Effect of Controlled Hypotension on Cerebral Oxygen Saturation

For a successful functional endoscopic sinus surgery (FESS), it is crucial to provide effective controlled hypotension to reduce blood loss and provide a relatively blood-free surgical environment to facilitate surgery. The goal of controlled hypotension is to maintain an arterial blood pressure which is sufficiently low to allow a reduction in bleeding with offering a superior intraoperative hemodynamic stability during stressful surgical events to maintain intact cerebral microcirculatory auto-regulation. Auto-regulation impairment during controlled hypotension might increase oxygen extraction ratio. Thus monitoring the cerebral oxygen saturation (rSO2) to measure cerebral oxygenation becomes essential and it remains a challenge to clinically assess cerebral oxygenation on a routine basis. Various recent studies reported based on facilitating the induction of controlled hypotension, but the effects of hypotension on cerebral perfusion and oxygenation and its effects on postoperative cognitive function are still poorly characterized. Moreover, the relationship between rSO2 and controlled hypotension has not been established in patients undergoing FESS. Within the last decade, near infrared spectroscopy (NIRS) INVOS® monitors which is clinically most broadly spread technique, can be used for non-invasive assessment of cerebral perfusion by detecting changes in rSO2 by online monitoring of cerebral oxygenation. In our clinical routine for achieving a controlled hypotension, esmolol and remifentanyl are the most commonly used hypotensive agents. The aim of this prospective randomized single blind study was to investigate the influence of remifentanyl as a hypotensive agent in comparison to esmolol on rSO2 by using NIRS and postoperative cognitive function in patients undergoing FESS.