Spinal anaesthesia for caesarean section in a patient with severe pre-eclampsia and a platelet count of 78
A 31-year-old primigravida at 36 weeks presents with a blood pressure of 168/112 mmHg, 3+ proteinuria, and a platelet count of 78 x 10^9/L that has fallen from 145 two days ago. She has a headache and visual scotomata. Fetal heart rate shows late decelerations, and the obstetrician requests an urgent category 2 caesarean section. She is 155 cm tall and weighs 95 kg, with a Mallampati 3 airway and a short neck. Coagulation screen shows a fibrinogen of 2.1 g/L and a mildly prolonged APTT. The anaesthetic team must decide between neuraxial and general anaesthesia.
1. Compare the risks of spinal anaesthesia versus general anaesthesia in this patient and state which you would choose, with reasoning.
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Spinal anaesthesia:
- Advantages: Avoids the hypertensive response to laryngoscopy, avoids airway instrumentation in a potentially oedematous airway, and allows the mother to be awake for the delivery. It is generally preferred in pre-eclampsia because it reduces the risk of airway catastrophe.
- Risks: The platelet count of 78 x 10^9/L is in the range where neuraxial haematoma risk is increased, particularly with a rapidly falling count and abnormal coagulation. A falling count suggests evolving HELLP or consumptive coagulopathy, so the trend matters more than the absolute number.
General anaesthesia:
- Advantages: Avoids neuraxial bleeding risk.
- Risks: Difficult airway (Mallampati 3, short neck, obesity, airway oedema), aspiration, and a hypertensive surge at laryngoscopy that can cause intracranial haemorrhage or pulmonary oedema. The fetus is already compromised, so the induction-to-delivery interval must be short.
Decision: I would not proceed blindly on the platelet count alone. I would check a repeat count and fibrinogen urgently, involve haematology, and give steroids for fetal lung maturity if time permits. If the count is stable and above 75-80 x 10^9/L with normal fibrinogen, a single-shot spinal with a 25-27G pencil-point needle is reasonable. If the count is falling or coagulation is worsening, I would choose general anaesthesia with a careful airway plan and invasive blood pressure monitoring. The overall principle is that a rapidly falling platelet count with HELLP features favours general anaesthesia.
2. If general anaesthesia is chosen, describe the induction and maintenance plan that minimises the risk of intracranial haemorrhage and fetal compromise.
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Pre-induction:
- Treat the blood pressure with intravenous labetalol or hydralazine to a target systolic of 140-150 mmHg. Give magnesium sulphate for seizure prophylaxis per protocol.
- Place invasive arterial monitoring, and prepare for a difficult airway with video laryngoscopy, a bougie, and a second-generation supraglottic airway available. Preoxygenate for 3 minutes.
Induction:
- Rapid sequence induction with thiopentone 4-5 mg/kg (or propofol) and suxamethonium 1.5 mg/kg, with cricoid pressure per local policy.
- Attenuate the pressor response: ensure adequate depth before laryngoscopy, and consider a short-acting opioid (alfentanil 10-20 micrograms/kg) or esmolol. Avoid ketamine, which can raise blood pressure.
- Limit laryngoscopy to one optimised attempt; the aim is to minimise the hypertensive surge.
Maintenance:
- Volatile agent at 0.8-1.0 MAC with oxygen/air, plus a neuromuscular blocker. Avoid nitrous oxide if there is a risk of air embolism or bowel distension.
- Target systolic below 160 mmHg and mean arterial pressure above 65 mmHg to maintain uteroplacental perfusion.
- After delivery, give oxytocin as an infusion (5 IU over 5 minutes) rather than a bolus, because boluses cause hypotension. Avoid ergometrine, which raises blood pressure.
- Extubate awake and sitting up after full reversal, with adequate analgesia (intrathecal morphine if neuraxial is not used, or intravenous opioid PCA).