Quadratus lumborum block

The quadratus lumborum (QL) is a deep abdominal muscle and the quadratus lumborum block (QLB) is an ultrasound-guided block that finds its key to success in the thoracolumbar fascia (TLF). The TLF is a connective structure that links the anterolateral abdominal wall with the lumbar paravertebral space. The block is possibly effective from local anesthetic bathing the nerves lying within the fascia or from local anesthetic diffusing from the TLF into the paravertebral space. There are 4 different types of QLBs.

In the QLB 1, the lateral side of the QL muscle that is in contact with the transversalis fascia is targeted. The patient is placed in the supine position with a pillow under the spine; a transversely placed probe near the iliac crest is used to identify all 3 layers of the abdominal wall and followed until they taper off into an aponeurosis with the QL posterior to this ( Fig. 1 ). Local anesthetic is deposited into this space.

QL 1 block. Arrow, projected needle path; EO, external oblique; IO, internal oblique; TA, transversus abdominus.

In the QLB 2 (QLB 2), the area targeted is the posterior QL between the QL and the latissimus dorsi and paraspinal muscles; injecting into this space, local anesthetic spreads to the paravertebral space and bathes sympathetic fibers and mechanoreceptors found in the fascia. To achieve this block, the patient is placed in the supine position and the posterior aspect of the QL is identified; the needle tip is then placed in the TLF and local is injected.

In the QLB 3 (QLB 3), the front of the QL at its attachment to the L4 transverse process is targeted; this block sometimes is referred to as the transmuscular QLB . The patient is placed in the lateral position and the probe is placed transversely over L4. A needle is inserted transmuscularly through the QL in the anterolateral position with the needle tip positioned between the QL and psoas major. ^, The local anesthetic has been shown to spread cephalad with this technique and enter the thoracic paravertebral space. The correct ultrasound image for this block has been described as the shamrock sign, with the transverse process of L4 as the center of the shamrock and the QL, psoas muscle, and erector spinae muscles forming the 3 leaves of the shamrock ( Fig. 2 ) .

QL 3 block: shamrock view—3 leaves of the shamrock depicted by 3 muscles shown (erector spinae, QL, and psoas muscles). Arrow, projected needle path.

In the QLB 4, the local anesthetic is deposited into the muscle itself. The patient is placed in the supine position and the QL is identified on ultrasound; a needle then is placed within the muscle body of the QL and local anesthetic is injected.

The QLB has been found to offer more local anesthetic spread and better pain control than a transverse abdominis plane (TAP) block. In adults, it has been successfully utilized for a myriad of surgical procedures, including abdominal, transplant, and renal surgeries. In pediatrics, it has also been shown useful in many abdominal procedures, including lower abdominal procedures. It too has been shown to be more effective for postoperative analgesia than the TAP block in children. Complications of the QLB include local anesthetic toxicity; damage to the underlying organs, in particular the kidney; and unwanted/inadvertent femoral nerve (FN) block with the QL 3. ^,

Erector spinae plane block

The erector spinae plane (ESP) block is a regional technique where local anesthetic is injected into a plane deep to the erector spinae muscle and is utilized to provide analgesia to the thoracic and abdominal walls. It has been described as technically simpler than the paravertebral and thoracic epidural injections and has an additional layer of safety because it is more remote from the pleura and neuraxial structures. ^,

To perform an ESP block, an ultrasound is used to scan both longitudinally and transversely up and down the thoracic spine to confirm positioning of the transverse process at the appropriate level to be anesthetized. The probe then is placed longitudinally over the transverse process and the needle inserted in plane until the tip of the needle touches bone; this is directly under the erector spinae muscle and is where local anesthetic is injected ( Fig. 3 ). The block can be performed in the sitting, lateral, or prone position. In pediatrics, some clinicians have found that the ESP block technically is more difficult than in adults, secondary to thinner layers of muscle and sliding fascial planes, and finer needle manipulation is required.

Erector spinae nerve block. Arrow, projected needle path; T.P., transverse process.

Indications for the ESP block are vast. In adults, it has been used for treatment of acute, postoperative, and chronic pain. In pediatrics, it also has been shown to effective in a multitude of operations in the thoracic and abdominal cavities. ^, Complications are rare; the ESP block is further removed from the pleura compared with the paravertebral block but the risk of pneumothorax still remains.

Suprainguinal fascia iliaca block

The suprainguinal fascia iliaca (FI) block is a newer approach of the FI block, which first was described infrainguinally, to better cover pain after hip and knee surgery. The lateral femoral cutaneous nerve (LFCN), FN, and obturator nerve (ON) all provide sensation to the hip joint; the LFCN leaves the FI at the inguinal ligament whereas the branches of the FN that innervate the hip leave proximal to the inguinal ligament. The ON, FN, and LFCN, however, all are found in the suprainguinal FI.

To perform the suprainguinal FI block under ultrasound guidance, an ultrasound transducer is placed longitudinally medial to the anterior superior iliac spine and rotated 30° toward the umblilicus. The iliacus muscle lies between the oblique muscle and the ilium, and the local anesthetic is deposited below the fascia but above the muscle cephalad ( Fig. 4 ).

Suprainguinal FI block: bowtie made by boundary of fascia lata, FI, sartorius muscle, and intra-abdominal oblique muscles. Arrow, projected needle path; ASIS, anterior superior iliac spine.

The suprainguinal FI block has been shown effective in adults after total hip arthroplasty as demonstrated by decreasing opioid consumption. It also has been shown to treat perioperative pain in children after arthroscopic surgery, with a low complication rate. Overall, the suprainguinal FI block results in more reliable spread of local anesthetic to the LFCN, FN, and ON and more completely provides a sensory block of the medial, anterior, and lateral thigh compared with the infrainguinal approach.

Knee sensory blocks

A desire to provide a sensory block of the knee with little to no motor deficit allowing for early ambulation after knee surgery has led to the development of two blocks. The first, the adductor canal block, provides analgesia to the anterior knee. The second, the interspace between the popliteal artery and posterior knee (IPACK) block, provides analgesia to the posterior knee. ^,

Adductor canal block

The adductor canal is a tunnel extending from the start of the femoral triangle to the adductor hiatus on the thigh; it is bound medially by the adductor magnus, laterally by the vastus medialis, and superiorly by the sartorius. Its contents include the superficial femoral vessels, the saphenous nerve, and the nerve to the vastus medialis. The nerve to the vastus medialis is the only motor nerve in the canal; therefore, blocking in the adductor canal is associated with minimal muscle weakness and an ability to ambulate safely faster compared with the traditional FN block.

The block is performed at the midthigh level, halfway to two-thirds down from a line between the anterior superior iliac spine and the patella. A transducer is placed longitudinally at this level and the superficial femoral artery is identified in the canal; the saphenous nerve, a hyperechoic structure, should be seen anteriolateral to the artery (more distally toward the patella, the saphenous nerve will appear medial to the artery) ( Fig. 5 ). The canal is filled with local anesthetic with needle infiltation.

Adductor canal nerve block. Arrow, projected needle path; FA, femoral artery; SN, saphenous nerve.

The primary indication for the adductor canal block is postoperative analgesia to the anterior knee. Compared with continuous FN blocks, continuous adductor canal blocks demonstrate equivalent analgesia and opioid requirements in adult patients undergoing total knee arthroplasty (TKA). A large comparative analysis demonstrated that opioid consumption was comparable between FN block and adductor canal block but that the adductor canal block was associated with better quadriceps power, longer ambulation distance, and shorter hospital length of stay in adults undergoing TKA. In pediatrics, there is a single case series report following patients who received an adductor canal block for their patellar dislocation surgery. All subjects demonstrated acceptable numerical rating scale scores for postoperative pain control and there were no adverse effects during the 48 hours after surgery. An adductor canal block has a low risk of long-term neurologic injury; one other adverse effect is that even though the block seems to be quadriceps sparing, the quadriceps function is not completely normal, so fall precautions are needed.

Interspace between the popliteal artery and posterior knee block

IPACK block is a motor-sparing block to provide posterior knee analgesia to facilitate early ambulation while sparing the tibial and common peroneal nerves, thereby maintaining strength and sensation to the leg. ^, Anatomically, this block targets the articular branches of the tibial nerve and obturator nerve that travel through the space between the popliteal artery and posterior knee. ^,

To perform the block, the ultrasound probe is placed to view the adductor canal in the lower third of the medial thigh and then slid distally to visualize the popliteal artery diving into the popliteal fossa. The probe then is moved to visualize the space between the popliteal artery and shaft of the femur just above the femoral condyles, approximately 1 fingerbreadth above the patella ( Fig. 6 ). The needle then is inserted in plane to 2 cm beyond the artery; local anesthetic is given in divided doses as the needle is withdrawn.

IPACK block. Arrow, projected needle path; PA, popliteal artery; PV, popliteal vein.

Indications for the IPACK block include posterior knee pain after TKA and major ligament repair. One recent study has shown that in addition to adductor canal block, addition of the IPACK block allowed for better pain control, range of motion, and ambulation distance in TKA patients compared with adductor canal block alone. In pediatrics, a single case series has looked at IPACK blocks for anterior cruciate ligament repairs; they found that patients who received the IPACK block had minimal opioid needs in the postanesthesia care unit with no sciatic motor weakness. Adverse effects are thought to be low. Cadaver studies have shown the potential for local anesthetic spread to unintended locations, such as the tibial nerve and common peroneal nerve. Intra-articular injection is also possible.

α ₂ -Agonists

Dexamethasone

Dexamethasone has also been used to prolong blocks. It has an unknown mechanism of action and both perineural and systemic administration seem to prolong the block. It is hypothesized that it may prolong a block by attenuation of the C-fiber response, anti-inflammatory action, and/or immunosuppressive actions. A meta-analysis has demonstrated, however, that perineural dexamethasone prolongs analgesia more than dexamethasone given intravenously (IV). A Cochrane review found that the use of dexamethasone in upper limb surgeries prolongs peripheral nerve blocks, reduces opioid consumption, and reduces pain scores. The review could not find enough evidence, however, to support its use for lower limb surgery and found no evidence supporting its use in pediatric populations. More studies are needed to assess whether dexamethasone given perineurally prolongs blocks in pediatric patients.

Opioids

Various opioids have been added to peripheral nerve blocks with varying success. Morphine use has been studied the most extensively but the routine use of morphine in peripheral nerve blocks cannot be recommended because the benefits of its use do not surpass IV morphine and the side effects are increased. Buprenorphine, a partial opioid receptor agonist with local anesthetic-like capacity to block voltage-gated sodium channels, has been shown to prolong blocks but also has been shown to increase nausea. As such, its use is recommended only with coadministration of antiemetics. Numerous studies have shown that it can significantly prolong blocks in adults and provides better analgesia and longer duration of action compared with the addition of morphine. Tramadol has also been studied. It has analgesic effects on the mu-opioid and other nonopioid receptors; however, there have been only inconsistent results in adults with the addition of tramadol to blocks.

Epinephrine

Epinephrine has been used to prolong the effect of peripheral nerve blocks. It has 2 main effects on peripheral nerves blocks: it allows for an increased amount of local anesthetic that can be given and it prolongs the duration of the block. Epinephrine, however, can compromise neural blood flow and has shown only mixed efficacy for block prolongation. Therefore, it is not recommended for routine use of block prolongation.

Liposomal bupivacaine

Liposomal bupivacaine is a recent addition to peripheral nerve blocks. Liposomes act as a medication depot; as they slowly break down in the body, they slowly release the medication in their matrix. Therefore, liposomal bupivacaine allows for the extended release of bupivacaine. It initially was approved for local infiltration by the US Food and Drug Administration (FDA); it recently has gained approval for use in interscalene blocks in adults. It has been shown more effective than bupivacaine alone in TAP blocks; it has also been shown more effective than bupivacaine alone in lower extremity blocks but that is an off-label use. A Cochrane review demonstrated that liposomal bupivacaine infiltration at the surgical site reduced pain compared with placebo but was not superior to regular bupivacaine infiltration. It is not FDA approved for use in pediatric patients. There are studies in pediatrics that demonstrate a benefit in wound infiltration but no studies to date have looked at the use of liposomal bupivacaine in peripheral nerve blocks in children.

Opioids

Opioids remain a mainstay of managing pediatric pain. Some opioids have mixed antagonist and agonist actions or act on other nonopioid receptors. These medications are used in the hope of providing pain relief while minimizing unwanted side effects. Buprenorphine is a partial mu agonist, partial or complete opioid receptor like-1 agonist, and kappa and delta opioid antagonist. It has many benefits compared with pure opioid agonists. In addition, it causes internalization of opioid receptors, which decreases the risk of tolerance or dependence. Adding to its safety profile, it has a ceiling effect on respiratory depression. There are few studies, however, demonstrating its efficacy in pediatrics and its use is considered off-label in children. Nalbuphine is a kappa receptor agonist and mu receptor antagonist. Nalbuphine and morphine are considered equianalgesic but nalbuphine carries a lower risk of respiratory depression, itching, and euphoria. A Cochrane review, however, was unable to definitively show superiority of nalbuphine over placebo; the review could also not comment on the side effects of nalbuphine and recommends more studies to further assess its use in children. Lastly, tramadol is a weak mu opioid receptor agonist that also inhibits the reuptake of norepinephrine and serotonin. In studies, tramadol has shown to provide adequate analgesia for postsurgical pain compared with placebo but not compared with morphine. Pediatric patients who have overactive CYP2D6, however, have an increase in the active metabolites of tramadol, which can lead to an increase in side effects, including respiratory depression, over-sedation, and death. The FDA has recently issued a recommendation against the use of tramadol in patients under 12 years of age.

Nonsteroidal anti-inflammatory drugs

Nonsteroidal anti-inflammatory drugs (NSAIDs) are often used for pediatric pain. Perioperative NSAIDs have been shown to decrease pain and opioid consumption in some pediatric surgical populations. A meta-analysis also demonstrated that perioperative NSAID use was associated with less postoperative nausea and vomiting in pediatric patients. In a trial comparing ibuprofen to morphine to control post-tonsillectomy pain, there was no difference in analgesic effectiveness or tonsillar bleeding in the 2 groups. The number of respiratory adverse events, however, was higher in the morphine group. Unfortunately, a Cochrane review could not be certain of the efficacy or safety of ketorolac in treating postoperative pain in children.

Few studies have looked at NSAID use in the treatment of pediatric noncancer chronic pain. A Cochrane review concluded that the amount and quality of evidence for the use of NSAIDs to treat pediatric noncancer chronic pain is very low and that NSAID use in children for this indication is supported only by inference from adult guidelines. In comparison with acetaminophen, however, NSAIDs have shown superior at standard doses for the treatment of both acute and chronic pain.

Acetaminophen

The mechanism of action for acetaminophen is still not completely understood. Acetaminophen inhibits cyclooxygenase (COX) activities in the brain. It does not appear to be a direct COX inhibitor but rather seems to reduce the overall levels of COX. Studies have shown that compared with placebo, acetaminophen is superior for the treatment of postsurgical pain. This same review found that acetaminophen has equal safety compared with placebo. Other systemic reviews have shown that acetaminophen can decrease pain and opioid use when used perioperatively in the pediatric surgical patient. Since the arrival of IV acetaminophen, studies also have shown efficacy in the use of IV acetaminophen to treat acute pain in children. When comparing oral to IV formulations, the oral formulation offers a significant cost savings over the IV formulation. The IV formulation, however, has superior cerebrospinal bioavailability of the drug. A meta-analysis in adult literature showed no difference in pain control and opioid consumption between IV and oral acetaminophen. The benefit of IV versus oral acetaminophen has not been clearly established.

Ketamine

Ketamine is an N -methyl- d -aspartate (NMDA) antagonist that has been used for its anesthetic, analgesic, and antidepressant properties. The American Society of Regional Anesthesia and Pain Medicine consensus guidelines recommend ketamine in the perioperative setting both as a stand-alone treatment of pain and as an opioid adjunct. Studies have shown safety and efficacy in using low-dose ketamine (less than 0.3 mg/kg/h) in the non–critical care setting for acute pain. Although side effects frequently are reported with the use of ketamine infusions, these side effects tend to be minimal or mild and often do not result in discontinuation of the infusion. In pediatric populations, perioperative ketamine has been shown to reduce postoperative pain and opioid use.

Antiepileptics

Gabapentin and pregabalin are 2 antiepileptics that are now also used as pain medications. They are both potent inhibitors of the mechanisms that play a role in neuropathic pain models. They are well-tolerated medications with few side effects, which can include dizziness, fatigue, and worsening depression. In pediatric populations undergoing the Ravitch procedure, patients who received perioperative gabapentin had lower anxiety and needed fewer rescue antiemetics compared with patients who did not receive gabapentin. In pediatric patients presenting for amputation, perioperative gabapentin started 4 days before surgery and continued for 30 days after surgery was associated with less development of phantom limb pain and less acute postoperative pain. In the neonatal intensive care units, gabapentin also has been trialed and shown effective in reducing overall opioid consumption.

There are, however, some caveats with gabapentin use. A Cochrane systemic review found no evidence to support or refute the use of gabapentin or pregabalin to treat chronic noncancer pain in children and adolescents. In the adult literature, a recent review could not recommend gabapentinoids for use in postoperative pain.

Antidepressants

Antidepressant medications are often used to help treat adult, chronic noncancer pain. A recent review of the literature revealed few studies related to treating chronic noncancer pain in children with antidepressants. Adult trials show that some antidepressants, such as amitriptyline, can provide pain relief in noncancer pain. For pediatric functional abdominal pain, however, a recent review of the literature came to the conclusion that there is no evidence to support the routine use of antidepressants. More research on the efficacy of antidepressants and pediatric pain is needed.