- Design
- Retrospective multicentre cohort
- Population
- 151,036 adults having non-cardiac surgery under general anaesthesia, three Chinese hospitals
- Primary outcome
- Postoperative pneumonia within 30 days
- Effect
- 20% fall from baseline: sHR 1.108 (95% CI 1.068 to 1.149); absolute thresholds inconsistent
A retrospective cohort at three Chinese hospitals studied 151,036 adults having non-cardiac surgery under general anaesthesia, testing 12 definitions of intraoperative hypotension against postoperative pneumonia within 30 days. Thresholds included absolute mean arterial pressures from below 50 to below 70 mmHg and relative falls of 20% to 50% from baseline.
Pneumonia occurred in 2.3%. Relative falls were more consistently associated with it than absolute thresholds. At a 20% fall from baseline, the presence of hypotension was associated with pneumonia (subdistribution hazard ratio 1.11, 95% CI 1.07 to 1.15), and each additional episode added risk (sHR 1.08). Absolute thresholds were not consistently associated after adjustment. Risk rose steeply with small exposures and then plateaued across relative thresholds of 20% to 40%.
The association is modest and observational; patients who become hypotensive may differ in ways the model could not capture. The study does not test whether treating to a relative target prevents pneumonia.
It does support a practical habit: record a reliable baseline pressure before induction and treat a substantial fall from it, rather than relying solely on a single absolute floor for every patient.
- Record a reliable baseline blood pressure before induction for every patient.
- Treat a fall of about 20% or more from baseline, not only a MAP below a fixed number.
- Pay attention to repeated episodes: each one added risk in this cohort.
- Be especially careful in patients with a high baseline pressure, in whom a fixed floor allows a large relative fall.
Why it matters
It challenges the convenience of a single MAP threshold for all patients, at least where lung complications are concerned.
Don't overread it
This retrospective cohort shows association; it does not prove that maintaining baseline pressure prevents pneumonia.
The statistics, in plain English
A subdistribution hazard ratio of 1.11 means about 11% higher risk of pneumonia, accounting for patients who died first. On a baseline risk of 2.3%, that is a small absolute difference per patient but meaningful across many operations. The finding is an association from routine records, not proof of cause.
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