Comparison of the Effects of Hypothermia and Normothermia on Cognitive Functions After Coronary Artery Bypass Surgery

Cognitive impairment is among the most prevalent complications in patients undergoing CABG. Selection of the proper temperature is one of the main moderating factors in cognitive impairment following CABG. Today, heart surgery is done using the two methods of hypothermia and normothermia. However, there is no consensus over the method with the least side effects.

This study aims to compare the effects of hypothermia and normothermia on cognitive functions after undergoing CABG during the hospitalization period.

A total of 130 patients in this cohort observational study were divided into two groups of normothermic (n = 65) and hypothermic (n = 65). In the hypothermic group, the temperature was down to 32°C, and in the normothermic group, the temperature decreased to 35°C. After the surgery and transferring the patients to the ICU, demographic information and MMSE questionnaires were completed from the second to the sixth day at the same time.

The results showed no significant differences between the two groups in educational and social demographic characteristics (P > 0.05). Besides, there was no significant differences between the two groups in the history of the disease (P = 1.000). In addition, there was no significant relationship between cognitive performance scores of the two groups before the surgery (P = 1.000). However, there was a significant relationship between the two groups from the second (P = 0.003), third (P = 0.000) and the fourth day (P = 0.023) after the surgery. In the normothermic group, on the second, as well as third and fourth days 14 and 9 patients suffered from cognitive impairment, respectively. Besides, in the hypothermic group, on the second, third, and fourth days after surgery, 28, 30, and 23 patients suffered from cognitive impairment, respectively. However, there was no significant relationship between the two groups on the fifth and sixth days after the surgery (P = 0.079).

The present study showed that during hospitalization after undergoing CABG, cognitive impairment in patients with the normothermic method was less severe than that in patients with the hypothermic method. Besides, clinical outcomes were more satisfactory in the former group.