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A. Introduction
The medical consultant is often asked to evaluate an individual prior to surgery. The general goals of this consultation are to:
Identify unrecognized co-morbid disease and risk factors for medical complications of surgery.
Optimize preoperative medical condition.
Understand, recognize, and treat potential complications.
Work as a team with surgeon and anesthesiologist.
Risk and benefit of the proposed procedure must be balanced:
Why was the consult requested?
What is the benefit to the patient of the proposed procedure?
May one substitute a lower risk procedure?
What are the known risks?
What is the balance of risk-benefit?
What are the patient's goals?
The internist assesses risk; the £mal analysis rests with the surgeon and the patient. The internist may be seeing the patient for the first time or may be the primary care physician evaluating the patient in the office prior to considering a surgical referral.
B. Principles of Consultation
Restrict advice to the internist's unique areas of expertise.
Example: OK to advise on perioperative insulin management. The selection of anesthetic technique is better left to the anesthesiologist.
Keep number of recommendations to a minimum.
Adherence to recommendations diminishes for consults with more than 5 recommendations (Am J Med 1983;74:870).
Clarify the specific reason for the consult request. Content of consult will differ for "routine consult request than for request to evaluate risk of postoperative pulmonary complications in a high risk patient with COPD.
Adherence to consultant's recommendations is greater for consults requested early in a patient's hospital course (J Fam Pract 2006;42:259-63). This may relate to a greater degree of perceived urgency on the part of the referring physician early on in a patient's hospital stay.
Follow patients through the postoperative period as many perioperative complications occur during this time.
Remember: The preoperative patient is not being "cleared." This may incorrectly imply there is no risk. Rather, the consultant may determine that the patient is at average risk for the proposed procedure, which should be the assessment in the chart if no factors are found which increase perioperative risk.
Goldman's Ten Commandments of Consultation are useful guides for the consultant (Arch Int Med 1983;143:1753):
Determine the Question.
Establish Urgency.
Look for Yourself.
Be as Brief As Appropriate.
Be Specific.
Provide Contingency Plans.
Honor Thy Turf.
Teach ... with Tact.
Talk is Cheap ... and Effective.
Follow-up.
C. Effects of Anesthesia
Modem anesthesia is extremely safe.
Patient and surgical factors are more important risk predictors than anesthetic considerations (JAMA
1988;260:2859).
ASA (Dripps) Classification is a powerful predictor of overall perioperative mortality. It also predicts cardiac and pulmonary morbidity.
ASA Classification
| Class | Systemic Disturbance | Mortality* |
| 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 |
* Cohen et al. JAMA 1988; 260:2859
1. Sources of Anesthetic Risk
Stress response to anesthetic drugs and interventions.
Adverse drug effects.
Mechanical and operator error.
2. Organ Effects
Cardiac
Inhalational agents are all myocardial depressants.
Leads to "preload" dependence.
Therefore, accentuated hypotensive response to induction of anesthesia in patients who are volume depleted, overdiuresed, or have poor ventricular function.
Autonomic neuropathies, such as diabetic, also accentuate hypotension with anesthetic induction.
Pulmonary
Vital capacity decreased by 50%
Decreased FRC below closing volumes leads to atelectasis and V/Q mismatch
Decreased mucociliary clearance.
Loss of sighing breaths.
Depression of response to hypoxia and hypercarbia.
Diaphragmatic dysfunction, greatest in thoracic and upper abdominal surgery
3. Spinal (or epidural) versus general anesthesia
No difference in cardiac mortality.
Probable decrease in the risk of pulmonary complications.
D. Preoperative Evaluation of Healthy Individuals
Perioperative risk is very low in healthy individuals, estimated at 0.03% or less. Therefore, additional evaluation will by definition have a low yield and a high likelihood of false positive results.
1. History
The most important factor in evaluation of the healthy patient
Questionnaire studies have used simple screening instruments to define a low risk population.
In one questionnaire study, only 9 of 370 patients had surgically significant medical issues and screened incorrectly as low risk (Can J Anaesth 2006;45:87). This questionnaire follows:
1. Have you ever had a heart attack?
2. Have you ever had heart trouble?
3. Have you ever had heart failure?
4. Have you ever had fluid in your lungs?
5. Do you have a heart murmur?
6. Did you have rheumatic fever as a child?
7. Do you ever have chest pain, angina, or chest tightness?
8. Have you ever been treated for an irregular heart beat?
9. Do you have high blood pressure?
10. Do you ever have difficulty with your breathing?
11. Do you have asthma, bronchitis, or emphysema?
12. Do you cough frequently?
13. Does climbing one flight of stairs make you short of breath?
14. Does walling one city block make you short of breath?
15. Do you now or have you recently smoked cigarettes? How many packs? How many years?
16. Do you have liver disease, or a history of jaundice or hepatitis?
17. Do you drink more than three drinks of alcohol per day?
! 8. Do you have indigestion, heartburn, or a hiatus hernia?
19. Do you have a history of thyroid problems?
20. Do you have diabetes?
21. Do you have a kidney problem?
22. Do you have numbness or weakness of your arms or legs?
23. Do you have epilepsy, blackouts, or seizures?
24. Have you had problems with blood clots or excessive bleeding?
25. Do you have any other important medical problems? Please list.
26. Have you ever had an anesthetic? If yes, when was your last one?
27. Have you or a member of your family had a reaction to an anesthetic?
28. Do you have arthritis or pain in your neck or jaw?
29. Do you have dentures, capped or loose teeth?
30. Do you think you may be pregnant?
31. Have you taken prednisone, steroid medication, or cortisone-like drugs in the past year?
32. Please list any food or medication allergies that you have.
33. Please list any medications you are currently taking.
34. Please list any operations you have had in the past.
35. If this is the day of surgery, when did you last eat or drink?
36. Age Height Weight
Another study administered the following simple questionnaire. Patients who answered no to all questions were at average risk. There was no additional risk adjustment from history, exam, or labs in these patients (Br Med J 1980:1:509).
1. Do you feel unwell?
2. Have you had any serious illnesses in the past?
3. Do you get more short of breath on exertion than other people of your age?
4. Do you have any cough?
5. Do you have any wheeze?
6. Do you have any chest pain on exertion (angina type)?
7. Do you have any ankle swelling?
8. Have you taken any medicine or pills in the last 3 months? (including excess alcohol)?
9. Have you any allergies?
10.Have you had an anesthetic in the last 2 months?
11.Have you or your relatives had any problem with a previous anesthetic?
12.Observation of serious abnormality from "end of bed" (which might affect anesthetic)?
13.Date of last menstrual period?
Exercise capacity
Exercise capacity is an important determinant of perioperative risk
Clinicians should ask all patients about exercise capacity prior to surgery
Good exercise capacity generally predicts a low cardiac and pulmonary risk of surgery (Circulation 2006;93:1278)
Medication use
Include OTC meds such as ASA, NSAID's, etc.
Age
Age is variably reported as a risk factor for perioperative risk.
However, it is difficult to establish the risk of age itself from the risk of comorbidities common in older patients.
When adjusted for ASA class, the perioperative risk is the same across all age groups (Anesthesiology 1973;39:54-8).
2. Laboratory Testing
Routine screening labs add little to the low overall risk assessment in healthy patients.
Given the low prevalence of disease in patients who report they are healthy and have a negative questionnaire,
most positive test results are false positives.
The more "screening" lab tests are ordered, the more likely one will find a false positive abnormal result in a healthy patient.
Predictive Value and Prevalence for a Test with 95% Sensitivity and Specificity
| Prevalence of Disease (%) | Predictive Value of Positive Test (%) |
| 0.1 | 1.9 |
| 1 | 16.1 |
| 2 | 27.9 |
| 5 | 50.0 |
| 50 | 95.0 |
(Normal result defined as <2 S.D. from the mean)
| Number of Independent Tests | Probability of Abnormal Test (%) |
| 1 | 5 |
| 2 | 10 |
| 4 | 19 |
| 6 | 26 |
| 10 | 40 |
| 20 | 64 |
| 50 | 92 |
| 90 | 99 |
Support from the medical literature for restraint in test ordering.
2000 sequential patients in UCSF study (JAMA 1985;253:3576)
60% of routinely ordered tests not clinically indicated
0.22% surgically significant abnormal results
No instance where abnormal result recognized and acted on
| Test | #Tests |
#Abnormal
results |
#Unindicated
abnormal results |
#Unindicated surgically significant abnormal results |
| Prothrombin Time | 650 | 2 | 0 | 0 |
| PTT | 650 | 1 | 0 | 0 |
| Platelet Count | 1320 | 3 | 2 | 1 |
| CBC | 4660 | 22 | 2 | 0 |
| Differential Count | 1480 | 2 | 1 | 0 |
| SMA-6 | 3200 | 41 | 1 | 0 |
| Glucose | 3100 | 25 | 4 | 2 |
Similar outcome in Mayo Clinic study (Mayo Clinic Proc 1991; 66:155)
3782 patients.
160 abnormal results noted in routine preoperative testing
47 of which prompted further assessment