Physiologic changes that occur with reverse Trendelenburg positioning include the following:
- Decreased venous return can cause decreased cardiac preload, cardiac output, and mean arterial pressure. Compensatory mechanisms include increased heart rate, sympathetic tone, and peripheral vascular resistance.
- Lung volumes and functional residual capacity increase, compared with supine.
- Cerebral perfusion pressure decreases with the head above the heart. Measurement of blood pressure at the level of the Circle of Willis gives a more accurate representation of cerebral perfusion than measurement at the level of the upper arm. Arm cuff measurements should be adjusted to account for the gradient in hydrostatic pressure.
For further information, refer to UpToDate content on patient positioning for surgery and anesthesia.
Illustration by Kiran Guthikonda, MD, PhD, Dartmouth-Hitchcock Medical Center.
