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IAAC > Patient positioning > Flashcards

Patient positioning Flashcards

1
Q

Outline the CVS effects of supine positioning

A

Redistribution of pooled venous blood from LLs -> inc VR -> inc EDV -> inc preload -> inc SV and CO
May lead to inc myocardial O2 demand

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2
Q

Outline the pulmonary effects of supine

A

Upward movt of intra-abdominal contents on diaphragm -> dec total lung volume and FRC
Inc V/Q mismatch
Dec pulmonary compliance
Inc risk of aspiration from regurgitation

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3
Q

Which areas are particularly prone to pressure injury in supine positioning

A

Occiput, Elbows (esp Ulnar N), knees, sacrum, heels, greater trochanter of femur

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4
Q

Why is the ulnar N at particular risk in supine

A

Excessive head rotation can inc brachial plexus traction

Combined with excess abduction of the arm and forearm pronation = inc pressure on the Ulnar N in the ulna groove

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5
Q

Why is post-operative backpain a possible issue for patient’s in supine

A

Loss of natural lumbar lordosis in supine

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6
Q

What is Trendelenburg positioning and why is it used

A

Head down

Improves exposure of abdominal organs and pelvic surgery

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7
Q

Outline the pulmonary effects of trendelenburg

A

As for supine but more extreme
Dec FRC -> atelectasis -> V/W mismatch and risk of arterial hypoxaemia
Inc WOB for spont breathing pts
Higher airway pressures required to maintain adequate ventilation
Prolonged trendelenburg inc upper airway oedema -> inc risk of post-op airway obstruction
Endobronchial ETT migration, bronchospasm

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8
Q

Outline the CVS effects of Trendelenburg

A

As per supine
Inc VR -> inc blood volume ~1L -> inc SV & CO -> inc MAP
Baroreceptor reflex mediated systemic vasodilation and dec TPR to maintain MAP -> dec TPR, dec bloodflow -> dec perfusion pressure to organs

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9
Q

Outline the CNS effects of Trendelenburg

A

Gravity induced inc in CBF
Inc ICP due to gravity dependent dec in venous drainage
triggers vasoconstriction due to autoregulation -> inc CPP
Inc IOP for same reason

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10
Q

Is gastric aspiration more or less likely in Trendelenburg

A

Stomach positioned above ETT, inc risk of passive gastric aspiration on repositioning to supine

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11
Q

When is reverse Trendelenburg used

A

For head and neck, upper GIT and shoulder surgery

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12
Q

Outline the CVS effects of reverse Trendelenburg

A

Gravity induced inc in hydrostatic pressure which venous circulation must overcome -> inc venous pooling, dec venous return -> dec preload -> dec SV and CO -> dec MAP
Risk of air embolism
Increased head and neck venous drainage

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13
Q

Outline the respiratory effects of reverse Trendelenburg

A

Downward displacement of abdo contents and diaphragm -> inc FRC and VC
Dec risk of passive regurgitation
The dec MAP -> dec perfusion to non-dependent lung regions -> inc physiological dead space

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14
Q

Outline the CNS effects of reverse Trendelenburg

A

Dec MAP -> dec CPP which is counteracted by the gravity improved drainage of cranial veins dec ICP -> cerebral blood flow is maintained

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15
Q

When is Lithotomy positioning used

A

Lower GIT, urological and gynaecological surgery

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16
Q

What is lithotomy position

A

Hips flexed 80-100deg + hip abduction 30-45degs + knee flexion until lower legs are parallel to the torso

17
Q

Outline the CVS effects of Lithotomy

A

Leg elevation inc VR and SVR
Compensatory baroreceptor reflex dec TPR -> dec sympathetic outflow and HR to maintain MAP
Hypotension may occur with lowering of legs

18
Q

Outline the respiratory effects of lithotomy

A

Same as for supine

19
Q

Which nerves are at risk in lithotomy and why

A

Sciatic or obturator N stretch with femoral N compression if hips flexed >90degs
Common peroneal N at head of fibula and saphenous N at medial tibial condyle at risk of compression against supports

20
Q

Why is there an inc risk of VTE

A

The calf compression in the stirrups can lead to an inc risk of VTE or compartment syndrome

21
Q

When is lateral decubitus positioning used

A

Hip, thoracic and renal surgery

22
Q

Outline the respiratory effects of lateral positioning

A

With IPPV the dependent lung is relatively under-ventilated and overperfused, with the non-dependent lung have the opposite scenario -> inc V/Q mismatch
Dec movt of dependent ribs and diaphragm -> dec FRC and VC

23
Q

Outline the possible pressure areas with lateral positioning

A

Ensure adequate lateral support for head and neck
Support shoulder and pelvis to prevent rolling
Avoid pressure on abdomen
Dependent arm - risk of nerve compression and ischaemia
High risk of corneal abrasions and pressure on dependent eye
Common peroneal N and saphenous N at risk of compression if inadequate padding between legs

24
Q

When is prone positioning used

A

Access to posterior fossa of skull, posterior spine, buttocks, per-anal region, posterior compartments of the lower limbs

25
Q

Outline the CVS effects of prone

A

Abdominal compression of IVC or iliac vessels -> dec VR -> dec SV & CO
Flow is diverted through low pressure systems -> venous plexus engorgement (perivertebral, lumbar and intercostals) -> inc risk of intraoperative bleeding in spinal surg
Can be offset with placement of wedges/pillows under chest and pelvis

26
Q

Outline the pulmonary changes in prone

A

External pressure on abdo is transmitted to diaphragms -> dec FRC, dec compliance, inc peak airway pressure
BUT dorsal lung regions have inc FRC and improved V/Q = overall improved PaO2

27
Q

Outline the CNS effects of prone

A

If head positioned at level of the heart - nothing

If below level of the heart -> as per head down

28
Q

Which areas are at particular risk of pressure injury in prone

A

Forehead, nose, eyes, chest, breasts, genitals, pelvis (ASIS), knees and feet

29
Q

Which nerves are at particular risk in prone

A

Nerves exiting superior orbital fissure
Brachial plexus
Ulna N
Lateral cutaneous N of the anterior thigh

30
Q

How should the arms be positioned when in prone and why

A

Shoulder in anterior flexion + abduction + ER will minimise traction on axillary neurovascular bundle

IAAC (10 decks)

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