Analgesia, Anesthesia, and Sedation Tintinalli Chap 36, 37, 38, 39

1. Analgesia, Anesthesia, and SedationTintinalli Chap 36, 37, 38, 39 Nicholas Cardinal, DO

2. Acute Pain • Accompanies 50-60% of ED patient visits in U.S. and Great Britain • Pain • The physiologic response to a noxious stimulus • Accentuated by fear and anxiety • Affected by many factors • Medical Condition • Physical and Emotional Maturity • Cognitive State • Meaning of Pain • Family Attitudes, Culture, and Environment

3. Peripheral Nervous System • Responsible for somatic pain • Registers the original noxious stimulus and conducts it to the CNS • Components • Primary Afferent Peripheral Nociceptors • Dorsal Horn of the Spinal Cord • Supraspinal Centers

4. Pain Receptors • µ1 receptor • Stimulation produces supraspinal analgesia, euphoria, miosis, and urinary retention • µ2 receptor • Stimulation responsible for respiratory depression, gastrointestinal slowing, and cardiovascular slowing • Likely source of addiction • Κ receptor • Stimulation produces dysphoria and spinal-level analgesia

5. Evaluation • Assessment of Pain • Non-self-report Measurement • Self-report Measurement • Adjective Rating Scale • Visual Analog Scale • Numerical Rating Scale • Five-point Global Scale • Verbal Quantitative Scale • Global Satisfaction Question

6. Non-self-report Measurement • More useful as confirmatory tool than as primary assessment tool • Physiologic parameter variation • Respiratory • Cardiovascular • Changes in expression and movement

7. Self-report Measurement • Mainstay of pain assessment • Needs to be applied at onset of intervention and then re-evaluated frequently • Value assigned by patient should be used as a reference point on which to base pain control

8. Unique Patient Populations • Difficulty communicating places patients at risk for inadequate pain management • Cognitively impaired • Psychotic • Extremely young or old • Language Barriers • Extreme cultural or educational disparity

9. Modalities of Pain Management • Pharmacologic • Nonpharmacologic • Cognitive-behavioral • Physical techniques

10. Pharmacologic Modalities • Opioids • NSAIDs • Acetaminophen • Adjuncts • Anxiolytics • Antiemetics

11. Severity of Pain • Mild • NSAIDs • Moderate to Severe • Systemic opioids and/or NSAIDs • Local or Regional Neural Blockade

12. Opioid Agonists

13. Relative Potency Estimates • Basis for selecting appropriate starting dose, changing route of administration, or switching to another opioid

14. Meperidine • Once the mainstay of pain management in EDs • Should no longer be used for acute pain management • Is the lowest potency opioid and is often underdosed • Metabolite has been shown to cause CNS toxicity in patients with compromised renal function or who are taking MAOIs • Metabolite can produce prolonged states of sedation of up to 48 hours • Reported to produce more euphoria and may have an increased risk of addiction

15. Codeine • Standard dose produces little analgesic effect above that of acetaminophen or NSAIDs • Produces more nausea, vomiting, and dysphoria

16. Adverse Effects of Opioids • N/V • Constipation • Pruritus • Urinary retention • Confusion • Respiratory Depression

17. Analgesic Adjuncts • May provide pain relief at lower opiate dose • Anxiolytics • Not recommended • Synergy with opiates can produce additive adverse effects • Antiemetics • May potentiate opiates

18. Nonopioid Agents Acetaminophen NSAIDs Analgesic and anti-inflammatory Have significant opioid dose-sparing effects Adverse effects include platelet dysfunction, impaired coagulation, and gastrointestinal irritation and bleeding Acute Renal Failure in elderly, volume depleted • Mild to moderate pain • Is not an anti-inflammatory and does not affect platelet aggregation • No change required for renal or mild hepatic impairment

19. Nonopoid Agents Corticosteroids Other Agents Ketamine Nitrous Oxide Tricyclic Antidepressants Anticonvulsants • Potent inhibitors of inflammation • Used for visceral, orthopedic, and neuropathic pain • Short-term d/t adverse effects

20. Ketamine • “Dissociative” anesthetic • Causes minimal respiratory depression • Good for brief minor procedures • Adverse effects include elevated ICP, elevated intraocular pressure, hypersalivation, and reemergence phenomena • Avoid in closed head injury or suspected elevated ICP

21. Nitrous Oxide • Fast onset, short acting • Sedative analgesic • Inhalational • Useful in wound dressing and brief, minor procedures • Contraindications include altered mental status, head injury, suspected pneumothorax, and perforated abdominal viscus

22. Basic Dosing Guidelines • Titrate dose toward desired effect while minimizing unwanted effects • Decrease initial dosing in setting of comorbidity • Altered mental status • Hemodynamic instability • Respiratory dysfunction • Multisystem trauma

23. Elderly • May have more than one source of pain • Comorbidities • At increased risk for drug-drug interaction • More sensitive to analgesic effects, sedation, respiratory depression, and cognitive and neuropsychiatric dysfunction

24. Dosing Adjustments • Renal and Hepatic Dysfunction • Respiratory Insufficiency • COPD • Cystic fibrosis • Neuromuscular Disorders • Muscular Dystrophy • Myasthenia Gravis • Drug Interactions • Anxiolytics • Synergistic sedative effects • Monoamine Oxidase Inhibitors • Fatal reactions with meperidine • Tricyclic Antidepressants • May increase morphine levels

25. Nonpharmacologic Modalities • Heat/cold application • Immobilization and elevation of injured extremities • Cognitive-Behavioral techniqes • Transcutaneous Electrical Nerve Stimulation • Acupuncture

26. Pain Management in Trauma • Closed Head Injury • Must allow for continuous monitoring of neurovascular status • Maximal use of regional and nonpharmacologic modalities • Minor Trauma • NSAID use remains controversial d/t bleeding risk and acute renal failure in the volume depleted patient • Limb Injury • Continuous monitoring of neurovascular status

27. Local Anesthesia • Cocaine • First isolated in Europe between 1859-1860 • Toxic and addictive effects were rapidly noticed resulting in patient deaths and addicted medical staff • Ester Local Anesthetics • Tropocaine • Eucaine • Benzocaine • Procaine • Tetracaine • Amide Local Anesthetics • Lidocaine • Mepivacaine • Prilocaine • Bupivacaine

28. Local Anesthetic Agents • Synthetic drugs derived from cocaine • Weak bases supplied in an acidic solution • Anesthetic action produced by drug molecules interrupting and temporarily stopping conduction

29. Epinephrine • Acts through vasoconstriction • Avoided in end-arterial field • Advantages • Provides longer duration of anesthesia • Promotes wound hemostasis • Slows systemic absorption • Decreases potential for toxicity • Allows greater volume to be used for extensive laceration repair

30. Toxicity of Local Anesthetics • Related to potency and duration of action • Serious adverse reactions more common in amides than the esters • Enhanced by hypercarbia, hypoxemia, and acidosis • Usually due to inadvertent IV injection or excessive dose

31. CNS Toxicity • Due to conduction block • Directly related to lipid solubility • Symptoms range from perioral tingling and numbness to confusion, seizure and coma • Seizure activity is a warning for impending ventricular arrhythmias and cardiovascular collapse

32. Cardiovascular Toxicity • Dose-dependent • Mediate through sodium channel blockade within the heart • Worsened by pregnancy • Effects include myocardial depression and ventricular dysrhythmias • Bupivacaine has highest incidence and is contraindicated for use in regional anesthesia

33. Methemoglobinemia • Prilocaine and benzocaine cause oxidation of ferric form of hemoglobin to ferrous form • Visible cyanosis results when concentration exceeds 1.5 g/dL • Usually benign

34. Amide Local Anesthetics • Lidocaine • Most commonly used anesthetic in the ED • Excellent efficacy and low toxicity profile • Rapid onset and intermediate duration of action • Prilocaine • Low CV toxicity profile • May cause methemoglobinemia after large IV bolus • Used with lidocaine in EMLA cream • Bupivacaine • Slow onset and long duration of action • High CV toxicity potential • Use in prolonged procedures or when longer postprocedural anesthesia is required • Mepivacaine • Rapid onset and intermediate duration of action • Intermediate toxicity

35. Ester Local Anesthetics • Procaine • Slow onset • Short acting • Very short half-life • Tetracaine • Slow onset • Long duration of action • Injectable for spinal anesthesia • Topical for use on eye, mucous membranes, and skin

36. Alternative Agents • Diphenhydramine • Effective local anesthetic • Injection more painful than lidocaine • Can cause tissue irritation and skin necrosis • Benzyl Alcohol • As effective as lidocaine • Short duration usually requiring additional injections during procedure

37. Local Anesthetic Infiltration • Most common use of local anesthetics in ED • Rapid onset • Low risk of systemic toxicity • Used for wound repair and invasive procedures • Lidocaine for short procedures and bupivacainefor longer procedures

38. Minimizing Pain of Infiltration • 27- or 30-gauge needle • Deep, slow infiltration • Buffered lidocaine • Sodium bicarbonate reduces pain • Warm lidocaine • 37-42 degrees C • Injection through wound margins • Distraction techniques

39. Topical Anesthetics • Used to reduce discomfort of local procedures • Work better on head and neck than extremities • Advantages • Painless • Do not distort wound edges • May provide good hemostasis if formulation includes a vasoconstrictive agent

40. Topical Anesthetics • TAC • 0.5% Tetracaine, 0.05% Adrenaline, 11.8% Cocaine • Other mixtures are cheaper, have less toxicity, and do not contain a controlled substance • LET • 4% Lidocaine, 0.1% Epinephrine, 0.5% Tetracaine • Prepared in single-use 5-ml vials • Applied directly to wound for 20-30 minutes • Avoid contact with mucous membranes, fingers/toes, ear pinna, penis, and tip of nose

41. Topical Anesthetics • EMLA • Eutectic Mixture of Local Anesthetics (2.5% Lidocaine and 2.5% Prilocaine) • Available preparation is nonsterile and should only be applied to intact skin • Applied directly to skin and covered with occlusive dressing • Analgesia at 1 hour, peak at 2 hours • Lidocaine • Available in solution, ointment, cream and jelly preparations • Commonly used to facilitate placement of urinary catheters, nasogastric tubes, and fiberoptic scopes

42. Other Topical Anesthetic Agents • Benzocaine • Used for mucosal anesthesia to relieve pain from oral ulcers, wounds, inflammation and to facilitate passage of nasogastric tubes or endoscopy • Iontophoresis • Delivery of topical anesthetic with mild electrical current • Ethyl Chloride • Skin refrigerant or vapocoolant delivered by a spray • Causes anesthesia for 30-60 seconds • Not for use on mucosal surfaces

43. Regional Anesthetic Procedures • Can minimize opiate use • Decreases need for procedural sedation • Should be administered in lowest dosage that results in an effective block • Epinephrine can be added to enhance duration, efficacy, reliability, and safety

44. Peripheral Nerve Blocks • Advantageous for procedures on the digits, hand, and foot • Require less total anesthetic • Often less painful than local infiltration • Onset of anesthesia may be up to 15 minutes • Document neurovascular status prior to block • Complications include nerve injury and systemic toxicity

45. Wrist Blocks • Used for lacerations of the hand • Median Nerve • Ulnar Nerve • Radial Nerve

46. Digital Nerve Block • More rapid onset than metacarpal block • Used for laceration repair, I&D of paronychia, or finger/toenail removal • Large volumes of anesthetic can result in compartment syndrome

47. Foot Blocks • Anesthesia for surgical procedures of the foot • Sensation to foot supplied by 5 different nerves • Posterior Tibial Nerve • Sural Nerve • Saphenous Nerve • Superficial Peroneal Nerve • Deep Peroneal Nerve • Most blocks involve at least 2 nerves • Contraindications include peripheral vascular disease and traumatic circulatory compromise

48. Facial and Oral Blocks • Anesthesia to commonly injured areas • Forehead, chin, lips, nose, tongue, ear • Often require blockade of more than one nerve • Topical EMLA cream or refrigerant sprays should be applied prior to injection • 2% lidocaine can be applied to oral mucosa • Avoid direct infiltration of pinna d/t risk of tissue necrosis

49. Femoral Nerve Block • Effective for relieving pain of femoral neck fracture • Useful in multiple trauma patient

50. Intercostal Block • Management of pain following chest trauma or from a chest tube • Contraindications include local soft tissue disease and contralateralpneumothorax • High systemic absorption and toxicity