Six-minute walk distance before cardiac surgery predicts cognitive dysfunction afterward

In addition to six-minute walk distance, intensive care unit length of stay, age, and Mini-Mental State Examination score were found to be independent risk factors for postoperative cognitive dysfunction.

A lower six-minute walk distance (6MWD) before cardiac surgery was associated with higher risk of postoperative cognitive dysfunction, a recent study found.

The study included 181 Japanese patients with a mean age of 71.4 years who were undergoing cardiac surgery. Their 6MWD was measured at hospital admission. Postoperative cognitive dysfunction, defined as a decrease of two points or more in the Mini-Mental State Examination (MMSE) score, was found in 28% of the patients. Results were published online May 9 by Annals of Thoracic Surgery.

The group of patients who developed cognitive dysfunction had a significantly lower median preoperative 6MWD (400 m) than those who didn't (450 m). For each increase of 50 m in a patient's 6MWD, the odds ratio for postoperative cognitive dysfunction was 0.807. In addition to the 6MWD, intensive care unit length of stay, age, and MMSE score were found to be independent risk factors for postoperative cognitive dysfunction.

“To our knowledge, the present study is the first to indicate that the 6MWD is a useful screening tool for identifying patients at a high risk for [postoperative cognitive dysfunction]. It may be important to assess the functional exercise capacity in each patient to predict the risk of postoperative neurologic dysfunction,” the authors said. The decision to operate and perioperative management should be carefully considered in patients found to have a low 6MWD before surgery, the authors suggested, noting that exercise supervised by a physical therapist to increase functional exercise capacity is recommended in advance of cardiac surgery.

The study had a number of limitations that mean it should be interpreted cautiously, the authors said. It included only patients with MMSE scores of 24 or higher, so further research would be required in patients with mild cognitive impairment. Patients with severe comorbidities or postoperative complications were also excluded. The overall number of participants was small, and all were treated at a single medical center. “A validated scoring system should be created for a large number of participants,” the authors said.