**1. Introduction**

Though obesity is not a newly emerging problem with its epidemic character at both public and individual levels, there has been recent increase in the number of successful surgical interventions with low likelihood of serious morbidity. Body weight of more than 50% of adults in the United States (US) is 20% more than the body weight regarded optimum for the height. The percentage of such adults has increased from 30 to 50% just in 18 years [1].

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Overweight has been defined as an excess of total or expected "normal" body weight, including all tissue components (muscle, bone, water, and fat) of body composition. In practice, the terms obesity and overweight are often used interchangeably to refer to excess body fat, but ideally an index of obesity should reflect only excess adipose tissue and be independent of height, body fluids, and muscle, and skeletal mass.

Body mass index (BMI) is now the standard measure for describing different categories of obesity. It must always be remembered that BMI is an indirect measure of obesity since it only considers height and weight, irrespective of the source of any additional weight. BMI is calculated by dividing patient weight (kilograms, kg) by the square of their height (meters, m); BMI = kg/m<sup>2</sup> . An increased BMI can be present from any cause of excess weight (body building, ascites, and very large tumor) even in the absence of additional fat. The United States and many countries classify obesity according to BMI, as shown in **Table 1** [2].


Body mass index (BMI) = weight (kilograms, kg) divided by the square of height (meters, m); BMI = Wt (kg)/Ht (m<sup>2</sup>

**Table 1.** Classification of obesity by body mass index (BMI).

While many obesity complications that pose threat to perioperative period (e.g., airway difficulties or joint problems) may be observed by physical inspection, other complications such as sleep apnea, systemic and pulmonary hypertension, and diabetes mellitus should be comprehensively assessed by careful anamnesis, physical examination, and laboratory tests. Obesity itself, its complications and treatment, is also important for the anesthesiologist. An individual who has 30% excessive weight has a 40% increased mortality risk due to heart disease and a 50% increased mortality risk due to stroke. Hospital costs are also higher in obesity, with increased risk of perioperative morbidity and mortality [3].

Preoperative assessments make perioperative period more efficient, decrease anxiety of both healthcare providers and cared patients, and make patients have realistic expectations which increase satisfaction from pain management and entire perioperative experience. Obesity is a health problem associated with many medical conditions (**Table 2**). Preoperative assessment allows for detection of possible interindividual differences in terms of physiology of airways, pulmonary system, cardiovascular system, metabolic system, and nervous system. Another benefit is the important contribution of anesthesiologists to surgeons in terms of patient's psychological attitude and preparation [4].


**Table 2.** Obesity-related medical conditions.

Overweight has been defined as an excess of total or expected "normal" body weight, including all tissue components (muscle, bone, water, and fat) of body composition. In practice, the terms obesity and overweight are often used interchangeably to refer to excess body fat, but ideally an index of obesity should reflect only excess adipose tissue and be independent of

Body mass index (BMI) is now the standard measure for describing different categories of obesity. It must always be remembered that BMI is an indirect measure of obesity since it only considers height and weight, irrespective of the source of any additional weight. BMI is calculated by dividing patient weight (kilograms, kg) by the square of their height (meters, m);

ing, ascites, and very large tumor) even in the absence of additional fat. The United States and

While many obesity complications that pose threat to perioperative period (e.g., airway difficulties or joint problems) may be observed by physical inspection, other complications such as sleep apnea, systemic and pulmonary hypertension, and diabetes mellitus should be comprehensively assessed by careful anamnesis, physical examination, and laboratory tests. Obesity itself, its complications and treatment, is also important for the anesthesiologist. An individual who has 30% excessive weight has a 40% increased mortality risk due to heart disease and a 50% increased mortality risk due to stroke. Hospital costs are also higher in

Body mass index (BMI) = weight (kilograms, kg) divided by the square of height (meters, m); BMI = Wt (kg)/Ht (m<sup>2</sup>

).

Preoperative assessments make perioperative period more efficient, decrease anxiety of both healthcare providers and cared patients, and make patients have realistic expectations which

obesity, with increased risk of perioperative morbidity and mortality [3].

many countries classify obesity according to BMI, as shown in **Table 1** [2].

. An increased BMI can be present from any cause of excess weight (body build-

height, body fluids, and muscle, and skeletal mass.

**<20 kg/m2** Underweight **20–25 kg/m2** Normal **26–29 kg/m2** Overweight **30–39 kg/m2** Obese

**≥40 kg/m<sup>2</sup>** Morbid obese **≥50 kg/m<sup>2</sup>** Super-obese **≥60 kg/m<sup>2</sup>** Super-super obese

World Health Organization (WHO) classification: BMI

**30–34.9 kg/m<sup>2</sup>** Class I **35–39.9 kg/m2** Class II **>40 kg/m<sup>2</sup>** Class III

**Table 1.** Classification of obesity by body mass index (BMI).

BMI = kg/m<sup>2</sup>

74 Current Topics in Anesthesiology

**BMI**

### **2. Preoperative assessment**

It is essential to provide a clinical setting that makes obese patients feel comfortable with respect to physical conditions. Outpatient setting or room should be designed according to overweight/obese patients. Primary physicians or surgeons of the patients should not believe mistakenly that they have adequate knowledge about their patients' medical situation. Comorbidities or other accompanying diseases may not frequently be well-documented. Preoperative assessment by anesthesiologist should include the presence of hyperglycemia or type 2 diabetes mellitus, hyperlipidemia, hypertension, coronary artery disease, respiratory problems, liver disease, and obstructive sleep apnea (OSA). As per indicated surgical procedure, impacts of osteoarthritis should be considered regarding positioning of patient especially during elective surgery [5].

An often overlooked, albeit important issue is the evaluation of medical reasons for obesity. Incidence of endocrine disease other than type 2 diabetes mellitus was reported as 47.4% among morbidly obese patients considered for bariatric surgery. Prevalence of hypothyroidism, pituitary diseases, and Cushing's syndrome is shown to be 18.1, 1.9, and 16.3%, respectively. Newly established endocrine diseases are present in 16.3% of all patients [6].

Psychological tests of morbidly obese patients frequently revealed depression, social impairment, and loss of interest in interindividual behaviors. Physicians should be aware of the likelihood of the presence of psychosocial problems in obese patients during the perioperative period [7].

Routine laboratory tests indicated for obese patients are summarized in **Table 3**. If the obese patient had history of bariatric surgery such as gastric bypass or other which represents a potential for malabsorption, a significant protein, vitamin, iron, or calcium deficiency may be present. Therefore, further additional tests are required in such patients to assess metabolic alterations (**Table 4**) [8].

Anesthesiologist should question all current medication of the patient, including over-thecounter and prescribed appetite-stimulating and weight-lowering drugs since most of these agents are associated with serious heart and lung problems and important morbidity and mortality (**Table 5**) [8].


**Table 3.** Routine preoperative tests for obese patients.

#### **2.1. Assessment and optimization of airways and pulmonary system**

Factors increasing perioperative risks in obese patients in terms of airways and pulmonary system include airway anatomy, rapid desaturation developed during anesthesia induction secondary to reduced functional residual capacity (FRC), tendency to desaturation in supine position, need for induction and recovery in vertical position, tendency to sleep apnea, chronic respiratory insufficiency, pulmonary hypertension, predisposition to deep venous thrombosis and its consequences, and need for active participation to encourage for postoperative mobilization [9].

Psychological tests of morbidly obese patients frequently revealed depression, social impairment, and loss of interest in interindividual behaviors. Physicians should be aware of the likelihood of the presence of psychosocial problems in obese patients during the perioperative period [7].

Routine laboratory tests indicated for obese patients are summarized in **Table 3**. If the obese patient had history of bariatric surgery such as gastric bypass or other which represents a potential for malabsorption, a significant protein, vitamin, iron, or calcium deficiency may be present. Therefore, further additional tests are required in such patients to assess metabolic

Anesthesiologist should question all current medication of the patient, including over-thecounter and prescribed appetite-stimulating and weight-lowering drugs since most of these agents are associated with serious heart and lung problems and important morbidity and

**2.1. Assessment and optimization of airways and pulmonary system**

Especially in >60-year-old patients with established or suspected lung or heart disease

Other clinically indicated additional tests, such as echocardiography

**Table 3.** Routine preoperative tests for obese patients.

Factors increasing perioperative risks in obese patients in terms of airways and pulmonary system include airway anatomy, rapid desaturation developed during anesthesia induction secondary

Especially in >55-year-old women and >45-year-old men who has established or suspected heart disease or at higher

alterations (**Table 4**) [8].

76 Current Topics in Anesthesiology

mortality (**Table 5**) [8].

Electrolytes including sodium, potassium, calcium, and phosphorus Liver function tests including AST, ALT, total, and direct bilirubin

Renal function tests including creatinine level

Fasting plasma glucose

Complete blood cell count

25-Hydroxy vitamin D level

Electrocardiogram (ECG)

risk for heart disease P-A chest X-ray

Polysomnography

Testosterone level

Thyroid stimulating hormone (TSH)

Lipid profile

Ferritin Vitamin B12


**Table 4.** Preoperative laboratory tests recommended for patients with history of bariatric surgery.

Obesity is a common and important risk factor for obstructive sleep apnea (OSA). A near two-unit increment in BMI raises the probability of OSA by fourfold. While the prevalence of OSA in general population is 2 and 4% in women and men, respectively, it ranges from 3 to 25% and 40 to 78% in morbidly obese women and men, respectively. Sleep apnea in obese patients has usually obstructive character and originated from airway stenosis secondary to excessive amount of peripharyngeal adipose tissue and from reduction of upper airway muscle tonus during rapid eye movement (REM) sleep. BMI, neck diameter, lung function tests (LFT), arterial blood gas measurement during daytime room air, and sleep-related complaints could not adequately predict the presence and severity of OSA in obese patients [10].

Definitive diagnosis of OSA is established by polysomnography, where following criteria should be fulfilled: occurrence of ≥5 apneic events (≥10 s interruption of air flow despite attempting to breath) or ≥15 hypopneic events (>50% reduction of air flow for ≥10 s) per hour during 7-h sleep test. Apneic/hypopneic index (AHI) shows the total number of apneic and/or hypopneic events per slept hour. The severity of OSA is directly correlated with the increase in AHI [11].

The determination of OSA in obese patients has two important implications. First, patients with OSA are more prone to the suppressive effects of hypnotics and opioids on airway muscle tonus and respiration [12]. Postoperative parenteral or neuraxial opioid use may lead to respiratory complications that may result in death or potentially fatal events [13, 14]. Second, OSA complicates laryngoscopy and mask ventilation [15]. Moreover, oxygen stores are decreased due to reduced expiratory reserve volume (ERV) in obese patients [16]. Combination of these factors predispose to serious problems in airways.


**Table 5.** Weight lowering drugs.

Anamnesis is the easiest way of evaluation of OSA in the preoperative period in patients who did not undergo polysomnography before. Such useful data could be obtained from patient's roommate or sleep partner. Anamnestic data about snoring, interruption of breathing during sleeping (a short-time attempt to inspire after apneic episodes and wheezy breathing or resuscitative nasal breathing), decreased daytime performance, morning headache, and irritability suggest sleep apnea. Systemic hypertension and increased neck diameter (>40–42 cm at cricoid cartilage level) is consistent with probable OSA diagnosis [11, 17]. Other abnormalities of OSA detected during physical examination include somnolence and mask airway and/or intubation difficulties (e.g., Mallampati class III or IV hypognathia, short thyromental distance) [12, 14, 15].

Some obese patients develop chronic daytime hypoventilation, called as obesity-hypoventilation syndrome (OHS) [18]. These patients also have chronic daytime hypoxemia (PO2 < 65 mmHg), which could be easily detected by pulse oximetry at room air. Permanent hypercapnia ((PCO2 > 45 mmHg) in the absence of serious obstructive pulmonary disease is pathognomonic for this syndrome in obese patients. These patients usually have advanced obesity (BMI > 40 kg/m<sup>2</sup> ) and risk of OHS is markedly increased with increasing BMI [19]. Majority of patients with OHS has also OSA; however OHS is not common in OSA patients. Those patients being at the "severe" end of OHS spectrum with cor pulmonale signs and symptoms are called "Pickwickian" [10, 18].

tonus and respiration [12]. Postoperative parenteral or neuraxial opioid use may lead to respiratory complications that may result in death or potentially fatal events [13, 14]. Second, OSA complicates laryngoscopy and mask ventilation [15]. Moreover, oxygen stores are decreased due to reduced expiratory reserve volume (ERV) in obese patients [16]. Combination of these

Fluoxetine Selective serotonin reuptake inhibitor. Associated with diarrhea, nausea, headache, and

Sibutramine May lead to mild increases in blood pressure and heart rate. Associated with arrhythmia

Ephedra Hypertension, psychiatric symptoms, autonomic dysfunction, gastrointestinal

Pyruvate Death was reported in a patient with restrictive cardiomyopathy.

and hypertension, which is likely to be related to cardiac arrest and stroke.

Mazindol Pulmonary hypertension, atrial fibrillation, and syncope episodes were reported.

dry mouth. Bradycardia, hemorrhage, convulsion, hyponatremia, hepatotoxicity, and

**Drug Implications for anesthetic procedures (reported adverse effects)**

Dexfenfluramine Associated with pulmonary hypertension and cardiac valve disease. Fenfluramine Associated with pulmonary hypertension and cardiac valve disease.

extrapyramidal effects were reported.

Orlistat Diarrhea and reduced levels of lipid-soluble vitamins were reported. Phentermine Association with cardiopulmonary problems could not be excluded.

Anamnesis is the easiest way of evaluation of OSA in the preoperative period in patients who did not undergo polysomnography before. Such useful data could be obtained from patient's roommate or sleep partner. Anamnestic data about snoring, interruption of breathing during sleeping (a short-time attempt to inspire after apneic episodes and wheezy breathing or resuscitative nasal breathing), decreased daytime performance, morning headache, and irritability suggest sleep apnea. Systemic hypertension and increased neck diameter (>40–42 cm at cricoid cartilage level) is consistent with probable OSA diagnosis [11, 17]. Other abnormalities of OSA detected during physical examination include somnolence and mask airway and/or intubation difficulties (e.g., Mallampati class III or IV hypognathia, short thyromental distance) [12, 14, 15].

factors predispose to serious problems in airways.

78 Current Topics in Anesthesiology

Metformin No adverse effect was reported.

Phenylpropanolamine Increases risk of hemorrhagic stroke.

Diuretics Hypovolemia, hypokalemia.

Chitosan No adverse effect was reported. Chromium No adverse effect was reported.

Hydroxycitric acid No adverse effect was reported.

symptoms.

**Herbal products**

**Table 5.** Weight lowering drugs.

Diethylpropion Pulmonary hypertension and psychosis.

Careful determination of concomitance of obesity and OHS or COPD is important since this combination often leads to chronic daytime hypoxemia, which in turn causes pulmonary hypertension, right ventricular hypertrophy, and/or right ventricular failure. Perioperative morbidity and mortality rates are high in these disorders (Pickwickian), where patients need to undergo many tests to guide for perioperative medical optimization and postoperative care [10, 12, 20].

In perioperative setting, oxygenation is further diminished by reduction in muscular tonus of chest wall and diaphragm following general anesthesia induction and skeletal muscle relaxation. The net effect of this on obesity is the decrease of ERV and FRC by more than 50% and consequent decrease in the number of alveoli making efficient gas exchange, compared to the preinduction phase [21]. In addition, reduction in ERV and FRC increases predisposition to postoperative atelectasis and may inhibit effective clearance of secretions.

Main source of oxygen reserve during apnea is ERV. Therefore, preoxygenation is less effective in obese patients and the time required for hemoglobin desaturation to be reduced to below 90% after apnea is shortened [22]. Obese patients in relaxed condition under anesthesia have increased likelihood of hypoxemic complication due to "reduction in apneic oxygenation reserve" and difficulty of performing positive pressured mask ventilation [15]. In patients considered for bariatric surgery, elective awake tracheal intubation may be the safest approach if there are signs for difficult intubation (e.g., insufficient visualization of posterior pharyngeal wall). Before the induction, after placing a cylinder under the scapula and a support to the occipital region of the patient and asking for full extension at atlanto-occipital joint from the patient may ease awake or conventional laryngoscopy and intubation [23].

A study showed that laryngoscopy was more difficult to perform in obese patients (BMI > 30 kg/ m2 ) compared to patients with normal BMI [24]. However, authors in another study did not observe any correlation between difficult intubation and BMI, though they found an association between difficult intubation and increased neck diameter (>40–42 cm) or Mallampati score of III or IV [25]. This may be explained by higher probability of incidence of both increased neck diameter and increased Mallampati class in obese patients. Moreover, since obese patients have elevated gastric secretion volume and acidity in the preoperative period, premedication is applied by administration of cimetidine, ranitidine, citric acid, sodium citrate, or metoclopramide. Some investigators suggest this as an indication for awake intubation [26].

#### **2.2. Cardiac assessment**

#### *2.2.1. Assessment and prevention of venostasis and thromboembolism*

Evaluation of venous system should be prioritized in cardiovascular assessment as implied by mortality data. Venous emboli entered into pulmonary circulation are important causes of pulmonary dysfunction with a 30-day mortality of 1–2%. Majority of 30-day perioperative mortality after bariatric surgery originates from pulmonary embolism (the number of mortality for this reason is ≥ 3 times more than the number of mortality due to anastomosis leakage and consequent sepsis) [27]. Although several agents have been used to diminish the tendency to thrombosis, no consensus has been established. Since low-molecular-weight heparin may limit options for postoperative pain management, preoperative aspirin, and following warfarin (INR 2.0–3.0) may be considered as a reasonable choice. Use of warfarin, a vitamin K antagonist, may elicit some problems during the postoperative period as many patients develop malabsorption of lipids and lipid-soluble substances, including vitamin K after Roux-en-Y gastrojejunostomy (RNYG). Optimizing warfarin dosage may become difficult due to this malabsorption, where daily adjustments are required for at least a couple of weeks [28]. Preoperative exercise, prophylaxis through antithrombotic agents and variceal socks, hematocrit count below the level of polycythemia, increased cardiac output, and early ambulation decrease the risk in this patient group. Therefore, evaluation and prophylaxis including exercise status, pharmacological treatment, absence of symptoms and signs of venous disease and absence of evidence of venous disease, optimal hydration as well as early ambulation should be targeted [29].

#### *2.2.2. Cardiovascular assessment*

Cardiac output is expected to increase by 0.01/min for every kilogram of adipose tissue. Consequently, obese patients develop hypertension and associated cardiomegaly and left ventricular failure. To measure blood pressure accurately, an appropriate-sized cuff should be selected, which may not be as easy as it seems. Obesity not only leads to parenteral access difficulty, but also complicates noninvasive blood pressure monitoring. Direct arterial monitoring may be needed for accurate and continuous tracing of blood pressure and frequent arterial blood sampling, based on the extent of cardiopulmonary reserve [30].

Cardiac reserve may be limited in obese patients, where tolerance to hypotension, hypertension, tachycardia, or volume loading-induced stress in preoperative period may be diminished. Most of patients with Pickwickian syndrome also have right-sided heart failure. For this reason, routine preoperative assessment should also include electrocardiogram (ECG) in addition to anamnesis and physical examination featuring drug treatment and cardiopulmonary problems (especially in terms of left or right ventricular hypertrophy, ischemia, and conduction defects). In cases where biventricular failure is severe and not compensated with ≥2 month lasting exercises, measurement of central vascular volume when a large volume of blood loss is expected related to surgery or coagulation status. Physical examination of peripheral venous line may also allow for planning of the possible need for central venous catheter. Some physicians prefer transesophageal echocardiography to assess central volume instead of central venous pressure (CVP) measurement [31]. There are six risk factors to predict perioperative cardiovascular morbidity:


No additional cardiac tests are required for the elective surgery of patients where these risk factors are absent [32].

#### **2.3. Metabolic assessment**

#### *2.3.1. Diabetes mellitus*

**2.2. Cardiac assessment**

80 Current Topics in Anesthesiology

*2.2.2. Cardiovascular assessment*

*2.2.1. Assessment and prevention of venostasis and thromboembolism*

Evaluation of venous system should be prioritized in cardiovascular assessment as implied by mortality data. Venous emboli entered into pulmonary circulation are important causes of pulmonary dysfunction with a 30-day mortality of 1–2%. Majority of 30-day perioperative mortality after bariatric surgery originates from pulmonary embolism (the number of mortality for this reason is ≥ 3 times more than the number of mortality due to anastomosis leakage and consequent sepsis) [27]. Although several agents have been used to diminish the tendency to thrombosis, no consensus has been established. Since low-molecular-weight heparin may limit options for postoperative pain management, preoperative aspirin, and following warfarin (INR 2.0–3.0) may be considered as a reasonable choice. Use of warfarin, a vitamin K antagonist, may elicit some problems during the postoperative period as many patients develop malabsorption of lipids and lipid-soluble substances, including vitamin K after Roux-en-Y gastrojejunostomy (RNYG). Optimizing warfarin dosage may become difficult due to this malabsorption, where daily adjustments are required for at least a couple of weeks [28]. Preoperative exercise, prophylaxis through antithrombotic agents and variceal socks, hematocrit count below the level of polycythemia, increased cardiac output, and early ambulation decrease the risk in this patient group. Therefore, evaluation and prophylaxis including exercise status, pharmacological treatment, absence of symptoms and signs of venous disease and absence of evidence of venous

disease, optimal hydration as well as early ambulation should be targeted [29].

arterial blood sampling, based on the extent of cardiopulmonary reserve [30].

factors to predict perioperative cardiovascular morbidity:

Cardiac output is expected to increase by 0.01/min for every kilogram of adipose tissue. Consequently, obese patients develop hypertension and associated cardiomegaly and left ventricular failure. To measure blood pressure accurately, an appropriate-sized cuff should be selected, which may not be as easy as it seems. Obesity not only leads to parenteral access difficulty, but also complicates noninvasive blood pressure monitoring. Direct arterial monitoring may be needed for accurate and continuous tracing of blood pressure and frequent

Cardiac reserve may be limited in obese patients, where tolerance to hypotension, hypertension, tachycardia, or volume loading-induced stress in preoperative period may be diminished. Most of patients with Pickwickian syndrome also have right-sided heart failure. For this reason, routine preoperative assessment should also include electrocardiogram (ECG) in addition to anamnesis and physical examination featuring drug treatment and cardiopulmonary problems (especially in terms of left or right ventricular hypertrophy, ischemia, and conduction defects). In cases where biventricular failure is severe and not compensated with ≥2 month lasting exercises, measurement of central vascular volume when a large volume of blood loss is expected related to surgery or coagulation status. Physical examination of peripheral venous line may also allow for planning of the possible need for central venous catheter. Some physicians prefer transesophageal echocardiography to assess central volume instead of central venous pressure (CVP) measurement [31]. There are six risk Although 15% of patients with type I diabetes mellitus has also other comorbid autoimmune diseases such as Graves' disease, Hashimoto's thyroiditis, Addison's disease, and myasthenia gravis, no such an association has been reported in terms of obesity-related diabetes [33].

Current treatment of type II diabetics is initiated with exercise and dietary changes usually. A 5–10 kg weight loss, achieved by a 20% decrease in caloric intake and elevation of daily physical activity to 30 min for a total of 8 weeks often normalize fasting blood glucose levels. Nevertheless, this step is very difficult to achieve for most of patients, and patients will eventually switch to oral hypoglycemic agents, which stimulate secretion of insulin from pancreatic β-cells and improve insulin response of tissues by reversing postbinding defect [34]. Frequently used oral agents include tolazamide, tolbutamide, glyburide, and glipizide, the two latter being sulfonylurea class. Sulfonylureas have more long-lasting glucose-lowering effects (≥24 h) and lower drug-drug interaction potential [35].

By accelerating nonenzymatic glycosylation reactions, higher glucose concentrations lead to the formation of abnormal proteins which decrease flexibility and stretching resistance in wound healing, thereby causing toxic effects. Diminished flexibility may result in stiff joint syndrome and atlanto-occipital joint fixation which could hamper intubation [36].

Anastomosis-related infections are responsible for two-thirds of postoperative complications and about 20% of perioperative mortality in patients undergoing bariatric surgery and constitute number one risk in this patient group. Experimental data show that multiple factors may increase predisposition to infection in patients with glucose intolerance. Many alterations observed in leukocyte functions of hyperglycemic diabetic patients include decreased chemotaxis, impaired phagocytic activity of granulocytes as well as diminished intracellular destruction of pneumococci and staphylococci [37]. Phagocytic functions of granulocytes improve and intracellular killing capacity become near-normal if diabetic patients are aggressively treated, ensuring a blood glucose level <250 mg/dL [38].

#### *2.3.2. Hypocalcemia*

Inadequate calcium intake is both associated with obesity and hypertension; indeed, normalization of calcium intake could improve both hypertension and eating crises that lead to obesity [39].

#### *2.3.3. Hyperlipidemia and hypolipidemia*

Dietary control is an important treatment modality in all hyperlipidemia types [40]. Clofibrate and gemfibrozil, which are used for the management of hypertriglyceridemia, may cause myopathy especially in patients with hepatic or renal disease. Clofibrate may also increase the formation of gallbladder stones. Apart from bile acids, cholestyramine also binds to oral anticoagulants, digitalis class agents, and thyroid hormones. Nicotinic acid leads to peripheral vasodilatation, which should be likely to discontinue on the day of surgery. Probucol decreases synthesis of apoprotein A1. Rare malodorous perspiration and/or QT interval prolongation are seen during probucol usage, and sudden death in animals [41].

Hypolipidemia, albeit a rare condition, is associated with neuropathy, anemia, and renal failure. Although anesthesia experience is limited in patients with hypolipidemia, following may be recommended: maintenance of caloric intake and perioperative use of intravenous protein hydrolysates and glucose [42].

#### **2.4. Psychological assessment and psychiatric considerations**

Psychological assessment is very important for a successful outcome. Not just a week, but even a whole year following the surgery is not an easy period. Each patient needs to have increased awareness and strong-minded with a dedicated attitude of diarizing his/her diet [7]. Evaluations of anesthesiologist may provide important clues. Patient should be emotionally stable. Anesthesiologist may identify several factors about failure, which include drug abuse, untreated major psychiatric disorders, compulsive eating behavior, fibromyalgia, and chronic fatigue syndrome. Investigation, detection, and sharing of any of these may prevent potential frustration of surgical team and avoid patient getting stressed [43].

#### **2.5. Musculoskeletal system assessment and other considerations for patient positioning**

Several other considerations about obesity are also important for anesthesiologist in a prognostic and perioperative manner. Appropriate positioning of the patient, binding of monitoring devices, and performing intravenous access become complicated due to excessive and extensive subcutaneous fat tissue and enlarged extremities. Furthermore, assessment of blood pressure is also more difficult compared to normal-weighted patients (difficulty of selecting appropriate cuff) [44].

Assessment of positioning of obese patients prior to the surgery may abolish some postoperative problems. In a retrospective study, incidence of postoperative ulnar neuropathy was reported to be 29% in patients with BMI > 38 kg/m<sup>2</sup> , compared to 1% of the control group [45]. Upper brachial plexus injury may also occur secondary to excessive rotation of the head and cervical vertebra to the contralateral side. Hyperabduction of the arm on the affected side may also lead to lower nerve root injury [46].

#### **2.6. Risk classification**

*2.3.2. Hypocalcemia*

82 Current Topics in Anesthesiology

*2.3.3. Hyperlipidemia and hypolipidemia*

hydrolysates and glucose [42].

appropriate cuff) [44].

Inadequate calcium intake is both associated with obesity and hypertension; indeed, normalization of calcium intake could improve both hypertension and eating crises that lead to obesity [39].

Dietary control is an important treatment modality in all hyperlipidemia types [40]. Clofibrate and gemfibrozil, which are used for the management of hypertriglyceridemia, may cause myopathy especially in patients with hepatic or renal disease. Clofibrate may also increase the formation of gallbladder stones. Apart from bile acids, cholestyramine also binds to oral anticoagulants, digitalis class agents, and thyroid hormones. Nicotinic acid leads to peripheral vasodilatation, which should be likely to discontinue on the day of surgery. Probucol decreases synthesis of apoprotein A1. Rare malodorous perspiration and/or QT interval pro-

Hypolipidemia, albeit a rare condition, is associated with neuropathy, anemia, and renal failure. Although anesthesia experience is limited in patients with hypolipidemia, following may be recommended: maintenance of caloric intake and perioperative use of intravenous protein

Psychological assessment is very important for a successful outcome. Not just a week, but even a whole year following the surgery is not an easy period. Each patient needs to have increased awareness and strong-minded with a dedicated attitude of diarizing his/her diet [7]. Evaluations of anesthesiologist may provide important clues. Patient should be emotionally stable. Anesthesiologist may identify several factors about failure, which include drug abuse, untreated major psychiatric disorders, compulsive eating behavior, fibromyalgia, and chronic fatigue syndrome. Investigation, detection, and sharing of any of these may prevent potential

**2.5. Musculoskeletal system assessment and other considerations for patient positioning** Several other considerations about obesity are also important for anesthesiologist in a prognostic and perioperative manner. Appropriate positioning of the patient, binding of monitoring devices, and performing intravenous access become complicated due to excessive and extensive subcutaneous fat tissue and enlarged extremities. Furthermore, assessment of blood pressure is also more difficult compared to normal-weighted patients (difficulty of selecting

Assessment of positioning of obese patients prior to the surgery may abolish some postoperative problems. In a retrospective study, incidence of postoperative ulnar neuropathy was

Upper brachial plexus injury may also occur secondary to excessive rotation of the head and cervical vertebra to the contralateral side. Hyperabduction of the arm on the affected side may

, compared to 1% of the control group [45].

longation are seen during probucol usage, and sudden death in animals [41].

**2.4. Psychological assessment and psychiatric considerations**

frustration of surgical team and avoid patient getting stressed [43].

reported to be 29% in patients with BMI > 38 kg/m<sup>2</sup>

also lead to lower nerve root injury [46].

According to ASA Physical Status Classification System; patients with 30 < BMI < 40 are classified as ASA II, patients with a BMI ≥40 are classified as ASA III [47]. Also, for these patients, in 2007, DeMaria et al. suggested a risk stratification tool for bariatric patients. The Obesity Surgery-Mortality Risk Score (OS-MRS) assigns one point to each of five preoperative variables: BMI ≥ 50 kg m<sup>2</sup> , male gender, hypertension, pulmonary embolic risk factors, and age ≥45 years. A score of 0–1 is classified as "A," 2–3 as "B," and 4–5 as "C" with associated mortality risks of 0.2, 1.1, and 2.4%, respectively [30]. This system was later validated by a multicenter study of more than 4000 patients [48].
