Influence of neuromuscular block, mode of ventilation and respiratory cycle on pharyngeal mucosal pressures with the laryngeal mask airway

Comparison of the clinical performance of the flexible laryngeal mask airway in pediatric patients under general anesthesia with or without a muscle relaxant: study protocol for a randomized controlled trial

BACKGROUND

The insertion of a laryngeal mask airway (LMA) is difficult in children due to the unique features of their airways. Muscle relaxants have been reported to facilitate LMA insertion in adults; however, there is a lack of evidence supporting this in children. This trial is designed to assess the feasibility of LMA insertion with and without the use of muscle relaxants in pediatric patients under general anesthesia.

METHODS/DESIGN

This is a prospective, double-blind, single-center, parallel-arm, non-inferiority, randomized controlled trial to be conducted with participants aged 2-7 years who are undergoing elective ophthalmic surgery under general anesthesia. Participants are randomly assigned to one of two groups based on whether muscle relaxants are used (MR group, n = 64) or not used (Saline group, n = 64) prior to LMA insertion. The primary outcome is the oropharyngeal leak pressure (OLP) at a fixed gas flow of 3 L/min. The secondary outcomes are intubation time for successful insertion, ease of insertion and mask bagging, intubation attempt for successful insertion, successful insertion rate on the first attempt, fiberoptic view of the LMA position, postoperative complications, and changes in hemodynamic and ventilatory parameters.

DISCUSSION

We will compare the OLPs to determine whether the muscle relaxant provides better conditions for the manipulation of the LMA. This is the first randomized controlled trial to investigate whether muscle relaxants are beneficial to the clinical performance of LMA insertion in pediatric patients under general anesthesia. This trial will be a resource for improving the process and safety of pediatric LMA insertion under general anesthesia.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03487003 . Registered on 18 April 2018.

Muscle relaxant facilitates i-gel insertion by novice doctors: A prospective randomized controlled trial

STUDY OBJECTIVE

This study aimed to determine whether muscle relaxants facilitates insertion efficacy of the i-gel supraglottic device (i-gel) by novice doctors in anesthetized patients.

DESIGN

Randomized clinical trial.

SETTING

Operating room.

PATIENTS

Seventy adult patients scheduled for elective surgery under general anesthesia.

INTERVENTIONS

Seventy adult patients were assigned to the rocuronium (MR group; 35 patients) or control group (C group; 35 patients). Anesthesia was induced with propofol and remifentanil, and 0.9mgkg(-1) rocuronium was administered in the MR group.

MEASUREMENTS

The number of attempts to successful insertion, sealing pressure, and subjective difficulty of insertion were compared between the groups.

MAIN RESULTS

The total number of insertion attempts were as follows: one (MR group, 17 cases; C group, 4 cases), two (MR group, 13 cases; C group, 14 cases), three (MR group, 4 cases; C group, 14 cases), and failure (MR group, 1 case; C group, 3 cases), which was significantly different (P<.001). Sealing pressure was significantly higher in the MR group than in the C group (MR group, 22.1±5.4 cmH2O; C group, 18.7±3.2 cmH2O, P<.001). Subjective difficulty of insertion was significantly lower in the MR group than in the C group (C group, 72.4±19.0mm; MR group, 29.4±18.3mm; P<.001).

CONCLUSIONS

Our randomized clinical trial suggests that muscle relaxation facilitates i-gel insertion efficacy in anesthetized patients, as assessed by successful insertion rate, sealing pressure, and subjective difficulty of insertion.

Complications Associated with the Use of Supraglottic Airway Devices in Perioperative Medicine

Supraglottic airway devices are routinely used for airway maintenance in elective surgical procedures where aspiration is not a significant risk and also as rescue devices in difficult airway management. Some devices now have features mitigating risk of aspiration, such as drain tubes or compartments to manage regurgitated content. Despite this, the use of these device may be associated with various complications including aspiration. This review highlights the types and incidence of these complications. They include regurgitation and aspiration of gastric contents, compression of vascular structures, trauma, and nerve injury. The incidence of such complications is quite low, but as some carry with them a significant degree of morbidity the need to follow manufacturers' advice is underlined. The incidence of gastric content aspiration associated with the devices is estimated to be as low as 0.02% with perioperative regurgitation being significantly higher but underreported. Other serious, but extremely rare, complications include pharyngeal rupture, pneumomediastinum, mediastinitis, or arytenoid dislocation. Mild short-lasting adverse effects of the devices have significantly higher incidence than serious complications and involve postoperative sore throat, dysphagia, pain on swallowing, or hoarseness. Devices may have deleterious effect on cervical mucosa or vasculature depending on their cuff volume and pressure.

Muscle relaxant effects on insertion efficacy of the laryngeal mask ProSeal(®) in anesthetized patients: a prospective randomized controlled trial

BACKGROUND

Anesthesiologists often encounter LMA-ProSeal(®) (ProSeal) insertion difficulty due to its large cuff size. We performed a randomized clinical trial to examine how insertion efficacy and sealing pressure of ProSeal are affected by muscle relaxant administration in anesthetized patients.

METHODS

Our adult patients were either administered rocuronium (0.9 mg kg(-1)) as a muscle relaxant (R group; 40 patients) or not (C group; 40 patients). Anesthesia was induced with propofol and fentanyl. We compared the two groups with regard to the number of attempts required for successful insertion, sealing pressure, and subjective difficulty for insertion.

RESULTS

Total insertion attempts required for successful ventilation in the two groups were one (R group, 38 patients; C group, 28 patients), two (R group, one patient; C group, seven patients), and three (R group, one patient; C group, five patients), revealing a significant difference between groups (p < 0.001). Sealing pressure was significantly higher in the R group than in the C group (R group, 27.4 ± 5.4 cmH2O; C group, 21.2 ± 5.2 cmH2O; p < 0.001). Leakage volume by mechanical ventilation was significantly smaller in the R group than in the C group (R group, 17.4 ± 29.1 ml; C group, 46.8 ± 45.5 ml; p < 0.001). Subjective difficulty of insertion was significantly lower in the R group than in the C group (R group, 12.3 ± 23.1 mm; C group, 39.4 ± 31.9 mm; p < 0.001).

CONCLUSIONS

Muscle relaxation appears to facilitate ProSeal insertion efficacy by enabling higher successful insertion rates, higher sealing pressure, lower leakage volume, and lower subjective difficulty of insertion in anesthetized patients.

Does prewarming the i-gel supraglottic airway device fit the larynx better compared to keeping it at room temperature for non-paralysed, sedated patients: a randomised controlled trial

OBJECTIVE

This study aimed to test the hypothesis that the i-gel supraglottic airway device would fit the larynx and provide better sealing pressure if prewarmed to 42°C relative to the device kept at room temperature in non-paralysed, sedated patients.

METHODS

A total of 74 adult patients were assigned to the warm (i-gel prewarmed to 42°C; W group; 37 patients) or the control (i-gel kept at room temperature; C group; 37 patients) groups. Anaesthesia was induced with propofol and fentanyl. The i-gel was prewarmed to 42°C for 30 min before insertion in the W group, but kept at room temperature (approximately 23°C) for the C group. The number of attempts made until successful insertion and sealing pressure were compared between the two groups.

RESULTS

Insertion was successful with one attempt in 35 cases each for the W and C groups. Two attempts were needed in two cases for the W group and one case for the C group. There was one failed attempt in the C group, but none in the W group. None of the differences between the two groups were significant (p=0.51). Sealing pressure was slightly, but not significantly, higher in the W group than in the C group (W group 22.6±6.1 cm H2O; C group 20.7±6.1 cm H2O; p=0.15).

CONCLUSIONS

Prewarming of the i-gel to 42°C did not increase the success rate of insertion, nor did it significantly increase sealing pressure in anaesthetised, non-paralysed patients. Our data suggest that we can keep the i-gel at room temperature for emergency airway management for non-paralysed, sedated patients.

TRIAL REGISTRATION NUMBER

University Medical Information Network, Japan 000012287.

Directly measured mucosal pressures produced by the i-gel™ and Laryngeal Mask Airway Supreme™ in paralysed anaesthetised patients

The i-gel™ and LMA Supreme™ are extraglottic airway devices with non-inflatable and inflatable cuffs, respectively. We hypothesised that directly measured mucosal pressures would differ between these devices in anesthetised paralysed patients. Thirty patients were randomly allocated to receive one of these two devices. Four pressure sensors were attached to all airway devices used to measure mucosal pressure at the base of the tongue, the distal oropharynx, the hypopharynx and the pyriform fossa. At these four places, median (IQR [range]) i-gel mucosal pressures were 8.0 (2.7-10.7 [0-26.7]), 5.0 (2.7-7 [1.0-37.3]), 9.3 (2.7-13.3 [0-22.7] and 8.0 (2.7-10.7 [0-25.3]) cmH(2)O, respectively, and for the LMA Supreme, these were 5.0 (0.5-8.0 [0-33]), 4.0 (1.3-9.3 [0-24]), 10.7 (4-17.3 [0-26.7]) and 8.0 (0-10.7 [0-36]) cmH(2)O, respectively. Mucosal pressures were low and similar for both devices. The LMA Supreme mucosal pressures were higher in the hypopharynx than in the distal oropharynx (p = 0.04) and base of the tongue (p = 0.011). There were no pressure differences between the locations for the i-gel.

Randomised comparison of the LMA Supreme with the I-Gel in spontaneously breathing anaesthetised adult patients

We compared the performance of the LMA Supreme (SLMA) with the I-Gel during anaesthesia in spontaneously breathing adult patients. Ninety patients with American Society of Anesthesiologists physical status I or II were studied in a prospective randomised controlled study. Our primary outcome measure was oropharyngeal leak pressure. We also compared the overall insertion success rate, ease of insertion, adequacy of ventilation and incidence of complications. The mean (SD), oropharyngeal leak pressure for the SLMA was 25.6 (5.1) cmH2O, which was greater than for the I-Gel 20.7 (5.9) cmH2O (P = 0.0001). The first attempt and overall insertion success rates were similar between the two groups (SLMA 97.8 and 97.8%; I-Gel 93.3 and 100%, P = 0.132). The SLMA was rated easier to insert than the I-Gel (P = 0.011), but the time taken for insertion (P = 0.433) was similar. The incidence of complications was low in both groups. The grade of fibreoptic view was better with the I-Gel than the SLMA (P = 0.001). We conclude that in adults with normal airways, the SLMA is easier to insert and provides a higher oropharyngeal leak pressure, but fibreoptic views are better with the i-gel.

Lower intracuff pressure of laryngeal mask airway in the lateral and prone positions compared with that in the supine position

We compared the intracuff pressure (ICP) of a laryngeal mask airway (LMA) in the lateral and prone positions with that in the supine position. One hundred and eight patients, weighing 50-70 kg, scheduled for elective orthopedic and plastic surgery, were assigned to three groups, based on their body position during surgery. General anesthesia was induced and then a size 4 deflated LMA was inserted in each patient in the supine (group 1; n = 42), lateral (group 2; n = 45), or prone position (group 3; n = 21). The LMA cuff was inflated with 15 ml of air. Anesthesia was maintained without nitrous oxide, and the ICP was measured until LMA removal in the supine position. ICP in groups 2 and 3 was significantly lower than that in group 1 from immediately after insertion to the end of surgery. After surgery, turning from the lateral (group 2) or prone (group 3) position to the supine position significantly raised the ICP. Because the ICP is related to the seal pressure of the LMA and postoperative pharyngolaryngeal morbidity, we recommend evaluating and adjusting the ICP appropriately in each body position.

Measurement of tracheal wall pressure: a comparison of three different in vitro techniques

We compared three different tracheal wall pressure measuring techniques in vitro. Using a high-volume, low-pressure, cuffed tracheal tube with an internal diameter of 7.5 mm and a model trachea, the pressure difference technique, the wall pressure membrane technique and the microchip sensor probe technique with and without lubrication were studied. Wall pressures were measured after sequential injections of 0.5 ml of air into the cuff at cuff pressures ranging from 0 to 50 mmHg. The coefficient of variance was largest for the microchip sensor probe technique with lubrication (29%) and without lubrication (214%), and was lower for the wall pressure membrane technique (22%) and the pressure difference technique (19%). The wall pressure membrane and pressure difference techniques provided comparable results. The microchip sensor probe technique considerably underestimated wall pressure. These findings have an impact on the interpretation of published data on tracheal or pharyngeal wall pressure using the microchip sensor probe technique.

Brief review: Neuromuscular monitoring: an update for the clinician

PURPOSE

To review established techniques and to provide an update on new methods for clinical monitoring of neuromuscular function relevant to anesthesia.

SOURCE

A PubMed search of relevant article for the period 1985-2005 was undertaken, and bibliographies were scanned for additional sources.

PRINCIPAL FINDINGS

There is no substitute for objective neuromuscular monitoring; for research purposes, mechanomyography (MMG) is the gold standard; however, the most versatile method in the clinical setting is acceleromyography since it can be applied at various muscles and has a long track record of clinical utility. Kinemyography is valid to monitor recovery of neuromuscular transmission at the adductor pollicis muscle (AP), whereas phonomyography is easy to apply to various muscles and shows promising agreement with MMG. Monitoring of the corrugator supercilii muscle (CS) may be used to determine the earliest time for tracheal intubation as it reflects laryngeal relaxation better than monitoring at the AP. Recovery of neuromuscular transmission is best monitored at the AP, since it is the last muscle to recover from neuromuscular blockade (NMB). If train-of-four (TOF) stimulation is used, a TOF-ratio > 0.9 should be the target before awakening the patient. If surgery or the type of anesthesia necessitates NMB of a certain degree, e.g., TOF-ratio = 0.25, monitoring of muscles which best reflect the degree of NMB at the surgical site is preferable.

CONCLUSION

Objective methods should be used to monitor neuromuscular function in clinical anesthesia. Acceleromyography offers the best compromise with respect to ease of use, practicality, versatility, precision and applicability at various muscles. The CS is the optimal muscle to determine the earliest time for intubation, e.g., for rapid sequence induction.

Sex-based ProSeal laryngeal mask airway size selection: a randomized crossover study of anesthetized, paralyzed male and female adult patients

We compared the Size 4 and 5 ProSeal laryngeal mask airway (PLMA) in men and the Size 3 and 4, and 4 and 5 PLMA in women in terms of 1) ease of insertion, 2) oropharyngeal leak pressure (OLP), 3) ease of ventilation at a tidal volume of 10 mL/kg, 4) gas exchange, 5) location of gas leak, 6) anatomic position of the airway and drain tube, and 7) mucosal injury. Thirty male and 60 female (ASA physical status I-II; 18-80 yr old) anesthetized, paralyzed patients were studied in a crossover fashion in three equal-sized groups. PLMA insertion was performed by a single experienced operator by using digital manipulation. In male patients comparing the Size 4 and 5, OLP was higher (P = 0.0002) and leak fraction lower (P = 0.03) for the Size 5, but the number of insertion attempts, insertion time, mucosal injury, anatomic position, gas exchange, and location of gas leak were similar. In female patients comparing the Size 4 and 5 PLMA, OLP was higher for the Size 5 (P < 0.0001), but the number of insertion attempts was fewer (P = 0.02), insertion time was quicker (P = 0.02), and there was less mucosal injury (P = 0.01) with the Size 4. There were no differences in anatomic position, gas exchange, or location of gas leak. In female patients comparing the Size 3 and 4 PLMA, OLP was higher (P = 0.0005) and leak fraction was lower (P = 0.03) for the Size 4, but the number of insertion attempts, insertion time, mucosal injury, anatomic position, gas exchange, and location of gas leak were similar. There were no episodes of failed oxygenation, failed ventilation, or gastric insufflation. We conclude that if size is selected by sex, the Size 4 PLMA is preferable for women and the Size 5 PLMA for men.

IMPLICATIONS

When sex is used to select the appropriate size of the ProSeal laryngeal mask airway, the Size 4 ProSeal is preferable for women and the Size 5 ProSeal for men.

The proseal laryngeal mask: results of a descriptive trial with experience of 300 cases

BACKGROUND

The ProSeal laryngeal mask airway (PLMA) is a new laryngeal mask device with a modified cuff and a drainage tube.

METHODS

We assessed the PLMA in 300 anaesthetized adults either paralysed or breathing spontaneously. We assessed insertion characteristics, airway seal pressures, haemodynamic response to insertion, ease of gastric tube placement, gastric insufflation, and postoperative sore throat.

RESULTS

Insertion was successful in 294 patients (98%) and graded as easy in 274 patients (91%). We found no difference in ease of insertion or success rate with either the introducer or the finger insertion method, or in paralysed or non-paralysed patients. Mean airway seal pressure was 29 cm H2O, and 59 patients (20%) had seal pressures greater than 40 cm H2O. No gastric insufflation was detected. Gastric tube placement was successful in 290 of 294 patients (98.6%). There was no cardiovascular response to insertion, with a small reduction in heart rate 5 min after insertion and significant decreases in mean arterial pressure at 1 and 5 min after insertion. Sore throat was noted in 23% patients after operation and in 16% of patients after 24 h, with 90% of the sore throats described as mild.

CONCLUSIONS

The PLMA is a reliable airway management device that can give an effective glottic seal in paralysed and non-paralysed patients. The device allows the easy passage of a gastric tube, causes a minimal haemodynamic response to insertion, and an acceptable incidence of sore throat.