Mohs Micrographic Surgery is a specialized, highly precise technique for removing common skin cancers, such as basal cell carcinoma and squamous cell carcinoma, with a very high cure rate. Developed in the 1930s, the procedure offers the advantage of microscopically controlled tissue removal, ensuring all cancer cells are excised while sparing the maximum amount of healthy tissue. Because this method allows for complete margin control, it has become the gold standard treatment for many skin malignancies, especially those located in cosmetically or functionally sensitive areas. Understanding the standard anesthesia protocol is helpful for anyone preparing for this surgery.
The Standard Anesthesia Protocol
Mohs surgery is routinely performed using local anesthesia, meaning the patient remains fully awake and alert throughout the entire process. This procedure is typically conducted in an outpatient setting, often within the dermatologist’s office. The most common local anesthetic agents used are lidocaine, sometimes combined with bupivacaine, which are injected around the tumor site to numb the area. Lidocaine works by blocking pain signals in the nerve fibers, usually taking effect within minutes and providing numbness for one to two hours.
The surgeon administers the local anesthetic via a fine needle, using local infiltration or a nerve block to create numbness around the surgical site. The numbing injection is often cited as the most uncomfortable part of the procedure, but the surgical site is completely comfortable afterward. Using local anesthesia avoids the potential health risks and lengthy recovery period associated with general anesthesia. Additional anesthetic can be administered if the initial dose wears off or if wound closure requires more time.
Why Local Anesthesia is Essential for Mohs
The unique, multi-stage nature of Mohs surgery makes the patient’s awake status a practical requirement for the procedure to be performed efficiently. After the initial layer of tissue is removed, the patient is temporarily bandaged and waits while the surgeon examines the tissue under a microscope in an adjacent laboratory. This microscopic examination of 100% of the tissue margins, known as the Mohs cycle, often takes a significant amount of time, often an hour or more per stage.
The patient’s cooperation is necessary during this waiting period, as they may need to use the restroom, have a snack, or simply remain still while awaiting the results. If cancer cells are detected, the patient returns to the procedure room for another layer of tissue removal from the precise location where cancer remains. This cycle repeats until all tissue samples are cancer-free. The ability of the patient to reposition and communicate throughout this process is important, making general anesthesia impractical and significantly increasing cost.
Patient Comfort and Anxiety Management
Since the patient is awake, managing anxiety and ensuring comfort is a significant part of the Mohs experience. Anxiety can sometimes worsen the perception of pain. Non-pharmacological methods, such as playing music or providing patient education, are often used as simple distractions to alleviate nervousness.
For patients with profound anxiety, oral anti-anxiety medication or light intravenous (IV) sedation may be offered alongside the local anesthetic. This light sedation, often called Monitored Anesthesia Care (MAC), makes the patient drowsy and relaxed but avoids inducing deep sleep or unconsciousness. The goal is to maximize comfort and relaxation without compromising the patient’s ability to respond to the surgical team if needed.
When Heavy Sedation or General Anesthesia May Be Used
While local anesthesia is the standard for the Mohs portion of the surgery, deeper sedation or general anesthesia (GA) may be necessary in rare exceptions. These exceptions typically involve patients who cannot cooperate during the procedure.
Exceptions Requiring General Anesthesia
- Extreme needle phobia.
- Severe claustrophobia.
- Certain underlying mental health conditions.
- Pediatric patients, to ensure they remain still and comfortable during the meticulous procedure.
In some instances, the tumor is large or complex, requiring extensive reconstruction after the cancer is removed, such as a complicated skin graft or flap. Although the Mohs procedure is done under local anesthetic, the reconstructive phase may be performed under general anesthesia by a plastic surgeon in a hospital setting. The vast majority of Mohs cases, however, are completed entirely under local anesthesia in the outpatient clinic, with GA only used in a small fraction of cases.