You aspirate the catheter and no blood or csf comes back.

You can give a bolus of lidocaine, say 50 - 100 mg of a 1% solution (other options for a solution are possible).  This is a nice solution to use for a bolus.  It works quickly to produce analgesia, and if it goes intravacularly it will not produce toxicity, and if it goes intrathecally, the spinal it would produce will not last long. 

You give a bolus of lidocaine and the patient says she doesn't feel right.

Try another option