Nobuaki Asakura

Determination of end-tidal sevoflurane concentration for tracheal intubation and minimum alveolar anesthetic concentration in adults.

The purpose of this study was to determine both the concentration of sevoflurane required for tracheal intubation (MACEI) and its minimum alveolar anesthetic concentration (MAC) in adults. The study group consisted of 86 elective surgical patients, ASA physical status I or II, aged 16–59 yr. There was no premedication administered. For MACEI determination, after establishing and maintaining the predetermined end-tidal concentration for 20 min, tracheal intubation was attempted using a cuffed tracheal tube without muscle relaxant or other adjuvants. Each concentration at which tracheal intubation was attempted was predetermined as follows: 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, and 7.0%. For MAC determination, the patients examined were basically the same as those for MACEI determination, except for those who received muscle relaxant or other adjuvants because they were “not intubated smoothly.” After establishing and maintaining the predetermined end-tidal concentration at which skin incision was attempted was concentration at which skin incision was attempted was predetermined as follows: 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, and 3.0%. The MACEI of sevoflurane was 4.52% (95% confidence limits, 3.91%-5.21%), and the ED95 for tracheal intubation was 8.07%. The MAC of sevoflurane was 1.58% (95% confidence limits, 1.14%-1.98%), and the AD95 (anesthetic ED95) was 2.96%. The MACEI/ MAC ratio was 2.86 (95% confidence limits, 2.63–3.43). Anesthesia induction followed by tracheal intubation can be accomplished in adults when sevoflurane is administered as a sole anesthetic, but in excess of 8% end-tidal concentration.

End-tidal Sevoflurane Concentrations for Laryngeal Mask Airway Insertion and for Tracheal Intubation in Children

BACKGROUND: Sevoflurane, a new inhalational anesthetic agent characterized by a low blood-gas partition coefficient and nonpungent odor, appears suitable as an induction agent for children. The laryngeal mask airway is a new device for maintaining airway patency during anesthesia. This study was conducted to determine the sevoflurane concentrations required for insertion of a laryngeal mask (MACLMI) and for tracheal intubation (MACTI) in children. METHODS: Forty-two patients, aged 1-9 yr, scheduled for surgery during general anesthesia were randomly assigned into two groups: MACLMI (n = 21) and MACTI (n = 21). After the predetermined end-tidal concentration had been established and maintained for 20 min, laryngeal mask insertion or tracheal intubation was attempted without neuromuscular relaxants or other adjuvants. Each concentration at which laryngeal mask insertion or tracheal intubation was attempted was predetermined by the up-and-down method (with 0.5% as a step size). RESULTS: Sevoflurane MACLMI was 2.00 +/- 0.28%. Sevoflurane MACTI was 2.83 +/- 0.34%, significantly greater than MACLMI. CONCLUSIONS: Laryngeal mask insertion can be performed at a lesser sevoflurane concentration than that required for tracheal intubation.

A "bubble-tip" (Airguide) tracheal tube system: its effects on incidence of epistaxis and ease of tube advancement in the subglottic region during nasotracheal intubation.

Epistaxis and tubal obstruction in the subglottic region are difficulties encountered during nasotracheal intubation. Trauma to the nasal airway must be avoided, especially in patients receiving anticoagulant therapy. In addition, smooth passage of the tracheal tube through the larynx is desired. The tip of an Airguide® tracheal tube system has a soft, round, glossy balloon head which should be less traumatic to the nasal mucosa than other more commonly used tubes. We, therefore, determined whether the Airguide® reduces the incidence of epistaxis and increases smooth passage of the tracheal tube in the subglottic region during nasotracheal intubation. Sixty-six patients were divided into two groups, Airguide® (n = 39) and Standard (n = 27). Each group was divided into two subgroups, topical epinephrine application as a mucosal decongestant and nonepinephrine. The incidences of epistaxis and smooth passage were compared between the two groups. The Airguide® group had a significantly lower incidence of epistaxis (9/39 vs 13/26; P < 0.05; bleeding was not checked in one patient in the Standard group) and provided a significantly smoother passage in the subglottic region than the Standard group (tube impingement in the subglottic region, 0/39 vs 11/27; P < 0.01). There was no significant difference in the incidence of epistaxis between the subgroups with and without topical application of epinephrine. The Airguide® helps to minimize epistaxis and increases navigability in the subglottic region during nasotracheal intubation.

Determination of the distance between the laryngoscope blade and the upper incisors during direct laryngoscopy : comparisons of a curved, an angulated straight, and two straight blades

We compared visibility and dental complications from a variety of blades during tracheal intubation. Ninety-eight patients who received tracheal intubation were enrolled. They were divided into two groups: Study 1 (n = 50) and Study 2 (n = 48). Four laryngoscopic evaluations were planned for each patient using Miller and Wisconsin straight blades with different heel heights, a Macintosh curved blade, and a Belscope angulated straight blade (Study 1: Miller No. 3, Wisconsin No. 3, Macintosh No. 4, and Belscope medium; and Study 2 Miller No. 2, Wisconsin No. 2, Macintosh No. 3, and Belscope medium, respectively). All laryngoscopies were performed by the same anesthesiologist. The distance between the blade and the upper central incisors was measured when the optimum visibility of the glottis was obtained. The visibility was determined according to the Cormack and Lehane grading. Analysis of the distance between the blade and upper incisors was performed using the results of the 44 patients (166 distances) in Study 1 and the 48 patients (181 distances) in Study 2 who had a visibility of two or better. The Belscope blade provided a significantly greater visual field than the other types of blade. Two patients sustained a fracture of the central incisor and subluxation of the central incisor, respectively, during laryngoscopy in which a Wisconsin blade was used. The average incidence of dental injury was 1/191. The Belscope blade may contribute to a reduced likelihood of upper dental injuries during laryngoscopy.

Intraoperative combined administration of indomethacin and buprenorphine suppositories as prophylactic therapy for post-open-cholecystectomy pain.

Buprenorphine and indomethacin are quite different pharmacologically. The objective of this study was to determine the analgesic effect from their combined administration in suppository form. Eighty patients undergoing open cholecystectomy under nitrous oxide-oxygen-sevoflurane anesthesia, in addition to epidural anesthesia using lidocaine, were divided into four groups: Group A received buprenorphine 0.4 mg and indomethacin 50 mg; Group B, buprenorphine 0.4 mg; Group C, indomethacin 50 mg; and Group D, no drug. The drugs were administered after induction of general anesthesia. One patient was withdrawn because of the administration of the wrong drug. Patients in Group A required fewer analgesics, had a longer period of analgesic effect from the end of surgery, and enjoyed a better pain score. This group also included more patients who required no analgesics. We conclude that the combined administration of opioid and nonopioid suppositories may provide far better prophylactic analgesia than a single drug.

The effect of age on retrieval of local anesthetic solution from the epidural space.

We conducted this prospective study to determine whether advancing age is correlated with retrieval of local anesthetic solution from the epidural space.Three hundred forty-six patients (ASA physical status I or II, 20-93 yr of age, 177 female and 169 male patients) undergoing epidural anesthesia were enrolled. The epidural space was identified by a loss of resistance technique using air, and a catheter was introduced 3 cm. Three milliliters of 2% lidocaine with epinephrine was injected as a study dose by hand at a rate of 1 mL/s with the patient in the supine position. The syringe was immediately aspirated to retrieve the local anesthetic solution. A retrieved volume of 0.5 mL or more with a glucose concentration less than 6 mg/dL was defined as retrieval positive, and a volume of less than 0.5 mL was defined as retrieval negative. There was a significant correlation between age and retrieval volume among all the patients (Y = 0.008X-0.222, P < 0.0001) with a significant increase in the positive retrieval incidence and volume from the patients in their 50s (11%, 0.6 +/- 0.3 mL) to the patients in their 60s (26%, 1.0 +/- 0.6 mL) (P < 0.05 for both). The incidence of positive retrieval and the retrieval volume were greater in the patients in their 60s and older (30%, 1.1 +/- 0.63 mL) than in the younger than 60 (10%, 0.6 +/- 0.3 mL) (P < 0.0001 and P < 0.001). The glucose concentration was 2.3 +/- 1.2 mg/dL in the positive cases. We conclude that there is a weak positive correlation between age and the local anesthetic solution retrieved from the epidural space. Implications: We conducted a study in 346 patients to determine whether advancing age could be correlated with retrieval of local anesthetic solution from the epidural space. We found a weak positive correlation between advanced age and the amount of solution retrievable from the epidural space. Further studies are required to determine whether this phenomenon may call for dose adjustments in patients aged more than 60 yr. (Anesth Analg 1997;85:1091-6)

End-Tidal Sevoflurane Concentrations for Laryngeal Mask Airway Insertion and for Tracheal Intubation in Children

Background:Sevoflurane, a new inhalational anesthetic agent characterized by a low blood-gas partition coefficient and nonpungent odor, appears suitable as an induction agent for children. The laryngeal mask airway is a new device for maintaining airway patency during anesthesia. Tills study was conducted to determine the sevoflurane concentrations required for insertion of a laryngeal mask (MACLMI) and for tracheal intubation (MACTI) in children. Methods:Forty-two patients, aged 1-9 yr, scheduled for surgery during general anesthesia were randomly assigned into two groups: MACLMI (n=21) and MACTI (n=21). After the predetermined end-tidal concentration had been established and maintained for 20 min, laryngeal mask insertion or tracheal intubation was attempted without neuromuscular relaxants or other adjuvants. Each concentration at which laryngeal mask insertion or tracheal intubation was attempted was predetermined by the up-and-down method (with 0.5% as a step size). Results:Sevoflurane MACLMI was 2.00 ± 0.28%. Sevoflurane MACTI was 2.83 ± 0.34%, significantly greater than MACLMI. Conclusions:Laryngeal mask insertion can be performed at a lesser sevoflurane concentration than that required for tracheal intubation.