| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
The objective of this study was to evaluate the incremental cost effectiveness of anesthesia workforce staffing scenarios, as a function of skill mix, by using the technique of decision analysis. A decision tree model was constructed to compare the incremental cost effectiveness of alternative delivery systems for anesthesia care from the perspective of the payer. Five different staffing scenarios, ranging from physician-intensive to nurse-intensive, were modeled. In the nurse-intensive model, low- and intermediate-risk patients were cared for by solo certified registered nurse anesthetists (CRNAs) and high-risk patients were cared for by physicians. In the physician-intensive model, physicians anesthetized all patients. In the first-, second-, and third-team models, all high-risk patients were cared for by physicians working alone, and all intermediate-risk patients were cared for using an anesthesia care team approach with a ratio of one physician to two CRNAs. The low-risk patients were managed by using an anesthesia care team approach with physician to CRNA ratios of 1:2, 1:4, and 1:8 in the first-, second-, and third-team models, respectively. The findings of this decision-analysis model suggest that physician-only anesthesia is not cost effective. However, the third-team model is cost effective when compared with the nurse-intensive model. Implications: An anesthesia care-team approach with a physician to certified registered nurse anesthetist (CRNA) ratio of 1:2 is the preferred staffing scenario for intermediate-risk patients. Although medical direction of CRNAs caring for low-risk patients is cost-effective, the small improvement in outcome resulting from increasing the physician to CRNA ratio from 1:8 to 1:4 may not be justified by the added cost.
Market forces and legislative mandates are increasingly shaping the healthcare landscape. Anesthesia costs, which are estimated to be between 3% and 5% of the total health care expenditures (1), are the subject of scrutiny by both third-party payers and the government. Personnel accounts for most of this cost. The magnitude of the salary differential between certified nurse anesthetists (CRNAs) and anesthesiologists (2) is perceived by some as an opportunity for achieving cost savings through changes in the provider mix (3). The elimination of the federal requirement for supervision of CRNAs, recently proposed by the Health Care Financing Administration (4), would allow the substitution of lower-cost CRNAs for anesthesiologists. This proposal is supported by the American Association of Nurse Anesthetists and is strongly opposed by the American Society of Anesthesiologists. In other specialties, the number of nonphysician clinicians (NPCs) has increased. Similarly, changes in state regulations to expand the scope of practice and independence of NPCs may allow them to replace, rather than complement, their physician counterparts in certain settings (5). The impressive safety record of the anesthesiology specialty was recently cited in a Health Policy Report in the New England Journal of Medicine as an example to be emulated by the health care community in its search to improve quality (6). Therefore, any proposal to alter the current provider mix of physicians and nonphysicians in anesthesia to achieve cost reductions should consider the potential adverse effects of such a change on anesthesia outcomes. There are no outcome studies which definitively support the superiority of physician versus nonphysician anesthesia providers to help guide such an effort. Nevertheless, many anesthesiologists support the principle that the "skill mix of the provider influences the quality of service" (7). In contrast, the American Association of Nurse Anesthetists has used the lack of outcome studies to support the exploration of "alternative delivery systems for anesthesia care" (8) that use proportionately greater numbers of CRNAs to reduce overall labor costs. Unfortunately, it may not be possible to devise adequately powered studies to examine the effect of provider mix on anesthesia outcome. This lack of outcome data, coupled with the economics of increasing numbers of physicians and CRNAs, and the mounting pressure to decrease costs have generated some extreme positions within both communities of providers. There is no question that the pressure to reduce anesthesia costs will continue as part of the overall effort to control rising medical expenditures. Currently, payments for anesthesia services are based on time and base units; these are a function of the complexity and duration of the surgical procedure. Efforts to control anesthesia costs by third-party payers have focused primarily on reducing the cost per unit. Changing the proportion of physician to nonphysician anesthesia providers could also result in a lower overall cost from the payers perspective. However, current Medicare rules mandate an anesthesia provider-mix neutral approach to billing. Specifically, total anesthesia reimbursement is the same whether a patient is anesthetized by a CRNA working alone, a physician working alone, or an anesthesia care team (ACT). Outside of the Medicare fee structure, there is no consistent reimbursement formula for CRNAs. In the future, policy-makers may attempt to achieve further cost reductions by mandating lower reimbursement levels for and proportionately greater use of CRNAs. Changing the proportion of physician to nonphysician anesthesia providers, with modifications of the current fee schedule, could achieve a lower cost from the payers perspective. However, the use of unsupervised or minimally supervised CRNAs may also result in worse patient outcomes. Therefore, any effort to shift care to a delivery system that emphasizes the increased use of CRNAs must be accompanied by an analysis that balances the resultant cost savings against the potential for increases in adverse outcomes. The purpose of this study was to examine the cost effectiveness (C/E) of anesthesia workforce models in the context of a "provider-sensitive" fee structure by using decision-analysis modeling. In this analysis, it was assumed that anesthesiologists working alone result in better patient outcomes than CRNAs working either alone or with minimal medical direction. If this is correct, then should only physicians be giving anesthesia? Alternatively, are physicians working alone too expensive despite their improved outcomes? This simulation assessed the incremental C/E of various anesthesia care delivery systems ranging from physician-intensive to nurse-intensive. The purpose of this study was to determine the level (if any) at which increasing physician participation in the work force model was no longer cost effective. Such a finding may help guide the debate regarding the optimal staffing mix of physicians and CRNAs delivering anesthesia care. Moreover, such an approach allows this discussion to be framed in economic terms and reaches beyond the visceral response espoused by many practitioners.
Overview A decision-analysis model was constructed to evaluate the incremental C/E of anesthesia staffing scenarios by using different ratios of physician to nonphysician anesthesia providers. The model was based on limited outcome data from the literature as well as demographic and cost data based on a cohort of approximately 25,000 patients at a major university teaching hospital. In the absence of outcome studies comparing mortality as a function of anesthesia provider, baseline assumptions were developed by using the available literature. Sensitivity analysis was used to explore the effect of varying these baseline assumptions.
The Model
2. First-team model: physicians anesthetize all high-risk patients; intermediate and low-risk patients are anesthetized by an ACT with a physician to CRNA ratio of 1:2. 3. Second-team model: physicians anesthetize all high-risk patients; intermediate-risk patients are anesthetized by an ACT with a physician to CRNA ratio of 1:2; and low-risk patients are anesthetized by an ACT with a physician to CRNA ratio of 1:4. 4. Third-team model: physicians anesthetize all high-risk patients; intermediate-risk patient are anesthetized by an ACT with a physician to CRNA ratio of 1:2; and low-risk patients are anesthetized by an ACT with a physician to CRNA ratio of 1:8. 5. Nurse-intensive model: physicians anesthetize all high-risk patients; intermediate and low-risk patients are anesthetized by CRNAs who are not supervised by an anesthesiologist. Surgical procedures were divided into three categorieshigh, intermediate, and low-riskadapted from the risk stratification scheme developed by the American College of Cardiology/American Heart Association (10).
2. Intermediateintraperitoneal; intrathoracic; orthopedic; prostate 3. Lowendoscopic procedures; superficial procedures The Decision Tree. A multistate decision-tree model (Figure 1) simulating the C/E of five hypothetical staffing scenarios was written by using DATA 3.5 (Treeage Software, Williamstown, MA) decision-analysis software. DATA provides a structured methodology that permits quantitative analysis of "what if" scenarios using decision trees.
In the nurse-intensive model, patients were first grouped according to the risk of the procedure; the type of anesthesia provider was dictated by the patients risk category (Figure 2). Physicians anesthetized high-risk patients, and CRNAs working alone anesthetized intermediate- and low-risk patients. The proportion of nonsurvivors was postulated to be a function of two separate mortality rates: the primary and secondary mortality rates. The primary mortality rate encompasses events leading to patient death directly attributable to anesthesia, such as the failure to ventilate (11). The secondary mortality rate, however, refers to cases in which the anesthetic management is only partially responsible for the patient death. The secondary mortality rate is a function of the interaction between patient and procedure-related factors and the quality of anesthetic care (11). The primary and secondary mortality rates were also assumed to be a function of the risk-category for the surgery and of the provider mix. The outcomes of patients anesthetized either by CRNAs working alone or by ACTs were adjusted to reflect differences in provider skill mix. For survivors, the number of "years-of-life saved" (YLS) was calculated by using a Markov subtree. Each Markov-cycle tree followed a patient cohort over time and allowed yearly updates in the patients clinical status (live/die). The probability of death after a year-long cycle was a function of the patients age and was obtained from standard life-tables. Within each risk category, patients were further divided according to insurance coverage: Medicare, Medicaid, Blue Cross/Blue Shield, and "other."
In the physician-intensive sub-tree, all patients were anesthetized by physicians working alone. For the first-, second-, and third-team models, high-risk patients were anesthetized by solo anesthesiologists, and intermediate-risk patients by ACTs with a physician to CRNA ratio of 1:2. The low-risk patients were managed by using an ACT approach with physician to CRNA ratios of 1:2, 1:4, and 1:8 in the first-, second-, and third-team models, respectively. C/E. The measure of utility used in this analysis was YLS. Although quality adjusted life-years are a more commonly used measure of utility (12), there is no data on anesthesia related morbidity as a function of provider mix to derive this measure of effect. An annual discount rate of 5% was used to discount future YLS (13). This analysis was based on the perspective of the payer. Because it was assumed that drug and material costs would be independent of provider mix, only labor costs were included in the model. Costs were a function of the following factors: number of anesthesia units, type of insurance coverage, dollar charge per unit, and provider mix. All costs were calculated using 1998 US dollars. In comparing two strategies, one is considered dominated if it is more expensive but of equal or lesser effectiveness than another strategy. Alternatively, if one strategy is both more effective and more expensive, the incremental C/E can be derived as the ratio of the difference in cost over the difference in effectiveness (14). Interventions whose incremental C/E is less than $50,000 per quality adjusted life-year are considered to be within the range of currently accepted medical therapies (15).
Data and Assumptions The secondary mortality rate is a function of the interaction between patient and procedure-related factors and the quality of anesthesia care. In such cases, anesthesia contributes to but is not solely responsible for patient outcome. The secondary mortality rate, based on the CEPOD study, was assumed to be 7.4 in 10,000 in the overall population and to vary according to risk category. Although the CEPOD study was based on physician-only anesthesia, outcome data in this inquiry were extended to other provider mixes by incorporating "provider mix adjustment factors" (see below). There are no randomized, controlled trials evaluating patient outcome as a function of provider mix. Bechtoldt (18) conducted a retrospective review of two million anesthetics administered between 1969 to 1976 in North Carolina; the incidence of anesthesia-related deaths as a function of provider was similar across the range of provider mix. The major limitation of this study was that no attempt was made to adjust for case-mix. However, it is likely that physicians were involved in the care of the sicker patients and those having more complex surgeries. A prospective study from the Stanford Center for Health Care Research reported on 8593 patients (19). This study suggested a trend toward lower-risk adjusted mortality rates for physician-only and ACT environments as compared with unsupervised CRNAs. In a more recent study, using logistic regression modeling to analyze a data set of 5972 patients undergoing cholecystectomy and transurethral prostatomy, Silber et al. (20) demonstrated that the proportion of board-certified anesthesiologists is inversely related to the "failure to rescue" from adverse events. The relative risk of "failure-to-rescue" was 2.5 times higher in hospitals in which 0%33% of anesthesiologists were board-certified as compared with hospitals in which 66%99% of the anesthesiologists were board-certified. Because increases in the anesthesia-related mortality rate will result from "failure to rescue," nonboard certified anesthesiologists were assumed to have a 2.5 times higher anesthesia-related mortality rates than board-certified anesthesiologists. In our study, it was assumed that a CRNA working alone would have twice the mortality of a nonboard certified anesthesiologist. All anesthesiologists in the model were assumed to be board-certified. CRNAs working alone were assumed to have a 5 times higher mortality rate than that of solo anesthesiologists or of ACTs with physician to CRNA ratios of 1:2 or 1:4 (based on the assumption that unsupervised CRNAs were twice as likely to have "failure to rescue" than nonboard certified anesthesiologists). ACTs with a ratio of 1 physician to 8 CRNAs were assumed to have 2.5 times the mortality of solo anesthesiologists because of the nominal nature of physician supervision. The assumption that ACTs with a physician to CRNA ratio of 1:2 or 1:4 have outcomes equivalent to physicians working alone was based on the premise that the advantage of physician-only anesthesia was offset by the presence of two sets of eyes in an ACT.
Costs
Baseline Analysis Table 3 summarizes the results of the C/E analysis for the reference case. Incremental C/E was rounded up to the nearest $100. In the baseline analysis, the nurse-intensive model resulted in the highest mortality followed by the third-team model. The physician-intensive and first- and second-team models had the lowest overall mortality rate. The incremental C/E of the third-team model versus the nurse-intensive model was $4900/YLS. The incremental C/E of the second-team model versus the third-team model was $31,000/YLS. The second-team model dominated both the first-team and physician-intensive model strategies because all three strategies yielded equivalent outcomes, while the former was least expensive.
Sensitivity Analysis By using one-way sensitivity analysis, the effect of varying the estimates for the model variable through a range of plausible values was investigated (Table 4). As shown in Table 4, the results of the C/E analysis were relatively insensitive to variations in the primary mortality rate, proportion of high-risk patients, proportion of Medicare patients, and changes in the discount rate. However, the results of the baseline case analysis were sensitive to changes in the outcome adjustment factor, the secondary mortality rate, and the dollar cost per unit.
Power Analysis Finally, a power analysis was conducted to estimate the number of patients needed to conduct a randomized controlled trial to study the effect of anesthesia provider skill mix on the outcome of intermediate-risk patients. These results are shown in Figures 3 and 4. The y axis shows the number of patients; the x axis depicts the relative risk of secondary mortality (Fig. 3) for a patient anesthetized by an unsupervised CRNA versus an anesthesiologist. This power analysis is repeated in Figure 4 for the relative risk of primary mortality as a function of skill mix. This analysis was not formally repeated for low-risk patients given the even smaller number of negative outcomes in this patient group.
Five anesthesia staffing models were compared by using C/E analysis. The findings of this decision-analysis model for the reference case suggest that the optimal staffing model is one in which high risk patients are managed by anesthesiologists working alone, intermediate-risk patients by ACTs with a physician to CRNA ratio of 1:2 and low-risk patients by ACTs with a physician to CRNA ratio of 1:4. Increasing the physician to CRNA ratio for low-risk patients from 1:4 to 1:2 is not cost effective. Furthermore, the physician-intensive model, in which physicians working alone anesthetize all patients, is also not cost effective. Finally, medical direction by anesthesiologists of CRNAs caring for intermediate- and low-risk patients is supported by the results of this analysis. The effect of varying the model assumptions on the incremental C/E of the anesthesia staffing scenarios was explored by using sensitivity analysis. The results are sensitive to the secondary mortality ratedeaths in which anesthesia contributed to but was not solely responsible for the death of the patient. Medical direction of CRNAs for intermediate- and low-risk patients was cost effective over the entire range of the sensitivity analysis. However, an ACT with a physician to CRNA ratio of 1:4 was the preferred strategy for low-risk patients only if the secondary mortality rate was greater than 4.6 in 10,000; if the secondary mortality rate was <4.6 in 10,000, then the optimal staff mix for low-risk patients was an ACT with a physician to CRNA ratio of 1:8. The results of the analysis were not sensitive to changes in the primary mortality ratedeaths for which anesthesia was solely responsible. One of the fundamental assumptions underlying this decision analysis is that physician supervision leads to outcomes superior to those achieved by CRNAs working either alone or under nominal supervision. This assumption was incorporated into the model by using an outcome adjustment factor. The third-team model was cost effective over the entire range of the sensitivity analysis for this variable. However, the second-team model was not cost effective unless the secondary mortality rates of patients cared for by ACTs with a physician to CRNA ratio of 1:8 was at least twice that of patients cared for by ACTs with a physician to CRNA ratio of 1:4. The findings of this analysis are relatively insensitive to the proportion of both high-risk patients and of patients covered by Medicare. The model is also relatively robust when changes are made in reimbursement levels. The third-team model is cost effective, as compared with the nurse-intensive model, over the entire range of the reimbursement level. The second-team model is cost effective, compared with the third-team model, when the reimbursement level was between the range of 50% and 160% of current levels. The most significant limitation of this model is the absence of reliable data on anesthesia outcomes as a function of skill mix to use as the basis for the decision analysis. Nonetheless, there is consensus within the physician community that patient outcomes are better when anesthesiologists either directly administer or closely supervise anesthesia care (7,2225). This position is based on the premise that anesthesiology is the practice of medicine and, therefore, requires a specialized skill set and knowledge base acquired only through medical training. The corollary to this position is that nonphysician anesthesia care providers can only produce optimal outcomes in the context of medical direction by an anesthesiologist. The evidence supporting this position consists mainly of expert opinion and poorly controlled studies. Unfortunately, the sample size necessary to conduct a randomized, controlled trial to answer this question is very large. In conducting a sensitivity analysis on the effect of varying the outcome adjustment factor for the secondary mortality rate, it was assumed CRNAs working independently would have at least 2.5 times the secondary mortality rate of physicians or of CRNAs under medical direction (physician to CRNA ratio 1:2 or 1:4). Power analysis demonstrates (P < 0.05 and power = 80%) that the number of patients necessary for such a study is approximately 18,000. To demonstrate smaller differences in outcomes would require an even greater number of patients. Additionally, there is the problem of defining under what set of conditions anesthesia "contributes" to mortality. If such a study is instead limited to examining only the primary mortality rate, the number of patients necessary would be greater than 2,000,000. It is therefore unlikely that such studies will be performed in the future. Alternatively, logistic regression modeling could be used to examine the relative risk of mortality as a function of provider mix after adjusting for severity of disease and procedure risk. However, even if a sufficiently large database were available for such an analysis, it may not be possible to completely eliminate the possibility of selection bias. A second weakness in this model is that it limits outcomes to live/die and does not address significant morbidity resulting from anesthesia. Including anesthesia-related morbidity would have greatly increased the level of complexity of the model and the level of uncertainty of the model variables. Such an approach, although more comprehensive, might have resulted in more questionable conclusions. Finally, a structural weakness of the model is that it fails to account for situations in which the number of low-risk patients receiving anesthesia simultaneously is insufficient to allow for a 1:8 level of supervision. Given the inherent limitations of this model, what inferences can be drawn based on its findings? First, a physician-intensive model, in which intermediate- and low-risk patients are anesthetized by anesthesiologists working alone, may not be cost effective. Second, an anesthesia care team approach with a physician to CRNA ratio of 1:2 appears to be cost-effective for intermediate-risk patients when compared with staffing models in which CRNAs work independently. Finally, medical direction of CRNAs caring for low-risk patients is also cost effective when the CRNA to physician ratio is 1:8. C/E analysis provides an ideal framework for the discussion of the relative merits of alternative staffing scenarios in anesthesia. It seems intuitive, the lack of outcome studies notwithstanding, that using more highly trained physicians versus NPCs will result in improved outcomes. But, is the increased cost justified by the improvement in outcomes? It would appear, based on the results presented here, that the answer is that the most cost-effective staffing scenario involves a mix of physicians and NPCs. The findings of this study argue in favor of a staffing model that combines both physician and ACT approaches. However, they do not support CRNAs working independent of medical direction by an anesthesiologist. They support direct physician involvement in the care of higher-risk patients and more of a supervisory role in the care of lower-risk patients. The value of this study is that it presents an economic framework for the analysis of anesthesia staffing scenarios. The findings of this analysis, however, must be qualified by the lack of outcome data.
This article has been cited by other articles:
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|