Oxytocin Intravenous Infusion

Revised March 5, 2018

Section 2.1

Midwives without specialized practice certification may administer oxytocin via intravenous infusion for induction or augmentation of labour with a physician order. As with any induction or augmentation method where a physician has prescribed the pharmacological agent, the midwife shall continue to be involved in care as the condition warrants.

A midwife with specialized practice certification may, on her own responsibility, order and administer oxytocin via intravenous infusion for induction or augmentation of labour in hospital as per the CMBC Framework for Midwife Certification for Prescribing, Ordering, Administering and Managing Induction and Augmentation of Labour in Hospital and in conjunction with local hospital protocols

Oxytocin is a hormone that simulates uterine smooth muscle to contract by activating protein receptors which act on myofibrils. Oxytocin increases production of prostaglandin which further stimulates uterine contractions. Oxytocin in indicated for the induction or augmentation of labour.

Contraindications:

Hypersensitivity to oxytocin or any component of the formulation, any contraindication to labour or vaginal birth, known cephalopelvic disproportion, abnormal fetal heart rate, circumstances that make it impossible for a primary care provider to be present, inability to apply appropriate fetal health surveillance (EFM).

Warnings and Precautions:

Oxytocin is structurally and functionally related to vasopressin and its antidiuretic action can lead to water retention. For this reason electrolyte-containing solutions should be used when administering oxytocin. Water intoxication can lead to hyponatremia, confusion, convulsions, coma, congestive heart failure, and death. Fluid overload and hyponatremia with concurrent oxytocin administration may be prevented by strict intake and output recordings and use of balanced salt solutions such as normal saline or lactated Ringer’s. Oxytocin should also be used with caution in individuals with prior uterine surgery or caesarean delivery, history of difficult or traumatic delivery, a history of five or more term pregnancies, over distention of the uterus, uterine hypertonus and/or malpresentation.

Pregnancy:

Compatible for induction or augmentation of labour

Lactation:

Category L2 – Limited Data – Probably Compatible

Adverse Reactions:

Arrhythmias, hypertensive episodes, nausea, vomiting, uterine hypertonicity, tetanic contraction of the uterus, uterine spasm, anaphylactic reaction, subarachnoid hemorrhage, severe water intoxication with convulsions, coma, and death is associated with a slow oxytocin infusion over 24 hours.

Dosage and Administration:

Oxytocin must be delivered diluted in an isotonic solution through an IV infusion pump. Concurrent continuous electronic fetal monitoring is recommended due to the risk of tachysystole. Oxytocin can be used after the use of prostaglandins: 30 minutes after dinoprostone insert (Cervidil) removal, four hours after oral misoprostol administration and/or six hours after vaginal prostaglandin E2 gel administration.

Low-dose oxytocin

Initiate oxytocin infusion at 1-2 mU/min.

Increase oxytocin by 1-2 mU/min every 30 minutes until regular uterine activity is established.

Usual dose for labour = 8-10 mU/min.

Indications: All augmentations in 2nd stage, parous augmentation, grand multiparous induction, VBAC augmentation/induction (increase by 1 mU/min).

High-dose oxytocin

Initiate oxytocin infusion at 2-4 mU/min.

Increase oxytocin by 4 mU/min every 30 minutes until regular uterine activity is established.

Indications: Parous induction, nulliparous augmentation/induction in 1st stage.

Maximum dosage:

Low-dose- 20-30mu/min (20mu/min for VBACs)

High-dose: 30mu/min

Onset of Action:

IM: 2-5 minutes

IV: 1-5 minutes

Half-life:

IM and IV: 3 minutes.

Elimination:

Excreted by the kidneys.

*Reference ranges for the onset and duration of action and half-life are varied in the literature