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Persisting concentrating and second gas effects on oxygenation during N 2 O anaesthesia
Author(s) -
Peyton P. J.,
StuartAndrews C.,
Deo K.,
Strahan F.,
Robinson G. J. B.,
Thompson B. R.,
Pierce R.
Publication year - 2006
Publication title -
anaesthesia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.839
H-Index - 117
eISSN - 1365-2044
pISSN - 0003-2409
DOI - 10.1111/j.1365-2044.2006.04579.x
Subject(s) - medicine , nitrous oxide , oxygenation , anesthesia , general anaesthesia , perfusion , ventilation (architecture) , oxygen , breathing , cardiology , mechanical engineering , chemistry , organic chemistry , engineering
Summary Theoretical modelling predicts that the concentrating effect of nitrous oxide (N 2 O) uptake on alveolar oxygenation is a persisting phenomenon at typical levels of ventilation – perfusion (V/Q) inhomogeneity under anaesthesia. We sought clinical confirmation of this in 20 anaesthetised patients. Arterial oxygen pressure ( P a o 2 ) was measured after a minimum of 30 min of relaxant general anaesthesia with an inspired oxygen ( F I o 2 ) of 30%. Patients were randomly allocated to two groups. The intervention group had N 2 O introduced following baseline blood gas measurements, and the control group continued breathing an identical F I o 2 in nitrogen (N 2 ). The primary outcome variable was change in P a o 2 . Mean (SD) in P a o 2 was increased by 1.80 (1.80) kPa after receiving a mean of 47.5 min of N 2 O compared with baseline conditions breathing O 2 /N 2 (p = 0.01). This change was significantly greater (p = 0.03) than that in the control group: + 0.09 (1.37) kPa, p = 0.83 and confirms the presence of significant persisting concentrating and second gas effects.