Anaesthesia for gynaecological laparoscopy--a comparison between the laryngeal mask airway and tracheal intubation

Effects of neuromuscular blockade on the surgical conditions of laparoscopic totally extraperitoneal inguinal hernia repair: a randomized clinical trial

PURPOSE

Unlike other laparoscopic techniques, the peritoneum is not incised in laparoscopic totally extraperitoneal inguinal hernia repair (TEP), and the preperitoneal space is developed as the surgical field by blunt dissection and CO₂ insufflation. While many studies have investigated the effect of neuromuscular blockade (NMB) on the surgical conditions and postoperative pain of laparoscopic intraperitoneal surgery, few studies have investigated those of TEP. In the present study, we investigated the effect of NMB on the surgical conditions and postoperative pain of TEP.

METHODS

Forty-two adult patients scheduled for unilateral TEP under general anesthesia with remifentanil and desflurane were randomly assigned to paralyzed or non-paralyzed groups. In the paralyzed group, rocuronium doses were administered to maintain post-tetanic count at ≤ 5 during surgery. Non-paralyzed subjects were not given any rocuronium. Postoperatively, surgeon-evaluated surgical conditions, assessed using a 100-mm visual analogue scale ranging from 0 mm (not acceptable) to 100 mm (excellent), were compared between the two groups. For evaluation of postoperative pain, the time from the end of anesthesia to the initial requirement of postoperative analgesia was compared by the log-rank test.

RESULTS

Median [interquartile range] score of surgical condition in the paralyzed and non-paralyzed groups were 84 [75-90] and 84 [78-87], respectively (P = 0.46). Significant differences in postoperative analgesic requirements between the two groups were not confirmed (P = 0.74).

CONCLUSION

NMB did not improve the surgical conditions nor reduce postoperative pain. NMB is not routinely needed for TEP just because it is a laparoscopic procedure.

CLINICAL TRIAL REGISTRATION

The trial was registered in the UMIN clinical trials registry (UMIN000029683, October 24, 2017; Principal investigator: Masafumi Fujimoto, https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000033920 ) prior to patient enrolment.

Comparison of airway management without neuromuscular blockers in laparoscopic gynecological surgery

New generation supraglottic airway devices are suitable for airway management in many laparoscopic surgeries. In this study, we evaluated and compared the ventilation parameters of the laryngeal mask airway-supreme (LM-S) and endotracheal tube (ETT) when a neuromuscular blocker (NMB) agent was not used during laparoscopic gynecological surgery. The second outcome was based on the evaluation of the surgical view because it may affect the surgical procedure.This was a randomized study that enrolled 100 patients between 18 and 65 years old with an ASA I-II classification. Patients were divided into 2 groups: Group ETT and Group LM-S. Standard anesthesia and ventilation protocols were administered to patients in each group. Ventilation parameters [airway peak pressure (Ppeak), mean airway pressure (Pmean), total volume, and oropharyngeal leak pressure] were recorded before, after, and during peritoneal insufflation and before desufflation, as well as after the removal of the airway device. Perioperative surgical view quality and the adequacy of the pneumoperitoneum were also recorded.The data of 100 patients were included in the statistical analysis. The Ppeak values in Group ETT were significantly higher in the second minute after airway device insertion. The Ppeak and Pmean values in Group ETT were significantly higher before desufflation and after removal of the airway device. No significant differences were found between the groups in terms of adequacy of the pneumoperitoneum or quality of the surgical view.The results of this study showed that gynecological laparoscopies can be performed without using a NMB. Satisfactory conditions for ventilation and surgery can be achieved while sparing the use of muscle relaxants in both groups despite the Trendelenburg position and the pneumoperitoneum of the patients, which are typical for laparoscopic gynecological surgery. The results are of clinical significance because they show that the use of a muscle relaxant is unnecessary when supraglottic airways are used for these surgical procedures.

Comparison of LM-Supreme™ and endotracheal tube in patients undergoing gynecological laparoscopic surgery

While laryngeal mask is widely used for laparoscopic interventions in some countries, concerns exist regarding pulmonary aspiration and inadequate ventilation. We compared the LM-Supreme™ (LM-S) with the endotracheal tube (ETT) for laparoscopic gynecological interventions in terms of ventilation parameters and gastric distention. This prospective randomized and double-blind study. The patients were divided into two groups: ETT (n = 50) and LM-S group (n = 50). All patients in the LM-S and ETT groups recieved total intravenous general anaesthesia and standard ventilation protocols. Ventilation parameters (airway peak pressure, mean airway pressure, end-tidal carbon dioxide, total volume, oropharyngeal leak pressure) and perioperative laryngopharyngeal morbidity were recorded before peritoneal insufflation, during and after the peroperative period. The mean airway pressure values in the ETT group 2 min after airway device insertion were significantly higher. The gastric distension after the laparoscope entered the abdomen in the LM-S group was found to be significantly lower. In the first hour postoperative sore throat, disphonia and dysphagia were statistically significantly higher in the ETT group. In our study we concluded that LM-S provides reliable endotracheal intubation in ASA I & II patients undergoing laparoscopic gynecological surgery under positive pressure ventilation.ClinicalTrials.gov ID NCT02127632.

Advantages, Disadvantages, Indications, Contraindications and Surgical Technique of Laryngeal Airway Mask

The beauty of the laryngeal mask is that it forms an air tight seal enclosing the larynx rather than plugging the pharynx, and avoid airway obstruction in the oropharynx. The goal of its development was to create an intermediate form of airway management face mask and endotracheal tube. Indication for its use includes any procedure that would normally involve the use of a face mask. The laryngeal mask airway was designed as a new concept in airway management and has been gaining a firm position in anesthetic practice. Despite wide spread use the definitive role of the laryngeal mask airway is yet to be established. In some situations, such as after failed tracheal intubation or in oral surgery its use is controversial. There are several unresolved issues, for example the effect of the laryngeal mask on regurgitation and whether or not cricoids pressure prevents placement of mask. We review the techniques of insertion, details of misplacement, and complications associated with use of the laryngeal mask. We then attempt to clarify the role of laryngeal mask in air way management during anesthesia, discussing the advantages and disadvantages as well as indications and contraindications of its use in oral and maxillofacial surgery.

Comparison of laryngeal mask airway vs tracheal intubation: a systematic review on airway complications

To determine whether the laryngeal mask airway (LMA) has advantages over the tracheal tube (TT) in terms of incidence of cough, sore throat, laryngospasm, dysphagia, dysphonia, and blood staining. This is a systematic literature review performed at the Universtity Medical Center of Utrecht. The online databases PubMed, Embase, and the Cochrane Library were searched for relevant randomized controlled trials. Two independent reviewers selected relevant articles after title, abstract, and full text screening. Articles were assessed on risk of bias in accordance with the Cochrane risk of bias tool. Study results of the LMA and the TT were related to the method of selection of the device size and the method for cuff inflation. Of the 1718 unique articles, we included 19 studies which used the LMA Classic, the LMA Proseal, the Flexible Reinforced LMA, and the LMA Supreme compared with TT. After methodological inspection, data could not be pooled due to heterogeneity among the selected studies. Overall, no clear advantage of the LMA over the TT was found but the LMA Supreme was related to the lowest incidence of airway complications. In this review, no clear difference in incidence of postoperative airway complications could be demonstrated between LMA and TT. The LMA Supreme may reduce the incidence of airway complication in comparison to the TT but high quality randomized trials are recommended to further objectify if use of the LMA decreases the risk on postoperative airway complications.

Comparison between supraglottic airway devices and endotracheal tubes in patients undergoing laparoscopic surgery: A systematic review and meta-analysis

BACKGROUND

Comparisons between the efficacies of supraglottic airway devices (SGAs) and endotracheal tubes (ETTs) in patients undergoing laparoscopic surgeries have yielded conflicting results. Therefore, in this meta-analysis, we compared the clinical performance and incidence of complications between SGAs and ETT intubation in laparoscopic surgery.

METHODS

A comprehensive search was conducted using MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, and Google Scholar to identify randomized controlled trials that compared SGAs with ETTs in laparoscopic surgery.

RESULTS

In total, 1433 patients from 17 studies were included in the final analysis. SGAs and ETTs showed no difference in insertion success rate on the first attempt (relative risk [RR] 1.01, 95% confidence interval [CI] 0.99-1.03), insertion time (standardized mean difference 1.57, 95% CI -3.74 to 0.61), and oropharyngeal leak pressure (OLP) (mean difference -2.54, 95% CI -7.59 to 2.50). The incidence of desaturation (RR 3.65, 95% CI 1.39-9.62), gastric insufflations (RR 0.90, 95% CI 0.48-1.71), regurgitation (RR 0.98, 95% CI 0.02-49.13), and aspiration (RR 0.99, 95% CI 0.01-78.4) also showed no intergroup differences. However, the incidence of laryngospasm (RR 3.12, 95% CI 1.29-7.52), cough at removal (RR 6.68, 95% CI 4.70-9.48), dysphagia (RR 1.47, 95% CI 1.12-1.95) or dysphonia (RR 4.41, 95% CI 1.25-15.55), sore throat (RR 1.60, 95% CI 1.33-1.93), and hoarseness (RR 1.53, 95% CI 1.29-1.81) was higher in the ETT group than in the SGA group.

CONCLUSIONS

The incidence of laryngospasm, cough at removal, dysphagia or dysphonia, sore throat, and hoarseness were higher in the ETT group than in the SGA group. However, the groups showed no differences in the rate of insertion success on the first attempt, insertion time, OLP, and other complications. Therefore, SGAs might be clinically more useful as effective airways in laparoscopic surgery.

Is deep neuromuscular blockade beneficial in laparoscopic surgery? Yes, probably

BACKGROUND

Deep neuromuscular blockade during laparoscopic surgery may provide some clinical benefit. We present the 'Pro-' argument in this paired position paper.

METHODS

We reviewed recent evidence from a basic database of references which we agreed on with the 'Con-' side, and present this in narrative form. We have shared our analysis and text with the authors of the 'Con-' side of these paired position papers during the preparation of the manuscripts.

RESULTS

There are a few low risk of bias studies indicating that use of deep neuromuscular blockade improve surgical conditions and improve patient outcomes such as post-operative pain in laparoscopic surgery.

CONCLUSION

Our interpretation of recent findings is that there is reason to believe that there may be some patient benefit of deep neuromuscular blockade in this context, and more detailed study is needed.

Is deep neuromuscular block beneficial in laparoscopic surgery? No, probably not

BACKGROUND

There is currently a controversy regarding the need for and clinical benefit of maintaining deep neuromuscular block (post-tetanic counts of 1 or 2) vs. moderate block (train-of-four counts of 1-3) for routine laparoscopic surgery. Two recent review articles on this subject arrived at rather different conclusions. This manuscript is part of Pro/Con debate from the authors of these two reviews.

METHODS

The authors of the Pro and Con sides of the debate had the opportunity to read each other manuscripts and worked from the same basic database of references.

RESULTS

The present authors could find only one peer-reviewed paper which presented objective evidence supporting the proposition that deep neuromuscular block provides superior operating conditions for the surgeon during laparoscopic surgery.

CONCLUSION

There is not enough good evidence available to justify the routine use of deep neuromuscular block for laparoscopic surgery and the associated expense of high-dose sugammadex.

Role of laryngeal mask airway in laparoscopic cholecystectomy

Laparoscopic cholecystectomy is one of the most commonly performed surgical procedures and the laryngeal mask airway (LMA) is the most common supraglottic airway device used by the anesthesiologists to manage airway during general anesthesia. Use of LMA has some advantages when compared to endotracheal intubation, such as quick and ease of placement, a lesser requirement for neuromuscular blockade and a lower incidence of postoperative morbididy. However, the use of the LMA in laparoscopy is controversial, based on a concern about increased risk of regurgitation and pulmonary aspiration. The ability of these devices to provide optimal ventilation during laparoscopic procedures has been also questioned. The most important parameter to secure an adequate ventilation and oxygenation for the LMA under pneumoperitoneum condition is its seal pressure of airway. A good sealing pressure, not only state correct patient ventilation, but it reduces the potential risk of aspiration due to the better seal of airway. In addition, the LMAs incorporating a gastric access, permitting a safe anesthesia based on these commented points. We did a literature search to clarify if the use of LMA in preference to intubation provides inadequate ventilation or increase the risk of aspiration in patients undergoing laparoscopic cholecystectomy. We found evidence stating that LMA with drain channel achieves adequate ventilation for these procedures. Limited evidence was found to consider these devices completely safe against aspiration. However, we observed that the incidence of regurgitation and aspiration associated with the use of the LMA in laparoscopic surgery is very low.

Laparoscopic surgery and muscle relaxants: is deep block helpful?

It has been hypothesized that providing deep neuromuscular block (a posttetanic count of 1 or more, but a train-of-four [TOF] count of zero) when compared with moderate block (TOF counts of 1-3) for laparoscopic surgery would allow for the use of lower inflation pressures while optimizing surgical space and enhancing patient safety. We conducted a literature search on 6 different medical databases using 3 search strategies in each database in an attempt to find data substantiating this proposition. In addition, we studied the reference lists of the articles retrieved in the search and of other relevant articles known to the authors. There is some evidence that maintaining low inflation pressures during intra-abdominal laparoscopic surgery may reduce postoperative pain. Unfortunately most of the studies that come to these conclusions give few if any details as to the anesthetic protocol or the management of neuromuscular block. Performing laparoscopic surgery under low versus standard pressure pneumoperitoneum is associated with no difference in outcome with respect to surgical morbidity, conversion to open cholecystectomy, hemodynamic effects, length of hospital stay, or patient satisfaction. There is a limit to what deep neuromuscular block can achieve. Attempts to perform laparoscopic cholecystectomy at an inflation pressure of 8 mm Hg are associated with a 40% failure rate even at posttetanic counts of 1 or less. Well-designed studies that ask the question "is deep block superior to moderate block vis-à-vis surgical operating conditions" are essentially nonexistent. Without exception, all the peer-reviewed studies we uncovered which state that they investigated this issue have such serious flaws in their protocols that the authors' conclusions are suspect. However, there is evidence that abdominal compliance was not increased by a significant amount when deep block was established when compared with moderate neuromuscular block. Maintenance of deep block for the duration of the pneumoperitoneum presents a problem for clinicians who do not have access to sugammadex. Reversal of block with neostigmine at a time when no response to TOF stimulation can be elicited is slow and incomplete and increases the potential for postoperative residual neuromuscular block. The obligatory addition of sugammadex to any anesthetic protocol based on the continuous maintenance of deep block is not without associated caveats. First, monitoring of neuromuscular function is still essential and second, antagonism of deep block necessitates doses of sugammadex of ≥4.0 mg/kg. Thus, maintenance of deep block has substantial economic repercussions. There are little objective data to support the proposition that deep neuromuscular block (when compared with less intense block; TOF counts of 1-3) contributes to better patient outcome or improves surgical operating conditions.

Optimizing working space in laparoscopy: CT measurement of the influence of small body size in a porcine model

INTRODUCTION

In our continuing research into the determinants of laparoscopic working space, the influence of small body size was investigated.

METHODS

In eight 6-kg pigs, the effects of intraabdominal CO2 pneumoperitoneum pressure (IAP), prestretching of the abdominal wall, and neuromuscular blockade (NMB) on laparoscopic working space volume and distances were studied. Computed tomography was used to measure working space during two stepwise abdominal insufflation-runs up to an IAP of 15mm Hg. Results were compared with data from earlier experiments in 20-kg pigs.

RESULTS

Cardiorespiratory parameters were stable up to an IAP of 8-10mm Hg. In 6-kg pigs working-space dimensions were five times smaller than in 20-kg pigs. Working-space volume, anteroposterior (AP) diameter and symphysis-diaphragm distance increased linearly up to an IAP of 8mm Hg. Above 8mm Hg, compliance decreased. Eighty percent of the total volume (618ml) and of AP diameter (3cm) at 15mm Hg had been achieved at an IAP of 10mm Hg. Prestretching by a first insufflation resulted in a statistically significant increase in working space volume and in AP diameter during the second insufflation. This effect was significantly larger than in 20-kg pigs. Neuromuscular blockade did not have a significant effect on working-space.

CONCLUSIONS

Working space in growing individuals is very limited. Eighty percent of the working space created by an IAP of 15mm Hg was already achieved at 10mm Hg, while cardiorespiratory side effects at an IAP of 8-10mm Hg seem acceptable. Prestretching of the abdominal wall significantly increased working space, even more so than in 20-kg pigs. As in 20-kg pigs, NMB had no significant effect on laparoscopic working space. Prestretching of the abdominal wall is a promising cheap, safe and easy strategy to increase laparoscopic working space, lessening the need for prolonged high-pressure pneumoperitoneum.

Neuromuscular blockade for optimising surgical conditions during abdominal and gynaecological surgery: a systematic review

BACKGROUND

The level of neuromuscular blockade (NMB) that provides optimal surgical conditions during abdominal surgery has not been well established. The aim of this systematic review was to evaluate current evidence on the use of neuromuscular blocking agents in order to optimise surgical conditions during laparoscopic procedures and open abdominal surgery.

METHODS

A wide search was performed in PubMed, Cochrane library and Embase with systematic approach including PRISMA recommendations. Individual risk of bias was assessed and systematic data extraction were performed.

RESULTS

Fifteen studies with data from 998 patients were included. There is good evidence that the use of deep NMB compared with moderate NMB is associated with optimised surgical conditions during laparoscopic cholecystectomy, hysterectomy and nephrectomy/prostatectomy. In laparoscopic cholecystectomy during low pressure pneumoperitoneum, deep NMB marginally improves the surgical conditions. However, to ensure acceptable surgical conditions, it may be necessary to increase the intra-abdominal pressure in up to half of the patients regardless of level of NMB. There is good evidence that moderate NMB improves surgical conditions in some cases during open radical retropubic prostatectomy. However, good and excellent surgical conditions may be achievable even without NMB. There is good evidence to recommend deep NMB in laparoscopic cholecystectomy, nephrectomy and prostatectomy to improve surgical conditions. There is insufficient evidence to recommend an ideal level of NMB creating optimal surgical condition during laparotomy.

CONCLUSION

Use of deep NMB in certain laparoscopic procedures may improve surgical conditions. In open abdominal surgery, use of NMB may optimise surgical conditions under certain circumstances.

Optimizing working space in laparoscopy: CT-measurement of the effect of neuromuscular blockade and its reversal in a porcine model

OBJECTIVE

The objective of this paper was to determine the effect of neuromuscular blockade (NMB) on working space in a porcine laparoscopy model.

BACKGROUND

Conflicting results on the effect of NMB on laparoscopic working space are found in literature. Almost all studies are limited by absence of objective assessment of working space or use surrogate outcomes.

METHODS

In a standardized porcine laparoscopy model, laparoscopic working-space dimensions with and without NMB were investigated in 16 animals using computed tomography at intra-abdominal pressures of 0, 5, 10, and 15 mmHg during multiple runs of abdominal insufflation.

RESULTS

No statistically significant effect of NMB on abdominal dimensions and laparoscopic working-space volume was found during CO2 pneumoperitoneum. In contrast, the effect of pre-stretching of the abdominal wall by a previous abdominal insufflation was found to be significant.

CONCLUSIONS

This experimental study confirms the results from several clinical studies that NMB does not influence laparoscopic working space. Studies dealing with working space during laparoscopy should take note of pre-stretching bias.

Postoperative analgesia for gynecological laparoscopy

Gynecological laparoscopy is a commonly performed procedure. Providing anesthesia for this can present a challenge, particularly in the day surgery population. Poor analgesia, nausea, and vomiting can cause distress to the patient and increased cost for the health system, because of overnight admission. In this review we discuss anesthetic and analgesic techniques for day-case gynecological laparoscopy. The principles include multimodal analgesia, the use of the oral route wherever possible, and the contribution of the surgeon.

Laryngeal mask airways have a lower risk of airway complications compared with endotracheal intubation: a systematic review

PURPOSE

The purpose of the present study was to determine whether, in patients undergoing general anesthesia, those provided with a laryngeal mask airway (LMA) have a lower risk of airway-related complications than those undergoing endotracheal intubation.

MATERIALS AND METHODS

A systematic review of randomized prospective controlled trials was done to compare the risk of airway complications with an LMA versus an endotracheal tube (ETT) in patients receiving general anesthesia. Two independent reviewers identified 29 randomized prospective controlled trials that met the predetermined inclusion and exclusion criteria. The data for each individual outcome measure were combined to analyze the relative risk ratios (RRs). The Cochrane RevMan software was used for statistical analysis.

RESULTS

When an ETT was used to protect the airway, a statistically significant greater incidence of hoarse voice (RR 2.59, 95% confidence interval [CI] 1.55 to 4.34), a greater incidence of laryngospasm during emergence (RR 3.16, 95% CI 1.38 to 7.21), a greater incidence of coughing (RR 7.12, 95% CI 4.28 to 11.84), and a greater incidence of sore throat (RR 1.67, 95% CI 1.33 to 2.11) was found compared with when an LMA was used to protect the airway. The differences in the risk of regurgitation (RR 0.84, 95% CI 0.27 to 2.59), vomiting (RR 1.56, 95% CI 0.74 to 3.26), nausea (RR 1.59, 95% CI 0.91 to 2.78), and the success of insertion on the first attempt (RR 1.08, 95% CI 0.99 to 1.18) were not statistically significant between the 2 groups.

CONCLUSIONS

For the patients receiving general anesthesia, the use of the LMA resulted in a statistically and clinically significant lower incidence of laryngospasm during emergence, postoperative hoarse voice, and coughing than when using an ETT. The risk of aspiration could not be determined because only 1 study reported a single case of aspiration, which was in the group using the ETT.

Sparing the larynx during gynecological laparoscopy: a randomized trial comparing the LMA Supreme and the ETT

BACKGROUND

We designed a prospective randomized single-blind study to compare efficiency and post-operative upper airway morbidity when the laryngeal mask airway (LMA) Supreme is used as an alternative to the endotracheal tube (ETT).

METHODS

One hundred and thirty-eight elective pelvic laparoscopic ASA I-II female patients were assigned to receive either the LMA Supreme or the ETT for airway management. Balanced anesthesia and ventilation techniques were standardized to control end-tidal CO(2) and BIS value in the range 4.5-5 kPa and 40-50, respectively, and to maintain adequate hemodynamic stability. A single surgeon blinded to the airway management technique performed all surgical procedures. The ventilation efficiency of each airway was evaluated. Anesthesia- and surgery-related times were calculated and anesthesia details were recorded. Post-operative pain and pharyngolaryngeal morbidity were measured in a blind fashion using a numerical rating scale (NRS) (0-100).

RESULTS

Surgery duration was similar in both groups. Airway management duration was shorter with the LMA Supreme. Post-operative pharyngolaryngeal morbidity incidence and all symptoms' intensity were significantly increased after ETT as compared with LMA Supreme anesthesia. At the end of the PACU stage, the incidence and mean NRS of post-operative hoarseness were reduced when LMA Supreme was used as an alternative to the ETT (16% vs. 47%; P<0.01 and 9 vs. 19, P<0.01, respectively).

CONCLUSION

We demonstrated that choosing an LMA Supreme was an efficient pharyngolaryngeal morbidity-sparing strategy. Moreover, we showed that the LMA Supreme and the ETT were equally effective airways for a routine gynecological laparoscopy procedure.

Patient satisfaction with daycase laparoscopy

A prospective audit was performed on all patients preselected for daycase surgery over a 3-month period. The aim of the study was to evaluate patient acceptability and satisfaction with laparoscopy performed as a daycase procedure. Patients completed standard questionnaires before operation and at 4 weeks after surgery. Questions included satisfaction with daycase surgery, subjective pain experience, time taken to resume normal activities, adequacy of analgesia and necessity to call general practioners. Analysis of results revealed that 69% of patients were satisfied with day surgery laparoscopy. However there were highly significant differences (P less than 0.001) between resumption of normal activity, pain experienced and length of stay between patients satisfied and dissatisfied with daycase surgery. This study suggests that guidelines for daycase procedures may be overambitious as 31% of patients already pre-selected, were dissatisfied with daycase surgery.

Postoperative nausea, vomiting, airway morbidity, and analgesic requirements are lower for the ProSeal laryngeal mask airway than the tracheal tube in females undergoing breast and gynaecological surgery

BACKGROUND

We test the hypothesis that the frequency of postoperative nausea and vomiting is similar for the ProSeal laryngeal mask airway (LMA) and the tracheal tube.

METHODS

Two hundred consecutive female patients (ASA I-II, 18-75 yr) undergoing routine breast and gynaecological surgery were divided into two equal-sized groups for airway management with the ProSeal LMA or tracheal tube.

RESULTS

Ventilation was better and airway trauma less frequent for the ProSeal LMA. For the ProSeal group, the time spent in the post-anaesthesia care unit was shorter (69 vs 88 min, P < 0.0001); fewer doses of tropisetron were required in the post-anaesthesia care unit (P < or = 0.001) and ward (P = 0.004); morphine requirements were lower in the post-anaesthesia care unit (6.0 vs 8.1 mg, P = 0.005) and ward (6.1 vs 8.9, P = 0.004); nausea was less frequent at all times (overall: 13% vs 53%, P < 0.0001); vomiting was less frequent at 2 h (4% vs 18%, P = 0.003) and 24 h (5% vs 19%, P = 0.004); and sore throat was less frequent at all times (overall: 12% vs 38%, P < 0.0001).

CONCLUSIONS

The ProSeal LMA reduced the absolute risk of postoperative nausea and vomiting by 40% (53-13%). In patients without the need for morphine, the ProSeal LMA reduced the absolute risk of postoperative nausea and vomiting by 23% (37-14%). We conclude that the frequency of postoperative nausea, vomiting, airway morbidity, and analgesic requirements is lower for the ProSeal LMA than the tracheal tube in females undergoing breast and gynaecological surgery.

The use of the laryngeal mask in gynaecological laparoscopy

Use of the laryngeal mask airway in gynaecological laparoscopy is controversial, largely because of a concern about increased risk of regurgitation and pulmonary aspiration. The practice of evidence-based medicine provides a recommended strategy to resolve such an issue. We did a literature search and found limited evidence to support or refute the use of the LMA in this setting. We have found, however, that the reported incidence of aspiration or more serious morbidity associated with the use of the LMA in laparoscopic surgery is very low.

A comparison of the effect of two anaesthetic techniques on surgical conditions during gynaecological laparoscopy

In a prospective, randomised, controlled trial, we compared the effects of two anaesthetic techniques on surgical conditions during day-case, gynaecological laparoscopic procedures in 40 female patients. Patients were allocated randomly to two groups, either to breathe spontaneously through a laryngeal mask airway or to receive a neuromuscular-blocking agent (NMB) and have the lungs ventilated via a tracheal tube. We then measured the number of attempts of Verres' needle insertion, initial intra-abdominal pressure, time to reach a steady 15 mmHg (1.97 kPa) of intra-abdominal pressure, adequacy of the pneumoperitoneum, operative view and duration of operation. We found that the initial intra-abdominal pressure was higher and the operation time shorter in the laryngeal mask group. The adequacy of the pneumoperitoneum for trocar placement was better in the NMB group. We conclude that the anaesthetic technique of spontaneously breathing through a laryngeal mask airway reduces total operation time. However surgeons should be aware of the different abdominal pressure patterns produced by each anaesthetic technique, and anaesthetists must consider the implications of the anaesthetic technique on surgical safety.

Controversial issues in ambulatory anesthesia

Many controversies surround ambulatory anesthesia, but this article concentrates on two major areas: monitoring devices and airway management. Being able to monitor the depth of anesthesia has been a long-term goal with the aim of avoiding awareness during surgery. As monitoring devices are developed, they are being used to reduce anesthetic delivery and reduce costs, possibly increasing the risk of awareness. Management of the airway has been revolutionized by the laryngeal mask, and this article reviews some controversial uses. Several other airway devices that have been developed and promoted as suitable alternatives also are evaluated.

Randomized crossover comparison of the proseal with the classic laryngeal mask airway in unparalysed anaesthetized patients

BACKGROUND

The ProSeal is a wire-reinforced laryngeal mask airway with an additional drain tube that leads to the distal tip of the laryngeal cuff. The design should improve the seal with the larynx.

METHODS

The ProSeal and classic laryngeal mask airways were compared in 180 patients in a randomized crossover study. Patients were anaesthetized without neuromuscular blocking drugs.

RESULTS

The ProSeal took more time and more attempts to insert successfully than the classic laryngeal mask airway. Insertion was successful on the first attempt in 81% of cases with the ProSeal and 90% with the classic laryngeal mask airway. The ProSeal required more air to achieve an intracuff pressure of 60 cm H2O (6 ml more for size 4 and 12 ml more for size 5). Laryngeal seal pressure was better with the ProSeal than the classic laryngeal mask airway. Median seal pressure was 29 cm H2O with the ProSeal and 18 cm H2O with the classic laryngeal mask airway. Laryngeal seal pressure was greater than 20 cm H2O in 87% of patients with the ProSeal and 41% with the classic laryngeal mask airway. Laryngeal seal pressure was greater than 40 cm H2O in 21% of patients with the ProSeal and in none of the patients with the classic laryngeal mask. Once placed, the ProSeal remained a stable and effective airway. Gastric tube insertion through the drain tube was attempted in 147 cases and was successful in 135 (92%).

CONCLUSION

The ProSeal is more difficult to insert than the classic laryngeal mask airway but allows positive pressure ventilation more reliably than the classic laryngeal mask airway.

Anesthesia for laparoscopy with emphasis on outpatient laparoscopy

Laparoscopy has developed extremely rapidly and is currently applicable to virtually every surgical subspecialty. Most of the experience is with gynecologic laparoscopy, which has been performed for many years. Some of these procedures are simple and brief, with minimal gas insufflation. In these cases, respiratory compromise is limited, and spontaneous ventilation appears acceptable. Such procedures therefore can be performed with the patient under local or regional anesthesia, or using the LMA with general anesthesia, because the risk of aspiration is small. As laparoscopy has developed, more prolonged operations have become possible, but these normally require general anesthesia, controlled ventilation, and tracheal intubation. More sophisticated laparoscopic surgery has reduced postoperative morbidity, shortened hospital stays, and moved many procedures into the outpatient arena. These newer laparoscopic operations present many challenges, especially in the provision of adequate analgesia and the minimization of PONV. Analgesia should be multimodal, using local anesthesia and NSAIDs as first-line therapy. This combination may be sufficient for more minor procedures, and the elimination of opioids helps to reduce PONV. For more extensive operations, opioids also are required, but should not be the mainstay of analgesia. PONV should be treated effectively whenever it occurs, with consideration given to the use of prophylactic antiemetics in especially high-risk groups. Laparoscopic surgery clearly offers significant advantages in many cases. Although this technology can make some procedures technically possible on an outpatient basis, the morbidity following operations such as laparoscopic cholecystectomy is considerable. The ever-greater cost savings from the expansion of outpatient surgery is being achieved at the expense of patient discomfort and dissatisfaction. Extended care (23 h) could be a better option in some circumstances. The future will see further developments in laparoscopic surgery. Microlaparoscopy permits simple procedures to be performed with minimal analgesia and sedation in an office setting. At present, this technology allows only diagnostic and minor operative procedures, the stage at which conventional laparoscopy was in the early 1980s. Further developments in optical fibers could reduce the requirements for general anesthesia for other operations and substantially reduce postoperative morbidity. Until then, laparoscopy continues to present many challenges.

Anesthesia for laparoscopy in the pediatric patient

Pediatric laparoscopy is a novelty that has yet to be critically assessed in large, randomized controlled trials. Just because an operation can be performed laparoscopically does not mean it must be done that way. Many procedures can now be performed more quickly and cheaply through small incisions without the added cardiorespiratory risks seen in laparoscopy. Reports of serious complications are beginning to appear in publications. It will become important to compare laparoscopic techniques with both open surgery and the minimally invasive approach for the same procedure. Many published studies suggest laparoscopy offers significant advantages for some operations and for sicker patients. Practitioners must have a thorough understanding of the physiologic changes that follow pneumoperitoneum and extremes of positioning. As enthusiasm builds, it is essential to maintain safety standards. Endoscopists must be appropriately trained and peer reviewed. The use of virtual reality models now allows surgeons to develop and perfect their laparoscopic skills. When the laparoscopic approach is difficult, surgeons must be willing to convert to open surgery rather than persevere and risk iatrogenic damage. The role of pediatric laparoscopy has yet to be defined, although current trends suggest that it will assume an important position in pediatric surgery.

Gastric distension and ventilation during laparoscopic cholecystectomy: LMA-Classic vs. tracheal intubation

PURPOSE

The standard laryngeal mask airway LMA-Classic was designed as an alternative to the endotracheal tube (ETT) or the face mask for use with either spontaneous or positive pressure ventilation. Positive pressure ventilation may exploit leaks around the LMA cuff, leading to gastric distension and/or inadequate ventilation. We compared gastric distension and ventilation parameters with LMA vs ETT during laparoscopic cholecystectomy.

METHODS

One hundred and one, ASA I-II adults scheduled for elective laparoscopic cholecystectomy were randomly assigned to LMA-Classic or ETT. Patients with BMI >30 kg x m(-2), hiatus hernia or gastroesophageal reflux were excluded. Following induction of anesthesia, an in-and-out orogastric tube was passed to decompress the stomach before insertion of the LMA (women size #4, men size #5) or ETT (women 7 mm, men 8 mm). Anesthesia was maintained with isoflurane in nitrous oxide and oxygen (FIO2 0.3-0.5), rocuronium and fentanyl. The surgeon, blinded to the type of airway, scored gastric distention 0-10 at insertion of the laparoscope and immediately before removal at the end of the surgical procedure.

RESULTS

Incidence and degree of change in gastric distension were similar in both groups. Ventilation parameters during insufflation (mean +/- SD) for LMA and ETT were: S(P)O2 98 +/- I vs 98 +/- I, P(ET)CO2 38 +/- 4 vs 36 +/- 4 mm Hg and airway pressure 21 +/- 4 vs 23 +/- 3 cm water.

CONCLUSION

Positive pressure ventilation with a correctly placed LMA-Classic of appropriate size permits adequate pulmonary ventilation. Gastric distension occurs with equal frequency with either airway device.

The oesophageal-tracheal Combitube Small Adult

Airway management during gynaecological laparoscopy is complicated by intraperitoneal carbon dioxide inflation, Trendelenburg tilt, increasing airway pressures and pulmonary aspiration risk. We investigated whether the oesophageal-tracheal Combitube 37 Fr SA is a suitable airway during laparoscopy. One hundred patients were randomly allocated to receive either the Combitube SA (n = 49) or tracheal intubation (n = 51). Oesophageal placement of the Combitube was successful at the first attempt [16 (3) s]. Peak airway pressures were 25 (5) cmH2O. An airtight seal was obtained using air volumes of 55 (13) ml (oropharyngeal balloon) and 10 (1) ml (oesophageal cuff). Significant correlations were observed between patient's height and weight and the balloon volumes necessary to produce a seal. Similar findings were recorded for the control group, with tracheal intubation being difficult in three patients. The Combitube SA provided a patent airway during laparoscopy. Non-traumatic insertion was possible and an airtight seal was provided at airway pressures of up to 30 cmH2O.

Anaesthesia for daycase gynaecological laparoscopy: a survey of clinical practice in the United Kingdom

Gynaecological laparoscopy is a daycase procedure that can be associated with significant morbidity and patients may require admission to hospital for overnight stay. Following a decision to administer intraperitoneal bupivacaine routinely to such patients in our day surgery unit, we wished to establish whether this was routine practice elsewhere. We therefore carried out a postal survey of consultant anaesthetists in the UK who regularly anaesthetise patients undergoing daycase gynaecological laparoscopy, addressing a number of clinical issues. The results of the survey are presented, discussed and compared with published advice.

Recovery care facilities

In a world of rapidly changing policies in healthcare and the constant search for value-based medical care, the anaesthesiologist must be aware of new anaesthetic drugs and techniques utilized in daily practice, and most importantly, be updated on the implications of using these techniques in the ambulatory (day-case) setting without compromising patient safety or jeopardizing the physician-patient relationship. The ambulatory surgery movement has led to some of the most substantial changes in anaesthesia, with special emphasis on recovery care when the patient is rapidly brought into contact with their relatives or escorts shortly after emerging from a sedative or anaesthetic state.

Gastro-oesophageal reflux during day case gynaecological laparoscopy under positive pressure ventilation: laryngeal mask vs. tracheal intubation

This study aimed to evaluate whether or not the use of intermittent positive pressure ventilation via the laryngeal mask airway is associated with a higher risk of gastro-oesophageal reflux when compared with intermittent positive pressure ventilation via a tracheal tube in patients undergoing day case gynaecological laparoscopy in the head down position. Sixty healthy women were randomly allocated to receive either the laryngeal mask or cuffed tracheal tube for intra-operative airway maintenance. Using continuous oesophageal pH monitoring, four patients in the tracheal tube group and none in the laryngeal mask group had evidence of gastro-oesophageal reflux (as indicated by a decrease in oesophageal pH to below 4). The difference in the incidence of reflux did not achieve statistical significance (p = 0.11). In conclusion, we found no evidence to suggest that the use of intermittent positive pressure ventilation via the laryngeal mask increases the risk of gastro-oesophageal reflux in patients undergoing elective day case gynaecological laparoscopy.

Gastroesophageal reflux and tracheal contamination during laparoscopic cholecystectomy and diagnostic gynecological laparoscopy

Laparoscopy causes an increase in intraabdominal pressure and may lead to an increase in gastroesophageal reflux (GER). We designed this study to assess and compare the frequency of GER and tracheal contamination in patients undergoing laparoscopic cholecystectomy (LC) and gynecological laparoscopy (LG). We studied 20 LC and 17 LG patients. The pH was measured using monocrystalline antimony pH electrodes positioned in the middle to upper esophagus and on the posterior wall of the trachea distal to the tip of the endotracheal tube. Acid reflux was defined as a decrease in esophageal pH to 4.0 or less. Alkaline reflux was defined as an abrupt increase in esophageal pH of more than 1.0, not associated with previous acid reflux. More than 80% of all patients at baseline had a gastric pH < or = 2. Overall, acid GER alone occurred in 47% patients in the LG group and in 15% patients in the LC group. During recovery, a larger proportion of patients had acid reflux in the LG group (47%) than in the LC group (10%). In contrast, alkaline reflux occurred in 75% of LC patients and 11.7% of LG patients. After cholecystectomy, there is an acute increase in the incidence of alkaline reflux. This alkaline reflux may be due to duodenogastric reflux resulting in an alkaline gastric shift.

IMPLICATIONS

We studied the incidence of reflux of stomach contents in patients undergoing laparoscopic (keyhole) surgery for cholecystectomy or gynecology, using pH probes in the esophagus (gullet) and the trachea (windpipe). Acid reflux was very common but did not pass into the trachea. After gallbladder removal, the refluxed material became alkaline.

Use of the laryngeal mask airway as an alternative to the tracheal tube during ambulatory anesthesia

We designed a prospective, randomized, multicenter study to compare anesthetic requirements, recovery times, and postoperative side effects when a laryngeal mask airway (LMA) was used as an alternative to the tracheal tube (TT) during ambulatory anesthesia. After induction of anesthesia with midazolam 2 mg, fentanyl 1 microg/kg, and propofol 2 mg/kg, 381 patients were randomly assigned to receive either an LMA (n = 207) or TT (n = 174) for airway management. In patients assigned to the TT group, succinylcholine 1 mg/kg or a nondepolarizing muscle relaxant was administered to facilitate tracheal intubation. Anesthesia was maintained with volatile anesthetics in combination with nitrous oxide 60% and oxygen. The average time to placement of the two airway devices (5 min) and the failure rates (1%) were similar in the two groups. Although there was a significant decrease in the intraoperative fentanyl requirement in the LMA group, the difference was of little clinical significance. Furthermore, there were no differences in the volatile anesthetic requirements. The time from end of surgery to removal of the airway device (5 min) was also similar in the two study groups. Although duration of the postanesthesia care unit stay and time to ambulation were significantly shorter in the LMA group, there were no differences in the times to "home readiness." The incidence of nausea and vomiting and the need for rescue antiemetic treatments in the postoperative period were similar in the two airway management groups. However, the incidence of postoperative sore throat was significantly greater in patients receiving the TT (versus the LMA). In conclusion, this study suggests that the LMA is a useful alternative to the TT for airway management during ambulatory anesthesia.

IMPLICATIONS

Use of the laryngeal mask airway can obviate the need for insertion of a tracheal tube for many ambulatory surgery procedures, and thereby decrease the incidence of postoperative sore throats.

Use of the laryngeal mask airway in oral and maxillofacial surgery

PURPOSE

General anesthesia for the nonintubated oral and maxillofacial surgical patient presents unique anesthetic conditions. The primary concern is the maintenance of an unobstructed airway and protection against aspiration, while minimizing both interference and interruption of the surgical procedure. The laryngeal mask airway is an alternative to the nasal hood for such airway management. The purpose of this article is to inform the oral and maxillofacial surgeon of the clinical relevant information pertaining to the use of the laryngeal mask airway in oral and maxillofacial surgery. Experience with clinical use is discussed.

Survey of laryngeal mask airway usage in 11,910 patients: safety and efficacy for conventional and nonconventional usage

A survey of laryngeal mask airway (LMA) usage was conducted to provide general information about safety and efficacy with special emphasis on controversial issues such as positive pressure ventilation (PPV), prolonged anesthesia, and laparoscopic and nonlaparoscopic intraabdominal surgery. During the 2-yr study period, of the 39,824 patients who underwent general anesthesia, 11,910 (29.9%) patient airways were managed with the LMA. Forty-four percent underwent PPV. Placement was successful in 99.81%, and in 23 patients the LMA was abandoned in favor of the tracheal tube (TT). Use of the LMA for any intraabdominal procedure was considered nonconventional and occurred in 2222 (18.7%) patients. On 579 occasions procedures lasted > 2 h. A total of 44 critical incidents were documented. Eighteen (0.15%) were related to the airway and none required intensive care management. There were 26 critical incidents not related to the airway which resulted in two admissions to the intensive care unit and one death. There were three cases of failed tracheal intubation managed with the LMA. This survey demonstrates that the LMA technique is safe and effective for both spontaneous and controlled ventilation. Use of the LMA for gynecologic laparoscopy, gynecologic laparotomy, and procedures > 2 h also appears safe.

Insertion methods of the laryngeal mask airway. A survey of current practice in Wales

The efficacy of the laryngeal mask is widely accepted, but there is a lack of consensus on the best insertion method and on the use of the mask for certain surgical procedures. We sent a questionnaire to all anaesthetists in Wales to discover the frequency of use of the laryngeal mask and the preferred insertion method. The questionnaire also enquired about the use of the laryngeal mask during anaesthesia for laparoscopic clip sterilisation. Replies were received from 125 consultants (89% of those circulated) and 122 non-consultants (69%). The insertion method described in the manufacturer's instruction manual was preferred by 30% of consultants and 34% of the others. The next most popular option was insertion of the mask with the cuff partially inflated. Twenty-three per cent of consultants and 34% of non-consultants were prepared to use the laryngeal mask during anaesthesia for laparoscopic clip sterilisation. Although the insertion technique described in the instruction manual is the most widely employed, a large number of alternative methods are frequently used.

General anesthesia using the laryngeal mask airway during brief, laparoscopic inspection of the peritoneum in children

The authors prospectively examined the cardiorespiratory changes seen with general anesthesia using the laryngeal mask with spontaneous ventilation during brief laparoscopic inspection of the peritoneum in children. Anesthesia consisted of halothane in 50% oxygen/air and a caudal epidural block. The patient was allowed to ventilate spontaneously without assistance. Baseline measurements of heart rate, systolic blood pressure (SBP), end-tidal CO2 (ETCO2), tidal volume, respiratory rate, and oxygen saturation were recorded every 1 min for 5 min prior to the start of laparoscopy and every minute during the laparoscopic procedure. A total of 15 patients were enrolled in the study ranging in age from 15 to 90 months (35.5 +/- 23.8 months) and in weight from 10 to 26.4 kg (14.9 +/- 4.9 kg). The length of the laparoscopy varied from 3 to 9 min (6.1 +/- 2.1 min). Although clinically insignificant, there was an increase in the heart rate from a baseline value of 141 +/- 9 to 148 +/- 9 beats/min (p = 0.0016) and in the SBP from a baseline value of 97 +/- 6 mm Hg to 101 +/- 7 mm Hg (p = 0.0087). The baseline tidal volume prior to the start of laparoscopy was 5.2 +/- 1.1 mL/kg and increased to 6.4 +/- 1.4 mL/kg during laparoscopy (p < 0.0001) while the respiratory rate increased from 32 +/- 4 to 40 +/- 6 breaths/min (p < 0.0001). ETCO2 increased from a baseline value of 47 +/- 6 to 53 +/- 6 torr (p = 0.0059). The maximum value of the ETCO2 was 55 torr or greater in 6 patients, exceeded 60 torr in 3 patients, with a maximum value of 63 torr. The increased ETCO2 returned to baseline within 2 to 7 min (4.7 +/- 1.5 min) following completion of the laparoscopy. There was no significant change in oxygen saturation. Our initial experience suggests that general anesthesia may be provided using the laryngeal mask during brief laparoscopic inspection of the peritoneum.

Survey of laryngeal mask airway usage in 11,910 patients: safety and efficacy for conventional and nonconventional usage

A survey of laryngeal mask airway (LMA) usage was conducted to provide general information about safety and efficacy with special emphasis on controversial issues such as positive pressure ventilation (PPV), prolonged anesthesia, and laparoscopic and nonlaparoscopic intraabdominal surgery. During the 2-yr study period, of the 39,824 patients who underwent general anesthesia, 11,910 (29.9%) patient airways were managed with the LMA. Forty-four percent underwent PPV. Placement was successful in 99.81%, and in 23 patients the LMA was abandoned in favor of the tracheal tube (TT). Use of the LMA for any intraabdominal procedure was considered nonconventional and occurred in 2222 (18.7%) patients. On 579 occasions procedures lasted > 2 h. A total of 44 critical incidents were documented. Eighteen (0.15%) were related to the airway and none required intensive care management. There were 26 critical incidents not related to the airway which resulted in two admissions to the intensive care unit and one death. There were three cases of failed tracheal intubation managed with the LMA. This survey demonstrates that the LMA technique is safe and effective for both spontaneous and controlled ventilation. Use of the LMA for gynecologic laparoscopy, gynecologic laparotomy, and procedures > 2 h also appears safe.

Analysis of 1500 laryngeal mask uses by one anaesthetist in adults undergoing routine anaesthesia

An analysis of 1500 laryngeal mask airway uses by one anaesthetist using the standard insertion technique was conducted to determine successful insertion rates, position by fibreoptic larynoscopy, complication rates and whether there is a long-term learning curve. The correlation between laryngeal mask airway placement and modified Mallampati grade was also determined. The first time insertion rate was 95.5% with an overall failure rate after three attempts of 0.4%. One hundred and fifteen patients were Mallampati III or IV. All failed placements were Mallampati I or II. Problems occurred in 94 patients (6.27%), but oxygen saturation decreased below 90% on only ten occasions and below 80% on one occasion. There were no episodes of regurgitation. The vocal cords were visible from the mask aperture bars in 97.1%. Comparison of insertion rates, fibreoptic position and complications for the first and second 750 insertions provides evidence for a 'long' term learning curve. These data could be used as a guide for 'optimal' or expected successful laryngeal mask airway insertion rates in adults undergoing routine anaesthesia.

The advantages of the LMA over the tracheal tube or facemask: a meta-analysis

A meta-analysis was performed on randomised prospective trials comparing the laryngeal mask airway (LMA) with other forms of airway management to determine if the LMA offered any advantages over the tracheal tube (TT) or facemask (FM). Of the 858 LMA publications identified to December 1994, 52 met the criteria for the analysis. Thirty-two different issues were tested using Fisher's method for combining the P values. The LMA has 13 advantages over the TT and four over the FM. The LMA had two disadvantages over the TT and one over the FM. There were 12 issues where neither device had an advantage. Advantages over the TT included: increased speed and ease of placement by inexperienced personnel; increased speed of placement by anaesthetists; improved haemodynamic stability at induction and during emergence; minimal increase in intraocular pressure following insertion; reduced anaesthetic requirements for airway tolerance; lower frequency of coughing during emergence; improved oxygen saturation during emergence; and lower incidence of sore throat in adults. Advantages over the FM included: easier placement by inexperienced personnel; improved oxygen saturation; less hand fatigue; and improved operating conditions during minor paediatric otological surgery. Disadvantages over the TT were lower seal pressures and a higher frequency of gastric insufflation. The only disadvantage compared with the FM was that oesophageal reflux was more likely. The importance of these findings in terms of patient outcome could not be determined from the published data.

The incidence of aspiration associated with the laryngeal mask airway: a meta-analysis of published literature

STUDY OBJECTIVE

To determine the incidence of pulmonary aspiration with the laryngeal mask airway (LMA).

DESIGN

A meta-analysis of all published literature on the LMA to September 1993.

MEASUREMENTS AND MAIN RESULTS

All 547 publications were reviewed and coded, and those observational studies in which the LMA was the main form of airway management were analyzed. Pulmonary aspiration was defined as either the presence of bilious secretions or particulate matter in the tracheobronchial tree or, if bronchoscopy was not performed, a postoperative chest radiograph with infiltrates present on preoperative chest radiograph of physical examination. In the study population, there were 3 cases of aspiration in 12,901 patients, and when combined with four independent reports excluded from the detailed analysis, this gave a final incidence of 2 in 10,000. Ten confirmed pulmonary aspiration events from published case reports showed that most cases had one or more predisposing factors. No death of permanent disability occurred.

CONCLUSIONS

The evidence to date suggests that the pulmonary aspiration with the LMA is uncommon and comparable to that for outpatient anesthesia with the face mask and tracheal tube. Meticulous attention to selection of low-risk patients and appropriate operative procedures and avoidance of light anesthesia should reduce the incidence even further.

The laryngeal mask airway: its features, effects and role

The laryngeal mask airway was designed as a new concept in airway management and has been gaining a firm position in anaesthetic practice. Numerous articles and letters about the device have been published in the last decade, but few large controlled trials have been performed. Despite widespread use, the definitive role of the laryngeal mask has yet to be established. In some situations, such as after failed tracheal intubation or in anaesthesia for patients undergoing laparoscopic or oral surgery, its use is controversial. There are a number of unresolved issues, for example the effect of the laryngeal mask on regurgitation and whether or not cricoid pressure prevents placement of the mask. We review the techniques of insertion, details of misplacement, and complications associated with the use of the laryngeal mask. We discuss the features and physiological effects of the device, including the changes in intra-cuff pressure during anaesthesia and effects on blood pressure, heart rate and intra-ocular pressure. We then attempt to clarify the role of the laryngeal mask in airway management during anaesthesia, based on the current knowledge, by discussing the advantages and disadvantages as well as the indications and contraindications of its use. Lastly we describe the use of the laryngeal mask in circumstances other than airway maintenance during anaesthesia: fibreoptic bronchoscopy, tracheal intubation through the mask and its use in cardiopulmonary resuscitation.