Obesity Flashcards
What are the primary functions of adipose tissue?
It serves as a reservoir of readily convertible energy and serves as a heat insulator.
What is the formula for BMI?
BMI = (Weight in Kg)/(height in meters)(height in meters) which is to say, it is the weight in kilograms divided by the height in meters squared.
What is the formula for ideal body weight?
Male ideal body weight in kilograms = height in centimeters - 100. The female ideal body weight in kilgrams = height in centimeters - 105.
What are the classifications of obesity based on BMI?
A BMI < 18.5 = Underweight,
18.5-24.9 = Normal
, 25-29.9 = Overweight,
30-34.9 = Obesity Class I,
35-39.9 = Obesity Class II,
> 40 = Obesity Class III (morbid obesity)
What is gynecoid obesity?
Gynecoid obesity, also called peripheral obesity, is the deposition of fat primarily in the hips, buttocks, and thighs.
What is android obesity?
Android obesity, also called central obesity, is the deposition of fat primarily in the upper body. Compared to gynecoid obesity, it has a higher associated risk for cardiovascular disease.
How does obesity affect the choice of anesthetic?
No difference has been demonstrated in emergence following inhalation versus narcotic techniques. Many clinicians, however, recommend a ‘light’ general anesthetic combined with epidural anesthesia whenever possible as it reduces the need for opioids and facilitates coughing and deep breathing after surgery.
How should positioning for induction of an obese
patient be carried out?
The patient should have the shoulders and head ramped up with the head in sniffing position and the bed should be placed in reverse Trendelenburg to increase the FRC and allow large breasts to fall away from the neck. The acronym HELP may be
used to remember ‘Head Elevated Laryngoscopy Position’ for obese patients.
What measurable characteristic best predicts the
occurrence of a difficult airway in the obese patient? What factors are present in the obese airway that may result in a difficult airway?
Neck circumference is the single best predictor of a difficult airway. A neck circumference of 40 cm is associated with a 5% chance of difficult intubation while a neck circumference of 60 cm indicates a 35% chance of difficult intubation. Fat rolls
around the neck restrict neck motion while fat in the airway tissue decreases the glottic opening. Other anatomic abnormalities that are often associated with obesity include reduced temporomandibular and atlantoaxial motion.
What are the risks particular to obese patients
presenting for bariatric surgery?
Third-space losses generally exceed blood loss for bariatric procedures. At least one large-bore IV should be started and the patient should be typed and crossed for two units of PRBCs. IV fluids should be warmed and an estimated 10-15 mL/kg/hour of lactated ringer s solution or normal saline should be administered. The most important anesthetic considerations for bariatric surgery often has more to do with the patient class than the procedure itself. Morbidly obese patients have higher morbidity and mortality rates. They have a higher risk for sleep apnea, decreased chest wall compliance (but normal lung compliance), reduced expiratory reserve volume and reduced functional residual capacity. Hypertension is common in these patients and blood volume and cardiac output increase to maintain blood flow to the increased adipose tissue. Left ventricular dysfunction may be present, making it difficult for the patient to tolerate increases in blood volume or cardiac depression. Diabetes mellitus is often present and fatty infiltration of the liver can lead to altered metabolism and unpredictably prolonged drug actions.
Should obese patients undergo rapid-sequence
induction?
Obese patients are assumed to have a full-stomach and at risk for pulmonary aspiration. Because of this, it is generally accepted that patients up to a BMI of 50 should undergo rapid
sequence induction with cricoid pressure. Some clinicians postulate that because of the incidence of difficult airway, patients above a BMI of 50 should undergo awake intubation.
What parameters should be used to calculate drug
dosing in obese individuals?
Drugs that are distributed mainly to lean tissue should be dosed according to lean body weight. Drugs that are even distributed to lean and adipose tissue should be dosed according to total
body weight.
Name two anesthetic drugs that should be dosed
according to total body weight in the obese individual.
Succinylcholine and dexmedetomidine
How is the volume of distribution and elimination halflife of midazolam compare between obese and nonobese patients?
Both the volume of distribution and the elimination half-life are significantly increased in obese patients, resulting in prolonged duration of action in obese patients. A single intravenous dose
should be based on total body weight, but a continuous infusion should be based on lean body weight.
How should the local anesthetic dose for epidural
anesthesia be adjusted for an obese individual?
Due to fatty infiltration and vascular engorgement of the epidural space, the level and onset of an epidural block can be unpredictable. It is recommended that the local anesthetic dose
be reduced by 20% of that of a non-obese patient.
