Epidural block: technical aspects and complications.
In continuous epidural anaesthesia we rely heavily on the 'test dose' to confirm correct placement of the catheter. This is not always accurate and there are a number of new techniques designed to provide better information about epidural needle and catheter placement. These include: electrical stimulation of the catheter, use of ultrasound and the application of simple geometry. The use of epidurals in patients undergoing coronary artery bypass graft surgery is controversial because of the risk of vertebral canal haematoma. Neurological complications may arise during administration of the block, since the needle or catheter may result in direct nerve trauma. The injection of irritant drugs can also cause neurological damage. We must therefore be meticulous when injecting drugs into the epidural space. The increasing use of anticoagulant therapy in surgical patients and, in particular, the variety of low molecular weight heparins available, may make it difficult to safely perform epidural anaesthesia.