Efficient inspired concentration of sevoflurane for vital capacity rapid inhalation induction (VCRII) technique.

STUDY OBJECTIVES: To evaluate the efficient inspired concentration of sevoflurane for a vital capacity rapid inhalation induction (VCRII) technique with respect to induction time, characteristics, and acceptability. DESIGN: Prospective study. SETTING: Medical college hospital. PATIENTS: 68 unpremedicated healthy adult volunteers were assigned to one of four groups in order of sequential entry of informed consent. INTERVENTIONS: 3%, 4.5%, 6%, or 7.5% concentrations of sevoflurane were administered for 5 minutes (3% and 4.5%) or 3 minutes (6% and 7.5%) using a single breath technique. MEASUREMENTS AND MAIN RESULTS: The mean induction time required with 3%, 4.5%, 6%, or 7.5% sevoflurane was 120 +/- 26 sec, 79 +/- 18 sec, 52 +/- 15 sec, or 47 +/- 17 seconds, respectively. Each induction time was significantly different from the others (p < 0.05) except for that between 6% and 7.5%. There appeared to be a direct inverse relationship between the mean induction time and the logarithm of inspired concentration of sevoflurane, but this relationship did not extend beyond concentrations above 6%. Blood pressure decreased by approximately 18% from baseline at the end of inhalation of the drug, and heart rate remained constant in all groups. Except of one subject in the 7.5% group, no coughing was observed and laryngospasm, breath-holding, and secretions were not seen in any subjects. Slight limb movement was observed in a few subjects in each group. All subjects except one in the 3% group would accept undergoing a similar procedure again. CONCLUSION: Sevoflurane 6% can be recommended for VCRII, but increasing the concentration higher than this does not markedly shorten the induction time and thus seems to add little benefit.

Comparison of induction time and characteristics between sevoflurane and sevoflurane/nitrous oxide.

A previous investigation using nitrous oxide with 5% enflurane (3.8 MAC) for single breath induction produced a stage of excitement which may be related to the difference in blood/gas coefficient solubility of these agents. The closer blood/gas solubility coefficient of sevoflurane and nitrous oxide may eliminate this phenomenon. We therefore evaluated 40 volunteers in a randomized study using 7.5% sevoflurane (3.7 MAC) in oxygen (n = 21) or sevoflurane with nitrous oxide (n = 19) using a single breath induction technique. Sevoflurane in nitrous oxide and oxygen reduced induction time by 15% compared to sevoflurane in oxygen alone (41 +/- 16 and 48 +/- 16 sec (s.d.), respectively). This was, however, not statistically significant. There were scarcely induction-related complications, such as coughing, laryngospasm, breath-holding, movements of a limb and excessive salivation, in either group. Thus, the addition of nitrous oxide neither increased the number of complications, nor the speed of induction.

A comparison of vital capacity breath and tidal breathing techniques for induction of anaesthesia with high sevoflurane concentrations in nitrous oxide and oxygen.

Vital capacity breath and tidal breathing techniques were compared for induction of anaesthesia with 7.5% sevoflurane in nitrous oxide, and oxygen. Thirty five subjects were randomly assigned to a vital capacity breath group (19) or to a tidal breathing group (16). The mean time for induction was faster with vital capacity breath (41 s) than with tidal breathing (52 s, p < 0.05). Some involuntary movements were seen in the tidal breathing group but none in the vital capacity breath group. Coughing was seen in a quarter of the subjects in the tidal breathing group and in one subject of the vital capacity breath group. The vital capacity group showed excellent characteristics: rapid, and pleasant induction without premedication. We conclude that the vital capacity breath technique is necessary for the inhalation induction of anaesthesia; it provides enough overpressure to allow the subject to pass reliably and rapidly through the initial stages of excitement.

Assessment of preformed, coiled-tipped, micro spinal catheter.

We have developed a preformed, coiled-tipped, microspinal catheter made of Teflon, 30-gauge, 90 cm long and with a 3-cm long circled tip of 7 mm in diameter. We have studied the problems of using microcatheters, specifically the difficulty in placing the catheter and the maldistribution of local anaesthetic. In this study we have compared three types of spinal catheter: the new, coiled-tipped catheter, a standard, straight-tipped catheter and a 32-gauge microcatheter (TFX) with a stainless steel stylet embedded in the side wall (Microspinal, TFX/Rush Medical, Duluth, GA, USA). The coiled-tipped catheters were placed in the subarachnoid space more rapidly and with greater ease than the straight-tipped and TFX catheters (100%, 75% and 8% within 2 min, respectively), and had the highest success rate in achieving adequate block compared with the others (94%, 69% and 64%, respectively).

Rapid inhalation induction with high concentration of sevoflurane using a new vaporizer.

Sevoflurane allows a moderately rapid induction with only slight problems of induction. However, it has not been possible to conduct tests with more than 2.6 minimum alveolar concentration (MAC) of sevoflurane (4.5%) because of the limitations in the performance of the currently available vaporizer. We tested the performance of a new vaporizer and tried it with single breath induction. The new vaporizer could deliver a 4.3 MAC (7.5%) sevoflurane through oxygen of 8 liter/min. Twenty-one unpremedicated volunteers breathed 7.5% sevoflurane in oxygen. The mean time for induction of anesthesia was 48 +/- 16 seconds, reflecting its high concentration and low blood/gas solubility. Although coughing was observed in two subjects, laryngospasm, breath holding, and secretions did not occur during induction by this method. All subjects except one would be willing to undergo similar induction again. This study demonstrate that the new vaporizer can be used to administer 7.5% concentration of sevoflurane and to adequately perform smooth and rapid inhalation induction of anesthesia in young volunteers without premedication.

[Effects of succinylcholine on neuromuscular transmission during recovery from vecuronium].

Effects of succinylcholine (SCC), 1 mg.kg-1, given following incomplete recovery from muscle paralysis induced by vecuronium were investigated in 27 female patients undergoing elective surgery, which was performed under epidural anesthesia. Anesthesia was induced with thiamylal 5 mg.kg-1 followed by SCC to facilitate orotracheal intubation. Vecuronium bromide 0.08 mg.kg-1 was given and the lungs were ventilated with 67% N2O in O2 and 0.6% sevoflurane. Neuromuscular function was monitored by means of the induced EMG. The ulnar nerve was stimulated at the wrist. Supramaximal trains of four stimuli (2 Hz for 2 s: pulse width 0.2 ms) were administered every 20 s. The effect of SCC varied depending upon the degree of recovery from vecuronium. At the 25% recovery point, the response to SCC was biphasic, showing an initial reversal followed by an increase of the partial vecuronium block which recovered showing a fade phenomenon on train-of-four stimulation. At the 50% recovery point, an initial reversal was slight. Administered at 75% recovery from vecuronium, SCC produced total neuromuscular blockade without initial recovery. The overall duration of the SCC effect (time from the administration to 90% recovery) was 7-18 min. No prolonged paralysis from SCC occurred.

Vital capacity rapid inhalation induction technique: comparison of sevoflurane and halothane.

Induction of anaesthesia using the vital capacity rapid inhalation induction (VCRII) technique with either sevoflurane or halothane was compared. The induction time, characteristics, and acceptability were assessed. Thirty-two volunteers were given one of the vapours: 17 received sevoflurane and 15 halothane. Subjects were unpremedicated and breathed approximately 2.6 x minimum alveolar concentration (MAC) equivalent of either agent. There were no differences in the patients' cardiovascular or respiratory variables. The mean time for induction of anaesthesia with halothane (153 +/- 46 sec, SD) was slower than with sevoflurane (81 +/- 22 sec, SD, P < 0.05), reflecting its higher blood:gas solubility. There were fewer induction complications such as coughing and movement in the sevoflurane than in the halothane group. Subjects in the sevoflurane group found the smell of anaesthetic more acceptable than those in the halothane group (65% vs 13%, respectively). Subjects in both groups had no objection to undergoing the procedure again. It is concluded that both halothane and sevoflurane are effective in VCRII of anaesthesia without premedication. However, the slower speed of induction with halothane frustrated the anaesthetist because of the longer induction time, and may increase the chance of pronounced excitatory phenomena occurring.

Induction of anesthesia with sevoflurane, nitrous oxide, and oxygen: a comparison of spontaneous ventilation and vital capacity rapid inhalation induction (VCRII) techniques.

In this study, the vital capacity rapid inhalation induction of anesthesia (VCRII) technique and the conventional spontaneous inhalation induction technique, each using 4.5% sevoflurane in nitrous oxide and oxygen, were compared. The VSRII group (n = 32) and conventional group (n = 32) were each tested on unpremedicated volunteers. VCRII required only half the time of conventional inhalation induction (54 s and 108 s, respectively), and was not associated with cardiovascular instability. Each of the two techniques was found acceptable by most of the volunteers studied (more than 80%). However, sevoflurane is best used with the VCRII technique because VCRII resulted in fewer excitement movements that could lead to severe complications and pronounced excitement.

[Predicting the difficulty of laryngoscopy using the distance between the lower border of the mandible and the thyroid notch].

We examined the relationship between the degree of difficulty in visualization of the larynx and the distance from the lower border of the mandible to the thyroid notch (M-T distance). Patients were examined and the M-T distance was measured with their neck fully extended during preoperative period. Difficulty of laryngoscopy was graded as reported previously. Five hundred sixty one patients were assessed, and those with obvious neck and head pathology were excluded. There were 440 cases (78.4%) in grade 1, 116 cases (20.7%) in grade 2 and only 5 cases (0.9%) in grade 3. There were no grade 4 cases. The M-T distance was 5.4 +/- 0.6 cm in grade 1, 4.6 +/- 0.7 cm in grade 2 and 3.6 +/- 0.7 cm in grade 3. These were significantly different with each other (P < 0.05). If the M-T distance is 4.5 cm or less, the difficulty in visualization of laryngoscope increases. Therefore, in the case in which the M-T distance is 4.5 cm or less, we recommend further examination and preparation for difficult laryngoscopy.

Vital capacity breath technique for rapid anaesthetic induction: comparison of sevoflurane and isoflurane.

This study compares vital capacity rapid inhalational induction of anaesthesia with sevoflurane and isoflurane. Forty-six volunteers undergoing the procedure had one of the two agents: 25 had sevoflurane and 21 isoflurane. Subjects were unpremedicated and breathed approximately 1.7 MAC equivalents of either vapour. There were no significant differences in the patients' monitored cardiovascular, respiratory, and electrocardiographic variables. The mean time for induction of anaesthesia with sevoflurane (120 s) was significantly shorter than with isoflurane (145 s), reflecting its higher blood-gas solubility. There were fewer induction complications in the sevoflurane group. Subjects in the sevoflurane group found the induction of anaesthesia more pleasant and were more willing to undergo it again compared to subjects in the isoflurane group. We conclude that sevoflurane is superior to isoflurane in vital capacity rapid inhalational induction of anaesthesia, particularly in instances where premedication should be avoided.

[Anesthetic management of a patient with Chubby Puffer syndrome].

Chubby Puffer syndrome produces symptoms such as sleep apnea, cor pulmonale and upper airway obstruction due to adenotonsillar enlargement. We gave anesthesia for adenotonsillectomy in a 6-year-old boy with this syndrome. The child was massively obese. Anesthesia was induced with thiamylal, nitrous oxide and enflurane by monitoring SaO2. Tracheostomy was performed following orotracheal intubation because of possible difficult postoperative course. At the beginning of operation arterial blood studies showed hypoxemia. Positive end-expiratory pressure ventilation was effective to improve oxygenation. After adenotonsillectomy the symptoms were relieved.

[Intraoperative anoxic spells in patients with tetralogy of Fallot].

We experienced 5 cases of intraoperative anoxic spell in 48 patients with tetralogy of Fallot (TOF). One of 5 cases had tetralogy with pulmonary atresia (Type A), and the others had tetralogy alone (Type D). The patient of type A who had anoxic spells during preoperative period had been on chronic propranolol therapy. However, the patients of type D had no anoxic spells during preoperative period and one in this type had not been on beta-adrenergic blocking drugs preoperatively. One patient was anesthetized with fentanyl-diazepam-O2, and the others were anesthetized with morphine-diazepam-O2. We used mainly alpha-adrenergic drugs and sodium bicarbonate for the therapy of intraoperative anoxic spells. Concerning the intraoperative anoxic spell, we have to be aware in the management of the patients with TOF, whether the patient had anoxic spells during preoperative period or not.

[Comparative hemodynamic effects of midazolam and flunitrazepam as induction agents].

The cardiovascular effects of midazolam as induction agent in A.S.A. class 2 surgical patients (N = 6) were compared with a similar group of patients (N = 6) receiving flunitrazepam. An induction-sized dose of midazolam was 0.17 +/- 0.03 mg/kg and the dose of flunitrazepam was 0.036 +/- 0.0039 mg/kg. The induction-sized dose of midazolam produced a moderate cardiovascular depression, similar to flunitrazepam. Cardiac index, left ventricular stroke work index and mean pulmonary pressure were decreased significantly after injection of midazolam and mean arterial pressure, cardiac index and left ventricular stroke work index were decreased significantly after administration of flunitrazepam. Following the administration of midazolam, there were decreasing tendency of mean pulmonary pressure and pulmonary artery occluded pressure, and no change of central venous pressure, while increasing tendency of central venous pressure with flunitrazepam. Unlike flunitrazepam, midazolam may act capacitance vessels. However in this study, statistical significant differences between the hemodynamic effects of midazolam and those of flunitrazepam were not obtained.

[Pharmacokinetic study on the lidocaine concentration in serum during epidural anesthesia].

This study was performed on humans to find a safety format for clinical application of lidocaine, a most popular local anesthetic in Japan, by following serum concentration of the drug epidural anesthesia, with or without repeated supplemental addition of the anesthetic. Twenty-five patients (ASA 1-2) were used for observations of short duration and 7 patients (ASA 1-3) for long duration. Changes in serum drug concentration after single epidural or intravenous injection were analyzed pharmacokinetically in 7 and 15 patients with or without hepatic disfunction, respectively. The serum lidocaine concentration was determined by an EMIT assay. It was found that during epidural anesthesia of 3 h duration with 1.5% lidocaine E (priming dose 15-20 ml, supplemental doses one or two thirds of the priming dose) an interval of about 50 min was preferable for the first supplementation, followed by longer intervals: serum drug concentration did not exceed 5 micrograms/ml over which is dangerous clinically. During epidural anesthesia of longer duration (maximum 11 h), the peak concentrations remained below 5 micrograms/ml which was seen after the 9th supplementation. There was a trend of increase in serum drug concentration by each supplementation. Actual mean values were lower than those estimated pharmacokinetically. This was due partly to dilution effect induced by bleeding and transfusions that followed. Addition of epinephrine to lidocaine (lidocaine E) reduced reabsorption of supplemented lidocaine by 20%, thereby increased the local concentration of the drug, resulting in an elongation of interval for supplementation. The combination was beneficial to patients also by preventing a sharp rise of drug level even after repeated supplementation. No difference was observed in the absorption, degradation and excretion of the drug between patients with and without hepatic dysfunctions examined.