Oxytocin Augmentation and a Category II Fetal Heart Pattern
A 29-year-old G1P0 at 41 weeks and 2 days is admitted for induction of labour after a reassuring antenatal review. The cervix is 3 cm, 50% effaced, and the fetal head is at -1. Oxytocin is started at 2 mU/min and increased by 2 mU/min every 30 minutes to 12 mU/min over three hours. The midwife now observes contractions every 2 minutes lasting 70 to 75 seconds on the tocograph, with a baseline fetal heart rate of 165 beats/min and minimal variability; there are no decelerations. The maternal pulse is 100 beats/min, blood pressure 110/70 mmHg, temperature 37.8°C, and the woman reports feeling hot and tired. The oxytocin bag is labelled 30 IU in 500 mL of sodium chloride 0.9%, and the pump is running at 12 mL/hour. The obstetrician is in theatre and the senior midwife is available. The midwife must decide what to stop, what to check, and what to report.
1. Interpret the contraction pattern and fetal heart rate. What is your immediate management?
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The pattern is tachysystole with uterine hypertonus: contractions every 2 minutes lasting 70–75 seconds leave little resting time, and the fetal heart is tachycardic at 165 with minimal variability. This is a non-reassuring (category II) pattern and may reflect reduced placental exchange, maternal fever, or medication. Immediate actions: stop the oxytocin infusion at the pump, call the obstetrician and senior midwife, turn the woman to the left lateral position, give an intravenous crystalloid bolus such as 500 mL sodium chloride 0.9% over 15–20 minutes unless contraindicated, apply continuous CTG, check maternal pulse and temperature, and consider oxygen only if hypoxic. Do not restart oxytocin until the pattern normalises and the cause is addressed. If there is no improvement, discuss tocolysis with terbutaline 250 mcg subcutaneously with the obstetrician, provided there is no maternal tachycardia or cardiac contraindication. Prepare for urgent delivery if the fetal heart does not recover.
2. Perform a medication safety check on the oxytocin infusion. What errors are possible and what would you correct?
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Check the bag, line, and pump: 30 IU in 500 mL is 60 mU/mL; at 12 mL/hour that is 720 mU/hour, or 12 mU/min, so the arithmetic matches. However, 30 IU/500 mL is a high-concentration preparation. If a different concentration such as 10 IU/500 mL (20 mU/mL) is used with the same pump setting, the dose would be wrong by a factor of three. Errors are possible at prescribing, preparation, labelling, programming, and handover. Use the unit's standard concentration, label the bag with drug, dose, concentration, time, and initials, and use an infusion pump with a guardrail or an independent double-check. Oxytocin is a high-alert medication: never give it as a bolus, titrate against contractions and fetal heart, and document the rate and response. After resolution, restart at a lower rate, for example half the previous rate, only on senior advice.
3. What maternal diagnosis would you consider for the fever and fetal tachycardia, and what actions follow?
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The combination of maternal temperature 37.8°C, maternal pulse 100, fetal tachycardia, and uterine overactivity raises concern for chorioamnionitis, even though the temperature is only low-grade. Other causes include dehydration, epidural-related fever, and the oxytocin itself, but infection must be excluded. Actions: repeat the temperature, ask about uterine tenderness, offensive discharge, and duration of membrane rupture; obtain blood cultures and a full blood count as ordered; notify the obstetrician; start broad-spectrum intravenous antibiotics promptly according to the unit protocol after review; continue fetal monitoring; and anticipate delivery. Do not attribute the fetal tachycardia solely to oxytocin. Document the timeline, maternal observations, interventions, and the response. If delivery is needed, inform the neonatal team.