BACKGROUND: LMA has larger dead-space than tracheal tube, ventilation may be influenced by difference of dead space. Closed circuit mechanical ventilation has high risk of hypercarbia because of inadequate CO2 elimination or gas supply. Thus, end-tidal carbon dioxide tension (EtCO2) and arterial carbon dioxide tension (PaCO2) were compared during closed circuit mechanical ventilation with LMA or tracheal tube. METHODS: Thirty adult patients scheduled for general anesthesia were divided into 2 groups. After induction of general anesthesia, laryngeal mask airway (Group 1, n=15) or tracheal tube (Group 2, n=15) were randomly inserted and closed circuit mechanical ventilation was initiated. When steady state had been reached, PaCO2 and EtCO2 were recorded. RESULTS: The PaCO2 was 32.2+/-2.8 (Group 1), 31.5+/-2.2 (Group 2) and the EtCO2 was 33.0+/-2.9, 31.6+/-2.4 respectively and there was no statistical significance between groups. The difference of arterial and end-tidal carbon dioxide tension in each group was -0.8+/-2.6, -0.03+/-2.2 respectively and there was no statistical significance between groups. CONCLUSIONS: The results indicate that in patients who are mechanically ventilated via the closed circuit system, EtCO2, PaCO2, and the difference between arterial and end-tidal carbon dioxide tension were not significantly different between groups.
Adult ; Anesthesia, Closed-Circuit* ; Anesthesia, General ; Carbon Dioxide ; Humans ; Laryngeal Masks ; Respiration, Artificial ; Ventilation*

After the establis banent for the necessity of denitrogenation in rebreathing anesthesia circuits some decades ago, many techniques were recommended for venilation with oxygen before induction of anestesia for the purpose of maintaining arterial oxygenation during laryngoscopy and tracheal intubation. For this point of view, we compared PaO2, MAP, PaCO2, pH of non-preoxygenation group (oxygen was given after succinylcholine was injected) with those of preoxygenation group (oxygen was given after thiopental sodium was injected). The cases were selected randomly ASA class I or II (without cardiopulmonary abnormalities) and ages between 27 years and 66 years old. Before induction of general anesthesia, we cannulated the radial artery after Allen's test and sampled arterial blood before anesthesia, after thiopenthal and succinylcholine were injected respectively, and when tracheal intubation was done in the two groups and measured PaO2, PaCO2, MAP, pH respectively. PaCO2, MAP, pH changes in the two groups were not significant and of no clinical significance. PaO2 after tracheal intubation showed a marked increase in the preoxygenation group compared to the non-preoxygenation group but the mean PaO2, remained within normal range in the non-preoxygenation group with the apneic period of taecheal intubation. We found that non-preoxygenated patients also had a normal range of PaO2 during the whole process of induction of anesthesia. But we think preoxygenation technique of any method can reserve more time and will do more effeclively, especially when time consuming events of difficult intubation of any reason occur.
Aged ; Anesthesia ; Anesthesia, Closed-Circuit ; Anesthesia, General* ; Humans ; Hydrogen-Ion Concentration ; Intubation ; Laryngoscopy ; Oxygen ; Radial Artery ; Reference Values ; Succinylcholine ; Thiopental

BACKGROUND: Adequate humidification of anesthetic gases has been recommended both for the prevention of pulmonary damage during endotracheal anesthesia and for the maintenance of body temperature, especially in long-duration operated patients. Partial rebreathing anesthesia technique frequently lacks adequate humidity. So, this study was designed to compare inspired humidities in partial rebreathing anesthesia method with and without humidifier in the system. METHODS: The author examined inspired humidity using a controlled partial rebreathing anesthesia method with and without Bird humidifier in 10 and 22 healthy adult patients respectively. The patients were divided into two groups (1 and 2). All patients were anesthetized with pancuronium, halothane or enflurane, nitrous oxide-oxygen, 50-50 per cent, and their lungs were mechanically ventilated. Inspired humidity was measured for three hours at 30-min intervals in both groups. RESULTS: Significant differences were found among group 1- and 2-inspired humidities for 3 hours. While group 2-inspired humidity remained constant between 13 and 16 mgH2O/L during entire anesthesia procedure group 1-inspired humidity remained under 9 mgH2O/L. CONCLUSIONS: The humidities in all partial rebreathing anesthesia method with Bird humidifier not only exceeded those of method without humidifier but also seemed to be high enough to prevent dysfunction of tracheobronchial ciliated epithelium, while the standard partial rebreathing anesthesia method does not provide adequate inspired humidity.
Adult ; Anesthesia ; Anesthesia, Closed-Circuit* ; Anesthetics, Inhalation ; Birds* ; Body Temperature ; Enflurane ; Epithelium ; Gases* ; Halothane ; Humans ; Humidity* ; Lung ; Pancuronium

BACKGOUND: The effect of anesthetic techniques, such as closed circuit anesthesia (CCA) using semiclosed circuit system and semiclosed circuit anesthesia (SCCA), on the work of breathing has not been studied yet in detail. This study was purposed to compare the work of breathing according to anesthetic technique (CCA, SCCA). METHODS: Thirty patients were assigned to receive either SCCA group or CCA group (n = 15). Anesthesia was induced with propofol 2 mg/kg with 2% lidocaine 1 ml. Two percents isoflurane with O2 and N2O 2 L/min were given for 10 min to patients initially to wash in functional residual capacity and the breathing circuits. In SCCA group, anesthesia was maintained with 2% isoflurane in O2 2 L/min and N2O 2 L/min throughout the surgery. In CCA group, O2 was reduced to 200 ml/min and N2O to 100 ml/min with isoflurane vaporizer setting adjusted to 4% for anesthesia maintenance. When the operation was ended, the vaporizer setting of isoflurane deceased to zero and then O2 was increased to 4 L/min for the arousal of the patient. We measured the inspiratory/expiratory concentration of isoflurane, end-tidal CO2, the hemodynamic parameters, the change of airway pressure, the work of breathing, and compliance at anesthetic induction and emergence in both groups. RESULTS: There were no significant differences in the inspiratory/expiratory concentrations of isoflurane, the hemodynamic parameters, end-tidal CO2, airway pressure, the work of breathing and compliance between the groups. CONCLUSIONS: CCA using semiclosed circuit system does not increase the work of breathing compared to SCCA.
Anesthesia ; Anesthesia, Closed-Circuit* ; Arousal ; Compliance ; Functional Residual Capacity ; Hemodynamics ; Humans ; Isoflurane ; Lidocaine ; Nebulizers and Vaporizers ; Propofol ; Respiration ; Work of Breathing*

After the description of the necessity of denitrogenation in rebreathing anesthesia circuits some decades ago, many methods were recommended for techniques of ventilation with oxygen before induction of anesthesia for the purpose of maintaining arterial oxygenation during laryngoscopy and tracheal intubation . In this point of view, we compared PaO2, MAP, PaCO2, pH of non-preoxgenation group(oxygen was given after succinylcholine was injected) with those of preoxygenation group(owygen was given after thiopental sodium was injected). The cases were selected randomly who blongs to ASA class l or ll(without cardiopulmonary abnormalities) and ages betweens 27 years and 66 years old. Before induction of general anesthesia, we cannulated radial artery after Allen's test and sampled arterial blood before anesthesia, after thiopenthal and succinylcholine were injected respectively, when tracheal intubation was done in the two groups and measured PaO2, PaCO2, MAP, pH respectively. PaCO2, MAP, pH changes in the two groups were not significant and of no clinical significanses. PaO2 after tracheal intubation showed marked increase in preoxygenation group compared to non-preoxygenation group but mean PaO2 was maintained within normal range in non-preoxygenation group with the apnetic period of tracheal intubation. WE found that non-preoxygenated patients also had normal range of PaO2 during the whole process of induction of anesthesis. But I think preoxygenation technique of any method can reserve more time and will do more effectively, especially when times consuming events of difficult intubation of any reason occurs.
Aged ; Anesthesia ; Anesthesia, Closed-Circuit ; Anesthesia, General* ; Humans ; Hydrogen-Ion Concentration ; Intubation ; Laryngoscopy ; Oxygen ; Radial Artery ; Reference Values ; Succinylcholine ; Thiopental ; Ventilation

BACKGROUND: Core body temperature (TC) can decrease during general anesthesia. Particularly in elderly patients, more aggressive strategies to prevent intraoperative hypothermia may be required. Here, we investigated the effect of a heated humidifier on intraoperative TC decrease in the elderly. METHODS: Twenty-four elderly patients were randomly assigned into two groups: those who used a heated humidifier (group H) and those who used a conventional ventilator circuit with a heat moisture exchanger (group C). TC was measured continuously at the esophagus at several time-points during surgery. RESULTS: In group C, TC significantly decreased 90 minutes after skin incision (P < 0.001), while significant differences were not noted in group H during surgery. Comparing the two groups, TC decreased more in group C than in group H at 60, 90, 120, and 150 minutes after skin incision (group C vs. group H: -0.6℃ vs. -0.3℃, P = 0.025; -0.7℃ vs. -0.4℃, P = 0.012; -0.9℃ vs. -0.4℃, P = 0.006; and -1.0℃ vs. -0.5℃, P = 0.013, respectively). There were no significant differences between the two groups for any other parameters. CONCLUSIONS: A heated humidifier is more effective in preventing intraoperative TC decrease in elderly patients than a heat moisture exchanger. However, further studies with a larger population are required to substantiate its clinical use.
Aged* ; Anesthesia, Closed-Circuit ; Anesthesia, General ; Body Temperature* ; Esophagus ; Heating ; Hot Temperature* ; Humans ; Humidity ; Hypothermia ; Observational Study* ; Prospective Studies* ; Skin ; Ventilators, Mechanical

With the increased concern regarding air pollution in the operation theatre and the high cost of vapor anesthetics, closed circuit anesthesia has much to commend it. Since the demise of flammable anesthetics such as diethyl ether and cyclopropane, closed circuit anesthesia has been applied infrequently. Ernst and Lowe recently established a theoretic basis and reported quantitative data and a formula for closed circuit anesthesia. This involves frequent calculations to adjust the nitrous oxide flow and the vaporizer disls in accordance with the elapsed time. We attempted to evaluate their formula against our simplified method of adjusting only the N2O flow according to the N2O uptake rate calculated by Severinghaus. This method allows the output of the vapor from the plenum type vaporizer to diminish according to the decrease of N2O flow. Eighty patients undergoing closed circuit anesthesia were randomly divided into 4 groups of 20 patients each follows: Group l: Adjustment of the N2O flow and the halothane vaporizer dial by elapsed time, according to Ernst and Lowe. Group ll: Adjustment of the N2O flow and the enflurane vaporizer dial by elapsed time, according to Ernst and Lowe. Group lll: Adjustment of the N2O flow only and fixed dial setting on the halothane vaporizer, calculated from the measured end-tidal concentration at 16 min. Group lV: Adjustment of the N2O flow only and a fixed setting on the enflurane vaporizer, calculated from the measured end-tidal concentration at 16 min. The results were as follows: 1) In group l & ll, the inhalation anesthetic concentration decreased gradually and in 10 of 40 patients failed to maintain a satisfactory anesthetic condition after 50 minutes, requiring adjustment of the vaporizer dial setting. No failure occurred in groups lll & lV. 2) There were no abnormal values for the inspired oxygen fraction or the end-tidal CO2 tension at any time. 3) There were no significant differences between groups in the amount of a neuromuscular blocking agent, pancuronium, required. In conclusion, the method of closed circuit anesthesia when administer by adjusting only the flow of N20 and setting the vaporizer dial to a fixed point determined at 15 min may be convenient and efficacious. Attention to the patients safety can be maintained by the use of monitoring devices to measure the inspired oxygen fraction, the end-tidal CO2 tension and vital signs even without monitoring the anesthetic vapor concentration.
Air Pollution ; Anesthesia, Closed-Circuit* ; Anesthetics ; Enflurane ; Ether ; Halothane ; Humans ; Inhalation ; Nebulizers and Vaporizers ; Neuromuscular Blockade ; Nitrous Oxide ; Oxygen ; Pancuronium ; Vital Signs