Erector spinae plane block versus thoracic paravertebral block for pain management after total bilateral mastectomies

Abstract

This prospectively designed, clinical quality improvement project compared pain scores and opioid consumption between ultrasound-guided, erector spinae plane blocks (ESPB) and thoracic paravertebral blocks (PVB) in patients undergoing total bilateral mastectomies without reconstruction. Twenty-five patients were included in an enhanced recovery pathway and received an ESPB on one side and a PVB on the contralateral side. Numeric rating scores at rest and with movement for each side were recorded in the recovery room at 2, 6, 12, 24, and 48 hours and on days 3 to 7. There were no significant differences in the resting or movement-evoked pain scores between sides receiving ESPB or PVB at any time point up to day 7 after surgery. Both ESPB and PVB confer equal analgesic effects in patients undergoing mastectomies. ESPB provides an alternative to PVB in reducing postoperative pain in patients undergoing mastectomy as part of an enhanced recovery pathway.

Breast surgery is associated with moderate to severe postoperative pain, which can adversely influence postoperative recovery and return to activities of daily living.^1,2 Regional analgesic techniques are an important component of a multimodal analgesic strategy,^2,3 with the aim of reducing postoperative pain as well as reducing opioid requirements and opioid-related adverse events.⁴ Because thoracic paravertebral blocks (PVB) provide excellent pain relief,² they are often included in enhanced recovery pathways.^5–7 Newer fascial plane blocks such as erector spinae plane blocks (ESPB) could provide an alternative to PVB.^8,9 In this prospective quality improvement project, we compared the analgesic efficacy of PVB and ESPB when used as part of an opioid-sparing multimodal analgesic regimen in patients undergoing total bilateral mastectomies without reconstruction.

METHODS

A quality improvement project was designed to assess the analgesic efficacy of PVB and ESPB in 25 patients undergoing elective total bilateral mastectomies without reconstruction. All included patients had breast cancer on a unilateral side, and contralateral mastectomy was performed for risk reduction. A waiver for this project was obtained from the institutional review board of the University of Texas Southwestern Medical Center, Dallas, Texas.

This surgical cohort spanned from November 9, 2018 to November 13, 2019. Patients included in an enhanced recovery pathway received a PVB on one side and an ESPB on the contralateral side, if there were no contraindications.¹⁰ Side selection was left to the discretion of the faculty anesthesiologist performing the blocks. All patients were offered regional analgesia blocks as part of the standard enhanced recovery pathway; however, those on chronic opioid therapy and with a history of psychiatric illness were excluded from analysis.

With the patient in sitting position and following aseptic preparation of both injection sites, the ultrasound transducer was placed in a parasagittal orientation approximately 2 to 3 cm lateral to the spinous processes. Using external landmarks and real-time ultrasound imaging, the T4 transverse process was identified. For the ESPB, a 21-gauge 100 mm insulated needle (Pajunk, Germany) was introduced cephalad to caudad in plane to the ultrasound beam through the paraspinous muscles until reaching the T4 transverse process. With the needle tip visualized under the erector spinae muscles and on top of the T4 transverse process, 20 mL of the local anesthetic ropivacaine 0.5% was slowly and incrementally injected with frequent aspiration, raising the erector spinae muscle fascia off the transverse process. Spread of local anesthetic in the erector spinae plane was observed in real time via ultrasound guidance.

For the PVB, the ultrasound transducer was moved to the contralateral side, still in a parasagittal orientation, and the contralateral transverse process of T4 was identified. A 21-gauge 100 mm insulated needle (Pajunk, Germany) was introduced cephalad to caudad in plane to the ultrasound beam through the paraspinous muscles until just reaching the paravertebral space between the costotransverse ligament and the parietal pleura. With the needle tip visualized, 20 mL of the local anesthetic ropivacaine 0.5% was incrementally injected with frequent aspiration. Spread of local anesthetic in the paravertebral space was observed in real time via ultrasound guidance.

In addition to receiving PVB and ESPB, the analgesic regimen included acetaminophen 1.5 g and gabapentin 600 mg orally approximately 2 hours preoperatively. As a part of the enhanced recovery pathway, a standardized general anesthetic technique with an opioid-sparing approach was used for all patients. All patients received antiemetic prophylaxis with dexamethasone 8 mg and ondansetron 4 mg intravenously. For patients at high risk of postoperative nausea and vomiting, a scopolamine patch was placed. Ketorolac 15 to 30 mg and hydromorphone 0.2 to 0.4 mg were administered intravenously approximately 20 to 30 minutes prior to the end of the procedure.

In the recovery room, patients complaining of ≥4/10 pain via numeric rating scores (0 = no pain, 10 = worst pain) received boluses of hydromorphone 0.2 to 0.4 mg intravenously. The postoperative analgesic regimen included scheduled acetaminophen 1 g orally every 8 hours and meloxicam 15 mg orally once a day. Rescue analgesics included hydromorphone 0.2 to 0.5 mg intravenous boluses every 4 hours as needed for severe pain and oxycodone immediate release 10 mg orally every 8 hours as needed for moderate pain. Rescue antiemetics were administered for complaints of nausea and/or vomiting and included ondansetron intravenously or oral disintegrating tablet and/or promethazine 0.625 mg intravenously.

Data obtained from the electronic medical records by one of the two coauthors (MS, JR) not involved in the block placement included demographic information (i.e., age and body mass index), the duration of surgery and recovery room stay, and the intraoperative and postoperative opioid requirements for up to 7 postoperative days. Opioid doses were then converted to morphine equivalents,¹¹ and cumulative opioid use was calculated in the operating room, post-anesthesia care unit, and then at 24-hour intervals.

Pain scores were assessed at rest and on deep breathing for each breast separately preoperatively (baseline), in the recovery room, and at 2, 6, 12, 24, and 48 hours as well as on days 3, 4, 5, 6, and 7 postoperatively by the same coinvestigators. Sensation changes to pinprick on each side of the chest were recorded in the recovery room at 2, 6, and 12 hours. Patients and personnel evaluating pain were not informed to the type of block performed on each side. After discharge, the coinvestigators called the patients at home to obtain the aforementioned variables.

The primary outcome measure was site-specific pain scores. The sample size was calculated using PASS software (PASS 2019, NCSS, LLC, Kaysville, UT) retrospectively. With 25 subjects enrolled, the study was powered to detect a medium effect size (Cohen’s d = 0.6) in pain score with 80% power and a two-sided significance level of 0.05. Assuming a standard deviation of 2 points in pain scores, a medium effect size (d = 0.6) translates to a 1.2-point mean difference in pain scores. A difference in pain scores of >1/10 was considered clinically relevant.¹² Assumptions of normality for continuous variables were assessed using normal probability plots. Resting and movement pain scores between the two blocking methods were compared using Wilcoxon signed rank test followed by Bonferroni corrections for multiple comparisons to adjust the overall type I error rate. Statistical significance was assessed at P < 0.05. All analyses were done using SAS 9.4 (SAS Inc., Cary, NC).

RESULTS

Table 1 shows the demographic and clinical data of 25 patients undergoing bilateral mastectomies who received both PVB and ESPB for postoperative pain control. Of note, PVB was performed on the cancer side in 14 cases, while ESPB was performed on the cancer side in 11 cases. After adjusting for multiple comparisons, there were no significant differences in the median resting or movement-evoked pain scores between PVB and ESPB at any postoperative time point (all P > 0.077) (Figures 1 and 2).

Table 1.

Demographic and clinical characteristics of the study cohort

Variable	Mean ± SD
Age (years)	48.7 ± 10.1
Height (cm)	162.8 ± 6.1
Weight (kg)	72.2 ± 19.4
Body mass index (kg/m2)	28.4 ± 5.1
Procedure duration (min)	264.8 ± 84.2
PACU length of stay (min)	57.4 ± 15.8

PACU indicates post-anesthesia care unit; SD, standard deviation.

Figure 1.

Postoperative pain scores at rest at various time points after surgery. Data are expressed as mean ± standard error. No statistically significant differences between groups were noted after Bonferroni adjustments for multiple comparisons. ESPB indicates erector spinae plane block; NRS, numeric rating score; PACU, post-anesthesia care unit; PVB, paravertebral block.

Figure 2.

Postoperative pain scores with movement at various time points after surgery. Data are expressed as mean ± standard error. No statistically significant differences between groups were noted after Bonferroni adjustments for multiple comparisons. ESPB indicates erector spinae plane block; NRS, numeric rating score; PACU, post-anesthesia care unit; PVB, paravertebral block.

Opioid usage over the study period is presented in Table 2. Sensory changes, described as decreased sensation in one side relative to the other, are shown in Figure 3. The number of patients reporting decreased sensation was significantly greater (P < 0.05) with PVB than with ESPB. There were no reported adverse events related to ESPB and PVB. The perioperative course of all patients was uneventful, and they were discharged home within 48 to 60 hours postoperatively.

Table 2.

Perioperative opioid consumption of the study cohort

Opioid	Time	Median (IQR)
Fentanyl (mcg)	Intraoperative	200 (100, 250)
IV hydromorphone (mg)	PACU	0.4 (0.0, 0.4)
	0–24 h	0.4 (0.0, 0.8)
	24–48 h	0.0 (0.0, 0.0)
	0–48 h	0.4 (0.0, 1.0)
IV morphine equivalents (mg)	0–24 h	15 (5, 20)
	24–48 h	20 (10, 22.5)
Oral morphine equivalents (mg)	Day 3	15 (7.5, 30)
	Day 4	15 (10, 30)
	Day 5	15 (10, 30)
	Day 6	15 (5, 30)
	Day 7	15 (0, 15)
	Total	115 (67.5, 170)

IQR indicates interquartile range; IV, intravenous; PACU, post-anesthesia care unit.

Figure 3.

Postoperative sensory changes at various time points after surgery. Data were summarized as frequency and percentages reflecting decreases in sensation of one side relative to the other. Decreased sensation on the side receiving the PVB was significant in the PACU only (*P < 0.05). ESPB indicates erector spinae plane block; PACU, post-anesthesia care unit; PVB, paravertebral block.

DISCUSSION

This quality improvement project demonstrated no significant differences in the resting or movement-evoked pain scores between PVB and ESPB at any time points up to day 7 after surgery. Our findings are in agreement with those of Gürkan et al¹³; however, these investigators did not use optimal postoperative pain management, which includes basic analgesics such as acetaminophen and nonsteroidal anti-inflammatory drugs.³ In addition, several types of breast surgical procedures with a variable degree of postoperative pain were combined.¹³ Furthermore, the duration of postoperative follow-up was only 24 hours.

Clinical quality improvement initiatives are a better way to evaluate perioperative outcomes in real-world patient care than randomized controlled trials.¹⁴ The use of evidence-based clinical pathways allowed uniformity in patient care throughout the perioperative course, including after discharge from the hospital, which improves confidence in observed results.¹⁵ Also, we used a procedure-specific, opioid-sparing pain management strategy including acetaminophen and nonsteroidal anti-inflammatory drugs,¹⁶ which contrasts with most of the studies evaluating analgesic techniques. In addition, unlike most pain studies, we followed patients for a prolonged period (i.e., 7 days), including after discharge home. Another strength of this study is that the patients acted as their own controls, directly comparing one side to the other, minimizing patient-related factors (e.g. anxiety, depression, catastrophizing-coping, and neuropathic pain related to neoadjuvant therapy) that might affect perioperative pain by influencing a patient’s tolerance to pain. Also, unlike typical pain studies in which patients rate overall pain, this study assessed pain specifically at the surgical site, which is of utmost relevance when comparing regional analgesic techniques.

One of the limitations of this study is that it was not a randomized, placebo-controlled trial. However, as discussed above, clinical quality improvement initiatives provide significant benefits. Another limitation of this study is our inability to evaluate the differences in opioid requirements between the two blocks. Opioid use is a commonly used outcome measure to compare analgesic techniques based on the assumption that patients titrate opioid use for the sole purpose of optimizing analgesia. Thus, differences in opioid use, particularly differences in opioid-related adverse events, may be an important comparator for analgesic studies. However, the use of a multimodal analgesia regimen with an emphasis on an opioid-sparing strategy as well as patient education regarding the need for limiting postoperative opioid intake reduces overall opioid use.^3,4 Thus, with this approach, opioid-related adverse events may not be influenced.^3,4 Another limitation of this study is that the sample size was inadequate to compare the differences in adverse effects between PVB and ESPB. However, the choice of regional analgesic technique depends on multiple factors including potential adverse effects, particularly with the use of thromboprophylaxis, as well as the ease of performing such procedures. Our analysis shows that because the analgesic efficacy of ESPB is similar to PVB, it is a viable alternative for mastectomy surgery, and anesthesiologists could select the technique that best suits their skill set and the needs of the patient.

In summary, we found no significant differences in resting pain scores or movement-evoked pain scores between PVB and ESPB in patients undergoing bilateral mastectomies. Future randomized controlled trials directly comparing ESPB and PVB in patients undergoing breast surgery would help to confirm the findings of our investigation as well as help elucidate differences in opioid consumption. It is critical that these future studies include nonopioid analgesics (i.e., acetaminophen and nonsteroidal anti-inflammatory drugs) as a component of overall pain management strategies.¹⁶ Furthermore, adequately powered trials are necessary to evaluate long-term pain-related outcomes (e.g. persistent pain and persistent opioid use).

DISCLOSURE

GPJ, JCA, and IG have received honoraria from Pacira Pharmaceuticals. GPJ has received honoraria from Baxter Pharmaceuticals. The other authors have nothing to disclose.