For a patient in the kidney rest position for Pelvolithotomy with the operative side on the left flank and lying on their right side, should the NIBP cuff be placed on the right or left arm?

NIBP Cuff Placement in Lateral Decubitus Position for Pelvolithotomy

Place the NIBP cuff on the left arm (non-dependent, upper arm) for accurate blood pressure monitoring during this procedure. 1

Rationale for Left Arm Selection

The fundamental principle of accurate blood pressure measurement requires the cuff to be positioned at the level of the right atrium (mid-sternum) to avoid hydrostatic pressure errors. 2, 1 When your patient is lying on his right side for left flank pelvolithotomy:

• The left arm (non-dependent/upper arm) can be properly supported and positioned at the exact level of the right atrium, allowing accurate measurements as recommended by the American College of Cardiology and American Heart Association. 1

• The right arm (dependent/lower arm) will be compressed against the operating table and positioned below heart level, which would produce falsely elevated readings due to hydrostatic pressure effects. 1

Critical Positioning Requirements

To ensure measurement accuracy, you must:

• Support the left arm at mid-sternum level using an armboard or padded support—do not allow it to hang unsupported or be held by the patient, as muscle tension and improper positioning create clinically significant errors. 2, 1

• Position the middle of the cuff at the exact level of the right atrium (fourth intercostal space/mid-sternum), as deviations from heart level cause approximately 2 mmHg error for every inch of vertical displacement. 2, 1

• Ensure the cuff bladder encircles at least 80% of the arm circumference and is positioned with the lower edge a few centimeters above the antecubital fossa. 2, 1

Magnitude of Positioning Errors

Understanding the clinical significance of improper arm positioning:

• Arm below heart level produces falsely HIGH readings by approximately 2 mmHg per inch below heart level, potentially 10 mmHg or more total error. 1

• Arm above heart level produces falsely LOW readings by the same magnitude. 1

• Unsupported arm positioning causes falsely elevated readings due to isometric muscle tension from the patient holding their arm up. 1

Device Selection

• Use a validated oscillometric device appropriate for intraoperative monitoring, with recognition that oscillometric devices are not validated for use in atrial fibrillation. 2, 1

• Ensure the device has been clinically validated according to current standards, as only 6% of commercially available devices have been adequately tested. 2

Common Pitfall to Avoid

Never place the cuff on the right (dependent) arm in this position—the arm will be compressed against the table, positioned below heart level, and impossible to support properly at the right atrial level, resulting in consistently inaccurate readings that could mislead intraoperative hemodynamic management. 1