Effect of high laryngeal mask airway intracuff pressure on the laryngopharyngeal mucosa of dogs

[Impact of the practising anesthesiologist team member on the laryngeal mask cuff pressures and adverse event rate]

OBJECTIVE

We have planned to evaluate the laryngeal mask cuff pressures (LMcp) inflated by anesthesia workers of several seniority, without using manometer.

METHODS

180 patients scheduled to have short duration surgery with laryngeal mask were included in the study. Five anesthesia specialists (Group S), 10 residents (Group R) and 6 technicians (Group T) inflated the LMc; thereafter LMcp were measured with pressure manometer. Participants have repeated this practice in at least five different cases. LMcp higher than 60cm H2O at the initial placement or intraoperative period were adjusted to normal range. Sore throat was questioned postoperatively. Groups were compared in terms of mean LMcp and occupational experience.

RESULTS

At the settlement of LM, LMcp pressures within the normal range were determined in 26 (14.4%) cases. Mean LMcp after LM placement in Group S, R and T were 101.2±14.0, 104.3±20.5cm H2O and 105.2±18.4cm H2O respectively (p>0.05). Mean LMcp values in all measurement time periods within the groups were above the normal limit (60cm H2O). When groups were compared in terms of LMcp, no difference has been found among pressure values. Occupational experience was 14.2±3.9; 3.3±1.1 and 6.6±3.8 years for specialists, residents and technicians respectively and measured pressure values were not different in regard of occupational experience. Seven (3.9%) patients had sore throat at the 24th hour interview.

CONCLUSION

Considering lower possibility of normal adjustment of LMcp and ineffectiveness of occupational experience to obtain normal pressure values, it is suitable that all anesthesia practitioners should adjust LMcp with manometer.

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.

Impact of the practising anesthesiologist team member on the laryngeal mask cuff pressures and adverse event rate

OBJECTIVE

We have planned to evaluate the laryngeal mask cuff pressures (LMcp) inflated by anesthesia workers of several seniority, without using manometer.

METHODS

180 patients scheduled to have short duration surgery with laryngeal mask were included in the study. Five anesthesia specialists (Group S), 10 residents (Group R) and 6 technicians (Group T) inflated the LMc; thereafter LMcp were measured with pressure manometer. Participants have repeated this practice in at least five different cases. LMcp higher than 60 cm H2O at the initial placement or intraoperative period were adjusted to normal range. Sore throat was questioned postoperatively. Groups were compared in terms of mean LMcp and occupational experience.

RESULTS

At the settlement of LM, LMcp pressures within the normal range were determined in 26 (14.4%) cases. Mean LMcp after LM placement in Group S, R and T were 101.2 ± 14.0, 104.3 ± 20.5 cm H2O and 105.2 ± 18.4 cm H2O respectively (p > 0.05). Mean LMcp values in all measurement time periods within the groups were above the normal limit (60 cm H2O). When groups were compared in terms of LMcp, no difference has been found among pressure values. Occupational experience was 14.2 ± 3.9; 3.3 ± 1.1 and 6.6 ± 3.8 years for specialists, residents and technicians respectively and measured pressure values were not different in regard of occupational experience. Seven (3.9%) patients had sore throat at the 24th hour interview.

CONCLUSION

Considering lower possibility of normal adjustment of LMcp and ineffectiveness of occupational experience to obtain normal pressure values, it is suitable that all anesthesia practitioners should adjust LMcp with manometer.

Comparison of laryngeal mask airway supreme and laryngeal mask airway proseal for laryngopharyngeal trauma and postoperative morbidity in children

BACKGROUND AND OBJECTIVES

Laryngeal mask airway (LMA), which has been used frequently in airway management, can cause laryngopharyngeal injury and morbidity. In this trial, we compare the macroscopic changes on laryngopharyngeal structures and the postoperative laryngopharyngeal morbidity by using LMA supreme with LMA proseal in children.

METHODS

We divided patients into two groups. We inserted size three LMA proseal into the first group and size three LMA supreme into the second group. Before LMA insertion and after LMA removal, we performed direct laryngoscopy on the patients. We compared hyperemia, mucosal injury and blood staining on LMA removal, as well as insertion time, rate of success in gastric tube insertion on the first attempt, nausea, vomiting, and sore throat between the two groups.

RESULTS

We recorded no significant differences between the two groups for mean operation time, sex, age, weight, rate of success in gastric tube insertion on first attempt, nausea, vomiting, sore throat and mucosal injury. Mean insertion time for the LMA proseal group was significantly longer than the LMA supreme group (p = 0.0001). The ratio of blood staining on LMA removal was significantly higher in the LMA proseal group than the LMA supreme group (p = 0.034). The patients with blood staining on LMA removal exhibited significantly more mucosal hyperemia and injury than the patients with clear LMA (p = 0.0001, p = 0.020).

CONCLUSION

LMA supreme insertion is faster and easier than LMA proseal and causes less laryngopharyngeal injury than LMA proseal in children.

The effect of head rotation on efficiency of ventilation and cuff pressure using the PLMA in pediatric patients

Background

This study examined whether changing the head position from neutral to side can affect expiratory tidal volume (TV) and cuff pressure when the appropriate sizes of a Proseal™ Laryngeal Mask Airway (PLMA)-depending on the body weight -are used in pediatric patients during pressure controlled ventilation (PCV).

Methods

Seventy-seven children (5-30 kg) were divided into three groups according to their body weight, PLMA#1.5 (group I, n = 24), #2 (group II, n = 26), and #2.5 (group III, n = 27). After anesthesia induction, a PLMA was placed with a cuff-pressure of 60 cmH₂O. The TV and existence of leakage at the peak inspiratory pressure (PIP) of 20 cmH₂O, and the appropriate PIP for TV 10 ml/kg were examined. Upon head rotation to the left side, the TV, PIP, cuff pressure changes, and the appropriate PIP to achieve a TV 10 ml/kg were evaluated.

Results

Head rotation of 45 degrees to the left side during PCV caused a significant increase in cuff pressure and a decrease in TV, and there was no definite leakage. Changes in PIP and TV were similar in the three groups. The cuff pressure increased but there was no significant difference between the three groups.

Conclusions

Although cuff pressure and TV of the PLMA were changed significantly after turning the head from the neutral position to the side, a re-adjustment of the cuff pressure and PIP to maintain a TV of 10 ml/kg can make the placed PLMA useful and successful in pediatric patients under general anesthesia.

Morphological findings in the tracheal epithelium of dogs exposed to the inhalation of poorly conditioned gases under use of an endotracheal tube or laryngeal mask airway

PURPOSE

To study morphological findings in the tracheal epithelium of dogs exposed to the inhalation of poorly conditioned gases under use of an endotracheal tube (ET) or laryngeal mask airway (LMA).

METHODS

Twelve dogs randomly were allocated to two groups: ET group (n-6) and LMA group (n-6), anaesthetized and mechanically ventilated, without CO(2) reabsorption. Haemodynamic and ventilatory parameters, tympanic temperature, temperature, relative and absolute humidity of the ambient and inhaled gases were analyzed during three hours. The animals were submitted to euthanasia and biopsies were carried out along the tracheal segment to morphological study. Three healthy dogs were used to morphological control.

RESULTS

Inhaled gas temperature was maintained between 24ºC and 26ºC, relative humidity between 10% and 12%, and absolute humidity between 2 - 3 mg H(2)O.L(-1) with no significant differences between groups. In both groups, histological analysis showed epithelial inflammation and congestion in the corion and scanning electron microscopy showed ciliary grouping and disorganization. Transmission electron microscopy showed higher alterations in ET group than LMA group as widening of cell junctions, ciliary disorientation, cytoplasmic vacuolization, nuclear abnormalities, picnosis and chromatin condensation.

CONCLUSION

LMA determined less pronounced changes in the tracheal epithelium in dogs exposed to the inhalation of poorly conditioned gases.

Feasibility of the laryngeal tube airway for artificial ventilation in pigs and comparison with the laryngeal mask airway

Airway management in anesthetized pigs is known to be technically demanding, and the 'gold standard' technique of endotracheal intubation is particularly difficult to master. The authors investigated the feasibility of the laryngeal tube as an alternative technique for airway management in German Landrace pigs (n = 5). They compared this method with the laryngeal mask, which is considered to be an effective yet relatively straightforward tool for porcine airway management. One after the other, investigators attempted to establish an airway in each anesthetized, artificially ventilated pig using each device. The laryngeal tube was too short to intubate the largest pig (weighing 45 kg), and it took investigators slightly longer to insert this device compared with the laryngeal mask. With the laryngeal mask, there were several incidents of gastric insufflation. Despite these complications, all investigators were able to establish a secure airway and maintain oxygenation with the laryngeal tube, and all subjectively rated both devices as easy to use.

Cuff filling volumes and pressures in pediatric laryngeal mask airways

BACKGROUND

Hyperinflation of LMA cuffs carries the risk of airway morbidity by exerting pressure on laryngeal and pharyngeal structures. Cuff hyperinflation in LMAs can result from nitrous oxide diffusion into the LMA cuff and from deliberate manual cuff inflation.

METHODS

In an in vitro set up, maximum recommended cuff filling volumes for size 1, 1.5, 2, 2.5, 3 disposable LMAs from different manufacturers [SoftSeal LMA (Portex); Unique LMA (Intavent); Marshall LAD, LaryngoSeal (Tyco)] and reusable Classic and ProSeal LMAs (Intavent) were inflated into completely emptied LMA-cuffs and into LMA-cuffs at resting volume. Cuff pressures were measured using a cuff manometer. Experiments were performed eight times using two exemplars of each brand/size.

RESULTS

Maximum recommended cuff filling volumes for pediatric LMAs resulted in hyperinflation (cuff pressure >60 cmH(2)O) in almost all LMAs, starting with emptied cuff. Starting from resting cuff volume, the maximum recommended inflation volume resulted in cuff pressures of >120 cmH(2)O in all LMAs and sizes except in the ProSeal size 3 (101 +/- 1 cmH(2)O).

CONCLUSIONS

Since the volume of air which is effectively required depends on several factors and varies between patients, the cuffs should be inflated only with the minimum volume of air required to form an effective seal with the respiratory and gastrointestinal tracts and the cuff pressure should be controlled.

Nitrous oxide diffusion into the cuffs of disposable laryngeal mask airways

The aim of this study was to investigate cuff pressure changes found in disposable size 3 laryngeal mask airways (LMAs) from different manufacturers during nitrous oxide exposure and to compare the results with the re-usable Classic LMA. In an in vitro experiment, laryngeal mask airway cuff pressures starting from a baseline pressure of 40 cm H(2)O were recorded using a pressure transducer for 60 min with the laryngeal mask airway cuff exposed to 66% N(2)O in oxygen. Cuff pressure increases within 5 min of nitrous oxide exposure were > 250% in the Classic LMA and were not significantly different from those found in the Marshall laryngeal mask airway. However, they were significantly greater than those in the Soft Seal, the Unique, the AMBU, and Intersurgical laryngeal mask airways, all of which demonstrated stable cuff pressure levels within the first 5 min. The cuff pressure increase following 60 min of nitrous oxide exposure was 13.0 +/- 1.1 and 14.6 +/- 0.7 cm H(2)O in the Intersurgical and Unique laryngeal mask airways, respectively, which was significantly lower than the cuff pressure increase in the Soft Seal and in the Ambu laryngeal mask airways (28.3 +/- 2.9 and 30.9 +/- 1.2 cm H(2)O, respectively). Unlike the re-usable Classic LMA and the disposable Marshall laryngeal mask airway, which have silicone cuffs, the disposable Ambu, Intersurgical, Portex Soft Seal and Unique laryngeal mask airways have cuffs constructed from PVC, which seems to be less susceptible to hyperinflation caused by nitrous oxide diffusion.

Complicações das vias aéreas relacionadas à intubação endotraqueal

Descrevemos as principais complicações das vias aéreas relacionadas à intubação endotraqueal, por meio de revisão da literatura e apresentação dos resultados de pesquisas clínicas e experimentais realizadas pelo nosso grupo de estudo. Procuramos alertar os profissionais de saúde quanto à alta incidência de complicações secundárias à intubação, as quais podem ser reduzidas com a adoção de medidas profiláticas simples e de cunho prático, estabelecidas após a compreensão da fisiopatologia das lesões.