One-Minute Oscillometry vs Continuous Arterial Pressure Monitoring

Key Takeaways

• One-minute oscillometric monitoring met the prespecified noninferiority criterion for the primary induction hypotension endpoint.
• Vasopressors, particularly phenylephrine, were used less often in the oscillometry group than in the continuous monitoring group.
• Investigators described induction hypotension as rare and said high-frequency oscillometric monitoring may be a pragmatic alternative in relatively healthy patients.

In a bicenter randomized trial of anesthetic induction, 1-minute oscillometric monitoring was noninferior to continuous arterial pressure monitoring for the primary hypotension measure in adults undergoing noncardiac surgery with planned arterial catheterization. Among 253 analyzed patients, the upper 97.5% confidence limit for the geometric mean ratio was 1.63, below the prespecified noninferiority margin of 3.50.

The trial was conducted at two tertiary university hospitals and randomly assigned patients to one of two induction monitoring strategies. Among the 253 analyzed patients, 127 were assigned to continuous monitoring and 126 to 1-minute oscillometry. All were adults undergoing noncardiac procedures with planned arterial catheterization, and 71% were classified as ASA physical status I or II. Patients received either unblinded continuous arterial pressure monitoring or 1-minute interval oscillometric monitoring, while intra-arterial pressures were blinded during induction in the oscillometry group.

The primary outcome was the area of mean arterial pressure below 65 mmHg during the initial 15 minutes of induction. Noninferiority was prespecified as a 10 mmHg·min absolute increase in the observed median primary outcome compared with continuous monitoring, and the analysis used a geometric mean ratio. Median values were 3.0 (interquartile range, 0 to 20 mmHg·min) in the continuous group and 3.3 with the same range in the 1-minute oscillometry group. The upper 97.5% confidence limit for the geometric mean ratio was 1.63, the noninferiority margin was 3.50, and P was less than 0.001 for noninferiority.

Secondary descriptive findings showed more frequent vasopressor treatment in the continuous monitoring group than in the oscillometry group, at 61% versus 41%. The difference was driven mainly by phenylephrine use, at 24% versus 7%. These differences accompanied the primary noninferiority result during induction.