It is not uncommon for patients with previous head or spinal cord injury to become pregnant. Many of these women will seek pre-conception advice, but others will present in the antenatal period.
Problems and special considerations
The extent of the problems depends on the neurological deficit. For head-injured patients, the main concerns are related to:
• The presence of upper motor neurone lesions (causing difficulties with positioning and mobility; possible hyperkalaemic response to suxamethonium)
• Immobility (increasing the risk of thromboembolism, pressure sores and atelectasis following general anaesthesia)
• Any associated injuries, especially neck (affecting the airway) and pelvis or vertebral column (affecting mode of delivery and regional analgesia/anaesthesia)
• Difficulties in communication
For spinal-cord-injured patients, the above concerns may also exist. The level of the neurological deficit is the most important issue; the major considerations are:
• Pulmonary function and the effect of pregnancy and delivery. If the level is above T4, there is likely to be some reduction in respiratory reserve. The phrenic nerve supply to the diaphragm arises from cervical roots 3-5, so this muscle is usually spared in paraplegics. However, the intercostal nerves, which contribute to ventilation and which may be particularly important in pregnancy, will be affected.
• Risk of autonomic hyperreflexia. This is usually associated with injuries above T4-6 and results in increased sensitivity of sympathetic reflexes in response to cutaneous or visceral stimulation below the level of the lesion, leading to exaggerated sympathetic nervous activity and release of catecholamines. There is resultant labile blood pressure, typically causing massive vasoconstriction and hypertension that may be severe enough to cause seizures or stroke. Arrhythmias may occur, and there may be a compensatory bradycardia. Susceptibility usually develops within a few weeks of injury.
• Mode of delivery. A sensory level above T10 is usually associated with a painless labour, and these women are also more likely to deliver prematurely. This may result in a painless precipitous delivery. Some of these women will suffer from muscle spasms, and many will need an assisted delivery.
Management options
These women should be seen antenatally, and any neurological deficit should be carefully assessed. A thorough history should seek to elicit symptoms and triggers of autonomic hyperreflexia, and details of previous spinal surgery should be obtained. The delivery plan should take the above points into consideration, with epidural analgesia part of the management in most cases.
Epidural analgesia has been shown to be effective in prophylaxis and treatment of autonomic hyperreflexia. The epidural should be carefully managed to minimise any cardiovascular changes, and a low concentration of local anaesthetic combined with an opioid is usually considered the method of choice, although the need for more concentrated local anaesthetic has been suggested in order to block the powerful afferent triggers of autonomic hyperreflexia. Autonomic hyperreflexia is difficult to treat pharmacologically, and a- and β-blocking drugs and nifedipine are of limited value. The use of magnesium sulfate has been described, although experience is limited.
Regional anaesthesia is the anaesthetic of choice for operative delivery in most cases. If general anaesthesia is used, alternatives to suxamethonium should be considered if within the period of risk of hyperkalaemia (10 days to 6-7 months after injury). Care must be taken to avoid autonomic hyperreflexia, and deep anaesthesia is needed.
Key points
• Any patient who has had a past neurological trauma requires individual assessment of her neurological deficit and associated injuries in order to estimate her risk factors.
• Regional analgesia and anaesthesia are indicated in most cases.
• Autonomic hyperreflexia is best prevented or controlled by epidural block.
Further reading
Vercauteren M, Waets P, Pitkanen M. Neuraxial techniques in patients with pre-existing back impairment or prior spine interventions: a topical review with special reference to obstetrics. Acta Anaesthesiol Scand 2011; 55: 910-17.