Does it matter what a hospital is “high volume” for? Specificity of hospital volume-outcome associations for surgical procedures: analysis of administrative data
BMJ 2004; 328 doi: https://doi.org/10.1136/bmj.38030.642963.AE (Published 25 March 2004) Cite this as: BMJ 2004;328:737
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EDITOR –Urbach et al show that short-term outcomes following complex
surgical procedures are improved within hospitals with a high volume of
such procedures. What is new is that the authors have also shown that
hospitals with a high volume of surgical procedures different to the index
procedure have improved outcomes.1 This novel finding may give some
insight into the mechanisms that underly volume-outcome associations.
Several explanations are commonly used to account for these
associations.2,3 The findings from this study contribute to a degree to
the first and most attractive explanation – ‘practice makes perfect’.
This postulates that the enhanced experience acquired through high volumes
explains the improved outcomes seen within high volume providers.
However, within the same hospital it is unlikely that the same surgical
team would perform both aortic aneurysm repair and lung resection and yet
in this study the outcomes of the former appear to be influenced by the
hospital volume of the latter.1 This would therefore seem to demonstrate
that it is not only the skills of the operating surgeon, but also those of
other professionals within the healthcare system as a whole, that are
important in determining short-term outcome. It would have further aided
our understanding if this study had adjusted for either the effects of
surgeon volume or for the interaction effects between hospital and surgeon
volume.
A further explanation has been described as ‘selective referral’.
This proposes that improved outcomes correlated with volume occur as a
result of providers acquiring good reputations and thus attracting
increased numbers of referrals, not only from other healthcare
professionals but also from being actively sought out by informed
patients. To some extent we believe that this study challenges this
explanation in that it is unlikely that patterns of referral would be
influenced according to outcomes (perceived or actual) from similar
complex surgical procedures within the same hospital other than that for
which the patient is being referred. Further studies from countries such
as the UK that have both differing healthcare systems and patterns of
referral to either the US or Canada (where the overwhelming majority of
volume-outcome studies have been conducted) would be helpful in
determining whether ‘selective referral’ is a feasible explanation.
1. Urbach DR, Baxter NN. Does it matter what a hospital is ‘high
volume’ for? Specificity of hospital volume-outcome associations for
surgical procedures: analysis of administrative data. BMJ 2004;328:737-
740.
2. Birkmeyer JD, Siewers AE, Finlayson EVA, Stukel TA, Lucas FL,
Batista I et al. Hospital volume and surgical mortality in the United
States. New Eng J Med 2002;346:1128-1137
3. Ihse I. The Volume-Outcome relationship in cancer surgery. Ann
Surg 2003;238:777-781.
Competing interests:
None declared
Competing interests: No competing interests
I read with interest the article published by David R Urbach and
Nancy N Baxter (1) showing a positive relationship between the outcome
following major surgical procedures and the volume of works carried out in
any hospital. This is true to some extent. It is also well known that
the rate of complications and the ultimate outcome following any surgery
is dependent on the experience of the surgeon and his own specialty
interest. A general surgeon with no specialty interest in vascular
surgery is very likely to have an increased mortality following an
abdominal aortic aneurysm repair, in both emergency and elective
situations. The outcome is also dependent on individual patient, that is,
case selection, which is also dependent on the practice of individual
surgeon. It would be interesting to know if there is any data available
on the level (trainees vs. consultants) and the specialty interests of the
surgeons involved in relation to the outcome of the procedures mentioned
in the paper.
Competing interests:
None declared
Competing interests: No competing interests
Drs Urbach and Baxter show that improved outcome of a high risk
surgical procedure is not dependent on the volume of that specific type of
surgery but rather on the experience with high risk surgery in general in
that hospital. They argue against regionalisation based on the concept
that only a certain type of surgery should be centralised. The intriguing
hypothesis is that it might be the overall organisational structure that
determines outcome and not only the surgeons experience. Possible elements
are then the quality of the department of anaesthesia and intensive care.
Nursing might also be an important factor. The data should therefore be
analysed further to know what makes the difference. We have to know what
determines outcome in order to improve the outcome of our health care at
least to the level of the best performing hospital. A new leading
principle might be that high risk surgery has to take place in a hospital
with the best (most experienced) supportive care i.e. nursing, anaesthesia
and intensive care.
Competing interests:
None declared
Competing interests: No competing interests
Relative Importance of Institutional Versus Individual Surgeon Influence on Outcome
Editor- We read with interest the paper by Drs Urbach and Baxter (1).
The findings that operative mortality appears to be lower in
hospitals that not only perform a higher volume of the same procedure but
also in hospitals that have a higher volume of different procedures should
not be a surprise to many surgeons. It does support our belief that the
surgeon is only one of many interrelated factors, which will influence
surgical outcome. As we had previously said (2) variability in outcome has
been is due to the complex interplay of multiple factors including;
surgical ability, surgical technique, case mix, case volume, institutional
influences peri-operative care and anaesthetic care. Though mistakenly
often seen as the most significant determent of outcome, the surgeon is
but one factor in the outcome, though one of the most easy to identify.
This paper emphasises that good surgical results are the consequence of
these multiple factors within the environment of a multidisciplinary team,
which reflects the nature of modern surgery. (3)
It is interesting to see that this paper showed little evidence of an
association between volume and outcome for colorectal resection which
varied between the hospitals examined, ranging from an yearly average of
none to 150 operative cases. Colorectal resections made up 60% of the
total procedures examined, the median hospital volume of 53 cases was
reasonable, and although not stated it could be expected that the majority
of the cases were colonic, technically much easier than rectal resections
with a low expected mortality. It is unfortunate that no differentiation
was made between colonic or rectal, and elective to acute resections, as
case-mix and referral patterns have been shown to influence outcome (4).
Surgical technique and volume in low rectal resection has been shown
to influence recurrence rate (5,6). Hospital volume not individual surgeon
volumes were used in this paper but it would have also been interesting to
see individual surgeon volume, as earlier studies ( eg CPOD) have shown
the importance of individual surgeon volumes. With the database this
group will have it be possible to try and determine the relative
importance of each of these issues.
Another important point, which we have raised before, is that
measurements and comparisons of surgical outcome is difficult. To make a
meaningful assessment operative mortality, postoperative morbidity and
quality of life measurements need to be made, and that just examining
mortality is simplistic.(3)
The issue of specialisation and centralisation of services within
general surgery is an issue debated in New Zealand as well as the UK (7).
The interpretation of data encouraging increased subspecialisation must be
carefully looked at, when one sees the influence on outcome of the
institutional factors, independent of the surgeon. This paper raises
important questions, which are still unanswered about allocation of
limited health resources to maximise patient care and outcome.
References:
1) Does it matter what a hospital is "high volume" for? Specificity
of hospital volume-outcome associations for surgical procedures: analysis
of administrative data
David R Urbach, Nancy N Baxter BMJ 2004;328:737-740
2) Surgeon is only one influence on outcome
Frizelle FA, Frye J BMJ 2003; 326:832-3
3) Mortality control charts: assessment of outcome is complex.
Frizelle FA, Frye J BMJ. 2003;326: 1397
4) Sagar PM, Hartley MN, Mancey-Jones B, Sedman PC, May J, Macfie J.
Comparative audit of colorectal resection with POSSUM scoring system. Br J
Surg 1994;81: 1492-4
5) Bissett IP, McKay GS, Parry BR, Hill GL. Recurrence and survival
after potentially curative surgery for colorectal cancer. Aust NZ J Surg
2000; 70 : 704-9
6) Heald RJ. Total mesorectal resection is optimal surgery for rectal
cancer; a Scandinavian consensus. Br J Surg 1995; 82: 1297-9
7) Specialisation within the speciality of general surgery; can the
potential advantages be realised ?
Frizelle FA, Beasley SW, Roake JA, Sykes PH. N Z Med J. 2002 115, 295-298.
Competing interests:
None declared
Competing interests: No competing interests