The McGrath® Series 5 videolaryngoscope vs the Macintosh laryngoscope: a randomised, controlled trial in patients with a simulated difficult airway.

We compared the McGrath® Series 5 videolaryngoscope with the Macintosh laryngoscope in a simulated difficult airway, using manual in-line stabilisation in 88 anaesthestised patients of ASA physical status 1-2. The primary outcome was laryngoscopic view. Secondary outcomes included rates of successful tracheal intubation and complications. A Cormack and Lehane grade-1 or -2 view was found in all patients when using the McGrath compared with 45 (51%, p < 0.0001) using the Macintosh laryngoscopes. The mean (SD) percentage of glottic opening was 82 (23)% using the McGrath compared with 13 (23)% using the Macintosh (p < 0.0001). In 66 out of 88 patients (75%), the McGrath improved the glottic view by one to three grades compared with the Macintosh (p < 0.001). Intubation of the trachea was successful in all patients using the McGrath, while the Macintosh was successful in 26 (59%, p < 0.001). There was no significant difference in the complication rates between the devices.

Removal of the stylet from the tracheal tube: effect of lubrication.

We compared the work needed to retract a non-lubricated and a lubricated stylet from a tracheal tube over 24 h. Stylets were lubricated with sterile water, silicone fluid, lidocaine spray, lidocaine gel, MedPro(®) lubricating gel or Lacri-Lube(®). The mean (SD) work in joules needed to retract the stylet by 5 cm from the tracheal tube was recorded immediately (time 0), at 5 and 30 min and at 1, 3 and 24 h. At time 0 lubrication with sterile water (0.53 (0.09); p = 0.001), silicone fluid (0.43 (0.10); p < 0.001), lidocaine gel (0.60 (0.15); p = 0.01) and MedPro gel (0.57 (0.07); p = 0.005), were better than no lubrication (0.94 (0.28)). Where a tracheal tube is pre-loaded with a stylet for use at an indeterminate time, silicone fluid was the best choice of lubricant as it performed consistently well up to 24 h. At 24 h only silicone fluid (0.49 (0.01)) outperformed no lubrication (0.77 (0.24); p = 0.04).

The effect of sterilisation on the light intensity of the reusable Trachlight™.

We examined the light intensity delivered by the Trachlight™ reusable lightwand and the effect of repeated sterilisation on this light intensity. Using a light meter and test chamber, the light intensity of 12 new Trachlights and 31 Trachlights available in operating theatres was measured. In addition, five new devices underwent 30 repeated sterilisations with light intensity measurement after each cleaning. There was no difference between the light intensity of new Trachlights (median (IQR [range]) 2282 (2202-2780 [1970-4400])) lux and the devices currently in service (2295 (2018-2796 [1649-3280]) lux (p = 0.27)). The median (range) number of uses for devices currently in service was only 3 (0-9). There was, however, significant light intensity loss after 10, 20 and 30 cleanings (p = 0.001). After 10 cleanings, the mean light intensity was 75% of initial output, and after 30 cycles, light intensity was 59% of initial output.

Lightwand intubation using the Trachlight: a brief review of current knowledge.

PURPOSE: About 1% to 3% of laryngoscopic intubations can be difficult or impossible. Light-guided intubation has been proven to be an effective, safe, and simple technique. This article reviews current knowledge about the newer version lightwand: the Trachlight (TL). SOURCE: To determine its clinical utility and limitations, we reviewed the current literature (book and journal articles) on the TL since its introduction in 1995. PRINCIPAL FINDINGS: TL has been shown to be useful both in oral and nasal intubation for patients with difficult airways. It may also be useful in "emergency" situations or when direct laryngoscopy or fiberoptic endoscopy is not effective, such as with patients who have copious secretions or blood in the oropharynx. TL can also be used for tracheal intubation in conjunction with other devices (laryngeal mask airway -LMA-, intubating LMA, direct laryngoscopy). However, TL should be avoided in patients with tumours, infections, trauma or foreign bodies in the upper airway. CONCLUSIONS: Based on the clinical reports available, the TL has proven to be a useful option for tracheal intubation. In addition, the device can also be used together with other intubating devices, such as the intubating LMA and the laryngoscope, to improve intubating success rates. A clear understanding of the principle of transillumination of the TL, and an appreciation of its indications, contraindications, and limitations, will improve the effectiveness of the device as well as reducing the likelihood of complications. Finally, regular practice with the TL with routine surgical patients requiring tracheal intubation will further improve intubation success rates.

Light-guided tracheal puncture for percutaneous tracheostomy.

PURPOSE: To determine the effectiveness of lightwand-guided tracheal puncture for percutaneous tracheostomy. METHODS: The desired puncture site was marked on the skin of the anterior neck. A lightwand (Trachlight) was inserted into the patient's endotracheal tube (ETT), so that the number indicator on the lightwand matched the number indicator of the ETT of the patient. At this position, the light bulb of the lightwand was exactly placed at the tip of the endotracheal tube. With the lightwand turned on, the lightwand together with the endotracheal tube (ETT-LW) was slowly withdrawn from the trachea until a bright glow in the anterior neck could be seen 1 cm above the marked puncture site. At this position, the tip of the ETT was 1 cm above the puncture site. RESULTS: Percutaneous tracheostomy via a light-guided tracheal puncture was performed on 11 neurosurgical patients. The withdrawal of the endotracheal tube to a location above the puncture was accomplished easily with the lightwand. All percutaneous tracheostomies performed were successful, with ease and without any complications. The procedure time was 17.8 +/- 5.3 min. Mechanical ventilation was not interrupted during the whole procedure. CONCLUSION: The lightwand guided intratracheal puncture for percutaneous tracheostomy is a simple, effective, and safe procedure. This technique can avoid the risk of puncturing the endotracheal tube and/or cuff, thus allowing adequate ventilation and oxygenation during the percutaneous tracheostomy. Furthermore, this technique is inexpensive and minimizes the risk of damaging equipment like the fibreoptic bronchoscope.

Head elevation reduces head-rotation associated increased ICP in patients with intracranial tumours.

PURPOSE: To quantify the effects of graded head rotation and elevation on intracranial pressure (ICP) in neurosurgical patients, before and after induction of general anesthesia. METHODS: Patients with supratentorial tumours (n=12), scheduled for craniotomy with planned ICP monitoring, underwent baseline ICP measurements awake and supine (0 degrees rotation and elevation). Incremental degrees of head rotation (15 degrees) and of head elevation (10 degrees) were performed independently and in combination. Paired measurements of ICP at all levels of head rotation and elevation were also performed before and after induction of general anesthesia (n=6). RESULTS: The baseline ICP was 12.3 +/- 6.4 mmHg (n=12). Changes of ICP were proportional to the degree of head rotation or elevation. Head rotation of 60 degrees maximally increased ICP to 24.8 +/- 14.3 mmHg (P < 0.05). Head elevation above 20 degrees reduced ICP with a maximal reduction to -0.2 +/- 5.5 mmHg at 40 degrees elevation (P < 0.01). Head elevation to 30 degrees reduced the intracranial hypertension associated with head rotation. No differences were observed between ICP measurements made before or after induction of general anesthesia (n=6). Three patients experienced headache with extreme head rotation (<60 degrees) and intracranial hypertension (ICP > 20 mmHg). CONCLUSION: Head rotation of 60 degrees caused an increase in ICP. Concomitant head elevation to 30 degrees reduced the intracranial hypertension associated with head rotation. Headache with head rotation may provide a useful clinical warning of elevated ICP.

A comparative study of tracheal intubation using an intubating laryngeal mask (Fastrach) alone or together with a lightwand (Trachlight).

STUDY OBJECTIVE: To determine if the Trachlight lightwand can facilitate Fastrach intubation by guiding the tip of the endotracheal tube into the trachea. DESIGN: Open-label, prospective, randomized, comparative study. SETTING: General operating suites of a tertiary teaching hospital. PATIENTS: 172 elective surgical patients requiring general anesthesia with endotracheal intubation. INTERVENTIONS: With general anesthesia, the Fastrach, which is a new intubating laryngeal mask airway, was inserted into the oropharynx. Ventilation was ensured before the insertion of an endotracheal tube via the Fastrach. Tracheal intubation was then performed randomly (coin toss) using either the endotracheal tube alone (Fastrach group), or endotracheal tube with the Trachlight, a lightwand (Fastrach/Trachlight group). The time to place the Fastrach and endotracheal tube, to remove the Fastrach, and the total time to intubate were recorded. The number of attempts, failures, trauma, sore throats, and hemodynamic changes were also recorded. Data were analyzed using unpaired t-test, ANOVA with repeated measures, or Chi-squares contingency table where appropriate. MEASUREMENTS AND MAIN RESULTS: Although there were no differences in the times to place the Fastrach, and endotracheal tube, the hemodynamic changes, and postoperative complications, there were significantly more attempts and failures in the Fastrach group compared to the Fastrach/Trachlight group. There were no differences in the incidence of sore throat and trauma in between the groups. CONCLUSIONS: Although tracheal intubation is effective using a Fastrach alone (76% success rate), it is more effective when the Fastrach is used in conjunction with the Trachlight (95%). These results suggest that the lightwand is a useful adjunct for Fastrach intubation. However, the role of Fastrach intubation together with the Trachlight in the management of patients with a potential difficult airway remains to be determined.

Pharmacokinetics and hemodynamic effects of diltiazem in healthy volunteers: comparing resting with the effect of exercise.

PURPOSE: To determine the steady-state plasma concentrations of diltiazem (DTZ) and hemodynamic effect in humans at rest and during exercise. METHODS: Healthy volunteers (10 F, mean age 22, and 11 M, mean age 24) were recruited. Prior to receiving DTZ, each volunteer performed two 3-minute stages of treadmill exercise according to the Bruce protocol. Intra-arterial BP and ECG recordings were obtained before, during and immediately post exercise. Each volunteer then received DTZ 60 mg qid for one week. The same exercise protocol was repeated 1 h after the last dose. Steady-state plasma concentrations of DTZ were determined by a previously reported HPLC. RESULTS: DTZ decreased resting DBP from 84 +/- 13 to 79 +/- 10 mmHg (p > 0.05), and HR from 89 +/- 11 to 82 +/- 13 bpm (p < 0.05). During exercise, an average of 32 and 10% increase in SBP and DBP, respectively, and a 47% increase of HR was found (p < 0.05). DTZ limited these increases to 21% for SBP, 5% for DBP, and 44% for HR (p < 0.05 for drug effect). Steady-state plasma DTZ concentrations were 141 +/- 56 ng/ml. CONCLUSION: DTZ significantly decreased resting HR but not BP in health volunteers. It decreased both hemodynamic variables during exercise. Thus, the hemodynamic effects of diltiazem are more profound during exercise, and may be more useful surrogate markers for calcium antagonists and other cardiovascular agents in healthy volunteer studies.

Tracheal intubation using Bullard laryngoscope for patients with a simulated difficult airway.

PURPOSE: To evaluate the utility and safety of orotracheal intubation in adult patients with simulated difficult airways using the Bullard Laryngoscope (BL). METHODS: A rigid cervical collar was used to simulate the difficult airway. The study consisted of two phases. Phase I evaluated the BL used in conjunction with an independently styletted endotracheal tube (ISETT) passed freehand into the trachea. Phase II evaluated the new Multifunctional Intubating Stylet (MFIS). Forty patients were studied in each phase. Following induction of anesthesia a rigid cervical collar was applied and the laryngoscopic grade assessed. Tracheal intubation was then performed using the BL with either an ISETT or the MFIS. The total time to intubate, number of attempts, failures, hemodynamic changes during intubation were recorded. RESULTS: The rigid collar effectively simulated a difficult laryngoscopy, 65% of patients had a grade 3 view. The success rates for tracheal intubation using the ISETT and MFIS were 88% and 83% respectively. The average times to intubation were similar for both intubating techniques (45.4 +/- 26.8 sec for the ISETT and 41.2 +/- 25.2 sec for the MFIS). Although there were minor hemodynamic changes, mucosal bleeding and sore throat following intubation, there were no major complications in any of the study patients. CONCLUSIONS: The BL, used with either an ISETT or the MFIS, is an effective and safe intubating device for patients with simulated restricted cervical spine movement. Further studies are needed to compare the effectiveness and safety of these two techniques in managing patients with a difficult airway.

The unanticipated difficult airway with recommendations for management.

PURPOSE: To review the current literature and generate recommendations on the role of newer technology in the management of the unanticipated difficult airway. METHODS: A literature search using key words and filters of English language and English abstracted publications from 1990-96 contained in the Medline, Current Contents and Biological Abstracts databases was carried out. The literature was reviewed and condensed and a series of evidence-based recommendations were evolved. CONCLUSIONS: The unanticipated difficult airway occurs with a low but consistent incidence in anaesthesia practice. Difficult direct laryngoscopy occurs in 1.5-8.5% of general anaesthetics and difficult intubation occurs with a similar incidence. Failed intubation occurs in 0.13-0.3% general anaesthetics. Current techniques for predicting difficulty with laryngoscopy and intubation are sensitive, non-specific and have a low positive predictive value. Assessment techniques which utilize multiple characteristics to derive a risk factor tend to be more accurate predictors. Devices such as the laryngeal mask, lighted stylet and rigid fibreoptic laryngoscopes, in the setting of unanticipated difficult airway, are effective in establishing a patient airway, may reduce morbidity and are occasionally lifesaving. Evidence supports their use in this setting as either alternatives to facemask and bag ventilation, when it is inadequate to support oxygenation, or to the direct laryngoscope, when tracheal intubation has failed. Specifically, the laryngeal mask and Combitube have proved to be effective in establishing and maintaining a patent airway in "cannot ventilate" situations. The lighted stylet and Bullard (rigid) fibreoptic scope are effective in many instances where the direct laryngoscope has failed to facilitate tracheal intubation. The data also support integration of these devices into strategies to manage difficult airway as the new standard of care. Training programmes should ensure graduate physicians are trained in the use of these alternatives. Continuing medical education courses should allow physicians in practice the opportunity to train with these alternative devices.

Light-guided retrograde intubation.

PURPOSE: Transillumination of the soft tissues using a lightwand (Trachlight) can guide the endotracheal tube (ETT) into the glottis to facilitate the retrograde intubation. This study evaluated the effectiveness and safety of this intubating technique for patients with cervical spine instability. METHODS: After obtaining institutional approval and informed consent, 27 patients were studied. Light-guided retrograde intubation was performed either awake, or under general anaesthesia. Following cricothyroid membrane puncture using a # 18 i.v. catheter, an epidural catheter was advanced cephalad into the oropharynx. While pulling the epidural catheter taut, the ETT, with the Trachlight in place, was advanced into the glottis. When the tip of the ETT entered the glottis, a bright glow was seen in the anterior neck. The number of attempts, failures, complications, the times required to puncture the cricothyroid membrane, insert the epidural catheter, and insert the ETT into the trachea were recorded. RESULTS: In all patients, the tracheas were successfully intubated. The mean (+/-sd) time to perform cricothyroid puncture, insert the epidural catheter, and place the ETT into the trachea were 66.1 +/- 56.2, 74.0 +/- 25.2, and 72.8 +/- 42.5 sec respectively. The average total-time for this light-guided retrograde intubating technique was 205.8 +/- 78.3 sec. Apart from minor bleeding at the cricothyroid membrane puncture site, there were no major complications. CONCLUSION: In a small number of patients, we have shown that light-guided retrograde intubation is effective and sale for patients with cervical spine instability. This simple and inexpensive technique may prove to be a valuable adjunct in the management of difficult airways.

Comparative topical anaesthesia of EMLA and liposome-encapsulated tetracaine.

BACKGROUND: The eutectic mixture of local anaesthetics (EMLA) provides effective topical anaesthesia after a minimum of 60 to 90 min application. Since liposome-encapsulated tetracaine (LET) can provide rapid dermal penetration, the goal of this study was to compare the local anaesthetic effects of EMLA and LET in human volunteers after 60 min application. METHODS: After obtaining institutional approval and informed consent, healthy volunteers were recruited in a double blind, crossover, randomized trial. The study creams (0.5 ml EMLA and 0.5 ml LET 5%) were applied randomly to opposite arms for 60 min. The discomfort of i.v. catheterization was assessed using a visual analogue pain score (VAS). Cutaneous side effects of the creams were recorded. RESULTS: Sixty-one subjects were studied. Twenty-one were excluded because of technical difficulties. Forty subjects completed the study and were included in the data analysis. The mean ( +/- SD) VAS was lower for LET than for EMLA (10.9 +/- 9.0 mm vs 22.7 +/- 17.1 mm, P < 0.001). Erythema secondary to vasodilatation occurred more frequent in the LET group than in the EMLA group (33 vs 3, P < 0.001). One subject with a history of atopy developed a rash at the LET application site. CONCLUSION: Liposome-encapsulated tetracaine can provide a more effective topical anaesthesia than EMLA for intravenous catheterization after 60 min application. Clinical evaluations are necessary to determine the efficacy and safety of LET in providing topical anaesthesia for various invasive percutaneous procedures in other patient populations.

Effect of diltiazem on plasma concentrations of oxypurines and uric acid.

To determine the clinical effect of diltiazem on the metabolism of adenosine, and its importance in ischemic heart disease, arterial plasma concentrations of the purine metabolites were determined in 21 healthy volunteers (10 female and 11 male) and 19 patients with effort angina (8 female and 11 male) before, during, and immediately after standard treadmill exercise tests conducted before and after they had taken 60 mg diltiazem (Cardizem; Hoechst Marion Roussel, Laval, QC, Canada) four times a day for 1 week. The results showed that the cardiac patients had significantly lower mean plasma concentrations of uric acid (46.82 +/- 25.51 versus 95.47 +/- 35.41 micrograms/ml, p 0.05), inosine (0.25 +/- 0.19 versus 0.84 +/- 0.17 microgram/ml, p < 0.05), and hypoxanthine (0.28 +/- 0.35 versus 0.50 +/- 0.27 microgram/ml, p < 0.05). Diltiazem decreased the mean resting plasma concentrations of uric acid in patients (uric acid 43.47 +/- 22.26 versus 46.82 +/- 25.51 micrograms/ml, p < 0.05) and healthy volunteers (uric acid 85.68 +/- 26.71 versus 95.47 +/- 35.41 micrograms/ml, p < 0.05). There was no statistically significant change in the plasma concentrations of the purine metabolites during exercise (p < 0.05). Female subjects had significantly lower plasma concentrations of uric acid than males (patients, 34.87 +/- 26.93 versus 55.78 +/- 21.25 micrograms/ml; healthy volunteers, 84.79 +/- 32.07 versus 104.22 +/- 37.05 micrograms/ml; p < 0.05 for both). Results of the study suggest that normal therapeutic doses of diltiazem may modulate the metabolism of adenosine and that some of the purine metabolites may be useful markers for specific types of ischemic heart disease.

Effect of diltiazem on intraarterial blood pressure and heart rate during stress testing in patients with angina: a gender comparison study.

The purpose of this study was to measure the blood pressure and electrocardiographic responses of a small, matched group of women (n = 8) and men (n = 9) who experienced typical, effort angina during an exercise on the treadmill (up to the second stage of a Bruce protocol). These responses were measured before and after therapy with diltiazem (60 mg four times daily for 1 week). Reports of previous studies have described significant gender differences in blood pressure responses to diltiazem in healthy volunteers tested with the same protocol. In contrast to the data in healthy individuals, gender differences in blood pressure responses to exercise before and after diltiazem administration were not observed. Results of analysis of pulse pressure responses to exercise were also similar in male and female patients with angina. A significant postexercise drop in blood pressure was observed, which was augmented by diltiazem. These data suggest that gender differences in drug action may be difficult to demonstrate in patients with vascular disease.

Comparative absorption kinetics of intramuscular midazolam and diazepam.

PURPOSE: This study investigates the rate and extent of absorption following intramuscular injection of midazolam and diazepam. METHODS: Four healthy male volunteers were recruited in this randomized three-way cross-over study. On one occasion each subject received simultaneous im injections of 5 mg midazolam and 10 mg diazepam in separate deltoid muscles. On two other separate occasions each subject received an iv infusion of 7.5 mg midazolam and 30 mg diazepam over five minutes. Frequent arterial blood samples were collected for up to two hours and venous blood samples were collected for up to 24 hours for midazolam and ten days for diazepam. A gas chromatography assay was used to determine the plasma concentrations of midazolam and diazepam. The im absorption profiles were estimated using constrained least-squares deconvolution. RESULTS: There were substantial intersubject variabilities in the estimated pharmacokinetic parameters (volume and clearances) of intravenous midazolam and diazepam. The mean (+/-sd) time to peak plasma concentration (Cmax) was shorter for im midazolam (17.5 +/- 6.5 min) relative to diazepam (33.8 +/- 7.5 min). The mean (+sd) time to peak absorption rate was also shorter for midazolam (9 +/- 2 vs 13.8 +/- 7.5 min). The peak rate of absorption was identical (0.18 mg. min-1) and bioavailability was 1.0 for both drugs. CONCLUSIONS: We conclude that midazolam has more rapid absorption than diazepam following im administration.