Hormonal Functions: Oxytocin and Water Retention

Questions and Answers

What is one of the primary uses of oxytocin after the delivery of the placenta?

To manage preeclampsia

To increase fetal heart rate

To produce a firm contraction of the uterus (correct)

To induce labor

Which of the following indicates a reason to stop oxytocin infusion?

Stable mother's vitals

Severe nausea in the patient

Abnormal uterine contractions (correct)

Persistent dizziness

How is oxytocin administered for cases of breast engorgement?

Intranasally (correct)

Intravenously

Intramuscularly

Orally

What is the primary action of oxytocin in the uterus?

Stimulates the frequency and force of uterine contractions Signup and view all the answers

What dosage of oxytocin is typically given intranasally to promote milk ejection?

40 i.u. Signup and view all the answers

Why is the immature uterus resistant to oxytocin?

Lack of oxytocin receptors in the immature uterus Signup and view all the answers

How does oxytocin affect renal function?

Promotes renal retention of water Signup and view all the answers

Which of the following is NOT associated with maternal dangers when using oxytocin?

Diminished uterine tone Signup and view all the answers

What occurs to the sensitivity of the uterus to oxytocin as pregnancy progresses?

Sensitivity increases significantly in late pregnancy and labor Signup and view all the answers

What ion influx is primarily stimulated by oxytocin in myometrial cells?

Calcium ions (Ca2+) Signup and view all the answers

What effect does endogenous PGE2 have on the cervix during the birthing process?

It promotes cervical ripening Signup and view all the answers

Which of the following is NOT a pharmacological effect of prostaglandins?

Stimulation of progesterone secretion Signup and view all the answers

When is the response of the uterus to prostaglandins typically at its maximum?

In the middle trimester Signup and view all the answers

What is the primary mechanism through which cervical ripening occurs?

Activation of collagenase Signup and view all the answers

Which medication is known to sensitize the uterus to the action of prostaglandins?

Mifepristone Signup and view all the answers

What is one of the primary uses of oxytocin during labor induction?

To maintain uterine contractions during and after delivery Signup and view all the answers

Which of the following is NOT an indication for using oxytocin?

To manage maternal hypertension Signup and view all the answers

What dosage is typically given of oxytocin to manage third-stage labor?

5 I.U. intramuscularly or slow intravenous Signup and view all the answers

At what rate should oxytocin infusion for labor induction begin?

0.2 ml/min Signup and view all the answers

Which is a therapeutic use of oxytocin in late pregnancy?

To induce labor and manage uterine inertia Signup and view all the answers

What serious maternal condition can occur due to oxytocin administration in high doses?

Water intoxication Signup and view all the answers

Which of the following risks is associated with uterine rupture due to oxytocin?

Grand multiparity Signup and view all the answers

What is a potential fetal complication from uterine hyperstimulation induced by oxytocin?

Fetal distress Signup and view all the answers

Which sign indicates water intoxication due to excessive oxytocin use?

Hyponatremia Signup and view all the answers

How can the risk of water intoxication from oxytocin be minimized?

By using lower dosages of oxytocin for short durations Signup and view all the answers

What is the primary therapeutic use of oxytocin?

To induce labor near term Signup and view all the answers

Where is oxytocin synthesized in the body?

Hypothalamus Signup and view all the answers

Which physiological function does oxytocin NOT promote?

Blood pressure regulation Signup and view all the answers

How is oxytocin transported from the synthesis site to its release location?

Along nerve axons Signup and view all the answers

Which of the following triggers the secretion of oxytocin?

Sensory stimulation from the cervix and vagina Signup and view all the answers

What change occurs in uterine sensitivity to oxytocin as pregnancy progresses?

Sensitivity increases as pregnancy advances. Signup and view all the answers

Which hormone is primarily responsible for milk ejection during breastfeeding?

Oxytocin Signup and view all the answers

How does oxytocin affect water retention in the body?

It mimics the action of antidiuretic hormone. Signup and view all the answers

What role does the milk-ejection reflex play in breastfeeding?

It stimulates the release of oxytocin for milk transfer. Signup and view all the answers

During which stage of pregnancy is uterine responsiveness to oxytocin the lowest?

Early pregnancy Signup and view all the answers

What is the primary goal of labor induction?

To stimulate uterine contractions for vaginal delivery Signup and view all the answers

When should labor induction generally be considered?

When pregnancy poses greater risks than induction Signup and view all the answers

What circumstance is primarily recommended for labor induction?

Pregnancy beyond 42 weeks Signup and view all the answers

Which of the following is commonly used to achieve uterine contractions during labor induction?

Oxytocin Signup and view all the answers

What is a significant risk factor for considering labor induction?

Greater risk from ongoing pregnancy Signup and view all the answers

What is the primary site of synthesis for oxytocin?

Hypothalamus Signup and view all the answers

How is oxytocin primarily administered to achieve effective results?

Intravenously Signup and view all the answers

What is the typical half-life of oxytocin in non-pregnant women?

10-15 minutes Signup and view all the answers

Which cell type is primarily responsible for the release of oxytocin?

Myoepithelial cells Signup and view all the answers

What significant effect does oxytocin have on uterine contractions?

Increases force, frequency, and duration Signup and view all the answers

Which drugs are classified as oxytocics used to stimulate uterine contractions?

Prostaglandins Signup and view all the answers

What is the primary purpose of tocolytic drugs?

To prevent uterine contractions Signup and view all the answers

Which of the following is NOT an oxytocic drug?

Fentanyl Signup and view all the answers

Which of the following statements about oxytocics is correct?

They stimulate the contraction of uterine muscles. Signup and view all the answers

What is the role of Prostaglandins in the context of uterine function?

To stimulate cervical ripening and induce labor. Signup and view all the answers

Study Notes

Oxytocin Overview

Oxytocin, a peptide hormone from the posterior pituitary, promotes uterine contractions and milk ejection.
Structurally similar to antidiuretic hormone (ADH), it can retain water, albeit to a lesser extent than ADH.

Role of Oxytocin in Uterus

Stimulates force and frequency of uterine contractions, resembling physiological labor contractions.
The immature uterus is less responsive, with sensitivity increasing significantly in the last weeks of pregnancy.
Administration typically occurs only when the cervix is soft and dilated for effectiveness.

Mechanism of Action

Binds to myometrial cell receptors, facilitating calcium influx, which stimulates uterine contractions.

Indications for Oxytocin Use

Control of postpartum hemorrhage (PPH): administered IM or IV after placenta delivery for effective uterine contraction.
Acceleration of abortion, especially combined with prostaglandins.
Treatment of bleeding post-evacuation of the uterus.
Promotion of milk ejection via intranasal administration before breastfeeding.

Contraindications for Oxytocin Infusion

Abnormal uterine contractions (frequency less than every 2 mins, duration over 60 secs).
Evidence of fetal distress.
Maternal signs indicating a need to halt infusion.

Dangers of Oxytocin

Maternal Risks:
- Uterine hyperstimulation can lead to abnormal fetal heart rates.
- Uterine rupture risk particularly high in grand multipara, malpresentation, and excessive dosages.
- Water intoxication due to antidiuretic effects manifests as hyponatremia, leading to potentially severe complications.
Fetal Risks:
- Fetal distress or death may result from reduced placental blood flow due to hyperstimulation.

Therapeutic Applications of Oxytocin

Early Pregnancy: abortion acceleration and bleeding control after evacuation.
Late Pregnancy: labor induction, cervical ripening, labor augmentation, and management of third-stage labor to reduce blood loss.

Administration Details

Induction of labor involves slow IV infusion to produce and maintain uterine contractions, ideally continuing 30-60 minutes postpartum.

Prostaglandins (PGs) Overview

Local hormones, originally isolated from seminal fluid, particularly PGE2, PGF2a, and PGE1, are utilized in obstetrics for labor induction and control of PPH.
Stimulates cervical ripening and myometrial contractions.

Physiologic and Pharmacologic Effects of Oxytocin

Uterine stimulation ability increases as gestation progresses due to raising oxytocin receptor numbers.
Milk ejection occurs via the myoepithelial cells surrounding milk channels upon infant suckling.

Pharmacokinetics of Oxytocin

Not effective orally; administered IV or as a nasal spray.
Rapidly metabolized by the liver and kidneys, exhibiting a brief duration of action (approx. 20 minutes in general, shorter in pregnancy).

Oxytocics: stimulate uterine contractions (e.g., Oxytocin, Ergot Alkaloids, Prostaglandins).
Tocolytics: cause uterine relaxation, preventing preterm labor.

Summary of Oxytocics

Oxytocin (Syntocinon): Primary agent for inducing labor and managing postpartum hemorrhage.
Ergot Alkaloids: Used similarly in uterine contraction stimulation.
Prostaglandins: Viable for cervical ripening and labor induction, especially in conjunction with other agents.

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Description

This quiz covers the role of oxytocin in water retention and its effects on the uterus. It highlights the similarities between oxytocin and antidiuretic hormone, focusing on their impact on kidney function and uterine contractions. Test your knowledge on these critical hormonal interactions in the body!