Evaluation of Ultrasound-Guided Erector Spinae Plane Block and Oblique Subcostal Transversus Abdominis Plane Block in Laparoscopic Cholecystectomy: Randomized, Controlled, Prospective Study.

BACKGROUND: Oblique subcostal transversus abdominis plane block (OSTAP) is a recently described regional anesthetic technique used in upper abdominal surgeries such as laparoscopic cholecystectomy (LC). Erector spinae plane block (ESPB) has also been reported for postoperative analgesia in LC. AIM: We aimed to compare the effectiveness of OSTAP and ESPB in providing postoperative analgesia in patients undergoing these surgeries. SETTING AND
DESIGN: This study was designed as a double-blinded, prospective, randomized, efficiency study in a tertiary university hospital, postoperative recovery room, and ward.
MATERIALS AND METHODS: A total of 72 patients were recruited and 60 patients were randomized into three equal groups (ESPB, OSTAP, and control group). Pain intensity between groups was compared using Numeric Rating Scale (NRS) scores. In addition, consumption of paracetamol and tramadol and additional rescue analgesic requirement were measured. Standard multimodal analgesia was performed in all groups, while ESPB block was also performed in Group ESPB and OSTAP block was also performed in group OSTAP. STATISTICAL ANALYSIS USED: Descriptive statistics were expressed as mean ± standard deviation. Independent t-test, Mann-Whitney U-test, Chi-square test, Fisher's exact test, Shapiro-Wilk test, one-way ANOVA, and post hoc Tukey's analysis were used for statistical analysis.
RESULTS: NRS was lower in block groups during the first 3 h. There was no difference in NRS scores at other hours. Analgesic consumption and rescue analgesic requirement were lower in groups ESPB and OSTAP when compared to those of control group. Block groups were similar.
CONCLUSION: Bilateral ultrasound-guided ESPB and OSTAP performed at the end of LC lead to akin analgesia requirement and improve the quality of multimodal analgesia.

INTRODUCTION

Interfascial plane blocks – regional anesthetic techniques first described with anatomical landmarks and pop-up – have become safer and easier to perform with the use of ultrasonography. Ultrasound guidance and anatomic studies have led to the description of many new interfascial plane blocks.[1] While there are now many regional anesthetic techniques for use in thoracic and abdominal procedures, very few of these techniques are appropriate for postoperative analgesia in laparoscopic cholecystectomy (LC). LC leads to somatic pain from the supraumbilical abdominal area and also visceral pain due to pneumoperitoneum and surgical manipulation.[2]

One of the suitable regional anesthetic techniques for use in postoperative analgesia in LC is oblique subcostal transversus abdominis plane block (OSTAP). OSTAP is a modification of transversus abdominis plane block, and there are a few randomized controlled studies of its use in LC.[345]

Erector spinae plane block (ESPB) is a recently described peri-paravertebral plane block. A randomized controlled trial performed at our institute demonstrated that bilateral ESPB leads to effective postoperative analgesia in LC.[6] While the mechanism of the effect of ESPB has not been clarified, it is accepted that the local anesthesia (LA) spreads to the anterior and posterior of the transverse process and effects the ventral and dorsal rami, leading to sensorial block of a large area.[78910]

In this study, we aimed to compare the effect of ESPB and OSTAP on postoperative analgesia requirement and pain scores in patients undergoing LC.

MATERIALS AND METHODS

Study design

This single-blinded, prospective, randomized, efficiency study was performed after Local Ethics Committee approval (No: 2018.08/021, August 2018) and in accordance with the principles outlined in the Declaration of Helsinki. The study was registered with clinicaltrials.gov (Registration No: NCT03508531), and CONSORT checklist was used for enrollment and allocation of patients [Figure 1]. Recruitment was performed between March 2018 and May 2018. All patients gave written informed consent for inclusion into this study.

Figure 1

Consort diagram of the study

Patients aged 18–65 years with an American Society of Anesthesiologists (ASA) physical status classes of I and II who were scheduled to undergo elective LC were included in this study. Patients who refused enrollment or were unable to provide informed consent, had contraindications to or a known allergy to regional anesthesia, those with bleeding diathesis, use of anticoagulants, presence of severe kidney or liver disease or psychiatric disorders, or a history of previous upper gastrointestinal surgery were excluded from the study.

Patient grouping and randomization

The study was designed to include three groups of twenty patients each. Patients in Group C (Control group) received our institute's standard analgesia plan with no block. Patients in Group ESPB and Group OSTAP received the same standard analgesia plan and also underwent ESPB and OSTAP blocks, respectively. The sealed envelope technique was used to randomize patients into groups. Randomization and blocks were performed by the same anesthesiologist (ST) who was not involved in data collection or analysis. Recovery room and ward follow-up was performed by medical staff who were blinded to which group the patient was in.

Anesthetic application

Premedication, general anesthesia induction, and maintenance were the same for all patients. Standard monitoring procedures included pulse oximetry, electrocardiography, and noninvasive arterial pressure prior to anesthetic induction. All patients were premedicated with intravenous (i.v.) midazolam 1–2 mg and antibiotic prophylaxis, according to the hospital's protocol. Induction was performed using propofol 2–3 mg/kg, fentanyl 100 μg, and rocuronium bromide 0.6 mg/kg. 0.6 minimum alveolar concentration sevoflurane and 0.08 μg/kg/min remifentanil infusion was used for anesthetic maintenance. Remifentanil dosage was adjusted according to hemodynamic parameters, up to 2 μg/kg/min. No local anesthesia was used for surgical sites, nor was it applied by intraperitoneal nebulization. Pneumoperitoneum was evacuated in all patients at the end of surgery. After completion of surgery and blocks, the patients were extubated and transferred to the postoperative recovery room.

Performing blocks

All blocks were performed under general anesthesia under sterile conditions following the completion of LC. All blocks were performed under ultrasonographic guidance using a convex or linear ultrasound probe (Mindray DP 9900 plus; Mindray Bio-Medical Electronics, Shenzhen, China).

LA mixture included 20 mL of bupivacaine 0.5%, 10 mL of lidocaine 2% and 10 mL of normal saline to make a mixture totaling 40 mL. 20 mL of this mixture was applied to each side.

Erector spinae plane block

Patients were placed on their left side so that their right side was superior. The linear ultrasound transducer was placed in a longitudinal parasagittal orientation 2.5–3 cm lateral to the T9 spinous process. The erector spinae muscles were identified superficial to the tip of the T9 transverse process. A 21G 10-cm needle (Stimuplex A, B Braun, Melsungen, Germany) was inserted using an out-of-plane approach. The tip of the needle was placed into the fascial plane on the deep (anterior) aspect of the erector spinae muscle. The location of the needle tip was confirmed by visible fluid spread lifting the erector spinae muscle off the bony shadow of the transverse process on ultrasonographic imaging. A volume of 20 mL of LA mixture was injected. Due to reports that ESPB blocks visceral pain especially that of peritoneal distention, and as at least one trocar is placed in the midline, the same procedure was repeated for the opposite side. Probe position and sonographic view are shown in Figure 2.

Figure 2

Probe position and sonoanatomic view of erector spinae plane block performed at T8–T9 transverse process. ESM = Erector spinae muscle, TP = Transverse process, Yellow point (*) is injection point

Oblique subcostal transversus abdominis plane block

Blocks were performed in the supine position using a high-frequency linear transducer with the in-plane technique. The transducer was placed immediately below the costal margin on the oblique plane. The rectus abdominis, transverse abdominis, and internal oblique and external oblique muscles were identified. A 21G 10-cm needle (Stimuplex A, B Braun, Melsungen, Germany) was inserted using an in-plane approach from medially to laterally. 20 mL of LA was applied between the fascia immediately above the rectus abdominis muscle. The same procedure was applied bilaterally. The same volume and mixture of LA was performed, as described previously for ESPB. Probe position and sonographic view are shown in Figure 3.

Figure 3

Probe position and sonoanatomic view of oblique subcostal transversus abdominis plane block performed at interfascial plane between transverse abdominis muscle and rectus abdominis muscle. Yellow points (*) are injection points

Standard analgesia protocol and rescue analgesics

Perioperatively, all patients received 1 g paracetamol and 20 mg tenoxicam. During the postoperative period, fentanyl 25 μg was applied if Numeric Rating Scale score (NRS) >3/10 in the recovery room. Thereafter, basal infusion-free tramadol PCA (3 mg/ml, 10 mg bolus, lockout time 20 min) was programmed and scheduled with 1 g paracetamol i.v. every 8 h. Paracetamol dose was skipped if NRS <2 and/or patient refused. When required, diclofenac Na IM 75 mg was performed as rescue analgesia if NRS >3/10.

Evaluation of pain

Postoperative pain was evaluated using the NRS. The NRS is a segmented numeric version of the Visual Analog Scale (VAS) in which a respondent selects a whole number (0–10 integers) that best reflects the intensity of his/her pain. It is considered a one-dimensional measure of pain intensity in adults. The 11-point numeric scale ranges from “0” representing one pain extreme (“no pain”) to “10” representing the other pain extreme (“pain as bad as you can imagine” or “worst pain imaginable”). Changes in NRS at rest and on movement were recorded at intervals.

Outcome measures

Outcome measures were NRS pain scores at the 20th and 40th min as well as at the 1st, 3rd, 6th, 9th, 12th, 18th, and 24th h both at rest and when coughing and postoperative analgesia requirements (paracetamol, tramadol, and rescue analgesics).

In addition to the above measures, shoulder pain during the first 24 h and presence of postoperative nausea and vomiting were noted. The severity of nausea was assessed by patients on a 4-point scale (none, mild, moderate, and severe). Nurses noted any incidence of vomiting in the recovery room or in the ward. Finally, the number of patients receiving ondansetron was recorded.

Sample size

There are no previous clinical studies comparing ESPB and OSTAP for postoperative analgesia in any surgical procedure. We used a power of 0.90 and significance level of 0.05 to calculate a sample size of 18 patients for three groups when compared with ANOVA. Considering the possibility of dropouts, we designed the study to include twenty patients for each group, totaling sixty patients.

Statistical analysis

Statistical Package for the Social Sciences version 16.0 statistical package program (SPSS Inc., Chicago, IL, USA) was used for statistical analysis. All analyses were performed by a single author (DTT) who was blinded to the groups. Descriptive statistics were expressed as mean ± standard deviation. For univariate analysis f of means between groups a 2-sample, independent t-test assuming equal variances was used. For data without normal distribution, Mann–Whitney U-test was performed. Ratios were compared using Chi-square test. Categorical variables were compared using Fisher's exact test. Continuous variables were tested for normality via the Shapiro–Wilk test. One-way ANOVA was used to compare average NRS scores and tramadol consumption between groups. Post hoc Tukey's analysis was performed to determine differences between groups, when ANOVA revealed a significant difference.

P < 0.05 was considered statistically significant. For NRS scores, Bonferroni correction was applied, and statistical significance was accepted as P < 0.005, for measurements from ten time points. NRS was also analyzed using repeated measures analysis.

RESULTS

Seventy-two patients scheduled to undergo LC were evaluated for inclusion in this study. Two patients were excluded for bleeding diathesis, seven for previous abdominal surgery, and three due to psychiatric disorders. Descriptives of each group are provided in Table 1. Average age, male-to-female ratio, ASA scores, average surgical time, and body mass index were similar in all groups. There was no statistical difference between block performing time for ESPB and OSTAP groups.

Table 1

Descriptive statistics for each group

	Mean±SD			P
	Group ESPB	Group OSTAP	Group C
Age	51.95±12.39	50.1±12.65	48.5±11.86	0.676
Gender (female/male)	14	12	12	0.750
ASA I/II (n)	5	7	9	0.415
Surgical time (min)	52.33±6.31	53.15±4.91	50.3±5.0	0.242
Block performing time (min)	6.65±1.08	5.7±0.92	-	0.491
BMI (kg/m2)	28.19±4.16	27.34±4.21	28.19±4.62	0.774

ESPB=Erector spinae plane block, OSTAP=Oblique subcostal transversus abdominis plane block, BMI=Body mass index, SD=Standard deviation, ASA=American Society of Anesthesiologists

All blocks were performed smoothly with no block-related complications (bleeding, emphysema, pneumothorax, LA toxicity, etc.) observed in the study. Nausea requiring ondansetron was observed in two patients in Group C, one in group ESPB, and none in group OSTAP. Right shoulder pain was seen in three patients in Group C, two in group OSTAP, and none in group ESPB.

Pain measurements

NRS scores at rest and when coughing for each group are shown in Tables 2, 3 and Figures 4, 5, respectively. When average NRS scores for 24 h were compared between groups, no statistically significant difference was found (P > 0.05). There was a statistically significant difference at the 20th min, 40th min, 1st h, and 3rd h NRS scores at rest and coughing (P < 0.005 and P < 0.005, respectively; post hoc comparison between control group vs. ESPB and control group vs. OSTAP at the 20th min: P < 0.001 and P = 0.002, 40th min: P < 0.001 vs. P = 0.004, 1st h: P < 0.001 and P = 0.002, and 3rd h P < 0.001 and P < 0.001, respectively). No difference was found between the two block groups (P > 0.005). Statistical evaluation was same for NRS score on coughing.

Table 2

Evaluation of Numeric Rating Scale scores at rest

	Mean±SD			P
	Group ESPB	Group OSTAP	Group C
20th min	1.15±2.43	1.5±2.19	3.9±2.43	0.000
40th min	0.75±1.50	1.25±1.48	2.65±1.50	0.000
1st h	0.85±1.03	1.05±0.76	2.00±1.03	0.000
3rd h	1.25±1.57	1.3±0.80	3.15±1.57	0.000
6th h	1.6±1.34	1.75±0.97	2.3±1.34	0.094
9th h	1.7±0.69	1.85±0.67	2.05±0.69	0.314
12th h	1.75±0.99	2.2±0.89	2.35±0.99	0.087
18th h	1.9±0.72	2.15±1.09	2.1±0.72	0.596
24th h	1.65±0.69	1.85±0.67	1.55±0.69	0.307

ESPB=Erector spinae plane block, OSTAP=Oblique subcostal transversus abdominis plane block, SD=Standard deviation

Table 3

Evaluation of Numeric Rating Scale scores during coughing/movement

	Mean±SD			P
	Group ESPB	Group OSTAP	Group C
20th min	1.55±2.16	1.95±2.50	4.50±2.54	0.000
40th min	1.55±1.00	1.90±1.37	3.3±1.34	0.000
1st h	1.65±0.59	1.60±0.60	2.55±1.23	0.001
3rd h	1.9±0.91	1.80±0.89	3.7±1.92	0.000
6th h	2.45±0.60	2.15±1.18	3±1.69	0.096
9th h	2.25±0.85	2.2.±0.89	2.55±0.60	0.328
12th h	2.1±0.55	2.50±1.05	2.70±1.26	0.164
18th h	2.25±0.72	2.55±0.94	2.45±0.51	0.437
24th h	2±0.56	2.30±0.47	1.95±0.60	0.102

ESPB=Erector spinae plane block, OSTAP=Oblique subcostal transversus abdominis plane block, SD=Standard deviation

Figure 4

Average Numeric Rating Score scores at rest, for groups erector spinae plane block, oblique subcostal transversus abdominis plane block, and control at various time points of follow-up

Figure 5

Average Numeric Rating Score scores during coughing/movement, for Groups erector spinae plane block, oblique subcostal transversus abdominis plane, block and control at various time points of follow-up

We compared the average NRS scores during various time frames. While there was a statistically significant difference between NRS for the 0–3-h time frame (average NRS in ESPB: 1 ± 1.10, OSTAP 1.27 ± 1.41, and control 2.95 ± 1.81; P < 0.001), there was no statistically significant difference for 3–12-h and 12–24-h time frames (P > 0.05).

Analgesic requirements

Analgesic requirements are shown in Table 3. Fentanyl was administered to 11 patients in Group C, five in group ESPB, and six in group OSTAP (P > 0.05).

Average paracetamol requirement during the first 24 h was 2.80 ± 0.41 g in Group C, 2.30 ± 0.86 g in group ESPB, and 2.25 ± 0.72 g in Group OSTAP (P < 0.05). Post hoc analysis revealed a difference between Group C versus group ESPB and Group C versus OSTAP (P < 0.05 and P < 0.05, respectively), whereas there was no difference between group ESPB and group OSTAP (P > 0.05) [Table 4].

Table 4

Paracetamol and tramadol consumption for all groups

	Mean±SD			P
	Group ESPB	Group OSTAP	Group C
Paracetamol (gr), first 24 h	2.30±0.86	2.25±0.72	2.80±0.41	0.026
Tramadol (mg), first 12 h	64.00±55,00	74.00±52.36	108.50±54.70	0.029
Tramadol (mg), second 12 h	80.00±65.80	70.00±72.25	110.00±90.50	0.246
Total tramadol (mg), first 24 h	144.00±75.40	144.00±82.25	218.50±95.50	0.008

ESPB=Erector spinae plane block, OSTAP=Oblique subcostal transversus abdominis plane block, SD=Standard deviation

Table 4 shows the tramadol consumption for the first 12 h and second 12 h postoperatively. Tramadol consumption was statistically different between groups during the first 12 h (P < 0.05), but similar during the second 12 h (P > 0.05). Post hoc analysis demonstrated that tramadol consumption was similar between two block groups at the first 12 h (P > 0.05), but lower in both block groups when compared to the control group during this time frame (comparison between control group vs. ESPB and control group vs., OSTAP at the first 12 h P < 0.05 and P < 0.05, respectively).

Tramadol consumption through PCA was statistically significantly different between these groups. Table 3 demonstrates the tramadol consumption for the first 12 h and second 12 h. Tramadol consumptions were significantly different for the first 12 h (P < 0.05). In post hoc analyses, the first 12 h tramadol consumption was similar between the two block groups (P > 0.05), but significantly higher in the controls when compared to both block groups (comparison between control group vs., ESPB and control group vs. OSTAP at the first 12 h; P < 0.05 and P < 0.05, respectively). There was no difference between groups for tramadol consumption at the second 12 h.

The number of patients requiring rescue analgesia during the first 12 h was three in group ESPB, four in group OSTAP, and 11 in Group C (P < 0.05). This difference was statistically significant at post hoc analysis between Group C and both block groups (P < 0.01 and P < 0.01, respectively). Rescue analgesia requirement was similar for the second 12 h (P > 0.05) [Table 5].

Table 5

Rescue analgesic requirement for all groups

	Mean±SD			P
	Group ESPB	Group OSTAP	Group C
Average opioid use in recovery room (fentanyl µg)	6.25±11.11	11.25±18.98	30.10±22.46	0.000
Opioid requirement in recovery room (n)	5	6	11	0.108
Rescue analgesia requirement, first 12 h (n)	3	4	11	0.010
Rescue analgesia requirement, second 12 h (n)	2	3	5	0.431

ESPB=Erector spinae plane block, OSTAP=Oblique subcostal transversus abdominis plane block, SD=Standard deviation

DISCUSSION

Our study has shown that ultrasound-guided bilateral single-shot ESPB and bilateral single-shot OSTAP performed at the end of the surgery in LC patients significantly lowered NRS at rest and coughing/movement in the first 3 h and led to less analgesic agent requirement in the first 24 h when compared to a control group where no block was performed.

Our NRS scores were higher in the control group when compared to those in block groups in the first 3 h. This is probably due to the time it takes for tramadol to reach effective plasma concentrations. While the difference mentioned was statistically significant, it is not clinically significant as the average NRS scores were <4 for all groups at all times.

Postoperative pain after LC has two causes. The first is visceral pain due to the trauma of gallbladder resection, peritoneal CO2 exposure, and stretching, and the second is somatic pain caused by skin incision.[2] Therefore, any analgesic protocol after LC must be effective on both sources of pain.

We previously reported the effect of ESPB on postoperative pain and analgesia requirement, in a randomized controlled trial of LC patients.[6] In this study, ESPB was performed preoperatively under sedoanalgesia from the 9th thoracic vertebral level with 20 mL 0.375% concentration of bupivacaine as LA. We demonstrated that ultrasound-guided bilateral single-shot ESPB performed before general anesthetic induction in LC patients significantly lowered NRS at rest in the first 3 h and led to less analgesia requirement in the first 24 h when compared to a control group. In the current study, we performed blocks after completion of the surgical procedure so that remifentanil doses would be similar between groups, and therefore not effect our outcome measures therefore not effect our outcome measures. In the current study, we used a lower concentration of bupivacaine and performed blocks at the end of the surgical procedure versus a higher concentration of bupivacaine and block preoperatively. The results in our present study are similar to our previous one demonstrating that lower concentrations of LA and performing the block after completion of surgery offer similar outcomes. There are no similar studies of ESPB in LC. The ideal concentration of LA for ESPB in thoracic and abdominal surgeries has yet to be determined.[11] In a mini-review, 3.6 mL of LA per vertebral level was reported to be adequate in ESPB.[12] However, LA distribution at different thoracic or lumbar vertebral levels may differ, leading to clinicians to determine LA volume according to patients’ age and type of surgery to be performed.[13141516] Although reports and clinical experience may differ, 20 mL of LA applied at T4 has been shown to spread caudal and cephalad for three to seven vertebral levels.[17]

This study has also demonstrated that OSTAP is just as effective as ESPB, also leading to effective analgesia in our group of patients. There are a few studies reporting similar results.[341819] In a study reporting sensorial block distribution and effect time in OSTAP, the authors reported blockage of at least T7–T12 dermatomes, leading to sensorial blockage of the mid-abdomen and spreading partially to the lateral abdomen for at least 10 h.[20] This sensorial distribution seems adequate for the incisions performed on the anterior side of the abdomen in LC.

Although it is accepted that OSTAP leads to only blockage of somatic pain, the deeper fibers of the anterior and lateral cutaneous branches of 7–11th thoracic intercostal nerves which partially innervate the parietal peritoneum may have an effect on visceral pain.[6] It is claimed that ESPB is an effective method for the blockage of both somatic and visceral pain.[2691021]

Has this study been able to determine a difference of effect of postoperative pain and analgesia requirements between ESPB – a modality that is thought to have a high rate of effect on visceral pain, OSTAP – a modality where there is limited evidence of its effect on visceral pain? Our results have shown no such difference and that ESPB and OSTAP have similar effect. The severity and time of visceral pain is dependent on surgical procedure time, insufflation pressure and time, as well as the complete or partial evacuation of pneumoperitoneum. Maybe the answer posed at the beginning of this paragraph will better be answered through randomized controlled trials involving procedures that last longer and therefore have longer insufflation time, such as laparoscopic bariatric procedures. This report is the first controlled study to compare the fairly new and rarely reported thoracic ESPB with a different regional anesthetic technique.

Our study has several limitations. The first and most important limitation is that no data were collected to assess the sensorial coverage of ESPB and OSTAP. We, therefore, may have missed some block failures. A suitable and inclusive multimodal analgesia regime led to adequate analgesia in all of our patients. Another limitation was all blocks were performed under general anesthesia after completion of the surgical procedure. The rationale behind this was explained previously, in the methods’ section of this report.

In nearly all studies of regional anesthetic techniques, pure LA or LA diluted with normal saline is used. We added lidocaine to our LA mixture as we required low onset time, as blocks were performed at the end of surgery. It was important that block effect began during the time from when the patient was extubated and transferred into the recovery room.

Studies evaluating regional anesthetic techniques generally use morphine consumption as a comparison. Although we had no reason for not using morphine PCA, tramadol has been shown to have the same effect as morphine in patients undergoing LC.[22]

Our sample size was calculated for the minimum number of patients required to find a statistically significant difference in our results. It was not large enough to determine block-related complications such as nausea and vomiting.

CONCLUSION

Bilateral ultrasound-guided ESPB and OSTAP performed at the end of LC lead to decreased first 24 h analgesia requirement and improve the quality of multimodal analgesia when compared to a control group. Further studies are required to determine the effect, feasibility, and ideal volume and concentration and to determine the cause of effect of ESPB and OSTAP.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.