Background and Rationale

Securing the airway is one of the primary concern of anaesthesiologist in patient undergoing surgery in general anaesthesia. Tracheal intubation has been for years the technique of choice for airway management during surgical procedures under general anesthesia. However, it is not a procedure without risk and limitation. Besides technical challenges in tube placement there are some complication that range from events such as trauma in airway,laryngospasm, laryngeal edema, to other minor events such as hoarseness of voice and postoperative sore throat. There have been very limited studies comparing the LMA Blockbuster and Baska mask. Therefore, the aim of this study is to compare the effectiveness of the LMA blockbuster and the Baska mask in terms of ease of insertion, quality of ventilation, oropharyngeal leak pressure and incidence of post-operative complications. We hypothesized that the Baska mask would withstand higher inflation pressure with the cuffless membranous bowl without having a problem with diffusion of nitrous oxide, have faster placement time with less laryngopharyngeal morbidity in postoperative period as compared to LMA Blockbuster in patients undergoing elective surgeries for laparoscopic cholecystectomy.

Importance of the research proposal: The study will be able to provide better option for laparoscopic cholecystectomy procedures

Research Hypothesis:

·         There should be a significant difference in outcomes of patients undergoing laparoscopic cholecystectomy using LMA Blockbuster and Baska mask.

OBJECTIVES

Primary Objective:

·         To compare oropharyngeal leak pressure (OLP) between Baska mask and LMA Blockbuster in patients undergoing laparoscopic cholecystectomy.

Secondary Objective:

·         Ease of insertion

·         Haemodynamic parameters

·         Complications during insertion like laryngospasm, trauma and blood staining

·         Post-operative airway morbidity (hoarseness of voice, sore throat, dysphagia)

Study design and methods:

Study Settings:

The study will be conducted in Department of Anaesthesiology in collaboration of general surgery department of King George’s Medical University, Lucknow after taking written and informed consent from the patients.

Study design:

Prospective, Randomized, Comparative study.

Study duration:  One year

Sample size: Total 86 cases included in the study

Inclusion and exclusion criteria:

Inclusion Criteria:

            • Patients of either sex

            • Aged 18-60 years

            • ASA physical status I-II

            • Undergoing elective laparoscopic cholecystectomy of less than 2hrs

Exclusion criteria:

·         Patients not giving written informed consent

·         Patients having anticipated difficult airway

·         Inter incisor distance < 2.5 cm

·         Any associated neurological disorders, gastroesophageal reflux disease

·         Body mass index ≥30kg/m2

·         Any contraindication to supraglottic airway devices

·         Inadequate fasting, full stomach, pregnancy, reactive airway disease etc.

Sample size:

Sample size is calculated on the basis of proportion of ease of insertion in Baska Mask and LMA Blockbuster groups using the formula

Where p1 = 0.58 (58%) proportion of ease of insertion in Baska Mask group p2 = 0.76 (76%) proportion of ease of insertion in LMA Blockbuster group e = 0.25(p1/p2), the risk ratio considered to be clinically significant Type I error, α=5% Type II error β=10% for detecting results with power of study 90%

The sample size is n = 43 each group

(Chaudhary UK, Mahajan SR, Mahajan M, Sharma C, Sharma M. A comparative analysis of the baska mask versus I-gel for general anesthesia in surgical patients undergoing laparoscopic cholecystectomy. Acta Med Int 2018;5:69-73)

METHODOLOGY:

The study will be conducted after getting approval from ethics committee of King George’s Medical University, Lucknow. A computer-generated system will be used for randomization by creating a list of number each number referred to one of the two groups.

Group A: Patients in which SAD used is Baska mask

Group B: Patients in which SAD used is LMA Blockbuster

On arrival in the operating room, patients will be subjected to the standard monitoring like ECG, noninvasive blood pressure, heart rate, temperature and SpO2 and a baseline vitals parameter will be recorded.

They all will be subjected to the same anaesthetic protocol. Induction will be done in supine position with fentanyl (2 mcg/kg) and propofol (2 mg/kg) after 3-minute preoxygenation with 100 % O2 followed by muscle relaxant vecoronium (0.1mg/kg), to facilitate device placement Baska mask, LMA Blockbuster to be used of size 3,4 no. of either device as their size varies according to weight of the patient.

All SADs will be lubricated on back surface of cuff before insertion. SAD placement will be done after achieving adequate relaxation. The time of successful placement of LMA will be defined as the duration from the time anesthesiologist picks up the LMA till the capnography tracing is obtained. Effective ventilation will be tested by observation of chest wall movement and capnography curve on the monitor. Ventilation will be set at an inspired tidal volume of 6-8 ml/kg and respiratory rate of 12 minutes, inspiratory expiratory ratio of 1:2 with no PEEP. If there is no chest wall movement and no capnography tracing on monitor, that attempt will be considered as failed. We will also note total no of attempt in each case and no. of successful placement in first attempt. During the procedure hemodynamic changes will be recorded. The study will be able to provide better option for laparoscopic cholecystectomy procedures.

After successful placement of either device oropharyngeal leak pressure will be measured. OLP test will be performed after the loss of spontaneous respiration. The OLP is defined as the plateau airway pressure reached with the fresh gas flow at the rate of 6 lit/min and pressure adjustment valve set to 70 cm H20. The peak pressure at which leaking from airway device will be confirmed by hearing noisy sound or stethoscope then setting will be back to previous normal.

After completion of surgery device will be removed and patient will be shifted to postoperative recovery room. Two hours after surgery patient will be assessed for any airway morbidity by asking him like sore throat (constant pain), dysphonia(hoarseness) or dysphagia. Device will also be checked for any blood stain to assess any trauma during insertion.

We had assessed and recorded OLP just after and 30 min after insertion of the device. It will be determined by closing the expiratory valve at a fixed gas flow of 5 L/min and recording the airway pressure at which equilibrium will be reached. The airway pressure will be not allowed to exceed 40 cm of water. We also assessed the time taken for insertion of device, i.e., ease of insertion, i.e., easy insertion – insertion at first attempt with no resistance; difficult insertion – insertion with resistance or at second attempt; and failed insertion – insertion not possible even after two attempts. Manipulations will be done in the form of increasing the depth of insertion; giving jaw thrust or changing size of the device. For standardization, intra-abdominal pressure (IAP) will be maintained at 12–16 mmHg. We also assessed gastric tube insertion time. The PAP, leak fraction, hemodynamic responses (heart rate and mean arterial blood pressure), SPO₂ and end tidal carbon dioxide (EtCO₂)will be also recorded at 1 min after induction (T1), 5 min before carboperitonium (T2), 5 min after carboperitonium (T3), 5 min before removal of carboperitonium (T4), and 5 min after removal of carboperitonium (T5) along with the baseline (T0) value. To maintain target SPO₂ (>95%) and EtCO₂ (<45 mm Hg) by adjusting the fraction of inspired oxygen, respiratory rate, and tidal volume. When SPO₂ was 94%–90%, the oxygenation will be graded as suboptimal, and the oxygenation will be graded as failed if SPO₂ was <90%. The leak fraction will be calculated by the formula: tidal volume inspires − tidal volume expired/tidal volume inspired (Vinsp − Vexp/Vinsp) × 100 to assess the device stability. Incidence of gastric distension/desaturation/aspiration/cough/any lip, tongue, and dental injury will be recorded. Postoperative laryngo-pharyngeal morbidity (pain in throat/change of voice/difficulty in swallowing) will be assessed after 2 h of removal of the device. The study will be able to provide better option for laparoscopic cholecystectomy procedures.

Statistical analysis:

All data will be  statistically analyzed using SPSS statistical software, Version 22^nd.  The quantitative data (OLP, times for insertion of SGA and gastric tube) will be analyzed using the one-way analysis of variance test and Bonferroni post hoc multiple comparison test. Qualitative data (ease of insertion of SGA and gastric tube, first attempt insertion success rate, number of insertion attempts, and any complications) will be compared using Chi-squared or Fisher’s exact test. A P < 0.05 was considered significant.

References:

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