Acute Postoperative Pain Management Flashcards
According to the International Association for the study of Pain what is a clear definition of pain?
An unpleasant sensory and emotional experience associated with actual or potential tissue damage
What does JCAHO consider pain?
The fifth vital sign
What year did JCAHO implement standards addressing pain management?
2001, also identified responsibilities of hospitals and all types of healthcare agencies regarding pain
What does the term nociception mean?
The detection, transduction and transmission of noxious stimuli
What are the two categories of pain?
Acute pain
Chronic pain
What is the primary cause of acute pain?
Primarily due to nociception
What is thought to cause chronic pain?
May be due to nociception, but also affected by psychological and behavioral factors
What are some characteristics of acute pain?
Short duration <6wks
Cause usually known
Located in area trauma or damage
Resolve spontaneously with healing
What are some characteristics of chronic pain?
Beyond normal duration of recovery
Cause my not be identifiable
Affects patients self image and sense of well being
What five surgical procedures have a high incidence of chronic pain?
Thoracotomy Sternotomy Mastectomy Hysterectomy Inguinal hernia repair
Define nociceptive pain.
Appropriate response to identifiable tissue damage
Define neuropathic pain.
May be abnormal, unfamiliar pain, probably caused by dysfunction in the PNS or CNS
Define Idiopathic pain.
Pain not attributed to identifiable processes
Define psychogenic pain.
Pain sustained by psychological factors
How does nociceptive pain occur?
Due to activation or sensitization of peripheral nociceptors that transduce noxious stimuli
What are the four processes that result in nociceptive pain?
Transduction
Transmission
Modulation
Perception
What nociceptive process occurs from the transformation of a noxious stimulus (chemical, mechanical, thermal) into an action potential?
Transduction
What nociceptive process occurs from the process by which an action potential is conducted from the periphery to the CNS?
Transmission
What nociceptive process occurs by involving altering neural afferent activity along the pain pathway, it can suppress or enhance pain signals?
Modulation
What nociceptive process occurs once the signal is recognized by various areas of the brain?
Perception
What are the two types of somatic pain?
Superficial somatic
Deep somatic
What are characteristics of superficial somatic pain?
Well localized, sharp, pricking, throbbing or burning
Where does superficial somatic pain usually originate?
Skin, subcutaneous and mucous membranes
What are characteristics of deep somatic pain?
Dull, aching, less well localized
Where does deep somatic pain arise?
Muscles, tendons, joints or bones
When might visceral pain occur?
From a disease process or abnormal function of an internal organ
Why is visceral pain sometimes difficult to treat?
May be localized or referred pain
How does neuropathic pain occur?
Result of an injury or acquired abnormalities of the peripheral or central neural structures
What are the two subtypes of neuropathic pain?
Central generator
Peripheral Generator
What occurs during a central generator pain?
Central pain due to injury of the brain or spinal cord
What is an example of central generator pain?
Phantom limb pain
What occurs during peripheral generator pain?
Pain originates in nerve root, plexus or nerve
What is an example of peripheral generator pain?
Diabetic neuropathy
What is idiopathic pain?
Pain in the absence of an identifiable physical or psychological cause (perceived to be excessive for injury)
What is psychogenic pain?
Pain sustained by psychological factors, patients have an effective and behavioral disturbance
Absence of pain perception.
Analgesia
Exaggerated response to noxious stimuli.
Hyperalgesia
Perception of an ordinarily non-noxious stimulus is pain.
Allodynia
Functional abnormality of one or more nerve roots.
Radiculopathy
Abnormal sensation perceived without stimulus.
Paresthesia
Absence of all sensation.
Anesthesia
Pain in nerve distribution.
Neuralgia
What factors help categorize peripheral nerve afferent fibers?
Size
Degree of myelination
Speed of conduction
Distribution of fibers
What are the three groups of peripheral nerve afferent fibers?
Class A
Class B
Class C
How many fiber subtypes are in Class A?
Four: A Alpha
A Beta
A Delta
A Gamma
What are characteristics of Class A peripheral nerve fibers?
Large, myelinated fibers
Low threshold for activation
Conduct impulses at various speeds
1-20mcm in diameter
What are characteristics of Class A delta fibers?
Mediates pain sensation
Transmits fast or first pain
Sharp, stinging, pricking type pain
5-25 m/s
What are characteristics of Class A Alpha fibers?
Transmits motor and proprioceptive impulses
60-120 m/s
What are characteristics of Class A Beta fibers?
Cutaneous touch and pressure
60-120 m/s
What are characteristics of Class A Gamma fibers?
Cutaneous touch and pressure
15-35 m/s
What type of fibers are class B fibers?
Postganglionic sympathetic and visceral affarent
What are characteristics of Class B fibers?
Medium sized
Myelinated
Slower conduction than Class A
Higher threshold than Class A, lower than Class C
What are characteristics of Class C fibers?
Unmyelinated or thinly myelinated
What type of fibers are Class C fibers?
Preganglionic autonomic and pain fibers
What pain characteristics are associated with Class C fibers?
Transmits slow or second pain
Burning, persistent, aching or throbbing pain
What is the major neurotransmitter for A-Delta pain fibers?
Glutamate
What receptors does the neurotransmitter for A-Delta fibers bind to?
NMDA
AMPA
Located on the postsynaptic membrane
What is the major neurotransmitter for C pain fibers?
Substance P
What receptor does the neurotransmitter for C pain fibers bind to?
NK-1 on post synaptic membrane
What neuronal pathway modulates pain?
Descending dorsolateral spinal tract
What sites in the brain do IV opioids typically work at?
Limbic system
Hypothalamus
Thalamus
What type of analgesia is mediated by the Mu-1 receptors?
Supraspinal
What site do IV opioids work to produce spinal analgesia?
Periventricular/periaquaductal gray matter
Mu-2 receptors
What is the mechanism of action behind the use of neuraxial opioids?
Decrease the release of substance P by binding to Mu-2 receptors (spinal anesthesia)
What are some cardiovascular effects from the surgical stress response?
HTN Tachycardia Enhanced myocardial irritability Increase SVR (angiotensin II release) Increase CO from catecholamine release May result in an increase in O2 demand --> Ischemia
What are some respiratory effects from the surgical stress response?
Increase in minute ventilation
Increased WOB
Pain may decrease chest expansion –> atelectasis
V/Q Mismatch
What are some endocrine effects from the surgical stress response?
Hyperglycemia (increase Cortisol)
Salt and water retention (increased aldosterone and ADH)
What are some GI effects from the surgical stress response?
Increased sphincter tone and decreased smooth muscle tone –> ileus or PONV
Decreased oral intake
Hyper secretion of gastric acids promotes stress ulcers
What are some immunologic effects from the surgical stress response?
Stress response produces leukocytosis with lymphopenia and depresses the reticuloendothelial system predisposing the patient to infection
What are some hematologic effects from the surgical stress response?
Increased platelet adhesiveness and diminished fibrinolysis promotes a hyper coagulable state
Immobility exacerbates this problem
What effects does general anesthesia have on the surgical stress response?
Not effective in attenuating the SNS response except with high narcotic technique
What effects does regional anesthesia have on the surgical stress response?
Diminishes the intensity of afferent impulses getting to the spinal cord
Reduces catecholamine and other stress hormone responses during operative period
What type of procedures ranked among this highest in pain?
Trauma on extremities and
Orthopedic
What class of medications are typically used in post operative pain management?
Opioids, safe and effective pain control used in treating moderate to severe pain
What are some undesirable side effects of opioids?
N/V Constipation Lethargy Sedation Respiratory depression
What is the minimum effective analgesic concentration?
The analgesic blood level at which the patient experiences analgesia and the severity of pain rapidly diminishes
What mechanisms are thought to contribute to opioid induced hyperalgesia?
Enhanced release of neurotransmitters
Sensitization of primary and secondary afferents
Upregulation of spinal and supra spinal pathways
Occurs when a patient receives opioids, exhibits diminished pain threshold and enhanced pain sensitivity?
Opioid-induced Hyperalgesia
What is preemptive analgesia?
Pain perception can be decreased by using analgesics capable of inhibiting CNS sensitization before painful stimulus occurs
What drugs can be used in preemptive analgesia technique?
NSAIDs Opioids Local anesthetics NMDA antagonists Alpha 2 agonists
What are some benefits of utilizing a multimodal approach in analgesia?
Use of different agents allows reduced dosages of each thus reducing the side effects of each
Synergistic effects between drug classes enhances analgesic effect of each drug
Effective in patients at an increased risk for side effects seen with opioid use (elderly, chronic pain, OSA)
What type of pain are NSAIDs useful in treating?
Mild to moderate pain
What adverse effects should be watched for with NSAID use?
GI bleeding
Renal autoregulation is altered and
Hepatotoxicity
What type of patients should we avoid the use of NSAIDs?
Hypersensitivity
Renal Compromise
Peptic ulcer disease
(caution in elderly declining renal function)
What type of drug is Ketamine?
NMDA receptor antagonist
What effects can Ketamine have in relation to opioid consumption?
Reduced morphine consumption and pain intensity up to 6 weeks following spinal surgery
What type of drug is methadone?
D-isomer NMDA receptor antagonist
What is the dose of methadone?
0.2mg/kg
How can anticonvulsants contribute to a multimodal pain therapy approach?
Manage spontaneous firing of sensory neurons associated with neuropathic pain
Attenuates neuronal sensitization response
What two anticonvulsants can be used in multimodal paint management?
Pregabalin
Gabapentin
What type of medication is dexmedetomidine?
Alpha 2 agonist
What beneficial effect does dexmedetomidine have in post operative patients?
Decreased incidence of PONV
What population especially benefits from dexmedetomidine use?
Obese patients
What type of drug is Clonidine?
Alpha 2 agonist
What are some risks of using Clondine for pain management?
Increased risk for hypotension and bradycardia
What sites do alpha 2 agonists work in order to decrease post operative pain?
Central, spinal and peripheral
What sites do anticonvulsants work in order to decrease post operative pain?
Central and spinal
What sites NMDA antagonists work in order to decrease post operative pain?
Central, spinal and peripheral
What is the preemptive dose of acetaminophen in a multimodal pain management approach?
15mg/kg
What electrolyte has shown to have some analgesic effects for a multimodal pain management approach?
Magnesium
What effects do glucocorticoids contribute to a multimodal pain management approach?
Potent anti-inflammatory agent that plays a role and reduces post op pain
Also works well to decrease PONV
What effects do local anesthetics contribute to a multimodal pain management approach?
Given as a nerve block
Could be given by the surgeon at the site
Lidocaine infusion
In what case would regional anesthesia be a good method of pain management?
For pain control to a specific part of the body
What are some benefits to utilizing regional anesthesia?
Eliminating need for IV pain meds
Earlier discharge
What are some disadvantages to regional anesthesia?
Block failure
Hematoma
Bleeding
Neurological injury
What are the major side effects of neuraxial opioid use?
Itching --> most common Nausea Urinary retention Respiratory depression Sedation CNS excitation
What type of respiratory depression is seen with hydrophilic opioids placed intrathecally?
Leads to LATE respiratory depression (6-12h) due to rostral spread (uptake of systemic circulation is minimal?
What type of respiratory depression is seen with hydrophilic opioids placed in the epidural space?
EARLY respiratory depression (within 2h) since systemic uptake is greater
What is thought to be the cause of late respiratory depression?
Rostral spread in CSF
What type of respiratory depression is seen with lipophilic opioids?
EARLY respiratory depression due to significant systemic uptake with both intrathecal and epidural placement (more pronounced in epidural)
Why doesn’t late respiratory depression occur in the use of lipophilic neuraxial opioids?
Diffusion of lipophilic opioids out of the CSF is substantial, therefore rostral spread is minimal
How can a provider get the maximum benefits of using distraction as an adjunct in pain management?
If introduced preoperatively
What is the thought process behind using a TENS for pain management?
Thought to produce analgesia by stimulating large afferent fibers
Gate theory of pain suggests that the afferent input from the large fibers competes with that from smaller pain fibers
How does the application of cold help in pain management?
It alters pain threshold, reduces swelling and decreases tissue metabolism
What condition is cold therapy for pain contraindicated in?
Raynaud’s
How does the application of heat help in pain management?
It decrease joint stiffness and increases blood flow to the area
