The ESP protocol, or erector spinae plane block, is a regional anesthesia technique used to manage pain during and after surgery. A numbing medication is injected into the space beneath the erector spinae muscles, the long muscles that run along your spine, where it spreads to block the nerves that carry pain signals. First described for chronic pain, it has since become a widely used option for surgeries ranging from the shoulder down to the hip.
How the Block Works
The erector spinae muscles sit in layers along the back of your spine. Beneath them, a thin fascial plane (essentially a sheet of connective tissue) separates the muscle from the bony transverse processes that jut out from each vertebra. When a numbing agent is injected into this plane, it spreads along the tissue and reaches the spinal nerve branches that transmit pain from the chest wall, abdomen, and back.
The block consistently numbs the dorsal rami, the nerve branches that supply the muscles and skin of your back. In most cases, the medication also reaches the ventral rami, which carry sensation from the chest and abdomen, though this spread is more variable from patient to patient. Occasionally, some of the medication tracks toward the epidural space around the spinal cord, but this is less common and not the primary way the block works.
What the Procedure Looks Like
The block is performed using real-time ultrasound guidance, which lets the clinician see the needle, the muscles, and the bony landmarks on a screen. You’ll be positioned sitting up, lying on your side, or face down. The ultrasound probe is placed lengthwise along the spine, roughly 3 centimeters from the midline, to visualize the transverse process at the target vertebral level.
A needle is advanced toward the tip of the transverse process until it makes contact with bone. To confirm the needle is in the right spot, a small amount of saline is injected first. If it’s placed correctly, the fluid visibly lifts the erector spinae muscle off the transverse process on the ultrasound screen. Once confirmed, the full dose of local anesthetic is injected in small increments, with pauses between each to check for any accidental entry into a blood vessel.
Surgeries That Use the ESP Block
The level of the spine where the block is placed determines which area of the body it covers. Injecting 20 milliliters of local anesthetic at a single level can numb a wide band of the torso, with studies showing coverage from the second thoracic vertebra down to the tenth. This flexibility is a major reason the block has been adopted across so many surgical specialties.
For upper body procedures, the injection is typically placed between the second and fifth thoracic vertebrae. Surgeries in this category include:
- Shoulder arthroscopy
- Mastectomy (with or without reconstruction)
- Thoracotomy and video-assisted thoracic surgery
For abdominal and pelvic procedures, the injection moves lower, between the sixth and eleventh thoracic vertebrae. This covers laparoscopic and open gallbladder removal, hernia repair, hysterectomy, nephrectomy, and bladder surgery. For hip and knee operations or gynecological procedures, the block can be placed at lumbar levels. It has even been used at the fourth lumbar vertebra to treat nerve pain following hip surgery.
How It Compares to Epidural Analgesia
Thoracic epidural analgesia has long been considered a gold standard for post-surgical chest and abdominal pain, but it carries risks related to its proximity to the spinal cord and requires more technical skill to place. A randomized study of 50 cardiac surgery patients compared the two techniques head to head. Pain scores at rest and during coughing were statistically comparable for the first 12 hours after surgery. At 24, 36, and 48 hours, the epidural group had modestly better scores, but the ESP group’s average pain rating still remained at or below 4 out of 10, a level generally considered manageable. Time on the ventilator, breathing capacity measured by spirometry, and length of ICU stay were equivalent between the two groups.
The takeaway from this and similar comparisons is that the ESP block provides a meaningful alternative when an epidural is not feasible or carries too much risk for a given patient. It is simpler to perform and, because the injection site is far from the spinal cord and major blood vessels, it comes with a different safety profile.
Safety and Potential Complications
The ESP block is considered one of the safer regional anesthesia techniques available. A retrospective review of 342 consecutive lumbar spine cases found no sensory, motor, blood-related, or blood pressure complications associated with the block. The only major event was a single case of pneumothorax (a partially collapsed lung) in one patient, and even that was judged unlikely to be related to the block itself. No patients in that series experienced seizures or cardiovascular collapse from the anesthetic entering the bloodstream.
In broader mixed-surgery data, the rate of local anesthetic systemic toxicity (a reaction caused by the numbing drug entering the bloodstream) was about 1.6%, but none of those cases were severe. Other possible complications include infection at the injection site, accidental puncture of a blood vessel, and a block that simply doesn’t work as intended. The overall risk is low largely because the needle target, the transverse process, is a superficial bony landmark that sits well away from the lung lining, major arteries, and the spinal canal.
What Patients Can Expect
If you’re scheduled for a procedure that includes an ESP block, it will typically be placed either before your surgery begins (while you’re awake or lightly sedated) or after you’re under general anesthesia. The block itself takes only a few minutes. You may feel pressure when the needle contacts bone, but the ultrasound guidance makes the process quick and precise.
A single-shot block provides hours of pain relief, though the exact duration depends on the anesthetic concentration used and the surgical site. For longer-lasting coverage, a thin catheter can be threaded into the fascial plane so that numbing medication is delivered continuously over one or more days after surgery. This is common in cardiac, thoracic, and major abdominal procedures where pain management needs extend well beyond the operating room.
The practical benefit for you as a patient is reduced reliance on opioid painkillers after surgery. Effective regional blocks lower the total amount of systemic pain medication needed, which translates to fewer side effects like nausea, sedation, and constipation during your recovery.