Preoperative Assessment


Medical Evaluation

  1. History and Physical
    • risk of surgery is very low in healthy individuals
    • goal of the preop evaluation is to identify and quantify any comorbidities that may affect the operative outcome
    • the goal is not to screen for undiagnosed disease

    1. Age
      • minor component of preoperative coronary risk after multivariate analysis
      • independent risk factor for postoperative pulmonary complications
      • much of the risk associated with age is due to increasing numbers of comorbidities (cognitive impairment, functional impairment, malnutrition, frailty)

    2. Exercise Capacity
      • important determinant of overall perioperative risk
      • no cardiac evaluation is necessary if the patient can expend ≥ 4 METS (climb up 2 flights of stairs, walk up a hill, heavy housework, walk at 4 mph at ground level)

      Metabolic Equivalents Chart
    3. Medications
      • provides insight into patients’ medical condition – diabetes, hypertension, CAD, etc
      • must specifically ask about ASA, Plavix, NSAIDs, beta-blockers, anticoagulants

    4. Nutritional Status
      • weight loss > 10% over 6 months or 5% in a month is significant
      • temporal wasting, cachexia, ascites, peripheral edema may corroborate the history
      • however, obesity is not protective of malnutrition – it is possible for overweight patients to have micro- and macronutrient deficiencies
      • albumin, transferrin, and prealbumin have historically been used to support a diagnosis of malnutrition, but they are not considered to be adequate in isolation
      • if necessary, a registered dietician can be consulted for a complete nutritional assessment

    5. Obesity
      • BMI > 40 is associated with increased perioperative mortality
      • often associated with other comorbid conditions: hypertension, CHF, ischemic heart disease, sleep apnea
      • is an independent risk factor for pulmonary embolism/DVT
      • also associated with increased wound infections

    6. Obstructive Sleep Apnea (OSA)
      • increases risk of cardiac arrest, hypoxemia, respiratory failure, reintubation, and ICU transfer
      • most patients with OSA are undiagnosed
      • consider screening at-risk patients for OSA before surgery

    7. Alcohol Abuse
      • associated with increased post op complications (wound infections, other infections, cardiopulmonary complications
      • must identify any underlying liver disease
      • withdrawal can be a major issue
      • optimal period of cessation is unknown (? 4 weeks)

    8. Drug Use
      • chronic opioid use is associated with tolerance, which can make pain control difficult
      • drug withdrawal is also a major issue
      • pain management specialists may need to be involved in the patient's perioperative care

    9. Smoking
      • associated with increased complications – poor wound healing, wound infections, pneumonia, respiratory failure, and cardiovascular events
      • smoking cessation ≥ 6 weeks before surgery may reduce the risk of postoperative complications

    10. Family History
      • bleeding problems
      • complications from anesthesia – malignant hyperthermia

  2. Laboratory Evaluation
    • routine preoperative testing is not indicated in the absence of clinical indications
    • false-positive results lead to unnecessary follow up tests, increased costs and risks, as well as delay in surgery
    • selective testing is appropriate in patients with known underlying diseases or risk factors that would affect operative management

    1. CBC
      • anemia is rare (1%) in asymptomatic patients
      • however, preop anemia predicts postop mortality
      • data is unclear if the anemia is the risk factor, or if it is a marker of risk
      • baseline Hg measurement is recommended for patients ≥ 65 who are undergoing major surgery
      • also recommended in younger patients undergoing surgery that may result in significant blood loss

    2. Renal Function
      • mild to moderate renal dysfunction is asymptomatic and prevalent with increasing age
      • creatinine > 2.0 is one of 6 independent risk factors that predict postoperative cardiac complications
      • renal insufficiency also necessitates drug dosage adjustments
      • appropriate to obtain serum creatinine level in patients > 50 undergoing intermediate or high risk procedures

    3. Electrolytes
      • frequency of unsuspected electrolyte abnormalities is < 1%
      • routine electrolyte measurements are not necessary unless the history suggests their presence (renal disease, diuretic use)

    4. Blood Glucose
      • insulin-dependent diabetes is a risk factor for postop cardiac complications
      • no evidence that asymptomatic hyperglycemia, in a patient not known to have diabetes, increases surgical risk
      • routine measurement of serum glucose is not necessary in healthy patients

    5. Liver Function Tests
      • significant liver disease is suggested by the history
      • mild elevations of LFTs in patients with no known liver disease is not associated with increased morbidity/mortality
      • routine LFTs are not indicated

    6. PT/PTT
      • history, physical exam, and family history should suggest the presence of a bleeding disorder
      • not routinely indicated

    7. Urinalysis
      • goal is to detect unsuspected UTIs or renal insufficiency
      • unclear whether treating an asymptomatic UTI decreases rates of wound infection
      • may be of value in patients undergoing prosthetic joint replacements

    8. Pregnancy Testing
      • mandatory in all women of reproductive age
      • pregnancy alters surgical management and decision making, especially in elective cases

    9. EKGs
      • not indicated in asymptomatic patients undergoing low-risk procedures
      • can be considered in asymptomatic patients undergoing riskier procedures (cardiac risk ≥ 1%)

    10. Chest X-Rays
      • only necessary if there is a history of cardiopulmonary disease
      • abnormal findings are common, and result in additional tests and costs that do not benefit the patient

Risk Factors Most Predictive of Postoperative Mortality

  1. National Surgical Quality Improvement Program (NSQIP)
    • has been used to develop predictive models for post-op morbidity/mortality
    • ASA 4/5 is associated with the largest odds ratio (8:1)
    • ASA 3 (3.5:1), DNR (3.9:1), disseminated cancer (2.9:1), emergency procedure (2.6:1) are also significant independent predictors of postoperative complications

    ASA Classification

Evaluation of Cardiac Risk

  1. Incidence
    • among unselected patients > 40 years old, perioperative MI occurs in 1.4% and cardiac death in 1%
    • among patients with some selection criteria, perioperative MI occurs in 3.2% and cardiac death in 1.7%

  2. Mechanism
    • surgery predisposes to myocardial ischemia: blood loss, volume shifts, increased myocardial oxygen consumption from heart rate and BP elevations
    • patients with underlying cardiac and peripheral vascular disease have high incidences of coronary artery disease and low ejection fractions

  3. Preoperative Evaluation
    1. History
      • symptoms: angina, dyspnea, syncope, palpitations
      • history: hypertension, diabetes, kidney disease, cerebrovascular or peripheral vascular disease
      • functional status: inability to climb 2 flights of stairs or walk 4 blocks is associated with increased cardiac complications

    2. Physical Exam
      • BP measurement, auscultation of the heart and lungs, abdominal palpation, examine extremities for edema and pulses
      • important findings include evidence of CHF or a murmur

    3. EKG
      • should be obtained in all patients with cardiovascular disease, unless it is a low-risk procedure
      • should be evaluated for Q waves, ST-segment changes, arrhythmias, bundle branch blocks, etc

  4. Surgery Specific Risk
    1. High Risk Procedures
      • risk of cardiac death or nonfatal MI > 5%
      • aortic or major vascular surgery

    2. Intermediate Risk Procedures
      • risk of cardiac death or nonfatal MI 1-5%
      • laparotomies, thoracotomies, major urologic or orthopedic procedures

    3. Low Risk Procedures
      • cardiac complication rate < 1%
      • day surgery procedures: hernias, breast biopsies, endoscopies

  5. Estimating Perioperative Risk
    • patient-specific risk factors, combined with surgery specific risk factors, are used to estimate the risk of adverse postoperative cardiac events
    • Goldman Cardiac Risk Index was first devised in 1977
    • Revised Cardiac Risk Index was developed in 1999, and uses 6 easily obtained predictors of complications to estimate cardiac risk in noncardiac surgical patients
    • predictors were developed through multivariate analysis
    • each independent predictor is worth one point
    • points are then added together to yield a total, which has been correlated with operative risk

    Revised Cardiac Risk Index
    Revised Cardiac Risk Index

    Perioperative Cardiac Complication Rates
    Perioperative Cardiac Complication Rate

  6. Management Based on Risk
    • low risk patients (<1%) require no additional testing
    • higher risk patients may require additional cardiac testing

  7. Additional Cardiac Testing
    • additional testing should only be done if it is indicated in the absence of the proposed surgery
    • “preop” is not a valid reason for additional testing

    1. Stress Testing
      • used to diagnose obstructive coronary artery disease
      • strong relationship between extent of myocardial ischemia and prognosis
      • however, there is no evidence that prophylactic revascularization improves outcomes

    2. Echocardiography
      • used to evaluate left ventricular systolic function and valvular heart disease, which are associated with postoperative heart failure

    3. 24-hour Monitoring
      • used primarily for patients with syncope or arrhythmias

  8. Cardiac Interventions
    1. Revascularization
      • goal of risk assessment is to determine if any cardiac intervention will reduce the risk of a post-op cardiac event
      • CABG vs angioplasty vs stenting
      • bare metal stents require a minimum of 1 month of dual antiplatelet therapy
      • drug-eluting stents require a minimum of 6 months of dual antiplatelet therapy
      • ideally, all elective procedures should de deferred for one year after stent placement
      • wait 4 – 6 weeks after an MI before performing elective surgery

    2. Medical Therapy
      • beta blockers are the most studied drugs
      • purpose is to decrease the adrenergic surge after surgery and halt platelet activation and microvascular thrombosis
      • in 1996, a study was published that showed a large decrease in post-op cardiac complications in medium – high risk patients receiving beta blockers in the perioperative period
      • in 2007, another study (POISE) showed the potential harm of perioperative beta blockers
      • POISE study confirmed the reduction in post-op cardiac morbidity/mortality
      • however, these gains were negated by an increased stroke and total mortality rate
      • current recommendations for beta blockers: 1) continue them in patients taking them preoperatively; 2) consider them for high-risk patients; 3) don’t give them to low-risk patients

Pulmonary Evaluation

  1. Risk Factors for Post-Op Pulmonary Complications
    • type of surgery: upper abdominal, thoracic
    • general risks: age, functional status, poor nutrition, weight loss, possibly obesity
    • specific risks: COPD, asthma, pneumonia, smoking, sleep apnea, dyspnea

  2. Pulmonary Function Testing
    • indications: lung resections, single lung ventilation cases, major abdominal surgery with significant pulmonary symptoms
    • tests: FEV1, forced vital capacity, diffusing capacity of carbon monoxide
    • patients with FEV1 < 30% of predicted (0.8 Liter/sec) have high risk of post-op pulmonary insufficiency

  3. Preoperative Interventions
    • goal is to reduce post-op complications
    • bronchodilator therapy, steroids for asthmatic patients, antibiotics for pneumonia
    • ? smoking cessation
    • exercise – walking 3 miles several times/week
    • consider spinal or epidural anesthesia where appropriate

Renal Evaluation

  1. Pre-op Considerations
    • pre-op creatinine > 2.0 is an independent risk factor for cardiac complications
    • renal patients usually have coexisting cardiac, metabolic, endocrine problems
    • patients may be volume overloaded
    • anemia is common
    • qualitative platelet dysfunction

  2. Pre-op Interventions
    • erythropoietin to correct anemia if an elective case
    • correction of volume status
    • calcium replacement for hypocalcemia
    • phosphate binders for hyperphosphatemia
    • correction of hyperkalemia
    • dialysis may be necessary to correct volume and electrolyte abnormalities

  3. Post-Operative Management
    • avoid nephrotoxic drugs
    • use renal dosing
    • strict attention to volume status

Hepatic Evaluation

  1. Child-Pugh Scoring System
    • stratifies operative risk in cirrhotic patients
    • Child A mortality = 10%; Child B, 31%; Child C 76% for abdominal operations

    Child's Classification
  2. Model for End-Stage Liver Disease (MELD)
    • another commonly used risk stratification tool
    • uses a formula based on bilirubin, creatinine, INR

    MELD Score
  3. Umbilical Hernia Repair in Cirrhotics
    • may rupture if tense ascites is present, with increased mortality rates
    • preoperatively, need to reduce ascites to a minimum with aggressive diuretic therapy
    • mortality rate may be as high as 14%

  4. Cholecystectomy in Cirrhotic Patients
    • consider non-operative management since mortality is high
    • when surgery is necessary, lap choly is associated with less bleeding than open choly

Diabetes

  1. Perioperative Diabetic Management
    • pre-op goal is to identify diabetic complications that will affect the patient’s perioperative management (cardiac disease, PVD, renal dysfunction)
    • hemoglobin A1c > 8% is associated with postoperative infectious complications such as wound infection, pneumonia, and sepsis

  2. Perioperative Medical Management
    • withhold oral agents on the morning of surgery; resume once able to take PO
    • rapid and short-acting insulins are held once patient is NPO
    • intermediate and long-acting insulins are given as two-thirds the normal evening dose the night before surgery, and one-half the morning dose the day of surgery
    • frequent bedside glucose determinations
    • hyperglycemia is treated with short-acting insulins
    • 5% dextrose infusion should be started the morning of surgery

Steroid Replacement

  1. Determine if Patient has Adrenal Suppression
    • patients who have taken > 20 mg prednisone for > 3 weeks are presumed to have adrenal suppression
    • patients who have taken 5 – 20 mg prednisone for > 3 weeks in the past year are considered to be at risk for adrenal suppression
    • low doses of steroids or minor procedures are not associated with adrenal suppression
    • if unclear, low-dose ACTH stimulation test to determine suppression can be done

  2. Steroid Replacement
    • titrate replacement dose to degree of surgical stress
    • moderate stress operations (cholecystectomy): 50 mg IV hydrocortisone before induction; 25 mg IV q 8 hr for 24 – 48 hrs; then resume usual dose
    • major stress operations (colectomy): 100 mg IV hydrocortisone before induction; 50 mg IV q 8 hrs for 24 – 48 hrs; then resume usual dose







References

  1. UpToDate, Preoperative Medical Evaluation of the Healthy Patient. August 10, 2015. Pgs 1 – 19.
  2. UpToDate, Evaluation of Cardiac Risk Prior to Noncardiac Surgery. December 30, 2014. Pgs 1 – 15.
  3. Sabiston, 20th ed., Pgs 210 – 230
  4. Cameron, 11th ed., pgs 1163 - 1169
  5. Cameron, 13th ed., pgs 1331 - 1334