289 LOCAL anesthetic ADMINISTRATION Local anesthetic administration Local in \201 ltration anesthesia Local in \201 ltration is the technique used most often in the ED. The LA injected subcutaneously in the immediate area of the wound acts within 1 \200\2232min. Anesthesia lasts 30 \200\22360min with plain lidocaine or 8 90min with lidocaine and adrenaline. In clean wounds the pain of injection can often be d by inserting the needle through the cut surface of the wound. Do not do this in dirty or old wounds, because of the risk of spreading infection. Less pain is produced by injecting slowly through a thin needle, injecting in a fan- shaped area from a single in jection site, and by inserting the needle in an area already numbed by an earlier injection . Rapid injection of LA, especially in scalp wounds, can cause spraying of solution from th e tip of the needle or from separation of the needle from the syringe. Slow injection and t he use of goggles should d risk of transmission of infection. Field block This involves in \201 ltration of LA subcutaneously around the operative \201 eld. Sometimes it is only necessary to block one side of the area, depending on the di rection of the nerve supply. Field block can be useful for ragged and dirty wounds, and for cleaning gravel abrasions. Check the max safe dose before starting a \201 eld block. If relatively large volumes of anesthetic might be needed, consider 0.5 % lidocaine or lidocai ne with adrenaline ( b p.285). Haematoma block A Colles \200\231 fracture ( b p.444) can be manipulated after in \201 ltr ation of LA into the fracture haematoma and around the ulnar styloid. This often pro- vides less effective anesthesia than Bier \200\231s block ( b p.290) and a poorer reduction. It converts a closed fracture into an open one and so there is a theoretical risk of infection , but in practice this is rare. Contraindications and warnings \200 Fractures > 24 hours old (since organization of the h aematoma would prevent spread of the LA). Infection of the skin over the fracture. \200 Methaemoglobinaemia (avoid prilocaine). Dru g and dosage 15mL of 1 % plain prilocaine. Lidocaine can be used, but there is a lower marg in of safety. Never use solutions containing adrenaline. Technique Use a 20mL syringe and 0.6 \227 25mm needle. Full asepsis is essential. Insert t he needle into the fracture haematoma and aspirate blood to con \201 rm this. Inject slowl y to minimize pain and reduce the risk of high blood levels and toxicity. Anesthesia develo ps in 8 5min and lasts for 30 \200\22360min. Sometimes anesthesia is inadequate for proper manipulation and so an alternative anesthetic is needed. 290 CHAPTER 7 Analgesia and anesthesia Bier \200\231s block Bier \200\231s block (IV regional anesthesia) is often used to provide anesthesia for reduction of Colles \200\231 fractures or for minor surgery below the elbow . Bier \200\231s block uses a large dose of LA and so there is a risk of a toxic reaction, although this is minimized by correct technique. Ensure that the patient has fasted for 4 h ours. Pre-operative assessment is necessary, including recording of BP and weight. Obtain w ritten consent for the operation. Bier \200\231s block should only be performed by doctors who are competent to deal with severe toxic reactions. At least two trained staff must be p resent throughout the procedure. Contraindications \200 Severe hypertension or obesity. \200 Severe peripheral vascular disease. \200 Raynaud \200\231s syndrome. \200 Sickle cell disease or trait. \200 Met haemoglobinaemia. \200 Children aged <7 years. \200 Uncooperative or confused patient. \200 Procedures needed in both arms. \200 Surgery that may last > 30min. \200 Surgery that may need the tourniquet to be released. Proceed with caution in epileptic patients be cause of the risk of a \201 t from LA toxicity. Drug and dose The only drug suitable for Bier \200\231s block is prilocaine, from a single dose vial without preservative. Never use solutions with adrenaline. Do not use lidocaine o r bupivacaine, which are more likely than prilocaine to cause toxic effects. The ideal conc entration of prilocaine is 0.5 % . If only 1 % prilocaine is available dilute it with an eq ual volume of 0.9 % saline to make 0.5 % prilocaine. The dose of prilocaine is 3mg/kg, which is 42mL of 0.5 % prilocaine for a 70kg adult, or 30 mL of 0.5 % prilocaine for a 50kg patient. Equipment \200 Special tourniquet apparatus is essential, with a 15cm wide cuff for adults. Check the tourniquet apparatus and cuff regularly. \200 Ordinary BP cuffs and sphygmomano meters are not reliable enough, and should not be used for Bier \200\231s blocks. Check that resuscitation equipment and drugs are available to hand. \200 Ensure that the patient is on a tipping trolley. \200 Monitor the ECG, BP and SpO 2 throughout. 291 BIER \200\231S BLOCK Technique for Bier \200\231s block 1 \200 Insert a small IV cannula in the dorsum of the hand on the side of opera- tion (ready for injection of prilocaine) and another IV cannula in the opposite arm (for emergency use if needed). Check the radial pulse. Place the tourniquet high on the arm over padding, but do not in \202 ate it yet. Elevate the arm for 3min while pressing over the brachial artery, to try to exsanguinate th e limb. (Do not use an Esmarch bandage for this purpose, because of pain). While the arm is elevated in \202 ate the tourniquet to 300mmHg, or at least 100mmHg above the systolic BP. Lower the arm on to a pillow and check that the tourniquet is not leaking . Record the tourniquet time. A trained person must observe the tourni- quet pressure constantly during the procedure. Slowly inject the correct volume of 0.5 % plain prilocaine into the iso- lated limb, which will become mottled. If the operation is on the hand, squeeze the forearm during injection to direct LA peripherally. Test for anesthesia after 5min. If anesthesia is inadequate inje ct 10 \200\22315mL 0.9 % saline to \202 ush the prilocaine into the arm. Occasionally, no adequate anesthesia is achieved and GA is needed instead. Complete the manipulation or operation. Before applying a POP back slab remove the cannula from the injured arm. The tourniquet cuff must remain in \202 ated for at least 20min and a maximum of 45min. Obtain a check X-ray while the tourniquet cuff is still in \202 ated (in case remanipulation is required). If the check X-ray is satisfactory de \202 ate the tourniquet slowly and record the time. Maintain a conversation with the patient and watch carefully for any sign of toxicity. If a ny toxic effects occur re-in \202 ate the tourniquet and give any necessary treatment ( b p.284). After release of the tourniquet the arm becomes warm and \202 ushed. Sensation returns after a few minutes. Observe the patient carefully for at least 30mins after a Bier \200\231s block in case of d elayed toxicity. Check the circulation of the limb before the patient is discharged home. R eactive swelling can occur: elevate the limb in a sling and give POP instructions. 1 College of Emergency Medicine Clinical Effectiveness Committee ( 2010 ) Intravenous regio nal anesthesia for distal forearm fractures (Bier \200\231s block) . College of Emergency M edicine , London . 292 CHAPTER 7 Analgesia and anesthesia Local anesthetic nerve blocks LA nerve blocks are very useful in the ED for many minor oper ations and to provide analgesia. Several nerve blocks are described in the following sectio ns. Many other nerve blocks and regional blocks are possible, but are not normally appropri ate in the ED. Some should only be performed by doctors with anesthetic training, or in a f ew cases, dental training. Equipment for nerve blocks Ordinary injection needles can be used for most local blocks in the ED. Anesthetists sometimes use special pencil-point or short bevel needles when blockin g large nerve trunks and plexuses. General procedure for nerve blocks \200 Follow the general principles of LA ( b p.282). \200 Review the relevant anatomy for the block. Determine the site of injec- tion by feeling for local structures such as arteries or tendons. When performing a nerve block hold the needle with the bevel in the line of the nerve (rath er than across it), to reduce the risk of cutting nerve \201 bres. Ask the patient about tingling in the area supplied by the nerve. Do not try to elicit para esthesiae. If paraesthesiae occur withdraw the needle 2 \200\2233mm before injecting. Wait for the nerve block to work, but do not leave the patient alone during this time. Tell the nurse when to call you back, in case you are busy with other patients. Estimate when a nerve block should be effec- tive and do not test sensation before then. Small nerves may be blocked in 5min, but large nerves may take up to 40min. Failed nerve block If a nerve block does not work, consider waiting longer or giving anothe r injection. Before giving any more LA, review relevant anatomy, consider using ultrasound guidance, and check that the maximum safe dose of the drug will not be exceeded. Entonox can be helpful as a supplement to LA for some procedures, such as reduction of dislocation s. Alternatively, sedation ( b p.308) may be useful in some cases. Occasionally, one has to abandon LA and arrange GA instead. Ultrasound guidance for nerve blocks 1 Ultrasound guida nce can help in identifying nerves and other struc- tures and allows visualization of the n eedle position and the spread of LA. Precise injection of LA adjacent to a nerve gives a fa ster onset and longer duration of anesthesia with a smaller volume of LA, less pain and a r educed risk of complications. Ultrasound is unnecessary for some nerve blocks, eg digital n erves and supraorbital nerve block. Ultrasound allows nerve blockade away from identifying structures, eg medial nerve block in the forearm. Successful use of ultrasound for LA requires appropriate equipment, knowledge of relevant a natomy, and training in ultrasound techniques. 1 Marhofer P ( 2008 ) Ultrasound Guidance for Nerve Blocks . Oxford University Press , Oxfo rd . This page intentionally left blank 294 CHAPTER 7 Analgesia and anesthesia Digital nerve block Digital nerve block is used frequently for simple operations on the \201 ngers and toes. (The term \200\230ring block \200\231 is often used, but is incorrect since it implies that LA is injected in a ring around the \201 nger, which is unnecessar y and might cause ischaemia due to vascular compression). A dorsal and a palmar digital nerve run along each side of the \201 nger and thumb. Simil arly, there are dorsal and plantar nerves in the toes. 1 % plain lidocaine is often used, but bupivacaine (0.5 % plain) is preferable because it i s less painful on injection, and gives prolonged anesthesia and analgesia. The traditional advice is never to use adrenaline or any other vasoconstrictor. In an adult use 1 \200\2232 mL of LA on each side of the \201 nger, thumb, or big toe. Use smaller volumes in the oth er toes or in children. Technique \200 Use a 0.6 \227 25 mm (23G) needle (0.5 \227 16 mm, 25G, in small childre n). \200 Insert the needle from the dorsum on the lateral side of the base of the digit, angled slightly inwards towards the midline of the digit, until the needle can be felt unde r the skin on the \202 exor aspect. \200 Aspirate to check the needle is not in a blood vessel. \200 Slowly inject 0.5 \200\2231mL. Continue injecting as the needle is withdraw n. \200 Repeat on the medial side of the digit. \200 If anesthesia is needed for the na il bed of the great toe give an addi- tional injection of LA subcutaneously across the dors um of the base of the proximal phalanx, to block the dorsal digital nerves and their branch es. This is also required for anesthesia of the dorsum of the digit proximal to the middle phalanx. Anesthesia develops after 8 5min. Autonomic nerve \201 bres are blocked, as well as senso ry nerve \201 bres, so when the block works the skin feels dry and warm. Occasionally, an esthesia remains inadequate and another injection is needed. The maximum volume that can be used in a \201 nger, thumb, or big toe is 5mL. Use less in the other toes or in children . Single injection digital nerve block Anesthesia of the distal phalanx and DIP joint can be achieved by a single subcutaneous injection in the volar aspect of the base of the \201 n ger. Pinch the soft tissues just distal to the proximal skin crease. Insert a 25G needle ju st beneath the skin at the midpoint of the skin crease and inject 2 \200\2233mL of 0.5 % bu pivacaine. Massage the LA into the soft tissues. Digital nerve block at metacarpal level Digital nerves can be blocked where they run in the interspaces between the metacarpals. Insert a thin needle in the palm through the distal p almar crease, between the \202 exor tendons of adjacent \201 ngers. Injection of 3 \200 \2234mL of 1 % plain lidocaine will block the adjacent sides of these two \201 ngers. Ane sthesia develops after 5 \200\22310min. Alternatively, a dorsal approach can be used: this is often preferred because it is less painful, but there is an i risk of inadvertent venepu ncture and the digital nerves are further from the dorsal surface, so a deep injection is n eeded. 295 DIGITAL NERVE BLOCK Digital nerve block Needle position 3 1 2 Digital artery Digital nerve 3 1 Digital nerve block at the base of the finger Distal palmar crease Site of injection Digital nerve block at metacarpal level Fig. 7.1 Digital nerve block. 296 CHAPTER 7 Analgesia and anesthesia Nerve blocks at the wrist: 1 The median nerve supplies sensation to the radial half of the palm, the thumb, index and middle \201 nger, and the radial side of the ring \201 nger. The ulnar nerve supplies the ulnar side of the hand, the little \201 nger, and the ulnar side of the ring \201 nger. The radial nerve supplies the dorsum of the radial side of t he hand. The different nerve distributions overlap. In some people, the radial side of the ring \201 nger and the ulnar side of the middle \201 nger are supplied by the ulnar, ra ther than median nerve. LA block of one or more nerves at the wrist provides good anesthesi a for minor surgery on the hand and \201 ngers. Median nerve block At the wrist the median nerve lies under the \202 exor retinaculum on the anterior aspect of the wrist, under or immediately radial to the tendon of palmaris lon gus and 5 \200\22310mm medial to the tendon of \202 exor carpi radialis. Just proximal to the \202 exor retinaculum, the median nerve gives off the palmar cutaneous branch, which travels super \201 cially to supply the skin of the thenar eminence and the central palm. Carpal tunnel syndrome is a contraindication to median nerve block. Technique \200 Use a 0. 6mm (23G) needle and 8 5 \200\22310mL of 1 % lidocaine. \200 As k the patient to \202 ex the wrist slightly and bend the thumb to touch the little \201 nger, in order to identify palmaris longus. Insert the needle vertically at the proximal wrist skin crease, between palmaris longus and \202 exor carpi radialis, angled slightly towards palmaris longus, to a depth of 1 cm. I f paraesthesiae occur withdraw the needle by 2 \200\2233 mm. Inject 8 5mL of LA slowly. \200 Block the palmar cutaneous branch by injecting another 1 \200\2232mL SC while withdrawing the needle. Some people do not have a palmaris longus tendon \200\224 in this case, identify \202 exor carpi radialis and insert the needle on its ulnar side. Ultrasound allows blockade of the median nerve in the forearm. Ulnar nerve block In the distal forearm the ulnar nerve divides into a palmar branch (which travels with the ulnar artery to supply the hypothenar eminence and palm) and a dorsal bra nch (which passes under \202 exor carpi ulnaris to supply the ulnar side of the dorsum of the hand). Technique \200 Use a 0.6mm (23G) needle and 5 \200\22310mL of 1 % lidocaine. Avoid adrenaline in peripheral vascular disease. Check the radial pulse before blocking the ulnar nerve. \200 Feel the ulnar artery and \202 exor carpi ulnaris tendon and insert the needle between them at the level of the ulnar styloid process. Aspirate and look for blood in the syringe. Withdraw the needle 2 \200\2233mm if paraesthesiae occur. Inject 5mL of LA. \200 Block the dorsal branch of the ulnar nerve by SC in \201 ltration of 3 \200\2235mL of LA from \202 exor carpi ulnaris around the ulnar border of the wrist . 297 NERVE BLOCKS AT THE WRIST: 1 Nerve blocks at the wrist Radial nerve Median nerve Ulnar nerve Median nerve Flexor carpi radialis Palmaris longus Ulnar nerve Flexor carpi ulnaris Ulnar artery Fig. 7.2 Nerve blocks at the wrist. 298 CHAPTER 7 Analgesia and anesthesia Nerve blocks at the wrist: 2 Radial nerve block In the distal part of the forearm the radia l nerve passes under the tendon of brachioradialis and lies subcutaneously on the dorsum of the radial side of the wrist, where it separates into several branches and supplies the ra dial side of the dorsum of the hand. Technique \200 Use a 0.6mm (23G) needle and 5mL of 1 % lidocaine, with or without adrenaline. In \201 ltrate LA subcutaneously around the radial side and dorsum of the wrist from the t endon of \202 exor carpi radialis to the radio-ulnar joint. Beware of inadvertent IV inje ction. Radial nerve block involves an in \201 ltration technique and often has a more rapid onset and shorter duration of action than median nerve and ulnar nerve blocks. In combined block s, experts may use lidocaine with adrenaline in order to prolong the anesthetic and d the r isk of lidocaine toxicity. Other nerve blocks in the arm Nerve blocks at the elbow The median, ulnar, and radial nerve s can be blocked at the level of the elbow, but this is rarely necessary. The onset of anes thesia is slower than with blocks at the wrist. Brachial plexus blocks These should only be used by doctors with anesthetic training. Brach ial plexus blocks can provide good anesthesia for operations on the arm but the onset of an esthesia is often slow (30 \200\223 45min) and there is a risk of LA toxicity because of th e large dose required. The axillary approach can be used in outpatients. If the supraclavic ular approach is used, admission to hospital is necessary, because of the risk of a pneumot horax. Ultrasound guidance helps to allow accurate positioning of the injection, which impr oves the effective- ness of the block and reduces the risk of complications. 299 NERVE BLOCKS AT THE WRIST: 2 Radial nerve block at the wrist Radial nerve Fig. 7.3 Radial nerve block at the wrist. 300 CHAPTER 7 Analgesia and anesthesia Nerve blocks of forehead and ear Nerve blocks of the forehead Many wounds of the forehead a nd frontal region of the scalp can be explored and repaired conveniently under LA block of the supraorbital and supratrochlear nerves. The supraorbital nerve divides into medial and lateral branches, and leaves the orbit throu gh two holes or notches in the superior orbital margin, 8 2.5 cm from the midline. The bran ches of the supraorbital nerve supply sensation to most of the forehead and the frontal reg ion of the scalp. The supratrochlear nerve emerges from the upper medial corner of the orbit and supplies sen sation to the medial part of the forehead. Technique \200 Use 5 \200\22310mL of 1 % lidocaine, with or without adrenaline. \200 In sert the needle in the midline between the eyebrows and direct it laterally. Inject LA subcutaneously from the point of insertion along the upper margin of the eyebrow. If the wound extends into the lateral part of the forehead SC in \201 ltration of LA may b e needed lateral to the eyebrow to block the zygomatico- temporal and auriculotemporal nerv es. Possible complications \200 Injury to the eye can occur if the patient moves during the i njection. \200 It is possible to block the supraorbital nerve at the supraorbital foramen , but this is not advisable since inadvertent injection into the orbit may cause temporary blindness if the LA reaches the optic nerve. Nerve blocks of the ear The auricle (pinna) of the ear is supplied by branches of the great er auricular nerve (from inferiorly), lesser occipital nerve (posteriorly), and the auricul otemporal nerve (anteriorly/superiorly). These nerves can be blocked by SC in \201 ltratio n of up to 10mL of 1 % plain lidocaine in the appropriate area, or in a ring around the ear . To block the greater auricular nerve in \201 ltrate 1cm below the ear lobe from the poster ior border of the sternomastoid muscle to the angle of the mandible. Block the lesser occipital nerve by in \201 ltration just behind the ear. When blocking the auriculotemporal nerve by in \201 ltration just anterior to the external auditory meatus, aspirate carefully to avoid inadvertent injection into the super \201 ci al temporal artery. 301 NERVE BLOCKS OF FOREHEAD AND EAR Nerve blocks: forehead and ear Supraorbital nerve Supratrochlear nerve Auriculotemporal nerve Superficial temporal artery Lesser occipital nerve Greater auricular nerve Fig. 7.4 Nerve blocks of the forehead and ear. 302 CHAPTER 7 Analgesia and anesthesia Dental anesthesia Intraoral injections of local anesthetic are used frequently for dental p ro- cedures, but can also be useful for cleaning and repair of wounds of the lips, cheeks, and chin. Instruction by a dentist or oral surgeon is required. Give dental anesthetics wit h dental syringes and cartridges of LA. An appropriate drug for most purposes is lidocaine 2 % with adrenaline 1 in 80,000. Some dental syringes do not allow aspiration prior to inje ction. Disposable dental syringes are preferable to reusable syringes, to d risk of needles tick injury from resheathing of needles. Infra-orbital nerve block The infra-orbital nerve supplies the skin and mucous membrane of the cheek and upper lip, and also the lower eyelid and the side of the nose. The nerve emer ges from the infra-orbital foramen, which is 0.5cm below the infra-orbital margin and verti cally below the pupil when the eyes are looking forwards. The nerve can be blocked at the i nfra-orbital foramen by injection through the skin, but the intraoral approach is preferabl e, because it is less unpleasant for the patient. Insert the needle into the buccogingival fold between the \201 rst and second premolars, and direct it up towards the infra-orbita l foramen. Mental nerve block The mental nerve supplies sensation to the lower lip and the chin. It em erges from the mental foramen, which is palpable on the mandible on a line between the \201 rst and second premolar teeth. The nerve can be blocked at the mental foramen with 1 \200\2232mL of LA, using either an intra- or extra-oral approach. Avoid injecting into the mental canal, since this may damage the nerve. If the wound to be repaired extends across t he midline bilateral mental nerve blocks will be needed. The nerves to a single lower incisor may be blocked by submucous in \201 ltration of LA in the buccal sulcus adjacent to the tooth. 303 INTERCOSTAL NERVE BLOCK Intercostal nerve block Intercostal nerve blocks can give useful analgesia for patients wit h rib fractures who are admitted to hospital, but it is not a routine procedure and require s training and experience. These blocks must not be used in outpatients and should not be p erformed bilaterally because of the risk of pneumothorax. Patients with obesity or severe o bstructive airways disease have i risk of complications. Alternative procedures used in ICU are interpleural analgesia and thoracic epidurals, but these are not appropriate in the ED . 304 CHAPTER 7 Analgesia and anesthesia Femoral nerve block Femoral nerve block is a simple technique and provides good analgesia w ithin a few minutes for pain from a fractured shaft of femur. It may be used in children, a s well as in adults. Perform femoral block on the clinical diagnosis of a fractured shaft o f femur, before X-ray or the application of a traction splint. Femoral nerve block can be used with a block of the lateral cutaneous nerve of the thigh fo r anesthetizing a skin donor site. Anatomy The femoral nerve passes under the inguinal ligament, where it lies lateral to the femoral artery. The femoral nerve supplies the hip and knee joints, the skin of the medial and anterior aspects of the thigh, and the quadri- ceps, sartorius and pectineus muscles in the anterior compartment of the thigh. Technique \200 Use a mixture of lidocaine and bupivacaine to give both rapid onset and pr olonged anesthesia. In an adult give 5mL of 1 % lidocaine and 5mL of 0.5 % bupivacaine. In a child use 0.1mL/kg of 1 % lidocaine and 0.1mL/kg of 0.5 % bupivacaine. Check the maximum dose carefully, especially in children or if bilateral femoral nerve blocks are needed. Use a 0.8 \227 40 mm (21G) needle in adults and a 0.6 \227 25 mm (23G) needle in children. Blocking the right femoral nerve is best performed from the patient \200\231s left side (and vise versa). Using your non-dominant hand palpate the femoral artery just below the inguinal ligament. Clean the skin. \200 Insert the needle perpendicular to the skin and 1cm lateral to the a rtery to a depth of 8 3cm. If paraesthesiae occurs, withdraw the needle 2 \200\2233mm. Aspirate and check for blood. \200 Inject LA while moving the needle up and down and fann ing out later- ally to 8 3cm from the artery. (The distances quoted refer to adults.) \200 If the femoral artery is punctured compress it for 5 \200\22310min. If no bleeding is apparent, continue with the femoral nerve block. This \200\230blind \200\231 technique for femoral nerve block has a high success rate and usually provides rapid and effective analgesia. However, ultrasound ( b p.292) can be helpf ul to delineate the anatomy of the femoral nerve (which can vary between patients) and to a llow precise positioning of the injection adjacent to the nerve. 305 FEMORAL NERVE BLOCK Femoral nerve block Anterior superior iliac spine Femoral nerve Femoral artery Femoral vein Femoral artery Fig. 7.5 Femoral nerve block. 306 CHAPTER 7 Analgesia and anesthesia Nerve blocks at the ankle Indications \200 Cleaning, exploration and suturing of wounds o f the foot. \200 Removal of FB. Drainage of small abscesses on the sole of the foot. \200 Analgesia for crush injuries of the forefoot. \200 LA blocks at the ankle are parti cularly useful for anesthetizing the sole of the foot, where local in \201 ltration is ver y painful and unsatisfactory. Anatomy Sensation in the ankle and foot is supplied by 5 main nerves: \200 Saphenous nerv e (medial side of ankle). \200 Super \201 cial peroneal nerve (front of ankle and dorsum of foot). \200 Deep peroneal nerve (lateral side of big toe and medial side of 2nd toe). Sural nerve (heel and lateral side of hind foot). \200 Tibial nerve (which forms the medi al and lateral plantar nerves, supplying the anterior half of the sole). There are individual variations and signi \201 cant overlap between the areas supplied by different nerves, especially on the sole of the foot. It is often necessary to block more t han one nerve. For each of these blocks use a 0.6mm (23G) needle and 5mL of 1 % lidocaine (with or without adrenaline) or 0.5 % bupivacaine. Check the maximum dose (b p.283), especially for multipl e blocks. Ultrasound can help to allow accurate injection of LA, so smaller amounts are nee ded. Do not use adrenaline in patients with peripheral vascular disease. Saphenous nerve In \201 ltrate LA subcutaneously around the great saphenous vein, anterior to and just above the medial malleolus. Aspirate carefully because of the risk of IV injec tion. Super \201 cial peroneal nerve In \201 ltrate LA subcutaneously above the ankle joint fro m the anterior border of the tibia to the lateral malleolus. Deep peroneal nerve Insert the needle above the ankle joint between the tendons of tibialis anterior and extensor hallucis longus. Inject 5mL of LA. Sural nerve Lie the patient prone. Insert the needle lateral to the Achilles tendon and in \201 ltrate subcutaneously to the lateral malleolus. Tibial nerve Lie the patient prone. Palpate the posterior tibial artery. Insert the needle medial to the Achilles tendon and level with the upper border of the medial malleolus, so t he needle tip is just lateral to the artery. Withdraw slightly if paraesthesiae occur. Aspi rate. Inject 5 \200\22310mL. 307 NERVE BLOCKS AT THE ANKLE Nerve blocks at the ankle Sural nerve Medial plantar nerve Lateral plantar nerve Sural nerve Tendo Achilles Lateral malleolus Posterior tibial artery Tibial nerve Medial malleolus Tendo Achilles Fig. 7.6 Nerve blocks at the ankle. 308 CHAPTER 7 Analgesia and anesthesia Sedation Sedation is often used in the ED to help patients tolerate distressing procedures, such as reduction of dislocations. It carries the same risks and complications as GA. When appropriate, sedation may be used with an analgesic or LA, but do not use sedation as a su bstitute for adequate analgesia or anesthesia. Sedative drugs may be given PO, IM, IV, or b y inhalation. Oral sedation may be helpful in children. Inhalational sedation and analgesia with nitrous oxide (Entonox , b p.278) is rapidly revers- ible, relatively risk-free, a nd can be used when appropriate in adults and some children. IV sedation of children is par ticularly hazardous because of the narrow margin between sedation and anesthesia, so it sho uld only be performed in the ED by staff with speci \201 c training. Risk assessment Main risks of sedation are respiratory depression, d cardiac output and inhalation of gastric co ntents. Patients at i risk of respiratory or cardiac complications include elderly, obese a nd those with pre-existing heart/lung disease. Patients with renal or hepatic disease may r equire d drug dosage. Ideally, patients should be fasted before IV sedation. Ask about and record pre-existing medical conditions, drug therapy, allergies, and time of last food and drink. Record pulse and BP. If there is any uncertainty, postpone the procedure or get expe rt help. Equipment Use a trolley which can be tilted head-down. Ensure suction, resuscitati on equipment and drugs are immediately available. Staff Sedation should only be given by do ctors trained in resuscitation. A second person (doctor or nurse) must be present throughou t to assist. Some sedatives cause amnesia and transient confusion \200\224 the presence of a chaperone may avoid dif \201 culties if there is any allegation of impropriety. Drugs f or IV sedation All sedative drugs will produce anesthesia if given in excessive dosage. Use the minimum dose that will give adequate sedation and allow the procedure to be completed satisfactorily. Midazolam is the most suitable benzodiazepine. It has a plasma half-life of about 2hr in young adults (longer in elderly or obese) and metabolites are relatively inac tive. There are three concentrations (1, 2, and 5mg/mL) which are easily confused. In \201 t adults initial dose of midazolam is 2mg IV over 1min. If sedation is inadequate afte r 2min, give incremental doses of 0.5 \200\2231mg (0.25 \200\2230.5mL of 10mg/5mL solution) . When fully sedated, the patient will be drowsy with slurred speech, but will obey command s. The usual dose range is 2.5 \200\2237.5mg. Elderly patients are more susceptible to benz odiazepines \200\224 give smaller doses. Give 0.5 \200\2231mg as an initial dose: the tota l dose needed is usually 1 \200\2233mg. Diazepam is not suitable for IV sedation of outpati ents, since it has a prolonged action and an active metabolite with a plasma half-life of 8 3 \200\2235 days. Opioids such as morphine ( b p.276) may be used IV combined with midazol am, but there may be a synergistic effect with i risk of respiratory depression. Give the o pioid \201 rst in d dosage, followed by careful titration of midazolam. Other drugs Propo fol ( b p.316) can give excellent sedation for short procedures, with rapid recovery, but i ts use requires anesthetic training. Ketamine ( b p.278) may be given IV or IM, but require s special training. 309 SEDATION Monitoring during IV sedation Ensure patients given IV sedation receive O 2 , pulse oximetr y monitoring and have a venous cannula. Monitor ECG. Antagonists The speci \201 c antagonists \202 umazenil (for benzodiazepines) and naloxon e (for opioids) must be available immediately, but should be needed very rarely. If respira tory depression occurs, standard techniques to maintain the airway and breathing are more i mportant than giving antagonists. Flumazenil and naloxone have shorter durations of action than the drugs they antagonize, so careful observation is essential if either drug is used. Recovery and discharge after sedation If IV sedation is used, monitor the patient carefully until recovery is complete. Monitoring and resuscitation equipment and drugs must be available. Minimum criteria for discharging a patient are: \200 Stable vital signs. \200 Ability t o walk without support. \200 Toleration of oral \202 uids and minimal nausea. \200 Ad equate analgesia. \200 Adequate supervision at home by a responsible adult. Instruct the patient (both verbally and in writing) not to drive, operate machinery, make any important decisions or drink alcohol for 24 hours. Arrange appropriate follow-up. Ensure the adult ac companying the patient knows who to contact if there is any problem. Sedation in children Many children (and their parents and staff) are distressed by proce- d ures such as suturing of minor wounds under LA. Sedation is helpful to prevent distress and allows procedures to take place with minimal physical restraint. Sedation may be given by oral or nasal routes, IM or IV. Pediatric IV sedation requires anesthetic experience becaus e of the narrow therapeutic margin between sedation and anesthesia. Ketamine given IM in a dose of 2 \200\2232.5mg/kg is currently the method of choice for ped iatric sedation in the ED by doctors with appropriate training ( b p.278). This dose of ket amine does not provide full anesthesia and so local anesthesia is required for cleaning and suturing of wounds. Oral midazolam is advocated by some specialists. Oral sedation with promethazine is not adv isable, since it is often ineffective. 310 CHAPTER 7 Analgesia and anesthesia General anesthesia in the emergency department GA may be needed in the ED for many differen t conditions: \200 Minor surgery (eg drainage of abscesses, manipulation of fractures). \200 Cardioversion. \200 Airway problems (eg facial trauma, burns, epiglottitis). \200 Respiratory failure (eg asthma, chronic obstructive airways disease, pulmonary oedema, chest injuries). To protect the airway and control ventilation after head injuries and to keep the patient immobile for a CT scan. To protect the airway and maintain ventilation in status epilepticus unresponsive to standard drug therapy. Immediate major surgery (eg thoracotomy or laparotomy for trauma, ruptured ectopic pregnanc y or aortic aneurysm). If at all possible take the patient to the operating theater before anesthesia, as the loss of sympathetic tone after the onset of anesthesia can cause catastr ophic hypotension in a hypovolaemic patient. In extreme emergencies, it may be necessary to operate in the ED. GA in the ED tends to be stressful for the anesthetist and potentially hazardous for the pa tient, who is usually unprepared for anesthesia, with a full stomach and increased risk of aspiration. GA should only be given by doctors with anesthetic training, but other staff sh ould know what is required so they can help when necessary. Pre-operative assessment This is essential for safe anesthesia. If time allows, assess the patient before contacting the anesthetist to arrange the anesthetic. However, if emergency anesthesia is needed, call the anesthetist immediately so that he/she can come and assess t he patient, and get senior help if necessary. A checklist of questions to ask before GA is shown opposite. Fitness for GA The American Society of Anaesthesiologists (ASA) classi \201 - cation of pr e-operative \201 tness is widely used by anesthetists: 1 Healthy patient with no systemic disease. 2 Patient with a mild to moderate disease which does not limit their activity in any way (eg treated hypertension, mild diabetes, smoker). 3 Patient with a severe systemic disturbance from any cause which limits activity (eg IHD with d exercise tolerance, severe COPD). 4 Patient with a severe systemic disease which is a constant threat to life (eg severe chronic bronchitis, advanced liver disease). 5 Moribund patient who is unlikely to survive 24 hours with or without treatment. The risk of complications from GA correlates well with ASA group. Only patients in ASA grou ps 1 and 2 should be given an elective anesthetic by a junior anesthetist in the ED. Childr en aged <7 years should not usually have a GA in the ED, except in an emergency. 311 GENERAL anesthesia IN THE EMERGENCY DEPARTMENT Pre-operative investigations No investigation except \200\230dipstick \200\231 urinalysis is needed, unless pre-operative assessment reveals a problem. Measure Hb in any patient who appears anemic. Check for sickle cell disease in any patient of Afro-Caribbean, Cypriot or Indian origin. Measure U&E in patients on diuretics, and blood glucose in diabetics. ECG a nd CXR are not needed, unless clinically indicated. Perform a pregnancy test if pregnancy i s possible. Checklist for pre-operative assessment in the ED Age. \200 Weight. \200 Time of last drink. \200 Time of last food. \200 Drugs. \200 Drugs given in the ED. \200 Time of last analgesia. \200 Allergies. \200 Sickle cell risk? \200 Infection risk? \200 Family history of GA problems? \200 Is the pati ent expected to go home after recovery from anesthetic? \200 Is there a responsible adult who can look after the patient at home? Airway problem? \200 Dentures/crowns/loose teeth? \200 Chest disease? \200 Smoker? \200 Cardiac disease? \200 Blood pressure. \200 GI problem? \200 Other illness? \200 Possibility of pregnancy? \200 Previous GA? (problems?) \200 Consent form signed? Preparation for GA Ideally, the patient should have nothing to drink for 4 hours and no foo d for 6 hours before anesthesia. Explain why this is necessary. Fasting does not guarantee an empty stomach. Trauma, pregnancy and opioids delay gastric emptying. If the patient is in pain, give analgesia and an antiemetic. Discuss with the anesthetist a ny other drug treatment that is required. Patients with a hiatus hernia or gastro-oesophage al re \202 ux need antacid prophylaxis (eg ranitidine 50mg IV and an antacid). Explain the proposed operation and anesthetic to the patient (and relatives if appropriate) and ensure valid consent is obtained. The patient must be clearly labeled with a wrist-ban d. Remove contact lenses, false teeth and dental plates.