Deliberate hypotension.

Deliberate hypotension can reduce major blood loss and indelicate operations can produce a drier field increasing the ease of surgery and the likelihood of a good result. The techniques used to induce hypotension can also be used to avoid dangerous hypertension during and after surgery. These benefits must be weighed against the risks of inadequate perfusion: especially cerebral, myocardial, or renal. In previously normotensive patients these risks are minimal when the arterial pressure is held above 80 torr systolic, and may be acceptably small even at mean pressure of 50 to 60 torr. Previously hypertensive patients show signs of cerebral ischemia at higher pressures; they should probably not be subjected to deliberate hypotension, but they also can be harmed by severe hypertension which can be avioded by the proper use of hypotensive agents. For most situations a balanced technique is suitable: after a stable anesthetic level has been achieved using halothane or enflurane, hypotension can be induced with sodium nitroprusside or trimethaphan camsylate. Longer-acting agents such as pentolinium are sometimes desirable, but the shorter-acting agents are easier to control. Careful monitoring with observation of intra-arterial pressure, electroencephalogram, electrocardiogram, and determination arterial blood gas tensions is likely to make for safer conduct. Close postoperative observation is essential. With careful preparation and monitoring deliberate hypotension can be a safe technique for reducing blood loss or facilitating delicate procedures.