Bilateral total knee replacement using the same anesthetic is not justified by assessment of the risks.

The question of whether simultaneous bilateral knee replacement is associated with an increased risk of perioperative morbidity and mortality remains controversial. There are no true prospective randomized studies that address this question. There is general agreement that the risk is higher for older patients and for those with considerable medical comorbidities, particularly those with a history of cardiac disease. There is no general agreement on the appropriate threshold for age or comorbidities in order to minimize risk. Based on available retrospective data, there is evidence to suggest that there may be some patient selection bias favoring patients with simultaneous bilateral knee replacements; despite this bias, the perioperative risks are higher for these healthier patients. The highest risk for the patient having simultaneous bilateral knee replacement seems to be that of early postoperative mortality followed by the risk of a cardiac event. The risks of thromboembolic, gastrointestinal, and neurologic dysfunction also are increased. These patients also have a higher likelihood of requiring homologous blood transfusions and of requiring posthospitalization transfer to a rehabilitation center. Because of the absence of established patient selection criteria, thresholds for assessment of the increased risks, the patient having simultaneous bilateral replacement faces an increased risk of perioperative mortality and morbidity on a random basis. Patients should be aware of this information when deciding whether to proceed with simultaneous bilateral knee replacement.