Risk and Preoperative assessment
The risk is usually defined by the intense of physiologic effects of the procedure and the likelihood of complications. There are clinical predictors which together with the functional capacity METs system help clinicians decide whether or not to proceed with the procedure or do preoperative cardiac work up. First, here some examples of various levels of procedure risk to be taken into consideration when evaluating a patient preoperatively as well as examples of clinical predictors at various levels.
Levels of risks of various surgeries:
Very Low Risk Procedures:
- Eye surgery under Monitored Anesthesia Care
- Simple GI endoscopy (without stents)
- Dental procedures
Low Risk Surgeries:
- Hernia repair
- ENT procedures without planned flap or neck dissection
- Diagnostic cardiac catheterization
- Interventional radiology
- Interventional GI endoscopy
- Eye surgery requiring General Anesthesia
- Cystoscopy
Intermediate Risk Surgeries:
- 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
High Risk Surgeries:
- Aortic surgery
- Peripheral vascular surgery
- Major orthopedic-spinal reconstruction
- Major reconstruction of the GI tract
- Major vascular surgery
- Major genitourinary surgery (e.g., radical prostatectomy)
- Thoracic procedures
- Intracranial procedures
- Major procedures on the oropharynx
- Major vascular, skeletal, neurologic repair
- Total joint revisions
Very High Risk Surgeries:
- Cardiovascular surgeries such as coronary artery bypass grafting (CABG) and valve replacements
- Major cancer operations like pancreatectomy, esophagectomy, gastrectomy, and lung resection
Clinical predictors of increased perioperative complications:
Low risk:
- Uncontrolled hypertension
- History of CVA
- Abnormal EKG
Intermediate risk:
- Diabetes mellitus
- CKD
- History of MI
- Mild angina
- Compensated CHF
High risk:
- Decompensated CHF
- MI within 30 days
- Severe angina
- Severe valvular disease
- High-grade AV block
- Uncontrolled arrythmias
In general, low risk clinical predictors are ok to proceed with surgery without further cardiac testing unless the patient has low functional capacity. Intermediate risk predictors will need testing if have low functional capacity based on METs criteria. One metabolic equivalent (MET) is defined as the basal oxygen consumption of a 40-year-old 70 kg man. When someone perform and activity a certain number of METs is given to categorize the individual's functional capacity. For example, showering is 2 METs while climbing up two flights of stairs is 4 METs. People who can perform activity with 4 METs or above are considered lower risk unless they have high risk conditions or undergoing high risk surgeries that indicates further preoperative cardiac testing.
Various activities METs equivalent:
1 METs: Dressing, eating, working at a desk
2 METs: Vacuuming, showering, walking down eight steps
3 METs Walking at 3 mph
4 METs Walking up two flights of stairs, raking leaves, pushing a power mower
5 METs Walking at 4 mph, washing a car
6 METs Nine holes of golf carrying clubs, heavy carpentry using a push mower
7 METs Digging, spading soil, singles tennis, carrying 60 pounds
8 METs Moving heavy furniture, jogging slowly, rapidly climbing stairs, carrying 20 pounds upstairs
9 METs Bicycling at a moderate pace, sawing wood, slow jumping rope
10 METs Brisk swimming, bicycling uphill, walking briskly at 6 mph
11 METs Running at 7 mph, full-court basketball
12 METs Running at 8 mph
Assessment of functional capacity:
- People with METs < 4 have a poor functional capacity
- People with METs 4-7 have moderate functional capacity
- People with METs >7 has excellent functional capacity