Bench-to-bedside review: Molecular pharmacology and clinical use of inert gases in anesthesia and neuroprotection

Table 1 Physical properties of the inert gases and nitrogen

Physical property	Helium	Neon	Nitrogen	Argon	Krypton	Xenon
Atomic number	2	10	7	18	36	54
Atomic mass (g/mol)^a	4.0	20.2	14.0	39.9	83.8	131.3
Density (g/l) (0°C)^a	0.1785	0.900	1.251	1.784	3.736	5.887
Thermal conductivity (W/m/K) (300 K)^b	0.1499^a	0.0491	0.0260^a	0.0178	0.0094	0.0056
Polarizability α (Å³)^c	0.21	0.39	1.74	1.64	2.48	4.04
Water/gas partition coefficient at 25°C^d	0.0085	0.010	0.015	0.031	0.053	0.095
Oil/gas partition coefficient at 25°C^d	0.016	0.019	0.07	0.14	0.44	1.9
General anesthesia (atm)^d	Not anesthetic	Not anesthetic	39	15.2	4.5	0.95 (mouse), 0.6 to 0.7 (human)

Partition coefficients are experimentally measured Bunsen coefficients. Anesthetic potency data for nitrogen, argon and krypton are for loss of righting reflex in mice. For xenon, values are given for loss of righting reflex in mice and general anesthesia minimum alveolar concentration in humans (see text for minimum alveolar concentration values). Data compiled from the following sources: ^aCRC Handbook of Chemistry & Physics [107]. ^bSelovar [108]. ^cTrudell and colleagues [106]. ^dRoth and Miller [109].

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