Respiratory effects of sevoflurane used in combination with nitrous oxide and surgical stimulation.
OBJECTIVE
To evaluate the respiratory effects of sevoflurane anesthesia with and without nitrous oxide (N2O) during surgical stimulation.


METHODS
Randomized study.


METHODS
Operating theater at a university hospital.


METHODS
10 patients scheduled for minor head or neck surgery.


METHODS
Sevoflurane anesthesia was administered alone or in combination with N2O. After basal measurements were recorded, the following end-tidal anesthetic concentrations were administered: Group 1 = 1.3 minimum alveolar concentration (MAC) sevoflurane alone; Group 2 = 0.9 MAC sevoflurane with 0.4 MAC N2O; Group 3 = 1.5 MAC sevoflurane alone; Group 4 = 1.1 MAC sevoflurane with 0.4 MAC N2O.


RESULTS
PaCO2, minute volume (VE), respiratory rate, tidal volume (VT), percentage of rib cage contribution to tidal volume (%RC), rate of inspiratory time in a breath cycle (TI/Ttot, where TI = inspiratory time and Ttot = tidal respiratory time), and mean inspired flow (VT/TI) were measured. The substitution of 0.4 MAC N2O for sevoflurane decreased PaCO2 and increased VE, with a consequent increase in VT. At 1.3 MAC sevoflurane-N2O anesthesia, spontaneous respiration maintained PaCO2 at appropriate levels (42.7 +/- 3.6 mmHg). At 1.3 MAC sevoflurane alone and 1.5 MAC sevoflurane-N2O anesthesia, spontaneous respiration was moderately depressed. Sevoflurane and N2O combined did not change %RC or TI/Ttot.


CONCLUSIONS
Sevoflurane administered at an appropriate anesthetic depth maintained spontaneous respiration at acceptable levels during surgical stimulation, especially when combined with N2O.
Doi
M
M
Department of Anesthesiology and Intensive Care, Hamamatsu University School of Medicine, Japan.
Takahashi
T
T
Ikeda
K
K
D000293:Adolescent; D000758:Anesthesia; D000777:Anesthetics; D004987:Ethers; D005260:Female; D006801:Humans; D008297:Male; D008738:Methyl Ethers; D008875:Middle Aged; D013511:Minor Surgical Procedures; D009609:Nitrous Oxide; D012119:Respiration / Q000187:drug effects* / Q000502:physiology; D000077149:Sevoflurane
D000777:Anesthetics; D004987:Ethers; D008738:Methyl Ethers; D000077149:Sevoflurane; D009609:Nitrous Oxide