According to the 2010 U.S. Census, there are 40 million people (13% of the population) older than 65 years of age living in the U.S. This population has increased dramatically during the last two decades. Currently more than half of all surgeries are performed on this group of patients in the U.S.
Frailty is typically defined by the presence of three of the five following criteria: a) unintentional weight loss; b) exhaustion; c) muscle weakness; d) slowness while walking and; e) low level of activity. Older patients often have impaired physiological reserves and comorbid conditions that make them susceptible to postoperative complications, prolonged hospital stays, discharge to long-term facilities or nursing homes, and high mortality rate. In addition, socioeconomic factors have also been known to affect surgical mortality. Older patients should, therefore, be carefully screened before being submitted to major surgical procedures.
Current methods of preoperative risk stratification are limited and do not measure elderly patients’ physiological reserves appropriately. In 1941, the American Society of Anesthesiologists (ASA), introduced a classification system that has been used over the years to assess the physical status of patients undergoing surgery. Patients are categorized into groups from I to V depending on the presence or absence of systemic disease. In case of emergency operations, an E is added to the Roman numeral (IE to VE).
ASA Classification System
ASA I: healthy patient
ASA II: mild systemic disease
ASA III: systemic disease with definite functional limitation on life
ASA IV: systemic disease that is a constant threat to life
ASA V: moribund patient not expected to survive 24 hours with or without surgery
Although researchers have noted that ASA III and IV patients have higher morbidity and mortality rates than those with ASA I or II, the classification has been found to lack scientific precision due to lack of inter-rater reliability.
Other researchers have evaluated a battery of tests to try to determine surgical risk in elderly patients. The result is the Comprehensive Geriatric Assessment (CGA), which closely assesses patients’ frailty and provides a better assessment of patient’s physiological reserves than the conventional ASA classification.
In a 2014 study, Kim et al further fine-tuned the CGA by enrolling 358 patients who were tested before undergoing surgery. They were followed up for more than one year postoperatively. Overall, 275 patients were available for analysis. Patients who survived at least one year after the operations predominantly had benign disease, higher albumin levels, a lower Charlson index, fewer ADL difficulties, better cognitive function and nutritional status, lower risk of delirium, and longer mid-arm circumference than non-survivors.
Through regression analysis, a new scoring index (the Multidimensional Frailty Score or MFS) was established based on the following 9 factors. Each factor is rated from 0 to 2, with 0 being the best and 2 the worst:
- Malignant disease
- Charlson comorbidity index
- Albumin, g/dl
- Activities of daily living (ADL)
- Instrumental ADL
- Risk of delirium
- Mini-nutritional assessment (MNA)
- Mid-arm circumference, cm
The MFS was found to predict all cause-mortality rates more accurately than the ASA classification system. The sensitivity and specificity for predicting all cause-mortality rates were 84.0% and 69.2% respectively.
Patients with a total MFS score lower than 15 usually survived the operation and returned home. The MFS is predictive for survival and better than the conventional ASA classification as a risk predictor.
The study, although encouraging, was performed at a single hospital. It needs to be validated in a large population and across multiple institutions.