European Journal of Cardiovascular Medicine

Inadequate postoperative pain control after cardiac surgery is linked with higher rates of complications and slower recovery. Multimodal analgesia that combines intravenous opioids with nonsteroidal anti-inflammatory drugs is commonly used, but effective relief often requires higher opioid doses, which in turn raises the risk of respiratory depression, nausea, vomiting, and pruritus.

Thoracic epidural analgesia has been used for pain control after cardiac surgery, yet it can cause hypotension and carries a risk of epidural hematoma in the setting of intraoperative or postoperative heparinization [3]. This has driven interest in regional techniques that can deliver targeted analgesia while minimizing risk. Ultrasound guidance has expanded the use of these blocks by offering real-time visualization of nerves, needle trajectory, and local anesthetic spread, which helps reduce complications such as inadvertent intravascular injection [5,6].

The paravertebral block (PVB) is a well-established method for interrupting intercostal nociceptive pathways and provides reliable unilateral thoracic analgesia [4]. However, the anatomy of the paravertebral space makes pleural puncture and pneumothorax possible, and other serious complications have been reported [5,6]. With the evolution of regional anesthesia, newer fascial plane techniques have gained attention for their technical simplicity and safety profile. Among these, the serratus anterior plane block (SAPB) and the erector spinae plane block (ESPB) target branches of the intercostal nerves and may reduce pain intensity and opioid consumption during and after surgery [7–10].

Multiple studies have compared PVB with either ESPB or SAPB individually, but direct head-to-head comparisons of both fascial plane blocks against PVB in adult cardiac surgery remain limited. To address this gap, we designed a randomized, prospective, single-blinded study to compare the effectiveness of ultrasound-guided SAPB and ESPB with PVB for postoperative surgical pain in adult cardiac surgeries, with a focus on analgesic efficacy and opioid-related outcomes.

After approval from institutional ethical committee, this randomized, prospective, single-blinded trial was conducted in the Department of Anaesthesia, Sri Aurobindo Medical College and PG Institute, Indore (M.P). in adult patients scheduled for cardiac surgery under general anaesthesia. The goal was to compare the analgesic effectiveness and safety of ultrasound-guided serratus anterior plane block (SAPB) and erector spinae plane block (ESPB) against paravertebral block (PVB). Written informed consent was obtained from all patients after explaining the study protocol and confidentiality was maintained.

Inclusion and Exclusion Criteria: Eligible patients were 18 to 85 years of age with cardiac disease undergoing surgery. We excluded patients who could not provide informed consent, had contraindications to regional Anaesthesia such as allergy to local anesthetics or dermatologic conditions at the block site, had a body mass index greater than 40, or had disorders of consciousness or difficulty with verbal communication.

Sample size and power

Sample size calculations were based on analysis of variance with alpha 0.05 and power 80 to 90 percent. With a conservative population standard deviation of 4 to 5, the required group size was about 20 to 24 patients. For repeated pain measurements in the first 48 hours with eight assessments, the required group size was about 20 patients. The final allocation of 24, 24, and 30 patients provided an estimated power of 97 percent for the planned main comparisons.

Screening and allocation

Eighty-six patients were screened. Eight were excluded, five declined consent, and three were disqualified after the preliminary ultrasound scan because PVB could not be performed. Seventy-eight patients were randomized to three groups: SAPB (n = 24), ESPB (n = 24), and PVB (n = 30). A computer-generated randomization table created in Microsoft Excel assigned patients to groups. The study used a single-blind design in which participants were unaware of their allocation.

Figure 1. Consort diagram

Block techniques

All blocks were performed preoperatively under ultrasound guidance using a high-frequency linear probe by an experienced anesthesiologist. Skin at the puncture site was infiltrated with 1 mL of 1 percent lidocaine. A 23G spinal needle was used for block placement. For every block, the injectate was 20 mL total, prepared as 10 mL of 2 percent lidocaine with adrenaline plus 10 mL of 0.5 percent bupivacaine.

• Serratus anterior plane block (SAPB): The probe was placed on the mid-axillary line at the level of the fourth rib to identify the serratus anterior and latissimus dorsi muscles. The needle was advanced in-plane. After contacting the rib beneath the serratus anterior, local anesthetic was deposited between the serratus fascia and the rib periosteum, consistent with a deep SAPB.
• Paravertebral block (PVB): The probe was placed between the fourth and fifth ribs to visualize the paravertebral space. The needle was advanced in-plane beneath the internal intercostal membrane. After negative aspiration, local anesthetic was injected with visible pleural displacement away from the chest wall.
• Erector spinae plane block (ESPB): The probe was placed in the paravertebral region to visualize the transverse process and the fifth rib. The needle was introduced out-of-plane until it contacted the periosteum of the transverse process. The probe was then rotated 90 degrees to maintain needle visualization, and local anesthetic was injected between the erector spinae fascia and the transverse process periosteum.

Illustrative ultrasound images for ESPB and SAPB techniques were captured for documentation, along with a schematic for thoracic PVB.

Figure 2. A, Erector spine block technique; B, after injection and withdrawal of the needle; C, with a needle in place.

Figure 3. Serratus anterior plane block technique.

Figure 4. Thoracic Paravertebral Block

Anaesthesia and perioperative management

Anaesthesia and perioperative management

After block placement in the operating room, anaesthesia followed a standardized protocol. Patients received midazolam 1 mg and fentanyl 0.2 mg for co-induction, pre-oxygenation with 100 percent oxygen, and intravenous induction with propofol 2 mg per kg. Succinylcholine 2 mg per kg, dosed by ideal body weight, was used to facilitate tracheal intubation. Anaesthesia was maintained with sevoflurane. An additional 0.1 mg fentanyl was administered at sternotomy. At the end of surgery, patients were transferred to the cardiac intensive care unit and monitored until fully conscious.

Outcomes

Efficacy outcomes

1. Total intraoperative fentanyl consumption.
2. Total postoperative buprenorphine administered as part of standard analgesia.
3. Pain intensity at rest and during coughing using an 11-point numerical rating scale, where 0 is no pain and 10 is worst pain. Pain was recorded in the first postoperative hour and then at 6-hour intervals for 48 hours, for a total of eight time points.

Safety outcomes

Block-related adverse events were recorded, including vascular puncture, local anesthetic systemic toxicity, pleural puncture and pneumothorax, hypotension, hematoma, infection, and failed or incomplete block.

Statistical analysis

Analyses were performed using SPSS version 22.0 and Microsoft Excel 10.0. Continuous variables are summarized as mean, standard deviation, median, minimum and maximum, and 95 percent confidence intervals. Categorical variables are presented as counts and percentages. Group comparisons for continuous outcomes such as fentanyl and buprenorphine doses used one-way analysis of variance, with non-parametric tests if normality assumptions were not met. Pain scores over time were analyzed with a repeated-measures approach that included factors for group and time, with appropriate corrections for multiple comparisons. Categorical outcomes were compared with the chi-square test or Fisher exact test. Two-sided P values less than 0.05 were considered statistically significant.

Seventy-eight adults were analyzed and allocated to three groups: SAPB (n=24), PVB (n=30), and ESPB (n=24).

Baseline characteristics: Age, body weight, and BMI were comparable across groups. Mean ages were 66.5, 66.5, and 62.5 years for SAPB, PVB, and ESPB (p=0.4577). Mean body weights were 74.1, 69.3, and 73.9 kg (p=0.2898). Mean BMIs were 28.9, 27.4, and 27.8 kg/m² (p=0.7089). Mean heights were 159.5, 158.7, and 163.9 cm, with a significant pairwise difference showing PVB patients were shorter than ESPB patients (p=0.0291). ASA status did not differ (ASA I: 4.2%, 3.4%, 8.3%; ASA II: 95.8%, 96.6%, 91.7% for SAPB, PVB, ESPB; p=0.7008). Preoperative pain was minimal and similar (mean NRS 0.48, 0.41, 0.29; p=0.7710). [Table 1]

Table 1. Baseline characteristics by group

*Pairwise: PVB shorter than ESPB for height (p=0.0291).

Surgical procedures: A total of 78 procedures were included. Lung decortication was most frequent (n = 47). The remainder comprised coronary artery bypass grafting (n = 12), mitral valve replacement (n = 10), aortic valve replacement (n = 3), ventricular septal defect repair (n = 2), atrial septal defect repair (n = 1), and double valve replacement (n = 1). The distribution of procedures did not differ by block group (global p = 0.8031). [Table 2]

Table 2. Comparative characteristics of the studied groups (SAPB—serratus anterior plane block; PVB—paravertebral block; ESPB—erector spinae plane block) regarding the type of procedure

*CABG-Coronary artery bypass graft, MVR-Mitral Valve Replacement, DVR-Double Valve Replacement, AVR-Aortic Valve Replacement, ASD- Atrial Septal Defect, VSD-Ventricular Septal Defect

Intraoperative opioid use: Intraoperative fentanyl use was comparable across groups (SAPB 0.12 mg, PVB 0.12 mg, ESPB 0.11 mg; p = 0.4246). Postoperatively, morphine requirements differed significantly: ESPB patients required more morphine (9.4 mg) than SAPB (5.4 mg; p = 0.0074) and PVB (4.4 mg; p = 0.0005), as summarized in Table 3.

Table 3. Intraoperative fentanyl and postoperative morphine consumption by group

¹ ANOVA/Kruskal–Wallis global test; ²Post-hoc comparisons: ^aESPB > SAPB (p = 0.0074); ^bESPB > PVB (p = 0.0005).

Pain during coughing (NRS): Cough-evoked pain at 1 hour in the recovery room was the same across groups (mean NRS 4.8 for all; p=0.8809). On day 0, differences emerged at 4:00 PM and 8:00 PM, with higher pain in the ESPB group compared with SAPB and PVB (global p=0.0010 for both time points; ESPB vs SAPB p=0.0080; ESPB vs PVB p=0.0045). On day 1, ESPB remained higher than PVB at 8:00 AM (global p=0.0128; pairwise p=0.0478) and at 12:00 PM (global p=0.0097; pairwise p=0.0253). By 4:00 PM on day 1, between-group differences were no longer significant (p>0.05). Measurements scheduled for 12:00 AM and 4:00 AM could not be tested due to small numbers.

Table 4. Pain intensity during coughing (NRS) by time point and block

Notes: ¹ Global comparison by ANOVA/Kruskal–Wallis.; ² Post-hoc tests: ^a SAPB vs ESPB; ^b PVB vs ESPB

Thoracic regional Anaesthesia is central to pain control after adult cardiac surgery, where effective cough, chest physiotherapy, and early mobilization depend on adequate analgesia. Paravertebral block (PVB) is a long-standing benchmark but involves needle passage near the pleura. Newer fascial plane techniques such as the serratus anterior plane block (SAPB) and erector spinae plane block (ESPB) offer simpler sono-anatomy and a potentially safer profile.

The rationale for this study was to clarify whether SAPB or ESPB can match PVB for perioperative analgesia in a cardiac population managed under a standardized anesthetic pathway. Prior reports have been heterogeneous in procedure types, operator expertise, and endpoints, which makes it difficult to translate their conclusions to cardiac surgery.

Our findings show balanced groups at baseline and similar surgical case mix, supporting internal validity. The groups were well matched at baseline, which supports a fair comparison of block performance. Ages, weights, BMIs, ASA class, and preoperative pain were similar, and the surgical mix did not differ across groups. These balances reduce the chance that case complexity or patient factors explain the observed analgesic differences.

The results showed that Baseline characteristics and procedure types were well balanced. Intraoperative fentanyl use did not differ. The ESPB group required more postoperative morphine and reported higher cough-evoked pain at several early time points compared with SAPB and PVB, with differences resolving by late day 1.

In this trial, SAPB and ESPB provided intraoperative analgesia comparable to PVB. Intraoperative fentanyl requirements did not differ between groups, aligning with findings reported by Gabriel [11]. The similarity likely reflects that sternotomy-related nociception during the index period is largely covered by balanced Anaesthesia and intraoperative dosing rather than by block choice alone, provided the block is technically adequate.

Postoperatively, SAPB achieved analgesia comparable to PVB in our cohort. Pain scores and opioid consumption were similar between these two groups. Gabriel et al. reported higher pain and opioid use with SAPB than with PVB [11], and Gupta et al. found a shorter duration of analgesia and greater rescue requirements after SAPB than after PVB, attributing this to the broader neural spread achievable with PVB [12]. Differences from our results may relate to case mix and execution. In our study, all blocks were performed by a single experienced anesthesiologist in a cardiac surgical population with standardized anesthetic and postoperative pathways. Prior reports included operator heterogeneity and noncardiac procedures, which may influence dermatomal coverage and clinical endpoints.

ESPB was inferior to PVB for postoperative pain control. Patients in the ESPB group required more morphine and reported higher cough-evoked pain at several early time points. This pattern is consistent with studies showing higher opioid use and/or higher pain scores with ESPB compared with PVB [16–18]. The advantage of PVB likely reflects its more reliable spread within the paravertebral space to ventral rami and sympathetic fibers, which broadens analgesic coverage [19].

In respect to postoperative analgesia, ESPB was also less effective than SAPB. Despite greater postoperative opioid use, ESPB patients reported higher pain. Literature comparing these fascial blocks is mixed. Elsabeeny et al. found no difference between ESPB and SAPB in breast surgery, although their control regimen relied on morphine rather than PVB and rescue ketorolac rather than PCA-based opioid metrics, which limits comparability to our endpoints [20]. Mekhaeil et al. reported superior analgesia with SAPB over ESPB in coronary artery bypass grafting, including lower pain scores, less perioperative analgesic use, and longer analgesia duration. [21] Ahuja et al. did not detect a significant difference, but only reported the proportion needing rescue analgesia rather than continuous opioid consumption, which may reduce sensitivity to between-group differences.[22] Taken together with our findings, SAPB appears at least noninferior to ESPB in adult cardiac surgery, and may be preferable when broad lateral thoracic coverage is needed.

Across comparisons, PVB remained a robust benchmark, while SAPB delivered similar postoperative outcomes in this setting without the pleural puncture risk that can accompany paravertebral access. ESPB was simpler to perform but yielded higher pain scores and opioid needs early after surgery. Choice of block should consider dermatomal targets, anticipated coughing and chest physiotherapy, operator experience, and the patient’s risk profile.

Several limitations merit consideration. Only the first assessment occurred exactly one hour after surgery, while subsequent assessments were at fixed clock times, introducing timing variability. Randomization was not stratified by surgeon or anticipated procedure duration, factors that can influence analgesic demand. Sensory mapping of dermatomal spread was not performed, so mechanistic inferences about distribution remain indirect. The study was single-center with single-operator block performance, which enhances consistency but may limit generalizability, and outcomes focused on the early postoperative window without longer-term functional or pulmonary endpoints.

In summary, within a standardized cardiac Anaesthesia pathway, SAPB provided postoperative analgesia comparable to PVB, whereas ESPB was less effective than both. Considered alongside prior work, these results support PVB and SAPB as preferred options to minimize early postoperative pain and opioid exposure in adult cardiac surgery, with block selection tailored to dermatomal targets, operator expertise, and patient safety considerations.

In adults undergoing cardiac surgery within a standardized anesthetic pathway, all three techniques—SAPB, ESPB, and PVB—provided comparable intraoperative analgesia. Postoperatively, SAPB achieved pain control and opioid sparing equivalent to PVB, whereas ESPB was associated with higher pain scores at several early time points and greater morphine consumption than both SAPB and PVB. These findings support SAPB and PVB as the preferred options for early postoperative analgesia in this setting, with block selection guided by dermatomal targets, operator expertise, and patient risk. Multicenter trials with sensory mapping and longer-term clinical outcomes are warranted to refine technique choice and confirm generalizability.

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