This document discusses managing pain after surgery. It notes that persistent postsurgical pain is often overlooked and can be prevented. A multimodal approach using combinations of analgesics like opioids, NSAIDs, and nerve blocks can improve pain relief while reducing side effects from individual drugs. Identifying patients at risk of chronic pain and using multimodal acute pain management may decrease the risk of acute pain becoming persistent after surgery.

1. Managing Pain After
Surgery
Dr Yeo Sow Nam
Director, The Pain Specialist,
Mount Elizabeth Hospital &
Founder and Past Director, Pain
Management and Acupuncture
Services, Singapore General Hospital
MBBS (Singapore)
MMED (Anesthesiology, S’pore)
FANZCA (Anesthesiology, Aust/NZ)
FFPMANZCA (Pain Medicine,
Aust/NZ)
FAMS, Registered Acupuncturist

2. Sites and mechanisms responsible
for acute & chronic postsurgical pain
Kehlet H, et al. Lancet 2006;367:1618-1625.
1. Denervated Schwann cells and infiltrating macrophages distal tp nerve injury produce local and systemic chemicals that drive
pain signalling; 2. Neuroma at site of injury is source of ectopic spontaneous excitability; 3. Changes in gene expression in dorsal
root ganglion; 4. Central sensitization at dorsal horn; 5. Modulation of pain transmission at brainstem; 6. Contributions from limbic
system and hypothalamus; 7. Sensation of pain generated in cortex; 8. Genomic DNA predisposes (or not) to chronic pain
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3. Postoperative pain vs persistent
postsurgical pain
Patient 1- PoP
Severity of Pain
Patient 2- PoP + PPP
Surgery
Time
Acute- PoP Chronic- PPP
Persistent Postsurgical Pain (PPP) Postoperative Pain (PoP)
• Pain that persists beyond the usual course of • Pain resulting from the inflammation associated
healing and is neuropathic in nature with surgical intervention
• Pain is irresolvable and becomes chronic • Pain is resolvable and acute
through irreversible changes to the pain pathway • All surgical interventions result in the
• Incidence of PPP depends on surgery, intensity development of PoP
of PoP, and genetic factors
3

4. Risk factors for development of
persistent postsurgical pain1,2
1. Genetic susceptibility
2. Moderate to severe preoperative pain
3. Psychosocial factors
4. Age and sex
5. Poor surgical technique
6. Poorly controlled postoperative pain
1. Kehlet H, et al. Lancet 2006;367:1618-1625;
2. Durkin B, et al. Expert Opin Pharmacother 2010;11:2751-2758.
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5. Persistent postsurgical pain:
Manifestation of neuropathic pain
• Postsurgical chronic pain is the consequence
of either ongoing inflammation or, much
more commonly, a manifestation of
neuropathic pain resulting from surgical
injury to major peripheral nerves
– If nerves are injured during surgery, a
neuropathic component of the pain might develop
immediately and then persist in the absence of
any peripheral noxious stimulus or ongoing
peripheral inflammation. This pain, once
established, is likely to be resistant to COX-2
inhibitors.
Kehlet H, et al. Lancet 2006;367:1618-1625.
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6. Persistent postsurgical pain:
Persistently overlooked
• Development of chronic postsurgical pain
may be the most overlooked negative sequel
of elective operations
– In the UK, surgery is the second most common
reason patients give for having developed chronic
neuropathic pain
• Patients who present for surgery are often
not told of this risk, and the surgeons and
anaesthesiologists caring for them may not
be aware of the prevalence of the problem
Durkin B, et al. Expert Opin Pharmacother 2010;11:2751-2758.
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7. Estimated incidence of chronic
postsurgical pain1,2
Estimated incidence Estimated incidence of Estimated US
of chronic severe (disabling) pain surgical volumes
postsurgical pain (1000s)
Inguinal hernia repair 10% 2–4% 600
Lower limb 30–50% 5–10% 160
amputation
Breast surgery 20–30% 5–10% 480
(lumpectomy or
mastectomy)
Thoracotomy 30–40% 10% 200
Total knee 12% 2–4% 550
arthroplasty
Coronary artery 30–50% 5–10% 598
bypass surgery
Caesarean section 10% 4% 220
1. Kehlet H, et al. Lancet 2006;367:1618-1625;
2. Durkin B, et al. Expert Opin Pharmacother 2010;11:2751-2758.
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8. Sub-optimal pain management
can have economic consequences
Re-admissions following day-care surgery
Other • Mean charges for
Surgical
17%
21% patients re-admitted
due to pain were
ADE $1,869 4,553 per
3% visit*
Medical
14% • 38% of patients re-
admitted for pain had
undergone
Bleeding
orthopaedic
Pain procedures
4%
38% N/V
3%
*Mean inpatient re-admissions for pain $13,902 11,732 per visit
ADE, adverse drug event
N/V, nausea/vomiting Coley et al. J Clin Anesth 2002;14:349.
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9. Persistent postsurgical pain:
Potential for prevention
• Avoidance of intraoperative nerve injury
– Careful dissection
– Reduction of inflammatory responses
– Use of minimally invasive surgical techniques
• Pre-emptive and aggressive multimodal
analgesia
– Afferent blockade, COX-2 inhibitors and opiates
to alleviate inflammatory pain
– Anti-neuropathic pain agents to prevent
neuropathic pain
Kehlet H, et al. Lancet 2006;367:1618-1625.
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10. Multimodal analgesia: Rationale
• Although opioid-based patient-controlled analgesia
(PCA) is widely used as an effective method to control
postoperative pain, it is associated with a high
incidence of side effects, such as nausea, vomiting and
respiratory depression1,2
• In recent years, a multimodal approach based on the
combination of opioids and other adjuvant drugs (eg,
nonsteroidal anti-inflammatory drugs, ketamine, local
anesthetics and α2δ ligands) has been extensively
attempted to decrease opioid-related adverse effects1,3
1. Kim JC, et al. Spine 2011;36:428-433;
2. Grass JA, et al. Anesthesiology 1993;78:642-648;
3. White PF. Curr Opin Investig Drugs 2008;9:76-82.
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11. Multimodal analgesia
• Current state of the art in the management
of acute surgical pain
• Strategy utilizing two or more modalities from
the acute pain armamentarium to enhance
analgesia and/or minimize risk of side effects
• For multimodal analgesia to be maximized,
the modes of analgesia should be procedure-
and patient-specific
Durkin B, et al. Expert Opin Pharmacother 2010;11:2751-2758.
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12. Benefits of multimodal analgesia
Opioid • Decreased doses of each
analgesic
Potentiation • Improved anti-nociception
due to synergistic/additive
effects
Paracetamol
NSAIDs/coxibs
Α2δ ligands
• Decreased severity of side
Ketamine effects of each drug
Nerve blocks
Durkin B, et al. Expert Opin Pharmacother 2010;11:2751-2758;
Kehlet H, Dahl JB. Anesth Analg 1993;77:1048-1056;
Playford RJ, et al. Digestion 1991;49:198-203.
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13. Pain sensitization by injury:
Hyperalgesia and allodynia
HYPERALGESIA Sensitized
pain response
10
Pain intensity Normal
8 for stimulus X: pain response
Sensitized
Pain intensity
pain response
6 Injury
Pain intensity
4 for stimulus X:
Normal
pain response
2
0
X
ALLODYNIA
Stimulus intensity
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14. Anti-hyperalgesic therapy:
Opioid-sparing
Sensitized Partially desensitized
pain pain response
10 response
~30% Normal
8
reduction pain
response
Pain intensity
6
Anti-
4 Hyper-
Opioid
Opioid
algesic
2
0
X
Stimulus intensity
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15. Prevention of persistent
postsurgical pain
Chronic postsurgical pain is a problem worldwide,
but it is often overlooked or minimized. Several
million patients each year may develop chronic
pain due to nerve injury sustained during surgery.
Identifying these patients and modeling a
multimodal acute pain management plan to
decrease the conversion of acute to chronic pain is
an important therapeutic goal.
Durkin B, et al. Expert Opin Pharmacother 2010;11:2751-2758.
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16. Summary
• Postsurgical chronic pain is a problem worldwide, but it is
often overlooked or minimized
• Postsurgical chronic pain is the consequence of either
ongoing inflammation or, much more commonly, a
manifestation of neuropathic pain resulting from surgical
injury to major peripheral nerves
• Identifying these patients and modeling a multimodal acute
pain management plan to decrease the conversion of acute
to chronic pain is an important therapeutic goal
• Postsurgical chronic pain can be prevented by various ways
• Recently, a multimodal approach has been extensively
attempted to decrease opioid-related adverse effects
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