Thoracic epidural analgesia via the caudal approach in pediatric patients undergoing fundoplication using nerve stimulation guidance

Postoperative Apnea in a Neonate Following an Epidural Bolus Dose Through a High Thoracic Epidural Catheter

Regional anesthesia is being used more frequently in the practice of pediatric anesthesia including neonates and infants. While generally safe and effective, adverse effects may occur related to catheter placement or its subsequent use. We present the rare occurrence of high motor blockade with apnea following the administration of a bolus dose of the local anesthetic agent, 2-chloroprocaine, into the thoracic epidural catheter of a 4-week-old, 2.2-kg former premature neonate. The patient had an epidural catheter that had been threaded from the caudal space to the thoracic level to provide analgesia following an abdominal surgical procedure. Subsequent investigation with a standard chest radiograph revealed a higher than intended placement of the epidural catheter (T4 instead of T8-10) which resulted in a transient high motor blockade with apnea. The epidural infusion was discontinued and assisted ventilation was provided by bag-valve-mask ventilation. Immediately, the heart rate and oxygen saturation returned to baseline values, and within 5 min the patient became more active, spontaneous ventilation resumed, and a strong cry was noted. The epidural catheter was removed and the remainder of the postoperative course was unremarkable. Adverse effects of epidural anesthesia in neonates are discussed and options for identifying the correct placement of a thoracic epidural catheter are reviewed.

The Migration of Caudally Threaded Thoracic Epidural Catheters in Neonates and Infants

BACKGROUND

The migration of pediatric thoracic epidural catheters via a thoracic insertion site has been described. We assessed the migration of caudally threaded thoracic epidural catheters in neonates and infants at our institution.

METHODS

The anesthesia records and diagnostic imaging studies of neonates and infants who had caudal epidural catheters placed during a 26-month period at our hospital were analyzed. Imaging studies were reviewed for changes in epidural catheter tip position.

RESULTS

Eighty-five patients 1-325 days of age (median, 51 days; interquartile range, 39-78 days) and weights of 2.5-9.5 kg (median, 5 kg; interquartile range, 4.3-5.8 kg) met the study criteria. Fifty-four (64%) of the patients (95% CI, 52%-73%) experienced catheter migration of 1 or more vertebral levels (range, 3 levels caudad [outward] to 3 levels cephalad [inward]), and 23 (27%) of the patients (95% CI, 18%-38%) experienced catheter migration to the T4 level or higher. Migration of 2 or more vertebral levels occurred only in children who weighed <6 kg and were under 73 days of age.

CONCLUSIONS

Epidural catheter migration occurs commonly in neonates and infants. Postoperative imaging is crucial to confirm catheter tip location after epidural catheter placement, as failure to assess catheter migration might result in suboptimal analgesia or other undesirable outcomes.

Caudal epidural blocks in paediatric patients: a review and practical considerations

Caudal epidural blockade in children is one of the most widely administered techniques of regional anaesthesia. Recent clinical studies have answered major pharmacodynamic and pharmacokinetic questions, thus providing the scientific background for safe and effective blocks in daily clinical practice and demonstrating that patient selection can be expanded to range from extreme preterm births up to 50 kg of body weight. This narrative review discusses the main findings in the current literature with regard to patient selection (sub-umbilical vs mid-abdominal indications, contraindications, low-risk patients with spinal anomalies); anatomical considerations (access problems, age and body positioning, palpation for needle insertion); technical considerations (verification of needle position by ultrasound vs landmarks vs 'whoosh' or 'swoosh' testing); training and equipment requirements (learning curve, needle types, risk of tissue spreading); complications and safety (paediatric regional anaesthesia, caudal blocks); local anaesthetics (bupivacaine vs ropivacaine, risk of toxicity in children, management of toxic events); adjuvant drugs (clonidine, dexmedetomidine, opioids, ketamine); volume dosing (dermatomal reach, cranial rebound); caudally accessed lumbar or thoracic anaesthesia (contamination risk, verifying catheter placement); and postoperative pain. Caudal blocks are an efficient way to offer perioperative analgesia for painful sub-umbilical interventions. Performed on sedated children, they enable not only early ambulation, but also periprocedural haemodynamic stability and spontaneous breathing in patient groups at maximum risk of a difficult airway. These are important advantages over general anaesthesia, notably in preterm babies and in children with cardiopulmonary co-morbidities. Compared with other techniques of regional anaesthesia, a case for caudal blocks can still be made.

Prediction of Successful Epidural Catheter Placement by a ‘Cold Test’

We tested the hypothesis that the patients’ feeling of cold sensation down the back during epidural drug administration through the epidural catheter was a reliable predictor of correct epidural catheter placement. In a prospective study of 80 patients, an epidural catheter was placed in the lumbar epidural space. During epidural drug injection, patients were asked to report feeling of the cold sensation in their back by pressing a bell. After 15 minutes, the patients were assessed for cold sensation in the thoracic to sacral dermatomes bilaterally and the dermatomal block recorded. Of 80 patients, three had inadvertent dural puncture. Seventy-two of 77 patients reported feeling cold sensation in their back during local anaesthetic injection, and all had successful epidural blockade. Of the five patients who did not report any cold sensation, three had failed epidural block and two successful epidural block. There were no false positive results. Of three patients who had inadvertent dural puncture and had normal saline 5 ml injected through the Tuohy needle, none reported cold sensation. The perception of cold sensation in the back during epidural administration of a test dose and/or subsequent full dose of local anaesthetic is useful in predicting successful epidural catheter placement.

Neonatal pain management

The past 2-3 decades have seen dramatic changes in the approach to pain management in the neonate. These practices started with refuting previously held misconceptions regarding nociception in preterm infants. Although neonates were initially thought to have limited response to painful stimuli, it was demonstrated that the developmental immaturity of the central nervous system makes the neonate more likely to feel pain. It was further demonstrated that untreated pain can have long-lasting physiologic and neurodevelopmental consequences. These concerns have resulted in a significant emphasis on improving and optimizing the techniques of analgesia for neonates and infants. The following article will review techniques for pain assessment, prevention, and treatment in this population with a specific focus on acute pain related to medical and surgical conditions.

The use of ultrasound-guided regional anaesthetic techniques in neonates and young infants

Optimal pain therapy during the perioperative period or at the neonatal intensive care unit and subsequent reduced use of opioids and various sedative drugs is an important factor for patients care. The use of various regional anaesthetic techniques in experienced hands provides excellent pain relief and has the potency to reduce the requirement for perioperative mechanical ventilation. Most of regional anaesthesia techniques are applicable also in neonates and young infants and can be used in an effective and safe manner. Ultrasound guidance should be used for all regional anaesthetic techniques to increase efficacy and safety. The spectrum of indications for ultrasound-guided regional anaesthesia in babies and infants are surgery, selective pain therapy and sympathicolysis. This review reflects an expert-based description of the most recent developments in ultrasound-guided regional anaesthetic techniques in babies and infants.

Stimulating thoracic epidural placement via a lumbar approach causes significant spinal cord damage in a porcine model

BACKGROUND

Continuous thoracic epidural analgesia is a valuable and common technique for analgesia but involves risk to the spinal cord. There is significant pediatric experience safely placing thoracic epidurals via a caudal approach. The use of a stimulating catheter offers the advantage of real-time confirmation of appropriate catheter placement. We hypothesize that the tip of a stimulating epidural catheter can be reliably advanced to the thoracic epidural space with lumbar insertion in a porcine model.

METHODS

This prospective experimental porcine study evaluated the feasibility of placing the tip of a stimulating epidural catheter to a predefined thoracic epidural location after percutaneous lumbar epidural access in six live pigs. After the lumbar epidural space was accessed, a stimulating epidural catheter was advanced until the targeted thoracic myotome was stimulated. The final position of the catheter in relation to the targeted location was determined by fluoroscopy. All animals were euthanized at the end of the experiment, necropsy and spinal cord histology were then performed to assess the extent of spinal cord damage.

RESULTS

In all animals the epidural catheter tip could be accurately advanced to the targeted thoracic myotome. Gross subdural bleeding occurred in three of the six animals and deep spinal damage was observed in two of the six animals. In one animal, the catheter was placed in the subarachnoid space.

CONCLUSIONS

Accurate access to the thoracic epidural space is possible via a lumbar approach using a stimulating epidural catheter. Based on gross and histopathological examination, this technique resulted in frequent complications, including subdural hemorrhage, deep spinal cord damage, and subarachnoid catheter placement.

From the Journal archives: Epidural anesthesia in young children: what have we learned in the past 60 years?

Francis G. Ruston MD CITATION: Ruston FG. Epidural anaesthesia in infants and children. Can Anaesth Soc J 1954: 1: 37-44.

PURPOSE

The author describes the use of single-shot epidural anesthesia in a series of 44 infants and children. The patients were anesthetized in hospitals in Hamilton, Ontario from 1949 until the time of publication in 1954. The study aimed to describe the indications and efficacy of this technique as well as any apparent complications. A detailed description of the management of these patients was given, including many tips and suggestions that are still applicable in 2013.

PRINCIPAL FINDINGS

Seventy-seven infants and children received epidural anesthesia for a variety of procedures, particularly for pyloric stenosis. Forty-four of the procedures were carried out by the author. All patients survived, apart from one child who died of recurrent intestinal obstruction unrelated to the anesthetic. It was found, after some experience, that the sitting position was preferable for epidural needle insertion. Use of the hanging drop technique for identification of the epidural space proved to be simple and reliable. Surgical conditions were found to be excellent and relaxation was profound; however, some sedation was often required to obtain optimal conditions for surgery. The surgeons became sold on the technique and began to request an epidural on a regular basis.

CONCLUSIONS

Epidural anesthesia in infants and young children is effective for a variety of procedures below the diaphragm, even in moribund patients.

Perioperative management of classic bladder exstrophy

The exstrophy-epispadias complex is a rare congenital malformation of the genitourinary system, abdominal wall muscles, and pelvic structures. Modern surgical repairs focus on reconstruction of the bladder and its adjacent structures, with the goal of achieving urinary continence, a satisfactory cosmetic result, and a high quality of life. Complex surgery in neonates and young children, as well as a prolonged postoperative course require close collaboration between surgeons, anesthesiologists, intensivists, pediatricians, and an experienced nursing staff. This article will review the spectrum of bladder exstrophy anomalies, the surgical repair, and the perioperative interdisciplinary management.

Recent developments in paediatric neuraxial blocks

Paediatric anaesthesia and paediatric regional anaesthesia are intertwined. Almost all surgeries unless contradicted could be and should be supplemented with a regional block. The main objective of this review is to elaborate on the recent advances of the central neuraxial blocks, such as application of ultrasound guidance and electrical stimulation in the pursuit of safety and an objective end point. This review also takes account of the traditional technique and understand the benefits as well the risk of each as compared with the recent technique. The recent trends in choosing the most appropriate peripheral block for a given surgery thereby sparing the central neuroaxis is considered. A penile block for circumcision or a sciatic block for unilateral foot surgery, rather than caudal epidural would have a better risk benefit equation. Readers will find a special mention on the recent thoughts on continuous epidural analgesia in paediatrics, especially its rise and fall, yet its unique importance. Lastly, the issue of block placements under sedation or general anaesthesia with its implication in this special population is dealt with. We conducted searches in MEDLINE (PubMed) and assessed the relevance of the abstracts of citations identified from literature searches. The search was carried out in English, for last 10 years, with the following key words: Recent advances in paediatric regional anaesthesia; ultrasound guidance for central neuraxial blocks in children; role of electrical stimulation in neuraxial blocks in children; complications in neuraxial block. Full-text articles of potentially relevant abstracts were retrieved for further review.

Caudal blocks

Caudal anesthesia is the single most important pediatric regional anesthetic technique. The technique is relatively easy to learn (1), has a remarkable safety record (2), and can be used for a large variety of procedures. The technique has been reviewed in the English (3) and French (4) literature, as well as in German guidelines (5) and in pediatric anesthesia textbooks (6).

Drip infusion method as a useful indicator for identification of the epidural space

BACKGROUND

Cervical epidural anesthesia (CEA) is used for pain control and surgical procedures of the head and neck or upper arm areas. However, the failure rate of CEA is reported to be high, is the failure rate being quite higher than other sites, because of the anatomical differences of the cervical spine. We hypothesized that the loss of resistance (LOR) method combined with the drip infusion method for confirmation of the cervical epidural space can reduce the failure rate. This study investigated the usefulness of the drip infusion method.

METHODS

One hundred chronic renal failure patients undergoing arteriovenous bridge graft for hemodialysis at the upper arm under cervical epidural anesthesia were recruited for this study. In the cervical epidural puncture, we identified the cervical epidural space using a combination of the LOR method with the drip infusion method. After confirmation of the epidural space with LOR method, we decided it was the true epidural space when fluid dripping to the space was present. Otherwise, if fluid dripping was not present, we designated it was pseudo LOR, and we found the true epidural space using the drip infusion method only.

RESULTS

In all cases, the combined LOR with drip infusion method, identify the epidural space.

CONCLUSIONS

Combined LOR with drip infusion method is an efficacious method for the confirmation of the cervical epidural space.

A plantar flexion response to nerve stimulation indicates needle misplacement in the epidural/spinal space during psoas compartment block

We report two cases of plantar flexion due to epidural misplacement of the needle during psoas compartment block, providing a response feedback for needle position during this procedure. In one case, the response occurred contralaterally, and in the other bilaterally. In the first patient, the cause of contralateral plantar flexion could not be determined and no injection was made. In the second patient, the anteriorposterior-fluoroscopic image showed that the tip of the needle was placed at the midline of the column. At this point, 3 ml of radiopaque medium was injected, and it diffused throughout the epidural space. Subsequently, single-shot epidural anesthesia was achieved by injection through this needle.

An evaluation of the epidural catheter position by epidural nerve stimulation in conjunction with continuous epidural analgesia in adult surgical patients

BACKGROUND

The epidural stimulation test to confirm epidural catheter position has been described as being simple, fast, and reliable. We evaluated the feasibility of the epidural stimulation test and its potential in contributing to effective postoperative continuous epidural analgesia.

METHODS

Thirty adult patients (ASA I-III) undergoing major abdominal surgery or thoracotomy were to receive continuous epidural analgesia at a thoracic level postoperatively. The epidural stimulation test was performed after catheter placement, after local anesthetic boluses, and during epidural analgesia, up to six times in each patient. Catheter positions were verified by epidurography (before start of epidural analgesia and again on the second postoperative day).

RESULTS

Several technical issues (e.g., need to flush catheter with saline in order to maintain adequate stimulation during >25% of all measurements) and interpretation problems (e.g., interference of respiratory activity [n = 6]) made the implementation of the epidural stimulation test rather time consuming, both at the time of catheter placement and during epidural analgesia. Immediately after catheter placement (before test dose) the epidural stimulation test did not identify four of four catheters positioned outside the spinal canal. In addition, the initial epidural stimulation test indicated a possible intrathecal or paravertebral placement in 3 of 25 catheters correctly positioned in the epidural space. During 107 of 122 (88%) measurements with the catheter tip situated epidurally and with preceding or simultaneous administration of epidural local anesthetic, the epidural stimulation test elicited a motor response. Continuous epidural analgesia provided adequate pain relief in all 25 patients having positive epidurography.

CONCLUSIONS

The epidural stimulation test was often associated with technical difficulties and interpretation problems. The role of the repeated use of the epidural stimulation test for quality assurance in patients undergoing postoperative continuous epidural analgesia remains undetermined.

Cervical epidural analgesia via a thoracic approach using nerve-stimulation guidance in adult patients undergoing total shoulder replacement surgery

BACKGROUND

Continuous cervical epidural anesthesia can provide excellent peri- and post-operative analgesia, although several factors prevent its widespread use. Advancing catheters from thoracic levels to the cervical region may circumvent these barriers, provided they are accurately positioned. We hypothesize that guiding catheters from thoracic to cervical regions using low-current epidural stimulation will have a high success rate and enable excellent analgesia in adults undergoing total shoulder arthroplasty.

METHODS

After Institutional Review Board approval, adult patients were studied consecutively. A 17-G Tuohy needle was inserted into the thoracic epidural space using a right paramedian approach with loss of resistance. A 20-G styletted epidural catheter, with an attached nerve stimulator, was primed with saline and a 1-10 mA current was applied as it advanced in a cephalad direction towards the cervical spine. Muscle twitch responses were observed and post-operative X-ray confirmed final placement. After a test dose, an infusion (2-8 ml/h) of ropivacaine 2 mg/ml and morphine 0.05 mg/ml (or equivalent) was initiated. Verbal analog pain scale scores were collected over 72 h.

RESULTS

Cervical epidural anesthesia was performed on 10 patients. Average current required to elicit a motor response was 4.8 +/- 2.0mA. Post-operative X-ray of catheter positions confirmed all catheter tips reached the desired region (C4-7). The technical success rate for catheter placement was 100% and excellent pain control was achieved. Catheters were positioned two to the left, four to the right and four to the midline.

CONCLUSION

This epidural technique provided highly effective post-operative analgesia in a patient group that traditionally experiences severe post-operative pain and can benefit from early mobilization.

Innovative approaches to neuraxial blockade in children: the introduction of epidural nerve root stimulation and ultrasound guidance for epidural catheter placement

Continuous epidural blockade remains the cornerstone of pediatric regional anesthesia. However, the risk of catastrophic trauma to the spinal cord when inserting direct thoracic and high lumbar epidural needles in anesthetized or heavily sedated pediatric patients is a concern. To reduce this risk, research has focused on low lumbar or caudal blocks (ie, avoiding the spinal cord) and threading catheters from distal puncture sites in a cephalad direction. However, with conventional epidural techniques, including loss-of-resistance for localization of the needle, optimal catheter tip placement is difficult to assess because considerable distances are required during threading. Novel approaches include electrical epidural stimulation for physiological confirmation and segmental localization of epidural catheters, and ultrasound guidance for assessing related neuroanatomy and real-time observation of the needle puncture and, potentially, catheter advancement. The present article provides a brief and focused review of these two advances, and outlines recent clinical experiences relevant to pediatric epidural anesthesia.

Epidural anaesthesia and analgesia for surgery: still going strong?

PURPOSE OF REVIEW

The discussion on the value of epidural anaesthesia and analgesia for surgery is fuelled by current controversies regarding effects on postoperative morbidity and mortality, potential benefits for outcome and the fear of rare, but catastrophic neurological complications. This review of the most recent publications on the topic since April 2002 illustrates some of the aspects contributing to the ongoing discussion.

RECENT FINDINGS

In contradiction to previous meta-analyses, recent trials could not demonstrate significant improvements of overall morbidity or mortality by epidural anaesthesia and analgesia. However, the technique was shown again to provide superior analgesia and a reduction of perioperative stress response and respiratory complications. Analysis of the current literature strongly supports that epidural anaesthesia and analgesia remains a safe practice with a low rate of severe complications, in particular in paediatric surgery. Several developments in equipment, techniques and especially drugs have been reported, resulting in improved balanced anaesthesia and analgesia and contributing to the safety of this technique.

SUMMARY

In an era of evidence-based medicine, further meta-analyses and well-planned large randomized trials have to address the controversial issues of epidural anaesthesia and analgesia and postoperative outcome. In the context of a more holistic 'rehabilitative' management of the perioperative period, this technique might well represent a key factor to improve outcome, reduce hospital stay and thereby healthcare costs. Recent innovations and developments in techniques and drugs as well as established guidelines should further minimize potential errors and harmful complications.

Epidural catheter placement in children: comparing a novel approach using ultrasound guidance and a standard loss-of-resistance technique

BACKGROUND

We report a prospective, randomized study to evaluate ultrasound guidance for epidural catheter placement in children 0-6 yr of age.

METHODS

Epidural catheters were placed at lumbar or thoracic cord levels in 64 children undergoing major surgery, using either ultrasonography or loss-of-resistance (LOR) for guidance. Using a 5-10 MHz linear ultrasound probe, the neuraxial structures were identified, the skin-epidural depth and epidural space was measured, the advancing epidural catheter visualized, and the spread of local anaesthetic verifying catheter position was confirmed. Epidural placement procedures were analysed for bone contacts and speed of execution. Children under 6 months were analysed separately.

RESULTS

Epidural placement involved bone contacts in 17% of children in the ultrasound group and 71% of children in the LOR group (P<0.0001). Epidurals were executed more swiftly in the ultrasound group [162 (75) s vs 234 (138) s; P<0.01]. Children under 6 months revealed a 0.9 correlation between skin-epidural depth and body weight.

CONCLUSIONS

Ultrasonography is a useful aid to verify epidural placement of local anaesthetic agents and epidural catheters in children. Advantages include a reduction in bone contacts, faster epidural placement, direct visualization of neuraxial structures and the spread of local anaesthetic inside the epidural space. Ultrasound guidance requires additional training and good manual skills, and should only be used once experience in ultrasound-guided techniques of regional anaesthesia has been acquired.

Imaging techniques for regional nerve blockade and vascular cannulation in children

PURPOSE OF REVIEW

This review identifies the most serious complications likely to be encountered in the current practice of paediatric anaesthesia.

RECENT FINDINGS

The findings of the ASA Closed Claims Project, published in 1993, showed a higher proportion of closed paediatric malpractice claims related to respiratory events than to cardiovascular events. The Pediatric Perioperative Cardiac Arrest Registry--an offshoot of the American Society of Anesthesiologists Closed Claims Project--reviewed cardiac arrest data collected between 1994 and 1997, revealing a shift in the aetiology of cardiac arrest during paediatric anaesthesia over the past 20 years. The study found that reported cardiac arrests were now more prevalent from cardiovascular causes than respiratory causes, unlike the findings in the previous Closed Claims Project. Follow-up data collected by both the Pediatric Perioperative Cardiac Arrest Registry and the American Society of Anesthesiologists Closed Claims Project confirm this trend.

SUMMARY

Outcomes for paediatric patients undergoing anaesthesia have improved over the years as a result of advances in monitoring and equipment, safer and more easily titratable anaesthetic agents, and possibly the practice of subspecialization. Preventable complications still, however, occur. An awareness of frequently encountered complications during paediatric anaesthesia may lead to the earlier detection and treatment of perioperative problems, leading to better outcomes.

Anesthesia and analgesia during and after surgery in neonates

BACKGROUND

Historically, the use of anesthetics and analgesics in neonates and infants has been based on extrapolations from studies performed in adults and older children. Over the past 20 years, there has been a growing body of research on the clinical pharmacology and clinical outcomes of these agents in neonates and infants.

OBJECTIVE

This article summarizes clinical pharmacology and clinical outcomes studies of opioids, opioid antagonists, sedative-hypnotics, nonsteroidal anti-inflammatory drugs and acetaminophen, and local anesthetics in neonates and infants to highlight gaps in the available knowledge, review some concerns about study design, and identify drugs that should receive high priority for future study.

METHODS

Relevant studies were identified through a search of MEDLINE and a review of textbooks, conference proceedings, and abstracts. The available literature was subjected to expert committee-based review.

CONCLUSIONS

There is a growing body of information on analgesic and anesthetic pharmacokinetics, pharmacodynamics, and clinical outcomes in neonates and infants, permitting safe and effective use in some clinical settings. Major gaps in knowledge persist, however. Future research may involve a combination of clinical trials and preclinical studies in suitable infant animal surrogate models.

Thoracic epidural catheters via the caudal and lumbar approaches using styletted multiple port catheters in pediatric patients: a report of three cases

Advancing catheters from the lumbar and caudal epidural spaces to the thoracic level has been reported to be an alternative to the direct thoracic approach. However, as children grow, the threading of catheters in the epidural space becomes increasingly difficult. This report describes three cases of thoracic epidural placement using a multiport catheter threaded from the caudal and lumbar spaces using electrical stimulation guidance. In the first case, a multiport catheter was threaded 22 cm from the lumbar space to T8 following a failed attempt with a single-port catheter in a 9-year-old boy scheduled to undergo a right nephrectomy. In the second case, a multiport catheter was threaded 26 cm from the caudal space to T9 in a 3-year-old girl undergoing fundoplication. In the last case, a multiport catheter was inserted at the completion of a fundoplication in a 2-year-old girl after it had been confirmed that the single-port catheter inserted prior to surgery had not advanced to the desired thoracic level. The multiport catheter was threaded 17 cm without resistance from the caudal space to T9. In all cases, electrical stimulation was used to confirm the location of the catheter tip at the time of insertion. The position of the catheters was later confirmed by X-ray. The multiport catheter incorporates a stylet, which extends to a closed distal tip, within a catheter body that ejects fluid from three lateral holes in a direction perpendicular to the advancing catheter. These properties may facilitate the reliable advancement of catheters in the epidural space.

Pediatric acute pain management

Children are benefiting from the advances made in developmental neurobiology and analgesic pharmacology over the past few decades. Heightened public awareness and increased political pressure from external regulatory agencies are helping to maintain the momentum in improving pediatric pain management. As a result, methods of assessing and managing children's pain are being refined, and new modalities of pain relief are being explored. This review summarizes selected current topics in pediatric acute pain management, with the major emphasis on acute postoperative pain management.

Can continuous low current electrical stimulation distinguish insulated needle position in the epidural and intrathecal spaces in pediatric patients?

BACKGROUND

Muscle twitches elicited with electrical stimulation (6-17 mA) during epidural insertion indicate correct epidural needle placement while muscle twitches at a lower current (<1 mA) may indicate intrathecal needle placement. This study examined whether applying continuous electrical stimulation at 6 mA could indicate needle entry into the epidural space without inadvertently penetrating the intrathecal space.

METHODS

After institutional review board (IRB) approval, 10 pediatric patients scheduled for lumbar puncture were studied. Following sedation with propofol, an insulated 24-gauge Pajunck unipolar needle was inserted through an 18-gauge introducer needle placed at the L4-5 interspace. The needle was first connected to a nerve stimulator (6 mA) and advanced. At the first sign of muscle twitching, needle advancement was stopped and the threshold current for motor activity was determined. The current was then turned off, the stylet was removed and the needle checked for cerebrospinal fluid (CSF). If CSF was not present, the needle was advanced into the intrathecal space (as confirmed by the presence of CSF). Ten pediatric patients (ASA II or III) aged 7.8 +/- 4.3 years (2.8-16.0 years) were studied.

RESULTS

All patients had two distinguishable threshold currents as the needle advanced. The mean threshold current to elicit muscle twitch in the presumed epidural space was 3.84 +/- 0.99 mA. CSF was not present in any of the patients at this location. The mean threshold current in the intrathecal space was 0.77 +/- 0.32 mA. The average estimated distance from the first threshold location to the intrathecal space was 3 mm. All muscle twitches were at the L3-5 myotomes. Nine muscle twitches were unilateral and one was bilateral.

CONCLUSIONS

Monitoring with an insulated needle with electrical stimulation at 6 mA may prevent unintentional placement of epidural needles into the intrathecal space.

An In Vitro Comparison of the Electrical Conducting Properties of Multiport Versus Single-Port Epidural Catheters for the Epidural Stimulation Test

Effective conduction of electricity through a catheter is essential for the success of the epidural stimulation test. In this in vitro study we examined the electrical conductivity of single and multiport epidural catheters (with and without embedded metal elements) after being primed with normal saline. Seven different types of 19-gauge catheters (n = 5), either single-port or multiport catheters, with or without embedded metal elements, were studied. The proximal end of each epidural catheter was connected to the cathode of a nerve stimulator via an electrode adapter. The catheter, primed with normal saline, was placed at the bottom of a syringe filled with 5 different volumes of saline (1, 2, 3, 4 and 5 mL) and attached to an electrode adapter. The voltage of the peripheral nerve stimulator was measured using an oscilloscope. The electrical resistance between the proximal and distal end of the catheter was calculated using Ohm's Law. In catheters without metal elements the electrical resistances were too high to be measured. In catheters that had metal elements, the mean electrical resistances of the same catheter design (single-port or multiport) were similar. However, the electrical resistances of the multiport metal reinforced epidural catheters were significantly lower (P < 0.05) than the single-port metal coil reinforced epidural catheters. The volume of saline in the syringe had no impact on the measured electrical resistances. This study suggests that multiport metal reinforced epidural catheters have low electrical resistances and, thus, are a reasonable alternative to single-port catheters for transmitting sufficient current for performing the epidural stimulation test. On the other hand, epidural catheters without metal elements (single-port or multiport) are not suitable for performing the stimulation test.

The Electrical Properties of Epidural Catheters: What Are the Requirements for Nerve Stimulation Guidance?

We designed the present study to investigate the electrical resistance of commercially available epidural catheters and to search for products and procedures suitable for nerve stimulation-guided insertion. Four types of epidural catheters were evaluated: 2 nonwire-reinforced catheters (19-gauge and 20-gauge nylon) and 2 wire-reinforced catheters (19-gauge without stylet and 20-gauge with stylet). The resistance of a catheter was calculated from the voltage level proportional to the fixed resistance in series circuit. In case of physiologic saline, the resistance of nonreinforced catheters was more than 700 kOmega, whereas the wire-reinforced catheter was 14.4 +/- 0.20 kOmega without stylet and 10.1 +/- 0.42 kOmega with stylet. When the stylet was passed through a 20-gauge nylon catheter, the resistance decreased to 49.2 +/- 1.96 kOmega. When catheters were primed with 10% hypertonic saline, the resistance of both nonreinforced catheters decreased by one third compared with physiologic saline. The electrical resistance of the saline-filled epidural catheters significantly differed among products tested. We conclude that epidural catheterization that is guided by electrical stimulation should be performed only with catheters equipped with spiral stainless steel wire reinforcement or with a stainless steel stylet.

Thoracic epidural analgesia via the lumbar approach using nerve stimulation in a pediatric patient with Down syndrome

This case illustrates the threading of an epidural catheter with electrical stimulation guidance from the lumbar epidural space to the thoracic space in a pediatric patient. A 17-year-old boy with Down syndrome, weighing 48 kg, was scheduled to undergo a laparotomy for duodenal obstruction and gastrostomy tube insertion. Combined general and continuous epidural anesthesia was selected for his anesthetic. Following the induction of general anesthesia and tracheal intubation, a 17G Tuohy needle (Arrow International, Inc., Reading, PA) was inserted into the lumbar space (L3-4) using loss of resistance with air. A 20G styletted epidural catheter was then inserted and threaded cranially. As the catheter was advanced, a low electrical current (1-10mA) was applied to the catheter. Motor response was observed from the lower limb muscles to the upper abdominal muscles as the catheter advanced cranially. After 22 cm of the epidural catheter had been inserted, intercostal muscle movement (T9 - 10) was observed at 3.0 mA. Radiographical imaging later confirmed the catheter tip at T10. The patient awoke without distress and was discharged to the ward with subsequent good pain control from a continuous epidural infusion of bupivacaine 0.1% with 1 microg ml(-1) fentanyl at 4-6 ml(-1).

Threshold Current of an Insulated Needle in the Intrathecal Space in Pediatric Patients

A threshold current of <1 mA has been suggested to be sufficient to produce a motor response to electrical stimulation in the intrathecal space. We designed this study to determine the threshold current needed to elicit motor activity for an insulated needle in the intrathecal space. Twenty pediatric patients aged 7.3 +/- 3.9 yr scheduled for lumbar puncture were recruited. After sedation with propofol, patients were turned to the lateral position and an 18-gauge or 20-gauge introducer needle was placed at the L4-5 level through which an insulated 24-gauge Pajunck unipolar needle (with a Sprotte tip and stylet) was inserted. The needle was advanced into the intrathecal space as suggested by the presence of a "pop." At this point, a nerve stimulator was attached to the insulated needle and the current was gradually increased until motor activity was evident. The needle hub was checked for cerebrospinal fluid. If cerebrospinal fluid was not present, the needle was advanced further until cerebrospinal fluid was present. The threshold current was retested. The mean current in the intrathecal space required to elicit a motor response was 0.6 +/- 0.3 mA (range, 0.1-1 mA). In 19 patients, the twitches were observed at the L4-5 myotomes and 1 patient had twitches at L2. Twitches were observed unilaterally in 19 children and bilaterally in one child. This confirms the hypothesis that the threshold current in the intrathecal space is <1 mA and that it differs significantly from the threshold currents reported for electrical stimulation in the epidural space.

Inadvertent Extra-Epidural Catheter Placement in an Infant

We report the inadvertent passage of an epidural catheter threaded from the caudal space out of a lumbar intervertebral foramen and into the lower thoracic paravertebral space in an infant. We identified the errant catheter by radiography and removed it without sequelae.

Pain management for pediatric thoracic surgery

PURPOSE OF REVIEW

Pain management after thoracic surgery in children presents the challenge of providing adequate analgesia without excessive sedation, and maintaining adequate respiratory function in the face of compromise resulting from existing pathology, surgical trauma, single-lung ventilation and postoperative ventilation-perfusion abnormalities. In the pediatric population, pain assessment and reporting present additional challenges. The number and complexity of surgical procedures, including video-assisted thoracoscopic procedures, is increasing in the pediatric population. There is a need to explore pain management for these types of patients.

RECENT FINDINGS

There are effective and safe strategies whereby analgesia can be provided to this pediatric population. This review will outline the progress that has been made in this field, including the use of regional techniques. The routine use of caudal catheters in neonates and infants for thoracic surgical procedures and the use of electrical guidance of epidural catheters, the 'Tsui' technique, are reviewed.

SUMMARY

These techniques, applied within a comprehensive pain management strategy, can be extremely beneficial in the care of the pediatric thoracic patient.

Threshold Current for an Insulated Epidural Needle in Pediatric Patients

We designed this study to determine the threshold current for nerve stimulation of an insulated needle in the epidural space. The intended dermatome was identified using the bony landmarks of the spine. An 18-gauge insulated Tuohy needle was inserted perpendicularly to the skin and advanced until "loss of resistance" was felt. A nerve stimulator was then connected to the insulated needle. Twenty patients were studied using an insulated Tuohy needle and one patient was studied using a noninsulated Tuohy needle. Muscle twitch was elicited with a current of 11.1 +/- 3.1 mA (mean +/- sd) in all patients in which an insulated needle was used. Muscle twitches were within 2 myotomes of the intended level (based on bony landmarks). Muscle twitch was not elicited with a noninsulated needle. After catheter threading, positive stimulation tests were elicited via epidural catheters in all patients (4.9 +/- 2.3 mA). Postoperative radiograph confirmed all catheter placements within 2 myotomes of the muscle twitches. Electrical stimulation may be a useful adjuvant tool to loss of resistance for confirming proper thoracic epidural needle placement. The threshold current criteria for an insulated needle (6-17 mA) would be higher than the original Tsui test criteria described for an epidural catheter (1-10 mA) in the epidural space.

The threshold current in the intrathecal space to elicit motor response is lower and does not overlap that in the epidural space: a porcine model

PURPOSE

Using electrical epidural stimulation, a current of 1 to 10 mA is required to confirm the presence of the tip of an epidural catheter in the epidural space. The purpose of this study was to examine the hypothesis that the threshold current required to elicit a motor response in the intrathecal space is significantly lower than that in the epidural space in a porcine model.

METHODS

Four 20-kg pigs were used in this experiment. Eighteen gauge, insulated, Tuohy needles were advanced into the epidural space using the loss of resistance technique at five different spinal levels in each pig. When the epidural space was entered, an electrical current was applied to the needle and increased progressively until a motor response was elicited. The needle was then further advanced until cerebrospinal fluid (CSF) was observed or until the needle had been advanced a maximum of 1 cm. At this point, the current was reapplied and increased until motor activity was evident.

RESULTS

A total of 20 needles were inserted in four pigs. The current required to produce a motor response in the epidural space was 3.45 +/- 0.73 mA (mean +/- SD). The current required to produce a motor response in the intrathecal space (entry confirmed by the presence of CSF) was 0.38 +/- 0.19 mA (mean +/- SD). Two needles were advanced 1 cm without obtaining CSF but the current thresholds were similar to those obtained when CSF was evident (0.4 mA and 0.3 mA, respectively).

CONCLUSION

The threshold current of an insulated needle required to elicit a motor response in the intrathecal space, was significantly (P < 0.01) lower than that in the epidural space in a porcine model.

Inadvertent cervical epidural catheter placement via the caudal route using electrical stimulation

Inadvertent placement of an epidural catheter in the cervical region via the caudal route is described in an infant who underwent revision of a fundoplication. We attempted electrical stimulation (the Tsui test) via the epidural catheter to confirm correct placement and positioning of the catheter tip. In this case, the epidural catheter was inadvertently advanced to the cervical region, resulting in stimulation of the phrenic nerve. These diaphragmatic twitches were misinterpreted as chest wall twitches, and it was incorrectly assumed that the catheter was in the thoracic region. To avoid misinterpretation of the stimulation level, the catheter should be continuously stimulated while it is advanced. We also recommend that the catheter length be estimated before insertion (although doing so did not help in this case) and that the catheter position be radiographically confirmed after surgery.