The Effect of Rewarming on the Cognitive Status of Patients After Open-heart Surgery: A Randomized Clinical Trial

Hypothermia is usually used during cardiac surgery to further protect against cardiac and cerebral ischemia. However, cognitive impairment could be a common complication after open heart surgery. This study aims to determine the effect of rewarming on the cognitive status of patients after open heart surgery. 

The present study was conducted as a double-blind, randomized clinical trial at Tehran Heart Center, Tehran, Iran. In this clinical trial, 80 patients referred for open heart surgery were selected and randomly assigned into the intervention (n=40) and control (n=40) groups. In the intervention group, rewarming the mattress was started after the patient entered the intensive care unit. Warming continued until the patient’s body temperature reached the normothermia level (37°C to 37.5°C). The data were collected by demographic-clinical questionnaire and Mini-Mental State Examination at three time points: before, 7 days, and 1 month after the surgery. The data were analyzed in SPSS software, version 16 using descriptive statistics, independent t test, chi-square test, repeated measure ANOVA, and paired t test. The significance level was considered less than 0.05.

The difference between the mean±SD scores of cognitive status in the intervention group before the surgery (28.73±0.87), 7 days (27.63±1.03), and 1 month after the surgery (28.93±1.21) was significant (P=0.008). The difference between the mean±SD scores of cognitive status in the control group before the surgery (28.42±1.02), 7 days (26.61±0.86), and 1 month after the surgery (27.85±1.06) was also significant (P=0.042). The results indicated that the mean score of cognitive status improves after 1 month, and it is greater in the intervention group (F=20.37, df=2, P<0.001). Significant differences were observed between the first and second time of measurements (P<0.0001) and also the second and third time of measurements (P<0.0001).

Rewarming patients after open heart surgery improves their cognitive status. Therefore, this procedure can be used as a safe and non-invasive method to prevent cognitive complications by nurses after open heart surgery.