Cardiovascular Effects of Intravenous Oxytocin in Elective Caesarean Section - A Study from Alappuzha, Kerala

Abstract

BACKGROUND Oxytocin is a peptide hormone produced in the hypothalamus, stored, and released by the posterior pituitary. Oxytocin is commonly administered during caesarean section to minimise blood loss. It can cause hypotension, tachycardia, arrhythmias, and decrease in cardiac output and ST-T wave changes which may be deleterious in hypovolemic and high-risk cardiac patients. Cardiovascular effects of oxytocin have not been well investigated. The purpose of this study was to determine the cardiovascular effects of oxytocin (5U) administered as rapid intravenous infusion over 1 minute followed by a maintenance infusion of 10U, study other adverse effects of oxytocin, assess uterine tone and the need for additional uterotonics and also assess the blood loss. We also wanted to maintain adequate uterine contractility to minimise blood loss and prevent post partum haemorrhage and also know if the cardiovascular effects of oxytocin could be tolerated by normal parturients. METHODS This is a prospective study. Hundred parturients undergoing elective caesarean delivery, under spinal anaesthesia were given 5U of oxytocin as rapid intravenous infusion over 1 minute followed by a 10U maintenance intravenous infusion. Intraoperative heart rate, non-invasive blood pressure (NIBP) and continuous electrocardiograph (ECG) changes were noted. Patients were observed for other adverse effects like chest pain, dysrhythmias, nausea, vomiting and generalised flushing. Uterine tone and the need for additional uterotonics were assessed. RESULTS Tachycardia was observed for the initial 2 minutes after oxytocin bolus which returned to the baseline values within 15 minutes. Diastolic blood pressure (12.7 %) and mean arterial pressure (9.6 %) showed greater fall than systolic blood pressure (5.9 %) due to the effects of oxytocin. Among the 100 parturients, one parturient complained of chest pain which developed during oxytocin bolus and subsided after 2 minutes, one had ST depression and another one developed atrial arrhythmias. CONCLUSIONS It can be inferred that oxytocin in the dose studied is safe in parturients who are normovolemic and without cardiac risk factors. It is effective in achieving adequate uterine tone and reducing blood loss. KEY WORDS Oxytocin, Cardiovascular Effects, Caesarean Section, Uterine Tone