With the advancement of medical technology, the percentage of older adults undergoing operative procedures is increasing. As such, specific complications that disproportionally impact this population, such as postoperative delirium (POD), have garnered interest. POD is a state of disorientation and alterations in consciousness that can have many causes. Consequences of POD have included increased length of hospital admission, risk of death, and healthcare spending. Risk factors related to POD have been under investigation, given the benefit of identifying high-risk patients earlier such that preventive measures can be instituted. A meta-analysis published in April 2021 sought to identify such risk factors in those who had recently undergone cardiac surgery.
The meta-analysis included 14 studies which were evaluated for preoperative, intra-operative, and postoperative risk factors for POD following cardiac surgery. To be included in the analysis, strict criteria were defined. For example, studies were required to have had delirium diagnosed using an approved clinical tool. In addition, included studies were subject to rigorous bias assessment.
Unsurprisingly, age was frequently cited as a risk factor for POD. However, other risk factors included carotid artery stenosis, diabetes, preoperative depression, and cognitive impairment. Heart failure with reduced ejection fraction was also associated with POD. In fact, investigators found that improved ejection fraction was protective against POD. The meta-analysis also identified that ICU length of stay and the amount of time a patient was placed on mechanical ventilation were also risk factors. Indeed, the risk of POD increased with days in the ICU and hours on mechanical ventilation.
Limitations of this analysis include the potential for confounding factors and the retrospective study design of various included studies. However, the review had many strengths worth considering, such as a large sample size, low bias of included studies, and high confidence in the quality of included results. Although no causative relationships can be determined from the results, they may guide future research that aims to validate conclusions within this study. They may also assist in developing clinical protocols for triaging patients deemed high risk for POD following cardiac procedures.