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Growth Rates in Pediatric Diagnostic Imaging and Sedation

Wachtel, Ruth E. PhD, MBA*; Dexter, Franklin MD, PhD; Dow, Angella J. BS

doi: 10.1213/ane.0b013e3181981f96
Economics, Education, and Policy: Research Reports

BACKGROUND: Workload has increased greatly over the past decade for anesthesia providers administering general anesthesia and/or sedation for pediatric diagnostic imaging.

METHODS: Data from an academic medical center were studied over a 12-yr period. Growth in the number of children 0–17 yr of age undergoing magnetic resonance imaging (MRI) and/or computerized tomography (CT) scans who received care from anesthesia providers was compared with the increase in the total number of MRI and CT procedures performed in children. Anesthesia providers included anesthesiologists, residents, Certified Registered Nurse Anesthetists, and student Certified Registered Nurse Anesthetists. Toward the end of the study, a team of sedation nurses was employed by the hospital to administer moderate sedation. They provided an alternative to anesthesia providers from the anesthesia department, who usually administered general anesthesia. Use of sedation nurses versus anesthesia providers, and the relationship to scan duration and patient age, were studied over a 6-mo period.

RESULTS: The number of children receiving care from anesthesia providers for MRI and CT scans grew at the same 8%–9% annual rate as the number of scans performed. The percentage of children receiving anesthesia care did not change over the 12 yr. Creation of a nurse sedation team that provided moderate sedation did not alter the number of children receiving care from anesthesia providers but did increase the total number of children receiving hypnotics. Anesthesia was rarely used for scans shorter than 30 min in duration. Increases in scan duration were associated with increased utilization of anesthesia providers for both MRI and CT after stratifying by age. An age of 3–5 yr was associated with the highest rates of anesthesia care.

CONCLUSIONS: Future workload for anesthesia providers administering general anesthesia and/or sedation for pediatric diagnostic imaging will depend on trends in the total number of scans performed. Workload may also be sensitive to factors that increase scan duration or alter the percentage of patients in the 3–5 yr age group. It may additionally depend on reimbursements from insurance companies.

IMPLICATIONS: The number of children receiving care from anesthesia providers for diagnostic imaging has increased to the same extent as the number of procedures performed. Utilization of anesthesia providers was highest for scans of long duration and for children 3–5 yr of age.

From the *Department of Anesthesia, University of Iowa, Iowa City, Iowa; Departments of Anesthesia and Health Management and Policy, University of Iowa, Iowa City, Iowa; and ‡Farrell Growth Group, LLC, Liberty, Missouri.

Accepted for publication October 31, 2008.

FD is editor of Economics, Education, and Policy for the Journal. This manuscript was handled by Steven L. Shafer, Editor-in-Chief, and Dr. Dexter was not involved in any way with the editorial process or decision.

Address correspondence to Franklin Dexter, MD, PhD, Division of Management Consulting, Department of Anesthesia, University of Iowa, Iowa City, IA 52242. Address e-mail to Franklin-Dexter@UIowa.edu. Web site www.FranklinDexter.net.

Anesthesiology departments that provide sedation for pediatric radiology and diagnostic imaging often commit clinical and administrative resources that are disproportionately large relative to the services provided.1,2 Patient scheduling is challenging because of the need for appointments that coordinate3 multiple physician and clinic visits on the same day as the imaging study.4 Several different information systems may be involved.3,5 Anesthesia providers may be less productive for diagnostic imaging than for surgery because Current Procedural Terminology (CPT) codes do not predict anesthesia times accurately.6,7 Times between cases can be long when patients are transported long distances to a postanesthesia care unit.5 Reimbursement may be poor compared with the same time spent performing surgical cases.1,2 Reimbursement per anesthesiologist per day may also be low when logistics prevent anesthesiologists from medically directing multiple cases simultaneously.

Many anesthesia groups have experienced large growth in the demand for general anesthesia or sedation for diagnostic imaging. Almost all of such services involve magnetic resonance imaging (MRI) and computerized tomography (CT).8

Over the past decade, MRI and CT procedures have increased greatly across all age groups.9–14 Growth in the number of cases attended by anesthesia providers for MRIs and CTs could simply be a consequence of the increased number of pediatric diagnostic procedures. Alternatively, the percentage of children receiving anesthesia care could be rising. The first part of our study evaluated whether the increased workload of anesthesia providers for diagnostic imaging was due solely to an increase in the number of procedures in children or was due partly to increased utilization of these providers for general anesthesia and/or sedation.

The second part of our study examined factors that may influence the demand for anesthesia services in the future. For surgery, anesthesia groups can utilize several techniques to forecast and even influence future workload.15–17 We believe this to be the first study to report the sensitivity of anesthesia imaging workload to patient and scan characteristics.

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METHODS

This project was performed as a quality improvement initiative to forecast future staffing needs at an academic medical center. Publication of these results was approved by the University of Iowa Institutional Review Board.

For our first analysis, radiology records were used to determine every MRI and CT scan performed on children (aged 0–17 yr) at the study hospital from July 1996 through December 2007. Scans performed the same day in the same machine were considered one imaging study. CT-guided biopsies, aspirations, etc., were included because they were associated with scans. The number of MRI scans and CT scans was summed for each 6-mo period, and the logarithm taken. The compounded annual rate of growth was estimated by calculating the slope over time (Systat 12, Systat Software, San Jose, CA). Least absolute values regression was used because the method is distribution-free. Parameters were estimated using the simplex method. The two-sided 95% confidence intervals (CI) and P values were estimated asymptotically.

Anesthesia billing data for the same 12 yr were used to determine the number of children who received care from anesthesia providers for MRIs or CTs. Mean anesthesia time for elective scans was also calculated for each 6-mo period. Trend over time was determined as above for MRI and CT scans combined. Anesthesia care was provided by a resident, certified registered nurse anesthetist (CRNA), or student CRNA under the medical direction of an anesthesiologist. In 2007, billing records showed that sevoflurane and/or propofol were used for the majority of cases. The level of sedation attained would be considered deep sedation or general anesthesia,18 because airway support was provided. Although anesthesia care may have occasionally involved Monitored Anesthesia Care and light sedation rather than general anesthesia, we considered the services of anesthesia providers to be the equivalent of “general anesthesia” because of the providers’ ability to rescue the airway and convert sedation to general anesthesia if needed. Most children undergoing MRIs or CTs during the 12-yr period did not receive any form of anesthesia or sedation.

The second analysis examined the sensitivity of the number of anesthetics for elective MRIs and CTs to various factors. Such information can be used to forecast future staffing needs based on economic considerations. Nonelective scans with anesthesia were excluded from analysis because they were performed by the call team and did not influence staffing requirements or planning of resources. Data were obtained by manual review of scanner logs from the first 6 mo of 2007. Patient age and scan duration were logged for 1003 of the 1109 procedures.

Patient age and scan duration were used to create nine groups, which are listed in Table 1. Age categories were chosen to be physiologically meaningful,6 while yielding roughly equal numbers of scans associated with anesthesia care in each group. At 0–2 yr, the services of a pediatric anesthesiologist are especially important during physiologically complex surgery. At this age, many children will lie quietly and sleep through a procedure. At 3–5 yr, children are unlikely to remain still, even for a short procedure. Beginning at about 6 yr, some children will understand their situation sufficiently to be cooperative and follow instructions, depending on procedure length.

Table 1

Table 1

The use of anesthesia providers was related to scan duration for MRI and CT combined using the Mann– Whitney test for binomial data, with separate analyses for the three age groups (StatXact-7, Cytel Software Corporation, Cambridge, MA). Two-sided P values were calculated to within 10−5 using Monte-Carlo simulation. In addition, MRI and CT were analyzed separately. P values for the differences in the incidence of general anesthesia between MRI and CT were calculated using Fisher’s exact test. P values for the differences in scan times between MRI and CT were calculated using the Mann–Whitney test.

A nurse-administered moderate sedation program was initiated in January 2007. One anesthesiologist was assigned daily to supervise four nurses employed by the hospital.19 Log books documented that almost all of their patients (>95%) received one dose of oral or IV pentobarbital. Nurses provided moderate sedation,18 aiming for a score of 2 on the Ramsey Sedation Scale. Neither the supervising anesthesiologist, the sedation nurses, nor the hospital billed for this moderate sedation. Addition of the nurse sedation service provided an opportunity to determine the elasticity of the demand for anesthesia providers. The Cochrane-Armitage trend test (StatXact-7) was used to test for a change over time in the percentage of procedures performed by anesthesia providers after pooling counts in 2 wk periods. The 95% CI were calculated for the difference between the first and last 6 wk.

For brief scans, we estimated the influence20 of alternatives to anesthesia providers on the demand for the services of anesthesia providers. Let k = 1 to k = 9 refer to each of the n = 9 groups based on age and length of scan, as described in Table 1. Each group is a market segment. Then k = 1 refers to the first of those 9 segments, 0–2 yr olds undergoing brief scans. Similarly, k = 9 refers to the last segment, children 6–17 yr undergoing scans of 61–240 min. Let ak refer to the number of anesthesia provider cases, so that a1 is the number of 0–2 yr olds who received anesthesia care for scans ≤30 min in duration. Let n1 refer to the number of 0–2 yr olds who received either care from the sedation nurses or no sedation at all for scans ≤30 min in duration. The contribution20 of brief scans among 0–2 yr olds to the influence of the sedation nurses and no sedation combined on the overall market for anesthesia providers equals.

CV

CV

The same calculation was performed for k = 2 and k = 3 to determine the contribution of brief scans in the other age categories to the influence of the sedation nurses and no sedation combined on the general anesthesia market. This equation is not intuitive. Derivations and examples are given in Figures 1 and 2 of Ref. 20 and in Figure 6 and Eqs. 5 and 6 of Ref. 21. Corresponding 95% CI were estimated using Monte-Carlo simulation as described in Ref. 20.

Figure 1

Figure 1

Figure 2

Figure 2

Patients receiving no sedation were grouped together with those receiving care from the sedation nurses because “no sedation” was another alternative to the anesthesia providers. The intent of this competition analysis was to study the influence of alternatives to anesthesia providers on the utilization of anesthesia providers.

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RESULTS

Over 12 yr, the annual increase in the number of pediatric imaging studies was 8.1% (Fig. 1, 95% CI: 6.8%–9.4%, MRI 7.8% and CT 8.2%, P < 0.0001). Anesthesia care for pediatric patients for MRI and CT increased 8.5% per year (95% CI: 6.3%–10.6%, P < 0.0001). The percentage of procedures performed with anesthesia providers was unchanged (+0.1% per year, 95% CI: −0.2% to +0.3% per year, P = 0.59). Mean anesthesia time per elective case was also unchanged (−1.0 min per case per year, 95% CI: −3.4 to 1.4 min, P = 0.38).

Anesthesia providers were rarely used for elective scans shorter than 30 min in duration (P < 0.0001 for all age groups) (Fig. 2). Only 3.3% (95% CI: 2.0%–5.0%) of patients undergoing brief scans received care from anesthesia providers. The percentage of children receiving anesthesia care was much greater for MRI than CT (Table 2). Increases in scan duration were associated with increased utilization of anesthesia providers after stratifying by age (P < 10−5 for MRI, for CT, and for the two combined). Children 3–5 yr of age had the highest rates of anesthesia care (Table 2).

Table 2

Table 2

There was minimal competitive effect of sedation nurses and/or no sedation for brief scans on the overall number of scans involving anesthesia providers (Fig. 3, overall 5%, 95% CI: 2%–11%). This analysis shows that alternatives to anesthesia care for brief scans had little to no effect on this anesthesia department’s workload for pediatric diagnostic radiology.

Figure 3

Figure 3

Over the 6-mo period studied, involvement of the sedation nurses increased from 0% to 14% of all imaging studies (P < 0.0001). However, the availability of the sedation nurses did not reduce the workload of anesthesia providers (−0.9%, 95% CI: −8.6% to +6.7%, P = 0.52). Most nurse sedation cases involved brief scans (59%, 95% CI: 49%–69%) and the competitive effect was not substantive. The total number of children who received some type of hypnotic became greater, and the percentage of children who received no sedation was reduced (−8.1%, 95% CI: −16.0% to −0.1%, P = 0.017).

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DISCUSSION

The number of pediatric MRI and CT studies at the medical center under study increased by approximately 8% per year over the past 12 yr. Although the rate of growth may seem high, it is less than that reported for Medicare patients.11 The increase in anesthesia workload for these imaging studies was entirely consistent with the increase in the number of studies. The percentage of children receiving anesthesia services for imaging was unchanged.

To plan for future needs, anesthesia groups in the United States should be aware of changing patterns in imaging. Rates may not increase as they have in the past. Requirements for insurance preauthorization have resulted in declines in use of MRI and CT.22,23 Lower reimbursements to radiologists may reduce the availability of personnel and/or restrict scanner time.24 In contrast, technological changes that increase scan times may boost demand for anesthesia providers, whereas changes that reduce the noise and claustrophobia of MRI scanners may reduce future workload. Concern over radiation exposure may favor use of MRI over CT,25 resulting in longer average scan times (Table 2). The importance of scan duration and age in determining the need for anesthesia providers should be recognized when forecasting anesthesia staffing.

The use of anesthesia providers for imaging in the United States may also be influenced by reimbursement patterns. Treatment of dental caries in children rose substantially when health insurance plans were required to cover the costs of general anesthesia.26 Increasing numbers of anesthesiologists are providing services for gastrointestinal endoscopies,27,28 but the number of cases performed depends on the payment policies of local insurance carriers.27 Scans of short duration may be particularly susceptible to limited or no reimbursement because of greater difficulty in demonstrating medical necessity for anesthesia services. Problems may also arise if insurance companies cover anesthesia for longer scans but not shorter ones, and use CPT codes as a basis for preauthorization decisions. CPT codes reflect the organs imaged and the workload of radiologists. CPT codes are frequently not reliable predictors of scanner times.6 Although some codes are generally associated with brief scans,6 such as a CT of the head, other codes, such as an MRI of the brain, are not necessarily indicative of scan duration for an individual patient. Furthermore, given the exceedingly large number of combinations of codes that can comprise a single procedure, uncertainty in predicting scan duration is high if only CPT codes are used.6

Creation of a nurse sedation program at this hospital did not cannibalize the anesthesia department’s business. It merely increased the number of children receiving hypnotics. This result differs from that of hospitals where most sedation was initially being administered by personnel with limited training in pediatric sedation.29 Anesthesiologists were often needed to rescue failed sedations and were thought to increase scan quality.30,31 When sedation nurses are used in lieu of radiologists with less experience in sedation, the nurses may decrease use of anesthesiologists.

Regardless of other factors, anesthesia providers will likely continue to provide sedation and/or general anesthesia for pediatric diagnostic radiology at our institution. Anesthesia providers are needed for children with known or suspected airway problems. General anesthesia may improve image quality when sedation is insufficient to prevent an uncooperative child from moving.

We do not know whether the consistency over time in the percentage of children receiving anesthesia care is universal, or whether other institutions would report different findings. Few facilities have sufficient historical data to perform such analyses. The specific results obtained for this hospital regarding the sedation nurses are likely not applicable to other institutions. Our results reflect the well-established role of anesthesia providers arising from their guaranteed availability3,5 in providing services for pediatric diagnostic imaging.

However, the findings regarding age and scan length, and the principles associated with changes in MRI usage and reimbursement for anesthesia care, are appropriate for consideration by anesthesia groups nationwide to aid in planning future workload.

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