CHAPTER 27 Anesthesia for Obese Patients

Introduction

The word obesity is coined from a Latin word obesus, which means fattened by overeating. Body mass index (BMI) is the most commonly used epidemiological tool to assess obesity, which is obtained as follows:

BMI = body weight (kg)/height (metre²).

Other useful terms are as follows:

Ideal body weight (IBW) in kg = height (cm) – 100 in males and 105 in females.
Lean body weight (LBW) = total body weight, excluding body fat.

The WHO classification of obesity is summarized in Table 27.1.

Table 27.1 WHO classification of obesity according to BMI

**Table 27.1** WHO classification of obesity according to BMI
Classification	BMI (kg/m²)
Underweight	<18.5
Normal weight	18.5–24.9
Overweight	25.0–29.9
Obese
Class I	30.0–34.9
Class II	35.0–39.9
Class III	40.0–49.9
Superobese	≥50

Abbreviation: BMI, body mass index.

The number of obese individuals is on the rise worldwide, and so is the number of patients reaching to the operation theater. An obese patient may come for weight-reduction surgery (bariatric surgery) or nonbariatric surgery. The anesthetic management of obese individuals is often challenging and complicated because of multiple comorbidities and associated difficult airway. The various medical and surgical diseases related to obesity are mentioned in Table 27.2.

Table 27.2 Medical/surgical conditions associated with obesity

**Table 27.2** Medical/surgical conditions associated with obesity
Organ system	Disorders
Cardiovascular	Coronary heart disease Cardiomyopathy Hypertension
Respiratory	Restrictive lung disease Obstructive sleep apnea Obesity hypoventilation syndrome
Nervous system	Cerebrovascular disease
Endocrine	Diabetes mellitus Hypothyroidism Cushing’s syndrome Metabolic syndrome
Musculoskeletal	Osteoarthritis
Malignancy	Carcinoma of endometrium, cervix, prostate, breast, colon

Anesthetic Management of Obese Patients

Minimally invasive surgical treatment (bariatric surgery) is increasingly popular worldwide. The surgical procedure can be classified into the following:

Restrictive type (sleeve gastrectomy, laparoscopic adjustable gastric banding).
Malabsorptive type (jejunoileal bypass, biliopancreatic diversion).

The goal of surgery is to reduce the volume of the stomach in order to achieve desired weight loss. A thorough preoperative evaluation of the obese patient with a focus on cardiovascular system, respiratory system, and airway is necessary.