Negative pressure in the middle ear in children after nitrous oxide anaesthesia

A study was conducted to measure the pressure in the middle ear in healthy children, following nitrous oxide anaesthesia. Premedication with chloral hydrate and scopolamine orally was similar in all patients and awake patients received thiopentone 4-5 mg X kg-1 for induction of anaesthesia. All received nitrous oxide (66 per cent) in oxygen and halothane or isoflurane as required. Exposure to nitrous oxide varied from 17-100 minutes, mean 47 minutes. All patients developed negative pressure in one or both ears in the first day following anaesthesia. This is a higher incidence than previously reported and may be explained by the inability of children to equilibrate negative middle ear pressure via the eustachian tube.