Haemodynamic Effects of Oxytocin as Intravenous Bolus or Infusion on Women Undergoing Caesarean Section

Oxytocin is commonly used in obstetric practice as uterotonic drug for induction and augmentation of labour (1) and remains the drug of choice for facilitating uterine contractions during vaginal and operative delivery (2). Several regimens of oxytocin have been tested during cesarean delivery (CD) with variable wanted (uterotonic) and unwanted (cardiovascular) effects (3-7). When given as a rapid IV bolus it causes hypotension and tachycardia (1). Whilst its cardiovascular effects are widely know there is little agreement as to the mechanism by which they occur. Some studies suggest that the preservative chlorobutanol is the cause of these haemodynamic changes. Oxytocin is an octapeptide secreted by the posterior pituitary alongwith ADH. oxytocin is inactive orally and is generally administered by intramuscular or intravenous routes. It's rapidly degraded in liver and kidney with a plasma half life of 6 min and is still shortened at term. oxytocin action on myometrium is independent of innervation. During pregnancy oxytocin is indicated for the initiation or improvement of uterine contractions. Where this is desirable and considered suitable for a reason of foetal or maternal concern in order to achieve vaginal delivery. It is indicated for induction of labour in patients with an indication for the excitation of labour such as rh incompatibility, maternal diabetes preeclampsia at or near term when delivery is in the best interest of mother and foetus or when membranes are prematurely ruptured and delivery is indicated (8) stimulation or reinforcement of labour as in selected cases of uterine inertia (9) as adjunctive therapy in the management of incomplete or inevitable abortion. In the first trimester curettage is generally considered primary therapy. In the second trimester oxytocin is successful in emptying the uterus. Introduction Abstract The haemodynamic effects of oxytocin in women undergoing caesarean section include tachycardia, hypotension and decrease in cardiac output. These can be sufficient to cause significant compromise in high risk patients. We aimed to find a simple way to decrease these risks while retaining the benefits of oxytocin for attaining uterine contractions and decrease bleeding after delivery. We recruited 50 patients undergoing elective caesarean section. They were randomly allocated to receive 10 U of oxytocin either as bolus injection over 15 seconds (Group A, n=25) or an infusion over 5 minutes (Group B, n= 25). Uterine tone was assessed as adequate or inadequate by an obstetrician. Intraoperative heart rate, noninvasive blood pressure, and EKG changes were recorded. The haemodynamic data along with the estimated blood loss were compared between the groups.Marked cardiovascular changes occurred in the bolus group the heart rate increased by the 27(13.9) beats per min compared with 7 (±4.7) beats per min in the infusion group. The mean arterial pressure decreased by 27(±8.4)mmhg in the bolus compared with 8 (±2.7) mm hg in the infusion group.In elective caserean cases, oxytocin infusion result In lesser hemodynamic changes than bolus oxytocin with lesser emetic episodes and that oxytocin is equally effective in reducing bleeding when given as an infusion.