Supraglottic Airway Devices (SADs) are a diverse category of devices used to provide ventilation, oxygenation, and anaesthetic gas administration during respiratory arrest or during a surgical procedure performed under general anaesthesia [1]

Second generation supraglottic airway devices provide many advantages over endotracheal intubation. It includes reduced haemodynamic response, decreased anaesthetic requirement for airway tolerance and lesser pharyngolaryngeal morbidity [2-3].

Second generation supraglottic airway devices incorporate a suction port in their construction to separate the respiratory and alimentary tract. They offer better oropharyngeal seal and improved protection against regurgitation and aspiration. The AMBU AURAGAIN laryngeal mask airway (Ambu A/S, Ballerup Denmark) is a newer second-generation supraglottic airway device launched in June 2014. It is a single use SAD which promises to provide high seal pressures. It has an integrated gastric access, a bite block and a wider airway tube [2-3].

Laparoscopic surgeries are done under general anaesthesia which institute the use of nitrous oxide, oxygen and volatile anaesthetic agents along with pneumoperitoneum. SAD cuff is highly permeable to nitrous oxide and carbon dioxide through the cuff wall. Hence nitrous oxide and carbon dioxide are expected to diffuse into the air filled cuff of the SAD. Thus cuff volume and cuff pressure would be expected to increase during laparoscopic surgeries [4-5].

Hence maintenance of adequate cuff pressure is not only important to avoid ventilatory leak during mechanical ventilation but also important to prevent aspiration. Conversely, several postoperative complications such as cough, sore throat, hoarseness and blood-streaked expectorations are associated with excessive cuff pressure [6]. So, it is important to maintain cuff pressure to a recommended level during laparoscopic surgery. 

Various studies have been conducted to assess the efficacy of supraglottic airway devices for maintaining airway during general anaesthesia. But there is paucity of literature comparing clinical performance of Ambu AuraGain during laparoscopic surgeries under general anaesthesia. Hence, the present study was aimed to determine cuff-pressure in different positions in laparoscopic surgeries done using Ambu  AuraGain. 

Aim and Objectives

To determine intra cuff pressure in laproscopic surgeries in Trendenlenburg and Reverse Trendenlenburg position with the use of Ambu AuraGain SGA. 

Materials and Methods

• Study design: Prospective cohort study 

• Study site: Department of Anaesthesia, Dr RPGMC Kangra at Tanda

• Study duration: The study was conducted over the period of 18 months including data collection, data organization, presentation, analysis, and interpretation from January, 2020 to June 2021.

• Sample size: Total of 46 patients were included which were categorized into two groups. In the first arm of study less number of patients participated than calculated sample size due to covid -19 pandemic containment restrictions. Further research is needed with adequate sample to rule out effect of chance if any from obtained results or power analysis to check adequacy of sample size. 

Group A

Comprised of 16 patients who underwent Surgeries in Trendelenburg position including gynaecological surgeries like Diagnostic Laparoscopy for infertility and ectopic pregnancy, Laparoscopic cystectomy, TAP surgery for hernia and Laparoscopic appendicectomy.

Group B

Comprised of 30 patients who underwent surgeries in Reverse Trendelenburg position including Laparoscopic surgery for gall bladder disease, i.e. Laparoscopic cholecystectomy.

Trendelenburg Position 

(Group A)

Reverse Trendelenburg Position

(Group B)

Figure 1: Comparison of Surgical Procedures in Trendelenburg (Group A) and Reverse Trendelenburg (Group B) Positions

Inclusion criteria 

• Patients (age 18 to 60 years) of either sex

• Body Mass Index  18.5 to 30 kg/m2

• American Society of Anesthesiologists physical status I or II

• Undergoing elective laparoscopic surgery involving Trendelenburg and Reverse Trendelenburg position with an anticipated duration of 30-120 minutes will be included in the study

Exclusion criteria 

• Obesity (Body Mass Index >30)

• All the contraindications for supraglottic airway

• Oropharyngeal diseases

• If Laparoscopic surgery was converted into open surgery in any of cases

• If in any case supraglottic airway had to be replaced by endotracheal tube

• Limited mouth opening (inter-incisor gap < 20 mm)

• Patients at risk of aspiration (full stomach, previous upper gastrointestinal surgery, hiatus hernia)

• Refusal to participate in the study

The study was commenced after obtaining Institutional Ethics Committee approval---dated 21-12-2019, NO-HFW- H DRPGMC/Ethics/2019/239. The patients were classified into Trendelenburg and Reverse Trendelenburg position depending upon the laparoscopic surgeries they were scheduled for.

• Group A: Trendelenburg position (Head Down 20-30⁰⁾, n=16

• Group B: Reverse Trendelenburg position (Head Up 20-30⁰), n=30

In Goup A

All patients were explained the procedure and written, well informed consent was taken. All patients were instructed to remain fasting for 8 hours prior to surgery and medicated night before surgery with Tablet alprazolam 0.25 mg and Tablet Ranitidine 150 mg. In Operation theater, intravascular fluid (Normal Saline) was started with 18G cannula. A multichannel monitor showing pulse rate, electrocardiogram, oxygen saturation, non-invasive blood pressure (NIBP) was connected and baseline readings were recorded. 

All patients of group A were given Inj.glycopyrrolate 0.2 mg, Inj. midazolam 0.02 mg/kg, and Inj. fentanyl 2 μg/kg IV. Pre-oxygenation was done for 3-5 minutes and induction was done with Inj. Propofol 2mg/kg IV in slow incremental dose till the loss of verbal command, eyelash reflex and ease of mask ventilation was noted. After confirming adequate mask ventilation Inj. Atracurium 0.5 mg/kg IV was administered to facilitate insertion of Ambu AuraGain. Once the jaw relaxation was achieved, supraglottic device was inserted in supine position. 

Size selection of Ambu AuraGain was done according to weight of the patients, SGA size 4 (weight 50-70 kg). For the lubrication, water based lubricating jelly was applied on the dorsum of the device. Initially, the handle (Shaft) was kept approximately parallel to the patient’s chest and then the device was pushed along the hard palate after. Its placement might require higher tangential force due to bulky and acute angle of the device. It was straightened like of classical LMA before insertion to avoid any complication. 

Ambu AuraGain was inflated by recommended amount of air i.e. not more than 30 ml. If any leak around the Ambu AuraGain was found clinically, cuff was inflated with more air up to recommended limits. Adequate ventilation was confirmed by auscultation, chest movements, and EtCO2 waveforms. The pilot balloon was attached to cuff manometer, and cuff pressure was measured with cuff manometer, which further helped in getting an effective oropharyngeal seal and keep peak airway pressure and tidal volume within normal limits. 

Monitoring of Cuff Pressure

The peak airway pressure and cuff pressure were monitored: 

• After placement of SGA

• Before insufflations of CO2

• Once pneumoperitoneum was made and intraabdominal pressure was kept at recommended values (12-14 mmHg)

• Patient was given Tredenlenburg position i.e. Head down 20-300

• Thereafter every 10 minutes cuff pressure and peak airway pressure were monitored until pneumoperitoneam was released, and till SGA was removed 

• If intracuff pressure increased beyond the recommended level i.e. not more than 60 cm of H2O. Its pressure was brought to baseline pressure by releasing air with the help of cuff manometer and we noted the number of time it was done

After the completion of procedure, when the patient showed initial sign of respiratory efforts, the neuromuscular block was reversed with Inj. neostigmine 0.05 mg/kg and Inj. glycopyrrolate 0.02 mg/kg. When extubation criteria was met the Ambu AuraGain was removed with the cuff deflated. Post-operatively, the patients were assessed over 24 hours. 

In Group B

i.e. Reverse Tredenlenburg position (head up 20- 30^o) all patients were monitored for same parameters at same time interval as in Group A.

Statistical Analysis

Statistical analyses were performed using IBM SPSS Statistics for Windows, Version 25.0. Armonk, NY: IBM Corp. Results on continuous measurements were presented on Mean±SD (Min-Max) & categorical as Frequency (Percentage). Inferential statistics like Chi-square test/Fischer Exact test, Independent t test was applied. The significance of level adopted was 5%.  

The present study was conducted on 46 patients in Department of Anaesthesia, Dr RPGMC Kangra at Tanda, Himachal Pradesh to determine cuff-pressure in laparoscopic surgeries in Trendelenburg and Reverse Trendelenburg position with the use of Ambu AuraGain The patients were categorised into Trendelenburg and Reverse Trendelenburg position depending upon the laparoscopic surgeries they were scheduled for-

• Group A: Trendelenburg position (n=16) 

• Group B: Reverse Trendelenburg position (n=30)

The mean age of patients in Group A was 44.44±11.11 years whereas the mean age of patients in Group B was 45.50±11.78 years. The comparison of mean age of two groups was not found to be statistically significant (p>0.05). The mean BMI of patients in Group A was found to be 22.28±1.58 kg/m² and mean BMI of patients in Group B was 22.57±2.54 kg/m². Upon statistical analysis, this was not found to be significant (p>0.05).

Table No. 1: Comparison of Mean Age of Study Participants

Table No. 2: Distribution of Study Participants According to Gender, ASA Status and Duration of Surgery

Table No 3: Comparison of Cuff Pressure (Cmh₂o) of Study Participants at Different Intervals

Table No.4: Intervention Done by Release of Air Using Cuff Manometer

Group A comprised of 2 (12.5%) males and 14 (87.5%) females whereas Group B comprised of 12 (40%) males and 18 (60%) females. The comparison of number of males and females between two groups was not found to be statistically significant (p>0.05). Group A comprised of 11 (68.8%) patients with ASA status I and 5 (31.2%) patients with ASA status II. On the other hand, Group B had 15 cases each with ASA status I and II. This was not found to be statistically significant (p>0.05). The average duration of surgeries in Group A was 80-90 minutes whereas the average duration of surgeries in Group B was 70-80 minutes.

The mean cuff pressure for Group A after SGA placement, before CO2 insufflation, after CO2 insufflation, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, on release of pneumo-peritoneum and till SGA removal was found to be 41.13±1.26, 41.38±1.59, 45.63±2.45, 47.75±2.62, 49.13±3.42, 50.50±3.62, 52.38±3.28, 54.00±3.72, 55.00±4.00, 55.50±4.23 and 55.50±4.23 respectively.

The mean cuff pressure for Group B after SGA placement, before CO2 insufflation, after CO2 insufflations, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, on release of pneumo-peritoneum and till SGA removal was found to be 40.60±0.93, 41.00±1.37, 44.13±1.96, 45.60±2.06, 46.87±2.39, 48.00±2.78, 49.33±3.08, 49.93±3.13, 50.27±3.05, 50.60±3.02 and 50.60±3.02respectively.

The comparison between mean cuff pressure of two groups was found to be statistically significant at all recorded time intervals except after SGA placement and before CO2 insufflation (p>0.05). Cuff pressures were higher in Group A than Group B.    

Only 2 patients in Group A and no patient in Group B required intervention i.e. release of air with the help of cuff manometer when pressure increased beyond recommended levels (60 cm of H₂O). This was not found to be statistically significant (p>0.05).

The position of the patient in the laparoscopic surgery has an effect on cardiovascular and respiratory functions. The changes to the lithotomy, Trendelenburg, and reverse Trendelenburg positions reduce lung compliance by altering the location of intestinal contents and diaphragm. Pneumoperitoneum created by CO₂ insufflation during laparoscopic surgery elevates the diaphragm and intrathoracic pressure, which in turn also affects lung compliance.⁷ The impact of these positions on the cardiopulmonary function has been discussed by Srivastava A et al. [8]. In Trendelenburg position, there is an increase preload due to an increase in the venous return from lower extremities. This position results in cephalic shifting of viscera, which accentuates the pressure on the diaphragm. In case of reverse Trendelenburg position, pulmonary function tends to improve as there is caudal shifting of viscera, which improves tidal volume by decrease in the pressure on the diaphragm. This position also decreases the preload on heart and causes a decrease in the venous return leading to fall in blood pressure. The pooling of blood in the lower extremities increases the stasis and predisposes the deep vein thrombosis (DVT). In the present study, we evaluated and compared the intra cuff pressure in Trendelenburg and Reverse Trendelenburg position. To the best of our knowledge, this is the first study to evaluate and compare intra cuff pressures in two positions with the use of Ambu AuraGain.

In the present study, the two groups were comparable in terms of demographic and clinical characteristics like age, gender, BMI (p>0.05) and ASA status II. The average duration of surgeries in Group A was 80-90 minutes whereas the average duration of surgeries in Group B was 70-80 minutes.

The comparison between mean cuff pressure of two groups was found to be statistically significant at all recorded time intervals which was found to be higher in group A than Group B. cuff pressure does not rise from SGA placement and before CO2 insufflation (p>0.05). This could be attributed to the conformational change of trachea by abdominal insufflations and increased peak airway pressure in Group A that would conduct and press part of the cuff, along with gravitational effect of head down tilt in Trendelenburg position which could be the underlying mechanism behind elevated cuff pressure in Group A. 

In a study by Khadse MA et al. [9], it was observed that the cuff pressure increased after giving Trendelenburg position but not in the Reverse Trendelenburg position. The cuff pressure measured after surgical position was 28.16±0.37 cm of H₂O in Trendelenburg position. The cuff pressure continued to increase in Trendelenburg position throughout the procedure but not in the reverse Trendelenburg position. The cuff pressures in Trendelenburg position were higher than in Reverse Trendelenburg position at each observation time point. The cuff pressure increased by an average of 5 cm of H₂O after in Trendelenburg position group and an average of 2cm of H₂O in Reverse Trendelenburg position group. This difference in the cuff pressures was statistically significant at all times during their observation period.

Wu CY et al. [10] studied changes in endotracheal tube cuff pressure during laparoscopic surgery in head-up or head-down position. They studied 70 patients undergoing elective laparoscopic colorectal tumor resection (head-down position, n = 38) and laparoscopic cholecystectomy (head-up position, n = 32) and compared them to 15 patients undergoing elective open abdominal surgery. Changes of cuff and airway pressures before and after abdominal insufflation in supine position and after head-down or head-up positioning were analysed and compared. They found no significant cuff and airway pressure changes during the first fifteen minutes in open abdominal surgery. After insufflation, the cuff pressure increased from 26±3 to 32±6 and 27±3 to 33±5 cmH₂O in patients of laparoscopic cholecystectomy and laparoscopic colorectal tumour resection respectively (both p < 0.001). The head-down tilt further increased cuff pressure from 33±5 to 35±5 cmH₂O (p < 0.001). They concluded that increase of endotracheal tube cuff pressure occurred during laparoscopic surgery especially in the head-down position. Our study results are similar with cuff pressure increasing in response to pneumoperitoneum as well as Head Down or Trendelenburg position. This could be due to rapid diffusion of nitrous oxide and carbon dioxide through cuff wall which led to increase the cuff pressure. This was supported in a study by Lumb AB et al. [11] that studied the effect of nitrous oxide and carbon dioxide on the cuff pressure of a laryngeal mask both in vitro and in vivo. They showed that nitrous oxide and carbon dioxide diffuse across the cuff wall much more rapidly than nitrogen and oxygen.   

In the beginning of Covid-19 pandemic, there have been concerns raised about the possible generation of aerosols contaminated with SARS Cov-2 from leaked CO₂ and smoke generation after the use of energy devices in laparoscopic surgeries. This apprehension leads to decreased number of laparoscopic surgeries during Covid-19 pandemic [12]. Even the elective gynaecological surgeries were limited during Covid pandemic due to concern regarding risk of viral transmission and safety of health care workers [13]. This situation leads to smaller sample size of our study. Studies with larger sample size are required to validate the findings of the present study. 

Limitations

The COVID-19 pandemic led to the decreased sample size of our study as there were less number of elective surgical procedures performed during this period. Studies with larger sample size are required to validate the findings of the present study.

The present study highlights the importance of position of patient during surgery on the cuff pressures while using Ambu Aura Gain Supraglottic airway device during laparoscopic surgeries. We found in this study that Trendelenburg or Head down position increases intra cuff pressure as compared to Reverse Trendelenburg position. So, it is recommended to monitor intra cuff pressure of SGA frequently in laparoscopic surgeries.

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