**2. Preoperative evaluation**

### **2.1 General considerations**

According to the guidelines provided by the European Society of Anesthesia and Intensive Care (ESAIC) for noncardiac surgery, patient's eligibility for surgery should not be based exclusively on strict criteria related to surgery indication, patient's age, weight, and comorbidity, but it is the result of patient's multidimensional assessment with the aim to evaluate the patient's capacity to face and recover from surgery and anesthesia. Such assessment includes the evaluation of the presence and the degree of severity of cardiovascular and respiratory diseases, smoking habit, obstructive sleep apnea syndrome (OSAS), kidney diseases, diabetes, obesity, liver diseases, and alcohol abuse [6]. The assessment of the American Society of Anesthesiologists (ASA) physical status classification system and patient's functional capacity, expressed in terms of metabolic equivalents of task (METS) used to assess energy cost for physical activities or exercise capacity, are two pivotal tools in the evaluation of all patients but may not be sufficient [7, 8]. Interestingly, although the absolute risk for 90-day mortality following total hip replacement is small, a significant increased relative risk has been reported for patients with osteoarthritis younger than 60 and without comorbidity when compared with subject with the same characteristics not undergoing hip surgery [9]. Such increased risk disappears in the long term. On the contrary, there is no increased risk for mortality both in the short and long terms for patients older than 60 and with mild-to-severe comorbidity burden [9]. Such findings indicate that although total hip replacement is a low-risk procedure, it still imposes a risk that becomes most evident in patients with a low baseline mortality risk. The increased relative risk among patients who are young or with a good preoperative prognostic profile may reflect patient-related factors, such as obesity, which may be associated with both the development of osteoarthritis at a young age and an increased procedure-related risk of adverse outcome, including death, as well as system-related factors that might include a lower level of awareness by health professionals toward the prevention, detection, and treatment of thromboembolic complications in patients considered to have a low risk. In addition, relevant comorbidities associated with an increased risk of postoperative mortality, such as liver disease [10], may be undiagnosed in young patients and lead to an inaccurate estimate of the patient's general conditions. Another possible explanation may be the fact that any surgical procedure carries a risk, which, added to a small baseline risk in these patients, results in a high relative mortality.

In conclusion, a systematic preoperative multidimensional assessment of patients undergoing hip replacement should be routinely adopted to detect unrecognized disease and risk factors that may increase the risk associated with the surgical procedures and/ or anesthesia techniques above baseline and to propose strategies to reduce this risk.
