. Enjoy food	4.0(4.0,5.0)	5.0(5.0,5.8)	0.006
3. Feeling rested	7.0(7.0,8.0)	8.5(8.0,9.0)	< 0.001
4. Sleep	7.0(6.0,7.0)	8.0(7.0,8.0)	< 0.001
5. Able to look after personal toilet and hygiene	9.0(8.0,9.0)	10.0(9.0,10.0)	< 0.001
6. Support from hospital	10.0(10.0,10.0)	10.0(10.0,10.0)	1.000
7. Communicate with family and friends	10.0(10.0,10.0)	10.0(10.0,10.0)	1.000
8. Well enough for home or work	3.0(2.0,4.0)	6.0(5.0,6.0)	< 0.001
9. Comfortable and in control	8.0(7.0,8.0)	8.0(8.0,8.8)	< 0.001
10. General well-being	7.0(7.0,8.0)	8.0(7.0,8.0)	0.016
11. Moderate pain	6.0(4.0,6.0)	7.0(6.3,7.8)	< 0.001
12. Severe pain	6.0(4.0,7.0)	9.0(8.0,10.0)	< 0.001
13. Nausea or vomiting	8.0(6.3,9.0)	10.0(9.0,10.0)	< 0.001
14. Feeling worried or anxious	10.0(10.0,10.0)	10.0(10.0,10.0)	1.000
15. Feeling sad or depressed	10.0(10.0,10.0)	10.0(10.0,10.0)	1.000
24 h total QoR-15 score	113.0(109.0, 115.0)	127.0 (124.3,129.0)	< 0.001
QoR-15 scores at 48 h
1. Able to breathe easily	10.010.0,10.0)	10.0(10.0,10.0)	0.696
2. Enjoy food	6.0(6.0,7.0)	7.0(6.0,7.0)	0.037
3. Feeling rested	9.0(9.0,10.0)	9.5(9.0,10.0)	0.112
4. Sleep	9.0(8.0,9.0)	9.0(8.0,9.0)	0.226
5. Able to look after personal toilet and hygiene	10.0(10.0,10.0)	10.0(10.0,10.0)	0.003
6. Support from hospital	10.0(10.0,10.0)	10.0(10.0,10.0)	1.000
7. Communicate with family and friends	10.0(10.0,10.0)	10.0(10.0,10.0)	1.000
8. Well enough for home or work	6.0(5.0,7.0)	8.0(7.0,8.0)	< 0.001
9. Comfortable and in control	9.0(8.0,9.0)	9.0(9.0,9.8)	< 0.001
10. General well-being	8.0(8.0,9.0)	10.0(9.0,10.0)	< 0.001
11. Moderate pain	7.0(7.0,8.0)	9.0(8.0,9.8)	< 0.001
12. Severe pain	9.0(8.0,10.0)	10.0(9.0,10.0)	< 0.001
13. Nausea or vomiting	10.0(8.3,10.0)	10.0(9.0,10.0)	0.915
14. Feeling worried or anxious	10.0(10.0,10.0)	10.0(10.0,10.0)	1.000
15. Feeling sad or depressed	10.0(10.0,10.0)	10.0(10.0,10.0)	1.000
48 h total QoR-15 score	132.5(129.0,135.0)	139.0 (137.0, 141.0)	< 0.001

Overall Quality of Recovery (QoR-15) score and detailed scores from each of the 15 parameters evaluated within the QoR-15 in the TPVB and GA groups at 24 h and 48 h after MBS. Data shown are median (Q1, Q3). Items 1–10 were scored inverted: 0 ‘none of the time’ to 10 ‘all the time’. Items 11–15 were scored inverted: 10 ‘none of the time’ to 0 ‘all the time’

Secondary Outcomes

At postoperative time points of 2 h, 6 h, 12 h, 24 h, and 48 h, the NRS scores in the TPVB group were consistently lower than those in the GA group, with statistically significant inter-group differences (P < 0.0001), as shown in Fig. 3. Detailed NRS data are provided in Supplementary Table 1.

Fig. 3.

Comparison of the NRS scores between the two groups. The TPVB group shows significantly lower pain scores compared to the GA group at postoperative time points of 2 h, 6 h, 12 h, 24 h, and 48 h time points. **** indicating a p-value of < 0.0001

Notably, in the intensive monitoring of NRS scores, the proportion of patients experiencing moderate to severe pain was significantly lower in the TPVB group, with the peak time for moderate to severe pain occurring 12 h postoperatively (as detailed in Supplemental Table 2).

Intraoperative sufentanil consumption was significantly lower in the TPVB group compared to the GA group [0.5 (0.4, 0.6) vs. 1.0 (0.8, 1.1), P < 0.001]. Additionally, the use of various postoperative rescue analgesics was reduced in the TPVB group compared to the GA group (P < 0.001). No block-related complications were observed in the TPVB group. These differences between the groups were statistically significant, as detailed in Table 3.

Table 3.

Comparison of secondary outcomes between two groups

	GA group (n = 40)	TPVB group (n = 40)	P value
Sufentanil consumption(μg/kg)	1.0(0.8,1.1)	0.5(0.4,0.6)	< 0.001
Paracetamol consumption (g)	3.0(2.0,3.8)	1.0(0.3,2.0)	< 0.001
Tramadol consumption (mg)	100.0(50.0,100.0)	0(0,38.0)	< 0.001
Morphine consumption (mg)	5.0(0,8.8)	0(0,0)	< 0.001
Time of extubation (min)	40.5(29.3,83.8)	37.0(25.0,47.8)	0.037
Time of first anal exhaust(h)	41.5(39.3,43.8)	22.0(20.0,23.0)	< 0.001
Time of first urination(h)	2.0(2.0,3.0)	2.0(2.0,3.0)	0.840
Postoperative hospital stay(d)	6.0(4.3,6.8)	5.0(4.0,6.0)	0.432
Block complication	0	0	-

All data shown are median (Q1, Q3). No statistical adjustment was made for multiple comparisons

Both groups of patients were extubated within 2 h postoperatively. The TPVB group had a significantly earlier extubation time compared to the GA group (P < 0.05). The time of first anal exhaust was also earlier in the TPVB group compared to the GA group. There was no significant difference in the time to first postoperative urination and length of postoperative hospitalization between the two groups of patients, as shown in Table 3.

Discussion

In this prospective randomized trial, we evaluated the impact of TPVB combined with GA on the postoperative recovery quality of patients undergoing MBS. The results showed that patients who received TPVB in combination with GA prior to surgery had higher recovery quality within 24 h to 48 h postoperatively, as evidenced by significant higher QoR-15 scores compared to those who received GA alone. In addition, NRS pain scores, intraoperative sufentanil usage and postoperative rescue analgesia were lower in the TPVB group compared to the GA group. These findings further support the value of TPVB in MBS.

Laparoscopic sleeve gastrectomy is a common MBS procedure that often causes moderate-to-severe postoperative pain [18]. This includes parietal pain from trocar incisions (50%–70%), visceral pain from organ manipulation (10%–20%), and referred pain from diaphragmatic irritation (20%–30%), typically experienced in the left shoulder [19]. In relation to the trocar sites discussed above, parietal pain involves the T7–T10 dermatomes; ociceptive impulses from the stomach are conveyed predominantly via sympathetic fibers through the celiac plexus and sympathetic trunks into the T6–T10 spinal segments, with the vagus nerve also contributing; and referred pain is transmitted by the phrenic nerve to the cervical plexus. Daniela Marhofer et al. demonstrated that local anesthetic can spread both cranially and caudally, with a caudal predominance [20]. In this trial, multipoint paravertebral blocks were performed bilaterally at T6 and T9. Administering 10 ml of a local anesthetic at each site, followed by ultrasound confirmation of the spread to the T5-T11 paravertebral space, ensures broader coverage of the analgesic area necessary for MBS. This approach provides more comprehensive intraoperative and postoperative pain control compared to single-point injection, improving overall block effectiveness. By implementing these adjustments, TPVB can be used more safely and effectively in patients with obesity, leading to improved precision and better clinical outcomes.

Very few studies have explored the use of TPVB in the context of MBS. Specifically, S. Kanawati et al. [21] performed bilateral paravertebral blocks from T6 to T11 combined with superficial cervical plexus block and supplemental sedation and analgesia in five patients with obesity-associated diseases undergoing MBS. All of these patients ultimately underwent laparoscopic sleeve gastrectomy under regional anesthesia. These findings highlight the promising potential of TPVB in MBS. However, the need for multiple injection sites can make the technique more time-consuming and requires good patient cooperation. In this study, the entire TPVB procedure, from patient positioning to completion of the block, took approximately 15 to 20 min, significantly reducing the preoperative preparation time. In addition, the current trend is to perform MBS under GA because of several factors, including good muscle relaxation which allows better manipulation of laparoscopic tools. The possibility of completing the procedure with an awake paravertebral block was not evaluated. However, this approach may be particularly important for patients with obesity and obesity-associated diseases who require surgery but are not suitable candidates for general anesthesia. The use of multipoint TPVB in this study significantly enhanced postoperative recovery quality and reduced opioid consumption, potentially lowering postoperative risks in patients with obesity.

Although complications related to TPVB are relatively rare, especially with advancements in ultrasound technology, they should still be carefully monitored. According to statistics, the overall incidence of complications associated with TPVB is generally below 5%, with hypotension being the most common (4.6%), followed by vascular puncture (3.8%), pleural puncture (1.1%), and pneumothorax (0.5%) [22]. A meta-analysis by R.G. Davies et al. further reported an incidence of hypotension of approximately 2.3% following bilateral paravertebral block [23]. In this study, BP fluctuations after TPVB remained within 20% of baseline levels, and no significant hypotension was observed. Consistently ensuring that the needle tip is visible under ultrasound guidance, performing frequent aspiration to check for inadvertent intravascular placement or resulting pneumothorax, and closely monitoring the patient's condition can significantly reduce the incidence of block-related complications under real-time ultrasound imaging.

Ultrasound guidance allows real-time visualization, significantly improving the accuracy and safety of needle placement. It is particularly suitable for patients with severe obesity or significant anatomical variations. In contrast, nerve stimulator-guided techniques are relatively simple, cost-effective, and suitable for resource-limited settings. However, they lack real-time anatomical imaging, which increases the risk of pleural or vascular puncture, especially in patients with obesity where landmarks are often unclear. Additionally, the technique is highly dependent on the operator’s experience. Multiple studies have shown that, compared to nerve stimulator guidance, ultrasound guidance reduces the time required to perform the block and procedural pain. This difference is even more pronounced in patients with obesity [22, 23].

The literature indicates that various regional anesthesia techniques can be utilized in MBS, one of which is the transversus abdominis plane block (TAPB). This provides significant analgesia to the anterolateral abdominal wall by blocking the thoracolumbar nerves originating from the T6 to L1 spinal roots by injecting local anesthetic into the plane between the internal oblique and transversus abdominis muscles [24]. Several previous studies have demonstrated that the use of ultrasound-guided TAPB in MBS reduces patients'postoperative pain scores, decreases the need for opioids, reduces the incidence of postoperative nausea and vomiting, and promotes early ambulation [25, 26]. However, TAPB can be technically challenging in patients with obesity due to increased subcutaneous fat and greater depth of the TAP, which may compromise block success. Moreover, while TAPB effectively relieves somatic pain, it offers limited visceral analgesia [27]. In contrast, TPVB provide more comprehensive analgesia by directly blocking the spinal nerves and their branches, thereby covering both somatic and visceral components..

The erector spinae plane block (ESPB) is also a viable option for postoperative analgesia in MBS. ESPB has been shown to significantly reduce opioid consumption compared with controls [28]. Ki Jinn et al. found that bilateral ESPB at the level of the T7 transverse process were effective in relieving visceral pain after MBS [29]. No ESPB-related complications were observed in the available studies. Although increased adipose tissue in patients with obesity prolongs the distance over which ultrasound must travel, thereby reducing its penetration and the success of the block, recent literature suggests that ESPB is not particularly difficult to perform in patients with obesity [30]. Whether diffusion of local anesthetics in the plane of the erector spinae muscle is affected in patients with obesity is not clear, and the specific mechanism of action of ESPB is not yet fully understood [31], and further research is needed to achieve the goal of maximizing analgesia. In contrast, the diffusion plane of paravertebral block drugs is relatively clear, easier to target to achieve the need to control the plane of analgesia.

Another alternative method used in MBS is the Quadratus Lumborum Block (QLB), and studies have shown that QLB reduces opioid consumption and the need for postoperative analgesia in patients undergoing MBS [32]. Some studies have shown that the duration of the block and analgesia are superior in the QLB group compared to ESPB and TAPB [32, 33]. However, in patients with severe obesity, the accumulation of adipose tissue affects muscle visualization, which increases the difficulty of the block and may lead to block failure.

The QoR-15 is a patient-reported outcome questionnaire to measure the quality of recovery after surgery and anesthesia. Proposed by Peter A Stark, it covers five dimensions of psychological support, physical comfort, emotional state, pain and physical independence [34]. The study conducted by Myles PS and Kleif J et al. suggested a minimal clinically important difference of 8.0 for the QoR-15 questionnaire [35, 36]. A later recalculation by Myles PS et al. suggested that it should be updated to 6.0 [37]. The postoperative 24 h in the present study between the two groups The difference in the QoR-15 scores of the two groups in this study was clinically significant [127.0 (124.0,129.0) vs. 113.0 (109.0,115.0)], which, in combination with the NRS scores in the 24 h period, suggests that a multipoint TPVB significantly reduces the patients'postoperative pain and significantly improves the quality of their postoperative recovery. The difference in QoR-15 scores at 48 h postoperatively was clinically significant under the new criteria [139.0(137.0,141.0) vs 132.5(126.0,135.0)], and as the effect of bilateral TPVB was weakened, the difference in terms of pain, physical comfort, and emotional state of the patients in the two groups was reduced, but it still improved the quality of postoperative recovery of the patients to a certain extent.

Patients with obesity are at a significantly higher risk of respiratory depression after anesthesia and sedation compared to individuals with normal weight [38]. This is primarily due to the accumulation of fat in the thoracic and abdominal regions, which reduces chest compliance, elevates the diaphragm, and lowers functional residual capacity (FRC), vital capacity, and total lung capacity [39]. Additionally, when lying supine, the upward pressure from abdominal contents further limits diaphragm movement, reducing FRC and lung compliance. This leads to significant ventilation-perfusion imbalances and worsens hypoxemia [40]. Furthermore, fat deposits in the head and neck region, along with the enlargement of oropharyngeal soft tissues, narrow the upper airway, particularly the pharyngeal cavity, raising the risk of OSA syndrome, hypoventilation syndrome, and difficult airway management [41]. Therefore, maintaining airway patency in postoperative patients with obesity is critical, and caution must be exercised when using sedatives and analgesics to avoid overdose or drug accumulation.

The use of multipoint TPVB in MBS supports the use of reduced or even opioid-free anesthesia. Stéphane et al. found that patients in the opioid-free anesthesia group had lower pain scores and significantly reduced opioid consumption 24 h after surgery compared to those who received opioid-based anesthesia [42]. The advantages of opioid-free anesthesia may be especially beneficial for high-risk patients, such as those with OSA, obesity, or chronic opioid use/abuse [43].

This study has several strengths that enhance the reliability of these results. First, we chose T6 and T9 for insertion to ensure that we could block the surgical site thereby providing good analgesia. Second, we used ultrasound guidance to accurately locate the insertion site, employing the 12th rib as a landmark and counting up from T12 to precisely identify the transverse processes of T9 and T6, making this approach more accurate than traditional anatomical landmark techniques. Third, we used in-plane needle insertion technique under ultrasound guidance, allowing real-time visualization of the needle tip to ensure precise injection of the drug into the paravertebral space. Finally, procedural consistency was ensured by having all TPVB procedures performed by the same experienced anesthesiologist, and all MBS were completed by the same skilled surgical team, minimizing technical variability.

This study demonstrates the multiple benefits of TPVB in MBS. The results indicate that: 1) standardized multi-point TPVB combined with GA can significantly improve postoperative recovery quality in patients undergoing MBS; 2) the application of multi-point TPVB can reduce opioid usage, effectively alleviate postoperative pain, and decrease the need for postoperative rescue analgesia, thereby reducing opioid-related adverse effects. Overall, these results suggest that multi-point TPVB combined with GA might have significant clinical values in enhancing postoperative recovery quality and providing superior analgesia in MBS.

Limitations

This present study had several limitations. First, we did not compare TPVB with other regional anesthesia techniques. Second, this is a single center study and generalizability in our hospitals needs to be studied in a multi-center study. Furthermore, we intend to conduct a comparative multicenter study evaluating different regional anesthesia techniques.

Conclusions

In conclusion, the multipoint TPVB combined with general anesthesia significantly enhances early postoperative recovery, lowers pain scores, reduces opioid consumption, and promotes faster functional recovery in patients undergoing MBS.

Supplementary Information

Below is the link to the electronic supplementary material.

Author Contribution

Li: Data curation, Formal analysis, Methodology, Writing – original draft; Wang: Data curation, Formal analysis, Methodology,Writing – original draft; Hu: Data curation, Formal analysis; Xu: Conceptualization, Methodology, Supervision, Validation, Writing – review and editing; Huang: Methodology, Writing – review and editing. All authors reviewed the manuscript. Authors Li and Wang contributed equally to this work.

Data Availability

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Declarations

Competing interest

The authors declare no competing interests.