Many NSAIDs are available and all can cause serious adverse effects, but ibuprofen, diclofe nac and naproxen are relatively safe and cover most requirements. Ibuprofen has the lowest incidence of side effects, is the cheapest of these drugs and may be bought without prescri ption. Ibuprofen is useful in children as an analgesic and antipyretic, especially when par acetamol is insuf \201 cient. \200 Ibuprofen dosage 1.2 \200\2231.8g daily in 3 \200\223 4 divided doses (max 2.4g daily). Child ( > 7kg): 20mg/kg daily in 3 \200\2234 divided doses. Diclofenac (oral or rectal) 75 \200\223150mg daily in 2 \200\2233 divided doses. \200 Nap roxen 500mg initially, then 250mg 6 \200\2238-hourly (max 1.25g daily). Acute gout 750mg initially, then 250mg 8-hourly until pain resolves. Injectable NSAIDs Some NSAIDs may be given by injection for musculoskeletal pain (eg acute low back pain), or for renal or biliary colic. The contra indications and side effects are the same as for oral treatment. Intramuscular (IM) injections are painful and can cause ste rile abscesses, so oral or rectal treatment is preferable. NSAIDs provide effective analges ia for renal colic, but the onset is slower than with IV opioids, which some prefer. A NSAI D is particularly useful in suspected drug addicts who claim to have renal colic. \200 Ke torolac may be given IM or slowly IV (initial dose 10mg over at least 15sec: see BNF ). It is useful as an adjunct for MUAs. Diclofenac must be given by deep IM injection (not IV, which causes venous thrombosis). Dos e: 75mg, repeated if necessary after 30min (max 150mg in 24 hours). Topical NSAIDs NSAID gels or creams applied to painful areas provide some analgesia, but ar e less effective than oral treatment. Systemic absorption may occur and cause adverse effec ts as for oral NSAIDs. 276 CHAPTER 7 Analgesia and anesthesia Analgesics: opioids Morphine Morphine is the standard analgesic for severe pain. As well as providing analgesia, it is sometimes used for cardiogenic pulmonary oedema ( b p.101) to r elieve distress and to help increase venous capacitance. Morphine often causes nausea and vomiting in adults, so consider giving an anti-emetic (cyc lizine 50mg IV/IM or prochlorperazine 12.5mg IM). Anti- emetics are not usually necessary i n children aged < 10years. Other side-effects of opioids include drowsiness and constipation. Respiratory depression a nd hypotension may occur, especially with large doses. Pinpoint pupils can complicate neuro logical assessment. Naloxone ( b p.188) reverses the effects of opioids. In acute condition s, give morphine by slow IV injection, which provides rapid but controlled analgesia. The d ose varies with the patient and the degree of pain. Titrate the dose depending on the respo nse: 2mg may be adequate in a frail old lady, but sometimes > 20mg is needed in a young \201 t person with severe injuries. Dilute morphine with 0.9 % saline to 1mg/mL (label the syringe clearly) and give it slowly IV (1 \200\2232mg/min in adults) in 1mg increments unti l pain is relieved. Give further analgesia if pain recurs. IV morphine dose in children is 100 \200\223200micrograms/kg, given in increments, repeated as necessary. Patient-controlle d analgesia using a computerized syringe pump is very good for post-operative analgesia, bu t rarely appro- priate in the ED. IM injections provide slower and less controlled effects than IV analgesia: avoid their use , especially in shocked patients. IM morphine could be used in children needing strong anal gesia but not IV \202 uids (eg while dressing super \201 cial burns), but oral or nasal analgesia is preferable. \200 Morphine may be given orally as Oramorph oral solution: child aged 1 \200\2235 years: max dose 5mg (2.5mL); \200 child aged 6 \200\22312 years: m ax dose 5 \200\22310mg (2.5 \200\2235mL). Codeine is given orally for moderate pain (30 \200\22360mg 4hrly, max 240mg daily) and has side effects similar to morphine. Codeine may also be given IM (but not IV, because it may cause hypotension). Dihydrocodeine is very similar to codeine. \200 Diamorphine (heroin) has similar effects to morphine, but is more soluble and so can be dissolved in a very small volume of diluent. Nasal diamor- phine provides effective analgesia in children ( b p.281). Fentanyl is a short-acting opioid which is often used in anesthesia. \200 Pethidine provi des rapid but brief analgesia, but is less potent than mor- phine. It is sometimes used for renal or biliary colic in preference to morphine, which occasionally causes smooth muscle spasm ( b p.277). Pethidine is given slowly IV, titrated as necessary (usual adult dose 50m g IV), or less effectively IM (50 \200\223100mg). Give an anti-emetic with it. 277 ANALGESICS: OPIOIDS Smooth muscle spasm due to opioid analgesics In a few patients opioids such as morphine can cause severe pain due to smooth muscle spasm, especially spasm of the sphincter of Oddi. A bout 5 \200\22320 minutes after morphine has been given, severe colicky abdominal pain deve lops. This may be typical of biliary colic but can mimic renal colic, intestinal perforatio n or myocardial infarction. Pain from spasm of the sphincter of Oddi may be relieved by glucagon (1mg IV, repeated if n ecessary) although this is liable to cause vomiting. Naloxone (0.2mg IV, repeated if necess ary) is also effective, but may reverse desired analgesia. GTN can also relieve smooth musc le spasm of the sphincter of Oddi. Glucagon is probably the treatment of choice for this ra re complication of opioid analgesia. 278 CHAPTER 7 Analgesia and anesthesia Analgesics: Entonox and ketamine Entonox Entonox is a mixture of 50 % N 2 O and 50 % O 2 . It is stored as a compressed gas in blue cylinders with a blue and white shoulder. It is unsuitable for use at < \200\2236 C, since the gasses separate and a hypoxic mixt ure could be given. Entonox diffuses more rapidly than nitrogen and so is contra indicat ed with the following: undrained pneumothorax (since it may produce a tension pneumothorax) , after diving ( i risk of decompression sickness), facial injury, base of skull fracture, intestinal obstruction, d conscious level. Entonox is controlled by a demand valve and i nhaled through a mask or mouthpiece, often held by the patient. It gives rapid and effectiv e analgesia and is widely used in prehospital care. In the ED, Entonox is useful for ini tial analgesia, eg while splinting limb injuries, and for many minor proce- dures, such as reduction of a dislocated patella or \201 nger. Tell the patient to breathe deeply throug h the mask or mouthpiece, and warn that he may feel drowsy or drunk, but that this will wea r off within a few minutes. Ketamine Ketamine is a dissociative anesthetic drug which may be given IM or IV by experts, and which provides strong analgesia in sub-anesthetic dosage. It is rarely used in hospita l practice for adults, because it may cause severe hallucinations, but these are less of a problem in children. It is very useful for sedation of children for procedures such as sutu ring of minor wounds. Ketamine is particularly useful in prehospital care and is the most a ppro- priate drug in the rare cases when a GA is needed outside hospital for extrication or emergency amputation. Airway-protective re \202 exes are maintained better with ketamine than with other inducti on agents, but airway obstruction and aspiration of gastric contents are still potential ha zards. Respiratory depression is uncommon at normal dosage. Ketamine is a bronchodilator an d may be used in asthmatics. It stimulates the cardiovascular system and often causes tachy cardia and hypertension, so avoid it in severe hypertension. Hallucinations are less likely if a small dose of midazolam is given and the patient is not disturbed during recovery fro m anesthesia. Ketamine is available in 3 strengths : 10, 50, and 100mg/mL, which are easily confused. The IV dose for GA is 1 \200\2232mg/kg over 1min, which is effective after 2 \200\2237min and provides surgical anesthesia for 5 \200\22310min. The IM dose for GA is 10mg/kg, which is e ffective after 4 \200\22315min and gives surgical anesthesia for 12 \200\22325min. Further doses (10 \200\22320mg IV or 20 \200\22350mg IM) can be given if major limb movements or i muscle tone prevent extrication of the patient. For sedation of children undergoing suturin g or other minor procedures, ketamine may be given IM (2.5mg/kg) or IV (1mg/kg over at leas t 1min). With this dose of ketamine, LA is needed for cleaning and suturing of wounds, but little physical restraint should be needed to allow the pro- cedure to take place. Occasion ally, a second dose of ketamine (1mg/kg IM or 0.5mg/kg IV) is required to achieve adequate sedation. Larger initial doses provide deeper sedation, but are more likely to cause side e ffects (eg vomiting or agitation) during recovery. With low doses of ketamine, agitation is unlikely and there is no need to add midazolam. 279 ANALGESIA FOR TRAUMA Analgesia for trauma Multiple injuries Entonox may be useful for analgesia during transp ortation and initial resusci- tation, but only allows administration of 50 % O 2 and should not be used if there is an undrained pneumothorax. As soon as practicable use other forms of analgesia, usually IV morphine ( b p.276) and/or nerve blocks ( b p.292), and splint fra ctures to d pain and d blood loss. Head injury Relief of pain is particularly important in head-injured patients, since pain a nd restlessness i ICP, which can exacerbate secondary brain injury. Headache following a he ad injury can usually be treated with paracetamol, diclofenac or codeine phosphate (which m ay cause less central depression than stronger opioids such as morphine). If the headache i s severe or increasing, arrange a CT scan to look for an intracranial haematoma. Try to avo id strong opioids, because of concern about sedation and respiratory depression, but if pai n is severe give morphine in small IV increments: the effects can be reversed if necessary with naloxone. Femoral nerve block is particularly useful in a patient with a head injury a nd a fractured femur, since it d or avoids the need for opioids. Small children with minor head injuries often deny having headaches, but look and feel much better if given paracetam ol ( b p.274). Give further doses if necessary over the following 12 \200\22324 hours. Chest injury Chest injuries are often extremely painful. Good analgesia is essential to rel ieve distress and d risk of complications such as pneumonia and res- piratory failure. Avoi d Entonox if a pneumothorax is a possibility, until this has been excluded or drained. G ive high concentration O 2 as soon as possible and check SpO 2 and ABG. Give morphine in sl ow IV increments ( b p.276) and monitor for respiratory problems. Intercostal nerve blocks ( b p.303) provide good analgesia for fractured ribs, but may cause a pneumothorax and shou ld only be used in patients being admitted. In severe chest injuries get anesthetic or ICU help: thoracic epidural anaes- thesia can sometimes avoid the need for IPPV. Before a thora cic epidural is performed, check X-rays of the thoracic spine for fractures. 280 CHAPTER 7 Analgesia and anesthesia Analgesia in speci \201 c situations Children Injured children are distressed by both fear and pain. Parental support can be very helpful. Sensitive treatment, explanation and reass urance are important, but give analgesia whenever necessary. Oral analgesia is usually with paracetamol ( b p.274), but if this is inadequate add ibuprofen ( b p.275), dihydrocodeine elixir, or Oramorph : \200 Ibuprofen dose: 20mg/kg daily in divided doses as ibuprofe n suspension (100mg in 5mL) 1 \200\2232 years: 2.5mL; 3 \200\2237 years: 5mL; 8 \200\22312 years: 10mL; all 3 \200\2234 times daily. Dihydrocodeine elixir dose: 0.5 \200\2231mg/kg PO 4 \200\2236-hourly. \200 Children in se vere pain may bene \201 t from oral morphine (as Oramorph oral solution \200\224 b p.276). Entonox (b p.278) gives rapid analgesia without the need for an injection. IV morphine is appropriate in severe injuries, but take particular care if there is a head injury, since sedation may occur. Femoral nerve block ( b p.304) provides good analgesia fo r femoral fractures and is usually well tolerated. Digital nerve block with bupivacaine ( b p.294) is useful for painful \201 nger injuries, especially crush injuries. Provide this before X-ray: when the child returns from X-ray the \201 nger may then be cleaned and dr essed painlessly. IM morphine could be used to provide analgesia for small burns or fractured arms, but oral morphine or nasal diamorphine are preferable, since IM injections are painful and unpleasan t. Nasal diamorphine is not licensed, but is playing an increasing role in the provision of pa in relief in children (see Table 7.1 ). Acute abdominal pain It is cruel and unnecessary to withhold analgesia from patients with a cute abdominal pain. Adequate analgesia allows the patient to give a clearer history, and o ften facilitates examination and diagnosis: tenderness and rigidity become more localized, and masses more readily palpable. Good X-rays cannot be obtained if the patient is distress ed and restless because of renal colic or a perforated ulcer. Morphine by slow IV injection ( b p.276) is appropriate in severe pain, unless this is due to renal or biliary colic, in which an NSAID ( b p.275) may be preferred. Morphine occasionally causes severe abdominal pain due to smooth muscle spasm of the sphincter of Oddi ( b p.277). Toothache Toothache or pain after dental extractions can often be eased by aspirin, a NSAID or paracetamol. Do not give opioids such as codeine or dihydrocodeine, which may make the pain worse. Drainage of a dental abscess may be required to relieve toothache. 281 ANALGESIA IN SPECIFIC SITUATIONS Nasal diamorphine for analgesia in children1,2 In the UK, diamorphine is licensed for use I V, IM, SC and PO. Nasal diamorphine is unlicensed, but clinical studies and experience have shown that this is an effective and acceptable method of analgesia for children with limb fractures or small burns who do not need immediate venous access. It should be given as soo n as possible, prior to X-rays. Contraindications: age <1 year (or weight <10kg), nasal obstruction or injury, basal skull fracture, opioid sensitivity. Verbal consent for nasal diamorphine should be obtained from the child \200\231s parents (a nd the child if appropriate), since this is an unlicensed route of administration of this d rug. Follow local protocols. The dose of nasal diamorphine is 0.1mg/kg, given in a syringe in a volume of 0.2mL. The chi ld is weighed. The appropriate concentration of solution for the weight of child is achieve d by adding a suitable volume of 0.9 % saline to a 10mg ampoule of diamorphine. Table 7.1 Dosage of nasal diamorphine in children Weight (kg) Volume of saline (mL) Dose of diamorphine (mg) in 0.2mL 10 2.0 1.0 15 1.3 1.5 20 1.0 2.0 25 0.8 2.5 30 0.7 2.9 35 0.6 3.3 40 0.5 4.0 50 0.4 5.0 60 0.3 6.7 0.2mL of this solution is drawn up into a syringe and given in one or both nostrils, whilst the child \200\231s head is tilted backwards. Turn the head to each side, maintaining each position for several secs. A small syringe can be used to drip the solution into the nose, but if possible use an aerosol device (eg MAD ), allowing for the dead space of the dev ice (0.1mL for MAD, so draw up 0.3mL). Record the time of administration. Monitor conscious level for 20min. Respiratory depression is unlikely, but resuscitation facili- ties and na loxone must be available. Nasal diamorphine provides rapid analgesia which lasts up to 4 hr . Fentanyl may also be used nasally (initial dose 2micrograms/kg) as an alternative to nasal diamorphine. 1 College of Emergency Medicine Clinical Effectiveness Committee ( 2009 ). Guideline for th e management of pain in children . College of Emergency Medicine , London . 2 http://intranasal.net/PainControl/default.htm 282 CHAPTER 7 Analgesia and anesthesia Local anesthesia (LA) Indications for LA in the emergency department LA is indicated in any situation in which it will provide satisfactory analgesia or safe and adequate conditions for operations or procedures. These include the following: \200 Insertion of venous cannu lae (0.1mL of 1 % lidocaine SC 30 secs prior to cannulation d pain of cannulation without a ffecting the success rate). Cleaning, exploration and suturing of many wounds. \200 Analgesia for some fractures , eg shaft of femur. \200 Minor operations/procedures, eg manipulation of some fractures and dislocations, insertion of chest drain, drainage of paronychia, removal of corneal FB. Contraindications to local anesthetic \200 Refusal or poor co-operation by the patient. \200 Allergy to local anesthetic Severe allergic reactions to LA are rare, but anaphylaxis can occur. If allergy to a LA is alleged, obtain full details of the circumstances and the drug involved and check with a senior before giving any LA. It may be possible to use a di fferent drug. Some reactions are caused by the preservative in multi-dose vials, rather tha n the drug itself, so single dose ampoules may not cause a problem. Some alleged \200\230a llergies \200\231 are actually toxic effects due to overdosage, or faints due to fear and p ain. Infection at the proposed injection site Injection into an in \202 amed area is painful an d could spread infection. High tissue acidity from in \202 ammation d effectiveness of LA drugs. Hyperaemia causes rapid removal of the drug and so a short duration of action and i risk of toxicity. LA nerve block at a site away from the infected area can provide good ana es- thesia, eg digital nerve block for paronychia or nerve blocks at the ankle for an absce ss on the sole of the foot. Bleeding disorder Anticoagulant therapy and thrombocytopenia are contraindications for nerv e blocks in which there is a risk of inadvertent arterial puncture. Special cautions ( i risk of toxicity) \200 Small children. \200 Elderly or debilitated . \200 Heart block. \200 Low cardiac output. \200 Epilepsy. \200 Myasthenia gravis. \200 Hepatic impairment. \200 Porphyria. \200 Anti-arrhythmic or B -blocker therapy (risk of myocardial depression). \200 Cimetidine therapy (inhibits metabolism of lidocain e). 283 LOCAL anesthesia (LA) Lidocaine (lignocaine) Lidocaine is the LA used most often for local in \201 ltration and for nerve blocks. It is available in 0.5 % , 1 % and 2 % solutions, either \200\230plain \200\231 (without adrenaline) or with adrenaline 1:200,000. For routine use the most suitab le choice is 1 % plain lidocaine. Duration of action Lidocaine acts rapidly and the effects last from 30 \200\22360min (for p lain lidocaine) to 90min (lidocaine with adrenaline). The duration of action varies with th e dosage and the local circulation. For plain lidocaine the maximum dose is 200mg (20mL of 1 % solution) in a healthy adult or 3mg/kg in a child. For lidocaine with adrenaline the maximum dose is 500mg (50mL of 1 % solution) in a healthy adult or 7mg/kg in a child. These are the maximum total doses for one or more injections of LA given together for local in \201 ltration or nerve block (with care to avoid intravascular injection). Reduce the dose in debilitated or elderly patients, or if there is a particular risk of toxicity (see opposite). Lidocaine can also be used for anesthesia of the skin (with prilocaine in EMLA cream, b p.288), urethra and cornea, and also as a spray for anesthetizing mucous membranes in the m outh and throat. Bupivacaine Bupivacaine is particularly useful for nerve blocks since it has a long duratio n of action (3 \200\2238hr), although its onset of anesthesia is slower than lidocaine. It may also be used for local in \201 ltration, but not for Bier s block ( b p.290). Bupivaca ine is available in concentrations of 0.25 and 0.5 % with or without adrenaline: the usual choice is 0.5 % bupivacaine without adrenaline. The maximum dose of bupivacaine (with or wi thout adrenaline) for a \201 t adult is 150mg (30mL of 0.5 % or 60mL of 0.25 % ) and for a child 2mg/kg. Prilocaine Prilocaine has a similar duration of action to lidocaine. It can be used for loc al in \201 ltration or nerve blocks, but is particularly useful for Bier \200\231s block ( b p.290). High doses (usually > 600mg) may cause methaemoglo- binaemia. The maximum dose o f prilocaine for a healthy adult is 400mg (40mL of 1 % solution) and for a child 6mg/kg. Tetracaine (amethocaine) Tetracaine is used for topical local anesthesia of the cornea ( b p.535) and skin ( b p.288). Proxymetacaine Proxymetacaine is also used for topical local anesthesia of the cornea. It c auses less initial stinging than tetracaine and is particularly useful in children. 284 CHAPTER 7 Analgesia and anesthesia Local anesthetic toxicity Toxic effects These result from overdosage of LA or inadvertent i ntravascular injection. The \201 rst symptoms and signs are usually neurological, with nu mbness of the mouth and tongue, slurring of speech, lightheadedness, tinnitus, con- fusion and drowsiness. Muscle twitching, convulsions and coma can occur. Cardiovascular toxicity may initially result in tachycardia and hypertension, but later the re is hypotension with a bradycardia and heart block. Ventricular arrhythmias and cardiac a rrest occur occasionally, especially with bupivacaine. Early signs of toxicity These may be detected if the doctor maintains a conversation with t he patient while injecting LA. Toxic effects may start immediately if an intravascular inje ction is given. However, peak blood levels usually occur 8 10 \200\22325min after injection \200\224 so if a relatively large dose has been given, do not leave the patient alone whi le anesthesia develops. Occasionally, patients initially agree to LA, but become hysterical or faint (even while ly ing \202 at) when an injection is given. In such circumstances it may be dif \201 cult t o distinguish immediately between the effects of anxiety and those of drug toxicity. Treatment of LA toxicity \200 Stop the procedure. \200 Call for help. \200 Clear and maintain the airway. \200 Give 100 % O 2 and ensure adequate lung ventilation. \200 Obt ain reliable IV access. If possible take blood for U&E. \200 Monitor ECG. Record pulse, B P, respiratory rate and conscious level. \200 If convulsions occur ensure adequate oxygen ation and give lorazepam (adult dose 2 \200\2234mg slowly IV; child: 100micrograms/kg, max 4mg) or diazepam (adult 5 \200\22310mg slowly IV; child 100micrograms/kg). Treat hypotension by raising the foot of the trolley. If systolic BP remains <90mmHg in an adult, give IV \202 uids (eg colloid 500mL). In a child give 20mL/kg if systolic BP <70mm Hg. Bradycardia usually resolves without treatment. If bradycardia and hypotension persist give atropine and consider IV lipid emulsion. In cardiac arrest due to LA toxicity, give lipid emulsion using Intralipid 20 % 1.5mL/kg IV over 1min (bolus of 100mL for 70kg patient) then 15mL/kg/hr (500mL over 30min for 70kg patient). Continue CPR. If circulation is still inadequate repeat IV bolus of Intralipid tw ice at 5min intervals then IVI 30mL/kg/hr (500mL over 15min). Maximum total dose of 20 % li pid emulsion is 12mL/kg). See b p.187 and http://www.aagbi.org/publications/guidelines/docs/ la_toxicity_2010.pdf 285 LOCAL anesthetic TOXICITY Adrenaline (epinephrine) in local anesthesia Most local anesthetics cause vasodilatation, s o adrenaline is sometimes added as a vasoconstrictor. This d blood loss, i duration of anes thesia and d toxicity by delaying absorption of the LA. Lidocaine with adrenaline is often useful in scalp wounds, in which bleeding can be profuse but the bleeding point is not visi ble. Bupivacaine with adrenaline is recommended for intercostal nerve block to d risk of toxicit y from rapid absorption in a relatively vascular area. Lidocaine with adrenaline can be use d in some situations (see below for contraindications) if a relatively large volume of LA i s needed, since the max dose for a healthy adult is 500mg (50mL of 1 % solution) compared t o 200mg (20mL of 1 % ) for plain lidocaine. Other possibilities in such circum- stances inc lude 0.5 % lidocaine, prilocaine (max dose: 40mL of 1 % solution) or GA. The maximum concentration of adrenaline in LA is 1 in 200,000, except for dental anesthesia in which 1 in 80,000 may be used. The maximum total dose of adrenaline in a healthy adult is 500micrograms. Contraindications and cautions Never use adrenaline for injections in the nose, ears, or pe nis, nor in Bier s block ( b p.290). Avoid adrenaline for injections in or near \202 ap l acera- tions, since vasoconstriction could cause ischaemic necrosis. Adrenaline is traditio nally regarded as dangerous in digital nerve blocks of \201 ngers and toes, because of th e risk of ischaemia, but some hand surgeons have used LA with adrenaline uneventfully to re duce bleeding and avoid the need for a \201 nger tourniquet However, LA without adrenalin e is advisable for routine use in \201 ngers and toes, to avoid concerns about ischaemia. Avoid adrenaline in: \200 Ischaemic heart disease. \200 Hypertension. \200 Peripheral vascular disease. \200 Thyrotoxicosis. \200 Phaeochromocytoma. \200 Patients on beta -blockers. The BNF states that LA with adrenaline appears to be safe in patients on tricycl ic antidepressants. Storage Keep ampoules and vials of LA with adrenaline in a locked cupboard separate from th ose without adrenaline, so that they are only available by special request and are not used inadvertently or inappropriately. 286 CHAPTER 7 Analgesia and anesthesia General principles of local anesthesia Obtain a brief medical history and record drug treat ment and allergies. Think about possible contraindications and cautions for LA ( b p.282). Obtain expert advice if you have any query. Consent for local anesthetic Explain to the patient what is planned. Verbal consent is adeq uate for most LA procedures in the ED. Written consent is needed: \200 If there is a signi \201 cant risk of a toxic reaction o r complication, including procedures needing large doses of LA. Bier s block ( b p.290). \200 Intercostal nerve block (risk of pneumothorax). Safety Ensure that resuscitation equipment and drugs for toxic reactions are readily availa ble. Monitoring and IV access are not needed for routine simple LA, but are essential if th ere is a risk of complications or toxicity. Calculate the maximum dose of LA that could be used ( b p.283) and think how much might be needed. Before drawing up any LA check the drug label carefully, especially if adrenaline is contraindicated. Giving local anesthetic \200 Lie the patient down in a comfortable position with the site of injec- tion accessible and supported. Some patients faint if LA is injected while they are sitting up. Warm the LA to body temperature prior to use. \200 Wash your hands, use gloves, and clean the skin. \200 Use a \201 ne needle if possible. Before inserting the needle warn the patient and hold the relevant part \201 rmly to prevent movement. Aspirate and check for blood in the syringe before injecting any LA. If the needle moves, aspirate again. Inject LA slowly to d pain. Do not use force if there is resistance to injection. Maintain a conversation with the patient, to allay anxieties and also to detect any early signs of toxicity ( b p.284). Further details of techniques and precautions are listed on other pages: Topical anesthesia : b p.288. Local in \201 ltration and \201 eld blocks : b p.289. Haematoma block for fra ctures : b p.289. Bier \200\231s block (IV regional anesthesia): b p.290. Nerve blocks: b p p.292 \200\223306. Recording the local anesthetic Write clearly in the notes to record the time and site of in jection and the type and quantity of LA given. 287 GENERAL PRINCIPLES OF LOCAL anesthesia Local anesthesia in children The general principles are the same as for adults. LA is very useful in chil- dren, but requires experienced staff. Many children tolerate LA without any problem, but in some sedation with midazolam ( b p.308) or keta- mine ( b p.278) can be he lpful. Weigh the child if possible and calculate the maximum dose of LA ( b p.283). In an a verage size child a simple initial estimate of the maximum dose of 1 % plain lidocaine is 1 mL per year of age (ie 3mL for a 3-year-old child). If a larger volume may be needed, consi der using 0.5 % solution or lidocaine with adrenaline ( b p.285), or possibly a GA instead. Prepare everything before bringing the child into the room \200\224 rattling equipment an d drawing up LA within sight of a patient causes unnecessary anxiety. Most parents prefer t o stay with their child during the procedure and this is often helpful. Position the child and parent comfortably. Explain simply and honestly what is going to happen. Have adequate help to keep the child still. Use a small needle if possible and inject slowly to minimize pain from the injection. 288 CHAPTER 7 Analgesia and anesthesia Topical anesthesia LA applied directly to mucous membranes of the mouth, throat or urethra will diffuse through and block sensory nerve endings. Development of anesthesia may take se veral minutes and the duration is relatively short because of the good blood supply. Over-d osage is dangerously easy because most topical preparations contain high concentrations of lidocaine (2 % in lidocaine gel, 5 % in ointment, and 4 % or 10 % in lidocaine spray). Lidocaine gel has been used to allow cleaning of gravel burns, but this is not advisable: a bsorption of lidocaine can easily cause toxicity and the degree of anesthesia is rarely sat isfactory. Scrubbing is often necessary to remove embedded gravel, so proper anesthesia is essential. Field block may be adequate for a small area, but GA is often necessary for clea ning large or multiple gravel burns, in order to avoid tattooing. Topical anesthesia EMLA cream \200\230Eutectic mixture of local anesthetics \200\231 (E MLA ) cream contains lidocaine 2.5 % and prilocaine 2.5 % , and is used for topical anes thesia of the skin. EMLA is of limited value in the ED because it must only be applied t o intact skin (not wounds) and the onset of anesthesia is slow, usually 8 1 hour. EMLA m ust not be used in children aged <1 year and caution is needed in patients with anemia or m ethaemoglobinaemia. EMLA can usefully d pain of an injection or cannulation. Apply a thi ck layer of EMLA cream to the skin and cover it with an occlusive dressing, which must b e left undisturbed for 1 hour. Tetracaine (amethocaine) gel (Ametop ) This is similar to EMLA , but acts more quickly and causes vasodilatation, which aids venous cannulation. It must not be used in wounds because of the risk of rapid absorption and toxicity. Other topical LA agents Topical agents such as TAC (tetracaine, adrenaline, and cocaine) or LET (lidocaine, epinephrine and tetracaine) are sometimes used to provide anesthesia for w ound repair. These preparations can provide effective anesthesia, but toxic effects may occ ur from excessive absorption (especially of cocaine) and they are not licensed in the UK. Ethyl chloride Ethyl chloride is a clear \202 uid which boils at 12.5 C. Spraying the liquid on the skin causes rapid cooling and freezing of the surface. In the past ethyl chlo ride was used for incision of paronychias and small abscesses, but it rarely provides adequ ate anesthesia and it cannot be recommended. Ethyl chloride is highly in \202 ammable and is a GA, so it must be handled with care if it is used at all. 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.