= Nicolas Demartines
{c}
\b[Nicolas Demartines] is a <surgeon> whose CHUV professional background includes visceral and liver/pancreatic cancer surgery. A dated institutional announcement identifies that clinical and academic context.<Changement à la tête du CHUV by CHUV (15 December 2022)>[Biographical paragraph, 15 December 2022]{ref}
Demartines coauthored the 2004 complication-classification study with <Daniel Dindo> and <Pierre-Alain Clavien>. It evaluated the reporting scheme in a surgical cohort and through an international surgeon survey.<Classification of Surgical Complications: A New Proposal With Evaluation in a Cohort of 6336 Patients and Results of a Survey by Daniel Dindo and others>[Byline and Patients and Methods]{ref} Standardizing outcome categories helps comparison, but does not by itself standardize the patients being compared.
An original <case mix> example makes that limitation quantitative. Suppose a low-risk stratum has complication probability $0.05$ and a high-risk stratum $0.30$ in each of two hypothetical centers. Center A treats 80 low-risk and 20 high-risk patients, giving expected complications
$$
80(0.05)+20(0.30)=10.
$$
Center B treats 20 low-risk and 80 high-risk patients, giving
$$
20(0.05)+80(0.30)=25.
$$
The crude expected rates are therefore $10\%$ and $25\%$, despite identical stratum-specific risks in this constructed example.
Using the same illustrative $50:50$ reference mix gives
$$
0.5(0.05)+0.5(0.30)=0.175
$$
for both centers. This calculation shows what changes when the patient mix is held fixed; it is not a measured comparison of actual centers or a complete adjustment for every clinical difference.
The <Clavien-Dindo classification> addresses a different part of the measurement problem: identifying and grading a complication consistently. A credible outcome comparison also specifies its denominator, follow-up and patient selection. <Causal inference> about the effect of an operation requires more than observing a difference in crude rates. The documented contribution is Demartines's participation in the shared classification research, without assigning every methodological component to an individual author.
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