The paravertebral block numbs one side of the chest or the upper belly by laying local anesthetic in the wedge of space beside the spine, where the spinal nerve comes out from between the bones. The drug bathes the nerve there, before it has split into its branches. Ultrasound shows the wedge between a bony shelf above and the lining of the lung below. A correct injection pushes that lining down and opens the space wider. The lung lying right there is the reason the block is done under the eye.
A block of one side
A schematic of the sympathetic connections at the spinal nerve. Where the nerve leaves the spine it lies beside the sympathetic chain ganglion, the two linked by the small rami communicantes. The paravertebral block bathes the spinal nerve and the chain together, so it numbs the body wall and quiets the sympathetic supply of one side at once. Diagram: OpenStax College, CC BY 3.0.
The paravertebral block numbs the body in a band down one side. The spinal nerve carries the feeling of a strip of the chest wall, from the back around to the front. The drug laid in the space catches that nerve at its root, so the whole strip on that side goes numb. The other side keeps its feeling.
The reach of the block is read in strips of the body, the way the nerves divide it. Each level of the spine feeds one strip, a band that wraps from the back around to the front. A block of three or four levels covers a wide field, the strips stacked one on the next. The map of which level feeds which strip is what the anesthesiologist works from in setting the block.
The block reaches more than the nerve of sensation. The sympathetic chain runs in the same space, and the drug bathes it too. The strip of skin loses its pain. The same strip flushes warm, its small vessels opened by the block. The block quiets the feeling and the sympathetic supply of one side together.
This is the block often likened to an epidural of one side. An epidural numbs both sides from the midline. The paravertebral block numbs the one side that the surgery is on. The relief is much the same on that side. The blood pressure holds steadier, since only one side loses its sympathetic tone.
The wedge beside the spine
The sympathetic trunk running down alongside the thoracic spine, its chain of small ganglia against the back of the chest. This chain passes through the paravertebral space the block fills, so a block here reaches the sympathetic supply along with the spinal nerve. Engraving: Gray’s Anatomy, public domain.
The paravertebral space is a small wedge that runs alongside each vertebra of the chest. It has a clear shape, set by what bounds it. In front and to the side lies the lining of the lung, the parietal pleura. Behind it sits a tough ligament that bridges the bones. Toward the midline it opens at the gap where the spinal nerve leaves the spine.
Inside the wedge lies what the block aims for. The spinal nerve crosses the space as it emerges, still bare of the sheath it gathers further out. The sympathetic chain runs along the front of it. A little fat fills the rest. A drug laid in this wedge meets the nerve and the chain at close range, with nothing thick between them and the spread.
The shape of the wedge guides the spread of the drug. Local anesthetic placed in it pools against the pleura and climbs and falls along the spine to the spaces above and below. One pool can reach several levels this way. The open shape of the space is what lets a single injection numb a band of more than one strip.
The band it numbs
The block numbs a band of the body wall on one side, the width of the band set by how many levels the drug reaches. A block at the chest covers a strip of the ribs and the skin over them. A block lower down reaches the upper belly wall. The level of the spine that is blocked decides the strip that goes numb.
The wider the band the surgery needs, the more levels the block must cover.
This one-sided, banded reach suits a clear set of operations. Surgery on the breast draws its pain from these nerves, and the block eases a mastectomy well. An opening of the chest for lung surgery is covered by a block over those levels. Broken ribs on one side, a sharp and lasting pain, are quieted by a block of the same band.
The block serves a surgery that sits on one side of the body. A kidney operation, an opening of the gallbladder, a repair high in the groin all lie within its reach. The band of numbness is matched to the cut, level by level, so the strip the surgeon works in is the strip the block covers.
Breast surgery is the use this block is best known for. A mastectomy draws its pain from the same nerves the block bathes. A paravertebral block gives strong relief at the wound, with less of the heavy opioid load. The block is thought to lower the chance of a lasting pain that can follow breast surgery. It has become a fixture of care for the breast for these reasons.
Setting up the scan
The patient sits leaning forward, or lies on the side with the side to be blocked uppermost. The back is bared and the skin cleaned and draped for a sterile field. The level of the spine for the block is counted out, from a landmark such as the lowest rib or the bony bump at the base of the neck.
The probe is laid along the spine, a finger’s breadth out from the midline, in a line that runs up and down the back. This parasagittal view shows the bones of the spine in profile. A lower frequency is chosen in a heavier patient, where the space lies deep. The depth is set so the bony shelves and the lung below them fill the screen.
The space can be read in two ways. The probe along the spine, in the up-and-down line, shows the bony shelves in a row and the lung between them. The probe turned across the back shows one shelf and the space beside it in cross-section. Many operators learn the up-and-down view first, for the clear row of landmarks it gives, and turn across the back to confirm the depth.
The space on the screen
The picture of the paravertebral space is read off a few clear marks. The transverse processes, the bony shelves that jut from each vertebra, show as rounded humps of bright bone, each with a dark shadow below it. Between two humps the picture opens, and the lining of the lung shows there as a bright line that slides with the breath.
Above that sliding line, between the bony humps, lies the wedge of the space. A tough ligament roofs it, a faint band that stretches from one bony shelf to the next. The space sits under that ligament and over the pleura. The needle has to pass the ligament to enter the wedge.
The lung is the mark that anchors the whole picture. Its bright line, sliding with each breath, sits at the floor of the view. The bony humps stand on either side. The space the block aims for is the small gap framed by the bone above and the lung below. Reading those three marks is the whole of finding the space. The bone, the ligament, and the lung name themselves once the eye has met them a few times.
The pleura pushed down
The sign that the block is laid where it belongs is the lung pushed down. The needle is brought in from one end of the probe, in plane, and passed through the tough ligament that roofs the space. The tip comes to rest in the wedge, above the bright sliding line of the lung. A small test injection tells the rest. Local anesthetic let into the true space presses the lining of the lung downward and forward, away from the needle. Each push of the drug opens the space wider. That downward press of the pleura is the sign the block looks for. It shows the drug is in the space, spreading where it should, lifting the roof and pushing the floor apart. The lining of the lung also brightens a little under the press of the drug, a second small sign of the right place. The drug is followed on the screen, climbing and falling along the spine, spreading to the spaces above and below the one entered, so a single pool can reach a band of more than one level. A spread that fails to move the lung, or that opens no space at all, is a tip in the wrong place, a cue to stop and look again. The same lung that the drug pushes down is the lung a careless needle can pierce. The pleura is the front wall of the space, a breath away from the tip the whole time. A needle driven too deep, or pushed on without the tip in view, can cross that wall and let air around the lung, the pneumothorax that is the marked risk of this block. The two facts are one: the pleura is both the sign of a good block and the danger of a bad one. The needle is held in plane and in view from the first pass, the tip watched as it nears the space, never advanced into the dark below the ligament without the screen to show it. The injection is given in slow steps, the lung watched as it sinks away with each push. A tip that stays above the sliding line, and a drug that presses the line down and stays clear of it, is the whole of a safe block here. The eye on the pleura, from the first touch of the needle to the last of the drug, is what keeps the block in the space and out of the lung.
Bringing the needle in
The needle enters in plane with the probe, from the lower or the upper end, so its full length shows on the screen. It is walked down toward the space between the bony humps, the tip held in view at each step. It passes the roofing ligament with a small give that can be felt and seen.
The placement is read off the test dose and the lung that sinks with it. The local anesthetic then follows in slow steps, the pleura watched as it presses further down with each push. A spread that opens the space and travels along the spine is the mark of a needle laid right.
The tip is kept above the lung the whole time, in the wedge under the ligament. A draw-back on the syringe before each push checks for a vessel, since small vessels run in and near the space. The drug is laid around the nerve and the chain, in the open wedge that holds them. The space sits a short way under the skin in a slim patient, deeper in a heavier one.
One injection or several
A band of more than one strip can be numbed in two ways. A single large pool laid in one space climbs and falls to the levels above and below, spreading the block over a span of the spine from the one spot. The reach of that spread varies from one patient to the next, so the spread is read on the screen and the block is checked once it has set.
The other way lays a smaller pool at each of several levels in turn. The needle is moved to each space, the drug given level by level, so the band is built up one strip at a time. This takes longer to do. It places the drug more surely over a known span of the wall. Surgery on the breast is often covered this way, with a small pool at each of several levels in turn, to numb the wide band the operation needs.
For pain that runs on past a single dose, a fine catheter can be left in the space, feeding local anesthetic over days. A catheter in the paravertebral space holds a chest comfortable after a lung operation or a row of broken ribs. The same scan that places the single shot threads the catheter into the wedge, and the spread is checked through it.
From the loss of resistance to the picture
The paravertebral block was first done by feel. The needle was walked in from the back until it passed the roofing ligament, felt as a give, and then a touch further into the space. The depth was judged by hand and by the feel of the tissues. The lung lay close, with no sight of where the tip had come to rest.
The blind method asked great care. The lung was reached more than was safe. Ultrasound changed the block from a feel to a sight. The bony humps, the roofing ligament, the lung line, the needle, and the spreading drug are all on the screen now. The block grew safer, and its use widened to the bedside and the ward.
Staying out of trouble
Three deeper dangers set the limits of this block, and each is watched on the screen. Each lies a little deeper than the wall blocks face, so the block asks a trained hand and a careful eye.
The lung is the first. The pleura forms the front wall of the space, so the needle works close to it the whole time. The tip is held above the sliding line, in plane and in view, never pushed into the dark below the ligament unseen. A pneumothorax is the risk a careless depth can bring, and a tip kept in sight is the guard against it.
The spine is the second. The space opens toward the midline at the gap where the nerve leaves the bones, and a drug pushed too far that way can track inward to the covering of the cord. A spread that runs toward the midline can reach the epidural space, or further, for a block of both sides or a deeper effect. The needle is aimed along the space and out from the midline, and the spread is watched to stay in the wedge.
The blood is the third. Small vessels run in and around the space, so the syringe is drawn back before each push to check for a vessel, and the drug is given in divided doses. The dose is held within the limit for the weight, since local anesthetic carried into the blood can bring on toxicity. The three dangers share one guard: the needle and the spread kept in plain sight.
The paravertebral block and the epidural
The paravertebral block and the epidural reach for the same kind of relief. The epidural lays its drug in the midline, and it numbs both sides of the body from there. The paravertebral block lays its drug to one side, and it numbs the one side the surgery is on. For an operation on a single side, the two give much the same relief.
The one-sided block carries some gains for that case. The blood pressure holds steadier, since only one sympathetic chain is bathed. The bladder is less prone to hold its water. The patient on blood thinners may be served by it, since an epidural near the cord gives more pause. The choice between them weighs the surgery, the patient, and the hands that will do the block.
The paravertebral block sits at the deep end of the wall blocks. A block of the belly wall lies shallow and far from the lung. The paravertebral block works close to the lung and the cord, on a smaller and deeper space. It asks a steadier hand and a careful eye, and it gives, in return, a block that rivals the epidural for one side of the body.
After the block
The block comes on over a quarter of an hour or more, the drug spreading along the space. The band of the wall on that side grows warm, then numb. A long-acting drug holds the strip comfortable for many hours, well past the surgery and into the first part of recovery.
The warmth of the skin is a sign to know. The strip on the blocked side flushes warm and dry. This warmth is a sign the block has taken, the sympathetic supply to that strip now bathed. A check with a cold swab over the band tells where the numbness reaches and where it falls short, before the patient relies on it.
A block that spreads high in the chest can reach the small nerves to the face. A drooping eyelid and a small pupil on that side, the sign called Horner syndrome, can follow a high spread. It clears when the block wears off. The patient is told of it ahead of time, so it brings no alarm.
A chest wall freed of pain changes the days that follow. A patient who can breathe deep and cough without dread keeps the lungs clear and holds off a chest infection. The deep, easy breath that the block allows is part of how a patient comes through a chest operation well.
The block is one part of a wider plan for the pain. It is paired with other medicines that reach what the block leaves, so the patient leans less on strong opioids and keeps a clearer head. The paravertebral block does its share in getting the patient breathing, moving, and home.
One side, named on the screen
The paravertebral block treats one side of the chest or belly wall. The drug is laid where the nerves leave the spine, in the small space in front of their bony humps. From there it numbs a band down that one side. A mastectomy, a set of broken ribs, an opening of the chest: each is a one-sided pain the block is shaped to meet. The level on the spine is picked to match the site of the surgery.
The space sits a short way under the skin in many patients, in reach of a linear probe at the bedside. The bony humps and the sliding line of the lung mark the space on the screen. The pleura is watched the whole time, since it forms the front wall of the space. It lies right under the needle.
What the picture buys is the lung kept in sight. The needle is brought down to the space under direct view. The drug is seen to sink the pleura as it goes in. A block once placed by feel, close to the lung, is now placed under sight from the first pass to the last.
Common questions about the paravertebral block
What is a paravertebral block used for?
It numbs one side of the chest or upper belly wall in a band, for surgery such as a mastectomy, an opening of the chest, or a kidney operation, and for the pain of broken ribs on one side. It blocks the spinal nerve and the sympathetic chain at the levels it reaches. The band of numbness is matched to the site of the surgery.
How is a paravertebral block different from an epidural?
An epidural lays its drug in the midline and numbs both sides. A paravertebral block lays its drug to one side and numbs that side alone. For an operation on a single side the relief is much the same. The blood pressure tends to hold steadier with the paravertebral block, since only one sympathetic chain is bathed.
What does the paravertebral space look like on ultrasound?
The transverse processes show as rounded humps of bright bone with shadow below, and between them the lining of the lung shows as a bright line that slides with the breath. The space sits under a roofing ligament and over that lung line. A correct injection presses the lung line downward and opens the space.
Why is pneumothorax a risk with this block?
The lining of the lung forms the front wall of the space, so the needle works close to the lung the whole time. A needle driven too deep can cross that lining and let air around the lung. Ultrasound keeps the lung line in view and the needle above it, which holds the block in the space and out of the lung.
Does a paravertebral block lower blood pressure?
It bathes the sympathetic chain on one side, so it can lower the blood pressure a little on that side. The fall is gentler than with an epidural, which bathes both chains from the midline. A spread that crosses to both sides can lower the pressure more, so the spread is watched.
How long does a paravertebral block last?
A single injection lasts several hours, often well into a day with a long-acting drug. A thin catheter left in the space can carry the block on for days. It is usually combined with other pain relief after surgery.
About the Author
Julien Mercier
Senior R&D Engineer · Medical Ultrasound Transducer Development
Senior R&D Engineer with an M.S. in Applied Physics and over 15 years of experience in medical ultrasound transducer development, specializing in the design verification and performance testing of high-frequency imaging transducers. Currently leading the development and verification of the company’s next-generation high-frequency linear-array transducer, responsible for imaging performance evaluation and reliability analysis in preclinical testing. Brings extensive hands-on experience in piezoelectric element tuning, beamforming parameter optimization, and system-level performance testing.
