Occurs at ALL levels of the pain pathway 

Pain is not hard wired, system keep it in balance similar to coagulation 

Pain is a dynamic process 

Warning sign, signals impending or actual tissue damage

Helps individual to prevent further damage

Limits movement

Alerts person to seek medical help

Maintains body integrity

Activates fight or flight response- not in chronic pain

SC9A genetic deletion- Na Channel

Nerve growth factor mutation

Self- Mutilation

Joint deformities/bone fractures

Burns/multiple scars/infections

Early death 

Delays recovery from surgery

Peripheral/Central Sensitization-Hyperexcitation

Expansion of Pain receptive field

DNA changes

Promotes chronic pain

Causes adverse physiologic effects= more pain @lesser stimulus 

Fight or Flight Response

HPA axis= increased sympathetic tone

Increased Catecholamines

Increased Catabolic Hormones

Decreased Anabolic Hormones 

Na and Water Retention

Hyperglycemia

Increased Metabolism: Increasd O2 usage, Increased Glycogen breakdown, Increased Lactate, Ketones, FFA's

Negative Nitrogen Balance 

Hypercoagulation, Poor Wound Healing, Decreased Immune Function 

Release of Catecholamines

Vasconstriction

Tachycardia

Increased CO

Changes in O2 Supply/Demand - can cause myocardial ischemia 

Splinting-Spinal Reflex: Thoracic >Abd>Peripher

Poor Inspiratory Effort and Poor Cough

Phrenic nerve 

Fatigue

Causes Atelectesis, hypoxemia, hypercarbia 

Myelinated Fast Fibers

Rex Laminae I and V 

Unmyelinated, Slow fibers

Rex Laminae II and III 

aka Substantina Gelantinosa 

Mechanical damage

Heat 

Pressure

Damage 

Bladder distention

Mechanical

Heat 

Prostaglandins

Bradykinins

TNF- tumor necrosis factor- alpha 

CGRP- Calcitonin Gene Related Peptide

Serotonin

Substance P 

TENS

Spinal/Epidural LA only

Spinal/Epidural with Narcotics 

Works at Rexed Laminae-A beta fibers

Closes gate 

NV is less with lipophilic

Pruritis less with lipophilic

Respiratory depression- primarily early, minimal delay

Both early (<6 hrs), hydrophilic can cause delayed

(> 6hrs )

Fentanyl, sufentanil

Rapid onset (5-10 min)

Shorter Duration (2-4 hr)

Minimal spread

Morphine, Hydromorphone

Delayed Onset (30-60 min)

Longer Duration (6-24 hr)

Extensive spread

Sympathetic Block= hypotension and bradycardia

NV

Motor Block- LA

Respiratory Depression- 1%

Pruritis- sufenta-?100%

Urinary Retention- up to 30% 

Increased Sensitivity

Longer Duration

Longer Circulation- be patient before redosing

Postop Delirium related to Increased Pain- narcs do not usually cause the delirium

Multimodal approach with caution

High Risk for Respiratory Arrest/Hypoxemia

Up to 25% incidence of complications

Epidural Analgesia Less Complications

Use Multimodal Approach: Epidural, Nerve Blocks, NSAIDs, IV analgesia 

Non-painful stimulus perceived as painful

Not sure why...

Visual Analogue Scale

(VAS)

Conceptually Simple, Efficient, Minimally Intrusive

Valid-Statistics

Correlates with verbal and other numerical scoring systems

Disadvantage- one dimensional 

Prevalence: 7-64%

LBP lifetime prevalence: 80% 

HA Lifetime Prevalence: 80%

12 million Consults/year

5% of US population

2.5 million referrals to specalist

4.8 million referrals to chiropractor

2 million spent on MRI/CT

Heath Care Costs- $33 Billion

Society Costs- $120 Billion 

Loss of Warning Function

Loss of Fight or Flight Response

Pain tolerance is reduced to other stimuli

Vegetative Signs- fatigue, sleep disturbance, irritability, social withdrawl, depression, decreased activity 

Tissue Damage: RA, Joint Arthropathy, Whiplash, Cerival pain, Abdominal Pain

Nerve Damage: Diabetic Neuropathy, Herniated Disk, Post Herpatic Neuralgia

Long Acting Narcotics

Duragesic (Fentanyl) Patch

Morphine

Methadone

Opana ER

Oxycotin

Exalgo 

24 hour dosing

(Morphine)

12 hr dosing

(Morphine)

6-12 hr dosing 

(Morphine)

Opana ER

(Oxymorphone)

Respiratory Depression

NV

CNS- Sedation/Hallucinations

Urinary Retention

Constipation

Withdrawl 

Equianalgesic Dosages are averages

Differences in Mu Receptors

Changing Medications: withdrawl, respiratory depression, death

Err on the "light side": 25-75% reduction in dose 

Pneumothorax

Carotid injction= Seizures

Subarachnoid Injection= total spinal

Recurrent Laryngeal Paralysis= hoarseness 

NO BILATERAL BLOCKS 

Continuous Somatic= Easiest

Intermittent Somatic

Continuous Visceral

Intermitternt Visceral

Continuous Neuropathic= Medium

Intermittent Neuropathic

Pyschogenic= Hardest 

Maintain home narcs if possible

Assume higher tolerance- except in cases of incomplete cross tolerance

PCA- higher demand- shorter interval- higher 4 hr lock out

Use Multi-modal approach 

LA

NSAIDs

Different route narcs 

Wound Infiltration

Spinal/Epidural

Nerve Blocks: Interscalene/Illioinguinal

Continuous Nerve Blocks: Femoral/Saphenous/Popliteal

EMLA/Lidoderm 

Tramadol/Ultram: mu and 5HT

Anti-Seizure: Lyrica/Neurotin

Steroids

Antidepressants: Elavil-TCA, Celexa/Paxil- SSRI, Cymbalta/Effexor-SNRIs

Esmolol