Case Reports: Letters to the Editor
To the Editor
Interest in xenon anesthesia is on the rise.1 An increase in tidal volume and a decrease in respiratory rate (5 breaths/min) have been described at 40% xenon.2 We report a patient with a respiratory rate of 1 breath per minute during 32% xenon anesthesia seated in a MEG (magnetoencephalogram) recorder. He was the fourth subject to form a pilot series leading into an imminent crossover trial to investigate the effects of various concentrations of xenon and nitrous oxide upon simultaneous electroencephalogram (EEG) and MEG readings in healthy volunteer adult males. There were 3 anesthesiologists present, one of whom was in the MEG with the subject. He had lost consciousness (as judged by close observation and persistent loss of responsiveness to auditory signal), and there was no respiratory obstruction or desaturation. Modification of the circuit prevented an accurate measurement of tidal volume; however, the end-tidal CO2, measured close to the facemask, remained constant.
This subject is a recreational free diver with a vital capacity of 124% predicted. Free diving involves long periods of apnea, and physiological adaptations such as increased vital capacity are reported.3 The patient had no recall of voluntarily apnea during the xenon administration. Hemodynamics remained stable. Although xenon is rarely used as a sole anesthetic in the spontaneously breathing patient, this extremely low respiratory rate is reported to add to the previously noted mild respiratory rate decrease.
John R. Cormack, MDDepartment of Anaesthesia and Pain ManagementSt. Vincent’s Hospital MelbourneMelbourne, Australiacormackj@ozemail.com.au
Jarrod GottDepartment of Health and Medical SciencesSwinburne UniversityMelbourne, Australia
Sarah Kondogiannis, MDDepartment of Health and Medical SciencesSwinburne UniversityMelbourne, Australia
1. Maze M, Pirracchio R. Will xenon be a valuable addition in perioperative and critical care settings? Anesth Analg. 2016;122:593596.
2. Bedi A, McCarroll C, Murray JM, Stevenson MA, Fee JP. The effects of subanaesthetic concentrations of xenon in volunteers. Anaesthesia. 2002;57:233241.
3. Ostrowski A, Strzała M, Stanula A, Juszkiewicz M, Pilch W, Maszczyk A. The role of training in the development of adaptive mechanisms in freedivers. J Hum Kinet. 2012;32:197210.