Hemodynamics changes with spinal anesthesia is mainly due to sympathetic block which causes mainly hypotension & bradycardia. Post spinal hypotension usually leads to various adverse maternal and fetal outcomes. Hence, effective prevention and treatment of maternal hypotension is of great clinical significance. Various studies have been done for the prevention of subarachnoid block induced hypotension but the optimal choice of vasopressors for the maintenance of hemodynamic stability during cesarean under spinal anesthesia is still unclear. The ideal vasopressor would be the one which is reliable and easy to use , has rapid onset, short duration of action, easily tritatable, can potentially be used prophylactically and lack any adverse maternal and fetal impact. Thus, aim of study is to compare the hemodynamic stability of mephenterime and phenylephrine during elective cesarean section under spinal anesthesia. The methodology of the study will be prospective, randomized double blinded study where patient meeting inclusion criteria for the study is divided into two groups ( Group M n=21) and ( Group P n= 21) i.e. Group M receives intravenous bolus of mephentermine 6mg and intravenous bolus of 50mcg. Hemodynamics changes in blood pressure and heart rate will monitored and compared among the study groups receiving intravenous boluses of study drugs. Data will be collected in proforma and saved by entering in the MS- EXCEL as well. Data will be analyzed using the statistical package for the social sciences (SPSS) version 27. The categorical data will be analyzed with Chi-square test and numerical variables of hemodynamic parameters between the study groups will be analyzed using student t- test. P-value < 0.05 will be considered statistically significant.

Hence, mephenterime and phenylephrine effectiveness will be studied for hemodynamic stability during cesarean section under spinal anesthesia

Spinal anesthesia is the most common administered neuraxial anesthetic technique for patient undergoing cesarean section due to its rapid and reliable onset and remains preferred choice for cesarean deliveries. The advantage of spinal anesthesia includes no airway manipulation, profound analgesia and anesthesia, minimal maternal and fetal drug exposure stable hemodynamic parameters (based on level of anesthesia), decrease intraoperative blood loss and provide postoperative pain control. Hemodynamics changes is due to sympathetic block which causes reduction in venous return which further reduces the cardiac output and blood pressure by activation of Bezold Jarisch reflex In addition, the vasodilatory effect due to prostaglandins, progesterone relaxin and nitric oxide during pregnancy and loss of intrinsic sympathetic vascular tone further exaggerated fall of blood pressure with prevalence of 50-90% despite of fluid preload and uterine displacement Various preventive measures like fluid preload , left lateral tilt , left uterine displacement and along with vasopressors such as mephentermine , phenylephrine have been tried to prevent hypotension Phenylephrine is currently recommended as 1st line of vasopressor which acts as alpha 1 agonist with negligible beta action increasing blood pressure due to vasoconstriction whereas it causes dose dependent bradycardia and decrease cardiac output Mephentermine non catecholamine nondirectly acts on both adrenergic alpha and beta receptors and indirectly by releasing norepinephrine and epinephrine that increases blood pressure and augments cardiac output whereas tachyphylaxis may occur rapidly.

This study would help to compare the effectiveness of phenylephrine and mephentermine for maintenance of hemodynamic parameters in patient undergoing cesarean section under spinal anesthesia.

Inclusion Criteria:

• Patient undergoing elective cesarean section under spinal anesthesia
• Age between 18-48 years
• ASA class II ( all pregnant are categorized as ASA II)

Exclusion Criteria:

• Patient refusal
• Contraindication to spinal anesthesia like coagulation disorder , localized infection , sepsis, raised intracranial pressure etc
• Patchy spinal block , failed spinal block converting to GA
• Hypersensitivity to any drugs
• High Risk Pregnancy ( preeclampsia, eclampsia, preterm, Gestational Diabetes , etc )

All parturient meeting the study inclusion criteria and receiving sub-arachnoid block for undergoing elective cesarean section at KIST MEDICAL COLLEGE AND TEACHING HOSPITAL

The patients will be randomly allocated to the two groups of study by sealed envelope method. Group M patients who will receive intravenous bolus dose of mephentermine 6mg and Group P who will receive intravenous bolus dose of phenylephrine 50 mcg The drug preparations phenylephrine 50mcg/ml and mephenterime 6mg/ml will be done and labelled with code numbers by anesthesia assistant for all the patient and it is provided to anesthesiologist for administration who is not involved in the study as they will not be actively involved in the study nor in the patient care. The other anesthesia assistant or intern will be monitoring and recording information on proformas. Therefore investigator and participant of the study were blinded to the study drugs.