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What is pain?

An unpleasant sensory and emotional experience associated with actual or potential tissue damage


What are the general problems with pain

  1. It's often under-treated
  2. Uncontrolled pain produces detrimental SE that we don't want
  3. The treatment of pain carry risks and/or side effects
  4. Many patients and providers have misconceptions about the treatment of pain
    • fear of addiction
    • fear of side effects (ex: constipation)
  5. Pain increases the patient's stay in PACU, ICU, and the hospital in general


What is acute pain?

  • Pain caused by a noxious stimulus d/t injury, trauma, acute disease process, or abnormal function of muscle or viscera
  • almost always nociceptive pain
  • results in neuroendocrine response
    • ​stress response with HPA and SNS activation


Endocrine and CV response to pain


  1. Increased catecholamines
  2. Increased cortisol
  3. Increased aldosterone and ADH, renin, and angiotensin II
  4. Immune system suppression


  1. Increased HR, BP, SVR, CO, contractility
  2. Enhanced myocardial irritability
  3. Vasoconstriction, including coronary artery constriction
  4. Increased myocardial O2 consumption with decreased myocardial O2 supply (think ischemia)
  5. Increased plasma viscosity
  6. Increased water retention
  7. Vasoconstriction and fluid retention increase the workload of the heart


Pulmonary Effects of Pain

  • Decreased lung volumes (VC, TV,FRC)
  • Phrenic nerve dysfunction
  • Inadequate cough (don't want to agitate the pain)
  • Inadequate ventilation
    • (will decrease TV, VC, and FRC --> FRC may approach closing volume and cause atelectasis and VQ mismatch)
  • May have limited movement of respiratory muscles due to spasm of muscles
  • Decreased ability to clear airway secretions
  • Susceptible to pneumonias
  • Increased total body O2 consumption which increases respiratory workload Increased CO2 production


Heme Effects of Pain

  1. Hypercoagulability
    • Natural anticoagulants decrease
    • natural procoagulants increase
    • Inhibition of fibrinolysis 
    • Increased platelet reactivity/adhesiveness 
    • Increased plasma viscosity 
    • Increased risk of DVTs and vascular grafting failure, poor wound healing, MI risk
  2.  Immunosuppression→ Potentiates postoperative immunosuppression (poor wound healing)
    • Depressed lymphocyte response 
    • Decreased cell mediated immunity 
    • Alterations in balance of T-helper cells 
    • Increased interleukins and cytokines


GI/GU Effects of Pain


  1. Hypersecretion of gastric acid
  2. Slowed GI motility
  3. (risk of aspiration and paralytic ileus)


  1. Urinary retention


Neurendocrine Response to Pain

Basically reacting as if the body is in stress:

  1. Increased catecholamines
  2. Increased catabolic hormones
    • increased cortisol
    • increased glucagon → mobilize glucose stores
  3. Decreased anabolic hormones
    • Decreased insulin
  4. Increased ADH, Aldosterone, renin, and angiotensin II
    • Sodium and water retention
  5. Increased
    • Blood glucose
    • Free fatty acids
    • Ketone bodies
    • Lactate


What is chronic pain?

  • Pain that serves no purpose
  • Pain that persists beyond the usual coarse of an acute disease after a reasonable amount of time for healing to occur
  • Poorly controlled acute pain can transition to chronic pain
    • Intensity of acute pain is significant predictor of chronic pain


Chronic Pain may occur after these procedures

  1. Limb amputations (30-83%)
  2. Thoracotomy (22-67%)
  3. Sternotomy (28%)
  4. Breast surgery
  5. Gallbladder surgery


Chronic pain is associated with an imbalance in _____

Neuromodulation controls

  • Attenuated neuroendocrine response (unlike acute pain) →
  • Exhausted supplies of endorphins and serotonin →
  •  Predominance of C-fiber stimulation


Chronic pain is associated with ____ in the periphery

chronic inflammation

  1. Continuous release of inflammatory mediators in the periphery sensitizes functional nociceptors and activates dormant nociceptors
    • There is sensitization of nociceptors and hyper-excitability
  2. Functional changes occur in the dorsal horn of the spinal cord (neuroplasicity)
  3. Dormant nociceptors are activated
  4. Recruitment of additional nerve fibers and pathway tracts
  5. Pain is perceived as more painful
  6. Reflexes can create excessive muscle tension, with actual disruption of microcirculation


Cancer pain

Pain caused by:

  1. tumor invasion of the bone
  2. tumor compression of peripheral nerves
  3. Treatments of cancer (chemo and radiation)
    • mostly d/t tissue destruction


Physical and psych components of cancer pain


  • worse due to loss of sleep, appetite, nausea & vomiting


  • heightened anxiety
  • feelings of loss
  • low self-esteem
  • changes in life goals
  • disfigurement


What is allodynia?

Pain in response to a stimulus that shouldn't normally cause pain


Pain Preop Evaluation

  1. Evaluate pain
    • Pain history
    • Physical exam
    • Self report measurement scales
    • Medications for pain
    • Document
  2. Preparation
    • Adjustments and/or continuation of meds
  3. Develop plan


Benefits of adequate post-op pain control

  1. Reduction of the stress response
  2. Shorter times to extubation
  3. shorter ICU stay
  4. early discharge
  5. Improved respiratory function
  6. Earlier return of bowel function
  7. Earlier enteral nutritional intake
  8. Early mobilization
  9. decreased risk DVTs
  10. Reduction in:
    • sensitization
    • neuroplasticity
    • wind-up phenomenon and
    • transition to chronic pain
  11. Increased patient satisfaction


When does post-op pain control begin?


Goal is to prevent pain before it happens.


Who requires that we do a pain assessment of our patients?



Respiratory and routes of opioid administration

Incidence of respiratory depression does not vary across routes. You get depression despite whatever route you choose.


Preferred routes of opioid administration


Then sublingual or rectal (avoid first pass effect)


Opioids exert their effects via these receptors

Mu and Kappa


Is there an analgesic ceiling with opioids?


The dose is only usually limited by tolerance or SE.


Most common drugs for PCA use

Morphine and hydromorphone


NSAIDs work by inhibiting ____



By using NSAIDs with opioids, the pain response is attenuated in both these locations

The spinal cord (opioids) and in the periphery (NSAIDs)


Using NSAIDs can decrease opioid requirement by ___%




  1. Decreased hemostasis
    • Platelet dysfunction
    • Inhibition of thyromboxane A2
  2. Renal dysfunction
  3. GI hemorrhage
  4. Liver dysfunction
  5. Effects on bone healing/ osteogenesis


Ketamine as an adjuvant drug

Small doses to act as adjunct to LAs and opioids. Enhances the analgesic effect and reduces SE.


These drugs may be used as adjuvants

  1. Ketamine
  2. Tramadol (Ultram)
  3. Nalbuphine (Nubain)
  4. Methadone
  5. Acetaminophen


Tramadol as an adjuvant

  • Weak PO opioid that induces serotonin release and inhibits NE re-uptake
  • Contraindicated in those on MAOIs and those with seizures


Nalbuphine as an adjuvant

Agonist-antagonist (fewer SE) 

Really only used in OB.


Methadone as an adjuvant

Very long 1/2 life (15-29 hours)

Can be given IV for nice post-op pain control (20mg IV)


What provides better analgesia: Regional blocks or systemic opioids?

Regional blocks


Benefits of neuraxial analgesia

  1. Better analgesia than systemic opioids
  2. Reduced stress response
  3. Facilitates return of GI motility
  4. Fewer pulmonary complications (less chance of resp depression)
  5. Less incidence of coagulation-related adverse effects
    • less complications d/t bleeding (ex- from NSAIDs)


Hydrophilic Opioids used in Neuraxial Blocks

Morphine and Dilaudid

  1. Tend to stay in the CSF
  2. Extensive CNS spread
  3. Delayed onset of action (unable to penetrate the neuron)
  4. Longer DOA (not taken up by fat quickly)
  5. High incidence of SE (d/t cephalad spread of the opioid)


Lipophilic Opioids used in Neuraxial Blocks

Fentanyl and Sufentanil

  1. Rapid onset
  2. short DOA (systemic uptake)
  3. Minimal spread
    • d/t segmental analgesic effect)
  4. fewer SE


These opioids may be given in neuraxial blocks

  1. Fentanyl
  2. Sufentanil
  3. Morphine
  4. Hydromorphone
  5. Meperidine (Demerol)


Can epidurals be connected to a PCA?


Benefits :

  1. Allows for individualization

  2. Lower drug use

  3. Increased patient satisfaction

  4. Side effects similar to continuous epidural infusions

  5. Background infusion with demand dose common


What needs to be considered in continuous epidural analgesia?

  1. Choice and dose of the agent used  
  2. Location of catheter placement
  3. Onset and duration of periop use
  4. SE and risks
  5. Will pain management personnel be around to manage the catheter if issues arise?


Options for what agents to place in an epidural

  1. LA only
    • High failure rate
    • High chance of motor blockade
    • Hypotension is common
  2. Opioid only
    1. Avoids motos block
    2. Less hypotension
    3. Has other SE ex: respiratory depression and pruritis
  3. LA + Opioid
    1. Better choice
    2. Limits regression of sensory block
    3. Decreases the total dose of LA needed (avoids toxicity) 
    4. Able to give low concentration of LA and low dose of opioid
    5. Work synergistically by working on two separate MOAs
    6. Less  motor block
      • allows for earlier ambulation
    7. Good choice for thoracic, abdominal, pelvic, and orthopedic lower extremity procedures


Adjuvant neuraxial drugs

  1. Clonidine
    • A2 agonist
    • Prolongs duration of block
    • SE: Hypotension, bradycardia, sedation
      • these limit the use of clonidine
  2. Epi and phenylephrine
    • Prolongs duration of block
    • Increases intensity of block


Where to place an epidural catheter

what are the advantages?

Location congruent to the incisional dermatome

it results in optimal postoperative analgesia by infusing analgesic agents to the appropriate incisional dermatomes


  1. provides superior analgesia
  2. utilizes less drug
  3. minimizes side effects
  4. decreases morbidity 


Recommended epidural catheter levels for various surgeries

  • Thoracic sx = T4-8
  • Upper Abdominal or cholecystectomy = T6-8
  • Nephrectomy = T7-10
  • Lower abdominal = T8-11
  • Lower Extremities = L1-4


SE of neuraxial blockade

Medication related + sympathectomy and possible motor blockade

  • Resp depression
  • N/V
  • Pruritis
  • Urinary retention
  • Hypotension
  • Motor blockade


Risks of epidural block

  1. Complications with the placement
    • Epidural hematoma
    • Abcess
    • Neurologic/Cord injury
  2. Misplacement of injection 
    • IV, subarachnoid, or subcutaneous injection
  3. Complications r/t anticoagulatnts:
    • pt may need to be started on them post-op (r/t surgery type) or given intra-op


Non-pharmacologic adjuncts to pain management

  1. Ice
  2. Extremity elevation
  3. TENS (transcutaneous nerve stimulator)
  4. Acupuncture
  5. Phych approaches
    • hypnosis
    • imagery
    • distraction
    • music
  6. Surgical
    • local infiltration
    • intra-articular analgesia
    • pain pumps (ex: onQ)


Considerations for ambulatory patients

  1. Severe post-op pain will prolong hospital stay
  2. Common to have pain after discharge
  3. N/V common
    • may interfere with ability to take PO analgesics
  4. Best to do a multimodal approach to pain management (opioid, non-opioid, LA, ice, etc)


Considerations for elderly patients

  1. Old people have lots of changes: in their
    1. physiology
      • less N/V than other populations
      • more co-morbidities
        • may have dementia or communication issues that serve as barriers to pain management
      • decreased physiologic reserves
    2. pharmacodynamics
    3. kinetics 
    4. processing of pain information
      • increased pain threshold
      • decreased pain tolerance
      • decreased pain perception
  2. Titrate drugs slowly
  3. Regional may be a better option
    • preserves cognitive function
    • earlier ambulation
    • return of GI function, etc.


Considerations for opioid-tolerant patients

(not addicted, just tolerant)

  1. Higher doses to relieve pain
  2. They are often worried about risk of addiction or medication-related SE
  3. Goals
    1. Provide their baseline opioid requirement (maybe some SR meds)
    2. Anticipate that they will need higher doses than normal post-op
    3. Maximize the use of adjunct drugs and techniques (consider regional anesthesia)


Considerations for pediatric patients

  • Myth - Kids don't experience pain the same as an adult or won't remember it. Because of this myth, there are issues with pain being undertreated.
  • Assessing the level of a child's pain can be difficult.
  • RA and PCAs are encouraged.
  • Avoid IM (duh, why would you do this?)
  • Preferred routes are IV, PO, and rectal.


Considerations for obesity and OSA patients

  • High risk for pulmonary complications and respiratory arrest
  • Goals
    • Avoid resp depressants
    • Consider epidurals w/o opioids
    • NSAIDs
    • Will probably need CPAP post-op


TCAs for chronic pain

  • Elevates mood and helps with sleep
  • Use smaller doses than used for depression
  • Blocks the reuptake of serotonin and NE
  • Potentiates opioids
  • Use smaller doses than indicated for depression
  • NEED to monitor drug levels
  • Has anticholinergic SE
    • dry mouth
    • sedation
    • fatigue
    • hypotension
    • arrhythmias


Anticonvulsants for chronic pain

  • Alters ion channels along the nerve fiber, blocking pain transmission
  • Treats neuropathic pain from lesions of the peripheral NS (herpes, DM, etc) or CNS (stroke)
  • Drugs used:

    • Carbamazepine (Tegratol)

    • Phenytoin (Dilantin)

    • Gabapentin (Neurontin)

    • Clonazepam (Klonipin)

  • SE

    • Sedation

    • dizziness

    • ataxia.


Corticosteroids for chronic pain

  • Reduces inflammatory mediators
    • prevents the release of prostaglandins and stimulate appetite
  • Dexamethasone - most commpnly used for pain


Chronic pain adjuvants

  1. Muscle relaxants
    • Baclofen, flexeril, etc.
    • Reduces muscle spasms
  2. NMDA receptor antagonists
    • Ketamine and dextromethorphan
  3. A2 Agonists
    • Clonidine & Dexmedetomidine
    • work pre and post-synaptically in the dorsal horn to inhibit neuron firing
    • Precedex also works by inhibiting substance P release*
  4. GABA receptor agonists
    • Baclofen
    • Inhibitory NT that works in the cord - prevents release of excitatory NT
  5. LAs
    • PO mexiletine and tocainide
    • high 1st pass effects - are not as effective


Nerve Blocks for Chronic Pain

  1. Myofascial pain
    • Treat with trigger point injections
    • Use LA of botulinum toxin
    • TENS
  2. Lower back pain
    • Epidural steroid injections
      • Reduces swelling at the nerve root and stabilizes nerve membranes
  3. Sympathetic Nerve Blocks
  4. Somatic Nerve Blocks
    • Normal PNB blocks we think of but more localized to the source of pain


What is a Neurolytic Block for Chronic Pain?

Permanent destruction of the nerve causing chronic pain using alcohol and phenol.


What are the most common neurolytic blocks?

  1. Lumbar sympathetic chain
  2. Celiac plexus
  3. Hypogastric plexus
  4. Ganglion impar
  5. Intercostal blocks


Spinal Cord Stimulation for Chronic Pain

  • Stimulating electrodes are placed in the epidural space around the entry level of noxious stimuli into the spinal cord
  • This activates the descending modulatory system and inhibits sympathetic outflow
    • electric current that drown out the pathway
  • Treats phantom limb pain, PVD, and spinal cord lesions.



Transcutaneous electrical nerve stimulation

  1. Hyperstimulation of the nervous system - drowns out the pain signals
  2. Good for:
    • myofascial pain
    • peripheral nerve injuries
    • phantom limb pain
    • stump pain


Radiofrequency Ablation (RFA)

Dysfunctional tissue is ablated using heat (microwaves)

Nerves can also be ablated with cold (cryoneurolysis)


___-___% of cancer pain can be treated well with pharmacotherapy alone.

However, ___-___% of patients with cancer pain do not receive enough pain control.




Why is cancer pain often inadequate?

  1. Poor pain assessment and treatment plans
    • ​r/t so many ppl involved in their care
  2. Lack of knowledge about available analgesics
  3. Fear of addiction
  4. Fear of respiratory depression
    • CA patients & prescribers fear that it will hasten their demise


Ladder of cancer pain

  1. Step One (mild pain)
    • Non-opioid analgesics
    • ASA, tylenol, NSAIDs
  2. Step 2 Mild (Moderate Pain)
    • Weak oral opioids
    • Codeine, oxycodone, hydrocodone
  3. Step 3 (Moderate-Severe Pain)
    • Potent IV opioids
    • Morphine - Hydromorphone (Dilaudid) - Fentanyl
  4. Step 4 (Intractable Pain)
    • Invasive therapy
    • Regional blocks - Neurolytic blocks


Chronic Pain Continuum

  1. Diagnosis
  2. Level 1 Therapies
    • Cognitive & Behavioral modification
    • Over the Counter meds
    • NSAIDs
    • TENS
    • Rehab
    • Exercise
  3. Level 2 Therapies
    1. Systemic opioids
    2. Nerve blocks and neyrolysis
    3. Thermal procedures
  4. Level 3 Therapies
    1. Surgery
    2. Neuroablation
    3. Implantable drug pumps (onQ)
    4. Spinal cord stimulation


Organization that developed clinical practice guidelines and pain management standards


Joint Commission on Accreditation of Healthcare Organizations


Organization that developed national practice guidelines for management of acute pain


Agency for Healthcare Research and Quality


Organization that defined pain


World Health Organization


Organization that develops pain management standards


American Pain Society



  1. syndrome of sustained
    • burning pain
    • allodynia, and
    • hyperpathia
    • after a traumatic nerve lesion
  2. often combined with vasomotor and motor dysfunction
  3. later can lead to trophic changes.




Increased sensitivity to stimulation, excluding the special senses



Increased pain from a stimulus that normally provokes pain



Pain in the distribution of a nerve or nerves


Preemptive Analgesia

What is it? What are the benefits?


  1. Pain management before pain occurs
  2. Blockade of noxious stimuli response with the extension of this blockade into the postoperative period
    • takes the whole peri-operative period in consideration


  1. Reduces postoperative pain
  2. Accelerates recovery
  3. Attenuates (stops) peripheral and central sensitization and hyperexcitability to pain  
    • therefore, stops the development of chronic pain


Pain - Multimodal Approach

What is it? Why do it? How to do it? Issues?


  • An extension of “clinical pathways”  into effective postoperative rehabilitation pathways


  1. to control postoperative pain
  2. to attenuate the perioperative stress response


  • through the use of
    • regional anesthetic techniques and a combination of analgesic agents (multimodal analgesia)


  • more complex
  • can have synergistic effects



What are they (in relationship to pain management)?

how they work



  • Gold standard in pain management
  • Exert their analgesic effect through mu and kappa opioid-receptors in the CNS
  • No analgesic ceiling
  • Disadvantages
    • side effects
      • esp. respiratory depression
      • hypotension
      • nausea/ vomiting
      • sedation
      • pruritus
      • urinary retention
    • variability
    • tolerance


sxs of intra-op pain

  • increased HR
  • increased BP
  • fast & shallow breathing
  • pupil dilation
  • sweating

think SNS activation



What is it

Most common drugs used


Pain management option with 

  • Reservoir and Infusion controller
  • Button pushed by patient
    • Demand (bolus)
    • Lockout interval
    • Continuous background
    •  infusion

Most Common used drugs:

  • Morphine Sulfate
  • Hydromorphone


  • Cost-effective
  • Higher degree of patient satisfaction
  • Total drug consumption is less
  • Harder to over medicate self
  • Prevents the “pain/ no pain” cycle


Continuous Epidural Analgesia Benefits

  1. Superior analgesia to systemic drugs
  2. Faster patient recovery
  3. Attenuates stress response to surgery
  4. Lessens pulmonary complications


Cancer Pain Management Adjuncts

  1. `Corticosteroids
    • Prevent release of prostaglandins and stimulate appetite
  2. Non-invasive analgesics
    • psychotherapy, guided-imagery, hypnosis, PT
  3. Antidepressants
    • Elevate mood, help with sleep, block reuptake of serotonin, potentiate opioid analgesics
  4. ​Regional analgesia
    • Disadvantage—short term relief
  5. Neurolytic blocks
    • Disadvantage—motor loss
  6. Hospice