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931: Advanced Principles of Anesthesia I > Anesthesia considerations in the patient with obesity > Flashcards

Anesthesia considerations in the patient with obesity Flashcards

1
Q

Overweight is defined as

A

increased body weight above a standard related to height

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2
Q

Obesity is defined as

A

excessive body weight for the patient’s age, gender, & height” (body weight of 20% or more above ideal body weight)

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3
Q

In the US population,

A

68% are overweight

33% are obese

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4
Q

Describe the BMI calculations

A

weight (kg)/height ^2 (m)

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5
Q

Ideal body weight is the

A

weight associated with maximum life expectancy for a given height & gender
IBW is useful in calculating some drug doses to avoid toxicity or hemodynamic instability

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6
Q

Adjusted body weight takes into account

A

metabolically active tissue

ABW= 0.4 (ABW-IBW)+ IBW

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7
Q

Lean body mass is useful for

A

drug dosing in obese patients because it takes into account the muscle that are used to carry weight
it is 120% of IBW

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8
Q

Overweight is defined as BMI of

A

25-29 kg/m^2

approx. body weight 20% more than IBW

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9
Q

Obesity is defined as BMI of

A

> 30

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10
Q

Describe the classes of obesity

A

Class I: 30-34.9 BMI
Class II: 35-39.9 BMI
Class III: 40-49.9 BMI

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11
Q

Extreme obesity is defined as

A

BMI >50

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12
Q

BMI >30 (obese) is associated with increased

A

morbidity related to stroke, ischemic heart disease, HTN, and diabetes

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13
Q

Android obesity is

A

abdominal (central) obesity
- more common in men, higher incidence of metabolic disturbances, increased risk of ischemic heart disease, stroke, diabetes, death

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14
Q

Gynecoid obesity is

A

fat around hips & buttocks

more common in females

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15
Q

Associated disturbances with obesity include

A

OSA/hypoventilation syndrome, restrictive lung disease, HTN, CAD, HLD, GERD, DMII, gall bladder disease (cholelithiasis), cirrhosis/fatty liver disease, venous stasis/ thromboembolic disease, degenerative joint/disc disease, increased breast, prostrate, cervical, uterine, and colorectal cancer, psychological and socioeconomic impairment

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16
Q

Respiratory alterations in obesity include

A

chest wall and lung compliance reduced due to fat accumulation in thorax and abdomen
lung volume changes- reduced FRC, VC, TLC, & ERV

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17
Q

RV & CC are not changed but the relationship between FRC & CC is adversely affected leading to

A

increased metabolic demand, work of breathing, closure of small airways with VQ mismatch & resulting hypoxemia

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18
Q

Patients who are obese may have these spinal conditions that affect respiration.

A

thoracic kyphosis/lumbar lordosis

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19
Q

Patients who are obese have (pulm. blood volume, O2 consumption, & CO2 production)

A

increased pulmonary blood volume, increased O2 consumption and carbon dioxide production

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20
Q

PFTs in the obesity may remain normal until

A

the obesity worsens and you see lung disease & pulmonary HTN

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21
Q

Describe minute ventilation and work of breathing in the obese patient.

A

increased minute ventilation

increased work of breathing

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22
Q

Frequent episodes of apnea during sleep leads to

A 
chronic hypoxia, hypercapnia, pulmonary & systemic vasoconstriction (HTN)
snoring
sleep fragmentation/daytime somnolence
impaired concentration/memory problems
morning headache
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23
Q

Repeated episodes of apnea/hypoventilation lead to

A

oxygen desaturation, sympathetic arousal, awakening leading to fragmented sleep

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24
Q

Obstructive apnea is caused by

A

mechanical obstruction of upper airway, loss of respiratory drive or both

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25
Q

Risk factors for OSA include

A

middle age, male, obesity (BMI >30), ETOH use, drug induce sleep aids, abdominal fat distribution, neck girth (41 cm)

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26
Q

For the obese patient, respiratory changes are exaggerated with

A

operative positions- supine, trendelenburg, lateral, & prone

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27
Q

Rapid desaturation may be seen when anesthesia is induced in the

A

recumbent/supine position

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28
Q

Types of OSA include

A

OSA< central sleep apnea, & pickwickian Syndrome (most severe)

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29
Q

Describe Pickwickian syndrome

A

severe chronic OSA leading to cor pulmonale

related to morbid obesity

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30
Q

Describe central sleep apnea

A

cessation of both airflow & respiratory efforts

problem in ventilatory center of medulla–> d/t exposure to chronic hypercarbia

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31
Q

Describe obstructive sleep apnea.

A

cessation of airflow but maintain respiratory effort

abnormal relaxation of genioglossus & pharyngeal muscles will pull tongue forward

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32
Q

AHI index is

A

> 30 severe
16-30 moderate
15 or < mild

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33
Q

This test is needed for the diagnosis of obstructive sleep apnea

A

polysomnography

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34
Q

Hypoapnea is a

A

50% reduction in size or number of breaths that lasts at least 10 seconds compared to normal; or a reduction sufficient enough to cause a 4% or >decrease in arterial SaO2

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35
Q

Apnea is considered to be

A

> 10 seconds total cessation of airflow despite respiratory effort against a closed glottis

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36
Q

Corrective procedures for OSA include

A

uvulopalatopharyngoplasty (UPPP)- enlarges airway through removal tonsils, part of soft palate, uvula
diathermy palatoplasty- heat tissue producing scar which tightens in 6-8 weeks

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37
Q

OSA treatment includes

A

CPAP

-attenuates hemodynamic responses induced by apnea including BP surges and increased sympathetic nerve activity

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38
Q

CPAP may also include O2 therapy for those with

A

severe arterial oxygen desaturation

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39
Q

OSA results in

A

hypoxemia, RHF, hypercapnia, pulmonary & systemic vasoconstriction, polycythemia, respiratory acidosis during sleep, arterial hypoxemia, systemic hypertension, and pulmonary hypertension

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40
Q

Pickwickian syndrome or obesity hypoventilation syndrome is due to

A

extreme obesity with hypercapnia, hypoxia, cyanosis induced polycythemia, somnolence, and eventual RHF and pHTN

41
Q

Pickwickian syndrome is clinically distinct from OSA because

A

OSA–> nocturnal sleep disruption

OHS–> nocturnal central apneic events (apnea without respiratory effort)

42
Q

Pickwickian syndrome CO2 is

A

PCO2 >45 mmHg in an obese patient without significant COPD is diagnostic

43
Q

Pickwickian syndrome is characterized by:

A

obesity, hypercapnia, chronic daytime hypoxemia, hypersomnolence, pHTN, respiratory acidosis, RHF, & airway difficulty

44
Q

Airway changes in obesity include

A

TMJ & atlanto-axial joint & cervical spine movement limited by upper thoracic and low cervical fat pads

45
Q

Patients who are obese have redundant tissue folds in the

A

mouth & pharynx leading to a narrowed upper airway

46
Q

As neck circumference increases, the incidence of

A

difficult intubation increases

47
Q

OSA increases the risk of

A

excess pharyngeal tissue on lateral walls

48
Q

Obesity creates difficulty maintaining

A

mask airway, laryngoscopy, and intubation

49
Q

CV alterations in obesity include

A

increased total blood volume
increased CO- expanded blood volume puts strain on myocardium
increased RAAS & SNS activity (increased risk for HTN)
risk of CAD is double and presents with angina, CHF, acute MI and sudden death
increased left sided heart pressures and left ventricular hypertrophy

50
Q

Patients who are obese must undergo (CV related)

A

ECG to identify left or right ventricular hypertrophy, ischemia, and conduction defects

51
Q

Eventually LV wall thickening fails to keep pace with ventricular dilation and systolic function

A

or obesity cardiomyopathy

results with eventual biventricular failure

52
Q

Hematologic alterations in obesity include

A

polycythemia & hypercoagulation leading to thromboembolic risk

53
Q

Thromboembolic risk in the obese patients casues

A

risk of DVT to double
polycythemia leads to increased blood viscosity
increased intra-abdominal pressure
immobility leads to venostasis

54
Q

There is an increased incidence of these GI alterations in obesity:

A

hiatal hernia, GERD, gallbladder disease, & high risk for aspiration pneumonitis

55
Q

Obesity in itself does not increase the risk of

A

aspiration; it is by virtue of being prone to other diseases

56
Q

Hepatic alterations in the obese patient include

A

fatty infiltration of the liver- inflammation, cirrhosis, focal necrosis, high prevalence of NAFLD
abnormal LFTS

57
Q

Renal alterations in the obese patient include

A

increased renal plasma flow & increased GFR
increased renal tubular resporption & impaired naturesis secondary to SNS & RAAS activation
eventually nephron function can be lost

58
Q

Obese patients secrete more

A

insulin but resistant to the effects of insulin

-develop type 2 diabetes

59
Q

Metabolic syndrome is the presence of at least three of the following signs

A

large waist circumference (central obesity), high triglyceride levels, low HDL levels, glucose intolerance, and hypertension

60
Q

Musculoskeletal changes in obesity include

A

OA & degenerative joint disease- mechanical loading of weight bearing joints, inflammatory response, back pain, stress fractures (bone demineralization)

61
Q

CNS changes in obesity include

A

ANS dysfunction, peripheral neuropathies, stroke, idiopathic intracranial HTN

62
Q

Increased LDL and decreased HDL cholesterol is linked to

A

atherosclerosis

63
Q

Hyperlipidemia can lead to

A

premature coronary artery disease, premature vascular disease, pancreatitis

64
Q

Pharmacokinetics in the obese patient include

A

increased blood volume & CO, decreased total body water, adipose and lean tissue increase, variable alterations in protein binding, organomegaly

65
Q

Clearance changes in the obese patient due to

A

-hepatic clearance unchanged despite histological and LFT alterations
renal clearance of drugs increased (GFR, RBF, & tubular secretion)
liphophilic drugs have an increased elimination half-life because of increased Vd but have normal clearance

66
Q

Dosing for weak or moderate liphophilic drugs should be dose on

A

IBW or LBM

67
Q

Describe the dosing of propofol for obese patients.

A

induction- LBW

maintenance- TBW

68
Q

Describe the dosing of benzodiazepines for obese patients.

A

highly liphophilic
initial dose LBW- may titrate to TBW
infusions LBW

69
Q

Describe NMBD dosages in obese patients.

A

pseudocholinesterase activity increases as weight and ECF increase- dose succinylcholine on TBW
-Vec, roc, atricurium, & ciastricurium based on LBW
exhibit prolonged DOA & recovery

70
Q

Describe opioid dosages in obese patients.

A

fentanyl & sufentanil are highly lipid soluble so increased Vd & elimination half life- dose fentanyl on LBW (Miller says TBW) may need to dose sufentanil on TBW but then decrease maintenance to LBM

71
Q

Describe remifentanil dosages in obese patients.

A

dosing based on LBW

72
Q

Describe dexmedetomidine dosages in obese patients.

A

nice adjunct to consider when respiratory depression avoidance is priority
dose on TBW 0.2-0.7 mcg/kg/hr

73
Q

Describe volatile anesthetics in obese patients.

A

metabolism is greater in obese patients= greater increase in inorganic fluoride
greater incidence of halothane hepatitis
N2O often avoided to maximize PaO2

74
Q

Describe medications that can be used to treat obesity.

A

lipase inhibitors & SSRIs/sympathomimetics

75
Q

Describe the MOA of lipase inhibitors (arlistat)

A

acts by blocking absorption and digestion of dietary fat & binding lipases in GI tract

76
Q

Describe the use of SSRIs/sympathomimetics.

A

appetite suppressants- unacceptable side effects (primary pHTN & valvular heart disease)
phentermine is currently approved but can only be used for <3 months d/t side effects

77
Q

Describe the obesity preop evaluation.

A

be non-judgmental
emphasis should be on the difficulties obesity presents to the anesthesia provider
discuss the likely post-operative course

78
Q

Morbid obesity is an independent risk factor for sudden death from

A

acute PE

79
Q

Thromboprophylaxis for the obese patient includes

A

LMWH, heparin, & pneumatic compression stockings

80
Q

Pulmonary HTN signs include

A

dyspnea, fatigue, syncope, tricuspid regurgitation on echo, ECG (RVH, tall precordial R waves, right axis deviation), prominent pulmonary artery on CXR

81
Q

Preop considerations of the obese patient include high incidence of

A

HTN, pHTN, right/left ventricular failure, & CAD

82
Q

Excess adipose tissue may hide signs of

A

cardiac failure

83
Q

Airway preop for the obese patient includes

A 
does patient have a history of previous difficult airway
obstructive sleep apnea
assess ROM of cervical spine
mouth opening
TM distance
interior of the mouth
mallampati classification 
Neck size is the single best predictor of problematic intubation
84
Q

Symptoms of severe respiratory disease include

A

orthopnea, sleep apnea, obesity hypoventilation syndrome, & previous history of upper airway obstruction especially regarding a past anesthetic

85
Q

What does STOPBANG stand for?

A

snoring, tired, observed, high BP, BMI, age, neck size, gender

86
Q

Respiratory pre-op labs that may be indicated include

A

chest XR, room air SaO2, ABGs, optimize pulmonary status pre-op, PFTs

87
Q

Signs of HTN, RV/LV hypertrophy and pHTN should be assessed by

A

assess venous access, EKG, chest XR, ECHO, LV ejection fraction, cardiac clearance if needed, previous diet aids

88
Q

Describe the endocrine, metabolic and GI preop concerns for the obese patient.

A

fasting blood sugar, diabetes, does the patient have a history of reflux

89
Q

Additional pre-op labs for the obese patient include

A

LFTs, albumin level, glucose, consider clotting studies (if risk factors present)

90
Q

Aspiration prophylaxis includes

A

great risk to morbidly obese patients, pre-operative anxiety

treatment includes: H2 receptor antagonists, bicitra, metoclopramide, omeprazole

91
Q

For laryngoscopy of the obese patients, it is important to

A

have head elevation, ramping, and ear to sternal notch

92
Q

General anesthesia for the obese patient recommendations include:

A

higher doses of Sux
des, sevo, iso are useful
avoid nitrous due to O2 demands
short-acting opioids to minimize respiratory depression
dexmedetomidine- no adverse effects on respiration
profound muscle relaxation needed for laparoscopy

93
Q

The number one problem for emergence of the obese patient is

A

respiratory failure

94
Q

Emergence of the obese patient includes

A

extubation after fully awake & reversed
semi-upright position (>30 degrees head up)
wean on pressure-support ventilation w/ PEEP
oxygen 100%
placement of nasopharyngeal airway

95
Q

Ventilatory support postop may include

A

CPAP, BiPAP, mechanical ventilation, & respiratory monitoring

96
Q

Fluid management for the obese patient should be calculated on

A

lean body weight or IBW

there is greater blood loss compared to non-obese r/t technical difficulties /extensive surgical dissection

97
Q

Describe the mechanical ventilation for the obese patient

A

PEEP can improve FRC and arterial oxygenation- watch BP
recruitment maneuvers to improve oxygenation
pressure-controlled ventilation may help
changing I:E ratio

98
Q

Postop analgesia includes

A

opioids based on IBW
local infiltration of wound
peripheral nerve blocks
multimodal approach is recommended because opioid-induced ventilatory depression is a concern

931: Advanced Principles of Anesthesia I (22 decks)

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