لخّصلي

1 INTRODUCTION Anxiety is an emotional response to stimuli that humans perceive as threatening.However, there is no previous meta-analysis about nursing interventions (interventions managed or applied exclusively by nurses) for preoperative anxiety as it happens with other interventions.1.1 Background Preoperative anxiety can produce physio-pathological effects such as tachycardia, arrhythmias or hypertension, causing a greater surgical risk, greater anaesthetic requirements, increased postoperative complications such as an increase in postoperative pain levels, nausea and vomiting, as well as a delay in hospitalization or postoperative stay (Celik & Edipoglu, 2018; Jaruzel & Gregoski, 2017).Many researchers have investigated different interventions for reducing preoperative anxiety, being some effects sizes estimated with meta-analysis, using intervention with guided imagery, music therapy, art therapy, clowns, or therapeutic play, among others (Alvarez-Garcia & Yaban, 2020; Gomez-Urquiza et al., 2016; He et al., 2015; Zhang et al., 2017) with positive results.There are currently two classifications of anxiety disorders, presented by the American Psychiatric Association in its diagnostic and statistical manual of mental disorders (DSM-5), and in the medical classification (ICD-10) (Ruiloba et al., 2015).Anxiety implies responses that not only affect the psychological and emotional sphere, but also have physiological and functional consequences (Stamenkovic et al., 2018).However, when the organism reacts in a non-adaptive way and this reaction is exaggerated, anxiety is considered pathological, that is, as a mental disorder (Ruiloba et al., 2015).Anxiety as a trait implies a habitual and prolonged tendency over time to react anxiously, being related to the personality of the subject, while anxiety as a state refers to the reaction in the present moment (Ruiloba et al., 2015).In addition, the volume of registered surgical interventions has increased in recent years.

1 INTRODUCTION
Anxiety is an emotional response to stimuli that humans perceive as threatening. Anxiety implies responses that not only affect the psychological and emotional sphere, but also have physiological and functional consequences (Stamenkovic et al., 2018). According to some authors, anxiety under normal conditions improves adaptation to the external environment for avoiding or facing danger (Aritsu, 2000). However, when the organism reacts in a non-adaptive way and this reaction is exaggerated, anxiety is considered pathological, that is, as a mental disorder (Ruiloba et al., 2015).

There are currently two classifications of anxiety disorders, presented by the American Psychiatric Association in its diagnostic and statistical manual of mental disorders (DSM-5), and in the medical classification (ICD-10) (Ruiloba et al., 2015). Anxiety can be considered as a trait or as a state. Anxiety as a trait implies a habitual and prolonged tendency over time to react anxiously, being related to the personality of the subject, while anxiety as a state refers to the reaction in the present moment (Ruiloba et al., 2015).

This response of the organism, can occur in specific situations, for example is a common feeling experienced by many patients who are going to be operated (Stamenkovic et al., 2018). The main reasons for this problem are the lack of knowledge and information, not only about surgical intervention, but also about anaesthesia, complications arising from it, fear of side effects, dependence on third parties and the possibility of death. Therefore, the perioperative process is worrying and stressful for most patients and generates preoperative anxiety (Moreno Fernández, 2018; Mulugeta et al., 2018).

1.1 Background
Preoperative anxiety can produce physio-pathological effects such as tachycardia, arrhythmias or hypertension, causing a greater surgical risk, greater anaesthetic requirements, increased postoperative complications such as an increase in postoperative pain levels, nausea and vomiting, as well as a delay in hospitalization or postoperative stay (Celik & Edipoglu, 2018; Jaruzel & Gregoski, 2017).

In addition, the volume of registered surgical interventions has increased in recent years. According to a study published in the newsletter of the World Health Organization, it was estimated that 312.9 million operations were performed in 2012, while in 2004, there were 226.4 million (Weiser et al., 2016). Surgical interventions are an important part of the health systems of many countries. Thus, it is import using a correct approach to the perioperative process and the preoperative anxiety that may appear, to avoid possible complications throughout the patient's recovery process.

Many researchers have investigated different interventions for reducing preoperative anxiety, being some effects sizes estimated with meta-analysis, using intervention with guided imagery, music therapy, art therapy, clowns, or therapeutic play, among others (Álvarez-García & Yaban, 2020; Gómez-Urquiza et al., 2016; He et al., 2015; Zhang et al., 2017) with positive results.

Nurses are a key part of the preoperative period. They have to check and identify risk factors for the surgery, assess patients’ needs, managing patients´ expectations and understanding patient vulnerabilities (Malley et al., 2015). Thus, nurses have close contact with patients in the preoperative period. However, there is no previous meta-analysis about nursing interventions (interventions managed or applied exclusively by nurses) for preoperative anxiety as it happens with other interventions. Taking into account the key-role of nurses in the preoperative period and the importance of reducing preoperative anxiety, it is important to review nursing interventions and to estimate the effect size of nurses´ interventions to reduce preoperative.