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.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1051.
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.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1051.
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.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1275.
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)
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1051.
What is gynecoid obesity?
Gynecoid obesity, also called peripheral obesity, is the
deposition of fat primarily in the hips, buttocks, and thighs.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1275.
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.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1275.
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.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1063.
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.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1061-1062.
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.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1060.
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.
Jaffe RA, Samuels SI. Anesthesiologist’s Manual of Surgical
Procedures. 4th ed. Philadelphia, PA: Lippincott Williams and
Wilkins, 2009: 603.
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.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1061.
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.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1281.
Name two anesthetic drugs that should be dosed
according to total body weight in the obese individual.
Succinylcholine and dexmedetomidine
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1282.
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.
Longnecker DE, Newman MF, Brown DL, Zapol WM.
Anesthesiology. 2nd ed. New York: McGraw-Hill; 2012: 309.
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.
Lee CY. Manual of Anesthesiology. Singapore: McGraw-Hill;
2006: 261.
