Posição Flashcards
1
Q
- What are the cardiovascular and hemodynamic changes that occur in the awake patient reclining from an upright to a supine position?
A
- When the awake patient reclines from an upright to a supine position venous return to the heart increases, which increases preload, stroke volume, and cardiac output. Briefly arterial blood pressure increases until this effect is countered by parasympathetic impulses to the sinoatrial node and myocardium. The parasympathetic outflow is mediated by baroreceptors in response to the increase in arterial blood pressure. The net result is that systemic arterial blood pressure is maintained within a narrow range during postural changes in the awake patient. (321)
2
Q
- What are the physiologic pulmonary changes that occur in the awake patient reclining from an upright to a supine position?
A
- When the awake patient reclines from an upright to a supine position the functional residual capacity (FRC) decreases due to the diaphragm shifting upward. Under general anesthesia the decrease in FRC is more pronounced and often FRC can fall below closing capacity, leading to ventilation-perfusion mismatch and hypoxemia. (322)
3
Q
- Who is responsible for checking patient positioning in the operating room?
A
- Anesthesia providers, operating room nurses, and surgeons all share responsibility for checking patient positioning for safety. Anesthesia providers should document positioning checks throughout the procedure and particularly following positioning changes. (322)
4
Q
- Why is patient positioning under anesthesia so important?
A
- Under general anesthesia patients lose the ability to change position, which normally protege them from pressure injury and excessive stretch. This prolonged immobility puts skin, soft tissue, and nerves at risk for compression, stretch, and potential injury. (322)
5
Q
- What is the most common patient position for surgery?
A
- The supine position is the most common patient position for surgery. (322)
6
Q
- How should the patient’s arms be placed during supine positioning?
A
- In the supine position, the patient’s arms may be abducted or adducted; if abducted, the angle should not exceed 90 degrees to prevent brachial plexus injury. The hands and forearms should be kept in a neutral position, either supinated or with palms toward the body, to minimize external pressure on the ulnar nerve. (322)
7
Q
- How can brachial plexus injury occur secondary to improper supine positioning?
A
- Brachial plexus injury in the supine position may occur if the arm is abducted beyond 90 degrees, allowing the head of the humerus to impinge into the axilla. (322)
8
Q
- How can ulnar nerve injury occur secondary to improper supine positioning?
A
- Ulnar nerve injury may result from external pressure on the ulnar nerve during improper supine positioning. (322)
9
Q
- What are some advantages of the lawn-chair position over the supine position?
A
- The lawn-chair position offers advantages such as facilitated venous drainage from the elevated legs, reduced stress on the back, hips, and knees, and decreased tension on the abdominal musculature; além disso, é melhor tolerada em pacientes acordados ou sob anestesia monitorada. (322)
10
Q
- How can hip dislocation occur secondary to improper frog-leg positioning?
A
- Hip dislocation can occur if, during frog-leg positioning, the knees are not adequately supported and external pressure is applied to the leg. (322)
11
Q
- What are some common indications for Trendelenburg positioning?
A
- Indications for Trendelenburg positioning include increasing venous return during hypotension, improving surgical exposure in abdominal and laparoscopic procedures, and preventing air emboli during central line placement or removal. (322)
12
Q
- How does the Trendelenburg position affect a patient’s cardiovascular system?
A
- In the Trendelenburg position, there is an autotransfusion from the legs resulting in approximately a 9% increase in cardiac output in 1 minute, an effect sustained for about 10 minutes before returning to baseline. (322)
13
Q
- How does the Trendelenburg position affect a patient’s pulmonary system?
A
- The Trendelenburg position decreases functional residual capacity (FRC) and pulmonary compliance due to the upward displacement of the diaphragm by abdominal contents. (322)
14
Q
- How does the Trendelenburg position affect intraocular pressure (IOP) and intracranial pressure (ICP)?
A
- The Trendelenburg position increases both intraocular pressure (IOP) and intracranial pressure (ICP). (323)
15
Q
- How can brachial plexus injury occur secondary to improper Trendelenburg positioning?
A
- In Trendelenburg positioning, brachial plexus injury can occur either if the patient slides downward, stretching the plexus, or due to external compression from shoulder braces. (323)
16
Q
- How does the reverse Trendelenburg position affect a patient’s hemodynamics?
A
- The reverse Trendelenburg position decreases venous return and may lead to hypotension, particularly in hypovolemic patients. (323)
17
Q
- At what patient level should invasive arterial blood pressure monitors be zeroed when a patient is in the reverse Trendelenburg position?
A
- In the reverse Trendelenburg position, invasive arterial blood pressure monitors should be zeroed at the level of the external auditory meatus to optimize cerebral perfusion. (323)
18
Q
- Why might a patient wake up with a backache after supine positioning for surgery?
A
- A backache may result from loss of the normal lumbar lordotic curvature during general anesthesia or neuraxial blockade; extra padding or slight flexion of the hips and knees can help alleviate this. (323)
19
Q
- What is the concern for positioning an obese patient supine in the reverse axis on the operating table?
A
- In obese patients positioned supine in the reverse axis, the torso (the heaviest part) is at the head of the table opposite the weighted base, potentially causing the table to tilt or tip if weight limits are exceeded. (324)
20
Q
- Why do a patient’s legs need to be raised and lowered simultaneously during lithotomy positioning?
A
- Simultaneous movement of the legs in lithotomy positioning prevents torsion or injury to the spine. (324)
21
Q
- Which lower extremity nerve is particularly at risk for injury during lithotomy positioning?
A
- The common peroneal nerve, which wraps around the head of the fibula, is particularly susceptible to injury during lithotomy positioning. (324)
22
Q
- How can finger injuries occur during lithotomy positioning?
A
- Finger crush injuries can occur when the foot portion of the table is raised or reattached at the end of surgery, potentially trapping the fingers in the hinge mechanism. (325)
23
Q
- What are the cardiopulmonary changes that occur when placing the patient in the lithotomy position?
A
- Elevation of the legs in lithotomy positioning transiently increases venous return and cardiac output, while the upward displacement of the diaphragm by abdominal contents decreases lung compliance. (325)
24
Q
- How can lower extremity compartment syndrome occur secondary to lithotomy positioning?
A
- Compartment syndrome may result from inadequate arterial blood flow due to leg elevation or venous outflow obstruction from compression or excessive hip flexion. (325)
25
Q
- What are the risk factors for positioning-related compartment syndrome?
A
- Risk factors include prolonged surgery (greater than 5 hours) in lithotomy or lateral decubitus positions. (325)
26
Q
- How should the patient’s extremities be placed when in the lateral decubitus position?
A
- In the lateral decubitus position, the dependent leg should be flexed with a pillow between the knees, the dependent arm positioned in front on a padded arm board, and the non-dependent arm supported with pillows or an arm rest. (325)
27
Q
- When the patient is in the lateral decubitus position, where should an axillary roll be placed and what is its purpose?
A
- An axillary roll should be placed caudal to the axilla (not directly in the axilla) to prevent compression injury to the brachial plexus and axillary vessels on the dependent side. (325)
28
Q
- Which arm is the best choice for placement of invasive arterial monitors in the lateral decubitus position and why?
A
- In the lateral decubitus position, invasive arterial monitors should be placed in the dependent arm to better detect neurovascular compression in the axilla. (325)
29
Q
- What are some head and neck concerns when placing a patient in the lateral decubitus position?
A
- It is important to maintain the head and neck in a neutral position, prevent excessive pressure or folding on the dependent ear, and avoid external compression on the dependent eye. (325)
30
Q
- How can injury to the brachial plexus occur secondary to improper lateral decubitus positioning?
A
- Brachial plexus injury in lateral decubitus can occur from lateral rotation of the neck and stretch of the plexus, or if an arm is abducted more than 90 degrees, causing compression against the humeral head. (325)
31
Q
- What are the pulmonary changes associated with lateral decubitus positioning?
A
- In lateral decubitus positioning, the mediastinum’s lateral weight and cephalic pressure on the diaphragm reduce lung compliance of the dependent lung. (325)
32
Q
- What are some concerns when turning a patient from the supine to prone position?
A
- When turning a patient from supine to prone, it is critical to secure and prevent dislodgment of intravenous and arterial lines, as well as the endotracheal tube, while maintaining the head, neck, and spine in a neutral alignment. (325)
33
Q
- What parts of the face are at risk for injury during prone positioning?
A
- The face’s bony prominences (forehead, malar regions, chin) are at risk for compression injuries during prone positioning; care must also be taken to avoid pressure on the eyes, nose, and mouth. (325-326)
34
Q
- How should the extremities be placed when in the prone position?
A
- In the prone position, the legs should be padded and slightly flexed at the hips and knees. The arms can be tucked at the sides or placed on arm boards near the head, ensuring they are not abducted more than 90 degrees. (326)
35
Q
- What is the ideal placement of bolsters beneath the patient in the prone position and why?
A
- Bolsters should be placed from the clavicle to the iliac crests to reduce abdominal compression, thereby minimizing decreases in pulmonary compliance and venous return. Bolsters should not extend beyond the iliac crests to protect the genitalia and femoral vessels, with the abdomen and breasts positioned medially to avoid compression. (328)
36
Q
- What are the cardiopulmonary changes that occur with prone positioning?
A
- Prone positioning improves pulmonary function by increasing functional residual capacity (FRC) and oxygenation, while hemodynamics remain well maintained. (328)
37
Q
- For which surgical procedures might the patient be placed in the sitting position?
A
- The sitting position is advantageous for surgeries involving the superior cervical spine and posterior fossa, and a modified sitting (beach-chair) position is commonly used for shoulder surgery. (328)
38
Q
- How should the extremities be placed in the sitting position?
A
- In the sitting position, the arms should rest at the sides with adequate padding; the shoulders should be even or slightly elevated to minimize neck-shoulder stretch, and the knees should be supported and slightly flexed to reduce tension on the sciatic nerve. (328)
39
Q
- What are some complications that can occur as a result of placing the patient in the sitting position?
A
- Complications in the sitting position include venous air embolism, pneumocephalus, hypotension, cerebral hypoperfusion, and macroglossia. (328)
40
Q
- How can an intraoperative venous air embolus be detected?
A
- An intraoperative venous air embolus can be detected using transesophageal echocardiography (TEE) or precordial Doppler ultrasound in a patient with adequate intravascular volume. (329)
41
Q
- What are some other complications that can occur as a result of a venous air embolus?
A
- Other complications include paradoxical air embolism, arrhythmias, acute pulmonary hypertension, and circulatory collapse. (329)
42
Q
- What is the concern regarding the patient with an anatomic intracardiac shunt scheduled for surgery in the sitting position?
A
- A patient with an intracardiac shunt is at risk for paradoxical air embolism, which can lead to stroke or myocardial infarction; preoperative identification of such a shunt is a contraindication for surgery in the sitting position. (329)
43
Q
- What is the risk of pneumocephalus in the sitting position?
A
- Pneumocephalus occurs in nearly all patients undergoing cervical spine or posterior fossa surgery in the sitting position, although clinically significant cases are rare. (329)
44
Q
- What are some symptoms of clinically significant postoperative pneumocephalus?
A
- Clinically significant postoperative pneumocephalus may present with headache, confusion, seizures, and temporary hemiparesis. (329)
45
Q
- What is a concern regarding excessive head flexion in the sitting position?
A
- Excessive head flexion in the sitting position can impede cerebral venous outflow and arterial inflow, leading to brain hypoperfusion; it may also cause macroglossia, especially when combined with TEE monitoring. A minimum of two fingerbreadths between the mandible and sternum is recommended. (329)
46
Q
- What unique positioning challenges does robotic surgery pose?
A
- Robotic surgery often requires steep Trendelenburg positioning and secure patient fixation (eg, with bean-bags or nonslip mattresses and strapping). Caution with shoulder braces is needed to minimize neck and shoulder stretch, as steep positioning can lead to laryngeal edema and optic neuropathy. (329)
47
Q
- What are the consequences of docking the robot?
A
- Docking the robot limits direct access to the patient; the patient’s head may be farther from the anesthesia provider and arms tucked, sometimes necessitating a metal tray above the face to protect against surgical equipment. (329)
48
Q
- What physiologic changes occur during robotic surgery?
A
- Robotic surgery combines laparoscopic insufflation with Trendelenburg positioning, leading to decreased functional residual capacity (FRC) and pulmonary compliance. (329)
49
Q
- In what time course can a pressure injury occur?
A
- Pressure injuries can develop in as little as 2 hours with a force of 70 mm Hg, as demonstrated in animal studies. (330)
50
Q
- In what time course do pressure injuries present after surgery?
A
- Pressure injuries are typically observed within 72 hours following surgery. (330)
51
Q
- What tissue is at risk in pressure injuries?
A
- Pressure injuries may affect skin, soft tissue, and muscle; notably, muscle damage can occur prior to skin and subcutaneous tissue injury due to higher oxygen demands. (330)
52
Q
- What body areas are at risk of pressure injuries in each of the supine, prone, and sitting positions?
A
- In the supine position, the sacrum, heels, and occiput are at risk; in the prone position, the chest and knees; and in the sitting position, the ischial tuberosities. (330)
53
Q
- In which surgical procedures are patients most likely to incur pressure injuries?
A
- Pressure injuries are more likely in cardiac, thoracic, orthopedic, and vascular surgeries, particularly when surgery is prolonged. (330)
54
Q
- Which subset of patients are most at risk for self-inflicted bite injuries during general anesthesia?
A
- Patients undergoing procedures with transcranial motor evoked potentials (Tc-MEPs) are at risk for bite injuries, most commonly involving the tongue, but also the lips and teeth. (330)
55
Q
- What is the most common neuropathy represented by claims to the American Society of Anesthesia (ASA) database?
A
- Ulnar neuropathy (28%) is the most common, followed by brachial plexus (20%), lumbosacral nerve root (16%), and spinal cord injuries (12%). (330)
56
Q
- What are the possible causes of peripheral nerve injuries?
A
- Causes include stretch, compression, ischemia, metabolic derangements, and direct trauma or laceration during surgery. (330)
57
Q
- What is the best way to prevent perioperative neuropathies?
A
- Although no definitive preventive measure exists, maintaining a neutral position, avoiding excessive extension or flexion, and ensuring adequate padding are essential. (330)
58
Q
- What have retrospective studies of ASA closed claims shown to be risk factors for ulnar nerve injuries?
A
- Risk factors for ulnar nerve injuries include diabetes, alcoholism, cigarette smoking, and cancer. (333)
59
Q
- What positions or surgeries are associated with brachial plexus injury?
A
- Brachial plexus injury is associated with arm abduction over 90 degrees, lateral rotation of the head, asymmetric sternum resection during internal mammary dissection in cardiac surgery, and direct trauma. (333)
60
Q
- How common are injuries to the radial or median nerves?
A
- Injuries to the radial or median nerves are rare. (333)
61
Q
- What patient position is most likely to lead to common peroneal or sciatic nerve injury?
A
- The lithotomy position is most likely to lead to common peroneal or sciatic nerve injury due to stretch, external rotation, or hyperflexion at the hip. (333)
62
Q
- What are some potential causes of obturator nerve injury?
A
- Obturator nerve injury may occur during difficult forceps delivery, excessive thigh flexion toward the groin, or due to lithotomy positioning. (333)
63
Q
- How should a postoperative nerve deficit be evaluated and treated?
A
- A postoperative nerve deficit should be evaluated by documenting the sensory and motor deficits and obtaining a neurologic consultation; most deficits resolve spontaneously, but patient reassurance and follow-up are recommended. (333)
64
Q
- What is the typical time course to recovery from sensory and motor neuropathies?
A
- Sensory neuropathies are generally transient, while motor neuropathies may take 4 to 6 weeks to recover; in cases of axonal injury, recovery may extend from 2 to 12 months. (334)
65
Q
- What is the value of electrophysiologic evaluation of an intraoperative nerve injury?
A
- Early electrophysiologic evaluation (within the first week) can provide initial insights, while assessments after 4 weeks yield more detailed information regarding the site, nature, and severity of the injury. (334)
66
Q
- What are the risk factors for corneal abrasion under general anesthesia?
A
- Risk factors include advanced age, prolonged surgery, prone or Trendelenburg positioning, and supplemental oxygen delivery in the postanesthesia care unit. (334)
67
Q
- What are the symptoms of a corneal abrasion?
A
- Symptoms include a foreign body sensation in the eye, photophobia, blurry vision, and erythema. (334)
68
Q
- What are some precautions that can be taken to minimize the risk of corneal abrasion?
A
- Precautions include taping the eyelids immediately after induction, protecting the eyes from dangling objects, using ophthalmic ointments, and closely monitoring patients as they awaken to prevent rubbing of the eyes. (334)
69
Q
- What is the cause of postoperative vision loss due to central retinal artery occlusion?
A
- Central retinal artery occlusion is caused by direct retinal pressure. (334)
70
Q
- What are the surgical and patient risk factors for postoperative vision loss due to ischemic optic neuropathy (ION)?
A
- Risk factors for ION include prolonged hypotension, long surgery duration, significant blood loss, large-volume crystalloid use, anemia or hemodilution, increased intraocular or venous pressures from prone positioning, and patient factors such as hypertension, diabetes, atherosclerosis, morbid obesity, and tobacco use. (334)
