The Effect of Concentration of Nitrous Oxide on Bispectral Index and Sedation Score / 대한마취과학회지

BACKGROUND: Bispectral index (BIS) has been designed to measure objectively the degree of sedation and hypnosis for several anesthetics. It is predicted that sedation and hypnosis during nitrous oxide inhalation affect BIS in an unusual manner due to a different mechanism compared to usual hypnotics. The aim of this study was to evaluate the effect of different concentration of nitrous oxide inhalation on BIS and sedation score. METHODS: Forty unpremedicated ASA physical status I or II patients scheduled for lower extremity surgery were studied. After performing epidural anesthesia, patients inhaled gradually increasing concentrations of nitrous oxide from 0 to 67% (15 minutes for each concentration) via a tightly sealed face mask. At the end of each inhalation, BIS and OAA/S scale (Observers's Assessment of Alertness/ Sedation scale) were assessed. RESULTS: The increasing concentrations of inhaled nitrous oxide resulted in significant reduction of the OAA/S scale but in no change of BIS. Concentrations of nitrous oxide exceeding 50% affected behavior or emotion of the patients. CONCLUSIONS: Following increasing concentrations of inhaled nitrous oxide, sedation score was reduced significantly but BIS was not affected.

Hypercarbia Due to Mistaken Supply of Carbon Dioxide Originating from Nitrous Oxide Gas Tank: A case report / 대한마취과학회지

A 49 year-old male was scheduled for a cholecystectomy, thereafter a 37 year-old female scheduled for removal of a epidural hematoma in the same operating room. Both of them had no specific medical problems and past medical histories for anesthesia. For those reasons, anesthesia was induced with thiopental sodium and succinylcholine with endotracheal intubation. After induction, vital signs including body temperatures were stable. But moisture dew in the unidirectional valves and corrugated tubes, and color changes of soda lime were discovered. At that time, severe hypercarbia was recognized by arterial blood gas analysis in both cases. In both cases, there were no malfunctions in unidirectional valves, expiratory valves, corrugation tubes, soda lime, ventilators and there connection parts in the anesthetic machines. Also there were no abnormalities of blood pressures, electrocardiograms, pulse oxymeters, temperatures and the pulse in the patient monitoring systems except capnography. At first, we thought that medical signs revealed malignant hyperthermias. But vital signs, air way pressures and functions of all kinds of anesthetic machine components including ventilators were normal. After discontinuing N2O gas deliveries in the operation room, hypercarbias disappeared. Thus, anesthetic gas delivery systems via central piping systems were checked and it was discovered that CO2 gas was in the N2O gas tank instead of N2O.

The Cardiovascular Effects of Epinephrine Used for Hemostasis under Enflurane-N2O Anesthesia during Tonsillectomy / 대한마취과학회지

BACKGROUND: Exogenously administered epinephrine under enflurane anesthesia was known to have mild myocardial sensitizing effect. And N2O activates the sympathetic nervous system mildly. We planed this study to confirm cadiovascular effects of clinically administered epinephrine for hemostasis under the enflurane-N2O anesthesia during tonsillectomy. METHODS: Eighty children scheduled to have tonsillectomy were selected randomly and divided into 2 groups as follows; Group E: 1:100,000 epinephrine 2ug/kg and Group EL: 1:100,000 epinephrine containing 1% lidocaine 2 g/kg. Blood pressure, heart rate, and the occurrence of arrhythmia were evaluated before injection, at injection, 1 min, 2 min, 3 min, 5 min and 10 min after injection and 1 min after operation start. RESULTS: In both groups, systolic and diastolic blood pressure and heart rate are increased. But there are no significant statistical differences in each group and between groups. One min after operation, there are significant increases in systolic and diastolic blood pressure and heart rate in both groups (p<0.05), but there is no significant difference between groups. CONCLUSION: Under the enflurane-N2O anesthesia of children, 1:100,000 epinephrine 2ug/kg used for hemostasis could be used comparatively safe without any significant hemodynamic changes. But because there is always the possibility of myocardial sensitization, careful observation is necessary during epinephrine injection under the enflurane-N2O anesthesia.

Comparison of Propofol-N2O and Propofol-fentanyl Anesthesia for Outpatient Surgery / 대한마취과학회지

BACKGROUND: The choice of anesthetic agents and adjuvants during outpatient surgery is of critical importance. Propofol is widely used for the induction and maintenance of outpatient anesthesia. Because propofol lacks analgesic properties, very high concentrations may be required when propofol is used as the sole anesthetic drug. Propofol is used with adjuvants such as nitrous oxide or opioid. This study was designed to evaluate the intraoperative hemodynamic response, recovery characteristics and side effects of propofol-fentanyl anesthesia compared with propofol-N2O anesthesia for outpatient surgery. METHODS: Twenty six healthy and unpremedicated patients scheduled for outpatient surgery were randomly allocated to receive either propofol-N2O anesthesia (N-group) or propofol-fentanyl anesthsia (F-group). The patients in N-group were ventilated with nitrous oxide 60~70% in oxygen and the patients in F-group were ventilated with oxygen 40% in nitrogen via laryngeal mask airway (LMA). RESULTS: There was no significant difference in blood pressure during anesthesia, recovery time and side effects between two group. There was significant decrease of heart rate in F-group. CONCLUSION: We concluded that nitrous oxide and fentanyl are reasonable adjuvants of propofol anesthesia in outpatient anesthesia.