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Pharmacology > 3. Inhalational Agents > Flashcards

3. Inhalational Agents Flashcards

1
Q

Sevoflurane

MAC
Metab by
releases

A

Mac 2.5

By P450 2E1 to hexafluoroisopropanol and the release of inorganic fluoride ions.

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2
Q

Enflurane
B:G
Mol wt
BP

A

blood:gas partition coefficient - 1.8
Wt - 184
BP 56.5

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3
Q

Isoflurane
B;G
Mol wt

A

Blood g 1.4

Mol wt 184

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4
Q

Desflurane
B:G coeff

Problems

A

fluorinated methyl ether

approximately one-fifth the potency of isoflurane.

All volatile anaesthetic agents are weak calcium channel antagonists and therefore potentiate neuromuscular blocking agents.

It has a boiling point of approximately 23°C

The induction of anaesthesia can stimulate the sympathetic system as can change in inspired concentrations.

MAC 4-6%
B:G 0.42

way irritation leading to coughing, apnoea and laryngospasm

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5
Q

Halothane
B:G
BP

A

B;G 2.4
BP 23.5

Type 1 halothane hepatitis is characterised by a transient derangement of the liver function tests together with an acute hepatitis on histology. It may resolve without treatment and has no long term side effects.

Type 2 halothane hepatitis is thought to have an auto-immune aetiology and has a significant mortality.

Thymol is a preservative added to halothane, which accumulates on the wicks and effects the efficiency of the vapouriser if it is not emptied regularly.

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6
Q

MAC increased by

A

Hyperthyroidism

hyperthermia

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7
Q

MAC decreased by

A

Hypotension
Hypothermia
Hypoxia

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8
Q

HPV inhibited by

no effect

A

Agents that inhibit HPV

Ether
Halothane
Desflurane (>1.6 MAC)

Salbutamol

Agents with minimal or no effect on HPV

Thiopentone
Fentanyl
Desflurane (1MAC)
Isoflurane (<1.5MAC)
Sevoflurane (1MAC)
Propofol.
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9
Q 
Oil gas coeff &amp; mac of 
Desflurane
Isoflurane
N2O
Sevo
Xenon
A

The physicochemical properties of all drugs influence pharmacokinetic behaviour in vivo.

                     Oil/gas 	       (MAC)
Desflurane            	18	        6
Isoflurane	        90	        1.2
Nitrous oxide     	1.4       	104
Sevoflurane           	53.4      	2
Xenon	                1.9  	        71

Clinical potency is measured using the minimal alveolar concentration (MAC).

The anaesthetic agent with the highest oil:gas partition coefficient has the lowest MAC.

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10
Q

Halothane hepatitis

A

Minor derangement in liver function tests to fulminant hepatic failure.

appearance of liver damage within 28 days of halothane exposure

Seventy five per cent of patients with halothane hepatitis

avoided if:

Previous exposure has occurred within three months
There is known adverse reaction to halothane
Family history of adverse reaction
Pre-existing liver disease.

Halothane increases cerebral blood flow but reduces intraocular pressure.

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11
Q

MH & triggers

A

`Life threatening autosomal dominant condition linked with other myotonic disorders

Intracellular calcium transport is deranged with generalised muscular contraction generating excess heat.

Trigger
Sux
Inhaled agents - Trichloroethylene, cycloprop

Rx Dantrolene

Haloperidol - NLMS -Rx dantrolene also / bromocriptine

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12
Q

MAC is

A

(MAC) is defined as the alveolar concentration required in order to prevent movement to a standard surgical stimulus in 50% of unpremedicated patients at a pressure of 1 atmosphere.

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13
Q

Meyer-Overton hypothesis

A

Meyer-Overton hypothesis states that potency (lipid solubility) is proportional to the oil:gas partition co-efficient. The relationship between log oil:gas partition coefficient and MAC is linear with a high oil:gas partition coefficient equating to a low MAC (higher potency).

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14
Q

The blood:gas partition coefficient

A

The blood:gas partition coefficient is a measure of the solubility of an anaesthetic agent in blood. The lower the solubility, the greater the partial pressure it exerts and the faster the onset.

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15
Q

Nitrous Oxide

affect on cerebral
flow
metab

Affect on NMDA

Affect on CO2 reactivity

Whats the second mssgr

A

causes direct cerebral stim=
increases cerebral blood flow.

Increased metabolism specifically in the frontal lobes and limbic system =
increases the cerebral metabolic rate of oxygen consumption (CMRO2).

Cerebral autoregulation is impaired
used with propofol maintained.

Nitrous oxide antagonises NMDA receptors (it is not an NMDA agonist), which may result in neurological damage, but this effect may be limited by the concurrent use of GABA agonists or inhalational anaesthetics.

Carbon dioxide reactivity remains unaffected.

Cyclic guanosine monophosphate (cGMP - 2nd messenger

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16
Q

Xenon

A

Inert gas

not negatively inotropic
Not cause vasodilatation.

Xenon gives rapid induction and recovery,

low blood/gas solubility coefficient (0.115),
MAC of 71%
boiling point is −108°C
oil/gas solubility coefficient of 1.9.

Its low blood solubility can cause diffusion hypoxia if supplementary oxygen is not provided at the end of anesthesia.

Xenon:

Has a low toxicity
Is not teratogenic
Is not metabolised within the body, and
Is not a trigger for malignant hyperpyrexia.
Several studies have shown that xenon exhibits neuroprotective properties without co-existing neurotoxicity by protecting neural cells against ischaemic injury.

Xenon is produced as a by-product of the fractional distillation of liquid air and is an expensive process and is thus delivered in closed circuit breathing systems.

Xenon-133, unlike elemental xenon, is a radioactive gas produced by fission of uranium-235, which is used in diagnostic inhalational tests.

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17
Q

Ideal volatile agent for an inhalational induction

A

Pleasant smell and not pungent
Not irritant to the respiratory tract, that is, induces breath-holding, coughing or laryngeal spasm
Rapid onset and offset of action. (e blood:gas partition coefficient)

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18
Q

Blood gas coeff of common inhal

A 
Halothane 2.3
Isoflurane 1.4
Sevoflurane 0.6
Desflurane 0.45
Nitrous oxide 0.47
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19
Q

Penthrox

what the blood gas coeff

mac

svp

properteis

metab

safe upper lim

A

Methoxyflurane - halogen ether

high blood gas - 16 - slow

Mac .16

SVP 49 @20

Non iritant, min fx systyemic

Neprhotx - lipid solubility
Pehtnrox = .3 mac hours
onset 4-5 min

50% hepatic meatb
Fluoride ion -
Neprhotox - safe lim 2mac hours

Up to 50% of methoxyflurane undergoes hepatic metabolism. The principal metabolites are fluoride ions, dichloroacetic acid and oxalic acid. Recent studies have shown that methoxyflurane also undergoes significant metabolism to fluoride within the kidney itself. The oxalic acid and fluoride are both nephrotoxic. The safe upper limit of exposure to methoxyflurane is 2 MAC-hours, which gives a serum fluoride level of 40 μmol/L, below the threshold for toxicity.

Methoxyflurane (PenthroxTM) is delivered from a self-administered inhaler with a volume of 3 mL that provides 25-30 minutes of analgesia with continuous use (intermittent use extends the duration of action).
The maximum exposure from a single methoxyflurane inhaler device is 0.3 MAC-hours, while the maximum recommended dose for analgesia of five inhalers a week
The onset of analgesic effect is 4-5 minutes.

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20
Q

MAC

Unaffected by

Increased by

Decreased by

A 
Unaffected 
Gender
Acidaemia
Alkalaemia
Body weight
Serum potassium variations and
The duration of the anaesthetic.

MAC is increased in:

Infants/children
Hyperthermia
Hypermetabolic states
Sympathetic increase and
Chronic alcoholism.

MAC is reduced in:

Hypothermia
Hypoxaemia
Old age
The presence of other depressant drugs,for example, opioids and
When the central nervous system has low levels of catecholamines, for example, alpha methyl dopa.

Carbon dioxide (levels >120 mmHg) has been used an anaesthetic - Hickman, which by an additive effect can be considered as decreasing MAC. On the other hand a markedly elevated CO2 (and even severe acidaemia) can stimulate the sympathetic system/release catecholamines and result in MAC increasing.

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21
Q

N2o manufactured by

What impurities formed
How reomoved

Examples of impurities
problems with the impurities

How do we test for these impurities

Problems with prolonged use of N2O

A

heating ammonium nitrate (not nitrite) to 240°C.

Ammonia
Nitric acid
Higher oxides of nitrogen),

Removed by passage through scrubbers and washers.

The higher oxides of nitrogen which are formed include:

Nitric oxide (NO)
Nitrogen dioxide (NO2)
Dinitrogen trioxide (N2O3) which decomposes to NO and NO2.

Irritant Respiratory tract -
pulmonary oedema hours
severe fibrotic reaction may occur after several weeks, which destroys the lung tissue.

Tested for contamination
Higher oxides of nitrogen,
Exposing moistened starch-iodide paper - gaseous contents of a cylinder, which turns blue if contaminants are present.

Prolonged use of N2O is associated with many side effects including the inhibition of methionine synthase, which results in bone marrow depression and a megaloblastic anaemia (not microcytic).

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22
Q

GWP100 of the following gases are as follows:

What is GWP100

What is it for 
Co2
Sevo
iso
des
sevo
methane
A 
The inhalation halogenated anaesthetic agents, isoflurane, sevoflurane, and desflurane absorb infra-red radiation within the range of 7-10 µm and have a significant GWP100.
The
Carbon dioxide 1
Methane 23
Sevoflurane 130
Nitrous oxide 310
Isoflurane 510
Desflurane 2540
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23
Q

The approximate percentage metabolism of the volatile agents is as follows:

Halothane
Iso
En
sevo
des
A

Desflurane 0.02%.

Isoflurane 0.2%

Enflurane 2%

Sevoflurane 3-6%

Halothane 20%

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24
Q

Halothane effect on vasoconstriction cerebral vs iso

BP
SVP

Affect on myocardium

MAC

A

Halothane causes less cerebral vasoconstriction than isoflurane, which explains why isoflurane is popular in neuroanaesthesia.

Halothane boils at 50°C and has a saturated vapour pressure (SVP) of 32.3 kPa. The SVP is almost identical to isoflurane, and this may allow them be delivered using the same vaporiser, for example, Oxford miniature vaporiser.

All volatile agents inhibit hypoxic pulmonary vasoconstriction and therefore increase shunting.

Halothane sensitises the myocardium to circulating catecholamines and this is one reason why surgeons usually ask the anaesthetist prior to infiltrating epinephrine (adrenaline) containing local anaesthetics.
Drop SVR 18%
barorec reflex decerease

ganlgiong blocking
central vasomot depressant action

The minimum alveolar concentration (MAC) of halothane is 0.7% (not 1.15%).

Halothane absorb Uv + IR -
causes change elsaticity of silicone rubber
can be determ using refractormer

Mol wt 197 vs N2o 44

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25
Convert MAC to PP
The partial pressure of a gas is proportional to its concentration, therefore, by transforming the MAC values for the volatile agents into partial pressures at 1 atmosphere (or 760 mmHg): MAC (Volume %) = ( partial pressure of volatile agent (x) / 760mmHg )x 100 Halothane for example = 0.75 =( x/760)x100 x=(0.75 x 760)/100 =5.7mmHg
26
Age related mac partial pressures
Age related MAC for 40-year-old patient population Halothane (MAC of 0.75%) has a partial pressure of 5.7 Isoflurane (MAC of 1.17%) has a partial pressure of 8.9 Enflurane (MAC of 1.68%) has a partial pressure of 12.8 Sevoflurane (MAC of 1.8%) has a partial pressure of 13.7 Desflurane (MAC of 6.6%) has a partial pressure of 50.2
27
Properties ideal anaesthetic | Phsyical
1. Liquid Room temp 2. High SVP - easy vape 3. Low latent heat vaporisation 4. Low specific heat capacity 5. Chemically stable in light & heat 6. Inert when in contact w/ metal rubber & soda lime 7. Non flammable /explosive 8. Long shelf life 9. Inexpensive 10 No additives / preservatives 11. Environmentally friendly 12. Non irritant/ nice smell
28
PK of Ideal inhalational
Low blood : gas coefficientg - fast onset High oil partiation coeff - low MAC Minimal metabolism - no Fl- prod Excretion via lungs
29
PD Ideal
``` CNS Smooth rapid indcution Only affect cns Rapidly reversbily No increase CBF/ICP Analgesic Not epileptogenic ``` CVS No depression No sensation of myaocardium No cor flow decrease Resp No breath holding laryngospasm broncholidation No resp depression MSK Releax Non MH trigg# GI Anti emetic Reanl haep haem No effects / flow not rterato
30
Onset is determined by
Blood: gas coefficient | Lower = faster
31
Potency
Oil:gas partition coeff | High - miore potent
32
Signif blood gas partition coeff
Ratio - amt anaes in blood to gas when equal vol in equil PParadox a/w speed induction Poorly soluble - high PP in blood - fast onset Converse - solube - rapidly enter blood - exert low PP Slower onset Effects related to PP in blood -> brain * not absolute amount present
33
Blood gas part coeff in order
``` Xenon .17 Des .42 NO .47 Sevo .68 Iso 1.4 En 1.9 Halo 2.3 ```
34
Onset influenced
Blood gas coeff Also - by mac Alveolar vent /; irritability Des - profound irritant
35
Equilibrium reached quicker with high or low blood g partition coeff
Reached more quick;y with those w/ a lower partition coeff
36
Factors influencing the speed appraoch equilibrium
Phsyiologty patient - factors related agents High inspire conc - rapid increase PP alveoli - rapid onset Increased alveolar vent - PP increase faster FRC large - Inspoire conc dilute - opposite affect CO - influces - low - more time for equilibration incres onset Conc grad mainatianed where COP increase - slower rise alveolar PP Cocnetration effect & second gas effect
37
Concentration effect
NO 20x more solube blood vs O2 / N High conc introduced - rapid upatke Reduction in volume alveoli - NO extracted fast than N Fract conc gas left in alveoli incrase = 'conc effect'
38
Second gas effect
Inahl coadmi w/ high conc - NO higher alverolar PP of inahlation Extration alveolar gas - augmented vent, trachael gas w/ onhal drawn in -INcrease equligibrium of alveolar fraction to inspire rati = increase onset
39
Oil gas coeff
Neuraonl cell membrane interactopm Odrect - secondary messnger - lipid solubility anaesthetic potenct
40
Meyer overton hypotehsis
Correl liid solublity & potency Aneaethsia - number inhal agent molecule dissolbe in lipid bilayer - If true product of oil:gas partici coeff - constant - not case Many sub w/ high lipid solubilty - no anaestheit effect Larger moleculew/ high lip solub - less potent Iso & en - structu iso sim oil:gas coeff Mac iso 1.17 70% that enflurane
41
Isoflurane Ideal agent?
Liquid room temp Chemically stable in light SVP 32kpa ``` Inert metal Soluble rubber Not flammable No stabilizers Cheap ``` Pungent Irritability Cough Breath holding May react soda lime = CO Bl:g 1.4 Oil g 98 Low mac 1.17 .2% metabolized Not toxic
42
Sevoflurane - ideal svp reactivty bl@g cost metab mol wt oil gas
Liquid room Stable light SVP 22 @ 20 Low solubility Rubber & plastic Non flammable No additives preservative Non irritant Pleasant odour Bl:G .7 Low mac Insol - rapid induction & recovery Expensive Unstable moist soda lime - compound a Hepatic metab 3-5% more other inhalation No renal mol wt 200 Oil gas 80 achiral
43
Desflurane ideal?
Liquid room temp Protected from light BP 23.5C SVP 89 @ 20 Volatile unsuitable conventional vaporiser TEC6 - heats liquid 39C - SVP 200 No additives Flammable @17% Oil:G 29 Mac 6.6 Bld:g .47 Rapid alter depth anaes & fast recovery Pungent breath holding secretions apnoea CHF2 group - react soda lime = CO .02 mean- min tox effects
44
PD of sevo iso des
Resp depression Decrease TV Broncho diln Iso des drop SVR Map & tachy SVP dose dep drop CV Red SVR MAP contractility All decrease cerebral vascular resistance Cmr CBF Intracranial pressure None epileptigoenic All dose depend relax uterus MH trigger
45
Sevo metab
Metab 3-5% hepatic cyp450 2e1 Hexaflurousoprpanol Inorg fl
46
Compund A
Vinyl ester CH2F-O-C(CF3)=CF2 Dose dep renal hepatic cerebral dng Rats not nan Nephrotoxic to animals? Lethal conc 300-400ppm sevp 3hrs Threshold humans 150-200ppm inferred Conc human less than toxic conc in animals Max conc <30ppm after 5h even low flow Not a/w deranged renals
47
Compounds form CO w. Dry soda lime & why
``` Inhaled w. CHF2 Passed dry warm soda lime / baralyme Iso En Des ```
48
Which form CO w. Dry soda lime
``` Inhaled w. CHF2 Passed dry warm soda lime / baralyme Iso En Desh ```
49
Halothane hepatits
Type 1 Mild Self limiting hepatotox 25-30% Trans rise enzymes & altered metabolism Reductive metab halothane D/t hepatic hypoxia Others metab lesser extent other mechanised ``` Type 2 Uncommon Centrilonular liver necrosis Fulminanr failure Jaundice fever v elevated transaminase ``` High mortality 30-70% Immune mediated Oxidative metabolism -> TFA Hapten bind covalent protein= antibody fomation Type 2 Susceptible Repeated exposure RF obesity, hypoxaemia, female, middle age Dx exclusion Avoid if Hx adverse reaction Previous exposure 3/12 Hx unexpl jaund/ pyrexia after exposure
50
Xenon
Inert odorless noble Fract distillation air No occupation / enviro hazards Makes 0.000087% atm Non flam Not combustible Mac 71% Low bl:g .14 Extreme rapid Non irritant Compat soda Not metab Red RR increase TV = Same MV Higher density/ viscosity Doesnt appear = diffusion hypoxia PONV Cardiostable. No sense to catechol, unalt contractilty Unconciousness, Significant analgesic, Muyscle relax >60% Not MH trigger Increases CBF - not neuroanest Used enhanced CTB Radio labelled xenon - organ blood flow v/q scan Massive cost - X2000 more NO No designed machine - use Difficulty monitoring conc - lack experience use
51
Helium
Light, inert Present air & natural gas Supply 100% - brown cylinders 137 bar Heliox w 21% O2 brown white / quart shoulder not support ocombustion ``` Lower density o2, n & air Upper auirway obstruction - reduce wob Increase alverolar o2 supply less usefl - lower airway Flow is laminar depnding on viscoisty - ``` Deep sea diving - avoid nitrogen narcosis Lower denisty - high vocal cord frequency sounds Lung volumes measure - Low Solublitiy
52
MAC
``` Min alveolar conc - inhalation agent Sea level 1 atm & 100% o2 50% un premedicated usbject - fail repsopnd standard midline incision ``` ED 50 - 50% subjects other 50 will be higher or lower MAC 95 I
53
MAC is related to
Inversely to potency High MAC - low potency Plt oil g coeff - using log sacle -linear Measured usign etconc Rapid cerebral bloow flow - equil occurs rapidly Reach - conc alveoli & brain ~equal Guide clinical dosage Used simulatneosy additive 0.5 Sev & 0.5 N2O = 1MAC Prevention of movment - not awareness Awareness is less than that to prevent movemnet
54
MAC BAR
Block adrenergic response Increase in HR BP response to stimulus prevent in 50%
55
MAC Awake
MAC - 50% not respond to commands when conc gradully increase from awake state Alv conc - response aprpro emergncing
56
What factors decrease MAC
Increase age - 10% per 10 years ``` Hypo: Volaemia Thermia Oxia Capnia Natraemia Thyroidism ``` Anaem Prgenancy Acute alcohol CNS depress - opioo bzd Other drugs clonidine, lidocaine, NO
57
Increased Unaffected by
Decrease age Hyperthermia Hypercapnia Hypernatraemia Thyrotox Chronic alcohol & opiod Severe anxiety Sympathadrenal stim Ambient pressure Unaffected gender, weight, height druation anaes
58
``` Mac of Halothane iso en sevo des xeno no ```
``` Halo 0.75 iso 1.15 en 1.68 sevo 2 des 6.6 xenon 71 N2O 105 ```
59
``` Oil gas patition coeff halo Iso En Seco des xenon N2o ```
``` halo 224 Iso 98 En 98 Seco 53 des 19 xenon 1.9 N2o 1.4 ```
60
N2O What is it Who invented it
Inorganic gas number uses GA adjunct Anaglesic labour painful procedures Cryotherapy Priestly Chemist - prouce 1772 Humphrey 0 invx further 1799 0 Wells 1844 Dental extractions Not much use again til 1863 - Colton
61
Manufactured
heat ammonum nitrate to 250C NH4NO3 -> N2o & 2h20 ``` Temp carefully controlled Or will result in contaminants\; Ammonia Nitrogen N2o Nitro diox Hno3 ``` If inhaled - irrtant Pulmonary oedmany Destructive pulonary fibrosis 2-2 week Actively removed in maufacture of N2o Scurbbers water & caustic soda
62
How is N20 stored
Frenchblue cylidner as a liquid - w vapour on top Kept large cylinder in 2 manifold Gauge pressure 4400kpa - repesents content untill all in gaseosu phase Liquid less compressible gas - patially filled
63
Physical propetries N2O
Colouless gas - sweet smell Non flammble Does support comubstion Mol tw 44 BP -88 Crit temp 36.5 MAc 105% Oil: gas sol coeff 1.4 Blood gas sol ceff - 0.47
64
Advantages N2o
Potent analgesic - better anglesia than pethdine Weak anaes - >:80% - render unconc MAC 105% - comb w/ other - redcues mac Usfeul carier - Rapid onset - ow blood g coeff Incrase alveolar conc other agent - due to rapid uptake from alveolar Accel induction 'second gas effect'
65
Disadvantages
High diffsuing capactiy x25 N Non compliant - air filled vaity - middle ear Increase rapidly - diffusing into cavity Compliant air fill cavity - pnuemothorax / owel -diffuse in and increase volume Emtic effect: Opiod receptor Sympathtmietic effect Bowel distension Toxic effect BM suppresion Neurotox Second gas - duffsion hypoxia - doesnt present signif - resolve w/ supp O2 Resp depress - mcrase rate - red TV neg ino - exacrb IHD Pollution
66
explain analgesic effects of N20
Several ways 1. Opiod receptor potency of morhine - short time 2. Modulation of endorphin & encphalins -stim effect on dopaminergic neurones - release endog op pep -explains can antag w/ nalox 3. Supra spinal descending pain ihin system - release encephalins
67
Entonox
50:50 Mix N2O & O2 Analgesia - labour / procedure Store french blue - blue white shoulder 13700 kpa Crti temp 36.5 = n2o Mixture - -5.5 'Pseudocritical temp' Below temp = liquefaction -& seperation = mix N2o /w 20% dissolved O2 & high conc o2 above liquid O2 drawn first - reamin dissovled comes out solution = hypoxic mix ~ cloose 100% N2O Sep = 117 bar Delivery via pipleine 4 bar = pseudocrit
68
Poynting effect
Bubbling of O2 thru liq N2O Vaporisnation of liquid - form gaseous mix entonox - 2 gas dissolve into each behave diff as mix vs indicudal NOT what causes them to seperate
69
Explain the concentration effect
Conc effect - greater rate increase in alveolar conc when compared to inspire conc N2o High conc inspired N2O only = only n2o gets used in high conc demonstrate Large gradient generated by high concentration of N2o Ability to diffuse so rapidly Fills alveoli - large amount diffuse into pulmonary capillary - drawing gas from conducting airway into alveoli -> keep volume constant Ventilation increased to supply extra volume causes alveolar conc change more rapidly when conc are higher
70
Second gas efffect
D/T concnetration effect another gas - eg oxygen / volatile Use alongisde high conc n2o Conc alveoli x2 reasons 1 - rapid uptake of N20 2 - Increased ventilation Result 0- indction time shorted - increased conc volatile & increase O2 level
71
Explain diffusion hypxoia
Reverse second gas effect End anes - cease inhal N20 & gases turn off Volume diffuse blood into alveolus - great than gas diffuse alvoley to blood Dilution of o2 in alveolus & pooss hypxia Patient switch to 100% O2 - end of anaesthetic - no impact -clincally relevant if not oxygnated at end
72
Toxic effects of N2O
Inhibits mehtionine synthease Responsible for synthesis of Methionine, thymidine & tetrahydrolfate Oxise cobalt atom in b12 & b12 is cofactor Show occurs 40m N2o mewthionine prcuirese for myelin Low level - suiabacte degen cord in b12 defic Dorsal column impairment accutely Tetrahydrolfoate Important nucoletide in dna synth - N2o - Megaloblstic anaemi b12 & folate defic Terato gen - provne rat Meth synt - alpha adregno agonism A/w develop disorder situs inversus Toxic effects reverse folinic acid - another source tetrahydrolfate
73
Boliling points of the follow ``` triethyylne enflurane cholorform sevo des iso halothane cycolproane ```
The approximate boiling points of the different volatile agents are as follows: ``` Trichloroethylene 87°C Enflurane 56°C Chloroform 61°C Sevoflurane 58°C Halothane 50°C Isoflurane 48°C Desflurane 24 °C. Cyclopropane has a boiling point of −33°C. ```
74
MAC
Eger merkel = 1963 Conc anes prevent movement 50% to stim Index potencty inhaled product - oil gas coeff cant be determind by probit anaylsis
75
SVP is whats it dietyhl ether halothane constant boiling point =?
is the PP of vapour above liquid in closed container at equilibrium indicator of volatility varies with te`mp (increase) diethyl ether 59kpa halothane 32 at bp svp = atm pressure
76
Desflurance formula
CHF2 OCHFCF3
77
Sevo formula
CH2FOCHCF3(cf3)
78
Halothane mol wt bp svp oil gas macc blgas metab
mol wt 197 Da Bp 50 SCV 32 kpa O:G 224 Mac .75 B:G 2.4 20%
79
Isoflurane mol wt bp svp oil gas macc blgas metab
Mol 184 BP 48 SVP 33 Oil:G 98 Mac 1.17 B G 1.4 Metab 0.2
80
Sevo mol wt bp svp oil gas macc blgas metab
Sevo 200 48 33 80 1. 8 2.2 0. 7 3. 5
81
Des mol wt bp svp oil gas macc blgas metab
Des 168da 23.5 89 29 7.3 b;G .45 .02
82
N20 mol wt bp svp oil gas macc blgas metab
44 -88C 5200kPa 1.4 150 .47 0.01
83
Enflurane mol wt bp svp oil gas macc blgas metab
Enflurane 184. 5 56. 5C 23. 3 Oil@G 120 1.68 mac B:G 1.91 2%
84
Xenon mol wt bp svp oil gas macc blgas metab
131 -108 n/A 1.9 71mac .14 bl g na metab
85
N2o can be contam with which of these can prod pulm oedma and what afte rhow long How is it manufcat
Nictric oxide NO2 (nitrogen dioxide) Higher oxides = pulm oedema pulmonary fibrosis 2-3 weeks later Also prod methaem Heat ammon nitrate 240 Ammonia produces may contam also causes pul oed
86
Max PPM of subs 10 50 100
10- halothane 50 max - Iso + Enflurane 100 nitrous oxide
87
Which agent at steady state does amt deliver most closely match amount removed via lungs
Nitrous - as least metab .01% Iso .2% metab steady sate - pp agent alveoli ==== arterial blood == brain - difference delivered + removed equal meatb agent min metab - sml diff amount deliver remove des .02% metab
88
Iso and enflurane what about eeg
structual isomers .2% iso metab 2% enflurane 3hz spike eeg - a/w high conc enflurane in hypocapnic
89
Partition coeff -
ratio sub present 1 phase vs other 2 phases - equal vol in equil
90
Otswald solubil - is nitrous more soluble in oil or blood
indicates slubility in blood Oil 37 -1.4 will dissolbe in oil vs .47 im b;ppd
91
malignant hyperpyrexia
Autosomal dominant p may be more complex 1:5000 / 1:10000 Ryanodine rec chr 19 increase intra cell Ca Reduction tendnecy with increasing age (most seem to have had 3 prev uneventful GA) Mortalilty ~ 70% without flush machine 100% for 20-30 mins
92
Dantrolene
Skeletal muscle relaxant directly affects excitation contraction cpupling ibn skel muscle reducing amt ca rel from SR No effect NMTmission/memb potent/excitability Effective in Rx mH do 1-10mg May reduce sux pains if given preop
93
Mol wts
Des 164 Iso En 184 Halo 197 Sevo 200

Pharmacology (15 decks)

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