Pain and Opioids: damage and danger, mechanism and meaning

Mark Sullivan, MD, PhD
University ofWashington
BC Pain Research Network Conference on Pain, Affect and Opioids

 Consulting
 Aetna, ChronoTherapeutics, State ofWA
 Research grants
 Pfizer and Purdue and NIDA and PCORI

 Usual errors cited:
 Pain proportional to
tissue damage
 Only afferent neuronal
activity relevant to pain
 Additional errors:
 Why is the boy’s foot in
the fire?
 What to do next?
 Who will help?

 Chronic pain prevalence
 15% of world population (Murray, Lopez, 2013)
 30% of US population, $600B cost/yr. (IOM 2011)
 Chronic pain severity
 33% rate their chronic pain as severe (Breivik 2006)
 40% are not satisfied with their care (Johannes 2010)

 38 yr old married RN with 2 children, 8yr, 5yr
 MVA 3 years ago when she was rear-ended
 Initially she had whiplash, chronic neck pain
which gradually spread down her spine and
then her limbs and whole body
 Unable to work since her accident
 Spine MRI reveals only degen. disc disease
 She reports 10/10 pain despite oxycodone SR
80mg BID (240mg MED), asks for more

 IASP defines pain as "an unpleasant sensory and
emotional experience associated with actual or
potential tissue damage, or described in terms
of such damage.”
 This aversive sensory experience can prompt a
separate protective motor response, which can
include reflexive withdrawal, splinting and
resting of the painful body part, and avoidance
of activities that can increase pain.
 This sensory understanding of pain implies that
the pain experience must be reduced to reduce
motor reactions (Sullivan andVowles, 2017)

 Pain includes feelings and also behaviors:
 Protective and communicative behaviors
 Usually considered consequences not integral
 “without a pain behavior system there would
be no adaptive value to the pain signal itself”
 “as adaptive as a fire station without firemen”
 Biopsychomotor; “sensory component is
accompanied by a behavioral system”
(MJSullivan, 2008)

 CRPS-1: Chronic regional pain syndrome
 exquisitely painful disorder of limb
 loss of sensorimotor integration
 distorted body representation
 learned neglect and disuse
 Pharmacological, procedural, psychological
treatment effective only if it promotes use of
affected limb for intentional action

 Clinicians have long hoped that reducing pain of injured workers
with opioids would promote rehabilitation and return to work.
 Unfortunately, multiple prospective cohort studies have shown
that early opioid therapy decreases the likelihood of an injured
worker with back pain returning to work. (Franklin 2008)
 A national study of early opioid therapy that adjusted for injury
severity, demographic characteristics, and job tenure found an opioid
dose-related increase in the duration of job disability. (Webster 2007)
 The deactivating effect (physical, social) of opioids appears to be
more potent and important in injured workers than the chronic
pain relieving effect. (Deyo, 2015)

 OLD Melzack: pain intensity encoded in
distributed neuromatrix of brain centers
 NEW Legrain: these brain centers more
properly considered a multisensory salience
network activated not just by nociception,
but also by visual, auditory etc. stimuli that
provide the context determining relevance of
nociception to organismic survival
 Borsook: “pain is not a purely sensory
experience”

 Legrain: “Under the assumption that this
(salience) network acts as a defensive system
signaling potentially damaging threats for the
body, emphasis is no longer on the quality of the
sensation elicited by noxious stimuli but on the
action prompted by the occurrence of potential
threats.”
 In this salience-focused approach, the purpose
of the network is not to produce a sensation of
some specific intensity but to produce effective
threat-defusing action.

 Expanding available repertoire of patient
action in the presence of pain is a viable goal
for chronic pain treatment
 Pain intensity is often the last thing to improve in
successful chronic pain treatment
 Increasing opportunities for purposive action by
patients may alter pain salience
 Fordyce: “people who have something better
to do don’t suffer (hurt) as much”

 Perception as enaction not representation:
pain serves action and is shaped by it
 pain   action, not pain  behavior
 Enactivism argues that cognition arises
through a dynamic interaction between an
acting organism and its environment. It
claims that our environmental niche is one
which we selectively create through our
capacities to interact with the world.

 Noe: “…perceiving is a way of acting.
Perception is not something that happens to
us, or in us. It is something we do.”
 “The world makes itself available to the
perceiver through physical movement and
interaction…. Only through self-movement
can one test and so learn the relevant
patterns of sensorimotor dependence.”
 “…when we perceive, we perceive in an idiom
of possibilities for movement.”

 “Experience is not caused by and realized in
the brain, although it depends causally on the
brain. Experience is realized in the active life
of the skillful animal.”
 “…my brain is affected not only by what
happens to me; by sights, sounds, odors, etc.
What I do also brings about changes in my
brain.”
 Pain arises from active animal w active brain

 Kucyi and Davis 2015:
 “Given that pain is intrinsically salient, it can
dramatically affect behavior. Conversely, attention-
demanding tasks, stimuli, and thoughts can alter the
quality and salience of pain and neural processing of
nociceptive input.Thus, pain and attention mutually
influence one another.”
 “Regardless of noxious stimulation level, pre-existing
brain states determine what level of pain will
subsequently be perceived and whether near-
threshold stimuli will be perceived as painful or not”

fMRI reveals 3 brain systems involved in pain attention:
Salience network: aINS, MCC,TPJ, dlPFC
Default mode network: PCC, precuneus, mPFC, lat and med parietal
Descending pain modulation network: PAG, RVM
Kucyi and Davis, 2015

 Baliki/Apkarian: “One commonly forgets the fact
that most humans… spend most of their lives
free of pain and with no obvious tissue injuries.
This must be ascribed to active nociceptors,
because there are no other alternative neuronal
mechanisms available to continuously protect
the body and subvert the potential for injury and
resulting pain perception.”
 “acute pain is not a warning signal but rather is
the failure of the machinery (nociceptor activity)
designed to avoid pain.

 Danger/safety/reward can override damage
 “…conscious acute pain perception is highly malleable and
a standardized nociceptive barrage does not translate into
a fixed brain activity or to a prototypical perception.”
 Consider when nociception signals reward
 “ for rodents…food trumps pain-related escape behavior
when both are simultaneously present”
 “Pavlov was able to train his dogs
to salivate for painful stimuli”

 Pain motivates injury avoidance and healing behaviors in the
immediate body vicinity
 Anxiety is as an emotional state with sympathetic arousal that
promotes safety within relatively short time and space scales.
 Depression is a more global generalization of perceived averseness to
one’s environment.
 B+A: “Overall, there seems to be a remarkable overlap
between the brain structures that either impart vulnerability
or are affected by pain chronification and pathological
negative moods. It is therefore not surprising that these
conditions are often comorbid…

 “Long-term shifts in the threshold mechanisms
that gate the conversion from nociception to
pain also underlie the transition to chronic pain.
We further propose that the threshold shift is
dependent on… a lowered mesolimbic
threshold for the conscious perception of pain”
 “Ventral striatal circuitry links nociception, acute
pain, and chronic pain.This circuitry assesses
salience of impending pain as well as expected
reward value for relief of pain.”

 Prospective fMRI study of patients w LBP
(Hashimi, 2013)
 LBP progresses- acute subacute chronic
patterns of brain activation shift from
sensory/nociceptiveemotion-affect regions
 But as LBP shifts from somatogenic to
psychogenic, it feels the same to the patient
 This LBP thus does not have a single cause or
“neurological signature” (Wager)

 Enactive pain
 Pain perception is an active process. It arises
through and serves action promoting survival.
 Damage-danger protection
 Nociception is received by an active brain that is
processing other survival-relevant inputs
 Nociception, acute pain, chronic pain support a
continuum of protective feelings and actions that
include anxiety and depression

 What relevance does this discussion of pain
mechanisms have for clinical care and policy?
 Does this discussion help us understand and
address the opioid epidemic?
 Turn back to Ms. B and her fibromyalgia…

 Altered CNS nociceptive processing similar to
IBS, IC,TMD, tension HA (Clauw 2014, 2015)
 Increased activation on fMRI: salience network,
secondary somatosensory cortex… (Kutch 2017)
 Increased connectivity between insula and
default mode network, proportional to pain
 Elevated substance P, NGF, glutamate in CSF
 Reduced conditioned pain modulation
 Endogenous opioid tone increased
 More tonic, less phasic opioid release

 As part of her initial work-up at pain clinic,
she scored 5/5 on PC-PTSD5 screener
 She re-experiences her MVA in nightmares
 She avoids driving in that part of town
 She is easily startled, angered, w insomnia
 She has withdrawn from colleagues, friends
 She cannot stop blaming herself for the MVA
 She appears to have PTSD

 Prevalence of PTSD in US is 7.8%
 Chronic pain reported in 35-50% of PTSD pts.
 Among patients presenting for care of
chronic pain, 7-50% meet PTSD criteria.
 Common chronic pain: pelvic pain, low back
pain, facial pain, bladder pain, fibromyalgia

 PTSD+: more intense pain, affective distress,
disability
 PTSD+: opioid therapy more likely, higher
doses, multiple opioids, concurrent benzos,
early refills, adverse events (Seal, 2012)
 PTSD+: linear association with wide range of
chronic pain outcomes: pain intensity, activity
interference, sleep, disability, global health,
opioid risk (Langford, 2018)

 As you work with Ms. B to address PTSD sxs.
(prazosin), depression (duloxetine) and
disability (PT, OT) she reveals that she was
beaten by her first husband (age 20-23)
 She eventually left this husband, but had
nightmares of beatings for years
 These had resolved a decade before her MVA

 Most prefer broken leg over broken heart, but
medicine treats broken legs as more real
 Social rejection, exclusion, loss can be the most
“painful” experiences of human life
 Physical injury and social rejection produce
activation of same brain structures on fMRI:
anterior cingulate, anterior insula (salience
network) (Eisenberger 2003)
 Eisenberger: “social attachment system may
have piggybacked onto opioid substrates of
physical pain system to maintain proximity with
others…”

 Sensitivity to physical and social pain linked
 Same people
 Experiments show persons more sensitive to
physical noxious stimuli also more sensitive to
social rejection (Eisenberger 2006)
 Same treatments
 Physical and social pain respond to same meds
▪ opioids relieve separation distress (Panksepp, 1978)
▪ Acetaminophen reduces social and physical pain (Dewall,
2010)

 Invertebrates have no EOS
 Amphibians, reptiles, fishes have an EOS that
modulates only physical injury pain
 Suppresses pain if injured while fleeing predator
 Rats forced to swim in ice water
 Injured patients who do not feel pain until at ED
 Mammalian EOS also modulates the pain of
physical injury, but…

 In mammals, opioids also serve to promote
social bonds essential for survival.
 In non-primate mammals, most crucial bonds
are with mates and offspring
 Known to be supported by oxytocin system
 But EOS supports these most basic bonds too
 Rat pups w deficient EOS do not bond to mothers
 EOS necessary for development of social play

 Primate EOS allows complex social networks
 As social networks grow from rodents to primates
benefits and conflicts increase
 Endorphin release during primate grooming helps
defuse these stresses and assure relationships
available, but limited to group size of about 20

 Human social bonds more complex, extensive
so need support beyond grooming (Dunbar):
 Laughter “primitive chorusing vocalization”
 Singing, dancing, drama, religious ceremonies
 Adult attachment style related to EOS
 PET: avoidant attachment related to lower mu
receptor availability in amygdala, ACC, insula, PFC
 BPD, ASP show EOS dysregulation (Bandelow)

 In humans, EOS supports social play which
fosters social bonding and social, cognitive,
emotional development and pain tolerance
 Adult social relationships  pain tolerance
 fMRI: partner caress EOS  pain tolerance

Mu Opioid Receptor-Mediated
Neurotransmission
AMY
CAU/
NAC/
VP
THA
CING
4
3
2
1
BP
Distributed in pain
regions but also
“affective / motivational
circuits” - neuronal
nuclei involved in the
assessment of stimulus
salience and cognitive-
emotional integration.
Descending
CNS Inhibitory Controls
From Zubieta JK

 During a session on pain coping with MSW,
Ms. B speaks of nightmares of molestation
 She says her grandfather used to visit her
room at night when stayed with them
 This occurred age 7-13 until he died
 She tried to tell her mother, but she said that
“Grandpa wouldn’t do such a thing.”
 Ms. B also reports she drank heavily and took
“pain pills” until she left her first husband

 Ms. B’s trauma history now includes the
essential elements of helplessness and
loneliness (Bergman)
 Survival required dissociation from the self
that has been overwhelmed and destroyed
 Repeat trauma breaks through dissociation
once again making Ms. B helpless and alone
 So she turns to opioids (safety)
 “heroin is like being hugged by God”

 Opioid use increased among FM patients with
history of physical or sexual abuse (Alexander 1998)
 Adverse childhood experiences associated with
increased prescription medication use and
psychotropic medication use (Anda 2007, 2008)
 Childhood trauma shows dose-response
relationship to adult opioid use, misuse,
injection drug use (Austin 2018, Quinn 2016)
 Emotional abuse, physical abuse  1.5x rx opioid use
 Neglect, emotional abuse, parental incarceration,
binge drinking  25-55% increased opioid misuse
 Sexual abuse, witnessed violence  3-5x incr. inj. use

 Targeted rejection events (e.g., fired, broken up)
 assoc. with 22x increase in depression (Kendler 2003)
 MDE patients show MOR deactivation but controls
show MOR activation in amygdala (Hsu 2015)
 These social rejections are a threat to physical survival
for intensely social primates (Holt-Lunstead 2015)
 SNP in OPRM1 increases sensitivity to physical
pain and social rejection (Slavich 2014,Way 2009)
 G allele carriers need more opioids after surgery, tend
to fearful adult attachment (Sia 2013,Troisi 2012)

 CRF coordinates autonomic, behavioral, and
cognitive response to stress w endocrine syst.
 In acute stress, CRF acts on LC to increase
arousal, attention, behavioral flexibility
 EOS has opposite effect on LC, helps neurons
and organism recover after stressor is gone
 With chronic stress (PTSD), opioid tolerance
and dependence may develop w/o meds
Opioids Vs. steroids

 Neuroscience suggests that human pain is a
survival-oriented behavioral drive rather than
an injury-caused aversive sensation
 EOS continuously modulates the transmission of
nociception to promote survival
 Brain encodes pain salience (not pain intensity) as
determined by survival-relevant context

 DA: in reward-driven actions-- “wanting”
Opioids: in hedonic tone– “liking”
 These systems are integrated to modulate
the valence (positive/negative) and
salience (strong/weak) of pain
 DA encodes motivational salience of pain
 whether pain should be endured for rewards
 when pain has positive valence or low salience

 Chronic pain disrupts hedonic homeostasis,
increasing relevance and reward of pain relief
(Elman and Borsook)
 As persistent stress, chronic pain increases
endogenous opioid tone, but decreases phasic
changes in endogenous opioids in response to
transient stressors.
 Similarly, exogenous opioid therapy initially
induces pain relief, but then induces tolerance
(to pain relief and mood elevation) and
dependence (a need for opioids to avoid pain
and distress).

 Oxycodone provided relief of pain, insomnia,
anxiety, agitation and anger
 But Ms. B kept needing more oxycodone,
developing tolerance and dependence
 Opioids reduce hyperarousal, re-experiencing
but deepen numbing and avoidance
 This leads to PTSD perpetuation

 Human physical and social pain systems are
linked because human physical survival is
dependent on social survival (Wilson 2012)
 Humans thrive in social cooperation, but
must modulate disruptive stresses
 Endogenous opioids are crucial to social
cooperation, but are disrupted by continuous
exposure to exogenous opioid medications

 As substances increase, relationships decrease
 Does not require development full addiction,
dependence may be enough
 Opioids provide illusion of safety
 To reduce substances, recover relationships
 Reach for the phone rather than pill bottle (AA)
 But complicated restoration process in those with
early, multiple or severe trauma (trust, safety)

 Ms. B attempted opioid taper, but became
too anxious, angry and overwhelmed
 Opioids simulated safety too well
 She transitioned onto SL buprenorphine with
improvement in her pain and anxiety
 Currently engaged in Cognitive Processing
Therapy to address her PTSD and trauma
 Hopes to taper off opioids in the future

 Pain is the product of an active brain in an
active organism
 Human pain is a survival oriented behavioral
drive that exists to promote both physical
and psychological survival.
 Mammalian social pain system piggybacked
onto physical pain system of non-mammals.
 EOS (+steroid, +dopamine) modulates the
pain of both broken arms and broken hearts
to promote species survival

Pain and Opioids: damage and danger, mechanism and meaning

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