Elsevier

The Spine Journal

Volume 14, Issue 1, 1 January 2014, Pages 31-38
The Spine Journal

Clinical Study
ASA grade and Charlson Comorbidity Index of spinal surgery patients: correlation with complications and societal costs

https://doi.org/10.1016/j.spinee.2013.03.011Get rights and content

Abstract

Background context

The Charlson Comorbidity Index (CCI) and the American Society of Anesthesiologists (ASA) Physical Status Classification System (ASA grade) are useful for predicting morbidity and mortality for a variety of disease processes.

Purpose

To evaluate CCI and ASA grade as predictors of complications after spinal surgery and examine the correlation between these comorbidity indices and the cost of care.

Study design/setting

Prospective observational study.

Patient sample

All patients undergoing any spine surgery at a single academic tertiary center over a 6-month period.

Outcome measures

Direct health-care costs estimated from diagnosis related group and Current Procedural Terminology (CPT) codes.

Methods

Demographic data, including all patient comorbidities, procedural data, and all complications, occurring within 30 days of the index procedure were prospectively recorded. Charlson Comorbidity Index was calculated from International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes and ASA grades determined from the operative record. Diagnosis related group and CPT codes were captured for each patient. Direct costs were estimated from a societal perspective using Medicare rates of reimbursement. A multivariable analysis was performed to assess the association of the CCI and ASA grade to the rate of complication and direct health-care costs.

Results

Two hundred twenty-six cases were analyzed. The average CCI score for the patient cohort was 0.92, and the average ASA grade was 2.65. The CCI and ASA grade were significantly correlated, with Spearman ρ of 0.458 (p<.001). Both CCI and ASA grade were associated with increasing body mass index (p<.01) and increasing patient age (p<.0001). Increasing CCI was associated with an increasing likelihood of occurrence of any complication (p=.0093) and of minor complications (p=.0032). Increasing ASA grade was significantly associated with an increasing likelihood of occurrence of a major complication (p=.0035). Increasing ASA grade showed a significant association with increasing direct costs (p=.0062).

Conclusions

American Society of Anesthesiologists and CCI scores are useful comorbidity indices for the spine patient population, although neither was completely predictive of complication occurrence. A spine-specific comorbidity index, based on ICD-9-CM coding that could be easily captured from patient records, and which is predictive of patient likelihood of complications and mortality, would be beneficial in patient counseling and choice of operative intervention.

Introduction

Evidence & Methods

It is foreseeable that a classification system delineating comorbidities can be used to predict the likelihood of certain complications with spinal surgery.

In this prospectively designed study, the authors found that both CCI and ASA grades correlated with the likelihood of complications following spinal surgery, but imperfectly so.

Providing patients with the best possible information regarding risks is vital to truly informed consent. Such information is equally valuable to surgeons hoping to avoid or prepare for complications. CCI and ASA appear to be helpful and commensurate with most surgeons' experience and common sense. The authors' suggestion for a spine surgery specific grading system might prove quite beneficial.

Several studies have reported various patient comorbidities that increase the likelihood of complication occurrence after spinal surgery [1], [2]. Patients electing for operative treatment of a spinal disorder may have greater comorbidity level compared with patients who opt for nonoperative therapy [3]. Accurate risk stratification methods are important for spinal surgical decision making. Although many such risk stratification schemes exist (Acute Physiology and Chronic Health Evaluation II [APACHE II] and Physiological and Operative Severity Score for the enUmeration of Mortality and Morbidity [POSSUM]) [4], [5], few have been used specifically in the spinal surgery patient population.

The American Society of Anesthesiologists (ASA) Physical Status Classification System is a six-point scale commonly used as a measure of a patient's preoperative global health [6]. In a recent study of the Scoliosis Research Society Morbidity and Mortality database, increasing ASA grade significantly correlated with increasing rate of surgical complication [7]. American Society of Anesthesiologists grade is also predictive of patient mortality after adult spinal deformity surgery [8]. The Charlson Comorbidity Index (CCI) [9], modified by Deyo et al. [10] to use International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) diagnosis codes, has been used to predict patient outcomes, including mortality and complications after spinal surgery [11], [12]. A retrospective review of 200 patients with spinal metastases reported that CCI score was the most significant predictor of 30-day complications [13]. Neither of these measures has been used in prospective assessment of spine surgery complications.

Accurate assessment of spine patient comorbidities is relevant for efforts to control health-care costs. There is sparse literature regarding the impact of patient comorbidities on overall costs associated with spinal surgery [14]. Smoking and a diagnosis of previous spinal surgery are associated with increased costs of lumbar fusion [15]; similarly, advanced age, diabetes, and obesity increase the overall cost of spinal surgery [16]. We recently reported that patient comorbidities of a preoperative neurologic deficit, systemic malignancy, hypertension, and cardiac disease are each independently associated with increased societal costs after spinal surgery [17].

Our research group previously completed a prospective assessment of complications in patients undergoing a variety of spine surgery procedures; the results of these investigations have been reported [17], [18], [19], [20]; (Ratliff J, personal correspondence, 2011). This study evaluates the ASA Physical Status Classification System and the CCI as predictors of early complications after spinal surgery. In addition, this study seeks to examine the correlation between these risk stratification mechanisms and the direct cost of health care related to spinal surgery from the perspective of society.

Section snippets

Study design

A prospective observational assessment of all patients undergoing any spine surgery at a single academic tertiary center over a 6-month period (5/08 to 12/08) was completed using an independent auditor. Demographic data, including all patient comorbidities, procedural data, and all complications or adverse events occurring within 30 days of the operation, were prospectively recorded. All patients were followed at a single clinic site postoperatively, allowing capture of complications that

Baseline demographics

Two hundred sixty-four patients were prospectively followed during the study period. Of these, 226 had adequate operative, administrative, and anesthesia records for inclusion in this analysis. Table 1 contains general demographic data on the study population. The most common comorbidity was hypertension (49%), and the least common comorbidity was alcohol and drug abuse (4%) (Table 2). The average CCI score for the patient cohort was 0.92, and the average ASA grade was 2.65.

Correlation of ASA grade and CCI

The CCI and ASA

ASA and CCI grading

Both ASA and CCI grading are used in the literature as means of risk assessment for spinal conditions. In this assessment, each methodology showed an association to the rate of complications, with CCI related to overall complication incidence and occurrence of minor complications, and ASA grade relating only to occurrence of major complications. Both measures were positively correlated with expected demographic and comorbidity variables such as increasing patient age and patient BMI. Similarly,

Conclusions

This is the first effort to correlate established comorbidity indices, the CCI and ASA grade, with both the likelihood of a complication after spinal surgery and the overall cost of care. Both risk assessment tools analyzed in this study were useful, but neither was completely predictive. There is need for development of a spine-specific comorbidity index, based on ICD-9-CM coding, which is predictive of patient functional outcomes, likelihood of complications, mortality, and cost.

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    FDA device/drug status: Not applicable.

    Author disclosures: RGW: Nothing to disclose. JHS: Nothing to disclose. CV: Nothing to disclose. PGC: Nothing to disclose. SY: Grant: DePuy Spine, Inc. (B, Paid directly to institution/employer). GMG: Nothing to disclose. MGM: Nothing to disclose. JKR: Royalties: Biomet Spine (E); Stock Ownership: Johnson and Johnson (0 shares); Consulting: Stryker Spine (Financial, D).

    The disclosure key can be found on the Table of Contents and at www.TheSpineJournalOnline.com.

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