Day 6: Pain management and Analgesics Flashcards
what is pain
An unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage
classification of pain according to duration
acute and chronic
classification of pain according to site of injury
nociceptive
neuropathic
nociplastic
What characterizes acute pain?
Acute pain typically has a recent onset, lasting for a short duration (usually less than 6 weeks).
What are common triggers for acute pain?
Acute pain is often associated with trauma, surgery, or acute illness.
How does acute pain typically manifest in terms of location and resolution?
Acute pain is usually limited to the area of damage and resolves as healing occurs.
What defines chronic pain?
Chronic pain persists beyond the usual course of an acute illness or injury or beyond normal tissue healing times.
How does chronic pain differ from acute pain in terms of duration and association with tissue healing?
Chronic pain is no longer associated with normal tissue healing processes and can last for an extended period.
What are the key differences between acute and chronic pain?
Acute pain has a recent onset, short duration, and is associated with trauma, surgery, or acute illness, while chronic pain persists beyond the usual healing period and is no longer related to tissue healing processes.
What is nociceptive pain?
Nociceptive pain arises from actual or threatened damage to non-neural tissue, triggered by the activation of nociceptors—pain receptors located throughout the body.
What characterizes neuropathic pain?
Neuropathic pain results from a lesion or disease affecting the somatosensory nervous system, which includes the nerves responsible for transmitting sensory information.
What is nociplastic pain?
Nociplastic pain is characterized by altered nociception without clear evidence of tissue damage or disease affecting the somatosensory nervous system.
How do nociceptive, neuropathic, and nociplastic pains differ?
Nociceptive pain arises from actual or potential tissue damage and activates nociceptors. Neuropathic pain results from nerve damage or disease affecting the somatosensory system. Nociplastic pain involves altered nociception without clear evidence of tissue damage or somatosensory system dysfunction.
nociception
The neural process of encoding noxious stimuli
nociceptive pain: somatic characteristics
-sharp, dull, aching, throbbing
-localised
noceciptive pain: visceral characteristics
- gnawing, squeezing, cramping
-diffuse, poorly localised, referred pain
neuropathic pain: characteristics
-burning, electric shocks, allodynia
-dermatomal or diffuse
-tingling, pins and needles, numbness, itching
pain management: chronic
- gabapentinoids: gabapentin and pregabalin
-low dose TGA: amitriptyline
-SNRIs: venlafaxine and duloxetine
analgesic ladder
simple analgesics
weak opioids
strong opioids
strong opioids
morphine
oxycodone
diamorphine
fentanyl
weak opioids
tramadol
codeine
dihydrocodeine
simple analgesics
paracetamol
aspirin
NSAIDS
pain management: acute
simple analgesia
NSAIDS and COX 2 inhibitors
opioids
local anesthetics
hypnotic agents (NO AND Ketamine)
alpha- agonists
miscellaneous
NSAIDS side effects
gastric irritation
renal dysfunction
platelet dysfunction
bronchospasm
hepatotoxicity
myocardial infarction
long acting strong opioids
morphine
short acting strong opioids
fentanyl,
remifentanil,
sufentanyl &
alfentanyl
opioids: side effect
Nausea and vomiting
Constipation
Urinary retention
Itchiness/ pruritis
Respiratory depression
Sedation
Histamine release (morphine)
Bradycardia
Muscle rigidity
naloxone
opioids antagonist
1-4mcg/kg IV
naloxone side effects
Arrythmias
Pulmonary oedema
Hypertension
Anti-analgesic
ketamine
NMDA receptor antagonist
Tachycardia/ hypertension
Bronchodilation
Salivation
Emergence phenomenon
Allodynia:
Allodynia refers to the experience of pain in response to a stimulus that does not normally provoke pain. In other words, it is the perception of pain from a non-painful stimulus, such as light touch or gentle pressure, due to sensitization of the nervous system.
Hyperalgesia:
Hyperalgesia is an increased sensitivity to painful stimuli, resulting in an exaggerated response to stimuli that are normally painful. It can occur as a result of sensitization of the nociceptive pathways in the nervous system, leading to heightened perception of pain.
nomenclature: opioid
General name for the class
Includes all drugs that act on opioid receptors
nomenclature: opiate
Refers specifically to naturally occurring opioids from the opium poppy
Includes morphine and codeine
opioids receptors
Most opioid drugs act on the MOP (also called µ or mu) receptors
Located in CNS (brain and spinal cord)
effects of opioids
-centrally mediated analgesia
**decreased neural discharge
**intense in nautre
-decreased sympathetic response
-sedation
**Can contribute to anaesthesia
**In very high doses: loss of consciousness
-cough suppression
**methadone
**codeine
opioid side effects
-respiratory depression
- euphoria/ dysphoria
-prolonged recovery
-git (N/V/ constipation)
-tolerance. addiction and withdrawal
-pruritis (histamine release)
-may cross placenta
uses of opioids in anaesthesia
-Mainstay of intraoperative analgesia
**Mainly fentanyl and morphine
-Establishing pre-emptive analgesia
-Maintaining intraoperative analgesia (IV boluses or infusion)
-Dampening of intubation response (alfentanil)
=Additive to LA in neuraxial blockade
=Target controlled infusion of remifentanil for intraoperative analgesia
=Opioid-based anaesthesia
=Cardiovascular instability (trauma, emergencies, cardiac surgery)
morphine: general
The reference opioid drug
Naturally occurring opiate from the opium poppy
morphine: IV
=Intraoperative analgesia
=Postoperative analgesia in high care setting
=Patient controlled analgesia (PCA) pump
=IV infusion in ICU and high care
morphine IM
Postoperative analgesia in ward
Given 4-6 hourly
Labour analgesia
morphine: orally
Severe chronic pain
Syrup or tablets
Palliative care cancer pain
codeine
Codeine is also naturally occurring
A prodrug that is metabolized into morphine
Mainly used in oral preparations
semi- synthetic opioids
heroin (diamorphine)
oxycodone
synthetic
-pethidne
-fentanyl and derivatives (end in nil)
How can fentanyl be administered for patient-controlled analgesia?
Fentanyl can be used as boluses of 10 µg in patient-controlled analgesia (PCA) systems.
In what context can fentanyl be added to analgesic mixtures?
Fentanyl can be added to local anaesthetic mixtures for spinal and epidural analgesia.
What is the administration method for fentanyl in patient-controlled analgesia (PCA)?
Fentanyl can be used as boluses of 10 µg in PCA systems, allowing patients to self-administer pain relief within preset limits.
How does fentanyl contribute to spinal and epidural analgesia?
Fentanyl, when added to local anaesthetic mixtures, enhances the duration and quality of pain relief in spinal and epidural analgesia techniques.
What is the status of fentanyl in anaesthesia?
Fentanyl is the most commonly used synthetic opioid in anaesthesia.
How long does it typically take for fentanyl to take effect?
Fentanyl typically has an onset of action within 10 minutes of administration.
What is the duration of analgesia provided by fentanyl?
Fentanyl provides intense analgesia for approximately 30-45 minutes.
In what surgical scenario is fentanyl particularly useful?
Fentanyl is particularly useful for pre-emptive surgical anaesthesia due to its rapid onset and potent analgesic properties.
alfentanil
fentanyl derivative
onset of alfentanil
Rapid onset and offset — lasts 5 minutes
dose of alfentanil
Typical dose: 0.5 to 1 mg IV
can we use alfentanil in GA for C section
yes, it doesn’t cross the placenta
use of alfentanil
-Useful for blunting intubation response
-Emergency “rescue” intraoperative analgesia
-Diagnostic use for insufficient analgesia
sufentanil
fentanyl derivatives
potency of sufentanil
Very potent (typical dose 5–10 µg) i.e. 1000 x more potent than morphine
CVS side effects of sufentanil
few CVS side effects
remifentanil characteristics
-Ultra-short acting
-Regardless of dose, metabolised into inactive compounds after 10 minutes
-“Context sensitive half-time” of 10 minutes
Spontaneous recovery
administration of remifentanil
must be given via infusion requires infusion pump
indications of remifentanil
-Sleep apnoea
-Morbid obesity
-Avoiding postoperaitve respiratory depression
-Deep intraoperative analgesia required
patient will require additional analgesia post op
tramadol
weak synthetic opioid
also has actions of noradrenergic and serotonin receptors
administration of tramadol
orally
which kind of pain do you administer tramadol
moderate to severe pain
how can you administer tramadol
solo or combined preparation with paracetamol
What is one notable pharmacological effect of naloxone?
Naloxone rapidly displaces opioids from receptors, effectively reversing their effects.
In what medical situation is naloxone particularly useful?
Naloxone is useful for the emergency management of respiratory depression, particularly in cases of opioid overdose.
How is naloxone utilized in neonatal care?
In neonatal care, naloxone is used for opioid reversal in mothers who have received opioids during labor or as part of general anesthesia before delivery.
Apart from its therapeutic uses, what diagnostic value does naloxone offer?
Naloxone has diagnostic value in cases where opioid overdose is suspected but not confirmed. Its administration can confirm opioid involvement if there is a response to treatment.
What important consideration should be kept in mind regarding naloxone administration in cases of opioid overdose?
It’s important to note that naloxone is not a cure for opioid overdose, and patients must be carefully monitored afterward, as opioids can re-bind to receptors, leading to recurrent respiratory depression.
What potential complication can arise from the abrupt cessation of opioids through naloxone administration?
Abrupt cessation of opioids through naloxone administration can induce sudden opioid withdrawal, which can be extremely distressing for the patient.
