The effect of inhalation aromatherapy in patients undergoing cardiac surgery: A systematic review and meta-analysis of randomized controlled trials

•The review analyzed published trials regarding inhalation aromatherapy efficacy on alleviating symptoms after cardiac surgery.•It revealed the effects of inhalation aromatherapy on anxiety, pain, and different vital signs.•It gives explanations for underlying mechanisms.•Implications for clinical practice and further research are discussed. The goal of this study was to synthesize evidence regarding the efficacy of inhalation aromatherapy in patients undergoing cardiac surgery. We conducted an electronic search of four authentic databases. Randomized controlled trials (RCTs), which compared inhalation aromatherapy versus control in patients undergoing cardiac surgery, were included. Data were extracted from eligible studies and pooled in a meta-analysis model. We sought to evaluate anxiety, pain, stress, and vital signs including heart rate, systolic and diastolic blood pressure. Nine RCTs were included in this study with a total of 656 patients. Our analysis showed inhalation aromatherapy was significantly effective in reducing anxiety (MD= −3.11, 95 % CI [−5.26, −0.96], p = 0.005), and pain (MD= −0.83, 95 % CI [−1.59, −0.07], p = 0.03) in patients undergoing cardiac surgery. Additionally, inhalation aromatherapy significantly reduced heart rate compared to control group (MD= −5.49, 95 % CI [−9.07, −1.81], p = 0.003). However, no significant differences were found between both groups in mental stress, systolic and diastolic blood pressure. Inhalation aromatherapy administration especially with lavender can significantly reduce anxiety, pain, and heart rate in patients performed cardiac surgery. However, it is not associated with significant differences in systolic and diastolic blood pressure. Further studies are needed to confirm our results.