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Peripheral and local anaesthetic techniques for paediatric surgery
Paediatrics
Peripheral and local anaesthetic techniques for paediatric surgery Saiprasad Annadurai Steve Roberts
Abstract Peripheral nerve blocks (PNBs) in paediatric patients are usually used as an adjunct to general anaesthesia, providing intra- and postoperative pain relief. These blocks provide good-quality analgesia and have opioidsparing effects, preventing morbidity related to pain. PNBs aid early patient recovery and discharge, which is essential in day-case surgery. Like all invasive techniques, PNBs are associated with complications and side effects. They should therefore be performed only after careful analysis of the risk:benefit ratio for each child. This article discusses a general approach to PNBs in children. It covers a small selection of limb and trunk blocks, and introduces the benefit of ultrasound guidance.
Figure 1 A child having a block in a child-friendly environment.
General approach The essential requirements for the performance of each nerve block are described below. • History and clinical examination: allergies, previous anaesthetics, current medications, weight (to calculate maximum dose of local anaesthetic), and, where possible, examination of the potential puncture site. • Identification of the most suitable block, depending on site of surgery and other potentially painful events (e.g. tourniquet use or graft sites). The most peripheral option should be selected. • Consent after explanation of potential advantages, side effects, complications, alternative methods of pain relief, and analgesia plan if the block fails.
Keywords children; paediatrics; peripheral nerve blocks; regional anaesthesia
The peripheral nerve blocks (PNBs) performed in adults can also be performed in children. Limb blocks provide excellent analgesia for both orthopaedic and plastic surgery; in the latter they convey the additional advantage of sympathetic block. PNBs should be performed or supervised only by those with the appropriate equipment, training and experience. For children in the UK most of these blocks are performed under general anaesthesia. When blocks are performed on an awake patient (for very minor surgery, following trauma or in the older more cooperative child) the correct information, environment (Figure 1) and reassurance are essential to minimize the child’s anxiety and stress. A prospective survey of the French-language Society of Paediatric Anaesthesiologists evaluated the practice of regional anaesthesia and its complications.1 Caudal epidurals accounted for 60% of all regional techniques and had a complication rate of 1.5%, while there were no complications relating to PNBs. These findings have encouraged the use of PNBs in paediatric patients. The use of ultrasound to locate nerves is increasingly used in paediatric patients as it increases the speed of onset, reliability and safety of PNBs (Table 1). However, using this technique to identify the nerve is not a replacement for a good understanding of the anatomy.
Ultrasound-guided nerve blocks Advantages • No ionizing radiation • Portability (laptop-sized machines) • Visualization of the nerve and adjacent structures (vessels, pleura) • Visualization of the spread of local anaesthetic solution (avoidance of intravascular or intraneural injection) • Increased efficacy (faster onset, longer duration and increased success rates) • Decreased incidence of complications • Lower volumes of local anaesthetic • Can be performed in presence of muscle relaxants Disadvantages • Cost of equipment • Operator dependent • Training (long learning curve with some blocks) • Obese patients (poor visualization of structures) • Poor resolution with increasing depth
Saiprasad Annadurai, MBBS, FRCA, is Clinical Fellow at the Royal Liverpool Children’s Hospital NHS Trust. Steve Roberts, MBChB, FRCA, is Consultant Anaesthetist at the Royal Liverpool Children’s Hospital NHS Trust.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 8:5
Table 1
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© 2007 Elsevier Ltd. All rights reserved.
Paediatrics
General side effects • Failure of block. • Local anaesthetic toxicity. • Intraneural injection. • Anaphylaxis (rare). • Infection. • Haematoma.
• Resuscitation equipment: oxygen, intubation trolley, resuscita tion drugs, including 20% intralipid. • Intravenous access prior to performing block. • Full monitoring. • Trained experienced staff, with a good understanding of anatomy, to perform or supervise block. • Trained assistance. • Equipment: insulated short-bevelled needle with extension tubing, with or without peripheral nerve stimulator (for mixed nerves), ultrasound machine with high-frequency probe (sterile gel and probe covers), gauze swabs, antiseptic solution, sterile gloves, sterile drapes, syringe, and local anaesthetic. • When using a peripheral nerve stimulator the current should initially be set at 2 mA. The needle should then be advanced towards the nerve, seeking out the relevant motor response. With increasing proximity the current is then decreased, aiming to reach 0.5 mA. An initial injection of 1 ml of local anaesthetic abolishes twitch as the nerve is pushed away from the needle tip. • Absolute sterile technique. • In the awake patient a distraction can be provided by a parent, play specialist and/or audio-visual aids. Ametop gel can be used on the proposed puncture site; however, the skin should be infiltrated with lignocaine first. Entonox can be used during block insertion. • The skin should be nicked with a sharp needle before inserting a short-bevelled needle. If this is not done, underlying fascias can be missed when the short-bevelled needle is passed through the skin. • The maximum dose of local anaesthetic should be calculated and not exceeded. • The injection should be done slowly with initial and frequent aspiration to exclude intravascular injection. • When using a bolus of long-acting local anaesthetic, the duration of action is usually limited to 6–12 hours. • Catheter techniques can be used to extend analgesia. • To decrease the incidence of dislodgement the catheter should be tunnelled. • Continuous nerve blockade requires a standard nerve catheter kit, adhesive plasters, intravenous cannula for tunnelling, and a syringe driver. • Postoperative advice regarding protection of the anaesthetized area should be given to the patient. The advice should include warnings of decreased sensation, especially in respect of temperature and weakness of muscles. Arms should be kept in a sling. Appropriate means of mobilizing or returning home should be provided for those patients with lower limb blockade.
Local anaesthetics Neonates and infants are more prone to local anaesthetic toxicity because of immature blood–brain barrier, decreased protein binding and immature liver metabolic systems. It has been suggested that the dose of local anaesthetic should be halved in this group. The toxicity is related to the absolute level of local anaesthetic and also the rate of rise in concentration in plasma. Levobupi vacaine remains the drug of choice because of its longer duration of action, and low cardio- and neurotoxicity. A concentration of 0.125 to 0.25% is given when a PNB is used in conjunction with a general anaesthetic. In neonates and infants the infusion should be limited to 48 hours because of the risk of toxicity (Table 2). Upper limb blocks The approaches described are limited to the parascalene and the axillary. Brachial plexus anatomy is described in detail in Anaesthesia and intensive care medicine 8:4: 144. The brachial plexus is formed from the anterior primary rami of C5, C6, C7, C8 and T1. These nerve roots emerge from the intervertebral foramina between the scalenus anterior and scalenus medius muscles and are enclosed by a fascial sheath from these muscles. The nerve roots unite to form the trunks. C5 and C6 unite to form the superior trunk, C7 forms the middle trunk and the C8 and T1 roots unite to form the lower trunk. The trunks pass from the interscalene groove over the first rib supero-posterior to the subclavian artery, and at the lateral border of the first rib they divide into anterior and posterior divisions. The anterior divisions of the upper and middle trunk unite to form the lateral cord; the anterior division of the lower trunk forms the medial cord; and the posterior divisions of the three trunks unite to form the posterior cord. These cords are named on the basis of their relation to the axillary artery and divide into the nerves that supply the upper limb.
General contraindications • Lesions (infective) at the site of injection. • Bleeding disorders (ultrasound can help to avoid inadvertent damage to blood vessels). • History of allergy to local anaesthetic. • Lack of consent.
Local anaesthetic dose
Relative contraindications • Neuromuscular disorders. • Risk of compartment syndrome, especially following trauma (discuss with surgeon). • Systemic infection (catheter techniques).
ANAESTHESIA AND INTENSIVE CARE MEDICINE 8:5
Drug
Single-shot techniques (mg/kg)
Continuous infusions (mg/kg/hour)
Maximum dose per 4-hour period (mg/kg)
Levobupivacaine Ropivacaine Lignocaine
2 3 3
0.125–0.40 0.40 –
2.0 1.6 –
Table 2
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© 2007 Elsevier Ltd. All rights reserved.
Paediatrics
• Lateral cord – lateral root of median nerve, musculocutaneous nerve. • Medial cord – medial root of median nerve, ulnar nerve, medial cutaneous nerves of arm and forearm. • Posterior cord - axillary and radial nerves. Parascalene block: only experienced paediatric regional anaesthetists should perform this block. It could be argued that this block should be performed only under ultrasound guidance. The disadvantage with this approach is the sparing of the lower nerve roots. With ultrasound, this lack of spread can be identified and remedied. A history of previous neck surgery or contralateral pneumothorax is a relative contraindication. Indications – surgery of the shoulder, upper arm. Technique – the patient is placed supine with a roll under the shoulder and head turned slightly to the opposite side. A line is drawn from the cricoid cartilage to the posterior border of sterno cleidomastoid; a second line is drawn from the midpoint of the clavicle to the lateral end of the first line. The needle is inserted perpendicular to the skin at the junction of the upper two-thirds and the lower third of the second line. Contractions in the distal muscles of the upper limb are sought. 0.3–0.4 ml/kg of 0.25% levobupivacaine is used. Complications – vascular injection, pneumothorax, phrenic and recurrent laryngeal nerve blockade, and Horner’s syndrome.
Figure 2 Ultrasound of axilla in the transverse plane. (a) Axillary artery; (b) biceps muscle; (c) coracobrachialis muscle; (d) median nerve; (e) musculocutaneous nerve; (f) radial nerve; (g) triceps muscle; (h) ulnar nerve; (i) axillary vein.
through the rectus muscle to give off sensory branches to the paraumbilical skin. The rectus sheath adheres tightly to the muscle anteriorly but is attached loosely posteriorly, so forming a potential space. Technique – the landmarks are the umbilicus and lateral margins of the rectus abdominis muscles. A short-bevelled needle is introduced at the lateral margin of the rectus muscle. It is aimed medially at an angle of 60° towards the umbilicus until a ‘give’ is felt as the needle passes through the anterior rectus sheath. As the needle is advanced it is moved gently from side to side; a ‘scratch’ is felt on reaching the posterior sheath. An injection of 0.2–0.3 ml/kg/side of 0.25% levobupivacaine is made. The process is repeated for the opposite side. Complications – intraperitoneal injection and visceral damage.
Axillary blockade is the most commonly used approach to block the brachial plexus in children. Four techniques have been described. Of these the transarterial approach is contraindicated because of the risk of vessel damage. Indications – surgery of the elbow, forearm and hand. Technique – the patient is positioned supine with the arm abducted 90° and elbow flexed 90°, to maintain this position the hand is taped to the trolley. One and two injections – the arterial pulsation is felt for high in the axilla. The needle is inserted just above the pulse at 45° to the skin, aiming cephalad. A ‘pop’ is felt when the fascia is pierced; then local anaesthetic is injected. In the two-injection technique equal amounts of local anaesthetic are injected above and below the arterial pulsation. If a nerve stimulator is used, contractions of distal muscles are easily elicited. To avoid tourniquet pain, local anaesthetic is injected around the upper aspect of the arm to block the intercosto-brachial and medial cutaneous nerves of the arm. The musculocutaneous nerve is commonly spared as it leaves the sheath higher up, the application of pressure distal to the injection site may improve proximal spread. Alternatively, it can be blocked separately within the coracobrachialis muscle. With ultrasound it is easy to identify this nerve (Figure 2). Complications – haematoma (1.1%) and nerve injury (rare).
Ilioinguinal and iliohypogastric nerve block Anatomy – the ilioinguinal (L1) and iliohypogastric (T12, L1) nerves are terminal branches of the lumbar plexus. They lie deep
Truncal blocks Rectus sheath block Indications – periumbilical surgery. Anatomy – the nerves that innervate the umbilicus arise from T10 intercostal nerves and initially travel between the internal oblique and transversus abdominis muscles. The rectus muscle sheath is formed from the aponeuroses of the three lateral abdominal muscles (Figure 3). The nerves run anteriorly
ANAESTHESIA AND INTENSIVE CARE MEDICINE 8:5
Figure 3 Ultrasound of abdominal wall (transverse plane). (a) External oblique muscle; (b) internal oblique muscle; (c) peritoneum; (d) rectus muscle; (e) semilunaris; (f) transversus abdominis muscle.
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Paediatrics
Anatomy – the femoral, lateral cutaneous nerve of thigh and the obturator nerve are formed from the anterior rami of the first four lumbar nerves. The femoral nerve provides sensory innervation to the anterior and medial aspects of the thigh. The lateral cutaneous nerve of thigh provides sensory innervation to the lateral aspect of the thigh, and the obturator nerve the medial aspect of thigh, and knee joint. The femoral nerve lies in the femoral triangle lateral to the femoral artery (Figure 5). The fascia lata covers the femoral nerve and the vessels, while the fascia iliaca covers the nerve and passes under the femoral artery. Technique – a short-bevelled needle is inserted lateral to the pulsation of the artery, 1–2 cm below the inguinal ligament. It is inserted at a 45° angle in a cephalad direction. With a nerve stimulator, contraction of the quadriceps muscle is aimed for. A volume of 0.2–0.3 ml/kg of 0.25% levobupivacaine is injected, which is increased to up to 0.7 ml/kg (maximum 20 ml) if a 3-in-1 block is required. Complications – vascular injection, haematoma and incomplete blockade.
to the internal oblique (Figure 4). The iliohypogastric nerve pierces the internal oblique and runs under the external oblique superior to the inguinal canal. The ilioinguinal nerve continues in the inguinal canal. In infants, the average nerve–peritoneum distance is 3.3 mm. Indications – inguinal hernia repair, orchidopexy, hydrocele and varicocele. Technique – the point of injection is 0.25–0.50 cm medial to the anterior superior iliac spine (ASIS) along a line connecting the ASIS and umbilicus. Nick the skin with a sharp needle before inserting a short-bevelled needle because this makes it easier to appreciate the fascia planes beneath. A short-bevelled needle is then inserted perpendicular to the skin, and after the first ‘pop’ 0.3 ml/kg of 0.25% levobupivacaine is deposited. The disadvantage of the block is that it does not abolish visceral pain due to traction of the spermatic cord. Complications – visceral perforation and femoral nerve blockade (up to 11%). Penile blocks Anatomy – the dorsal nerves of the penis are branches of the pudendal nerve, which lie deep to Scarpa’s fascia in the suprapubic space. This space is divided into two by the suspensory ligament. Indications – circumcision and distal hypospadias repair. Technique – the penis is gently pulled caudad, and the symphysis pubis and the lower border of the pubic bones are identified. A short-bevelled needle is inserted perpendicular to the skin just below the pubic ramus 0.5–1.0 cm from the midline. An initial ‘pop’ is felt as the superficial fascia is passed and a second ‘pop’ is felt when it pierces Scarpa’s fascia. Local anaesthetic is deposited and the block is repeated on the other side. Adrenaline is contraindicated. Complications – vascular compromise and haematoma.
Fascia iliaca block is an alternative approach to the 3-in-1 block. It has the advantage of not requiring any special equipment, and has a high success rate, especially in blocking the lateral cutaneous nerve of the thigh. Indications – procedures on the hip, knee (combined with sciatic nerve block), analgesia for fractured femur, and operations on the anterior and lateral thigh. Technique – a line is drawn from the pubic tubercle to the anterior superior iliac spine. The needle is inserted perpendicularly a centimetre below the junction of the outer and middle thirds of this line. After feeling for two ‘pops’ 0.25% levobupi vacaine deposited (0.7 ml/kg, maximum 20 ml). Complications – no complications have been reported with this technique.
Lower limb blocks Femoral nerve, 3-in-1 block Indication – procedures on the hip, knee (combined with sciatic nerve block), analgesia for fractured femur, and operations on the anterior and lateral thigh.
Proximal sciatic nerve block: the sciatic nerve can be blocked by anterior, posterior and lateral approaches at the hip or at the popliteal fossa. Anatomy – the sciatic nerve (L4–S3) leaves the pelvis through the greater sciatic foramen, and in the buttock it lies between
Figure 4 Ultrasound of the ilioinguinal and iliohypogastric nerves (circled). (a) Anterior superior iliac spine; (b) internal oblique muscle; (c) peritoneum; (d) transversus abdominis muscle.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 8:5
Figure 5 Ultrasound of infrainguinal region (transverse plane). (a) Femoral artery; (b) iliopsoas muscle; (c) femoral nerve; (d) femoral vein.
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Paediatrics
the greater trochanter and the ischial tuberosity covered by the gluteus maximus muscle. Indications – all operations on or below the knee when combined with femoral or saphenous nerve block. Posterior technique – the patient is placed in the lateral Sims position or a knee–chest position, with both hips and knees flexed. The needle is inserted perpendicular to the skin at the midpoint of a line connecting the greater trochanter and the tip of the coccyx. With a nerve stimulator, plantar or dorsiflexion of the foot is looked for and 0.5 ml/kg of 0.25% levobupivacaine is deposited.
• The superficial peroneal nerve and the saphenous nerve. Both nerves are blocked by a subcutaneous injection in a line between the medial and lateral malleoli. • The deep peroneal nerve is blocked immediately lateral to the pulsations of the anterior tibial artery. Local anaesthetic is deposited deep to the extensor retinaculum of the ankle joint. Metatarsal block Indications – all operations on the toes. Technique – at a point lateral to the base of the metatarsal the needle is inserted through the extensor to the plantar surface of the foot (taking care not to pierce it). As the needle is withdrawn 1–4 ml of 0.25% levobupivacaine is injected. The injection is then repeated on the medial side. Addition of adrenaline is contraindicated. ◆
Popliteal block Anatomy – the sciatic nerve enters the back of the thigh passing deep to the long head of the biceps femoris and descends towards the apex of the popliteal fossa. It usually divides in the lower third of the thigh into the common peroneal and tibial nerves, although this can occur as high as the piriformis muscle. Indications – all operations on the lower limb when combined with a saphenous nerve block. Technique – the needle is inserted at a point just lateral to the apex of the triangle formed by the biceps femoris laterally and the semimembranosus and semitendinosus tendons medially. This high approach improves the chances of blocking both divisions of the sciatic nerve. With a nerve stimulator, a twitch is obtained in the distribution of either the common peroneal nerve or the posterior tibial nerve, and about 0.5–1.0 ml/kg of 0.25% levobupivacaine is used. Complications – injury to popliteal vessels.
Reference 1 Giaufre E, Dalens B, Gombert A. Epidemiology and morbidity of regional anesthesia in children – a one year prospective survey of the ADARPEF. Anesth Analg 1996; 83: 897–900. Further reading Borgeat A. Regional anesthesia, intraneural, injection and nerve injury: beyond the epineurium (editorial). Anesthesiology 2006; 105: 647–8. Marhofer P, Greher M, Kapral S. Ultrasound guidance in regional anaesthesia. Br J Anaesth 2005; 94: 7–17. Morton NS. Local and regional anaesthesia in infants. Contin Educ Anaesth Crit Care Pain 2004; 4: 148–51. Peutrell JM, Mather SJ, eds. Regional anaesthesia for babies and children. Oxford: Oxford University Press, 1997. Tobias JD. Brachial plexus anaesthesia in children. Paediatr Anaesth 2001; 11: 265–75. Tobias JD. Regional anaesthesia of the lower extremity in children. Paediatr Anaesth 2003; 13: 152–63.
Ankle block Indications – operations on the foot or toes. Technique – the foot is supplied by five nerves, which can be blocked at the ankle. • The tibial nerve runs deep to the flexor retinaculum behind the medial malleolus and posterior to the posterior tibial artery. The needle is inserted at the level of the upper border of the medial malleolus midway between the Achilles tendon and the medial malleolus. Local anaesthetic is injected at a depth midway between skin and bone. • The sural nerve passes infero-posteriorly to the lateral malle olus. The needle is inserted at the midpoint of the Achilles tendon and the posterior border of the calcaneum. Local anaesthetic is deposited subcutaneously.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 8:5
Acknowledgement The authors would like to thank Sonosite for the loan of a MicroMaxx ultrasound machine.
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© 2007 Elsevier Ltd. All rights reserved.
Peripheral and local anaesthetic techniques for paediatric surgery Saiprasad Annadurai Steve Roberts
Abstract Peripheral nerve blocks (PNBs) in paediatric patients are usually used as an adjunct to general anaesthesia, providing intra- and postoperative pain relief. These blocks provide good-quality analgesia and have opioidsparing effects, preventing morbidity related to pain. PNBs aid early patient recovery and discharge, which is essential in day-case surgery. Like all invasive techniques, PNBs are associated with complications and side effects. They should therefore be performed only after careful analysis of the risk:benefit ratio for each child. This article discusses a general approach to PNBs in children. It covers a small selection of limb and trunk blocks, and introduces the benefit of ultrasound guidance.
Figure 1 A child having a block in a child-friendly environment.
General approach The essential requirements for the performance of each nerve block are described below. • History and clinical examination: allergies, previous anaesthetics, current medications, weight (to calculate maximum dose of local anaesthetic), and, where possible, examination of the potential puncture site. • Identification of the most suitable block, depending on site of surgery and other potentially painful events (e.g. tourniquet use or graft sites). The most peripheral option should be selected. • Consent after explanation of potential advantages, side effects, complications, alternative methods of pain relief, and analgesia plan if the block fails.
Keywords children; paediatrics; peripheral nerve blocks; regional anaesthesia
The peripheral nerve blocks (PNBs) performed in adults can also be performed in children. Limb blocks provide excellent analgesia for both orthopaedic and plastic surgery; in the latter they convey the additional advantage of sympathetic block. PNBs should be performed or supervised only by those with the appropriate equipment, training and experience. For children in the UK most of these blocks are performed under general anaesthesia. When blocks are performed on an awake patient (for very minor surgery, following trauma or in the older more cooperative child) the correct information, environment (Figure 1) and reassurance are essential to minimize the child’s anxiety and stress. A prospective survey of the French-language Society of Paediatric Anaesthesiologists evaluated the practice of regional anaesthesia and its complications.1 Caudal epidurals accounted for 60% of all regional techniques and had a complication rate of 1.5%, while there were no complications relating to PNBs. These findings have encouraged the use of PNBs in paediatric patients. The use of ultrasound to locate nerves is increasingly used in paediatric patients as it increases the speed of onset, reliability and safety of PNBs (Table 1). However, using this technique to identify the nerve is not a replacement for a good understanding of the anatomy.
Ultrasound-guided nerve blocks Advantages • No ionizing radiation • Portability (laptop-sized machines) • Visualization of the nerve and adjacent structures (vessels, pleura) • Visualization of the spread of local anaesthetic solution (avoidance of intravascular or intraneural injection) • Increased efficacy (faster onset, longer duration and increased success rates) • Decreased incidence of complications • Lower volumes of local anaesthetic • Can be performed in presence of muscle relaxants Disadvantages • Cost of equipment • Operator dependent • Training (long learning curve with some blocks) • Obese patients (poor visualization of structures) • Poor resolution with increasing depth
Saiprasad Annadurai, MBBS, FRCA, is Clinical Fellow at the Royal Liverpool Children’s Hospital NHS Trust. Steve Roberts, MBChB, FRCA, is Consultant Anaesthetist at the Royal Liverpool Children’s Hospital NHS Trust.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 8:5
Table 1
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© 2007 Elsevier Ltd. All rights reserved.
Paediatrics
General side effects • Failure of block. • Local anaesthetic toxicity. • Intraneural injection. • Anaphylaxis (rare). • Infection. • Haematoma.
• Resuscitation equipment: oxygen, intubation trolley, resuscita tion drugs, including 20% intralipid. • Intravenous access prior to performing block. • Full monitoring. • Trained experienced staff, with a good understanding of anatomy, to perform or supervise block. • Trained assistance. • Equipment: insulated short-bevelled needle with extension tubing, with or without peripheral nerve stimulator (for mixed nerves), ultrasound machine with high-frequency probe (sterile gel and probe covers), gauze swabs, antiseptic solution, sterile gloves, sterile drapes, syringe, and local anaesthetic. • When using a peripheral nerve stimulator the current should initially be set at 2 mA. The needle should then be advanced towards the nerve, seeking out the relevant motor response. With increasing proximity the current is then decreased, aiming to reach 0.5 mA. An initial injection of 1 ml of local anaesthetic abolishes twitch as the nerve is pushed away from the needle tip. • Absolute sterile technique. • In the awake patient a distraction can be provided by a parent, play specialist and/or audio-visual aids. Ametop gel can be used on the proposed puncture site; however, the skin should be infiltrated with lignocaine first. Entonox can be used during block insertion. • The skin should be nicked with a sharp needle before inserting a short-bevelled needle. If this is not done, underlying fascias can be missed when the short-bevelled needle is passed through the skin. • The maximum dose of local anaesthetic should be calculated and not exceeded. • The injection should be done slowly with initial and frequent aspiration to exclude intravascular injection. • When using a bolus of long-acting local anaesthetic, the duration of action is usually limited to 6–12 hours. • Catheter techniques can be used to extend analgesia. • To decrease the incidence of dislodgement the catheter should be tunnelled. • Continuous nerve blockade requires a standard nerve catheter kit, adhesive plasters, intravenous cannula for tunnelling, and a syringe driver. • Postoperative advice regarding protection of the anaesthetized area should be given to the patient. The advice should include warnings of decreased sensation, especially in respect of temperature and weakness of muscles. Arms should be kept in a sling. Appropriate means of mobilizing or returning home should be provided for those patients with lower limb blockade.
Local anaesthetics Neonates and infants are more prone to local anaesthetic toxicity because of immature blood–brain barrier, decreased protein binding and immature liver metabolic systems. It has been suggested that the dose of local anaesthetic should be halved in this group. The toxicity is related to the absolute level of local anaesthetic and also the rate of rise in concentration in plasma. Levobupi vacaine remains the drug of choice because of its longer duration of action, and low cardio- and neurotoxicity. A concentration of 0.125 to 0.25% is given when a PNB is used in conjunction with a general anaesthetic. In neonates and infants the infusion should be limited to 48 hours because of the risk of toxicity (Table 2). Upper limb blocks The approaches described are limited to the parascalene and the axillary. Brachial plexus anatomy is described in detail in Anaesthesia and intensive care medicine 8:4: 144. The brachial plexus is formed from the anterior primary rami of C5, C6, C7, C8 and T1. These nerve roots emerge from the intervertebral foramina between the scalenus anterior and scalenus medius muscles and are enclosed by a fascial sheath from these muscles. The nerve roots unite to form the trunks. C5 and C6 unite to form the superior trunk, C7 forms the middle trunk and the C8 and T1 roots unite to form the lower trunk. The trunks pass from the interscalene groove over the first rib supero-posterior to the subclavian artery, and at the lateral border of the first rib they divide into anterior and posterior divisions. The anterior divisions of the upper and middle trunk unite to form the lateral cord; the anterior division of the lower trunk forms the medial cord; and the posterior divisions of the three trunks unite to form the posterior cord. These cords are named on the basis of their relation to the axillary artery and divide into the nerves that supply the upper limb.
General contraindications • Lesions (infective) at the site of injection. • Bleeding disorders (ultrasound can help to avoid inadvertent damage to blood vessels). • History of allergy to local anaesthetic. • Lack of consent.
Local anaesthetic dose
Relative contraindications • Neuromuscular disorders. • Risk of compartment syndrome, especially following trauma (discuss with surgeon). • Systemic infection (catheter techniques).
ANAESTHESIA AND INTENSIVE CARE MEDICINE 8:5
Drug
Single-shot techniques (mg/kg)
Continuous infusions (mg/kg/hour)
Maximum dose per 4-hour period (mg/kg)
Levobupivacaine Ropivacaine Lignocaine
2 3 3
0.125–0.40 0.40 –
2.0 1.6 –
Table 2
190
© 2007 Elsevier Ltd. All rights reserved.
Paediatrics
• Lateral cord – lateral root of median nerve, musculocutaneous nerve. • Medial cord – medial root of median nerve, ulnar nerve, medial cutaneous nerves of arm and forearm. • Posterior cord - axillary and radial nerves. Parascalene block: only experienced paediatric regional anaesthetists should perform this block. It could be argued that this block should be performed only under ultrasound guidance. The disadvantage with this approach is the sparing of the lower nerve roots. With ultrasound, this lack of spread can be identified and remedied. A history of previous neck surgery or contralateral pneumothorax is a relative contraindication. Indications – surgery of the shoulder, upper arm. Technique – the patient is placed supine with a roll under the shoulder and head turned slightly to the opposite side. A line is drawn from the cricoid cartilage to the posterior border of sterno cleidomastoid; a second line is drawn from the midpoint of the clavicle to the lateral end of the first line. The needle is inserted perpendicular to the skin at the junction of the upper two-thirds and the lower third of the second line. Contractions in the distal muscles of the upper limb are sought. 0.3–0.4 ml/kg of 0.25% levobupivacaine is used. Complications – vascular injection, pneumothorax, phrenic and recurrent laryngeal nerve blockade, and Horner’s syndrome.
Figure 2 Ultrasound of axilla in the transverse plane. (a) Axillary artery; (b) biceps muscle; (c) coracobrachialis muscle; (d) median nerve; (e) musculocutaneous nerve; (f) radial nerve; (g) triceps muscle; (h) ulnar nerve; (i) axillary vein.
through the rectus muscle to give off sensory branches to the paraumbilical skin. The rectus sheath adheres tightly to the muscle anteriorly but is attached loosely posteriorly, so forming a potential space. Technique – the landmarks are the umbilicus and lateral margins of the rectus abdominis muscles. A short-bevelled needle is introduced at the lateral margin of the rectus muscle. It is aimed medially at an angle of 60° towards the umbilicus until a ‘give’ is felt as the needle passes through the anterior rectus sheath. As the needle is advanced it is moved gently from side to side; a ‘scratch’ is felt on reaching the posterior sheath. An injection of 0.2–0.3 ml/kg/side of 0.25% levobupivacaine is made. The process is repeated for the opposite side. Complications – intraperitoneal injection and visceral damage.
Axillary blockade is the most commonly used approach to block the brachial plexus in children. Four techniques have been described. Of these the transarterial approach is contraindicated because of the risk of vessel damage. Indications – surgery of the elbow, forearm and hand. Technique – the patient is positioned supine with the arm abducted 90° and elbow flexed 90°, to maintain this position the hand is taped to the trolley. One and two injections – the arterial pulsation is felt for high in the axilla. The needle is inserted just above the pulse at 45° to the skin, aiming cephalad. A ‘pop’ is felt when the fascia is pierced; then local anaesthetic is injected. In the two-injection technique equal amounts of local anaesthetic are injected above and below the arterial pulsation. If a nerve stimulator is used, contractions of distal muscles are easily elicited. To avoid tourniquet pain, local anaesthetic is injected around the upper aspect of the arm to block the intercosto-brachial and medial cutaneous nerves of the arm. The musculocutaneous nerve is commonly spared as it leaves the sheath higher up, the application of pressure distal to the injection site may improve proximal spread. Alternatively, it can be blocked separately within the coracobrachialis muscle. With ultrasound it is easy to identify this nerve (Figure 2). Complications – haematoma (1.1%) and nerve injury (rare).
Ilioinguinal and iliohypogastric nerve block Anatomy – the ilioinguinal (L1) and iliohypogastric (T12, L1) nerves are terminal branches of the lumbar plexus. They lie deep
Truncal blocks Rectus sheath block Indications – periumbilical surgery. Anatomy – the nerves that innervate the umbilicus arise from T10 intercostal nerves and initially travel between the internal oblique and transversus abdominis muscles. The rectus muscle sheath is formed from the aponeuroses of the three lateral abdominal muscles (Figure 3). The nerves run anteriorly
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Figure 3 Ultrasound of abdominal wall (transverse plane). (a) External oblique muscle; (b) internal oblique muscle; (c) peritoneum; (d) rectus muscle; (e) semilunaris; (f) transversus abdominis muscle.
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Anatomy – the femoral, lateral cutaneous nerve of thigh and the obturator nerve are formed from the anterior rami of the first four lumbar nerves. The femoral nerve provides sensory innervation to the anterior and medial aspects of the thigh. The lateral cutaneous nerve of thigh provides sensory innervation to the lateral aspect of the thigh, and the obturator nerve the medial aspect of thigh, and knee joint. The femoral nerve lies in the femoral triangle lateral to the femoral artery (Figure 5). The fascia lata covers the femoral nerve and the vessels, while the fascia iliaca covers the nerve and passes under the femoral artery. Technique – a short-bevelled needle is inserted lateral to the pulsation of the artery, 1–2 cm below the inguinal ligament. It is inserted at a 45° angle in a cephalad direction. With a nerve stimulator, contraction of the quadriceps muscle is aimed for. A volume of 0.2–0.3 ml/kg of 0.25% levobupivacaine is injected, which is increased to up to 0.7 ml/kg (maximum 20 ml) if a 3-in-1 block is required. Complications – vascular injection, haematoma and incomplete blockade.
to the internal oblique (Figure 4). The iliohypogastric nerve pierces the internal oblique and runs under the external oblique superior to the inguinal canal. The ilioinguinal nerve continues in the inguinal canal. In infants, the average nerve–peritoneum distance is 3.3 mm. Indications – inguinal hernia repair, orchidopexy, hydrocele and varicocele. Technique – the point of injection is 0.25–0.50 cm medial to the anterior superior iliac spine (ASIS) along a line connecting the ASIS and umbilicus. Nick the skin with a sharp needle before inserting a short-bevelled needle because this makes it easier to appreciate the fascia planes beneath. A short-bevelled needle is then inserted perpendicular to the skin, and after the first ‘pop’ 0.3 ml/kg of 0.25% levobupivacaine is deposited. The disadvantage of the block is that it does not abolish visceral pain due to traction of the spermatic cord. Complications – visceral perforation and femoral nerve blockade (up to 11%). Penile blocks Anatomy – the dorsal nerves of the penis are branches of the pudendal nerve, which lie deep to Scarpa’s fascia in the suprapubic space. This space is divided into two by the suspensory ligament. Indications – circumcision and distal hypospadias repair. Technique – the penis is gently pulled caudad, and the symphysis pubis and the lower border of the pubic bones are identified. A short-bevelled needle is inserted perpendicular to the skin just below the pubic ramus 0.5–1.0 cm from the midline. An initial ‘pop’ is felt as the superficial fascia is passed and a second ‘pop’ is felt when it pierces Scarpa’s fascia. Local anaesthetic is deposited and the block is repeated on the other side. Adrenaline is contraindicated. Complications – vascular compromise and haematoma.
Fascia iliaca block is an alternative approach to the 3-in-1 block. It has the advantage of not requiring any special equipment, and has a high success rate, especially in blocking the lateral cutaneous nerve of the thigh. Indications – procedures on the hip, knee (combined with sciatic nerve block), analgesia for fractured femur, and operations on the anterior and lateral thigh. Technique – a line is drawn from the pubic tubercle to the anterior superior iliac spine. The needle is inserted perpendicularly a centimetre below the junction of the outer and middle thirds of this line. After feeling for two ‘pops’ 0.25% levobupi vacaine deposited (0.7 ml/kg, maximum 20 ml). Complications – no complications have been reported with this technique.
Lower limb blocks Femoral nerve, 3-in-1 block Indication – procedures on the hip, knee (combined with sciatic nerve block), analgesia for fractured femur, and operations on the anterior and lateral thigh.
Proximal sciatic nerve block: the sciatic nerve can be blocked by anterior, posterior and lateral approaches at the hip or at the popliteal fossa. Anatomy – the sciatic nerve (L4–S3) leaves the pelvis through the greater sciatic foramen, and in the buttock it lies between
Figure 4 Ultrasound of the ilioinguinal and iliohypogastric nerves (circled). (a) Anterior superior iliac spine; (b) internal oblique muscle; (c) peritoneum; (d) transversus abdominis muscle.
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Figure 5 Ultrasound of infrainguinal region (transverse plane). (a) Femoral artery; (b) iliopsoas muscle; (c) femoral nerve; (d) femoral vein.
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the greater trochanter and the ischial tuberosity covered by the gluteus maximus muscle. Indications – all operations on or below the knee when combined with femoral or saphenous nerve block. Posterior technique – the patient is placed in the lateral Sims position or a knee–chest position, with both hips and knees flexed. The needle is inserted perpendicular to the skin at the midpoint of a line connecting the greater trochanter and the tip of the coccyx. With a nerve stimulator, plantar or dorsiflexion of the foot is looked for and 0.5 ml/kg of 0.25% levobupivacaine is deposited.
• The superficial peroneal nerve and the saphenous nerve. Both nerves are blocked by a subcutaneous injection in a line between the medial and lateral malleoli. • The deep peroneal nerve is blocked immediately lateral to the pulsations of the anterior tibial artery. Local anaesthetic is deposited deep to the extensor retinaculum of the ankle joint. Metatarsal block Indications – all operations on the toes. Technique – at a point lateral to the base of the metatarsal the needle is inserted through the extensor to the plantar surface of the foot (taking care not to pierce it). As the needle is withdrawn 1–4 ml of 0.25% levobupivacaine is injected. The injection is then repeated on the medial side. Addition of adrenaline is contraindicated. ◆
Popliteal block Anatomy – the sciatic nerve enters the back of the thigh passing deep to the long head of the biceps femoris and descends towards the apex of the popliteal fossa. It usually divides in the lower third of the thigh into the common peroneal and tibial nerves, although this can occur as high as the piriformis muscle. Indications – all operations on the lower limb when combined with a saphenous nerve block. Technique – the needle is inserted at a point just lateral to the apex of the triangle formed by the biceps femoris laterally and the semimembranosus and semitendinosus tendons medially. This high approach improves the chances of blocking both divisions of the sciatic nerve. With a nerve stimulator, a twitch is obtained in the distribution of either the common peroneal nerve or the posterior tibial nerve, and about 0.5–1.0 ml/kg of 0.25% levobupivacaine is used. Complications – injury to popliteal vessels.
Reference 1 Giaufre E, Dalens B, Gombert A. Epidemiology and morbidity of regional anesthesia in children – a one year prospective survey of the ADARPEF. Anesth Analg 1996; 83: 897–900. Further reading Borgeat A. Regional anesthesia, intraneural, injection and nerve injury: beyond the epineurium (editorial). Anesthesiology 2006; 105: 647–8. Marhofer P, Greher M, Kapral S. Ultrasound guidance in regional anaesthesia. Br J Anaesth 2005; 94: 7–17. Morton NS. Local and regional anaesthesia in infants. Contin Educ Anaesth Crit Care Pain 2004; 4: 148–51. Peutrell JM, Mather SJ, eds. Regional anaesthesia for babies and children. Oxford: Oxford University Press, 1997. Tobias JD. Brachial plexus anaesthesia in children. Paediatr Anaesth 2001; 11: 265–75. Tobias JD. Regional anaesthesia of the lower extremity in children. Paediatr Anaesth 2003; 13: 152–63.
Ankle block Indications – operations on the foot or toes. Technique – the foot is supplied by five nerves, which can be blocked at the ankle. • The tibial nerve runs deep to the flexor retinaculum behind the medial malleolus and posterior to the posterior tibial artery. The needle is inserted at the level of the upper border of the medial malleolus midway between the Achilles tendon and the medial malleolus. Local anaesthetic is injected at a depth midway between skin and bone. • The sural nerve passes infero-posteriorly to the lateral malle olus. The needle is inserted at the midpoint of the Achilles tendon and the posterior border of the calcaneum. Local anaesthetic is deposited subcutaneously.
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Acknowledgement The authors would like to thank Sonosite for the loan of a MicroMaxx ultrasound machine.
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