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Advanced Principles of Anesthesia > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

Two most common reasons for spinal surgery

A

Spinal stenosis and intervertebral disc herniation

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2
Q

Which spine procedures can be done minimally invasive

A

perc endoscopic lumbar discectomy, vertebroplast and kyphoplasty, cervical discectomy and foraminectomy, intradiscal electrothermal therapy

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3
Q

What is the greatest anesthetic challenge of neuroskeletal surgery

A

positioning

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4
Q

What is the prone position’s effect on cardiac output

A

Reduced CO

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5
Q

Prone position’s effect on SVR and PVR

A

Increased

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6
Q

What occurs in the prone position when the patient’s head is rotated 60 degrees

A

Compression of the contralateral vertebral artery begins to constrain blood flow

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7
Q

What occurs in the prone position when patient’s head is rotated 80 degrees

A

Contralateral vertebral artery becomes completely occluded

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8
Q

Intraabdominal and intrathoracic pressures in the prone position are…

A

Increased

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9
Q

What hemodynamic parameters are decreased in the prone position

A

Stroke volume and cardiac index

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10
Q

What complication is associated with general anesthesia and prone positioning

A

Post operative vision loss

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11
Q

What are risk factors for postoperative vision loss

A

Male
Obesity
Use of Wilson Frame
Anesthesia duration >6 hr
Large blood loss
Intraoperative hypotension
Colloid administration
History of obstructive sleep apnea

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12
Q

Which type of surgery is most highly associated with POVL

A

prone spine

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13
Q

What are the two main causes of vision loss

A

Retinal vascular occlusion and ischemic optic neuropathy

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14
Q

What are the key features of POVL

A

typically bilateral, painless, no light perception, non-reactive pupil, decreased or absent color vision, occurs within 24-48 hours post op

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15
Q

When should an ophthalmologist be consulted

A

At the first sign that patient has altered vision after procedure

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16
Q

What positioning interventions can be done to prevent povl

A

5-10 degree reverse Tberg position during prone spine procedures
During Steep Tberg procedures, use a 5 minute supine rest stop at the 4 hour timeframe
Assess and document that the eyes are free of pressure throughout the prone procedure
Stage lengthy procedures performed with patient prone
Position the head in a neutral position with the face down and the head level with or higher than the heart to minimize venous outflow obstruction

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17
Q

What medication can be used when there is evidence of increased IOP

A

dorzolamide-timolol (cosopt) drops
Also can consider antiplatelet agents and steroids

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18
Q

What medications may be used as part of ERAS multimodal pain protocols

A

Acetaminophen, gabapentin, lidocaine, ketamine, mag, dexamethasone, dexmedetomidine
(But may not be able to use precedex or mag if neuromonitoring!)

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19
Q

What is an important factor in preop assessment for an anterior cervical discectomy and fusion (ACDF)

A

Airway assessment: important to assess cervical mobility and if they have pain while moving head/neck and where the pain/symptoms are

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20
Q

What techniques should be utilized for intubation for ACDF

A

passive immobilization, inline traction, video +/-
Avoid flexion, extension, and lateral rotation of the head when intubating

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21
Q

What is standard positioning for ACDF

A

supine, arms tucked, shoulder roll (to allow for better neck access)

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22
Q

Induction type for ACDF

A

GA with OET
Tape the ETT to the side opposite where the surgeon stands
If neuromonitoring, check baseline before and after intubation (soft bite blocks)

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23
Q

What structures can be potentially damaged during ACDF

A

RLN, major arteries, veins, esophageal perforation, pneumothorax

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24
Q

What medications should be avoided during ACDF if MEPs used

A

NMBA and magnesium

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25
Q

When should neurologic function be assessed after emergence from ACDF

A

Before leaving the operating room

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26
Q

What two complications should be assessed for after ACDF

A

RLN damage and hematoma

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27
Q

What is lumbar laminectomy indicated for

A

Symptomatic nerve root or spinal cord compression
Disc herniation usually at the L4 to L5 or L5 to S1 intervertebral space

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28
Q

What is an important preop aspect for lumbar laminectomy or fusion

A

Assess and document neurologic deficits of the lower extremities

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29
Q

What positions might be used for lumbar laminectomy or fusion

A

prone, lateral, or knee-chest

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30
Q

Most common anesthetic technique for lumbar laminectomy or fusion

A

GA
Local with sedation is also possible but not typical

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31
Q

Epidural for lumbar laminectomy or fusion requires analgesia to what level and what is the benefit of epidural

A

T7-T8
Reduces blood loss and shrinks epidural veins

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32
Q

What type of anesthesia CANNOT be used if using neuromonitoring

A

Regional

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33
Q

Which lumbar lami/fusion anesthetic technique is most likely to cause hypotension that can be accentuated with position changes

A

Spinal

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34
Q

How often should the face check be done and documented during lumbar lami/fusion

A

every 15 minutes

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35
Q

What is the most likely cause of sudden profound hypotension during lumbar lami/fusion

A

Major intraabdominal vessel (iliac, aorta) damage

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36
Q

What is the max dose of crystalloid that should be given in prone position in order to decrease the incidence of ischemic optic neuropathy

A

no more than 40 ml/kg

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37
Q

What position should extubation take place in for lumbar lami/fusion

A

Supine

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38
Q

What are the postop complication of lumbar lami/fusion

A

Hemorrhage
Neurologic deficits - assess and ensure they can move all extremities!
Visual loss

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39
Q

Surgery above what level requires a double-lumen ETT to collapse the lung on the operative side

A

T8

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40
Q

Which has greater risk of damage to the spinal cord, thoracic or lumbar fusion

A

Thoracic fusion

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41
Q

What is a source of anesthetic concerns for anteroposterior fusion

A

intraoperative position changes

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42
Q

When is surgery indicated for scoliosis

A

when curvature is severe - cobb angle greater than 40-50 degrees or rapidly progressing

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43
Q

What PFT results indicates that you may need to keep the patient intubated

A

Vital capacity is less than 40% of predicted

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44
Q

What is the main concern with controlled hypotension

A

compromising spinal cord blood supply

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45
Q

What are complications of a wake up test

A

Uncontrolled pt movement may have consequences
Forceful inspiratory efforts may provoke VAE

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46
Q

What is intervention if patient moves the hands and not the feet during a wakeup test

A

surgeon should decrease the spinal distraction

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47
Q

What spinal cord transection level is incompatible with survival

A

C2-C4

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48
Q

What disease process can cause spontaneous dislocation of C1 on the C2 vertebra

A

rheumatoid arthritis

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49
Q

What in the most frequent nontraumatic cause of spinal cord transection

A

Multiple sclerosis

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50
Q

Where are temperature regulation and spinal cord reflexes lost in spinal cord injuries

A

Below the level of injury

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51
Q

What is the initial product of spinal cord transection

A

Flaccid paralysis with total absence of sensation below the level of injury

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52
Q

What is the initial phase of spinal cord injury

A

Spinal shock: 1-3 weeks

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53
Q

What happens in the chronic phase of spinal cord injury

A

some regeneration of reflexes

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54
Q

What considerations should be given to succinylcholine in spinal cord injury

A

While ok from a potassium standpoint within the first 24 hours after injury, fasciculations may make the injury worse. Should probably be avoided

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55
Q

What type of patient should not receive ketamine for their spinal cord injury procedure

A

Trauma patient who also has a head injury

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56
Q

Injury above what level can cause autonomic hyperreflexia

A

T6

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57
Q

What precipitates autonomic hyperreflexia

A

cutaneous or visceral stimuli below the spinal cord lesion

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58
Q

Symptoms of autonomic hyperreflexia

A

severe HTN and severe bradycardia

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59
Q

Treatment for autonomic hyperreflexia

A

Remove the stimulus (see if BP and HR recover)
If it doesn’t then try diluted nitro

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60
Q

Emergence for spinal cord injury

A

Halo device or body jacket
Fully awake
Prevent coughing and bucking
Extubation criteria
Airway patency test
Nerve stimulator won’t be useful!

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61
Q

Postop consideration for SCI

A

Airway obstruction
Respiratory insufficiency
BLeeding
Neuro deficits
DVT
Pneumonia

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62
Q

What 4 types of injury/stress can impact evoked potentials?

A

Injuries to neural structures caused from heat (electrocautery)
Mechanical stress (retraction)
Ischemia (ligation, edema, vessel damage)
Loss of functional integrity (transection)

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63
Q

What is the elastic limit of nerves

A

20% - stretching further may produce irreversible damage

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64
Q

What 4 patient factors can affect evoked potentials?

A

hypothermia
hypotension
positioning
anemia

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65
Q

What represents the intensity of the evoked response

A

Amplitude

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66
Q

What is indicative of the time necessary for the evoked response to be measured in the brain

A

Latency

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67
Q

What % changes in amplitude and latency suggest possible ischemia

A

50% decrease in amplitude
or
10% increase in latency

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68
Q

Lipophilic agents that interfere with neuronal membrane conduction also interfere with…..

A

subcortical conduction

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69
Q

Lipophilic agents cause an increase in what aspects of neuromonitoring

A

Interpeak latencies
Control conduction time

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70
Q

What is the effect of inhalation and IV anesthetic agents on EP waveforms

A

They depress EP waveforms in a dose-dependent manner

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71
Q

Which has a greater depressant effect on EP waveforms, inhaled agents or IV agents

A

Inhaled

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72
Q

What effect does the combo on inhaled and IV agents have on SSEP waveforms

A

Synergistic

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73
Q

What pathway do SSEPs monitor?

A

Sensory pathway through the dorsal root ganglia and posterior column. They monitor the integrity of the posterior (dorsal) columns.

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74
Q

Which nerves are typically stimulated for SSEP monitoring?

A

Ulnar or median nerve for upper extremity.
Posterior tibial nerve for lower extremity.

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75
Q

What agents are SSEPs most sensitive to?

A

All inhalational agents and nitrous oxide

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76
Q

Which IV anesthetics increase SSEP amplitude

A

Ketamine and etomidate

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77
Q

Which medications decrease amplitude and increase latency of SSEPs

A

Halogenated agents
N2O
Barbiturates (ok to use when burst suppression on EEG)
Propofol (least pronounced, best iv agent to use with ssep)
Opioids (mildly, bolus more so than infusion, ok to use)

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78
Q

Which medication increases amplitude and latency of SSEPs

A

Etomidate

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79
Q

Which medications increases amplitude and causes no change in latency of SSEPs

A

Ketamine

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80
Q

Which medications have little effect on SSEPs

A

Benzos

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81
Q

What pathway is monitored by MEPs

A

The motor pathway - including the motor cortex, corticospinal tract, nerve root, and peripheral nerve - by transcranial electric (sometimes magnetic) stimulation of the motor cortex

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82
Q

Are MEPs or SSEPs more sensitive to the effects of anesthetic agents

A

MEPs

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83
Q

Which changes occur first, changes in MEPs or SSEPs

A

MEPs

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84
Q

Where are MEPs most susceptible to anesthetic agents

A

Motor cortex and anterior horn cells (alpha motor neurons and interneurons)

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85
Q

What are the effects of NMBAs on SSEP and MEP

A

SSEP = no effect
MEP = increased latency, decreases amplitude

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86
Q

What are the effects of precedex on SSEP and MEP

A

No effect on latency in either.
Decreases amplitude in both.

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87
Q

What 2 hormones are secreted by the thyroid gland

A

T3 - triiodothyronine
T4 - thyroxine

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88
Q

Where is the thyroid gland located

A

Anterior to trachea
Below (caudad to) the hyoid bone
Caudad to the thyroid cartilage
On top of the parathyroid glands
Between cricoid cartilage and suprasternal notch

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89
Q

Where does the thyroid gland receive its vascular supply

A

Superior and inferior thyroid arteries

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90
Q

What laterally borders each thyroid lobe and is commonly injured during procedure

A

Recurrent laryngeal nerves

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91
Q

What are the functional units of the thyroid gland

A

Follicles - contain colloid and are lined by epithelial cells

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92
Q

What makes up most of the colloid and is responsible for synthesis and storage of thyroid hormones

A

Thyroglobulin

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93
Q

What is the rate limiting step of thyroid hormone synthesis

A

iodine trapping

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94
Q

What are the effects of excess iodine

A

Decreased thyroid gland size and TH production

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95
Q

What hormone is responsible for iodine trapping

A

TSH (anterior pituitary)

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96
Q

Where are T3 and T4 synthesized and what is required for synthesis?

A

Synthesized in follicles.
Controlled by TSH.
Also requires tyrosine (on thyroglobulin) and iodine

97
Q

What controls the release of T4 and T3

A

TSH

98
Q

Which thyroid hormone makes up 93% of released hormone

A

T4

99
Q

Which hormone makes up 7% of released hormone

A

T3

100
Q

Which thyroid hormone has a longer half life

A

T4: 6-7 days
T3: 24 hours

101
Q

Which thyroid hormone is the primary stimulus at the target tissue, is more potent, and is less bound in circulation

A

T3

102
Q

What are the major functions of thyroid hormone

A

Increased cellular metabolic activity: vasodilation and increased blood flow to tissues.
Normal growth in infants and children: Brain development.
Direct and indirect excitability of the heart: HR and force of contraction.
Increase hormone secretion from other endocrine glands: insulin, digestive enzymes, appetite.

103
Q

Where is thyroid regulating hormone (TRH) released from

A

Hypothalamus

104
Q

What acts on the anterior pituitary to stimulate it to release TSH

A

Thyroid regulating hormone (TRH)

105
Q

What mechanism controls the secretion of hormones from the anterior pituitary and hypothalamus

A

Inhibitory feedback by T4

106
Q

What lab findings are expected in primary hypothyroidism

A

Increased TSH
Normal or Low T3/T4

107
Q

What are common causes of primary hypothyroidism

A

Iodine abnormalities
Colloid goiter
Iatrogenic (surgery, radiation)
Amiodarone
Tyrosine kinase inhibitors
Lithium
(problem is actually within the thyroid gland)

108
Q

What type of problem is hashimoto thyroiditis

A

Primary hypothyroidism

109
Q

What lab findings are expected in secondary hypothyroidism

A

Decreased TSH
Decreased T3 and T4

110
Q

Common causes of secondary hypothyroidism

A

Pituitary or hypothalamic disorders
(Occurs somewhere outside of the thyroid gland)

111
Q

What cardiac symptoms should be expected with hypothyroidism

A

Bradycardia
Dysrhythmias
Cardiomegaly
Impaired contractility
Abnormal baroreceptor function
Heart failure
Labile BP

112
Q

Noncardiac signs/symptoms of hypothyroidism

A

Goiter
Slowed metabolism
Intolerance to cold
Fatigue and depression
Joint and muscle pain
Dry, brittle hair/skin, puffy face

113
Q

Treatment of hypothyroidism

A

Thyroid hormone replacement: synthetic T4
Careful monitoring of CV and thyroid status

114
Q

What are 3 airway implications for a patient with hypothyroidism?

A

Goiter
Tracheal deviation/compression
Enlarged tongue (macroglossia)

115
Q

Considerations for the patient with hypothyroidism

A

Consider concurrent adrenal suppression
May have slowed metabolism and clearance of meds
Depression of ventilatory responses to hypercarbia and hypoxia
Monitor body temp closely
Should be euthyroid prior to surgery

116
Q

Should thyroid medication be given on day of surgery?

A

Yes!

117
Q

What response to anesthetic agents might a patient with hypothyroidism have?

A

Exaggerated CNS depression

118
Q

What are the signs of myxedema coma

A

Hypothermia, hypoventilation, hypotension, hyponatremia

119
Q

Expected lab findings of myxedema coma

A

Hypoglycemia
Hypoxemia, hypercapnia
Hyponatremia
Prolonged QT, low voltage
Pericardial effusion

120
Q

Precipitating factors of myxedema coma

A

Infection
Cold exposure
Stroke
Meds - amiodarone and lithium

121
Q

Management of myxedema coma

A

Supportive - airway, rewarming
Hydrocortisone
Levothyroxine (T4)
May need IV thyroid medications

122
Q

What is Grave’s disease

A

Autoimmune stimulation of thyroid gland by TSH-receptor antibodies (IgG)
Causes gland enlargement and excess T3/T4

123
Q

Risk factors for Grave’s disease

A

Female
Genetics
Stress
Cigarette smoking

124
Q

Causes of hyperthyroidism

A

Graves disease, nodules, pituitary tumor, thyroid cancer, and amiodarone (iodine rich)

125
Q

Signs/symptoms of hyperthyroidism

A

Hypermetabolic state
Tachycardia
Warm, moist skin
Tremor
Diarrhea
Osteopenia
Muscle weakness
Weight loss
Anxiety
Heat intolerance
Ocular abnormalities

126
Q

Expected lab values with primary hyperthyroidism

A

Low TSH
High T3/T4

127
Q

Grave’s disease lab level alterations

A

Thyroid-stimulating immunoglobulins, alkaline phos, calcium

128
Q

Expected lab values with subclinical hyperthyroidism

A

Low TSH
Normal T3/T4

129
Q

Treatment of hyperthyroidism

A

Radioactive iodine: absorbed by the thyroid gland and destroys secretory cells
Antithyroid drugs and beta blockade: thionamides inhibit TH synthesis
Thyroidectomy: partial or total, for cancer or ineffective treatment

130
Q

Risk factors for thyroid cancer

A

Female
Radiation exposure
Inherited syndromes

131
Q

Relevant nearby structures regarding thyroidectomy

A

Anterior to larynx, pharynx, esophagus, trachea
Below thyroid and cricoid cartilage and hyoid bone

132
Q

Relevant nearby vessels regarding thyroidectomy

A

Internal jugular veins
Carotid arteries
Thyroid veins/arteries

133
Q

Relevant nearby nerves regarding thyroidectomy

A

Superior laryngeal nerve
Recurrent laryngeal nerve

134
Q

Most common anesthetic choice for thyroidectomy

A

GETA
But can also use LMA, local and sedation: bilateral cervical plexus block

135
Q

What is the purpose of intraop nerve monitoring for thyroidectomy

A

Assists with identifying, dissecting, and confirming function of recurrent laryngeal nerve.
Used to minimize nerve injury

136
Q

What ett is used for nerve monitoring in thyroidectomy

A

EMG ETT aka NIM tube
Ensure the electrodes are in contact with the vocal cords via video laryngoscopy
Use a short acting NMBD (succ) for induction only

137
Q

What adjunct medication can be given when using a NIM tube

A

Remifentanil, often used to suppress cough reflex

138
Q

What medications should be avoided during thyroidectomy induction

A

Ketamine, vagolytics, pancuronium - agents that stimulate the SNS
Patient is often already baseline hyperthyroid

139
Q

What anesthetic technique is usually used for thyroidectomy maintenance

A

TIVA (decreases PONV). Should decrease possibility of PONV when operating around the neck as it could result in ruptured sutures or hematoma

140
Q

Direct vs. indirect acting vasopressors for thyroidectomy

A

Choose phenylephrine over ephedrine because the patient may have already high levels of circulating catecholamines at baseline

141
Q

What are 3 priorities for extubation following thyroidectomy

A

Assess for airway compromise and laryngeal edema
Minimize coughing and bucking
Aggressive treatment of PONV

142
Q

What is the intervention for bilateral recurrent laryngeal nerve injury

A

Reintubation

143
Q

What would be expected in an acute hypothyroid state following thyroidectomy

A

Hypocalcemia, tingling in fingertips/lips, stridor, laryngospasm

144
Q

When might thyroid storm mostly likely occur

A

6-18 hours postop thyroidectomy

145
Q

Clinical manifestations of thyroid storm

A

Fever >38.5 degrees
Tachycardia
Confusion and agitation
Tremor
Weakness
Dysrhythmias
Nausea and vomiting
Hypertension
Heart failure

146
Q

What medications should be avoided for cooling during thyroid storm

A

Salicylates (asa) - they can displace the t3 and t4 from their proteins and convert them to their active form. Choose acetaminophen instead

147
Q

What is the curative treatment for thyroid storm

A

Antithyroid medications - PTU and methimazole

148
Q

What is the function of the parathyroid glands

A

Produce parathyroid hormone which regulates calcium levels

149
Q

What is the normal total serum calcium level

A

8.5-10.5 mg/dl

150
Q

Does albumin affect total calcium or ionized calcium

A

Total

151
Q

Does blood pH affect total or ionized calcium

A

Ionized

152
Q

What is the effect of alkalosis on calcium-protein binding and ionized calcium

A

Increases calcium-protein binding and decreases ionized calcium

153
Q

What is the effect of acidosis on calcium-protein binding and ionized calcium

A

Decreases calcium-protein binding and increases ionized calcium

154
Q

Which form of calcium exerts physiologic effects

A

Only the ionized form

155
Q

What are the functions of ionized calcium

A

Hemostasis (platelet aggregation, blood coagulation)
Hormone and neurotransmitter release
Muscle contraction
Bone formation
Cell division and function

156
Q

Which has a greater affect on calcium levels, PTH or vitamin D

A

PTH

157
Q

What are the effects of vitamin D on calcium

A

Promotes dietary absorption
Increases kidney reabsorption
Stimulates release from bone

158
Q

What are the effects of PTH on calcium and phosphate

A

Increases calcium and decreases phosphate

159
Q

What stimulates the release of PTH from the parathyroid gland

A

low ionized calcium states

160
Q

What is activated by parathyroid hormone

A

Osteoclasts: to breakdown bone to release calcium and phosphate
Vitamin D: to promote absorption of calcium and phosphate from intestines
Increases calcium reabsorption and phosphate excretion in the kidney

161
Q

What hormone is secreted from the thyroid parafollicular cells (C cells) in response to elevated serum ionized calcium

A

Calcitonin

162
Q

What hormone opposes the actions of parathyroid hormone

A

Calcitonin - reduces serum calcium

163
Q

What is the effect of calcitonin on osteoclasts

A

Inhibits osteoclasts

164
Q

What lab finding is expected in hypoparathyroidism

A

Low serum calcium levels
(due to low PTH or resistance to PTH)

165
Q

What are the symptoms of low serum calcium

A

Hyperexcitability of nerve and muscle cells
Muscle spasms, cramps, paresthesia, hyperactive deep tendon reflexes and tetany (trousseau sign and chvostek sign)
Stridor and laryngospasm

166
Q

What is the treatment of hypoparathyroidism

A

Vitamin D
Calcium
Magnesium
Recombinant PTH

167
Q

What lab findings are seen in hyperparathyroidism

A

Hypercalcemia
Elevated serum PTH

168
Q

Causes of hyperparathyroidism

A

Hypersecretion of parathyroid adenomas
Hyperplasia
MEN (multiple endocrine neoplasia) syndrome
Carcinoma

169
Q

Are these features of hyper or hypoparathyroidism:
Hypertension
Cardiac conduction disturbances
Shortened QT interval

A

Hyperparathyroidism

170
Q

Are these features of hyper or hypoparathyroidism:
Prolonged QT interval
Hypotension
Decreased cardiac contractility

A

Hypoparathyroidism

171
Q

What is the appropriate management of hypercalcemia in hyperparathyroidism

A

Isotonic saline: dilutes serum ca, increases GFR and excretion
Loop diuretics

172
Q

What are three anesthesia implications for hyperparathyroidism

A

Management of hypercalcemia
Correction of electrolyte abnormalities (Mag and K)
Management of CV complications

173
Q

After parathyroidectomy, should iPTH levels increase or decrease?

A

Levels should decrease

174
Q

How many calories of energy are available from 1 gram of fat

A

9 calories

175
Q

What are the terminal consequences of excessive adipose tissue

A

Insulin resistance
Inflammation throughout the body

176
Q

Where can android fat be found

A

Central distribution - mostly upper body
Truncal, cushingoid, apple

177
Q

Where can gynecoid fat be found

A

Peripheral distribution - hips, buttocks, thighs
Gluteal, pear

178
Q

Which fat distribution is associated with increased o2 consumption, DM, and CV disease (LV dysfunction)

A

Android

179
Q

Which fat distribution is less metabolically active and has less CV comorbidities

A

Gynecoid

180
Q

What is the new standard used as a marker of abdominal obesity?

A

Waist circumference:
>102 cm (40.2 in) in men
>88 cm (35 in) in women

181
Q

What risks are associated with waist circumference >40.2 in in men and 35 in in women

A

Increased risk for CV disease, DM II, HTN, dyslipidemia, and death

182
Q

Formula for BMI

A

weight (in kg) / height (in meters)squared

183
Q

What is the consequence of dosing a drug to total body weight in a morbidly obese individual

A

Overdose

184
Q

What is ideal body weight

A

Ideal weight associated with maximum life expectancy for a given height

185
Q

How do you calculate ideal body weight

A

Male: height (cm) - 100
Female: height (cm) - 105

186
Q

What is the difference between the total body weight and fat mass

A

Lean body weight

187
Q

How much is lean body weight increased in obese individuals

A

30%

188
Q

Calculation for lean body weight

A

IBW x 1.3

189
Q

Which body weight measurement will underestimate the dose for an obese patient

A

Ideal body weight

190
Q

Which body weight is probably the best estimate of dose

A

Lean body weight

191
Q

What calculation should be done for obese patient in the case of strongly hydrophilic drugs

A

Instead of calculated LBW, add 20% to the ideal body weight to account for the increase in lean body tissue content

192
Q

What is the ideal metric for dosing in the case of strongly lipophilic drugs

A

Lean body weight

193
Q

What 4 things effect the volume of distribution of a drug in an obese patient

A

Increased blood volume
Increased cardiac output
Altered plasma protein binding
Lipid solubility of a drug

194
Q

What happens to the volume of distribution of hydrophilic and lipophilic drugs in an obese patient

A

Vd increases for both type of drugs, however the Vd of lipophilic drugs increases more

195
Q

What is the effect of obesity on ventilation

A

Restrictive ventilatory effect
Decreased chest wall compliance
Difficulty getting air IN

196
Q

What is the relationship between BMI and FRC

A

As BMI increases, FRC decreases at the same rate

197
Q

When does small airway collapse occur

A

When FRC is less than closing capacity

198
Q

What lung volumes are decreased in obesity

A

FRC = ERV + RV
IC = TV + inspiratory reserve capacity
VC = TV + IRV + ERV
ERV

199
Q

Which lung volumes are increased in obesity

A

Closing volume

200
Q

What are the most commonly reported abnormalities of pulmonary function in the obese patient

A

Decreased FRC and ERV

201
Q

What is the most sensitive indicator of the effect of obesity on pulmonary function

A

ERV

202
Q

What is the result of FRC falling below closing capacity in an obese patient

A

V/Q mismatch, shunt, hypoxemia (hypercapnia)

203
Q

What is the most common blood gas abnormality in obesity and what causes it

A

Arterial hypoxemia resulting from atelectasis and R to L shunt

204
Q

What constitutes apnea

A

Cessation of respiration for > or equal to 10 seconds

205
Q

Define hypopnea

A

Any respiratory patterns that leads to increased CO2 accumulation (decreased volume or decreased rate)

206
Q

What is obstructive apnea

A

Continued respiratory effort despite no air flow

207
Q

What are the criteria for sleep apnea

A

Airflow reduced by 50% x 10 seconds for > or equal to 15 times
Per hour of sleep
Associated with snoring
4% decrease in SpO2

208
Q

What can obesity hypoventilation syndrome lead to?

A

Central apnea - apnea without respiratory effort

209
Q

What does central apnea reflect?

A

Desensitization of the respiratory centers to nocturnal hypercarbia

210
Q

What are the characteristics of obesity hypoventilation syndrome

A

OSA
Hypercapnia
Daytime hypersomnolence
Arterial hypoxemia
Cyanosis-induced polycythemia (due to long term low pao2 levels)
Respiratory acidosis
Pulmonary HTN
R sided heart failure (from increased PVR)

211
Q

Diagnostic criteria for obesity hypoventilation syndrome

A

BMI >30
Awake PCO2 > 45 (daytime hypoventilation)
Sleep-disordered breathing in the absence of other pathophysiology

212
Q

Is CO increased or decreased in obesity

A

Increased

213
Q

Is total body oxygen demand increased or decreased in obesity

A

Increased (primarily due to increased lean body mass)

214
Q

Is cardiac preload increased or decreased in obesity

A

Increased

215
Q

Is cardiac afterload increased or decreased in obesity

A

Can be either
Normotensive pts usually decreased, however prevalence of HTN is high due to chronic sympathetic activation which is attributed to chronic hypoxia of OSA

216
Q

What is the effect of obesity on LV contractility

A

Impaired
There is increased LV wall thickness and chamber volume.
LV diastolic function is often impaired Expanded volume = greater demand on myocardium = increased stress on LV wall = LVH

217
Q

Are RV preload and afterload increased or decreased in obesity

A

Increased leading to RV failure

218
Q

How much is cardiac output increased in obesity

A

0.1 L/kg of excess body fat

219
Q

What is the impact of obesity on total and relative blood volume

A

Total BV = Increased
Relative BV = Decreased (adipose tissue is poorly perfused)

220
Q

what is the EBV for an obese individual

A

45 ml/kg

221
Q

What factors contribute to the increased risk of thrombosis in obesity

A

Immobility
Polycythemia (increased red cell mass associated with chronic hypoxia leading to hyperviscosity)
Adipose tissue releases cytokines, chemokines, and hormones that promote pro-inflammatory state leading to CV disease)
High factor VIII
2 x greater risk of DVT

222
Q

What makes obese patients a high risk for aspiration

A

90% have gastric volume >0.35ml/kg and gastric pH <2.5 (mendelson’s criteria)
Delayed gastric emptying

223
Q

What are the diagnostic criteria for Metabolic Syndrome (Syndrome X)

A

Central obesity
Serum triglycerides >150 mg/dl
Reduced serum HDL
HTN (>135/85)
Elevated fasting serum glucose >110
*diagnosis requires 3/5

224
Q

What is the single major predictor of problematic intubation in morbidly obese patients

A

Neck circumference

225
Q

Is BMI an independent predictor of a difficult airway?

A

No

226
Q

What are the induction implications of a decreased FRC and increased o2 consumption in an obese patient

A

Desaturation in 1/2 the time of a non-obese adult during apnea

227
Q

What is the number 1 nerve injury related to bariatric surgery

A

Carpal tunnel

Followed by:
Ulnar
Brachial plexus
Radial
Peroneal
Sphenoid

228
Q

Which position is best for diaphragmatic excursion in an obsese pt

A

lateral decubitus

229
Q

Which position provides the longest safe apnea time during induction for an obese pt

A

Head-up (reverse Trend, Fowler’s)

230
Q

What are the benefits of HELP (head elevated laryngoscopy position)

A

Improves view
Increases safe apnea time
Better position for rescue ventilation techniques such as bag-valve mask ventilation or insertion of LMA

231
Q

What medications are first line for pain management in obese patients

A

NSAIDs

232
Q

How do local anesthetic requirements change when using regional on an obese patient

A

LA requirements can be up to 20% lower than non-obese for neuraxial blockade due to decreased volume of the epidural space from intra-abdominal pressure

233
Q

What is the fio2 goal to prevent atelectasis in an obese patient

A

fio2 <80% to prevent absorption atelectasis

234
Q

What are the benefits of recruitment maneuvers

A

improves FRC, V/Q matching, and arterial oxygen

235
Q

What is the only vent parameter shown to improve respiratory function in obese patients

A

PEEP

236
Q

What is the optimal PEEP setting for obese patients

A

Around 20 cmH2O

237
Q

How should vent settings be changed for obese patients

A

Still 6-8 ml/kg tidal volume (increasing TV can cause shear stress to lungs)
May need higher resp rate to maintain PaCO2
Increased PEEP

238
Q

What is the most sensitive indicator of post-gastric bypass anastomotic leak

A

tachycardia (hr >120 should prompt investigation)

239
Q

What is the most common cause of postop mortality after bariatric surgery

A

thromboembolism

Advanced Principles of Anesthesia (2 decks)

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