Management of Obstetric Crises

This document addresses three critical scenarios in obstetric anesthesia: failed spinal anesthesia, unexpected difficult airway, and intraoperative seizures. The content is derived from an expert panel discussion.

1. Failed Spinal Anesthesia

This section covers the definition, incidence, causes, and management strategies for failed spinal anesthesia in a parturient, using a specific case example of an obese patient with pre-eclampsia.

What is the case scenario presented for failed spinal anesthesia?

The scenario involves a 32-year-old primigravida with a BMI of 42 and pre-eclampsia, posted for an emergency LSCS. The spinous processes were barely palpable, but a spinal anesthetic was administered with difficulty. After 5 minutes, there was only heaviness in the limbs, with a sensory blockade level of T10 on one side and T8 on the other, creating a dilemma about whether to proceed with the spinal or use an alternative technique.

What is the definition and incidence of failed spinal anesthesia?

Failed spinal anesthesia is defined as when an intrathecal drug is administered with clear CSF flow, but the expected block level does not occur. The Royal College of Anaesthetists (RCA) guidelines indicate that failure rates should be less than 1% for elective LSCS, below 5% for category 2-3 LSCS, and up to 15% for category 1 (emergency) LSCS.

Statistics show that failed spinal requiring conversion to general anesthesia occurs in about 1 to 1.9% of patients,
while 2.7 to 10.2% of patients may need repeat spinal or additional sedation.

What are the key factors that can contribute to failed spinal anesthesia?

Multiple factors can contribute to a failed spinal, including:

Patient Anatomy: Obesity can make technique difficult. A low BMI or early gestational age may lead to a larger CSF volume, diluting the drug.
Technique: Incorrect needle placement (e.g., subdural or extradural) or administering the spinal at a low level (L4-L5 or L5-S1) can result in the drug pooling in the sacral region rather than spreading to the required thoracic level.
Drug Factors: Using a low volume of local anesthetic (less than 2.2 ml) is associated with higher failure rates. Adding lipophilic opioids like fentanyl improves block quality.
CSF Volume: The sensory and motor block are inversely related to the volume of CSF in the lumbar region. A larger volume can dilute the drug, leading to failure.
Other Factors: Previous C-section (due to scarring requiring a denser block), prolonged surgical duration, and patient positioning (sitting position may have higher failure rates than lateral).

How should a clinician manage a suspected failed spinal anesthesia?

Management should be stepwise and adaptable to the urgency of the situation:

Wait and Assess: Do not immediately accept defeat. Monitor for signs of sympathetic blockade (fall in BP, heart rate stabilization), which can indicate the spinal is working. A slight head-down tilt can help a hyperbaric solution spread. Guidelines suggest waiting up to 15 minutes to assess for complete onset.
Counsel and Supplement: Reassure the patient. If the block is progressing slowly, supplement with gas/oxygen (50/50) and consider small doses of agents like propofol or ketamine, being cautious not to create an unsafe cocktail that risks loss of airway reflexes.
Repeat Spinal: If there is no change after waiting and the obstetrician can wait, a repeat spinal can be considered. Use a slightly reduced volume (e.g., 1.4 to 1.6 ml) in the sitting position, with or without fentanyl, while closely monitoring for hypotension.
Convert to General Anesthesia (GA): If the obstetrician is in a hurry or the block is absent, prepare for GA. Be aware that after a spinal, converting to GA carries risks of significant hypotension and loss of airway reflexes due to sedative drugs already given.

What is the recommended way to assess the adequacy of a spinal block for C-section?

According to the French practice bulletin, the most effective block for C-section is confirmed by a bilateral T6 dermatome level evaluated with light touch, plus a bilateral T4 level evaluated with cold sensation.

2. Unexpected Difficult Airway and "Can't Intubate, Can't Oxygenate" (CICO)

This section addresses the management of an unexpected difficult airway after induction of general anesthesia in an obstetric patient, following the principles of the Indian Association of Difficult Airway guidelines.

What is the difficult airway case scenario?

The scenario is a 32-year-old first-time mother with borderline obesity, rushed for an emergency LSCS due to fetal distress. After a rapid sequence induction of GA, the anesthesiologist encounters an unexpected difficult intubation with a swollen airway, poor Cormack-Lehane view, and falling oxygen saturation levels.

What is the incidence of desaturation and failed intubation in obstetrics?

Desaturation in the obstetric operating room is relatively common, occurring in approximately 1 in 6 cases, or 17%. The incidence of failed intubation is higher in obese pregnant individuals, estimated at around 1 in 200.

What is the immediate stepwise management for a failed intubation in obstetrics?

The management should follow a systematic algorithm:

Call for Help: Immediately summon additional assistance.
Simultaneous Re-oxygenation:
- Par oxygenation: Use two oxygen sources. Give high-flow oxygen (10 L/min) via a tight-fitting face mask. Simultaneously, provide nasal oxygen at 15 L/min via nasal prongs throughout the intubation attempts. This prolongs the safe apnea time.
Optimize for Second Intubation Attempt:
- Optimize patient position (ramping).
- Change the laryngoscope blade or operator.
- Allow gentle mask ventilation (with pressures <20 cm H2O) and apply cricoid pressure, with a low threshold to release it if it hinders the view.
- Maintain depth of anesthesia.
- Only attempt intubation if SpO2 is >95%. Use a videolaryngoscope if available.
- Confirm tube placement with five waveforms of EtCO2 without a decline.
If Second Intubation Fails:
- Re-oxygenate the patient as in step 2.
- Insert a second-generation supraglottic airway device (e.g., LMA with a gastric port). Limit attempts to two.
- If successful, proceed with surgery, accepting the low aspiration risk. After delivery, consider intubating through the device only if absolutely necessary and with a fiberoptic scope.
If Supraglottic Airway Ventilation Fails (Complete Ventilation Failure):
- Make a final attempt at face mask ventilation with optimal technique, airway adjuncts, and ensuring adequate neuromuscular blockade.
- If this fails, declare Complete Ventilation Failure (the Indian Association's equivalent of CICO).
- Proceed to front-of-neck access: perform an emergency cricothyroidotomy using a scalpel technique or one you are familiar with. Do not wait for the baby to be delivered; perform a perimortem C-section to deliver the baby, which aids in resuscitating the mother.

What are the key strategies from the Indian difficult airway guidelines for obstetrics?

Key recommendations from the Indian guidelines include:

Ramping: Position the patient to improve functional residual capacity (FRC), pre-oxygenation, and intubating conditions.
Par oxygenation: Use two oxygen sources (face mask and nasal prongs) to prolong safe apnea time.
Wait for 95%: Do not attempt laryngoscopy or escalate airway maneuvers unless SpO2 is above 95%.
Limit Attempts: Limit intubation and supraglottic airway attempts to two each.
Confirmation: Confirm tracheal tube placement with five waveforms of EtCO2.
Complete Release of Cricoid Pressure: Upcoming guidelines recommend complete, not partial, release of cricoid pressure if it is impairing laryngeal view.

Why is extubation a critical phase after a difficult airway?

Extubation is as critical as intubation because the risk of complications, such as laryngospasm or regurgitation, remains high. Reintubation in a patient with a known difficult airway is extremely challenging. Therefore, a planned extubation strategy is essential, and the event must be thoroughly documented to guide future anesthetics.

3. Intraoperative Seizures on the Table

This section discusses the differential diagnosis and management of a patient who presents with a seizure upon arrival in the operating room for an emergency LSCS.

What is the seizure case scenario?

The scenario is a 42-year-old lady shifted to the operating table for an emergency LSCS who immediately throws a seizure.

What are the key differential diagnoses for a seizure in an obstetric patient?

The major causes of seizure in an obstetric patient include:

Eclampsia: Pre-eclampsia plus seizures.
Amniotic Fluid Embolism (AFE): Presents with acute right heart failure, respiratory failure, and can include seizures.
Local Anesthetic Systemic Toxicity (LAST): Can occur if local anesthetic is inadvertently injected intravascularly.
Subdural Block: A rare complication of neuraxial techniques where the drug is injected into the subdural space, potentially causing a high block and convulsions.
Metabolic and Electrolyte Disturbances: Hypoglycemia, hyponatremia, hypocalcemia, and hypomagnesemia can trigger seizures.
Posterior Reversible Encephalopathy Syndrome (PRES): Often associated with eclampsia, presenting with vasogenic edema visible on MRI.

What are the key management points for eclampsia?

Management of eclampsia includes:

ACLS Protocol: Airway, Breathing, Circulation support.
Anticonvulsants: Magnesium sulfate is the drug of choice. Monitor for toxicity by checking deep tendon reflexes, respiration rate (>40 breaths/cycle), and urine output (>30 ml/hr). Therapeutic serum levels are 4-7 mEq/L.
Antihypertensives: Control severe hypertension.
Fluids: Careful fluid management.
Delivery: Expedite delivery of the fetus.

What is the significance of PRES in this context?

PRES (Posterior Reversible Encephalopathy Syndrome) is a clinicoradiological syndrome often associated with eclampsia. It is characterized by vasogenic edema, typically in the posterior cerebral hemispheres, and is diagnosed via MRI (T2 hyperintensities). Although termed "reversible," it can sometimes lead to irreversible brain injury if not managed promptly.

4. Panel Discussion and Key Takeaways

This section captures the final questions and expert commentary from the panel discussion, summarizing the most critical practical points.

Can a fiberoptic bronchoscope (FOB) be used as a second option in an unanticipated difficult airway?

The panel's response was that FOB can be used, but it depends entirely on its immediate availability and the clinician's familiarity and expertise with the technique. If those conditions are met, it is a valid option. Otherwise, a second-generation supraglottic airway device remains the recommended fallback.

What is a practical tip for ensuring a second source of oxygen?

If an anesthesia workstation lacks a second oxygen source, a simple and effective measure is to keep a B-type oxygen cylinder with a flow meter in the operating room. This is particularly vital in obstetrics where two lives are at stake.

What is the key take-home message regarding oxygenation during airway management?

The emphasis has shifted from simple pre-oxygenation to "par oxygenation." This means continuing to deliver oxygen (via nasal prongs or other means) throughout the entire period of apnea and intubation attempts. This technique prolongs the safe apnea time, reduces the incidence of desaturation, and improves patient safety.

What is a critical, often-overlooked point in difficult airway management?

The panel emphasized that successfully intubating the patient does not solve the whole problem. The extubation phase is equally, if not more, dangerous. A patient can be lost during extubation due to complications like regurgitation and aspiration. A proper extubation strategy and ensuring the return to a normal, safe airway is paramount.