Supine position

If the arm is adducted in the supine position, it should be positioned with the palm facing the patient's body (ie, neutral) and not in contact with the bed frame. The arm should be secured by loosely wrapping the lift sheet around the arm and then under the patient. For pregnant patients, and for those with a mobile abdominal mass, the table should be tilted left or a wedge placed under the left hip to avoid aortocaval compression by the abdomen.
Physiologic changes that occur in the supine position include the following:
- Right-sided filling pressures and cardiac output increase, often resulting in decreased heart rate and decreased peripheral vascular resistance.
- Abdominal contents displace the diaphragm cephalad, which results in decreased tidal volume and functional residual capacity during spontaneous ventilation. During anesthesia with mechanical ventilation, ventilation/perfusion mismatch may occur due to overventilation of anterior lung fields.
For further information, refer to UpToDate content on patient positioning for surgery and anesthesia.

Illustration by Kiran Guthikonda, MD, PhD, Dartmouth-Hitchcock Medical Center.

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