NYSORA - The New York School of Regional Anesthesia: Pediatric Epidural and Caudal Analgesia and Anesthesia in Children Pediatric Epidural and Caudal Analgesia and Anesthesia in Children ================================================================================ Solme Kim on 14/03/2009 20:04:00 Epidural analgesia has many beneficial effects in the pediatric patient population. In clinical practice, it is commonly used to augment general anesthesia and to manage postoperative pain. TABLE OF CONTENTS (click here to expand) *Epidural Blockade For Pediatric Surgery (General Aspects) *Introduction *Anatomical Considerations *Considerations For Choosing Local Anesthetic Solution For Epidural And Caudal Anesthesia And Analgesia *Selection Of Epidural Local Anesthetic Solutions *Adjuvants To Local Anesthetics Solutions *Complications Associated With Epidural And Caudal Analgesia *Epidural Block Technique *Introduction *Confirmation Of Proper Epidural Needle/Catheter Placement *Epidural ECG Technique *Continuous Caudal Epidural To Lumbar Or Thoracic Space *Lumbar Epidural Anesthesia *Thoracic Epidural Analgesia *Managing Epidural Infusions Postoperatively EPIDURAL BLOCKADE FOR PEDIATRIC SURGERY (GENERAL ASPECTS) INTRODUCTION Epidural analgesia has many beneficial effects in the pediatric patient population. In clinical practice, it is commonly used to augment general anesthesia and to manage postoperative pain. Effective postoperative pain relief from epidural analgesia has numerous benefits including earlier ambulation, rapid weaning from ventilators, reduced time spent in a catabolic state and lowered circulating stress hormone levels.1 Precise placement of epidural needles and catheters for single-shot and continuous epidural anesthesia ensures the dermatomes involved in the surgical procedure are selectively blocked, allowing for lower doses of local anesthetics and sparing of unnecessary blockade in the regions where blockade is not desired. 2-4. ANATOMICAL CONSIDERATIONS Significant anatomic differences in comparison with adults, should be considered while utilizing regional anesthesia in children. For instance, in neonates and infants, the conus medullaris is located lower in the spinal column (at approximately the L3 vertebra) compared to adults where it is situated at approximately the L1 vertebra. This dissimilarity is a result of different rates of growth between the spinal cord and the bony vertebral column in infants. However, at approximately 1 year of age the conus medullaris reaches similar L1 level as in an adult. The sacrum of children is also more narrow and flat compared to the adult population. At birth, the sacral plate, which is formed by five sacral vertebrae, is not completely ossified and continues to fuse until approximately 8 years of age. The incomplete fusion of the sacral vertebral arch forms the sacral hiatus. The caudal epidural space can be accessed easily in infants and children through the sacral hiatus. Due to the continuous development of the sacral canal roof, there is considerable variation in the sacral hiatus. In children, the sacral hiatus is located more cephalad compared to adults. Therefore, caution is warranted when placing caudal blocks in infants as the dura may end more caudad thereby increasing the risk of accidental dural puncture. It has also been suggested that the epidural fat is less densely packed in children than in adults.5 This loosely packed epidural fat may facilitate not only the spread of local anesthestic, but it may also allow the unimpeded advancement of epidural catheters from the caudal epidural space to the lumbar and thoracic level. Clinical Pearls * In the neonate the intercristal line bisects L5 (cf L4 or L3/4 interspace in the adult) and the spinal cord ends at L3 in first year of life (cf L1 in the adult). * As a general rule the epidural space will be found at 1 mm/kg of body weight, however, there is considerable individual variation. CONSIDERATIONS FOR CHOOSING LOCAL ANESTHETIC SOLUTION FOR EPIDURAL AND CAUDAL ANESTHESIA AND ANALGESIA Newer local anesthetics with favorable potencies, durations of effect and decreased toxicity profiles have been introduced in the past decade. Local anesthetic concentration and volume are important factors in determining the density and level of blockade. Since most pediatric patients receive epidural analgesia in conjunction with a general anesthetic, the main purpose of the epidural catheter is to deliver sufficient local anesthetic solution for effective intraoperative and postoperative analgesia. Knowledge of total drug dose is important to avoid local anesthetic toxicity, particularly in pediatric patients. Clinical Pearls * High concentrations of local anesthetics such as 0.5% bupivacaine or 0.5% ropivacaine are rarely used in pediatric population * Instead, larger volumes of more dilute local anesthetic are more commonly used to cover multiple dermatomes. A more detailed description of local anesthetics solutions, their characteristics and toxic potential has been described elsewhere in this text. As a general rule, however, high concentrations of local anesthetics such as 0.5% bupivacaine or 0.5% ropivacaine are seldom used in pediatric population particularly in the epidural space. Instead, larger volumes of more dilute local anesthetic are more commonly used to cover multiple dermatomes. Opioids prolong the duration of analgesia of local anesthetic, but have also been associated with unacceptable side effects, particularly in pediatric outpatients. Various non-opioid adjuncts like clonidine and alpha-2 agonist offer more favorable side effect profiles; however relatively little information is available regarding their use pediatric patients. SELECTION OF EPIDURAL LOCAL ANESTHETIC SOLUTIONS Clinical Pearls * In pediatric population, body weight is a better correlate than patient age in predicting spread of local anesthetic following a caudal block. * For caudal use, the optimum concentration of bupivacaine is 0.125-0.175%. * The maximal safe dose of bupivacaine is 2.5 mg/kg. to 4 mg/kg * For continuous epidural infusion, bupivacaine 0.2 mg/kg/h for neonates and 0.4 mg/kg/h for older children is often used. * For a single-shot caudal block, a bolus of 1 ml/kg of 0.2% ropivacaine is recommended. * A continuous infusion of 0.2 mg/kg/hr of 0.1% ropivacaine in infants and 0.4 mg/kg per hour in older children for 48 hrs, has been shown to be effective and safe regimen Bupivacaine and ropivacaine are the two most commonly used local anesthetics for neuraxial anesthesia in children. Lidocaine is not often used because of its short duration of action and excessive motor block. Body weight is usually a better correlate than patient age in predicting spread of local anesthetic following a caudal block.58 The maximal safe dose of bupivacaine is 2.5 mg/kg. to 4 mg/kg59 For caudal use, the optimum concentration of bupivacaine is 0.125-0.175%.60 Compared with the 0.25% preparation, this concentration provides a similar duration of postoperative analgesia (4 to 8 hours) but with less motor blockade.60 Some clinicians prefer administering doses on a volume per weight basis. A dose of 1.0 mL/kg of a dilute solution such as 0.125% bupivacaine to a maximum volume of 30 mL can reliably provide T10 sensory block without exceeding maximum levels recommended in the literature.6 Higher doses such as 1.25 mL/kg, or even 1.5 mL/kg, may be administered to provide a more cephalad block without the risk of local anesthetic toxicity.6 For continuous epidural infusion, a commonly accepted dosage guideline of bupivacaine is 0.2 mg/kg/h for neonates and 0.4 mg/kg/h for older children.7 Cumulative toxicity is a concern even at lower rates of local anesthetic solution infusions. 3 The alternate use of 2-chloroprocaine may be well tolerated by neonates.61 Newer local anesthetic agents include the levo-entiomers ropivacaine and levobupivacaine. Ropivacaine has a higher therapeutic index than the older local anesthetic bupivacaine.62-65 At low concentrations, ropivacaine may produce less motor block and comparable analgesia when compared to bupivacaine with decreased incidence of cardiac and central nervous system toxicity.6 Due to its possible vasoconstricting properties, ropivacaine may undergo slower systemic absorption than bupivacaine.66,67 This may have clinical implications when a prolonged local anesthetic infusion is used in children with impaired hepatic function.68 For a single-shot caudal block, a bolus of 1 ml/kg of 0.2% ropivacaine is recommended.69,70 An infusion of 0.2 mg/kg/hr of 0.1% ropivacaine in infants and 0.4 mg/kg per hour in older children lasting no longer than 48 hrs, has also been shown to be effective and safe.70 Levobupivacaine, the S (-)-isomer of bupivacaine, is less likely to cause myocardial depression and fatal arrhythmias and is also less toxic to the central nervous system than racemic bupivacaine. A dose of 0.8 ml/kg of 0.25% levobupivacine injected caudally provides analgesia in children having penile or groin surgery.71 For continuous epidural infusions, the dose for levobupivacaine is similar to racemic bupivacaine.7 ADJUVANTS TO LOCAL ANESTHETICS SOLUTIONS Adjuvants may be used to prolong the duration of blockade, particularly for single-shot caudal epidural blocks.72 Single-shot caudal block is mainly used for ambulatory surgery. The major problem associated with this technique is the limited duration of analgesia and unwanted motor blockade. Recent research has focused on trying to resolve these problems with the addition of various adjuvants. (i) Epinephrine: The most commonly used adjuvant for single-shot caudal anesthesia is epinephrine in a concentration of 1:200,000. Epinephrine has the added benefit of serving as a marker for an inadvertent intravascular injection. (ii) Opioids: Epidural opioids may enhance and prolong analgesia. However, opioid use in an ambulatory setting may not be advisable due to the potential for respiratory depression and other unfavorable side effects (e.g. nausea and vomiting, itching, urinary retention).59 As a result, the use of caudal epidural opioids in children should be restricted to special clinical situations.73-75 Fentanyl has been used with desirable effects for epidural analgesia in adults for a number of years. Whether there is benefit for fentanyl as an additive in children undergoing single-shot caudal blockade is still debated amongst clinicians.76,77 One study found an increased incidence of nausea and vomiting when fentanyl was added to the local anesthetic solution for a single-shot caudal block.77 A dose of 2 µg/kg of fentanyl for single-shot caudal anesthesia along with the standard local anesthetic solution has been recommended for more extensive or painful procedures or in patients who have a urinary catheter in the postoperative period. The addition of 1 µg/mL to 2 μg/mL of fentanyl to 0.1% bupivacaine for continuous epidural infusions has also been used with success in neonates and children in a well monitored inpatient setting.15 (iii) Clonidine: Clonidine, an alpha-2 agonist, acts by stimulating descending noradrenergic medullo-spinal pathways which inhibits the release of nociceptive neurotransmitters in the dorsal horn of the spinal cord. The addition of clonidine (1 to 5 µg/kg) can improve the analgesic effect of local anesthetics for single-shot caudal blockade as well as prolong its duration of action without the unwanted side effects of epidural opioids.78 For continuous epidural infusions clonidine 0.1 µg/kg/h has been used with good effect.79 It should be cautioned that higher doses have been associated with sedation and hemodynamic instability in the form of hypotension and bradycardia, and doses as low as 2 µg/kg have been associated with postoperative sedation.80 In addition, epidural clonidine blunts the ventilatory response to increasing levels of end-tidal carbon dioxide (PCO2). Although respiratory depression does not appear to be a common problem,81 apnea has been reported in a term neonate who received a caudal block consisting of 1 mL/kg of 0.2% ropivacaine with clonidine 2 µg/kg.82 Caution should be exercised while using clonidine in very young infants due to the sedation and hypotension that may ensue. (iv) Ketamine: The addition of ketamine or S-ketamine to single-shot caudal block prolongs the analgesic effect of local anesthetics. The min disadvantage of ketamine are its psychomimetic effects. However, at low doses ( 0.25-0.5 mg/kg), ketamine is effective without noticeable behavioral side effects.78 Ketamine 1 mg/kg can also be used as an effective caudal analgesic solely without the addition of local anesthetic solution.83,84 The combination of S(+)-ketamine (0.5- 1 mg/kg) and clonidine (1 or 2 µg/kg) has shown to provide effective analgesia after inguinal herniotomy in children with prolonged duration of effect (>20 hours) without any adverse CNS effects or motor impairment.84,85 However, the safety of ketamine for central neuraxial block has been questioned, particularly with the racemic formulations that contain preservatives. Results from a small clinical trial and case series indicate a single bolus administration of preservative-free S-ketamine appears to be safe and efective.7,59 Regardless, these reports lack statistical power and detailed postoperative evaluations to draw definitive conclusions regarding the safety of ketamine for neuraxial use. An additional concern regarding use of ketamine in neonates relate to a controversial series of animal studies that suggest ketamine can produce apoptotic neurodegeneration in the developing brain.86,87 Other infant animal studies have demonstrated that ketamine may have a neuroprotective effect.88,89 Nevertheless, many anesthesiologists are hesitant to introduce caudal S-ketamine into their routine clinical practice and it is unlikely ketamine will be widely adopted in countries where preservative-free formulas are not available. (v) Midazolam: Epidural midazolam (50 µg/kg), when used alone, produces postoperative analgesia without motor weakness or behavioral changes.78 This is due to its ability to inhibit GABA receptors in the spinal cord. When added to local anesthetic solutions, midazolam can prolong the duration of analgesia but this effect has not been consistently demonstrated.90 Similar to ketamine, the safety of midazolam for neuraxial use has not been established and a preservative-free formulation is not universally available.59 (vi) Neostigmine: Neostigmine (2 µg/kg) alone produces postoperative analgesia by inhibiting the breakdown of acetylcholine at muscarinic receptors in the dorsal horn.1 When combined with bupivacaine, a significant synergistic effect is observed. The addition of neostigmine (2 μg/kg) to 0.25% bupivacaine prolongs the duration of analgesia from 5 to 20 hours after hypospadias repair.1,91 However, it is associated with an unacceptably high incidence of vomiting (20-30%).91 This will likely preclude its use particularly in an ambulatory setting. Preservative–free neostigmine has not been widely available and has limited applications in pediatric regional anesthesia. COMPLICATIONS ASSOCIATED WITH EPIDURIAL AND CAUDAL ANALGESIA Neurologic Injury Major complications from either single-shot or continuous epidural blocks are rare if proper technique is employed.33,34 A large prospective study, which summarized data from over 15,000 central blocks in children, reported no incidence of permanent neurologic injuries and concluded that the incidence of complications is rare.92 However, three infant deaths and two other incidences of paraplegia and quadriplegia were reported in another large retrospective report published in 1995 with over 24,000 epidural blocks in children.93 This study also reported two cases of transient paraesthesia.93 Although the overall risk seems very low, devastating complications from direct damage to the spinal cord can occur during direct thoracic and high lumbar epidural needle placement. Since the placement of epidural needles/catheters are usually performed under sedation or general anesthesia, the fact that unconscious patients are unable to report pain or paresthesias (the currently accepted warning sign of needle encroachment on the spinal cord) raises concern.43,48-50 Recently, a case report described a spinal cord injury after placing single shot thoracic epidural under general anesthesia for appendectomy.52 This case reports highlights the need for clinicians to routinely assess risk/benefit ratio of placing direct thoracic epidurals for less extensive surgery. Thoracic and high lumbar epidural catheter placement in particular should be limited to extensive thoracic and abdominal procedures and should be performed by anesthesiologists with experience in thoracic epidural placement. Before using a direct thoracic approach in patients less than 2 years old, some prefer to make an attempt in threading the epidural catheter from the lumbar or caudal space with a proper epidural confirmation technique. Epidural Hematoma Epidural hematoma associated with epidural analgesia is extremely rare. This may be because anticoagulation protocols are rarely indicated during the perioperative period in pediatric patients. Nonetheless, epidural analgesia should be avoided in patients with clinically significant coagulopathy or thrombocytopenia. The guidelines for use of epidural anesthesia in anticoagulated adult patients should probably also be applied in pediatric patients. Infection Compared to lumbar epidural catheters, there is some concern regarding catheter infection with the prolonged use of caudally placed catheters due to the proximity of the sacral hiatus to the rectum. Although studies have not found clinical evidence of higher infection rates with the caudal approach, bacterial colonization has been reported as higher. Staphylococcus epidermidis is the predominant microorganism colonized on the skin and catheters of lumbar and caudal epidurals.94 Gram-negative bacteria has also been demonstrated on the tips of the caudal catheter. 94 While the overall infection rate associated with caudal epidural catheters appears to be quite low, there have been isolated case reports of infection related to epidural catheters in children. Even with widely used single-shot caudal blocks, infection such as sacral osteomyelitis can still occur.95 Perforation of the rectum may occur if the caudal needle is angled too steeply.96 To reduce the risk of contamination by stool and urine techniques such as catheter tunneling or fixing the catheter with occlusive dressing in a cephalad direction can be used.15,97 A strict aseptic technique including the use of a sterile closed infusion system should also be employed and care should be taken to avoid local tissue trauma. Daily inspection of the dressing and entry site are also important. Dural Puncture And Post-dural Headache Dural puncture during caudal epidural analgesia is uncommon if caution is taken to avoid advancing the needle too far into the sacral canal. Treatment for post-dural puncture headache (PDPH) include bed rest, oral or intravenous hydration, simple analgesia such as regular acetaminophen, non-steroidal anti-inflammatory agents, and anti-emetics. Bed rest, although relieving the severity of the headache, has no effect on the incidence or duration of PDPH. Hydration should be maintained in order to continue CSF production and to avoid dehydration which may alleviate symptoms. Simple analgesics can be all that is required until there is spontaneous resolution of symptoms. In adults, caffeine has been used for both prophylaxis and treatment for PDPH. Caffeine causes cerebral vasoconstriction by blocking adenosine receptors, which dilate vessels when activated. Reducing cerebral blood flow decreases the amount of blood in the brain and may lessen the traction on pain sensitive intracranial structures, relieving PDPH.98 Caffeine is not frequently used in children for relief of PDPH and an optimal dose is not known. Side effects are usually mild and may include nausea, insomnia, restlessness and lightheadedness. The use of epidural blood patch (EPB) to treat PDPH has been used with success in adults since 1960.99 There are now many reports of its successful use in children as well.99 EPB is thought to be effective through the formation of a gelatinous cover over the dural hole by the injected blood. In the short term, EPB seals the hole and relieves CSF hypotension both by mass effect from CSF cranial displacement and by increasing the intracranial volume and pressure.100 Actual healing takes place over the longer term. In children it is recommended that approximately 0.3 mL/kg is injected , in the awake or mildly sedated patient if possible, in order to detect the appearance of radicular symptoms. Hemodynamic Effects And Total Spinal Anesthesia Significant changes in blood pressure are uncommon in pediatric patients after the proper administration epidural analgesia. A high sympathetic single-shot caudal block to T6 had no significant changes in heart rate, cardiac index and blood pressure in children.101,102 Even when thoracic epidural block is combined with general anesthesia, cardiovascular stability is usually maintained in otherwise healthy pediatric patients. Hypotension should prompt anesthesiologists to immediately rule out a total spinal and/or intravascular injection leading to local anesthetic toxicity. Once these complications are ruled out, other causes such as hydration status, intravascular filling pressure, inotropic state, and the depth of anesthesia should be assessed. If a total spinal occurs, supportive measures have to provided until the effect of the block have dissipated. However, in the event of life-threatening extensions of total spinals and if attempted supportive measures are neither effective nor an option, cerebrospinal lavage can be considered as a last maneuver. A recent case report, suggested that 20 mL to 30 mL of CSF can be withdrawn and replaced with 30 to 40 ml of preservative-free normal saline, Ringer’s lactate or Plasma-lyte via the epidural catheter.103 It is believed this intervention may possibly shorten the recovery times, minimize potential neurotoxic insult and reduce the incidence of postdural puncture. In light of the limited experiences and information on cerebrospinal lavage, the potential risks and benefits should be evaluated on a case-by-case basis before using this technique. Local Anesthetic Toxicity Local anesthetic toxicity often stems from accidental intravascular injection into epidural blood vessels. This complication can often be avoided by using careful aspiration and test dosing, Table 1. Table 1: Test-Dosing for Epidural Blockade Recomendations *Use test dosing routinely, even while recognizing that test dosing with all available agents is not 100% sensitive. In addition, because the true incidence of intravascular placement is relatively low, most of the positive tests (heart rate increases) will be false positives. When there is a borderline response, repeating the test dose may increase the specificity and sensitivity. *Continuously monitor the ECG and cycle the blood pressure cuff repeatedly. With epinephrine-containing solutions, if the heart rate does not increase, an increase in blood pressure should also raise suspicion of intravascular placement. *Avoid performing test dosing when the child is in a very light plane of anesthesia or when there is stimulation (e.g. repositioning the patient on the operating table, instrumentation of the airway, incision, etc.). Performing the test dose under these conditions increases the likelihood of false-positive, stimulation-induced increases in heart rate or blood pressure. *Following the test dose, the remainder of the full dose should be administered incrementally. Incremental dosing and continuous monitoring helps increase the odds that intravascular placement will be detected and further injection will be halted before full cardio-depressant doses are administered. For single shot caudal, this is more likely to occur when needles are advanced too far into the caudal canal or when sharp-tipped needles are used.104 For continuous epidural infusion, neonates and very young infants are at greater risk for local anesthetic toxicity.3 Seizures have been reported in children receiving continuous infusions of local anesthetics.2,105 This can be avoided by using dilute solutions of local anesthetics (≤ 0.125% bupivacaine) and by following current dosing recommendations (see local anesthetic section).106 More importantly, vigilant monitoring during the administration of epidural analgesia should be priority. Other Adverse Effects In a retrospective review based on a prospective collected data from 286 pediatric patients; pruritus (26.1%), nausea and vomiting (16.9%), and urinary retention (20.8%) were the most common side effects encountered during epidural anesthesia using an infusion of bupivacaine and fentanyl infusion.15 Sedation and excessive block each occurred in less than 2% of patients. The incidence of respiratory depression was 4.2%, but the administration of naloxone, for severe respiratory depression, was never necessary. Table 2 summarizes the recommended treatment for the common adverse effects. Table 2: Side-effects of epidural analgesia and suggested treatment A. Itching * Exclude and/or fix other remediable causes * Low-dose naloxone infusions or partial agonist-antagonists (nalbuphine) are both more effective and less sedating than antihistamines * If itching persists despite naloxone or nalbuphine, consider substituting clonidine for opioid in the epidural infusion. B. Nausea * Exclude and/or fix other remediable causes * 5-HT antagonists, e.g. ondansetron, dolasetron * Low-dose naloxone infusions or nalbuphine * Substitute clonidine for opioids in epidural infusion C. Ileus and bowel dysfunction * Exclude and/or fix other remediable causes * Laxatives, if not otherwise contraindicated * Substitute clonidine for opioids in epidural infusion * Low-dose naloxone infusions or nalbuphine * Peripherally or enterally-constrained opioid antagonists, including methylnaltrexone or alvimopan (investigational) D. Sedation or hypoventilation Exclude and/or fix other remediable causes * Depending on severity, reduce or hold dosing of opioids or clonidine * Awaken, stimulate, encourage deep breathing * If severe, consider naloxone or assisted ventilation as needed E. Urinary retention * Exclude and/or fix other remediable causes * Avoid use of anticholinergics or antihistaminics if alternatives are available * Low-dose naloxone infusions or nalbuphine * Bladder catheterization * Selective alpha-1a antagonists such as Flomax * Substitute clonidine for opioids in the epidural infusion EPIDURAL BLOCK TECHNIQUE INTRODUCTION Epidural analgesia can be delivered via a single-shot or a continuous infusion technique. These needles and catheter can be inserted at the caudal, lumbar or thoracic level. Aspiration tests and test doses indicate possible inadvertent intravascular or intrathecal needle/catheter placement. Other new advances in the field of epidural analgesia have focused on accurately positioning continuous epidural catheters. Epidural stimulation, epidural ECG and ultrasound techniques have been developed in addition to conventional x-ray imaging to assist with accurate epidural needle/catheter placement. CONFIRMATION OF PROPER EPIDURAL NEEDLE/CATHETER PLACEMENT Aspiration/test Dose An aspiration test performed prior to local anesthetic injection is used to avoid a total spinal and intravascular injection. However, a negative aspiration of blood or cerebrospinal fluid (CSF) should not be considered as an absolute indicator of proper needle and catheter placement.6 The specificity of ECG changes, (i.e. >25% increase in T wave) following the injection of an epinephrine test dose (0.5 µg/kg), on the other hand, can help predict intravascular injection.7,8 When used, the ECG should be continuously monitored while injecting local anesthetic via the caudal space, Table 3. Table 3: Electrical stimulation test Catheter Location Motor Response Current Subcutaneous None >10 mA Subdural Bilateral (many segments) < 1 mA Subarachnoid Unilateral or Bilateral < 1 mA Epidural space Against Nerve Root Unilateral < 1 mA Nonintravascular Unilateral or Bilateral 1-10 mA (threshold current increase after local anesthetic injected) Intravascular Unilateral or Bilateral 1-10 mA (no change in threshold current after local anesthetic injected) Radiographic Methods X-ray imaging in conjunction with a contrasting agent precisely identifies the tip of the catheter at a specific spinal level.9 However, without contrast, a radiograph will not be able to distinguish inadvertent intrathecal or subdural catheter placement from proper epidural placement. In addition, standard x-ray does not allow the anesthesiologist to adjust the position of the catheter during insertion unless fluoroscopy is utilized. While fluoroscopy permits the real-time monitoring and adjustment of advancing catheters, it requires additional set-up, incurs increased expense, and increases a patient’s exposure to ionizing radiation. As a result, fluoroscopy is not routinely used and is usually limited to difficult and/or special circumstances such as long-term epidural catheter placement for cancer pain. Ultrasound-guided Techniques Ultrasound allows the real-time visualization of anatomical structures and offers the potential to guide epidural needle and catheter placement. Ultrasound can be beneficial for guiding peripheral nerve block placement in both in adult patients,10,11 and in children. Although the images produced by ultrasound can be used to guide caudal needle placement, they may be of limited value in older children.12,13 Calcification of the posterior vertebral bodies in children greater than 6 months prevents reliable imaging of `the spinal cord.13 At the present time, ultrasound guidance can be helpful for caudal and epidural blocks only in infants and small children, as the sacrum and vertebrae are not fully ossified. Epidural Stimulation Test Recently, the use of low current electrical stimulation has been suggested to monitor and guide the position of the of the epidural catheter during insertion.14,15 The epidural stimulation test (Table 3) can be used confirms epidural catheter placement through stimulation of the spinal nerve roots (not the spinal cord) with low electrical current conducted through normal saline in the epidural space via an electrically conducting catheter.14 Table 3: Confirmation of the Epidural Catheter Position Intraoperatively (while the patient is under general anesthesia) *Radiography with contrast *Electrical stimulation *ECG *Ultrasonography (infant) Postoperatively (while the patient is awake, whether or not they can give verbal responses) * Electrical stimulation * Radiography with contrast * Chloroprocaine test: Incremental dosing of chloroprocaine 3% solution to demonstrate analgesia (by self-report or behavioral measures as appropriate) and signs of segmental effect * lumbar catheter tip: at least partial sensory and motor blockade in both legs warming of the volar surface of the toes * lower thoracic catheter tip: reduced strength in hip flexion reduced abdominal skin reflexes some reduction in heart rate and blood pressure * upper thoracic catheter tip: some reduction in heart rate and blood pressure warming of the volar surface of the hands unilateral or bilateral Horner’s syndrome *Dosing is given in 4 increments at 60 second intervals according to body weight: 0-10 kg - 0.2 ml/kg increments (0.8 ml/kg total) 10-25 kg - 0.15 ml/kg increments (0.6 ml/kg total) 25-40 kg - 0.1 ml/kg increments (0.4 ml/kg total) > 40 kg - 0.075 ml/kg increments (0.3 ml/kg total, to a maximum of 20 mls) Figure 1. Epidural stimulation test: Equipment. The stimulating catheter set-up requires the cathode lead (black for block) of the nerve stimulator to be connected to the epidural catheter via an electrode adapter while the anode lead is connected to an electrode on patient’s skin as the grounding site The stimulating catheter set-up requires the cathode lead (black for block) of the nerve stimulator to be connected to the epidural catheter via an electrode adapter while the anode lead is connected to an electrode on patient’s skin as the grounding site, Figure 1. To avoid misinterpretation of the stimulation response (e.g. local muscle contraction may be confused with epidural stimulation), the ground electrode is placed on the lower extremity for thoracic epidurals and on the upper extremity for lumbar epidurals. Correct placement of the epidural catheter tip (1-2 cm from the nerve roots) is indicated by a motor response elicited with a current between 1-10 mA.14,16,17 A motor response observed with a significantly lower threshold current (