Associations Between Charlson Comorbidity Index and Surgical Risk Severity and the Surgical Outcomes in Advanced-age Patients
By Weingarten, Toby N | |
Proquest LLC |
The Charlson Comorbidity Index (CCI) has not been assessed for elderly (95 years of age or older) surgical patients. We examined the association between the CCI and life-threatening complications and 30-day mortality rate. Medical records of patients 95 years old or older from 2004 through 2008 were reviewed for major postoperative morbidity or death. Logistic regression analyses of age, sex, the CCI,
INTHEUNITEDSTATES, thepopulation olderthan 85 years will double during the next 20 years.1 Elderly surgical patients are at increased risk of perioperative morbidity and death with the relative risk of death estimated to increase by 1.4 for every decade of life over the age of 50 years.2 Recent studies of nonage- narian surgical patients have reported 30-day mortality rates exceeding 10 per
Recently, published studies have used the Physio- logical and Operative Severity Score for the Enumera- tion of Mortality and Morbidity (POSSUM)7 to predict perioperative morbidity and death in patients 90 years of age or older with mixed results.3, 4 The POSSUM assessment tool relies on preoperative, perioperative, and postoperative variables; thus, it is more applicable to audit surgical practices than to provide preoperative risk assessment.8
In contrast, the Charlson Comorbidity Index (CCI)9 relies on preoperative factors to calculate mortality rate and has been used in various medical and surgical pa- tient populations to predict death.2, 10-13 However, the use of the CCI has not been assessed in a mixed surgical patient population of advanced age. The aim of the present study was to describe the anesthesia course of patients 95 years of age or older and to examine the association between CCI and the life-threatening com- plications and death at 30 days postoperatively.
Methods
The present study was approved by the
Study Design and Setting
We conducted a retrospective observational study of a patient cohort representing approximately the upper one per cent of age in our surgical practice to de- termine the rate of postsurgical severe morbidity and death within 30 postoperative days. The study was set at a major academic tertiary care facility. Comparisons were made among patients who had morbidity or died and those who did not.
Study Population
From an institutional database, patients aged 95 years or older who underwent anesthetic care for surgical procedures from
Data Abstraction
All data were abstracted from the electronic medical records (EMRs) and entered manually into the Web- based Research Electronic Data Capture system (Version 3.6.7;
Surgical risk was stratified as minimal, moderate, or high on the basis of the
Severe postoperative complications and death that occurred during hospitalization and within 30 post- operative days were reported as well as death at 90 postoperative days. Postoperative complications were considered when they had severity of Grade III (re- quiring surgical, endoscopic, or radiologic intervention) or Grade IV (life-threatening complication requiring intensive care management [ie, low-output heart fail- ure]) in the classification system for surgical com- plications by Dindo et al.20 Cardiac dysrhythmias were considered only when they resulted in hemodynamic instability or required prompt intervention such as sustained ventricular tachycardia, atrial fibrillation with rapid ventricular response, or symptomatic bradycardia.
Data Analysis
Potential patient and surgical factors for severe postoperative complications and death were assessed through descriptive statistics. To further evaluate the association that these factors share with poor out- comes, logistic regression analyses were performed with patients who were separated into two categories: event- free recovery and poor outcomes. Logistic regression analyses included patient age, sex, CCI, surgical se- verity category, and mode of surgery as explanatory variables because these factors have been associated previously with increased operative risk.21
For the present study, the CCI was unadjusted for age2 because age of patients in this study cohort was mostly confined to one decade (95 to 105 years) and year of life was included as an explanatory variable in multivariable analysis. A secondary multivariable lo- gistic analysis was performed where the CCI was substituted with ASA-PS as an explanatory variable. Findings from the logistic regression analyses are summarized as odds ratios (ORs) and corresponding 95 per cent confidence intervals (CIs). In all cases, two-sided tests were used with a P value of 0.05 or less denoting statistical significance. Statistical analyses were performed using SAS software (Version 9.2;
Results
During the study timeframe, 187 patients aged 95 years or older who underwent anesthetic care were identified. Table 1 summarizes patient and surgical characteristics with a majority of patients (58.8%) un- dergoing moderate- to high-risk surgery. Patients had a high burden of disease (median [interquartile range] CCI, 4 [2 to 6]). Twenty patients (10.7%) died within 30 days of their operation and another 20 had major postoperative complications (Table 2). Half of the 30-day mortality cases were surgical repair of hip fracture (10 of 54 repairs [18.5%]), whereas only one death was a complication of the ophthalmologic, car- diac, and vascular cases. Causes of 30-day mortality included seven cases of pneumonia or respiratory failure, two myocardial infarctions, one cardiac arrest, one stoke, one from sepsis, one intraoperative death during major spine surgery from embolization of sur- gical cement, and the remainder from unknown causes. Ninety-day postoperative death occurred in 35 cases (18.7%) with surgical repair of hip fractures most common (14 of 54 cases [25.9%]).
Univariate analysis found that the surgical risk cat- egory and emergent status were associated with death and major postoperative complications occurring within 30 days (Table 3). After adjustment for other explan- atory variables, poor outcomes were associated with only the moderate- and high-risk surgical categories. An additional multivariable analysis was performed that substituted ASA-PS score for CCI and found that a poor outcome had an OR of 2.33 (95% CI, 0.94 to 5.82; P 4 0.07). Because a large proportion of the cohort had hip surgery and also had poor outcomes, we performed an additional post hoc multivariable anal- ysis that substituted hip fracture surgery for CCI and found that a poor outcome had an OR 1.98 (95% CI, 0.92 to 4.30; P 4 0.08).
Discussion
In this study, the oldest one per cent of surgical patients had high rates of morbidity and death after surgery. More specifically, only the surgical risk cat- egory was associated with poor outcomes, and the overall patient disease burden as assessed by the CCI was not. High-risk surgery is problematic particularly with 50 per cent of patients having a poor outcome. When considering the occurrence of death within 90 days of surgery, the mortality rate increases to 18 per cent, a troubling finding. These findings suggest that even patients with no major comorbidities but who are of advanced age do not tolerate major surgical pro- cedures well.
The high rates of morbidity and death are similar to those reported in previous reports. From 1975 to 1985, a cohort of nonagenarians undergoing a routine non- ophthalmologic surgical procedure had morbidity rates or mortality rates of 9.2 per cent and those undergoing an emergent operation had rates of 22.4 per
The ability to assess risk of morbidity and death after surgery in this patient population would be of great value. We tested the hypothesis that the presence of comorbid conditions, as assessed by the CCI, would be associated with poor outcomes. The CCI is an attrac- tive method of quantifying the degree of risk secondary to comorbid conditions; it provides a composite score built on a weighted value of each assessed condition on the basis of the relative risk of 1-year death.9 Studies have found a positive association between the CCI and poor surgical outcomes in various clinical settings, including oncologic, vascular, and hip fracture opera- tions.10-13 In patients undergoing elective surgery, each CCI unit point represents a 1.4 increase in the relative risk of 5-year postsurgical death.2 In patients with lung cancer, an age-adjusted CCI score of 3 or 4 was associated with major postoperative complications (OR, 9.8 [95% CI, 2.1 to 45.9]).10
Many studies have found that advanced age is also associated with poor outcomes.4, 12 When assessing patients of different ages, the CCI easily allows for adjustments in decade of life.2 In this study, we did not adjust the CCI for age because, by study design, the ages among study patients were mostly within one decade.
Interestingly, we did not find an association between the CCI and major complications or death. One possible explanation is because many extremely old persons have multiple chronic diseases, most have elevated CCI scores, as evidenced by the high median CCI scores in this cohort. It is plausible that in a subset of patients with high comorbidity index scores, such indices are less useful in differentiating among those with high risk versus lower risk than the other markers of overall health such as measures of disability and frailty.31
Comorbidities, disability, and frailty are separate entities when evaluating a patient's overall health. Although the occurrences of these entities overlap, there is no concordance.31 In patients aged 65 years or older who undergo major surgery, an association was found between 6-month death and frailty, disability, and comorbidity.32 Frailty and disability may be better metrics than a comorbidity index in distinguishing which extremely old patients will have better out- comes. However, determining or measuring the degree of these two factors is difficult when relying on ret- rospective data.
The POSSUM and related assessment tools rely on preoperative, perioperative, and postoperative vari- ables, including physiologic variables, to assess post- operative mortality and morbidity rates.3, 4 However, these tools cannot be relied on to assess risk preop- eratively. The ASA-PS provides a more global view of vitality, and higher ASA-PS scores have been found to correlate with increased postoperative morbidity and death in nonagenarian surgical patients.3-5, 33 In our cohort, there was only a trend that higher ASA-PS score was associated with poor outcome. However, the majority of our patients was ASA-PS 3 or 4, which could limit our ability to find an association.
The factor associated with increased morbidity and death was the degree of surgical risk, as defined by the
This report suffers from the inherent limitations of retrospective studies. Undoubtedly, many more elderly patients required surgical intervention but, after con- sultation with their surgeon, decided not to pursue surgery. How these patients would have fared is un- known. Another important limitation is the reliance on the CCI to assess disease burden because it relies on retrospective data and ICD-9 codes and may not ade- quately capture all comorbid conditions and thereby may underestimate the overall disease burden,8 yet at these extremes of age, many patients have various chronic conditions that limit the ability of comorbid indices to distinguish patient risk. Measures of frailty or disability ultimately may be better predictors of outcome in this population, and they are not assessed in the CCI. Finally, our data come from a major aca- demic institution and our findings may not be appli- cable to other healthcare settings.
In conclusion, patients of advanced age have high rates of death and morbidity after surgical procedures. The rate of these adverse events is associated with the extensiveness of surgery and is independent of pre- existing comorbidities.
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Funding provided by Research Electronic Data Capture (REDCap) system supported by a
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