Mastectomy pain blocks: A comparison of preoperative versus intraoperative pectoralis nerve blocks

Authors: Bhakta P, Ayad S, Hossain MS, Black N, Pratt D, Bernard S, Hofstra RL, Araujo-Duran J, Tu C, Valente SA

Affiliation: Cleveland Clinic

Journal: The American Journal of Surgery, 2026

PMID: 41880699

Key takeaways

• Preoperative and intraoperative pectoralis nerve blocks provided similar early opioid-sparing analgesia after mastectomy.

• Block timing was not independently associated with PACU opioid use or morphine milligram equivalents (MME).

• More than one-third of patients required no opioids in the post-anesthesia care unit (PACU).

• Preoperative acetaminophen was the most consistent modifiable factor associated with lower opioid use.

• Intraoperative blocks may improve workflow without compromising early analgesic efficacy.

Background

Pectoralis nerve blocks (PNBs) are increasingly used in multimodal analgesia for mastectomy because they reduce opioid exposure and, compared with paravertebral blocks, PNBs offer simpler technique, shorter performance time, and lower complication rates.. However, the optimal timing of block placement remains unclear: anesthesia can perform ultrasound-guided blocks preoperatively, or surgeons can perform direct-visualization blocks intraoperatively after mastectomy.

This study asks a practical perioperative question: does timing matter, or can institutions choose the approach that best fits workflow and available expertise?

Objective

To compare postoperative opioid requirements after preoperative versus intraoperative pectoralis nerve blocks in patients undergoing unilateral or bilateral mastectomy, with or without implant-based reconstruction.

Methods

• Design: Retrospective single-institution cohort study, Cleveland Clinic, 2021–2022; Level III.

• Population: 122 mastectomy patients receiving pectoralis nerve blocks: preoperative block (n = 69) or intraoperative block (n = 53).

• Procedures: Unilateral or bilateral mastectomy, with or without immediate implant-based reconstruction.

• Interventions:

  • Preoperative pectoralis nerve block: anesthesia-performed ultrasound-guided PECS I/II block in the preoperative holding area.

  • Intraoperative pectoralis nerve block: surgeon-performed PECS I/II and field block under direct visualization after mastectomy, before closure.

• Local anesthetic: All patients received 20 mL of 1.3% liposomal bupivacaine plus variable-dose bupivacaine hydrochloride chosen by the treating clinician based on weight and formulation; bilateral cases received added saline for volume.

• Outcomes: PACU opioid use, PACU MME, intraoperative MME, pain score at first PACU analgesic, antiemetic use, PACU time, admission/discharge, and block-related complications.

• Statistics: Group comparisons plus multivariable regression adjusting for age, BMI, laterality, reconstruction, nodal surgery, preoperative medications, local anesthetic use, and operative time; subgroup analyses by unilateral versus bilateral mastectomy.

Results

• Cohort: 69 preoperative blocks (57%) and 53 intraoperative blocks (43%); baseline demographics and cancer/prophylactic indications were similar.

• Safety: No block-related complications occurred in either group.

• Operative/workflow findings: Preoperative blocks took median 7 minutes; median time from block completion to incision was 59 minutes. Intraoperative blocks were consistently performed in less than 2 minutes.

• Opioid-free PACU recovery: 36.1% of all patients required no opioids in PACU.

• Unadjusted opioid use: More intraoperative-block patients received PACU opioids than preoperative-block patients (75.5% vs 55.1%; P = 0.033), but this difference did not persist after adjustment.

• Adjusted analysis: Block timing was not associated with PACU opioid use (PPNB OR 0.26; P = 0.13) or PACU MME (β −3.1 MME; P = 0.59).

• Acetaminophen signal: Omission of preoperative acetaminophen independently increased odds of PACU opioid use (OR 4.87; P = 0.010) and increased PACU MME (β +11 MME; P = 0.002).

• Subgroup analysis: No statistically significant opioid-use or MME differences by block timing in unilateral or bilateral mastectomy subgroups.

• PACU time: PACU stay was shorter with preoperative blocks (107 vs 165 minutes; P = 0.012), but discharge planning differed substantially between groups, limiting interpretation.

Conclusion

Pectoralis nerve blocks are safe and useful within multimodal mastectomy analgesia. In this cohort, preoperative versus intraoperative timing did not independently affect early postoperative opioid requirements, suggesting that block timing can reasonably be guided by institutional workflow, provider expertise, and patient experience.

Strengths

• Directly compares a common anesthesia-performed preoperative strategy with a practical surgeon-performed intraoperative strategy.

• Uses multivariable adjustment and subgroup analyses to address important procedural differences.

• No block-related complications were observed, supporting safety of both approaches in this cohort.

Limitations

• Retrospective design; block timing was determined by surgeon preference, creating confounding by practice pattern.

• Small cohort, especially after subgrouping by laterality and reconstruction type.

• No standardized enhanced recovery after surgery protocol; acetaminophen, scopolamine, dexamethasone, and opioid administration were provider-dependent.

• Outcomes were limited mainly to PACU analgesia; post-discharge opioid consumption, rebound pain, satisfaction, and chronic pain were not assessed.

• Reconstruction type and laterality were imbalanced between groups, reflecting surgeon practice rather than random allocation.

Clinical relevance

The practical takeaway is that pectoralis nerve blocks are effective components of multimodal analgesia after mastectomy, but the timing of block placement can be adapted to local workflow and provider expertise. Although preoperative blocks are theoretically appealing because they interrupt nociceptive signaling before incision, this study did not show a clear opioid-sparing advantage over intraoperative blocks placed near closure.

The more actionable message is that block timing matters less than the consistency of the overall pain pathway. Preoperative acetaminophen was the most reliable modifiable factor associated with lower opioid use, reinforcing that regional anesthesia works best when embedded in a standardized enhanced recovery protocol rather than used as an isolated intervention.