Obesity PDF

Anesthesiology Obesity Obesity classified by using the body mass index (BMI) scoring system into :- 1. Overweight is defined as a BMI of 24 kg/m2 or higher. 2. Obesity class 1 and 2 as a BMI of 30 or higher. 3. Extreme obesity ( termed “morbid ob...

Anesthesiology Obesity Obesity classified by using the body mass index (BMI) scoring system into :- 1. Overweight is defined as a BMI of 24 kg/m2 or higher. 2. Obesity class 1 and 2 as a BMI of 30 or higher. 3. Extreme obesity ( termed “morbid obesity”) as a BMI of more than 40. BMI is calculated by dividing the weight (in kilograms) by the height (in meters) squared. The risks of increase mortality and morbidity associated with the degree of obesity and with increased abdominal distribution of weight. Men with a waist measurement of 40 in. or more and women with a waist measurement of 35 in. or more are at increased health risk. Anesthetic considerations A. Comorbidity or coexisting diseases Obesity is associated with many diseases, including:- 1. Type 2 diabetes mellitus, 2. Hypertension, 3. Coronary artery disease,  4. Obstructive sleep apnea, 5. Degenerative joint disease (osteoarthritis). B. Respiratory considerations in obese patients. 1. Possibility of a difficult airway, 1. Risk of asthma. 2. Breathing or obstructive sleep apnea (OSA), 3. Restrictive lung disease, 4. Chronic hypoxia with or without polycythemia. 5. Pulmonary hypertension. 6. The most important is Obesity is typically associated with hypoxemia, the mechanisms of hypoxemia which include: A. Increased work of breathing. Because of an increased chest wall mass, decreased chest wall compliance, and abdominal cavity adipose tissue decreasing diaphragmatic excursion, work of breathing is 2 to 3 times greater than normal. B. Restrictive lung disease develops, areas of the lung become underventilated and atelectatic, ventilation/perfusion mismatch occurs, and the lungs compensate by selective vasoconstriction of poorly ventilated regions. Ultimately pulmonary hypertension develops, which leads to right-sided heart failure. C. Large tissue mass increases the total oxygen consumption and carbon dioxide production. D. Increase Oxygen demand, CO2 production, and alveolar ventilation are elevated because metabolic rate is proportional to body weight. E. Excessive adipose tissue over the thorax decreases chest wall compliance Whereas obese patients are often hypoxemic, only a few are hypercapnic, which lead to serious form called complications called OSA (obstructive sleep apnea).  Obesity hypoventilation syndrome, or obstructive sleep apnea (OSA). Is a complication of extreme obesity characterized by in addition to above 1. Hypercapnia, 2. Cyanosis-induced polycythemia, 3. Right-sided heart failure, and 4. Somnolence. 5. Hypoxia, 6. Hypertension 7. Arrhythmias 8. Myocardial infarction 9. Pulmonary edema 10. Stroke, and death These patients appear to have blunted respiratory drive and loud snoring and upper-airway obstruction during sleep. dry mouths and daytime somnolence; bed partners frequently describe apneic pauses. The potential for difficult mask ventilation and difficult intubation during induction followed by upper airway obstruction during recovery. For patients with known or suspected OSA, postoperative continuous positive airway pressure (CPAP) should be considered until the anesthesiologist can be sure that the patient can protect his or her airway and maintain spontaneous ventilation without evidence of obstruction. C. Cardiovascular considerations  Increased O2 demand lead to increase Cardiac output, (0.1 L/min/kg of adipose tissue) , stroke volume, and circulating blood volume increase  Association of Arterial hypertension which leads to left ventricular hypertrophy.  Pulmonary hypertension and cor-pulmonale. D. GIT considerations 1. Gastroesophageal reflux disease, 2. Delayed gastric emptying, and 3. Hyperacidic gastric fluid 4. Fatty infiltration of the liver also occurs and may be associated with abnormal liver tests, E. Musculoskeletal considerations  Blood pressures must be taken with a cuff of the appropriate size.  Potential sites for intravenous access should be checked in anticipation of technical difficulties.  Obscured landmarks, difficult positioning, and extensive layers of adipose tissue may make regional anesthesia difficult with standard equipment and techniques.  Obese patients may be difficult to intubate as a result of limited mobility of the temporomandibular and atlantooccipital joints, a narrowed upper airway, and a shortened distance between the mandible and sternal fat pads.  Anesthetic Managements :- A. Preoperative For the reasons outlined above, obese patients are at an increased risk for developing 1. Pretreatment with H2 antagonists and metoclopramide and should be considered because of risk of Aspiration pneumonia. Preoperative testing should include chest radiograph, 1. ECG, and 2. Arterial blood gas analysis. PaO2 and PaCO2 3. A complete blood count 4. Blood sugar, 5. Pulmonary function testing may also be necessary to characterize the extent of disease and amenability to preoperative optimization. B. Intraoperative 1.Because of the risks of aspiration pneumonia and hypoventilation, morbidly obese patients are should be intubated for all general anesthetics.  If intubation appears likely to be difficult, the use of a fiberoptic bronchoscope or video laryngoscopy is recommended.  Positioning the patient on an intubating ramp is helpful.  Auscultation of breath sounds may prove difficult.  Controlled ventilation may require to increased inspired oxygen concentrations to prevent hypoxia, particularly in lithotomy, Trendelenburg, or prone positions. 2.Although dosage requirements for epidural and spinal anesthesia are typically require 20–25% less local anesthetic per blocked segment because of epidural fat and distended epidural veins. Continuous epidural anesthesia has the advantage of providing pain relief and the potential for decreasing respiratory complications in the postoperative period. 3.Regional nerve blocks, when appropriate for the surgery, have the additional advantages of not interfering with the postoperative deep vein thrombosis prophylaxis, rarely producing hypotension, and of reducing the need for opioids. Advantages and disadvantages of offering regional anesthesia to obese patients  Advantages Decreased cardiopulmonary depression Improved postoperative analgesia with decreased need for narcotics Less postoperative nausea and vomiting, shorter post–anesthetic care unit stay   Disadvantages Technical difficulties. Failed peripheral nerve or neuraxial blocks. C. Postoperative 1.Respiratory failure is a major postoperative problem of morbidly obese patients. The risk of postoperative hypoxia is increased in patients with preoperative hypoxia, following surgery involving the thorax or upper abdomen (particularly vertical incisions). Extubation should be delayed until the effects of NMBs are completely reversed and the patient is awake. An obese patient should remain intubated until there is no doubt that an adequate airway and tidal volume will be maintained. If the patient is extubated in the operating room, supplemental oxygen should be provided during transportation to the postanesthesia care unit. A 45° modified sitting position will improve ventilation and oxygenation. The risk of hypoxia extends for several days into the postoperative period, and providing supplemental oxygen or CPAP, or both, should be routinely considered. Other common postoperative complications in obese patients include 2.wound infection, 3.deep venous thrombosis, and 4.Pulmonary embolism.