Patient Position During Anesthesia
David Roy Godden CRNA, MSN
Gain an understanding of safe positioning basics
Identify the potential nerve injuries from mask ventilation
State the correct hand and arm positioning for supine, lateral decubitus and prone positions.
Be able to recite the potential nerve injuries of each patient position.
Identify the complications of the sitting position.
Define and understand the hemodynamics of each patient position.
Understand and be able to verbalize - that means know thoroughly - the respiratory and autonomic responses of differing patient positions while awake and under general anesthesia.
Discuss Post Operative Visual Loss (POVL) Case Study: Complications of Prone position
Look for Key Points
Positioning is often a compromise between what is required for surgical exposure and patient comfort! Do not place sedated or anesthetized patients in positions that they are not comfortable with when awake.
If in doubt about patients safety have the patient assume the position on the OR table before induction to see how they tolerate the position.
Patient positioning is the joint responsibility of OR Nursing, Anesthesia and Surgery. All three individuals and groups that represent them will be held liable if errors in positioning cause patient harm. Document!
Documentation of Positioning
The only thing that represents what was done in the operating room in a court of law is your testimony and your documentation. How much do you think you can remember from one case to the next and how much of your “story” will the court officers “believe” without your careful documentation in the anesthesia record?
What to document? Pre-operative patient limitations in movement strength and nerve abnormalities. Does the patient have numbness tingling or loss of sensation to any extremity pre-operatively? Does the patient have foot drop?
Potential for corneal abrasion is always present when mask ventilating patients.
Face straps which are tight across the patients face with prolonged use may cause injury to the facial nerve. What are the five branches of the facial nerve remembering the mnemonic, “Two zebras bit my cat” The bucal branch is most likely injured with a face strap compression.
Dorsal Decubitus Positions
Gravity effects blood flow and much of pulmonary mechanics.
Humans, giraffes and dinosaurs share one thing in common. What is it?
In the supine position gravity equalizes blood pressure gradients between heart and arteries in the head and lower extremities
Correct Anatomical Position
What is the ventral surface?
What is the dorsal surface
Note: Dorsal to dorsal and ventral to ventral
Dorsal Decubitus Positions
Head tilt either upwards or downwards will change the pressure gradients. A movement of 2.5 cm in vertical elevation will change the blood pressure 2 mm Hg.
In the parturient an IV bag under the right hip will shift the gravid uterus to the left. Have you heard of Aorto-caval syndrome?
Lying at attention requires correct arm and hand position to minimize the chances of nerve injuries.
Arms are to be less than 90 degrees lateralized from the thorax in correct anatomical position looking at the shoulders. This will minimize the chance of brachial plexus injury.
Arms at side of body must be in correct dorsal to dorsal alignment with the arms supinated OR palms toward the body is OK as well. The ulnar nerve passes close to the surface of the skin in the medial condyle of the elbow. The olectranon will protect the nerve if placed downwards.
Radial nerve injury is possible with ether screen compression to the lateral arm. Radial nerve injury may result in wrist drop.
What is Supination
Correct anatomical position is lying at attention or
Palms are ventral surface so ventral to ventral
Dorsal to dorsal mean back of hands to back.
Head down things
Lowering the head will increase the pressure in the cerebral veins which may lead to vascular head ache, congestion of nasal mucosa and conjunctiva in healthy individuals. This may lead to edema in the larynx as well. The sclera is the window to the vocal cords!
Head lowering in patients with intra-cranial lesions will exacerbate the condition raising CPP and ICP (what's the formula for this?)
Aortic arch and carotid sinus house barorecetors that are part of the bodies homeostatic mechanism to maintain blood pressure within a narrow range. Increased firing of the receptors when stretched from an increase in blood pressure is part of a negative feed back loop.
The increased firing from the baroreceptors enhances the parasympathetic nervous system lowering blood pressure and slowing the heart rate. Remember this!
What are the nerves responsible for the baroreceptor reflexes?
Respiratory mechanics will suffer in the head down position how? Review West’s zones of the lung.
Normal excursion of the diaphragm in head down position is impeded and increase the work of breathing. In the paralyzed mechanically ventilated patient, higher peak pressures will be required for adequate ventilation.
Supine patients develop VQ mismatch due to vascular congestion in the dorsal portions of the lung and changes in compliance. The dorsal lung (now zone 3) will have reduced compliance. Passive ventilation tends to distribute gas preferentially to the more easily distensible substernal units where pulmonary blood flow volume is less (Barish, 2006).
More Respiratory things
To prevent development of significant V-Q imbalance during use of controlled ventilation, tidal volumes must be used that are greater than the average amount that is sufficient for the spontaneously breathing conscious pt.
Compare and contrast the awake spontaneously breathing pt and the paralyzed mechanically ventilated pt in the lateral position.
How would you attempt to decrease Peak pressures during mechanical ventilation in the paralyzed anesthetized patient? Hint: deepen anesthetic, muscle relaxation, decrease Vt and increase Rate, change I:E ratio from 1:2 to 1:1.5. Consider Pressure Control ventilation due to its decelerating waveform.
Variations in the Dorsal Decubitus Position
Supine otherwise known as lying at attention. Places strain on lower segments of lumbar spine.
Lawn chair is a more physiologically tolerated position due to decreased stretch on lower back.
Frog leg (heal to heal with lateralization of knees) for peroneal examinations may place excessive stretch on back, hips and pelvic structures. Pad under knees. Complications of excessive stretch may include 1) postoperative hip and back pain; 2) dislocated hip or fracture of an osteoporotic femur; 3) obturator nerve injury.
Complications of Dorsal Decubitus
Pressure Alopecia due to prolonged compression of hair follicles. Most alopecia occurs between the 3rd and 28th postoperative day while re-growth usually occurs within 3 months (Barish, 2006).
Placement of gel pad or donut under head is worthwhile. Frequent repositioning of the head is warranted.
Complications of Dorsal Decubitus
Pressure point reactions occur when bony prominences are unsupported for prolonged periods. Hypothermia and hypotension enhance the ischemic process. The heals, elbows and sacrum should be gel padded. NOTE: There are no studies proving decreased incidence of peripheral neuropathies due to gel padding.
Back pain due to loss of lordosis. Lawn chair position best.
Lithotomy position traditionally has been used during gynecologic and urologic surgery. The hips are flexed 80 to 100 degrees and the hips are abducted 30 to 45 degrees from midline.
Hip flexion greater than 90 degrees may cause stretch of the inguinal ligaments and impinge the lateral femoral cutaneous nerves which pass through the inguinal ligament which leads to numbness in the lateral thigh.
The legs should be moved into and out of position simultaneously. The knees are brought to midline and the legs slowly unflexed to the supine position at the end of the surgical procedure.
Complications in Lithotomy
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time：32 month ago
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