Placenta Accreta
On occasion, the placenta can be adherent to the implantation
site with an absent decidua, an abnormality that produces an absence of the physiologic
line of cleavage through the decidual layer. This condition is termed "placenta
accreta" and may produce life-threatening challenges. As shown in Figure
58-18
, placenta accreta may be classified
Figure 58-18
Classification of placenta accreta, increta, and percreta.
(From Birnbach DJ, Gatt SP, Datta S [eds]: Textbook of Obstetric Anesthesia.
New York, Churchill Livingstone, 2000, p 406. Originally from Kamani AAS, Gambling
DR, Christilaw J, et al: Anesthetic management of patients with placenta accreta.
Can J Anaesth 34:613, 1987. Data from Miller DA, Chollet JA, Goodwin TM: Clinical
risk factors for placenta previa-placenta accreta. Am J Obstet Gynecol 177:210,
1997.)
according to the degree of placental penetration of the myometrium. The condition
occurs when the placenta is adherent to the myometrium. Placenta increta occurs
when the placenta invades the myometrium. Placenta percreta occurs when the placenta
extends through the myometrium and may adhere to surrounding structures. Patients
with one or more previous cesarian sections have an increased likelihood of placenta
accreta, as highlighted in Figure
58-19
. With recent improvements in ultrasonography, it is now possible
to diagnose most cases of placenta accreta antenatally.[260]
The extent of trophoblast invasion can also be evaluated with magnetic resonance
imaging (MRI).[261]
If detected by radiologic studies,
techniques such as arterial embolization under radiologic guidance may be used to
decrease the extent of bleeding before or during cesarean hysterectomy.[262]
[263]
Although controversy exists with regard to
the use of cell salvage techniques during cesarean section, blood loss may be so
massive in these cases that the benefits outweigh the potential risks of introduction
of amniotic components into the maternal circulation. Two reports have described
successful use of the cell salvage technique during cesarean hysterectomy.[264]
[265]
This technique may also be of benefit to
a
Jehovah Witness parturient, in whom a blood transfusion is not an alternative.
Optimal anesthetic management of patients for cesarean hysterectomy
is dependent on many factors, including the stability of the patient, the experience
of the anesthesiologist, the availability of ancillary services, and patient wishes.
In an early report by Chestnut and Redick, 7 of 25 patients undergoing cesarean
hysterectomy required general anesthesia. Reasons for the use of general anesthesia
included "patient discomfort" and "inadequate
Figure 58-19
Relationship between the number of previous cesarean
sections and the incidence of placenta accreta. (From Clark SL, Koonings
PP, Phelan JP, et al: Placenta previa/accreta and prior cesarean section. Obstet
Gynecol 66:89, 1985; and Miller DA, Chollet JA, Goodwin TM. Clinical risk factors
for placenta previa-placenta accreta. Am J Obstet Gynecol 177:210, 1997.)
operating conditions."[266]
A subsequent prospective
multi-institutional study evaluated this subject and reported that continuous epidural
anesthesia can be used safely for many cases of elective cesarean hysterectomy.[267]
Because of the ever-present possibility that conversion to general anesthesia will
be necessary, some anesthesiologists prefer to initially use general anesthesia in
women with a high risk of placenta accreta. The timing of epidural catheter removal
is controversial and warrants caution in cases in which massive hemorrhage and transfusion
precipitate DIC.[268]
