Optimizing Orthopaedic Analgesia: Key Strategies for Relief

1. ORTHOPAEDIC ANALGESIA

PHARMACOLOGY: CLASSES OF DRUGS

1. Local anesthetics
2. Vasoconstrictors
3. Opioids
4. Sedatives (benzodiazepines)
5. Others

LOCAL ANESTHETICS

1. Basic function
2. These drugs act by blocking voltage-gated sodium channels in axons, preventing action potential.
3. Local effect
4. Block is most effective in smaller, myelinated fibers that fire at high frequency.
5. Pain and temperature fibers are much more sensitive than pressure fibers, which are more sensitive than motor and proprioceptive fibers.
6. Toxicity
7. Central nervous system (CNS)
8. Results from intravenous absorption or injection and high plasma levels.
9. They block inhibitory pathways, leading to unopposed excitatory components.
10. Signs and symptoms include dizziness, tongue numbness , nystagmus, and seizures (tonic–clonic).
11. Cardiovascular-depressive effects
12. Weaker contraction and arteriolar dilatation occur.
13. High doses can result in ventricular fibrillation, which is difficult to treat. Twenty percent
    intralipid is now being used as an agent to reverse significant cardiac toxicity.
14. Neurotoxicity
15. In high concentrations, they can directly damage peripheral nerve fibers.

16. Lidocaine: rapid, potent, high penetration

17. Short acting

18. Most widely used local anesthetic: local anesthesia, regional, spinal, epidural

19. Bupivacaine: slower, potent

20. Longer lasting than lidocaine
21. Can separate motor and sensory block by altering concentration
22. Increased cardiac toxicity possibly
23. Ropivacaine
24. “Safer” version of bupivacaine with same analgesic characteristics considered to be associated with a lower incidence of significant cardiac toxicity
25. Maximal dose of commonly used local anesthetics

26. Lidocaine: 5 mg/kg (7 mg/kg if combined with epinephrine)

27. Calculation example:

    
    Percent concentration × 10 = mg/mL of drug 1% lidocaine = 10 mg/mL of lidocaine
28. 30-kg child, 1% lidocaine without epinephrine 10 mg/mL of lidocaine
    5 mg/kg × 30 kg = 150 mg allowed
    150 mg/10 mg/mL = 15 mL of 1% lidocaine

29. Bupivacaine: 1.5 mg/kg (3 mg/kg with epinephrine)

VASOCONSTRICTORS

1. Allow for longer lasting blockade (decreased blood flow, less drug leaves area).
2. They may also decrease local blood loss.
3. Epinephrine
4. Most widely used, diluted to 1/200,000
5. Should not be used for a digital block, Bier block, or ankle block

6. Mnemonic for areas not to use epinephrine: nose, hose (penis), fingers, toes

7. Phenylephrine is occasionally used in spinal anesthesia.

OPIOIDS

1. They are derived from the seed of the opium poppy, Papaver somniferum .
2. Morphine and codeine are directly from the plant; others are synthesized.
3. They act by binding to specific opioid receptors in the CNS ( μ , δ, κ).
4. Th μ receptor is the one most responsible for the analgesic effect.
5. The action is both presynaptic and postsynaptic.
6. Central action/pain modulation
7. When activated, the μ receptor inhibits γ -aminobutyric acid (GABA)-ergic neurons that would otherwise inhibit pain inhibitory neurons.
8. They may also affect neurons in the thalamus and midbrain to modulate pain stimuli.
9. CNS effects
10. Analgesia, euphoria, sedation, respiratory depression, cough suppression, miosis, nausea
11. Peripheral effects

12. Cardiovascular: bradycardia

13. Gastrointestinal: decreased motility, constipation, constriction of biliary tree

14. Genitourinary: decreased renal function and increased sphincter tone

15. Morphine
16. Naturally occurring, oldest member of this drug class
17. Dosing for adults
18. Loading dose of 0.05 to 0.10 mg/kg intravenously (IV) followed by 0.8 to 10.0 mg/hour IV titrated to pain

19. Onset: 5 minutes

20. Relatively long lasting: 3 to 4 hours

21. Better for continuous dull pain rather than sharp/severe pain
22. Used for postoperative patient-controlled analgesia (PCA) 1-mg increments with a lockout of 6 to 10 minutes. Basal rates tend to increase episodes of hypoxia.
23. Meperidine (Demerol)
24. Most common emergency department narcotic
25. One-tenth as potent as morphine
26. Dosing for adults
27. Fifteen to 35 mg/hour slow IV infusion or 50 to 150 mg subcutaneously/intramuscularly every 3 to 4 hours as needed

28. Poorly titrated: 5- to 10-minute onset and 2- to 3-hour duration

29. Potential for CNS stimulation
30. Less commonly used for pain than in the past
31. Concern about bad interactions with monoamine oxidase inhibitors (MAOIs)
32. Fentanyl
33. 100× more potent and 7,000× more lipophilic than morphine

34. Rapid uptake: 30 to 60 seconds with peak analgesia in 2 to 3 minutes

35. Duration: 20 to 30 minutes

36. Dose: 1 μ g/kg slowly, with sedation often at 3 to 4 μ g/kg

37. Risks: “tight chest syndrome,” bradycardia, respiratory depression

38. Naloxone, naltrexone (Narcan)
39. Opioid antagonist
40. Strong affinity for μ receptor
41. Binds to receptor but does not activate it, rapidly reversing the opioid effect within 1 to 3 minutes

42. Usual dose: 0.1 to 0.4 mg IV (0.01 mg/kg in children)

43. Shorter half-life than most agonists, so multiple doses may be necessary

SEDATIVES

1. Benzodiazepines
2. In general, they produce anxiolysis and sedation and encourage sleep.
3. They are metabolized in the liver and excreted in the urine.
4. Mechanism
5. They act centrally, bind to, and activate the GABA-A receptor.
6. GABA is major inhibitory neurotransmitter in the CNS.
7. The GABA receptor is the chloride channel.
8. When activated, they hyperpolarize the membrane, making it less excitable.
9. Effects
10. Sedation, hypnosis, anesthesia, amnesia (anterograde), anticonvulsant effects, muscle relaxation, respiratory depression (especially in pulmonary patients)
11. Often increased when combined with opioids
12. Midazolam

13. Peak effect: 2 to 3 minutes

14. Water soluble, hepatic metabolization
15. Easily titrated with doses every 5 to 7 minutes
16. 1 to 2 mg per dose (0.1 mg/kg/dose in children)
17. Flumazenil
18. Blocks the effect of benzodiazepines at the GABA receptor level.
19. It has a much shorter half-life than most benzodiazepines that are used clinically.
20. The dose is 0.1 to 0.2 mg IV (0.02 mg/kg in children).
21. Use with caution because it may precipitate seizures.
22. Ketamine
23. Dissociative anesthetic
24. Catatonic, amnestic, without loss of consciousness or loss of protective reflexes
25. Blockade of glutamic acid at the N -methyl-D-aspartate receptor subtype
26. May stimulate cardiovascular system and increase blood flow

27. Dose: 1 mg/kg IV

28. Rapid onset: 1 to 3 minutes

29. Duration: 15 to 20 minutes

30. Occasional hallucinations on emergence: can be avoided with a small dose of midazolam

31. May increase salivation: atropine, 0.01 mg/kg, given before ketamine

32. Propofol
33. Isopropylphenol compound
34. Rapid onset, short duration (half-life 30 minutes but lipid soluble so clinical duration is less)
35. Minimal gastrointestinal side effects or nausea

36. Provides general anesthesia: sedation, hypnosis, without analgesia or amnesia

37. Complications: respiratory depression, hypotension, pain at injection site

38. Need for anesthesia/emergency department assistance with airway

39. Dose: 0.5 to 1.0 mg/kg for induction of sedation

40. Highly titratable: 25 to 100 μ g/kg/minute infusion after initial bolus

NITROUS OXIDE

1. Inhaled agent
2. Given in varying 50/50 to 70/30 mixture with oxygen
3. Flow controlled by patient holding the mask
4. Provides analgesia and anxiolysis, some sedation
5. Rapid onset and offset

6. Short duration: resolves within 5 minutes of removing mask

7. Often used as an adjunct with other forms of anesthesia or for short procedures
8. Very safe for brief procedures

REGIONAL BLOCKS AND CONSCIOUS SEDATION

Hematoma block, regional blocks, Bier block (if proper equipment and training available), and conscious sedation can all be effectively used by orthopaedists for fracture reduction and select procedures. Hematoma Block 41. This replaces the fracture hematoma with local anesthetic.
42. It provides analgesia for closed reductions.
43. It provides postreduction analgesia.
44. Technique
1. Sterile preparation of the fracture site is indicated.
2. Enter the fracture hematoma with a large-bore needle, aspirating hematoma fluid.
3. Replace the hematoma with 10 to 15 mL of 1% lidocaine without epinephrine.
1. Bupivacaine may be added to help with postreduction pain. Give in safe dose such as 10 mL of 0.25% .
4. Wait 5 to 7 minutes, then perform the reduction maneuver.
45. Risks
1. Systemic toxicity
1. Potential risk of the local anesthetic’s entering the bloodstream directly via the bone’s blood supply.
2. Infection
1. Theoretically converting a closed fracture to an open one. Single case report in orthopaedic literature. Regional Blocks
46. They provide anesthesia to a certain area of the body, without general whole-body effects.
47. They are useful in fracture-dislocation reduction, as well as minor and major surgical procedures on the extremities.
48. They are also beneficial for postprocedure analgesia.
49. Local anesthetic is injected around the peripheral nerves or plexi .
50. Length of block depends on the choice of anesthetic, as well as the use of epinephrine.
Digital Block
51. Indications include finger fracture, laceration, nail bed injury, and finger/nail bed infection.
52. Do not use epinephrine.
53. Technique ( Fig. 7.1)
1. Pronate the hand (skin on the dorsum is less sensitive).
2. Use two injection sites, at each side of the metacarpophalangeal.
3. Use about 2 mL per nerve (8 mL total).


Wrist Block ( Fig. 7.2)


54. Median nerve
1. Indications include multiple finger fractures and finger/nail bed lacerations.
2. Technique
1. Supinate the forearm.
2. The needle is placed between the palmaris longus and the flexor carpi radialis, 2 cm proximal to the wrist flexion crease.
3. If paresthesia is elicited, inject 3 to 5 mL at this site.
4. If no paresthesia occurs, then inject 5 mL in fan-shaped fashion.
55. Ulnar nerve
1. ## Indications: ulnar-sided lacerations, reductions of boxer’s fracture (if anesthesia is required)
2. ## Technique: supinated hand, 6 cm proximal to wrist crease, just radial to flexor carpi ulnaris, 8 to 10 mL (more distal block will miss the dorsal branch, which can be blocked by a wheal ulnar to the flexor carpi ulnaris)
56. Radial nerve
1. Indications include thumb and dorsum of hand lacerations.
2. Technique
1. Field block is performed on the pronated hand at the level of the snuff box.
2. This is superficial to the extensor palmaris longus tendon.
3. Start at the snuff box and continue over the entire dorsum of the hand.
4. A dose of 5 to 8 mL is required.
Elbow Block
57. Indications include procedures of the hand and wrist.
58. ## Four nerves are involved: median, ulnar, radial, and lateral antebrachial cutaneous
59. Median nerve
1. Draw a line between the medial and lateral condyles of the humerus.
2. The skin wheal is just medial to the brachial artery.
3. Advance the needle until paresthesia is obtained.
4. Inject 3 to 5 mL of lidocaine.
60. Ulnar nerve
1. The elbow is flexed.
2. Inject 1 cm proximal to the line that connects the medial epicondyle and the olecranon.
3. Use 3 to 5 mL of lidocaine.
4. Inject very superficially.
5. Too much fluid can cause “compartment syndrome.”
61. Radial/musculocutaneous (lateral antebrachial cutaneous nerve)
1. At the intercondylar line, inject 2 cm lateral to the biceps tendon.
Axillary Block
62. Indications
1. These include hand and forearm procedures and some elbow procedures.
63. Technique ( Fig. 7.3)
1. The patient is supine with the shoulder abducted and externally rotated.
2. Palpate the axillary artery in the distal axilla.
3. Some advocate going through the artery, depositing two-thirds of the total anesthetic (20 to 30 mL) behind the artery and one-third superficial to it.
4. Others suggest going on either side of the palpable artery.
5. Think of the four nerves in four quadrants:
1. ## Musculocutaneous: 9 to 12 o’clock
2. ## Median: 12 to 3 o’clock
3. ## Ulnar: 3 to 6 o’clock
4. ## Radial: 6 to 9 o’clock
6. Other techniques include ultrasound-guided blocks and nerve stimulation techniques.


Ankle Block
64. Indications include any foot and ankle procedure.
65. ## The block must include all five nerves: tibial, superficial and deep peroneal, and saphenous and sural nerves ( Fig. 7.4).
1. Tibial
1. Posterior to the posterior tibial artery, halfway between the medial malleolus and the calcaneus
2. Deep peroneal
1. Just lateral to the anterior tibial artery and the extensor hallucis longus
3. Superficial peroneal and saphenous
1. Field block medially and laterally from a deep peroneal site
4. Sural
1. Lateral border of the Achilles tendon, halfway between the lateral malleolus and the calcaneus


Popliteal Block
66. Indications include foot and ankle surgery.
67. Technique
1. The patient is prone, with the knee flexed.
2. Identify the popliteal fossa.
3. Inject 7 cm superior to the skin crease, 1 cm lateral to the midline, lateral to the artery.
4. Advance in an anterosuperior direction.
1. Add a field block of the saphenous distal to the medial tibial plateau for a more complete block.
2. Ultrasound-guided and nerve stimulation techniques can be used for this block.
Bier Block ( Fig. 7.5)


68. It is also known as regional IV anesthesia.
69. This was developed by August Bier in 1908.
70. Indications include hand/wrist procedures and fracture reductions.
71. Technique
1. Start the IV infusion in the hand. Place IV catheter. Do not run IV fluid .
2. Place double tourniquets around the upper arm.
3. Exsanguinate the upper extremity.
4. Inflate the more proximal tourniquet.
5. Inject lidocaine without epinephrine (1.5 mg/kg dilute solution or 3 mg/kg, ~50 mL 0.5%) and without any preservative.
6. The tourniquet must stay inflated for 25 to 30 minutes. If the patient has tourniquet pain, the
distal tourniquet may be inflated followed by deflation of the proximal tourniquet.
72. Risks
1. Tourniquet pain
2. Length of block most often limited by the ability to tolerate the tourniquet
3. Systemic toxicity
4. ## Theoretic risks: severe cardiovascular and CNS side effects with early release of the tourniquet and a large intravascular bolus of lidocaine

MODERATE SEDATION

1. Alteration in consciousness
2. Decreased anxiety
3. Pain relief
4. Patient able to maintain patent airway and have intact protective airway reflexes
5. Patient able to respond to verbal or physical stimuli
6. Sedation a continuum
7. Awake/light sedation
8. Anxiolysis, patient essentially responding normally
9. Conscious sedation
10. Response requiring verbal or physical stimuli, airway maintained
11. Deep sedation
12. Repeated or painful stimuli necessary for response, airway patency questionable
13. General anesthesia
14. Unarousable, airway not protected
15. When to use it?
16. Anytime a potentially painful procedure needs to be performed in the outpatient setting
17. For procedures not requiring general anesthesia and that are reasonably short in duration
18. When appropriate monitoring equipment is available
19. When patient is appropriately nothing by mouth (NPO)
20. Contraindications
21. Clinically unstable patient requiring other more urgent procedures
22. Refusal by a competent patient

23. Relative contraindication: long-lasting procedures, likely to require general anesthetic for success

24. Appropriate equipment
25. IV access
26. Pulse oximetry
27. Electrocardiographic monitor
28. Blood pressure cuff
29. Airway management equipment
30. Supplemental oxygen
31. Reversal medications (naloxone, flumazenil)
32. Technique
33. This typically involves combining an opioid (morphine or fentanyl) for analgesia and a benzodiazepine (midazolam) for sedation, relaxation, and amnesia.
34. Titrate dosing to achieve appropriate level of sedation while minimizing the risk of adverse
    outcome.
35. The patient should at all times be responsive to physical or verbal stimuli (therefore should have protective airway reflexes intact).
36. Remember that these patients have likely already had large doses of opioids for pain control.
37. Be aware of “dose stacking,” giving additional doses of narcotics before waiting to see the effects of the prior doses.
38. Risks
39. Respiratory depression/hypoventilation
40. Risk of respiratory depression potentiated by a combination of opioids and benzodiazepines
41. Moderated by appropriate dosing, monitoring, and presence of reversal agents
42. Aspiration
43. Theoretic risk in nonfasted, sedated patients
44. No reported incidences of aspiration during emergency department conscious sedation in the current literature
45. Disposition
46. Vital signs, mental status, motor function returning to baseline
47. Pain control with oral analgesics
48. Adequate oral intake
49. Responsible adult present to monitor for continued effects of sedatives