Takayuki Kunisawa

The Pentax‐AWS® rigid indirect video laryngoscope: clinical assessment of performance in 320 cases*

The Pentax‐AWS® airway scope system is a rigid indirect video laryngoscope with integrated tube guidance. Laryngoscopy and intubation are visualised using a built in LCD monitor which displays the view obtained by a CCD camera mounted in the tip of the laryngoscope. We describe its clinical performance in 320 patients. The Pentax‐AWS significantly improved the laryngeal view compared to the Macintosh laryngoscope. Forty‐six patients (14%) who were classified as Cormack Lehane glottic view grade 3 or 4 using the Macintosh laryngoscope were classified as grade 1 (45 cases) or 2a (1 case) using the Pentax‐AWS airway scope. Laryngeal views measured by percentage of glottic opening score were improved significantly using the Pentax‐AWS. Intubation using the Pentax‐AWS was successful in all cases, 96% at the first and 4% at the second attempt. The mean (SD) time required to place the tracheal tube was 20 (10) s. The Cormack Lehane grade obtained with the Macintosh blade did not affect the total time to correctly position the tube using the Pentax‐AWS. Intubation difficulty scale (score = 0 in 305 patients, score = 1 in 14 and score = 2 in one patient) indicates that tracheal intubation was performed easily in most cases. The Pentax‐AWS not only improves the laryngeal view, but its tube guide also facilitates rapid, easy and reliable tracheal intubation under vision. It can be useful in routine anesthesia care and may be advantageous in the situation of unanticipated difficult intubation.

Dexmedetomidine suppresses the decrease in blood pressure during anesthetic induction and blunts the cardiovascular response to tracheal intubation

STUDY OBJECTIVE To evaluate the effect of dexmedetomidine combined with fentanyl on hemodynamics. DESIGN Prospective, double-blinded, randomized study. SETTING Operating room of a university hospital. PATIENTS 30 ASA physical status II and III patients with mild-to-moderate cardiovascular disease. INTERVENTIONS Patients were assigned to one of three groups: Group D-F2 [dexmedetomidine, effect-site concentration (ESC) of fentanyl = two ng/mL]; Group F2 (placebo, ESC of fentanyl = two ng/mL), or Group F4 (placebo, ESC of fentanyl = 4 ng/mL). MEASUREMENTS Dexmedetomidine (an initial dose of 1.0 microg/kg for 10 min, followed by a continuous infusion of 0.7 microg x kg(-1) x hr(-1)) or placebo saline was administered 15 minutes before anesthetic induction. Anesthesia was induced with propofol and fentanyl using a target-controlled infusion system. Hemodynamic parameters: systolic (SBP) and diastolic blood pressures (DBP), and heart rate (HR) during anesthetic induction were measured and the percent changes were calculated for both induction and intubation. MAIN RESULTS After inducing anesthesia, SBP was significantly higher in Group D-F2 (127 +/- 24 mmHg) than Group F2 (90 +/- 20 mmHg) or Group F4 (77 +/- 21 mmHg). The SBP in Groups F2 and F4 reached 160 +/- 31 mmHg and 123 +/- 36 mmHg, respectively, after intubation, but no significant change in SBP was noted in Group D-F2. The percent increase in SBP due to tracheal intubation in Group D-F2 was 3% +/- 4% and was significantly lower than that of Group F2 (70% +/- 34%) or Group F4 (45% +/- 36%). CONCLUSION Dexmedetomidine combined with fentanyl during anesthetic induction suppresses the decrease in blood pressure due to anesthetic induction and also blunts the cardiovascular response to tracheal intubation.

Effect of age on pulmonary gas exchange during laparoscopy in the Trendelenburg lithotomy position

Background:  Physiological changes in respiratory mechanics caused by aging may lead to a deterioration in pulmonary gas exchange, an increase in the alveolar–arterial oxygen gradient [(A–a)Do2] and a difference between the arterial carbon dioxide (CO2) tension (Paco2) and expired end‐tidal CO2 tension (PETco2) [P(a–ET)co2] during laparoscopy in the Trendelenburg lithotomy position (TLP).

Ultrasound-guided cannula cricothyroidotomy.

1128 November 2012 W HEN difficulty with airway management is anticipated, standard guidelines recommend that the airway is secured in the awake patient.1 In the “cannot intubate, cannot ventilate” situation, surgical or cannula cricothyroidotomy is required.1 However, identification of the cricothyroid membrane by palpation is frequently inaccurate, even under elective conditions.2 Preoperative evaluation of the anterior neck with an ultrasound may be a viable technique of increasing the safety of cricothyroidotomy. An 82-yr-old man with a difficult intubation profile as a consequence of cervical spine disease was scheduled for percutaneous nephrolithotripsy in the prone position. Before awake fiberoptic intubation, his neck was scanned with an ultrasound linear probe to identify the cricothyroid membrane. Because he had a history of hypertension and ischemic heart disease, we decided to apply tracheal anesthesia before intubation. The distance from skin surface to the membrane was measured as 0.84 cm, and neither vessel nor abnormal structure was observed. Cannula cricothyroidotomy was then performed with a 22G intravenous catheter under ultrasonographic guidance in an out-of-plane configuration, because this is a more reliable technique of achieving exact midline puncture.3 The figure shows the anterior-posterior view of the larynx and sternocleidomastoid muscle (asterisk) as the cannula (arrow) enters the cricothyroid membrane (dashed line) from the 12 o’clock direction. As soon as loss-of-resistance sensation was detected, air was aspirated. Lidocaine was injected through the cannula, and then fiberoptic bronchoscope intubation was performed uneventfully. Preoperative examination of the larynx with sonography can accurately identify the cricothyroid membrane and may provide other anatomical information. Though the cricothyroid membrane puncture is less frequently used to achieve airway anesthesia, ultrasound guidance may improve safety whenever this technique is used, including prophylactic and emergency cannula cricothyroidotomy.

Comparison of the Pentax-AWS Airway Scope with the Macintosh laryngoscope for nasotracheal intubation: a randomized, prospective study

STUDY OBJECTIVE To evaluate the effectiveness of the Pentax-AWS Airway Scope (AWS) in comparison to the Macintosh laryngoscope during nasotracheal intubation. DESIGN Prospective randomized study. SETTING Operating room of a university-affiliated hospital. PATIENTS 90 ASA physical status 1 and 2 adults, aged 18 to 72 years, scheduled for orthodontia surgery requiring nasotracheal intubation. INTERVENTIONS Patients were randomly assigned to three groups to undergo tracheal intubation with a Macintosh laryngoscope (Group Mac; n = 30), AWS with its tip inserted into the vallecula for indirect elevation of the epiglottis (Group AWS-I; n = 30), or AWS with its tip positioned posterior to the epiglottis for direct elevation of the epiglottis (Group AWS-D; n = 30). MEASUREMENTS Percentage of glottic opening (POGO) score at the time of laryngeal exposure, time required for intubation, and intubation difficulty scale (IDS) were measured. The frequency of postoperative sore throat and hoarseness also were noted. MAIN RESULTS Patient demographics did not differ among the groups. In Groups AWS-I and AWS-D, IDS scores were reduced significantly, and the percentages of glottic opening were significantly improved, compared with the Macintosh group. Time to place the endotracheal tube was significantly shortest in Group AWS-I. In one case from each group, intubation within two attempts failed and a different approach was required. CONCLUSION The AWS offers better intubation conditions than the Macintosh laryngoscope during nasotracheal intubation. The AWS may be used to elevate the epiglottis both directly and indirectly for nasotracheal intubation.

A comparison of the Pentax Airway Scope™ with the Airtraq™ in an infant manikin

We compared the Pentax Airway ScopeTM with the AirtraqTM optical laryngoscope in an infant manikin. Twenty‐three anaesthetists randomly performed tracheal intubation: at rest, (a) with the Airway Scope and (b) with the Airtraq; and during chest compressions, (c) with the Airway Scope and (d) with the Airtraq. The success rate, modified Cormack and Lehane classification for glottic view, time taken to view the glottis, and time to place the tracheal tube were recorded. There was no difference in intubation success rate or quality of glottic view between the two devices. The median (IQR [range]) time taken to obtain a view of the glottis was 4.5 (3.7–6.4 [1.8–14.0]) s using the Airway Scope compared with 7.1 (5.5–9.6 [3.3–12.0]) s using the Airtraq (p = 0.001), and to successful placement of the tracheal tube was 8.3 (6.8–9.4 [3.7–20.7]) s using the Airway Scope compared with 11.2 (10.4–13.8 [4.9–23.7]) s using the Airtraq (p = 0.001). During chest compressions, the median (IQR [range]) time taken to view the glottis was 5.1 (4.0–7.2 [2.0–12.4]) s using the Airway Scope compared with 7.5 (5.0–13.2 [4.2–26.4]) s using the Airtraq (p = 0.006), and to successful placement of the tracheal tube was 9.5 (6.6–13.7 [4.5–16.2]) s using the Airway Scope compared with 11.7 (9.1–18.1 [6.2–37.4]) s using the Airtraq (p = 0.022). We conclude that both devices provided good quality views of the glottis and successful tracheal intubation in an infant manikin both at rest and during external chest compressions. Use of the Airway Scope resulted in a shorter time to view the glottis and perform successful tracheal intubation compared with the Airtraq.

Parker Flex-Tip Tube facilitates intubation when the Pentax-AWS fails to reach the larynx

To the Editor: Pentax-AWS Airway Scope (AWS: Hoya, Tokyo), a new rigid, indirect videolaryngoscope with integrated tube guidance, has been successfully used in patients with both normal and difficult airways. In some case, however, the blade tip cannot be advanced beneath the epiglottis, even after multiple attempts [1], and the intubation frequently fails due to blade configuration [2]. Several authors proposed the use of tube introducer (elastic bougie) to solve the problem [3]. We propose the use of the Parker Flex-Tip Tube to facilitate intubation under this situation. Preoperative airway assessment of a 61-year-old man scheduled for general anesthesia indicated a risk of difficult intubation because of relatively small mandible, his thyromental distance being 4 cm. Since the patient did not have risk factors of difficult mask ventilation, he was anesthetized with propofol and rocuronium. After complete paralysis was confirmed with the peripheral nerve stimulator, laryngoscopy was performed with a Macintosh no. 4 blade, but only the epiglottis was visualized, and it was graded as Cormack‐Lehane grade 3b. We next used the AWS for the second intubation attempt. However, the tip was not able to be advanced beneath the epiglottis but inserted into the vallecula. The epiglottis was indirectly elevated, and the laryngeal exposure was approximately 80% of the glottic opening. We tried to insert the standard bevel tube (Phycon Tube, Fuji System, 7.5 mm ID, 10 mm OD) set in the channel, but the tube tip impinged onto the epiglottis, and intubation failed. Next, we used the Parker Flex-Tip Tube (Kobayashi Medical, 7.5 mm ID, 10 mm OD), and the tube was inserted smoothly into the glottis without trapping on the arytenoids. The Parker Flex-Tip Tube has a tapered, curved tip and has been shown to facilitate intubation with the Bullard laryngoscope [4] and fiberoptic bronchoscope [5]. The advantage of using the Parker tube in combination with the AWS has not been well evaluated. Figure 1 shows the two tubes, with the same outer diameter as those used in this case, protruding from the channel. We can see more space from the blade tip to the Parker tube than with the standard tube. It seems that this space allows the Parker tube to be advanced without impinging upon the epiglottis, and the tapered, curved tip glides on the posterior surface of the epiglottis to lead the

Cardiovascular responses to tracheal intubation with the Airway Scope (Pentax-AWS).

The recommended laryngoscopy technique with the AWS involves using the blade tip to elevate the epiglottis directly. This procedure is very similar to that used with the Bullard laryngoscope (BuLS; Gyrus ACMI, Southborough, MA, USA). Araki et al. [2] demonstrated that there were no signifi cant differences in cardiovascular responses after intubation between the BuLS and the McL in 30 patients without airway problems. The Airtraq laryngoscope (ATQ; Prodol, Vizcaya, Spain) is another device similar to the AWS, but the view of the glottis can be optimized either by lifting the epiglottis directly, as with the AWS or BuLS, or indirectly by tensioning the hyoepiglottic ligament after the blade tip is positioned in the vallecula. Maharaj et al. [3] demonstrated that increases in HR were less when intubation was achieved with the ATQ than with the McL. Both the AWS and the ATQ provide a view of the glottis from behind the dorsum of the tongue, and therefore both devices probably require less lifting force than that required during direct laryngoscopy. It is unlikely that the technique of epiglottis elevation could cause this different result, (i.e., ATQ, but AWS attenuates cardiovascular responses), because the McL blade tip is alCardiovascular responses to tracheal intubation with the Airway Scope (Pentax-AWS)

A comparison of the absolute amplitude of motor evoked potentials among groups of patients with various concentrations of nitrous oxide.

PurposeIt has been shown in previous studies that nitrous oxide (N2O) suppresses the amplitude of motor evoked potentials (MEPs) in individual subjects. In the present study, we compared the absolute amplitude and latency of MEPs among groups of patients with various concentrations of N2O.MethodsThe subjects were 60 patients who were scheduled to undergo craniotomy with MEP monitoring. Anesthesia was induced and maintained with propofol and fentanyl. The patients were randomly assigned to one of three groups based on the concentration of N2O: 0% N2O (N0 group), 50% N2O (N50 group), and 66% N2O (N66 group). MEPs were elicited by transcranial electrical stimulation. The effect-site concentrations (ESCs) of anesthetics were calculated retrospectively. The effects of anesthetics on MEP were analyzed by analysis of covariance (ANCOVA) followed by Tukey’s method.ResultsMEPs were elicited in all cases. The absolute amplitude of the MEP was significantly higher in the N0 group than in the N50 and N66 groups [4.16 ± 0.42 vs 1.00 ± 0.26 mV and 1.00 ± 0.27 mV, respectively (mean ± SD); P < 0.05]. In contrast, there was no significant difference in the latency of the MEP among the three groups of subjects (N0: 16.64 ± 0.72, N50: 16.78 ± 0.66, and N66: 16.82 ± 0.63 ms).ConclusionThe results suggest that N2O can suppress the absolute amplitude of the MEP in patients under propofol and fentanyl anesthesia. Although monitoring of MEP as a trend is feasible even if N2O is used, the use of N2O may be better avoided.

Ultrasound-guided superior laryngeal nerve block and translaryngeal block for awake tracheal intubation in a patient with laryngeal abscess

To the Editor: When airway management is anticipated to be difficult, awake intubation using a fiberoptic bronchoscope (FOB) is indicated [1]. To achieve successful awake intubation, patient cooperation in combination with appropriate local anesthesia is essential. Superior laryngeal nerve block (SLNB) is an airway anesthesia technique that can paralyze the lingual radix, epiglottis, and cricothyroid muscle, and is thus expected to suppress the gag and cough reflexes. SLNB has conventionally been performed with palpation of the greater horn of the hyoid as an anatomical landmark. The needle is inserted in an anteroinferomedial direction until the lateral aspect of the greater horn is contacted, and local anesthetic is then injected while the carotid artery is displaced posteriorly. However, it is sometimes difficult to recognize landmarks when the patient is obese or has an anatomical abnormality due to a pathology. Ultrasound-guided nerve block has been widely used recently, and this technique can provide visual information on the anatomy [2]. Here, we report a case in which awake tracheal intubation was performed under ultrasound-guided bilateral SLNB. A 19-year-old female complained of submental pain after odontotherapy, and she was scheduled for incisional drainage of a laryngeal abscess. As the abscess involved the medial pterygoid muscle (Fig. 1a), she presented restricted mouth opening (less than one finger). After obtaining written informed consent, semi-awake FOB intubation under nerve block was scheduled. Prior to nasal FOB intubation, 2 mg of midazolam and 50 lg of fentanyl were administered. Nasal mucosa was topicalized with 8 % lidocaine. Although we attempted to perform SLNB, her left hyoid bone was difficult to find by palpation. However, when we scanned her neck using US (5–10 MHz linear probe, S-Nerve, Sonosite Japan, Tokyo, Japan), the bone was easily identified in the transverse view. The distance from the skin surface to the bone was measured as 1.1 cm, and neither vessel nor abnormal structure was observed. With a 22G needle, 2 ml of 2 % lidocaine were injected into the surface of the greater horn of the hyoid under ultrasound guidance in an in-plane configuration (Fig. 1b). The procedure was repeated on the right side. The tracheal membrane was also topicalized with ultrasound-guided translaryngeal block through the cricothyroid membrane. Ultrasound-guided SLNB seemed effective and FOB intubation was successfully performed while the patient was semi-awake without any discomfort. The patient complained of slight hoarseness after surgery but this disappeared within a day. There was no other notable complication. We have previously reported ultrasound-guided translaryngeal block through the cricothyroid membrane for awake The work was attributed to both the Department of Anesthesiology and Critical Care Medicine and the Department of Emergency Medicine and Intensive Care at Asahikawa Medical University.