Inhalational anaesthetic agents

[SH4:p42; BH1:p47]

=== Unfinished ===

Transpose the tables when I get a chance.

Gases on the left hand side, and properties on top (to bring it in line with LAs, IV, and local)

======

History

1840s - Discovery of anaesthetic properties of diethyl ether, nitrous oxide, and chloroform
1930s - Discovery that fluorination of molecules decreased flammability and toxicity
1950s - First fluorinated agent (fluroxene) introduced

Introduction for clinical use

1951 - Fluroxene
1956 - Halothane
1960 - Methoxyflurane
1973 - Enflurane
1981 - Isoflurane
1992 - Desflurane
1994 - Sevoflurane

Overview

[SH4:p43]

Only halothane and sevoflurane are not stable in soda lime at 40 degrees
Halothane and sevoflurane are non-pungent
Only halothane requires preservative

Inhalational anaesthetics

Halothane Enflurane Isoflurane Desflurane Sevoflurane N2O Xenon Comment

Blood:gas coefficient [SH4:p43] 2.54 1.90 1.46 0.42 0.69 0.46 0.115 Use this

Blood:gas coefficient [EEW1:p45] 2.4 1.4 0.45 0.65 0.46

Oil:gas coefficient [RDM6:p236] 90 18.7 53.4 1.4 1.9

Oil:gas coefficient [EEW1:p45] 224 98 19 47 1.4

MAC [SH4:p43] 0.75% 1.63% 1.17% 6.6% 1.80% 104% 63-71% Use this

MAC [RDM6:p236] 1.15% 6% 1.71% 105% 71%

MAC [RDM6:p115] 0.74% 1.68% 1.15% 6% 2.05% 104% 71%

MW 197 184 184 168 200 44 131

Boiling point (degree Celcius) 50.2 56.5 48.5 22.8 58.5 -88.5 -108

Vapour pressure at 20C (mmHg) 244mmHg 172 mmHg 240mmHg 669mmHg 170mmHg gas gas

Inhalational anaesthetics
	Halothane	Enflurane	Isoflurane	Desflurane	Sevoflurane	N2O	Xenon	Comment
Blood:gas coefficient [SH4:p43]	2.54	1.90	1.46	0.42	0.69	0.46	0.115	Use this
Blood:gas coefficient [EEW1:p45]	2.4		1.4	0.45	0.65	0.46
Oil:gas coefficient [RDM6:p236]			90	18.7	53.4	1.4	1.9
Oil:gas coefficient [EEW1:p45]	224		98	19	47	1.4
MAC [SH4:p43]	0.75%	1.63%	1.17%	6.6%	1.80%	104%	63-71%	Use this
MAC [RDM6:p236]			1.15%	6%	1.71%	105%	71%
MAC [RDM6:p115]	0.74%	1.68%	1.15%	6%	2.05%	104%	71%
MW	197	184	184	168	200	44	131
Boiling point (degree Celcius)	50.2	56.5	48.5	22.8	58.5	-88.5	-108
Vapour pressure at 20C (mmHg)	244mmHg	172 mmHg	240mmHg	669mmHg	170mmHg	gas	gas

Simplied table of inhalational anaesthetics

Halothane Enflurane Isoflurane Desflurane Sevoflurane N2O Xenon Comment

Blood:gas 2.54 1.90 1.46 0.42 0.69 0.46 0.115 Xe = lowest,

Oil:gas 224 98 19 47 1.4 N2O less oil soluble, but more blood soluble than desflurane

MAC 0.75% 1.63% 1.17% 6.60% 1.80% 104% 71% Hal = lowest, N2O > 100%

MW 197 184 184 168 200 44 131 S>H>E=I>D

Boiling point 50.2 56.5 48.5 22.8 58.5 -88.5 -108 Des = lowest, Iso = second lowest, Sev = highest

Vapour pressure at 20C 244 mmHg 172 mmHg 240 mmHg 669 mmHg 170 mmHg gas gas Des = highest, Sev = lowest

Simplied table of inhalational anaesthetics
	Halothane	Enflurane	Isoflurane	Desflurane	Sevoflurane	N2O	Xenon	Comment
Blood:gas	2.54	1.90	1.46	0.42	0.69	0.46	0.115	Xe = lowest,
Oil:gas	224		98	19	47	1.4		N2O less oil soluble, but more blood soluble than desflurane
MAC	0.75%	1.63%	1.17%	6.60%	1.80%	104%	71%	Hal = lowest, N2O > 100%
MW	197	184	184	168	200	44	131	S>H>E=I>D
Boiling point	50.2	56.5	48.5	22.8	58.5	-88.5	-108	Des = lowest, Iso = second lowest, Sev = highest
Vapour pressure at 20C	244 mmHg	172 mmHg	240 mmHg	669 mmHg	170 mmHg	gas	gas	Des = highest, Sev = lowest

Carbon monoxide production

Carbon monoxide is produced when inhalational anaesthetics degrades during interaction with the strong base in desiccated carbon dioxide absorber

Desflurane produces the highest carbon monoxide
Then enflurane and isoflurane
Negligible with halothane and sevoflurane