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

The effect of class 3 obesity on the functionality of supraglottic airway devices: a historical cohort analysis with propensity score matching

PURPOSE

Supraglottic airway devices (SGAs) have been increasingly used as a primary airway in patients undergoing anesthesia as an alternative to endotracheal tubes. Second-generation devices have expanded their applicability to include uses in patients with obesity. Nevertheless, there is limited evidence of SGA suitability for patients with class 3 obesity (body mass index [BMI] ≥ 40 kg·m-2). As such, we compared rates of SGA functionality between patients with class 3 obesity and patients without class 3 obesity undergoing general anesthesia.

METHODS

We performed a propensity score matching analysis using inverse probability of treatment weighting to compare the functionality of SGAs in adult patients with class 3 obesity vs without class 3 obesity. These patients underwent surgery at a hospital in Queensland, Australia from November 2017 to September 2020 and had a SGA inserted as part of their anesthetic care. All data were collected from patients' electronic medical records. We included 321 patients in the cohort with class 3 obesity and 471 in the cohort without class 3 obesity (control/comparison). The estimated effect of class 3 obesity on SGAs was calculated using adjusted odds ratios (AORs) with their 95% confidence intervals (CIs).

RESULTS

The overall weighted prevalence of nonfunctional SGAs was 3.2%, with a significantly higher rate in the class 3 obesity cohort compared with the control cohort (4.7% vs 2.1%) (P = 0.04). This adjusted analysis illustrates that class 3 obesity was associated with an almost four times higher odds of a nonfunctional SGA (odds ratio [OR], 2.3; 95% CI, 1.0 to 5.1; AOR, 3.9; 95% CI, 1.4 to 10.6) than patients without class 3 obesity.

CONCLUSION

Patients with class 3 obesity (BMI ≥ 40 kg·m-2) had greater than three-fold odds of nonfunctional intraoperative SGAs than patients without class 3 obesity.

The Influence of Positive End-Expiratory Pressure on Leakage and Oxygenation Using a Laryngeal Mask Airway: A Randomized Trial

BACKGROUND

The value of positive end-expiratory pressure (PEEP) in maintaining oxygenation during ventilation with a laryngeal mask airway (LMA) mask is unclear. To clarify the potential benefit or harm to PEEP application during positive pressure ventilation with a ProSeal LMA® mask, we compared the effect of PEEP versus zero end-expiratory pressure (ZEEP) on gas leakage and oxygenation. We hypothesized that a PEEP of 8 mbar (8.2 cm H2O) would be associated with an increased incidence of gas leakage compared to ZEEP.

METHODS

We designed a prospective, controlled, randomized, single-blinded, multicenter clinical trial. Patients >18 years of age with an American Society of Anesthesiologists (ASA) physical status I/II without increased risk of aspiration were enrolled if they were scheduled for elective surgery under general anesthesia with an LMA mask. Patients were randomized to a control group managed with ZEEP or an intervention group managed with a PEEP of 8 mbar. Both groups received positive pressure ventilation. The primary end point was the occurrence of gas leakage. The Student t test and χ2 test were used for statistical analysis.

RESULTS

A total of 174 patients were enrolled in the ZEEP group, and 208 were enrolled in the PEEP group. The incidence of gas leakage did not differ between the 2 groups (ZEEP: 23/174, 13.2%; PEEP: 42/208, 20.2%; P = .071; odds ratio [OR], 1.611; 95% confidence interval [CI], 0.954-2.891). However, more patients required reseating of the LMA mask in the PEEP group (ZEEP: 5/174, 2.9%; PEEP: 18/208, 8.7%; P = .018; OR, 3.202; 95% CI, 1.164-8.812). The need for endotracheal intubation did not differ between groups (ZEEP: 2/174, 1.1%; PEEP: 7/208, 3.4%; P = .190; OR, 2.995; 95% CI, 0.614-14.608). After positive pressure ventilation for 25 minutes, the mean peripheral oxygen saturation (Spo2) was higher in the PEEP than in the ZEEP group (98.5 [1.9]% vs 98.0 [1.4]%; P = .01). Peak inspiratory pressure (PIP; 16 [2] vs 12 [4] mbar; P < .001) and dynamic compliance (57 [14] vs 49 [14] mL/mbar; P < .001) were both higher in the PEEP group than in the ZEEP group.

CONCLUSIONS

Use of PEEP did not affect the overall incidence of gas leakage. However, PEEP did result in a higher incidence of attempts to reseat the LMA mask compared to ZEEP, whereas the incidence of rescue intubation did not differ between groups. We concluded that a PEEP of 8 mbar did not increase overall gas leakage during positive pressure ventilation with an LMA mask, but it did slightly improve gas exchange and compliance. Overall, our study does not provide strong arguments for using PEEP during ventilation with an LMA mask in elective surgery.

Comparison of intragastric pressure between endotracheal tube and supraglottic airway devices in laparoscopic hepatectomy: A randomized, controlled, non-inferiority study

BACKGROUND

Supraglottic airway (SGA) devices do not definitively protect the airway from regurgitation of gastric contents. Increased gastric pressure and long operation time are associated with development of complications such as aspiration pneumonia. The aim of this study was to compare intragastric pressure between second-generation SGA and endotracheal tube (ETT) devices during long-duration laparoscopic hepatectomy.

METHODS

A total of 66 patients was randomly assigned to 2 groups; 33 patients each in the ETT and SGA groups. Intragastric pressure was continuously measured via a gastric drainage tube with a three-way stopcock connected to the pressure monitoring device. Normal saline was added to the end of the gastric drainage tube at each operation time point.

RESULTS

Intragastric pressure during pneumoperitoneum was no different between the 2 groups (P = .146) or over time (P = .094). The mean (standard deviation [SD]) pH of the SGA tip measured after operation was 6.7 (0.4), and a pH <4 was not observed. Relative risk of postoperative complications was significantly higher in the ETT group relative to the SGA group (sore throat, 5.5; cough,13.0).

CONCLUSIONS

Use of SGA devices does not further increase intragastric pressure, even during prolonged upper abdominal laparoscopic surgery. Also, the frequency of postoperative sore throat and cough was significantly lower when the second-generation SGA device was used.

Comparison of the Baska Mask® and Endotracheal Tube on Hemodynamic and Respiratory Parameters in Septoplasty Cases

Laryngeal mask (LM) types have been used as an airway device for an alternative to the standard endotracheal tube (ETT). One of the novel type of LM, the Baska Mask®, can be a safe alternative among the airway devices. The purpose of this study is to compare the effects of the new generation supraglottic airway device the Baska Mask® and the ETT on hemodynamic parameters (heart rate, mean arterial pressure), airway pressure and end tidal carbon dioxide (EtCO2) in patients undergoing general anesthesia. After the approval of the ethics committee, 70 patients who underwent septoplasty were included in the study. Written informed consent forms were taken from these patients. Demographic data of the patients were recorded. Hemodynamic data of patients were measured and recorded preoperative, during induction, at the time of intubation 1th, 3th and 5th minute and during extubation. Also, airway pressure and EtCO2 values of the patients were measured and recorded at the time of intubation, 1th, 3th and 5th minutes. Demographic data were similar in both groups. Mean arterial pressure, heart rate and airway pressure were lower in the group 2 (the Baska Mask® group) than in the group 1 (ETT group) and the difference was statistically significant (p&lt;0.05). EtCO2 values were similar in both groups. No patients had tube leakage. In terms of hemodynamic and respiratory parameters the Baska Mask® is more advantageous than the ETT in short-term surgeries.

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.

Comparison of clinical performance of i-gelⓇ and Baska MaskⓇ during laparoscopic cholecystectomy

BACKGROUND

The supraglottic airway device is an appropriate alternative to tracheal intubation in laparoscopic surgery. We compared the Baska MaskⓇ with i-gelⓇ by measuring the oropharyngeal leak pressure (OLP) and hemodynamic and respiratory parameters during laparoscopic cholecystectomy.

METHODS

A total of 97 patients were randomly allocated to either i-gel group (n = 49) or Baska Mask group (n = 48). Insertion time, number of insertion attempts, fiber-optic view of the glottis, and OLP were recorded. Heart rate, mean arterial pressure, peak airway pressure (PAP), lung compliance, and perioperative complications were assessed before, during, and after pneumoperitoneum.

RESULTS

There were no significant differences between the two groups regarding demographic data, insertion time, fiber-optic view of the glottis, and the use of airway manipulation. The OLP was higher in the Baska Mask group than in the i-gel group (29.6 ± 6.8 cmH2O and 26.7 ± 4.5 cmH2O, respectively; P = 0.014). Heart rate, mean arterial pressure, PAP, and lung compliance were not significantly different between the groups. The incidence of perioperative complications was small and not statistically significant.

CONCLUSIONS

Both the i-gel and Baska Mask provided a satisfactory airway during laparoscopic cholecystectomy. Compared with the i-gel, the Baska Mask demonstrated a higher OLP.

Comparison of early postoperative recovery between laryngeal mask airway and endotracheal tube in laparoscopic cholecystectomy: A randomized trial

BACKGROUND

Laryngeal mask airway (LMA) insertion provokes fewer stress responses than endotracheal intubation. This study aimed to evaluate the LMA Protector for assessing improvements in intraoperative hemodynamic stability and to reduce postoperative discomfort compared with endotracheal intubation in laparoscopic cholecystectomy.

METHODS

Fifty-six patients who underwent laparoscopic cholecystectomy while under sevoflurane-based general anesthesia were randomly allocated to airway management using LMA (LMA group) or endotracheal tube (ETT group). Heart rate, blood pressure, and peak airway pressure were recorded before and after carboperitoneum. Postoperative pain and analgesic requirements were assessed, in addition to nausea, hoarseness, dysphonia, and sore throat during the first 1 hour postoperatively and until postoperative day 1.

RESULTS

All patients underwent successful LMA or ETT placement within 2 attempts. There was no difference in highest mean (SD) peak airway pressure during carboperitoneum between the LMA and ETT groups (17.7 [2.8] mm Hg vs 19.1 [3.8] mm Hg, P = .159, respectively). The incidence of high systolic blood pressure and bradycardia was higher in the LMA group. The highest pain scores 1 hour postoperatively and on postoperative day 1 were lower in the LMA group than in the ETT group (3.9 [2.0] vs 5.4 [2.3], P = .017 and 5.6 [1.9] vs 6.7 [1.7], P = .042, respectively); requirements for analgesics were similar in the 2 groups. The incidence of nausea was lower in the LMA group than in the ETT group until postoperative day 1 (4/28 [14%] vs 12/28 [43%], P = .031, respectively).

CONCLUSION

The LMA Protector was an effective ventilator device associated with fewer intraoperative hemodynamic stress responses and improved the quality of early recovery after laparoscopic cholecystectomy.

Short-lasting pediatric laparoscopic surgery: Are muscle relaxants necessary? Endotracheal intubation vs. laryngeal mask airway

PURPOSE

Technical advances have led to lower insufflation pressures and shorter anesthesia times for children undergoing laparoscopic procedures. In this study we compared the use of endotracheal tube (ETT) and laryngeal mask airway (LMA) with or without muscle relaxant (MR) in children undergoing laparoscopic repair for inguinal hernia.

METHODS

Children undergoing laparoscopic inguinal hernia repair were randomized into four groups which underwent procedure with either ETT+MR (group 1), ETT without MR (group 2), LMA with subparalytic dose of MR (group 3) or LMA without MR (group 4). Surgical, anesthesia and recovery times, intragastric pressures and peak airway pressures during insufflation were compared.

RESULTS

After exclusion criteria and discontinued interventions, groups 1 and 3 contained 20, groups 2 and 4 contained 19 patients each. Surgical times were similar between groups. Anesthesia times were statistically significantly different between groups with shortest time in group 4 and longest time in group 1. Recovery time was statistically significantly longer in group 1 when compared to other groups. There was no difference between basal intragastric pressure, average intragastric pressure during insufflation, peak airway pressure, and average peak airway pressure during insufflation of groups.

CONCLUSION

Use of muscle relaxants in short-lasting laparoscopic procedures in children is not absolutely necessary and LMA with subparalytic dose of muscle relaxant or with no muscle relaxant is a safe alternative.

TYPE OF STUDY

Treatment study.

LEVEL OF EVIDENCE

Level II.

ProSeal versus Classic laryngeal mask airway (LMA) for positive pressure ventilation in adults undergoing elective surgery

BACKGROUND

The development of supraglottic airway devices has revolutionized airway management during general anaesthesia. Two devices are widely used in clinical practice to facilitate positive pressure ventilation: the ProSeal laryngeal mask airway (pLMA) and the Classic laryngeal mask airway (cLMA). It is not clear whether these devices have important clinical differences in terms of efficacy or complications.

OBJECTIVES

To compare the effectiveness of the ProSeal laryngeal mask airway (pLMA) and the Classic LMA (cLMA) for positive pressure ventilation in adults undergoing elective surgery.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2017, Issue 3) in the Cochrane Library; MEDLINE (Ovid SP, 1997 to April 2017); Embase (Ovid SP, 1997 to April 2017); the Institute for Scientific Information (ISI) Web of Science (1946 to April 2017); and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) (EBSCO host, 1982 to April 2017).We searched trial registries for ongoing studies to April 2017.We did not impose language restrictions. We restricted our search to the time from 1997 to April 2017 because pLMA was introduced into clinical practice in the year 2000.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that compared the effectiveness of pLMA and cLMA for positive pressure ventilation in adults undergoing elective surgery. We planned to include only data related to the first phase of cross-over RCTs.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by the Cochrane Collaboration.

MAIN RESULTS

We included eight RCTs that involved a total of 829 participants (416 and 413 participants in the pLMA and cLMA groups, respectively). We identified six cross-over studies that are awaiting classification; one is completed but has not been published, and data related to the first treatment period for the other five studies were not yet available. Seven included studies provided data related to the primary outcome, and eight studies provided data related to more than one secondary outcome.Our analysis was hampered by the fact that a large proportion of the included studies reported no events in either study arm. No studies reported significant differences between devices in relation to the primary review outcome: failure to adequately mechanically ventilate. We evaluated this outcome by assessing two variables: inadequate oxygenation (risk ratio (RR) 0.75, 95% confidence interval (CI) 0.17 to 3.31; four studies, N = 617) and inadequate ventilation (not estimable; one study, N = 80).More time was required to establish an effective airway using pLMA (mean difference (MD) 10.12 seconds, 95% CI 5.04 to 15.21; P < 0.0001; I² = 73%; two studies, N = 434). Peak airway pressure during positive pressure ventilation was lower in cLMA participants (MD 0.84, 95% CI 0.02 to 1.67; P = 0.04; I² = 0%; four studies, N = 259). Mean oropharyngeal leak (OPL) pressure was higher in pLMA participants (MD 6.93, 95% CI 4.23 to 9.62; P < 0.00001; I² = 87%; six studies, N = 709).The quality of evidence for all outcomes, as assessed by GRADE score, is low mainly owing to issues related to blinding and imprecision.Data show no important differences between devices with regard to failure to insert the device, use of an alternate device, mucosal injury, sore throat, bronchospasm, gastric insufflation, regurgitation, coughing, and excessive leak. Data were insufficient to allow estimation of differences for obstruction related to the device. None of the studies reported postoperative nausea and vomiting as an outcome.

AUTHORS' CONCLUSIONS

We are uncertain about the effects of either of the airway devices in terms of failure of oxygenation or ventilation because there were very few events. Results were uncertain in terms of differences for several complications. Low-quality evidence suggests that the ProSeal laryngeal mask airway makes a better seal and therefore may be more suitable than the Classic laryngeal mask airway for positive pressure ventilation. The Classic laryngeal mask airway may be quicker to insert, but this is unlikely to be clinically meaningful.

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.

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.

Gastric distension with SLIPA versus LMA ProSeal during laparoscopic cholecystectomy: a randomized trial

BACKGROUND

We compared the quantitative clinical performances of the streamlined liner of the pharynx airway (SLIPA) and the ProSeal laryngeal mask airway (LMA ProSeal) regarding intensity of gastric distension in patients undergoing laparoscopic cholecystectomy.

METHODS

A total of 124 anesthetized, paralyzed patients (ASA 1 to 2; aged, 18 to 80 y) were randomly allocated for airway management with the SLIPA or LMA ProSeal. After induction of general anesthesia using total intravenous anesthesia and rocuronium, the intensity of gastric distension was accessed twice by 2 raters, respectively. We also compared the fiberoptic bronchoscopic view of the glottis, the severity of blood stain, and postoperative sore throat.

RESULTS

There were no statistically significant differences between groups for each gastric size. The change of gastric size within the SLIPA group was not statistically significant for both raters. Change within the LMA ProSeal group was significant in rater 2 (P=0.045) and marginally significant for rater 1 (P=0.056). Anatomic fit, complications during emergence, and the severity of blood stain and postoperative sore throat were similar in both groups.

CONCLUSIONS

SLIPA is as efficacious as LMA ProSeal for use in patients without severe complications who are undergoing laparoscopic cholecystectomy.

Extraglottic airway devices: A review

Extraglottic airway devices (EAD) have become an integral part of anesthetic care since their introduction into clinical practice 25 years ago and have been used safely hundreds of millions of times, worldwide. They are an important first option for difficult ventilation during both in-hospital and out-of-hospital difficult airway management and can be utilized as a conduit for tracheal intubation either blindly or assisted by another technology (fiberoptic endoscopy, lightwand). Thus, the EAD may be the most versatile single airway technique in the airway management toolbox. However, despite their utility, knowledge regarding specific devices and the supporting data for their use is of paramount importance to patient's safety. In this review, number of commercially available EADs are discussed and the reported benefits and potential pitfalls are highlighted.

Is muscle relaxant necessary in patients undergoing laparoscopic gynecological surgery with a ProSeal LMA™?

STUDY OBJECTIVE

To test the hypothesis that muscle relaxant is not necessary in patients who are undergoing laparoscopic gynecological surgery with a ProSeal Laryngeal Mask Airway (ProSeal LMA™).

DESIGN

Prospective, randomized study.

SETTING

Operating room of Sichuan Provincial Hospital for Women and Children.

PATIENTS

120 adult, ASA physical status 1 and 2 women, aged 18 to 55 years.

INTERVENTIONS AND MEASUREMENTS

Patients were randomly assigned to two groups (n=60) to receive a muscle relaxant (Group MR) or not (Group NMR). General anesthesia was used in patients of both groups for airway management with the ProSeal LMA. Peak airway inflation pressures, airway sealing pressure, minimum flow rate, and recovery time were assessed. Surgical conditions were assessed by the operating gynecologist. The frequency of sore throats was recorded.

MAIN RESULTS

ProSeal LMA insertion was 100% successful. Patients' lungs were ventilated with a maximum sealing pressure of 32 ± 5.1 cm H(2)O (Group MR) or 31 ± 4.9 cm H(2)O (Group NMR) (P = 0.341). The seal quality in both groups permitted the use of low flows: 485 ± 291 mL/min in Group MR and 539 ± 344 mL/min in Group NMR (P = 0.2). Surgical conditions were comparable between the two groups. There was no difference in the frequency of sore throats (20% vs 21.7%; P = 0.28). In Group NMR, there was a statistically significant reduction in recovery time versus Group MR (4.5 ± 2.6 min vs 10.3 ± 4.2 min; P < 0.01).

CONCLUSION

Muscle relaxant is not necessary in general anesthesia with a ProSeal LMA.

Pressure-controlled inverse ratio ventilation using laryngeal mask airway in gynecological laparoscopy

BACKGROUND

It is well documented that pressure-controlled ventilation (PCV) improves oxygenation and ventilation compared to volume-controlled ventilation and reduces peak airway pressure in gynecological laparoscopy. PCV with moderately inversed inspiratory-expiratory (I: E) ratio can successfully recruit collapsed alveoli and has been proved to be beneficial in intensive care. We tested the hypothesis that altering the I: E ratio to 1.5:1 in PCV improves ventilation during gynecological laparoscopy using laryngeal mask airway (LMA).

OBJECTIVE

To study pressure-controlled inverse ratio ventilation (PCIRV) with I: E ratio 1.5:1 as against PCV with I: E ratio 1:2 in gynecological laparoscopy with LMA using noninvasive parameters.

MATERIALS AND METHODS

Intraoperative hemodynamics and side-stream spirometry recordings were noted in 20 consecutive patients undergoing major gynecological laparoscopy with LMA. Flexible LMA or LMA supreme were used depending on normal body mass index (BMI) or high BMI, respectively.

RESULTS

REVERSING THE I: E ratio to 1.5:1 increased the tidal volume, mean airway pressures, and dynamic lung compliance significantly, all indicating better oxygenation at comparable peak airway pressures as against PCV with I: E ratio 1:2. There was no change in the end-tidal carbon dioxide. There was no auto-positive end expiratory pressure (PEEP) or change in the hemodynamics.

CONCLUSION

REVERSAL OF I: E ratio with PCV can be beneficially used with LMA in laparoscopy.

Comparison of streamlined liner of the pharynx airway (SLIPA™) with the laryngeal mask airway Proseal™ for lower abdominal laparoscopic surgeries in paralyzed, anesthetized patients

Context:

Supraglottic airway devices have been used as an alternative to tracheal intubation during laparoscopic surgery.

Aims:

The study was designed to compare the efficacy of Streamlined Liner of the Pharynx Airway (SLIPA) for positive pressure ventilation and postoperative complications with the Laryngeal Mask Airway ProSeal (PLMA) for patients undergoing lower abdominal laparoscopies under general anesthesia with controlled ventilation.

Settings and Design:

Prospective, crossover randomized controlled trial performed on patients undergoing lower abdominal laparoscopic surgeries.

Methods:

A total of 120 patients undergoing lower abdominal laparoscopic surgeries were randomly allocated into two equal groups; PLMA and SLIPA groups. Number of intubation attempts, insertion time, ease of insertion, and fiberoptic bronchoscopic view were recorded. Lung mechanics data were collected 5 minutes after securing the airway, then after abdominal insufflation. Blood traces and regurgitation were checked for; postoperative sore throat and other complications were recorded.

Statistical Analysis:

Arithmetic mean and standard deviation values were calculated and statistical analyses were performed for each group. Independent sample t-test was used to compare continuous variables exhibiting normal distribution, and Chi-squared test for noncontinuous variables. P value <0.05 was considered significant.

Results:

Insertion time, first insertion success rate, and ease of insertion were comparable in both groups. Fiberoptic bronchoscopic view was significantly better and epiglottic downfolding was significantly lower in SLIPA group. Sealing pressure and lung mechanics were similar. Gastric distension was not observed in both groups. Postoperative sore throat was significantly higher in PACU in PLMA group. Blood traces on the device were significantly more in SLIPA group.

Conclusions:

SLIPA can be used as a useful alternative to PLMA in patients undergoing lower abdominal laparoscopic surgery with muscle relaxant and controlled ventilation.

Anesthetic management of a patient with congenital diaphragmatic eventration

Congenital diaphragmatic eventration is uncommon in adults and is caused by paralysis, aplasia or atrophy of the muscular fibers of the diaphragm. It may cause severe dyspnea, orthopnea and hypoxia in adult patients. Most symptomatic patients may be managed efficiently without the need for surgical correction, although any event that leads to an increase in intra-abdominal pressure puts them at the risk of spontaneous diaphragmatic rupture. This case report presents the successful anesthetic management of an adult female with congenital diaphragmatic eventration undergoing diagnostic laparoscopy and hysteroscopy using a total intravenous anesthesia technique. Essential steps to prevent any rise in intrathoracic and intra-abdominal pressures along with care to minimize intragastric volume were taken.

Comparison of volume-controlled and pressure-controlled ventilation using a laryngeal mask airway during gynecological laparoscopy

Background

Several publications have reported the successful, safe use of Laryngeal Mask Airway (LMA)-Classic devices in patients undergoing laparoscopic surgery. However, there have been no studies that have examined the application of volume-controlled ventilation (VCV) or pressure-controlled ventilation (PCV) using a LMA during gynecological laparoscopy. The aim of this study is to compare how the VCV and PCV modes and using a LMA affect the pulmonary mechanics, the gas exchange and the cardiovascular responses in patients who are undergoing gynecological laparoscopy.

Methods

Sixty female patients were randomly allocated to one of two groups, (the VCV or PCV groups). In the VCV group, baseline ventilation of the lung was performed with volume-controlled ventilation and a tidal volume of 10 ml/kg ideal body weight (IBW). In the PCV group, baseline ventilation of the lung using pressure-controlled ventilation was initiated with a peak airway pressure that provided a tidal volume of 10 ml/kg IBW and an upper limit of 35 cmH₂O. The end-tidal CO₂, the peak airway pressures (P_peak), the compliance, the airway resistance and the arterial oxygen saturation were recorded at T1: 5 minutes after insertion of the laryngeal airway, and at T2 and T3: 5 and 15 minutes, respectively, after CO₂ insufflation.

Results

The P_peak at 5 minutes and 15 minutes after CO₂ insufflation were significantly increased compared to the baseline values in both groups. Also, at 5 minutes and 15 minutes after CO₂ insufflation, there were significant differences of the P_peak between the two groups. The compliance decreased in both groups after creating the pneumopertoneim (P < 0.05).

Conclusions

Our results demonstrate that PCV may be an effective method of ventilation during gynecological laparoscopy, and it ensures oxygenation while minimizing the increases of the peak airway pressure after CO₂ insufflation.

The use of ProSeal laryngeal mask airway in caesarean section--experience in 3000 cases

Rapid sequence induction is currently the recommended technique in general anaesthesia for caesarean section. However, the usefulness of the ProSeal laryngeal mask airway as a rescue airway in the event of difficult or failed intubation has been recognised in numerous case reports. In this study, we report the experience of the use of the ProSeal laryngeal mask in 3000 elective caesarean sections in a single centre, using a method of insertion that allows a rapid establishment of a patent airway together with gastric drainage.

Supraglottic airway devices in the ambulatory setting

Supraglottic airway devices (SGAs) offer certain advantages over endotracheal intubation, making them particularly well suited for the specific demands of outpatient anesthesia. Patients may tolerate the placement and maintenance of an SGA at a lower dose of anesthetic than that needed for an endotracheal tube; neuromuscular blocking agents are rarely necessary for airway management with an SGA; the incidence of airway morbidity is lower with SGAs than with endotracheal tubes; and SGAs may facilitate faster recovery and earlier discharge of patients. Two limitations of SGAs are incomplete protection against aspiration of gastric contents and inadequate delivery of positive pressure ventilation. Newer variants of the original laryngeal mask airway, the LMA Classic (LMA North America, Inc), as well as an array of other recently developed SGAs, aim to address these limitations. Their utility and safety in specific patient populations (eg, the morbidly obese) and during certain procedures (eg, laparoscopic surgery) remain to be determined.

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.

Anesthetic management of a pediatric patient with severe Williams-Campbell syndrome undergoing surgery for giant ovarian tumor

We performed anesthetic management for a patient with severe Williams-Campbell syndrome, which is a congenital deficiency of cartilage in the subsegmental bronchial tree. An 11-year-old girl with this syndrome had labored breathing because of abdominal distension caused by a giant ovarian tumor, and removal of the tumor was scheduled. Because she had been receiving home oxygen therapy for 10 years due to hypoxia, it was possible that positive-pressure ventilation may have increased the risk of perioperative pulmonary complications. So we selected combined spinal and epidural anesthesia with general anesthesia, using a ProSeal (Laryngeal Mask Company, Henley on Thames, UK) laryngeal mask airway. We placed an epidural catheter and induced spinal anesthesia blockade under general anesthesia as the main analgesia technique, in order to maintain spontaneous breathing. The surgery was completed uneventfully and the patient emerged from anesthesia without dyspnea. She had an uneventful recovery and was discharged home.

A randomized prospective study comparing the Cobra Perilaryngeal Airway and Laryngeal Mask Airway-Classic during controlled ventilation for gynecological laparoscopy

BACKGROUND

An increasing number of noninvasive, supraglottic airway devices are currently available. In this randomized single-blind study, we compared the Cobra Perilaryngeal Airway (CobraPLA) to the [Laryngeal Mask Airway (LMA)-Classic] during gynecological laparoscopy.

METHODS

Forty patients received either an LMA-Classic or a CobraPLA. Insertion, ventilation and removal characteristics were noted, as well as any throat morbidity.

RESULTS

Devices were similar for insertion characteristics, adverse events, and throat morbidity. Before pneumoperitoneum, peak airway pressures were 20.3 +/- 4.9 cm H2O in the LMA-Classic group versus 25.5 +/- 7.9 cm H2O in the CobraPLA group, P = 0.01. This difference was maintained during pneumoperitoneum; LMA-Classic (22.8 +/- 6.1 cm H2O) and CobraPLA (28.1 +/- 8.5 cm H2O), P = 0.04. Macroscopic blood occurred only on the CobraPLA, seen on 40% of the devices after removal, P = 0.001.

CONCLUSION

During gynecological laparoscopy, the CobraPLA provides similar insertion characteristics, but higher airway sealing pressures than the LMA-Classic. The usefulness of this finding requires further investigation.

Strategies for prophylaxis and treatment for aspiration

The absolute incidence of aspiration is difficult to define because of its relatively low occurrence and difficulty in diagnosis. The gastric volume predisposing to aspiration is larger than 30 ml. Fasting times for fluids have reduced; however, a large meal may require 9 hours of preoperative fasting. Preoperative carbohydrate-enriched beverages may attenuate postoperative catabolism. Aspiration occurs most frequently during induction and laryngoscopy. Awake fibre-optic intubation may be a suitable alternative in high-risk cases for aspiration. The role of cricoid pressure in anaesthesia needs re-evaluation as radiological and clinical evidence suggest that it may be ineffective and may impede intubation and ventilation. Chemoprophylaxis does not reduce the severity of aspiration pneumonitis as gastric bile is unaffected by these agents and induces a worse pneumonitis than gastric acid. Patients may be discharged home 2 hours after aspirating provided they are clinically unaffected and have postoperative surveillance.

Standard Laryngeal Mask Airway and LMA-ProSeal during laparoscopic surgery

STUDY OBJECTIVE

To compare the frequency of airway seal and sore throat with the LMA-ProSeal (PLMA) and the standard Laryngeal Mask Airway (LMA) during laparoscopic surgery.

DESIGN

Prospective, controlled, randomized, nonblinded clinical study.

SETTING

University-affiliated hospital.

PATIENTS

60 adult, ASA physical status I, II, and III patients undergoing laparoscopic surgery with general anesthesia, without contraindication to the use of the laryngeal mask.

INTERVENTIONS

Patients were randomized to receive mechanical ventilation [tidal volume (V(T)) 7 mL/kg(-1); positive end-expiratory pressure (PEEP) 10 cmH(2)O] through the PLMA or the standard LMA, both equipped with a gastric tube.

MEASUREMENTS

Heart rate, arterial pressure, inspiratory and expiratory V(T), airway pressure, end-tidal CO(2) partial pressure, and pulse oximetry were recorded. The leak fraction was calculated as the difference between the inspiratory and expiratory V(T) divided by the inspiratory V(T). Postoperative sore throat frequency was scored in the recovery room ("early") and 1 week after surgery ("late").

MAIN RESULTS

All patients were successfully ventilated through the assigned laryngeal mask. The leak fraction was 7 +/- 3% with the LMA and 7 +/- 4% with the PLMA (p = 0.731). In one patient, the PLMA drainage tube was not patent despite a leak fraction of 5%, and there was no clinically detectable air leak. During the recovery room stay, the frequency of sore throat was scored as mild in 13% and 10% of patients with the standard LMA and the PLMA, respectively, and was absent in the remaining patients (p = 0.99, between groups). There were no differences in the frequency of sore throat between the "early" and "late" evaluations (p = 0.99).

CONCLUSIONS

The PLMA and the LMA show similar airtight efficiency during laparoscopy. The patency of the PLMA drainage tube should always be confirmed. The sore throat evaluation performed in recovery room appears as reliable as later evaluations.

Gastric insufflation pressure, air leakage and respiratory mechanics in the use of the laryngeal mask airway (LMA) in children

BACKGROUND

The objective of the present study was to evaluate the prelaryngeal position of the laryngeal mask airway (LMA(TM)) in children, and to determine the influence of mask positioning on gastric insufflation and oropharyngeal air leakage.

METHODS

A total of 100 children, 3-11 years old, scheduled for surgical procedures in the supine position under general anaesthesia were studied. After clinically satisfactory LMA placement, tidal volumes were increased stepwise until air entered the stomach, airway pressure exceeded 30 cmH(2)O, or air leakage from the mask seal prevented further increases in tidal volume. LMA position in relation to the laryngeal entrance was verified using a flexible bronchoscope.

RESULTS

The insertion of the LMA with a clinically satisfactory position was achieved in all patients at the first attempt. Gastric air insufflation occurred in five of 49 patients with malpositioned LMA. No incident of gastric air insufflation was observed in 51 patients with correctly positioned LMA. The minimum inspiratory pressure leading to mask leakage was 17 cmH(2)O for incorrectly positioned LMA, and 25 cmH(2)O for correctly positioned LMA. Clinically unrecognized LMA malposition was associated with a significantly increased incidence of either oropharyngeal leakage (r = 0.59; P = 0.0001) or gastric insufflation (r = 0.25; P = 0.01).

CONCLUSIONS

Clinically undetected LMA malpositioning is a significant risk factor for gastric air insufflation in children between 3 and 11 years, undergoing positive pressure ventilation, especially at inspiratory airway pressures above 17 cmH(2)O.

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.

LMA-Classic and LMA-ProSeal are effective alternatives to endotracheal intubation for gynecologic laparoscopy

PURPOSE

To compare the laryngeal mask airways (LMA), LMA-Classic(TM) (LMA-C) and LMA-ProSeal(TM) (PLMA) with the endotracheal tube (ETT) with respect to pulmonary ventilation and gastric distension during gynecologic laparoscopy.

METHODS

We stratified 209 women, aged > or = 18 yr, ASA physical status I-III, by body mass index as non-obese (< or = 30 kg x m(-2)) or obese (> 30 kg x m(-2)) and randomized them to LMA-C/PLMA or ETT groups for airway management. Anesthesia was induced with propofol, fentanyl and succinylcholine or rocuronium. In the LMA-C/PLMA group we used a size 4 LMA-C in non-obese patients and size 4 or 5 PLMA in obese patients. In the ETT group we used a cuffed 7.0 mm ETT in all patients. Anesthesia was maintained with isoflurane in nitrous oxide and 30-50% oxygen, fentanyl and neuromuscular blockade with mechanical ventilation (tidal volume 10 mL x kg(-1)). The staff surgeon, blinded to the type of airway, scored stomach size on an ordinal scale 0-10 at initial insertion of the laparoscope and immediately before the conclusion of the surgical procedure.

RESULTS

There were no crossovers and no statistically significant differences between LMA-C/PLMA and ETT groups for SpO(2,) P(ET)CO(2) or airway pressure before or during peritoneal insufflation in short (< or = 15 min) or long (> 15 min) periods of peritoneal inflation. Differences between groups with respect to stomach size changes during surgery were not statistically significant.

CONCLUSION

A correctly placed LMA-C or PLMA is as effective as an ETT for positive pressure ventilation without clinically important gastric distension in non-obese and obese patients.

What is the role of neuromuscular blocking drugs in ambulatory anesthesia?

PURPOSE OF REVIEW

During ambulatory anesthesia, muscle relaxants should be used judiciously because of their impact on operating room efficiency and the potential for morbidity and mortality.

RECENT FINDINGS

Short-acting and low doses of medium-acting muscle relaxants are appropriate for the typically short period of anesthesia required in ambulatory settings, but they are not necessarily indicated. Their adverse effects range from annoying to lethal. Even when the effects are relatively benign, delays may reduce efficiency. Direct laryngoscopy and endotracheal intubation can often safely be accomplished with opioids and propofol, or with topical anesthesia. Procedures such as laparoscopic cholecystectomies can safely be performed with anesthesia via a laryngeal mask airway; with other procedures, a regional technique or monitored anesthesia care is satisfactory. New agents may improve upon currently available muscle relaxants in terms of rapid onset, short duration, and minimal adverse effects.

SUMMARY

Anesthetic and surgical needs should dictate the use of muscle relaxants, and alternatives to their use should be considered.

The LMA-ProSeal is an effective alternative to tracheal intubation for laparoscopic cholecystectomy

PURPOSE

To compare LMA-ProSeal (LMA-PS) with endotracheal tube (ETT) with respect to pulmonary ventilation and gastric distension during laparoscopic cholecystectomy.

METHODS

We randomized 109 ASA I-III adults to LMA-PS or ETT after stratifying them as non-obese or obese (body mass index > 30 kg x m-2). After preoxygenation, anesthesia was induced with propofol, fentanyl and rocuronium. An LMA-PS (women #4, men #5) or ETT (women 7 mm, men 8 mm) was inserted and the cuff inflated. A #14 gastric tube was passed into the stomach in every patient and connected to continuous suction. Anesthesia was maintained with nitrous oxide, oxygen and isoflurane. Ventilation was set at 10 mL x kg-1 and 10 breaths x min-1. The surgeon, blinded to the airway device, scored stomach size on an ordinal scale of 0-10 at insertion of the laparoscope and upon decompression of the pneumoperitoneum.

RESULTS

There were no statistically significant differences in SpO2 or P(ET)CO2 between the two groups before or during peritoneal insufflation in either non-obese or obese patients. Median (range) airway pressure at which oropharyngeal leak occurred during a leak test with LMA-PS was 34 (18-45) cm water. Change in gastric distension during surgery was similar in both groups. Four of 16 obese LMA-PS patients crossed over to ETT because of respiratory obstruction or airway leak.

CONCLUSIONS

A correctly seated LMA-PS or ETT provided equally effective pulmonary ventilation without clinically significant gastric distension in all non-obese patients. Further studies are required to determine the acceptability of the LMA-PS for laparoscopic cholecystectomy in obese patients.

ProSeal versus the Classic laryngeal mask airway for positive pressure ventilation during laparoscopic cholecystectomy

BACKGROUND

We tested the hypothesis that the ProSeal laryngeal mask airway (PLMA) is a more effective ventilatory device than the Classic laryngeal mask airway (LMA) for laparoscopic cholecystectomy.

METHODS

Eighty anaesthetized, paralyzed patients (ASA 1-2, aged 18-80 yr) were randomly allocated for airway management with the PLMA or LMA. Ease of insertion and efficacy of seal were determined. Peak airway pressures were recorded immediately before and after carboperitoneum to 2.0 kPa. The inspired oxygen concentration and/or the ventilatory variable were adjusted according to a protocol to maintain SpO2 > or = 95% and E'CO2 < 6.0 kPa. Oxygenation was considered suboptimal if SpO2 fell to 94-90% and failed if SpO2 was < 90%. Ventilation was considered suboptimal if E'CO2 was > 6.0-7.3 kPa and failed if E'CO2 was > 7.3 kPa.

RESULTS

First-time insertion success rates were higher for the LMA (40/40 vs 33/40; P = 0.02). Seven patients required two attempts with the PLMA. Oropharyngeal leak pressure was higher for the PLMA [29 (SD 6) vs 19 (4) cm H2O; P < 0.001]. There was a similar, significant increase in peak airway pressure after carboperitoneum for both devices (P < 0.001). Before carboperitoneum, oxygenation and ventilation were optimal in all patients in both groups. After carboperitoneum, oxygenation was optimal in all patients in both groups, but ventilation was suboptimal more frequently with the LMA (8 vs 0; P = 0.01). In three of these eight patients, ventilation failed but was subsequently optimal with the PLMA.

CONCLUSION

The PLMA is a more effective ventilatory device for laparoscopic cholecystectomy than the LMA. We do not recommend the use of the LMA for laparoscopic cholecystectomy.

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.

The laryngeal mask airway is effective (and probably safe) in selected healthy parturients for elective Cesarean section: a prospective study of 1067 cases

PURPOSE

To report on the use of the laryngeal mask airway (LMA) for elective Cesarean section in 1067 consecutive ASA I-II patients preferring general anesthesia.

METHODS

Patients were excluded if they had pharyngeal reflux, a pre-pregnancy body mass index >30, or had a known/predicted difficult airway. Patients were fasted for six hours and given ranitidine/sodium citrate. A rapid sequence induction was performed with thiopentone and suxamethonium. The LMA was inserted by experienced users. Anesthesia was maintained with N(2)O and 50% O(2) and a volatile agent. Cricoid pressure was maintained until delivery, but was relaxed if insertion/ventilation was difficult. Patients were intubated if an effective airway was not obtained within 90 sec, or SpO(2) <94%, or end-tidal CO(2) >45 mmHg. Postdelivery, vecuronium and fentanyl were administered.

RESULTS

An effective airway was obtained in 1060 (99%) patients, 1051 (98%) at the first attempt and nine (1%) at the second or third attempt. Air leakage or partial airway obstruction occurred in 22 (21%) patients, and seven (0.7%) patients required intubation. There were no episodes of hypoxia (SpO(2) <90%), aspiration, regurgitation, laryngospasm, bronchospasm or gastric insufflation. Surgical conditions were satisfactory and all APGAR scores were >/=7 after five minutes.

CONCLUSION

We conclude that the LMA is effective and probably safe for elective Cesarean section in healthy, selected patients when managed by experienced LMA users.