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Oxytocin (Pitocin)

Anesthesia Implications

Updated On: December 2, 2024

Classification:
Uterotonic
Therapeutic Effects:
Induce/augment labor, uterine contraction, reduce uterine hemorrhage
Time to Onset:

IV - Immediate IM - 3-5 minutes

Time to Peak Effects:

IV: < 20 minutes IM: 40 minutes

Duration:

IV: 20 - 60 minutes IM: 2 - 3 hours

Primary Considerations:

Pressors - Oxytocin potentiates sympathomimetic effects of pressors (eg. ephedrine, phenylephrine) Water Intoxication - Structurally, oxytocin is similar to antidiuretic hormone, which is where the concern for water intoxication comes from. Watch fluid intake carefully. Transient vasodilation - high doses of oxytocin can produce transient vasodilation and subsequent hypotension, which is usually accompanied by a baroreceptor reflex (temporary increase in heart rate). Uterine Rupture - When used for labor induction, oxytocin MAY increase the risk of uterine rupture Side effects - water retention, hyponatremia, hypotension, hypertension, reflex tachycardia, coronary vasoconstriction, nausea, vomiting, subarachnoid hemorrhage. Math conversion - Each unit of Oxytocin is roughly 1.7 mcg.

Contraindications:

Significant cephalopelvic disproportion Fetal distress (where delivery is not imminent) Use with caution in patients with preeclampsia, essential hypertension, cardiac disease

IV infusion dose:

10-40 units added to 1 liter of crystalloid. Typically infused 'wide open' after delivery of the baby. The exact dose for adequate uterine tone (in 95% of parturients) in a non-laboring elective cesarean delivery is a 1 unit bolus of oxytocin followed by an infusion rate of oxytocin at 7.72 units/hr.

IM dose:

3-10 units

Method of Action:

Endogenous oxytocin is naturally released from the posterior pituitary in response to cervical, vaginal, or breast stimulation. With oxytocin, uterine contractions become more forceful and in higher frequency. Uterine tone is increased.

Metabolism:

Hepatic


Reference

Omoigui. Sota Omoigui's anesthesia drugs handbook. Fourth edition. 2012.p. 379-381
Nagelhout. Nurse anesthesia. 5th edition. 2014.
Qian. The ED50 and ED95 of oxytocin infusion rate for maintaining uterine tone during elective caesarean delivery: a dose-finding study. 2020