Nerve Block on Pain After Mammaplasty: A Meta-Analysis of randomized controlled studies

Abstract

Background:

Nerve block showed some potential in alleviating pain after mammaplasty. This systematic review and meta-analysis was conducted to investigate the efficacy of nerve block for pain control after mammaplasty.

Methods:

The databases including PubMed, Embase, Web of Science, EBSCO, and Cochrane library databases were systematically searched for collecting the randomized controlled trials (RCTs) regarding the impact of nerve block on pain intensity after mammaplasty.

Results:

This meta-analysis included 4 RCTs. Compared with control group after mammaplasty, nerve block resulted in remarkably reduced pain scores at 1 hour (mean difference [MD] = −1.84; 95% CI = −2.49 to −1.20; P < .00001), 3 hours (MD = −1.04; 95% CI = −1.47 to −0.62; P < .00001), 6 hours (MD = −0.96; 95% CI = −1.48 to −0.43; P = .0004), and analgesic consumption (standard mean difference = −1.27; 95% CI = −1.73 to −0.82; P < .00001), but showed no significant impact on pain scores within 24 hours (MD = −0.31; 95% CI = −1.05 to 0.43; P = .41).

Conclusions:

Nerve block was associated with substantially reduced pain intensity after mammaplasty.

Introduction

Patients with mammaplasty such as breast reconstruction and augmentation commonly suffer from a significantly high level of acute postoperative pain which may result in poor recovery and the development of chronic postoperative pain. ^{1 -5} Many methods have been developed to reduce the pain after mammaplasty, and they mainly include intravenous and local infiltration of analgesics, indwelling pain catheters. ^{6 -9} However, they have no consistent benefits.

Nerve blocks are reported to be effective for pain relief and have the ability to prolong the time to first postoperative pain and time to first analgesic requirement. ^{10 -12} Paravertebral block is known as the regional anesthesia modality and obtains great popularity. ¹³ Paravertebral block using bupivacaine as an adjunct to general anesthesia for breast cancer surgery shows a significant reduction in early postoperative visual analogue scale pain scores 30, 60, 90, and 120 minutes and 6 hours postoperatively. ¹⁴ Paravertebral blockade with ropivacaine is associated with reduced propofol requirement and decreased average postoperative pain than local infiltration for breast augmentation. ⁴ This result is consistent with another study for prosthetic breast reconstruction. ¹³ However, in one randomized controlled trial (RCT) involving 47 patients undergoing breast reconstruction, intraoperative intercostal and pectoral nerve blocks with 0.25% bupivacaine with 1:200 000 epinephrine and 4 mg of dexamethasone are found to have no significant effect on overall quality of recovery and pain control. ¹⁵

Recently, several studies on the effect of nerve block on pain intensity after mammaplasty have been published, and the results have been conflicting. ^4,13,15 Considering these inconsistent effects, we therefore conducted a systematic review and meta-analysis of RCTs to evaluate the efficacy of nerve block on pain management after mammaplasty.

Materials and Methods

Preferred Reporting Items for Systematic Reviews and Meta-analysis statement ¹⁶ and the Cochrane Handbook for Systematic Reviews of Interventions ¹⁷ are used to guide the performance of this systematic review and meta-analysis. Two investigators have independently searched articles, extracted data, and assessed the quality of included studies.

Literature Search and Selection Criteria

Several databases including PubMed, Embase, Web of Science, EBSCO, and the Cochrane library are systematically searched using the keywords: mammaplasty or breast augmentation or breast reconstruction, and nerve block or paravertebral block or intercostal block. The time in publishing the studies is from inception to December 2019, and studies are published in English. Mammaplasty is defined as any operation procedure for the insertion of a mammary prosthesis during breast reconstruction or augmentation.

The inclusion criteria are as follows: (1) study design is RCT, (2) study population are patients undergoing mammaplasty, and (3) intervention treatments are paravertebral block (or intercostal nerve block) versus sham procedures.

Data Extraction and Outcome Measures

Some information is collected for summarizing the baseline characteristics of patients in the included RCTs, and they include first author, publication year, sample size, body mass index, the number of unilateral/bilateral surgery/implant exchange and detail methods of 2 groups.

The primary outcomes are pain scores at 1 hour and 3 hours. Secondary outcomes include pain scores at 6 hours and 24 hours, analgesic consumption.

Quality Assessment in Individual Studies

The methodological quality of included RCTs is evaluated using the Jadad Scale, which is composed of 3 evaluation elements including randomization (0-2 points), blinding (0-2 points), dropouts, and withdrawals (0-1 points). ¹⁸ One point would be allocated to each element based on the description, randomization, and/or blinding of the included RCTs. The score of Jadad Scale has a range from 0 to 5 points, and a study with Jadad score ≥3 is thought to have the high quality. ¹⁹

Statistical Analysis

Review Manager Version 5.3 (The Cochrane Collaboration, Software Update) is used for all statistical analyses. We have calculated the mean differences (MDs) or standard mean differences (Std. MDs) with 95% CIs for continuous outcomes (pain scores at 1 hour, 3 hours, 6 hours, and 24 hours, analgesic consumption). Heterogeneity is quantified with the I ² statistic, and an I ² value greater than 50% represents the significant heterogeneity. The random effect model with DerSimonian and Laird weights is applied for all the meta-analyses regardless of the heterogeneity. When significant heterogeneity is present, sensitivity analysis is conducted to detect the influence of a single study on the overall estimate or perform subgroup analysis. Publication bias is not evaluated because of the limited number of studies (<10). P < .05 is thought to be statistically significant.

Results

Literature Search, Study Characteristics, and Quality Assessment

Figure 1 demonstrates the flow chart for the selection process and detailed identification. A total 462 publications are searched after the initial search of databases; 134 duplicates and 321 papers after checking the titles/abstracts are excluded. Three studies are removed because of the study design and 4 RCTs are ultimately included in the meta-analysis. ^4,5,13,15

Figure 1.

Flow diagram of study searching and selection process.

Table 1 shows the baseline characteristics of 4 eligible RCTs. The 4 studies are published between 2000 and 2018, and total sample size is 218. The detail methods of nerve block for mammaplasty are summarized in Table 1. Three RCTs involve paravertebral block ^4,5,13 and the remaining one RCT involves intercostal nerve block. ¹⁵ Two studies involve the breast reconstruction, ^13,15 while the remaining 2 studies involve breast augmentation. ^4,5

Table 1.

Characteristics of Included Studies.

No.	Author	Nerve block group					Control group					Jada scores
		Number	Age (years)	Body mass index (kg/m 2 )	Unilateral/bilateral surgery/implant exchange	Methods	Number	Age (years)	Body mass index (kg/m2)	Unilateral/bilateral surgery/implant exchange	Methods
1	Lanier et al (2018)	23	48 (43-58), median (IQR)	26 (23-32)	5/18/0	Intercostal nerve blocks with 0.25% bupivacaine with 1:200 000 epinephrine and 4 mg of dexamethasone (volume, 30 mL per side)	22	50 (42-57), median (IQR)	26 (20-30)	10/12/0	Sham nerve blocks with normal saline	5
2	Wolf et al (2016)	35	48.43 ± 11.48	27.85 ± 4.83	12/4/19	Paravertebral block technique by unilateral multilevel injection technique of 1% and 0.5% ropivacaine with epinephrine diluted by 1:400,000 into the ipsilateral paravertebral spaces of T1 through T6, plus general anesthesia	39	51.49 ± 10.19	27.14 ± 4.82	8/10/21	General anesthesia alone	4
3	Gardiner et al (2012)	20	33.4 ± 10.0	20.1 ± 2.7	-	Paravertebral blockade with ropivacaine	20	34.9 ± 8.0	20.5 ± 1.8	-	Local infiltration with ropivacaine	4
4	Klein et al (2000)	29	48 ± 14	-	1/18/22	Thoracic paravertebral block (levels T1-7) plus general anesthesia	30	44 ± 14	-	1/13/16	General anesthesia	3

Abbreviation: IQR, interquartile range.

Among the 4 RCTs, 3 studies report pain scores at 1 hour, ^4,13,15 2 studies report pain scores at 3, 6, and 24 hours, ^13,15 as well as 3 studies report analgesic consumption. ^5,13,15 Jadad scores of the 4 eligible studies vary from 3 to 5, and thus this quality assessment confirms these studies with high quality.

Primary Outcomes: Pain Scores at 1 Hour and 3 Hours

The random effect model is used for the analysis of primary outcomes. The results find that compared to control intervention after mammoplasty, nerve block is associated with substantially reduced pain scores at 1 hour (MD = −1.84; 95% CI = −2.49 to −1.20; P < .00001) with no heterogeneity among the studies (I ² = 0%, heterogeneity P = .81, Figure 2) and 3 hours (MD = −1.04; 95% CI = −1.47 to −0.62; P < .00001) with no heterogeneity among the studies (I ² = 0%, heterogeneity P = .65, Figure 3).

Figure 2.

Forest plot for the meta-analysis of pain scores at 1 hour.

Figure 3.

Forest plot for the meta-analysis of pain scores at 3 hours.

Sensitivity Analysis

The meta-analysis of pain scores at 1 hour and 3 hours has no heterogeneity among the included studies, and thus we do not perform sensitivity analysis by omitting one study in each turn or conduct the subgroup analysis.

Secondary Outcomes

In comparison with control intervention after mammaplasty, nerve block results in significantly reduced pain scores at 6 hours (MD = −0.96; 95% CI = −1.48 to −0.43; P = .0004; Figure 4), but has no positive influence on pain scores at 24 hours (MD = −0.31; 95% CI = −1.05 to 0.43; P = .41; Figure 5). In addition, nerve block can remarkably reduce analgesic consumption after the surgery (Std. MD = −1.27; 95% CI = −1.73 to −0.82; P < .00001; Figure 6).

Figure 4.

Forest plot for the meta-analysis of pain scores at 6 hours.

Figure 5.

Forest plot for the meta-analysis of pain scores at 24 hours.

Figure 6.

Forest plot for the meta-analysis of analgesic consumption.

Discussion

Postoperative pain control following breast surgery has become a significant concern. ^{20 -23} In one prior retrospective cohort study of 132 patients with tissue expander and implant breast reconstruction, nerve blocks are associated with less requirement of morphine and diazepam, shorter length of stay compared with peri-incisional infiltration. ²⁴ Paravertebral block before mastectomy with immediate reconstruction also results in the reduction in length of stay, time to conversion to oral narcotics, and the episodes of postoperative nausea and vomiting. ²⁵ Improved intraoperative compliance and decreased pain scores are observed after using paravertebral block for subpectoral breast augmentation. ⁴

Our meta-analysis includes intercostal and paravertebral nerve block following mammaplasty, and the results find that nerve block can substantially reduce pain scores at 1 hour, 3 hours, 6 hours and analgesic consumption but shows no significant impact on pain scores at 24 hours. These indicate that the short periods of pain relief can be promoted by nerve block for mammaplasty. Longer acting agents may prolong the analgesic efficacy of nerve block. Implementing nerve blocks requires multidisciplinary planning, team coordination, and preoperative communication between the anesthesiologist, surgeon, and nurses in the operating room and the recovery room.

A recent meta-analysis shows that paravertebral nerve block is a feasible and effective method to improve postoperative analgesia after breast surgery. ²⁶ Effective blocking of pain pathways enables to reduce the acute (surgical) stress response and improve the quality of recovery. ²⁷ Furthermore, paravertebral blockade with ropivacaine resulted in reduced propofol requirement and decreased postoperative pain than local infiltration for breast augmentation. ⁴ Two published studies (538 patients) reports the paravertebral nerve block for breast surgery, and there are no reports of systemic toxicity. The included RCTs report no complications after the nerve block. ^5,13,15

There are still several limitations. Firstly, only 4 RCTs are included in this meta-analysis, and all of them have a relatively small sample size (n < 100). These may lead to overestimation of the treatment effect in smaller trials. Although there is no heterogeneity among the included studies, different procedures of mammaplasty can produce various pain intensity scales which may affect the pooled results. Finally, intercostal and paravertebral nerve block are both included in this meta-analysis, and they may lead to some bias to the pooled effect.

Conclusion

Nerve block may be effective and safe for pain relief after mammaplasty and is recommended for these patients.