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Just an Itch Beyond Benadryl

Objectives. Understand the relationship between pain (sensation and treatment) and pruritisUnderstand basic pathophysiologic mechanisms for itchingIdentify effective treatments for various causes of itchingPsychologically induce everyone here to scratch themselves at least once.

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Just an Itch Beyond Benadryl

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    1. Just an Itch? Beyond Benadryl™ Michael Greenwald, MD Assistant Professor, Pediatrics Emory University Children’s Healthcare of Atlanta

    6. Objectives Understand the relationship between pain (sensation and treatment) and pruritis Understand basic pathophysiologic mechanisms for itching Identify effective treatments for various causes of itching Psychologically induce everyone here to scratch themselves at least once

    7. #1 Help this patient A 12 y/o with Sickle Cell Disease presents to the ED with an acute vaso-occlusive crisis. After his first dose of morphine he experiences generalized intense itching. His pain is still high (7/10). So now you have 2 problems - what do you recommend?

    8. #2 Match D/O with Antipruritic Lymphoma Chronic Renal Failure Liver Failure Conjunctivitis Eczema Penicillin Reaction Activated Charcoal Cimetidine Toradol Odansetron Diphenhydramine Topical Steroids

    9. Part I: Understanding the Itch Definition Epidemiology Pathophysiology Why We Scratch

    10. Part II: How to treat an Itch (Understand the Cause!) Inhibit mediators of itch Block chemicals that induce pruritis Treat effects of diseases which induce itching

    12. Defining Pruritis An unpleasant localized or generalized sensation on the skin, mucus membranes or conjunctivae which the patient instinctively attempts to relieve by scratching or rubbing

    13. Diversity of Causes and Presentation Many Causes, Many Treatments Trivial to Life threatening (mosquito bite) (malignancy) 10-50% of cases with generalized itching have systemic disease

    14. Diseases & Itching Infections Infestations (scabies) Inflammatory skin conditions (eczema, contact derm, psoriasis) Chronic Renal Failure Cholestatic liver disease Depression/anxiety

    15. Assessment Challenges No assessment tool validated to study levels of distress from itching Most rely on 0-10 VAS similar to pain scores

    16. Poorly Understood & Managed Relies on similar components of the pain system: receptors, neurotransmitters, spinal pathways and centers in the brain Stimulating pain can relief itching Treating pain with some analgesics relieves itching, others trigger itching Pruritis is a common side-effect of opioid administration, sometimes worse than the pain

    17. Pruritogenic Stimuli Pressure Low-intensity electrical or punctate stimuli (TENS) Histamine: acts directly on free nerve endings in skin

    18. Itch Pathways Cutaneous (pruritoceptive) Neurogenic Neuropathic Mixed Psychogenic

    19. Pain vs Itch Nerves Itch transmitted from specialized pain receptors: a subclass of C-nociceptors Mechano-insensitive Histamine sensitive Nerve endings cluster around “itch points” which correspond to areas very sensitive to pruritogenic stimuli

    20. Itch pathways Fibers originate @ dermal/epidermal jxn ? Thin unmyelinated axons, lots of branching ? Ipsilateral dorsal horn of spinal cord ? Synapse with itch-specific secondary neurons Cross to opposite anterolateral spinothalamic tract to thalamus ? Somatosensory cortex of postcentral gyrus SLOW transmission and BROAD receptor field

    22. Itch Mediators Histamine Prostaglandins Leukotrienes Serotonin Acetylcholine Substance P Proteases Peptides Enzymes Cytokines

    24. Why do you scratch? Histamine activates both the anterior cingulate cortex (sensory, emotions) and the supplemental motor area

    25. Lateral Inhibition: “Gate Theory” Noxious stimuli of skin adjacent to pruritic trigger attenuates initial itch sensation Scratching stimulates large fast-conducting A-fibers adjacent to slow unmyelinated C fibers A-fibers synapse with inhibitory interneurons and inhibit C-fibers

    27. Pain & Itch Painful stimuli (thermal, mechanical, chemical) can inhibit itching Inhibition of pain (opioids) may enhance itching

    28. Part II: How to Treat an Itch (Understand the Cause!) Inhibit mediators of itch: histamine, prostaglandins, substance P, serotonin, cytokines Block chemicals that induce pruritis: opioids, antimicrobials Treat effects of diseases which induce itching: eczema, CRF, LF, heme, neuro, endo

    29. Itch Mediators: Histamine Different effects on different H receptors applied into epidermis ? itch applied into dermis ? pain Only a few types of itch relieved by anti-histamines (i.e. those caused by histamine release in the skin): insect bites, allergic skin reactions, cutaneous mastocytosis 85% H receptors in skin are H1 15% H receptors are H2

    30. NSAIDs for itching? Prostaglandins cause itch directly on conjunctiva (but no effect when directly applied to skin) Potentiates histamine elicited itch Ketorolac eases itch in conjunctiva

    31. Match D/O with Antipruritic Lymphoma Chronic Renal Failure Liver Failure Conjunctivitis Eczema Penicillin Reaction Activated Charcoal Cimetidine Toradol Odansetron Diphenhydramine Topical Steroids

    32. Match D/O with Antipruritic Lymphoma Chronic Renal Failure Liver Failure Conjunctivitis Eczema Penicillin Reaction Activated Charcoal Cimetidine Toradol Odansetron Diphenhydramine Topical Steroids

    33. Substance “P” (“P” for pain and pruritis?) Neuropeptide synthesized in C-fibers @ DRG Transmitted to free nerve endings to modulate pain and pruritis Substance P containing C-fibers most abundant near junction b/epidermis & dermis (esp in lips, fingertips, prepuce and breast) Induces pruritis directly & indirectly by releasing histamine from mast cells Hemodialysis-associated itch Atopic dermatitis Psoriasis

    34. Substance P Depletion Capsaicin cream: excites C-fibers ?release substance P & calcitonin gene-related peptide ?depletion of both .025% 5 times a day for notalgia paraesthetica

    35. Other Peptides Bradykinin: pain, inflammation & itch Neurotension, Vasoactive Intestinal Peptide, Somatostatin, Melanocyte-stimulating hormone: ? histamine release from dermal mast cells

    36. Acetylcholine Intra-dermal injection usually ? burning In eczema ? itching Independent of histamine

    37. Serotonin Some patients with refractory itch have been relieved by serotonin antagonist odansetron (Zofran)

    38. Itch & Inflammation Cytokines: LMW mediators of inflammatory signals b/cells (e.g. TNF) Induce cells to secrete chemokines which cause migration of inflammatory cells from vascular space to inflammatory site

    39. Chemically induced itching: Systemic Opioids Usually face (trigem. nerve), neck, upper thorax 0-90% Not necessarily related to dose ? incidence during pregnancy (interaction b/ estrogen & opiate receptors) Morphine, sufentanil > fentanyl > butorphenol Histamine is released, but not the main cause of itching Site of injection vs distal to injection

    40. Opioid induced itching: Systemic vs Local Nonimmunologic release of histamine from morphine, codeine, meperidine Attentuated by opioid receptor antagonists Intradermal morphine reduced by H1 antihistamines but not naloxone H2 blockers alone not effective but enhance H1 blockers

    41. Help this patient A 12 y/o with Sickle Cell Disease presents to the ED with an acute vaso-occlusive crisis. After his first dose of morphine he experiences generalized intense itching. His pain is still high (7/10). So now you have 2 problems - what do you recommend?

    42. Help this patient A 12 y/o with Sickle Cell Disease presents to the ED with an acute vaso-occlusive crisis. After his first dose of morphine he experiences intense itching. His pain is still high (7/10). So now you have 2 problems - what do you recommend? Nubain

    43. Chemically induced itching: Neuroaxial Intrathecal, epidural opioids commonly complicated by pruritis Direct action on medullary dorsal horn and trigeminal nucleus of medulla – not t/histamine release Blocked by naloxone (therefore opioid receptor mediated) Also possibly related to antagonism to inhibitory neurotransmitters GABA and Glycine and 5-HT receptors (ondansteron effective)

    44. Chemically induced itching: Neuroaxial Spinal anesthesia with lidocaine: 30-100% pruritis Fentanyl: Intrathecal 67-100% Epidural 67% Morphine Intrathecal 62-82% Epidural 65-70%

    45. Treatments: opioid related pruritis Diphenhydramine – for systemic opioids For Neuraxial Opioids: Ondansteron Naloxone (1-2mcg/kg/hr) Nalbuphine (10-20 mcg/kg/hr) Propofol (.5-1mg/kg/hr) Lidocaine (2mg/kg/hr) NSAIDs (diclofenac, tenoxicam) Droperidol

    46. Chemically induced itching: Antibiotics Penicillin: immediate type I hypersensitivity reaction Vancomycin: massive nonimmunologic release of histamine ?“Red Man Syndrome” (flushing CP, pruritis, muscle spasms, hypotension) Related to rate of infusion Potentiated by muscle relaxants and opioids Attenuated by H1 blockers Rifampin

    47. Match D/O with Antipruritic Lymphoma Chronic Renal Failure Liver Failure Conjunctivitis Eczema Penicillin Reaction Activated Charcoal Cimetidine Toradol Odansetron Diphenhydramine Topical Steroids

    48. Match D/O with Antipruritic Lymphoma Chronic Renal Failure Liver Failure Conjunctivitis Eczema Penicillin Reaction Activated Charcoal Cimetidine Toradol Odansetron Diphenhydramine Topical Steroids

    49. Chemically induced itching: Other drugs Fentanyl: itching decreased when mixed with bupivicane, increased when mixed with procaine Drug induced cholestasis esp phenothiazenes, estrogens, tolbutamide, anabolic steroids

    50. Diseases Associated with Itching Renal Hepatic H Pylori Infection Hematologic d/o Metabolic/Endocrine Neurologic HIV Skin Diseases

    51. Eczema & Itching Hallmark of atopic dermatitis >80% pts recognize stress as a trigger for increased itching Alexithyma: Patients with chronic dermatosis who develop abnormal language development as a result of the perception that touch is noxious

    52. Eczema & Itching: Treatment cool compresses emollients topical steroids antidepressants anxiolytics antibiotics

    53. Match D/O with Antipruritic Lymphoma Chronic Renal Failure Liver Failure Conjunctivitis Eczema Penicillin Reaction Activated Charcoal Cimetidine Toradol Odansetron Diphenhydramine Topical Steroids

    54. Match D/O with Antipruritic Lymphoma Chronic Renal Failure Liver Failure Conjunctivitis Eczema Penicillin Reaction Activated Charcoal Cimetidine Toradol Odansetron Diphenhydramine Topical Steroids

    55. Systemic Treatment: Histamine blockers H1-receptor antagonists: diphenhydramine Side effects: anticholinergic effects, paradoxical agitation, excessive sedation H2-antagonists may enhance H1-blockers No quality studies demonstrating efficacy of oral antihistamines for atopic dermatitis!

    56. Renal Diseases and Itching Chronic Renal Failure: 25-86% itching (not in acute renal failure) Attrib to accumulation of pruritogens: histamine (?mast cells), serotonin ?Ca, Phos, Mg, Al, vit A also implicated 1/3 uremic patients not on dialysis Maintenance hemodialysis: 70-80%

    57. Renal Diseases and Itching Tx for uremic itching: renal transplant Effective even when transplant is failing as long as immunosuppresants are given Antihistamines not effective Also effective: moisturizers, UV-B tx (?vit A in skin), oral activated charcoal, cholstyramine, naltrexone, ondansterone, topical capsaicin, azelastin, thalidomide, IV lidocaine, erythropoetin, electric needle stim

    58. Match D/O with Antipruritic Lymphoma Chronic Renal Failure Liver Failure Conjunctivitis Eczema Penicillin Reaction Activated Charcoal Cimetidine Toradol Odansetron Diphenhydramine Topical Steroids

    59. Hepatic Diseases & Itching 20-25% janudiced patients with hepatobiliary disease associated with cholestasis 100% primary biliary cirrhosis Viral hepatitis Attrib to bile salts in serum and tissues Begins palms and soles & spreads inward

    60. Hepatic Diseases & Itching Tx: reverse cholestatis, liver transplant Also helpful: oral guar gum (dietary fiber) binds bile acids; cholestyramine; rifampin! (inhibits bile uptake), opioid antagonists, codeine, propofol, ondansetron Not helpful: scratching

    61. Match D/O with Antipruritic Lymphoma Chronic Renal Failure Liver Failure Conjunctivitis Eczema Penicillin Reaction Activated Charcoal Cimetidine Toradol Odansetron Diphenhydramine Topical Steroids

    62. Hematologic Disease & Itching Polycythemia vera (50%) hydroxyurea tx iron def anemia, lymphomas (Tx: cimetidine) Hodgkins – 30% T-cell: almost all leukemias, plasma cell dyscrasias, mastocytosis

    63. Match D/O with Antipruritic Lymphoma Chronic Renal Failure Liver Failure Conjunctivitis Eczema Penicillin Reaction Activated Charcoal Cimetidine Toradol Odansetron Diphenhydramine Topical Steroids

    64. Match D/O with Antipruritic Lymphoma Chronic Renal Failure Liver Failure Conjunctivitis Eczema Penicillin Reaction Activated Charcoal Cimetidine Toradol Odansetron Diphenhydramine Topical Steroids

    65. Neurologic Disorders & Itching Central: MS, CNS abscess, spinal and cerebral tumors (17%), CVAs Attrib to effects on descending pathways which ? itching Neurogenic Shingles (10-15% in US) Notalgia paresthetica: sensory entrapment syndrome causing neuropathy of T2-6 dorsal spinal nerves

    66. Endocrine D/O & Itching Diabetes Thyrotoxicosis Myxodema Postmenopausal syndrome Most common trigger: mucocutanious candidiasis

    67. What to Ask of the Itchy Patient Local vs generalized? Sequence of events: itch vs rash Description of sensation Timing & severity

    68. General Approach to Itching Treat the Cause Treat the Co-morbidities

    69. Conclusions Pruritis is common and often disabling Pruritis has many similarities to pain Pruritis is related but not identical to pain Effective interventions are possible Antihistamines are not always the most effective treatment

    70. Questions?

    72. Systemic Treatment: Opioids Naloxone (.8mg) for biliary cirrhosis Nalmefene (5mg BID): more potent and longer duration (12-48hrs) May induce w/drawl sx if stopped abruptly

    73. Take Home Points Pain and Itching are intimately related Cause/Triggers Patho-physiology Treatment Different mechanisms for itching call for different treatments Antihistamines are effective for a select few causes of itching

    75. Treatment Cooling skin (eczema and other dermatoses) Vibration, TENS for localized and generalized pruritis (effectiveness dissipates w/use) UV therapy for chronic renal failure Inhibits release of histamine and proliferation of dermal mast cells

    76. Treatment: Topicals Moisturizers, calamine, antihistamines, corticosteroids, EMLA Capsaicin cream: excites C-fibers ?release substance P & calcitonin gene-related peptide ?depletion of both .025% 5 times a day for notalgia paraesthetica

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