Amnioinfusion

Definition

An amnioinfusion is a technique of instilling an isotonic fluid, such as a normal saline or lactated ringer’s solution, into the amniotic cavity with the purpose of thinning out a thick meconium that has been found to pass into the amniotic fluid.

This is usually done when a woman is in labor by way of an intrauterine pressure catheter (IUPC) being introduced through transcervical route, after cervical opening is considered sufficient and the fetal membranes has ruptured.

The rationale of performing the infusion is to augment the volume of amniotic fluid by reducing or getting rid of problems that involves a severe reduction, or in cases of an amniotic fluid absence during severe status of variable decelerations that happen during the labor process.

Indications

Based on the findings of the World Health Organization (WHO), amnioinfusion has been efffective in the following as a treatment for cases of cord compression where corrections are made involving:

Fetal heart rate abnormalities
APGAR scores for those with low scores
Asphyxia during time of birth
Decreasing the rates of cesarean birth related with FHR problem

Amnioinfusion is also effective during labor, in the assessment of moderate to thick amount of meconium being noted which meconium aspiration syndrome to include cases of:

Decreasing cesarean route of birth
Decreasing the incidence of meconium noted below the vocal cords of newborn babies

General indications of Amnioinfusion:

Repetitive variable decelerations – This is used effectively to resolve cases of repetitive variable decelerations which are linked to an umbilical cord compression.
Meconium stained amniotic fluid – Amnioinfusion is done to reduce the incidence of meconium aspiration syndrome (MAS) among newborns and to minimize cases of those who have meconium just below the vocal cords; this is not effective in preventing MAS.
Fetal survey in cases of severe oligohydramnios – Transabdominal diagnostic amnioinfusion helps in showing fetal sonographic imaging in cases of severe oligohydramnios.
Failed external cephalic version (ECV) – The route of transabdominal amnioinfusion is being used to facilitate an ECV.
Preterm premature rupture of membranes – One third of cases have shown that adequate amniotic fluid is maintained with amnioinfusion.

The efficacy and safety in the performance of amnioinfusion procedure is not very certain yet, so that it is best recommended to perform it on clinical settings, where the health care professionals are specialized in doing invasive procedures in fetal medicine in a multidisciplinary team approach.

Contraindications

The major contraindication to transcervical amnioinfusion is among women diagnosed to have placenta previa. The transabdominal amnioinfusion is also contraindicated if the needle must have to pass through and traverse an anterior type of placenta, such as in cases associated with isoimmunized women.

Procedure

The amnioinfusion procedure involves the use of an intrauterine pressure catheter (IUPC), or a single or double lumen type of IUPC.

The IUPC has been designed to attain an accurate monitoring of uterine contractions among women in the intrapartum period. It has a special port from which the saline fluid or lactated ringer’s solution is being injected, passing through the tubing and going its way into the uterus.

Trancervical approach is mostly preferred as the method of choice for women in labor, since the IUPC can be utilized for a repeated fluid infusion and ultrasound imaging is not necessary to guide the procedure all along.

An IUPC is inserted through standard technique once the membranes ruptures, and then it is attached to intravenous extension tubing. If IUPC is not available, a pediatric nasogastric tube can be used instead.

Lactated ringer’s solution without dextrose is infused into the amniotic cavity; normal saline can be an acceptable fluid alternative.

Protocols vary from one institution to another. Some obstetrical units have used the following methods in decreasing the order of frequency in infusing fluids:

A fluid bolus of 50 to 100 ml is followed by constant infusion
Serial boluses of 200 ml to 10000 ml is being administered every 20 minutes to 4 hours
Constant infusion of 15 ml to 2250 ml per hour is given

As based on a randomized trial finding, the performance of continuous and intermittent infusions has reached similar effectiveness level to patients who have amnioinfusion.

Complications

The complications involved with amnioinfusion are very rare and there have been reports of cases about the occurrence of maternal amniotic fluid embolism, although a clear association has not been proven and well demonstrated up to now.

References:

http://www.uptodate.com/contents/amnioinfusion-technique#H4

http://www.birthsource.com/scripts/article.asp?articleid=42

http://sinalib.ir/uptodate/contents/mobipreview.htm?5/8/5252?source=see_link

Porat S, Amsalem H, Shah PS, Murphy KE (2012). Transabdominal amnioinfusion for preterm premature rupture of membranes: a systematic review and metaanalysis of randomized and observational studies. Am J Obstet Gynecol. 207: 393.

Hsu TL, Hsu TY, Tsai CC, Ou CY (December 2007). “The experience of amnioinfusion for oligohydramnios during the early second trimester”. Taiwan J Obstet Gynecol 46 (4): 395–8.

Fraser WD, Hofmeyr J, Lede R; et al. (September 2005). “Amnioinfusion for the prevention of the meconium aspiration syndrome”. N. Engl. J. Med. 353 (9): 909–17.