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How does the peripheral pathophys of pain work? What are the 2 peipheral fibres?

-Painful stimulus causes cell damage
-Damage received by nociceptors, turning noxious stimuli into impulses and transmit along peripheral nerve fibres (A delta fibers or C fibres)

-A DELTA --> Thermal or mechanical cellular changes transmit pain quickly through densely myelinated fibres. Result in "prickling" or "sharp" pain

-C FIBRES --> Less myelinated, transmit chemical changes in cellular environment. Associated with "dull", "aching", or "diffuse" pain


How does central pathophys of pain work?

Neurotransmitters (Substance P) carry impulses across synapse from PNS to the central nervous system.

-Impulse enters dorsal horn of spinal cord and travels along spinothalamic tract
-Pain interpreted at the CEREBRAL CORTEX
-Body produces endorphins to reduce the pain, produced in the brainstem and travel down the spinal cord and block the transmission of pain


What do synthetic opioid analgesics mimic?

Mimic action of natural endorphins produced at the brainstem and travel down the spinal cord binding to nerve receptor sits to block pain transmission


What is the pain assessment hierarchy?

1) Self report (NRS, non-verbal communications)
2) Behavioural pain assessment tool
3) Minimize emphasis of physiological indicators of pain


What are valid physiological indicators of pain?


Changes may arise from multiple causes associated with catecholamine release, difficult to isolate to pain. They can be used as a CUE to begin pain assessment


How is morphine used for pain management?

For acute pain, mod-severe

Dose: 2-4mg IVP
Onset: 5 min
Duration: 4-5 hrs

For hemodynamically stable pts, causes histamine release that can cause hypotension (especially with hypovolemia). Can cause resp. depression


How is hydromorphone used for pain management?

For acute pain, mod-severe

Dose: 0.2-1mg IVP
Onset: 5 mins
Duration: 3-4 hrs

Less side effects than morphine (pruritus, sedation, N/V), approx 10 times stronger than morphine


How is fentanyl used for pain management?

For acute pain, mod-severe

Dose: 25-100mcg IVP (MCG)
Onset: 1-2min
Duration: 30-60 min

For hemodynamically unstable pts, procedural analgesic, renal impairment, no histamine release, more rapid onset than morphine but drug accumulation in liver.


What are 2 routes opiates can be administered in ICU?

1) Intravenous
2) Epidural

-Push, continuous infusion, patient controlled analgesic


When is epidural opiate route recommended?

For pts with abdominal aortic surgery and traumatic rib fractures


What is sedation?

State where pt is calm, relaxed, and relatively pain free. Used in management of anxiety, agitation, and short turn procedural intervention


What is agitation?

Excessive, usually non purposeful motor activity associated with muscle tone and catecholamine release


What is anxiety?

Prolonged state of apprehension in response to real or perceived fear


How can sedation be assessed?

Riker Sedation Agitation Scale (SAS)
EEG or Bispectral Index (BIS) record brain wave activity illustrating sedation


How is midazolam / versed used for sedation?

Acute rapid sedation, short term / immediate use

Onset: Short half life, shortest acting benzo
Metabolism: Liver, metabolite causes hypotension

-If used as continuous infusion, short acting benefits are lost and drug accumulates in fatty tissue. Tolerance can develop and risk of delirium


How is propofol used for sedation?

Useful for neuro pts requiring waking for assessment, post op, short term, or long term use, management of increased ICP

Onset: Short acting, rapid onset
Metabolism: Liver (rapidly metabolized)

-Does not have analgesic properties, monitor triglyceride levels after 2 days of use, associated with hypotension


Why must we balance sedation?

Prolonged sedation = delayed weaning
Inadequate sedation = anxiety, agitation


How do we avoid over-sedation?

1) Daily sedation interruption
2) Light sedation


What are symptoms of sedation withdrawal?

-Increased HR, BP, RR
-Irritability, anxiety, delirium
-Confusion, short term memory issues


How are Alpha 2 agonists used?

Can be used as a sedative as they inhibit effects of norepinephrine. Traditionally used as anti-hypertensive but also has sedative and anxiolytic properties.

-Used to wean off sedatives and opioids, or in withdrawal syndrome

-Clonidine, dexmedetomidine are examples


Why is it important to manage delirium?

-Increased length of ICU stay, hospital stay
-Increased mortality
-Long term cognitive impairment


What is delirium?

Syndrome characterized by acute onset of cerebral dysfunction associated with:

1) Disturbed LOC
2) Change in cognition


What are the 3 subtypes of delirium?

1) Hypoactive (Lethargy, decreased LOC)
2) Hyperactive (Agitation, restlessness)
3) Mixed (fluctuation)


What is the pathophys of delirium?

Unknown, but possibly imbalance of neurotransmitters such as serotonin, acetylcholine, or dopamine


What are risk factors for delirium?

-Pre-existing dementia
-High severity of illness
-Benzo use
-Sleep deprivation


What are the most valid pain scales in ICU?



What is the recommendation for first line analgesic therapy?

IV opioids. Use non-opioid analgesics to reduce opioid side effects. Use gabapentin or carbamazepine in conjunction to IV opioids for neuropathic pain.


Should procedural pain be pre-treated?

Yes, pre-treat procedural pain


What are the most valid scales for assessing sedation?

RASS and SAS, suggest using brain function monitors for pts on NMBA


What are the most valid delirium scales?