Inhaled Anethetics Flashcards
Why chloroform bad/good
Bad: hepatotoxic, cv depressant, deaths assoc, hard to admin
Good: good odor, nonflammable
First halogenated hydrocarbon anesthetic, why taken off market
Fluroxene. Organ tox
Methoxyflurane: pro and con
Pro: potent, mac 0.16, soluble
Bad: vasopressin resistant high output renal failure
Guedel stages of anesthesia
1- amnesia/analgesia
2- delirium/excitement
3- surgical anes 4 planes
4- OD
N20
Mac
Blood gas partition coefficient
105%. 0.47
Balanced technique=
N20 + induction agent + muscle relaxant + opioids +/- volatile agent
N20
Effective ___
70% n20 + 02 ___ mac for halothane, Enflurane, ISO, sevo, and des
Analgesic
Reduces
Contraindications to N2O
Air embolism, ptx, intestinal obstruction (acute), intracranial air, pulm air cysts, intraocular air bubbles, tympanic membrane grafting. Others: 1st tri preg, b12 def, CAD
Drug consid w N2O
Can’t use alone (high MAC), decreases MAC reqs of other agents, potentiates NMB
Halothane
VP
B/G
MAC %
VP 243
B/G 2.3
MAC .74
Enflurane
VP
B/G
MAC
VP 175
B/G 1.8
MAC 1.68
Isoflurane
VP
B-G
MAC
VP 239
B-G 1.4
MAC 1.15
Des
VP
B-G
MAC
VP 664
B-G 0.69
MAC 6
Sevo
VP
B-G
MAC
VP 157
B-G 0.69
MAC 2.05
N20
VP
B-G
MAC
38, 770
0.47
104
Factors that dont affect MAC 6
Variable stimuli, species, gender, duration of anesthesia, acid-base disturbances, Pa02 (40-500 torr)
Factors that decrease MAC
Inc age, hypothermia, low Na, BP <40, pregnancy, 02 <38, anemia 4.3, opioids, ketamine, benzos, clonidine, A2 agonists, LAs, ETOH acute
Factors that increase MAC
Hyperthermia, CNS stimulants, under 1 year old
___% move at 1 MAC
Give what to avoid movement when no muscle relaxant given
50%
Give 10-30% above 1 mac (1.3)
MAC awake
Concentrations you have to give of anesthetics
1/3: des, sevo, iso
1/2: halothane
60%: n20
Which inhaled agent decreases BP the least
N20- no change
Sevo- mild decrease
Which inhaled agents increase HR
Methoxyflurane, enflurane, isoflurane, Des (or no change)
Which inhaled agents decrease or dont affect hr
N20 (n/c), halothane decreases, sevo (inc or n/c), sevo (n/c)
Which agents drastically decrease SVR
Isoflurane, desflurane
Which agents mildly decrease SVR
Enflurane, sevoflurane
Which agents decrease CO
Halothane, methoxyflurane, isoflurane (the most), des (or n/c), sevoflurane
Which agents decrease TV a lot
Halothane, methoxyflurane, enflurane, isoflurane
Which agents decrease TV a little
N2O, desflurane, sevoflurane
Which agents inc RR a lot
Halothane, methoxyflurane, enflurane
Which agents inc rr a little
N20, isoflurane, desflurane, sevoflurane
Which agents inc paco2 the most
Enflurane and desflurane
Which agent inc cerebral bf the most
Halothane
Which agents inc ICP the most
Halothane, enflurane
Which agents dec cmro2 the most
Isoflurane, desflurane, sevoflurane
Which agent inc seizures
Enflurane (all others decrease them)
Which agent inc NMDR 1 on scale of 1-3
N20
Which agent inc NMDR 2 on scale of 1-3
Halothane, methoxyflurane, sevoflurane
Which agents inc NMDR the most
Enflurane, isoflurane, desflurane
Which agents dec renal bf the least
Desflurane and sevoflurane
Which agents dec hepatic bf the most
Halothane, methoxyflurane, enflurane
Metab %
Halothane
Enflurane
15-20%
2.5-3%
Metab %
Sevoflurane
Isoflurane
2-5%
0.2-2%
Metab %
Desflurane
N20
- 02%
0. 004% (gi tract)
When to not use halothane
CAD Arrhythmias, epi use Hepatotoxicity (esp prev halothane exposure) Hypovolemia AS Pheochromocytoma MH- most potent trigger
Halothane drug interac
Myocardial dep w/: bb and ccb. TCAs and MAOI may cause BP instability. Aminophylline- v dysrhythmias
When to not use enflurane
Seizures, renal disease, MH trigger
Isoflurane contraindications
Peds (laryngospasm), CAD (coronary steal), MH
When to not use Des
Not used for inhalation in peds bc of smell, neurosurgery, MH
Sevo
When to use/not use
Good for peds. Fast on/off.
Not: kidney function dec, MH
