Selective Intraoperative Administration of Local Anesthesia in Breast Reconstruction

One in eight women will develop breast cancer in her lifetime, and many of these women undergo mastectomy followed by breast reconstruction by insertion of a tissue expander below the pectoralis major muscle. Women undergoing breast reconstruction have been shown to have a significantly higher level of acute postoperative pain and postoperative narcotic requirement compared to women who undergo mastectomy alone without reconstruction. In addition to the inherently worthwhile end of providing patient comfort in the immediate postoperative period, decreased narcotic use carries with it the potential benefit of decreasing the incidence of other adverse effects such as nausea, vomiting, allergic reaction, and respiratory depression.

Importantly, the intensity of pain in the immediate postoperative period has been implicated as an important factor predisposing patients to the development of chronic postoperative pain. Chronic pain following mastectomy is a significant and disabling problem, affecting up to 49% of patients in some series. Though breast reconstruction has been shown not to be an independent predictor of the development of chronic breast pain, improved control of acute pain in the immediate postoperative period carries significant promise in decreasing the incidence of this disabling condition for all breast cancer survivors treated with mastectomy. In addition, improving management of acute postoperative pain can shorten hospital stay, expedite return to daily normal activities and increase patient satisfaction.

A variety of other adjuncts for pain control have been attempted in studies of variable methodological rigor, including injection of botulinum toxin into the pectoralis muscle, indwelling pain catheters, paravertebral blocks under ultrasound guidance, or simple irrigation of the general area of dissection during breast surgery with a solution containing local anesthestic. While each of these adjuncts has demonstrated some success, none has been widely adopted. Problems with these methods include cost, risk of adverse events, as well as anatomically incomplete or non-selective application.

During mastectomy all breast tissue is removed, leaving the patient with denervated skin flaps. For breast reconstruction, a tissue expander is placed in a subpectoral pocket dissected between the pectoralis major and minor muscles. At the end of the procedure the pectoralis major muscle is placed under variable degree of tension depending on the amount of fluid placed inside the expander. This muscle stretch believed to be at least partially responsible for postoperative pain. In addition cut nerve endings in the superficial fascia likely contribute as well. The anatomy of nerves supplying the breast and involved muscles are well-described in rigorous cadaver studies.

In this study we hypothesize that performing a block of the intercostal nerves responsible for innervating the breast tissue and skin and the pectoral nerves innervating the pectoralis major muscle should optimize immediate postoperative pain control in this patient population. Of adjuncts described in the literature, paravertebral blocks are the most anatomically targeted, but drawbacks include the need for a separate procedure preoperatively while the patient is awake by an anesthesiologist with facility performing these blocks as well as the risk of pneumothorax. Advantages of our proposed method include lack of pain as the patient is asleep, easy and speed of application, a decreased risk of pneumothorax as the injections are under direct visualization, as well as a decrease in cost and improved efficiency as the only a single provider (i.e. the operative surgeon) is required. Precedent for our technique has been described in the context of breast augmentation and breast lift, with a favorable safety profile and providing adequate analgesia to perform these procedures without the use of a general anesthetic.