Amnioinfusion is a medical procedure involving the introduction of sterile fluid, typically saline or lactated Ringer’s solution, into the uterus during pregnancy or labor. This technique aims to increase the volume of amniotic fluid surrounding the fetus. The rate at which this fluid is administered is a precise consideration, carefully managed by healthcare providers to achieve therapeutic goals while maintaining safety for both the mother and the baby.
Reasons for Amnioinfusion
Amnioinfusion is performed to address specific conditions that can affect fetal well-being. One common reason is recurrent variable decelerations in the fetal heart rate, which often result from umbilical cord compression. When amniotic fluid levels are low, the umbilical cord can become squeezed during uterine contractions, reducing blood and oxygen flow to the fetus.
Another indication for amnioinfusion is severe oligohydramnios, a condition characterized by an abnormally low volume of amniotic fluid. This can occur due to various factors, including premature rupture of membranes. Increasing the fluid volume through amnioinfusion provides a cushion around the umbilical cord, helping to prevent compression and improve fetal oxygenation. The added fluid also creates a more protective environment for the fetus, which can be beneficial in cases of meconium-stained amniotic fluid by diluting the meconium.
Determining and Administering the Infusion Rate
The amnioinfusion rate is not standardized; healthcare providers determine it individually. This determination is based on the specific medical reason for the procedure, the condition’s severity, and the mother’s and fetus’s response to treatment.
Administration typically begins with an initial “bolus” infusion, involving a rapid fluid delivery to quickly increase amniotic fluid volume. This bolus might range from 250 to 500 mL, administered over 20 to 30 minutes. Following the bolus, a “continuous” or “maintenance” infusion sustains the fluid level and ensures ongoing cushioning around the fetus. This maintenance rate often varies between 60 to 180 mL per hour.
Monitoring and Safety During Amnioinfusion
Close monitoring is performed throughout amnioinfusion to ensure the safety of both mother and baby. Uterine tone and pressure are continuously observed using an intrauterine pressure catheter (IUPC) to prevent overdistension of the uterus, a potential complication. If the uterine resting tone increases by more than 15 mmHg above the baseline, the infusion may be temporarily stopped until the pressure normalizes.
Fetal heart rate is also continuously tracked for signs of improvement in variable decelerations or any indications of distress. Fluid intake and output are carefully managed to avoid fluid overload in the mother. Adjustments to the infusion rate are made in real-time based on these monitoring findings, allowing the medical team to optimize the procedure for the best possible outcomes.