perioperative risk assessment

Notes

• spinal anesthesia is NOT safer than general anesthesia
• poor functional capacity (< 4 METS) indicates high risk
  • perioperative mortality correlates with functional status, independent of age
• screen for alcohol abuse (AUDIT-C)
  • alchohol abuse before surgery increases risk of postoperative complications
  • abstinence prior to surgery diminishes risk
• screen for obstructive sleep apnea

Cardiac (also see cardiac stress testing)

• complications:
  • death
  • myocardial infarction (MI)
    • greatest risk with 3-vessel or left main coronary artery disease
    • greatest risk within 1st 24-72 hours after surgery
    • most perioperative MIs are asymptomatic
  • pulmonary edema
  • unstable angina
  • arrhythmia (life-threatening)
• risk factors (in descending order of importance)
  • coronary artery disease (CAD)
    • defined as any of:
      • typical angina
      • Q-waves on ECG
      • prior myocardial infarction (MI)
      • prior angiographic evidence of CAD
      • prior functional study (i.e. treadmill) indicating CAD
    • high risk (5-25% complication rate)
      • unstable coronary syndromes
      • severe stable angina
    • low risk (1-5% complication rate)
      • mild stable angina
      • good functional status
      • preoperative electrocardiogram indicated
    • consider non-invasive ischemia testing in patients with
      • known or suspected CAD
      • unreliable or unknown function status
      • intermediate scores on Eagle criteria or on cardiac risk index
      • tests include Bruce protocol (treadmill), dipyridamole-thallium; dobutamine echocardiography
    • asymptomatic patients s/p CABG are at low risk
    • delay post-MI non-cardiac surgery (if possible)
      • 4-6 weeks after uncomplicated MI
      • 6 months after complicated MI
    • no benefit from coronary intervention before non-cardiac surgery
  • congestive heart failure (CHF)
    • decompensated CHF
      • high risk for perioperative pulmonary edema
      • increased risk of death
      • optimize therapy, if possible, prior to surgery
    • compensated CHF
      • increased risk of perioperative pulmonary edema
      • no known risk for other complications
      • conservative management
    • dilated & hypertrophic cardiomyopathies are associatedmwith an increased perioperative risk of CHF
  • severe valvular heart disease
    • symptoms are the most important risk factor
    • aortic stenosis
    • mitral stenosis
    • acute mitral or aortic regurgitation
    • valve repair prior to non-cardiac surgery may be indicated
  • significant cardiac arrhythmia
    • high risk
      • high grade AV block
      • symptomatic ventricular arrhythmias with structural heart disease
      • supraventricular arrhythmias with uncontrolled ventricular response
    • low risk
      • rhythm other than sinus rhythm (i.e. atrial fibrillation)
      • ECG evidence of left ventricular hypertrophy
      • left bundle-branch block
      • ST-T abnormalities
  • hypertension (low risk)
    • systolic blood pressure (SBP) > 200 mm Hg, or
    • diastolic blood pressure (DBP) > 120 mm Hg
    • increased risk of MI & pulmonary edema
  • pulmonary hypertension

Pulmonary

• complications
  • occur in 1/3 of patients post-operatively
  • account for 50% of peri-operative mortality
  • respiratory failure with prolonged mechanical ventilation
  • pneumonia
  • atelectasis
  • bronchospasm
  • bronchitis
  • pulmonary embolism
• risk factors
  • older age
  • chronic obstructive pulmonary disease
  • tobacco: current use or 20 pack-year history
  • chronic heart failure
  • poor general health status &/or functional dependence
  • low serum albumin
  • renal insufficiency
  • morbid obesity (> 250 lbs)*
  • obstructive sleep apnea
  • pulmonary hypertension
  • upper abdominal or cardiothoracic surgery
  • proximity of surgical procedure to diaphragm
  • head & neck surgery
  • neurosurgery
  • major vascular surgery
  • surgeries lasting > 3 hours
  • emergency surgery
  • general anesthesia*

* minor or possible risk factor

• pulmonary function testing
  • FEV1
    • good predictor of surgical risk
    • if FEV1 > 2L, patient can safely undergo procedure
    • if FEV1 < 1L
      • high risk of post-operative pulmonary complication
      • avoid elective procedures adjacent to diaphragm
  • indications
    • suspected moderate to severe underlying lung disease
    • pulmonary resection

neuropsychiatric

• complications
  • stroke
  • delirium
• risk factors
  • stroke
    • cardiac or vascular surgery
    • older age
    • postoperative atrial fibrillation
    • symptomatic carotid stenosis (> 50%)
  • delirium
    • older age
    • poor cognitive status
    • poor functional status
    • history of alcoholism
    • thoracic surgery
    • abdominal aortic aneurysm repair
    • abnormal electrolytes
    • abnormal glucose
    • perioperative use of Demerol or benzodiazepines
  • depression (Geriatric Depression Scale score > 4) increase risk for postoperative delirium

Hepatic

• complications
  • electrolyte & fluid imbalances
  • delirium
  • coagulation disorders & bleeding
  • infections
  • impaired clearance of medications
  • renal failure
  • liver failure
  • death
• risk factors
  • cirrhosis (Child's class C >> Child's class A)
  • acute hepatitis (especially viral or alcoholic)

Hematologic

• considerations
  • bleeding risk
  • severity &/or stability of anemia
  • in older patients, preoperative hematocrit levels outside the normal range are associated with higher mortality after noncardiac surgery
  • even mild preoperative anemia may increase 30 day morbidity & mortality after noncardiac surgery
• evaluation
  • bleeding history
  • bleeding time does not predict the risk of perioperative bleeding
  • assess the need for preoperative transfusion
• laboratory:
  • no history of bleeding, but high-risk surgery
    • aPTT & platelet count
  • suggestive history of bleeding disorder & high-risk surgery
    • aPTT, PT, fibrinogen, platelet count, vWF assays, factor VIII, factor IX, clot lysis, alpha-2 plasmin inhibitor, factor XIII ) prophylaxis for venous thromboembolism

Endocrine

• risk factors
  • diabetes mellitus, especially insulin-dependent diabetes mellitus
  • hypothyroidism
  • adrenal insufficiency
  • hyponatremia

Renal

• complications of end-stage renal disease (ESRD)
  • infection, especially pneumonia
  • hyperkalemia
• complications of chronic renal insufficiency
  • progressive renal dysfunction
  • hyponatremia
• serum creatinine >= 2.0 mg/dL constitutes cardiac risk factor
• a BUN/creatinine ratio indicates azotemia, but does not confer an increased risk for postoperative delirium

More general terms

• risk assessment

More specific terms

• cardiac risk index (CRI)
• Eagle criteria
• Goldman criteria

Additional terms

• cardiac stress testing
• perioperative management
• perioperative risk stratification (relative risk of non-cardiac surgeries)
• post-operative management
• postoperative complication
• preoperative evaluation & management
• preoperative laboratory testing
• simple fitness questions that predict risk of post-operative morbidity