Positive end-expiratory pressure increases arterial oxygenation in elderly patients undergoing urological surgery using laryngeal mask airway in lithotomy position

Ventilation Strategies During General Anesthesia for Noncardiac Surgery: A Systematic Review and Meta-Analysis

BACKGROUND

The optimal ventilation strategy during general anesthesia is unclear. This systematic review investigated the relationship between ventilation targets or strategies (eg, positive end-expiratory pressure [PEEP], tidal volume, and recruitment maneuvers) and postoperative outcomes.

METHODS

PubMed and Embase were searched on March 8, 2021, for randomized trials investigating the effect of different respiratory targets or strategies on adults undergoing noncardiac surgery. Two investigators reviewed trials for relevance, extracted data, and assessed risk of bias. Meta-analyses were performed for relevant outcomes, and several subgroup analyses were conducted. The certainty of evidence was evaluated using Grading of Recommendations Assessment, Development and Evaluation (GRADE).

RESULTS

This review included 63 trials with 65 comparisons. Risk of bias was intermediate for all trials. In the meta-analyses, lung-protective ventilation (ie, low tidal volume with PEEP) reduced the risk of combined pulmonary complications (odds ratio [OR], 0.37; 95% confidence interval [CI], 0.28-0.49; 9 trials; 1106 patients), atelectasis (OR, 0.39; 95% CI, 0.25-0.60; 8 trials; 895 patients), and need for postoperative mechanical ventilation (OR, 0.36; 95% CI, 0.13-1.00; 5 trials; 636 patients). Recruitment maneuvers reduced the risk of atelectasis (OR, 0.44; 95% CI, 0.21-0.92; 5 trials; 328 patients). We found no clear effect of tidal volume, higher versus lower PEEP, or recruitment maneuvers on postoperative pulmonary complications when evaluated individually. For all comparisons across targets, no effect was found on mortality or hospital length of stay. No effect measure modifiers were found in subgroup analyses. The certainty of evidence was rated as very low, low, or moderate depending on the intervention and outcome.

CONCLUSIONS

Although lung-protective ventilation results in a decrease in pulmonary complications, randomized clinical trials provide only limited evidence to guide specific ventilation strategies during general anesthesia for adults undergoing noncardiac surgery.

Prewarming non-inflatable cuff laryngeal mask for mechanical ventilation: A systematic review and meta-analysis with trial sequential analysis

BACKGROUND

Non-inflatable cuff laryngeal masks are generally composed of thermoplastic material. The thermoplastic nature of the non-inflatable cuff will become soft and match the laryngeal anatomy better as it reaches body temperature after intubation. This meta-analysis aims to evaluate the clinical validity of prewarming non-inflatable cuff laryngeal mask before insertion.

METHODS

We searched PubMed, Cochrane Library, Embase, Web of Science, Ovid Medline, CNKI, Wan Fang Database and VIP Database to find randomized controlled trials (RCTs) researching the clinical validity of prewarming non-inflatable cuff laryngeal mask. The retrieval time is up to June 2022. Articles published in the English and Chinese languages were considered. Quality assessment was conducted with the Cochrane Collaboration's tool and GRADE (Grading of Recommendations Assessment, Development and Evaluation) method. Subgroup analyses and trial sequential analysis (TSA) were performed to control the risk of random errors. Publication bias was assessed by funnel plots and Egger's regression test. The outcomes included sealing pressure immediately after successful ventilation, the first-attempt intubation success rate and the incidence of postoperative pharyngeal pain.

RESULTS

Eight RCTs evaluating 683 patients were identified. Pooled results showed that compared to the control group, prewarming non-inflatable cuff laryngeal mask provided a higher sealing pressure immediately after successful ventilation (mean difference: 1.73 cm H2O; 95% confidence interval [CI]: 0.95-2.52; P < .0001; I2 = 16; high quality), higher first-attempt intubation success rate (risk ratio [RR]: 1.05; 95% CI: 1.01-1.09; P = .01; I2 = 26%; high quality, number needed to treat [NNT] = 22 [95% CI 12.5-100]) and lower incidence of postoperative pharyngeal pain (RR: 0.59, 95% CI: 0.46-0.75; P < .0001; I2 = 0; high quality, NNT = 6 [95% CI 4.17-9.09]). The results were confirmed by TSA.

CONCLUSION

Prewarming non-inflatable cuff laryngeal mask could provide better mechanical ventilation efficiency with higher sealing pressure, a higher first-attempt intubation success rate and a lower incidence of postoperative pharyngeal pain.

TRIAL REGISTRATION NUMBER

PROSPERO CRD42021245350.

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.

Prewarming i-gel laryngeal mask for mechanical ventilation: a meta-analysis of randomised control trials and trial sequential analysis

OBJECTIVE

To systematically evaluate the efficiency of prewarming i-gel laryngeal mask for mechanical ventilation by meta-analysis and trial sequential analysis.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Cochrane library, Web of Science, Ovid Medline and PubMed were searched from their inception to 31 August 2020. Only articles published in English language were considered.

METHODS

Randomised controlled trials (RCTs) comparing the efficiency of prewarming i-gel laryngeal mask versus keeping it at room temperature for mechanical ventilation were included. Primary outcome was sealing pressure immediately after successful ventilation. Secondary outcomes were the first-attempt insertion success rate and the incidence of postoperative pharyngeal pain. Two authors independently selected studies. Quality analysis was performed using the modified Jadad Scale. Trial sequential analysis (TSA) was used to control risk of random errors. Sensitivity analysis was done to assess the effect of a single study on the pooled estimates. Publication bias was assessed by funnel plots and Egger's regression test.

RESULTS

Four RCTs comprising 374 patients were included. The results of meta-analysis showed that compared with the control group, prewarming i-gel laryngeal mask provides a higher sealing pressure immediately after successful ventilation (mean difference 2.19 cm H₂O; 95% CI (1.17 to 3.21); p<0.0001; high quality), with firm evidence from TSA and lower publication bias (p=0.7372). No significant difference was observed in the first-attempt insertion success rate (relative ratio (RR) 1.06; 95% CI (1.00 to 1.12); p=0.07; high quality) with lower publication bias (p=0.1378). The TSA indicating further trials are required. No significant difference was assessed in the incidence of postoperative pharyngeal pain (RR 1.0; 95% CI (0.14 to 6.90); p=1.0; high quality).

CONCLUSION

Prewarming i-gel laryngeal mask provides higher sealing pressure compared with keeping it at room temperature. But prewarming i-gel laryngeal mask did not increase the first-attempt insertion success rate, nor did it decrease the incidence of postoperative pharyngeal pain.