Anesthesia Positioning
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Created by:
Maryjononnemacher on March 21, 2012
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Prof Bennett's lecture
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69 terms
Terms | Definitions |
|---|---|
 What are the structures that respond to changes in pressure and where are they located? | Pressoreceptors - located in carotid sinuses, aortic arch, pulm arteries. act to mediate changes which regulate systemic blood pressure |
| Physiologic effects of increased blood pressure | impulses inhibit the medullary vasoconstrictor center and excite the vagus nerve. leading to bradycardia, peripheral vasodilation, and decreased myocardial workload |
| Physiologic effects of decreased blood pressure | decreased BP causes sympathetic stimulation leading to tachycardia, peripheral vasoconstriction (increase in SVR), and increased myocardial contraction |
| Giving a patient anesthetic gas will caused an exaggerated ______________ in BP | decrease. gas has a sympatholytic effect |
| Describe the effect of positioning on a patient's MAP | for every 1" above/below the heart, there is a 2 mmHg change (+/-) change in MAP at the level of the circle of willis. in the sitting position, If you compare the blood pressure in the patients calf (using a blood pressure cuff) to that at the circle of willis, the calf pressure will be higher. |
| What is the chief etiology of nerve damage from positioning? | stretching or direct compression of a nerve. also, compression of blood supply to the nerve. |
| Which nerve is the most vulnerable to damage from malpositioning? | Brachial plexus. stretching is primary cause |
| According to closed case claims, what nerve is the most frequently injured? What are other commonly injured nerves? | Ulnar nerve injury accounts for 28%, followed by brachial 20%, lumbosacral 16% and spinal 13% |
| Abduction and dorsal extension of the arm board at more than ________ degree angle can lead to... | 90 degree angle, can lead to brachial plexus injury |
| Excessive sternal retraction may cause _______ and injure the __________ | may cause fracture of the 1st rib, and may injury the brachial plexus bundle |
| Should the arm be placed on the arm board with the hand pronated or supinated? | Supinated (palms up). the fossa at the elbow is free of pressure - nerve runs right in that groove. |
| Why do males have a higher incidence of ulnar injury? | more muscle, less adipose tissue increases the risk of compression |
| How may damage to the ulnar nerve present? | Clawhand and sensory deficit of the middle part of the hand, ring finger and little finger |
| How can the radial nerve get injured in anesthesia? | Blood pressure cuff being cycled too often, or prolonged use of a tourniquet at high pressure. 2 hour max for tourniquet time |
| What is the least likely arm nerve to be damaged? | Median nerve |
| Highest litigation payments are a result of... | epidural hematomas - can cause permanent spinal cord injury. EPIDURAL = EMERGENCY |
| When are ulnar nerve injuries usually reported? | 2-7 days after surgery, 3 days post op most common |
| How does radial nerve injury present? | wrist drop and an inability to extend the metacarpophalangeal joints secondary to paralysis of the extensor muscles in the forearm |
| What are the most frequently damaged nerves of the lower extremity? | Peroneal and saphenous nerves |
| Mechanism of damage for common peroneal nerve | lithotomy position d/t compression between the lithotomy stirrup and the fibula, resulting in foot drop |
| Mechanism of damage for saphenous nerve | the legs are suspended lateral to the vertical braces or stirrups |
| Why is it important to know PIP and ETCO2 before insufflation? | So you can tell if there is a major difference. If ETCO2 changes, you can increase the respiratory rate and decreased tidal volume to compensate. (if you would increase tidal volume, you would only increase the PIPs higher) |
| You increase FRC from ______________ position to __________ position | Increase in FRC from supine to prone position. the pressure causes expansion of alveoli. |
| In the lateral position, the down (dependent) lung has (better/worse) ventilation in an unanesthetized patient | The dependent lung has BETTER ventilation in an unanesthetized patient. this is because the wt of the viscera and increased hydrostatic pressure. there is greater excursion of the diaphragm on the dependent side |
| In the anesthetized patient, the __________ lung is better ventilated | upper, independent lung (in lateral position) is preferentially ventilated. compliance is greater due to lower pressure from abdominal contents and less perfusion. |
| _______ have a greater reduction in compliance in the anesthetized state | Men. all the tissue becomes dead weight making ventilation more difficult. |
| Obesity can be ___________ in relation to ventilation | restrictive |
| In the steep, foot down position, the risk of aspiration is increased, why? | If gastric contents enter the oropharynx, intrathoracic pressure can pull the secretions down around the cuff and into the lungs |
| Is the risk of aspiration greater with steep foot down position or steep head down position? | Steep foot down position. The intragastric pressure is lower but if regurgitation does occur, the risk of aspiration is increased. |
| Why is a patient at risk for injury under spinal and general anesthesia? | these techniques produce complete muscle relaxation, leaving the patient without natural protective reflexes to prevent injury. |
| Which has a higher incidence of backache: lithotomy or lateral position? | Lithotomy because of the stretching of back muscles |
| What are the 6 patient positions? | 1) supine- most common 2) prone 3) lithotomy 4) sitting 5) lateral 6) flexed lateral |
| Another name for supine position | Dorsal decubitus |
| What are the pressure points in supine position? | occiput, shoulders, spine, hips and heels |
| How should you position the arms at the side in supine position? | Tuck arms under the draw sheet but DO NOT put arms under the buttocks |
| What can be damaged during a prolonged mask case? | Optic nerve and facial nerve. the optic nerve is from the pressure of the mask on the face. facial nerve is from having the little finger near jaw notch and exerting pressure. |
| How do you tuck a draw sheet around a patient's arm? | Pull sheet over top of the arm and tuck under the patient. going from the sheet tucked under the patient, pulling over the top of their arm, and towards the outer edge of the OR table, and then back towards the patient, but tucking it underneath them |
| How do you use shoulder rolls in the prone patient and why? | rolled up blankets vertically extending from clavicles to iliac crests. improves circulation and respiration, causing less resistance, and less compression of the vena cava and lymphatic system. also decreased intra-thoracic pressure. vena cava compression leads to increased bleeding in back cases. |
| When using shoulder rolls in the prone patient, how should you position their arms? | at the same level as the thorax to prevent pull and stretch on the brachial plexus |
| How do you position the feet during prone position? | place rolls under the dorsum of the foot, helps take pressure off lower back |
| a complication of prolonged prone position and spine surgery in prone position | ischemic optic neuropathy (ION) - recovery of vision in 56% of cases. incidence is 0.056%. |
| risks for ischemic optic neuropathy? | HTN, DM, morbid obesity, smokers |
| the patient is at risk for what injury when moving patient from supine to prone? | injury to the spinal cord and bony spine during to lack of muscular support. MUST DO LOG ROLL, keep pulse ox on during roll |
| What nerves are at risk in lithotomy position and why? | obturator, saphenous, and femoral nerves are at risk due to compression from the supports and straps. |
| which type of stirrups are preferred and why? | stirrups with an adjustable foot plate and leg support because they evenly distribute patient weight |
| a laminectomy is usually performed in what position? | prone: kneeling-chest position |
| How can you prevent joint and spinal injury when positioning a patient in lithotomy? | flex and extend both legs simultaneously to prevent injury |
| If the legs rest against the uprights in lithotomy position, what can happen? | Damage to the common peroneal nerve |
| what nerve is damaged when the legs are suspended lateral to the vertical braces or stirrups? | saphenous nerve |
| Precordial doppler detects what percent of VAE? | 40% of venous air embolism |
| What are examples of procedures that are performed in the sitting position? What is another name for this position? | "Beach chair". procedures that are performed this way are shoulder surgeries and cranies |
| What should you check before and after placing the patient in lithotomy? and why? | Check BP before lithotomy (in just supine position) and check after in lithotomy because putting the legs in stirrups causes an increase in venous return (which increases BP) |
| What complications of the sitting position? | 1) hypotension 2) flexed neck can cause macroglossia, facial edema, quadriplegia (need 3 fingers between chin and chest) 3) brachial plexus injury 4) stretch of sciatic nerve 5) venous air embolism |
| How can a venous air embolism occur? | when pressure within an open blood vessel is sub atmospheric. a negative pressure gradient between the operative site and right heart and when the surgical site is above the heart. |
| What is the best method for early detection of a venous air embolism? | precordial doppler detects 40%; it is very sensitive, easy to use and noninvasive |
| Why is precordial doppler preferred over TEE? | TEE requires constant visual attention and is very expensive. but it does detect 76% of VAE |
| Where should the precordial doppler be placed? | at the level of the right atrium. 4th intercostal space to the right of the sternum. PLACE ONLY AFTER PT IN SITTING POSITION |
| How can you test the precordial doppler? | inject 0.25-1.0ml air into RA port, will have a mill wheel murmur on doppler |
| Signs and symptoms of venous air embolism | - sudden profound hypotension - sudden decrease in cardiac output due to airlock in RV - RV failure - impaired LV filling due to distended RV - decreasing ETCO2 and increasing PaCO2 - hypoxemia - presence of nitrogen in exhaled gases |
| Treatment of venous air embolism | 1) Stop procedure 2) Flood field with fluid (covers exposed vessels so it won't entrain more air) 3) pack bone with bone wax 4) turn off nitrous, give 100% O2 5) head down, tilt left, prevent air from going to pulm artery (left lateral decub) 6) aspirate from central line if possible |
| How do you position the arms in lateral position? | upper arm - elevated position with blankets or double arm board or on padded Mayo stand. lower arm - create a tunnel for the lower arm using a small rolled towel, covered sandbag or covered liter IV bag to prevent over stretching and compression of dependent brachial plexus |
| How are the legs positioned in lateral position? | bottom leg is bent and a pillow is placed between the legs |
| In flexed lateral position, where is the kidney rest placed? | At the level of the iliac crest |
| The Jack Knife position is used for what type of surgeries? | hemorrhoids |
| changing from erect to supine position causes what cardiovascular changes? | increases cardiac output secondary to increase in stroke volume and venous return. |
| Who is most at risk for hypotension in the supine position? | those with increased abdominal girth, such as tumors, pregnancy, obesity |
| How does the supine position affect FRC? | Decreases functional residual capacity secondary to the abdominal contents impinging on the diaphragm |
| How do trendelenberg and lithotomy influence pulmonary compliance? | compression of the lung bases resulting in further decreases in pulmonary compliance |
| ICP is increased in what positions? | trendelenberg and lithotomy, secondary to increased central venous pressure and decreased cerebral drainage |
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