Novel Self-inflating Resuscitators Maintaining High FiO2 with High Minute Ventilation / 대한마취과학회지

BACKGROUND: Self inflating resuscitators are widely used for the patients who need positive pressure ventilation during transport. During self inflating resuscitator ventilation, the FiO2 may decreases even with the use of the oxygen reservoir. Such phenomenon may increase the difficulty and risk of transport of the critically ill patients. Twin self inflating resuscitator was assembled by being modified from two conventional ones to achieve more stable FiO2. METHODS: The twin self inflating resuscitator and one conventional adult self inflating resuscitator were tested on a test lung. In the twin resuscitator, two adult self inflating resuscitators were connected serially without distal unidirectional valve plate. The resuscitators were compressed at variable tidal volumes, respiratory rates and oxygen flow rates, guided by the monitor. RESULTS: With conventional self inflating resuscitator ventilation, the FiO2 was maintained over 95% until minute ventilation of 7,500, 1,4000, 17,500 ml at respectively 5, 10, 15 L/min oxygen flow rate. With serial type, the FiO2 started to decrease with the minute ventilation over 12,500, 24,000, 28,000 ml at 5, 10, 15 L/min oxygen flow rate. CONCLUSIONS: By simple connection of two self inflating resuscitators, the FiO2 during self inflating resuscitator ventilation could be maintained during almost two times of minute ventilation compared to conventional ones.

Blind Tracheal Intubation through Laryngeal Mask Airway is Dependent on the Types of Tracheal Tube or Introducer? / 대한마취과학회지

BACKGROUND: Tracheal tubes are different on the flexibility, material and bevel angle according to the manufacturers. These may affect the success rate of blind tracheal intubation through laryngeal mask airway (LMA). In addition, using straight-tip exchanger or curved-tip introducer, we tried to compare the success rate of tracheal tube insertion through LMA. METHODS: After receiving informed consents, 30 patients were enrolled. Blind tracheal intubation was tried with reinforced tracheal tube (M group), or one of two kinds of conventional tracheal tube (P group and B group). Tracheal tube was selected in random order and advanced into the trachea through LMA one by one. If all the three attempts was unsuccessful, we considered the blind tracheal intubation through LMA a failure. We also compared the success rate of blind tracheal insertion through LMA using straight-tip exchanger or curved-tip introducer. The first trial was performed on the neutral head position. The exchanger or introducer was rotated during the second trial. If the second attempt was unsuccessful, the exchanger- or intubator-guided intubation was performed on the sniffing position and, as a last and fourth trial, while mandible was being elevated with hands. RESULTS: Success rate of blind tracheal intubation through LMA was 50% (15/50) in group P and 36.7% (11/30) in group M, 33.3% (10/30) in group B (P=0.05). By using curved-tip introducer, intubation through LMA was successful in 80% (16/20), while it was successful only in 35% (7/20) via straight-tip exchanger. CONCLUSION: Blind tracheal intubation through LMA was dependent on the types of tracheal tube. Also, curved tip introducer may be a more valuable aid in performing blind tracheal intubation through LMA. Its use seems to be better technique than directly inserting tracheal tube through LMA.

Effect of Saline-Filled or Viscous Lidocaine-Filled Cuff on the Laser-Induced Polyvinyl Chloride Endotracheal Tube Fires and Tidal Volume / 대한마취과학회지

BACKGROUND: There have been a lot of methods that prevent catatrophic airway fires during laser surgery, but none of them can protect endotracheal tube cuff exposed directly to laser beam. This study was performed to know the preventive effect of viscous lidocaine-filled cuffs on laser-induced combustion, and to know how long we can maintain positive pressure ventilation if laser beam broke out cuff perforation. METHODS: Transparent acrylic trachea attached to artificaial lung was intubated with 8.0 ID polyvinylchloride endotracheal tube. Cuff was filled with 8ml of saline or saline and viscous lidocaine mixture with 2:1 or 4:1 ratio. Positive pressure ventilation with air in tidal volume of 500 ml was begun. The laser output was set to 10 watt/sec in the continuous mode with beam diameter of 1 mm. Laser beam was directed perpendicularly at the part of the cuff protruding between endotracheal tube shaft and acrylic trachea, and laser emission was continued until the cuff was perforated or combusted. RESULTS: There was no case of laser-induced fires. After the perforation of cuff, the tidal volume was slowly decreased in 2:1 mixture of saline and viscous lidocaine filled cuff compared to others (P<0.05). CONCLUSION: 2:1 mixture of saline and viscous lidocaine may be used as an efficient inflating material of endotracheal tube cuffs on laser airway surgery.

Tests to Differentiate Cerebrospinal Fluid from Local Anesthetics during Epidural Anesthesia / 대한마취과학회지

BACKGROUND: One of the most serious risks of epidural anesthesia is total spinal blockade from unintentional dural puncture. We evaluated the glucose test and the thiopental precipitation test to differentiate cerebrospinal fluid (CSF) from local anesthetics (LA). METHODS: (1) Experiment 1: CSF from twenty patients was serially diluted with 2% lidocaine or 0.5% bupivacaine. The ratio of CSF to LA-CSF mixture (CSF/(LA+CSF)) was from 0 to 1.0 at an interval of 0.1. We measured the glucose level of each sample with blood sugar meter. (2) Experiment 2: CSF from a hydrocephalus patient was serially diluted and its glucose level of each sample was measured in the same way as Experiment 1. We performed a urine stick test with each sample. Ten anesthetists blinded to the nature of the sample were asked to identify the results of the tests. (3) Experiment 3: Two milimeters of 2.5% thiopental was respectively mixed with local anesthetics, the amount of which was from 0.1 to 1.0 ml at an interval of 0.1 ml. Sixteen anesthetists blinded to the nature of sample were asked to identify the results of the tests. RESULTS: (1) Experiment 1: We can measure glucose level at CSF/(LA +CSF) of 0.5 in 2% lidocaine group and 0.6 in 0.5% bupivacaine group. (2) Experiment 2: We can detect glucose at lower level of CSF/(LA +CSF) by glucose meter than urine stick test (p<0.05). (3) At least 0.35 ml of 2% lidocaine and 0.29 ml of 0.5% bupivacaine was needed respectively to detect precipitation. CONCLUSION: We suggest that blood glucose meter be used instead of glucose test strip. For thiopental precipitation test, we have to adjust the amount of thiopental depending on the amount of test fluid.

Tests to Differentiate Cerebrospinal Fluid from Local Anesthetics during Epidural Anesthesia / 대한마취과학회지

BACKGROUND: One of the most serious risks of epidural anesthesia is total spinal blockade from unintentional dural puncture. We evaluated the glucose test and the thiopental precipitation test to differentiate cerebrospinal fluid (CSF) from local anesthetics (LA). METHODS: (1) Experiment 1: CSF from twenty patients was serially diluted with 2% lidocaine or 0.5% bupivacaine. The ratio of CSF to LA-CSF mixture (CSF/(LA+CSF)) was from 0 to 1.0 at an interval of 0.1. We measured the glucose level of each sample with blood sugar meter. (2) Experiment 2: CSF from a hydrocephalus patient was serially diluted and its glucose level of each sample was measured in the same way as Experiment 1. We performed a urine stick test with each sample. Ten anesthetists blinded to the nature of the sample were asked to identify the results of the tests. (3) Experiment 3: Two milimeters of 2.5% thiopental was respectively mixed with local anesthetics, the amount of which was from 0.1 to 1.0 ml at an interval of 0.1 ml. Sixteen anesthetists blinded to the nature of sample were asked to identify the results of the tests. RESULTS: (1) Experiment 1: We can measure glucose level at CSF/(LA +CSF) of 0.5 in 2% lidocaine group and 0.6 in 0.5% bupivacaine group. (2) Experiment 2: We can detect glucose at lower level of CSF/(LA +CSF) by glucose meter than urine stick test (p<0.05). (3) At least 0.35 ml of 2% lidocaine and 0.29 ml of 0.5% bupivacaine was needed respectively to detect precipitation. CONCLUSION: We suggest that blood glucose meter be used instead of glucose test strip. For thiopental precipitation test, we have to adjust the amount of thiopental depending on the amount of test fluid.

The Effects of Intravenous Injection of Atropine on Airway Pressure, Respiratory Compliance and Resistance in Normal Subjects during General Anesthesia / 대한마취과학회지

Atropine, an anticholinergic agent, has bronchodilating effects, so it had been used to treat bronchospasm. But, bronchodilating effects in normal man is controversial. In this study, after anesthetizing patients who did not have any respiratory disease, intravenous injection of atropine to the subjects was done, and then we monitored airway pressures to see the changes in respiratory mechanics indirectly. ASA physical status class 1 or 2 patients were studied. Without premedication, intravenous injection of fentanyl 3 mcg/kg, midazolam 0.1 mg/kg, thiopental 3 mg/kg and vecuronium 0.15 mg/kg was done consecutively. Ventilation was controlled by face mask with O2-N2O(50%)-isoflurane( < 0.5 vo1.%) for 5 minutes with closed circuit anesthetic machine(Physio-Flex) and then intubation was done. After intubation anesthesia was maintained with O2-N2O(50%)-isoflurane( < 0.5 voL%) and ventilation was controlled with tidal volume 9 ml/kg, respiratory rate 11/min and inspiratory tlow rate was maintained constantly for each subject. When airway pressure was stabilized, atropine 0.015 mg/kg was injected intravenously. Thereafter, for 20 minutes peak airway pressure(P), plateau pressure(P(peak)), mean airway pressure(P(plateau)), mean arterial pressure and heart rate were monitored every minute interval. And we calculated dynamic compliance, static compliance and resistance of total respiratory system. Atropine produced significant decrease in P(peak) and increase in dynamic compliance but did not produce significant changes in P(plateau) P(mean) , and static compliance and resistance. In CONCLUSION, atropine has bronchodilating effect in normal subjects anesthetized with isoflurane of low concentration.