Managing Pain After Surgery

Dr Yeo Sow NamDirector, 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

Sites and mechanisms responsible for acute & chronic postsurgical pain

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

Kehlet H, et al. Lancet 2006;367:1618-1625.

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Postoperative pain vs persistent postsurgical pain

Acute- PoP

Time

Sev

erity

of

Pa

in

Surgery

Patient 1- PoP

Patient 2- PoP + PPP

Chronic- PPP

Persistent Postsurgical Pain (PPP) Postoperative Pain (PoP)

• Pain that persists beyond the usual course of healing and is neuropathic in nature

• Pain is irresolvable and becomes chronic through irreversible changes to the pain pathway

• Incidence of PPP depends on surgery, intensity of PoP, and genetic factors

• Pain resulting from the inflammation associated with surgical intervention

• Pain is resolvable and acute• All surgical interventions result in the

development of PoP

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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

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Risk factors for development of persistent postsurgical pain1,2

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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• 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.

Persistent postsurgical pain: Manifestation of neuropathic pain

Kehlet H, et al. Lancet 2006;367:1618-1625.

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• 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

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Persistent postsurgical pain: Persistently overlooked

Durkin B, et al. Expert Opin Pharmacother 2010;11:2751-2758.

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Estimated incidence of chronic postsurgical pain1,2

1. Kehlet H, et al. Lancet 2006;367:1618-1625;2. Durkin B, et al. Expert Opin Pharmacother 2010;11:2751-2758.

Estimated incidence of chronic

postsurgical pain

Estimated incidence of severe (disabling) pain

Estimated US surgical volumes

(1000s)

Inguinal hernia repair 10% 2–4% 600

Lower limb amputation

30–50% 5–10% 160

Breast surgery (lumpectomy or mastectomy)

20–30% 5–10% 480

Thoracotomy 30–40% 10% 200Total knee arthroplasty

12% 2–4% 550

Coronary artery bypass surgery

30–50% 5–10% 598

Caesarean section 10% 4% 220

Surgical21%

Medical14%

Pain38%

ADE3%

N/V3%

Bleeding4%

Other17%

Sub-optimal pain management can have economic consequences

• Mean charges for patients re-admitted due to pain were $1,869±4,553 per visit*

• 38% of patients re-admitted for pain had undergone orthopaedic procedures

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*Mean inpatient re-admissions for pain $13,902±11,732 per visitADE, adverse drug eventN/V, nausea/vomiting Coley et al. J Clin Anesth 2002;14:349.

Re-admissions following day-care surgery

• 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

Persistent postsurgical pain: Potential for prevention

Kehlet H, et al. Lancet 2006;367:1618-1625.

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• 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

Multimodal analgesia: Rationale

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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• 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

Multimodal analgesia

Durkin B, et al. Expert Opin Pharmacother 2010;11:2751-2758.

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Potentiation

Opioid

ParacetamolNSAIDs/coxibs

Α2δ ligandsKetamine

Nerve blocks

• Decreased doses of each analgesic

• Improved anti-nociception due to synergistic/additive effects

• Decreased severity of side effects of each drug

Benefits of multimodal analgesia

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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Pain sensitization by injury:Hyperalgesia and allodynia

Normalpain response

Sensitizedpain response

Injury

X

HYPERALGESIA

Stimulus intensity

Pain intensityfor stimulus X:

Normalpain response

Pain intensityfor stimulus X:

Sensitizedpain response

ALLODYNIA

Pai

n in

tens

ity

10

8

6

4

2

0

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Anti-hyperalgesic therapy: Opioid-sparing

~30%reduction

Op

ioid

Op

ioid

Pai

n in

tens

ity

10

8

6

4

2

0

XStimulus intensity

Anti-Hyper-algesic

Normalpain

response

Sensitizedpain

response

Partially desensitizedpain response

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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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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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