Obesity and Anesthesia Flashcards
What is the 2nd leading preventable cause of death in US
Obesity
Mortality is _____ related to weight gain
Linearly
Risk of morbidity and mortality ____ with increases in BMI
increases
BMI
Calculated by:
Body Mass Index (adiposity normalized for height)
Kg/m^2
(Reminder 100 cm = 1 m)
BMI Classifications
(all of them)
Underweight <18.5
Normal 18.5 - 24.9
Overweight 25 - 29.9
Obese 30 - 34.9
Severely Obese 35 - 39.9
Extremely Obese >= 40
Super Obese >= 50
Patients with _____ or/AKA _____ obesity have increased perioperative risk + disease of HTN/DM
visceral or/AKA truncal
Ideal Body Weight (IBW)
What is it?
Measure of height and body mass exhibiting lowest M&M
How do we calculate IBW for men and women?
MEN: Height (cm) - 100
WOMEN: Height (cm) - 105
Lean Body Weight calculation
IBW (x) 1.3
Lean body weight is increased ~30% in obese patients to allow for increased muscle mass to carry the weight
____ ____ ____ is useful in drug calculation and IV dosing in morbidly obese patients
Ideal body weight
If administered according to actual body weight we could see toxicity, renal damage, hemodynamic instability
T/F: No drugs are ever given based on actual body weight
FALSE
Some drugs must be given according to actual weight to achieve effect
Obesity is associated with increased incidence of what conditions?
long list
Type 2 DM, coronary heart disease, HTN, HLD, cerebrovascular disease, CHF, pulmonary HTN, sleep apnea
and many many more
Adipose tissue is an example of a(n) _____ organ.
Endocrine
-reservoir of energy
-maintain heat insulation
Childhood obesity results from what?
Increased # of fat cells
Adult onset obesity results from what?
Hypertrophy of already existing fat cells
Apple (android) or Pear (Gynecoid) body fat distribution is associated with higher risks?
Apple (android)
aka visceral, central, abdominal - all the same
_____ is the established marker for abdominal obesity
Waist circumference
A waist circumference of > than _____ in men or _____ in women have higher risks of heart dx, DM, HTN, HLD, death.
MEN: >102 cm (40 in)
WOMEN: >88 cm (35 in)
What is the biggest anesthesia risk for our apple/android/central/abdominal (all same) body fat patients?
Difficult airway + intubation
Pear / gynecoid / peripheral (all same) body fat is associated with?
Varicose veins, joint disease, reduced rate of non-insulin-dependent diabetes
**LOWER risk
Body size is dependent on ____ and ____ factors
Genetic and environmental
Respiratory function is compromised to ____% of predicted values in obese patients
35%
From compression of abdomen, diaphragm, thoracic structures. Causes rapid and shallow breathing (restrictive lung dx).
*FRC, ERV, TLC, FRC all decline with increases in BMI. WILL NOT TOLERATE APNEIC PERIOD
Premature airway closure causes
Increased dead space, CO2 retention, ventilation-perfusion mismatch, shunting, hypoxemia
T/F: Obese patients are predisposed to respiratory failure.
TRUE: bolded point
Mild pulmonary or systemic insults can send these patients over the edge
Risk of getting OSA:
upper airway collapse leading to 10 sec breathing cessation
STOP BANG
>50, male, obese, fat neck, drinker or smoker, big tongue, craniofacial abnormalities
Risks associated from having OSA:
Increased CAD, HTN, CHF, CVA
Anesthesia risks of OSA:
USE YOUR STOP BANG PRE-OP TO BE PREPARED
Difficult airways, increased sensitivity to anesthesia, increased postop complications
OSA is officially diagnosed by:
Polysomnography (PSG) using an apnea-hypopnea index
AHI: 5-15 is mild
AHI: 15-30 moderate
AHI: >30 severe
Perioperative management of OSA:
- Use PAP - reduction in cardiovascular M&M in severe OSA patients
- Regional anesthesia or combined techniques to limit opioids
- Short acting drugs
- Monitoring appropriate postop
Obesity Hypoventilation Syndrome is characterized by:
aka Pickwickian Syndrome (4-20% of OSA patients)
BMI >30, OSA, awake hypercapnia, daytime hypersomnolence, arterial hypoxemia (PaO2 <70), cyanosis-induced polycythemia, respiratory acidosis, pulmonary hypertension, and right-sided heart failure
_____ disease is primary cause of M&M with obesity. It manifests as ____, ____, and ____.
CV disease
ischemic heart disease, hypertension, HF
CO is increased by ____ for each kg of fat acquired
0.1L/min
HR remains the same, so it has to be through SV increases.
_____ is often seen alongside HTN in obese pts and predisposes them to atherosclerosis and/or CVA.
Hypercholesterolemia
*HTN >2x as likely to be seen in obese pts compared to lean pts
____ is more common in obese individuals with central android fat distribution.
Ischemic Heart Disease
Look at cardiopulmonary sequelae pic/slide
In summary:
-obesity (OSA/OHS) –> hypercapnia/hypoxia –> pulm HTN –> RV failure
PLUS
-Obesity –> increased CO –> increased LV workload –> LV hypertrophy –> LV failure
PLUS
-Possible HTN and/or HF
-Final result = biventricular failure
Obese patients are at high risk of what GI issue pertinent to anesthesia?
Aspiration
Increased gastric residuals + reflux + increased abdominal pressure
Obese patients are at high risk of what GI issue pertinent to anesthesia?
Aspiration
Increased gastric residuals + reflux + increased abdominal pressure
NASH (aka fatty liver) is present in up to 90% of obese patients. This means what for us?
Altered liver function, altered drug metabolism
What is metabolic syndrome?
truncal obesity, HTN, insulin resistance, dyslipidemia
-Increased CV disease and DM
-Increased postop complications
Because of higher concentrations of _____ in bile we will commonly see obese patients for a cholecystetomy.
increased cholesterol concentrations
Obese pts have higher incidence of ____ due to mechanical stress of weight bearing joints
osteoarthritis
-linear relationship between weight and degree of arthritis
Pediatric obesity defined as:
Weight-for-height > 90th percentile
OR
BMI >/= 95th percentile specific to age and gender
Obese adolescents have a ___-___% chance of being obese adults
70-80%
-higher rates of premature death/disability
T/F: Neonatal outcomes are worse when the mom is obese as compared to normal BMI mom.
FALSE. There is no difference in neonatal outcomes
-mom higher risk of preeclampsia, PIH, infection, c-section, and more
T/F: Mom is at higher risk of postpartum hemorrhage if obese.
FALSE. There is no increased risk of postpartum hemorrhage
-Likely a c-section (40%), difficult epidural placement, difficult airway, higher infection, higher VTE risk, larger procedural blood loss
Non-surgical options for obese patients:
-Weight loss programs to lower DM/CV risks
-Lifestyle changes and education
-Drug therapy if BMI >30 or between 27-29.9 and pre-existing dx
Pharmacotherapy options for obese patients:
2 meds
- Orlistat: lipase inhibitor
*Check co-ags, vitamin K deficient - Phentermine: sympathomimetic significant refractory hypotension with anesthesia! so we hold 7-14 days before surgery
4 most common bariatric procedures:
- Roux-en-Y gastric bypass
*Most common - Lap adjustable gastric bypass
*No permanent change in anatomy - Lap sleeve gastrectomy
- Biliopancreatic diversion with duodenal switch
____ is the gold standard for surgical obesity management.
Laparoscopy
-Decreased surgical times and decreased M&M
Bariatric surgery indications:
-BMI >40 (>35 with medical comorbidity worse w obesity)
-Failed dietary therapy
-Psych stable
-Motivated and educated on procedure
What tests should be considered routine before bariatric surgery?
EKG and blood sugar
-Due to high risk and incidence of cardiovascular dx and diabetes
____ is considered an appropriate position for airway management in the obese pt.
Reverse trendelenburg
-Pt comfort, reduced reflux, easier masking, maintains FRC
Adequate _____ is a vital step in the induction sequence in the obese population
Preoxygenation (full 3-5 mins with positive pressure if tolerated)
-These pts will desaturate quickly. Remember that this also effects them on extubation.
Rather than our favorite “sniffing” position, we will have the greatest success in the _____ position in obese patients.
“ramped” position
-Patient should be optimally positioned for laryngoscopy PRIOR to anesthesia induction
A LBBB is found on your preoperative EKG. What does this mean in our obese pt?
This is not normal, an echo is probably a good idea here
A RBBB is found on your preoperative EKG. What does this mean in our obese pt?
Can be normal in our obese pt
-Symptomatic of possible right heart failure
Due to increased HTN causing HF incidence in the obese pt, a ____ at minimum should be done preoperatively.
EKG, possibly echo
T/F: All obese pts undergoing surgery should receive a prophylactic anticoagulant dose.
TRUE.
-Due to increased VTE risk
-Pts with BMI >50 need an increased dose
Takeaway point
bolded info for our knowledge
Increased BMI = increased comorbidities = increased risk
What are some specific anesthesia related concerns with the obese pt that we can do something about?
-Proper planning with appropriate tables
-Proper sized monitoring devices OR plan for invasive
-Proper positioning for likely difficult airway (Plan A/B/C)
-GI prophylaxis!!! High aspiration risk
-Extensive postoperative monitoring
Pharmacokinetic Changes in obesity
INCREASES: Increased fat mass, increased CO, increased BV, increased lean body weight, increased renal clearance, increased volume of distribution for lipid-soluble drugs
DECREASES: reduced total body water, decreased pulmonary function
OTHER: changes in plasma protein binding, abnormal liver function
Repetitive, but very preventable problem in obese with positioning specifically
Appropriate table size to support extra weight!!
Water-soluble drugs are dosed according to what?
Ideal Body Weight, but with 30% adjustment if obese pt (Lean Body Weight)
MEN: Height (cm) - 100
WOMEN: Height (cm) - 105
LBW: IBW (x) 1.3
Lipid-soluble drugs are dosed according to what?
Total Body Weight
____ and ____ inhalation agents have shown better recovery profiles in obese patients
Desflurane and Sevoflurane
T/F: Nitrous oxide cannot be used in the obese population.
FALSE. It is increasingly being used in extremely obese patients and may even have a analgesic effect for postoperative pain.
If a NMB is used in the obese patient, what is crucial at the end of the procedure?
Full reversal and recovery
-Especially important in these patients due to their difficult airways and high postoperative complications
The most effective pain treatment for obese patients
Multimodal
-Reduces complications. Limit opioids
Propofol dosing
Induction based on:
Maintenance based on:
Induction: Lean body weight
Maintenance: Total body weight
-due to cardiac depression in huge doses
Succinylcholine dosing
Intubation dose based on:
Total body weight
-This ensures adequate paralysis
Rocuronium/Vecuronium/Cisatracurium dosing
All dosing based on:
Ideal Body Weight
-Hydrophilic drugs given according to IBW will ensure shorter duration and a more predictable recovery in this respiratory-challenged population
Fentanyl/Sufentanil dosing
Loading dose based on:
Maintenance dose based on:
Loading dose: Total body weight
Maintenance: Lean body weight + response
-Elimination times correlate with degrees of obesity
Remifentanil dosing
Infusion dose based on:
Ideal body weight
-Distribution volumes and elimination rates are similar to normal-sized individuals; fast offset requires planning for postoperative analgesia
Dexmedetomidine dosing
Infusion rate
Constant 0.2mcg/kg per min
Sugammadex dosing
Reversal dose based on:
Total body weight
Fluid management of the obese patient:
-The same as with a normal weight patient
-Same for blood products also
Ventilation Technique of obese patient:
-Lung protective strategy (6-8 mL/kg)
_____ is the only parameter shown to improve respiratory function in the obese patient.
PEEP
-Alveolar recruitment maneuvers can be beneficial
Waking up the obese patient:
-Full reversal in presence of NMB
-Extubate AWAKE with head elevated
Your case has finished and you don’t feel great about your obese pt’s breathing. What do we do?
Leave em intubated
What position is most likely going to be best for neuraxial in the obese patient?
Sitting upright
-Skin falls down and improves visibility of landmarks
Issues/Concerns with neuraxial in obese pt?
-Catheters may migrate due to excess fat tissue
-Lack of predictability of the LA spread –> be careful with high doses due to already high risk of respiratory complications
In a perfect world, a BMI of ____ would not be seen at an ambulatory surgery center.
> /= 50
