Errors in pressure measurements due to changes in pressure transducer levels during adult cardiac surgery: a prospective observational study.

Background: Blood pressure measurement is an essential element during intraoperative patient management. However, errors caused by changes in transducer levels can occur during surgery.

Methods: This single center, prospective, observational study enrolled 25 consecutive patients scheduled for elective cardiac surgery with invasive arterial and central venous pressure (CVP) monitoring. Hydrostatic pressures caused by level differences (leveling pressure) between a reference point (on the center of the left biceps brachii muscle) and the transducers (fixed on the right side of the operating table) for arterial and central lines were continuously measured using a leveling transducer. Adjusted pressures were calculated as measured pressure - leveling pressure. Hypotension (mean arterial pressure < 80, <70, and < 60 mmHg), and CVP (< 6, ≥6 and < 15, or ≥ 15 mmHg) and pulmonary artery pressure (PAP, mean > 20 mmHg) levels were determined using unadjusted and adjusted pressures.

Results: Twenty-two patients were included in the analysis. Leveling pressure ≥ 3 mmHg and ≥ 5 mmHg observed at 46.0 and 18.7% of pooled data points, respectively. Determinations of hypotension using unadjusted and adjusted pressures showed disagreements ranging from 3.3 to 9.4% depending on the cutoffs. Disagreements in defined levels of CVP and PAP were observed at 23.0 and 17.2% of the data points, respectively.

Conclusions: The errors in pressure measurement due to changes in transducer level were not trivial and caused variable disagreements in the determination of MAP, CVP, and PAP levels. To prevent distortions in intraoperative hemodynamic management, strategies should be sought to minimize or adjust for these errors in clinical practice.

Trial Registration: cris.nih.go.kr (KCT0006510).