Postop Pain Management Flashcards
Pain is considered the
5th vital sign
Pain is defined as an
unpleasant sensory and emotional experience associated with actual or potential tissue damage
In 2001, JCAHO identified responsibilities including
assessment of pain in all patients
educate about pain management strategies
orient staff to be competent to assess pain
record assessments and reassessment of pain
The categories of pain include
acute: primarily due to nociception
chronic: may be due to nociception but also affected by psychological and behavioral factors
Nociception refers to the
detection, transduction, and transmission of noxious stimuli
Acute pain is
of short duration (<6 weeks)
cause usually known
temporary and located in area of trauma or damage
Resolves spontaneously with healing
Chronic pain is
persists beyond normal duration of recovery from acute injury or disease
cause may not be identifiable
affects patients self image and sense of well being
Procedures with high incidence of chronic pain include:
thoracotomy, sternotomy, mastectomy, hysterectomy, inguinal hernia repair
Pain can be classified by:
etiology: postoperative, cancer
pathophysiology: nociceptive, neuropathic, idiopathic, psychogenic
affected area
Psychogenic pain is
sustained by psychological factors
Idiopathic pain is
not attributable to identifiable causes
Nociceptive pain is
the appropriate response to identifiable tissue damage
Nociceptive pain is due to the
activation or sensitization of peripheral nociceptors that transduse noxious stimuli
the result of four processes: transduction, transmission, modulation, and perception
Transduction is
stimuli translated into electrical energy at the site
Transmission is
propagation of the impulse through the nervous system
Modulation is
alteration of the stimuli that can be amplified or attenuated
Perception is
based on the psychological framework of the patient
Subtypes of nociceptive pain include:
Somatic & visceral pain
Somatic pain can be
superficial: arises from skin, subcutaneous tissues, or mucous membranes
characterized as well-localized, sharp, pricking, throbbing, or burning
Deep somatic pain: arises from muscles, tendons, joints or bones
dull, aching quality that is less well-localized
Visceral pain is due to
disease process or abnormal function of internal organ
may be localized or referred
Neuropathic pain is the result of
injury or acquired abnormalities of peripheral or central neural structures
Neuropathic subtypes include
Central generator: central pain due to injury to brain or spinal cord; phantom pain
Peripheral generator: originates in nerve root, plexus, or nerve; polyneuropathies, mononeuropathies
Idiopathic pain is perceived to be
excessive for the extent of the pathology
Allodynia is the
perception of an ordinarily non-noxious stimuli as pain
Analgesia is the
absence of pain perception
Anesthesia is the
absence of all sensation
Hyperalgesia is the
exaggerated response to noxious stimuli
Neuralgia is
pain in nerve distribution
Paresthesia is an
abnormal sensation perceived without stimulus
Radiculopathy is the
functional abnormality of one or more nerve roots
Peripheral nerve afferent fibers are categorized into three groups based on
size, degree of myelination, speed of conduction, and distribution of fibers
The three groups of afferent nerve fibers include:
Class A- alpha, beta, delta, gamma
Class B
Class C
Class A peripheral nerve fibers are
large, myelinated fibers
have low threshold for activation
1-20 micrograms in diameter
Class A delta fibers
mediates pain sensation- transmits fast or first pain
sharp, stinging, pricking type pain
conducts impulses at 5-25 m/s
Class A alpha fibers
transmits motor and proprioceptive impulses
60-120 m/s
Class A Beta fibers
cutaneous touch and pressure
60-120 m/s
Class A gamma fibers:
cutaneous touch and pressure
15-35 m/s
Class B peripheral nerve fibers are
medium sized myelinated fibers
conduction speed 3-14 m/s
diameter less than 3 micrometers
have higher threshold (lower excitability) than Class A fibers
Lower threshold than Class C fibers
Postganglionic sympathetic and visceral afferents are class B
Class C peripheral nerve fibers are
unmyelinated or thinly myelinated
conduction speeds of 0.5-2 m/s
Diameter 0.4-1.2 micrometers
Preganglionic autonomic fibers and pain fibers are Class C- transmits slow or second pain; burning, persistent, aching, throbbing pain
A-Delta Fibers transmit
“First” or “Fast” pain
it is well localized; sharp, stinging, pricking
duration of pain coincides with painful stimulus
pain from parietal peritoneum carried here
The major neurotransmitter involved in A-Delta fibers is
glutamate and binds to NMDA and AMPA receptors on postsynaptic membrae
C Fibers transmit
“Second” or “slow” pain
diffused and persistent; burning, aching, throbbing; duration exceeds stimulus; pain from viscera is carried here
The major neurotransmitter involved in C Fibers is
substance P which bids to NK-1 receptors on the postsynaptic membrane
Pain is modulated in the
descending dorsolateral spinal tract
IV opioids act primarily at other sites in the brain including
the limbic system, hypothalamus, and thalamus; this supraspinal analgesia is mediated by Mu-1 receptors
IV opioids can also produce
spinal analgesia by working in the periventricular/periaqueductal gray where they stimulate Mu-2 receptors
Neuraxial opioids work at the same receptor site as
enkephalin; their mechanism of action is to decrease the release of Substance P by binding to Mu-2 receptors; this is known as spinal anesthesia
Pain management is important because
effective intraoperative and postoperative pain relief is vital to your patient’s outcome
Prompt treatment can help prevent the development of negative sequelae that pain can precipitate
Pain is not just an unpleasant experience; it causes a multitude of systemic effects
The cardiovascular surgical stress response includes
HTN, tachycardia, enhanced myocardial irritability, increased SVR (angiotensin II), CO increases except in patients with compromised left ventricular function
May result in increased myocardial O2 demand and precipitate ischemia
The respiratory surgical stress response includes
increase in total body O2 consumption and CO2 production causes increase in minute ventilation
increases work of breathing
pain may decrease chest expansion and result in atelectasis, intra-pulmonary shunting, hypoxemia, and hypoventilation
increases in skeletal muscle tension that results from pain impulses may lead to V/Q mismatch
The endocrine surgical stress response includes
hyperglycemia- secondary to increased glucagon, increased epinephrine, and decreased insulin
Vasoconstriction, increased myocardial contractility, tachycardia- secondary to increased cortisol, increased catecholamines, activation of renin-angiotensin system
Salt & water retention (increased aldosterone & ADH) may lead to CHF
The gastrointestinal surgical stress response includes
increased sphincter tone with decreased smooth muscle tone that may lead to formation of ileus and lead to PONV
decreased oral intake is associated with septic complications and delayed wound healing- hypersecretion of gastric acid promotes stress ulcers; abdominal distension further aggravates loss of lung volume and pulmonary dysfunction
The immunological surgical stress response
produces leukocytosis with lymphopenia & depresses the reticuloendothelial system predisposing patients to infection
The hematological surgical stress reponse
increases platelet adhesiveness and diminished fibrinolysis promotes a hypercoagulable state; immobility exacerbates this problem
Describe the impact that general anesthesia has on the surgical stress response:
not effective in attenuating the response except with high dose narcotic technique
Describe the impact that regional anesthesia has on the surgical stress response:
diminishes the intensity of afferent impulses getting to the spinal cord
reduces catecholamine and other stress hormone responses during perioperative period
Pain management points:
effective pain program is based on an understanding of pain
pain management requires patient evaluation preoperatively, postoperatively and thru discharge
education of the patient is key to pain management
pain management is geared at balancing the advantages, disadvantages, and patient considerations
A pain assessment involves
history of current and persistent pain
physical examination
pain attributes- intensity, onset, duration, location, descriptors of what exacerbates or relieves pain
behavioral manifestations
impact of pain on ADLs
current & past treatments
are the patient’s expectations for pain relief realistic
Postoperative pain intensity is rate the highest in
orthopedic/trauma on extremities
These surgeries are ranked among 25 with highest pain intensity:
appendectomy, cholecystectomy, hemorrhoidectomy, tonsillectomy
some laparoscopic procedures are ranked unexpectedly high
Opioids are the ____and can be given___
mainstay for postoperative analgesia; may be given IV, PO, IM, subQ, PCA, or neuraxial
Opioids are safe and effective in treating
moderate to severe pain
Opioids should be administered via
the most effective route and limiting side effects
Side effects of opioids include
N/V, constipation, lethargy, sedation, and respiratory depression
The minimum effective analgesic concentration is the
analgesic blood level at which the patient experiences analgesia and the severity of pain rapidly diminishes
Opioids can lead to opioid-induced
hyperalgesia; patients receiving opioids may exhibit diminished pain threshold and enhanced pain sensitivity
-escalating opioids worsens pain perception
The mechanism for opioid-induced hyperalgesia is possibly due to
enhanced release of neurotransmitters
sensitization of primary and secondary afferents
upregulation of spinal and supraspinal pathways- critical component is activation of excitatory NMDA receptor & central glutamatergic system
Demonstrated in patients receiving high-dose intraoperative opioids such as fentanyl and remifentanil
Pain perception can be decreased by using
analgesics capable of inhibiting CNS sensitization before painful stimulus occurs
clinical role of preemptive analgesia still uncertain and much debated
Drug options for preemptive analgesia include
NSAIDs, opioids, local anesthetics, NMDA antagonists, alpha-2 agonists
A multi-modal approach is
use of different agents allows reduced dosages of each thus, reduced side effects
may include more than 1 route of administration
The synergistic effects between drug classes enhances
analgesic effects of each drug
Multi-modal approach is effective in patients at risk of
side effects from large doses of opioids such as obstructive sleep apnea, chronic pain, and frail elderly
NSAIDs are effective in treating
mild to moderate pain
Adverse effects of NSAIDs include
GI bleeding, ARF, and hepatotoxicity
NSAIDs should be avoided in patients with
hypersensitivity, significant renal compromise, & PUD
NSAIDs should be used in caution in
elderly patients due to increased risk for renal impairment
Ketamine is a
NMDA receptor antagonist
Ketamine dosage is
0.5 mg/kg bolus followed with infusion at 4 mcg/kg/min.
Ketamine is able to reduce
morphine consumption and pain intensity up to 6 weeks following spine surgery
Methadone is a
D-isomer NMDA receptor antagonist
The dose of methadone is
0.2 mg/kg
Methadone results in a
50% reduction in post-op opioid consumption and pain scores at 48 hours after complex spine surgery
Anticonvulsants include
pregabalin & gabapentin
Anticonvulsants are used to manage
spontaneous firing of sensory neurons associated with neuropathic pain
-attenuate neuronal sensitization response
Anticonvulsants are able to reduce the incidence of
chronic postoperative pain syndrome- decrease opioid consumption and neuropathic pain 3-6 months following total knee replacement
Alpha 2 agonists include _____ and the risk associated with these drugs is
dexmedetomidine & clonidine
hypotension & bradycardia
Dexmedetomidine is particularly useful in reducing
morphine consumption 2-14 hours post-op; decreased PONV
significantly reduces opioid consumption in obese population
Clonidine results in
reduced morphine consumption 12-24 hours post-op; also decreased PONV
Additional drugs that can be administered in a multi-modal approach include
acetaminophen and magnesium
Infiltration of local anesthetic can be done
by the surgeon at the end of the case
ilioinguinal and femoral nerve blocks can be placed by the anesthetist
Glucocorticoids are
potent anti-inflammatory agents that play a role in reducing postop pain and can help to manage PONV
Side effects of neuraxial opioids include:
itching (most common)
nausea, urinary retention, respiratory depression (early & late), sedation, CNS excitation, neonatal morbidity
Regional anesthesia is preferred to provide
postoperative pain control to a specific part of the body
Benefits of regional anesthesia include
eliminating the need for IV pain medications and early discharge of ambulatory patients
Disadvantages of regional anesthesia include
block failure, bleeding, hematoma, & neurological injury
Central neuraxial blocks include
spinal & epidural
Peripheral nerve blocks include
lumbar plexus blocks & interscalene nerve blocks
Intrathecal placement of neuraxial opioids can lead to
LATE respiratory depression (6-12 hours) due to rostral spread
early respiratory depression does not occur because uptake by systemic circulation is minimal
Epidural placement of neuraxial opioids can lead to
EARLY respiratory depression (within 2 hours) may occur since systemic uptake is greater then with intrathecal placement
late respiratory depression is more likely due to rostral spread in CSF
Hydrophilic opioids onset of analgesia
is slow, duration, prolonged
With lipophilic opioids the onset of analgesia is
rapid with short duration
EARLY respiratory depression occurs due to significant systemic uptake with both intrathecal & epidural placement
-respiratory depression is most pronounced after epidural placement
Discuss lipophilic opioids and late respiratory depression.
Late respiratory depression DOES NOT occur because diffusion of lipophilic opioids out of the CSF is substantial, therefore rostral spread is minimal
Distraction can be used
as an adjunct to analgesic interventions
can include music or imagery
requires patient cooperation
The maximal benefit of distraction is when
it is introduced preoperatively
Hypnosis is a
state of focused attention combined with decrease in external awareness
Hypnosis may not be as frequently used because
it may not work on all patients
social stigma
conflicting data on efficacy
Heat is used to
decrease joint stiffness and increase blood flow
easy to use
Cold is used to
alter pain threshold, reduce swelling, and decrease tissue metabolism
easy to use
Cold is contraindicated in patients with
decreased circulatory states such as Raynaud’s
Transcutaneous electrical nerve stimulation (TENS) is 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
With a TENS unit,
electrodes are applied to the same dermatome as the pain
requires professional to instruct in use
The benefit of using a TENS unit is that there is an
absence of significant side effects
Immobilization can include
healing process as well (i.e. casting)
Positioning can be done
every two hours
improves blood flow and prevents decubitus ulcer development
Exercise can assist in the
CPM, ambulation, physical therapy
assists with edema and DVT formation
