question

Who is ultimately in charge of patient positioning?

answer

Anesthesia.

question

as a human being reclines from an erect to a supine position

answer

The resultant increase in arterial blood pressure activates afferent baroreceptors from the aorta (via the vagus nerve) and within the walls of the carotid sinuses (via the glossopharyngeal nerve) to decrease sympathetic outflow and increase parasympathetic impulses to the SA node and myocardium.

question

What increases mean intrathoracic pressure?

answer

Positive pressure ventilation increases mean intrathoracic pressure, diminishing the venous pressure gradient from peripheral capillaries to the right atrium. PEEP further increases mean intrathoracic pressure, as do conditions with low lung compliance (airway disease, obesity, ascites, and light anesthesia. Venous return and cardiac output may be further compromised.

question

When compared with the nonanesthetized state, how does the breathing of awake pts differ?

answer

Pts who are breathing spontaneously have a reduced tidal volume and functional residual capacity and an increased closing volume .

question

How does positive pressure ventilation with muscle relaxation ameliorate ventilation-perfusion mismatches under general anesthesia?

answer

By maintaining adequate minute ventilation and limiting atelectasis.

question

How does the diaphragm change under anesthesia?

answer

The diaphragm assumes an abnormal shape due to the loss of muscle tone and is displaced less in the dependent portions of the lung. This decreases VQ matching and consequently arterial Po2.

question

How can you retain diaphragmatic function under anesthesia?

answer

Diaphragmatic function is retained if general anesthesia and muscle relaxation are not concurrently administered.

question

Normal distribution of ventilation is determined by what?

answer

The excursion of the diaphragm, movement of the chest wall, and compliance of the lung.

question

With spontaneous ventilation in either position, diaphragmatic movement is greatest where?

answer

Adjacent to the most dependent portions of the lung, which helps to bring new ventilation to the zones of the lung that are preferentially perfused.

question

Describe when and why the prone position might be beneficial.

answer

The prone position has been utilized to improve respiratory function in patients with ARDS. In anesthetized pts, the prone position has advantages over the supine position with regard to lung volumes and oxygenation without adverse effects upon respiratory mechanics. This benefit has also been shown in obese and pediatric patients. When pts are prone, weight should be distributed to the thoracic cage and bony pelvis, allowing the abdomen to move with respiration.

question

What position is dorsal decubitus?

answer

Supine

question

In the supine position, abduction of the arm should be kept to how many degrees? Why?

answer

Less than 90 degrees whenever possible to minimize the likelihood of brachial plexus injury by caudad pressure in the axilla from the head of the humerus.

question

Positioning of the hands and forearms during supine position

answer

The hand and forearm are either supinated or kept in a neutral position with the palm toward the body to reduce external pressure on the ulnar nerve.

question

Are shoulder braces used during trendelenberg positioning?

answer

No. Shoulder braces are not recommended because of considerable risk of compression injury to the brachial plexus

question

Pulmonary effects of Trendelenberg position

answer

The cephalad movement of abdominal viscera against the diaphragm also decreases FRC and pulmonary compliance. In spontaneously ventilating patients the work of breathing increases. In mechanically ventilated patients, airway pressures must be higher to ensure adequate ventilation.

question

What are some special considerations prior to extubating a pt who has been in a prolonged trendelenberg position?

answer

Because of the risk of edema to the trachea and mucosa surrounding the airway during surgeries in which patients have been in the Trendelenburg position for prolonged periods of time, an air leak should be verified around the ETT or the larynx visualized prior to extubation.

question

What is pressure alopecia? What can increase its incidence?

answer

due to ischemic hair follicles is related to prolonged immobilization of the head with its full weight falling on a limited area, usually the occiput. Hypothermia and hypotension during surgery may increase the incidence of this complication.

question

What can you do to prevent pressure alopecia?

answer

-Lumps such as those due to monitoring cable connectors, should not be placed under head padding, as they may create focal areas of pressure. -During prolonged surgery, periodic rotation of the head to redistribute the weight may be considered.

question

Backache can occur during general and neuraxial anesthesia because the tone of what muscle is lost?

answer

Paraspinous musculature

question

Patients with extensive kyphosis, scoliosis, or previous history of back pain may require what during positioning?

answer

extra padding of the spine or slight flexion at the hip and knee. Lastly, tissues overlying all bony prominences, such as the heels and sacrum, must be padded to prevent soft tissue ischemia due to pressure, especially during prolonged surgery.

question

What is the most common peripheral nerve injury during anesthesia?

answer

Ulnar neuropathy.

question

What are the current recommendations to prevent ulnar neuropathy?

answer

Limit arm abduction in the supine patient to less than 90 degrees at the shoulder with the hand and forearm either supinated or kept in a neutral position. Also, maintaining the head in a relatively midline position can help minimize the risk of stretch injury to the brachial plexus.

question

What surgeries is lithotomy typically used for?

answer

Gynecologic, rectal, and urologic surgeries.

question

How are the hips flexed and legs abducted in the lithotomy position?

answer

Hips- flexed 80 to 100 degrees from the trunk Legs - abducted 30 to 45 degrees from the midline. The knees are flexed until the lower legs are parallel to the torso. The legs are held by supports or stirrups, usually "candy cane," knee crutch, or calf support style.

question

When raising the foot of the table at the end of surgery, pay strict attention to the position of what?

answer

HANDS to avoid a potentially disastrous crush injury to the fingers. For this reason, positioning the arms on armrests far from the table hinge point is recommended at all times during the lithotomy position.

question

How should the legs be positioned for lithotomy?

answer

Use coordinated positioning of the lower extremities by two assistants to avoid torsion of the lumbar spine. Both legs should be raised together, flexing the hips and knees simultaneously.

question

What are the cardiovascular changes during lithotomy?

answer

Preload increases, causing a transient increase in cardiac output and, to a lesser extent, cerebral venous and intracranial pressure in otherwise healthy patients.

question

What are the respiratory changes during lithotomy?

answer

abdominal viscera displaces the diaphragm cephalad, reducing lung compliance and potentially resulting in a decreased tidal volume.

question

True or False: If the patient is obese or a large abdominal mass is present (tumor, gravid uterus), abdominal pressure may increase significantly enough to obstruct venous return to the heart.

answer

TRUE.

question

Why can the lithotomy position aggravate existing lower back pain?

answer

The normal lordotic curvature of the lumbar spine is lost in the lithotomy position.

question

What is the most common lower extremity motor neuropathy after lithotomy positioning?

answer

Common peroneal nerve injury due to compression of the nerve between the lateral head of the fibula and the bar holding the legs.

question

During lithotomy, special attention must be paid to avoid compression when what type of stirrups are used?

answer

Candy cane.

question

Common peroneal nerve injury is most common in what types of patients who are placed in lithotomy position?

answer

Low body mass index, recent cigarette smoking, or prolonged duration of surgery.

question

During lithotomy, ____________ can occur when perfusion to an extremity is inadequate, resulting in ischemia, edema, and extensive rhabdomyolysis from increased tissue pressure within a fascial compartment.

answer

Lower extremity compartment syndrome (rare complication)

question

How can you prevent lower extremity compartment syndrome during lithotomy?

answer

Compartment pressures increase over time in the lithotomy position. Therefore, it is recommended to periodically lower the legs to the level of the body if surgery extends beyond several hours.

question

The lateral decubitus position is most frequently used for surgery involving what?

answer

The thorax, retroperitoneal structures, or hip.

question

Where are the arms positioned in the lateral decubitus position?

answer

The arms are usually positioned in front of the patient. The dependent arm rests upon a padded arm board perpendicular to the torso. The nondependent arm is often supported over folded bedding or suspended with an armrest or foam cradle. If possible, the arm should not be abducted more than 90 degrees.

question

What should be checked frequently when the patient is in the lateral decubitus position?

answer

Ears and Eyes. The dependent ear should be checked to avoid folding and undue pressure. The eyes should be securely taped before repositioning if the patient is asleep. The dependent eye must be checked frequently for external compression.

question

Why would you use an axillary roll during the lateral decubitus position, and where should it be placed?

answer

To avoid compression injury to the dependent brachial plexus or vascular compression. Place it just caudal to the dependent axilla. It should never be placed in the axilla. Its purpose is to ensure that the weight of the thorax is borne by the chest wall caudad to the axilla and avoid compression of the axillary contents.

question

In the lateral decubitus position, where should the arterial pulse and/or pulse oximetry be monitored?

answer

In the dependent arm for early detection of compression to axillary neurovascular structures. Hypotension measured in the dependent arm may be due to axillary arterial compression; therefore, the ability to measure arterial blood pressure in both arms is helpful. Vascular compression and venous engorgement in the dependent arm may alter the pulse oximetry reading; a low saturation reading may reflect compromised circulation.

question

What can be used to minimize excessive pressure on bony prominences and stretch of low extremity nerves during lateral decubitus positioning?

answer

A pillow or other padding placed between the knees with the dependent leg flexed.

question

How can VQ mismatch worsen during lateral decubitus positioning?

answer

The combination of the lateral weight of the mediastinum and disproportionate cephalad pressure of abdominal contents on the dependent diaphragm decreases compliance of the dependent lung and favors ventilation of the nondependent lung. At the same time, pulmonary blood flow to the underventilated, dependent lung increases because of the effect of gravity.

question

Your patient is in the lateral decubitus position for one-lung ventilation. Is the minute ventilation of the dependent lung increased or decreased when the nondependent lung is collapsed?

answer

Increased. The increase in minute ventilation combined with decreased compliance due to positioning may further exacerbate the airway pressure required to achieve adequate ventilation.

question

What position is ventral decubitus?

answer

Prone.

question

What surgeries is the prone position used for?

answer

Primarily for surgical access to the posterior fossa of the skull, the posterior spine, the buttocks and perirectal area, and the lower extremities

question

Why might pulmonary function improved in the prone position?

answer

If there is no significant abdominal pressure and the patient is properly positioned.

question

How should the legs be placed during prone positioning?

answer

The legs should be padded and flexed slightly at the knees and hips.

question

When turning the patient prone, what is the anesthesia provider primarily responsible fore?

answer

Coordinating the move and for the repositioning of the head.

question

What is reassessed immediately after turning a patient prone?

answer

ETT position and adequate ventilation.

question

In patients with cervical arthritis or cerebrovascular disease, lateral rotation of the neck may do what?

answer

May compromise carotid or vertebral arterial blood flow or jugular venous drainage.

question

What type of ETT may be considered when positioning the patient prone?

answer

Wire-enforced ETT

question

What are the main advantages to the anesthesia provider when the pt is in sitting position?

answer

Superior access to the airway, reduced facial swelling, and improved ventilation, particularly in obese patients

question

How should the arms be positioned while the patient is in sitting position?

answer

Because gravity is pulling the arms caudad, they must be supported to the point of slight elevation of the shoulders to avoid traction on the shoulder muscles and potential stretching of upper extremity neurovascular structures.

question

How are the knees placed in the sitting position?

answer

Slightly flexed for balance and to reduce stretching of the sciatic nerve, and the feet are supported and padded

question

Why are patients particularly prone to hypotensive episodes during the sitting position?

answer

Due to the pooling of blood into the lower body under general anesthesia

question

Why is excessive cervical flexion detrimental during the sitting position?

answer

It can impede both arterial and venous blood flow causing hypoperfusion or venous congestion of the brain. It may impede normal respiratory excursion. Excessive flexion can also obstruct the endotracheal tube and place significant pressure on the tongue, leading to macroglossia.

question

What distance should be maintained between the mandible and the sternum during sitting position?

answer

At least 2 fingers' distance.

question

Sitting position places the patient at risk for what complication?

answer

Venous air embolism due to the elevation of the surgical field above the heart and the inability of the dural venous sinuses to collapse because of their bony attachments

question

What is the best method for detecting VAE?

answer

TEE

question

True or False: If the foramen ovale is patent, even small amounts of venous air may result in a stroke or myocardial infarction due to paradoxical embolism.

answer

True.

question

Who most commonly experiences perioperative ulnar neuropathy?

answer

Males, an older population, and with a delayed onset (median of 3 days)

question

What are some other risk factors for ulnar neuropathy?

answer

diabetes mellitus, vitamin deficiency, alcoholism, cigarette smoking, and cancer

question

How does radial nerve injury manifest?

answer

Wrist drop with an inability to abduct the thumb or extend the metacarpophalangeal joints.

question

Isolated median nerve injury most often occurs when?

answer

During the insertion of an intravenous needle into the antecubital fossa in an anesthetized patient where the nerve is adjacent to the medial cubital and basilic veins.

question

Patients with median nerve injury display what symptoms?

answer

Unable to oppose the first and fifth digits and have decreased sensation over the palmar surface of the lateral ½.

question

How can the sciatic nerve be injured in the lithotomy position?

answer

Because of its fixation between the sciatic notch and the neck of the fibula, the sciatic nerve can be stretched with external rotation of the leg

question

Injury to the femoral or obturator nerves generally occurs when?

answer

During lower abdominal surgical procedures with excessive retraction. The obturator nerve can also be injured during a difficult forceps delivery or by excessive flexion of the thigh to the groin.

question

A femoral neuropathy will present how?

answer

Decreased flexion of the hip, decreased extension of the knee, or a loss of sensation over the superior aspect of the thigh and medial/anteromedial side of the leg.

question

An obturator neuropathy will present how?

answer

Inability to adduct the leg and decreased sensation over the medial thigh.

question

What is the most common type of perioperative eye injury? What is it associated with?

answer

Corneal abrasion. It is associated with direct trauma to the cornea from facemasks, surgical drapes, or other foreign objects. Also decreased basal tear production or swelling of the dependent eye in patients in the prone position

question

How can you prevent corneal abrasions?

answer

Early and careful taping of the eyelids following induction of anesthesia, care regarding dangling objects when leaning over patients, and close observation as patients awaken. Before they are completely awake, patients often try to rub their eye or nose.

question

What are some perioperative factors associated with an increased risk of ischemic optic neuropathy (ION)?

answer

Prolonged hypotension, long duration of surgery especially in the prone position, large blood loss, large crystalloid use, anemia or hemodilution, and increased intraocular or venous pressure from the prone position.

question

Patient risk factors for ischemic optic neuropathy (ION) include?

answer

Hypertension, diabetes, atherosclerosis, morbid obesity, and tobacco use.

question

What are the recommendations for preventing post-op vision loss for high risk patients undergoing complex spine surgery?

answer

1. Discuss the possibility of staging the spine surgery with the surgeon. 2. Avoid excessive increase in IOP from head position below the body as well as external compression of the abdomen or chest. Keep the head neutral. 3. Use colloids along with crystalloids to maintain intravascular volume. Consider CVL 4. Consider informing the pt of a small, unpredictable risk of perioperative visual loss if high risk. 5. Careful attention to factors related to oxygen delivery including oxygen tension, maintenance of adequate intravascular volume and CO, and frequent eye checks, which may help prevent central retinal artery occlusion, although the required frequency has not been established.

question

For motor neuropathy, what test can be performed to determine the exact location of the injury?

answer

Electromyogram (EMG)

Basics of Anesthesia Chapter 19: Patient Positioning and Associated Risks – Flashcards

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