Surgical mortality rates are increasingly used to measure hospital quality.
It is not clear, however, how many hospitals have sufficient caseloads to
reliably identify quality problems.
To determine whether the 7 operations for which mortality has been advocated
as a quality indicator by the Agency for Healthcare Research and Quality (coronary
artery bypass graft [CABG] surgery, repair of abdominal aortic aneurysm, pancreatic
resection, esophageal resection, pediatric heart surgery, craniotomy, hip
replacement) are performed frequently enough to reliably identify hospitals
with increased mortality rates.
Design and Setting
The US national average mortality rates and hospital caseloads of the
7 operations were determined using the 2000 Nationwide Inpatient Sample (NIS),
and sample size calculations were performed to determine the minimum caseload
necessary to reliably detect increased mortality rates in poorly performing
hospitals. A 3-year hospital caseload was used for the baseline analysis,
and poor performance was defined as a mortality rate double the national average.
Main Outcome Measure
Proportion of hospitals in the United States that performed more than
the minimum caseload for each operation.
The national average mortality rates for the 7 procedures examined ranged
from 0.3% for hip replacement to 10.7% for craniotomy. Minimum hospital caseloads
necessary to detect a doubling of the mortality rate were 64 cases for craniotomy,
77 for esophageal resection, 86 for pancreatic resection, 138 for pediatric
heart surgery, 195 for repair of abdominal aortic aneurysm, 219 for CABG surgery,
and 2668 for hip replacement. For only 1 operation did the majority of hospitals
exceed the minimum caseload, with 90% of hospitals performing CABG surgery
having a caseload of 219 or higher. For the remaining operations, only a small
proportion of hospitals met the minimum caseload: craniotomy (33%), pediatric
heart surgery (25%), repair of abdominal aortic aneurysm (8%), pancreatic
resection (2%), esophageal resection (1%), and hip replacement (<1%).
Except for CABG surgery, the operations for which surgical mortality
has been advocated as a quality indicator are not performed frequently enough
to judge hospital quality.