The Effect of Increased Minute Ventilation on the Changes of End-Tidal Isoflurane Concentration and Bispectral Index / 대한마취과학회지

BACKGROUND: An increase in ventilation is known to accelerate the rate of the rise of alveolar concentration of inhalation anesthetics and increase the rate of anesthetic induction. However, it is still debatable whether or not a rise of alveolar isoflurane concentrations by increased minute ventilation (MV) actually increases the depth of anesthesia. METHODS: After anesthetic induction by intravenous thiopental and succinylcholine, and after the bispectral index (BIS) had recovered to 75 after intubation, isoflurane anesthesia was begun (inspired concentration:2 vol.%, respiratory rate:12/min, tidal volume: group I; 8 ml/kg, group II; 12 ml/kg). BIS, spectral edge frequency (SEF), blood pressure, pulse rate were recorded 1 minute before induction, and 1, 2, 3, 4, 5, 7 and 10 minutes after isoflurane anesthesia. End-tidal concentrations of isoflurane and CO2 (ET-iso and -CO2) were recorded at 1, 2, 3, 4, 5, 7 and 10 minutes after isoflurane anesthesia. RESULTS: The increase of ET-iso and the decrease of ET-CO2 were significantly fast in group II. There was no difference in BIS and SEF between the two groups. CONCLUSIONS: Increasing MV induced a rapid rise of alveolar isoflurane concentrations, but changes of BIS and SEF were not affected by increased MV.

Is It Mandatory to Incise Immediately after Intubation in Cesarean Section? / 대한마취과학회지

BACKGROUND: If general anesthesia is used for cesarean section, important considerations include minimizing the duration of general anesthesia. One may think that skin incision should be started immediately after endotracheal intubation. If so, intra-operative awareness and perception of pain may occur due to light anesthesia. Allowing skin incision to be started 5 min after intubaton while administering 50% nitrous oxide and isoflurane 0.75%, we investigated the changes of BIS (bispectral index), and Apgar scores. METHODS: The investigation was carried out on 33 full-term ASA 1 or 2 patients underwent elective cesarean section under general anesthesia. If any fetal abnormalities were found, we excluded those cases. Premedication was omitted. After rapid sequence induction with sodium thiopental 4 mg/kg, succinylcholine 1 mg/kg, we made skin incision immediately after intubation in control group (n = 18) and 5 min after intubation in experimental group while administering 50% nitrous oxide and isoflurane 0.75%. Muscle relaxation was maintained with intravenous administration of atracurium 0.5 mg/kg. We measured BIS, mean arterial pressure (MAP), heart rate in 1 min interval from preinduction period to delivery and recorded Apgar scores 1 and 5 min after delivery, skin incision to delivery time and uterine incision to delivery time. And we counted the number of patients whose BIS values had been below 60 and 70 from skin incision to delivery in each group. RESULT: Apgar scores recorded 1 and 5 min after delivery did not show significant differences between control and experimental group. During the periods of abdominal wall traction, uterine incision and delivery, BIS values of experimental group were significantly lower than control group and moreover, tended to remain below 60 while those of control group during the same periods tended to be above 60 (P < 0.05). The number of patients of experimental group, whose BIS values had been below 60 from skin incision to delivery, was twice as much as that of control group (P < 0.05), but in case of BIS value below 70, there was no significant difference between control and experimental group. During the periods of skin incision and abdominal wall traction, the MAP's of experimental group were significantly lower than control group (P < 0.05). In cases of heart rate, skin incision to delivery time and uterine incision to delivery time, there were no significant differences between control and experimental group. CONCLUSION: Allowing the skin incision to be started 5 min after intubation while administering 50% nitrous oxide and isoflurane 0.75%, BIS values remained below 60 from abdominal wall traction to delivery, and anesthetics-induced fetal depression did not occur.

The Spectral Analysis of EEG according to Change in the Concentration of Isoflurane / 대한마취과학회지

BACKGROUND: Adequate depth of anesthesia requires a sufficient amount of the agent to secure unconsciousness and other components of anesthesia as needed for that particular surgical procedure, without jeopardizing vital organ functions. To evaluate the relationship of depth of anesthesia to EEG, we studied the effects of increasing minimum alveolar concentration (MAC) of isoflurane (arousal, 1, 1.3, 1.5 MAC) on power spectral analysis of the EEG. METHODS: To determine 1 MAC, we studied sixty patients undergoing general anesthesia who were randomly allocated to receive isoflurane at several predetermined end-tidal concentration. A minimum of 15 min was allowed between induction and skin incision to allow steady state condition. Patients were observed for gross purposeful movement for 60 seconds after incision. The MAC was calculated using maximum likelihood solution to a logistic regression model. Another forty patients were randomly allocated to have their EEGs recorded. General anesthesia was induced with oxygen and isoflurane only. After loss of consciousness, succinylcholine 1.5 mg/kg was given and intubation followed. The EEG was recorded awake and after 15 min at steady state conditions of 1, 1.3 and 1.5 MAC isoflurane had been achieved. Spectral edge frequency 95% (SEF95), median spectral frequency (MSF), total power (TP) and relative power in the delta, theta, alpha and beta band were calculated. RESULTS: The MAC of isoflurane was 1.21 vol% (20 - 40 years) and 1.09 vol% (40 - 60 years). The distribution of spectral EEG indices of the EEGs were established and compared. The threshold value of SEF95 14 Hz to differentiate between arousal and 1.3 and 1.5 MAC had a sensitivity of 60.5% (1.3 MAC), 71% (1.5 MAC) and specificity of 74.4% (1.3 and 1.5 MAC) and that of MSF 5 Hz had a sensitivity of 71% (1.3 MAC), 81.5% (1.5 MAC) and specificity of 48% (1.3 MAC), 48.8% (1.5 MAC). CONCLUSIONS: With regard to the dose-related decrease in SEF95 and MSF under increasing end- expiratory concentrations of isoflurane as described in the present study, future studies may have todetermine whether EEG feedback control of volatile anesthetic administration may be used successfully. It seems that if neglected parts by MSF and SEF95, which are really true values are considered in the future studies, those would increase the sensitivity and specificity of EEG could be used as tool for determining depth of anesthesia.

Monitoring of Anesthetic Depth by BIS & Anemon Monitor / 대한마취과학회지

BACKGROUND: Monitoring of "Depth of anesthesia" is an ongoing problem in anaesthesia. In this study, the author has compared the bispectral index (BIS) and Anemon monitor for monitoring depth of anesthesia in propofol or isoflurane anesthesia. METHODS: Anemon-1 and BIS index were obtained from 24 patients (ASA I, II) during general anesthesia with propofol or isoflurane. For patients in the propofol group, anesthesia was induced with fentanyl 100ng followed by propofol 2 mg/Kg. For patients in the isoflurane group, anesthesia was induced with thiopental 5 mg/Kg. The author observed changes of these values at 5 major times: before induction, during induction, after induction, at sKin incision, before extubation, after extubation. RESULTS: The anemon index showed a significant increase during induction (propofol group: 86.9 +/- 26.4, isoflurane group: 106.0 +/- 18.6) and at sKin incision (propofol group: 89.9 +/- 22.7, isoflurane group: 92.0 +/- 23.1), but this did not correlate with the level of consciousness. The BIS index showed a significant decrease in the score after induction (propofol group: 55.0 +/- 9.6, isoflurane group: 61.0 +/- 17.2), but no response to surgical stimuli. CONCLUSIONS: BIS had a good correlation with level of consciousness. The Anemon-1 index was recognized to reflect invasive stimulus. As the BIS and Anemon-1 had no correlation, it was not possible to assume changes of each index from the other. Both the anemon-1 index and BIS are useful to monitor the anesthesia level during surgery.

Perioperative Changes of Blood Coagulation by a Thromboelastograph in Patients Undergoing Clipping of Cerebral Aneurysms / 대한마취과학회지

BACKGROUND: Patients undergoing brain surgery have a high risk of developing a number of perioperative coagulation disorders. Anesthesia and surgical stress may affect blood coagulation and fibrinolysis. The aim of this study was to evaluate perioperative changes in hemostatic parameters of patients undergoing clipping of cerebral aneurysms with a thromboelastograph (TEG) in combination with simple laboratory tests. METHODS: Twenty adult patients who had cerebral aneurysms and no history of coagulation disorders were studied. Isoflurane and N2O were used for all anesthetic proceedings. Preanesthetic, intraoperative (after skin incision and after clipping of cerebral aneurysms) and postanesthetic measurements included a TEG and simple laboratory tests. The TEG variables included r time (reaction time for clot formation), k time (clot formation time), alpha angle (rate of clot growth), MA (maximal amplitude of clot strength) and LY30 (fibrinolytic index). RESULTS: In simple laboratory tests, prothrombin time (PT) and partial thromboplastin time (PTT) at intraoperation and postanesthesia were longer than those at preanesthesia (p < 0.05). In the TEG, r and k time at intraoperation and postanesthesia were shorter than those at preanesthesia (p < 0.05). However the alpha angle at intraoperation and postanesthesia was longer than that at preanesthesia (p < 0.05). There was no significant difference in MA and LY30 except an increase in MA after the skin incision (p < 0.05) compared to the MA at preanesthesia. CONCLUSIONS: These results indicate a general hypercoagulability during and after a cerebral aneurysms operation in terms of TEG, although, the level of the PT and PTT can be at the upper limits within normal. Therefore perioperative use of coagulants in cerebral aneurysms may increase the risk of a thromboembolism because of accelerating blood coagulability. By early intraoperative and postoperativeevaluation of the hemostatic abnormality with a TEG, appropriate measures might be initiated to prevent postoperative complications due to hypercoagulability.

The Effects of Isoflurane on the Expression of iNOS mRNA in Endotoxemic Rats / 대한마취과학회지

BACKGROUND: It has been known that alveolar macrophage exposed to bacterial lipopolysaccharide (LPS) induces a lots of nitric oxide (NO) and inducible nitric oxide synthase (iNOS) mRNA expression. The Authors elucidated the effects of iNOS mRNA expression by inhalational anesthetics (isoflurane) on endotoxemic rats and positive pressure ventilation with and without LPS. METHODS: Fifty Sprague-Dawley rats (250 - 270 g) were anesthesized with urethane injected in the peritoneal cavity. Then the expression of iNOS mRNA in the alveolar macrophages of the rats were measured after injection of LPS, 2 hours of isoflurane (0.5 - 2.5%) anesthesia, and 2 hours of positive pressure ventilation. The activities of iNOS in macrophages were measured by analysing iNOS mRNA expression by Northern blot analysis with autoradiography using the polymerase chain reaction (PCR) method. RESULTS: The size and patterns of the iNOS mRNA band in the 0.5 - 2% isoflurane group were almost same as with the control group. The size of the iNOS mRNA band in the 2.5% isoflurane group increased more than in the control group. In the continous positive-pressure ventilation with LPS group, the iNOS mRNA band was slightly increased compared to the normal lung and the continous positive-pressure ventilation without LPS group. CONCLUSIONS: Higher concentrations of isoflurane anesthesia may evoke the expression of iNOS mRNA in a septic model. Positive pressure ventilation in sepsis may induce iNOS mRNA production.

The Effect of Age on the Cardiovascular Responses Induced by High Concentration of Isoflurane / 대한마취과학회지

BACKGROUND: The inhalation of a high concentration of isoflurane transiently increases heart rate (HR) and blood pressure. The current study examined the effects of age on isoflurane-induced circulatory responses. METHODS: One hundred-ten patients were randomly allocated into one of four groups according to age: under 10 years (Group 1), 20 - 40 years (Group 2), 41 - 60 years (Group 3), and over 65 years (Group 4). In each group, the inspired concentration of isoflurane via mask was increased to 5.0 vol% abruptly. The target was to produce an end-tidal concentration of isoflurane (ETisof) of 2.6 vol% which was maintained until the end of the study by adjusting the vaporizer setting when necessary. HR, mean arterial pressure (MAP), ETisof, and end-tidal concentration of carbon dioxide were measured at baseline and every 30 seconds for 5 minutes after inhalation of isoflurane and for 2 minutes after intubation. RESULTS: HR and MAP significantly increased after inhalation of isoflurane in all four groups compared with the baseline. The time from administration of isoflurane to the maximal HR was less than that for MAP. However, there were no significant differences among the groups for ETisof at the maximal HR and MAP. In Groups 1 and 4, the times for maximal HR were shorter than in Groups 2 and 3. In aged patients (Group 4), the isoflurane-induced HR increase was less than in the other three groups. There were no significant differences among the groups in increases of MAP. CONCLUSIONS: The high concentration of isoflurane transiently increases HR and MAP during inhaled anesthesia induction. In aged patients, the increase in HR is less than in younger-aged patients.

Comparison of the Effect of Isoflurane and Propofol on Postoperative Liver Function Test after Hepatic Resection with Portal Triad Clamping / 대한마취과학회지

BACKGROUND: Anesthesia and surgery may exacerbate liver function in patients with pre-existing liver disease so it is important to choose less hepatotoxic anesthetics in patients with chronic liver disease. METHODS: This study was designed to examine the postoperative liver function test in 150 patients after hepatectomy with portal triad clamping through retrospective chart review. Patients were divided into an isoflurane group (group I, n = 56) and a propofol group (group P, n = 57) by used anesthetics for maintaining anesthesia. Aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase, alkaline phosphatase, total bilirubin, albumin, and prothrombin time were checked at preoperation, and postoperatively at 1, 3, 7 and 14 days in the two groups. Indocyanine retention rate (ICG-R15) was measured at preoperation, and postoperatively at 1 and 7 days. RESULTS: AST values increased postoperatively at 1, 3, 7, and 14 days compared with preoperation. ALT values increased postoperatively at 1, 3 and 7 days compared with preoperation and there was difference between group I (443.8 +/- 52.1 U/L) and group P (202.7 +/- 24.7 U/L) at postoperative 1 day. Other values had no significant difference between the two groups. CONCLUSIONS: Though it might need a well controlled study to find the differences in effect between isoflurane and propofol on the postoperative liver function test, we concluded that total intravenous anesthesia using propofol is also one of the safest anesthetic methods for hepatic resection with minimal hepatotoxicity.

The Effect of Isoflurane or Propofol on Hepatic Transaminase in Healthy Hepatitis B Carrier Patients / 대한마취과학회지

BACKGROUND: Isoflurane or propofol has been known to have a low potential for hepatotoxicity. The purpose of this study is to evaluate the effect of isoflurane or propofol on hepatic transaminase in healthy hepatitis B carrier patients. METHODS: Forty-six patients who were healthy hepatitis B carriers were studied following an orthopedic surgery. The patients were randomly assigned to Group I (n = 22) who received isoflurane, or group P (n = 24) who received propofol. The plasma concentrations of aspartate aminotransferase (AST), and alanine aminotransferase (ALT) were measured on the day before the operation, and 1, 3, and 7 days after the operation. RESULTS: The plasma concentrations of AST were not changed significantly until the 7th day post-operatively in both groups, and there were no significant differences between the two groups. The plasma concentrations of ALT were significantly decreased at 1 and 3 days postoperatively (P < 0.05) in both groups. However, it recovered to baseline concentrations at 7 days postoperatively. There were no significant differences between the two groups. CONCLSIONS: The use of isoflurane or propofol does not increase the plasma concentrations of hepatic transaminase in Hepatitis B carrier patients after an operation.

Comparison of Propofol and Propofol-Isoflurane Anesthesia for Outpatient Surgery / 대한마취과학회지

BACKGROUND: Outpatient surgery has recently grown at a substantial rate. The development and use of short acting anesthetic and analgesic agents have played a major role in the growth of outpatient surgery. This study was designed to evaluate the intraoperative hemodynamic responses and recovery characteristics, using propofol or isoflurane to maintain the anesthesia. METHODS: A total number of 30, ASA physical status I-II patients scheduled for outpatient surgery, all of whom were to undergo excision of breast mass. The patients were randomly allocated to receive either total intravenous anesthesia with propofol, or inhalation anesthesia with isoflurane after induction of anesthesia with propofol. All patients were ventilated via a laryngeal mask airway (LMA) using a mixture of oxygen and air so that the FiO2 would be 0.4. RESULTS: There were no significant differences in hemodynamic changes during anesthesia in recovery time, or in complications between the two groups. CONCLUSIONS: We conclude that both methods provide reasonably rapid and reliable recovery from anesthesia and are equally acceptable to the patients.

Comparison of the Effects of Propofol and Isoflurane Anesthesia on Respiratory Gas Exchange during Laparoscopic Cholecystectomy / 대한마취과학회지

BACKGROUND: Introduction of a pneumoperitoneum using CO2 is accompanied by significant alterations in respiratory function and pulmonary gas exchange during laparoscopic cholecystectomy. Previous studies have shown differing results concerning pulmonary gas exchange: a significant decrease of PaO2 was induced with isoflurane. In contrast, no significant changes were observed with propofol. The purpose of the present study was to compare the effects of propofol vs isoflurane on pulmonary gas exchange during general anesthesia for laparoscopic cholecystectomy. METHODS: Forty patients were divided randomly between isoflurane and propofol groups. After induction of anesthesia, ventilation was controlled and intra-abdominal pressure was maintained automatically at 12 mmHg by a CO2 insufflator. After the measuring of baseline values of blood pressure, heart rate, PaO2, PaCO2 and PetCO2 before CO2 insufflation, measurements were also made immediately, 30min after CO2 insufflation and 5 min after CO2 exsufflation. RESULTS: In the isoflurane group, PaCO2, PetCO2, PaO2, and P(a-et)CO2 changed significantly 30 min after CO2 insufflation and 5 min after CO2 exsufflation (P < 0.05). In the propofol group, PaCO2 and PetCO2 increased significantly 30 min after CO2 insufflation and 5 min after CO2 exsufflation (P < 0.05), but PaO2 and P(a-et)CO2 remained constant. When the two groups were compared, there were significant differences in PaO2, PaCO2, PetCO2 and P(a-et)CO2 at 30min after CO2 insufflation and 5 min after CO2 exsufflation (P < 0.05). CONCLUSIONS: These results indicate that during laparoscopic cholecystectomy the PaO2 was significantly lower and PaCO2 and P(a-et)CO2 were significantly higher in the isoflurane group compared with the propofol group.

The Effects of the Rate of Increase in Inhaled Isoflurane Concentration on the Circulatory Responses / 대한마취과학회지

BACKGROUND: A rapid increase in isoflurane concentration induces tachycardia and hypertension and increases plasma catecholamine concentration. The current study examined the effects of the rate of increase in inhaled isoflurane concentration on the circulatory responses. METHODS: Unpremedicated sixty three ASA physical status 1 patients, aged 20-40 years, scheduled for elective surgery under general anesthesia were randomly allocated into one of three groups. In each group, the inspired concentration of isoflurane via mask was increased up to 5 vol% at the rate different from other groups. The inspired concentration of isoflurane via mask was increased to 5.0 vol% abruptly (group 1), for 100 seconds (group 2), or 200 seconds (group 3). The target was to produce an end-tidal concentration of isoflurane (ETisof) of 2.6 vol% which was maintained until the end of the study by adjusting the vaporizer setting, when necessary. Heart rate (HR), mean arterial pressure (MAP), ETisof, end-tidal concentration of carbon dioxide, and peripheral oxygen saturation were measured at baseline and every 30 seconds for 5 minutes after inhalation of isoflurane and for 2 minutes after intubation. RESULTS: HR and MAP were significantly increased in all three groups compared with baseline, but significant differences in maximum values were not observed in three groups. There were significant differences among the groups in time from the onset of isoflurane inhalation to the maximal effect on HR and MAP. However, there were no significant differences among the groups of the ETisof at the maximal HR and MAP were seen. CONCLUSIONS: The high concentration of isoflurane transiently increase HR and MAP during inhaled anesthesia induction. However, the rate of increase in inhaled isoflurane concentration does not affect the circulatory responses.

On the Usefulness of Intravenous Anesthesia for Patients Undergoing Postoperative Radiologic Examination / 대한마취과학회지

BACKGROUND: In most brain operations, the endotracheal tube is kept in postoperatively for airway maintenance during radiologic examinations. But the endotracheal tube causes tracheal irritation and hemodynamic changes. Inhalation anesthetics can not be administered during transport, and minimal concentration is exhaled for several hours after the end of inhalation. The present study was designed : (1) to determine the end tidal isoflurane concentration after the end of administration ; (2) to investigate the effects of intravenous anesthetics in patients with tracheal intubation during radiologic examination postoperatively. METHODS: We selected forty adult patients who were scheduled for elective neurosurgical operation with postoperative brain CT (computerized tomography). The study was performed in 2 steps; in the step 1 (n = 10), end tidal isoflurane concentration was checked after ending inhalation. In the step 2 (n = 30), patients were divided into one of three groups according to anesthesia method; group I (using isoflurane), group P (change from isoflurane to propofol about an hour before operation end), group M (using midazolam instead of propofol, compared to group P). In each group, the frequency of bucking and incidence of hypertension were checked during postoperative radiologic examinations. RESULTS: Minimal concentrations of isoflurane were detected in exhaled gas for about 2 hours after the end of isoflurane inhalation. The frequency of bucking was significantly lower in the group P and M than in group I (P = 0.002). In group P, the incidence of hypertension was significantly reduced compared to group M and I (P = 0.031). CONCLUSIONS: These results suggest that the change of anesthetic technique (from inhalation to intravenous) in the late period of operation, provides postoperative hemodynamic stability, a more comfortable state and minimal environmental pollution in comparison to inhalation anesthesia only.

On the Usefulness of Intravenous Anesthesia for Patients Undergoing Postoperative Radiologic Examination / 대한마취과학회지

BACKGROUND: In most brain operations, the endotracheal tube is kept in postoperatively for airway maintenance during radiologic examinations. But the endotracheal tube causes tracheal irritation and hemodynamic changes. Inhalation anesthetics can not be administered during transport, and minimal concentration is exhaled for several hours after the end of inhalation. The present study was designed : (1) to determine the end tidal isoflurane concentration after the end of administration ; (2) to investigate the effects of intravenous anesthetics in patients with tracheal intubation during radiologic examination postoperatively. METHODS: We selected forty adult patients who were scheduled for elective neurosurgical operation with postoperative brain CT (computerized tomography). The study was performed in 2 steps; in the step 1 (n = 10), end tidal isoflurane concentration was checked after ending inhalation. In the step 2 (n = 30), patients were divided into one of three groups according to anesthesia method; group I (using isoflurane), group P (change from isoflurane to propofol about an hour before operation end), group M (using midazolam instead of propofol, compared to group P). In each group, the frequency of bucking and incidence of hypertension were checked during postoperative radiologic examinations. RESULTS: Minimal concentrations of isoflurane were detected in exhaled gas for about 2 hours after the end of isoflurane inhalation. The frequency of bucking was significantly lower in the group P and M than in group I (P = 0.002). In group P, the incidence of hypertension was significantly reduced compared to group M and I (P = 0.031). CONCLUSIONS: These results suggest that the change of anesthetic technique (from inhalation to intravenous) in the late period of operation, provides postoperative hemodynamic stability, a more comfortable state and minimal environmental pollution in comparison to inhalation anesthesia only.

Endotracheal Intubation, but not Laryngeal Mask Airway Insertion, Produces Reversible Bronchoconstriction / 대한마취과학회지

BACKGROUND: Intubation of the trachea frequently results in a rise in respiratory system resistance (Rrs) that is reversed by inhaled bronchodilators. In asthmatics, this reflex may occasionally result in profound bronchoconstriction, and anesthesiologists often try to avoid tracheal intubation if possible in asthmatics. The hypothesis of this study was that insertion of a laryngeal mask airway (LMA) would be less likely to result in reversible bronchoconstriction than would insertion of an endotracheal tube (ETT). METHODS: A total of 52 (45 male, 7 female) patients were randomized to placement of a 7.5 mm (females) or 8.0 mm (males) endotracheal tube or a #4 (females) or #5 LMA (males). Anesthesia was induced with 2 microgram/kg fentanyl and 5 mg/kg thiopental and airway placement facilitated with 1 mg/kg succinylcholine. After ensuring that a seal to greater than 20 cmH2O existed, Rrs was measured immediately following airway placement using the isovolumic method during positive pressure ventilation with oxygen. Correction was made for the resistance of the ETT but not for the resistance of the LMA, which was insignificant at the flows used. Inhalation anesthesia was then begun with isoflurane (ISF) to achieve an end-tidal concentration of 1.0% for ten minutes. Rrs was then measured again under identical conditions. In the LMA patients, fiberoptic laryngoscopy was then performed to ensure that the scope could be passed to the level of the cords without epiglottic obstruction. RESULTS: Among LMA patients, the initial Rrs was significantly lower than among ETT patients (9.2 0.7 vs 13.4 1.9 cmH2O/L/s, P <0.05). After 10 minutes of ISF, the resistance declined to 8.6 0.7 in the ETT group but remained unchanged at 9.1 0.7 cmH2O/L/s in the LMA group. The decline in Rrs in the ETT group of 4.7 1.4 cmH2O/L/s was highly significant compared to the lack of change in the LMA group (P <0.01). CONCLUSIONS: Despite the inclusion of the resistance of the LMA and the laryngeal resistance, Rrs in LMA patients was still clearly lower than in ETT patients. Furthermore, resistance dropped rapidly only in ETT patients after ISF, a potent bronchodilator, suggesting that reversible bronchoconstriction was present in ETT patients but not LMA patients. We conclude that an LMA is a better choice of airway to minimize airway reaction.

Endotracheal Intubation, but not Laryngeal Mask Airway Insertion, Produces Reversible Bronchoconstriction / 대한마취과학회지

BACKGROUND: Intubation of the trachea frequently results in a rise in respiratory system resistance (Rrs) that is reversed by inhaled bronchodilators. In asthmatics, this reflex may occasionally result in profound bronchoconstriction, and anesthesiologists often try to avoid tracheal intubation if possible in asthmatics. The hypothesis of this study was that insertion of a laryngeal mask airway (LMA) would be less likely to result in reversible bronchoconstriction than would insertion of an endotracheal tube (ETT). METHODS: A total of 52 (45 male, 7 female) patients were randomized to placement of a 7.5 mm (females) or 8.0 mm (males) endotracheal tube or a #4 (females) or #5 LMA (males). Anesthesia was induced with 2 microgram/kg fentanyl and 5 mg/kg thiopental and airway placement facilitated with 1 mg/kg succinylcholine. After ensuring that a seal to greater than 20 cmH2O existed, Rrs was measured immediately following airway placement using the isovolumic method during positive pressure ventilation with oxygen. Correction was made for the resistance of the ETT but not for the resistance of the LMA, which was insignificant at the flows used. Inhalation anesthesia was then begun with isoflurane (ISF) to achieve an end-tidal concentration of 1.0% for ten minutes. Rrs was then measured again under identical conditions. In the LMA patients, fiberoptic laryngoscopy was then performed to ensure that the scope could be passed to the level of the cords without epiglottic obstruction. RESULTS: Among LMA patients, the initial Rrs was significantly lower than among ETT patients (9.2 0.7 vs 13.4 1.9 cmH2O/L/s, P <0.05). After 10 minutes of ISF, the resistance declined to 8.6 0.7 in the ETT group but remained unchanged at 9.1 0.7 cmH2O/L/s in the LMA group. The decline in Rrs in the ETT group of 4.7 1.4 cmH2O/L/s was highly significant compared to the lack of change in the LMA group (P <0.01). CONCLUSIONS: Despite the inclusion of the resistance of the LMA and the laryngeal resistance, Rrs in LMA patients was still clearly lower than in ETT patients. Furthermore, resistance dropped rapidly only in ETT patients after ISF, a potent bronchodilator, suggesting that reversible bronchoconstriction was present in ETT patients but not LMA patients. We conclude that an LMA is a better choice of airway to minimize airway reaction.

Effects of Isoflurane and Propofol on Hydrogen Peroxide-Induced Injury of Trachea in Guinea-Pig / 대한마취과학회지

BACKGROUND: Oxygen free radicals are likely to be involved in decreases of the tracheal epithelial barrier function, increases of permeability, and inhibitions of ciliary activity. The present study was undertaken to determine the interaction between isoflurane, propofol and oxidative injury with respect to the contractile force of tracheal smooth muscle in guinea-pig. METHODS: Strips of guinea-pig trachea were suspended in organ chambers, and their isometric tension was recorded by a MacLab. Tissues were allocated to 7 groups (each: n = 10) of control, 2%, 3%, and 4% isoflurane, 25 micrometer, 50 micrometer, and 100 micrometer propofol. All strips were challenged with 10 5 M acetylcholine (ACh) to get maximal contractions and followed washout. All strips were exposed to 10 4 M H2O2 contained modified Krebs solution for 30 minutes after the strips were perfused with each concentration of anesthetics for 20 minutes. After washout of organ chambers and 30 minutes of rest, all strips were contracted with ACh. Several strips were prepared for microscopic evaluation. RESULTS: The contractile heights to H2O2 showed 36.7+/-20.2% of control value in the control group, and there were significant differences between the control and the propofol 100 micrometer group as shown by Tukey test. There were no significant differences in contractile heights to the second ACh in any of the 6 groups except the 100 micrometer propofol group. Microscopic morphological changes were not detected by 1,000 light microscopic evaluation. CONCLUSIONS: We suggest that the contractile heights of strips to H2O2 which were lower in four anesthetic groups than in the control group indicated a counteracting relaxation of smooth muscle caused by anesthetics. We suggest that there might be some functional effects of H2O2 on smooth muscle cells other than epithelial injury and that 100 micrometer propofol might have some protective effects against smooth muscle cell injury from 10- 4 H2O2.

Effects of Isoflurane and Propofol on Hydrogen Peroxide-Induced Injury of Trachea in Guinea-Pig / 대한마취과학회지

BACKGROUND: Oxygen free radicals are likely to be involved in decreases of the tracheal epithelial barrier function, increases of permeability, and inhibitions of ciliary activity. The present study was undertaken to determine the interaction between isoflurane, propofol and oxidative injury with respect to the contractile force of tracheal smooth muscle in guinea-pig. METHODS: Strips of guinea-pig trachea were suspended in organ chambers, and their isometric tension was recorded by a MacLab. Tissues were allocated to 7 groups (each: n = 10) of control, 2%, 3%, and 4% isoflurane, 25 micrometer, 50 micrometer, and 100 micrometer propofol. All strips were challenged with 10 5 M acetylcholine (ACh) to get maximal contractions and followed washout. All strips were exposed to 10 4 M H2O2 contained modified Krebs solution for 30 minutes after the strips were perfused with each concentration of anesthetics for 20 minutes. After washout of organ chambers and 30 minutes of rest, all strips were contracted with ACh. Several strips were prepared for microscopic evaluation. RESULTS: The contractile heights to H2O2 showed 36.7+/-20.2% of control value in the control group, and there were significant differences between the control and the propofol 100 micrometer group as shown by Tukey test. There were no significant differences in contractile heights to the second ACh in any of the 6 groups except the 100 micrometer propofol group. Microscopic morphological changes were not detected by 1,000 light microscopic evaluation. CONCLUSIONS: We suggest that the contractile heights of strips to H2O2 which were lower in four anesthetic groups than in the control group indicated a counteracting relaxation of smooth muscle caused by anesthetics. We suggest that there might be some functional effects of H2O2 on smooth muscle cells other than epithelial injury and that 100 micrometer propofol might have some protective effects against smooth muscle cell injury from 10- 4 H2O2.

Effect of Sevoflurane and Isoflurane on Hypoxic Pulmonary Vasoconstriction in the Isolated Rabbit Lung / 대한마취과학회지

BACKGROUND: In vitro and in vivo studies have shown that inhalation anesthetics inhibit hypoxic pulmonary vasoconstriction (HPV). The aim of this study was to investigate the effect of isoflurane and sevoflurane on HPV in the isolated rabbit lungs. METHODS: Isolated constant-flow perfused lungs from New Zealand white rabbit were randomly allocated to treatment with either isoflurane (n=8) or sevoflurane (n=8). HPV, defined as an increase in pulmonary arterial pressure at constant flow, was elicited by decreasing inspiratory oxygen concentration from 95% to 3% for 5 min. This effect was determined without and with increasing concentration of anesthetics (at 0.5, 1.0, and 2.0 MAC of isoflurane, and at 0.6, 0.9, and 1.2 MAC of sevoflurane). The HPV response in the presence of anesthetics was expressed as a percentage of the pressor response in the absence of anesthetics and dose-response relationship were calculated using the nonlinear least-squares method. RESULTS: The percent hypoxic pressor response (%deltaP) of isoflurane were 100%, 78.4%, 45.1%, and 19.6% at 0, 0.5, 1.0, and 2.0 MAC, respectively. The %deltaP of sevoflurane were 100%, 66.6%, 40.0%, and 22.2% at 0, 0.6, 0.9, and 1.2 MAC, respectively. Values (mean+/-SD) for the half-inhibition values (ED50) were 0.90+/-0.14 and 0.81+/-0.15 MAC, and for the slopes were 1.97+/-0.52 and 1.84+/-0.59 for isoflurane and sevoflurane, respectively. There were no statistical difference between the values for ED50 or between the values for slope. CONCLUSIONS: We conclude that sevoflurane and isoflurane inhibit the HPV reponse in a dose-related manner with same potency and slope.

A Comparision of Hemodynamic Changes of Total Intravenous Anesthesia (TIVA) and Isoflurane for Tonsillectomy in Children / 대한마취과학회지

BACKGROUND: In anesthesia for tonsillectomy in children, deep general anesthesia, rapid recovery to consciousness and the return of protective airway reflexes are desirable. This study was designed to estimate the efficacy of TIVA with propofol and fentanyl compared with isoflurane-N2O. METHODS: Forty pediatric patients in ASA class I for tonsillectomy were allocated randomly to either TIVA with propofol and fentanyl (n=20, T) or isoflurane-N2O (n=20, I) group. Anesthesia was induced with propofol 1 mg/kg, fentanyl 3 microgram/kg IV and was maintained by continuous infusion of propofol 6~10 mg/kg/hr, fentanyl 6~10 microgram/kg/hr in T group and was induced with thiopental 5 mg/kg IV and maintained by inhalation of 1.2~2.5 vol% isoflurane in I group. The changes of hemodynamics, recovery time and complications were evaluated. RESULTS: Systolic and diastolic pressure were increased in I group than T group at 1 min after intubation (p<0.05). Heart rate was increased in I group than T group at 1 min after intubation, 1 min and 5 min after incision, changing tube, end of operation and 5 min after end of operation (p<0.05). The recovery time was shorter in T group than I group (p<0.05). Pain on injection was more frequent in T group than I group (p<0.05), and excitatory effect during emergence was more frequent in I group than T group (p<0.05). CONCLUSIONS: TIVA with fentanyl and propofol is better than isoflurane-N2O for anesthesia of tonsillectomy in children in view of small hemodynamic change, early and gentle recovery pattern and side effects.