Post-laser amniodrainage

TTTS. Post-laser amniodrainage

Surprisingly, the topic of how much fluid should be removed during a therapeutic amniocentesis has received relatively little attention.18 Descriptive terms such as ‘aggressive’ or ‘radical’ have been used to describe the philosophical objective of the procedure. 

Objectively, goals range from decreasing the amniotic fluid volume to the level of oligohydramnios or to low-normal levels, using either MVP (maximum vertical pocket) or AFI (amniotic fluid index) as the measuring parameter.19–22 Most centers advocate reducing the MVP to a level of 5–6 cm. 

Presumably, the lower the amniotic fluid volume at the end of the amniocentesis, the less frequent the number of procedures that will be required to reach viability and a successful outcome. Anecdotally, placental abruption has been reported as a potential complication of largevolume amnioreduction.21 A therapeutic amniocentesis is also performed at the end of laser surgery. 

We normally perform this with the suction–irrigation trumpet to which wall-suction tubing is attached at 300 mmHg. In contrast to patients treated solely with therapeutic amniocentesis, there is no need to drain the amniotic cavity of the recipient twin to inordinately low levels because the disease has now been effectively treated. Instead, the amniotic fluid volume is reduced to upper-normal or low polyhydramnios range, to avoid the potential complication of placental abruption. 

We have noted the development of bradycardia in some stuck donor twins during amniodrainage, presumably as a result of cord compression, which resolves with partial restoration of the amniotic fluid volume. 

In our current post-laser amniodrainage technique, fluid is removed in 500 ml increments for the first 1000 ml, followed by judicious removal of fluid until the MVP has reached approximately 9–10 cm, with constant ultrasound monitoring of the fetal heart rate of the twins. If bradycardia of the donor twin is detected, the amniodrainage procedure is halted and an amnioinfusion may be necessary. If bradycardia of the donor does not develop, the amniodrainage is continued until an MVP of 8–10 cm is reached.