Some current controversies in paediatric regional anaesthesia

Adjuvant Drugs for Peripheral Nerve Blocks: The Role of NMDA Antagonists, Neostigmine, Epinephrine, and Sodium Bicarbonate

The potential for misuse, overdose, and chronic use has led researchers to look for other methods to decrease opioid consumption in patients with acute and chronic pain states. The use of peripheral nerve blocks for surgery has gained increasing popularity as it minimizes peripheral pain signals from the nociceptors of local tissue sustaining trauma and inflammation from surgery. The individualization of peripheral nerve blocks using adjuvant drugs has the potential to improve patient outcomes and reduce chronic pain. The major limitations of peripheral nerve blocks are their limited duration of action and dose-dependent adverse effects. Adjuvant drugs for peripheral nerve blocks show increasing potential as a solution for postoperative and chronic pain with their synergistic effects to increase the duration of action and decrease the required dosage of local anesthetic. N-methyl-d-aspartate (NMDA) receptor antagonists are a viable option for patients with opioid resistance and neuropathic pain due to their affinity to the neurotransmitter glutamate, which is released when patients experience a noxious stimulus. Neostigmine is a cholinesterase inhibitor that exerts its effect by competitively binding at the active site of acetylcholinesterase, which prevents the hydrolysis of acetylcholine and subsequently retaining acetylcholine at the nerve terminal. Epinephrine, also known as adrenaline, can potentially be used as an adjuvant to accelerate and prolong analgesic effects in digital nerve blocks. The theorized role of sodium bicarbonate in local anesthetic preparations is to increase the pH of the anesthetic. The resulting alkaline solution enables the anesthetic to more readily exist in its un-ionized form, which more efficiently crosses lipid membranes of peripheral nerves. However, more research is needed to show the efficacy of these adjuvants for nerve block prolongation as studies have been either mixed or have small sample sizes.

Pediatric Ambulatory Continuous Peripheral Nerve Blocks

Despite the widespread use of ambulatory continuous peripheral nerve blocks in adults, its use in children has been sporadic. Indications for the use of ambulatory continuous peripheral nerve block in children involve orthopedic procedure, where significant pain is anticipated beyond 24 hours. Techniques to place the perineural catheters in children are similar to that used in adults. The incidence of serious side effects in pediatric ambulatory continuous peripheral nerve block is extremely rare. When this is combined with the potential to increase patient and family satisfaction and decrease opioid-related side effects, ambulatory continuous peripheral nerve block become a compelling choice.

A comparative study of dexmedetomidine and fentanyl as adjuvants to levobupivacaine for caudal analgesia in children undergoing lower limb orthopedic surgery

Background:

Levobupivacaine is an effective local anesthetic agent with less systemic toxicity than racemic bupivacaine, but it has short postoperative analgesic duration. Dexmedetomidine and fentanyl are promising adjuncts to provide excellent and prolonged postoperative caudal analgesia. This study compared the effects of caudal levobupivacaine plus dexmedetomidine and levobupivacaine plus fentanyl for postoperative analgesia and sedation in children undergoing lower limb orthopedic surgery.

Patients and Methods:

Ninety children, whose age ranged from 1 to 7 years, American Society of Anesthesiologists I-II, undergoing orthopedic lower limb surgery under general anesthesia received caudal block for postoperative analgesia. The children were randomly allocated into three groups: Group L (control) received 0.75 ml/kg levobupivacaine 0.25% diluted in saline; Group LD received 0.75 ml/kg levobupivacaine 0.25% with dexmedetomidine 1 μg/kg; and Group LF received 0.75 ml/kg levobupivacaine 0.25% with fentanyl 1 μg/kg. Following the administration of the drugs; hemodynamic variables, the total anesthesia time, sedation score, Face, Legs, Activity, Cry, Consolability score, duration of analgesia, and side effects were recorded.

Results:

Demographically, all the groups were comparable, both the baseline and the intraoperative hemodynamic profile were similar in all groups. The mean duration of analgesia and the mean sedation score in the Group LD were significantly greater as compared to both the other groups.

Conclusion:

Dexmedetomidine may be a better additive to levobupivacaine than fentanyl for caudal postoperative analgesia, arousable sedation with comparable hemodynamic and side effect profile in children.

Comparison of regional vs. systemic analgesia for post-thoracotomy care in infants

BACKGROUND

In infants, post-thoracotomy analgesia traditionally consists of systemic opiates, while regional techniques have gained more favor in recent years. We compare the two techniques for thoracotomy in infants.

METHODS

All consecutive patients below 6 months of age who underwent thoracotomy for congenital pulmonary malformations in the study period were retrospectively divided according to the chosen postoperative analgesia: Group S systemic opiates, Group R continuous regional (epidural or extrapleural paravertebral) block. We studied the following outcomes: need for NICU and mechanical ventilation, pain score, requirement for additional analgesics, heart rate 1 h postsurgery, time to pass first stool and to full feed, complications, and duration of hospitalization.

RESULTS

Forty consecutive patients were included, 19 in Group S and 21 in Group R. Median age at surgery was 89 days (40-110) and 90 days (46-117), respectively. Five of 19 patients in Group S vs none in Group R required postoperative intensive care (P = 0.017). Patients in Group R had significantly lower postoperative heart rate (145 [138-150] vs. 160 [152-169] b·min(-1) , P = 0.007), earlier passage of first stools (24 h [12-24] vs. 36 h [24-48] P = 0.004), and earlier time to full feed (36 h [24-48] vs. 84 h [60-120] P = 0.0001) than those in Group S. The only observed complication was one catheter dislocation.

CONCLUSION

In infants undergoing thoracotomy, loco-regional analgesia is effective and associated with a reduced intensity of postoperative care and earlier full feeding than systemic analgesia; it should therefore be considered a better option.

Neuraxial analgesia in neonates and infants: a review of clinical and preclinical strategies for the development of safety and efficacy data

Neuraxial drugs provide robust pain control, have the potential to improve outcomes, and are an important component of the perioperative care of children. Opioids or clonidine improves analgesia when added to perioperative epidural infusions; analgesia is significantly prolonged by the addition of clonidine, ketamine, neostigmine, or tramadol to single-shot caudal injections of local anesthetic; and neonatal intrathecal anesthesia/analgesia is increasing in some centers. However, it is difficult to determine the relative risk-benefit of different techniques and drugs without detailed and sensitive data related to analgesia requirements, side effects, and follow-up. Current data related to benefits and complications in neonates and infants are summarized, but variability in current neuraxial drug use reflects the relative lack of high-quality evidence. Recent preclinical reports of adverse effects of general anesthetics on the developing brain have increased awareness of the potential benefit of neuraxial anesthesia/analgesia to avoid or reduce general anesthetic dose requirements. However, the developing spinal cord is also vulnerable to drug-related toxicity, and although there are well-established preclinical models and criteria for assessing spinal cord toxicity in adult animals, until recently there had been no systematic evaluation during early life. Therefore, in the second half of this review, we present preclinical data evaluating age-dependent changes in the pharmacodynamic response to different spinal analgesics, and recent studies evaluating spinal toxicity in specific developmental models. Finally, we advocate use of neuraxial drugs with the widest demonstrable safety margin and suggest minimum standards for preclinical evaluation before adoption of new analgesics or preparations into routine clinical practice.

Regional anesthesia in children: the future

Pediatric regional anesthesia continues to evolve. Education and attention to anatomical detail remain key elements to successful outcomes. New techniques, some adapted from adult practice, provide analgesia for pediatric surgical procedures such cleft palate or congenital hip dysplasia. Despite technological advances a number of controversial issues remain unresolved.

Efficacy and adverse effects of ketamine as an additive for paediatric caudal anaesthesia: a quantitative systematic review of randomized controlled trials

BACKGROUND

The aim of this quantitative systematic review was to assess the efficacy and adverse effects of ketamine added to caudal local anaesthetics in comparison with local anaesthetics alone in children undergoing urological, lower abdominal, or lower limb surgery.

METHODS

The systematic search, data extraction, critical appraisal, and pooled data analysis were performed according to the PRISMA statement. All randomized controlled trials (RCTs) were included in this meta-analysis and relative risk (RR), mean difference (MD), and the corresponding 95% confidence intervals (CIs) were calculated using the Revman(®) statistical software for dichotomous and continuous outcomes.

RESULTS

Thirteen RCTs (published between 1991 and 2008) including 584 patients met the inclusion criteria. There was a significant longer time to first analgesic requirements in patients receiving ketamine in addition to a local anaesthetic compared with a local anaesthetic alone (MD: 5.60 h; 95% CI: 5.45-5.76; P<0.00001). There was a lower RR for the need of rescue analgesia in children receiving a caudal regional anaesthesia with ketamine in addition to local anaesthetics (RR: 0.71; 95% CI: 0.44-1.15; P=0.16).

CONCLUSIONS

Caudally administered ketamine, in addition to a local anaesthetic, provides prolonged postoperative analgesia with few adverse effects compared with local anaesthetics alone. There is a clear benefit of caudal ketamine, but the uncertainties about neurotoxicity relating to the dose of ketamine, single vs repeated doses and the child's age, still need to be clarified for use in clinical practice.

Pediatric regional anesthesia: what is the current safety record?

The use of regional anesthetics, whether as adjuncts, primary anesthetics or postoperative analgesia, is increasingly common in pediatric practice. Data on safety remain limited because of the paucity of very large-scale prospective studies that are necessary to detect low incidence events, although several studies either have been published or have reported preliminary results. This paper will review the data on complications and risk in pediatric regional anesthesia. Information currently available suggests that regional blockade, when performed properly, carries a very low risk of morbidity and mortality in appropriately selected infants and children.

Ultrasound-guided axillary plexus block in a child with dystrophic epidermolysis bullosa

We report the use of ultrasound-guided axillary brachial plexus block in a child with dystrophic epidermolysis bullosa needing surgical treatment of the right hand. The regional anaesthesia was used in association with sedation/ anaesthesia. This technique is suitable for these difficult patients because it can minimise the risk of new bullae formation due to palpation of landmarks or unintentional intra- or subcutaneous injections. Initial anaesthesia/sedation was provided with sevoflurane until intravenous access was obtained, following which intravenous propofol infusion with ketamine boluses without any invasive airway management was continued for performance of the block and the procedure. This management plan provided good surgical conditions, early postoperative analgesia, minimised stress for the patient and avoided the need to manipulate the airway with instruments and the associated risk of mucosal bullae. The classification and breadth of clinical manifestation of epidermolysis bullosa is complex and briefly summarised. The anaesthetist should clarify the details of a particular patient's form of epidermolysis bullosa, especially in terms of mucosal involvement, as this may greatly influence planning for a procedure.

Validation of a preclinical spinal safety model: effects of intrathecal morphine in the neonatal rat

BACKGROUND

Preclinical studies demonstrate increased neuroapoptosis after general anesthesia in early life. Neuraxial techniques may minimize potential risks, but there has been no systematic evaluation of spinal analgesic safety in developmental models. We aimed to validate a preclinical model for evaluating dose-dependent efficacy, spinal cord toxicity, and long-term function after intrathecal morphine in the neonatal rat.

METHODS

Lumbar intrathecal injections were performed in anesthetized rats aged postnatal day (P) 3, 10, and 21. The relationship between injectate volume and segmental spread was assessed postmortem and by in vivo imaging. To determine the antinociceptive dose, mechanical withdrawal thresholds were measured at baseline and 30 min after intrathecal morphine. To evaluate toxicity, doses up to the maximum tolerated were administered, and spinal cord histopathology, apoptosis, and glial response were evaluated 1 and 7 days after P3 or P21 injection. Sensory thresholds and gait analysis were evaluated at P35.

RESULTS

Intrathecal injection can be reliably performed at all postnatal ages and injectate volume influences segmental spread. Intrathecal morphine produced spinally mediated analgesia at all ages with lower dose requirements in younger pups. High-dose intrathecal morphine did not produce signs of spinal cord toxicity or alter long-term function.

CONCLUSIONS

The therapeutic ratio for intrathecal morphine (toxic dose/antinociceptive dose) was at least 300 at P3 and at least 20 at P21 (latter doses limited by side effects). These data provide relative efficacy and safety for comparison with other analgesic preparations and contribute supporting evidence for the validity of this preclinical neonatal safety model.

Postoperative analgesia for the surgical correction of congenital clubfoot: comparison between peripheral nerve block and caudal epidural block

BACKGROUND AND OBJECTIVES

Correction of congenital clubfoot (CCF) is associated with severe postoperative pain. Caudal epidural block associated with general anesthesia is the anesthetic technique used more often in children, but it is limited by the short duration of the postoperative analgesia. Peripheral nerve blocks are associated with a low incidence of complications and prolonged analgesia. The objective of this study was to compare the duration of analgesia in peripheral nerve blocks and caudal block, as well as morphine consumption in the first 24 hours after correction of CCF in children.

METHODS

This is a randomized, double-blind study with children undergoing surgeries for posteromedial release of CCF, who were divided in four groups according to the anesthetic technique: caudal (ACa), sciatic and femoral block (IF), sciatic and saphenous block (IS), and sciatic block and local anesthesia (IL), associated with general anesthesia. In the first 24 hours, patients received oral dypirone and acetaminophen, and they were evaluated by anesthesiologists who were unaware of the technique used. Oral morphine (0.19 mg x kg(1) per day) was administered according to the scores of the CHIPPS (Children's and infants' postoperative pain scale) scale.

RESULTS

One hundred and eighteen children separated into four groups: ACa (30), IF (32), IS (28), and IL (28) participated in this study. The mean time between the blockade and the first dose of morphine was 6.16 hours in group ACa, 7.05 hours in group IF, 7.58 in IS, and 8.18 hours in IL. Morphine consumption was 0.3 mg.kg-1 per day in all four groups. Significant differences were not observed among the groups.

CONCLUSIONS

peripheral nerve blocks did not promote longer lasting analgesia or a decrease in morphine consumption in the first 24 hours in children undergoing CCF correction when compared to caudal epidural block.

Compartment Syndrome and Patient-Controlled Analgesia in Children – Analgesic Complication or Early Warning System?

We present two cases of children who developed compartment syndrome after upper limb fractures. Morphine patient-controlled analgesia was used in a bolus-only mode for analgesia (bolus 20 μg/kg, five minute lockout and hourly limit of 150 μg/kg). An increase in patient-controlled analgesia use was observed up to 12 hours before the decision was made to proceed to fasciotomy but neither child exceeded the hourly limit or had an excessive increase in pain scores. Clinical risk factors for compartment syndrome should be identified and appropriate monitoring instituted. A subtle increase in patient-controlled analgesia use may be an early indicator of impending compartment syndrome before classical signs such as reporting of pain, pallor, paraesthesiae, paralysis and pulselessness develop. These cases and review of the literature suggest techniques which may assist earlier diagnosis of compartment syndrome include setting a more conservative hourly limit of morphine patient-controlled analgesia such as 80 to 100 μg/kg/hour and graphing of patient-controlled analgesia demands and boluses, pain scores at rest and pain scores with passive flexion and extension of digits. These practices could identify trends that pain or analgesia requirement is increasing leading to earlier diagnosis of compartment syndrome.

A randomised double blind trial of the effect of pre-emptive epidural ketamine on persistent pain after lower limb amputation

Persistent pain has been reported in up to 80% of patients after limb amputation. The mechanisms are not fully understood, but nerve injury during amputation is important, with evidence for the crucial involvement of the spinal N-methyl d-aspartate (NMDA) receptor in central changes. The study objective was to assess the effect of pre-emptively modulating sensory input with epidural ketamine (an NMDA antagonist) on post-amputation pain and sensory processing. The study recruited 53 patients undergoing lower limb amputation who received a combined intrathecal/epidural anaesthetic for surgery followed by a randomised epidural infusion (Group K received racemic ketamine and bupivacaine; Group S received saline and bupivacaine). Neither general anaesthesia nor opioids were used during the peri-operative period. Pain characteristics were assessed for 12 months. The primary endpoint was incidence and severity of post-amputation pain. Persistent pain at one year was much less in both groups than in comparable studies, with no significant difference between groups (Group K=21% (3/14) and 50% (7/14); and Group S=33% (5/15) and 40% (6/15) for stump and phantom pain, respectively). Post-operative analgesia was significantly better in Group K, with reduced stump sensitivity. The intrathecal/epidural technique used, with peri-operative sensory attenuation, may have reduced ongoing sensitisation, reducing the overall incidence of persistent pain. The improved short-term analgesia and reduced mechanical sensitivity in Group K may reflect acute effects of ketamine on central sensitisation. Longer term effects on mood were detected in Group K that requires further study.

Periduralanästhesie

In epidural anaesthesia, the anaesthetist injects one or more drugs into the epidural space bordering on the spinal dura mater to achieve a "central" and/or "neuraxial" block. It is one of the earliest techniques in anaesthesia, originally performed exclusively with local anaesthetic agents. Adding other drugs and combining epidural with general anaesthesia or adapting the technique to the needs of children has extended the list of indications. Continuous epidural analgesia is an important tool in postoperative pain management. More and more often, the increasing proportion of patients who have comorbidities or are permanently taking medication that modulates the clotting system demands that the anaesthesiologist balance the individual risks and benefits before inducing epidural anaesthesia.

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.