Anesthesia for the Obese Patient

1. Anesthesia for the Obese Patient By Ireatha L. Wardsworth

2. Objectives Discuss anesthetic management: preanesthetic evaluation Discuss anesthetic management: preparation Discuss anesthetic management:maintenance Discuss anesthetic management: postoperative care

3. Preanesthetic Evaluation Includes Medications Laboratory Tests Cardiac Assessment Respiratory Evaluation Airway Evaluation Vascular Access

4. Goals of Preanesthetic evaluation Obtain pertinent data regarding the patient�s medical or surgical history Optimize current physiologic functioning Determine an appropriate anesthetic care plan

5. Preanesthetic Evaluation Patient Education Explanations of anticipated events during preoperative preparation (multiple venipunctures, central and arterial lines insertions, awake intubation, pain management) and protection of the patient�s privacy will relieve anxiety

6. Medications Obese person must be assessed for use of weight reducing substances, herbal supplements, and anorexiant drugs (drugs that action the brain to reduce the appetite). Chronic use of noradrenergic and serotonergic therapy can produce hypertension, tachycardia, anxiety, psychosis, and catecholamine depletion

7. Medications Catecholamine depletion can summate in profound hypotension during induction and maintenance of anesthesia, which is refactory to indirect acting vasprossors such as ephedrine. Phyenylephrine hydrochloride (Neo-Synephrine) is usually effective in reversing low blood pressure.

8. Medications At least weeks of abstinence from the drugs is recommended for adequate catecholamine levels to be recovered

9. Laboratory Tests Given the current climate of cost consciousness and cost efficiency only the laboratory test appropriate in light of the patient�s history, physical examination and planned surgery should be ordered Routine testing includes assessment of a complete blood count and electrolyte panel.

10. Laboratory Tests Complete blood cell counts may reveal hematocrits as high as 65, which can result from contracted blood volume or polycythemia associate with cardiopulmonary disease Leukocytosis (greater than 11,000) is a strong predictor of risk for acute myocardial infarction independent of tobacco smoking

11. Laboratory Tests Arterial blood gas analysis that compares samples taken with the patient lying supine and sitting while breathing room with the patient lying supine and sitting while breathing room with the patient lying supine and sitting while breathing room air provides baseline values and can distinguish simple obesity from OHS

12. Laboratory Tests A renal panel may reflect abnormal glucose and potassium levels, which are indicators of insulin resistance and potentiation of myocardial irritability. Diuretics and certain cardiac medications can worsen electrolyte disturbances Blood urea nitrogen (BUN) and creatinine levels may be elevated in response to dehydration or renal dysfunction

13. Laboratory Tests Lver function test are typically elevated in obese patients, it is do to the infiltration of the hepatocytes with triglycerides (fatty liver, liver steatosis). The severity of fatty infiltration may alter pharmacologic effects of many anesthetic drugs, thereby requiring dose reductions Coagulation studies are necessary if regional anesthesia is planned or if coagulopathy exists. Patients taking anticoagulants for treatment of deep vein thrombosis or atrial fibrillation may exhibit elevated prothrombin and partial thromboplastin times.

14. Nonsteroidal antiinflammatory drugs may prolong bleeding times and affect surgical hemostasis Obese patients undergoing abdominal or thoracic surgery should have a pulmonary test to assist with the anesthetic planning Chest radiography is necessary to determine the presence of cardiomegaly, pulmonary infiltrates, and evidence of COPD

15. Cardiac Assessment Evaluation of cardiac function is essential in overweight and obese patients undergoing surgery Investigation of prior MI, presence of HTN, angina, or PVD is crucial. Limitations in exercise tolerance, history orthopnea, and paroxysmal nocturnal dyspnea may indicate left ventricular dysfunction A careful elicitation of drug history give clues about the patient coexistent diseases

16. Cardiac Assessment When possible cardiac medications should be continued up to and including the morning of surgery An electrocardiogram is essential for determination of resting rate, rhythm, and ventricular hypertrophy or strain Exercise testing may elicit valuable information about the myocardial function in morbidly obese patients Alternative test are satisfactory for determining myocardial adequacy Echocardiography is useful for determining whether akinesis or wall motion abnormalities are present in the obese myocardium

17. Cardiac Assessment Cardiomegaly, pulmonary congestion, elevated diaphragm, and a tortuous aorta can be identified by use of chest radiography The results of the radiographic study serves to guide preoperative pharmacologic and medical management (diuretics, beta 1 agonists, antibiotics)

18. Respiratory Evaluation Careful preoperative evaluation of the patient�s respiratory function identifies potential problems. A patient who becomes dyspneic and desaturates when recumbent experiences the same symptoms during induction in the supine position Questions must elicit information regarding the presence or absence of orthopnea, wheezing, sputum production or smoking history. Recent upper respiratory infection, snoring or sleep disturbances may indicate obstructive processes

19. Airway Evaluation A thorough airway evaluation is warranted for determination of the optimal airway management technique in obese patients. Most practitioners use evaluation of multiple patient physical characteristics to identify potential airway problems indicative of the unanticipated difficult airway.

20. Airway Evaluation Patient physical characteristics that identify potential airway problems are Measurement of interincisor distance Thyromental distance Head and neck extension Mallampati classification Body weight A history of difficult airway

21. Airway Evaluation Evaluation of the length of upper incisors Visibility of the uvula Shape of the palate Compliance of the mandibular space and length Thickness of the neck provides further criteria for assessment

22. Airway Evaluation Short, thick neck Pendulous breasts Hypertrophied tonsils and adenoids Beards Marginal room air pulse oximetry saturations Abnormal arterial blood gases

23. Airway Evaluation Anatomic aberrations of the upper airway induced by severe obesity include reduced tempormandibular and antlantooccipital joint movement Unsatisfactory mouth opening, presence of neck or arm pain, or inability to place the head and neck into sniffing position may indicate the need for awake fiberoptic intubation

24. Airway Evaluation Inspection of the oropharynx is necessary to determine Mallampati classification for intubation difficulty Increasing neck circumference and Mallampati classification >3 have been identified as the two most important factors morbidly obese patients

25. Patient Education about Airway Management Airway management techniques should be explained to the patient, with emphasis on intubation and the need for postoperative ventilation, if need be.

26. Vascular Access Venipuncture can be challenging in obese patients with excessive fat that obscures blood vessels from both visualization and palpation Hemorrhage, hypothermia and trauma also reduces the likelihood of accessing vessels. It is suggest that a portable ultrasound machine may improve central venous catheter placement to avoid iatrogenic pneumothorax

27. Anesthetic Management: Preparation Anesthetic management preparation consist of: Equipment Monitoring Aspiration prophylaxis Airway equipment

28. Anesthetic Management: Equipment Preparation The preparation for emergent operating room procedures or nonemergent hospital admission, and appropriate equipment must be ready. New model operating room tables can accommodate up to 600 pounds of weight. Older model operating room tables could accommodate up to 300 to 350 pounds of weight. In cases of extreme morbid obesity big boy hydraulic beds are obtained and used in the operating room

29. Anesthetic Management: Equipment Preparation Extra large cuffs can be used on upper/lower extremity. Bed warming devices, fluid warms and warm airflow blankets should be employed to prevent hypothermia, which can occur rapidly when large areas of body surface are exposed

30. Anesthetic Managementa; monitoring Intraoperative monitoring should address the needs of the patient. Selection of electrocardiographic leads when possible, should enhance detection of myocardial ischemia and pathology (leads II and V5). Placement of an arterial catheter is appropriate for the monitoring hemodynamic status and is advocated for all but minor procedures. Use of central venous and pulmonary artery catheters should be consider in patients undergoing extensive or those with serious cardiorespiratory disease.

31. Aspiration prophylaxis The anesthetized obese patient�s airway creates an increase risk for regurgitation and pulmonary aspiration Obese patients have great volumes and more gastric fluid than person of normal weight Gastroesophageal reflux and hiatus hernia are more prevalent in the obese, predisposing them to esophagitis and pulmonary aspiration. Other conditions that cause delayed gastric emptying, such as Diabetes Mellitus and traumatic injury, further increase the risk of aspiration.

32. Aspiration Prophylaxis For these reasons the obese patient is considered to have a �full stomach,� even if the prescribed nothing by mouth intake restriction has been followed. Timely preinduction administration of histamine-2 and dopamine receptor antagonist coupled with oral administration of nonparticulate antacids decreases morbidity resulting from pulmonary aspiration and Mendelson�s syndrome.

33. Aspiration Prophylaxis Head up position of the patient, with application of the Sellick maneuver during rapid-sequence induction, limits the volume of vomitus that enters the trachea if reguritation occurs. Nasogastric/orogastric suctioning before emergence further reduces the amount of fluid available for aspiration

34. Airway Equipment An equally important part of airway assessment is the preparation of equipment and personnel necessary to ventilate and intubate the morbidly obese patient An assortment of blades, laryngoscopy handles, endotracheal tubes, masks, oral and nasopharyngeal airways and stylets should be assembled. Laryngeal mask airways (LMAs), fiberoptic and bronchoscopic devices, Eschman introducers, a jet ventilator (or Venturi apparatus), and emergency tracheotomy and cricothyrotomy kits must be available in the event that ventilation by mask or endotracheal tube is unsuccessful. A difficult airway cart that has all of the available equipment should be placed in the operating room.

35. Anesthetic Management: Maintenance Anesthetic management maintenance consist of: Intubation Effects of General Anesthesia on Respiration Choice of Anesthetic Technique Volume Replacement Intraoperative Positioning Integumentary Concerns Extubation Regional Anesthesia

36. Intubation For airway management to be facilitated, the obese patient should be positioned with the head elevated (reverse Trendelenburg position) on the operating room table. This position promotes patient comfort, reduces gastric reflux, provides easier mask ventilation, improves respiratory mechanics and helps maintain functional residual capacity (FRC). Reduced FRC in obese patients contributes to the rapid desaturation that occurs with induction of general anesthesia.

37. Intubation To attenuate the desaturation and maximize oxygen content in the lungs, patients are preoxygenated with 100% mask oxygen for at least 3 to 5 minutes. The patients head, neck and should be carefully moved into �sniffing position� by using pillows, doughnuts or foam head supports. Without proper support and alignment of the oropharynx and trachea, ventilation may be obstructed and visualization of the laryngeal structures may be obscured.

38. Intubation Some practitioners advocate the use of an �awake look� to visualize the difficulty of the airway. Careful administration of sedative drugs and application of topical anesthesia to the oropharyngeal structures, possibly including transtracheal and superior laryngeal nerve blocks are performed. Nasal oxygen is used as a supplement during awake laryngoscopy.

39. Intubation If the epiglottic and laryngeal anatomy is easily visible, successful asleep intubation can be done, if not than, an intubating LMA or awake fiberoptic intubation should be used. The endotracheal tube must be safely secured to prevent movement during positioning and surgery. The surgeon and another skilled anesthesia provider must also be in attendance during the induction.

40. Intubation Muscle hypotonus in the floor of the mouth, followed by rapid occurrence of soft tissue obstruction and hypoxia, requires one person to support the mask and airway while another person bag ventilates the patient. In the case of inability to ventilate/intubate, the American Society of Anesthesiologist difficult airway algorigthm should be followed. Intubation of the obese patient can be safely accomplished with careful assessment, planning and use of airway techniques familiar to the anesthetist.

41. Effects of general Anesthesia on Respiration General anesthesia depresses respiration in normal subjects so any preexisting pulmonary dysfunction is exaggerated by anesthesia. The type of surgery, positioning and underlying disease pathology further compound the undesirable respiratory responses caused by obesity and anesthesia. General anesthesia causes a 50% reduction in FRC in the obese anesthesia, as compared with a 20% reduction in anesthetized non obese patients

42. Effects of General Anesthesia on Respiration FRC can be increased by ventilating with large tidal volumes (15 to 20 ml/kg), although this has been shown to improve arterial oxygen tension only minimally. Positive end-expiratory pressure (PEEP) achieves an improvement in both FRC and arterial oxygen tension but only at the expense of cardiac output and oxygen delivery. Current ventilation recommendations include using tidal volumes of 10 to 12 ml/kg to avoid barotrauma.

43. Effects of General Anesthesia on Respiration During laparoscopic surgeries the respiratory rate should be 12 to 14 breaths per minute. Prolonged (longer than 2 to 3 hours) and extensive procedures (those involving the abdomen, thorax, and spine) negatively influence respiratory function. Subdiaphragmatic packing, cephalad displacement of organs, and surgical retraction cause decreased alveolar ventilation, atelectasis, and pulmonary congestion.

44. Effects of General Anesthesia on Respiration Recumbent/trendelenburg positioning further reduces diaphragmatic excursion, which is already impaired by the weight of the panniculus. Trendelenburg positioning also causes elevated filling pressures which then increase right ventricular preload. Myocardial oxygen consumption, cardiac output, pulmonary artery occluding pressures, peak inspiratory pressures, and venous admixtures are increased above upright-sitting values

45. Effects of General Anesthesia on Respiration In a normal weight person, cardiac output increases in response to supine posturing to maintain hemodynamic stability. By increasing left ventricular output the centrally located circulating volume is propelled forward, thereby minimizing pulmonary congestion and hypoxia.

46. Effects of General Anesthesia on Respiration In a severely obese patient, positive-pressure, ventilation (which impedes venous return) and inability to increase cardiac output may result in cardiopulmonary decompensation. This is exhibited intraoperatively by hypoxia, rales, ventricular ectopy, congestive heart failure, and hypotension. Bag ventilation by hand may be useful in reducing hypotension resulting from positive pressure

47. Effects of General Anesthesia on Respiration Adequate ventilator settings inflate the morbidly obese thorax to minimize hypoxia. Pressure or volume controlled ventilators can be used to maintain adequate oxygenation and normocapnia. Avoidance of prolonged prone, trendelenburg, or supine positioning also decreases ventilation-perfusion mismatch.

48. Effects of General Anesthesia on Respiration Optimization of oxygenation by using no less than 50% flow of inspired oxygen is recommended. PEEP can reduce venous admixture and support adequate arterial oxygenation. PEEP can impair arterial oxygenation in some patients when it is superimposed on large tidal volumes. It is recommended PEEP should not exceed 15cm H20.

49. Effects of General Anesthesia on Respiration Intraoperative events, such as hemorrhage or hypotension, further impair ventilatory homeostasis and result in hypoxemia that extends into the postoperative period. A vertical abdominal incision, compared with a horizontal (transverse incision also prolongs postoperative hypoxia). Pain causes further reductions in diaphragmatic excursion and vital capacity, leading to atelectasis and ventilation-perfusion mismatch. 24 hours postop admission to a monitored bed is prudent for severely obese patients who exhibit higher morbidity and mortality apart from anesthesia and surgery.

50. Choice of Anesthetic Technique Selection of the anesthetic technique is dependent on the patient, coexisting history, planned surgical procedure, anesthetist skills and preference, and patient preference. Anesthetic management of obese patients can include local or monitored anesthesia; general (narcotic, inhalation) anesthesia; regional blocks; or a combination of techniques. The use of shorting acting water soluble anesthetic facilitates a smooth anesthetic induction, maintenance, and emergence from anesthesia.

51. Choice of Anesthetic Technique Objective for maintenance of anesthesia in the obese include: Strict maintenance of airway Adequate skeletal muscle relaxation Optimum oxygenation Avoidance of the residual effects of muscle relaxants Provision of appropriate intraoperative and postoperative tidal volume Effective postoperative analgesia

52. Choice of Anesthetic Technique Depending on the patient�s condition, the objectives previously mention can be achieved by either general or regional anesthesia. An epidural anesthetic with concomitant �light� general anesthesia is frequently chosen. A light general anesthetic can facilitate management of the airway, ventilation, and the patient�s level of consciousness, where as the epidural provides surgical analgesia and anesthesia. Epidural catheter can be used for postoperative analgesic administration and will enhance earlier return of deep breathing and coughing maneuvers.

53. Volume Replacement In obesity patients the estimated blood volume is actually diminished. Fat, which contains only 8% to 10% water, contributes less fluid to total body water than equivalent amounts of muscle. The normal adult percentage of total body water is 60% to 65%

54. Volume Replacement In severely obese it is reduced to 40. Therefore calculation of estimated blood volume should be 45 to 55 ml/kg of actual body weight rather than 70ml/kg apportioned in non obese adults. Accurate volume replacement and avoidance of rapid rehydration lessen cardiopulmonary compromise.

55. Volume Replacement Fluid management is guided by blood pressure, heart rate, and urine output measurements. Volume expanders should not be administered at greater than recommended volumes per kilogram of Ideal Body Weight (IBW) (20ml/kg). Dilutional coagulopathy, factor VIII inhibition, and decreased platelet aggregability can result from excessive administration.

56. Volume Replacement Blood loss replacement of 3:1 ratio (3 ml of crystalloid to 1 ml of blood loss) is applicable in severely obese patients. Blood products after careful identification, should be replaced according to the patient�s laboratory values and hemodynamic or surgical need.

57. Intraoperative Positioning Surgical positioning of morbidly obese patients necessitates extra precautions for the prevention of nerve, integumentary, and cardiorespiratory compromise.. Many peripheral nerves are subjected to possible ischemia or necrosis, the lunar, brachial plexus, radial, personal, and sphenoid nerves are the most vulnerable to injury in any anesthetized patient. In morbidly obese patients the incidence may be increased because of excessive weight on the anatomic structures. Care is necessary when one is positioning obese extremities in slings, draping them on Mayo stands or securing them in lithotomy stirrups.

58. Intraoperative Positioning Prolong hyperextension, external rotation or abduction can cause postoperative muscle pain, nerve palsies or paralysis. Therefore less flexion or abduction, and rotation of hips, legs, and arms my be necessary. Frequent repeated inspections of extremities for color and temperature can help diminish the incidence of positioning related injuries

59. Intraoperative Positioning Lower back pain can be aggravated by both spinal and general anesthesia because of ligamentous relaxation that results in loss of lumbar curvature. Surgical towels placed under the lumbar spine before induction will enhance lordosis and reduce postoperative discomfort

60. Integumentary concerns Decubitus, skin infection and wound dehiscence are exceedingly common in the severely obese Therefore ensure all pressure points are padded and properly position.

61. Extubation The risk of airway obstruction after extubation is increased in obese patients. A decision to extubate depends on evaluation of the ease of mask ventilation and tracheal intubation the length and type of surgery and the presence of preexisting medical conditions, including OSA.

62. Extubation Criteria for extubation consist of: Awake state, tidal volume and respiratory rate at preoperative levels Ability to sustain head lift or leg lift for at least 5 seconds Constant hand grip Effective cough Adequate vital capacity of at least 15ml/kg and inspiratory force of at least -25 to -30cm H20

63. Extubation Patients must be placed with the head up or in a sitting position. If doubt exist regarding the ability of the patient to breathe adequately, the endotracheal tube is left in place. Extubation over an airway exchange catheter or via a fiberoptic or bronchoscope may be performed

64. Regional Anesthesia Regional anesthesia can be used as the primary anesthetic in selected cases or as an accompaniment to postoperative pain and mobility management. Difficulties are frequently encountered with severely obese patients Anatomical landmarks are not easily visualized or palpable Brachial plexus anesthesia can be hampered by adipose tissue in the axillary region due to an inability to position the arm or undetectable pulses.

65. Regional Anesthesia Redudant rolls of adipose tissue, unsatisfactory ventilation and the inability of the patient to sustain optimal positioning making neuraxial anesthesia more challenging For subarachnoid or epidural anesthesia it is recommended that the patient is sitting upright so that landmarks such as C7 or L3 to L4 can be more easily identified Larger spinal needles should be used.

66. Regional Anesthesia Generous infiltration with local anesthetic will provide greater patient comfort during insertion due to the repeated insertions and repositioning of the needle or introducer. Another consideration regarding subarachnoid or epidural anesthesia in severely obese pregnant or surgical patients is the lack of predictability of spread of local anesthetic. Undesirable cephalad spread of local anesthetic can be obviated by reducing the volume and increasing the patient�s upright sitting time.

67. Anesthetic Management: Postoperative Care Postoperative Care includes: Pain Management Postoperative Complication

68. Pain Management Postoperative pain management is faciliated by the use of oral analgesics, nonsteroidal antiinflammatory agents, narcotics, patient-controlled analgesia, local infiltration of surgical site and epidural anesthesia Obese patients are more sensitive to the respiratory depressant effects of opioid analgesics; therefore caution and close monitoring are warranted. Supplemental oxygen and pulse oximetry monitoring are mandated.

69. Postoperative Complications Morbidity and mortality rates are higher in obese patients than non obese patients. Ventilation abnormalities are exacerbated in obese patients with OSA and OHS and may last for several days. The maximum decrease in partial pressure of arterial oxygen occurs 2 to 3 days postoperatively.

70. Postoperative Complications The risk of thromboembolism, wound infections, and atelectasis is amplified in patients with increased BMI. Thromboembolism is facilitated by immobility (Venous stasis, increased blood viscosity (polycythemia, hypovolemia) increased abdominal pressure, and abnormalities in serum procoagulants and anticoagulants. Antiembolic stockings and correctly fitting pneumatic compression boots can lessen the occurrence of deep vein thrombosis in the early postoperative period.

71. Postoperative Complications Early ambulation and maintenance of vascular volume further reduces the likelihood that clots will develop. Wound infections and pulmonary embolism are 50% higher in obese patients than non obese patients.

72. Case Presentation Calling for class participation Remember there are many ways to do it right and a few ways to do it wrong

73. Basic Data Name: Jack Daniels Age: 26 years old Gender: Male Occupation: Student Chief complaint: admitted for Lap. Adrenalectomy

74. Present Illness Hx of HTN taking Metoprolol (SBP around 140) Hospital abdominal CT showed adrenal tumor about 4 cm at right side Lab results show hypokalemia, hyperaldosteronism Pt admitted for adrenalectomy

75. Past History HTN: initially up to 200mmHg, controlled to 140 after medication No DM, CAD Denies smoking and alcohol use Medications: Concor, Adalat, Slow-K No operation history Drug allergy: NKDA Family history: non-contributory

76. Physical Examination Height: 166cm Weight: 109.9kg BMI:39.98 Consciousness E4V5M6 HEENT: conjunctiva: no pale; ictera: anicteric, Neck; no jugular vein engorement Chest: symmetric expansion, breath sound clear, no crackle, wheezing Heart: regular heart beat, no murmur Abdomen: soft, no tenderness, bowel sound Extremity: warm, no pitting edema

77. Anesthetic technique GETA (+/- epidural for postop analgesia). If postop epidural analgesia is planned, placement of catheter before anesthetic induction is helpful in establishing correct placement ( 5-7ml of lidocaine via the epidural

78. Induction Gentle IV induction (titrate to effect with pentothal or etomidate) and muscle relaxation (vecuronium 0.1mg/kg). Pt. should be adequately anesthetized before any stimulation. Unopposed to parasympatheic response to laryngoscopy can occur, with resultant bradycardia/asystole.

79. Maintenance Isoflurane Fentanyl Muscle relaxant (vecuronium), N20 2% lidocaine without epi continous infusion Nitroprusside for HTN Esmolol for tachycardia Phenylephrine or dopamine.

80. Emergence Depends on ease of the surgical procedure and the hemodynamic stability of the patient intraop. If patient is hemodynamically unstable, hypothermic, or has a large 3rd space fluid requirement, consider postop ventilation.

81. Blood /Fluid Requirements Anticipate large blood loss IV:14-16ga x2 NS/LR @10-15ml/kg/h Warm all fluids Humidify inhaled gases Cell saver

82. Monitoring Standard monitors Foley Arterial line CVP/PA catheter

83. Complications Labile HHTN Dysrhythmias Hypotension (post excision) Surgical manipulaton of the adrenal may cause hypertension and dysrhythmisas Alert surgeon and control BP with phenylephrine/dopamine infusions

84. Positioning Check and pad pressure points Check eyes

85. Are you Finish Yet! No Formulate an intraoperative Laparscopic Adrenalectomy anesthetic care plan. List the objectives for maintenance of anesthesia in the obese patient. List the patient physical characteristics that can identify potential airway problems. The decision to extubate the patient depends on 4 things. List the 4 things. The criteria for extubation consist of: