The Oxytocin Challenge Test (OCT) also known as the Contraction Stress Test (CST) is a specialized antenatal procedure used to assess fetal well-being by evaluating how the baby’s heart rate responds to uterine contractions. It’s typically performed in the third trimester when there are concerns about placental function or fetal oxygenation.
Definition
A test in which the fetus is exposed to the stress of uterine contractions to determine whether there is adequate placental perfusion under simulated labor conditions (induced uterine contractions).
Purposes for Oxytocin Challenge test
- To assess the fetal ability to cope with the continuation of a high-risk pregnancy.
- To determine the projected ability of the fetus to withstand the stress of labor.
Indications
- Intrauterine growth retardation.
- Post maturity.
- Hypertensive disorders of pregnancy.
- Diabetes mellitus.
- Women with nonreactive NST.
Contraindications
- Third trimester bleeding.
- Incompetent cervix.
- Multiple gestation.
- Previous classical uterine incision.
- Hydramnios.
- History of preterm labor.
- Premature rupture of membranes.
Articles
- All the articles required for NST (fetal monitor, monitor strip, transducers, and monitor belts).
- An intravenous (IV) line to administer a dilute dose of oxytocin (Pitocin).
- An IV infusion pump to monitor the flow rate.
- Injection oxytocin and IV fluids.
Procedure
| Nursing actions | Rationale | |
| 1. | Before procedure Explain to mother the procedure and its purpose. | Reduces anxiety and promotes full cooperation. |
| 2. | Make sure that the woman had eaten food and ask her to empty her urinary bladder. | Promotes patient’s comfort. |
| 3. | During procedure Turn on the monitor and press the”TEST”button to see that it is working and adjust the paper speed (set at 3 cm per minute). | Setting the paper speed at 3 cm per minute increases the accuracy of interpretation. |
| 4. | Perform an abdominal palpation (Leopold’s maneuver). | Identifies the fetal position and awakens the fetus. |
| 5. | Position the woman in semi-Fowler’s or lateral tilt position and place the monitor belts under her back so that they are flat against her skin. | Supine position is avoided to prevent compression of maternal blood vessels and potential supine hypotension. |
| 6. | Connect the ultrasound transducer and the tocotransducer to fetal monitor. Apply ultrasound gel to the ultrasound transducer. | Ultrasound gel improves sound conduction. |
| 7. | Confirm the presence of fetal heart tones with a fetoscope or stethoscope. | Ensures that the source of pulse detected by the electronic monitor is the fetal heart. |
| 8. | Place the ultrasound transducer on the maternal abdomen over the fetal back. Move the transducer until clear, audible fetal heart tones are heard and the signal light is flashing steadily. Secure the device in place with belt. | Aids monitoring of fetal heart tones during the procedure. |
| 9. | Place the tocotransducer on the fundus of the uterus and secure in place with the belt. | Facilitates monitoring of uterine contractions. |
| 10. | Run the monitor and evaluate the quality of the tracing to determine if it is adequate for interpretation. If it is not, reposition the transducer until interpretable data is obtained. | Obtains accurate information about fetal health. |
| 11. | Start the oxytocin infusion at the rate of 1 mU/min. | Initiates uterine contractions. |
| 12. | Step up the infusion rate every 15 minutes at the prescribed rate until effective uterine contractions are established. | Achieves desirable rate of uterine contractions. |
| 13. | Monitor the uterine contractions using hands to palpate the hardening of the uterus. | Abdominal palpation while observing the monitor tracing aids to confirm the uterine contractions. |
| 14. | Continue the infusion until the contractions are occurring at a frequency of at least one in a 10-minute period and lasting at least 30 seconds. | Obtains an optimal level of uterine activity and fetal tolerance. |
| 15. | After procedure The recorded strip is then taken out for interpretation and infusion of oxytocin discontinued. | Serves for fetal assessment after induced stress of uterine contractions. |
| 16. | An IV infusion without oxytocin is continued until contractions have diminished to their baseline activity. | Ensures safety of mother and fetus. |
Interpretations
- Negative: No late decelerations present throughout the test. Indicates fetal well-being and predicts that the fetus will continue to be alright for another week without intervention of delivery.
- Positive: Repeated late decelerations of fetal heart patterns occur during the test (more than three in a 10-minute period). Further assessment is done to decide on the need for immediate termination of pregnancy.
- Hyperstimulation: Contractions are more frequent than two per minute or for duration of more than 90 seconds. The test should be stopped and repeated within 24 – 48 hours with a more dilute solution.
- Suspicious: Occasional late decelerations with continued contractions. The CST should be repeated within 24 – 48 hours.
- Unsatisfactory: The recording is not of good quality to be interpreted. This may be due to problems inherent with monitoring.
Special considerations
Discontinue infusion when:
- Criteria are met.
- Hyperstimulation occurs.
- Prolonged deceleration/bradycardia occurs.
REFERENCES
- Annamma Jacob, Rekha, Jhadav Sonali Tarachand: Clinical Nursing Procedures: The Art of Nursing Practice, 5th Edition, March 2023, Jaypee Publishers, ISBN-13: 978-9356961845 ISBN-10: 9356961840
- Omayalachi CON, Manual of Nursing Procedures and Practice, Vol 1, 3 Edition 2023, Published by Wolters Kluwer’s, ISBN: 978-9393553294
- Sandra Nettina, Lippincott Manual of Nursing Practice, 11th Edition, January 2019, Published by Wolters Kluwer’s, ISBN-13:978-9388313285
- Annamma Jacob, Manual of Midwifery and Gynaecological Nursing, 4th Edition, 2023, Jaypee Publishers, ISBN: 978-9356961593
- Adrianne Dill Linton, Medical-Surgical Nursing, 8th Edition, 2023, Elsevier Publications, ISBN: 978-0323826716
- Donna Ignatavicius, Medical-Surgical Nursing: Concepts for Clinical Judgment and Collaborative Care, 11th Edition ,2024, Elsevier Publications, ISBN: 978-0323878265
- Lewis’s Medical-Surgical Nursing, 12th Edition,2024, Elsevier Publications, ISBN: 978-0323789615
- AACN Essentials of Critical Care Nursing, 5th Ed. Sarah. Delgado, 2023, Published by American Association of Critical-Care Nurses ISBN: 978-1264269884
- Ernstmeyer K, Christman E, editors. Nursing Fundamentals [Internet]. 2nd edition. Eau Claire (WI): Chippewa Valley Technical College; 2024. PART IV, NURSING PROCESS. Available from: https://www.ncbi.nlm.nih.gov/books/NBK610818/
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