1. Principles of Preoperative and Operative Surgery
Sabiston 2007
Presented in April 2008
By Dr. S. Noorshafiee

2. Preoperative Preparation of the Patient   
Systems Approach to Preoperative Evaluation   
Additional Preoperative Considerations  
 Preoperative Checklist   

3. PREOPERATIVE PREPARATION OF THE PATIENT
The modern preparation of a patient for surgery is epitomized by the convergence of the art and science of the surgical discipline. The context in which preoperative preparation is conducted ranges from an outpatient office visit to hospital inpatient consultation to emergency department evaluation of a patient.

4. Approaches to preoperative evaluation differ significantly, depending on the nature of the complaint and the proposed surgical intervention, patient health and assessment of risk factors, and the results of directed investigation and interventions to optimize the patient's overall status and readiness for surgery.

5. This chapter reviews the components of risk assessment applicable to the evaluation of any patient for surgery and attempts to provide some basic algorithms to aid in the preparation of patients for surgery.

6. Determining the Need for Surgery
Patients are often referred to surgeons with a suspected surgical diagnosis and the results of supporting investigations in hand. In this context, the surgeon's initial encounter with the patient may be largely directed toward confirmation of relevant physical findings and review of the clinical history and laboratory and investigative tests that support the diagnosis.

7. A recommendation regarding the need for operative intervention can then be made by the surgeon and discussed with the patient's family members. A decision to perform additional investigative tests or consideration of alternative therapeutic options may postpone the decision for surgical intervention from this initial encounter to a later time

8. It is important for the surgeon to explain the context of the illness and the benefit of different surgical interventions, further investigation, and possible nonsurgical alternatives, when appropriate

9. The surgeon's approach to the patient and family during the initial encounter should be one that fosters a bond of trust and opens a line of communication among all participants. A professional and unhurried approach is mandatory, with time taken to listen to concerns and answer questions posed by the patient and family members.

10. The surgeon's initial encounter with a patient should result in the patient being able to express a basic understanding of the disease process and the need for further investigation and possible surgical management. A well-articulated follow-up plan is essential.

11. Perioperative Decision Making
Once the decision has been made to proceed with operative management, a number of considerations must be addressed regarding the timing and site of surgery, the type of anesthesia, and the preoperative preparation necessary to understand the patient's risk and optimize the outcome.

12. These components of risk assessment take into account both the perioperative (intraoperative period through 48 hours postoperatively) and the later postoperative (up to 30 days) periods and seek to identify factors that may contribute to patient morbidity during these periods.

13. Preoperative Evaluation
The aim of preoperative evaluation is not to screen broadly for undiagnosed disease but rather to identify and quantify any comorbidity that may have an impact on the operative outcome

14. This evaluation is driven by findings on the history and physical examination suggestive of organ system dysfunction or by epidemiologic data suggesting the benefit of evaluation based on age, gender, or patterns of disease progression. The goal is to uncover problem areas that may require further investigation or be amenable to preoperative optimization

15. Routine preoperative testing is not cost-effective and, even in the elderly, is less predictive of perioperative morbidity than the American Society of Anesthesiologists (ASA) status or American Heart Association

16. The preoperative evaluation is determined in light of the planned procedure (low, medium, or high risk), the planned anesthetic technique, and the postoperative disposition of the patient (outpatient or inpatient, ward bed, or intensive care

17. In addition, the preoperative evaluation is used to identify patient risk factors for postoperative morbidity and mortality.

18. If preoperative evaluation uncovers significant comorbidity or evidence of poor control of an underlying disease process, consultation with an internist or medical subspecialist may be required to facilitate the workup and direct management. In this process, communication between the surgeon and consultants is essential to define realistic goals for this optimization process and to expedite surgical management

19. SYSTEMS APPROACH TO PREOPERATIVE EVALUATION

20. Cardiovascular
Cardiovascular disease is the leading cause of death in the industrialized world, and its contribution to perioperative mortality during noncardiac surgery is significant. Of the 27 million patients undergoing surgery in the United States every year, 8 million, or nearly 30%, have significant coronary artery disease or other cardiac comorbid conditions.

21. One million of these patients will experience perioperative cardiac complications, with substantial morbidity, mortality, and cost. Consequently, much of the preoperative risk assessment and patient preparation centers on the cardiovascular system.

22. One of the first anesthesia risk categorization systems was the ASA classification. It has five stratifications:
 I—Normal healthy patient  
 II—Patient with mild systemic disease   
III—Patient with severe systemic disease that limits activity but is not incapacitating  
IV—Patient who has incapacitating disease that is a constant threat to life
 V—Moribund patient not expected to survive 24 hours with or without an operation

23. There are more other systems for evaluation of cardiovascular risk such as:
Goldman cardiac risk index,1977
Detsky modified multifactorial index 1986
Eagle's Criteria for Cardiac Risk Assessment, 1989
Revised Cardiac Risk Index

24. Once these data have been obtained, the surgeon and consultants need to weigh the benefits of surgery against the risk and determine whether any perioperative intervention will reduce the probability of a cardiac event

25. This intervention usually centers on coronary revascularization via coronary artery bypass or percutaneous transluminal coronary angioplasty but may include modification of the choice of anesthetic or the use of invasive intraoperative monitoring

26. Patients who have undergone a percutaneous coronary intervention with stenting need to have elective noncardiac procedures delayed for 4 to 6 weeks, although the delay may be shortened depending on the type of stent used (drug eluting versus non–drug eluting

27. The optimal timing of a surgical procedure after myocardial infarction (MI) is dependent on the duration of time since the event and assessment of the patient's risk for ischemia, either by clinical symptoms or by noninvasive study

28. Any patient can be evaluated as a surgical candidate after an acute MI (within 7 days of evaluation) or a recent MI (within 7-30 days of evaluation). The infarction event is considered a major clinical predictor in the context of ongoing risk for ischemia

29. The risk for reinfarction is generally considered low in the absence of such demonstrated risk. General recommendations are to wait 4 to 6 weeks after MI to perform elective surgery

30. Improvements in postoperative care have centered on decreasing the adrenergic surge associated with surgery and halting platelet activation and microvascular thrombosis

31. Perioperative risk for cardiovascular morbidity and mortality was decreased by 67% and 55%, respectively, in ACC/AHA-defined medium- to high-risk patients receiving β-blockers in the perioperative period versus those receiving placebo.

32. Although the benefit was most noticeable in the 6 months after surgery, event-free survival was significantly better in the group that received β-blockers up to 2 years after surgery.The current AHA/ACC recommendations are to start β-blocker therapy in medium- to high-risk patients undergoing major- to intermediate-risk surgery as early as possible preoperatively and titrate to a heart rate of 60 beats per minute. The choice of agent and duration of therapy are still being debated

33. An easy, inexpensive method to determine cardiopulmonary functional status for noncardiac surgery is the patient's ability or inability to climb two flights of stairs. Two flights of stairs is needed because it demands greater than 4 metabolic equivalents (METs).

34. In a review of all studies of stair climbing as preoperative assessment, prospective studies have shown it to be a good predictor of mortality associated with thoracic surgery. In major noncardiac surgery, an inability to climb two flights of stairs is an independent predictor of perioperative morbidity, but not mortality.

35. Pulmonary
Preoperative evaluation of pulmonary function may be necessary for either thoracic or general surgical procedures.

36. Whereas extremity, neurologic, and lower abdominal surgical procedures have little effect on pulmonary function and do not routinely require pulmonary function studies, thoracic and upper abdominal procedures can decrease pulmonary function and predispose to pulmonary complications

37. Accordingly, it is wise to consider assessment of pulmonary function for all lung resection cases, for thoracic procedures requiring single-lung ventilation, and for major abdominal and thoracic cases in patients who are older than 60 years, have significant underlying medical disease, smoke, or have overt pulmonary symptomatology

38. Necessary tests include forced expiratory volume in 1 second (FEV1), forced vital capacity, and the diffusing capacity of carbon monoxide

39. Adults with an FEV1 of less than 0
Adults with an FEV1 of less than 0.8 L/sec, or 30% of predicted, have a high risk for complications and postoperative pulmonary insufficiency. Pulmonary resections need to be planned so that the postoperative FEV1 is greater than 0.8 L/sec, or 30% of predicted. Such planning can be done with the aid of quantitative lung scans, which can indicate which segments of the lung are functional

40. Preoperative pulmonary assessment determines not only factors that confer increased risk but also potential targets to reduce the risk for pulmonary complications

41. General factors that increase risk for postoperative pulmonary complications include increasing age, lower albumin level, weight loss, and possibly obesity

42. Concurrent comorbid conditions such as impaired sensorium, previous stroke, congestive heart failure, acute renal failure, chronic steroid use, and blood transfusion are also associated with increased risk for postoperative pulmonary complications

43. Specific pulmonary risk factors include chronic obstructive pulmonary disease, smoking, preoperative sputum production, pneumonia, dyspnea, and obstructive sleep apnea.

44. Preoperative interventions that may decrease postoperative pulmonary complications include smoking cessation (>2 months before the planned procedure), bronchodilator therapy, antibiotic therapy for preexisting infection, and pretreatment of asthmatic patients with steroids. Perioperative strategies include the use of epidural anesthesia, vigorous pulmonary toilet and rehabilitation, and continued bronchodilator therapy.

45. Renal
Approximately 5% of the adult population have some degree of renal dysfunction that can affect the physiology of multiple organ systems and cause additional morbidity in the perioperative period. In fact, a preoperative creatinine level of 2.0 mg/dL or higher is an independent risk factor for cardiac complications

46. Identification of coexisting cardiovascular, circulatory, hematologic, and metabolic derangements secondary to renal dysfunction are the goals of preoperative evaluation in these patients

47. A patient with known renal insufficiency undergoes a thorough history and physical examination with particular questioning about previous MI and symptoms consistent with ischemic heart disease. The cardiovascular examination seeks to document signs of fluid overload. The patient's functional status and exercise tolerance are carefully elicited.

48. Diagnostic testing for patients with renal dysfunction include an electrocardiogram (ECG), serum chemistry panel, and complete blood count (CBC). If physical examination findings are suggestive of heart failure, a chest radiograph may be helpful

49. Urinalysis and urinary electrolyte studies are not often helpful in the setting of established renal insufficiency, although they may be diagnostic in patients with new-onset renal dysfunction.

50. Laboratory abnormalities are often seen in a patient with advanced renal insufficiency. Some metabolic derangements in a patient with advanced renal failure may be mild and asymptomatic and are revealed by electrolyte or blood gas analysis

51. Anemia, when present in these patients, may range from mild and asymptomatic to that associated with fatigue, low exercise tolerance, and exertional angina. Such anemia can be treated with erythropoietin or darbepoietin preoperatively or perioperatively

52. Because the platelet dysfunction associated with uremia is often a qualitative one, platelet counts are usually normal. A safe course is to communicate with the anesthesiologist the potential need for agents to be available in the operating room to assist in improving platelet function.

53. Pharmacologic manipulation of hyperkalemia, replacement of calcium for symptomatic hypocalcemia, and the use of phosphate-binding antacids for hyperphosphatemia are often required.

54. Sodium bicarbonate is used in the setting of metabolic acidosis not caused by hypoperfusion when serum bicarbonate levels are below 15 mEq/L. It can be administered in intravenous (IV) fluid as 1 to 2 ampules in a 5% dextrose solution

55. Hyponatremia is treated by volume restriction, although dialysis is commonly required within the perioperative period for control of volume and electrolyte abnormalities

56. Patients with chronic end-stage renal disease undergo dialysis before surgery to optimize their volume status and control the potassium level. Intraoperative hyperkalemia can result from surgical manipulation of tissue or transfusion of blood. Such patients are often dialyzed on the day after surgery as well

57. Prevention of secondary renal insults in the perioperative period include the avoidance of nephrotoxic agents and maintenance of adequate intravascular volume throughout this period. In the postoperative period, the pharmacokinetics of many drugs may be unpredictable, and adjustments in dosage need to be made according to pharmacy recommendation.

58. In the acute setting, patients who have stable volume status can undergo surgery without preoperative dialysis, provided that no other indication exists for emergency dialysis.

59. Notably, narcotics used for postoperative pain control may have prolonged effects despite hepatic clearance, and nonsteroidal agents are avoided in patients with renal insufficiency.

60. Principles of Preoperative and Operative Surgery
Sabiston 2007
Presented in April 2008
By Dr. S. Noorshafiee

61. SYSTEMS APPROACH TO PREOPERATIVE EVALUATION

62. Hepatobiliary
Hepatic dysfunction may reflect the common pathway of a number of insults to the liver, including viral-, drug-, and toxin-mediated disease. A patient with liver dysfunction requires careful assessment of the degree of functional impairment, as well as a coordinated effort to avoid additional insult in the perioperative period

63. A history of any exposure to blood and blood products or exposure to hepatotoxic agents is obtained. Patients frequently know whether hepatitis has been diagnosed and need to be questioned about when the diagnosis was made and what activity led to the infection

64. Although such a history may not affect further patient evaluation, it is important to obtain in case an operative team member is injured during the planned surgical procedure.

65. A review of systems specifically inquires about symptoms such as pruritus, fatigability, excessive bleeding, abdominal distention, and weight gain. Evidence of hepatic dysfunction may be seen on physical examination

66. Jaundice and scleral icterus may be evident with serum bilirubin levels higher than 3 mg/dL. Skin changes include spider angiomas, caput medusae, palmar erythema, and clubbing of the fingertips. Abdominal examination may reveal distention, evidence of fluid shift, and hepatomegaly. Encephalopathy or asterixis may be evident. Muscle wasting or cachexia can be prominent

67. A patient with liver dysfunction undergoes standard liver function tests. Elevations in hepatocellular enzymes may suggest a diagnosis of acute or chronic hepatitis, which can be investigated by serologic testing for hepatitis A, B, and C. Alcoholic hepatitis is suggested by lower transaminase levels and an aspartate/alanine transaminase ratio (AST/ALT) greater than 2

68. Laboratory evidence of chronic hepatitis or clinical findings consistent with cirrhosis is investigated with tests of hepatic synthetic function, notably serum albumin, prothrombin, and fibrinogen

69. Patients with evidence of impaired hepatic synthetic function also have a CBC and serum electrolyte analysis. Type and screen is indicated for any procedure in which blood loss could be more than minimal.

70. In the event of an emergency situation requiring surgery, such an investigation may not be possible. A patient with acute hepatitis and elevated transaminases is managed nonoperatively, when feasible, until several weeks beyond normalization of laboratory values.

71. Urgent or emergency procedures in these patients are associated with increased morbidity and mortality. A patient with evidence of chronic hepatitis may often safely undergo surgery

72. A patient with cirrhosis may be assessed with the Child-Pugh classification, which stratifies operative risk according to a score based on abnormal albumin and bilirubin levels, prolongation of the prothrombin time (PT), and the degree of ascites and encephalopathy

73. This scoring system was initially applied to predict mortality in cirrhotic patients undergoing portacaval shunt procedures, although it has been shown to correlate with mortality in cirrhotic patients undergoing a wider spectrum of procedures as well.

74. Although the figures may not represent current risk for all types of abdominal operations, little doubt exists that the presence of cirrhosis confers additional risk for abdominal surgery and that this risk is proportional to the severity of disease

75. Other factors that affect outcomes in these patients are the emergency nature of a procedure, prolongation of the PT greater than 3 seconds above normal and refractory to correction with vitamin K, and the presence of infection

76. Two common problems requiring surgical evaluation in a cirrhotic patient are hernia (umbilical and groin) and cholecystitis. An umbilical hernia in the presence of ascites is a difficult management problem because spontaneous rupture is associated with increased mortality rates.

77. Elective repair is best after the ascites has been reduced to a minimum preoperatively, although the procedure is still associated with mortality rates as high as 14%.Repair of groin hernias in the presence of ascites is less risky in terms of both recurrence and mortality.

78. Several recent reports have shown decreased rates of complication with laparoscopic procedures performed in cirrhotic patients. Among the best-described procedures is laparoscopic cholecystectomy performed in patients with Child's class A through C. When compared with open cholecystectomy, less morbidity in terms of blood loss and wound infection has been observed.

79. Malnutrition is common in cirrhotic patients and is associated with a reduction in hepatic glycogen stores and reduced hepatic protein synthesis. Patients with advanced liver disease often have a poor appetite, tense ascites, and abdominal pain. Attention must be given to appropriate enteral supplementation, as done for all patients at significant nutritional risk.

80. Endocrine
A patient with an endocrine condition such as diabetes mellitus, hyperthyroidism or hypothyroidism, or adrenal insufficiency is subject to additional physiologic stress during surgery.

81. The preoperative evaluation identifies the type and degree of endocrine dysfunction to permit preoperative optimization. Careful monitoring identifies signs of metabolic stress related to inadequate endocrine control during surgery and throughout the postoperative course.

82. The evaluation of a diabetic patient for surgery assesses the adequacy of glycemic control and identifies the presence of diabetic complications, which may have an impact on the patient's perioperative course.

83. The patient's history and physical examination document evidence of diabetic complications, including cardiac disease, circulatory abnormalities, and the presence of retinopathy, neuropathy, or nephropathy

84. Preoperative testing may include fasting and postprandial glucose and hemoglobin A1c levels. Serum electrolyte, blood urea nitrogen, and creatinine levels are obtained to identify metabolic disturbances and renal involvement. Urinalysis may reveal proteinuria as evidence of diabetic nephropathy.

85. An ECG is considered in patients with long-standing disease
An ECG is considered in patients with long-standing disease. The existence of neuropathy in diabetics may be accompanied by cardiac autonomic neuropathy, which increases the risk for cardiorespiratory instability in the perioperative period.

86. A diabetic patient requires special attention to optimize glycemic control perioperatively. Non–insulin-dependent diabetics need to discontinue long-acting sulfonylureas such as chlorpropamide and glyburide because of the risk for intraoperative hypoglycemia; a shorter-acting agent or sliding-scale insulin coverage may be substituted in this period.

87. The use of metformin is stopped preoperatively because of its association with lacticacidosis in the setting of renal insufficiency. An insulin-dependent diabetic is told to withhold long-acting insulin preparations (Ultralente preparations) on the day of surgery; lower dosages of intermediate-acting insulin (NPH or Lente) are substituted on the morning of surgery

88. These patients are scheduled for early morning surgery, when feasible
These patients are scheduled for early morning surgery, when feasible. During surgery, a standard 5% or 10% dextrose infusion is used with short-acting insulin or an insulin drip to maintain glycemic control

89. A patient with diabetes mellitus that is well controlled by diet or oral medication may not require insulin perioperatively, but those with poorer control or patients taking insulin may require preoperative dosing and both glucose and insulin infusion during surgery

90. Frequent assessments of glucose levels are continued through the postoperative period. Current recommendations are to maintain the perioperative glucose level between 80 and 150 mg/dL, even in patients not previously diagnosed as being diabetic. Adequate hydration must be maintained with avoidance of hypovolemia.

91. Postoperative orders include frequent (every 2-4 hours) finger stick glucose checks and the use of short-acting insulin in the form of sliding-scale coverage. Twice-daily doses of intermediate-acting insulin can be supplemented with sliding-scale coverage until the patient is eating and can resume the usual regimen

92. Postoperative cardiac events can occur with unusual manifestations in these patients. Although chest pain needs to be evaluated with ECG and serum troponin levels, this same evaluation may need to be done for new-onset dyspnea, blood pressure alterations, or a decrease in urine output

93. Adequate prophylaxis for deep venous thrombosis (DVT) is essential because of the increased risk for thrombosis. The adequacy of perioperative glycemic control has an impact on wound healing and the risk for surgical site infection

94. Perioperative Diabetic Management
Management of diabetic patients has evolved over the past several years. The introduction of new drugs for non–insulin-dependent diabetics, in addition to new types of insulin and new insulin delivery systems in insulin-dependent diabetics, has changed the way that these patients are approached in the perioperative period.

95. Rapid-acting (Lispro) and short-acting (Regular) insulin preparations are usually withheld when the patient stops oral intake (NPO) and are used for acute management of hyperglycemia during the NPO period

96. intermediate-acting (NPH Lente) and long-acting (Ultralente, Glargine) insulin preparations are administered at two thirds the normal pm dose the night before surgery and half the normal am dose the morning of surgery, with frequent bedside glucose determinations and treatment with short-acting insulin as needed. An infusion of 5% dextrose is initiated the morning of surgery

97. If the planned procedure is expected to take a long time, an insulin infusion can be administered, again with frequent monitoring of blood glucose.

98. Insulin pumps are used by some patients as their method of glucose management. These pumps use short-acting insulin and have a variable delivery rate that can be programmed to more closely simulate endogenous insulin production

99. On the day of surgery, the patient continues with the basal insulin infusion. The pump is then used to correct the glucose level as it is measured. Patients generally have a correction or sensitivity factor that will decrease their glucose by 50 mg/dL. It is important to know this factor before the planned surgical procedure so that glucose can be managed in the operating room

100. Patients who take oral hypoglycemic agents typically withhold their normal dose the day of surgery. Patients can resume their oral agent once diet is resumed. Coverage for hyperglycemia is with a short-acting insulin preparation based on blood glucose monitoring. An exception is metformin. If the patient has altered renal function, this agent needs to be discontinued until renal function either normalizes or stabilizes.

101. patient with known or suspected thyroid disease is evaluated with a thyroid function panel. Evidence of hyperthyroidism is addressed preoperatively and surgery deferred until a euthyroid state is achieved, when feasible

102. These patients need to have their electrolyte levels determined and an ECG performed as part of their preoperative evaluation. In addition, if the physical examination suggests signs of airway compromise, further imaging may be warranted

103. A patient with hyperthyroidism who takes antithyroid medication such as propylthiouracil or methimazole is instructed to continue this regimen on the day of surgery

104. The patient's usual doses of β-blockers or digoxin are also continued
The patient's usual doses of β-blockers or digoxin are also continued. In the event of urgent surgery in a thyrotoxic patient at risk for thyroid storm, a combination of adrenergic blockers and glucocorticoids may be required and are administered in consultation with an endocrinologist

105. Patients with newly diagnosed hypothyroidism generally do not require preoperative treatment, although they may be subject to increased sensitivity to medications, including anesthetic agents and narcotics

106. Severe hypothyroidism can be associated with myocardial dysfunction, coagulation abnormality, and electrolyte imbalance, notably hypoglycemia. Severe hypothyroidism needs to be corrected before elective operations

107. Hematologic
Hematologic assessment may lead to the identification of disorders such as anemia, inherited or acquired coagulopathy, or a hypercoagulable state. Substantial morbidity may derive from failure to identify these abnormalities preoperatively. The need for perioperative prophylaxis for venous thromboembolism must be carefully reviewed in every surgical patient.

108. Anemia is the most common laboratory abnormality encountered in preoperative patients. It is often asymptomatic and can require further investigation to understand its cause. The history and physical examination may uncover subjective complaints of energy loss, dyspnea, or palpitations, and pallor or cyanosis may be evident

109. Patients are evaluated for lymphadenopathy, hepatomegaly, or splenomegaly, and pelvic and rectal examinations are performed. A CBC, reticulocyte count, and serum iron, total iron-binding capacity, ferritin, vitamin B12, and folate levels are obtained to investigate the cause of anemia.

110. The decision to transfuse a patient perioperatively is made with consideration of the patient's underlying risk factors for ischemic heart disease and the estimated magnitude of blood loss during surgery.

111. Generally, patients with normovolemic anemia without significant cardiac risk or anticipated blood loss can be managed safely without transfusion, with most healthy patients tolerating hemoglobin levels of 6 or 7 g/dL

112. Guidelines for Red Blood Cell Transfusion for Acute Blood Loss
Evaluate the risk for ischemia
Estimate/anticipate the degree of blood loss. Less than 30% rapid volume loss probably does not require transfusion in a previously healthy individual

113. Measure the hemoglobin concentration: <6 g/dL, transfusion usually required; 6-10 g/dL, transfusion dictated by clinical circumstance; >10 g/dL, transfusion rarely required

114. Measure vital signs/tissue oxygenation when hemoglobin is 6-10 g/dL and the extent of blood loss is unknown. Tachycardia and hypotension refractory to volume suggest the need for transfusion; O2 extraction ratio >50%, decreased Vo2, suggest that transfusion is usually needed

115. All patients undergoing surgery are questioned to assess their bleeding risk. Coagulopathy may result from inherited or acquired platelet or factor disorders or may be associated with organ dysfunction or medications

116. The inquiry begins with direct questioning about a personal or family history of abnormal bleeding. Supporting information includes a history of easy bruising or abnormal bleeding associated with minor procedures or injury.

117. A history of liver or kidney dysfunction or recent common bile duct obstruction needs to be elicited, as well as an assessment of nutritional status. Medications are carefully reviewed, and the use of anticoagulants, salicylates, nonsteroidal anti-inflammatory drugs (NSAIDs), and antiplatelet drugs are noted

118. Physical examination may reveal bruising, petechiae, or signs of liver dysfunction.

119. Patients with thrombocytopenia may have qualitative or quantitative defects as a result of immune-related disease, infection, drugs, or liver or kidney dysfunction.

120. Qualitative defects may respond to medical management of the underlying disease process, whereas quantitative defects may require platelet transfusion when counts are less than 50,000 in a patient at risk for bleeding

121. Although coagulation studies are not routinely ordered, patients with a history suggestive of coagulopathy undergo coagulation studies before surgery. Coagulation studies are also obtained before the procedure if considerable bleeding is anticipated or any significant bleeding would be catastrophic.

122. Patients with documented disorders of coagulation may require perioperative management of factor deficiencies, often in consultation with a hematologist

123. Patients receiving anticoagulation therapy usually require preoperative reversal of the anticoagulant effect. In patients taking warfarin, the drug is withheld for four scheduled doses preoperatively to allow the international normalized ratio (INR) to fall to the range of 1.5 or less (assuming that the patient is maintained at an INR of ).

124. Additional recommendations for specific diagnoses requiring chronic anticoagulation are based on risk-benefit analysis. Patients with a recent history of venous thromboembolism or acute arterial embolism frequently require perioperative IV heparinization because of an increased risk for recurrent events in the perioperative period

125. Systemic heparinization can often be stopped within 6 hours of surgery and restarted within 12 hours postoperatively. When possible, surgery is postponed in the first month after an episode of venous or arterial thromboembolism. Patients taking anticoagulants for less than 2 weeks for pulmonary embolism (PE) or proximal DVT are considered for inferior vena cava filter placement before surgery

126. All surgical patients are assessed for their risk for venous thromboembolism and receive adequate prophylaxis according to current guidelines.Patients are questioned to elicit any personal or family history suggestive of a hypercoagulable state. Levels of protein C, protein S, antithrombin III, and antiphospholipid antibody can be obtained

127. Risk factor stratification is achieved by considering multiple factors, including age, type of surgical procedure, previous thromboembolism, cancer, obesity, varicose veins, cardiac dysfunction, indwelling central venous catheters, inflammatory bowel disease, nephrotic syndrome, pregnancy, and estrogen or tamoxifen use.

128. A number of regimens may be appropriate for prophylaxis of venous thromboembolism, depending on assessed risk.Such regimens include the use of unfractionated heparin, low-molecular-weight heparin, intermittent compression devices, and early ambulation. Initial prophylactic doses of heparin can be given preoperatively, within 2 hours of surgery.

129. ADDITIONAL PREOPERATIVE CONSIDERATIONS
Older adults account for a disproportionate percentage of surgical patients. Risk assessment must carefully consider the effect of comorbid illness in this population. Although age has been reported as an independent risk factor for postoperative mortality, this observation may represent the unmeasured aspects of comorbid disease and the severity of illness.

130. In an older adult patient, the preoperative evaluation seeks to identify and quantify the magnitude of comorbid disease and optimize the patient's condition before surgery when possible. Preoperative testing is based on findings suggested in the history and physical examination.

131. Generally, elderly patients have an ECG, chest radiograph, CBC, and determination of glucose, creatinine, blood urea nitrogen, and albumin levels. Additional preoperative studies are based on the criteria discussed earlier for evaluation of patient and procedural risk.

132. Predicting and preventing postoperative delirium are important aspects of the perioperative care of the elderly. Patients with three or more of the following have a 50% risk for postoperative delirium:

133. 70 years or older; self-reported alcohol abuse; poor cognitive status; poor functional status; markedly abnormal preoperative serum sodium, potassium, or glucose level; noncardiac thoracic surgery; and aortic aneurysm surgery.

134. This risk is explained to the patient and the family along with the symptoms of postoperative delirium. If delirium does occur, metabolic and infectious causes need to be investigated before labeling the event as sundowning.

135. Nutritional Status
Evaluation of the patient's nutritional status is part of the preoperative evaluation. A history of weight loss greater than 10% of body weight over a 6-month period or 5% over a month is significant.

136. Albumin or prealbumin levels and immune competence (as assessed by delayed hypersensitivity reaction) may help identify patients with some degree of malnutrition, and physical findings of temporal wasting, cachexia, poor dentition, ascites, or peripheral edema may be corroborative. The degree of malnutrition is estimated on the basis of weight loss, physical findings, and plasma protein assessment

137. The adequacy of a nutritional regimen can be confirmed with a number of serum markers. Albumin (half-life, days), transferrin (half-life, 7 days), and prealbumin (half-life, 3-5 days) levels can be determined on a regular basis in hospitalized patients.

138. These proteins are responsive to stress conditions, however, and their synthesis may be inhibited in the immediate perioperative period. Once a patient is on a stable regimen and in the anabolic phase of recovery, these markers reflect the adequacy of nutritional efforts.

139. The effect of perioperative nutritional support on outcomes has been studied in a number of trials.

140. Patients with severe malnutrition (as defined by a combination of weight loss, visceral protein indicators, and prognostic indices) appear to benefit most from preoperative parenteral nutrition, as demonstrated in study groups treated with total parenteral nutrition for 7 to 10 days before surgery for gastrointestinal malignancy

141. The majority of studies show a reduction in the rate of postoperative complications from approximately 40% to 30%. The use of total parenteral nutrition postoperatively in similar groups of patients is associated with an approximately 10% increase in complication rates

142. Well-nourished patients undergoing surgery do not appear to benefit from aggressive perioperative nutritional support; parenteral nutrition is additionally associated with increased septic complications.

143. Generally, nutritional support begins within 5 to 10 days after surgery in all patients unable to resume their normal diet. Such support may take the form of nasoenteric feeding, parenteral nutrition, or a combination of the two

144. Obesity
The perioperative mortality rate is significantly increased in patients with clinically severe obesity (body mass index [BMI] >40 kg/m2 or BMI >35 kg/m2 with significant comorbid conditions). The goal of preoperative evaluation of an obese patient is to identify risk factors that might modify perioperative care of the patient.

145. Clinically severe obesity is associated with a higher frequency of essential hypertension, pulmonary hypertension, left ventricular hypertrophy, congestive heart failure, and ischemic heart disease

146. Patients with no or one of these risk factors receive a β-blocker preoperatively for cardioprotection. Patients with two or more risk factors undergo noninvasive cardiac testing preoperatively

147. Obesity is also a risk factor for postoperative wound infection
Obesity is also a risk factor for postoperative wound infection. The rate of wound infections is much lower with laparoscopic surgery in this group, which could have a bearing on selection of the operative approach. Obesity is an independent risk factor for DVT and PE; therefore, appropriate prophylaxis is instituted in these patients.

148. PREOPERATIVE CHECKLIST
preoperative evaluation concludes with a review of all pertinent studies and information obtained from investigative tests. Documentation of this review is made in the chart, which represents an opportunity to ensure that all necessary and pertinent data have been obtained and appropriately interpreted

149. Informed consent after discussion with the patient and family members regarding the indication for the anticipated surgical procedure, as well as its risks and proposed benefits, are documented in the chart. The preoperative checklist also gives the surgeon an opportunity to review the need for β-blockade, DVT prophylaxis, and prophylactic antibiotics.

150. Preoperative orders are written and reviewed
Preoperative orders are written and reviewed. The patient receives written instructions regarding the time of surgery and management of special perioperative issues such as fasting, bowel preparation, and medication use.

151. Antibiotic Prophylaxis
Appropriate antibiotic prophylaxis in surgery depends on the most likely pathogens encountered during the surgical procedure. The type of operative procedure is helpful in deciding the appropriate antibiotic spectrum and is considered before ordering or administering any preoperative medication.

152. Prophylactic antibiotics are not generally required for clean (class I) cases, except in the setting of indwelling prosthesis placement or when bone is incised. Patients who undergo class II procedures benefit from a single dose of an appropriate antibiotic administered before the skin incision.

153. For abdominal (hepatobiliary, pancreatic, gastroduodenal) cases, cefazolin is generally used. Contaminated (class III) cases require mechanical preparation or parenteral antibiotics with both aerobic and anaerobic activity.

154. Such an approach is taken in the setting of emergency abdominal surgery, as for suspected appendicitis, and in trauma cases. Dirty or infected cases often require the same antibiotic spectrum, which can be continued into the postoperative period in the setting of ongoing infection or delayed treatment.

155. The appropriate antibiotic is chosen before surgery and administered before the skin incision is made Repeat dosing occurs at an appropriate interval, usually 3 hours for abdominal cases or twice the half-life of the antibiotic, although the patient's renal function may alter the timing

156. Perioperative antibiotic prophylaxis generally is not continued beyond the day of surgery. With the advent of minimal-access surgery, the use of antibiotics seems less justified because the risk for wound infection is extremely low.

157. For example, routine antibiotic prophylaxis in patients undergoing laparoscopic cholecystectomy for symptomatic cholelithiasis is of questionable value. It may have a role, however, in cases that result in prosthetic graft (i.e., mesh) placement, such as laparoscopic hernia repair.

158. Preoperative Mechanical Bowel Cleansing
Mechanical bowel preparation with the addition of oral antibiotics was the standard of care for several decades for any intestinal surgery. More recent studies have evaluated the need for both oral antibiotics and mechanical cleansing

159. Oral antibiotics confer no benefit to the patient and may increase the risk for postoperative infection with Clostridium difficile. In addition, although it seems intuitive that removal of bulk fecal material would decrease the risk for anastomotic and infectious complications, the opposite is true.

160. A recent meta-analysis showed that both of these events are not decreased and may be increased with mechanical cleansing.

161. Review of Medications
Careful review of the patient's home medications is a part of the preoperative evaluation before any operation; the goal is to appropriately use medications that control the patient's medical illnesses while minimizing the risk associated with anesthetic-drug interactions or the hematologic or metabolic effects of some commonly used medications and therapies

162. The patient is asked to name all medications, including psychiatric drugs, hormones, and alternative/herbal medications, and to provide dosages and frequency.

163. In general, patients taking cardiac drugs, including β-blockers and antiarrhythmics, pulmonary drugs such as inhaled or nebulized medications, or anticonvulsants, antihypertensives, or psychiatric drugs are advised to take their medications with a sip of water on the morning of surgery.

164. Parenteral forms or substitutes are available for many drugs and may be used if the patient remains NPO for any significant period postoperatively. It is important to return patients to their normal medication regimen as soon as possible

165. Two notable examples are the additional cardiovascular morbidity associated with the perioperative discontinuation of β-blockers and rebound hypertension with abrupt cessation of the antihypertensive clonidine. Medications such as lipid-lowering agents or vitamins can be omitted on the day of surgery.

166. Some drugs are associated with an increased risk for perioperative bleeding and are withheld before surgery. Drugs that affect platelet function are withheld for variable periods: aspirin and clopidogrel (Plavix) are withheld for 7 to 10 days, whereas NSAIDs are withheld between 1 day (ibuprofen and indomethacin) and 3 days (naproxen and sulindac), depending on the drug's half-life

167. Because the use of estrogen and tamoxifen has been associated with an increased risk for thromboembolism, they probably need to be withheld for a period of 4 weeks preoperatively

168. The widespread use of herbal medications has prompted review of the effects of some commonly used preparations and their potential adverse outcomes in the perioperative period. These substances may fail to be recorded in the preoperative evaluation, although important metabolic and hematologic effects can result from their regular use

169. Generally, the use of herbal medications is stopped preoperatively, but this needs to be done with caution in patients who report the use of valerian, which may be associated with a benzodiazepine-like withdrawal syndrome.

170. Preoperative Fasting
The standard order of “NPO past midnight” for preoperative patients is based on the theory of reduction of volume and acidity of the stomach contents during surgery. Recently, guidelines have recommended a shift to allow a period of restricted fluid intake up to a few hours before surgery

171. The ASA recommends that adults stop intake of solids for at least 6 hours and clear fluids for 2 hours. When the literature was recently reviewed by the Cochrane group, they found 22 trials in healthy adults that provided 38 controlled comparisons.

172. Very few trials investigated the fasting routine in patients at higher risk for regurgitation/aspiration (pregnant, elderly, obese, or those with stomach disorders). There is also increasing evidence that preoperative carbohydrate supplementation is safe and may improve a patient's response to perioperative stress

173. There was no evidence that the volume or pH of gastric contents differed with the length and type of fasting. Though not reported in all the trials, there did not appear to be an increased risk for aspiration/regurgitation with a shortened period of fasting.

174. Surgeons and anesthesiologists should evaluate the evidence and consider adjusting their standard fasting policies.