Flashcards in Pain Management Deck (71):
What is pain?
An unpleasant sensory and emotional experience associated with actual or potential tissue damage
Why is having pain an issue in our patients?
1) It's often under-treated
2) Uncontrolled pain produces SE that we don't want
3) The treatment of pain has unwanted SE
4) Many patients and providers have misconceptions about the treatment of pain
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.
Acute pain is almost always ____ in nature and results in _____.
neuroendocrine response (stress response with HPA and SNS activation)
Endocrine and CV response to pain
Increased aldosterone and ADH, renin, and angiotensin II
Immune system suppression
Increased HR, BP, SVR, CO, contractility
Enhanced myocardial irritability
Vasoconstriction, including coronary artery constriction
Increased myocardial O2 consumption with decreased myocardial O2 supply (ischemia)
Increased plasma viscosity
Increased water retention
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
- Natural anticoagulants decrease and 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
- 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
- Hypersecretion of gastric acid
- Slowed GI motility (risk of aspiration and paralytic ileus)
- Urinary retention
Neurendocrine Response to Pain
Basically reacting as if the body is in stress:
Increased catabolic hormones
Decreased anabolic hormones
Increased ADH, Aldosterone, renin, and angiotensin II
Sodium and water retention
Increase blood glucose
Free fatty acids
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.
This may be a predictor of transition to chronic pain
Poorly controlled acute pain.
Intensity of acute pain is significant predictor of chronic pain.
Chronic Pain may occur after these procedures
Limb amputations (30-83%)
Chronic pain is associated with an imbalance in _____
- 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
Continuous release of inflammatory mediators in the periphery sensitizes functional nociceptors and activates dormant nociceptors
There is sensitization of nociceptors and hyper excitability.
Functional changes occur in the dorsal horn of the spinal cord (neuroplasicity) .
Dormant nociceptors are activated.
Recruitment of additional nerve fibers and pathway tracts. Pain is perceived as more painful.
Reflexes can create excessive muscle tension, with actual disruption of microcirculation
Causes of cancer pain
#1 - tumor invasion of the bone
#2- tumor compression of peripheral nerves
Treatments of cancer (chemo and radiation) can also result in cancer pain (tissue destruction)
Physical and psych components of cancer pain
Physical—worse due to loss of sleep, appetite, nausea & vomiting
Psychological—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
Every treatment plan for pain must be directed at
controlling the pain and the underlying pain process
Benefits of adequate post-op pain control
Reduction of the stress response
Shorter times to extubation, shorter ICU stay
Improved respiratory function
Earlier return of bowel function
Early mobilization, decreased risk DVTs
Reduction in sensitization, neuroplasticity, wind-up phenomenon, and transition to chronic pain
Earlier enteral nutritional intake
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 ___%
SE of NSAIDs
-Inhibition of thyromboxane A2
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
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)
Catheters can be placed in these PNB locations
What provides better analgesia? Regional blocks or systemic opioids?
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 complications d/t bleeding (ex- from NSAIDs)
Hydrophilic Opioids used in Neuraxial Blocks
Morphine and Dilaudid
Tend to stay in the CSF
Extensive CNS spread
Delayed onset of action (unable to penetrate the neuron)
Longer DOA (not taken up by fat quickly)
High incidence of SE (d/t cephalad spread of the opioid)
Lipophilic Opioids used in Neuraxial Blocks
Fentanyl and Sufentanil
Rapid onset and short DOA (systemic uptake)
Minimal spread and fewer SE
(Minimal spread is s/t segmental analgesic effect)
These opioids may be given in neuraxial blocks
Benefits of an epidural catheter
1) Superior analgesia compared to systemic opioids
2) Faster pt recovery
3) Attenuates the stress response to surgery (sympathectomy)
4) Fewer pulmonary complications
Can epidurals be connected to a PCA?
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
- Avoids motos block
- Less hypotension
- Has other SE though, like respiratory depression and pruritis
3) LA + Opioid
- Better choice
- Limits regression of sensory block
- Decreases the total dose of LA needed (avoids toxicity)
- Able to give low concentration of LA and low dose of opioid. Work synergistically by working on two separate MOAs.
- Lower LA concentration prevents motor block and allows for earlier ambulation
- Good choice for thoracic, abdominal, pelvic, and orthopedic lower extremity procedures
Adjuvant neuraxial drugs
- A2 agonist
- Prolongs duration of block
- SE: Hypotension, bradycardia, sedation
2) Epi and phenylephrine
- Prolongs duration of block
- Increases intensity of block
Where to place an epidural catheter
Location congruent to the incisional dermatome
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
Basically opioid SE + sympathectomy and possible motor blockade
Risks of epidural block
IV, subarachnoid, or subcutaneous injection
Non-pharmacologic adjuncts to pain management
Phych approaches (hypnosis, imagery, distraction, music, etc)
Surgical (local infiltration, intra-articular analgesia, pain pumps like onQ)
Considerations for ambulatory patients
Severe post-op pain will prolong hospital stay
Common to have pain after discharge
N/V common may interfere with ability to take PO analgesics
Best to do a multimodal approach to pain management (opioid, non-opioid, LA, ice, etc)
Considerations for elderly patients
Old people have lots of changes: in their physiology, pharmacodynamics, kinetics, and processing of pain information. Titrate drugs slowly.
The have an increased pain threshold.
Less N/V than other populations.
They have more co-morbidities and decreased physiologic reserves.
May have dementia or communication issues that serve as barriers to pain management.
Regional may be a better option for these patients --> preserves cognitive function, earlier ambulation, return of GI function, etc.
Considerations for opioid-tolerant patients (not addicted, just tolerant)
They need higher doses to relieve pain!
They are often worried about risk of addiction or medication-related SE.
- Provide their baseline opioid requirement (maybe some SR meds)
- Anticipate that they will need higher doses than normal post-op
- 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**
- Avoid resp depressants
- Consider epidurals w/o opioids
- 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
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)
Anticonvulsants used for chronic pain and their SE
SE: Sedation, dizziness, and ataxia.
Corticosteroids for chronic pain
Reduces inflammatory mediators (prevents the release of prostaglandins)
Chronic pain adjuvants
1) Muscle relaxants
- Baclofen, flexeril, etc.
- Reduces muscle spasms
2) NMDA receptor antagonists
- Ketamine and dextromethorphan
3) A2 Agonists
- these 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
- Inhibitory NT that works in the cord
- PO mexiletine and tocainide
Nerve Blocks for Chronic Pain
1) Myofascial pain
- Treat with trigger point injections
- Use LA of botulinum toxin
2) Lower back pain
- Epidural steroid injections
- Reduces swelling at the nerve root and stabilizes nerve membranes
3) Sympathetic Nerve Blocks
- Stellate block
- Sympathetic chain block
- Splanchnic block
- Lumbar sympathetic block
- Hypogastric plexus block
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?
Lumbar sympathetic chain
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.
Treats phantom limb pain, PVD, and spinal cord lesions.
Transcutaneous electrical nerve stimulation
Hyperstimulation of the nervous system drowns out the pain signals
Good for myofascial pain, peripheral nerve injuries, phantom limb pain, and 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?
Poor pain assessment and treatment plans.
Lack of knowledge about available analgesics.
Fear of addiction.
Fear of respiratory depression (CA patients fear that it will hasten their demise)
Ladder of cancer pain
Step One (mild pain)
- Non-opioid analgesics
- ASA, tylenol, NSAIDs
Step 2 Mild (Moderate Pain)
- Weak oral opioids
- Codeine, oxycodone, hydrocodone
Step 3 (Moderate-Severe Pain)
- Potent IV opioids
- Hydromorphone (Dilaudid)
Step 4 (Intractable Pain)
- Invasive therapy
- Regional blocks
- Neurolytic blocks