Pre-operative clearance


 * Associate Editor-In-Chief: Mohammed A. Sbeih, M.D. [mailto:msbeih@perfuse.org]

Overview
The goal of the preoperative clearance (Preoperative medical assessment) is to assess the patient's general medical condition in order to identify any unrecognized co-morbid diseases and optimize the patient's state for the procedure. The preoperative medical assessment helps the doctors to decide if the patient is suitable for the proposed surgery according to the patient's risk category, also it helps them to identify the factors that may reduce the patient's risk for complications and provide the best possible recommendations for the post-operative care. Preoperative clearance usually starts by identifying the type of surgery to be performed and the risk category of the patient who needs this surgery.

Perioperative risk of death
Patients can be divided into different risk categories based on the basis of their preoperative medical assessment. This helps the doctors to decide if the patient is suitable for the proposed surgery or procedure, and identify the factors that may reduce the patient risk. There are many factors that may influence the risk of perioperative complications, including death.


 * Anesthesia
 * Although the modern anesthesia is safe, the risk of surgical complications varies according to the type of anesthesia (general or regional).
 * The patient's factors and surgical factors are more important risk predictors for post operative complications.


 * The American society of anesthesiologists (ASA) classification is a predictor of perioperative mortality. It also predicts cardiac and pulmonary morbidity.


 * ASA classification
 * {| class="wikitable" border="1"

! Class !! Systemic disturbance !! Mortality rate
 * 1 || Healthy patient with no disease outside of the surgical process || <0.03%
 * 2 || Mild-to-moderate systemic disease caused by the surgical condition or by other pathologic processes || 0.2%
 * 3 || Severe disease process which limits activity but is not incapacitating || 1.2%
 * 4 || Severe incapacitating disease process that is a constant threat to life || 8%
 * 5 || Moribund patient not expected to survive 24 hours with or without an operation || 34%
 * E || Suffix to indicate an emergency surgery for any class || Increased
 * }
 * 4 || Severe incapacitating disease process that is a constant threat to life || 8%
 * 5 || Moribund patient not expected to survive 24 hours with or without an operation || 34%
 * E || Suffix to indicate an emergency surgery for any class || Increased
 * }
 * E || Suffix to indicate an emergency surgery for any class || Increased
 * }


 * Type of surgery
 * Perioperative risk of complications varies according to the type of surgery.


 * Patient age
 * Some studies showed that the risk of surgery increases with advancing age.


 * Emergency procedures
 * In emergency procedures the risk of complications may increases two to four times, or even more than that in elderly patients.


 * Pulmonary factors
 * There are several pulmonary factors that may increase the risk of complications in surgical patients, these may include:
 * Cigarete smoking.
 * Respiratory diseases.
 * Abnormal chest x-ray or phisical examination findings.
 * Thoracic or upper abdominal surgery.
 * Morbid obesity.
 * Age over 60.


 * Cardiac factors
 * There are several cardiac factors that may increase the risk of complications in surgical patients, these may include:
 * History of prosthetic valves.
 * History of rheumatic fever.
 * Congestive heart failure.
 * Arrhithmia.

Preoperative patient questionnaire
In general, the overall risk of surgery is extremely low in healthy individuals.

History
 * The patient should be asked about his age. Some studies found a small increased risk of surgery with advanced age of the patient. The mortality rate for most surgical procedures increases linearly with age due to increasing numbers of comorbidities with advancing age.


 * The patient should be asked if he had a history of:
 * Heart diseases,irregular heart beat, murmurs or rheumatic fever as a child.
 * Pulmonary diseases, such as asthma, bronchitis, or emphysema.
 * Chest pain, angina, or chest tightness.
 * Hypertension or hypotension.
 * Shortness of breath, cough.
 * Liver diseases, jaundice or hepatitis.
 * Gastrointestinal problems or indigestion.
 * Diabetes.
 * Thyroid problems.
 * Kidney problems.
 * Weakness or numbness in the extremities.
 * Seizures or blackouts.
 * Bleeding disorders.
 * Blood clotting abnormality.
 * Arthritis or joint pain.


 * The patient should be asked about:
 * Any allergies for food or medication.
 * A list of any medications he is currently taking, including over-the-counter medications and steroidal compounds. Nonsteroidal anti-inflammatory drugs are associated with :an increased risk of perioperative bleeding.
 * Any other medical conditions in the past.
 * Any previous surgeries or anesthesia.
 * pregnancy state.
 * Any problems with a previous surgery due to anesthesia.


 * The patient should be asked when did he last eat or drink on the day of surgery.
 * The patient should be asked about his height and weight. Studies showed that obesity is not a risk factor for most adverse postoperative outcomes, with the exception of :deep venous thrombosis and pulmonary embolism. However, some cardiac surgery studies have shown higher complication rates for obese patients, such as prolonged hospital stay, wound infections and prolonged mechanical ventilation.
 * The patient should be asked about his exercise capacity, patients with unlimited exercise tolerance generally have a low risk of postoperative complications. Those patients :can walk two blocks on level ground without symptoms,
 * The patient should be asked if he smokes cigarettes, how many packs per day and for how many years.
 * The patient should be asked if he drinks alcohol. There is increased risk for postoperative complications in patients who misuse alcohol on a regular basis.
 * The patient should be asked about his family history.

Preoperative laboratory testing
The American society of anesthesiologists recommends against routine preoperative laboratory testing in the absence of clinical indications. In specific circumstances, selective testing may be appropriate, such as in patients with underlying diseases or risk factors that would increase their risk for surgical complications. Also in specific high risk surgical procedures, these tests should be done. If there is no significant change in the clinical condition of the patient, it may be safe to use test results that were performed within the past four months. These tests include:

1. Complete blood count (CBC): Anemia maybe presents in asymptomatic patients and it is common following major surgery. Postoperative mortality maybe predicted by the preoperative hemoglobin level. CBC test should be done for:
 * Patients 65 years of age or older.
 * Patients who are undergoing major surgery.
 * Young patients who undergoing major surgery with the expectation to result in significant blood loss.
 * Patients with a history that suggests anemia.

2. Renal function test (RFT): Serum creatinine concentration should be ordered for patients over the age of 50 undergoing intermediate or high risk surgeries, also it should be ordered if hypotension is likely, or when nephrotoxic medications will be used. Mild to moderate renal impairment is usually asymptomatic. Dosage adjustment of some medications may be needed if the patient has renal insufficiency.

3. Electrolytes: It is not recommended to be done routinely if the patient does not have a history of electrolytes abnormality.

4. Blood glucose: Diabetes increases the operative risk in patients undergoing vascular surgery or coronary artery bypass grafting. Routine measurement of blood glucose is not recommended for healthy patients before the surgery, since some studies showed that unexpected abnormal blood glucose results do not often influence perioperative management.

5. Liver function tests (LFT): It is not recommended to do this test routinely unless the patient has a history of liver disease.

6. Hemostasis tests: It is not recommended to do prothrombin time (PT) or Partial thromboplastin time (PTT) blood tests routinely unless the patient has bleeding disorder or an unusual bleeding tendency. Some doctors have suggested to test all patients who undergoing intermediate to high risk surgeries. This avoids the chance that clinicians may forget to ask the patients about their bleeding history. The bleeding time is not useful in assessing the risk of perioperative hemorrhage.

7. Urinalysis: It is usually done to detect any urinary tract infection which has the potential to cause wound infection after the surgery, especially with prosthetic surgery. If the test is positive, the patient should be treated with antibiotics and proceed with surgery without delay. Some studies showed that there is no reduction in the risk of postoperative wound infection if the patient treated with antibiotics before the surgery, and so, it is not indicated to test for Urinary tract infection before the surgery for every patient.

8. Pregnancy testing: Pregnant women may need specific perioperative management, this includes specific anesthetic teqniques. An elective surgery may be cancelled or postponed in pregnant women. The American society of anesthesiologists recommends that clinicians consider pregnancy testing for all woman of childbearing age. Many institutions require pregnancy testing for all reproductive age women before surgery.

9. Electrocardiogram (EKG): This should be done to detect any recent myocardial infarction (MI) which known to be associated with increased surgical morbidity and mortality, also it may be important as a baseline to be compared with the one postoperatively. In general, EKG alone may be a poor indicator of postoperative cardiac complications. The 2007 American college of cardiology/American heart association (ACC/AHA) Guidelines on perioperative cardiovascular evaluation states that ECG is not useful in asymptomatic patients undergoing low risk procedures. Also, the European Society of Cardiology 2009 preoperative guidelines do not recommend ECG in patients without risk factors. According to the 2007 ACC/AHA guidelines the 12-lead ECG are recommended for the following patients:
 * Patients who are scheduled to undergo vascular surgery and have at least one of the following clinical risk factors:
 * Ischemic heart disease.
 * Compensated or prior heart failure.
 * Cerebrovascular disease.
 * Diabetes.
 * Renal insufficiency.
 * It is less strongly recommended to perform an ECG for patients scheduled to undergo vascular surgery with no clinical risk factors.


 * Patients who are scheduled to undergo intermediate-risk surgery with known cardiovascular disease, peripheral artery disease, or cerebrovascular disease.It is less strongly recommended to perform an ECG for patients scheduled to undergo intermediate-risk surgery with at least one clinical risk factor.

10. Chest radiograph (Chest x-ray): Its not recommended to do this test routinely before the operations in healthy patients, many studies showed that an abnormal chest x-ray findings may occur frequently, especially in elderly persons. According to the American College of Physicians (ACP), if there is a suspicion of cardiopulmonary disease from the patient's history or physical examination, then this test should be done, also in those older than 50 years of age who are undergoing abdominal aortic aneurysm surgery or upper abdominal/thoracic surgery. The American heart association (AHA) recommends preoperative chest x.ray for patients with morbid obesity (BMI ≥40 kg/m2).

11. Pulmonary function test (PFT): This test only recommended for patients who have dyspnea or other abnormal respiratory clinical findings such as decreased breath sounds, prolonged expiratory phase, rales, rhonchi, or wheezes.

ACC / AHA recommendations for perioperative cardiac assessment
This table below contains the ACC/AHA 2007 guidelines on perioperative cardiovascular evaluation and care for noncardiac surgery.

Class I
 * 1) Patients who have a need for emergency noncardiac surgery should proceed to the operating room and continue perioperative surveillance and postoperative risk :stratification and risk factor management. (Level of Evidence: C)
 * 2) Patients with active cardiac conditions* should be evaluated and treated per ACC/AHA guidelines and, if appropriate, consider proceeding to the operating room. (Level of Evidence: B)
 * 3) Patients undergoing low risk surgery are recommended to proceed to planned surgery.† (Level of Evidence: B)
 * 4) Patients with poor (less than 4 METs) or unknown functional capacity and no clinical risk factors should proceed with planned surgery.† (Level of Evidence: B)

Class IIa
 * 1) It is probably recommended that patients with functional capacity greater than or equal to 4 METs without symptoms‡ proceed to planned surgery.§ (Level of Evidence: B)
 * 2) It is probably recommended that patients with poor (less than 4 METs) or unknown functional capacity and 3 or more clinical risk factors who are scheduled for vascular surgery consider testing if it will change management.¶ (Level of Evidence: B)
 * 3) It is probably recommended that patients with poor (less than 4 METs) or unknown functional capacity and 3 or more clinical risk factors who are scheduled for intermediate risk surgery proceed with planned surgery with heart rate control.¶ (Level of Evidence: B)
 * 4) It is probably recommended that patients with poor (less than 4 METs) or unknown functional capacity and 1 or 2 clinical risk factors who are scheduled for vascular or intermediate risk surgery proceed with planned surgery with heart rate control.¶ (Level of Evidence: B)

Class IIb
 * 1) Noninvasive testing might be considered if it will change management for patients with poor (less than 4 METs) or unknown functional capacity and 3 or more clinical risk factors who are scheduled for intermediate risk surgery. (Level of Evidence: B)
 * 2) Noninvasive testing might be considered if it will change management for patients with poor (less than 4 METs) or unknown functional capacity and 1 or 2 clinical risk factors who are scheduled for vascular or intermediate risk surgery. (Level of Evidence: B)

§Noninvasive testing may be considered before surgery in specific patients with risk factors if it will change management. Clinical risk factors include ischemic heart disease, compensated or prior heart failure, diabetes mellitus, renal insufficiency, and cerebrovascular disease. ¶Consider perioperative beta blockade (see Table 12) for populations in which this has been shown to reduce cardiac morbidity/mortality.

High (Reported cardiac risk often greater than 5%)

 * Emergent major operations, particularly in the elderly.
 * Aortic and other major vascular surgery.
 * Peripheral vascular surgery.
 * Anticipated prolonged surgical procedures associated with large fluid shifts and/or blood loss.

Intermediate (Reported cardiac risk generally less than 5%)

 * Carotid endarterectomy.
 * Head and neck surgery.
 * Intraperitoneal and intrathoracic surgery.
 * Orthopedic surgery.
 * Prostate surgery.

Low (Reported cardiac risk generally less than 1%)

 * Endoscopic procedures.
 * Superficial procedure.
 * Cataract surgery.
 * Breast surgery.

Estimated energy requirements for various activities
The metabolic equivalent of task (MET), or simply metabolic equivalent, is a physiological concept expressing the energy cost of physical activities as multiples of resting metabolic rate (RMR) and is defined as the ratio of metabolic rate (and therefore the rate of energy consumption) during a specific physical activity to a reference rate of metabolic rate at rest, set by convention to 3.5 ml O2·kg-1·min-1 or equivalently 1 kcal·kg-1· h-1 or 4.184 kJ·kg-1· h-1. By convention 1 MET is considered as the resting metabolic rate obtained during quiet sitting. MET values of physical activities range from 0.9 (sleeping) to 18 (running at 17.5 km/h or a 5:31 mile pace).

Calculating the weekly energy expended in recreational-time physical activity using METs (Metabolic equivalent task) .