Authors: Nicholas M. Halzack, M.P.H. et al
ASA Monitor 10 2015, Vol.79, 10-12.
The relationship between surgical volume and patient outcomes has been studied extensively since the 1980s. The “volume” variable is often measured in two ways: hospital volume (the amount of surgeries the hospital performs) and surgeon volume (the amount of surgeries each surgeon performs). So, do high-volume hospitals and providers achieve better outcomes? Luft and colleagues first presented this theory in 1980 and proposed that a positive relationship existed between the two variables even after adjusting for hospital variables such as size, teaching status and geographic location.1 Since then, hundreds of studies have been published on the topic examining various surgical procedures as well as nonsurgical care such as trauma, critical care and cancer care. To summarize the existing literature about the relationship between hospital volume and patient outcomes in surgery, Pieper et al. recently conducted a systematic review of systematic reviews that serves as the focus of this month’s “Policy Matters.”2
Thirty-two systematic reviews based on more than 200 primary studies were selected for inclusion in Pieper’s review. The authors categorized the reviews by the type of surgical procedure and rated the strength of the volume-outcomes relationships for each of 14 surgical procedures examined.
The only procedure that does not show at least a slightly positive relationship between surgical volume and outcomes is knee arthroplasty, which was based on two systematic reviews and rated as “unclear.”
Pieper and colleagues conclude that although there is a positive overall relationship between volume and outcomes for most procedures, it does not affect all measures of patient outcomes, and the magnitude of the effect varies. For instance, two reviews about colorectal cancer found a convincing positive relationship between high volume and long-term survival but not for postoperative mortality,3 –4 while the reviews about lung cancer and breast cancer found inverse results.5 –6 The results for reviews that provided odds ratios for postoperative mortality in high-volume hospitals.
The 14 reviews account for 11 of the 14 types of surgeries examined by the authors. The results cover a wide range; for pancreatic surgery, the odds of mortality are 68 percent less in high-volume hospitals, while for colorectal surgery the odds are only 7 percent less (not statistically significant). An interesting discrepancy is seen with surgeries for colon cancer shows two reviews with statistically insignificant relationships (ORs=0.93 and 0.88), and one review with a strong, statistically significant relationship (OR=0.64).
The conclusions drawn by Pieper and colleagues have been corroborated by additional articles published since. HPR found four new systematic reviews and eight new primary articles,7 -19 and all but one agree that high surgical volume is a good predictor of high quality; however, the magnitude of that relationship varies.
Based on results from the review by Pieper et al. and articles published since, it seems apparent that a positive relationship between surgical volume and patient outcomes exists; however, there is little uniformity in how positive the relationship is, which outcomes it consistently affects and whether the type of surgery affects the relationship differently. One hypothesis about the volume-outcomes relationship is that increased provider experience may yield better patient outcomes – in essence, “practice makes perfect.” If that were the case, it could be expected that the relationship is more pronounced in rare, high-risk procedures. The ratings given by Pieper and colleagues seem to support that hypothesis as common procedures such as knee arthroplasty and colorectal surgery show limited evidence of a strong effect, while rarer risky procedures such as pancreatic surgery and cancer surgeries show a stronger relationship.
What should policymakers do with this information? Evans and Tsai suggest in a 2014 editorial20 that future policies should encourage regionalization of surgery and referral “cutoffs” (i.e., certain surgeries should not be performed at very low-volume hospitals); however, Mesman et al. argue in their 2015 review that the majority of evidence on the volume-outcome relationship does not focus on the underlying mechanisms (i.e., trying to regionalize care is an oversimplification of the problem). It is difficult to argue that more research is needed on the subject, as hundreds of primary articles have already been published about the volume-outcomes relationship in surgery, and many more have investigated this relationship in other areas of care. Maybe a shift in the focus of this research should occur. How does volume of providers other than the surgeon (such as physician anesthesiologists and perioperative nurses) influence outcomes? HPR could find only one article that examined the effect of physician anesthesiologist volume on outcomes, although the authors did not find a significant effect.19Can future research investigate more specifically why this relationship exists? Interestingly, the review by Mesman et al. was the only review HPR found on this subject that was published in a health policy-focused journal as opposed to a clinical one. The volume-outcomes relationship is complicated, as many factors (observed and unobserved) affect it. For example, little attention has been paid to the relationship between hospital volume and structures or processes of care, which could provide further insight into why volume affects outcomes. There is opportunity for anesthesiologist researchers to take the next step in this field of research, potentially informing future policy discussions and improving surgical care outcomes.
For a complete list of references, please refer to the back of the online version of the ASA MONITOR at asahq.org or email Jamie Reid at firstname.lastname@example.org.
Luft HS . The relation between surgical volume and mortality: an exploration of causal factors and alternative models. Med Care. 1980;18(9):940–959.
Pieper D, Mathes T, Neugebauer E, Eikermann M . State of evidence on the relationship between high-volume hospitals and outcomes in surgery: a systematic review of systematic reviews. J Am Coll Surg. 2013;216(5):1015–1025.
Van Gijn W, Gooiker GA, Wouters MWJM, Post PN, Tollenaar RAEM, van de Velde CJH . Volume and outcomes in colorectal cancer surgery. Eur J Surg Oncol. 2010;36(suppl 1):S55–S63
Archampong D, Borowski D, Wille-Jorgensen P, Iversen LH. Workload and surgeon’s specialty for outcome after colorectal cancer surgery. Cochrane Database Syst Rev. March 14, 2012;3:CD005391. doi: 10.1002/14651858.CD005391.pub3.
Von Meyenfeldt EM, Gooiker GA, van Gijn W, et al. The relationship between volume or surgeon specialty and outcome in the surgical treatment of lung cancer: a systematic review and meta-analysis. J Thorac Oncol.2012;7(7):1170–1178.
Gooiker GA, van Gijn W, Post PN, van de Velde CJH, Tollenaar RAEM, Wouters MWJM . A systematic review and meta-analysis of the volume-outcome relationship in the surgical treatment of breast cancer. Are breast cancer patients better off with a high volume provider? Eur J Surg Oncol.2010;36(suppl1):S27–S35.
Eskander A, Merdad M, Irish JC, et al. Volume–outcome associations in head and neck cancer treatment: a systematic review and meta-analysis. Head Neck.2014;36(12):1820–1834.
Trinh QD, Bjartell A, Freedland SJ, et al. A systematic review of the volume–outcome relationship for radical prostatectomy. Eur Urol. 2013;64(5):786–798.
Mesman R, Westert GP, Berden BJMM, Faber MJ. Why do high-volume hospitals achieve better outcomes? A systematic review about intermediate factors in volume–outcome relationships. Health Policy. 2015 ;119(8):1055–1067. doi: 10.1016/j.healthpol.2015.04.005.
Sepehripour AH, Athanasiou T . Is there a surgeon or hospital volume–outcome relationship in off-pump coronary artery bypass surgery? Interact Cardiovasc Thorac Surg. 2013;16(2):202–207.
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