Salivary amylase as a preoperative marker of anxiety in perioperative medicine

Abstract

Preoperative anxiety is an unpleasant state resulting from the anticipation of a threatening situation. It contributes to acute preoperative stress. Up to 40 % of patients experience anxiety before surgery that is associated with adverse intraoperative course and postoperative outcomes. Assessment of preoperative anxiety is challenging and mainly based on lengthy questionnaires or plasma biomarkers that cannot be used for bedside decision-making. There is a potential role for noninvasive, real-time, and point-of-care biomarkers such as salivary amylase (SA) to identify anxious patients and to target preoperative pharmacologic or non-pharmacologic interventions in these patients. SA is the principal saliva protein and is mainly secreted by the parotid glands. The autonomic nervous system plays a major role in SA secretion. An association between changes in SA during exposure to a stressful stimulus and changes in blood norepinephrine or heart rate variability indices strongly suggests that SA is an accurate marker of sympathetic nervous system activity. There is also an association between changes in SA during exposure to a stressful stimulus and changes in anxiety state. Saliva can be collected by many methods. SA activity (SAA) is measured by its enzymatic activity and depends on the collection method, which needs to be standardized. Point-of-care SAA measurement is now possible with a handheld format automated analyzer. SAA increases quickly after exposure to a stressful stimulus (i.e., less than 5 min) and returns rapidly to baseline (i.e., less than 15 min) during soothing conditions ("on-off" marker). The high amplitude of SAA variation between basal and stress conditions makes SAA a highly sensitive and dynamic marker of the acute stress response, including preoperative anxiety. However, several non-stress-related factors (time of day, smoking, food, alcohol or caffeine intake, physical exercise, drugs, and comorbidities) can influence basal and stress-induced SAA. Saliva flow rate, age, and sex have little influence on SAA. Its great within- and between-individual variations imply that SAA should be measured for each patient both before and during the stressful event. A twofold increase in SAA after exposure to a stressful stimulus can be considered biologically relevant. Several human studies demonstrate an increase in SAA after exposure to acute stressful stimuli, including arrival at the operating theater. The literature is still scarce about the association between preoperative SAA and intraoperative course or postoperative outcome. It remains a stimulating area of research.