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Ultrasound-Guided Pediatric Caudal Block

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In this video, we describe the approach to performing an ultrasound-guided caudal epidural block in young children. We go over the rationale, anatomy, sonoanatomy, local anesthetic volumes and choices, and tips and tricks for making this block work.

Foreign epidural block is one of the most frequently performed regional procedures on children it’s used to provide surgical or procedural analgesia from the umbilical region to the toes and provides infants and kids with better pain control less exposure to general anesthetic agents and a faster recovery while the landmark technique has been used since the

1930s the ultrasound guided method is simple slick satisfying and safe and has been shown to reduce block failure and complications in this video we’ll describe the rationale anatomy sonoanatomy and technique for ultrasound guided caudal block if you want to perform coddle blocks safely and effectively you must know the anatomy here’s a sagittal view of the end of

The vertebral column we see the last two lumbar vertebrae in the sacrum made up of five fused segments at the very end is a coccyx or tailbone the lumbar spinal canal runs between the vertebral bodies and the posterior arches of each vertebra and continues down to the sacral canal note that the posterior arch of s5 and sometimes s4 is absent the opening it leaves

Is called the sacral hiatus and this is how we’re going to access the caudal epidemic general space the sacral hiatus is covered by the sacrocoxygeal ligament the dural sac typically ends midway along the sacral canal at about s3 in infants and shifting cephalad to s2 by h3 it contains csf and ikata equina distal to the end of the dural sac is what we consider

The caudal space this is where we’re going to deposit our local anesthetic it contains the few remaining sacral nerves the coccygeal nerve as well as some epidural fat and a plexus of epidural veins the caudal epidural space here communicates easily with the thoracic lumbar epidural space so that with enough volume local anesthetic placed here can move north and

Get you a block of the lower trunk here’s a posterior view of the sacrum we can see the sacral hiatus at the most caudal aspect flanked by two bony prominences the sacral cornoa these are remnants of unfused vertebral arches in the landmark-based technique we’re taught to feel for the posterior superior iliac spines and imagine an equilateral triangle with the

Apex giving us a location of the hiatus between the cornua this sounds easy but it’s often challenging because of anatomic variation and excess subcutaneous fat which brings us to this question does imaging help you betcha here’s the issue most of the time the landmark technique works just fine but in up to 25 percent of cases the needle tip and local end up in

The wrong place subcutaneous injection is not uncommon leading to a failed block the ap distance of the sacral hiatus is not large usually about three to five millimeters so it’s easy to push the needle through and into the substance of the ventral sacrum especially because it’s incompletely ossified and quite soft finally the dural sac and newborns is about 10

To 15 millimeters away from the hiatus but can be less than five and intrathecal injection has been known to happen ultrasound helps by taking all the guesswork out and allowing you to place a needle accurately in the caudal epidural space ultrasound guidance has been shown to reduce the number of needle passes and incidence of subcutaneous bony or intravascular

Needle placement compared with the landmark approach these authors went so far as to say that ultrasound done use is so obvious as to remain unchallenged okay so let’s do it the patient position is exactly the same as a landmark block patient on their side with the hips and knees flexed this provides access to the sacral hiatus but also tends to pull the duralad

Slightly a linear high frequency transducer is placed over the midline of the sacrum just cephalad to the gluteal cleft you should see the vertebral bodies and arches of s2 3 and 4 and the bodies of s5 and the coccyx the dural sac can be observed as a hypoechoic structure coming to a pointed end around s2 or s3 the phylum terminali is a thin terminal extension of

The pia that attaches to the coccyx and anchors the dural sat caudally overlying the sacral hiatus is a sacrocoxygeal ligament with sub-q fat and skin overlying that the caudal space is occupied by epidural fat seen here traveling in a cephalet direction we see the continuation of the dural sac into the lower lumbar region as well as pulsations of the csf being

Transmitted to the epidural space once you have the appropriate view a needle is advanced in plane from the caudal aspect take care to stay shallow as the hiatus is not very deep especially in neonates we typically use a 21 gauge 100 millimeter block needle for its echogenicity as well as the enhanced appreciation for different tissue and fascial layers we get

Compared to a sharp needle let’s see what this looks like the needle is directed to contact and pass through the sacrocoxygeal ligament you may feel a slight give as this happens aspirate and give a test injection with half a ml of saline oops that looks like it’s expanding subcutaneously let’s redirect ah that’s better our test injection shows expansion within

The epidural fat of the caudal space we’ll switch to our local anesthetic aspirate one more time and administer the full dose slowly using intermittent aspiration for local anesthetic we like 0.2 rapidan with epinephrine at one to four hundred thousand you’re not after a motor block so a dilute solution like this is effective and safe like all epidural blocks it’s

Volume that determines the extent of the block if you’re after sacral dermatomes only safer generated urinary or perineal indications half a mil per kilo will do the trick the lumbar dermatomes say for lower limb surgery or inguinal hernia repair one ml per kilo is appropriate and then 1.25 mils per kilo is what you typically need to get up to the umbilicus and to

Provide visceral relief for manipulation of the spermatic cord and orchiopexy for indications above the umbilicus success rates tend to drop because of inconsistent cranial spread better to do a lumbar or thoracic epidural or erectus sheath block people have put lots of potions into the caudal cauldron but generally most don’t do much for block quality or duration

And may cause side effects these are the three most talked about clonidity does extend the sensory block and has been used extensively and safely in a one mic per kilo dose you won’t see much of the sedation hypotension and bradycardia seen with higher doses caudomorphine is a great analgesic therapy but does have the usual side effects such as nausea paritis and

Because of the risk for respiratory depression patients should be monitored postoperatively for 12 to 24 hours preservative free ketamine does work but concerns about toxicity to the neural tissues has pretty much killed its use if you want to extend your block for routine single injection caudal use clonidine or you can place a catheter called catheters are easy to

Place and can be threaded up even to thoracic levels rather than use a stiff tui needle an easy approach is to insert an 18 gauge iv cannula as in the single injection method then thread a regular 20 gauge epidural catheter through that the main challenge with carla catheters is knowing where the tip is because they don’t always go in a straight line historically

We used x-rays myelograms or stimulating catheters to confirm placement but hey we have ultrasound right especially in infants and toddlers it’s easy to scan the lumbar and thoracic epidural space and watch for dural displacement when saline is injected to confirm the level here are suggested volumes for dosing a caudal catheter as is always the case with epidural

Analgesia some titration to effect is required when should you not consider a caudal block well certainly if there’s something in the needle path such as the pilonidal cyst or local infection by the gluteal cleft like any naraxial procedure the patient must have normal hemostasis in case of vessel puncture and finally caudal blocks can be dangerous in patients with

Spinal dysrhaphism such as tethered cord syndrome or dermal sinus if a patient has signs of other spinal or meningeal anomalies or cutaneous stigmata such as sacral pits get a proper ultrasound or mri exam to ensure normal anatomy and yes things don’t always go as planned but in general caudal anesthesia is very safe the biggest complication is block failure and

Even that is only one percent now the data from this excellent study comes from high volume pediatric centers and it’s likely that the failure rate in less expert settings is somewhat higher blood aspiration occurs occasionally but the rest of this list and thankfully the very serious items are very rare thumbs up indeed here are some coddle tips and tricks first

A common novice error is to drive the needle deeper than necessary which usually results in hitting the coccyx or sacrum this is partly because that’s how we used to start the landmark technique with a steep angle through the skin and then flatten out to pop through the ligament with ultrasound stay shallow until the needle is visualized on the screen and then

Adjust as necessary second you may have read about the frog sign as a sonographic landmark this refers to a transverse scan of the hiatus showing you the two cornua the eyes of the frog the ligament and the sacrum itself while some find this truly riveting it’s unnecessary as the midline or slight paramedian sagittal position gives you everything you need and we

Don’t advocate doing this with an out of plane needle direction it could be a fragment of my imagination but sagittal imaging in babies and toddlers is easy commit to using it and you’ll be fine okay i’m done with the puns forgive me ultrasound guided caudal blocks are simple to do do and the imaging removes a lot of the mystery and anxiety for novices and prose alike

Transcribed from video
Ultrasound-Guided Pediatric Caudal Block By Regional Anesthesiology and Acute Pain Medicine