Decreased respiratory depression during emergence from anesthesia with sevoflurane/N2O than with sevoflurane alone.
OBJECTIVE
To investigate ventilation and gas elimination during the emergence from inhalational anesthesia with controlled normoventilation with either sevoflurane/N2O or sevoflurane alone.


METHODS
Twenty-four ASA I-II patients scheduled for abdominal hysterectomy were randomly allocated to receive either 1.3 MAC sevoflurane/N2O (n = 12) or equi-MAC sevoflurane (n = 12) in 30% oxygen (O2). Expired minute ventilation volumes (V(E)), end-tidal (ET) concentrations of O2, carbon dioxide (CO2), sevoflurane and N2O as well as pulse oximetry saturation (SpO2) and CO2 elimination rates (VCO2) were measured. The ET concentrations of sevoflurane and N2O were converted to total MAC values and gas elimination was expressed in terms of MAC reduction. Time to resumption of spontaneous breathing and extubation were recorded and arterial blood gas analysis was performed at the end of controlled normoventilation and at the beginning of spontaneous breathing.


RESULTS
Resumption of spontaneous breathing and extubation were 8 and 13 min less, respectively, in the sevoflurane/N2O than in the sevoflurane group. Spontaneous breathing was resumed in both groups when pH had decreased by 0.07-0.08 and PaCO2 increased by 1.3-1.5 kPa. Depression of V(E) and VCO2 were less, and MAC reduction more rapid in the sevoflurane/N2O than in the sevoflurane group.


CONCLUSIONS
Respiratory recovery was faster after sevoflurane/N2O than sevoflurane anesthesia. Changes in pH and PaCO2 rather than absolute values were important for resumption of spontaneous breathing after controlled normoventilation. In both groups, the tracheas were extubated at about 0.2 MAC.
Einarsson
S
S
Department of Anesthesia and Intensive Care, Reykjavik Hospital (University Teaching Hospital), Iceland. sveinng@shr.is
Bengtsson
A
A
Stenqvist
O
O
Bengtson
J P
JP
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000762:Anesthesia Recovery Period; D018685:Anesthetics, Inhalation / Q000008:administration & dosage* / Q000097:blood; D002245:Carbon Dioxide / Q000097:blood / Q000378:metabolism; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007044:Hysterectomy; D007442:Intubation, Intratracheal; D008451:Maximal Voluntary Ventilation / Q000187:drug effects; D008738:Methyl Ethers / Q000008:administration & dosage* / Q000097:blood; D008875:Middle Aged; D009609:Nitrous Oxide / Q000008:administration & dosage* / Q000097:blood; D010100:Oxygen / Q000008:administration & dosage / Q000097:blood; D011659:Pulmonary Gas Exchange / Q000187:drug effects; D012119:Respiration / Q000187:drug effects*; D000077149:Sevoflurane; D013990:Tidal Volume / Q000187:drug effects; D013997:Time Factors
D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D002245:Carbon Dioxide; D000077149:Sevoflurane; D009609:Nitrous Oxide; D010100:Oxygen