Comparison of Anaesthesia Requirement for Ventilation With Endotracheal Tube Versus Proseal Laryngeal Mask Airway

Comparison of Anaesthesia Requirement for Ventilation With Endotracheal Tube Versus Proseal Laryngeal Mask Airway

Anaesthesia Requirements for Ventilation With Endotracheal Tube Versus ProSeal Laryngeal Mask Airway During Automated Feedback-Loop Controlled Total Intravenous Anaesthesia in Patients Undergoing Laparoscopic Cholecystectomy: A Randomised Controlled Study

Endotracheal tube (ETT) is the gold standard conduit for providing controlled ventilation during general anaesthesia (GA). however, the supra-glottic airway (SGA) devices in particular the laryngeal mask airway (LMA) and its variants have become a reliable alternative to ETT for carrying out controlled ventilation. Of the several variants of LMA available today, the proseal LMA (PLMA) is preferred for controlled ventilation. The various advantages of LMA includes, a lower incidence of postoperative sore throat and superior haemodynamic profile during surgery. However, one aspect of providing anaesthesia with LMA compared to ETT is the ability of LMA to maintain equivalent depth of anaesthesia with lower anaesthetic requirement, is quiet intriguing and evidence to this regard is very limited. By measuring the anaesthesia requirement using a robust computerised delivery system such as the closed loop anaesthesia delivery system (CLADS) we can establish for sure the anaesthesia required for maintaining intraoperative mechanical ventilation with the use of these two (ETT and PLMA) airway management devices. This randomised controlled study aims to calculate the anaesthesia requirement as determined by the total amount of propofol consumed for maintaining anaesthesia with ETT versus PLMA

Endotracheal tube (ETT) is the gold standard conduit for providing controlled ventilation during general anesthesia (GA). However, since the introduction of classic laryngeal mask airway (LMA) in the 1980's and serial evolution of supra-glottic airway devices (SGA) thereafter, LMAs have become a reliable alternative to ETT for carrying out controlled ventilation. Interestingly, of the additional advantages that the LMA proffers, including, a lower incidence of postoperative sore throat (POST) and superior hemodyamic profile during surgery; its ability to maintain equivalent depth of anesthesia (in comparison to when ETT-GA) with lower anesthetic requirement, is intriguing. A handful of studies have demonstrated that the end-tidal isoflurane concentration required for maintenance of GA is 0.2 -0.53% greater with use of ETT as compared to LMA. However, the evidence generated by these studies remains unsubstantiated because in them, anaesthetic gas concentration was titrated to patient's clinical profile like heart rate and blood pressure without the backing of specific protocol for maintaining depth-of-anaesthesia. Therefore, for credible evidence, assessment of quantitative anesthetic requirement for achieving and sustaining a steady anesthesia depth with either LMA or ETT warrants confirmation with the use of an objective depth-of-anesthesia monitor, such as, bispectral index (BIS). Closed loop anaesthesia delivery system (CLADS) is an indigenously developed patented (502/DEL/2003) computer-controlled and BIS-guided automated anesthesia delivery system. CLADS, which runs on a control algorithm based on the relationship between diverse rates of propofol infusion and the processed EEG variable; delivers propofol infusion at a rate which is continuously adjusted by patient's state of depth of anesthesia as per BIS monitoring input. This automated system maintains anaesthesia depth with high accuracy and objectively determines propofol delivery quantitatively. Of the several variants of SGA available today, the ProSeal laryngeal mask airway (PLMA) 9 is preferred for controlled ventilation for its unique design that serves dual function of a ventilation tube and an oropharyngeal drainage tube for excluding gastric contents from getting aspirated through the peri-laryngeal cuff seal. Given that CLADS can help us to accurately quantify anaesthesia, we hypothesize that there is no difference in anesthesia requirement for GA maintained through an ETT or a PLMA. This randomized controlled study aims to compare: anaesthesia requirement as determined by total propofol consumption (primary objective); intraoperative hemodynamic profile and incidence of POST (secondary objectives) in patients undergoing laparoscopic surgery with controlled ventilation via ETT or PLMA.

160-patients will be randomly divided into one of the two groups: Group-I (ETT group, n= 80) ETT will be used as the airway device for maintaining ventilation Group-2 (PLMA group, n= 80) PLMA will be used as the airway device for maintaining ventilation

The attending anaesthesiologist will not be blinded to the technique utilized to administer GA. An independent assessor unaware of the technique utilized for administering GA will analyse the intraoperative data and conduct the postoperative follow up

Anesthesia will be induced with fentanyl-citrate (3µg/kg) and propofol (dose determined by automated system based on continuous BIS feedback from the patients). Atracurium besylate 0.5-mg/kg will be given to facilitate placement of airway device. Propofol administration rate will be controlled by a feedback loop facilitated by BIS monitoring using the closed-loop anaesthesia delivery system (CLADS). A BIS value of 50 will be used as the target point for induction and maintenance of GA. Intraoperative ventilation will be instituted through a polyvinyl chloride (PVC) ETT (Portex, Smiths Medical ASD, Inc, Minneapolis, USA). The size of the tube will be standardized for the male (7.5 mm ID) and the female (6.5 MM ID).

Anesthesia will be induced with fentanyl-citrate (3µg/kg) and propofol (dose determined by automated system based on continuous BIS feedback from the patients). Atracurium besylate 0.5-mg/kg will be given to facilitate placement of airway device. Propofol administration rate will be controlled by a feedback loop facilitated by BIS monitoring using the closed-loop anaesthesia delivery system (CLADS). A BIS value of 50 will be used as the target point for induction and maintenance of GA. intraoperative ventilation will be maintained with PLMA (Telefex Medical, Westmeath Ireland) whose size would be selected based on body weight. In patients weighing 30-50 kg PLMA # 3.0, 50-70 kg PLMA # 4.0, and 50-100 kg PLMA # 5.0 will be inserted.

After induction of anaesthesia patient will be intubated with polyvinyl chloride (PVC) ETT for maintaining intraoperative ventilation. Anaesthesia will be maintained with propofol and the administration rate will be controlled by a feedback loop facilitated by BIS monitoring using the closed-loop anaesthesia delivery system (CLADS). A BIS value of 50 will be used as the target point for induction and maintenance of GA.

After induction of anaesthesia ProSeal Laryngeal Mask Airway (PLMA) will be inserted for maintaining intraoperative ventilation. Anaesthesia will be maintained with propofol and the administration rate will be controlled by a feedback loop facilitated by BIS monitoring using the closed-loop anaesthesia delivery system (CLADS). A BIS value of 50 will be used as the target point for induction and maintenance of GA.

Determined by the percentage of the total anaesthesia time in which the BIS scores remain within a score of 10% of the target BIS (i.e. BIS-50) in both the study arms.

Determined by using Varvel criteria parameters; median performance error (MDP), median absolute performance error (MDAPE), wobble and global score in both the study arms

Comparison of intra-operative blood pressure- systolic, diastolic, and mean between both the arms will be done

Inclusion Criteria: ASA physical status I/II Undergoing elective laparoscopic cholecystectomy Exclusion Criteria: Anticipated difficult airway Body mass index > 30-kg/m2 Uncompensated cardiovascular disease (e.g. uncontrolled hypertension, atrio-ventricular block, sinus bradycardia, congenital heart disease, reduced LV compliance, diastolic dysfunction) Hepato-renal insufficiency Uncontrolled endocrinology disease (e.g. diabetes mellitus, hypothyroidism) Known allergy/hypersensitivity to the study drug (propofol) Drug dependence/substance abuse/psychiatric illness Requirement of postoperative ventilation Refusal to informed consent