Effect of Pre-operative Intravenous Crystalloid Bolus on Post-Induction Blood Pressure – a randomized blinded intervention trial

BACKGROUND: Post-induction hypotension in major non-cardiac surgery is common and a modifiable risk factor for adverse outcomes. There is an ongoing debate whether pre-operative crystalloid fluid administration can reduce the incidence or severity of post-induction hypotension. This study aims to assess whether a pre-operative intravenous crystalloid bolus reduces post-induction hypotension in high-risk patients under general anesthesia. METHODS: This was a prospective, randomized, single-blind clinical trial conducted at two centers in Austria (Medical University of Graz, Medical University of Vienna). Adult patients aged 45 years and older with cardiovascular risk factors undergoing major surgery were enrolled and randomly assigned to receive a pre-operative crystalloid bolus within 60 ± 15 minutes before anesthetic induction, or to receive standard care. The primary outcome was the time-weighted average mean arterial pressure of <65 mmHg within the first 20 minutes after induction or until surgical incision. RESULTS: Of the 504 patients analyzed (247 in the intervention group and 257 in the control group), no statistically significant difference in median time-weighted average of the mean arterial pressure <65 mmHg was observed (Intervention group: 0.0 mmHg (IQR 0.0-0.56); Standard of Care group: 0.0 mmHg (IQR 0.0-0.84, p=0.368). CONCLUSIONS: In this blinded randomized clinical trial, administering a crystalloid fluid bolus within 60 minutes before surgery did not significantly reduce the time-weighted average of a mean arterial pressure less than 65 mmHg compared to standard care in patients with cardiovascular risk factors undergoing major non-cardiac surgery. Our study suggests that administering crystalloids before surgery does not prevent post-induction hypotension.