Recommended Solution and Infusion Rate for Amnioinfusion
Normal saline (0.9% NaCl) is the preferred solution for amnioinfusion, with an initial bolus of 250-500 mL followed by a maintenance rate of 10-15 mL/minute.
Solution Selection: Normal Saline vs. Lactated Ringer's
Evidence for Normal Saline
- Multiple studies have demonstrated that both normal saline and Lactated Ringer's solution are safe for amnioinfusion, but normal saline has been more extensively studied and is traditionally preferred 1, 2, 3.
- Human studies show no clinically significant differences in neonatal electrolyte balance between the two solutions 1, 2, 3.
- Unlike animal models that showed concerns about hyperchloremia with normal saline, human studies found no evidence of hyperchloremia or electrolyte imbalance in neonates after normal saline amnioinfusion 1, 3.
Considerations for Lactated Ringer's
- While Lactated Ringer's solution contains electrolytes closer to physiological concentrations, including calcium and potassium, this theoretical advantage has not translated to measurable clinical benefits in amnioinfusion 2.
- In general fluid resuscitation guidelines, balanced crystalloids like LR are often preferred over NS due to lower rates of hyperchloremic metabolic acidosis 4, but this benefit has not been demonstrated in the specific context of amnioinfusion.
- A recent in vitro study showed that both solutions caused some amniotic membrane damage, with normal saline showing slightly higher cell death rates (56%) compared to Lactated Ringer's (48%), though both were inferior to a synthetic amniotic fluid 5.
Recommended Amnioinfusion Protocol
Initial Bolus
- Administer 250-500 mL of normal saline as an initial bolus
Maintenance Rate
- Continue at 10-15 mL/minute (600-900 mL/hour)
- Total volume typically ranges from 500-1000 mL depending on clinical indication and response
Monitoring During Amnioinfusion
- Continuous fetal heart rate monitoring
- Maternal vital signs
- Uterine tone and contraction pattern
- Amniotic fluid volume assessment
Clinical Indications for Amnioinfusion
- Variable fetal heart rate decelerations due to cord compression
- Thick meconium-stained amniotic fluid
- Oligohydramnios
Practical Considerations
- Warm solution to body temperature (37°C) before administration
- Use sterile technique for administration
- Consider intrauterine pressure catheter for accurate measurement and administration
- Discontinue if maternal or fetal status deteriorates, or if excessive uterine distension occurs
Potential Complications to Monitor
- Uterine overdistention
- Cord prolapse
- Amniotic fluid embolism (rare)
- Placental abruption
- Uterine hypertonus
While both solutions appear safe for amnioinfusion, normal saline remains the most commonly used and studied solution with a well-established safety profile in this specific clinical context.