rheum week 9

Vocabulary practice flashcards covering types of anaesthesia, induction agents, analgesics, muscle relaxants, neuroaxial blocks, and fundamental pharmacokinetics.

Anaesthesia

The absence of perception or sensation.

Conscious Sedation

A subtype of sedation where verbal contact is maintained, the cerebral cortex remains functional, and protective airway reflexes are preserved (e.g., used for cataract surgery).

Procedural Sedation

A subtype of sedation characterized by loss of verbal contact and cortex impairment, while the brainstem remains functional and protective airway reflexes (such as cough and gag) remain present (e.g., used for colonoscopy).

General Anaesthesia (GA)

A state acting principally on the brain where brainstem function is impaired, airway and protective reflexes are absent, and spinal cord sensation is inhibited.

Three Stages of General Anaesthesia

Induction (initiating anaesthesia), Maintenance (sustaining anaesthesia throughout the procedure), and Emergence (cessation of agents and recovery of consciousness/reflexes).

Polypharmacy (in Anaesthetics)

The clinical principle where administering a combination of multiple drugs permits using less of each individual drug, resulting in fewer side effects while maintaining the same or superior therapeutic effect.

Propofol

An intravenous induction agent and GABA agonist that exhibits rapid onset and offset; common side effects include loss of airway, profound respiratory depression, fall in blood pressure, bradycardia, and pain/stinging upon injection.

Thiopentone

An intravenous general anaesthetic agent noted as having the fastest induction speed.

Ketamine

A disassociative anaesthetic acting as an NMDA (glutamate) receptor antagonist that increases respiratory drive and blood pressure, but exhibits slow onset, causes nausea, and carries a $1:10\,000$ risk of psychosis.

Midazolam

A benzodiazepine that increases GABA receptor affinity to produce amnestic and anxiolytic effects; it potentiates propofol to reduce required propofol doses, but has an unpredictable, sluggish onset and exhibits a ceiling effect.

Fentanyl

A highly lipid-soluble opioid receptor agonist (lipid solubility of $580$) that provides rapid onset analgesia with haemodynamic stability, though it causes loss of airway, bradycardia, and profound respiratory depression.

Dexmedetomidine

An alpha-2 agonist that has no depressing effect on respiratory drive, but can cause a fall in blood pressure and cannot be administered as a bolus.

Sugammadex

A fast-acting reversal agent for non-depolarising neuromuscular block capable of reversing complete paralysis, but carries a higher financial cost and risk of anaphylaxis.

Neostigmine

A slow, inexpensive reversal agent for muscle relaxation that cannot reverse complete paralysis; it is co-administered with glycopyrrolate (or atropine) to counter unwanted muscarinic effects.

Depolarising Muscle Relaxants

A class of neuromuscular blocking agents exemplified by suxamethonium.

Non-Depolarising Muscle Relaxants

Neuromuscular blocking agents divided into aminosteroids (such as rocuronium, vecuronium, and pancuronium) and benzoisoquinoliniums (such as atracurium, cisatracurium, and mivacurium).

Spinal Anaesthesia

A single-shot neuroaxial regional technique where local anaesthetic is injected directly into the cerebrospinal fluid (CSF) after piercing the dura mater, having an onset of approximately $10\,\text{mins}$.

Epidural Anaesthesia

A neuroaxial regional technique where a catheter is positioned in the epidural space outside the dura mater; it requires a larger volume ($15\text{--}20\,\text{ml}$) to establish a block and can provide continuous infusion for up to $3\,\text{days}$.

Heavy Bupivacaine

A formulation of bupivacaine made denser than cerebrospinal fluid (CSF) so that it sinks gravitationally towards the sacral and thoracic curvatures after intrathecal injection.

pKa

The pH level at which a drug is $50\%$ ionized and $50\%$ unionized.

Zero-Order Kinetics

Pharmacokinetic clearance where a constant amount of drug is cleared per unit of time, regardless of plasma drug concentration.

First-Order Kinetics

Pharmacokinetic clearance where the rate of drug elimination is directly proportional to the plasma drug concentration.

Distribution Phase (Alpha Phase)

The initial rapid decrease in plasma drug concentration following an intravenous bolus, defined by the half-life equation $t_{1/2\,\alpha} = 0.693 \times tc$, representing drug movement from the central compartment to peripheral tissues.

Elimination Phase (Beta Phase)

The terminal, slower slope on a semi-logarithmic plasma concentration-time curve representing the clearance and metabolism of a drug from the body.

Maximum Dose of Lignocaine

$4\,\text{mg/kg}$ when administered plain, or $7\,\text{mg/kg}$ when combined with adrenaline.

Maximum Dose of Bupivacaine

$2\,\text{mg/kg}$.

Maximum Dose of Ropivacaine

$2\text{--}3\,\text{mg/kg}$.

Vessel Rich Group (VRG)

Highly perfused tissues—specifically the brain, heart, lungs, kidneys, and liver—that receive the initial high-flow distribution of anaesthetic drugs.

Volatile Anaesthetic Time Constant

The relationship governing the speed of uptake into tissue, expressed as $\text{Time} = \frac{\text{Volume} \times \text{Lipid solubility}}{\text{Flow}}$, where lower lipid solubility yields a smaller time constant, leading to faster induction and recovery.