Amniotic Fluid Embolism (Anaphylactoid Syndrome of Pregnancy)
Definition
Amniotic fluid embolism (AFE) is thought to be an abnormal maternal immune response to fetal antigens when the maternal-fetal immunological barrier is breached during labor, pregnancy termination, or shortly after delivery. It results in a triad of hypoxemia, hypotension, and coagulopathy.
Etiology
The etiology of cardiovascular collapse is not clear but may result from activation of a cascade of immune mediators that causes a massive systemic reaction
Typical Situations
Active labor
Pregnancy termination
Cesarean delivery
Induction of labor
Multiparity
Advanced maternal age
Ethnic minority groups
Placental abnormalities (placental abruption or placenta previa)
Operative delivery
Prevention
There are no known measures to prevent AFE
Create institutional plan for stat cesarean section of a parturient in cardiac arrest (“Code Blue Obstetrics”)
Drill and practice the management of stat cesarean section during cardiac arrest (using simulation if available)
Manifestations
Unexplained acute fetal distress may precede maternal deterioration in 20% of cases
Premonitory symptoms
Restlessness, agitation, paresthesia
Pulmonary symptoms
Acute onset of dyspnea, pleuritic chest pain, bronchospasm, coughing, or hemoptysis
Hypoxemia and cyanosis
CXR may initially be normal and later demonstrate ARDS
Respiratory arrest
Cardiovascular symptoms
Arrhythmias
Severe hypotension
Pulmonary hypertension with RV failure (early, first 30 minutes)
ECG signs of right heart strain
Left ventricular failure and pulmonary edema (following initial onset)
Cardiac arrest (PEA, asystole, VF, VT)
Neurologic symptoms
Hyperreflexia, seizure, coma
Acute severe consumptive coagulopathy
DIC
Massive hemorrhage
Obstetric complications
Uterine atony
Similar Events
Anaphylaxis (see Event 16, Anaphylactic and Anaphylactoid Reactions )
Pulmonary or venous air embolism (see Event 21, Pulmonary Embolism , and Event 24, Venous Gas Embolism )
Eclampsia (see Event 88, Preeclampsia and Eclampsia )
Sepsis (see Event 13, The Septic Patient )
Obstetric hemorrhage (see Event 87, Obstetric Hemorrhage )
Medication reaction (see Event 63, Drug Administration Error )
Local anesthetic overdose (see Event 52, Local Anesthetic Systemic Toxicity )
Total spinal anesthesia (see Event 89, Total Spinal Anesthesia )
Cardiac disease (MI or ischemia, aortic dissection, cardiomyopathy, Eisenmenger syndrome)
Seizures (see Event 57, Seizures , and Event 88, Preeclampsia and Eclampsia )
Management
Patients with AFE can rapidly deteriorate, are at high risk of maternal mortality, and have a high incidence of fetal distress. The key steps are early recognition, supportive management, prompt resuscitation, and delivery of the fetus.
Call for help
Labor and delivery team and additional anesthesia help
If the patient has arrested, start CPR immediately
Stat cesarean section may be necessary (if no return of spontaneous circulation after 4 minutes) with the goal of delivery within 5 minutes (see Event 82, Cardiac Arrest in the Parturient )
If the patient has NOT arrested, maintain left uterine displacement even if postpartum
Ensure adequate oxygenation and ventilation
Administer 100% O 2 by a nonrebreathing face mask
Patient may require urgent or emergent airway management
If urgent airway management is necessary, perform RSI with cricoid pressure
Etomidate IV, 0.2 to 0.3 mg/kg, or ketamine IV, 0.5 to 1.0 mg/kg
Succinylcholine IV, 1 to 2 mg/kg
Intubate the trachea if there is loss of consciousness, respiratory failure, or severe cardiovascular collapse
Stop MgSO 4 infusion, if running
If Mg 2 + toxicity is suspected, administer CaCl 2 IV, 500 to 1000 mg
Initiate basic monitoring if not already present
ECG, NIBP, pulse oximeter, RR, level of consciousness, temperature, fetal monitoring
Support the circulation
Ensure adequate IV access above the diaphragm (2 × large-bore IVs)
Rapidly infuse crystalloid and/or colloid
Treat hypotension with vasopressors, increasing doses as needed
Phenylephrine IV, 50 to 200 µg
Ephedrine IV, 5 to 10 mg
Epinephrine IV, 10 to 100 µg
Consider administering vasopressor infusions if the preceding measures are inadequate (see Event 9, Hypotension )
Place an arterial line and consider placement of CVP line for infusion of vasopressors
Prepare for massive transfusion and initiate MTP (if available)
Send for blood products if they are not already in the room
Inform the blood bank that more blood and blood products will be needed emergently
If crossmatched blood is not readily available, order uncrossmatched blood
Get help to set up a rapid infusor device
Transfuse blood products
Use a fluid warmer
Transfuse with an RBC:FFP ratio of 1:1 or 2:1
Transfuse RBCs to maintain hemoglobin > 7 g/dL
Transfuse additional FFP if PT/aPTT is prolonged
Transfuse platelets if < 50,000/µL
Transfuse cryoprecipitate if fibrinogen < 200 mg/dL
Consult hematology and the critical care team
Maintain normothermia
Frequent lab draws (ABG/CBC/PT/aPTT/fibrinogen/metabolic panel/Ca 2 + )
At any time, if the patient has no pulse, start CPR immediately (C-A-B: compressions, airway, breathing)
Follow (ACLS) guidelines with modifications for the parturient (see Event 2, Cardiac Arrest , and Event 82, Cardiac Arrest in the Parturient )
Complications
Electrolyte abnormalities
Massive hemorrhage
ARDS
Aspiration pneumonitis
Cerebral hemorrhage
Cerebral anoxia
Cardiac arrest or death
Fetal distress or death
Suggested Reading
Cardiac Arrest in the Parturient
Definition
Cardiac arrest in the parturient is the absence of effective mechanical activity of the heart in the pregnant patient.
Etiology
Hypovolemia
Hypoxemia
PE, venous air embolism, or AFE
Toxins (e.g., LAST)
Anesthetic complications
Uterine atony
Hypertensive disease of pregnancy
Placental abnormalities (placental abruption or placenta previa)
Cardiac disease (MI or ischemia, aortic dissection, cardiomyopathy, Eisenmenger syndrome)
Sepsis
Tension pneumothorax
Cardiac tamponade
Typical Situations
Anesthesia-related
Failed or difficult tracheal intubation
Unrecognized esophageal intubation
Total spinal anesthesia
LAST
Major hemorrhage
Uterine atony
Placental abnormalities
Placenta previa (placenta located in the lower uterine segment over the cervix)
Placenta accreta, increta, or percreta (placenta attaches to, into, or through the myometrium)
Placental abruption (premature separation of a normally implanted placenta after 20 weeks’ gestation)
Preexisting medical condition
Acquired or congenital cardiovascular disease (e.g., peripartum cardiomyopathy, aortic dissection in presence of bicuspid aortic valve, coronary artery disease)
History of a PE
Other
Prostaglandin use in pregnancy
Mg 2 + toxicity
AFE
Prevention
Create institutional plan for immediate cesarean section of a parturient in cardiac arrest (“Code Blue Obstetrics”)
Drill and practice the management of immediate cesarean section during cardiac arrest (using simulation if available)
Immediate intervention at first signs of maternal or fetal instability
Manually perform left uterine displacement
Administer 100% O 2 through a nonrebreathing face mask
Ensure adequate IV access
Assess for and treat reversible causes (e.g., hypotension)
Anesthesia-related issues
Evaluate airway and prepare for a difficult intubation
Exclude intrathecal and intravascular placement of epidural catheters before administering incremental doses of local anesthetic
Manage preexisting medical issues in collaboration with specialists
In high-risk patients, consider placing invasive monitors
Carefully administer medications to parturients
Patients with a history of drug allergies
Patients with cardiac disease taking tocolytic agents (β-adrenergic agonists)
Administer potent drugs through infusion pumps (e.g., MgSO 4 )
Manifestations
Unresponsive to verbal commands
Absence of pulse oximeter waveform if present
Loss of consciousness or seizure-like activity
No palpable carotid pulse (palpation of peripheral pulses unreliable)
NIBP unmeasurable
Absence of heart tones on auscultation
Agonal or absent respirations
Arrhythmias
VT, VF, PEA, asystole
Rhythm in PEA may appear normal
Significant fall in ET CO 2 if present
Cyanosis
Regurgitation and aspiration of gastric contents
Lack of ventricular contraction on TEE or TTE
Similar Events
Anaphylaxis (see Event 16, Anaphylactic and Anaphylactoid Reactions )
PE, venous air embolism, or AFE (see Event 21, Pulmonary Embolism , Event 24, Venous Gas Embolism , and Event 81, Amniotic Fluid Embolism )
Eclampsia (see Event 88, Preeclampsia and Eclampsia )
Sepsis (see Event 13, The Septic Patient )
Obstetric hemorrhage (see Event 87, Obstetric Hemorrhage )
Medication reaction (see Event 63, Drug Administration Error )
Local anesthetic overdose (see Event 52, Local Anesthetic Systemic Toxicity )
Total spinal (see Event 89, Total Spinal Anesthesia )
Hypotension (see Event 9, Hypotension )
Seizures (see Event 57, Seizures , and Event 88, Preeclampsia and Eclampsia )
Artifacts on monitoring devices
ECG artifact (always check the patient)
Pulse oximeter
NIBP or invasive BP
Management
The key steps are early recognition, prompt resuscitation, and delivery of the fetus. Attempts to transfer patients undergoing CPR to an OR for immediate cesarean section increase maternal and neonatal risk. Perimortem cesarean section should be performed at the site of the arrest to relieve aortocaval compression, increase maternal CO and allow more effective chest compressions.
Treat the patient, not the monitor
Verify that the patient is unresponsive and has no carotid pulse
Other patient monitoring, if present, may confirm absence of circulation (e.g., pulse oximetry, ET CO 2 , arterial line waveform)
Call a code
Call for labor and delivery team and additional anesthesia help
Prepare for stat cesarean section at the site of the arrest with the goal of delivery within 5 minutes
A cesarean section will be necessary if no return of spontaneous circulation after 4 minutes
Call for the crash cart
Apply defibrillation pads on chest
Do not delay defibrillation for shockable rhythms
Start CPR immediately (C-A-B: compressions, airway, breathing)
Chest compressions
Place hands slightly higher on sternum
Compressions should be at least 100 per minute and at least 2 inches deep
Rotate compressors every 2 minutes
Allow for complete recoil of the chest with each compression
Interruptions in compressions should be less than 10 seconds
Adequate compressions should generate an ET CO 2 of at least 10 mm Hg and a diastolic pressure of greater than 20 mm Hg (if an arterial line is in place). You MUST improve CPR quality if above conditions are not met.
Airway/ventilation
Until the patient is intubated, establish bag mask ventilation with 100% O 2 at a compression to ventilation ratio of 30:2 and prepare for endotracheal intubation
Place ETT and then ventilate at a rate of 10 per minute with continuous compressions
Assign tasks to skilled responders
Ensure adequate IV access
If difficult IV access, place IO line
Place an arterial line
Call for TEE or TTE machine
Turn off ALL anesthetics if in use (including epidural infusions)
Follow BLS and ACLS guidelines (see Event 2, Cardiac Arrest ) but with modifications for the parturient (see the following)
Employ cognitive aids (ACLS guidelines) to help determine diagnosis and treatment
Drug therapy, dosages, and defibrillation should follow standard ACLS guidelines
ACLS modifications in pregnant patients
Place hands slightly higher on sternum while performing chest compressions
Immediately intubate with an ETT and ventilate with 100% O 2
The routine use of cricoid pressure during cardiac arrest is not recommended, but if used, remove if impairing ventilation and/or intubation
Manual left uterine displacement to avoid aortocaval compression
Stop MgSO 4 infusion, if running
If Mg 2 + toxicity is suspected, administer CaCl 2 IV, 500 to 1000 mg
Remove external fetal monitors prior to defibrillation
If an internal fetal monitor is present, disconnect from power supply prior to defibrillation
If parturient does not respond to resuscitation within 4 minutes, immediate perimortem cesarean section is indicated at the site of the arrest
Continue all maternal resuscitative interventions (CPR, positioning, defibrillation, drugs, and fluids) during and after perimortem cesarean section
Continually reassess patient without interrupting chest compressions
Resumption of spontaneous circulation
ECG and return of palpable pulse or BP
Pulse oximetry waveform
Consider postresuscitation hypothermia for brain protection
Complications
Aspiration of gastric contents
Laceration of liver
Pneumothorax or hemothorax
Rib fracture
Hypoxic brain injury
Multiorgan failure
Maternal death
Fetal death
Suggested Reading
Difficult Airway in the Parturient
Definition
Difficult airway in the parturient includes difficult mask ventilation, difficult placement of an SGA, or difficult tracheal intubation.
Etiology
Patient factors (specific to pregnancy)
Airway edema
Increased Mallampati score compared to nonpregnant state
Breast engorgement
High risk of regurgitation
Decreased functional residual capacity
Increased O 2 consumption
Increased risk of bleeding from mucosal surface
Other anatomical causes of a difficult airway
Full dentition
Obesity/short neck
Physician factors
Inexperience with airway management in the parturient
Failure to respond effectively to a rapidly deteriorating situation
Equipment factors
Inexperience with equipment
Inadequate backup or alternative airway adjuncts or intubating devices
Typical Situations
Cesarean section under general anesthesia
Contraindication to neuraxial anesthesia
Failure of neuraxial technique
Insufficient time to place or dose neuraxial anesthetic
Maternal refusal to have neuraxial anesthesia
Maternal and preexisting anatomic abnormalities
Local anesthetic toxicity requiring airway management
Nonobstetric surgery during pregnancy
Prevention
Perform a complete airway assessment prior to inducing anesthesia (general or neuraxial)
In patients with known or anticipated difficult airway, perform awake fiberoptic intubation
Alert the obstetric team to the increased probability of difficult airway management during general anesthesia
Consider early placement of an epidural catheter in patients at risk of difficult intubation or stat/urgent cesarean section and ensure that the catheter is functional
Optimize patient positioning prior to induction of general anesthesia
Prepare for a difficult intubation and have contingency plans if you cannot ventilate and/or cannot intubate
Consider videolaryngoscope as primary choice for intubation
Review and practice difficult airway/failed intubation algorithm
Manifestations
Failure to intubate the trachea after two attempts by an experienced anesthesia professional
Difficult insertion of laryngoscope
Small or restricted mouth opening
Masseter spasm secondary to succinylcholine
Difficult visualization of vocal cords
Difficult passage of ETT through vocal cords
Failure to successfully mask ventilate after induction of anesthesia
Failure to successfully place an SGA
Similar Events
Anesthesia workstation malfunction (e.g., bag/switch malposition)
Normal airway but unsuccessful intubation due to inexperience of the intubator
Functional airway obstruction
Laryngospasm (see Event 97, Laryngospasm )
Bronchospasm (see Event 29, Bronchospasm )
Gastric distention with air
Endobronchial intubation (see Event 30, Endobronchial Intubation )
Management
Obstetric patients have a higher risk of both difficult and failed intubation
If difficult airway is known or anticipated, perform an awake fiberoptic intubation since this may be the safest option
Prepare primary and backup airway equipment
Have contingency plans if primary plan fails
Before induction of general anesthesia
Position patient appropriately (e.g., “ramp” patient for intubation, especially if obese)
Maintain left uterine displacement
Administer sodium citrate 0.3 M PO, 30 mL
Administer ranitidine IV, 50 mg, and metoclopramide IV, 10 mg
Preoxygenate with 100% O 2 with anesthesia breathing circuit
Prep and drape the patient BEFORE general anesthesia is induced
If unanticipated difficult intubation after induction
Call for additional anesthesia help stat if not already present (e.g., anesthesia professional, anesthesia tech)
Call surgeon capable of establishing surgical airway and obtain equipment for surgical airway
Call for difficult airway cart or supplies (including videolaryngoscope)
Have help set up additional airway equipment
Ensure adequate oxygenation and ventilation (may be difficult)
Place an oral airway
Consider two-person bag valve mask technique
Apply continuous cricoid pressure
Reposition the patient’s head and neck
Most experienced person should perform second laryngoscopy
Use videolaryngoscope
Use appropriately styleted ETT or bougie
Adjust cricoid pressure if it is impairing ventilation or intubation
Use smaller ETT
If intubation fails on second attempt
Place an SGA (e.g., LMA) to maintain oxygenation and ventilation
If SGA placement is successful, clinical situation will dictate whether or not to continue the anesthetic with this airway and deliver the fetus or awaken the patient
Confirm ventilation with ET CO 2
Maintain cricoid pressure after placement of SGA
After delivery, consider whether to attempt tracheal intubation through the SGA (see Event 3, Difficult Tracheal Intubation )
If SGA placement is UNSUCCESSFUL, attempt face mask ventilation
If face mask ventilation is adequate, but intubation is not possible
Wake the patient up and reevaluate for awake fiberoptic intubation
Patient will be at increased risk of awareness with prolonged intubation attempts
If face mask ventilation is UNSUCCESSFUL, decide whether to awaken the patient or establish a surgical airway
If muscle relaxation is wearing off, awaken the patient
If the patient CANNOT BE INTUBATED OR VENTILATED
Move early and aggressively to emergency cricothyrotomy or other emergency surgical airway. DO NOT WAIT for the O 2 saturation to fall precipitously
Consider transtracheal jet ventilation, weighing the significant risk of the procedure
If surgical airway is established, consider whether to awaken the patient or proceed with cesarean section
Failed airway management may result in maternal cardiac arrest (see Event 82, Cardiac Arrest in the Parturient )
Complications
Hypoxemia
Aspiration of gastric contents
Esophageal intubation
Airway trauma/bleeding/swelling
Dental damage
Cerebral anoxia
Awareness
Fetal death
Maternal death
Suggested Reading
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