Risk Stratification

Risk Stratification Before Elective Surgery

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.

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 Score	Surgery 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)

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 Score	Patient 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

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

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

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.

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

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

Risk Stratification