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Quality of Care/Patient Safety

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Researchers examine the impact of hospital volume on length of stay, readmissions, and patient outcomes

As evidence mounts that high-volume hospitals have better outcomes for selected surgical procedures, interest in volume-based referral initiatives is growing. On the other hand, payers want to know whether volume standards will also reduce costs and use of resources. The following two studies, which were supported in part by the Agency for Healthcare Research and Quality, address these issues.

Hodgson, C.D., Zhang, W., Zaslavsky, A.M., and others (2003, May). "Relation of hospital volume to colostomy rates and survival for patients with rectal cancer." (AHRQ grant HS09869). Journal of the National Cancer Institute 95(10), p. 708-716.

This study found that patients with rectal cancer who undergo surgery at a hospital that performs a high volume of these surgeries have better survival rates and are less likely to have a permanent colostomy than similar patients treated in low-volume hospitals. The investigators examined the association between hospital volume and colostomy rates, postoperative mortality, and overall survival of 7,257 patients with stage I, II, or III rectal cancer identified from the California Cancer Registry from 1994 through 1997. They linked the registry data to hospital discharge abstracts and zip-code-level data from the U.S. Census.

One-third of these patients received a permanent colostomy, which has been associated with depression, poor social functioning, and sexual dysfunction. After adjusting for demographic, clinical, and other factors, patients at hospitals that performed less than seven such surgeries each year (hospitals in the lowest volume quartile) had 37 percent greater risk of having a permanent colostomy than those treated at hospitals that performed more than 20 such surgeries each year (highest volume quartile). Patients in the lowest volume hospitals also had nearly three times the likelihood of dying within 30 days and a 28 percent greater risk of dying within 2 years than those in the highest volume hospitals.

Stratifying patients by tumor stage and coexisting illness did not appreciably affect the results. Also, pathologists evaluated fewer lymph nodes surrounding tumors removed in low-volume hospitals, suggesting that cancer staging may be less thorough at these hospitals. Identifying processes of care that contribute to these differences may improve patients' outcomes in all hospitals, suggest the researchers.

Goodney, P.P., Stukel, T.A., Lucas, F.L., and others (2003, August). "Hospital volume, length of stay, and readmission rates in high-risk surgery." (AHRQ grant HS10141). Annals of Surgery 238(2), pp. 161-167.

This study demonstrates that high-volume hospitals do not have shorter hospitals stays or lower readmission rates than low-volume hospitals for Medicare patients undergoing high-risk procedures. To the extent that length of stay and readmission rates reflect overall hospital costs, referral of patients to high-volume hospitals seems more likely to decrease mortality than the cost of delivering high-risk surgery, conclude the researchers.

They used the 1994-1999 national Medicare database to study postoperative length of stay and readmission rates within 30 days of hospital discharge after 14 high-risk cardiovascular and cancer procedures. They examined the relationship between length of stay, 30-day readmission, and hospital volume, adjusting for patient age, sex, race, coexisting illnesses, illness severity at admission, and mean social security income. The nature of the procedures themselves was a more important determinant of hospital stay and 30-day readmission rates than hospital volume.

Mean postoperative length of stay ranged from 3.4 days for carotid endarterectomy to 19.6 days for esophagectomy. Mean length of stay at very-low-volume and very-high-volume hospitals differed by more than 1 day for six procedures. However, the mean length of stay was shorter in high-volume hospitals for three procedures (pancreatic resection, esophagectomy, and cystectomy) but longer for three other procedures (aortic and mitral valve replacement and gastrectomy). The 30-day readmission rate also varied widely by procedure, ranging from 9.9 percent for nephrectomy to 22.2 percent for mitral valve replacement. However, volume was not related to 30-day readmission rate for any procedure.

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