Date post: | 22-Dec-2015 |
Category: |
Documents |
Upload: | charles-young |
View: | 222 times |
Download: | 0 times |
WHY DOES ENDOMETRIOSIS CAUSE SO MUCH PAIN?
Dr Michael W Platt MA MB BS FRCALead Clinician in Pain Medicine, Consultant in Anaesthetics,
Honorary Senior Lecturer, Faculty of Medicine, Imperial College London,
Department of Anaesthetics St Mary's Hospital, Imperial College Healthcare NHS Trust
Praed Street, London W2 1NY
2007 Dr Michael W PlattImperial College
• The pain associated with Endometriosis is the most difficult symptom to cope with for most women. For many, the pain they suffer severely interferes with every day life. It can be constant or it can be cyclical and coincide with a woman’s period.
2007 Dr Michael W PlattImperial College
2007 Dr Michael W PlattImperial College
2007 Dr Michael W PlattImperial College
2007 Dr Michael W PlattImperial College
What is pain?
• Emotional
• Sensory
• Acute or Chronic
• Totally subjective
• Can be described qualitatively
• Can be graded quantitatively
2007 Dr Michael W PlattImperial College
What is pain?
2007 Dr Michael W PlattImperial College
What is pain?
• Can be graded quantitatively:
2007 Dr Michael W PlattImperial College
Why do we have pain?
• Recognition of self
• Protection from trauma
• Reduction of trauma
• Warning sign of illness
• Warning sign of infection
2007 Dr Michael W PlattImperial College
What happens when pain is absent?
• Congenital insensitivity to pain
• Sensory nerve damage secondary to disease– Diabetes– Stroke– Trauma– Syphilis– Leprosy
2007 Dr Michael W PlattImperial College
Pain
• Acute (physiological) Pain:– An unpleasant sensory and emotional
experience associated with actual or potential tissue damage.
• Chronic (pathological, intractible) Pain:– Pain in the absence of, or persisting following
the removal of, a noxious stimulus.
2007 Dr Michael W PlattImperial College
PAIN
• Acute: Post-trauma, surgery etc.
• Chronic:– Neuropathic pain– Mechanical pain– Chronic inflammation– Complex regional pain syndrome
• Cancer pain
2007 Dr Michael W PlattImperial College
Complicated neurobiology of pain
• Not a simple ‘hard-wired’ system.
• Long-term changes occur in the PNS and CNS following a noxious stimulus.
• This ‘plasticity’ changes the body’s response to further stimuli
2007 Dr Michael W PlattImperial College
Pain Pathways
• Nociceptor
• Axon
• Dorsal Root Ganglion
• Dorsal Root
• Internuncial neurones
• Cross-over to opposite side
• Thalamus and Cortex
2007 Dr Michael W PlattImperial College
2007 Dr Michael W PlattImperial College
Peripheral sensitisation
• Inflammatory response:Release of mediators from mast cells etc:– Substance P– neurokinin A– calcitonin gene-related peptide– lead to further release of ‘inflammatory soup’:
• K, 5-HT, bradykinin, histamine etc
• Act to sensitise high-threshold receptors
2007 Dr Michael W PlattImperial College
‘Neuropathic pain’
• Burning, sharp, stabbing sensations
• eg diabetic neuropathy, post-amputation pain etc.
• Treatment of peripheral neuropathic pain include tricyclic antidepressants, anti-convulsants, clonidine, opioids, local anaesthetics and anti-arrhythmic agents.
2007 Dr Michael W PlattImperial College
Sympathetic nervous system
• Important role in generation and maintenance of chronic pain states.
• ‘Complex regional pain syndromes:– Sympathetic dysfunction:
• vasomotor & sudomotor changes
• abnormal hair & nail growth
• osteoporosis
• sensory symptoms: burning, hyperalgesis, allodynia
2007 Dr Michael W PlattImperial College
Gate Theory of Pain
2007 Dr Michael W PlattImperial College
2007 Dr Michael W PlattImperial College
Central sensitisation
• Changes that occur in the dorsal horn in response to an injury, following barrage of stimuli into the horn.
• Phenomenon of ‘wind-up’ involving the NMDA receptor, making neurons more sensitive - ie sensitising them.
• Expansion in receptive field size.
2007 Dr Michael W PlattImperial College
Ascending tracts
• 2nd order neurons ascend in spinothalamic, spinoreticular and spinomesencephalic tracts.
• Terminate in structures throughout the brain stem, thalamus, and cortex.
• Thalamus has 2 main groups of relays:– sensory discriminative aspects– affective-motivational aspects
2007 Dr Michael W PlattImperial College
Descending modulation
• descending inhibitory modulation from:– hypothalamus– PAG– locus coeruleus– nucleus raphe magnus– etc
• Involves opioids, 5-HT, n-adr, GABA
2007 Dr Michael W PlattImperial College
Visceral Pain
• There are specific nociceptors originating in viscera.
• They respond to:– tension (contraction)– chemical nociception– sensitisation of nociceptors– effects of ischaemia
2007 Dr Michael W PlattImperial College
Concept of referred pain
• Visceral nociceptors rarely activated
• Much more common to activate somatic nociceptors
• Spinal cord and brain interpret visceral signals as emanating from somatic source
• Convergence of visceral and somatic afferents may account for this
2007 Dr Michael W PlattImperial College
Diagnosis of Pain in Endometriosis
• Acute, cyclical pain – due to pressure, chemical irritation, nerve compression
• Chronic, non-cyclical pain – due to neuropathic pain, sources outside the pelvis (back, groin, etc.)
• Other visceral pain – especially bladder pain.
2007 Dr Michael W PlattImperial College
2007 Dr Michael W PlattImperial College
2007 Dr Michael W PlattImperial College
2007 Dr Michael W PlattImperial College
Measurement of Pain
• Visual Analogue Score– make as objective as possible– Straight line 10 cm long– No other markings
• Personality inventories– Help to score chronic pain in terms of
personality type and stress markers.
2007 Dr Michael W PlattImperial College
Treatment of Pain in Endometriosis
• Acute Pain:– NSAIDS– Hormonal – Oral Contraceptive– Systemic analgesia, opioids– Other techniques (TENS, Acupuncture)
2007 Dr Michael W PlattImperial College
Pain Ladder
• Minor pain: paracetamol, aspirin
• Moderate pain:– combination with minor opioids
• Co-proxamol (propoxifine), Co-dydramol (codeine)
– Minor opioids alone - eg Pethidine, Tramadol
• Severe pain:– Opioids: Morphine etc.
2007 Dr Michael W PlattImperial College
Endometriosis and Inflammatory Pain: Use of NSAIDS
• Cyclo-oxygenase pathway blocked– 2 forms:
• COX1 & COX2
• COX1 always present
• COX2 only induced by inflammation
• Also have central role, where both COX1 & COX2 are found as neuro-transmitters
2007 Dr Michael W PlattImperial College
NSAIDS
• COX 2 antagonists preferable where there is high-risk of peptic ulceration / bleeding
• Still not 100% guarantee.
2007 Dr Michael W PlattImperial College
Treatment of Pain in Endometriosis
• Chronic / Intractable Pain:– Multiple modality pain clinic - holistic
approach– Drugs– Nerve blocks– TENS, Acupuncture– Physio, occupational Ther., Psychology
2007 Dr Michael W PlattImperial College
Neuropathic Pain in Endometriosis
• Not responsive to opioids
• Two main classes of drugs used:– Tricyclic antidepressants (esp Amitriptyline)– Anti-epileptics:
• Carbamazepine
• Sodium valproate
• Clonazepam
• Gabapentin (Pregaballin)
2007 Dr Michael W PlattImperial College
Gracilis Adductor longus
Adductormagnus
Adductorbrevis
Obturatorexternus
Obturatorinternus
2007 Dr Michael W PlattImperial College
Other complicating factors
• Psychosocial & spiritual processes strongly influence the impact and expression of pain.
• (Saunders 1985, Portenoy 1992; Breitbart 1994)
2007 Dr Michael W PlattImperial College
Some factors:
• Pain interrelated with:
– depression (r = 0.33 with pain)– lack of family support (r = -0.15 with pain)– desire for death (r = 0.47 with depression)
2007 Dr Michael W PlattImperial College
Some correlates with severe pain:• Patient anxiety: r = 0.30
• Communication problems: r = 0.29
• Constipation: r = 0.24
• Poor co-ordination: r = 0.21
• Family anxiety: r = 0.19
• Nausea: r = 0.19
• Vomiting: r = 0.13
• Other symptoms: r = 0.11
Factors that diminishquality of life:
PainOther symptomsPsychological
distressSpiritual/existential
distressFamily distressSocial distressFinancial needsHealth care concerns (eg poor communication)
Perception &appraisal ofpain
Expressionof suffering
A MODEL OF SUFFERING
2007 Dr Michael W PlattImperial College
Summary
• The pain system is a very complex one.
• Endometrial Pain may be difficult to treat due to a variety of causes, and these should be addressed in the management of the patient:
• Adequate pain assessment, including those factors which are inter-related is essential.