This document discusses various patient positions used during surgery and their associated risks. It describes positions such as supine, lateral, prone, lithotomy, and variations like Trendelenburg. For each position, it details anatomical support, physiological impacts, and potential complications. Positioning-related nerve injuries, pressure points, vascular complications, and retinal ischemia are addressed. Proper padding, stabilization, and frequent reassessment are emphasized to prevent issues from sustained pressures.

1. Patient positioning and
associated risks
Presenter - Dr Tess Jose
PG resident anesthesia

2. SUPINE
• most common position
• Because the entire body is close to the level of the
heart, hemodynamic reserve is well maintained.
• Tissues overlying all bony prominences such as the
heels and sacrum, must be padded to prevent soft
tissue ischemia as a result of pressure, especially
during prolonged surgery.

3. Supine Concerns
• Greatest concerns are circulation and pressure points
• Most Common Nerve Damage:
• – Brachial Plexus: positioning the arm >90*
• –Radial and Ulnar: compression against the OR bed,
metal attachments, or when team members lean against
the arms during the procedure
• – Peroneal and Tibial: Crossing of feet and plantar
flexion of ankles and feet
• Vulnerable Bony Prominences:
• (due to rubbing and sustained pressure) – Occiput, spine,
scapula, Olecranon, Sacrum, Calcaneous

5. Effects
• 1.FRC reduced after induction leads to hypoxemia
• 2.Aortocaval compression
• 3.Pressure effect
• 4. Nerve injuries⇒ compression, excessive stretch,
ischemia
• Ulnar nerve is the commonest⇒ superficial compressed
against medial epicondyle→ forearm supinated and little
flexed, proper padding
• • Brachial plexus injury→ stretching arm should
abducted to less than 90 degrees, avoid external
rotation, head turned towards abducted arm or head in
neutral position

6. • 5.alopecia
• Caused by ischaemic hair follicles, is related to
prolonged immobilization of the head with its full
weight falling on a limited area, usually the occiput.
• 6.Backache
• May occur because the normal lordotic curvature is
often lost during GA with muscle relaxation or a
neuraxial block.

8. Variations of the Supine Position
• lawn-chair position
• frog-leg position
• Trendelenburg positions

9. LAWN CHAIR POSITION
• Back of the bed is raised
• Legs below the knees are
lowered to an equivalent
angle
• Slight trendelenburg tilt
•

10. • ADVANTAGES:
• Better tolerated by awake patient or under
monitored anesthesia care
• 15 degree flexion
• Venous drainage from lower extremities enhanced
• Xiphoid to pubic distance reduced and easing
closure of laparotomy incision

11. FROG LEG POSITION
• Allows access to perineum, medial thighs, genitalia
and rectum.
• Positioned supine, hips and knees are flexed with
hips externally rotated and soles facing each other.
• •Care must be taken to minimize stress and
postoperative pain in the hips and to prevent
dislocation by appropriately supporting the knees.

13. Trendelenburg
• The patient is placed in the supine position while the OR
bed is modified to a head‐down tilt of 35 to 45 degrees
resulting in the head being lower than the pelvis
• Arms are in a comfortable position –either at the side or
on bilateral arm boards
• The foot of the OR bed is lowered to a desired angle
• Walter Cannon, a Harvard physiologist, is credited with
popularizing the use of Trendelenburg positioning to
improve hemodynamics for patients in hypovolemic shock
during World War I.

14. • ADVANTAGES
To increase V.R after spinal anesthesia
To increase central venous volume to facilitate
central cannulation
To minimise aspiration during regurgitation

15. Trendelenburg Concerns
• ↑ CVP
• ↑ ICP
• ↑ IOP
• ↑ myocardial work
• ↑ pulmonary venous pressure
• ↓ pulmonary compliance
• ↓ FRC
• Swelling of face, eyelids, conjunctiva , tongue,
laryngeal edema observed in long surgeries

16. Reverse Trendelenburg
• The entire OR bed is tilted so the head is higher than
the feet
• Used for head and neck, laproscopic procedures
• Facilitates exposure, aids in breathing and decreases
blood supply to the area
• A padded footboard is used to prevent the patient from
sliding toward the foot
• Reduces venous return therefore hypotension
• Laproscopic cholecystectomy : reverse trendelenburg
position with right up

18. • Every 2.5 cm change of vertical ht. from the
reference point at level of the heart leads to a
change of MAP by 2 mmHg in the opposite
direction.
• •V & Q are best in dependent lungs.
• • Positive‐pressure ventilation provides the best
ventilation to non‐dependent lung zones ‐V/Q
mismatch.

19. Lithotomy
• With the patient in the supine position, the hips are flexed to
80‐100 o from the torso so that legs are parallel to it and legs are
abducted by 30‐45 * to expose the perineal region
• The patient’s buttocks are even with the lower break in the OR
bed (to prevent lumbosacral strain)
• The legs and feet are placed in stirrups that support the lower
extremities
• •The legs are raised, positioned, and lowered slowly and
simultaneously, with the permission of the anesthesia care
provider
• Adequate padding and support for the legs/feet should eliminate
pressure on joints and nerve plexus
• The position must be symmetrical
• The perineum should be in line with the longitudinal axis of the
OR bed

24. PHYSIOLOGICAL CHANGES
• Preload increases, causing a transient increase in
CO , cerebral venous and intracranial pressure
• Reduce lung compliance
• If obesity or a large abdominal mass is present
(tumor, gravid uterus)‐ VR to heart might decrease
• Normal lordotic curvature of the lumbar spine is
lost potentially aggravating any previous lower back
pain

26. Lower extremity compartment
syndrome
• a rare.
• Long surgical procedure time
• occurs when perfusion to an extremity is
inadequate because of either restricted arterial
flow (from leg elevation) or obstructed venous
outflow (direct limb compression or excessive hip
flexion).
• This results in ischemia, edema, and
rhabdomyolysis

27. • Local arterial pressure decreases 0.78 mm Hg for
each cm the leg is raised above the right atrium.
• Decompression fasciotomy -tissue pressure >30
mm Hg.
• Irreversible muscle damage -pressure >50 mm Hg.
• Long surgery time is a distinguishing characteristic
associated with this.

28. Lateral
• Anesthetized supine prior to turning
• Shoulder & hips turned simultaneously to prevent
torsion of the spine & great vessels
• Lower leg is flexed at the hip; upper leg is straight
• Head must be in cervical alignment with the spine
• Breasts and genitalia to be free from torsion and
pressure

30. • Axillary roll placed caudal to axilla of the downside
arm (to protect brachial plexus)
• Padding placed under lower leg, to ankle and foot
of upper leg, and to lower arm (palm up) and upper
arm
• Pillow placed lengthwise between legs and
between arms (if lateral arm holder is not used)
• Stabilize patient with safety strap and silk tape, if
needed

31. • Pulse should be monitored in the dependent arm
for early detection of compression to axillary
neurovascular structures.
• Low saturation reading in pulse oximetry may be an
early warning of compromised circulation.
• When a kidney rest is used, placed under the
dependent iliac crest to prevent inadvertent
compression of the inferior vena cava

34. • Pulmonary mechanics change in the lateral decubitus
position.
• In a patient who is mechanically ventilated, the
combination of the lateral weight of the mediastinum
and the disproportionate cephalad pressure of
abdominal contents on the dependent lung favors
overventilation of the nondependent lung.
• At the same time, the effect of gravity causes the
pulmonary blood flow to the underventilated,
dependent lung to increase.
• Consequently, ventilation-perfusion matching
worsens, potentially affecting gas exchange and
ventilation

35. PRONE
• The prone or ventral decubitus position is primarily
used for surgical access to the posterior fossa of the
skull, the posterior spine, the buttocks and perirectal
area, and the posterior lower extremities.

36. • the airway is secured in supine.
• securing and taping the endotracheal tube to
prevent dislodgement.
• Anesthesiologist is primarily responsible for
coordinating the move while maintaining inline
stabilization of the cervical spine and monitoring
the endotracheal tube.
• An exception might be the patient in whom rigid
pin fixation is used when the surgeon often holds
the pin frame.

37. • The endotracheal tube should be disconnected
from the circuit during the move from supine to
prone in order to prevent dislodgement.
• monitors and lines are disconnected.
• Ventilation and monitoring should be reestablished
as rapidly as possible.

38. Head position
• Turned to the side(45 degrees) if neck mobility is
fine.
• Check the dependent eye for external compression.

39. Head support devices used in
prone position

40. • The forehead and malar regions are supported by the horseshoe
headrest and allow for reasonable access to the airway

41. • Pin fixation, which is most used in cranial and cervical surgery, is
advantageous because there is no direct pressure on the face
• . Patient movement must be prevented when the head is held in pins;
movement in pins

42. • Regardless of the type of head-support technique,
proper positioning must be frequently verified
during the surgery, checking that there is no
pressure on the eyes, that the airway is secure, and
that the head weight lies on the bony facial
prominences only.
• The prone position is a risk factor for perioperative
visual loss (POVL).

43. • When patients are in the prone position, weight should be
distributed to the thoracic cage and bony pelvis, the
abdomen should hang freely in order to prevent
compression.
• Wilson frame, Jackson table, Relton frame, and
Mouradian/Simmons modification of the Relton frame.
• Breasts should be placed medially to the prone torso
supports (or bolsters), and genitalia should be clear of
compression.

44. Hemodynamics and Ventilation
• increases intraabdominal pressure, decreases VR to the
heart, and increases systemic and pulmonary vascular
resistance‐ HYPOTENSION
• Oxygenation and oxygen delivery, however, may
improve as
• 1) Perfusion of the entire lungs improves
• 2) Increase in intraabdominal pressure decreases chest
wall compliance, which under PPV, improves ventilation
of the dependent zones of the lung, and
• 3) Previously atelectatic dorsal zones of lungs may
open.

45. PRONE CONCERNS
• Because the abdominal wall is easily displaced, external
pressure on the abdomen may elevate intra abdominal
pressure.
• External pressure on the abdomen may push the
diaphragm cephalad, decreasing FRC, pulmonary
compliance and increasing peak airway pressure.
• Careful attention must be paid to the ability of the
abdomen to hang free and to move with respiration.
• Abdominal pressure also may impede venous return
through compression of the inferior vena cava.

49. Fowler’s Position & semi-fowler ‘s
position
• Patient begins in the supine position
• Foot of the OR bed is lowered slightly, flexing the knees, while the
body section is raised to 35 –45 degrees, thereby becoming a
backrest
• The entire OR bed is tilted slightly with the head end downward
(preventing the patient from sliding)
• Feet rest against a padded footboard
• Arms are crossed loosely over the abdomen and taped or placed
on a pillow on the patient’s lap
• A pillow is placed under the knees.
• For cranial procedures, the head is supported in a head rest and/or
with sterile tongs
• This position can be used for shoulder procedures ( BEACH CHAIR
POSITION)

51. • BEACH CHAIR POSITION RISKS
• 1. Venous air embolism
• 2. Cerebral injury due to hypotension therefore
essential to measure CVP at brain level since for
every 2.5 cm diff b/w BP cuff and brain –2 mmHg
fall in BP
• 3. Case reports of cutaneous neuropraxia – lesser
occipital , greater auricular nerve injury

52. Sitting position
• This is actually a modified
recumbent position as the legs are
kept as high as possible to promote
venous return.
• Arms must be supported to
prevent shoulder traction.
• Head holder support is preferably
attached to the back section of the
table

53. Sitting concerns
• Because of the pooling of blood into the lower body,
patients under GA are prone to hypotensive episodes.
• Excessive cervical flexion can impede arterial and
venous blood flow, causing hypo perfusion or venous
congestion of the brain.
• Because of the elevation of the surgical field above the
heart, and inability of the dura venous sinuses to
collapse because of their bony attachment, the risk of
venous air embolism is a constant concern.

54. venous air embolism (VAE)
• During intracranial procedures, a significant
amount of air can be entrained through the open
dural venous sinuses.
• Low venous pressure in the operative field creates
a gradient for air entry into the venous system

55. ROBOTIC SURGERY
• For surgeons, robotic surgery offers advantages
regarding range of motion and accuracy of laparoscopic
instrumentation.
• Robotic surgery is generally performed with the
patient in steep Trendelenburg (30 to 45 degrees) and
lithotomy with arms tucked in neutral position
bilaterally to the sides.
• The patient must be very well secured in order to avoid
slipping in steep Trendelenburg position.
• use a nonslip mattress (such as a bean bag and foam)
on the bed

56. • Physiologic changes during robotic surgery are due
to both laparoscopic insufflation as well as the steep
Trendelenburg positioning.
• Hemodynamic changes are largely due to
laparoscopic insufflation, whereas changes in
respiratory mechanics are also affectedby
positioning.
• FRC decreases with laparoscopy and the addition of
steep Trendelenburg, which further decreases it.
• . This is due to the combination of pressures of
abdominal contents from laparoscopy and
Trendelenburg pushing up on the diaphragm.

57. • Peak and plateau airway pressures rise as much as
50%.
• Other complications from robotic laparoscopic
surgeries include laryngeal edema and optic
neuropathy.
• Consider checking for airway leak at the start and
at the end of the surgical procedure prior to
extubation.

58. Peripheral Nerve Injury
• The ASA states that “postoperative signs and
symptoms related to peripheral nerve injury…may
include but are not limited to paresthesias, muscle
weakness, tingling, or pain in the extremities.

62. Mechanism of nerve injury
• complex phenomenon with a multifactorial cause
• Injuries occur when peripheral nerves are
subjected to compression, stretch, ischemia,
metabolic derangement, and direct
trauma/laceration during surgery.
• Because sensation is blocked by unconsciousness
or regional anesthesia, early warning symptoms are
absent.

63. PERI OPERATIVE VISUAL LOSS

65. RETINAL ISCHEMIA: BRANCH AND
CENTRAL RETINAL ARTERY
OCCLUSION
• : mechanisms
• (1) external compression of the eye,
• (2) decreased arterial supply (embolism to retinal
arterial circulation or decreased systemic blood
flow),
• (3) impaired venous drainage, and
• (4) thrombosis from a coagulation disorder

66. • The most common in the perioperative period is
improper positioning with external compression
high IOP to stop blood flow in the central retinal
artery.
• It most often occurs during spine surgery
performed in the prone position.

67. Clinical features
• painless visual loss,
• abnormal pupil reactivity,
• whitening of the ischemic retina, and narrowing of
retinal arterioles.
• BRAO is characterized by cholesterol, and calcific
or pale platelet fibrin emboli.
• cherry-red macula with a white ground-glass
appearance of the retina and attenuated arterioles
is a “classic” sign.

69. Branch retinal artery occlusion
• due to emboli or vasospasm
• mechanisms include non-perfusion, vascular leakage
and spasm, red blood cell sludging, and haemorrhage,
• Ocular massage can lower IOP and possibly dislodge an
embolus
• I.V. acetazolamide can be administered to increase
retinal blood flow, and 5% CO2 in oxygen inhaled to
enhance dilation and increase O2 delivery.
• Prognosis is poor

70. • Prevention
• In patients positioned prone for surgery, a foam
headrest should be used.
• Placing head in pins is an obviously more invasive
technique.
• Ensure that eyes are properly positioned and checked
intermittently by palpation or visualization.
• documentation on the record of eye checks will assist
in verifying that anaesthesia personnel followed
correct procedure.
• examine eyes for position change and absence of
external compression at least every 20 min

71. Ischaemic optic neuropathy

75. • prone positioning,
• lengthy spinal fusion surgery,
• decreased arterial pressure,
• blood loss, anaemia or haemodilution,
• change in venous haemodynamics,
• cerebrospinal fluid flow in the optic nerve (including
effects of patient positioning and perioperative fluid
resuscitation),
• abnormal optic nerve blood flow autoregulation,
• optic nerve blood supply anatomic variation,
• low cup-to-disc ratio,
• use of vasopressors,