Effect of Lemon Inhalation Aromatherapy on Postoperative Pain, Nausea and Vomiting, Delirium, and Inflammatory Markers After Coronary Artery Bypass Grafting: A Triple-Blind Randomized Trial

Complementary and integrative medicine has gained increasing attention as a safe adjunct for improving postoperative outcomes, particularly in cardiac surgery where pain, postoperative nausea and vomiting (PONV), and delirium remain common and debilitating complications.

This randomized clinical trial aimed to investigate the effect of lemon inhalation aromatherapy on postoperative pain, PONV, delirium, and inflammatory markers in patients undergoing coronary artery bypass grafting (CABG) surgery.

In this triple-blind, parallel-group randomized controlled trial, 104 adult patients scheduled for elective CABG surgery were randomly allocated to either lemon aromatherapy or an odorless placebo. Aromatherapy began the evening before surgery, was administered every two hours until anesthesia induction, and resumed continuously during mechanical ventilation and for 72 hours after extubation. Pain and PONV were assessed every 6 hours across eight postoperative shifts using a 0 - 10 Numeric Rating Scale. Delirium was evaluated at 24, 48, and 72 hours using the intensive care delirium screening checklist (ICDSC). Inflammatory markers [C-reactive protein (CRP), neutrophil-to-lymphocyte ratio (NLR)] were measured at baseline and 72 hours. Data were entered after double-checking into SPSS version 26. Continuous variables were tested for normality using the Shapiro-Wilk test; normally distributed variables were compared using independent t-tests, and non-normal variables with the Mann-Whitney U test. Categorical variables were analyzed using chi-square or Fisher's exact test. All analyses were two-tailed with a significance level of P < 0.05.

Of the 104 randomized patients, 103 completed the study (one patient in the intervention group was withdrawn due to postoperative cerebrovascular insult). The two groups were well-balanced at baseline with respect to demographic and clinical characteristics. Pain scores were significantly lower in the intervention group at all eight postoperative shifts (P < 0.001). Postoperative nausea and vomiting severity was significantly reduced across all shifts (P < 0.001), with fewer vomiting episodes and lower need for rescue antiemetic medications. The incidence of delirium was significantly lower in the intervention group at 24 hours (11.8% vs. 28.8%), 48 hours (15.7% vs. 34.6%), and 72 hours (7.8% vs. 23.1%) (all P < 0.05). Significant improvements were also observed in multiple ICDSC subscales, particularly inattention, disorientation, sleep-wake disturbances, and inappropriate speech/mood. At 72 hours, both CRP and NLR levels were significantly lower in the aromatherapy group, suggesting attenuation of the postoperative inflammatory response. No aromatherapy-related adverse events were observed.

Lemon inhalation aromatherapy was effective in significantly reducing postoperative pain, PONV, delirium incidence, and inflammatory markers following CABG surgery. As a safe, low-cost, and non-invasive complementary intervention, lemon aromatherapy may enhance postoperative recovery and represents a promising adjunct to standard care in cardiac surgery.