Risk Stratification Before Elective Surgery

On this page:
Surgery Risk | Patient Medical Risk | Cardiac Risk | Pulmonary Risk | Renal Risk | Cognitive Dysfunction Risk | Risk of Difficult Pain Management

Risk factors that increase the likelihood of perioperative morbidity and mortality may include the patient’s underlying health problems as well as factors associated with each specific type of surgery. By combining risk scores for patient co-morbidity and the complexity of surgery, we can stratify overall risk and determine which patients should undergo more extensive preoperative evaluation.

If a patient who is scheduled for a non-emergency procedure is found to have medical conditions that are not under ideal control, this preoperative evaluation process can include optimization, or “prehabilitation”, so that the patient can be in the best possible health before surgery. This process may address blood pressure control, diabetes management, nutritional status, exercise tolerance, smoking cessation, and treatment of anemia, as examples.

In the sections to follow, we outline a method of assigning a risk score to patient co-morbidity factors and surgical risk factors. We encourage referring physicians to send patients with risk scores of 7 or greater to our Preoperative Evaluation and Planning Center (PEPC) for an in-person visit and further evaluation. Patients with scores of 4 or less require no further screening, and will be interviewed by the physician anesthesiologist and the anesthesia team before surgery. Patients with intermediate risk scores may be referred for telephone screening by the PEPC staff.

Surgical Risk Score graph

back to top

Surgery Risk Stratification

The Surgical Risk Score assigns a numerical value to reflect the risk level associated with the procedure ranging from 1 (very low risk) to 5 (very high risk). These categories identify operations with increased potential for substantial blood loss or other intraoperative and postoperative risks.

Surgical Risk ScoreSurgery Types
1- Very Low Risk

Procedures that usually require only minimal or moderate sedation and have few physiologic effects

  • Eye surgery that can be performed under Monitored Anesthesia Care
  • Simple GI endoscopy (without stents)
  • Dental procedures
2- Low Risk

Procedures associated with minimal physiologic effect

  • Hernia repair
  • ENT procedures without planned flap or neck dissection
  • Diagnostic cardiac catheterization
  • Interventional radiology
  • Interventional GI endoscopy 
  • Eye surgery that requires General Anesthesia
  • Cystoscopy
3- Intermediate Risk

Procedures associated with moderate changes in hemodynamics, risk of blood loss

  • Intracranial and spine surgery
  • Gynecologic and urologic surgery
  • Intra-abdominal surgery without bowel resection
  • Intra-thoracic surgery without lung resection
  • Cardiac catheterization procedures including electrophysiology studies, ablations, AICD, pacemaker
4- High Risk

Procedures with possible significant effect on hemodynamics, blood loss

  • Colorectal surgery with bowel resection
  • Kidney transplant
  • Major joint replacement (shoulder, knee, and hip)
  • Open radical prostatectomy, cystectomy
  • Major oncologic general surgery or gynecologic surgery
  • Major oncologic head and neck surgery
  • Spine deformity surgery
5- Very High Risk

Procedures with major impact on hemodynamics, fluid shifts, possible major blood loss

  • Aortic surgery
  • Cardiac surgery
  • Intra-thoracic procedures with lung resection
  • Major transplant surgery (heart, lung, liver)

back to top

Patient Medical Risk Stratification

Pre-existing medical problems confer risk for perioperative complications, including cardiac decompensation, respiratory failure, acute kidney injury, and postoperative delirium or cognitive dysfunction.

Patient Risk ScorePatient Characteristics
1- Very Low Risk
  • No known medical problems, or minor medical problems, such as allergies and skin conditions.
2- Low Risk
  • Hypertension
  • Hyperlipidemia
  • Asthma
  • Other chronic, stable medical condition without significant functional impairment
3- Intermediate Risk
  • Age 70 or older
  • Non-insulin dependent diabetes
  • History of treated, stable CAD
  • Obesity (BMI > 30)
  • Anemia (hemoglobin < 10)
  • Mild renal insufficiency
4- High Risk
  • Coronary stent within 6 months
  • Chronic CHF
  • Insulin-dependent diabetes mellitus
  • Renal insufficiency: creatinine > 2
  • Moderate COPD: FEV1 50% to 70%
  • Obstructive sleep apnea
  • Morbid obesity (BMI >40)
  • History of stroke or TIA
  • Known diagnosis of dementia
  • Chronic pain syndrome
5- Very High Risk
  • Unstable or severe cardiac disease
  • Severe COPD: FEV1 < 50% predicted
  • Super morbid obesity (BMI >50)
  • Use of home oxygen
  • Pulmonary hypertension
  • Severe liver disease
  • Severe frailty; physical incapacitation

back to top

Cardiac Risk Factors

Very high risk – score of 5:

  • Unstable or severe angina
  • Recent MI
  • Decompensated CHF
  • Severe valvular disease

Moderate risk – patients with two or more of the following conditions receive a score of 4, and three or more conditions a score of 5:

  • History of ischemic heart disease
  • Chronic, stable CHF
  • History of stroke or TIA
  • Insulin-dependent diabetes mellitus
  • Renal disease with serum creatinine greater than 2 mg/dl

back to top

Pulmonary Risk Factors

Severe pulmonary disease – score of 5:

  • COPD with FEV1 less than 50 percent of predicted
  • Severe pulmonary hypertension
  • Need for home oxygen therapy

Moderate pulmonary disease – score of 4:

  • COPD with FEV1 between 50 and 70 percent of predicted
  • Moderate pulmonary hypertension
  • Obstructive sleep apnea
  • Greater than 20 pack-year smoking history

back to top

Renal Risk

The most significant risk factor for postoperative renal failure is preexisting renal disease. Patients with GFR less than or equal to 60 ml/min or serum creatinine greater than 1.5 mg/dl are assigned a risk score of 3.

back to top

Cognitive Dysfunction Risk

High risk – score of 4:

  • Current diagnosis of dementia or other cognitive disorder
  • Bed-bound state
  • Need for aid with activities of daily living
  • Significant impairment of vision or hearing

Moderate risk – score of 3:

  • Frailty
  • Age greater than 70
  • Unintentional weight loss
  • Exhaustion
  • Low physical activity
  • Slowness
  • Weakness

back to top

Risk of Difficult Pain Management

Postoperative pain control remains a key factor in length of stay, delay of intestinal motility after bowel resection, and patient satisfaction. Patients with chronic pain syndromes, high tolerance for opioids, or a history of substance abuse may be at high risk for difficult-to-manage postoperative pain.

We recommend that patients with any of the following risk factors be assigned a risk score of 5 and referred to PEPC phone screening for preoperative evaluation:

  • Use of more than 6 doses per day of hydrocodone or hydromorphone
  • Use of a long-acting or extended-release opioid such as Oxycontin
  • Use of Suboxone
  • History of complex regional pain syndrome (regional sympathetic dystrophy)
  • History of substance abuse
  • Intrathecal pump or spinal cord stimulator

back to top