Regional Anesthesia and Analgesia
The primary uses of regional techniques in pediat-ric anesthesia have been to supplement and reduce general anesthetic requirements and to provide bet-ter postoperative pain relief. Blocks range in com-plexity from the relatively simple peripheral nerve blocks (eg, penile block, ilioinguinal block); to bra-chial plexus, sciatic nerve, and femoral nerve blocks; to major conduction blocks (eg, spinal or epidural techniques). Regional blocks in children (as in adults) are often facilitated by ultrasound guidance, sometimes with nerve stimulation.
Caudal blocks have proved useful following a variety of surgeries, including circumcision, ingui-nal herniorrhaphy, hypospadias repair, anal surgery, clubfoot repair, and other subumbilical procedures. Contraindications include infection around the sacral hiatus, coagulopathy, or anatomic abnormali-ties. The patient is usually lightly anesthetized or sedated and placed in the lateral position.
For pediatric caudal anesthesia, a short-bevel 22-gauge needle can be used. If the loss-of-resistance technique is used, the glass syringe should be filled with saline, not air, because of the latter’s possible association with air embolism. After the characteris-tic pop that signals penetration of the sacrococcygeal membrane, the needle angle of approach is reduced and the needle is advanced only a few more milli-meters to avoid entering the dural sac or the ante-rior body of the sacrum. Aspiration is used to check for blood or cerebrospinal fluid; local anesthetic can then be slowly injected; failure of a 2-mL test dose of local anesthetic with epinephrine (1:200,000) to produce tachycardia helps exclude intravascular placement.
Many anesthetic agents have been used for caudal anesthesia in pediatric patients, with 0.125– 0.25% bupivacaine (up to 2.5 mg/kg) or 0.2% ropi-vacaine being most common. Ropivacaine, 0.2%, can provide analgesia similar to bupivacaine but with less motor blockade. Ropivacaine appears to have less cardiac toxicity than bupivacaine when compared milligram to milligram. Addition of epi-nephrine to caudal solutions tends to increase the degree of motor block. Clonidine, either by itself or combined with local anesthetics, has also been widely used. Morphine sulfate (25 mcg/kg) or hydromorphone (6 mcg/kg) may be added to the local anesthetic solution to prolong postoperative analgesia for inpatients, but it increases the risk of delayed postoperative respiratory depression. The volume of local anesthetic required depends on the level of blockade desired, ranging from 0.5 mL/kg for a sacral block to 1.25 mL/kg for a midthoracic block. Single-shot injections generally last 4–12 h. Placement of 20-gauge caudal catheters with contin-uous infusion of local anesthetic (eg, 0.125% bupi-vacaine or 0.1% ropivacaine at 0.2–0.4 mg/kg/h) or an opioid (eg, fentanyl, 2 mcg/mL at 0.6 mcg/kg/h) allows prolonged anesthesia and postoperative anal-gesia. Complications are rare but include local anes-thetic toxicity from increased blood concentrations (eg, seizures, hypotension, arrhythmias), spinal blockade, and respiratory depression. Postoperative urinary retention does not appear to be a problem following single-dose caudal anesthesia.
Lumbar and thoracic epidural catheters can be placed in anesthetized children using the standard loss-of-resistance technique and either a midline or paramedian approach. In small children, caudal epidural catheters have been passed into a thoracic position with the tip localized radiographically.
Unilateral transversus abdominis plane (TAP) blocks are commonly used to provide analgesia after hernia repair. Bilateral TAP blocks can be used to provide effective postoperative analgesia after abdominal surgery with a lower midline incision. Rectus sheath blocks can be used for midline inci-sion in the upper abdomen.
Spinal anesthesia has been used in some cen-ters for infraumbilical procedures in neonates and infants. Infants and children typically have mini-mal hypotension from sympathectomy. Intravenous access can be established (conveniently in the foot) after the spinal anesthetic has been administered. This technique has become more widely used for neonates and infants as the potential neurotoxic-ity risks of general anesthesia in these patients have received greater attention.
Most children will not tolerate placement of nerve blocks or nerve block catheters while awake; however, most peripheral block techniques can be performed safely in anesthetized children. When the area of operation is the upper extremity we recom-mend those brachial plexus procedures that can most readily be performed using ultrasound guidance, specifically axillary, supraclavicular, and infracla-vicular blocks. We suggest that interscalene block be performed only by those having experience and skill with ultrasound guidance and only for procedures where other block techniques would be inferior (eg, upper shoulder procedures) due to the reported rare occurrence of accidental intramedullary injections when interscalene blocks were performed in anes-thetized adults. Single-shot and continuous femo-ral and sciatic blocks are easily performed using ultrasound guidance. The latter can be performed using either a gluteal or a popliteal approach.
A wide variety of other terminal nerve blocks (eg, digital nerve, median nerve, occipital nerve, etc) are easily performed to reduce postoperative pain in children.