In an article published in this issue of Korean Journal of Anesthesiology (KJA), Song et al. [2] present the effect of tourniquet deflation on hemodynamics and regional cerebral oxygen saturation in older-age patients. In this issue, the authors show conclusively that tourniquet deflation caused significant changes in hemodynamic and metabolic status, but did not change regional cerebral oxygen saturation; in addition, the authors recommended to monitor neurologic status as well as hemodynamic and metabolic status to avoid serious complications especially in aged patients.

In actuality, the effect of pneumatic tourniquet during lower extremity surgery has been investigated in at several institutions. The results of this article are not much different from previous studies. Choi et al. [3] described increased HR after deflation, but there was no change in HR in elderly patients under general anesthesia. Kim et al. [4] reported there were no changes in HR in elderly hypertensive patients. This result might be related with decreased activity in the autonomic nerve system and in cardiac reserve [5].

Immediately after tourniquet deflation, mean arterial pressure (MAP) decreased with cardiac output (CO) due to a shift of blood back to the limb and post-ischemic hyperemia. These changes may cause decreased perfusion to brain. On the other hand, transient increases in arterial carbon dioxide pressure (PaCO2) after deflation may increase cerebral blood flow about 50%[6]. Increases in cerebral blood volume may result in secondary brain injury in patients with increased intracranial pressure. Therefore, it has become practice to monitor the central nervous system during orthopedic surgery when a tourniquet is in use. Compared with other monitoring tools, near-infrared spectroscopy (NIRS) is relatively simple, noninvasive, and reliable. Even though Song et al. observed no meaningful changes in regional cerebral oxygen saturation, the increased PaCO2 and decreased MAP and CO are enough reasons to monitor the CNS.

As mentioned above, aging is not only means declining of physiological functions that result in a decreased reserves, but also sometimes is combined with underlying diseases such as hypertension, diabetes mellitus, and cardiopulmonary disease, etc. Pre-existing concomitant diseases related with higher morbidity and mortality [7]. Therefore there are greater morbidity, mortality and recovery times from anesthesia for elderly patients than those for younger patients [8]. In this aspect, more research needs to be performed to manage older patients during perioperative periods in anesthetic research field.