In the present study, we found significantly higher preoperative MPV values among patients with high preoperative anxiety scores. Similarly, propofol consumption at 30 min was higher in patients with higher anxiety scores. However, we found no relationship between the time to achieve entropy value below 60 and anxiety scores.
Psychological factors have an effect on anesthetic requirements and postoperative pain in patients undergoing a selected surgical procedure. Kil et al. (10) investigated the effects of anxiety on the amount of propofol to achieve different levels of sedation. In addition, a high anxiety level increased the propofol requirement for both superficial sedation (BIS 85) and moderate sedation (BIS 75). Propofol requirements for deep sedation (BIS 65) were higher with chronic anxiety, whereas no significant difference was noted in relation to state anxiety. In another study, Maranets et al. (7) reported that the baseline anxiety level increased the intraoperative analgesic requirement and, similarly, Hong et al. (8) showed a remarkable correlation between the amount of propofol required for sedation and the level of anxiety. In the present study, the time required for anesthesia induction using a constant rate of infusion of propofol was similar for patients with and without anxiety, whereas propofol consumption at 30 min was significantly higher in the anxious group.
There are several studies in the literature evaluating the effects of age and sex on anxiety. Kil et al.(10) showed that advancing age was not related to anxiety; however, they reported a relationship with increasing pain sensitivity. Another study (12) reported higher anxiety levels in female patients, and similar to previous studies, there was a female predominance in the group of patients with higher anxiety scores. Different from the literature, however, the mean age was significantly higher in patients with a high anxiety score.
Previous studies also demonstrated a relationship between increased platelet activity and anxiety and depression. In a study of 15 patients, Canan and Ataoğlu (12) reported elevated MPV values in patients with major depression, and also a marked decrease in the MPV values of eight patients undergoing escitalopram therapy. Another study comparing 289 patients with major depression and healthy control subjects reported higher MPV values in the patient group (13). Multiple changes may occur in platelet parameters in patients with anxiety disorders (14). Increased MPV values may be indicative of increased platelet activation or the presence of enlarged and extremely flexible platelets (15). The possible mechanisms underlying platelet abnormalities in major depression are considered to be caused by changes in the platelet functions associated with alterations in intraplatelet monoamine and catecholamine concentrations, increases in plasma 5-HT and epinephrine concentrations, and increases in intraplatelet calcium mobilization (16). The underlying mechanism in anxiety disorders has been associated with serotonin mechanism. Vizioli et al. (17) showed that increased sympathetic activity could result in an increase in MPV values. Serotonin 5-HT2A receptors and serotonin transporter receptors in the platelets and brain are encoded by the same gene (18), and as a result, serotonin-related platelet activation was reported in patients with anxiety disorder (18). As opposed to other studies, Gul et al. (19) found lower MPV values in patients with anxiety disorder than in the control group. Although the authors were unable to explain the actual mechanism, they suggested that abnormal 5-HT metabolism in patients with panic disorder might have led to their finding. The MPV values were higher in patients with high anxiety scores in the present study. The calculation of the area under curve in the ROC analysis showed that preoperative MPV values performed better in detecting the presence of anxiety than the level of propofol consumption. A cut-off MPV value of 065 yielded the best sensitivity (73%) and specificity (46%) values.
The main limitation of the present study is that age and sex, which may affect platelet function and anxiety, were not taken into consideration when recruiting participants, and as a result, a difference was observed between the groups in terms of age and gender. Studies of more homogeneous groups involving single age and sex groups may eliminate the possible effects of age and sex on MPV values.