The supine position is one of the most commonly used surgical positions, particularly for abdominal, pelvic, open-heart, head and neck, and most extremity surgeries. This position involves the patient lying flat on their back, which provides optimal access to a wide range of surgical sites. The supine position has several variations, each with unique implications for patient care. These include the Lawnchair, Frog-leg, Trendelenburg, and Reverse Trendelenburg positions. While these variations share many of the same considerations as the standard supine position, they come with additional implications that anesthesia providers must consider.
Indications for Supine Position:
- The supine position is ideal for procedures involving the abdomen, pelvis, heart, head, neck, and extremities. Its versatility makes it a preferred choice for many surgical disciplines due to the accessibility it provides to these anatomical regions.
Application of Padding:
- Adequate padding should be applied to pressure points, including the heels, elbows, knees, spinal column, and occiput. This padding helps distribute pressure evenly and reduces the risk of pressure ulcers and nerve damage. Gel pads, foam cushions, and other protective materials can be used to cushion these vulnerable areas.
Prevention of Ulnar Nerve Injury:
- The ulnar nerve is particularly susceptible to injury during surgery while in the supine position. When the arms are adducted with the hands and forearms maintained in a neutral position, either with the palms facing the body or supinated, the external pressure on the ulnar nerve is minimized, significantly reducing the risk of injury.
To secure the arms in the correct position against the body, a "draw sheet" technique is often employed. This involves passing a sheet under the patient’s body and then over the arms before tucking it securely under the torso. This method ensures that the arms are held in the proper position, preventing movement that could lead to undue pressure or stretching of the ulnar nerve.
Prevention of Pressure Alopecia:
- To avoid pressure alopecia, which can occur due to prolonged pressure on the scalp, it is recommended to periodically rotate the patient’s head during long procedures. This practice helps to alleviate sustained pressure on any one area of the scalp and reduces the risk of hair loss.
Prevention of Brachial Plexus Injury:
- To prevent brachial plexus injury, the upper extremities should be abducted to less than 90 degrees with the hands and forearms in a supinated or neutral position. This positioning minimizes the risk of stretching or compressing the brachial plexus nerves, which can lead to neuropathy.
Padding of IV Tubing and Stopcocks:
- Any IV tubing and stopcocks that come into contact with the patient's skin should be padded to prevent pressure injuries. This includes ensuring that these devices do not create pressure points that could lead to skin breakdown or nerve compression.
Variations of the Supine Position
Lawnchair Position
This variation of the supine position involves slightly flexing the hips and knees above the level of the heart. This positioning relieves pressure on the back, hips, and knees, facilitates venous drainage from the lower extremities, and reduces tension on the abdominal musculature. It is particularly useful for enhancing patient comfort during long procedures.
Frog-leg Position
In the frog-leg position, the hips and knees are flexed, and the hips are externally rotated. This position facilitates access to the perineum, groin, rectum, and inner thigh, making it ideal for certain surgical procedures. However, the knees must be supported to avoid stress and dislocation of the hips.
Trendelenburg Position
The Trendelenburg position involves tilting the head of the bed down so that the pubic symphysis is the highest point of the trunk. This position facilitates venous return and improves exposure during abdominal and laparoscopic surgeries. Hemodynamic changes, such as increased venous return and cardiac output, are typically temporary, with most variables returning to baseline within ten minutes. Respiratory changes, including the upward displacement of abdominal contents into the diaphragm, decrease functional residual capacity and respiratory compliance, requiring higher airway pressures to maintain ventilation. Prolonged head-down positioning can increase intracranial pressure, intraocular pressure, and swelling of the face, larynx, and tongue, increasing the risk of postoperative airway obstruction. To prevent sliding and shifting, shoulder braces are often used, but caution is needed to avoid compression or stretch injuries to the brachial plexus.
Reverse Trendelenburg Position
The Reverse Trendelenburg position involves tilting the head of the bed upward so that the head is the highest point of the trunk. This position facilitates upper abdominal surgery by improving surgical site access. Hemodynamic changes include decreased venous return, which can result in hypotension. Gravitational changes combined with hemodynamic changes can decrease cerebral perfusion, making invasive arterial monitoring advisable where tight hemodynamic control is necessary. Additionally, sliding and shifting in this position can increase pressure over the posterior calcaneus, necessitating careful attention to padding and support.
