Anesthesiology: Analgesia and Pain

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Questions and Answers

What is the maximum dose of Paracetamol in 24 hours?

10g

6g (correct)

What is the mechanism of action of Ketamine?

NMDA receptor antagonist and opiate receptor mixed activity (correct)

Dopamine receptor antagonist

NMDA receptor agonist and opiate receptor antagonist

GABA receptor agonist

What is the analgesic dose of Ketamine via IV?

1-2mg/kg

5-10mg/kg

0.1-0.5mg/kg

0.2-0.5mg/kg (correct)

What is analgesia, according to the International Association for the Study of Pain (IASP)?

The absence of pain in response to stimulation that would normally be painful Signup and view all the answers

What is the effect of Alpha 2 agonists on blood pressure?

Hypotension Signup and view all the answers

What is the difference between Clonidine and Dexmedetomidine?

Dexmedetomidine has a higher receptor affinity Signup and view all the answers

What is the primary mechanism of pain transmission in the 1st order neuron?

Mechanical, chemical, and thermal stimulation Signup and view all the answers

What is the pediatric dose of Paracetamol?

15mg/kg Signup and view all the answers

What is the primary site of action for NSAIDs?

Cyclooxygenase pathway Signup and view all the answers

What is the primary goal of peri-operative pain management?

To improve patient satisfaction and comfort Signup and view all the answers

What is the effect of Ketamine on the sympathetic nervous system?

Stimulation Signup and view all the answers

What is the IV form of Paracetamol?

Perfalgan Signup and view all the answers

What is the primary mechanism of opioid action?

Hyperpolarization and inhibition of neurotransmitter release Signup and view all the answers

What is the primary side effect of NSAIDs?

Gastric irritation and peptic ulceration Signup and view all the answers

What is the primary indication for the use of paracetamol?

Treatment of fever Signup and view all the answers

What is the primary mechanism of tramadol action?

Inhibition of serotonin and norepinephrine reuptake Signup and view all the answers

What is the primary complication of opioid use?

Respiratory depression Signup and view all the answers

What is the primary characteristic of neuropathic pain?

Pain associated with nerve damage Signup and view all the answers

Study Notes

Analgesics and Pain Management

Terminology

Analgesia: absence of pain in response to stimulation that would normally be painful
Pain: unpleasant sensory/emotional experience associated with, or resembling that associated with, actual/potential tissue damage
Acute pain: sudden, sharp, or intense, serving as a warning sign of disease or threat to the body
Chronic pain: persisting or recurring for 3 months or more
Neuropathic pain: caused by pathology of the somatosensory nervous system
Referred pain: pain perceived other than at the site of stimulus/origin

Mechanism of Pain

1st order neurons: originating from dorsal root ganglia (DRG), nociceptors, and transmitting pain signals through A delta and C fibers
Glutamate, substance P, calcitonin gene-related peptide, and prostaglandins involved in pain transmission
2nd order neurons: spinothalamic and spinoreticular tracts
3rd order neurons: thalamus to cortex
Descending modulating pathways: from midbrain and medulla, influencing pain perception

Physiological Response to Pain

Increased heart rate, blood pressure, peripheral vascular resistance, and myocardial oxygen demand
Decreased vital capacity, cough inhibition, and increased risk of atelectasis, pneumonia, and hypoxemia
Decreased bowel motility, gastric emptying, and increased risk of GI infections and ileus
Decreased muscle activity, immobility, and increased risk of DVT, poor recovery, and wasting
Decreased urinary output, and increased risk of UTI, urinary retention
Catabolic hormone release, hyperglycemia, and impaired wound healing
CNS sensitization, increasing risk of developing chronic pain, anxiety, and fear

Measuring Pain

Not explicitly discussed in the provided text

Peri-operative Pain Management

Aims: patient comfort, satisfaction, adequate breathing, and decreased risk of lung infections
Pre-emptive analgesia: acting at nociception, DRG, and CNS to block central sensitization and decrease pain response intra-operatively and post-operatively
Post-operative pain management: using strong analgesics, NSAIDs, and patient-controlled anesthesia

NSAIDs

Cyclooxygenase inhibitors, inhibiting prostaglandin and thromboxane production
Non-selective NSAIDs: binding to COX 1 and 2, including aspirin, ibuprofen, diclofenac, indomethacin, and ketorolac
Selective NSAIDs: binding to COX 2 only, including celecoxib and parecoxib
Common side effects: gastric irritation, peptic ulceration, bronchospasm, platelet dysfunction, renal dysfunction, hepatotoxicity, and asthma exacerbation

Opioids

Opioid receptors: in the brain, spinal cord, and submucosal/mesenteric plexus, modulating pain by hyperpolarization and inhibiting neurotransmitter release
Endogenous endorphins: beta-endorphins, dynorphins, and enkephalins
Common side effects: nausea, vomiting, pruritus, constipation, urinary retention, reduced consciousness, muscle rigidity, and miosis
Dependence, tolerance, and overdose risks

Organ System Effects

CNS: sedation, euphoria, mental clouding, and altered mental state
CVS: hypotension, cutaneous vasodilation, and bradycardia
Respiratory: respiratory drive suppression, cough reflex inhibition, and increased intracranial pressures
GI: nausea, vomiting, decreased intestinal peristalsis, and constipation
Smooth muscle: biliary colic, ureteral and bladder sphincter hypertonicity, and increased uterine tone
Ocular: miosis

Specific Opioids and Analgesics

Codeine: 30-60mg PO 4-6 hourly
Tramadol: 50-100mg PO and IV 4-6 hourly, inhibiting 5-HT and NE reuptake
Pethidine: 50-100mg PO and IV 4-6 hourly
Morphine: 0.1-0.2mg/kg 4-6 hourly IV and IM, with tachycardia and dry mouth side effects
Fentanyl: 1-2μg/kg IV
Remifentanil: 1-2μg/kg IV, short-acting
Sufentanil and alfentanil: used in co-induction, inhibiting the “intubation response”
Paracetamol: weak COX 1 and 2 inhibitor, analgesic and antipyretic, with dose-dependent hepatotoxicity
Ketamine: NMDA receptor antagonist, opiate receptor mixed activity, dissociative amnesia, and analgesic effects
Amitriptyline (TCA), carbamezapine, gabapentine, and alpha 2 agonists (clonidine, dexmetomidine) also discussed

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Description

Learn about the definitions and concepts of analgesia, pain, and acute pain in the field of anesthesiology. Explore the importance of pain management and its impact on well-being.