Amniotic fluid embolism
is a rare and life-threatening complication that occurs when amniotic fluid or fetal particulates (skin cells, hair, vernix, meconium) enters the mother’s bloodstream during pregnancy or childbirth, causing obstruction in the pulmonary vessels.
AFE is the fifth most common cause of maternal mortality
Amniotic fluid embolism - Signs and symptoms + risk factors
Signs and symptoms - hypotension, fetal distress, pulmonary oedema, cardiopulmonary arrest, cyanosis, coagulopathy, respiratory distress, uterine atony, bronchospasm (with hypotension, hypoxia, and DIC / altered mental state present in 80-100% of affected women)
Risk factors - ‘Tumultuous’ contractions, Age over 35 years, especially primips, Caesarean section, Assisted vaginal delivery, IOL with prostaglandins or oxytocin, ARM, diabetes, hypertensive disorders
AFE - Assessment
ABC assessment
CPR
Correction of hypotension
Prevention of coagulopathy - uterine tone needs to be assessed almost constantly, as massive haemorrhage is common. Drugs such as oxytocin, ergometrine, and prostaglandins will be used as necessary
Clotting factors are assessed frequently, as well as FBC for H and platelets
? Emergency caesarean
Transfer to ICU after stabilisation
AFE Potential presentations
Presentation 1: Necrotic, fetal, or placental cells enter maternal circulation
- May block pulmonary artery → pulmonary embolism / pulmonary hypotension → sudden chest pain, tachycardia, dyspnoea → signs of R) sided and L) sided heart failure
Presentation 2: Necrotic, fetal, or placental cells enter maternal circulation
- May cause immunologic response → activation coagulation cascade / depletion of coagulation factors
→ abnormal bleeding → shock / postpartum haemorrhage
OR
→ microemboli → tissue hypoxia, renal failure, coronary insufficiency, respiratory failure, seizures, coma, haemolytic anaemia
Describe maternal collapse, its incidence
Maternal collapse is an acute life-threatening event in which the mother becomes unconscious due to cardiorespiratory or neurological compromise at any stage of pregnancy or up to 6 weeks postpartum
The incidence of maternal cardiac arrest is estimated 6 per 10000 births
The survival rate for maternal cardiac arrest is dependent on effective resuscitation, identification, and effective treatment of the underlying cause - cardiac arrest is usually related to peripartum events
Physiological changes of pregnancy that make resuscitation challenging
- Aortocaval compression - beyond 20 weeks gestation, all resuscitation efforts must be performed with left lateral tilt of the pelvis greater than 15 degrees to minimise aortocaval compression (wedging with pillow). If the vena cava is partly occluded due to the pregnant uterus, cardiac output can be reduced by up to 40% - potentially promoting maternal collapse
- Changes in lung function and risk of hypoxia - due to a 20% reduction in functional residual capacity of the lungs, pregnant women are more likely to develop hypoxia. Oxygen demand is increased during pregnancy due to the fetoplacental unit. This is further complicated by increased weight of abdominal contents and breasts in late pregnancy, which can make effective rescue breaths difficult to perform
- Difficult intubation and risk of aspiration - risk is increased due to a more relaxed lower esophageal sphincter muscle and elevated gastric acid volume production. Airway protection and effective ventilation via endotracheal tube should be established as soon as possible - however weight gain and laryngeal oedema can make intubation more difficult
- Circulation - pregnancy can increase circulation, blood volume and cardiac output. Blood loss is tolerated if there is no pre-existing anaemia or underlying maternal morbidity
- Perimortem caesarean section - the uteroplacental unit sequesters blood and hinders effective CPR. Survival is inversely proportional to the time between maternal cardiac arrest and delivery - a positive effect of delivery and maternal outcome during CPR is supported. Caesarean delivery within 4 minutes of collapse if there is no response to resuscitation efforts is recommended
4H’s (Reversible Causes)
Hypovolaemia - resuscitation must include an aggressive approach to volume replacement, abdominal US may be considered to discover concealed haemorrhage
Hypoxia - pay attention to signs of respiratory failure (tachypnoea, respiratory pattern) and secure a competent airway early if necessary
Hyperkalaemia and electrolyte disturbances - check early as possible
Hypothermia - consider if collapse occurred out of hospital
4T’s (Reversible Causes)
- Thromboembolism
- Toxicity - mainly due to pregnancy-specific drugs e.g., local anaesthetic overdoses due to inadvertent intravascular injection (symptoms of dizziness, metallic taste, seizures, loss of consciousness) (in severe cases arrhythmia and cardiac arrest)
- Tamponade - can occur after trauma or due to Type A aortic dissection - investigate with cardiac imaging
- Tension pneumothorax - most likely following trauma, but possible after central venous line insertion
Potential causes of maternal collapse
Haemorrhage - is the leading cause of maternal collapse (3.7 per 1000). Predisposing factors are multiple pregnancy, high parity, placenta praevia, uterine fibroids, multiple previous caesareans, prolonged labour, maternal clotting disorders, preeclampsia. Blood loss is often underestimated, and if haemodynamic changes become apparent, the mother has usually already lost one third of her circulating blood volume
Thromboembolism - blood clots. Careful risk assessment should occur pre- and postnatally. DVT of the pelvic venous system is often asymptomatic until pulmonary embolism develops
Amniotic fluid embolism - an unpreventable event, however speed of diagnosis determines the outcome. Clinical features include respiratory distress, cardiovascular collapse, haemorrhage due to coagulopathy within 30 minutes after delivery
Maternal cardiac disease - risk of myocardial infarction is increased 3 to 4 times in pregnancy and significantly greater for AMA
Sepsis
Complications of labour analgesia (due to hypotension)
Drug toxicity
Eclampsia, epilepsy, intracranial haemorrhage
Anaphylaxis
Resuscitation in pregnancy
- Prevention should be priority
- Unstable women should immediately be positioned in L) lateral or L) lateral tilt to prevent vena cava compression syndrome (or manually displacing the uterus)
- CPR - performed slightly higher on the sternum than usual, as the maternal diaphragm is elevated in later stages of pregnancy. Deliver efficient compressions with no interruption. Consider manual uterus displacement if tilt is affecting chest compressions
- AED - consider placement of pads
- High-flow oxygen should be administered and IV access established above the diaphragm
- Maternal hypotension should be treated with a fluid bolus of colloid or crystalloid infusion (1000ml QBL = 3L crystalloid)
- Consider 4T&H’s and treat as necessary
- S&T - Shout for help, ensure a Safe environment, Tile the patient to left lateral
- (A)BC - Assess and open Airway, intubate early, reverse trendelenburg, smaller tube, use of cricoid pressure (Seilick’s manouver - to occlude the oesophagus to prevent aspiration of gastric contents)
- A(B)C - Assess Breathing for 10 seconds - if not breathing normally, start CPR
- AB(C) - Circulation - check the carotid pulse and ensure volume replacement via two large-bore cannulas, higher CPR shocks OK, manual displacement, no amiodarone
Consider perimortem caesarean after 4 minutes of collapse and remove by 5 minutes (more so for the woman’s wellbeing than the baby necessarily)
