A pre-induction crystalloid bolus did not prevent hypotension after induction

Design

Randomised, single-blind trial, 2 Austrian centres

Population

504 adults ≥45 years with cardiovascular risk factors having major non-cardiac surgery

Primary outcome

Time-weighted average MAP below 65 mmHg in first 20 minutes after induction

Effect

Median 0.0 mmHg (IQR 0.0–0.56) vs 0.0 mmHg (0.0–0.84); P = 0.37

Many anaesthetists give a crystalloid bolus before induction to blunt the fall in pressure that follows. A blinded trial at two Austrian university hospitals randomised 504 patients aged 45 or older with cardiovascular risk factors, having major non-cardiac surgery, to a crystalloid bolus within about an hour before induction or to standard care.

The primary outcome — time-weighted average mean arterial pressure below 65 mmHg in the first 20 minutes after induction or until incision — did not differ. Median values were zero in both groups, meaning most patients in either arm had little or no hypotension by this measure.

The trial suggests the bolus adds fluid without adding protection. That matters for patients at risk of fluid overload, such as those with heart failure or kidney disease. Patients who are genuinely fluid depleted, for example after prolonged fasting or bowel preparation, were not the focus and still need assessment and correction.

• Consider stopping routine crystalloid preloading before induction in adults with cardiovascular risk factors.
• Correct genuine fluid deficits — from bowel preparation, vomiting or prolonged fasting — on clinical assessment rather than by protocol.
• Use induction dose adjustment and vasopressors as the main defence against post-induction hypotension.
• Be particularly cautious with preloading in patients with heart failure or advanced kidney disease.

Why it matters

It removes a common habit that adds fluid without measurable benefit, which matters most for patients who handle fluid poorly.

Don't overread it

The trial was single-blind, and most patients in both arms had little hypotension; it does not address patients who are fluid depleted.

The statistics, in plain English

The median time-weighted hypotension was 0.0 mmHg in both groups, meaning at least half of patients never fell below 65 mmHg. When an outcome is rare, a trial needs a large effect to show a difference, and none was seen (P = 0.37).

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