III. Obesity Flashcards
Excess body fat associated diseases picture
BMI equation
most commonly used quantifier of obesity
BMI
BMI does/does not measure adipose tissue directly.
does NOT
Distribution of body fat more important
Overweight BMI
25.0-29.9
Obesity (class I) BMI
30.0-34.9
Obesity (Class II) BMI
35.0-39.9
Morbid Obesity (Class III)
> 40
BMI Table Picture
Android obesity, characterized by truncal distribution of fat, is more common in what gender?
Male
Android vs Gynecoid:
associated with increase in oxygen consumption andn an increased incidence of CVD
Android
Gynecoid obesity more common in male/female
female
Gynecoid vs android obesity:
adipose distribution in hips, buttocks, thighs
gynecoid
intra-abdominal fat is particularly associated with ____ and ____.
CV risk, LVD
Obesity has a ____ pattern of ventilation
extrinsic restrictive
obesity changes in ventilation:
FRC:
ERV:
TLC:
Chest wall compliance:
Lung Compliance:
Airway resistance:
Closing Capacity:
FRC: ↓
ERV:↓
TLC:↓
Chest wall compliance: ↓
Lung Compliance: ↓
Airway resistance: ↑
Closing Capacity: ↑
____ becomes greater than FRC, resulting in atelectasis with normal tidal breathing
Closing Capacity
Obesity causes what type of V/Q mismatch?
R→L = arterial hypoxemia
Many obese patients have clinically significant ____.
OSA
Apnea is defined as ____ of total cessation of airflow despite continuous respiratory effort
10 seconds or more
OSA can lead to ____ syndrome.
Pickwickian Syndrome (OHS)
Pickwickian Syndrome is characterized by what daytime PaCO2 level?
> 45 mmHg
Chronic Pickwickian Syndrome can lead to:
- Pulmonary HTN Cor Pulmonale
- RV Failure (2/2 Pulmonary HTN)
What disease is a major cause of M&M in obese patients?
CVD
Obese patients suffer from systemic HTN 2/2 ____
hyperinsulinemia
Obese patients are at risk for CAD, especially those with ____ syndrome.
Metabolic
Metabolic syndrome includes high blood pressure, high blood sugar, too much body fat around the waist and irregular cholesterol levels.
Obese patients with CVD may also develop what other heart condition?
CHF
____ and ____ increase to perfuse additional fat stores
CO
blood volume
Obese patients may undergo LV Remodeling, which is characterized by:
Increased SV
Increased Cardiac Workload
Ventricular dilitation
Increased LV Wall stress leads to (5 things):
- LVH (2/2 systemic HTN)
- Reduced compliance
- Impaired LV filling
- Obesity cardiomyopathy
- Biventricular Failure (eventually)
Obesity CV Effects Picture
Obesity CV Effect Flowchart Picture
Obesity accelerates ____.
atherosclerosis
Obese patients that have systemic hypertension usually develop what cardiomyopathy?
LVH
Obese patients are at increased risk for hypercoagulability and therefore at risk of ____
VTE
obese patients should receive thromboembolism prophylaxis perioperatively (heparin)
____ is a mojor independent risk factor for sudden death from PE postoperatively.
MO (morbid obesity)
ABDOMINAL or PELVIC surgery increases risk moreso
Obesity: Aspiration Risk
co-existing issues that increase risk for HH, GERD, & Delayed Gastric Emptying are:
- Gastroparesis 2/2 DM2 (& weight loss Rx)
- non-fasting state
- difficult airway (risk of gastric insufflation)
- Trauma (non-fasting state)
- Pain Meds (osteoarthritis)
opioids will delay gastric emptying
Obesity: Effects on GI System
Gatric volume & acidity are decreased/increased.
increased
Obesity: Effects on GI System
Most fasted morbidly obese patients presenting for elective surgery have gastric volumes ____ and gastric fluid pH ____
> 25 mL
< 2.5
(generally accepted values that increase risk for pneumonitis 2/2 regurgitation and aspiration)
Obesity: Effects on GI System
no studies have documented increased incidence of aspiration related to ____ (Aspiration risk is multifactorial)
BMI
Obesity: Effects on GI System
Obese patients often exhibit delayed gastric emptying, larger ____ & ____.
- larger gastric volumes
- larger residual volumes
Obesity: Effects on GI System
____ & ____ are often seen in obese patients
Hiatal Hernia
GERD
Obesity: Effects on GI System
what organ function is often altered inn obese patients
hepatic
Especially if they have CHF = ↓Hepatic Blood Flow
Obesity: Diabetes
High risk for DM 2 = insulin ____
resistance
Obesity: Diabetes
Increased adipose tissue = Increased resistance of peripheral tissuses to ____ = ____ intolerance
- insulin
- glucose
Obesity: Diabetes
Increased stress during surgery will lead to hyperglycemia which may precipitate treatment with ____
exogenous insulin
challenging to dose, because we dont always know how patients will respond
Obesity: Diabetes
predisposed to ____
wound infection
Obesity: Diabetes
Increased risk ____ during periods of myocardial ischemia
acute myocardial infarction (AMI)
Obesity: Diabetes
Increased risk of ____ during periods of hypoxemia (with hyperglycemia)
cerebral ischemia
Obesity: Endocrine
Metabolic Syndrome has at least 3 of the following:
- Excess central obesity
- Atherogenic dyslipidemia
- HTN
- Dysglycemia
Obesity: Endocrine
Metabolic syndrome patients are at increased risk for:
- Increased risk of MI, Stroke and DM 2
- Higher incidence of adverse periop outcomes
Infection, atelectasis, postop ventilation
Obesity: Endocrine
Hypothyroid occurs in ____% of MO patients
25%
Obesity: Endocrine
Volume of Distribution (VD) in Obese patients is affected by:
- Decreased total body water
- Increased total body fat
- Decreased lean body mass
- Increased blood volume and CO
- Altered protein binding
- Altered lipid solubility
Obesity: Endocrine
Volume of Distribution is taken into account for ____ dosing
loading/induction
Obesity: Effects on Drug Elimination
Hepatic clearance is not usually affected, unless:
- significant fatty infiltration
- CHF (↓HBF = ↓Clearance)
Obesity: Effects on Drug Elimination
Renal clearance of drugs is increased in obesity. Why?
because of increased renal blood flow and glomerular filtration rate (due to ↑CO and ↑Preload)
Obesity: Effects on Drug Elimination
Clearance is considered for ____ dosing.
maintenance
weight
what weight you get when you weigh yourself
total body weight
lean body weight
TBW - ____
fat weight
generally need % body fat for calculation (sex, weight, height needed)
Ideal body weight is based on ____ and ____.
sex and height
IBW formula
IBW = 50kg + 2.3kg for each inch over 5 feet
obesity
highly lipophilic drugs (propofol, benzos, opioids) have a/an ____ volume of distribution
increased
obesity
highly lipophilic drugs are dosed based on ____
TBW
for normal patient, not obese?
obesity
less lipophilic drugs have what type of change on volume of distribution?
little to no change
obesity
less lipophilic drugs are dosed based on ____
Ideal or Lean body weight
Increased blood volumes in obese patients ____ plasma concentrations of rapidly injected IV drugs
decreases
Fat has poor blood flow and doses calculated on TBW could lead to ____.
excessive plasma concentrations
Subsequent dosing is based on ____
response to first dose
What consideration should be made when using succinylcholine with obese patients?
obese patients have a higher level of plasma cholinesterase and a greater volume of distribution
what method should be used when dosing succinylcholine in obese patients?
use TBW
morbidly obese patients will get the whole 200mg stick of succs (must avoid underdosing)
What two major systems should be focused on during a preoperative evaluation for an obese patient?
- cardiopulmonary system
- Airway
obese pt
What vitals & Labs should be reviewed?
BP, Glucose, HbA1c, GFR, ECG, ABG, TTE
obese
What are signs of cardiac failure that can be observed in preop
- Elevated jugular venous pressure
- Pulmonary Crackles
- Peripheral Edema
obese pt
Assume ____ HTN
pulmonary
obese pt
General anesthetic plan considerations
- Difficult IV
- A-Line
- Positioning
- BP cuff (large arms?/tucking)
- Consider regional/local/peripheral nerve blocks
- Minimize respiratory depression (post op opioids)
Anatomic changes that make difficult airways:
- Limited joint/cervical mobility (cervical fat pads)
- Redundant tissue in mouth, posterior pharynx
- Short thick neck
- shortened distance between mandible and sternal fat pad, enlarged breasts
- very thick submental fat pad
*OSA also predisposes to difficult airway.
single biggest predictor of problematic intubation:
neck circumference
40 cm neck circumference = ____% probability of problematic intubation
5%
60 cm neck circumference = ____% problematic intubation
35%
larger neck circumference is associated with:
- male sex
- higher mallampati
- Grade 3 views at laryngoscopy
- OSA
Obesity: Monitoring
____ should be brought from home (used on the floor, not so much in recovery)
CPAP devices
Obesity: BP Monitoring
- falsely ____ if too small
- forearm measurements will under/over estimate sys/dys BP
- high
- over
obese pt
what BP monitoring devices should be considered?
Clear site or Flo Track
Obesity: Pre-Op Meds
what type of prophylaxis medication should be considered?
- DVT Prophylaxis (SCDs, LMW Heparin)
- H2 Antagonists
- Non-Particulate Antacids
- PPIs
sequential compression device (SCD)
obesity:
intra-op considerations
- low threshold for intubation (2/2 to increased risk aspiration, hypoventilation, bad A/W)
- Video DL or FO
- PPV: may require increased FiO2, especially lithotomy, prone, T-burg
- Increased minute ventilation to lower EtCO2 prior to insufflation and T-burg
What positions may require increased FiO2?
- Lithotomy
- Prone
- T-burg
What are two instances where we would increase MV ahead of time IOT decreased EtCO2?
- prior to insufflation
- prior to T-burg
Hypercarbia will exacerbate pre-existing ____.
P. HTN
What are two physiologic reasons that obese patients may rapidly desaturate during induction of anesthesia?
- increased oxygen consumption
- Decreased FRC
____ during preoxygenation decreases atelectasis formation and improves oxygenation.
PPV
What position provides the longest safe apnea period during induction of anesthesia?
Reverse T-Burg
what other adjuncts may be used to optimize patient airway
Troop elevation pillow/ stacking pillows/ blankets
External auditory meatus should be in line with ____.
sternal notch
increase the angle between the chin and ____
sternum
angle of Dr. Martin
complications from supine position:
- ventilatory impairment
- inferior vena cava & aortic compression
Trendelenburg further worsens ____ and should be avoided
FRC
also decreased chest wall compliance
Reverse T-burg increases ____, which results in lower airway pressures (most favorable).
compliance
Complications with prone position:
- decrease lung & chest wall compliance, ventilation, & arterial oxygenation
- Increased intra-abdominal pressure worsens IVC and Aortic compression, further decreases FRC
Factors making controlled ventilation problematic
- Decreased pulmonary O2 reserves = desaturation
(2/2 Decreased FRC, increased O2 consumption) - Trendelenburg or Prone = Decrease chest wall compliance
- Insufflation = Increased intraabdominal pressure, worsens lung compliance
Why do obese patients desaturate quickly?
- Decrease FRC
- Increased oxygen consumption
the only ventilatory parameter that has consistently been shown to improve respiratory function in obese patients
Improves
PEEP
What are the benefits of PEEP?
- Improves FRC,V/Q matching and O2 sat
- Increases PIP’s, PAWP’s
Potential complication of PEEP
May reduce venous return and cardiac output
What may occur after insufflation with T-burg?
- Ventilation may be impeded
- PAWP, EtCO2 increasing,
- TV decreasing
- EtCO2: hypercarbia, respiratory acidosis, worsen pulmonary HTN
What to do IOT manage obese patients undergoing insufflation in T-burg?
- 7.5-8.0 ETT, cuff up (larger tube better)
- Hyperventilate after intubation - VERY IMPORTANT
- Increase I/E: if not a risk for auto PEEP, can limit increased PAWP (1:2 to 1:1)
- Recruitment maneuvers to prevent atelectasis
- Using pressure-controlled ventilation
- increase FiO2 (100%)
- Monitor the bellows (should be very smooth up/down)
Increasing the I:E ratio should be used with caution if patient has:
COPD (Emphysema, Chronic Bronchitis)
High-risk for Auto PEEP
These patients benefit from increasing EXPIRATORY phase, so they do not air trap (Auto PEEP can cause decreased venous return, extreme HoTN)
obesity: insufflation & T-burg
biphasic cardiovascular response
as intraabdominal pressure increases:
-10mmHg: ↑ venous return, CO, BP
-20mmHg:
↓venous return (LE), ↑renal vascular resistance (2/2
backup), ↓RBF, ↓GFR
**Aortic Compression: ↑SVR, LV wall stress, ↑myocardial O2
demand (therefore consider decreasing afterload)
**IVC compression* and see decreased preload & HoTN (Tx:
Milrinone?)
How to treat HTN 2/2 to T-burg and insufflation:
- start with increasing VA
- Systemic VD (Hydralazine, SNP, CCB)
In T-burg there is decreased femoral blood flow which puts patients at increased risk of ____.
DVT
P
Major post-operative concern:
Respiratory Failure
Postoperatively, obese patients are at increased risk of ____.
hypoxia
especially when hypoxia present preop
Safest way to extubate obese patients:
- Sitting upright
- awake
- Full NMB reversal
- Supplemental O2
- CPAP or BiPAP
Best method of analgesia:
multimodal (avoid opioids)
reason patients come in with low sats (92%)
baseline atelectasis
(will likely worsen perioperatively)
only way to treat low baseline sats?
incentive spirometer to try and re-expand airways
OSA picture
OSA is an independent risk factor for:
HTN
Cardiovascular morbidity and mortality
Sudden death
OSA: Greater risk for both ____ and postoperative airway ____ & ____.
- difficult mask ventilation/intubation
- obstruction
- hypoventilation
OSA patients may exhibt the following chronic complications:
o1. hypercapnia
2. cyanosis-induced polycythemia
3. Right HF
4. Somnolence
5. Blunted Respiratory Drive
6. A/W obstruction
7. Apnea
OSA causes what perioperative complications:
- HTN
- Hypoxia
- Arrythmias
- MI
- Pulm Edema
- Stroke
- Death
During Postop period, OSA patients are vulnerable, especially with ____
sedation
(supine patients may obstruct)
STOP BANG
- snore loudly
- Tired
- Observed stop breathing during sleep
- Pressure (high blood pressure)
- BMI > 35
- Age >50
- Neck >40 cm (15.7”)
- Gender (male)
0-2 = low risk
3-4 = intermediate risk
≥5 = high risk
3+ = Positive
AHI (Apnea-Hypopnea Index) scoring:
Combined average number apnea, hypopnea episodes occurring per hour of sleep
5-15: mild
15-30: moderate
>30: severe
What secondary variable does AHI look at to evaluate OSA severity?
O2 Saturation (“nadir”)
<90% = moderate
>80% = severe
Severe OSA, BMI’s > 45-50 = No/Yes to ASC
NO
patient with OSA unable to stay awake on PACU, RN must place O/A and jaw thrust to keep O2 Sats>90%. What is occuring physiologically?
- severe respiratory acidosis
- CO2 narcosis
- potential electrolyte imbalance (Potassium?)
- needs to be reintubated
STOP BANG questionnaire sensitivity increases with ____
increasing AHI Severity
5-15 = 83%
15-30 = 93%
>30 = 100%
Obese Patient Ramping Picture
Recommended Weights for Dosing of Common Anesthetic Drugs in Obese Picture
