PATIENT POSITIONING IN NEUROANAESTHESIA.

Dr. Rahul NorawatDr. Rahul Norawat

University College of Medical Sciences & GTB Hospital, Delhi

INTRODUCTION

• Positioning is the joint responsibility of the surgeon & anesthesiologist.

• Ideal pt. positioning involves balancing surgical comfort, against the risks related to the pt. position.

• Pt. positioning & postural limitation should be considered during the PAC.

• Positioning of neurosurgical patient:

– Adequate anesthetic depth, – Hemodynamic stability, – Oxygenation,– Preservation of monitors.

• Disconnection - create “blackout” state.

• ASA task force general guidelines.

Head Positioning

Ideal position of head for Craniotomies & spine procedures based on the 2 principles:

1) An imaginary trajectory from the highest point at skull surface to area of interest in brain should be the shortest distance between the 2 points.

2) The exposed surface of the skull & an imaginary perimeter of craniotomy should be parallel to the floor.

Types of Craniotomies

A. Ant. Parasagittal

B. Frontosphenotemporal

C. Sub-temporal

D. Lat Sub-occipital

E. Midline Sub-occipital

F. Post. Parasagittal

Fixation of the Head

For craniotomies or burr holes, head positioned on:

• Horseshoe headrest

(doughnut),

• Skeletally fixed with 3 (Mayfield frame) or 4-pins fixation device.

Application of a skeletal fixation pins

Tachycardia and hypertension

Rupture of untreated cerebral aneurysms

• Local infiltration

• iv anesthetic agent (propofol 0.5-1 mg/kg)

• Inhalational anesthetic

Benefits : Immobility, surgical comfort.

Risks : Bleeding, air embolism, scalp and eye laceration, pressure alopecia.

Head and Neck positioning: Rotation, Hyperflexion, Hyperextension

Brain stem & cervical spine ischemia.

Quadriparesis, quadriplegia & cerebral infarction.

• At risk Patients : – Osteophytes, – Arthritis, – Vascular atherosclerosis.

• Head safely rotated b/w 0-45°.

• For more rotation, a roll/pillow place under the opposite shoulder.

• Maintaining 2-3 finger breadths thyromental distance during neck flexion.

• Benefits: Surgical comfort & optimal access to the surgical area.

• Risks & complications: – Postoperative discomfort & pain,– Brachial plexus injury, – Obstruction of :

• Jugular veins & vertebral venous plexuses, • Cerebral lymphatic,• Vertebral or carotid arteries.• CSF flow,

Body Positioning

A. Supine Position (Dorsal Decubitus)

• Most frequently utilized position.

• Used for :– Cranial procedures,– Carotid endarterectomies,– Ant. approaches to cervical & lumbar spine.

A Horizontal position : poorly tolerated.

B Lawn chair position : 15° angulation's & flexion at trunk-thigh-knee & more physiological positioning of lumbar spine, hips and knees.

C Reverse Trendelenbourg position : 10-15° repositioning from the horizontal axis.

A - horizontal position, B - lawn chair (contoured) position,C - reverse Trendelenbourg position.

• Arms:– Abducted: < 90° to minimize brachial plexus injury. – Adducted

• Hand & forearm: – Supinated or neutral position to reduce external

pressure on spiral groove of humerus & ulnar nerve.

Benefits: • Simplest, • Not require special instrumentation & • Not require disconnection of tracheal tube & invasive monitors.

Risks: • Head rotation or flexion for optimal surgical conditions, • Pressure alopecia, • Pressure point reaction, • Nerve injury.

cubital tunnel retinaculum (CTR)

Hemodynamic and Ventilation.

• 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.

        CVS Respiratory   

CNS Benefits  Risks

Supine Compared to upright, awake and anesthetized

VR ↑, SV ↑

CO ↑, HR ↓

SVR ↓,

SBP ↔,

MAP↓↔

Compared to upright:

FRC ↓,

TLC ↓.

atelectasis of the dependent lung zones; Qs/Qt ↑,

V/Q mismatch↑      

Compared to

upright:

JVF ↑ ↔

JVR ↓ ↔

CPP ↔ ↓

CSF drainage may be impaired

The easiest position

Often needs head Flexion/ 

Extension /

Rotation,

Ulnar and 

peroneal nerve injury 

Modifications: a) Lawn-chair

b) Reverse

Trendelen

bourg

Improved VR from lower extremities.

Improved ventilation - dependent lung zones

Improved drainage –cerebral venous,

lymphatic, CSF

B. Lateral Position

» Temporal lobe craniotomy, » Skull base, » Posterior fossa procedures & » Retroperitoneal approach to thoracolumbar

spine.

A - Dependent arm is hung under the operating table, an upper arm is placed on the arm board,B - Dependent arm is positioned on the operating table and an arm board, an upper arm is placed over the trunk on the pillow.

A

B

Park-bench position: – Modification of lat. position.– Better access to posterior fossa. – Upper arm positioned along lateral trunk & upper

shoulder is taped towards table.

Hemodynamic and Ventilation. • In awake patient, Zone 3 West is occupying the dependent 18

cm of lung tissue. Lung tissue above 18 cm from bed level is not perfused.

• During GA & positive pressure ventilation, the non-dependent lung zones are ventilated better - worsening V/Q mismatch.

CVS Respiratory   

CNS Benefits  Risks

Lateral          

Compared to

supine,

Anesthetized

VR ↓, SV ↓,

CO↓

HR↑ ↔ 

SVR↑,

PVR↑, SBP↓,

MAP↓

Compared to

supine: 

FRC ↓, TLC↓ 

Qs/Qt ↑↑  

V/Q mismatch↑↑

Atelectasis of the dependent lung 

Compared to

supine:   

JVF↑↔   

with neck flexion:

JVF↓,

JVR↑,

ICP↑

Optimal approach to the temporal lobe. 

Brachial plexus injury,

Ear & eye injury,

Suprascapular nerve injury (of the dependent shoulder),

park bench

access to posterior fossa.

Stretch injuries (axillary trauma),

Decreased perfusion to the dependent arm.