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Principles 2 Test 2
Anesthesia for the Obese Patient / Bariatric Surgery
Question | Answer |
---|---|
What is obesity and what is the most common way to measure it? | abnormally high percentage of body fat, usually measured with BMI |
What percentage of Americans are overweight or obese? | 65% |
What percentage of adults are obese? | 30% |
Other than BMI, what are some indicators for obesity? | waist circumference (WC), waist height ratio (WHR), waist stature ratio (WSR) |
Obese patients have increased incidence of which health issues? | depression, OSA, gall bladder disease, reflux, cancer |
Obesity is an independent risk factor for which 2 heart related health issues? | ischemic heart disease and heart failure |
What are 5 obesity related diseases? | HTN, DM type 2, CAD, stroke, malignant tumors |
1 kg per year weight gain over 10 years..... | is an increased risk to health |
Central android fat distribution (apple shape) is associated with what? | increased O2 consumption, CV disease, ventricular disfunction, increased ETOH consumption, increased free fatty acids, increased LDL, increased insulin resistance |
Why is peripheral gynecoid/gluteal (pear shape) fat distribution associated with less health risks? | because fat distribution in the lower half of the body, not around the abdomen means the fat is metabolically static |
Which measure of obesity is the new standard for determining abdominal obesity? Why? | waist circumference (WC); it correlates better with mortality and obesity-related diseases |
WHR > ___ in women and > ____ in men is associated with increased morbidity and mortality. | 0.9 (women); 1.0 (men) |
It is recommended that WC not exceed 1/2 the ______. This is a measure of ______. | stature; WSR (waist stature ratio) |
In obese patients FRC, ERV, VC, TLC are all ____________ (decreased or increased). | decreased |
The decrease in FRC is primarily due to a marked reduction in _____ | ERV |
What lung function measure remains normal in the obese patient? | RV (residual volume) |
What is the most sensitive indicator of effects of obesity on pulmonary function testing? | decreased ERV |
Obesity causes an increase in the _________ of oxygen and a decrease in the _________ of oxygen | demand; supply |
Why is an obese patient's FRC reduced even more so when they are supine? | Because the extra abdominal weight pushes the diaphragm cephalad |
Restrictive airway disease is defined as a FEV1/FVC ratio of what? | 0.9 with reduced volumes |
Decreased functional residual capacity in the obese patient population causes ________________ to exceed normal tidal volume. | closing capacity |
What is closing capacity? | the volume in the lungs at which the smallest airways (respiratory bronchioles) collapse |
Increased closing capacity in the obese leads to what? | airway closure, atelectasis, VQ mismatch, IP shunt |
True or False: Regardless of pre oxygenation, obese patients experience rapid desaturation during apnea time on induction. | True |
Increased metabolic activity of excess fat and stress on supporting respiratory muscles in the obese leads to an increase in what 2 things? | CO2 production and VO2 |
How do obese patient's bodies try to cope with the increased demand for O2 and increased production of CO2? | by increasing minute ventilation and cardiac output |
Increased pulmonary blood volume in the obese leads to what? | decreased pulmonary compliance, pulmonary HTN, cor pulmonale |
Chronic hypoxia in the obsess leads to what? | polycythemia |
True or False: since obese patients are larger, their airways are also larger in diameter. | False! |
What is another name for Obesity Hypoventilation Syndrome? | Pickwickian Syndrome |
What is Pickwickian Syndrome? | Desensitization of the respiratory center in obesity leads to inefficient ventilation, hypercapnia, hypoxia, polycythemia, cyanosis and eventually right sided CHF and for pulmonale |
Obese patients are more or less sensitive to the respiratory depressant effects of general anesthesia? | more sensitive! |
What percentage of morbidly obese patients have Pickwickian Syndrome? | 10% |
What is considered a cardinal sign of Pickwickian Syndrome? | hypercapnia while awake |
Cardiac output is ______(increased or decreased?)____ in obesity. | Increased |
Renin-angiotensin is __(increased or decreased?)__ in obesity. | Increased --> more fluid retention |
Myocardial workload, VO2, CO2 are all ___(increased or decreased?)___ in obesity. | increased |
Is SVR increased or decreased in obesity? | increased |
Increased in cardiac output in obese patients is due primarily to an increase in heart rate or an increase in stroke volume? | stroke volume |
Increased preload in obesity leads to what cardiac abnormality? | cardiomegaly and atrial and biventricular dilation |
Are an obese person's ventricles more or less compliant than a healthy and normal weight person's? | Less |
What do obese patients have increased blood viscosity when compared with a normal weight patient? | polycythemia |
Does an obese patient have more or less circulating catecholamines? | more |
Explain how an obese patient could have undetected CAD. | decreased activity means less stress on the heart; symptoms typically appear when heart is stressed |
Without looking at a weight or BMI on a patient's chart, what could you look at that would lead you to suspect the patient may be obese? | EKG -- obesity typically causes left axis deviation meaning LVH which is associated with obesity |
In a preanesthetic assessment of an obese patient, why would you ask them if they can walk up 2 flights up stairs without stopping? | Because the stress on the body from walking up 2 flights of stairs is the same stress that is put on the body during laryngoscopy and induction and emergence of anesthesia |
Orthopnea can be an indication of what? | left ventricular dysfunction |
After an 8 hour fast, what percentage of morbidly obese patients have > 25 mls of gastric volume? | 80 - 90% |
Are obese patients more likely to have a more acidic or basic stomach compared to patients of normal weight? | acidic |
Are obese patients always treated as full stomachs? | No...there is much controversy over this issue |
What are some medications to consider in obese patients in terms of GI function? | any aspiration prevention measures possible.....gastrokinetics (reglan), pre-op PPI (protonix, nexium, omeprazole), H2 antagonists (zantac, pepcid) |
What 4 things constitute metabolic insulin resistance syndrome, which is associated with obesity? | insulin resistance, impaired glucose tolerance, HTN, dyslipidemia |
Risk for type 2 DM increases __________ with BMI increase. | linearly |
Lipophilic drugs have a(n) ___________ volume of distribution in obese patients. | increased |
Water soluble drugs have a(n) __________ volume of distribution in obese patients. | limited |
Explain how an obese patient reacts differently to Succinylcholine than a lean patient. | obese patients have increased plasma pseudocholinesterase activity, so they metabolize it faster; also they experience less gross fasiculations and myalgia due to proportionately lower muscle mass |
Obese patients have _______ albumin levels but ________ alpha 1 acid glycoprotein levels. | decreased; increased |
A prudent CRNA knows that in terms of drug dosing for obese patients, dosing of lipid soluble drugs should be based on ______ and maintenance doses should be given ______ frequently. Why? | TBW; less; slower clearance of lipid soluble drugs |
A prudent CRNA knows that in terms of drug dosing for obese patients, dosing of water soluble drugs should be based on ______. | IBW - dosing based on TBW could lead to overdose since volume of distribution of these drugs does NOT increase with body weight |
Inhalation agents take _________ to reach equilibrium in obese patients and __________ is delayed. | longer; emergence |
In terms of selecting inhalation agent for an obese patient, a prudent CRNA knows which agent is faster on and off than the other two? | desflurane |
Why is there a reduction of free drug concentrations in obese patients? | because they have increased alpha 1 acid glycoprotein levels |
Why do drugs depending on renal clearance have higher elimination in obese patients? | higher cardiac output |
In terms of NMBs, which are the only 2 that should be dosed on IBW in obese patients? | vecuronium and rocuronium |
Which is the only opioid that should be dosed on IBW in obese patients? | remifentanil |
How should you position an obese patient for intubation? | raise head of bed or put patient in reverse trendelenburg if possible |
Why is PEEP beneficial in obese patients? | reduces venous return thereby decreasing CO and VO2 |
What is the single best predictor of problematic intubation in an obese patient? | neck circumference |
True or False: regarding BP measurement, forearm is as reliable as the upper arm | true |
Is regional anesthesia easier or more difficult in an obese patient? | more difficult |
What percentage of patients who present for bariatric surgery have OSA? | > 70% |
What is the best treatment for OSA? | bi-pap/cpap; preferably, the patient's own from home |
True or False: some evidence suggests that patients who are treated for OSA pre-op have fewer peri-op complications than those who are untreated | True |
Which position is better for laryngoscopic view in obese patients: ramped or sniffing? | ramped |
Is RSI indicated for every bariatric surgery patient? | No; it needs to be considered on an individual basis |
True or false: the larger percentage of airway difficulties in bariatric surgery patients occur during induction and intubation rather than extubation and in the PACU during recovery. | False! more issues occur during extubation and in recovery period in PACU |
Studies have shown that in bariatric surgery expertise or drug selection/techinue is more important in promoting early return of the patient's airway reflexes? | expertise |
For medications with unknown pharmacodynamics and pharmacokinetics in morbidly obese individuals, dosing should be based on _____ | LBM (IBW) |