Acute Postoperative Pain Management Flashcards
definition of pain
an unpleasant sensory and emotional experience associated with actual or potential tissue damage; the 5th vital sign (acc to joint comission)
JCAHO Identified Responsibilities of Pain Management
- patient has right to appropriate assessment and management of pain
- assess existence of pain, its nature, and intensity
- record assessment in a way that facilitates reassessment/follow-up
- assure staff competency in pain assessment and management
- establish policies that support appropriate prescription of pain medications
- educate patient/family about pain management
- address patient needs for symptom management and discharge
nociception
detection, transduction and transmission of noxious stimuli
acute pain
- primarily due to nociception
- short duration (<6 weeks)
- cause usually known
- temporary
- located in area of trauma or damage
- resolve spontaneously with healing
chronic pain
- may be due to nociception but also affected by psychological/behavioral factors
- persists beyond normal duration of recovery from acute injury or disease
- cause may not be identifiable
- affects patient self image and sense of well-being
thoracotomy incidence of chronic pain
5-65%
sternotomy incidence of chronic pain
30-55%
mastectomy incidence of chronic pain
20-50%
hysterectomy incidence of chronic pain
32%
inguinal hernia repair incidence of chronic pain
5-35%
four classifications of pain pathophysiology
- nociceptive
- neuropathic
- idiopathic
- psychogenic
nociceptive pain
- appropriate response to identifiable tissue damage
- due to activation or sensitization of peripheral nociceptors that transduce noxious stimuli
- pain consistent with degree of tissue injury
neuropathic pain
- may be abnormal, unfamiliar pain, probably caused by dysfunction in the PNS or CNS
- result of injury or acquired abnormalities of peripheral or central neural structures
idiopathic pain
- pain not attributed to identifiable processes
- pain in absence of identifiable physical or psychological cause
- pain perceived to be excessive for the extent of pathology
psychogenic pain
- pain sustained by psychological factors
- more precisely characterized in psychiatric terminology
- patients have an effective and behavioral disturbance
4 processes of nociceptive pain
- transduction
- transmission
- modulation
- perception
transduction
stimuli translated into electrical energy at the site
transmission
propagation of electrical pain impulse through the nervous system
modulation
alteration of the stimuli that can be amplified or attenuated
perception
based on psychological framework of patient
two subtypes of nociceptive pain
- somatic
- visceral
superficial somatic pain
-arises from skin, subQ tissues, and mucous membranes -characterized as well-localized, sharp, pricking, throbbing, or burning
deep somatic pain
- arises from muscles, tendons, joints, or bones
- dull aching that is less well-localized
visceral pain
- due to disease process (appendicitis or pancreatitis) or abnormal function of an internal organ
- may be localized or referred
two subtypes of neuropathic pain
- central generator
- peripheral generator
central generator
central pain due to injury to brain or spinal cord; phantom pain
peripheral generator
originates in nerve root, plexus, or nerve; poly-neuropathies or mono-neuropaties
allodynia
perception of an ordinarily non-noxious stimulus as pain
analgesia
absence of pain perception
anesthesia
absence of all sensation
hyperalgesia
exaggerated response to noxious stimuli
neuralgia
pain in nerve distribution
paresthesia
abnormal sensation perceived without stimulus
radiculopathy
functional abnormality of one or more nerve roots
how are peripheral nerve afferent fibers categorized
- size
- degree of myelination
- speed of conduction
- distribution of fibers
three groups of peripheral nerve afferent fibers
- Class A (subtypes alpha, beta, delta, gamma)
- Class B
- Class C
Class A Fibers
- large, myelinated fibers
- low threshold for activation
- 1-20 micrometers in diameter
Class A delta
- mediates pain sensation
- transmits fast or first pain sensation
- sharp, stinging, pricking type pain
- conduction speed of 5-25 m/s
Class A alpha
- transmits motor and proprioceptive impulses
- conduction speed of 60-120 m/s
Class A beta
- cutaneous touch and pressure
- conduction speed of 60-120 m/s
Class A gamma
- cutaneous touch and pressure
- conduction speed of 15-35 m/s
Class B Fibers
- medium-sized myelinated fibers
- conduction speed 3-14 m/s
- diameter less than 3 micrometers
- higher threshold (i.e., lower excitability) than Class A fibers
- lower threshold than class C
- postganglionic sympathetic and visceral afferents
Class C Fibers
- unmyelinated or thinly myelinated
- conduction speed 0.5-2 m/s
- diameter 0.4-1.2 micrometers
- preganglionic autonomic fibers and pain fibers
- slow or second pain
- burning, persistent, aching, throbbing pain
pain conducting fibers
- A-delta fibers
- C fibers
A delta fiber pain pathway
- myelinated
- diameter 1-4 micrometers
- first or fast pain
- well localized - sharp, stinging, pricking
- duration of pain coincides with painful stimulus
- pain from parietal peritoneum carried here
- major NT glutamate binds to NMDA and AMPA receptors on postsynaptic membrane
C fiber pain pathway
- un-myelinated
- diameter 0.4-1.2 micrometers
- second or slow pain
- diffuse and persistent - aching, burning, throbbing
- duration exceeds stimulus
- pain from viscera carried here
- major NT substance P binds to NK-1 receptors on the postsynaptic membrane
pain pathway
- Release of NT/hormones into the blood from the destroyed cell and diffuse to primary afferent neuron (Histamine, Serotonin, Substance P, CGRP)
- Activate the primary afferent neuron by influx of Na into the cell
- AP propagated from the site of damage, through the DRG
- Primary afferent neuron synapses on the interneuron or secondary neuron in the (laminae 1, 2, 5)
- Secondary afferent neuron decussates to the spinothalamic tract on the dorsal (or posterior) portion of the spinal cord
- Secondary neuron traverses up the spinothalamic tract to the thalamus of the brain
- In the thalamus, secondary neuron synapses on tertiary neuron
- Tertiary neuron brings the afferent information to the somatosensory cortex in the brain
substances released from damaged cells that activate pain pathway
- bradykinin
- cations
- free radicals
- histamine
- prostanoids
- purines
- serotonin
- tachykinins
where is pain modulated?
descending dorsolateral spinal tract
supraspinal analgesia
- refers to the fact that IV opioids act primarily at other sites in the brain including the limbic system, hypothalamus, and thalamus
- mediated by Mu1 receptors
spinal analgesia
- refers to the fact that IV opioids can also produce effects by working in the periventricular area and periaquaductal gray
- stimulation of Mu2 receptors
spinal anesthesia
- neuraxial opioids work at the same receptor site as enkephalin
- MOA = decrease the release of substance P by binding to Mu2 receptors
CV effects of surgical stress response
- HTN
- tachycardia
- enhanced myocardial irritability
- increased SVR (ANG II)
- CO increase except in patient with compromised LV function
- increased MVO2 –> ischemia
respiratory effects of surgical stress response
- increased in O2 consumption + CO2 production causes increased minute ventilation
- increased WOB
- pain may decrease chest expansion (splinting), resultant atelectasis, shunting, hypoxemia, and hypoventilation
- increase in skeletal muscle tension that results from pain may lead to V/Q mismatch
endocrine effects of surgical stress response
- hyperglycemia secondary to increased glucagon + epi and decreased insulin
- vasoconstriction, increased myocardial contractility, and tachycardia secondary to increased cortisol + catecholamines and activation of RAAS
- salt and water retention due to increased aldosterone and ADH, may lead to CHF
GI effects of surgical stress response
- increased sphincter tone with decreased smooth muscle tone may lead to formation of ileus and lead to PONV
- decreased oral intake associated with septic complications and delayed wound healing
- hypersecretion of gastric acid promotes ulcers
- abdominal distention further aggravates loss of lung volume and pulmonary dysfunction
immunological effects of surgical stress response
stress response produces leukocytosis with lymphopenia and depresses the reticuloendothelial system predisposing patients to infection
hematological effects of surgical stress response
increased platelet adhesiveness and diminished fibrinolysis promote a hypercoagulable state; immobility exacerbates this problem
general anesthesia influence on surgical stress response
not effective in attenuating the response except with high dose narcotic techniques
regional anesthesia influence on surgical stress response
- diminishes intensity of afferent impulses getting to spinal cord
- reduces catecholamine and other stress hormone responses during perioperative period
pain assessment
- history of current and persistent pain
- physical exam
- pain attributes (intensity, onset, duration, location, descriptors, what exacerbates or relieves pain)
- behavioral manifestations
- impact of pain on ADLs
- current and past treatments
- are patient’s expectations for pain relief realistic?
postoperative pain intensity
- orthopedic/trauma on extremities rated highest
- also rated among top 25 - appendectomy, cholecystectomy, hemorrhoidectomy, tonsillectomy
- some laparoscopic procedures ranked unexpectedly high
traditional approach to pain mangement
- opioids = mainstay for postoperative analgesia; may be given IV, PO, IM, SubQ, PCA, or neuraxial
- safe and effective pain control used in treating moderate to severe pain
- should be administered via most effective route and limiting S/E
side effects of opioids
- N/V
- constipation
- lethargy
- sedation
- respiratory depression
Minimum effective analgesic concentration
analgesic blood level at which the patient experiences analgesia and the severity of pain rapidly diminishes
opioid induced hyperalgesia
- patients receiving opioids exhibit diminished pain threshold and enhanced pain sensitivity
- escalating opioids worsens pain perception
- not same thing as tolerance, but the two can happen simultaneously
mechanism of opioid induced hyperalgesia
- enhanced release of NT
- sensitization of primary and secondary afferents
- upregulation of spinal and supraspinal pathways
- critical component = activation of excitatory NMDA receptor and central glutamatergic system
- demonstrated in patients receiving high-dose intraoperative opioids like fentanyl and remifentanil
preemptive analgesia
- pain perception can be decrease by using analgesics capable of inhibiting CNS sensitization before pain stimulus occurs
- drug options = NSAIDs, opioids, LAs, NMDA antagonists, alpha-2 agonists
- still uncertain/debated
multi-modal approach to pain management
- may include more than 1 route of admin
- use of different agents allows decreased doses of each, thus reduced side effects
- synergistic effects between drug classes enhances analgesic effects of each drug
- effective in patients at risk of S/E from large doses of opioids
central acting non-opioid analgesics
- clonidine
- dexmedetomidine
- gabapentin
- pregablin
- ketamine
- lidocaine
- magnesium
spinal acting non-opioid analgesics
- clonidine
- dexmedetomidine
- gabapentin
- ketamine
- lidocaine
- magnesium
peripheral acting non-opioid analgesics
- clonidine
- dexmedetomidine
- dexamethasone
- ketamine
- lidocaine
NSAIDs
- effective with mild to moderate pain
- adverse effects = GI bleeding, ARF, hepatotoxicity
- avoid in patients with hypersensitivity, significant renal compromise, and PUD
- use with caution in elderly due to increased risk for renal impairment
ketamine
- NMDA receptor antagonist
- 0.5 mg/kg bolus followed by infusion at 4 mcg/kg/min
- shown to reduce morphine consumption and pain intensity up to 6 weeks following spine surgery
methadone
- D-isomer NMDA receptor antagonist
- 0.2 mg/kg
- shown to have a 50% reduction in post-op opioid consumption and pain scores 48 hours after complex spine surgery
anticonvulsants
- gabapentin, pregabalin
- manage spontaneous firing of sensory neurons associated with neuropathic pain (attenuate neuronal sensitization response)
- reduced incidence of chronic post-op pain syndrome
- decrease opioid consumption and neuropathic pain 3-6 months following total knee replacement
dexmedetomidine
- alpha 2-agonist
- reduced morphine consumption 2-14 hours post-op; also decreased PONV (most likely to reduced morphine consumption)
- significantly reduces opioid consumption in obese
- increased risk of hypotension and bradycardia
clonidine
- reduced morphine consumption 12-24 hours post-op; also decreased PONV (most likely to reduced morphine consumption)
- increased risk of hypotension and bradycardia
acetaminophen
- preemptive 15 mg/kg
- MOA unknown
Magnesium
- N-methyl-D-aspartate (NMDA) receptor antagonist
- 2 g
glucocorticoids
- potent anti-inflammatory agents that play a role in reducing post-op pain
- also works to manage PONV
infiltration of LAs
- may be done by surgeon at beginning or end of case
- ilioinguinal and femoral nerve blocks may be placed by anesthetist
regional anesthesia
- preferred to provide postop pain control to a specific part of the body
- have peripheral and central nerve blocks
regional anesthesia advantages
- eliminating need for IV pain medications
- earlier discharge of ambulatory patients
regional anesthesia disadvantages
- block failure
- bleeding
- hematoma
- neurological injury
peripheral nerve blocks
- lumbar plexus
- interscalene
central neuraxial blocks
- spinal
- epidural
neuraxial opioids side effects
- itching (most common)
- nausea
- urinary retention
- respiratory depression (early + Late
- sedation
- CNS excitation
- neonatal morbidity
respiratory depression with hydrophilic neuraxial opioids
- onset of analgesia slow, duration prolonged
- intrathecal placement = late respiratory depression (6-12 hours) due to rostral spread; early resp depression does not occur because uptake by systemic circulation is minimal
- epidural placement = early respiratory depression (within 2 hours) since systemic uptake is greater than with intrathecal placement; late resp depression more likely due to rostral spread in CSF
respiratory depression with lipophilic neuraxial opioids
- onset of analgesia is rapid with short duration
- early resp depression occurs due to significant systemic uptake with both intrathecal and epidural placement; resp depression most pronounced after epidural placement
- late resp depression does NOT occur because diffusion of lipophilic opioids out of CSF is substantial, therefore rostral spread is minimal
alternative approaches
- distraction
- hyponosis
- transcutaneous electrical nerve stimulation (TENS)
- cold
- heat
- immobilization
- positioning
- exercise
distraction
- useful as adjunct
- music or imagery
- max benefit if introduced preoperatively
- requires patient cooperation
hypnosis
- state of focused attention combined with decrease in external awareness
- may not work on all patients
- social stigma
- conflicting data on efficacy
TENS
- thought to produce analgesia by stimulating large afferent fibers
- gate theory of pain suggests that the afferent input from large fibers competes with that from smaller pain fibers
- electrodes applied to same dermatome as pain
- absence of significant S/E
- requires professional to instruct in use
cold
- alters pain threshold, reduces swelling, and decreases tissue metabolism
- easy to use
- contraindicated in patients with decreased circulatory state like Raynaud’s
heat
- decreases joint stiffness and increases blood flow
- easy to use
immobilization
-assists in healing process; i.e. casting
positioning
- done Q2H
- improves blood flow and prevents pressure related injuries
exercises
- CPM, ambulation, physical therapy
- assists with edema and DVT formation
