ABSTRACT
Epilepsy in pregnant women, usually starting in childhood or early life, is the commonest cause of seizures in pregnancy, affecting 1 in 200 women. Diagnostic confusion can occur with eclampsia, which is the most common cause of seizure during the peripartum period. Both can be confused with other conditions such as syncope, migraine, metabolic and cerebral disorders. Epilepsy was responsible for 10% to 15% of the indirect cause of maternal death in the U.K. Confidential Enquiry in Maternal Deaths reports during the period 1997 to 2006 (23). Interaction among anaesthetic drugs and antiepileptic drugs takes many forms. Phenytoin and other hepatic microsomal enzymes inducing AEDs will enhance the breakdown of opioids, neuromuscular blocking drugs and volatile anaesthetic agents. In turn, this affects drug dosing and production of toxic metabolites. Some anaesthetic agents are epileptogenic particularly in presence of hypocapnia. Pethidine and its metabolite norpethidine with its long half-life can cause CNS excitability. Propofol has been implicated in epileptogenesis, with myoclonic activity and opisthotonus. However, propofol effectively stops seizures in humans and animals (24) and seizure time is shortened when compared to methohexital for electroconvulsive therapy. Low serum concentrations of amide local anaesthetics are anticonvulsant, but at high serum concentrations they cause convulsions. The action of non-depolarising neuromuscular blockers may be enhanced by concomitant use of anticonvulsants. Anaesthetists must also be aware of the side effects of anti-epileptic drugs. Communication between anaesthetist, obstetrician and neurologist is important. Provision of effective labour analgesia to reduce anxiety and hyperventilation are the goals anaesthetic care. Anaesthetic evaluation should include an assessment of seizure control, side effects of therapy, the patient’s mental and physical status and proposed obstetric management. Parenteral opioid analgesia can be used with a dose modification to prevent worsening CNS depression in the parturient using anticonvulsants. However, epidural analgesia provides superior pain relief and does not depress the CNS. Patients with evidence of bleeding diathesis require coagulation assessment prior to regional analgesia. Low-dose epidural analgesia for labour pain and slow incremental to up for caesarean section would avoid high plasma concentrations of local anaesthetic, which are epileptogenic. Choice of general or regional anaesthesia for operative delivery is determined by a combination of maternal, fetal and obstetric factors. Post-ictal and druginduced somnolence and status epilepticus mandate general anaesthesia. Regional anaesthesia is appropriate for elective caesarean section. Potential local anaesthetic toxicity should be kept in mind. There is no contraindication to the administration of regional anaesthesia in patients with epilepsy. In a review of 100 epileptic parturients, 19 received general anaesthesia, 48 received spinal anaesthesia, 21 received epidural or caudal anaesthesia and 12 received pudendal block (25). Of the five patients who had a post-partum seizure, four had received spinal anaesthesia and one had received general anaesthesia. No seizure occurred in patients who received epidural or caudal anaesthesia. Transcutaneous electrical nerve stimulation (TENS) is not contraindicated in women with epilepsy.
