Download
Tips on Amniotic Fluid Embolism
Kayvan Aflaki
1
, Sena Aflaki
2
, Joel G. Ray
3,4
1
Institute of Medical Science, University of Toronto, Toronto, Canada;
2
Department of Anesthesia and Pain Management, St. Michael’s
Hospital, Toronto, Canada;
3
Department of Medicine, St. Michaels Hospital, Toronto, Canada;
4
Department of Obstetrics and Gynaecology,
St. Michaels Hospital, Toronto, Canada
Author for correspondence: Joel G. Ray: Joel.Ray@unityhealth.to
Received:
14 May 2020; Accepted after revision: 3 July 2020; Published: 21 June 2021
DOI:
https://doi.org/10.22374/cjgim.v16i2.458
Abstract
Amniotic fluid embolism (AFE) is a catastrophic, sudden-onset event that must be recognized
immediately. Despite the rarity of this condition, both maternal and perinatal morbidity and
mortality are significant with AFE, even in cases ideally managed. In this article, we present
five key statements covering the risk factors, clinical presentation, and management of AFE in
a clinical setting. The purpose of these tips is to provide clinicians with information that may
improve their ability to make a timely diagnosis and establish appropriate supportive treatment
to patients suffering from AFE.
Résumé
Lembolie amniotique est un événement catastrophique d’apparition soudaine qui doit être détecté
immédiatement. Malgré la rareté de cette affection, la morbidité et la mortalité maternelles et
périnatales sont importantes, même dans les cas où le traitement est idéal. Dans cet article, nous
présentons cinq énoncés clés qui portent sur les facteurs de risque, le tableau clinique et la prise en
charge de l’embolie amniotique dans un contexte clinique. Ces astuces visent à fournir aux cliniciens
de l’information qui pourrait améliorer leur capacité à poser un diagnostic en temps opportun et
à assurer un traitement de soutien approprié aux patientes atteintes dune embolie amniotique.
AFE must be rapidly identified to avoid a
catastrophic outcome
Amniotic fluid embolism (AFE) resembles both massive pulmonary
embolism and anaphylaxis occurring simultaneously, likely from
a breach of the maternal-fetal physiological barrier.
(1)
The four
main criteria for AFE are (i) sudden-onset of cardiorespiratory
arrest or systolic blood pressure <90 mm Hg, with concomitant
respiratory compromise; (ii) evidence of disseminated intravascular
coagulopathy (DIC), including bleeding, thrombocytopenia,
elevated INR, PTT, and hypofibrinogenemia <1.5 g/L; (iii) clinical
onset during labor or within 30 min of delivery of the placenta;
(iv) absence of intrapartum fever <38°C.
(1)
Approximately, 25%
of AFE cases present asymptomatically, with only respiratory
compromise and shock. Although AFE cannot be accurately
predicted, several risk factors are evident (Figure 1).
AFE is Rare but Deadly
Estimates of the incidence of AFE vary widely, but it is rare. It is
known fact that AFE cannot be accurately predicted, however,
several risk factors are palpable (Figure 1A). Almost half of
22 V o l u m e 1 6 , I s s u e 2 , 2 0 2 1 C a n a d i a n J o u r n a l o f G e n e r a l I n t e r n a l M e d i c i n e
GIM Practice
CJGIM_2_2021_177932.indd 22CJGIM_2_2021_177932.indd 22 07/06/21 3:48 PM07/06/21 3:48 PM
Figure 1. Significant risk factors for amniotic fluid embolism are shown in blue (A) (2). Potential immediate life-saving measures for a woman suspected of
having an amniotic fluid embolism are shown in red (B).
a
Tranexamic acid 2 g IV, then repeated hourly in first few hours.
b
Repeat packed red blood cell transfusion to maintain haemoglobin concentration > 70 g/L.
c
Repeat platelet transfusion to maintain platelet count > 50 × 10
9
/L.
d
Repeat fibrinogen replacement by cryoprecipitate or fibrinogen concentrate to keep blood fibrinogen level > 2.0 g/L.
e
Repeat fresh frozen plasma to keep INR < 1.5 and/or PTT < 35 s.
RR relative risk; CI confidence interval; IV intravenous; CBC complete blood count; INR international normalized ratio; PTT partial thromboplastin time; ECMO
extracorporeal membrane oxygenation.
Demographic factors:
Maternal age ≥ 35 y (RR 4.8, 95% CI 2.012)
African or Caribbean ancestry (RR 2.4, 95% CI
1.53.6)
Maternal health conditions:
Chronic hypertension (RR 9.5, 95% CI 2.241)
Preeclampsia (RR 7.3, 95% CI 4.312.5)
Abnormal placentation or excess amniotic fluid
status:
Placenta previa (RR 10.5, 95% CI 1.479)
Placental abruption (RR 13.3, 95% CI 1.8100)
Polyhydramnios (RR 3.0, 95% CI 1.27.3)
Labour and birth factors:
Vaginal prostaglandins for labour induction
(RR 3.4, 95% CI 1.334)
Caesarean or instrumental birth (RR 36.0, 95% CI
4.4300)
Vaginal breech birth (RR 151, 95% CI 9.42400)
Manual removal of placenta (RR 19.4, 95% CI 3.996)
Birth < 37 weeks gestation (RR 9.7, 95% CI 2.340.8)
2: Get help
Call for help. Consider transport to operating room.
Assign a team leader who is not managing the labour
and birth.
Activate massive transfusion protocol.
5: Consider ECMO
Consider consultation with a cardiac or vascular surgeon for
possible ECMO initiation, if available (see point 5 in text).
1: ABCs
sedation.
3: Perform rapid tests
Obtain maternal CBC, INR, PTT, and fibrinogen, blood culture,
blood gas, electrolytes, and calcium.
Initiate point of care hemostasis measurement, if available.
Attempt bedside echocardiography to assess the right ventricle.
4: Manage DIC
Following hemodynamic stabilization, tailor ongoing transfusion
management to serial CBC, INR, PTT, and fibrinogen.
ae
Managing DIC is paramount prevent medical bleeding.
Manage secondary sepsis, retained placental tissue, or ongoing/
unrealized surgical bleeding, as needed.
C a n a d i a n J o u r n a l o f G e n e r a l I n t e r n a l M e d i c i n e V o l u m e 1 6 , I s s u e 2 , 2 0 2 1 23
Aflaki K et al.
CJGIM_2_2021_177932.indd 23CJGIM_2_2021_177932.indd 23 07/06/21 3:48 PM07/06/21 3:48 PM
(A) (B)
1: ABCs
Begin high-flow oxygen and strongly consider intubation and sedation.
• Begin high-rate IV crystalloids (until blood products arrive).
• Begin IV infusion of a vasopressor agent.
• Secure an arterial and central venous line.
women with AFE die or experience permanent neurological
injury, especially those without an obstetrician or anesthetist
present at the time of the AFE event, and this befalls among
those not receiving prompt correction of their coagulopathy.
2
AFE is Characterized by a Biphasic Cardiovascular
Response
Initially, right ventricular failure leads to right ventricular
dilation, which impedes left ventricular filling and results in
low cardiac output.
3
Right ventricular failure may be evident on
rapid bedside echocardiography, if available.
3
The second phase
commences when right ventricular function improves and left
ventricular failure persists. Women who survive to the second
phase experience hemorrhage and massive DIC.
3
Rapid management of AFE is critical, and immediate steps
should be taken by anyone present, including a family physician
or midwife in a team-oriented manner (Figure 1B).
Rapid and coordinated management should be led by an
assigned team leader experienced with resuscitation.
4
DIC
should be managed aggressively, including 2 g of tranexamic
acid given intravenously, then repeated on an hourly basis in the
first few hours, packed red blood cells to maintain a hemoglobin
concentration >70 g/L, platelet transfusion to maintain platelet
count >50 × 10
9
/L, fibrinogen replacement with fibrinogen
concentrate or cryoprecipitate to keep the blood fibrinogen
level >2.0 g/L, and fresh frozen plasma to keep the INR <1.5
and/or PTT <35 s.
Extracorporeal membrane oxygenation (ECMO) may be
considered in cases of ongoing cardiovascular instability, despite
initial resuscitative measures (Figure 1B).
Depending on available resources and feasibility, urgent
consultation is required with a sub-specialty care center and
a team that can determine the value of ECMO.
5
Case reports
suggest successful use of ECMO in women with refractory AFE.
As anticoagulation is required for ECMO, the bleeding risk is
higher among women with ongoing DIC, or after Caesarean birth.
5
Declaration of Interest
The authors confirm that there are no known conflicts of interest
associated with this work.
Funding Statement
The authors received no specific funding for this work.
References
1. Knight M, Berg C, Brocklehurst P, et al. Amniotic fluid embolism incidence,
risk factors and outcomes: A review and recommendations. BMC Pregnancy
Childbirth. 2012;12. http://dx.doi.org/10.1186/1471-2393-12-7
2. Flitzpatrick KE, van den Akker T, Bloemenkamp KWM, et al. Risk factors,
management, and outcomes of amniotic fluid embolism: A multicountry,
population-based cohort and nested case-control study. PLoS Med.
2019;16:1–24. http://dx.doi.org/10.1371/journal.pmed.1002962
3. Stanten RD, Iverson LI, Daugharty TM, et al. Amniotic fluid
embolism causing catastrophic pulmonary vasoconstriction:
Diagnosis by transesophageal echocardiogram and treatment by
cardiopulmonary bypass. Obstet Gynecol. 2003;102:496–8. http://dx.doi.
org/10.1097/00006250-200309000-00013
4. Pacheco LD, Clark SL, Klassen M, et al. Amniotic fluid embolism: Principles
of early clinical management. Am J Obstet Gyneco. 2020;222:48–52. http://
dx.doi.org/10.1016/j.ajog.2019.07.036
5. Viau-Lapointe J, Filewood N. Extracorporeal therapies for amniotic fluid
embolism. Obstet Gynecol. 2019;134:989–94. http://dx.doi.org/10.1097/
AOG.0000000000003513
24 V o l u m e 1 6 , I s s u e 2 , 2 0 2 1 C a n a d i a n J o u r n a l o f G e n e r a l I n t e r n a l M e d i c i n e
Amniotic fluid embolism
CJGIM_2_2021_177932.indd 24CJGIM_2_2021_177932.indd 24 07/06/21 3:48 PM07/06/21 3:48 PM