Pharmacology: Inhalational & Intravenous Agents Flashcards

Question

What is the **induction** dose of thiopentone?

Answer 1

* Bolus: 4 L/kg * Steady State: Up to 60 L/kg

Answer 2

Non-competitive NMDA antagonist ## Footnote It is also a MOP antagonist and partial agonist at DOP and KOP.

Answer 3

1-4 hours ## Footnote Clearance of 6-10 mL/kg/min.

Answer 4

* **Ketamine**: phencyclidine * **Propofol**: phenol * **Thiopentone**: barbituric acid * **Etomidate**: imidazole

Answer 5

Desflurane has a **low boiling point**, and therefore fluctuations in temperature lead to significant fluctuations in saturated vapour pressure (SVP), which unless accounted for, would lead to **substantial variation** in the concentration of desflurane to the patient. ## Footnote To avoid this, the Tec 6 vapouriser is heated to 39 degrees and therefore the delivery of desflurane is predictable.

Answer 6

Enflurane and Isoflurane

Answer 7

Sevoflurane (200 g/mol)

Answer 8

4-10 mg/kg

Answer 9

Two or more substances mixed together where the heavier substance will eventually **settle out under gravity**.

Answer 10

A type of mixture where a substance is **evenly dispersed** through another which will not settle out under gravity. It may be made of solids, liquids and gases and consists of an internal phase (small particles) and an external phase through which internal phase is dispersed.

Answer 11

It is a ‘**liquid in liquid**’ colloid or a colloidal mixture of two or more immiscible liquids. Energy input is required from shaking or stirring and emulsifiers may be used to provide stabilisation.

Answer 12

* **pH < 4** (in vial) midazolam is **ionised** and exists in an open ring structure which is water soluble. * **pH > 4** (in blood) midazolam forms a **lipophilic**, closed ring structure.

Answer 13

* **Extravasation**: alkaline, causing significant local tissue damage. * **Intra-arterial**: crystallizes and occludes distal vasculature. ## Footnote Intra-arterial injection can be managed with papaverine or sympathetic block of the affected limb.

Answer 14

3.5% ## Footnote Metabolised to hexafluoroiso-propanol. This is the only ester that is NOT metabolised to trifluoroacetic acid.

Answer 15

**Rapid onset and offset**. It has the highest **global warming potential** of any volatile agent.

Answer 16

Nitrous oxide – Xenon – Desflurane – Sevoflurane – Enflurane – Isoflurane – Halothane

Answer 17

Metabolised to **trifluroacetyl metabolites**, which bind to liver proteins. ## Footnote This leads to an autoantibody response, which induces significant, life-threatening, centrolobular necrosis.

Answer 18

0.18% NaCl = 1.8 g NaCl per liter. Dividing by the molar mass (58.5 g/mol) gives ~0.031 mol/L. Since NaCl dissociates into Na⁺ and Cl⁻, total osmoles = 0.031 × 2 = 61 mosmol/L. **Sodium concentration is ~30.5 mosmol/L**.

Answer 19

* **Alpha-1**: sedative and hypnotic effects * **Beta-3**: hypnotic and anaesthetic effects ## Footnote NOTE: Benzodiazepines act on the alpha-1 receptor.

Answer 20

* Multiple exposure (more than once in 6 weeks) * Obesity * Biliary surgery * Drug dependency * Prolonged operations

Answer 21

* Ether * Halothane * Desflurane (≥1.6 MAC)

Answer 22

Exists as a racemic mixture of S(+) and R(-) in equal proportions. S(+) is 2-3 times more potent than R(-) and less likely to cause delirium and hallucinations.

Answer 23

* **Oral bioavailability**: 25% * **Half-life**: 2-3 hours ## Footnote Primarily metabolised by the liver.

Answer 24

Temperature at which a **50:50** mixture of **oxygen** and **nitrous oxide** separates, occurring at **-7 to -5.5°C** in cylinders and lower in pipelines due to reduced pressure.

Answer 25

Solubilised with polyethylene glycol or intralipid.

Answer 26

Powder held under nitrogen dissolves into alkaline form with water.

Answer 27

The pumping effect occurs when **back pressure during positive pressure** ventilation causes gas to **re-enter the vaporiser**, leading to **excess volatile agent delivery**. ## Footnote Modern machines use check valves to mitigate this, but it can still occur, especially at low fresh gas flows or with older equipment.

Answer 28

The partition coefficient is the **ratio of concentrations** of a compound in equal volumes of two immiscible compartments at equilibrium, indicating how the compound distributes between them. ## Footnote E.g. if 5 mL of agent dissolved 2 mL in blood and 3 mL in gas, the ratio is 0.66 (2:3)

Answer 29

It has a **C-F bond** which has a greater difference in electronegativity than the C-Cl bond.

Answer 30

* Opposite of the second gas effect. * **N₂O exits blood into alveoli** faster than N₂ can enter blood, causing **dilution of alveolar gases** and **reducing PAO₂**. Supplemental oxygen should be given after emergence from anesthesia with N₂O. ## Footnote This phenomenon can lead to hypoxia if not managed properly.

Answer 31

**Its low blood**: gas solubility coefficient means that **nitrous oxide diffuses into air-filled spaces** faster than nitrogen can leave. ## Footnote This can lead to a rapidly expanding pneumothorax.

Answer 32

Norketamine and Hydroxynorketamine

Answer 33

* Atmospheric half-life of **10 years**. * **Global warming potential** that is 2540x that of carbon dioxide.

Answer 34

**8 times more selective** for alpha-2 than clonidine.

Answer 35

* Its metabolism is **slow** and **saturable** (hepatic zero order). * It is **lipophilic** and can accumulate extensively in fat and muscle creating a reservoir.

Answer 36

* **Common Dead Space**: an alteration in the administration rate of one drug will affect the others. * **Reflux**: obstruction can cause drugs to go up gravity-fed lines (they need anti-reflux valves). * **Siphoning**: if a syringe driver is placed above the patient and the syringe plunger is not held firmly in place, the difference in hydrostatic pressure can make the drug flow freely. They have anti-siphon valves.

Answer 37

**Denitrogenate the breathing system** and the patient's FRC as well as **increasing the rate of uptake** of volatile anaesthetics.

Answer 38

Increase the frequency of activation of the receptors resulting in **increased chloride influx**.

Answer 39

**Ester hydrolysis** by non-specific plasma and **tissue esterases**.

Answer 40

**Adults**: 1-3 mg/kg **Children**: 2-6 mg/kg

Answer 41

**Onset**: 30 seconds **Offset**: 3-7 mins

Answer 42

**Onset**: 30 seconds **Offset**: 5-10 mins

Answer 43

**Onset**: 1-2 mins **Offset**: 5-10 mins

Answer 44

1-2 mcg/kg

Answer 45

Isoflurane has a **longer onset time** than sevoflurane (blood:gas coefficient 1.4 vs 0.7), and so this is **less suitable**.

Answer 46

Increased half-life occurs because **distribution clearance is high** compared to elimination clearance, leading to **fentanyl being stored in tissues** rather than cleared from plasma. ## Footnote Fentanyl's CSHT peaks around 5 hours after a 12-hour infusion.

Answer 47

R-ketamine is **less potent** and has more **hallucinogenic effects** than S-ketamine.

Answer 48

Isoflurane

Answer 49

Etomidate and Ketamine

Answer 50

* Flat for **24 hours** before use. * Invert at least **3 times** before use. ## Footnote This is because oxygen is less dense than N2O so would be delivered first, leaving an increasing concentration of N2O and, eventually, a hypoxic mixture as the canister is used up.

Answer 51

Non-competitive NMDA antagonists

Answer 52

**Sympathetic activation** and increased plasma catecholamine concentrations leading to an indirect positive inotropic effect

Answer 53

**Ester hydrolysis** by hepatic esterases; no active metabolites.

Answer 54

Alpha-subunit of GABA-A receptor only

Answer 55

* Diazepam * Chlordiazepoxide

Answer 56

* Adding an **alkyl group at the C5** position produces hypnotic activity. * Increasing the length of the side chain increases **hypnotic potency**. * Substituting **oxygen for sulphur** at C2 (thiopentone) increases lipid solubility.

Answer 57

* **HALOGENATED HYDROCARBONS**: Halothane, trichloroethylene, chloroform * **HALOGENATED ETHERS**: Enflurane, isoflurane, sevoflurane, desflurane

Answer 58

* Contains an amine group, making it a weak base with a pKa of 6.2. * Buffered in vials at pH 4 for ionization and water solubility. * At physiological pH, it becomes mostly unionized, forming a lipid-soluble benzodiazepine ring that crosses the BBB.

Answer 59

Sodium thiopental

Answer 60

* **Propofol**: emulsion in intralipid (egg phosphatide) * **Etomidate**: solubilized with polyethylene glycol or intralipid * **Sodium thiopental**: produced as a powder under nitrogen

Answer 61

* Propofol's **high lipid solubility** and **unionised** state mean it enters the brain fast but also redistributes quickly and stays trapped in fat, leading to a rapid drop in plasma levels and fast offset. * Fentanyl (pKa of 8.5), though also lipid-soluble, re-enters circulation from fat more readily due to ionisation, so its effect lasts longer.

Answer 62

Isoflurane and Enflurane

Answer 63

Halothane - halogenated hydrocarbon

Answer 64

The position of fluorine atoms makes isoflurane **less water soluble** and **more lipid soluble**, resulting in lower metabolism compared to enflurane.

Answer 65

**Patient Factors** * Children * Hyperthermia * Hyperthyroidism * Hypernatraemia **Pharmacological Factors** * Catecholamines and sympathomimetics * Chronic opioid use * Chronic alcohol use * Acute amphetamine intake

Answer 66

**Patient Factors** * Elderly * Pregnancy * Hypothermia * Hypothyroidism * Hypotension **Pharmacological Factors** * Acute opioid use * Acute alcohol intake * Sedatives

Answer 67

* Inspired concentration of anaesthetic * Minute ventilation/fresh gas flow * Functional residual capacity * Blood: gas partition coefficient

Answer 68

A steeper curve indicates a faster onset of action due to a quicker rise in alveolar partial pressure. Drugs with a low blood:gas partition coefficient reach equilibrium faster (i.e., have a more rapid rise in the FA/FI ratio).

Answer 69

The potency of an inhalational anaesthetic is directly proportional to its lipid solubility—the more lipid-soluble the agent, the more potent it is.

Answer 70

High concentrations of nitrous oxide during induction rapidly absorb into blood (20 times more soluble than N₂), decreasing alveolar volume as N₂ diffuses out slowly. This volume loss concentrates remaining gases, raising their partial pressures and leading to faster onset of action.

Answer 71

Accelerated uptake of an inhalational anaesthetic when given with N₂O. Rapid absorption of N₂O reduces alveolar volume, concentrating remaining gases and increasing their partial pressures, leading to faster anaesthesia onset.

Answer 72

* **Minute ventilation**: higher = faster onset * **Cardiac output**: lower = faster onset * **FRC**: lower = faster onset * **Cerebral blood flow**: higher = faster onset

Answer 73

Decreases pCO₂, reducing cerebral blood flow.

Answer 74

F(AE) = partial pressure of anaesthetic in lungs when vaporiser is off. ## Footnote FA/FI cannot be used since FI is 0.

Answer 75

Time for **plasma concentration of a drug** to decrease by half after stopping an infusion aimed at maintaining steady levels, considering the infusion duration.

Answer 76

* 90% decrement time. * Wake-up occurs when alveolar concentration is about 90% lower than maintenance.

Answer 77

5% ## Footnote 75% from nitrous oxide.

Answer 78

Desflurane (persists in the atmosphere for 14 years)

Answer 79

* Agent choice (sevoflurane > desflurane) * Avoiding nitrous oxide * Low-flow anaesthesia * BIS monitoring to avoid excessive dosing of inhalational anaesthesia * TIVA

Answer 80

* **pKa**: 6.5 * **Lipid Solubility**: 90 x Morphine * **Potency**: 10 x Morphine * **Volume of Distribution**: 0.6 L/kg * **Protein Binding**: 90%

Answer 81

197 Da (g/mol)

Answer 82

22.8 degrees centigrade

Answer 83

* **Short**: Midazolam (1-4 hours) * **Intermediate**: Lorazepam (10-20 hours), Temazepam (8-15 hours) * **Long**: Diazepam (48 hours), Chlordiazepoxide (24-48 hours)

Answer 84

* **Volume of distribution**: 0.4 L/kg * **pKa**: 7.1 * **Protein binding**: 70% * Moderately **lipophilic**

Answer 85

-5.5 degrees

Answer 86

Adult or child > 5 yrs: 5 mg Child < 5 yrs: 2.5 mg ## Footnote Remove HMEF or nebulise downstream.

Answer 87

5-12 hours

Answer 88

30-60 mL/kg/min

Answer 89

Thiopentone Ketamine

Answer 90

* **Volume of Distribution**: 4.5 L/kg * **Protein Binding**: 76% * **Onset**: 10-60 seconds * **Duration**: 6-10 minutes (terminal elimination 1-4.5 hours)

Answer 91

* Rapid metabolism by hepatic and plasma esterases * Inactive metabolites are mostly excreted by the kidneys (85%)

Answer 92

**10 mins** Elimination half-life is **2.5 hours**

Answer 93

**8 mins** Terminal elimination half-life is **11 hours**

Answer 94

**C**: imidazole derivative, single enantiomer (R) **U**: induction of anaesthesia, sedation **P**: 10 mL vials of 2 mg/mL as aqueous solution or lipid emulsion **A**: GABA-A agonist **D**: 0.3 mg/kg **O**: 30 secs --> 5 mins **S**: pain on injection, adrenal suppression, PONV, porphyria **A**: IV **D**: highly protein bound, mostly unionised (pKa 4.2) **M**: rapid hydrolysis by plasma esterases and hepatic microsomal enzymes **E**: 3-5 hours, inactive metabolites in urine and bile

Answer 95

**C**: phencyclidine derivative **U**: induction, sedation, analgesia, bronchodilation **P**: clear, colourless solution in various concentrations (10, 50 or 100 mg/mL), oral solution **A**: non-competitive NMDA antagonist **D**: 1-2 mg/kg IV induction, 10 mg/kg IM induction **O**: 60 secs --> 5 mins IV; 5 --> 30 mins IM **S**: hallucinations, emergency delirium **A**: 25% oral bioavailability **D**: Vd 2-3 L/kg **M**: hepatic via P450, hydroxynorketamine and norketamine are active **E**: renal, terminal half-life 2-4 hours

Answer 96

**C**: phenol, 2,6-diisopropylphenol **U**: induction, sedation, status epilepticus **P**: lipid-water emulsion containing soya bean oil and egg phosphatide, 1% or 2% concentration **A**: GABA-A **D**: 1-2 mg/kg IV **O**: 30 secs --> 5 mins **S**: reduced SVR, reduced CO, PRIS, pain on injection **A**: IV **D**: Vd 4 L/kg, 98% protein bound, pKa 11 **M**: hepatic - 40% to glucuronide, 60% to quinol, CSHT 20 mins after prolonged infusion **E**: renal NOTE: has antiemetic properties

Answer 97

**C**: barbituric acid derivative **U**: induction (RSI), status epilepticus **P**: 500 mg sodium thiopental as yellow powder with anhydrous sodium carbonate in nitrogen, diluted with 20 mL water to form 2.5% alkaline solution (pH 11) **A**: GABA-A agonist **D**: 3-7 mg/kg **O**: 30 secs --> 5 mins **S**: hypotension, porphyria, accumulation, extravasation, intra-arterial injection **A**: IV **D**: Vd 2.5 L/kg, 80% protein bound **M**: hepatic **E**: renal NOTE: reduces CMRO2, reduces CO and SVR, resp depression, no depression of laryngeal reflexes

Answer 98

* **Air**: black and white * **Oxygen**: white * **Nitrous Oxide**: blue * **Entonox**: blue and white * **Heliox**: brown and white * **Carbon Dioxide**: grey ## Footnote Based on cylinder shoulder colours

Answer 99

36.5 degrees

Answer 100

Volume of **gas dissolved** in a unit volume of liquid. ## Footnote **Ostwald**: at a given temperature (i.e. not STP) **Bunsen**: at STP

Answer 101

* Diffusion hypoxia * Gas-filled cavities (pneumothorax) * Bone marrow failure (oxidises cobalt in B12) * Increased ICP * PONV

Answer 102

* Labour * Trauma * Endoscopy

Answer 103

* Gaseous oxygen can be **bubbled through liquid nitrous oxide** causing the liquid to vaporiser and form a stable gaseous mixture that remains homogeneously mixed at room temperature. * The gases dissolve into each other and behave as a **single mixture** rather than separate entities.

Answer 104

Nitrous oxide is manufactured by **heating ammonium nitrate** to approximately 200°C, causing thermal decomposition: NH₄NO₃ → N₂O + 2H₂O.

Answer 105

* The first stage **lowers the pressure** to a safe level * The second stage consists of a **diaphragm connected to a mouth piece** - when negative pressure is generated on inspiration, the diaphragm tilts and allows entonox to travel to the patient.

Answer 106

* TOF > 0.9: reversal not required * TOF 0.4-0.9: 0.02 mg/kg (1-1.75 mg) * TOF < 0.4 or TOF count of 2-3: 0.02-0.05 mg/kg (1.5-3.5 mg) * NO TOF: wait until count is at least 2

Answer 107

* Increased respiratory rate * Decreased tidal volume * Blunted response to hypercapnia (desflurane > isoflurane > sevoflurane)

Answer 108

* Depresses laryngeal reflexes * Causes respiratory depression with initial apnoea * Abolishes peripheral chemoreceptor response to hypoxaemia

Answer 109

Preserves airway reflexes and spontaneous ventilation.

Answer 110

Inhibits 11-beta hydroxylase, the final step in cortisol synthesis, preventing hydroxylation of 11-deoxycortisol to cortisol.

Answer 111

* **Fentanyl**: 5 hours after 8-hour infusion * **Propofol**: 30-40 mins after 8-hour infusion * **Remifentanil**: 3-5 mins, context insensitive ## Footnote **Thiopental** continues to rise.

Answer 112

* **Alpha-1**: anxiolysis (spinal cord and cerebellum) * **Alpha-2**: sedative and anticonvulsant (spinal cord, hippocampus, cortex) ## Footnote Benzodiazepine are allosteric modulators of GABA-A that binds between the alpha and gamma subunits

Answer 113

40% ## Footnote So the oral/buccal doses are quite high in comparison to the IV dose.

Answer 114

200 µg slow IV bolus (then 100 µg every minute if required) ## Footnote Other details: max dose 1 mg, onset within 2 mins, half-life of 1 hour (may need infusion)

Answer 115

* **Advantages**: readily available, quick onset and offset, minimal respiratory depression/CVS effects. * **Disadvantages**: nausea, no lasting analgesia, environmental effects can laminate.

Answer 116

* **Desflurane**: 2540 (14 year lifespan) * **Isoflurane**: 510 (3 year) * **Nitrous Oxide**: 298 (100 year) * **Sevoflurane**: 130 (1 year) ## Footnote Volatiles account for 2% of the NHS carbon footprint (of which 50% is nitrous oxide).

Answer 117

* Cardiostable: no significant changes in blood pressure or heart rate. * Minimal respiratory effects. * Maintains cerebral perfusion pressure.

Answer 118

* Megaloblastic changes in bone marrow * Agranulocytosis * Subacute combined degeneration of the spinal cord ## Footnote Nitrous oxide oxidizes the cobalt ion in B12, preventing it from acting as a cofactor for methionine synthase.

Answer 119

* Impairs mitochondrial fatty acid metabolism. * **Metabolic**: hypertriglyceridaemia, hyperkalaemia, metabolic acidosis * **Cardio**: bradycardia, arrhythmia, heart failure, rhabdomyolysis

Answer 120

Solution is alkaline (pH 10.5). In blood, it can crystallize, potentially causing ischemia or arterial spasm.

Answer 121

* Stop injection * Keep cannula * Inject 0.9% NaCl to dilute thiopentone * Intra-arterial lidocaine can relieve pain **Vasodilation**: * Pharmacological: papaverine 40-80 mg * Sympatholytic: stellate ganglion or brachial plexus block * Intravenous heparin

Answer 122

* **Sevoflurane**: no effect * **Isoflurane** and **desflurane**: increase heart rate ## Footnote Desflurane has little effect on contractility, while others reduce contractility; all volatiles decrease SVR.

Answer 123

* Increased CBF * Reduced CMRO * Burst suppression on EEG * Nausea ## Footnote Volatiles also potentiate muscle relaxation and have some analgesic properties.

Answer 124

* **Type 1**: mild transient rise in liver enzymes * **Type 2**: 50% mortality; trifluoroacetyl chloride binds to hepatocyte proteins, activating the immune response and causing massive centrilobular necrosis.

Answer 125

* **PO Morphine**: 10 mg * **IV Morphine**: 3.3 mg * **Oral Oxycodone**: 6.6 mg * **Tramadol**: 100 mg * **Codeine**: 100 mg * **Transdermal Fentanyl**: 2.5 µg/hour

Answer 126

* Co-induction * TIVA * Adjunct to awake fibreoptic intubation * Antitussive during extubation

Answer 127

* Purpose-built, dry, well-ventilated, fireproof room * **Oxygen** stored outside * Full and empty kept separately * **C, D, and E** cylinders stored horizontally on shelving or upright in purpose-built racks

Answer 128

Oxygen supports combustion; leaks in an enclosed space risk explosions. Outdoors, leaks disperse safely.

Answer 129

**Advantages:** * Remain in intravascular compartment * Smaller volumes required * Less peripheral edema **Disadvantages:** * Increased anaphylaxis risk * Expensive * Not suitable for some patients (e.g., gelatine) * Dilute clotting factors due to volume expansion

Answer 130

* **Gelatins** (e.g., gelofusin): large molecular weight proteins in crystalloid solution; risk of anaphylaxis. * **Albumin**: 50% of plasma proteins; produced from sterile human plasma; risk of allergy. * **Starches**: no longer used due to renal injury. * **Blood products** (e.g., PRC, FFP).

Answer 131

* **0.9% NaCl**: 308 mOsmol/kg (hypertonic) * **Hartmann's**: 280 mOsmol/kg (isotonic) * **5% Dextrose**: 28 mOsmol/kg (hypotonic after metabolism)

Answer 132

* Osmotic diuresis * Renal vasodilation * Free radical scavenger * Initial volume expansion

Answer 133

* **CVS**: vasodilation, inhibits catecholamine release, reduces myocardial contractility * **RESP**: bronchodilation * **MSK**: loss of deep tendon reflexes, muscle paralysis (in toxicity) * **HAEM**: inhibits platelet activity

Answer 134

Small molecule that can stimulate the immune response when bound to a larger molecule. ## Footnote E.g. heparin + platelet factor 4

Answer 135

* GABA-A * NMDA * Two-pore domain K⁺ channels (hyperpolarize neurones, activated by volatiles)

Answer 136

* Metabolised in the liver via glucuronidation to inactive metabolites * There is some extrahepatic metabolism (e.g. lungs) * Excreted mainly by the kidneys

Answer 137

Pressure exerted by vapour in equilibrium with its liquid at a temperature below its critical point.

Answer 138

* Increases cerebral blood flow * Raises ICP * Elevates cerebral metabolic rate ## Footnote Chronic exposure to nitrous oxide is linked to a higher risk of miscarriage.

Answer 139

* **S-(+)-ketamine**: More potent analgesic and anesthetic effects, faster onset, fewer side effects. * **R-(–)-ketamine**: Less potent for anesthesia but may have longer-lasting antidepressant effects and fewer psychomimetic reactions.

Answer 140

* **Patient**: Low FRC (e.g., pregnancy), higher alveolar ventilation, lower cardiac output. * **Anaesthetic**: Fraction of inspired volatile, blood-gas solubility coefficient, fresh gas flow.

Answer 141

* Volatile > 1 MAC: increased CBF * Nitrous oxide: increased CBF ## Footnote Opioids do not affect CBF; **propofol** decreases CBF.

Answer 142

* **Onset**: 30 seconds * **Offset**: 60 seconds after discontinuation ## Footnote Labouring women should inhale when contractions begin.

Answer 143

* Air-filled spaces: pneumothorax, bowel obstruction, middle ear surgery, intracranial air * Vitamin B12 deficiency

Answer 144

* Consider regional anaesthesia * Avoid **suxamethonium** and volatile agents * Use **TIVA** * Ensure a clean machine (no prior volatile use) * Have **dantrolene** available * Monitor temperature and ETCO₂ closely

Answer 145

* **Halothane**: 10 ppm * **Sevoflurane**: 20 ppm * **Isoflurane** and **Enflurane**: 50 ppm * **Nitrous Oxide**: 100 ppm

Answer 146

* **Delta**: 0-4 Hz * **Theta**: 4-8 Hz * **Alpha**: 8-13 Hz * **Beta**: 13-30 Hz

Answer 147

In vitro muscle contraction studies using caffeine and halothane.

Answer 148

IV injection allows rapid dilution, preventing precipitation. ## Footnote Intra-arterial injection causes abrupt neutralization and crystallization of thiopentone.

Answer 149

* Hepatic oxidation via CYP450 * Causes auto-induction * Produces pentobarbital as an active metabolite * Follows zero-order kinetics when enzymes are saturated.

Answer 150

* **Propofol**: increases frequency of GABA-A chloride channel opening. * **Thiopentone**: increases duration of GABA-A chloride channel opening.

Answer 151

FE is lower than FI because the **lungs deliver volatiles** while they are absorbed into blood and tissues; the difference decreases as **alveoli and tissues equilibrate**.

Answer 152

* Delivery device * Flow rate * FiO2 * Target SpO2

Answer 153

* Short: thiopentone * Medium: pentobarbitone * Long: phenobarbitone

Answer 154

* **Respiratory**: reduced VT, increased RR, maintained MV * **CNS**: increased CBF, increased CMRO, increased ICP

Pharmacology: Inhalational & Intravenous Agents Flashcards

Explore pharmacology of induction agents and volatile anaesthetics, including mechanisms, uses, and adverse effects. (232 cards)