Erector Spinae Plane Block for Postoperative Analgesia in Cardiac Surgeries- A Systematic Review and Meta-Analysis

ABSTRACT

Ultrasound-guided erector spinae plane block (ESPB) has been used in many studies for providing opioid-sparing analgesia after various cardiac surgeries. We performed a systematic review and meta-analysis of randomized controlled trials to assess the efficacy of ESPB in cardiac surgeries. We searched PubMed, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), and Google Scholar to identify the studies in which ESPB was compared with the control group/sham block in patients undergoing cardiac surgeries. The primary outcomes were postoperative opioid consumption and postoperative pain scores. The secondary outcomes were intraoperative opioid consumption, ventilation time, time to the first mobilization, length of ICU and hospital stay, and adverse events. Out of 607 studies identified, 16 studies (n = 1110 patients) fulfilled inclusion criteria and were used for qualitative and quantitative analysis. Although, 24-hr opioid consumption were comparable in both groups group (MD, −18.74; 95% CI, −46.85 to 9.36, P = 0.16), the 48-hr opioid consumption was significantly less in ESPB group than control ((MD, −11.01; 95% CI, −19.98 to −−2.04, P = 0.02). The pain scores at various time intervals and intraoperative opioid consumption were significantly less in ESPB group. Moreover, duration of ventilation, time to the first mobilization, and length of ICU and hospital were also less in ESPB group (P < 0.00001, P < 0.00001, P < 0.00001, and P < 0.0001, respectively). This systematic review and meta-analysis demonstrated that ESPB provides opioid-sparing perioperative analgesia, facilitates early extubation and mobilization, leads to early discharge from ICU and hospital, and has lesser pruritus when compared to control in patients undergoing cardiac surgeries.

INTRODUCTION

The postoperative pain after cardiac surgeries namely coronary artery bypass grafting (CABG), valve replacement surgeries, and even minimal access cardiothoracic surgeries is severe and causes significant patient discomfort, delayed recovery, and at times prolonged hospital stay. The multifactorial pain could be due to many reasons like tissue damage, sternotomy, the presence of intercostal drains, rib fractures, and extensive retraction of the thoracic cage, especially for internal mammary artery harvesting.[1] Regional anesthesia techniques like thoracic epidural analgesia and paravertebral blocks are excellent options but are usually not popular due to systemic heparinization during cardiovascular surgeries.[2,3,4,5] In the last few years, several chest wall blocks have been described and investigated for various thoracic surgeries including cardiac surgeries.[6]

In 2016, Forero et al.[7] described the ultrasound (US) guided erector spinae plane block (ESPB) as an interfascial plane block. They performed the block in 2 cases with chronic neuropathic pain and found it to be effective. Among all the blocks, US-guided ESPB has been one of the most popular blocks not only for cardiac and non-cardiac thoracic surgeries but for many other indications as a postoperative analgesic intervention.[8] The reason is the ease of technique, reliable landmarks seen in the US, and could be safely administered in coagulopathic patients, although the last reason has not been reliably validated by adequately powered prospective studies yet.[9]

This systematic review and meta-analysis aimed to investigate the efficacy and safety of US-guided ESPB as an intervention providing perioperative analgesia in patients undergoing cardiothoracic surgeries.

METHODS

Search strategy and criteria

The protocol for this systematic review was registered with a prospective registry for systematic reviews: INPLASYS (INPLASY202270105). This systematic review and meta-analysis were performed in adherence to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and the Cochrane Handbook for Systematic Reviews of Interventions (supplementary file).[10]

Preliminary searches were done by (AN and PS) in PubMed and Embase to confirm the absence of any systematic review on the same topic. We searched PubMed/Medline, The Cochrane Central Register of Controlled Trials (CENTRAL), Embase, and Google Scholar starting from the year 2016 to July 31, 2022 for relevant articles. The language was restricted to English. A comprehensive search strategy was utilized using relevant search terms selected from Medical Subject Headings and Embase Subject Headings. The search strategy used was as follows: (erector spinae plane block OR ESPB) and (cardiac surgeries OR coronary artery bypass grafting OR valvular surgeries OR minimal access cardiac surgeries).

Study selection and data extraction

Two authors (AN and PS) screened the titles and abstracts independently and eliminated duplicates. Both authors reviewed the full texts of the potentially eligible studies and decided on the final articles to be included. Any disagreement and inconsistency were settled by a third author (NB).

Inclusion criteria

We included studies that compared ESPB with a control group (no block/sham block) in adult patients undergoing cardiac surgeries. Studies involving pediatric patients undergoing cardiac surgeries were also included. Searches were rerun before the final analysis.

Exclusion criteria

Conference abstracts, unpublished data, ongoing studies, and studies with incomplete data were excluded. Studies that did not have postoperative pain scores or opioid consumption as an outcome were excluded.

The primary outcome was 24 and 48 hours of opioid (morphine equivalent) consumption, and pain scores for the first 24 hours. The secondary outcomes were duration of ventilation, length of stay (LOS) in intensive care unit (ICU) and hospital, intraoperative opioid consumption, duration of ventilation, time to first rescue analgesia, sedation scores, time to mobilization, postoperative nausea/vomiting (PONV), complications due to block like pneumothorax, intravascular injection. We converted the dose of opioid used into an intravenous (IV) morphine. Outcomes reported in fewer than three studies were not for inclusion in the analysis.

Methodological quality assessment

The Revised Cochrane risk-of-bias tool for randomized trials (RoB 2) was used to access the methodologic quality and risk of bias of the included trials.[11,12] Six categories were taken into consideration for bias assessment: bias due to randomization, bias due to deviation from intended intervention, bias due to missing data, bias due to outcome measurement, bias due to selection of reported result, and overall bias.

Meta-analysis

All included studies that directly compared outcomes between patients who underwent cardiac surgeries with ESPB and with control (no block/sham block) will be included in the quantitative meta-analysis. An outcome of interest described by three or more studies was synthesized for meta-analysis and other outcomes were reviewed.

Statistical analysis

We used the Mantel–Haenszel method to analyze dichotomous variables and the risk ratio (RR) with the corresponding 95% confidence interval (CI) for the effect. For continuous variables, the Inverse Variance method was used, and mean difference (MD) with the corresponding 95% confidence intervals (CI) was calculated for units-unified continuous outcomes. When P > 0.01 and I² <50%, the fixed effects model was used for meta-analysis. When P < 0.01 and I² >50%, the random effects model was used for meta-analysis. We evaluated the heterogeneity between studies using the I² statistic which was defined as 0–40% – might not be important, 30–60% – may represent moderate heterogeneity, 50–90% – may represent significant heterogeneity, 75–100% – considerable heterogeneity. All statistical analyses were performed using Review Manager version 5.4.1 (Cochrane Collaboration, Software Update, Oxford, UK).[13]

The results were compared by the random effects model and fixed effects model, and the reliability of the combined results was eventually analyzed according to the consistency degree of the results. It was decided to construct a funnel plot to determine if there was a publication bias in the studies that fulfilled the inclusion criteria for a quantitative review.

RESULTS

Details of search strategy

We searched PubMed, Embase, CENTRAL, and Google Scholar for RCTs comparing ESPB with controls in patients undergoing cardiac surgeries. We identified 607 articles by searching the above-mentioned databases and registries. After removing duplicates and also articles that were not relevant, we identified 99 articles for scrutiny. A total of 25 studies were considered eligible. From these, 9 studies were excluded (study with no control group-1, review articles-4, articles with an active control group-3, unrelated primary and secondary outcomes-1). Finally, we included 16 studies which included 1110 patients for analysis (489 in ESPB and 621 in control), [Figure 1].[14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29] Table 1 summarizes the details of all the studies included in the analysis.

Figure 1.

PRISMA flow diagram showing the literature search process

Table 1.

Table summarizing all the studies included in the analysis with outcomes

Author/year	Type of study	Number of patients	Surgeries performed	Comparative group	Single shot/continuous	Location of block	LA used	Primary outcome	Secondary outcomes	Conclusion
Macaire et al./2019[22]	Patient-Matched, Controlled Before-and-After Study	67 (20- ESPB, 47- control)	CABG, Valve replacements, Bentall, Coarctation repair, Ebstein surgery	IV morphine	Continuous infusion	T4	0.25 ml/kg/side ropivacaine, Infusion of 0.2% ropivacaine 6 ml/side	Total morphine consumption at 48 h	Intraoperative sufentanil used, extubation time, pain scores 2 h after chest tube removal, pain during first mobilization and 1 month after surgery, times to chest tube removal	Morphine consumption was significantly decreased in the ESPB group in the first 48 h
Krishna et al./2018[14]	Prospective, randomized, controlled single-blinded study	106 (53 patients in each group)	CABG, MV repair, ASD closure	IV tramadol	Single shot	T6	3 ml/kg of 0.375% ropivacaine	To evaluate postoperative pain at rest.	Total opioid consumption (intra and postoperative), time to rescue analgesic, duration of analgesia.	Bilateral ESPB provides better pain relief at rest and for longer duration when compared to intravenous paracetamol and tramadol.
Kaushal et al./2019[27]	Prospective, randomized, single-blind, comparative study	80 children (40 patients in each group)	ASD and VSD closure	No block	Single shot	T3	1.5 ml/kg of 0.2% ropivacaine on each side	Modified Objective Pain Scores (MOPS) at 0, 1, 2, 4, 6, 8, 10, and 12 h post extubation	Intraoperative fentanyl consumption, extubation time, time to first rescue analgesic, postoperative cumulative fentanyl consumption up to 12 h, Ramsay sedation score10, ICU stay, and incidence of adverse events.	US-guided bilateral ESPB is an effective postoperative analgesic modality for pediatric cardiac surgeries with sternotomy.
Borys et al./2020[20]	Observational cohort study (MV/TV repair)	44 (19 in ESPB, 25 in control)	Mitral/tricuspid valve repair	No block	Single shot	T4	0.2 ml/kg of 0.375% ropivacaine	Total oxycodone consumption during the first postoperative day	Pain scores at 2, 4, 6, 8, 12, and 24 h, patient satisfaction.	Single-shot ESPB provides effective pain relief in patients undergoing right mini-thoracotomy for mitral and/or tricuspid valve repair.
Roy et al./2020[24]	Prospective, cohort study (pediatric: 5-17 yrs))	30 (10 in ESPB, 20 in control)	ASD/VSD repair, PAPVR, Anomalous aortic origin of coronary artery repair	No block	Continuous infusion	T4-5	Loading dose of LA- delivered 0.75 mL/kg of 0.2% ropivacaine mixed with 0.1 mL/kg of 1% lidocaine. Postoperative infusion: 0.1% ropivacaine at 0.25 mL/kg/h (maximum rate of 15 mL/h)	48-hr opioid consumption.	Pain scores (48-h), length of ICU and hospital stay, chest tube removal, mobilization	With the use of bilateral ESPB, there was a reduction in opioid use in the first 48 h after pediatric cardiac surgery.
Vaughan et al./2021[29]	Retrospective Cohort Study	43 (28-ESPB, 15 in control)	CABG, Aortic valve repair, ascending aortic surgery	No block	Continuous	T4-5	25 mL 0.5% ropivacaine bolus, infusion of 0.2% ropivacaine 3-7 mL/h/side and continued till chest tube removal	Opioid consumption during hospital stay	Time to extubation, length of stay	Preoperative continuous ESPB reduced opioid consumption, time to extubation, and length of stay when compared to no block.
Macaire et al./2021[23]	Randomized, double-blind, placebo-controlled trial	50 children (23 in ESPB, 27 in control)	Pediatric cardiac surgeries with midline sternotomy	Placebo	Continuous (programmed intermittent bolus)	T3-4	<1 year, bolus of 0.25 mg/kg side of ropivacaine 0.1%, more than 1 year, bolus of 0.50 mg/kg/side of ropivacaine 0.2%	48-hr morphine consumption	Pain scores, comfort score at extubation, drain removal time, length of hospital stay	Bilateral ESPB with ropivacaine decreases the postoperative morphine consumption at 48 h and provides better postoperative analgesia compared with a control group.
Wasfy et al./2021[25]	Prospective comparative randomized study	20 patients in each group	CABG	No block	Continuous	T5	15 ml of 0.25% bupivacaine on each side, 0.125% bupivacaine at 8 ml/hr for 48 h	Pain scores for 48-hrs	Intraoperative fentanyl and postoperative morphine consumption, time to extubation, peak inspiratory flow rate at 8, 12, 24 and 48 h using incentive respirometry	US-guided ESPB provided safe and effective, opioid-sparing analgesia for 48-hrs after CABG.
Athar et al./2021[15]	Randomized Double-Blind Controlled Trial	15 patients in each group	CABG, Valve replacement surgery	Sham block (saline)	Single shot	T5	20-ml bolus dose of 0.25% plain levobupivacaine on each side	24-hrs opioid (fentanyl) consumption	Time to rescue analgesia, median pain free time, intraoperative fentanyl consumption, duration of mechanical ventilation, sedation score, PONV, pruritus, complications	Single-shot ESPB provides superior, opioid-sparing analgesia as compared with sham block.
Sun et al./2021[28]	propensity score matched the retrospective cohort study	267 (93 in ESPB, 174 incontrol) Unilateral	Correction of congenital heart disease, ASD/VSD repair, valve repair/replacement, CABG, mass resection, coarctation repair, Ebstein deformity repair	No block	Continuous	T4	15 ml to 20 ml 0.375% to 0.75% ropivacaine was injected through the catheter, after surgery patients were administered intermittent boluses of 0.375%-0.75% ropivacaine 15-30 ml	Postoperative in-hospital cumulative opioid consumption	Intraoperative sufentanil used, PONV, pulmonary infection postoperatively, durations of ICU and hospital stays, and complications due to ESPB	Intermittent ESPB boluses was safe, effective, lead to lesser opioid and anti-emetic use in patients undergoing cardiac surgery through a lateral mini-thoracotomy
Oğur et al./2022[16]	Prospective, randomized controlled study	25 patients in each group	CABG	No block	Single shot	T4-5	0.5 ml/kg of 0.25% bupivacaine with 8 mg dexamethasone	Postoperative morphine consumption	Pain scores at rest and coughing, first PCA use after block, need for rescue analgesia, time for mobilization, opioid side effects, patient and surgeon satisfaction	Bilateral ESPB reduces opioid requirement compared to intravenous morphine PCA.
Güven et al./2022[17]	Prospective, randomized, single-blind, controlled trial	25 patients in each group	CABG, mitral/aortic valve replacement, ASD repair	No block	Single shot	T5	20 ml of 0.25% bupivacaine	24-hr morphine consumption	Intraoperative fentanyl consumption, duration of mechanical ventilation, LOS, time to first use of PCA, PONV in 24 h	Preoperative bilateral ESPB decreased postoperative pain scores and morphine Consumption.
Statzer et al./2022[26]	Retrospective case-control study	61 (23 in ESPB, 38 in control)	Minimally invasive mitral valve replacement surgery	No block	Continuous infusion	T5	30 ml of 0.5% ropivacaine followed by 0.2% ropivacaine 10 ml/hr	48-hr opioid consumption	Intraoperative morphine equivalents, extubation within 24 h, hospital and ICU LOS, reintubation, mortality	Statistically insignificant but clinically significant reduction in opioid consumption in 48 h
Silva et al./2022[18]	Randomized, controlled, and blinded comparative study	54 (25 in ESPB, 29 in control)	Cardiac surgery via sternotomy	No block	Single shot	T4-T6	20 ml of 0.5% ropivacaine bilaterally	24-hr morphine consumption	Pain scores (6, 12, 24 h)	No difference in 24-h morphine consumption between ESPB and control group.
Karacaer et al./2022[19]	prospective, blinded, randomized, controlled study	20 patients in each group	ASD/VSD closure, aortic membrane excision	No block	Single shot	T4-5		24-hr morphine consumption	Pain and sedation scores (0, 1, 2, 4, 6, 8, 10, 12, 16, 20 and 24 h postoperatively), extubation time, LOS in ICU	US-guided bilateral ESPB provides efficient postoperative analgesia and reduced morphine consumption at 24 h in children undergoing cardiac surgery.
Gado et al./2022[21]	randomized controlled, double-blinded clinical trial	98 (50 in ESPB, 48 in control)	ASD/VSD closure, AVSD closure, SAM resection, MV repair, supravalvular AS repair, Pulmonary artery banding	No block (48)	Single shot	T5	0.4 ml/kg of 0.25% bupivacaine bilaterally	Intraoperative fentanyl consumption	24-hr opioid consumption, time to first rescue analgesia, pain scores for 24 h	Bilateral US-guided ESPB reduces perioperative opioid consumption and pain scores in pediatric patients undergoing cardiac surgery through a sternotomy

Risk of bias

The risk of bias within the trials according to ROB 2 is shown in Figure 2a in the form of a traffic light plot. The summary plot of quality assessment for each study included according to ROB 2 is shown in Figure 2b. Six studies did not describe the randomization process and therefore were at high risk of bias. In 9 studies, the allocation sequence was not concealed until the participants were enrolled and assigned to interventions and thus was at a high risk of bias. In one study, details about missing outcome data were unclear. The details of the measurement of outcomes were not mentioned in one study and were unclear in another one. In 3 studies, the selection of the reported result was not described and unclear in 2 studies which raised concerns.

Figure 2.

(a)Traffic light plot showing the risk of bias within the trials. (b) Summary plot showing quality assessment for each included study

We constructed a funnel plot for 24-hrs and 48-hrs opioid consumption which showed asymmetry that was suggestive of a publication bias [Figure 3a and 3b].

Figure 3.

(a) Funnel plot of 24 and 48-hr postoperative opioid consumption in ESPB group versus control. (b) Funnel plot of 48-hr postoperative opioid consumption in ESPB group versus control

Primary outcome analysis

We converted various types of opioids (fentanyl, sufentanil, oxycodone) into IV morphine. Pain scores at various time intervals starting from zero hours (at extubation) till 48-hrs postoperatively were reported and showed inconsistency.

Meta-analysis of outcome- morphine consumption

Eight studies reported 24-hr morphine consumption[14,15,16,17,18,19,20,21] and 5 studies[22,23,24,25,26] reported 48-hr opioid consumption. For 24-hr morphine consumption, there were 232 patients in ESPB group and 240 patients in the control group. The 24-hr morphine consumption was comparable in the ESPB group when compared to the control group (MD, −18.74; 95% CI, −46.85 to 9.36, P = 0.16). A random effect model was applied (P < 0.00001, I² = 100%). For 48-hr morphine consumption, there were 96 patients in ESPB group and 152 patients in the control group. The 48-hr morphine consumption was significantly less in the ESPB group when compared to the control group (MD, −11.01; 95% CI, −19.98 to −2.04, P = 0.02). A random effect model was applied (P < 0.00001; I² = 97%) which was suggestive of a high level of heterogeneity [Figure 4].

Figure 4.

Forest plot showing comparison of opioid consumption at (a) 24-hr, (b) 48-hr, (c) intraoperative. (ESPB – erector spinae plane block, SD – standard deviation, CI – confidence interval, df – degree of freedom, IV – inverse variance)

Meta-analysis of outcome- pain scores

For 0 hour, pain scores were reported by 7 studies (ESPB-193, control-220),[16,17,19,21,27] at 1 hour by 5 studies(ESPB-160, control-158),[16,17,19,21,27] at 2 hours by 5 studies (ESPB-228, control-226),[14,15,16,17,19,21,27] at 4 hours by 7 studies (ESPB-248, control-246),[14,15,16,17,19,21,27] at 6 hours by 6 studies (ESPB-178, control-182),[16,17,19,21,27] at 8 hours by 7 studies (ESPB-233, control-231),[14,15,16,17,19,21,27] at 10 hours by 3 studies (ESPB-118, control-118),[14,17,27] at 12 hours by 8 studies (ESPB-248, control-246),[14,15,16,17,19,21,25,27] at 16 hours by 4 studies (ESPB-120, control-118),[17,18,20,22] and at 24 hours by 6 studies (ESPB-155, control-153).[15,16,17,19,21,25] [Figure 5]

Figure 5.

(a and b) Forest plot showing comparison of pain scores at 0, 1, 2, 4, 6, 8, 10, 12, 16, 24 hours postoperatively between ESPB group and control (ESPB – erector spinae plane block, SD – standard deviation, CI – confidence interval, df – degree of freedom, IV – inverse variance)

Pain scores were investigated at 0, 1, 2, 4, 6, 8, 10, 12, 16, 24 hours and included 7, 5, 7, 8, 6, 7, 3, 8, 4, and 6 studies, respectively The pain scores were significantly less in ESPB group than control at zero hour [MD: −0.96; CI: −1.38 to −0.54, P < 0.00001; I² = 69%], 1 hour [MD: −1.81; CI: −2.81, to − 0.81, P < 0.00001; I² = 91%], 2 hour [MD: −1.65; CI: −2.33, to −0.97, P < 0.00001; I² = 87%], 4 hours [MD: −1.13, CI: −1.70 to −0.57, P < 0.0001; I² = 84%], 6 hours [MD: −1.05; CI: −1.54 to − 0.55, P < 0.00001; I² = 48%], 8 hours [MD: −1.37, CI: −1.94 to −0.80, P < 00001; I² = 85%], 10 hours [MD: −0.54; CI: −0.81 to −0.27, P < 0.0001; I² = 0%], 12 hours [MD: −0.40; CI: −0.97 to −0.16, P = 0.001; I² = 81%], 16 hours [MD: −1.00, CI: −1.84 to 0.16, P < 0.00001; I² = 77%], and 24 hours [MD: −0.27; CI: −1.34 to −0.79, P = 0.62; I² = 95%].

Meta-analysis of outcome - intraoperative opioid consumption

This was described in 8 studies (ESPB-181, control-193).[15,17,19,24,25,26,27,29] The intraoperative opioid consumption (converted to IV morphine) was significantly less in the ESPB group when compared to the control (MD, −2.77; 95% CI, −4.38 to − 1.16, P = 0.00007). A random effect model was applied [P < 0.00001); I² = 96%] [Figure 4c].

Meta-analysis of outcome -LOS in ICU/hospital

A total number of 11 studies described LOS in ICU after cardiac surgeries (ESPB-35, control-457).[14,17,19,24,25,26,27,28,29] The LOS in the ICU was significantly less in ESPB group when compared to the control group (MD, −26.80; 95% CI, −26.91 to −26.69, P < 0.00001). A random effect model was applied [P < 0.00001); I² = 100%] which was suggestive of a high level of heterogeneity. A total of 6 studies described hospital stay (ESPB-197, control-294).[19,23,24,26,28,29] The overall hospital stay was significantly less in the ESPB group when compared to the control group (MD, −0.38; 95% CI, −0.56 to −0.21, P < 0.0001). A random effect model was applied [P = 0.65; I² = 0%] which was suggestive of low level of heterogeneity [Figure 6a and 6b].

Figure 6.

Forest plot comparing-(a) Length of stay in ICU (b) Length of stay in the hospital (c) Duration of postoperative ventilation (d) Time to first mobilization (e) PONV (f) Pruritus (ESPB- erector spinae plane block, SD – standard deviation, CI-confidence interval, df – degree of freedom, IV – inverse variance, RR – risk ratio, PONV – postoperative nausea and vomiting)

Meta-analysis of outcome-duration of ventilation/timing of extubation

This was described by 9 studies (ESPB-244, control-262).[14,15,17,19,22,23,25,27,29] The duration of postoperative mechanical ventilation or the timing of extubation was presented as outcomes in 9 studies [Figure 6c]. On pooled analysis, the duration of mechanical ventilation was significantly less in the ESPB group when compared to the control [MD: −43.65; CI: −66.15 to −21.15, P < 0.00001; I² = 99%].

Meta-analysis of outcome- time to first mobilization

A total of 5 studies described this outcome (EPSB-131, control-172).[14,17,22,23,24] The time to the first mobilization was presented in 5 studies [Figure 6d]. On pooled analysis, the time to the first mobilization was significantly early in ESPB group when compared to the control group [MD: −10.68; CI: −26.47, −5.10, P < 0.00001; I² = 100%].

Meta-analysis of outcome- complications/adverse events

PONV comparison was presented in 6 studies (ESPB-162, control-156, Figure 6e).[14,17,22,23,24] On pooled analysis, there was no difference in the incidence of PONV between ESPB and control group [RR: 0.60, CI: 0.30 to 1.22, P = 0.16; I² = 38%]. However, the incidence of pruritus was lesser in ESPB group than control group [RR: 0.29; CI: 0.08 to 1.12, P = 0.07; I² = 0%] [Figure 6f]. This was based on 3 studies (ESPB-92, control-86).[15,21,22]

DISCUSSION

Summary of results: This systematic review and meta-analysis demonstrate the clinical benefit of adding preoperative ultrasound-guided ESPB in patients undergoing cardiac surgeries. The addition of either single-shot ESPB or continuous analgesia via catheter reduces intraoperative opioid use, reduced 48-hr opioid consumption, reduced pain scores after extubation up to 16 hours, reduced duration of ventilation after surgery, reduced ICU and hospital stay, and early mobilization. However, the pooled analysis did not find a significant reduction in 24-hr opioid consumption, PONV, and pruritus in the ESPB group when compared to the control.

Opioid analgesics were considered a quintessential modality in the management of postoperative pain after cardiac surgeries. The problems with extensive opioid use are respiratory depression, PONV, ileus, and increased hospital stay to name a few. However, since the popularity of Enhanced Recovery After Surgery (ERAS) pathways in cardiac surgeries, the emphasis is now more on using regional anesthesia techniques if feasible and also on opioid-sparing multimodal analgesia.[30,31]

The Enhanced Recovery After Surgery (ERAS) society recommends using opioid-sparing, multimodal analgesia by tailoring it according to the patients underlying risk factors and as per requirements.[32] Neuraxial techniques like thoracic epidural anesthesia and paravertebral blocks can be used for providing perioperative analgesia after cardiac surgeries. But the intraoperative anticoagulation is a concern expressed by many anesthesiologists.[33] Several chest wall blocks have been described in the last two decades and have been successfully used in patients undergoing cardiac surgeries. These blocks are pectoral nerve blocks (PECS 1 and PECS 2), serratus anterior plane block, parasternal blocks like transversus thoracis muscle plane block, and the ESPB.[34,35]

ESPB has been the most popular block described in the last decade and has been used successfully for shoulder surgeries, thoracic (cardiac and non-cardiac) surgeries, upper and lower abdominal surgeries, and lower limb surgeries. This has been established by several case series, randomized controlled trials, systematic reviews, and meta-analyses.[36,37,38,39,40,41]

To the best of our knowledge, this is the first systematic review and meta-analysis that investigates the analgesic efficacy and opioid-sparing properties of ESPB in patients undergoing cardiac surgeries along with other outcome data like LOS in ICU and hospital, time to mobilization, and duration of ventilation. To reduce the bias which could have been possible if ESPB was compared with other interventions like thoracic epidural analgesia, thoracic paravertebral block, serratus anterior plane block, and pectoral nerve block; we compared ESPB with a sham block or no block as a control.

Our study demonstrated that when ESPB was used preoperatively in patients undergoing cardiac surgeries, there was a significant reduction in intraoperative and postoperative opioid use, but at 48-hrs and not at 24-hrs. The reason for this could be the presence of heterogenous patients included in the studies like adults, pediatric, patients undergoing sternotomy and also lateral thoracotomy or minimally invasive valvular surgeries, CABG and valve replacement surgeries, and continuous versus single shot ESPB. The local anesthetic used, its concentration, the total volume used, the site of performing ESPB, and unilateral versus bilateral ESPB could have led to variable pain scores thereby interfering with the analysis. The pain scores were significantly less in ESPB group than control at all times from extubation (zero hours) to 16 hours (P < 0.05) but not at 24 hours (P = 0.62). On analysis, we did not find any block-related complications like hematoma, infection, or LAST in ESPB group. Although a pneumothorax has been reported after ESPB, patients undergoing cardiovascular surgeries have a chest tube inserted at the end of the surgery.[42]

Many studies in which ESPB was used as an analgesic modality for cardiac surgeries were excluded from the analysis because they did not fulfill the inclusion criteria. In a study by Kurowicki et al.,[43] the authors conducted a prospective, open-label, observational study involving 30 patients (15 in each group) undergoing off-pump CABG using remifentanil and sevoflurane-based anesthesia. In one group, patients received bilateral ESPB and in another group, the patients received no block. In this study, the primary outcome was mean time to extubation with no comment on postoperative pain scores and opioid consumption. In a study by Gawęda et al.,[44] the authors compared ESPB with ESPB and PECS combined block. As this was against the inclusion criteria, the study was excluded. The RCT by Nagaraja et al.[45] were also excluded as they investigated ESPB with TEA which was an exclusion criterion.

There were several limitations to this study. The SRMA included studies that included adult and pediatric patients, patients undergoing cardiac surgery with a midline sternotomy and also with lateral thoracotomy, and patients who received single-shot and continuous infusion thereby adding clinical heterogeneity to the review. A sub-group analysis of single-shot ESPB studies and ESPB with continuous infusion, single-shot, continuous infusions, and unilateral and bilateral blocks was not done. Similarly, a sub-group analysis of studies involving pediatric cardiac surgeries and ESPB was not done due to the lesser number of studies. None of the studies documented the dermatomal level after ESPB which could be because cardiac surgeries take a long time and at the end of the surgery patients are mechanically ventilated. This lag could not give reliable information regarding the dermatomal level. The studies mentioned pain at rest only and not pain on movement or coughing. This was another limitation in describing the analgesic efficacy of ESPB. Time to the first analgesia was provided in less than 3 studies and therefore was not analyzed. The level of heterogeneity was very high in the results of the analysis due to variable sample sizes, different surgical approaches and surgeries, and single-shot and continuous blocks.

CONCLUSION

In conclusion, preoperative US-guided ESPB can provide opioid-sparing intraoperative and postoperative analgesia, with better pain scores of up to 24 hours. It also reduces LOS in ICU and hospital and facilitates early mobilization. Single-shot or continuous ESPB can be considered a safe intervention in patients undergoing cardiac surgeries.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.