it has many benefits over other iv induction agents , but it is associated with hypotension on induction of anesthesia . different methods have been employed with variable results to counter the hypotensive effects of propofol including slow drug administration , preloading with iv fluids , co - administration of ephedrine , phenylephrine , ketamine etc . ephedrine is a mixed - acting sympathomimetic drug that stimulates both alpha and beta adrenergic receptors . a thorough search of literature could not reveal any comparative study of these two drugs in equipotent doses during general anesthesia . the objective of this study was to comparatively evaluate the efficacy of ephedrine versus phenylephrine in preventing propofol induced hypotension during induction of anesthesia . this randomized , double blind study was conducted between september 03 , 2009 and september 09 , 2010 . after approval from ethical review committee of the hospital ( 1059-ane / erc-08 ) , 135 american society of anesthesiologists ( asa ) i - ii patients of either sex , aged between 18 and 60 years , undergoing elective surgery requiring general anesthesia , patients scheduled for emergency surgery , patients with known hypertension , thyroid disease , peripheral vascular disease , ischemic heart disease , cardiac arrhythmias or having cardiac pace maker , patients taking any heart rate modifying drugs , monoamine oxidase inhibitors , or drugs affecting autonomic nervous system and patients allergic to any of the study drugs were excluded from the study . after obtaining written informed consent , patients meeting the inclusion criteria were randomized and allocated to one of the three study groups by using sealed opaque envelope method . group propofol - phenylephrine ( pp ) : 2 ml ( 50 mcg / ml ) phenylephrine . group propofol - ephedrine ( pe ) : 2 ml ( 4 mg / ml ) of ephedrine . for purpose of comparison we calculated the equipotent doses of phenylephrine and ephedrine from the study of saravanan et al . that demonstrated a relative potency ratio for phenylephrine : ephedrine of 80:1 ( 100 mcg : 8 mg ) . study drug was prepared by drawing 20 ml propofol ( 1% ) and 2 ml lignocaine ( 2% ) in 25 ml syringe . the study drug was added to this mixture according to the study group mentioned above to make a total volume of 24 ml ( containing 8.33 mg / ml propofol ) . all the study drugs were prepared by an anesthesiologist who was not involved in data collection and analysis . all patients were premedicated with oral midazolam 7.5 mg 1 h before the operation . in the operating room , standard baseline sbp , dbp , map and heart rate were taken from an average of two readings taken 5 min apart by the primary investigator . after securing iv access , anesthesia was induced by using mixture of propofol , lignocaine and study drug , according to assigned group , over 1 min through an iv infusion pump ( graseby syringe pump 3400 ) by the primary investigator , who was blinded to the study drug . after administering the calculated induction dose ( 2 mg / kg ) of propofol , if needed an additional one ml of the same mixture was given every 10 s until hypnosis was achieved as assessed by loss of verbal response from the patient . any patient requiring more than three propofol increments was planned to be excluded from the study but none of our patients required more than three propofol increments . all the patients were ventilated with a bag valve mask for 5 min using 40% oxygen in nitrous oxide and isoflurane at 1% . sbp , dbp and mean blood pressure and heart rate readings were recorded every minute for upto 5 min after induction . at this point , the study was terminated , and rest of the anesthesia technique was left at the discretion of primary anesthetist . hypotension requiring treatment was defined as a decrease in map to 60 mmhg or less . in case of a decrease in map to 60 mmhg or less , 200 ml bolus of normal saline was infused over 2 min followed immediately by another 200 ml bolus if needed ( to a maximum of 400 ml ) . if this failed to raise the blood pressure to > 60 mmhg , incremental doses of either phenylephrine 100 mcg ( if heart rate was > 60 beats / min ) or ephedrine 8 mg ( if heart rate was < 60 beats / min ) were given . isolated bradycardia ( heart rate < 50/min ) without associated hypotension , was treated with injection atropine 0.5 mg intravenously . the number of patients required in each group was determined by using power analysis based on the previous study . the sample size required detecting 20% reduction in map from baseline at 5% level of significance and 80% power was 45 patients in each group . data was entered and analyzed in statistical software statistical package for social sciences ( spss ) version 19.0 , ( spss inc . , frequencies and percentage were computed for gender , asa level and hypotension among the groups and analyzed by chi - square test . means and standard deviations were estimated for age , weight , height , body mass index and for hemodynamic response like sbp and dbp , map , heart rate and analyzed by analysis of variance with post - hoc multiple comparison test after normality assumptions by kolmogorov  smirnov and shapiro  wilk test . chi - square test was used to compare proportion difference for prevention of hypotensive response among groups . a total of 135 patients scheduled for elective surgical procedure under general anesthesia were included in this study , and all of them completed the study . no significant differences were observed in age , weight , height , gender , asa level , baseline heart rate , sbp , dbp and mean blood pressure . comparison of demographic and bl data among groups mean hemodynamic responses of groups pp and pe ( study groups ) were compared with group ps ( control group ) and compared with each other to see significant differences . systolic blood pressure at each minute was compared among control group ( group ps ) and both study groups ( groups pp and pe ) . a statistically significant difference was found in groups pp and pe from min 1 to 5 as compared to control group [ figure 1 ] . similarly the difference in dbp at each minute was statistically significant from min 1 to 5 in group pp as compared to control the group . in group pe , dbp was found to be significantly different from min 2 to 5 as compared to control the group [ figure 2 ] . the map in groups pp and pe was significantly different at all times in comparison with group ps [ figure 3 ] . comparison of mean systolic blood pressure with respect to time among propofol - saline ( ps ) , (  ) , propofol - phenylephrine ( pp ) , (  ) and propofolephedrine ( pe ) , (  ) . * p < 0.05 ps versus pp ; p < 0.05 ps versus pe ; # p < 0.05 all multiple groups comparison significant comparison of mean diastolic blood pressure with respect to time among propofol - saline ( ps ) , (  ) , propofol - phenylephrine ( pp ) , (  ) and propofolephedrine ( pe ) , (  ) . * p < 0.05 ps versus pp ; p < 0.05 pp versus pe ; # p < 0.05 all multiple groups comparison significant comparison of mean arterial pressure with respect to time among propofol - saline , (  ) , propofol - phenylephrine , (  ) and propofol - ephedrine , (  ) . # p < 0.05 all multiple groups comparison significant the change in heart rate was significant in group pp in 1 and 2 min as compared to control the group . group pe did not show any significant difference in heart rate in comparison with the control group . results demonstrated decrease in heart rate in patients who received the phenylephrine [ figure 4 ] . comparison of mean heart rate with respect to time among propofolsaline ( ps ) , (  ) , propofol - phenylephrine ( pp ) , (  ) and propofol - ephedrine ( pe ) , (  ) . * p < 0.05 ps versus pp ; p < 0.05 pp versus pe 
 table 2 shows the rate of hypotension that was significantly higher in group ps than group pp ( 60% vs. 24.4% p = 0.001 ) . similarly , this difference was also significant in groups ps and pe ( 60% vs. 31.1% p = 0.006 ) . comparison of hypotension among groups in comparison of groups pp and pe , sbp values were significantly different from min 1 to 3 [ figure 1 ] . in contrast dbp values were significant for a longer period , that is , from 1 to 5 min [ figure 2 ] . the map also came to be significantly different from min 1 to 5 [ figure 3 ] . these values show better control of sbp , dbp and map in group pp than group pe . heart rate was found to be decreased from the baseline in group pp than group pe [ figure 4 ] . when the rate of hypotension was compared between groups pp and pe , significant difference was not observed as shown in table 2 ( 24.4% vs. 31.1% p = 0.48 ) . four patients in group ps , two patients in group pe and one patient in group pp required iv normal saline for treatment of hypotension and they responded adequately . none of the patient required ephedrine , phenylephrine or atropine for treatment of hypotension or bradycardia . hypotension following induction of anesthesia using propofol is caused by propofol - mediated decrease in sympathetic activity including decrease in systemic vascular resistance and decrease in cardiac output by a combination of venous and arterial vasodilation , impaired baroreflex mechanism and depression of myocardial contractility . independent of the presence of cardiovascular disease , the incidence of this propofol - mediated hypotension ranges from 25% to 67.5% . since we used a standard ( fixed ) dose of propofol , our population may have experienced more vasodilatation as compared to other populations . our study demonstrated a significant reduction in the incidence of propofol induced hypotension with simultaneous administration of phenylephrine or ephedrine mixed with propofol . our findings are consistent with the findings of imran et al . who have shown a dose related ( 50 mcg vs. 100 mcg ) incidence of hypotension ( 56% vs. 20% ) when phenylephrine was combined with propofol dhungana et al . in their study compared preloading with haemaccel ( colloid fluid ) and ephedrine for prevention of hypotension during propofol induction . they found that only 22.5% patients developed hypotension when ephedrine ( 0.2 mg / kg , mean dose 10 mg ) was used compared with 23.1% in colloid group and 67.5% in control group . in our study slightly more ( 31.1% ) patients in the ephedrine group became hypotensive which can be attributed to a relatively lower dose of ephedrine ( 8 mg ) used in our study . observed an attenuation of hypotension , associated with propofol induction with the use of a prophylactic ephedrine . they used ephedrine in the dose of 0.1 mg / kg and 0.2 mg / kg iv 1 min before induction of anesthesia with propofol and fentanyl . gamlin et al . observed effective obtundation of hypotension accompanied with tachycardia as higher doses of ephedrine ( 15 , 20 and 25 mg ) was used in their study . we did not observe a statistically significant increase in the heart rates in patients receiving ephedrine in our study . however we found statistically significant decrease in heart rates in patients receiving phenylephrine in the 1 and 2 min after induction of anesthesia . propofol alters the baroreflex mechanism , resulting in a smaller increase in heart rate for a given decrease in arterial pressure . recent studies suggest that induction of anesthesia with propofol attenuates desflurane - mediated sympathetic activation . this fact probably further contributed to the significant decrease in heart rate in patients who received phenylephrine ( group pp ) . ephedrine seems to counteract and compensate for the decrease in heart rate associated with administration of propofol , and the heart rate remained stable at baseline in patients who received ephedrine . we found that both phenylephrine and ephedrine effectively maintained a significantly higher level of map than the control group . in equipotent doses , phenylephrine is as good as ephedrine in preventing the hypotensive response to an induction dose of propofol .
background and aims : propofol , the most commonly used intravenous ( iv ) anesthetic agent is associated with hypotension on induction of anesthesia . 
 different methods have been used to prevent hypotension but with variable results . 
 the objective of this study was to evaluate efficacy of equipotent doses of phenylpehrine and ephedrine in preventing the hypotensive response to the induction dose of propofol.material and methods : one hundred thirty five adult patients were randomised to one of the study groups : propofol - saline ( ps ) , propofol - phenylephrine ( pp ) or propofol - ephedrine ( pe ) by adding study drugs to propofol . 
 anesthesia was induced with a mixture of propofol and the study drug . 
 patients were manually mask - ventilated for 5 min using 40% oxygen in nitrous oxide and isoflurane at 1% . 
 a baseline mean arterial pressure ( map ) was recorded prior to induction of anesthesia . 
 systolic , diastolic and mean blood pressure and heart rate were recorded every minute for up to 5 min after induction . 
 hypotension was defined as a 20% decrease from the baseline map.results:there were no significant demographic differences between the groups . 
 overall incidence of hypotension in this study was 38.5% ( 52/135 ) . 
 rate of hypotension was significantly higher in group ps than group pp ( 60% vs. 24.4% p = 0.001 ) and group pe ( 60% vs. 31.1% p = 0.005 ) . 
 in contrast , a significant difference in rate of hypotension was not observed between groups pp and group pe.conclusion:in equipotent doses , phenylephrine is as good as ephedrine in preventing the hypotensive response to an induction dose of propofol .