RETRACTED ARTICLE: Circulatory responses to laryngeal mask airway insertion or tracheal intubation in normotensive and hypertensive patients

The effects of laryngeal mask airway (LMA) insertion and tracheal intubation on circulatory responses were studied in normotensive (n = 24) and hypertensive (n = 22) patients. In a randomized, double-blind manner, LMA insertion or tracheal intubation was performed after induction of anaesthesia with thiopentone and muscle relaxation with succinylcholine. In both normotensive and hypertensive patients, heart rate (HR), mean arterial pressure (MAP) and rate-pressure product increased after tracheal intubation or LMA insertion compared with base-line (P < 0.05). The haemodynamic changes were greater after intubation than after LMA insertion (P < 0.05). Following intubation of the trachea or insertion of the LMA, HR increased more markedly in hypertensive patients than in normotensive patients (P < 0.05). Plasma adrenaline and noradrenaline concentrations after tracheal intubation or LMA insertion increased compared with baseline values (P < 0.05) in normotensive and hypertensive patients. The increase in noradrenaline concentration after tracheal intubation was greater than that after LMA insertion (P < 0.05). No patient revealed ECG evidence of myocardial ischaemia. We conclude that insertion of LMA is associated with less circulatory responses than tracheal intubation in both normotensive and hypertensive patients.     

Comparative effects of laryngeal mask airway and endotracheal tube insertion on intraocular pressure in children.

Intraocular pressure (IOP) measurements in children are frequently performed under halothane-nitrous oxide anesthesia; however, anesthesia face masks may limit access to the eyes, and tracheal intubation is associated with transient increases in IOP. Use of the laryngeal mask airway (LMA) permits the maintenance of a patent airway without the need for laryngoscopy and tracheal intubation. In a randomized study of 41 children, we compared the IOP, hemoglobin oxygen saturation, and hemodynamic responses to the insertion of an LMA or tracheal tube during a standardized steady-state anesthetic technique consisting of 1 MAC halothane and 66% nitrous oxide. Baseline measurements of IOP, hemoglobin oxygen saturation, heart rate, and arterial blood pressure were recorded and repeated within 15-30 s after insertion of the airway device and at 1-min intervals for 5 min. Insertion of the LMA required significantly less time (26 +/- 16 vs 39 +/- 17 s [mean +/- SD]) and was associated with higher hemoglobin oxygen saturation values compared with the tracheal intubation. The LMA did not increase IOP, heart rate, or arterial blood pressure above baseline values. In contrast, tracheal intubation was associated with significant increases of IOP, heart rate, and arterial blood pressure. We concluded that the laryngeal mask offers advantages over tracheal intubation and the face mask for airway management in patients undergoing IOP measurements.     

喉罩与气管插管在全麻或复合硬膜外阻滞时的心率和血压改变

目的比较喉罩与气管插管用于全麻或全麻复合硬膜外阻滞患者的HR和BP变化.方法妇科手术80例,随机分为全麻气管插管(T)组、全麻喉罩(L)组、硬膜外阻滞 全麻气管插管(ET)组、硬膜外阻滞 全麻喉罩(EL)组,每组20例.硬膜外阻滞用1%利多卡因 0.15%丁卡因.全麻诱导咪唑安定2 mg、芬太尼0.2 mg、丙泊酚1.5 mg/kg、琥珀胆碱1.5 mg/kg后插气管导管或喉罩.全麻维持50%N2O O2 异氟醚,静注阿曲库铵、芬太尼.于麻醉前(基础,入室静卧10 min后)、插管后1 min、切皮、进腹探查后5 min、拔管后1 min记录MAP、SpO2、HR、PETCO2.结果插管时HR和MAP均低于基础值,而两组喉罩HR低于插气管导管者,硬膜外复合全麻喉罩组MAP低于气管插管组.切皮时两组全麻MAP高于复合硬膜外组.探查时两组复合硬膜外者HR和MAP均低于基础值,且MAP低于单纯全麻者(P＜0.05).拔管时各组HR均显著高于基础值,MAP未复合硬膜外者显著高于基础值.结论(1)插喉罩对BP和HR的影响不如气管导管剧烈;(2)复合硬膜外阻滞时气管插管或喉罩置入应激反应轻,也可减轻探查时的BP波动.     

Effect of tracheal intubation or laryngeal mask airway insertion on intraocular pressure using balanced anesthesia with sevoflurane and remifentanil.

STUDY OBJECTIVES: To study the effect of tracheal intubation or laryngeal mask airway (LMA) insertion on intraocular pressure (IOP) in strabismus patients undergoing balanced anesthesia with sevoflurane and remifentanil. DESIGN: Open, prospective, randomized study. SETTING: Tertiary care academic medical institution. PATIENTS: 40 adult ASA physical status I and II patients scheduled for elective strabismus surgery. INTERVENTION: Patients were randomized to receive either tracheal intubation or LMA insertion following mask induction with sevoflurane in combination with IV remifentanil. MEASUREMENTS: Intraocular pressure, mean arterial pressure (MAP), and heart rate (HR) were measured before induction, immediately following induction, and after airway insertion. MAIN RESULTS: Intraocular pressure after tracheal intubation or LMA insertion did not differ significantly from preoperative baseline values. Mean arterial pressure and HR did not significantly differ between groups at any time point. CONCLUSIONS: Remifentanil and sevoflurane are not associated with an increase in IOP response during tracheal intubation or LMA insertion above baseline in healthy patients undergoing ophthalmic surgery.     

Electroencephalographic arousal response during tracheal intubation and laryngeal mask airway insertion after induction of anaesthesia with propofol

Laryngoscopy and tracheal intubation, or insertion of a laryngeal mask airway may lead to an arousal response on the electroencephalogram. We studied whether more intense stimulation (laryngoscopy and tracheal intubation) causes a greater arousal response than less intense stimulation (laryngeal mask airway insertion). Thirty-four patients (ASA I-II) were anaesthetised with propofol 3 mg.kg-1, followed by vecuronium 0.15 mg.kg-1 and a propofol infusion of 10 mg.kg-1.h-1. Three minutes after induction of anaesthesia, either laryngoscopy and tracheal intubation (n = 18), or laryngeal mask airway insertion (n = 16) was performed. Laryngoscopy and tracheal intubation caused a significantly greater increase in blood pressure (but not heart rate) than laryngeal mask airway insertion (p < 0.05). Electroencephalogram responses were not different. More intense stimulation does not cause a greater arousal response during propofol anaesthesia.     

Cardiovascular responses to insertion of the laryngeal mask

We have compared, in 40 healthy patients, the cardiovascular responses induced by laryngoscopy and intubation with those produced by insertion of a laryngeal mask. Anaesthesia was induced with thiopentone and maintained with enflurane and nitrous oxide in oxygen; vecuronium was used for muscle relaxation. Arterial pressure was measured with a Finapres monitor. The mean maximum increase in systolic arterial pressure after laryngoscopy and tracheal intubation was 51.3% compared with 22.9% for laryngeal mask insertion (p less than 0.01). Increases in maximum heart rate were similar, (26.6% v 25.7%) although heart rate remained elevated for longer after tracheal intubation. We conclude that insertion of the laryngeal mask airway is accompanied by smaller cardiovascular responses than those after laryngoscopy and intubation and that its use may be indicated in those patients in whom a marked pressor response would be deleterious.     

Insertion of laryngeal mask airway does not increase the intraocular pressure in children with glaucoma

Objectives:  It is hypothesized that in children with glaucoma, the insertion of laryngeal mask airway (LMA) will cause lesser rise in intraocular pressure (IOP) than tracheal tube (TT). Aim:  To compare the IOP response to LMA and TT insertion in children with glaucoma. Methods/Materials:  A prospective, randomized, single‐blind study was conducted in 30 glaucomatous ASA‐1 children, aged 1–10 years scheduled to undergo trabeculectomy. Anesthesia was induced with halothane and maintained for 5 min with 1 MAC of halothane after administering atracurium 0.5 mg·kg^?1 following which LMA or TT was introduced. IOP was measured in both the eyes before and after insertion of airway device for 5 min. Results:  The IOP increased significantly from 27.3 ± 5.2 to 31.2 ± 5.4 mmHg (P < 0.001) after tracheal intubation but returned to baseline within 5 min. The IOP did not change from the baseline after insertion of LMA. The IOP was significantly higher in group TT compared to group LMA at 2 min (P = 0.004) and 5 min (P = 0.01) after the device insertion. The heart rate (HR) increased significantly after tracheal intubation and returned to baseline 4 min after intubation. The HR increase was significantly more in TT group compared to LMA group at all times of observation. Both systolic blood pressure (SBP; P = 0.01) and diastolic blood pressure (DBP; P = 0.02) showed an increase at 1 min in children in group TT. Conclusion:  Insertion of LMA in glaucomatous children is not associated with an increased IOP response or cardiovascular changes.     

The pressor response and laryngeal mask insertion

The pressor response associated with laryngoscopy and tracheal intubation may be harmful to certain patients. The laryngeal mask airway avoids the need for laryngoscopy and allows positive pressure ventilation of the lungs in appropriate patients. This study compared the pressor response of tracheal intubation with that of mask insertion in two groups of 24 and 23 healthy patients respectively. All patients were anaesthetised with thiopentone, nitrous oxide, enflurane and paralysed with atracurium. We have shown a similar, but attenuated pattern of response associated with mask insertion in comparison with laryngoscopy and intubation; significant differences between the groups were evident in arterial diastolic blood pressure immediately after insertion and again 2 minutes later. Use of the laryngeal mask may therefore offer some limited advantages over tracheal intubation in the anaesthetic management of patients where the avoidance of the pressor response is of particular concern.     

Fibreoptic-guided tracheal intubation through i-gel® and LMA® ProtectorTM supraglottic airway devices - a randomised comparison

Fibreoptic-guided tracheal intubation using a supraglottic airway device as a conduit is a technique that can be used in anticipated and unanticipated difficult airway management. Although the i-gel^® supraglottic airway device has been examined for this purpose, the LMA^® Protector^TM, a recently introduced second-generation supraglottic airway device, has not been evaluated for this use in clinical trials. This prospective, randomised clinical trial compared fibreoptic-guided tracheal intubation via i-gel and LMA Protector supraglottic airway devices in two UK hospitals. Patients who were ASA physical status 1 or 2 and undergoing elective surgery requiring tracheal intubation were recruited to the study. A block randomisation list was generated for each study site. The primary outcome measure was time to successful tracheal intubation and secondary outcomes were tracheal intubation success rate, glottic view through flexible fibrescope, ease of tracheal intubation using operator visual analogue score, supraglottic airway device insertion time and insertion success rate. Ninety patients were randomly allocated to each device, and final data analysis was carried out for 92 patients in the i-gel group and 86 patients in the LMA Protector group. Mean (SD) tracheal intubation time in the i-gel and LMA Protector groups were 54.3 (13.8) s and 52.0 (13.0) s, respectively (p = 0.240). There were no significant differences in tracheal intubation success rate, glottic view and ease of tracheal intubation between the two groups. This study demonstrates that the LMA Protector supraglottic airway device is comparable to the i-gel supraglottic airway device as a conduit for fibreoptic-guided tracheal intubation.     

The cardiovascular response to insertion of the intubating laryngeal mask airway

Sixty-one patients received a standardised anaesthetic and were randomly assigned to three groups: tracheal intubation via direct laryngoscopy, tracheal intubation via an intubating laryngeal mask airway with immediate removal of the device, and tracheal intubation via an intubating laryngeal mask airway with delayed removal. The cardiovascular response to intubation was of a similar magnitude in all groups, although delayed removal of the intubating laryngeal mask airway was associated with a second pressor response. Norepinephrine changed significantly over time following direct laryngoscopy and following immediate removal of the intubating laryngeal mask airway, but not after delayed removal. The findings of this study do not support using the intubating laryngeal mask instead of direct laryngoscopy purely to decrease the response to intubation.     

Anaesthesia for adenotonsillectomy: A comparison between tracheal intubation and the armoured laryngeal mask airway

A prototype armoured laryngeal mask airway (LMA) was compared with tracheal intubation (ETT) for anaesthesia for adenotonsillectomy. Fifty-five children were randomised into the LMA group and 54 into the ETT group. During insertion of the LMA, peripheral oxyhaemoglobin desaturation (SpO₂) < 94% occurred in ten patients (18.2%) and in seven patients (13%) during tracheal intubation (NS). After opening the Boyle-Davis gag, airway obstruction occurred in ten patients (18.2%) in the LMA group and in three patients (6%) in the ETT group (P = 0.07). In five patients (9%) the LMA was abandoned in favour of tracheal intubation. In all others (91%), when the need for adequate depth of anaesthesia was realized, a satisfactory airway was achieved more rapidly than with tracheal intubation (P < 0.001), and maintained throughout surgery. Manually assisted ventilation was required in all patients in the ETT group, mean duration 373 ± 385 sec, and in 26 patients (52%) in the LMA group, mean duration 134 ± 110 sec, P < 0.001. Mean end-tidal CO₂ (PetCO₂) was 45.5 ± 6.21 mmHg in the ETT group and 46.6 ± 6.09 in the LMA group (NS). The LMA did not limit surgical access. Heart rate, MAP and blood loss in the LMA group were 110 ± 21, 74 ± 9 mmHg and 1.92 ± 1.22 ml · kg^?1 respectively, compared with 143 ± 13 (P < 0.001), 85 ± 12 mmHg (P < 0.001) and 2.62 ± 1.36 ml · kg^?1 (P < 0.05) with tracheal intubation. Fibreoptic laryngoscopy at the end of surgery in 19 patients in the LMA group revealed no blood in the larynx. In the LMA group postintubation stridor and laryngospasm occurred in five and three patients respectively, compared with 14 (P < 0.05) and six patients respectively (NS) with tracheal intubation. SpO₂ on admission to the PACU in the LMA group was 95.9 ± 2.21, and 93.5 ± 4.53 (P < 0.05) after tracheal intubation. Our study demonstrated that the LMA is a safe alternative to tracheal intubation for adenotonsillectomy. Control of airway reflexes by ensuring sufficient depth of anaesthesia is essential for successful use of the LMA in children.     

A complication of transtracheal jet ventilation and use of the Aintree intubation catheter during airway resuscitation

We report the management of a patient requiring surgical laryngoscopy with a view to laser resection of an epiglottic recurrence of laryngeal cancer. Previous attempts at tracheal intubation and awake nasal fibreoptic intubation had failed. During a previous anaesthetic the patient had been both 'impossible to intubate and to ventilate'. Neck scarring potentially complicated access for transtracheal jet ventilation. Nevertheless, a cricothyroid catheter was placed and surgery performed during low frequency 'volume' jet ventilation. Upper airway obstruction developed during the procedure, preventing exhalation, which led to raised intrathoracic pressure, cardiovascular collapse and barotrauma. The airway was re-established by insertion of an LMA Proseal. Fibreoptic placement of an Aintree intubation catheter through this allowed re-oxygenation and exchange for a cuffed tracheal tube. Some hours after the procedure, re-intubation was necessary. This was achieved using the Aintree intubation catheter as an aid to nasal fibreoptic intubation and as a tube exchanger. Novel roles of the Aintree intubation catheter and LMA Proseal in this case are discussed. Complications of transtracheal jet ventilation as well as possible methods for avoiding them are also reviewed.     

A randomised controlled trial comparing two insertion techniques for the Laryngeal Mask Airway Flexible™ in patients undergoing dental surgery

The Laryngeal Mask Airway Flexible^TM (LMA Flexible) has been widely utilised for dental, ophthalmology and otorhinolaryngology‐related procedures. Our study evaluates two different techniques of inserting the LMA Flexible for patients undergoing day‐case dental surgery. One hundred and eight patients were randomly assigned into two groups based on the LMA Flexible insertion technique – either laryngoscopy‐guided (n = 54) or digital manipulation (standard technique; n = 54). Patient and airway characteristics were recorded before induction of anaesthesia. The primary outcome was success rate at first insertion. Other outcomes assessed included fibreoptic assessment of laryngeal mask airway placement, haemodynamic changes, need for airway adjustment during surgery and sore throat. The success rate of insertion on the first attempt was higher for the laryngoscopy‐assisted technique compared with the standard technique (96.3% vs 81.5%, respectively, p < 0.05). Fibreoptic assessment showed that the former group had better placement of the laryngeal mask airway than the latter (59.3% vs 37% p < 0.05). There were no significant differences between the two groups for haemodynamic changes. Sore throat was more common in the group with the standard technique (35.2% vs 16.7%, p < 0.05). Our study suggests the use of the laryngoscope to guide insertion of the LMA Flexible for dental surgery is a better option compared with the standard technique of digital manipulation.     

Vergleich von zwei Larynxmaskenmodellen zur Atemwegssicherung bei Patienten mit Immobilisation der Halswirbelsäule

BACKGROUND: Reduced cervical spine mobility can impair laryngoscopy and tracheal intubation. Supraglottic airway devices can be important alternatives for oxygenation under these circumstances. The Ambu laryngeal mask (ALM) and the LMA-Classic (LMA) are compared in patients with immobilization of the cervical spine.METHODS: In 60 patients scheduled for elective ambulatory interventions, ALM or LMA were inserted after cervical immobilization with an extrication collar and assessment of laryngoscopic view. Insertion time (removal of facemask until first tidal volume), number of insertion attempts, airway leak pressure (cuff pressure 60 cm H(2)O), intraoperative complications and postoperative complaints were assessed.RESULTS: Demographical data, insertion attempts, insertion time (ALM 15.6+/-4.4 s, LMA 15.5+/-4.9 s) and airway leak pressure (ALM 25.6+/-5.2 cm H(2)O, LMA 26.5+/-6.5 cm H(2)O) were comparable. Traces of blood were found in 6 LMAs and 3 ALMs after removal, mild trouble with swallowing (visual analogue scale, VAS 2-4) in the recovery room and after 24 h were complaints by 1 ALM and 2 LMA patients.CONCLUSIONS: LMA-Classic and Ambu laryngeal masks are suitable for rapid and reliable airway management in patients with cervical immobilization.     

Success of Tracheal Intubation with Intubating Laryngeal Mask Airways: A Randomized Trial of the LMA Fastrach(TM) and LMA CTrach(TM)

Background: The LMA CTrach(TM) system (The Laryngeal Mask Company, Singapore) is a development of the LMA Fastrach(TM) system (The Laryngeal Mask Company, Singapore), with integrated fiberoptic bundles and a detachable liquid crystal display viewer. This randomized study of 271 patients compared tracheal intubation with these two systems.

Methods: In both groups, ventilation was optimized after insertion of the laryngeal mask conduit before proceeding further: intubation with the LMA Fastrach(TM), and optimizing the conduit placement and view and then intubation with the LMA CTrach(TM). The first-attempt and overall success rates of tracheal intubation, and the times required, were recorded.

Results: Tracheal intubation was successful on the first attempt in 93.3% of patients with the LMA CTrach(TM) and 67.9% of patients with the LMA Fastrach(TM) (P < 0.001). The success rates within three attempts were 100% with the LMA CTrach(TM) and 96.4% with the LMA Fastrach(TM) (P = 0.06). The median (interquartile range) time for the complete tracheal intubation process was 116 (82-156) s with the LMA CTrach(TM) and 100 (74-121) s with the LMA Fastrach(TM) (P = 0.002). There was no correlation between the grade of conventional laryngoscopy and success of intubation with either system.     

Brief review: The LMA Supreme? supraglottic airway

Purpose

This article is a review of the efficacy and safety of the Laryngeal Mask Airway (LMA) Supreme? as a stand-alone supraglottic airway during general anesthesia and as a conduit for tracheal intubation. Relevant articles were obtained using MEDLINE (1948-July 2011) and EMBASE (1980-July 2011). Only original studies with adult human patients and published in English were selected.

Principal findings

The LMA Supreme was found to be comparable with the LMA Proseal? with regard to success rate, insertion time, and complications. However, in three studies, oropharyngeal leak pressure was higher with the LMA Proseal than with the LMA Supreme. The LMA Supreme was superior to the LMA Classic? with regard to insertion time and oropharyngeal seal pressure. The LMA Supreme was also used successfully in two difficult airway cases, and it has been used as a conduit for tracheal intubation by utilizing an intubation introducer (gum elastic bougie) and subsequently railroading an endotracheal tube over the bougie into the trachea. Techniques for achieving tracheal intubation include the use of the Aintree Intubation Catheter?, a guidewire-exchange catheter, a gum elastic bougie, and a small (<6.0?mm internal diameter) endotracheal tube.

Conclusion

The LMA Supreme has been shown to be a safe and efficacious device as a stand-alone supraglottic airway and may also be used as a conduit for tracheal intubation. Further trials are needed to determine the efficacy of the LMA Supreme compared with other supraglottic airways in both elective and emergent airway management situations.     

Management of difficult pediatric airway

Anesthesiologists should be familiar with the management of airway and be able to recognize and identify potential difficult airway. These entities include congenital craniofacial deformities with micrognathia (e.g. Robin sequence, Treacher Collins, Goldenhar's, Crouzon's syndromes) and metabolic diseases causing the deposit of accumulated by-products (e.g., Hurler's, Morquio's, Beckwith-Wiedemann syndromes). Cormack and Lehane grades 3 and 4 at laryngoscopy are an indication for advanced techniques for intubation. The laryngeal mask airway (LMA) and fiberscope with a directable tip are useful and important modalities in handling difficult pediatric airway and intubation. LMA not only offers another mode of securing airway besides face mask and tracheal intubation, but also provides a conduit for tracheal intubation and a rescue airway in the CICV (cannot intubate, cannot ventilate) situations. Intubation with a fiberscope can be utilized through LMA or through a specially designed face mask. Face mask designed for fiberoptic intubation has a 15 mm port for connection with the breathing circuit and another 22 mm port covered with a rubber membrane through which the fiberscope is introduced and directed to the larynx and trachea followed by the tracheal tube while ventilating and anesthetizing the pediatric patients with inhalational anesthetics. Getting used to these two modalities, LMA and fiberoptic intubation of the trachea, gives a great advantage in handling of difficult pediatric airway and intubation.     

The ProSeal laryngeal mask airway is an effective alternative to laryngoscope-guided tracheal intubation for gynaecological laparoscopy

We tested the hypothesis that the ProSeal laryngeal mask airway is superior to laryngoscope-guided tracheal intubation for gynaecological laparoscopy. One-hundred and eighty consecutive patients (ASA grade 1-2, aged 18-80 y) were divided into two equal-sized groups for airway management with the ProSeal laryngeal mask airway or tracheal tube. Induction was with fentanyl/propofol, maintenance with sevoflurane and muscle relaxation with atracurium. The following primary variables were tested: time to achieve an effective airway, ventilatory capability, peak airway pressure before and after pneumoperitoneum, duration of surgery and pneumoperitoneum and haemodynamic responses. Data about gastric size, airway trauma and sore throat were collected. The number of attempts for successful insertion were similar but effective airway time was shorter for the ProSeal laryngeal mask airway (20 +/- 2s vs 37 +/- 3 s, P < 0.001). All devices were successfully inserted within three attempts. There was no episode of failed ventilation or hypoxia. The haemodynamic stress responses to insertion and removal were greater for the tracheal tube than the ProSeal laryngeal mask airway. The duration of surgery, duration of pneumoperitoneum and intra-abdominal pressures were similar Gastric size was similar at the start and end of surgery. There were no differences in the frequency of complications or sore throat. We conclude that the ProSeal laryngeal mask airway is a similarly effective airway device to conventional laryngoscope-guided tracheal intubation for gynaecological laparoscopy, but is more rapidly inserted and associated with an attenuated haemodynamic response to insertion and removal.     

Use of intubation introducers through a supraglottic airway to facilitate tracheal intubation: a brief review

Purpose

This article is a narrative review regarding the usage and effectiveness of introducers or catheters to facilitate tracheal intubation through a supraglottic airway (SGA) as an alternative intubation technique in normal and difficult airway management.

Sources

Relevant articles were obtained through Medline (1948-July 2011). The articles were subsequently cross-referenced for additional literature, and only articles published in English were included.

Principal findings

In this review, we consider 32 reports using the LMA Classic?, LMA Unique?, LMA ProSeal?, LMA Supreme?, AuraOnce?, and i-gel? as SGA conduits for intubation. In 13 articles, the use of an Aintree Intubation Catheter was described as an intubation introducer and resulted in high success rates in both elective and emergent situations. Eight studies used a guidewire exchange catheter technique. Although blind intubation using a guidewire resulted in a high failure rate, these studies found that using a bronchoscope improved successful intubation. Ten studies showed that insertion of a gum elastic bougie with a bronchoscope as an intubation introducer has high success rates compared with blind bougie insertion. One article described the use of a small endotracheal tube as an intermediary for tracheal intubation.

Conclusions

In failed intubation scenarios, supraglottic airways, such as the LMA Classic? or LMA ProSeal? can serve as a conduit for tracheal intubation. A number of techniques using introducers or catheters can facilitate the insertion of an adequately sized endotracheal tube, particularly guided by a bronchoscope. Usage of introducers or catheters through a supraglottic airway may be a useful alternative intubation technique in difficult airway management.     

Attenuation of haemodynamic responses to tracheal intubation by the styletscope

Tracheal intubation often causes a haemodynamic response probablygenerated by direct laryngoscopy. The StyletScope is a new intubationdevice that does not require direct laryngoscopy. We prospectivelymeasured haemodynamic changes after tracheal intubation usingthe StyletScope. The increase of heart rate was less duringtracheal intubation with the StyletScope when compared withthe Macintosh laryngoscope. Br J Anaesth 2001; 86: 275–7