A Comparative Study on The Role of Phenylephrine and Mephentermine in the Treatment of Hypotension During Spinal Anaesthesia for Caesarean Section

Introduction: Spinal anaesthesia used in Caesarean section can cause hypotension a common yet serious problem in anaesthesiology. Preloading with intravenous fluids, left uterine displacement with an aim to shift the pregnant uterus away from the aorta and vena cava and administration of vasopressor drugs are the standard techniques used to counter this spinal anaesthesia. Though various vasopressor agents have been tried but none has been proved to be conclusively better over the others. This study was undertaken to compare the effects of bolus intravenous phenylephrine and mephentermine in the treatment of hypotension during spinal anesthesia for Caesarean Section. Materials and Methods: This was a Prospective, Randomized, Parallel Group, Double Blind Study with Simple Random Sampling conducted in a 600 bed multi-speciality teaching hospital between April 2018 to March 2019. The study participants included a total of 100 singleton full term pregnant women of age-group 19-38 years planned for elective Caesarean section under spinal anaesthesia and developed hypotension subsequently. The study participants were randomly selected and allocated into 2 groups of 50 participants each. One group received 100 mcg phenylephrine while the other group received 6 mg mephentermine through bolus IV injection. The study was conducted following approval of the Institutional Ethics Committee. Results: The results were analysed using descriptive statistics, unpaired Student t-test, Chi-square test using SPSS version 19.0. Both the vasopressors maintained SBP above the hypotensive range though phenylephrine had significantly higher SBP at 6 minutes after its administration (p value 0.010) when compared to mephentermine. The DBP was also significantly higher in the group receiving phenylephrine (p<0.05). However, the heart rate was significantly higher for the group receiving mephentermine at all time points of comparison. The group receiving mephentermine also required more number of doses. Conclusion: The study concluded that through both the vasopressors can be used to treat hypotension during spinal anaesthesia for caesarean section, phenylephrine has some advantage over mephentermine.