L12: Acute Pain Management (Granone) Flashcards
5 processes that make up nociception and pain***
1) transduction
2) transmission
3) modulation
4) projection
5) perception
Nociception
Detection of potential or actual damaging stimuli and transmission of info to the brain
5 processes: transduction, transmission, modulation, projection, perception***
Nociception vs. pain
Nociceptors (n. Cell endings) initiate the sensation of pain, transduce electrical signals at site of tissue disruption.
Fx of spinal cord dorsal horn
- receives electrical signals from primary sensory n. Fibers (alpha-beta, alpha-delta, C fibers)
- signals modulated then sent to brain
Fx of brain in processing pain
- receives signals, then initiates physiologic and behavioral responses
- thalamus and somatosensory cortex discriminates pain signals and recognizes, learns, and remembers pain
Mechanism of inflammatory mediators and pain amplification
- depolarization of nerve endings
- dec. depolarization threshold of 1ary afferent nerves
- vasodilation, inc. vessel permeability –> inc. inflammatory mediators at injury site
Types of pain
1) somatic pain (MS pain)
2) visceral pain
- poorly localized
- mechanical stimuli ie. Stretched viscera
- ischemia
- chemical/thermal stimuli
- change in somatic m. Tone, autonomic responses
- usually referred
Adaptive pain = acute pain
Maladaptive pain = chronic pain
:)
Adaptive pain includes inflammatory pain
Objective pain assessment includes:
Physiologic variables (HR, RR, BP, rectal temp)
Plasma cortisol, catetcholamine, and beta-endorphin concs.
all are non-specific
Therapeutic Pain management ideals
1) Preemptive analgesia (analgesia BEFORE noxious stimuli)
2) Multimodal analgesia (uses >1 modality to obtain additive or synergistic effects)
NSAIDs properties
- weak analgesics
- effective anti-inflammatory
- anti-pyretic/endotoxemic/neoplastic
- inhibit COX-1 and COX-2 enzymes impairing prostaglandin synthesis –> analgesia
Subjective measures of pain
Numerical rating scales Simple descriptive scales Visual analog scale (100cm line) University of Melbourne pain scale (assess behavioral and physiological indices after surgery in dogs) CSU pain scale
Opioids provide analgesia without loss of:
Touch, proprioception, consciousness
Where do opioids act? Where metabolized/excreted?
Act on CNS, periphery, and locally
-activate afferent receptors in periphery
Hepatic metabolism (except rimifentanyl)
Biliary and renal excretion
Inflammation increases/decreases expression and synthesis of opioid receptors?
Increases
Buprenorphine = partial mu agonist
Torbugesic = kappa agonist and mu opioid antagonist
:)
Partial and full opioid reversals
Partial: torb
Full: meloxone
binding of mu opioid receptors –>
- Spinal and supraspinal analgesia
- sedation, resp. Depression, bradycardia, depression, drug dependence
Kappa opioid receptors vs. mu
Kappa provide spinal analgesia but with less sedation, resp. Depression, and bradycardia
not as useful in severe pain states
G-protein coupled receptors inhibit which NT release?
Ach, dopamine, NE, substance P, GABA
Epidural opioid effect on motor and SNS fx
Unaltered
-CAN cause urinary retention, resp. Depression, pruritis
Opioid side effects
Sedation/CNS depression (dogs)
Excite/dysphoria (cats) Bradycardia (due to vagal stim.) Resp. Depress Panting (resets thermoreg. Center) HA release (IV morphine, meperidine) Urinary retention Cough or laryngeal reflex Vomiting and defecation Constipation
Local anesthetics can sensitize PNS; they decrease transmission and transduction from occurring by blocking Na channels
:)
Factors affecting anesthetic activity
-dose
-site of injection
+/- vasoconstrictors
-mixing of LAs
-physiologic state of patient
-volume, conc.
