Prone Position
The prone position is commonly used to provide surgical access
to the posterior spine, lower extremities, and posterior fossa of the skull. Before
induction of anesthesia, the cervical range of motion the patient can achieve comfortably
(laterally and in flexion and extension) should be assessed along with the range
of motion of the shoulders. Older patients and those with shoulder problems often
cannot move their arms up to 90 degrees, and it is impossible to put their arms out
on armboards after the patients are prone; the arms are then tucked at their sides
intraoperatively, preventing access to intravenous and arterial lines.
Turning the head to the side is safe for most patients as long
as pressure on the down eye is avoided; this offers fair access to the airway and
endotracheal tube. Turning the neck can be difficult or impossible in the older
patient with an arthritic neck. For them, foam pillows are available that support
the forehead, cheeks, and chin but have cutouts for the eyes, mouth, and nose (Jackson
Table Headrest Pillow, Orthopedic Systems, Inc., Union City, CA). One device (Prone
View, Oceanside, CA) props the face in a foam pillow above a mirror so that the exact
position of the eyes and mouth can be seen. The horse-shoe headrest has been used
for this purpose, but it supports the head on only the cheeks and forehead, is unstable
during operating table adjustments, and makes it difficult to keep pressure off the
eyes. In patients with known cervical problems, the head is often positioned in
a pinion head holder so that the neck can be kept in neutral position, excessive
flexion and extension are avoided, the neck is stable throughout the surgical procedure,
and access to the airway is facilitated.
Inattentive positioning of a prone female's breasts can lead to
postoperative tenderness and possibly to tissue injury. Extremely large breasts
can lead to some instability of the thorax of a woman in the prone position. Although
lateral displacement of the breasts is possible, common
practice is to position them medially. Like most other aspects of positioning, no
controlled studies can be found. Martin wrote, "However, an informal, nonstatistical,
chaperoned interrogation of female patients and nursing personnel who represented
a variety of body habitus indicated that lateralizing traction on breasts was painful
to most women, whereas medial and cephalad compression was not."[36]
Chest rolls support the thorax and extend down to the hips. Their
primary purpose is to prevent increased abdominal pressure in the prone patient,
allowing room for diaphragmatic excursion. In addition to causing increased pulmonary
pressures for mechanically ventilated patients, increased pressure in the abdominal
cavity can also be transmitted to veins in the epidural space, leading to increased
bleeding in the surgical fields. In obese patients, it is easier to use special
tables and frames (e.g., Jackson table, Relton frame) that allow more space for the
abdomen to hang down.
Lumbar flexion is frequently used to facilitate surgical exposure
in that level of the spine. This can be produced by flexion of the table or by attachments
that allow the patient to be placed in a kneeling position with some weight supported
on the knees and shins. Table flexion usually causes the patient to move down on
the table, and the position of the head, face, and arms must be carefully checked
while these adjustments are being made.
The clinical impression is that hypotension occurs more often
in prone patients than in those in any other surgical position. Hypotension probably
is caused by venous pooling in the legs.
