Pharyngeal mucosal pressure and perfusion: a fiberoptic evaluation of the posterior pharynx in anesthetized adult patients with a modified cuffed oropharyngeal airway

Incidence of Postoperative Sore Throat and Associated Factors Among Pediatric Patients Undergoing Surgery Under General Anesthesia at Hawassa University Comprehensive Specialized Hospital, a Prospective Cohort Study

Background

Postoperative sore throat is one of the common postoperative complications following general anesthesia. Postoperative sore throat causes decreased patient satisfaction, and it affects patients' well-being after surgery, thus identifying its incidence and predictors helps to distinguish the preventable causes of postoperative sore throat. This study aimed to assess the incidence and associated factors of postoperative sore throat among pediatric patients undergoing surgery under general anesthesia at Hawassa university comprehensive specialized hospital.

Methods

A prospective cohort study was conducted among children in the age range 6-16 years old who underwent emergency and elective surgical procedures under general anesthesia. Data were entered and analyzed using SPSS version 26 software packages. Univariate and multivariate analyses were performed to investigate the independent predictors. The presence and severity of postoperative sore throat were assessed by using a four-point categorical pain scale at the 2nd, 6th, 12th, and 24th-hour postoperative time.

Results

A total of 102 children were recruited in this study, from which 27 children (26.5%) complained of sore throat postoperatively. This study found that endotracheal intubation (P value: 0.030; AOR: 3.155; 95% CI [1.114-8.933]) and several attempts greater than one (P value: 0.027 and AOR: 4.890; 95% CI: [1.203-19.883]) had statistically significant association with a postoperative sore throat.

Conclusion

The overall incidence of postoperative sore throat was 26.5%. Endotracheal intubation and the number of attempts greater than one were independent factors that were significantly associated with the occurrence of postoperative sore throat in this study.

Sealing mechanism study of laryngeal mask airways via 3D modelling and finite element analysis

Proper sealing of laryngeal mask airways (LMAs) is critical for airway management in clinical use. Understanding the sealing mechanism can significantly help front-line anaesthetists to reduce the incidence of adverse events. However, anaesthetists, who may not have the most substantial engineering backgrounds, lack intuitive ways to develop an understanding of the LMA sealing mechanism effectively. The paper aims to study the LMA-pharynx sealing mechanisms from the perspective of front-line anaesthetists. We use a computer-aided 3D modelling technique to visualise the LMA—pharynx interactions, which helps anaesthetists identify the critical areas of complications. Furthermore, we conduct a quantitative pressure distribution analysis of the LMA-pharynx contacting surface using the finite element analysis technique, which helps further understand the sealing mechanics in those areas. We present two cases studies based on one male volunteer, aged 50, inserted with a ProSeal LMA. In the first case, a relatively low cuff pressure (CP) was applied to simulate the clinical circumstances in which complications related to air leakage are most likely to happen; in the second case, we increase the CP to a relatively high value to simulate the scenarios with an increased risk of complications related to high mucosal pressure. The experiments suggest the follows: (1) Sore throat complications related to high mucosal pressure is most likely to occur in the hypopharynx with a high CP setting, particularly in the areas where the cricoid cartilage presses the mucosa. (2) The narrow hyoid bone super horn width likely causes LMA insertion difficulties. (3) Insufficient CP will significantly increase the risk of air leakage in the oropharynx. A complete sealing pressure line in the contacting surface will be formed with sufficient CP, thereby preventing the air leakage into the oral.

Transient unilateral lingual nerve injury following the use of laryngeal mask airway Supreme: a case report

Lingual nerve injury rarely occurs after using the laryngeal mask airway (LMA). A 40-year-old woman with no comorbidities visited the hospital for left breast-conserving surgery. Anesthesia was performed using LMA Supreme™. She complained of decreased sensation in the right front part of the tongue postoperatively. She received prednisolone and tongue sensation returned on postoperative day 28. The lingual nerve could be damaged by the LMA, particularly the lateral edge of the tongue base and inner part of the mandible around the third molar. When using the LMA, it is necessary to check the cuff pressure to prevent lingual nerve damage.

Comparison of Ambu AuraGain at low cuff pressure, Ambu AuraGain at high cuff pressure and i-gel in relation to incidence of postoperative upper airway complications

Background and Aims:

Postoperative upper airway complications are frequently encountered with the use of supraglottic airway devices (SADs). Cuff pressure is one of the risk factors for upper airway complications with SADs. Among SADs, i-gel has shown lesser incidence. The effect of different cuff pressures on the incidence of postoperative upper airway complications is not known with Ambu AuraGain and nor has Ambu AuraGain been compared with i-gel in this regard. So, we undertook this study.

Methods:

A total of 200 patients undergoing elective laparoscopic surgery were randomised into 3 groups based on the SAD used and intra-cuff pressure: i-gel (IG) (n = 66); Ambu AuraGain at 25 cmH₂O cuff pressure (AL) (n = 67); and Ambu AuraGain at 60 cmH₂O cuff pressure (AH) (n = 67). The oropharyngeal leak pressures (OLPs) were measured after insertion and generation of carboperitoneum. An observer who was blind to the intraoperative details assessed the patients for two postoperative days for sore throat, dysphagia, dysphonia, or any other upper airway complications.

Results:

The OLPs before and after carboperitoneum in the 3 groups were (IG-24.22 ± 7.87 and 28.31 ± 8.52, AL-24.40 ± 5.84 and 26.94 ± 5.93, AH-25.02 ± 5.02 and 28.91 ± 5.6) cmH₂O (P = 0.747 and P = 0.231). The overall incidence of postoperative sore throat among the 3 groups was: IG-5.7%, AL-14.9%, and AH-17.9%; P = 0.135. Dysphagia was seen only with Ambu AuraGain at high pressure in 4 patients (5.97%) (P = 0.017).

Conclusion:

Limiting cuff pressure in Ambu AuraGain to 25, as against 60 cmH₂O, does not affect the OLP but has the potential of reducing the incidence of dysphagia.

Comparison of Intracuff Pressure and Postoperative Sore Throat Following Use of Laryngeal Mask Airway Protector With or Without Nitrous Oxide Anesthesia

PURPOSE

In general anesthesia, the laryngeal mask airway (LMA) is a frequently used effective option. The effect of nitrous oxide on intracuff pressure of the LMA and postoperative sore throat is well known; however, there are no studies related to the second-generation LMA Protector. The purpose of this study was to determine the differences in intracuff pressure and postoperative sore throat, depending on the use of nitrous oxide during general anesthesia using the LMA Protector.

DESIGN

This randomized double-blind prospective study was conducted among 88 patients aged 20 to 70 years.

METHODS

The cuff pressure started with a baseline of 40 cm H₂O and was measured using a digital cuff pressure manometer for 30 minutes. Postoperative sore throat, dysphonia, dysphagia, and numeric rating scale scores were also recorded.

FINDINGS

Over time, the intracuff pressure of the nitrous oxide group increased significantly compared with that of the air group. Furthermore, postoperative sore throat and pharyngolaryngeal complications were not significantly different between the two groups.

CONCLUSIONS

Intracuff pressure of the LMA Protector increased during anesthesia using nitrous oxide. When the anesthesia time was less than 2 hours, however, there was no difference in postoperative sore throat.

Randomized Evaluation of the Single-use SoftSeal™ and the Re-useable LMA Classic™ Laryngeal Mask

A number of laryngeal masks are available, including both re-usable and single-use masks. Single-use laryngeal masks may decrease the risk of transmitting prion infections. We performed a single-blind randomized trial in 200 spontaneously breathing female patients under general anaesthesia with nitrous oxide, to compare a new single-use laryngeal mask, the SoftSeal™ (Portex Ltd, U.K.), with a re-usable laryngeal mask, the LMA Classic™ (Laryngeal Mask Company Ltd., Cyprus). The primary outcome was successful insertion at the first attempt. Size 4 single-use (n=99) or re-usable (n=100) laryngeal masks, inserted by experienced anaesthetists, were equivalent for successful placement at the first attempt (90% versus 91% respectively). The single-use mask was less easy to insert (47% difficult versus 9%, P<0.001). Clinical and anatomical tests of position and function were similar. The cuff pressure of the re-usable mask increased significantly compared with the single-use mask (median +10 cm versus –2 cm H 2 O, P<0.001). Forty per cent of patients allocated the single-use mask and 20% of those allocated the re-usable mask experienced sore throat at 24 hours postoperatively (P<0.05). An estimation of cost per patient use was greater for the re-usable mask.

We conclude that the SoftSeal™ single-use laryngeal mask and the LMA Classic™ re-usable laryngeal mask airway are of similar clinical utility in terms of successful insertion and airway maintenance. The re-usable laryngeal mask was easier to insert and associated with less postoperative sore throat, but costs were higher.

Clinical application of limiting laryngeal mask airway cuff pressures utilizing inflating syringe intrinsic recoil

BACKGROUND

Overinflation of the laryngeal mask airway (LMA) cuff may cause many of the complications associated with the use of the LMA. There is no clinically acceptable (cost effective and practical) method to ensure cuff pressure is maintained below the manufacturer's recommended maximum value of 60 cm H2O (44 mmHg). We studied the use of the intrinsic recoil of the LMA inflating syringe as an effective and practical way to limit cuff pressures at or below the manufacturer's recommended values.

METHODS

We enrolled 332 patients into three separate groups: LMAs inserted and inflated per standard practice at the institution with only manual palpation of the pilot balloon; LMA cuff pressures measured by a pressure transducer and reduced to < 60 cm H2O (44 mmHg); and LMA intra-cuff pressure managed by the intrinsic recoil of the syringe.

RESULTS

There were no statistically significant differences between the pressure transducer group and the syringe recoil group for initial cuff pressure or cuff pressure 1 hour after surgery. Both the syringe recoil group and pressure transducer group were less likely than the standard practice group to have sore throat and dysphagia 1 hour after surgery. These differences remained 24 hours after surgery.

CONCLUSIONS

Syringe recoil provides an efficient and reproducible method similar to manometry in preventing overinflation of the LMA cuff and decreasing the incidence of postoperative laryngopharyngeal complications.

Evaluation of the optimal cuff volume and cuff pressure of the revised laryngeal tube "LTS-D" in surgical patients

Background

Recent case reports have indicated significant cuff overinflation when using the standard filling volume based on the manufacturer’s recommendations in older models of laryngeal tubes. The aim of this study was to determine the minimum cuff pressure needed to perform standardized ventilation without leakage in the new, revised model of the laryngeal tube “LTS-D”.

Methods

After ethical approval, LTS-D was placed for ventilation in 60 anesthetized patients. The cuff was inflated to the recommended volume (#3: 60 ml, #4: 80 ml, and #5: 90 ml). After evaluation of the initial cuff pressure (CP), the CP was lowered in 10 cmH₂O steps until a minimal cuff pressure of 30 cmH₂O was achieved. The absence of an audible leak was required for a step-by-step reduction in the CP. Evacuated cuff volume, success rate, and airway injuries were documented. Data were expressed as medians (interquartile ranges [IQRs]). The comparison of CPs and cuff volumes was performed using the Mann-Whitney test.

Results

After initial inflation, the CP ranged from 105 cmH₂O [90–120; #5] to 120 cmH₂O [110–120; #3]. Lowering the CP to 60 cmH₂O resulted in a reduced cuff volume ranging from 47 ml [44–54; #3] to 77 ml [75–82; #5] compared to the initial inflation (p < 0.001). Leakage occurred more frequently when the CP was lowered to 40 cmH₂O compared to the initial inflation (44/54 [81%]; p < 0.01). Using a CP between 50 cmH₂O and 60 cmH₂O, a leakage rate of 3/54 (5%) was observed, compared to a rate of 11/54 (21%) when using a CP lower than 50 cmH₂O. The overall success rate was 90%, and airway injury occurred in 7% of patients (4/60).

Conclusion

We found significant overinflation of the revised LTS-D using the recommended volume for initial cuff inflation. A CP of 60 cmH₂O was found to be sufficient for ventilation in the majority of patients evaluated. Checking and adjusting the CP in laryngeal tubes is mandatory to avoid overinflation.

Trial registration

ClinicalTrials.gov NCT02300337. Registered: 20 November 2014.

Electronic supplementary material

The online version of this article (doi:10.1186/s12871-017-0308-4) contains supplementary material, which is available to authorized users.

Comparative evaluation of Ambu AuraGain™ with ProSeal™ laryngeal mask airway in patients undergoing laparoscopic cholecystectomy

Background and Aims:

Second generation supraglottic airways are increasingly being used in surgical patients undergoing laparoscopic surgery. Preventing aspiration at higher airway pressures may be at the expense of a higher cuff pressure which can impair mucosal perfusion. We attempted to elucidate whether Ambu AuraGain™ (AAU) would provide a higher oropharyngeal leak pressure (OLP) with a lower mucosal pressure in comparison to ProSeal™ laryngeal mask airway (PLMA).

Methods:

This was a prospective randomised study involving sixty patients undergoing laparoscopic cholecystectomy under general anaesthesia, using either AAU (Group AAU [n = 30]) or PLMA (Group PLMA [n = 30]) for elective ventilation. Primary outcome measure was the OLP. Number of insertion attempts, ease of insertion, time required for placement and calculated pharyngeal mucosal pressure were the secondary outcome measures. Data were analysed using Student's t-test and Chi-square test.

Results:

No significant difference in the OLP was noted in both groups. The ease of insertion and success rate at first attempt was similar between the groups. Time taken for insertion in Group AAU was longer than Group PLMA (13.57 ± 1.94 vs. 11.60 ± 2.22 s). The calculated pharyngeal mucosal pressures were lower with Group AAU than Group PLMA for all 3 sizes. The minimum cuff pressure and minimum cuff volume required to prevent leak were found similar in both groups.

Conclusion:

AAU provides adequate sealing pressures and effective ventilation with lower calculated pharyngeal mucosal pressure, compared to PLMA.

Laryngeal tube suction II or endotracheal intubation for laparoscopic radical prostatectomy in a head down position: A randomised controlled trial

BACKGROUND

The laryngeal tube suction II (LTS II) is a supraglottic airway device (SAD) with a gastric drainage tube and enhanced seal properties as compared with other SADs. Therefore, its use has been proposed in situations with an elevated risk of aspiration.

OBJECTIVES

To compare the safety and efficacy of airway management and controlled mechanical ventilation when using either an LTS II or an endotracheal tube for laparoscopic radical prostatectomy.

DESIGN

Randomised, controlled, blinded and single-centre study.

SETTING

Academic tertiary care centre in Leipzig from April 2014 to May 2015.

PATIENTS

It was planned to include 100 patients but the study was stopped after 50 patients following an interim analysis. These 50 patients were randomised to either the LTS II group or the endotracheal tube group. All male patients aged more than 18 years for elective laparoscopic radical prostatectomy were eligible. Exclusion criteria included a BMI more than 30, American Society of Anesthesiologists class III or greater, a history of gastroesophageal reflux or other factors known to increase the risk of aspiration and a known difficult airway.

INTERVENTIONS

All patients received general anaesthesia. Airway management was with either a LTS II or an endotracheal tube, according to the randomisation.

MAIN OUTCOME MEASURES

The primary endpoint was successful insertion of the particular airway device during anaesthesia for laparoscopic radical prostatectomy.

RESULTS

In 15 of the 28 patients randomised to LTS II, the device had to be removed and an endotracheal tube inserted, mainly because of an airway leak (n = 10) or swelling of the tongue (n = 3). Ventilation was successful in all patients (n = 22) randomised to endotracheal tube. Quality of ventilation was rated better in the endotracheal tube group.

CONCLUSION

Our data suggest that LTS II should not be the preferred method of airway management in patients undergoing laparoscopic radical prostatectomy.

TRIAL REGISTRATION

DRKS00008985 (German Clinical Trials Register).

[Preclinical duty of care during cuff pressure management]

BACKGROUND

Airway morbidity is influenced by different factors. Independent of the main emergency health problem, airway morbidity factors may exacerbate a possible poor outcome (e.g., bleeding, tongue swelling, nerve lesion).

OBJECTIVES

However, insertion technique and cuff pressure management are both important for duty of care out-of-hospital emergency medicine. After securing the airway (e.g., tracheal tube or supraglottic airway device cuff), pressure measurement is necessary.

MATERIALS AND METHODS

In a number of recent publications, a largely forgotten issue has come into the focus of preclinical science. This issue became particularly relevant in the admitting hospital.

RESULTS

The results from the aforementioned publications show that preclinical management of cuff pressure is not taken sufficiently into consideration, resulting in possible harm to the patient.

DISCUSSION

It is important and safe to use a cuff pressure device. The initial cuff pressure and if necessary corrected value should be documented.

Comparisons of clinical performance of Guardian laryngeal mask with laryngeal mask airway ProSeal

Background

The Guardian Laryngeal Mask Airway (G-LMA) is a new silicone-based single-use extraglottic device with the drainage port and a cuff pilot valve with pressure indicator. The aim of this study is to compare the clinical performance of this laryngeal mask airway with ProSeal laryngeal mask airway (P-LMA).

Methods

In this prospective randomized study, we included adult patients with ASA grading I and II scheduled for elective surgery requiring supine position under total intravenous anesthesia. The patients were randomly allocated to two groups, 40 in each. G-LMA and P-LMA were used in groups G and P respectively. The cuff of each device was air inflated to 60 cmH₂O. The primary outcome was to compare the airway sealing pressure and the secondary outcome was to compare the efficacy and safety of these two devices with respect to insertion success, insertion time, ease of insertion, volume of air for cuff inflation to 60 cmH₂O, intracuff pressure measurement, gastric tube insertion attempt, gastric tube insertion time, Fiberoptic laryngeal view, and postoperative pharyngolaryngeal morbidity.

Results

The airway sealing pressure at 60cmH₂O cuff pressure was significantly greater in G-LMA than P-LMA (p = 0.04).The first successful attempt of both groups were comparable (p = 1.000). Insertion time was significantly shorter in G-LMA than P-LMA (p < 0.0001). The first successful attempt for the gastric tube insertion in both groups was comparable (p = 0.431). Gastric tube insertion time was less in G-LMA than in P-LMA (p < 0.0001). The volume of air for cuff inflation to 60 cmH₂O was more in G-LMA than in P-LMA (<0.0001). The intracuff pressure measurement at 30, 60, 90 and 120 minutes were comparable (p = 0.823, 0.182, 0.870, 0.658).We did not find differences in ease of insertion (p = 0.60); Fiber-optic positions of airway devices were comparable (p = 0.83). In addition, blood staining (p = 1.00), sore throat and dysphagia at 1, 2 and 24 hour (p = 1.00) were comparable in both groups.

Conclusion

The Guardian laryngeal mask airway was associated with high airway sealing pressure with a quicker insertion of the device as well as gastric tube.

Trial registration

Clinical Trial.gov Identifier: NCT02063516. Date: June 2013

Electronic supplementary material

The online version of this article (doi:10.1186/s12871-015-0039-3) contains supplementary material, which is available to authorized users.

Comparison of the air-Q intubating laryngeal airway and the cobra perilaryngeal airway as conduits for fiber optic-guided intubation in pediatric patients

BACKGROUND

One of the methods proposed in cases of difficult airway management in children is using a supraglottic airway device as a conduit for tracheal intubation. The aim of this study was to compare the efficacy of the Air-Q Intubating Laryngeal Airway (Air-Q) and the Cobra Perilaryngeal Airway (CobraPLA) to function as a conduit for fiber optic-guided tracheal intubation in pediatric patients.

MATERIALS AND METHODS

A total of 60 children with ages ranging from 1 to 6 years, undergoing elective surgery, were randomized to have their airway managed with either an Air-Q or CobraPLA. Outcomes recorded were the success rate, time and number of attempts required for fiber optic-guided intubation and the time required for device removal after intubation. We also recorded airway leak pressure (ALP), fiber optic grade of glottic view and occurrence of complications.

RESULTS

Both devices were successfully inserted in all patients. The intubation success rate was comparable with the Air-Q and the CobraPLA (96.7% vs. 90%), as was the first attempt success rate (90% vs. 80%). The intubation time was significantly longer with the CobraPLA (29.5 ± 10.9 s vs. 23.2 ± 9.8 s; P < 0.05), but the device removal time was comparable in the two groups. The CobraPLA showed a significantly higher ALP (20.8 ± 5.2 cmH2O vs. 16.3 ± 4.5 cmH2O; P < 0.001), but the fiber optic grade of glottic view was comparable with the two devices. The CobraPLA was associated with a significantly higher incidence of blood staining of the device on removal and post-operative sore throat.

CONCLUSION

Both the Air-Q and CobraPLA can be used effectively as a conduit for fiber optic-guided tracheal intubation in children. However, the Air-Q proved to be superior due to a shorter intubation time and less airway morbidity compared with the CobraPLA.

Soft Palate Ulceration After Brief Use of an i-Gel Supraglottic Airway

We describe a case of extensive soft palate ulceration after the use of an i-gel supraglottic airway device (Intersurgical Ltd, Wokingham, United Kingdom) during a knee arthroscopy in a 61-year-old man. He presented with pain and soft palate ulceration, which eventually required hospital admission because of dehydration. The pharynx healed completely within 3 months, with a change in taste as the remaining symptom.

A pilot study to examine the effect of the Tulip oropharyngeal airway on ventilation immediately after mask ventilation following the induction of anaesthesia

The Tulip airway is an adult, disposable, single-sized oropharyngeal airway, that is connectable to an anaesthetic circuit. After a standardised induction of anaesthesia in 75 patients, the ease of insertion, intracuff pressure and intracuff volume were measured, as were the end-tidal carbon dioxide levels, airway pressures and tidal volumes over three breaths. Successful first-time insertion was achieved in 72 patients (96%, CI 88.8-99.2%) and after two attempts in 74 patients (99%, CI 92.8-100%). There was outright failure only in one patient. In 60 patients (80%, CI 72.2-90.4%), the Tulip airway provided a patent airway without additional manoeuvres, but in 14 patients, jaw thrust or head extension was necessary for airway patency. The main need for these adjuncts appeared to be an initial under-inflation of the cuff. These promising results are consistent with recent manikin studies using this device.

Postoperative pharyngolaryngeal adverse events with laryngeal mask airway (LMA Supreme) in laparoscopic surgical procedures with cuff pressure limiting 25 cmH₂O: prospective, blind, and randomised study

To reduce the incidence of postoperative pharyngolaryngeal adverse events, laryngeal mask airway (LMA) manufacturers recommend maximum cuff pressures not exceeding 60 cmH₂O. We performed a prospective randomised study, comparing efficacy and adverse events among patients undergoing laparoscopic surgical procedures who were allocated randomly into low (limiting 25 cmH₂O, L group) and high (at 60 cmH₂O, H group) LMA cuff pressure groups with LMA Supreme. Postoperative pharyngolaryngeal adverse events were evaluated at discharge from postanaesthetic care unit (PACU) (postoperative day 1, POD 1) and 24 hours after discharge from PACU (postoperative day 2, POD 2). All patients were well tolerated with LMA without ventilation failure. Before pneumoperitoneum, cuff volume and pressure and oropharyngeal leak pressure (OLP) showed significant differences. Postoperative sore throat at POD 2 (3 versus 12 patients) and postoperative dysphagia at POD 1 and POD 2 (0 versus 4 patients at POD 1; 0 versus 4 patients at POD 2) were significantly lower in L group, compared with H group. In conclusion, LMA with cuff pressure limiting 25 cmH₂O allowed both efficacy of airway management and lower incidence of postoperative adverse events in laparoscopic surgical procedures. This clinical trial is registered with KCT0000334.

ProSeal™ laryngeal mask airway cuff pressure changes with and without use of nitrous oxide during laparoscopic surgery

Background:

The ProSeal™ laryngeal mask (PLMA) is increasingly being used as an airway device for laparoscopic surgery. Its silicone cuff allows diffusion of nitrous oxide, carbon dioxide and other gases with resultant rise in its intracuff pressure during anesthesia. The present study was designed to investigate the intracuff pressure changes during anesthesia with and without nitrous oxide in patients undergoing laparoscopic surgery lasting up to two hours.

Materials and Methods:

One hundred patients, American Society of Anesthesiologists physical status 2 and 3, undergoing general anesthesia with muscle paralysis, were randomized into two groups of 50 patients each to receive an anesthetic gas mixture containing either oxygen and nitrous oxide (group N) or oxygen and air (group A). Following insertion of an appropriate size PLMA, its cuff was inflated with air to an intracuff pressure of 45 mm Hg. The cuff pressure was measured every 10 minutes for the entire course of anesthesia. The position of the device was also assessed fiberoptically and postoperative airway complications were recorded.

Results:

The maximum intracuff pressure recorded in group N was 103 ± 4.7 mm Hg vs. 45.5 ± 1.5 mm Hg in group A. The percentage rise in cuff pressure every 10 minutes was also highly significant (P < 0.001) being maximum in first 10 min in group N. The incidence of postoperative airway complications was comparable between the two groups.

Conclusion:

The results of this study demonstrate that the intracuff pressure of the PLMA increases progressively over time when the breathing gas mixture contains nitrous oxide.

Randomized comparison of the i-gel™, the LMA Supreme™, and the Laryngeal Tube Suction-D using clinical and fibreoptic assessments in elective patients

BACKGROUND

The i-gel™, LMA-Supreme (LMA-S) and Laryngeal Tube Suction-D (LTS-D) are single-use supraglottic airway devices with an inbuilt drainage channel. We compared them with regard to their position in situ as well as to clinical performance data during elective surgery.

METHODS

Prospective, randomized, comparative study of three groups of 40 elective surgical patients each. Speed of insertion and success rates, leak pressures (LP) at different cuff pressures, dynamic airway compliance, and signs of postoperative airway morbidity were recorded. Fibreoptic evaluation was used to determine the devices' position in situ.

RESULTS

Leak pressures were similar (i-gel™ 25.9, LMA-S 27.1, LTS-D 24.0 cmH2O; the latter two at 60 cmH2O cuff pressure) as were insertion times (i-gel™ 10, LMA-S 11, LTS-D 14 sec). LP of the LMA-S was higher than that of the LTS-D at lower cuff pressures (p <0.05). Insertion success rates differed significantly: i-gel™ 95%, LMA-S 95%, LTS-D 70% (p <0.05). The fibreoptically assessed position was more frequently suboptimal with the LTS-D but this was not associated with impaired ventilation. Dynamic airway compliance was highest with the i-gel™ and lowest with the LTS-D (p <0.05). Airway morbidity was more pronounced with the LTS-D (p <0.01).

CONCLUSION

All devices were suitable for ventilating the patients' lungs during elective surgery.

TRIAL REGISTRATION

German Clinical Trial Register DRKS00000760.

Tracheal traction exercise reduces the occurrence of postoperative dysphagia after anterior cervical spine surgery

STUDY DESIGN

We designed a novel anterior cervical spine surgery preoperative treatment comprising mechanical trachea/esophagus traction and compared the postoperative outcome regarding dysphagia with nontreated patients.

OBJECTIVE

We investigated whether the newly developed preoperative tracheal/esophageal traction exercise (TTE) treatment has an effect on postoperative dysphagia after anterior cervical spine surgery.

SUMMARY OF BACKGROUND DATA

Dysphagia is a postoperative complication that occurs after anterior cervical spine surgery, and known treatments are perioperative application of methylprednisolone, monitoring of endotracheal tube cuff pressure, and the use of low-profile plates. METHODS.: We compared the neck disability index, visual analogue scale scores for arm and neck pain, and Bazaz dysphagia scores, a dysphagia index, of 2 randomized groups, 1 week, 3 weeks, 6 weeks, 3 months, and 6 months after cervical spine surgery. One group received TTE treatment for 3 consecutive days before surgery, whereas the control group did not. RESULTS.: In the first week after operation, the Bazaz dysphagia scores for patients with second- to fourth-level fusions in the TTE group were significantly better than that in the control group (P = 0.000 for second- and third-level fusions and P = 0.013 for fourth-level fusion). Also at 3 weeks after surgery, the second- to fourth-level fusion patients in the TTE group had better Bazaz scores than those in the control group (P = 0.000 for second- and third-level fusions and P = 0.004 for fourth-level fusion). There was no significant difference of neck disability index and visual analogue scale scores between the 2 groups.

CONCLUSION

Dysphagia could be reduced in patients with multiple-level fusion after anterior cervical spine surgery by preoperative TTE treatment.

Randomised Comparison of the AMBU AuraOnce Laryngeal Mask and the LMA Unique Laryngeal Mask Airway in Spontaneously Breathing Adults

We conducted a randomised single-blind controlled trial comparing the LMA-Unique (LMAU) and the AMBU AuraOnce (AMBU) disposable laryngeal mask in spontaneously breathing adult patients undergoing general anaesthesia. Eighty-two adult patients (ASA status I–IV) were randomly allocated to receive the LMAU or AMBU and were blinded to device selection. Patients received a standardized anesthetic and all airway devices were inserted by trained anaesthetists. Size selection was guided by manufacturer recommendations. All data were collected by a single, unblinded observer. When compared with the LMAU, the AMBU produced significantly higher airway sealing pressures (AMBU 20 ± 6; LMAU 15 ± 7 cm H₂O; P = 0.001). There was no statistical difference between the two devices for overall success rate, insertion time, number of adjustments, laryngeal alignment, blood-staining, and sore throat (P ≥ 0.05). The AMBU AuraOnce disposable laryngeal mask provided a higher oropharyngeal leak pressure compared to the LMA Unique in spontaneously breathing adult patients.

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.

The effect of cuff pressure on postoperative sore throat after Cobra perilaryngeal airway

PURPOSE

The cuff volume of the Cobra perilaryngeal airway (CobraPLA) is larger than that of other alternative airway devices and makes it difficult to predict the effect of cuff pressure on the perilaryngeal mucosa. We tested the hypothesis that adjustment of the cuff pressure of the CobraPLA could reduce the incidence of postoperative sore throat (POST).

METHODS

After induction of general anesthesia and insertion of the CobraPLA by standardized method, the cuff pressure was set to 60 cmH(2)O (group C, n = 87) or adjusted to minimal seal-up pressure +5 cmH(2)O (group A, n = 87). The frequency and severity (0, none; 1, mild; 2, moderate; 3, severe) of throat soreness, pain, discomfort, and adverse effects were evaluated 1 and 24 h after removal of the CobraPLA.

RESULTS

Incidence of moderate POST in group C was higher than that in group A (11% vs. 2%, P = 0.021) whereas the overall POST incidence was not different between the two groups (31% vs. 20%, P = 0.092). The inflated air volume of group A was different from that of group C (41 vs. 50 ml, P = 0.009).

CONCLUSIONS

Adjustment of cuff pressure reduces the incidence of moderate POST after use of the CobraPLA.

Incidence of sore throat in children following use of flexible laryngeal mask airways - impact of an introducer device

BACKGROUND

Insertion of a flexible laryngeal mask airway (FLMA) is more difficult and therefore might result in a higher risk for trauma to the upper airway. To facilitate the insertion of FLMA, the use of an introducer device (Portex Limited, Hythe, Kent, UK) was promoted. However, the impact of the use of this device on the occurrence of postoperative sore throat is unknown.

METHODS

Four hundred children (3-21 years) undergoing elective ambulatory surgery were consecutively included in this study. In 196 cases, the FLMA was inserted using an introducer device. The FLMA cuff was then inflated and the pressure adjusted to below 60 cmH(2)O (according to manufacturers guidelines) using a calibrated cuff manometer (Portex Limited). Three types of FLMA were available: FLMA classic, FLMA unique (both FLMA PacMed, Richmond, Victoria, Australia) and FLMA ProBreathe (Well Lead Medical Co Ltd., Hualong, Guangzhou, China). Prior to discharge, patients' pain was assessed using an age appropriate scale.

RESULTS

Thirteen children (3.3%) developed sore throat, two (0.5%) sore neck and three (0.75%) sore jaw. Of those that developed sore throat, seven had a FLMA inserted with an introducer, six without an introducer. Using a laryngeal mask airways (LMA) with a polyvinyl chloride (PVC), surface was associated with a higher risk for sore throat compared with an LMA with a silicone surface (P = 0.0002).

CONCLUSION

In this study with controlled low cuff pressures, the incidence of sore throat was low. The use of an introducer device did not affect the rate of sore throat.

The impact of automatic retractors on the esophagus during anterior cervical surgery: an experimental in vivo study in a sheep model

Object

Postoperative dysphagia is a well-recognized complication of the anterior surgical approach to the cervical spine. However, its incidence and etiology remain unknown. The aim of this study was to investigate the impact of automatic retractor use on the esophagus and to describe the related pathological changes that might occur during cervical spine surgery.

Methods

A single-level cervical discectomy was performed via an anterior approach in 16 skeletally mature female sheep. Continuous retraction was applied with an automatic retractor system during surgery. The sheep model was chosen because of anatomical similarities to the human esophagus. The esophageal tract in every animal was examined using contrast radiographic examination. Eight animals were killed 3 days after the operation (Group 1). The remaining sheep were killed 4 weeks after the operation (Group 2). The esophagi were removed for histopathological study, which was performed using H & E and Masson trichrome staining. The changes in esophageal innervation were examined with nicotinamide adenine dinucleotide diphosphate–diaphorase histochemical staining.

Results

Only 1 animal (a Group 1 sheep) demonstrated any postoperative radiographic abnormality. In Group 1 sheep, histopathological study of the esophagi at the treated level revealed edema between the muscular fibers in the outer longitudinal and inner circular layers of the muscularis propria. At some points, obvious signs of vascular congestion, vascular damage, and inflammation were observed. In the Group 2 animals, there was mild-to-moderate fibrosis extending from the outer surface of the esophagus to the longitudinal layers of the muscularis propria in the area to which retraction had been applied. Enzyme-histochemical staining revealed the presence of normal myenteric plexus and ganglion cells, and nitrergic innervation in all parts of the esophagus wall.

Conclusions

The results of this study demonstrate that direct pressure induced by the medial retractor blade on the esophagus wall leads to local injury. Postoperative dysphagia in human patients who have undergone anterior cervical spine surgery could be a clinical manifestation of this phenomenon.

Impact of laryngeal mask airway cuff pressures on the incidence of sore throat in children

BACKGROUND

Hyperinflation of laryngeal mask airway cuffs can cause harm to the upper airway mainly by exerting high pressures on pharyngeal and laryngeal structures thus impairing mucosal perfusion. Although cuff manometers can be used to guide the monitoring of cuff pressures, their use is not routine in many institutions. In a prospective audit, we assessed the incidence of sore throat following day-case-surgery in relation to the intracuff pressure within the laryngeal mask airway.

METHODS

Four hundred children (3-21 years) were consecutively included in this study. The laryngeal mask airway was inflated as deemed necessary by the attending anesthetist. Cuff pressures were measured using a calibrated cuff manometer (Portex Limited, Hythe, Kent, UK, 0-120 cm H2O, pressures exceeding the measurement range were set at 140 cm H2O for statistical purposes) at induction of anesthesia.

RESULTS

Forty-five children (11.25%) developed sore throat, 32 (8%) sore neck and 17 (4.25%) sore jaw. Of those that developed sore throat, 56.5% had cuff pressures exceeding >100 cm H2O. In contrast, when cuff pressures were <40 cm H2O, there were no episodes of sore throat, whilst there was only a 4.6% occurrence of sore throat if cuff pressures were between 40-60 cm H2O.

CONCLUSION

We have demonstrated that intra cuff pressure in laryngeal mask airways is closely related to the development of sore throat with higher pressures increasing its likelihood. Hence, cuff pressures should be measured routinely using a manometer to minimize the incidence of sore throat.

Randomised comparison of the Classic Laryngeal Mask Airway with the Cobra Perilaryngeal Airway during anaesthesia in spontaneously breathing adult patients

We tested the hypothesis that the Cobra Perilaryngeal Airway (PLA) with its high volume low-pressure cuff would provide superior airway leakage pressure compared with the Classic Laryngeal Mask Airway (LMA) in spontaneously breathing adult patients. Ninety consecutive adult patients were randomly allocated to receive one of these two supralaryngeal devices. The airway leakage pressure was higher for the PLA compared with the LMA (22 +/- 9 cmH2O vs. 18 +/- 6 cmH2O; P < 0.05). The mean airway device intracuff pressure was lower for the PLA compared to the LMA (36.1 +/- 15.2 mmHg vs. 86.3 +/- 25.3 mmHg P < 0.0001). The time required to achieve successful insertion was greater for the PLA compared with the LMA (39 +/- 21 seconds vs. 27 +/- 10 seconds; P < 0.005). The number of attempts required to achieve successful insertion and the incidence of postoperative complications were similar in both groups. The findings suggest that the PLA provides a superior airway seal at a lower intracuff pressure compared to the LMA. However the time for successful insertion may be increased.

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.

[The laryngeal tube]

The laryngeal tube (VBM Medizintechnic GmbH, Sulz, Germany) is a supraglottic device designed for airway management in spontaneous or positive-pressure ventilation during anesthesia or in cardiopulmonary resuscitation. Currently, the tube is available in 4 versions: the standard laryngeal tube, the disposable tube (LT-D), the dual-lumen tube (with a tube for suction) (LTS II), and the disposable LTS (LTS-D). The design of the tube has been modified several times. It is easy to insert and the airway seal is more effective than that of the laryngeal mask. The incidence of complications is similar for both devices, though use of the laryngeal tube requires more adjustments. The standard tube is somewhat less effective than the ProSeal laryngeal mask, though the new LTS II has been improved considerably. The laryngeal tube is effective as an aid to management of the difficult airway. We reviewed the literature indexed on MEDLINE through December 2006 using the search terms laryngeal tube, anesthesia, equipment, and airway.

The impact of esophagus retraction on early dysphagia after anterior cervical surgery: does a correlation exist?

STUDY DESIGN

Prospective study of 92 patients who underwent anterior cervical surgery. Intraoperative esophagus retraction and postoperative dysphagia were recorded and evaluated.

OBJECTIVE

Early dysphagia after anterior cervical discectomy and fusion is an underestimated side effect. The aim of this study was to investigate whether postoperative swallowing disturbances correlate with the amount of intraoperative retraction of the pharynx/esophagus wall measured during the procedure.

SUMMARY OF BACKGROUND DATA

The anterior approach to the cervical spine is a routinely used and, in general, safe procedure. A recent prospective study focused on the underreported side effect of postoperative dysphagia, with an incidence of up to 50% at 1 month and 12.5% at 12 months. The etiology of postoperative dysphagia is not known in detail.

METHODS

An online pressure transducer between the retractor and pharynx/esophagus recorded the epi-esophageal pressure in 92 patients. In 31 patients, a transducer was additionally inserted into the pharynx/esophagus in order to measure the endo-esophageal pressure. The patients rated swallowing difficulty during the first postoperative 5 days using a 10-point score. A control group of 32 lumbar surgery patients was also evaluated for swallowing disturbances.

RESULTS

Mean epi-esophageal pressure after retractor opening was 76.3 mm Hg, and mean endo-esophageal pressure was 16.3 mm Hg. An adjustment to 75% and 76%, respectively, of the initial value occurred within the first hour. Of patients, 49.3% complained of swallowing disturbances. There was a significant prevalence of the female gender. No correlation between the amount of retraction and postoperative dysphagia was observed.

CONCLUSIONS

A correlation between intraoperative pharynx/esophagus retraction and postoperative swallowing disturbances could not be confirmed. The cause of the prevalence of the female gender is unknown. However, the absence of impaired deglutition in the control group suggests that a local phenomenon must be causative of swallowing disturbances following anterior cervical discectomy and fusion.

The CobraPLA during anesthesia with controlled ventilation: a clinical trial of efficacy

The CobraPLA (CPLA) is a relatively new supraglottic airway device that has not been sufficiently investigated. Here, we performed a prospective observational study to evaluate the efficacy of the CPLA during controlled ventilation. In 50 anesthetized and paralyzed patients undergoing elective surgery a CPLA was inserted and inflated to an intracuff pressure of 60 cm H2O. The success rate of insertion upon the first attempt was 82% (41/50), with a mean insertion time of 16.3 +/- 4.5 seconds. The adequacy of ventilation was assessed by observing the end tidal CO2 waveform, movement of the chest wall, peak airway pressure (13.5 cm H2O), and leak fraction (4%). We documented the airway sealing pressure (22.5 cm H2O) and noted that the the site of gas leaks at that pressure were either at the neck (52%), the abdomen (46%), or both (2%). In 44 (88%) patients, the vocal cords were visible in the fiberoptic view through the CPLA. There was no gastric insufflation during the anesthesia. Respiratory and hemodynamic parameters remained stable during CPLA insertion. Postoperative blood staining of CPLA was minimal, occurring in 22% (11/50) of patients. Mild and moderate throat soreness was reported in 44% (22/50) and 4% (2/50) of patients, respectively. Lastly, mild dysphonia was observed in 6% (3/50) of patients and mild dysphagia in 10% (5/50) of patients. Our results indicated that the CPLA is both easy to place and allows adequate ventilation during controlled ventilation.

[Oropharyngeal ulcers following anaesthesia with the laryngeal tube S]

We report a case of acute tongue and uvula ulcerations consecutive to the use of a laryngeal tube Sonda (LTS) for airway management. The LTS was used during general anaesthesia for hysteroscopy and resection of endometrial hyperplasia. No trouble occurred during LTS insertion and anaesthesia. Symptomatic treatment provided complete resolution within a few days. This event points out the potential risk of more serious lesions.

Haemodynamic and catecholamine stress responses to the Laryngeal Tube-Suction Airway and the Proseal Laryngeal Mask Airway

Supraglottic airway devices such as the ProSeal Laryngeal Mask Airway (PLMA) and Laryngeal Tube-Suction Airway (LTS) that provoke the least stress responses could be beneficial in many situations, especially in patients with cardiovascular disease. We compared the haemodynamic and catecholamine stress response of the LTS and PLMA in a randomised study of 36 patients. Mean arterial pressure, heart rate, epinephrine and norepinephrine levels were all reduced following induction of anaesthesia with no significant differences between the two groups. Following insertion of LTS, mean arterial pressure, heart rate, epinephrine and norepinephrine levels increased to pre-induction levels. However, following the insertion of the PLMA, mean arterial pressure, heart rate, epinephrine and norepinephrine levels remained significantly lower than pre-induction values. Mean arterial pressure, heart rate and epinephrine were significantly greater in the LTS group than in the PLMA group. We conclude that the LTS produces a greater and more sustained haemodynamic and catecholamine stress response than does the PLMA.

Intraoperative measurement of pharynx/esophagus retraction during anterior cervical surgery. Part I: pressure

Temporary dysphagia after anterior cervical discectomy (ACD) is common. However, its mechanism is poorly understood. Pressure induced by retractor blades onto pharynx/esophagus were measured intraoperatively in order to gain more information regarding traumatization of the pharynx/esophagus wall. Thirty-one patients underwent anterior cervical discectomy and fusion (ACDF) for degenerative disc disease. An online pressure transducer was applied to the rear side of the medial retractor blade (epi-esophageal-pressure, epi-P) and a cylindric, inflatable transducer was preoperatively inserted into the pharynx/esophagus under fluoroscopic guidance at the level to be operated on (endo-esophageal-pressure, endo-P). Pressure values were recorded continuously during the operation. Mean arterial pressure (MAP) and endotracheal cuff pressure (ETCP) were recorded additionally. An in vitro model was developed in order to analyze the impact of the retractor blade design onto the epi-esophageal-pressure. Mean epi-P before and following adequate retractor opening for exposure of the disc space was 58.3 and 92.7 mmHg. Thirty, 60 and 90 min later the epi-P decreased to 79, 70 and 66%, respectively. Mean basal endo-P was 9.8 mmHg and increased to 20.6 mmHg after retractor placement. Thirty, 60 and 90 min later the endo-P decreased to 80, 71 and 62%, respectively. The mean MAP was 76 mmHg and the ECTP was adjusted to 25 mmHg during the procedures. In the in vitro model retraction pressure correlated inversely with the contact area between visceral wall and retractor blade. During ACDF the retraction pressure onto the pharyngeal/esophageal wall exceeds MAP and even more the mucosal perfusion pressure of 25 mmHg. Over time the pharynx/esophageal wall adapts to the applied pressure induced by the retractor blade. The contact area between them influences the retraction pressure.

The laryngeal tube

The laryngeal tube (VBM Medizintechnik, Sulz, Germany) is a relatively new extraglottic airway, designed to secure a patent airway during either spontaneous breathing or controlled ventilation. In this review article, we have assessed the potential role of the laryngeal tube during anaesthesia and during cardiopulmonary resuscitation. There are four variations of the laryngeal tube: standard laryngeal tube, disposable laryngeal tube, laryngeal tube-Suction II and disposable laryngeal tube-Suction II. The design of the device has been revised several times. Insertion of the standard laryngeal tube is as easy as with the laryngeal mask airway classic. The laryngeal tube may provide a better sealing effect than the laryngeal mask. The incidence of complications with the two devices is similar, although the laryngeal tube may require more re-adjustments of its position to obtain a clear airway. Compared with the ProSeal laryngeal mask, the laryngeal tube may be less effective. The efficacy of the standard laryngeal tube is unclear, particularly in patients breathing spontaneously or in children. The efficacy of the laryngeal tube Suction-II and disposable devices is also not clear. From the limited number of studies and reports available, it can be concluded that the laryngeal tube is potentially useful in maintaining a clear airway during anaesthesia and cardiopulmonary resuscitation. In addition, the device may be useful as an aid to tracheal intubation.

Core temperature measurements through a new airway device, perilaryngeal airway (CobraPLA)

STUDY OBJECTIVE

The aim of this study was to test the hypothesis that the intraoperative pharyngeal temperatures obtained on the perilaryngeal airway (PLA), a novel airway device with a larger pharyngeal cuff (when inflated) than the laryngeal mask airway, are similar to tympanic membrane core temperatures.

DESIGN

This study is a prospective, simultaneous device comparison.

SETTING

This study was set at a university hospital.

PATIENTS

The study patients included 14 adults with American Society of Anesthesiologists physical statuses I and II, scheduled for minor gynecological or orthopedic surgery.

INTERVENTIONS

A PLA was inserted into the pharynx after induction of general anesthesia. Thermocouples were positioned at 3 sites on the PLA: (1) posterior portion of the head of the airway (tip), (2) midposterior portion of the cuff, and (3) left and right lateral-posterior portions of the cuff. Tympanic membrane thermocouples were inserted.

MEASUREMENTS

Temperature readings from the airway and the tympanic membrane thermocouples were recorded every 15 minutes throughout surgery.

MAIN RESULTS

Temperatures recorded from the lateral-posterior cuff were found to be virtually identical to tympanic membrane temperatures, with 97% of the values differing by less than 0.5 degrees C. Readings from the other 2 sites on the cuff differed considerably more from tympanic membrane values.

CONCLUSIONS

These data suggest that the PLA can be adapted to monitor core temperature reliably.