Update in Pediatric Regional Anesthesia

Combined Spinal/Caudal Catheter Anesthetic for Surgery in Infants: Practical Considerations

By Kristen O. Spisak, MD
Medical Director of Comprehensive Pain Services
Dayton Children’s Hospital
The Boonshoft School of Medicine
Wright State University
Dayton, Ohio

Exclusive use of regional anesthesia for infantile surgery is on the rise.  Awake spinal anesthesia (SA) is a safe and effective technique, especially in ex-premature infants, that reduces the risk of post-operative respiratory compromise, mechanical ventilation, and apnea.1,2  Advantages of spinal over general anesthesia (GA) include opioid avoidance, earlier recovery of bowel function, and attenuation of the surgical stress response.3-5  One major disadvantage of a single injection SA is its limited duration, which is why this technique is typically reserved for surgeries lasting less than 90 minutes.6  Use of a combined spinal and epidural anesthetic provides all of the aforementioned benefits of infantile regional anesthesia without the time limitation, allowing for completion of longer, more complex surgeries.7,8  In this article, I will share with you practical tips for executing a successful spinal/caudal catheter anesthetic based on my personal experience and discussions with peers.

Pre-Operative
Finding a receptive surgeon
Teamwork and shared patient outcome goals are of paramount importance when selecting a surgeon partner for a Combined Spinal/Caudal Catheter (SCC) anesthetic.  Performing this technique with a surgeon who has never operated on an infant under a single injection SA is a bad idea since they are not accustomed to operating conditions under exclusive regional anesthesia.  Of the surgeons who have adopted SA for short procedures like inguinal hernia repairs and circumcisions, I suggest to them that we start by performing a SCC anesthetic for a slightly longer surgery that might take all of 90 minutes, such as a simple hypospadias repair.  This approach allows you and the surgeon to become comfortable with the SCC process and technique while minimizing the chance of converting to GA if the epidural anesthetic portion fails.  With experience, you and the surgeon can use SCC anesthesia for increasingly longer, more complex cases, such as exploratory laparotomy, open ureteral reimplantation, and open pyeloplasty.

Patient (and parent) selection
The first conversation about utilizing an SCC anesthetic should take place between the surgeon and parents when the decision is made to schedule surgery.  In the outpatient setting, this should happen in the surgery clinic so that parents have ample time to think about their anesthetic options and ask questions prior to the day of surgery.  To help facilitate this conversation, I provide my surgeons with educational material to give to parents considering SCC anesthesia for their child’s surgery.  Surgeons can reference the educational pamphlet when discussing basic concepts of SCC versus GA, then defer more specific questions to the anesthesiologist on the day of surgery. 

Aside from screening for major contraindications to neuraxial anesthesia (uncorrected coagulopathy, infection at insertion site, local anesthetic allergy, increased ICP, etc.), I also ask the surgeons who are considering an SCC anesthetic to examine the patient for a sacral dimple in the clinic.  If the patient has a sacral dimple, they are sent for ultrasound to check for spina bifida occulta or tethered cord, conditions which could disqualify them for an SCC anesthetic.

The choice of GA or SCC is ultimately up to the parents, and one must present both the advantages and disadvantages of each.  Parents must feel confident in their anesthetic decision and not be made to feel that there is a “right” or “wrong” choice.  Additionally, if parents choose the SCC approach, I always consent for both types of anesthesia and thoroughly explain what circumstances would cause me to convert to GA (failed spinal or epidural, high spinal, poor operating conditions, addition of emergent surgery not covered by SCC, etc.). 

Pre-operative staff preparation
For pre-op personnel, there are only a few additional requirements for SCC anesthesia above the standard check-in questions like NPO status, allergies, and medical history.  Pre-op nurses can double check for sacral dimples or infections at puncture site and also apply a topical local anesthetic (LA) to the lower back about 30 minutes prior to surgery.  They can also secure extra pacifiers and Sweet-Ease to use intra-operatively since these supplies are usually not readily available in the typical OR.  Finally, one of the most important things in the pre-op setting is for all team members to be aware of the plan for SCC anesthesia.  It can be terribly confusing and stressful if someone in pre-op discusses a mask induction for GA when the parents have already made the decision with their surgeon and anesthesiologist to utilize SCC anesthesia.

Intra-Operative
OR staff preparation
Intra-operative staff also need to be notified of plans for an SCC anesthetic and its implications for the OR environment.  I remind OR staff that the baby will be awake and likely crying, as some feel quite distressed witnessing a baby fuss during SA placement.  For these staff, I invite them to leave the OR if they are non-essential or find a replacement who is unbothered by the situation.  Finally, everyone is reminded to keep noise and lights to a minimum throughout the surgery.  Some institutions place a sign on the outside of the OR door warning those who enter of an awake patient.

Order of events and timing
Planned workflow and efficiency of motion are of upmost importance when performing an SCC anesthetic.  Prior to the patient entering the OR, I have a sterile field with my prep, spinal needles, and intrathecal injectate ready to go.  Because of infants’ remarkable hemodynamic stability, the SA can be done first, before monitors and PIV are placed.  I avoid having my assistant put the patient in the sitting, spine flexed, and head down position until I am ready to insert the spinal needle since this motion typically leads to the infant crying and squirming, decreasing the chance of successful SA.  After SA placement, I remind all OR personnel not to elevate the patient’s legs and back to prevent an inadvertent high spinal blockade.

As soon as the intrathecal injection is complete, you have about 90 minutes at best until the spinal block begins to recede.  Goals during this time are obtaining IV access, placing a caudal epidural catheter, and getting surgery underway.  Once monitors are on and the patient has a dense spinal block, I have an experienced OR staff member place an IV in an insensate lower extremity.  If the child is still upset and crying at this point, I administer a sedative (usually IV dexmedetomidine bolus +/- infusion).  The patient is then rolled lateral for sterile preparation and placement of caudal epidural catheter.  After the catheter is secured, patient is returned supine so that incision can soon follow.  Time constraints of the initial SA requires the surgeon and staff to be in the OR ready to begin as soon as the SCC process is complete.

Caudal catheter placement and dosing
After the intrathecal injection, the goal of the second neuraxial anesthetic technique is timely placement of a functioning epidural catheter that covers the appropriate surgical levels.  In my practice, this is usually accomplished by blindly threading an epidural catheter to the desired thoracic level via a caudal puncture, since this approach is timely, about 85% successful9, and requires no additional equipment.  Alternatives include inserting the epidural catheter from the lumbar level, though this carries an increased risk of inadvertent dural puncture and injury to the infant’s lower lying spinal cord.  For real-time guidance of catheter placement and direct visualization of drug spread in the epidural space, portable ultrasonography is a tool that is readily available in most operating rooms.10-12  Theoretically, other techniques such as epidurography13 and trans-esophageal echocardiography14 can be used to confirm catheter position, but these require additional equipment and can be time consuming. 

The question of when to dose the epidural catheter during an SCC anesthetic depends on the medications being used for both the SA and epidural infusion.  A spinal injectate of 0.5% isobaric bupivacaine, clonidine, and epinephrine wash reliably lasts about 90 minutes, and the epidural can be dosed one hour after SA placement as the block begins to recede.8  Some anesthesiologists prefer to use plain 0.5% isobaric bupivacaine intrathecally and dose the epidural catheter after 30-40 minutes.5  Choice of epidural medications differ as well from 3% 2-chloroprocine to 1% lidocaine to variable concentrations of bupivacaine and ropivacaine.12,15  It is important to use a high enough concentration of local anesthetic through the caudal epidural catheter to achieve a dense surgical block since the SCC is the sole anesthetic.  For this reason, 3% 2-chloroprocaine is preferred over 2% 2-chloroprocaine.  Epidural infusions used to supplement general anesthesia or for post-operative analgesia usually consist of lower concentrations of local anesthetic. 

Patient Sedation
Many infants will fall asleep on their own during an SCC anesthetic due to the deafferentation caused by the SA.  Soothing measures may also include pacifiers dipped in Sweet-Ease, dim lighting, and soft, calming music.  For patients who remain restless, IV sedation can be given by bolus and/or infusion.  Some patients may not require any sedation until the spinal block begins to regress and they are under a primarily epidural anesthetic, so it is important to have medication prepared for use throughout the case.

Post-Operative
Caudal catheter removal
The timing of caudal epidural catheter removal depends on the type of local anesthetic used intra-operatively and the plan for post-op analgesia.  If one uses long acting epidural LA in the outpatient OR, the catheter can be removed at the conclusion of surgery.  Conversely, the caudal epidural catheter can remain in place for post-op pain control in a longer inpatient recovery situation.  In my practice, most infants are admitted only overnight.  Since I use 3% 2-chloroprocaine (2-CP) for my intra-op epidural infusion, I leave the caudal catheter in place at the conclusion of surgery.  About 45 minutes after the 3% 2-CP has been discontinued, I bolus the caudal catheter with a mixture of 0.2% ropivacaine and clonidine and remove in PACU.  Waiting for the 2-CP to wear off before administering ropivacaine reduces mixing of short and long acting LAs to allow for a longer lasting post-operative analgesic block.

PACU staff preparation
SCC patients arriving in the Post Anesthesia Care Unit usually require less nursing attention than patients recovering from GA since they have maintained hemodynamic stability and had no airway interventions.  Patients who required no sedation can even go directly from the OR to phase 2 recovery in the outpatient setting.  Important tasks for post-op staff include assessing patient for block resolution and having a bottle ready.  Additionally, if adjunct non-opioid pain meds such as acetaminophen and ketorolac were not required inter-operatively, they can be administered for post-op analgesia.

The spinal/caudal catheter for infantile surgery is a technique that requires expertise in pediatric neuraxial anesthesia as well as a coordinated effort with the surgeon and peri-operative staff.  Though the SCC approach can initially be labor intensive, the avoidance of airway instrumentation and opioid administration makes it an attractive option for our most fragile population.

REFERENCES

1. Williams RK, Adams DC, Abajian JC, et al.  The safety and efficacy of spinal anesthesia for surgery in infants: the Vermont Spinal Registry.  Anesth Analg.  2005;102:67-71.
2. William JM, Stoddart PA, Williams SA, Wolf AR.  Postoperative recovery after inguinal herniotomy in ex-premature infants: comparison between sevoflurane and spinal anesthesia.  Br J Anesth.  2001;86:366-371.
3. Huang JJ, Hirshberg G. Regional anesthesia decreases the need for postoperative mechanical ventilation in very low birth weight infants undergoing herniorrhaphy.  Pediatr Anesth.  2001;11:705-709.
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