What not to do in pheochromocytoma.

Use of a screening VMA procedure rather than a specific assay may yield false-positive results. Plasma catecholamine levels should be obtained in the unstressed, supine patient. Pharmacologic tests are less reliable than chemical tests. In the presence of a pheochromocytoma, phenoxybenzamine should be administered before any manipulative procedures, as well as prior to surgery. This agent should be given along initially; propranolol may be added preoperatively.