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.     

Intra-ocular pressure changes using the laryngeal mask airway and tracheal tube

Intra-ocular pressure was measured before and throughout airway establishment with either the laryngeal mask airway or tracheal tube. Similar measurements were made on removal of either airway and the amount of coughing noted in the first minute after removal. There was a significantly smaller increase in intra-ocular pressure (p less than 0.001) using the laryngeal mask airway, both on placement and removal, than with the tracheal tube. Postoperative coughing was significantly reduced using the laryngeal mask airway (p less than 0.001). There was a significantly greater rise in heart rate using the tracheal tube (p less than 0.01) probably related to an increased cardiovascular response. The laryngeal mask airway is recommended as an alternative to tracheal intubation in routine and emergency intra-ocular surgery.     

Oral midazolam premedication for day case breast surgery, a randomised prospective double-blind placebo-controlled study

We conducted a randomised prospective double-blind placebo-controlled study to assess the efficacy of oral midazolam premedication in 50 ASA I and II female patients scheduled to undergo day case breast surgery. Anxiety was assessed using 100-mm visual analogue scales (VAS) and The State-Trait Anxiety Inventory (STAI) psychometric questionnaire. Midazolam premedication did not significantly reduce either VAS or STAI score, although heart rate and systolic arterial pressure immediately before induction of anaesthesia were significantly lower in patients who received midazolam (p = 0.006 and 0.039, respectively). Induction of anaesthesia was achieved with a lower dose of propofol (p = 0.0009) and excellent (Grade I) conditions for insertion of a laryngeal mask airway were achieved more often after midazolam premedication (p = 0.038). Arterial desaturation during induction of anaesthesia and insertion of a laryngeal mask airway occurred more often in patients who received placebo (p = 0.022). There was a good correlation between VAS and STAI used to assess the anxiolytic effects of premedication. (Spearman coefficient 0.58, p < 0.0001).     

A comparison of laryngeal mask airway with tracheal tube for intra-ocular ophthalmic surgery

The use of the laryngeal mask was compared with tracheal intubation in 30 patients who underwent intra-ocular ophthalmic surgery and who received intravenous anaesthesia with propofol. Changes in intra-ocular pressure, heart rate and mean arterial pressure after the insertion of the laryngeal mask airway or the tracheal tube were not significantly different. However, at the end of the procedure, a significantly higher percentage of patients with a tracheal tube coughed, reacted to head movement and suffered breath-holding. In addition, significantly more patients in this group complained of a sore throat (p less than 0.05). During intravenous propofol anaesthesia, the laryngeal mask airway does not offer any advantage over tracheal intubation in the control of intra-ocular pressure for intra-ocular ophthalmic surgery. However, there were fewer complications immediately following surgery in the laryngeal mask group.     

Haemodynamic and electroencephalographic response to insertion of a cuffed oropharyngeal airway: comparison with the laryngeal mask airway

We have compared the cuffed oropharyngeal airway (COPA), a modified Guedel airway device with a specially designed cuff at its distal end, with the laryngeal mask airway (LMA), on haemodynamic and electroencephalographic (EEG) responses to insertion. In addition, we examined the haemodynamic and EEG changes during initiation of the effect-compartment controlled infusion. We studied 35 female patients undergoing ambulatory gynaecological surgery allocated randomly to received an LMA or COPA to manage the airway. After premedication with midazolam 0.03 mg kg-1 i.v. and low-dose alfentanil (0.01 mg kg-1), anaesthesia was induced and maintained with propofol, using an effect- compartment controlled infusion set at an effect-site concentration of 4 micrograms ml-1. After intercompartmental equilibration, the LMA (group I) or COPA (group II) was inserted and haemodynamic (arterial pressure, heart rate) and EEG (bispectral index (BIS)) responses to insertion studied. The effect-compartment controlled infusion of propofol caused only mild haemodynamic changes during induction. Changes in arterial pressure and heart rate after insertion were similar in both groups and not significantly different from baseline values before insertion. Changes in BIS after insertion were minor and similar between groups.      

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.     

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.     

Haemodynamic responses to the intubating laryngeal mask and timing of removal

We determined (a) the haemodynamic responses to intubating laryngeal mask (ILM) airway insertion/intubation and removal in anaesthetized patients, and (b) whether the timing of ILM removal influences these responses. One-hundred and twenty patients without cardiovascular disease were studied. ILM airway insertion/intubation was 5 min after induction with propofol 2 mg kg(-1) and maintenance of anaesthesia with sevoflurane 2% in oxygen 33% and nitrous oxide. Patients were randomly assigned for removal of the intubating laryngeal mask airway at 1, 3 and 5 min after successful intubation. Systolic and diastolic arterial pressures and heart rate were recorded preinduction (baseline), before ILM airway insertion/intubation, at 1-min intervals after insertion/intubation, and at 1-min intervals for 5 min after ILM removal. ILM insertion was successful at the first attempt in all patients, but 46 patients required more than one intubation attempt. Compared with baseline values, there were no increases in systolic or diastolic arterial pressure, but there was an increase in heart rate 1 min after ILM insertion/intubation (9%, P<0.001) and 1 min after ILM removal (8%, P<0.01). There was a significant increase in systolic and diastolic pressures and heart rate 1 min after ILM insertion/intubation (30%, 31% and 15%; all: P<0.002) compared with before ILM insertion/intubation values and 1 min after ILM removal (9%, 8% and 7%; all P<0.05) compared with 1 min after ILM insertion/intubation values. Removal of the ILM 1 min after successful intubation resulted in higher arterial pressure compared with removal at 3 min (systolic arterial pressure 10% higher for 1 min, P = 0.01) and 5 min (systolic arterial pressure 10-23% higher for 3 min, P<0.01; diastolic arterial pressure 10-20% higher for 4 min, P>0.02), but there were no differences in heart rate between groups. Systolic and diastolic arterial pressures were greater if more than one intubation attempt was required. Early removal or multiple intubation attempts did not exceed baseline haemodynamic values. We conclude that ILM insertion/intubation and removal in anaesthetized patients produces little or no haemodynamic response, even if multiple intubation attempts are required. The timing of removal exerts a small, but clinically unimportant influence on these responses.     

Efficacy and safety of the laryngeal mask airwayvs Guedel airway following tracheal extubation

PURPOSE: To compare the safety and efficacy of the laryngeal mask airway (LMA) with the Guedel airway during the recovery period. METHODS: In a prospective randomised trial in the Post Anesthesia Care Unit (PACU), 52 patients (ASA 1 and 2) were randomised to receive either a laryngeal mask airway (LMA: n = 26) or a Guedel airway (n = 26) during the recovery period after middle ear surgery. Ease of airway maintenance was graded and the presence of coughing was noted. Peripheral arterial oxygen saturation (SpO2) was measured continuously by pulse oximetry in the PACU. Readings were taken on arrival (time 0) and for five minutes afterwards. RESULTS: There was no difference in sex, age, weight or incidence of smoking between the two groups. In the LMA group 25 patients required no airway manipulation and only one patient required repositioning of the LMA. In the Guedel group severe difficulty maintaining the airway was experienced in two patients, moderate difficulty in five patients and mild difficulty in 12 patients. Seven patients required no airway manipulation. The LMA group showed higher ease of airway maintenance scores, (P = < 0.0001) and less coughing (P = 0.0496). At time 0 and at one minute the LMA group had higher median SpO2 (97% and 97%) than the Guedel group (95% and 96%), (P = 0.0002 and 0.0362). There was no further difference in SpO2. CONCLUSIONS: The LMA provides easier airway maintenance, less coughing and initially higher median SpO2 when compared with the Guedel airway in the recovery period.     

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.     

改良Proseal喉罩与改良普通喉罩在无痛纤维支气管镜检查中的气道管理

目的比较改良Proseal喉罩和改良普通喉罩在无痛纤维支气管镜检查中气道管理的效果。方法选择行纤维支气管镜检查患者40例,随机均分为两组:改良Proseal喉罩组(P组)和改良普通喉罩组(L组)。全麻诱导后徒手插入喉罩,接麻醉机,控制或辅助通气。记录两组麻醉前(T0)、插入喉罩即刻(T1)、插入喉罩3min(T2)的SBP、DBP、HR和SpO2,同时记录喉罩插入时间和并发症,并进行喉罩通气评估、纤维支气管镜评估和气道密封压测定。结果两组患者喉罩插入时间及各时点的SBP、DBP、HR和SpO2差异均无统计学意义;P组气道密封压明显高于L组(P<0.01);P组喉罩通气、纤维支气管镜评分优良率均为100%,明显高于L组的85%、80%(P<0.01);术毕P组1例喉罩粘血,明显少于L组的7例(P<0.05)。结论改良Proseal喉罩在气密性、通气评估、纤维支气管镜评估等方面好于改良普通喉罩,但对血流动力学的影响两者无明显差异。     

A randomised trial comparing the laryngeal mask airway Supreme™ with the laryngeal mask airway Unique™ in children

We conducted a randomised controlled trial comparing the laryngeal mask airway Supreme^? with the laryngeal mask airway Unique^? in children. Fifty children presenting for elective surgery were randomly assigned to receive either the laryngeal mask airway Supreme or laryngeal mask airway Unique. The outcomes measured were airway leak pressure, ease and time for insertion, insertion success rate, fibreoptic examination, incidence of gastric insufflation, ease of gastric tube placement through the laryngeal mask airway Supreme, quality of airway during anaesthetic maintenance and complications. Median (IQR [range]) time to successful device placement was shorter with the laryngeal mask airway Unique, 14.5 [13.5–16.3 (10.0–23.6)] s than with the laryngeal mask airway Supreme, 17.4 [14.8–19.8 (11.5–29.2)] s; p = 0.007. Median (IQR [range]) airway leak pressures for the laryngeal mask airway Supreme and laryngeal mask airway Unique were 20 [16–21 (12–22)] cmH₂O and 15 [14–18 (10–24)] cmH₂O, respectively (p = 0.001). The incidence of gastric insufflation was lower with the laryngeal mask airway Supreme (zero vs six patients), p = 0.01. In conclusion, the laryngeal mask airway Supreme performed as well as the laryngeal mask airway Unique and is a useful alternative for airway maintenance, particularly in children who require evacuation of gastric contents during anaesthesia.     

喉罩在小儿舌系带矫正手术中的应用

目的探讨喉罩往小儿舌系带矫正手术全身麻醉中的应用。方法 择期行小儿舌系带矫正手术患儿42例。所有患儿均采用静吸复合麻醉,术中应用喉罩通气。监测入室后麻醉前(T0)、麻醉诱导后患识和眼睑反射消失时(T1)、喉罩置入后即时(T2)、术中3~5分钟(T3)、术毕拔出喉罩时(T4)5个时间点患儿生命体征。记录每例患儿喉罩首次置入成功率和喉罩置入失败改为其他通气方式的比例。记录术中喉罩有无移位情况及术后24小时咽痛不适的发生情况。结果42例患儿喉罩首次置入成功36例,成功率为85.71%。术中喉罩均未发生漏气、移位,通气良好。术中患儿生命体征平稳。术后24小时咽痛6例,发生率为15%。T0时心率与T1、T2、T3、T4比较,差异有统计学意义(P0.05)。T1、T2、T3、T4间两两比较,差异无统计学意义(P0.05)。术中喉罩存在的两个时点(T2、T3)呼气末二氧化碳正压与喉罩不存在的3个时点(T0、T1、T4)比较,差异有统计学意义(P0.05)。入室麻醉前T0时点与麻醉后T1、T2和T3三个时点平均动脉压力比较,差异均有统计学意义(P0.05)。T1和T4时点平均动脉压力比较,差异有统计学意义(P0.05,)。所有患者脉搏氧饱和度均在95%以上。结论喉罩应用于小儿舌系带矫正手术的全身麻醉,安全性高,术中麻醉维持平稳,术后并发症少,安全可行。     

Tracheal intubation through the intubating laryngeal mask in patients with unstable necks

BACKGROUND: In patients with unstable necks, the neck should be stabilized during induction of anaesthesia, but this may make tracheal intubation difficult. Awake intubation may produce straining, which could be detrimental to the unstable neck. METHODS: We studied 20 patients with unstable necks to examine the efficacy of insertion of the intubating laryngeal mask under conscious sedation (to minimize the possibility of losing a patent airway and to facilitate fibrescope-aided intubation) followed by tracheal intubation through the laryngeal mask after induction of anaesthesia (to reduce stress response to intubation). After the patient had been sedated with midazolam (up to 5 mg) and fentanyl (up to 100 microg), the intubating laryngeal mask was inserted. General anaesthesia was then induced with sevoflurane and tracheal intubation attempted. RESULTS: In all patients, tracheal intubation through the laryngeal mask succeeded without airway obstruction. Neither insertion of the mask under conscious sedation nor tracheal intubation after induction of anaesthesia caused straining, and only two patients moved upper extremities at intubation. Insertion of the laryngeal mask did not significantly alter blood pressure or heart rate. Tracheal intubation significantly increased blood pressure and heart rate, but the increase was considered to be small. CONCLUSIONS: In the patient with an unstable neck with a low risk of pulmonary aspiration, insertion of the intubating laryngeal mask while the patient is sedated may minimize difficulty in obtaining a patent airway before tracheal intubation and may facilitate a fibrescope-aided tracheal intubation; subsequent induction of anaesthesia before tracheal intubation may minimize stress response to intubation.     

A comparison of the laryngeal mask airway and PA(Xpress) for short surgical procedures

Sixty adult patients undergoing minor peripheral surgery under general anaesthesia were randomly allocated to receive either the laryngeal mask airway (laryngeal mask airway; size 4 for females and size 5 for males) or the PAXpress (adult size), inserted by a single operator with experience of > 50 insertions of each device. The laryngeal mask airway was correctly placed on the first attempt in 27 patients (90%) compared with 20 patients (67%) when using the PAXpress (p < 0.01). No patient required more than two attempts at insertion and there were no failures with the laryngeal mask airway, compared with four (13%) who needed three attempts and two failures (7%) with the PAXpress (p < 0.001 and p < 0.01, respectively). Mean (SD) total placement time was shorter with the laryngeal mask airway [24.6 (3.1) s] than with the PAXpress[35.4 (2.5) s; p < 0.01]. The most common complication was sore throat, which occurred less frequently with the laryngeal mask airway (8 patients; 26%) than with the PAXpress (15 patients; 53.5%; p < 0.001).     

Evaluation of four airway training manikins as patient simulators for the insertion of single use laryngeal mask airways

We evaluated the performance of four manikins: Airsim(trade mark), Bill 1, Airway Management Trainer and Airway Trainer, as simulators for insertion of single-use laryngeal mask airways and the reusable LMA Classic. Sixteen volunteer anaesthetists inserted each laryngeal mask airway into each manikin twice. Insertions were scored for ease of insertion, clinical and fibreoptic position, and lung ventilation (maximum score 10). Scores < 7 were classified 'poor' and < 5 'failure'. We analysed manikin and laryngeal mask airway performance. Poor insertion rate was 15% (range 9-21%) and was lowest for the VBM manikin (p = 0.02). Insertion failure rate was 2.6% and did not differ significantly between manikins (p = 0.2). Overall manikin performance was significantly different (p < 0.0001). The VBM manikin scored best, with all other manikins equivalent. The VBM manikin performed significantly better for three individual laryngeal mask airways. Overall performance differences of laryngeal mask airways were statistically significant (p < 0.001) but individual comparisons were not. Silicone devices performed better than PVC devices (p < 0.05) Devices with and without grilles performed similarly. All manikins were adequate. The VBM manikin performed best overall and for several individual laryngeal mask airways. The methodology is useful for future evaluations of devices, both manikins and supraglottic airways. Further human clinical research is required.     

A comparison of the intubating and standard laryngeal mask airways for airway management by inexperienced personnel

Twenty-four inexperienced participants were timed inserting the intubating laryngeal mask airway and the laryngeal mask airway in 75 anaesthetised subjects. Adequacy of ventilation was assessed on a three-point scale. The pressure at which a leak first developed around the device's cuff was also measured. There was no significant difference in insertion time or the likelihood of achieving adequate ventilation between devices. However, the intubating laryngeal mask airway was better at providing adequate ventilation without audible leak (58/75 (77%) vs. 42/75 (56%); p = 0.009). The median (range [IQR]) pressure at which an audible leak developed was higher for the intubating laryngeal mask airway, 34.5 (14-40 [29-40]) cmH2O, than for the laryngeal mask airway, 27.5 (14-40 [22-33]) cmH2O (p < 0.001). The intubating laryngeal mask airway is worthy of further consideration as a tool for emergency airway management for inexperienced personnel.     

COMPARISON OF THE USE OF THE LARYNGEAL MASK AND FACE MASK BY INEXPERIENCED PERSONNEL

Ten junior doctors with no postgraduate anaesthetic experienceattempted to ventilate the lungs of 50 anaesthetized patients,using either a laryngeal mask or a Guedel airway and face mask.Success was defined as the production of two successive tidalvolumes exceeding 800 ml within 40 s. The failure rate was significantlygreater using the laryngeal mask compared with the face mask(P < 0.05) and the average time was significantly longerwith the laryngeal mask than with the face mask (P < 0.01). The results from this investigation suggest the laryngealmask airway cannot be recommended as a resuscitation devicefor use by inexperienced operators.     

The effect on intraocular pressure of endotracheal intubation or laryngeal mask use during TIVA without the use of muscle relaxants

BACKGROUND: Depolarizing and non-depolarizing muscle relaxants possess many untoward side effects. In most patients endotracheal intubation may be performed with a propofol and alfentanil combination. The purpose of this study was to compare the effect on intraocular pressure (IOP) and haemodynamics of endotracheal (ET) intubation or laryngeal mask (LMA) insertion during total intravenous anaesthesia (TIVA) without the use of muscle relaxants. METHODS: In a randomised study, 20 patients scheduled for elective orthopaedic surgery were assigned to two groups of 10 patients. Anaesthesia was induced with i.v. alfentanil 40 micrograms/kg and propofol 2.5 mg/kg. LMA insertion or ET intubation was achieved by the same anaesthesiologist. Airway score, insertion score, patient response and haemodynamics were recorded. IOP measurements were recorded before and after induction, 1 and 2 min after ET intubation or LMA insertion, and 1 and 2 min after extubation. RESULTS: Mean arterial pressure and heart rate after insertion of the airway management devices was significantly higher than induction values in the ET group (P < 0.05), while during 2-3 min no significant changes were observed in LMA group. In all patients following propofol and alfentanil induction, IOP was significantly lower than preinduction values (P < 0.001). IOP following extubation was significantly higher than preinduction values in the ET group, but not in the LMA group (P < 0.001). CONCLUSION: During TIVA without the use of muscle relaxants neither LMA insertion nor ET intubation increased the IOP, but ET extubation did.     

喉罩通气全麻应用于老年人腹部手术的临床观察

目的 探讨气管捕管和喉罩通气道用于老年全身麻醉对血液动力学的影响.方法 将40例老年全麻腹部手术患者随机分为2组.喉罩组(L组):全麻诱导后置入喉罩;插管组(M组):全麻后喉镜下气管插管维持通气.分别记录诱导前(T0)、簧喉罩或气管导管前(T1).喉罩置人或气插管即刻(T2),之后2min(T3),4min(T4),6...