Why is control of blood loss important during middle ear surgery?
Unlike many other types of surgery, the anticipated amount of blood lost during middle ear surgery is usually of little hemodynamic consequence. Nevertheless, even small amounts of hemorrhage impair the surgeon’s visual-ization through a dissecting microscope. Blood loss may be controlled by several methods. One popular technique is the injection of a vasoconstrictor, such as epinephrine 1:200,000, at the surgical site. Postural changes, such as a 10°–15° moderate head-up tilt may be beneficial. Patients who are free from major organ system impairment tolerate deliberate hypotension best. Pre-existing cardiovascular, central nervous system, renal, or pulmonary diseases are relative contraindications to induced hypotension. Combining deliberate hypotension and head-up tilt is a popular technique. However, these maneuvers may increase the risk of venous air embolism because central venous pressure is reduced and the operative field is ele-vated above the level of the heart. Induced hypotension in the presence of hypovolemia results in poor organ perfu-sion and organ hypoxia. Potent inhalation agents, sodium nitroprusside, nitroglycerin, α-adrenergic blockers, or β-adrenergic blockers have been employed for induced hypotension.
Complications of deliberate hypotension include impaired vital organ function, central nervous system thrombosis, renal vessel thrombosis, dizziness, and prolonged emergence. Properly selected patients who are at low risk for these complications, and the use of delib-erate hypotension, contribute to an improved surgical outcome.