propofol as sole anesthetic agent is extensively used for placement of supraglottic airway devices ( sgads ) such as classic laryngeal mask airway ( clma ) , i - gel , proseal lma , etc . the insertion of these devices requires sufficient depth of anesthesia for the relaxation of jaw muscles and suppression of upper airway reflexes such as coughing , gagging and laryngospasm . propofol is considered as the superior intravenous ( i.v ) induction agent in achieving the optimum conditions for lma insertion , compared with thiopentone and other i.v induction agents . limited number of studies are available on the anesthetic requirement needed for newer sgads , in comparison to the plethora of studies on dose requirements for clma . dixons up - and - down method has been successfully used previously to determine the dose of propofol required for insertion of supraglottic devices . a minimum of 6 cross - over points is needed for this method to be used effectively . our primary aim was to find the dose of propofol required for smooth insertion of i - gel in the first attempt and to compare it with the clma using dixon 's up - and down method . hemodynamic stability with these doses and complications , if any were studied as a secondary objective . we postulated that i - gel produces less stimulation to the airway and thus would require lesser dose of propofol than lma . the written informed consent was obtained from 60 american society of anesthesiologists ( asa ) grade i and ii patients between 18 and 65 years scheduled for elective surgery of < 2 h. patients were randomly assigned into two groups by computer generated randomized table that consisted of group l : lma insertion with propofol and group i : i - gel insertion with propofol . nonconsenting patients , pregnant women , lactating mothers , patients with unstable medical conditions , with known allergy to propofol and patients with difficult airway were excluded . on arrival in the operation theater , monitoring was commenced with noninvasive arterial blood pressure , electrocardiogram ( ecg ) monitor and pulse oximeter . patients were premedicated with injection glycopyrrolate 0.004 mg / kg i.v , injection ondansetron 0.08 mg / kg i.v , injection ranitidine 1 mg / kg i.v , injection fentanyl 2 ug / kg i.v , injection midazolam 0.02 mg / kg i.v . patients were preoxygenated for 5 min and ringer 's lactate 5 ml / kg was administered in this period . patients then received predetermined dose of propofol intravenously beginning with 2 mg / kg for the first patient in each group given over 30 s. i - gel or lma was inserted 60 s after propofol injection . the term  movement  was defined as resistance in mouth opening , gross purposeful movement , coughing , straining or laryngospasm occurring after insertion of the device or during airway manipulations before an effective airway is established . the term  no movement  was defined as the absence of bucking or gross purposeful movements after insertion of the device until an effective airway is established . when a patient 's response was  movement ,  additional bolus doses of propofol 0.5 mg / kg were given and insertion reattempted at 30 s intervals until insertion was successful or 3 attempts were reached . device was connected to the breathing system and bilateral , and equal air entry was confirmed by symmetrical chest movements and auscultation . adequate airway without leak was confirmed by capnography . in the case of failure to insert device in three attempts or any complications like desaturation , severe hypotension requiring endotracheal intubation , patient was oxygenated with 100% oxygen , succinyl choline 2 mg / kg was administered and trachea was intubated using cuffed endotracheal tube of appropriate size . hemodynamic parameters like pulse , blood pressure and ecg changes and respiratory parameters like spo2 and end tidal co2 were noted when the patient was taken inside the operation theatre ( 0 min i.e. , baseline ) , after 3 min of premedication , at the start of propofol bolus and every minute for next 5 min thereafter . all the patients were observed for adverse events like bronchospasm , laryngospasm during insertion , maintenance or after removal of the device . the device was removed at the end of surgery after patients were conscious , obeying verbal commands . postoperatively each patient was followed for 24 h to note the incidence of sore throat . the doses of propofol for each patient were predetermined by modifications of dixon 's up - and - down method . in each group , for the next patient , the dose of propofol was increased by 0.5 mg / kg if the response in preceding patient was judged as  movement  or decreased by 0.5 mg / kg if response in preceding patient was  no movement . the step size that is , 0.5 mg / kg approximates the estimated standard deviation derived from previous studies hence , each patient in the study group received a predetermined dose of propofol depending upon previous patient 's response . response of each patient with the dose used , was plotted on a graph , with the patient 's response on x axis and dosage in mg / kg on y axis . propofol dose was then determined by calculating the midpoint dose of all independent pairs of patients using a cross - over technique that is  movement  to  no movement . the ed50 for i - gel and lma groups were defined as the average of the cross - over midpoints in each group . for the successful use of this method we studied 30 patients in each group and obtained 10 - 11 cross - over midpoints in both the groups . with the appropriate starting dose , dixon 's up - and - down method requires a minimum of 6 cross - over points in each group for estimation of ed50 . assuming a positive result with the starting dose , a minimum of 13 patients would have to be recruited in each group . the starting dose has to be the minimum dose expected to result in a positive response that is , no movement to insertion of the device in our case . based on previous studies we started with a dose of 2 mg / kg of propofol for both devices . the step size , that is , 0.5 mg / kg , approximates to the estimated standard deviation derived from previous studies . given the less stimulatory nature of i - gel on the airway and based on our pilot study , we hypothesised that i - gel would require at least 0.5 mg / kg less propofol as compared to clma . to detect a difference of 0.5 mg / kg dose requirement of propofol ( power 90% , alpha error 0.05 and beta error 0.10 with a standard deviation of 0.5 mg / kg ) a minimum of 22 patients , 233 south wacker drive , 11 floor , chicago , il 60606 - 6412 ) . for each parameter mean and standard deviation were calculated to estimate the significance . difference between the groups was measured by anova test . for other categorical data like adverse events , with the appropriate starting dose , dixon 's up - and - down method requires a minimum of 6 cross - over points in each group for estimation of ed50 . assuming a positive result with the starting dose , a minimum of 13 patients would have to be recruited in each group . the starting dose has to be the minimum dose expected to result in a positive response that is , no movement to insertion of the device in our case . based on previous studies we started with a dose of 2 mg / kg of propofol for both devices . the step size , that is , 0.5 mg / kg , approximates to the estimated standard deviation derived from previous studies . given the less stimulatory nature of i - gel on the airway and based on our pilot study , we hypothesised that i - gel would require at least 0.5 mg / kg less propofol as compared to clma . to detect a difference of 0.5 mg / kg dose requirement of propofol ( power 90% , alpha error 0.05 and beta error 0.10 with a standard deviation of 0.5 mg / kg ) a minimum of 22 patients were required in each group . , 233 south wacker drive , 11 floor , chicago , il 60606 - 6412 ) . for each parameter mean and standard deviation were calculated to estimate the significance . difference between the groups was measured by anova test . for other categorical data like adverse events , there were no significant differences between both groups with respect to demographic variables [ table 1 ] . graphs 1 and 2 show propofol dose given to each patient in particular study group and response to device insertion that is ,  movement  and  no movement  at corresponding propofol dose . the cross - over points from movement to no movement are highlighted using arrows in graphs . ed50 of propofol , which was calculated as the average of the cross - over midpoints in each group was significantly higher in the lma group 2.70  0.28 mg / kg ( mean  standard deviation [ sd ] ) when compared to i - gel group 2.02  0.26 mg / kg ( mean  sd ) ( p < 0.001 ) [ table 2 ] . propofol dose in each patient with response laryngeal mask airway group propofol dose in each patient with response i - gel group ed50 of propofol by dixon 's up - and - down method the arterial pressure and heart rate were comparable between the two groups [ graph 3a  c ] . peripheral limb movements and resistance to mouth opening were the most common types of movement noted in both the groups , which were overcome by using additional dose of propofol . hiccups were noticed in one patient in i - gel group , which could be treated by additional propofol boluses [ table 3 ] . ( c ) comparison of mean diastolic blood pressure profile of response to device insertion adverse events such as bronchospasm , laryngospasm , hypotension , regurgitation and aspiration were not observed in any of the groups . four patients in lma group complained of sore throat , which was statistically more significant when compared to i - gel group where no patient had sore throat [ table 4 ] . the optimum dose of propofol required to insert sgads , without using neuromuscular blockers , while providing hemodynamic stability remains a challenge . the dose requirement can also influence the choice of sgad especially where hemodynamic stability is desired . the major finding of this study was that the propofol requirement for smooth insertion of the i - gel was significantly less ( p < 0.001 ) [ table 2 ] than that of lma insertion . this was expected because of the less stimulatory effect of the i - gel on the airway due to its composition of soft thermoelastic polymer . amr and amin found that use of propofol at 2.5 mg / kg produced comparable insertion conditions for i - gel compared with thiopentone sodium ( 7 mg / kg ) . they used fixed dose of propofol 2.5 mg / kg for every patients and premedication was not given unlike our study where we used dixons up - and - down method along with fentanyl 2 microg / kg and midazolam 0.02 mg / kg as premedication . our study estimated the ed50 of propofol required for lma insertion to be 2.70  0.28 mg / kg . this is higher than the study by tanaka and nishikawa who found propofol requirements after fentanyl for lma insertion to be 1.42  0.26 ( 1.15 - 1.69 ) mg / kg . also in the study conducted by burlacu et al . propofol requirement was 2.33  0.37 mg / kg , as they used alfentanil 5 microg / kg for co - induction unlike our study , where we used fentanyl 2 microg / kg . reported that co - administration of alfentanil - propofol provided better insertion condition for lma than fentanyl - propofol . also our criterion of smooth insertion ( i.e. , the definition of  no movement ) may have been relatively strict compared to study conducted by tanaka and nishikawa . the statistically significant difference in the requirements of propofol for the placement of the i - gel and lma suggests that upper airway stimulation is lesser during insertion of i - gel . it is possible that the potent inhibitory effect of fentanyl on the upper airway reflexes may have masked the different airway stimulating effects of the two devices . tanaka and nishikawa using similar study design demonstrated the same masking effect of co - induction when using fentanyl . in our study , there was neither any significant fall or increase in systolic and diastolic blood pressure and heart rate in both the groups . these findings were almost similar to study by helmy et al . where they found no statistical significant difference between both i - gel and lma regarding hemodynamic parameters . shin et al . also found no difference in hemodynamic data immediately after the insertion of i - gel , proseal lma and classic lma . propofol reduces arterial blood pressure due to reduction in sympathetic tone and direct venodilator effect . as the patients in the lma group received higher mean dosage of propofol , a steeper fall in blood pressure was expected . however the hemodynamic stability observed in our study can be contributed to the hypotension produced by propofol , which offsetted the pressor responses of lma . none of the patients either in lma or i - gel group developed coughing , gagging or laryngospasm which correlates with the study done by gatward et al . and kannaujia et al . this may be due to the use of dixon 's method for dose choice , where higher dose was used if previous patient had movement with lower dose instead of using a fixed dose for whole group . this method minimized the chances of oropharyngeal and laryngeal stimulation at lighter plane of anesthesia . we can not exclude the possibility of potent inhibitory effect of fentanyl on upper airway reflexes . none of the patients of both study groups had obvious aspiration or regurgitation similar to study done by kannaujia et al . and brimacombe et al . greenberg et al . observed that immediate postoperative sore throat was complained by 33 patients in patients with lma insertion . in our study , four patients in lma group had immediate postoperative sore throat as compared to none in i - gel group which correlates with the study by shin et al . this could be because of the soft gel like noninflatable cuff of i - gel , which causes minimal tissue compression and thus maintains blood flow to the laryngeal and perilaryngeal framework , whereas cuff of lma can absorb anesthetic gases leading to increased mucosal pressure . however , these results need to be interpreted as per the limitations of our protocol . the dose of propofol required has been calculated by use of dixon 's up - and - down method where we obtained 11 cross - over points against a minimum of 6 which is a valid technique . also the results for hemodynamic effects and incidence of sore throat need to be validated with a study of larger number of patients . we studied only low risk patients ( asa i or ii ) who had normal airways and were not obese . also comparing the performance of the likely competitors of the i - gel like proseal lma would help in clarifying the choice of sgads . propofol requirement for successful smooth insertion of i - gel was significantly less ( p = 0.0001 ) compared to classic lma . the postoperative complications are not significantly different among i - gel and lma patients except for overall low incidence ( 13.3% ) of sore throat seen only in the lma group .
background and aims : propofol is the drug of choice when used as sole anesthetic agent for placement of supraglottic airway devices . we aimed to find and compare the propofol dose required for smooth first attempt insertion of i - gel versus the classic laryngeal mask airway ( clma ) using dixon 's up - and - down method.material and methods : prospective randomized controlled trial ( n-60 ) was planned . 
 i - gel or clma was inserted 60 s after propofol injection whose dose was calculated based on previous patients response as per dixon 's up - and - down method . 
 propofol requirements for successful placement of devices was noted and compared . 
 difference between the groups was measured by anova . 
 a p < 0.05 was considered as statistically significant.results:significantly lower ( p < 0.001 ) propofol dose was required for i - gel ( 2.02  0.26 mg / kg ) insertion than clma ( 2.70  0.28 mg / kg).conclusions : i - gel requires significantly lower dose of propofol for insertion when compared to clma .