Acta Anaesthesiol Scand 2014; 58: 1049–1060 Printed in Singapore. All rights reserved

© 2014 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd ACTA ANAESTHESIOLOGICA SCANDINAVICA

doi: 10.1111/aas.12372

Review Article

The use of ultrasound-guided regional anaesthetic techniques in neonates and young infants P. Marhofer1 and P.-A. Lönnqvist2,3

1 Department of Anaesthesia and Intensive Care Medicine, Medical University Vienna, Vienna, Austria, 2Section of Anaesthesiology and Intensive Care, Department of Physiology and Pharmacology, The Karolinska Institute, Stockholm, Sweden and 3Paediatric Anaesthesia, Intensive Care and ECMO Services, Karolinska University Hospital-Solna, Stockholm, Sweden

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

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ith continuing advances of modern medicine, a growing number of interventions are carried out in neonates, infants and premature babies. This puts increasing demands to provide adequate anaesthesia and analgesia to these young and often immature babies. Inadequate pain relief is not only inhumane; it is also associated with negative consequences both in the short- and long-term perspective.1–7 The issue of providing adequate anaesthesia and analgesia to premature babies, neonates and infants has become more complex due to two new insights. First, based on rodent and primate studies, exposure to most commonly used general anaesthetics during the period associated with the brain growth spurt results in enhanced programmed cell death (apoptosis) and is also associated with long-term cognitive and behavioural dysfunction.8–11 Anaesthetic drugs that are either N-Methyl-D-Aspartatantagonists or Gamma-aminobutyric acid-agonists appear to be associated with this risk.12–16 Although the published epidemiological studies report con-

Individual contribution of authors: Both authors have equally contributed to the design and practical performance of this review article

regional anaesthesia in babies and infants are surgery, selective pain therapy and sympathicolysis. This review reflects an expertbased description of the most recent developments in ultrasound-guided regional anaesthetic techniques in babies and infants. Accepted for publication 24 June 2014 © 2014 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd

flicting results regarding the long-term consequences of neonatal exposure to general anaesthesia in humans,17–19 it is still difficult to disregard the risks associated with early exposure to anaesthetic drugs. Second, although morphine administration was previously judged as a good option to provide neonatal analgesia and stress reduction, the liberal administration of morphine has recently been questioned. Albeit being able to produce effective analgesia, morphine is well known to cause various unwanted post-operative side effects even in babies (e.g. respiratory depression, gastrointestinal dysfunction and delayed feeding).20 Morphine administration has also been shown to prolong the need for ventilator support when administered to premature babies21 and morphine may negatively affect both innate and acquired immunity, a fact that may be especially harmful in a high-risk population such as premature babies.22,23 Finally, neonatal exposure to morphine has recently been implicated to cause negative long-term effects (e.g. reduced head circumference and body weight at 5 years of age as well as a negative impact on neurocognitive, behavioural and adaptive outcomes).24

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P. Marhofer and P.-A. Lönnqvist

Regional anaesthetic techniques have potentials to improve neonatal anaesthesia and pain relief. It is important to declare that significant controlled studies are lacking where regional anaesthesia shows fundamental advantages as compared with general anaesthesia in terms of neurotoxicity in the early childhood. As long as these complex studies are not available, a reduction of systemic drug exposure is only a promising concept. The present review summarises current knowledge regarding ultrasoundguided regional anaesthesia in this context and point to new and exciting options that may prove particularly helpful in small infants. Subsequently, this article should serve as theoretical background to implement ultrasound-guided regional anaesthesia in the daily clinical practice of anaesthesiologists working in the field of neonatal and young infant care.

General comments regarding regional anaesthesia in neonates and young infants Numerous publications attest to the excellent pain relief associated with different regional anaesthesia options even in neonates and small children. The use of regional anaesthesia provides high-quality analgesia resulting in a beneficial modification of the surgical stress response.25,26 The use of thoracic epidural analgesia has been shown to reduce the need for post-operative ventilation after oesophageal atresia and diaphragmatic hernia repair.27–29 Thus, neonatal regional anaesthesia appears to be associated with the same added values as in the adult population. After being convinced about the many advantages of regional anaesthesia in neonates and infants, it is imperative to address the issue of safety. Very large-scale prospective studies in children, including neonates and infants, have shown that the risks for side effects and complications are very low (1/1000) and that the incidence of long-term sequelae is minimal (1/10,000).30–32 Although safety aspects are of importance to all clinicians, there does not exist any rational reasons for abstaining from the use of regional anaesthesia in young children. Addressing complications in association with regional anaesthesia, it is of course important to realise that the most common complication is block failure. Albeit this problem being of a multifactorial nature, there are two main issues associated with the incidence of block failure. To visualise the performance of the block procedure by ultrasound guid-

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ance is a major breakthrough when it comes to reducing the risk of block failure. Second, a crucial issue is how to provide adequate training of anaesthesiologists to improve the care of these often very tiny infants. Excellent knowledge is not only required regarding nerve anatomy, the clinician also needs appropriate awareness concerning ultrasound anatomy of all relevant structures involved with each specific regional anaesthetic technique. It is also very important to find effective programmes that will allow individuals who have been adequately trained but only infrequently deal with this group of patients, to preserve and enhance manual skills.

Applicable regional anaesthetic techniques in neonates and young infants All regional anaesthetic techniques which are performed in adults can be also used in neonates and small infants (Table 1). Nevertheless, only welltrained anaesthesiologists should perform regional anaesthesia in neonates and young infants. Ultrasound in our hands has become a standard technique to facilitate regional anaesthesia in children and adults.33–35 This tool allowing visualisation of the relevant neuronal and adjacent anatomy has several advantages. The ultrasound appearance of neuronal structures has been extensively outlined in recent publications. Thus, ultrasound guidance has now become the ‘golden standard’ for a majority of regional techniques in paediatric anaesthesia, although some exceptions to this rule still does exists (e.g. penile block).36

Epidural anaesthesia Perioperative epidural anaesthesia offers convincing advantages in children. These advantages include haemodynamic stability, reduced need for post-operative ventilation, improved analgesia without opioid-related negative respiratory effects, improved bowel function and reduced surgical neurohumoral stress response levels. It has been shown that epidural lidocaine hastens the recovery of gastrointestinal motility in rats after bowel ischemia,37 which might be due to vasodilation caused by a sympathetic block. Thoracic and abdominal surgeries are the two main indications for continuous epidural anaesthesia in neonates and small babies. The use of epidural anaesthesia in cardiac surgery is described in a large retrospective observational study where 89% of children could be extubated in the operation

Ultrasound-guided regional anaesthesia Table 1 Indications and contraindications of applicable central and peripheral regional anaesthetic techniques in neonates and small infants. Regional anaesthetic technique

Indications

Contraindications

Side effects

Epidural anaesthesia

Abdominal and thoracic surgery

Bradycardia, hypotension

Caudal blockade Infraclavicular brachial plexus blockade Femoral nerve blockade

Infra-umbilical surgery Surgery of one upper extremity, sympatholysis Surgery in the sensory area of the femoral nerve Surgery in the sensory area of the sciatic nerve, sympatholysis Inguinal surgery

Haemodynamic and/or respiratory instability, maldeformations of the spine, severe sepsis with coagulopathy Severe coagulopathy None

None Pneumothorax

None

None

None

None

None

Intraperitoneal puncture Intraperitoneal puncture

Sciatic nerve blockade Ilioinguinal-iliohypogastric nerve blockade* Transversus abdominis plane block*

Abdominal surgery

None

*Only applicable in anaesthetised children.

room.38 A large variety of abdominal surgery (e.g. necrotising enterocolitis, volvulus, etc.) can benefit from an epidural anaesthesia to achieve the potential advantages.28 If the advantages of intraoperative epidural catheterisation can be transferred also to the neonatal intensive care unit remains an open question. Whenever the pathophysiological reason for a particular disease is associated with a decreased gastrointestinal blood flow, a sympathetic block may be useful to influence the severity of symptoms. A reliable method for performing the epidural catheterisation will increase the popularity of this technique. Bösenberg et al. were the first to describe the caudal approach by which the catheter is advanced cephalad to the desired dermatome level.39 Large case series have illustrated that the regular percutaneous loss-of-resistance technique can successfully be performed even in very low weight premature babies.28 Direct visualisation of the relevant neuraxial structures, the correct spread of local anaesthetic and the advancement of a catheter inside the epidural space to a particular vertebral level are advantageous when compared with a pure loss-of-resistance technique. Contrary to older children and adults, the ossification of the vertebrae is incomplete in newborns and infants,40 thereby allowing excellent ultrasound visualisation of the spinal canal. It is possible to perform epidural catheter placement under ultrasound guidance,41 representing a development that should further enhance the practicability, safety and popularity of the technique. However, ultrasound does not have the potency to avoid all complica-

tions. Rare cases of severe complications that cannot be excluded by ultrasound guidance have been described,42,43 but most complications such as infection or drug error can be avoided by careful management and strict protocols when using the epidural technique in neonatal patients. Neonatal epidural blockade can be used for most abdominal and thoracic surgical procedures but certain contraindications exist. Apart from malformations of the spine, severe haemodynamic or respiratory (when the neonate does not tolerate lateral positioning) compromise commonly exclude the use of the epidural technique. Uncontrolled sepsis is also a relative contraindication, especially if associated with thrombocytopenia or coagulation disorders. The coagulation issue deserves further elaboration. Normal values for various coagulation tests in neonates are different compared with adults.44,45 Thus, if not using the correct neonatal values, the baby may appear as having a potential coagulopathy when in fact the baby is in a state of hypercoagulability. An alternative way to address coagulation problems is to use thromboelastometry (e.g. ROTEM or Thromboelastometry) prior to neonatal epidural catheterisation, even though the experience regarding this diagnostic tool in neonates is still limited.46,47 Practical performance of epidural catheterisation. With the neonate in lateral decubitus position, the area around the puncture site is aseptically prepared and an initial ultrasound investigation to assess the visibility and the depth of the relevant neuraxial structures is performed. We use a high frequency linear

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P. Marhofer and P.-A. Lönnqvist Table 2 Relevant technical and pharmacological details for neonatal epidural catheterisation. Ultrasound equipment Epidural catheter equipment Initial volume of ropivacaine 0.2% Continuous infusion rate of ropivacaine

Fig. 1. Sterile preparation of a linear ultrasound probe (SaferSonicTM, Ybbs, Austria). The cover has an adhesive front side and no ultrasound jelly is required between the probe and the inner face of the cover.

Alternatively: Bolus administration of ropivacaine†

38 or 50 mm 15 MHz linear ultrasound probe 19-G Tuohy cannula with a 21-G epidural catheter, 20-G Tuohy cannula with a 23-G epidural catheter 0.5 ml kg/h (= 1–2 mg/kg) 0.4–0.5 ml kg/h ropivacaine 0.2%* (ropivacaine 0.1% can be considered after the 1st post-operative day) 0.6 ml/kg ropivacaine 0.1–0.2% two to three times per day

*The dose is higher than described in the literature which is in accordance to our clinical experience. †We prefer bolus administration of ropivacaine due to lower drug load and improved extent of block.

Fig. 2. Three-hand technique of ultrasound-guided epidural puncture. The ultrasound probe is in a longitudinal and paramedian position cranial to the puncture side. The puncture itself is performed with the loss-of-resistance technique.

ultrasound probe (38 or 50 mm active area) which should be draped in a sterile manner (Fig. 1). The optimal view to the epidural space is achieved by a longitudinal paramedian and slightly medially rotated ultrasound probe. The puncture technique itself is a combination of loss of resistance and ultrasound observation of the spread of local anaesthetic inside the epidural space. This technique requires three hands (Fig. 2). Table 2 illustrates the relevant technical and pharmacological aspects for epidural catheterisation of neonates and small infants. We recommend ropivacaine without additives based on previously described pharmacokinetic data.48 It is recommendable to perform the loss-ofresistance injection with local anaesthetic to avoid unintentional dilution of the subsequent ropivacaine dose. Alternatively, saline can be used for loss of

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resistance, but the dilution effect must be considered. The expansion of the epidural space after the initial epidural fluid administration is a prerequisite for introducing the catheter. The advancement of epidural catheters can be directly observed by ultrasound (Supporting Information Movie S1), allowing optimal placement of the individual catheter. If it is difficult to visualise the tip position, an injection of microbubbles of air within the administered local anaesthetic will act as contrast to determine the level of the catheter tip. Fixation of epidural catheters should be performed with steristrips (3M Austria GmbH, Vienna, Austria) and a Tegaderm dressing (3M Austria GmbH). Two management strategies of epidural catheters are possible, repeated bolus or continuous infusion of the local anaesthetic (Table 2). Although not yet verified, it can be assumed that intermittent bolus administration may be associated with more extensive and predictable sensory block.28 Alternatively, a continuous infusion of ropivacaine 0.1–0.2% can be used. In our practice, we exclusively use ropivacaine 0.2% (2 mg/ml). Dependent on the clinical symptoms, a reduction of ropivacaine concentration to 0.1% can be considered on the first post-operative day. Additive drugs such alpha-2-receptor agonists can be used to prolong the duration of blockade and theoretically to reduce the dose of local anaesthetic. We avoid co-administration of opioid drugs in epidural catheters due to possible side effects such as respiratory depression, urinary retention or itching.49

Ultrasound-guided regional anaesthesia

Bacterial culture data as well as pharmacokinetic data support the safety of keeping the epidural catheters for 48 h.50,51 However, we use the epidural catheter up to 5 days dependent on the clinical situation. Children under therapeutic or prophylactic anticoagulation therapy (e.g. heparinisation, prostaglandin therapy) require particular care regarding subsequent removal of the catheter, which may need an interdisciplinary decision. Caudal catheterisation. A caudal puncture is an alternative to a direct lumbar or thoracic epidural puncture approach as in infants an epidural catheter can be advanced to a thoracic level.39 A technique where the epidural space and the level of the tip of the catheter is identified via electrostimulation of the dorsal nerve roots was previously described.52 The caudal catheterisation technique is not unproblematic and a risk of uncontrolled extraspinal or cephalad catheter migration and infections exist.53,54 A higher incidence of bacterial colonisation of caudal catheters as compared with the lumbar route (20% vs. 4%, P < 0.02) is described.55 Even if bacterial colonisation of epidural catheters appear to be a local problem without systemic implications, we believe that epidural puncture should ideally be performed directly at the lumbar or thoracic level in order to improve the safety profile regarding bacterial colonisation of catheters and the risk of systemic infection. Single shot epidural anaesthesia and caudal blockade. Single shot epidural anaesthesia performed as caudal blockade represents the most commonly used paediatric block.31 We use single shot caudal blockade during neonatal surgery in cases of severe haemodynamic and/or respiratory impairment and coagulopathies. Caudal blockade can be performed faster than epidural catheterisation when lateral positioning is not well tolerated. Due to the distal puncture site, coagulopathies are not assessed as contraindication for single shot caudal blockade. Although caudal blockade can be easily performed only using a landmark-based technique, we recommend the regular use of ultrasound visualisation in all age and weight groups. The use of ultrasound guidance will not only allow observation of the spread of the local anaesthetic (Fig. 3, Supporting Information Movie S2) but will also alert the clinician to unintentional intravascular injection of the local anaesthetic (identified by no visible local anaesthetic in the caudal epidural space following

Fig. 3. Ultrasound observation of the spread of local anaesthetic (LA) during caudal blockade. The vertical arrow indicates the dura mater which moves in an anterior direction during injection of the LA, and the oblique arrow indicates the cranial border of LA. The entire depth of the image is 18 mm; right side = caudal.

Fig. 4. Longitudinal and paramedian position of the high frequency linear ultrasound probe slightly cranial the puncture side of caudal blockade.

initial injection). The optimal ultrasound image can be achieved with a high frequency linear transducer in a longitudinal and slightly paramedian position (Fig. 4). There is a discrepancy between the ultrasound observed cranial spread of local anaesthetic and the sensory level of block, which is mainly based on a secondary spread of local anaesthetic.56 Recent studies have identified an inverse relationship between age, weight and height and the number of segments covered by the local anaesthetic as assessed by ultrasound immediately following the injection.57,58 Thus, for a given volume, the block will reach slightly more cranial in smaller patient than in larger patients. For routine use in infraumbilical surgery, we recommend the use of 1.0 ml/kg ropivacaine 0.2%. For infraumbilical surgery, caudal blockade can be used in neonates and small infants with light

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P. Marhofer and P.-A. Lönnqvist Table 3 Relevant peripheral nerve block techniques in neonates and infants. Relevant anatomical structures and ultrasound character of neuronal structures Infraclavicular approach to the brachial plexus Hyperechoic appearance of all three fascicles of the brachial plexus, subclavian artery, pectoralis muscles, pleura Femoral nerve blockade Hyperechoic femoral nerve, femoral artery, deep layer of the inguinal ligament, iliopsoas muscle Sciatic nerve blockade Hyperechoic sciatic nerve, biceps femoral muscle, semitendinosus and semimembranosus muscles

Needle guidance technique

Estimated volume of ropivacaine 0.2%

In-plane or out-of-plane

0.5 ml/kg

In-plane or out-of-plane

0.5–0.6 ml/kg

In-plane or out-of-plane

0.5–0.8 ml/kg

All ultrasound-guided techniques should be performed with a high frequency (13–15 MHz) 25 mm ultrasound probe and a 24-G Facette Tip cannula and injection line.

sedation.59 The technique of caudal anaesthesia under light sedation is described in 90 former preterm born babies with a post-conceptional age of < 60 weeks at the time of surgery without the use of ultrasound with a success rate of 98%. Avoidance of general anaesthesia reduces post-operative respiratory problems and prolonged apnoea. The few side effects which are observed in this study were airway related and easy to handle. The same study group introduced the routine use of the observation of the correct spread of local anaesthetic via ultrasound for caudal blockade and the current clinical routine indicates a success rate of 100%. Technically, caudal blockade in neonates and small infants is easy to perform, and ultrasound investigation of the spread of local anaesthetic enables an optimal success rate. The sacral administration of EMLA cream (AstraZeneca, Karlebyhus, Sweden) 30 min prior puncture is useful to avoid a painful stimulus during caudal puncture. Single shot spinal anaesthesia. Spinal anaesthesia can be used for a large spectrum of surgical indications in neonatal and early infant surgery. The main drawback of this technique is the relatively short duration of surgical anaesthesia. Ultrasound does not facilitate spinal puncture as compared with conventional manual palpation to identify an optimal intervertebral level.60 Thus, in our own clinical practice, spinal anaesthesia is now replaced by caudal blockade.

Peripheral nerve block techniques Peripheral nerve block techniques include single nerve blocks and blockade of complex neuronal structures such as the brachial plexus and the lumbosacral plexus. In principle, all techniques which are described in adults can be used in small

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children. The number of indications in neonates and small infants is limited, but a recent case report describes the successful application of an axillary brachial plexus block in a neonate for the treatment of ischemia secondary to arterial access.61 Selective pain treatment or therapeutic sympathicolysis should be considered as possible indications for peripheral regional anaesthetic techniques even in neonates and infants. These techniques require adequate experience in paediatric and adult peripheral regional anaesthesia. Table 3 summarises the recommendations regarding peripheral nerve block techniques in neonates and small infants. Upper limb blockade techniques. Previous practice using administration of the local anaesthetic blindly around the axillary artery62–64 implied that all important nerves would blocked. This does not reflect modern concepts in regional anaesthesia, where nerve and anatomical structures should be visualised by ultrasound and small volumes of local anaesthetic are administered around the target nerves under direct visual control.65 Despite the popularity of axillary brachial plexus blockade both in adults and in children and descriptions of the practical performance in neonates, this upper limb block technique is problematic in neonates and small infants due to the extreme superficial location of the nerves in the axilla.64 We therefore recommend a more proximal approach to the brachial plexus.66 The supraclavicular approach can be problematic in small infants. The extreme superficial position of nerve structures (< 3 mm) prevents accurate placement of the focus even with high frequency ultrasound probes. In addition, exact ultrasound visualisation of structures which are directly located

Ultrasound-guided regional anaesthesia

Fig. 5. Cross-sectional view of the infraclavicular portion of the brachial plexus in a 3.5-kg infant. The three cords are located lateral to the subclavian artery (A) and indicated by vertical and horizontal arrows. The oblique arrow indicates the pleura. The inserted image indicates the probe position. The entire depth of the image is 18 mm; right side = medial.

below the skin is problematic due reverberation artefacts caused by the skin. The periclavicular portion of the brachial plexus can be clearly visualised by ultrasound in all age and weight groups. Due to a larger probe-nerve distance at the infraclavicular location, this approach may be considered the most advantageous in the smallest patient category. Based on this rationale, only the infraclavicular brachial plexus block will be described. With the arm in a neutral position, a high frequency 25 mm ultrasound probe should be used to visualise the brachial plexus. With an in- or out-ofplane needle guidance technique, the tip of a 24-G facette tip cannula is placed lateral to the subclavian artery where the fascicles of the brachial plexus are located. These can be clearly identified below the pectoralis muscles and above the cervical pleura as hyperechoic structures (Fig. 5). It is difficult to recommend volumes of local anaesthetics for this kind of blocks, but usually 0.5–0.8 ml ropivacaine 0.2% is adequate for a successful blockade (Table 3). Lower limb blockade techniques. Due to the fact that caudal blockade covers the vast majority of indications for the lower limb(s), the indications for selective peripheral blockade of the lumbosacral plexus in neonates and small infants are extremely rare. Indications for lower limb peripheral nerve block techniques include sympatholysis for treatment of ischaemia and all surgical indications for one lower extremity where femoral and sciatic nerve blockade

Fig. 6. Cross-sectional ultrasound view of the femoral nerve (indicated by the arrows) lateral to the femoral artery (A) and slightly distal to the inguinal ligament. The fascial layer above the femoral nerve represents the deep layer of the inguinal ligament (iliopectineal arch). The entire depth of the image is 19 mm; left side = medial.

can be performed. Peripheral nerve blockade have advantages when compared with central regional techniques in anticoagulated children. Femoral and sciatic nerve blockade is the most useful lower limb block technique. More proximal approaches to the lumbosacral plexus are problematic due to the close proximity between the major psoas muscle and the retroperitoneum and the fact that nerve structures are inside the psoas major muscle.67 The optimal position for blockade of the femoral nerve is slightly distal the inguinal ligament, where the nerve can be visualised lateral to the large femoral vessels with a high frequency 25 mm ultrasound probe (Fig. 6) and blocked in a similar way as described for the infraclavicular portion of the brachial plexus. The major anatomical structures are the femoral artery, the deep layer of the inguinal ligament and the iliopsoas muscle. Care should be taken to avoid intraperitoneal puncture. Table 3 describes the dose regime for lower limb blocks. The sciatic nerve in small babies is best approached at a mid-femoral level. The nerve is easy visible with a high frequency 25 mm ultrasound probe (Fig. 7) and the puncture procedure is similar to that outlined earlier. The sciatic nerve contains a significant portion of sympathetic fibers and blockade of this nerve appears useful as an alternative for central blockade for therapeutic sympatholysis (e.g. end-artery ischaemia).

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Fig. 7. Cross-sectional view of a sciatic nerve in a 920-g neonate at the mid-femoral level (indicated by the oblique arrow). The inserted image indicates the probe position. The horizontal arrow indicates the femur. The entire depth of the image is 12 mm; left side = lateral.

Trunk block techniques Trunk blocks can be used for various indications as alternatives to neuraxial anaesthesia. The main argument for trunk blocks is the less invasive (= more peripheral) and the more focused blockade. Ilioinguinal-iliohypogastric nerve blockade. Ultrasound-guided ilioinguinal-iliohypogastric nerve blockade has been extensively described for paediatric indications.68,69 The maldistribution of local anaesthetic when ultrasound is not used is described in a clinical study.70 A correct administration of local anaesthetic between the internal oblique and transverse abdominal muscles was observed in only 14% according to their results with a subsequent low success rate. Thus, ultrasound is highly recommended also for this kind of regional anaesthetic technique. All kind of groin surgery can be performed with this nerve block technique. The block can be optimally performed medial to the anterior superior iliac spine, where the nerves are positioned between the internal oblique and the transverse abdominal muscles. The nerves are easily visible with a high frequency linear ultrasound probe (Fig. 8) and blockade can be performed in-plane or out-of-plane with a 24-G 30 mm cannula and 0.075–0.1 ml/kg ropivacaine 0.2–0.375%. This extreme small volume is difficult to visualise in neonates even when ultrasound is used. A practical advice is to administer the local anaesthetic until the nerve structures are surrounded by local anaesthetic with a maximum volume of 0.25 ml/kg.

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Fig. 8. Cross-sectional ultrasound view of the ilioinguinal (left arrow) and iliohypogastric nerves (right arrow) medial the anterior superior iliac spine (ASIS) and embedded between the internal oblique abdominal (IOAM) and transverse abdominal (TAM) muscles. The inserted image indicates the probe position. The entire depth of the image is 18 mm; left side = lateral.

General anaesthesia is usually required for an ilioinguinal-iliohypogastric nerve blockade in neonates and small infants. In cases where it is advisable to avoid general anaesthesia (e.g. expremature baby with bronchopulmonary dysplasia, increased risk of post-operative apnea or pre-existing laryngotracheal injury from previous endotracheal intubation), an awake or lightly sedated approach using caudal blockade is advisable in neonates and small infants for groin surgery (e.g. incarcerated inguinal hernia). Transversus abdominis plane (TAP) block. TAP block has become a popular technique, despite the lack of studies showing any major advantage compared with other regional anaesthetic technique. The technique is described for neonatal one-side abdominal surgery71 and for cases where neuraxial blockade is not possible (e.g. spinal dysraphism).72 The target structure for this technique is the fascia layer between the internal oblique and transverse abdominal muscles (Fig. 9) where the following nerves are passing through: T7–12 intercostal nerves, ilioinguinal and iliohypogastric nerves, and the lateral cutaneous branches of the dorsal rami of L1–3. The ultrasound-guided technique has been described in infants using a high frequency linear ultrasound probe placed on the lateral side of the abdomen between the 12th rib and the iliac crest.73 A 24-G facette tip cannula can be introduced in-plane and the administration of 0.5 ml/kg local anaesthetic is recommended. The needle has to be advanced with maximal care to avoid inadvertent peritoneal puncture due to the elastic fasciae and thin muscle layers in this anatomical region. Atten-

Ultrasound-guided regional anaesthesia

Fig. 9. Cross-sectional ultrasound view of the lateral abdominal wall in a 3.5-kg infant. The required needle tip position for a successful transversus abdominis plane (TAP) blockade is between the internal oblique abdominal (IOAM) and transverse abdominal (TAM) muscles. The inserted image indicates the probe position. The entire depth of the image is 18 mm; right side = caudal, EOAM = external oblique abdominal muscle.

tion is also needed to the maximum allowable volume of local anaesthetic if using a bilateral technique. Single shot and catheter techniques have been described.71,74–77 As with ilioinguinal-iliohypogastric nerve blockade, TAP blockade is only applicable in anaesthetised children. Thus, if surgery in awake or sedated neonates and small infants is required, neuraxial techniques are preferred.

Conclusions Regional anaesthesia in neonates and small infants provide excellent intra- and post-operative analgesia but is also associated with advantages such as reduced need for post-operative respiratory support, haemodynamic stability, improved splanchnic circulation and reduced need for general anaesthetics that may be associated with cerebral apoptosis / neurodegeneration. In particular, peripheral regional anaesthesia is not popular in neonatal care. Neuraxial neonatal regional anaesthesia is better described,27,28,39–41 but also underused in the daily clinical practice. Despite the fact that more or less all regional anaesthetic techniques are applicable in all age and weight groups, the practical implementation of neonatal

regional anaesthesia is still in its infancy. Concerns related to safety issues and technical difficulties have limited the implementations. Particular skills and experience are required to perform epidural anaesthesia or a brachial plexus block in babies < 1000 g. An often stated argument against the implementation of these techniques is that all surgical cases can be managed by opioid-based general anaesthesia neglecting potential disadvantages of systemic anaesthetic and analgesic drugs in neonates and small babies. Since the anatomy between various important structures is often very closely situated in babies and infants, sometimes only separated by a few millimetres, the regular use of ultrasound is strongly advocated for all regional anaesthetic techniques. Particular peripheral regional anaesthetic techniques can be used when specific pain therapy or therapeutical sympathicolysis is required. Hand skills, structured education and continuous training are the main prerequisites for the successful and safe implementation of ultrasound-guided regional anaesthesia in neonates and small infants in the daily clinical practice. Conflict of interest: Peter Marhofer receives honoraria for lectures from SonoSite Inc. Per-Arne Lönnqvist receives consulting fees from Maquet Inc. and honoraria from Abbott Scandinavia. Funding: Only departmental resources were used.

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Address: Peter Marhofer Department of Anaesthesia and Intensive Care Medicine Medical University of Vienna Waehringer Guertel 18-20 A-1090 Vienna Austria e-mail: [email protected]

Supporting Information Additional Supporting Information may be found in the online version of this article at the publisher’s web-site:

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Movie S1. Direct ultrasound visualisation of the advancement of an epidural catheter in a 2.6-kg neonate. Notably, the epidural catheter appears anterior relative to the spinal cord.

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Movie S2. Ultrasound visualisation of the spread from caudal (right side of the image) in a cranial direction. The movement of the dura mater (hyperechoic line) in an anterior direction is clearly visible.