Medical Consultation

Sanjiv J. Shah, M.D.

Gurpreet Dhaliwal, M.D.

 

General Guidelines

Preoperative Cardiac Evaluation

Perioperative Beta-Blockers

Preoperative Pulmonary Evaluation

Perioperative Management Of Diabetes Mellitus

DVT/PE Prophylaxis

Perioperative Management Of Anticoagulation

Prophylaxis For Bacterial Endocarditis

 

GENERAL GUIDELINES

 

·        Each hospital has its own professional climate and style.  Therefore, find out early which services want you to be hands-on (e.g. Orthopedics, co-management services) and which services want you to be hands-off (e.g. Cardiothoracic surgery).

·        If you are “curb-sided” always offer to do a formal consult.  In general curbside consults are only appropriate for basic questions that do not require your seeing the patient.

·        From the start of your conversation with the primary team, determine the question that is being asked; if there is no specific question—push for one.

·        Is this consult urgent?  Use your triage skills in order to figure out how soon you should see a given patient.

·        In your communication with the primary team (written and oral) be as specific and concise as possible.  Provide a plan of action along the lines of “if…., then….”.

·        Know your limits and boundaries and respect the primary team’s decision-making process—be tactful.

·        Avoid terms such as “cleared for surgery” or “okay for general anesthesia”.  Also stay away from comments such as “avoid hypotension” that are obvious.

·        Communication is key—communicate early and often with the primary team by phone or in person.  Be explicit about your recommendations and use an algorithmic approach in your recommendations whenever possible.

·        Always consider contacting the primary care provider of the patient on whom you are consulting.  Not only is it a matter of professional courtesy, it enhances patient care tremendously.

 

Goldman L, Lee T, Rudd P. Ten commandments for effective consultations. Arch Intern Med 1983; 143:1753-5.

 

Choi JJ. An anesthesiologist's philosophy on 'medical clearance' for surgical patients. Arch Intern Med 1987; 147:2090-2.

 

 

PREOPERATIVE CARDIAC EVALUATION

 

1.      Basic algorithm:

·        Is this an emergency surgery? If yes, proceed with surgery and evaluate cardiac risk postoperatively.  Is the patient young, without systemic disease, and going for a minor surgery or procedure? If yes, proceed with surgery.

 

2.      Revised Cardiac Risk Index:

• Assign 1 point to each of the following risk factors if present:

-        High risk surgery? (intraperitoneal, intrathoracic, suprainguinal vascular).

-        Ischemic heart disease? (history of MI or current angina, use of SL NTG, positive stress test, Q waves on ECG, or history of PTCA/CABG with ongoing chest pain).

-        History of CHF?

-        History of cerebrovascular disease (CVA/TIA)?

-        Diabetic requiring insulin?

-        Pre-op creatinine > 2.0 mg/dl?

·        Assign a risk class to determine cardiac complication rate (listed below):

-        Class I:       zero risk factors:            0.4%

-        Class II:      1 risk factor:                  0.9 %

-        Class III:     2 risk factors:                6.6%

-        Class IV:     3 or more risk factors:    11.0%

·        Exceptions: works well for all patients except those undergoing major vascular surgery.

·        If patients are Class III or Class IV, strongly consider preoperative noninvasive testing and risk reduction to limit cardiac complications.

 

3.      What if I have a patient undergoing major vascular surgery?

·        Use the AHA/ACC guidelines, which feature a complex algorithm that is based on functional capacity, clinical predictors, and procedure-specific risks (see reference below).

·        Delay surgery and proceed to direct treatment/risk reduction if patient has a major clinical predictor of postoperative cardiac complication.  Noninvasive testing may not be helpful here because of the high rate of false negatives.  Major clinical predictors are defined as:

-        Unstable coronary syndromes (recent MI, unstable or severe angina)

-        Decompensated CHF

-        Symptomatic or uncontrolled arrhythmias (such as symptomatic ventricular arrhythmias, SVT with uncontrolled rate, high grade AV block)

-        Severe valvular disease

·        Simplified version of the AHA/ACC algorithm: Use noninvasive testing if the patient has at least 2 of the following risk factors:

-        intermediate clinical predictors: mild angina, prior MI, compensated or prior CHF, diabetes mellitus, renal insufficiency

-        poor functional capacity, defined as < 4 METs: cannot do more than walk 1-2 blocks on level ground or light housework, such as washing the dishes or dusting.  Cannot climb a flight of stairs or walk up a hill.

-        high risk surgery: emergency procedure, vascular surgery, prolonged procedure, or anticipated large fluid shifts or blood loss.

 

4.      What are defined as cardiac complications?

·        Hard end-points: MI, cardiovascular death (by MI, arrhythmia, heart failure).

·        Soft end-points: non-fatal arrhythmia, CHF/pulmonary edema, ischemia.

 

5.      Perioperative MI: usually presents atypically (without chest pain).  Look for hypotension, pulmonary edema, altered mental status (especially in elderly patients), and arrhythmia.  Usually occurs within the first 2 days of surgery and carries a high mortality.

 

6.      How can you reduce cardiac risk?

·        Consider a lower risk alternative to the planned type of operation.

·        Consider using epidural or spinal anesthesia.

·        Correct, modify, and optimize the management of co-morbid medical conditions.

·        Recent MI: delay surgery for 6 months; if the surgery is semi-elective, fully evaluate/optimize from cardiac standpoint and wait at least 6-12 weeks.

·        CHF: optimize and avoid over-diuresis (patient should not be orthostatic)

·        Aortic stenosis: in general, go with symptoms (syncope, CHF, angina).  If the patient has symptoms, evaluate fully (obtain echocardiogram, rule out other causes of symptoms).  However, if the patient has no symptoms (make sure they are active enough to produce symptoms), then proceed with surgery.  This even applies to patients who have severe AS.  Patient with critical AS and without symptoms should only undergo procedures that are truly necessary.

·        Use perioperative beta-blockers (See Medicine Consultation: Perioperative Beta-Blockers).

 

7.      Take home points:

·        Since perioperative cardiac morbidity and mortality is very common and obviously important, cardiac risk assessment should take place in all pre-op medicine consults, even if you are not explicitly asked this question.

·        Most cases of cardiac risk assessment are determined simply by a good history and physical exam.

·        It is often helpful to give an estimate of the percentage risk of cardiac complications (see above, by risk class) so that the surgeons can make the most educated decision regarding whether or not to proceed with surgery.

·        Remember that guidelines are only one facet in the medical decision-making process¾they should not replace sound clinical judgment.  Evaluate each patient on an individual basis and avoid an algorithmic approach.

 

Lee TH, Marcantonio ER, Mangione CM, et al. Derivation and prospective validation of a simple index for prediction of cardiac risk of major noncardiac surgery. Circulation 1999; 100:1043-9.

 

Eagle KA, Berger PB, Calkins H, et al. ACC/AHA guideline update for perioperative cardiovascular evaluation for noncardiac surgery---executive summary a report of the ACC/AHA Task Force on Practice Guidelines. Circulation 2002; 105:1257-67.

 

 

PERIOPERATIVE BETA-BLOCKERS

 

1.      There is good evidence that beta-blockers reduce cardiac morbidity and mortality when used in the perioperative period in selected patients.

 

2.      Who should get beta-blockers?

• Does the patient meet two (2) or more of the following criteria? age > 65, hypertension, current smoker, total cholesterol > 240 mg/dl, or diabetes not requiring insulin.  If yes, give perioperative beta-blocker unless contraindicated.
• Does the patient meet any one (1) of the following criteria? high risk surgical procedure (intraperitoneal, intrathoracic, suprainguinal vascular), ischemic heart disease (history of MI or current angina, use of SL NTG, positive stress test, Q waves on ECG, or history of PTCA/CABG with ongoing chest pain), history of CVA/TIA, diabetes requiring insulin, or creatinine > 2.0 mg/dl. If yes, give perioperative beta-blocker unless contraindicated.

 

3.      Beta-blocker treatment protocol:

• Preoperative: atenolol 50-100 mg PO QD or continue outpatient therapy if previously on beta-blocker (beta-1 selective).  Titrate dose to HR < 65.  If NPO, use atenolol or metoprolol 2.5-10 mg IV until target HR achieved.
• Immediately post-op: use atenolol or metoprolol 5-10 mg IV to achieve target HR.
• Postoperative: transition back to the preoperative oral therapy when the patient is ready to take PO’s.  If patient is unstable, consider using esmolol.  Beta-blocker should be continued at least 1 month postoperatively.

 

4.      Don’t treat the numbers: resist the urge to blindly treat tachycardia in the perioperative period with beta-blockers.  If a patient has new, unexplained tachycardia, investigate first.   In cases like this, tachycardia may be the only sign of a potentially dangerous underlying condition.

 

Auerbach AD, Goldman L. beta-Blockers and reduction of cardiac events in noncardiac surgery: scientific review. JAMA 2002; 287:1435-44.

 

 

PREOPERATIVE PULMONARY EVALUATION

 

1.      Pulmonary complications are defined as: pneumonia, respiratory failure, need for mechanical ventilation, bronchospasm, atelectasis, or exacerbation of underlying lung disease.

 

2.      Risk factors:

• Smoking: RR 1.4-4.3 for post-op pulmonary complications; risk declines only if patient quits smoking 8 weeks or earlier prior to surgery.
• COPD: RR 2.7-4.7.  Treat COPD aggressively prior to surgery with inhalers, physical therapy, smoking cessation, and steroids and antibiotics when indicated.  Strongly consider delaying surgery if possible in COPD patients with active URI, bronchitis, or pneumonia.
• Asthma: RR ~2 though recent studies have not supported this risk.  In the preoperative period, aim for no wheezing and a peak flow > 80% predicted; can use short course of oral steroids (prednisone 60 mg PO QD) prior to surgery to reach these goals.
• Poor functional status: remember to ask about exercise tolerance preoperatively because this correlates with risk of post-op pulmonary complications.
• Current medical health: the Goldman Risk Index as well as the ASA classification both predict post-op pulmonary complications.
• Age: not a proven independent risk factor for post-op pulmonary complications.
• Obesity: not a proven independent risk factor for post-op pulmonary complications.
• Procedure-related risk factors: primarily based on how close the surgery is to the diaphragm (i.e. upper abdominal and thoracic surgery are the highest risk procedures).
• Length of surgery (> 3 hours) and general anesthesia (vs. epidural or spinal) are also risk factors for post-op pulmonary complications.

 

3.      Pre-op pulmonary evaluation:

• Ask about decreased exercise tolerance, chronic cough, and dyspnea and consider delaying surgery until these symptoms (if present) can be explained or treated.
• On physical exam, look for prolonged expiratory phase and any abnormal lung findings to guide further testing and evaluation.
• Routine pre-op PFT, ABG, and/or CXR are not warranted.  Only perform these tests if the history and/or physical exam guide you to do so (e.g. unexplained dyspnea in a patient undergoing upper abdominal surgery).

 

4.      Risk-reduction strategies:

• Preoperative: quit smoking > 8 weeks pre-op, treat COPD or asthma exacerbation, treat respiratory infection and delay surgery if possible, and begin patient education about lung expansion maneuvers.
• Intraoperative: limit surgery to < 3 hours, use spinal or epidural anesthesia, opt for laparoscopic procedure when possible, and try to limit upper abdominal or thoracic surgery when possible.
• Postoperative: control pain, consider epidural anesthesia for pain control, use deep breathing exercises and incentive spirometry in all patients, and use CPAP or similar ventilatory support when needed.

 

Smetana GW. Preoperative pulmonary evaluation. N Engl J Med 1999; 340:937-44.

 

 

PERIOPERATIVE MANAGEMENT OF DIABETES MELLITUS

 

1.      Cardiac complications are common in diabetic patients in the perioperative period.

• Complete full pre-op cardiac evaluation and do work-up (e.g. stress test) as necessary.

 

2.      The perioperative period is a significant stressor on glycemic control.  Whether or not diabetics have a higher incidence of wound infection or infection in general in the post-op period (after controlling for other risk factors) is a subject of debate.

 

3.      Preoperative assessment:

• Differentiate type 1 (always require some insulin) from type 2 (may or may not require insulin perioperatively; though can be at risk for DKA in peri-op period).
• If hemoglobin A1c > 10% or fasting blood glucose > 200 mg/dl, watch for dehydration and/or electrolyte imbalance.
• If poor pre-op diabetic control, admit early to achieve better control.

 

4.      Perioperative management:

• Prevent hypoglycemia, ketosis, and dehydration (from osmotic diuresis).
• Stop metformin at least 48 hours prior to surgery; all other oral hypoglycemics can be held the morning of the surgery unless they are longer-acting (stop earlier).
• Use insulin infusion if possible and if adequate nursing is available to prevent complications (e.g. hypoglycemia).  See Endocrine: Insulin Infusion.
• Don’t need insulin infusion in diabetics who are diet-controlled regardless of type of surgery.
• Don’t need insulin infusion in diabetics who are on oral agents only and are undergoing minor surgeries.
• If no insulin infusion available, cut outpatient NPH dose in half, give D₅½NS fluids, and administer insulin sliding scale.

 

5.      In post-op patients who are admitted to the ICU and remain on a ventilator, intensive insulin therapy (in the form of insulin infusion) should be used to keep glucose levels between 80-110 mg/dl.  This resulted in a 43% relative risk reduction in mortality, according to a recent NEJM study.

 

6.      Postoperatively, transition to outpatient regimen once patient is taking PO’s.  Remember that diabetics on metformin are at risk for lactic acidosis (especially if the patient is in concomitant renal failure) so you may want to hold off restarting this mediation until the patient goes home.

 

Schiff RL, Emanuele MA. The surgical patient with diabetes mellitus: guidelines for management. J Gen Intern Med 1995; 10:154-61.

 

van den Berghe G, Wouters P, Weekers F, et al. Intensive insulin therapy in the critically ill patients. N Engl J Med 2001; 345:1359-67.

 

 

DVT/PE PROPHYLAXIS

 

1.      The following recommendations, based on the UCSF Venous Thromboembolism Prophylaxis Order Form, do not replace clinical judgment.

 

2.      Evaluate for risk factors (RFs): assign points to risk factors and total them up.

·        Give one (1) point to each of the following RFs: age 41-60, prior history of post-op DVT, family history of DVT/PE, leg swelling/ulcer/stasis/varicose veins, MI/CHF, stroke with paralysis, IBD, central line, bed immobilization > 12 hours, or general anesthesia > 2 hours.

·        Give two (2) points to each of the following RFs: age 61-70, prior history of idiopathic or unprovoked DVT, major surgery, malignancy, multiple trauma, spinal cord injury with paralysis.

·        Give three (3) points to each of the following RFs: age > 70, prior history of PE, inherited thrombophilia, or acquired thrombophilia.

 

3.      Assess for any contraindications to pharmacologic prophylaxis: if contraindications exist, consider sequential compression devices (SCDs).

·        Relative contraindications: history of cerebral hemorrhage, GI/GU hemorrhage or stroke within last 6 months, thrombocytopenia, coagulopathy (PT > 18 sec), active intracranial lesions/devices, proliferative retinopathy, vascular access/biopsy sites that are inaccessible to hemostatic control.

·        Absolute contraindications: active hemorrhage, history of heparin-induced thrombocytopenia, pregnancy (heparin okay, warfarin not okay), severe trauma (head, spinal cord, extremity) within last 4 weeks, or epidural/indwelling spinal catheter.

·        Low molecular weight heparin: avoid in patients with renal insufficiency (defined as Cr > 2.0 or CrCl < 30 ml/min).  Also avoid in patients who are obese (weight > 120 kg).  Accurate dosing has not been established in these groups of patients.

 

4.      Prophylaxis regimens: determined by risk factor score.  Dosing: LDUH = low dose unfractionated heparin 5000 U SQ q8-12h.  LMWH = low-molecular weight heparin; see dosing below.  SCDs = sequential compression devices.  Warfarin = titrate dose to achieve INR 2-3.  IV heparin drip = titrate dose to target PTT of high normal (~ 35 seconds).

·        Low risk (zero risk factors):                    Early ambulation

·        Moderate risk (1-2 risk factors):              LDUH q12 hours, LMWH, or SCDs

·        High risk (3-4 risk factors):                     LDUH q8 hours, LWMH, or SCDs

·        Very high risk (> 4 risk factors):              LMWH, warfarin, or IV heparin drip

 

5.      Dosing recommendations for LMWH:

·        General surgery: enoxaparin 40 mg SQ qd, 1^st dose 2 hours pre-op.

·        Gynecologic surgery: enoxaparin 40 mg SQ qd.

·        Extensive urologic surgery: enoxaparin 30 mg SQ bid.

·        Major orthopedic surgery: enoxaparin 30 mg SQ bid; start early (12-24 hours post-op) and continue for 2 weeks (even as an outpatient if the appropriate resources are available).

·        Medical conditions: enoxaparin 40 mg SQ qd.

 

Geerts WH, Heit JA, Clagett GP, et al. Prevention of venous thromboembolism. Chest 2001; 119:132S-175S.

 

Hull RD, Pineo GF, Stein PD, et al. Extended out-of-hospital low-molecular-weight heparin prophylaxis against deep venous thrombosis in patients after elective hip arthroplasty: a systematic review. Ann Intern Med 2001; 135:858-69.

 

Hull RD, Pineo GF, Stein PD, et al. Timing of initial administration of low-molecular-weight heparin prophylaxis against deep vein thrombosis in patients following elective hip arthroplasty: a systematic review. Arch Intern Med 2001; 161:1952-60.

 

 

PERIOPERATIVE MANAGEMENT OF ANTICOAGULATION

 

1.      The dilemma: your patient is on warfarin (for atrial fibrillation, a mechanical heart valve, or DVT/PE) and is scheduled for an invasive procedure.  In the perioperative period, your job is to weigh the risks of stopping anticoagulation (chance for venous or arterial thromboembolism) against the risks of continuing anticoagulation (chance for major hemorrhagic event).

 

2.      There is no consensus on this topic.  Listed below are some helpful tips that can be used along with your clinical judgment in order to come up with a solution for the individual patient.

 

3.      General considerations:

• Invasive surgery is generally safe (from major hemorrhagic complication) when the INR < 1.5.
• It takes approximately 4 days for the INR to reach 1.5 once warfarin is stopped preoperatively.
• It takes approximately 3 days for the INR to reach 2.0 once warfarin is restarted postoperatively.
• All things considered, if warfarin is held 4 days pre-op and started immediately post-op, the patient is effectively without anticoagulation for 2 days (24 hours pre-op and 24 hours post-op).

 

4.      Risk of thromboembolism according to underlying medical condition:

• Nonvalvular atrial fibrillation: 4.5%/year (0.01%/day); note that the risk can be anywhere from  1-20%/year (0.003-0.055%/day) based on the patient’s underlying risk factors.
• Nonvalvular atrial fibrillation with previous embolism (stroke): 12%/year (0.03%/day).
• Mechanical heart valve: 8%/year (0.02%/day).
• DVT/PE after 1 month of anti-coagulation: 40% over the next month (1.3%/day).
• DVT/PE after 2-3 months of anti-coagulation: 10% over the next month (0.3%/day).
• DVT/PE patients on long-term anti-coagulation: 15%/year (0.04%/day).
• Acute arterial embolism: 15% over the next month (0.5%/day).

 

5.      Management tips:

• If INR pre-op is 2-3, stop warfarin 4 days prior to surgery (withhold longer if INR > 3.0 or if it is necessary to have an INR < 1.5 pre-op).
• Measure INR one day prior to surgery: if it is > 1.8, give 1 mg vitamin K PO/SQ.
• For patients with DVT/PE:

-        1^st month after thromboembolic episode: avoid elective surgery (high risk of recurrence off anticoagulation).  If your patient must go to the O.R., use IV heparin once the INR < 2.0.  Stop the heparin 6 hours pre-op.  If there is no active bleeding from the surgical site, restart IV heparin 12 hours post-op with no bolus.  If the risk of IV heparin is too high and the patient has had a PE or proximal DVT in the past 2 weeks, consider an IVC filter.

-        2-3 months after the thromboembolic episode: don’t need pre-op IV heparin.  However, use IV heparin post-op until INR > 2.0 because the risk of post-op DVT/PE is so high.

-        Long-term anticoagulation patients (last DVT/PE more than 3 months ago): no pre-op or post-op IV heparin; give post-op DVT/PE prophylaxis (see Medical Consultation: DVT/PE prophylaxis) until INR > 2.0.

• For patients with atrial fibrillation or mechanical heart valve:

-        If the patient has had an arterial thromboembolic episode (e.g. stroke) within the last month, avoid elective surgery.  If your patient must go to the O.R., give IV heparin as stated above pre- and post-op.

-        Long-term anticoagulation patients: no need for pre- or post-op IV heparin.

 

Kearon C, Hirsh J. Management of anticoagulation before and after elective surgery. N Engl J Med 1997; 336(21): 1506-11.

 

 

PROPHYLAXIS FOR BACTERIAL ENDOCARDITIS

 

1.      The most important aspect of prophylaxis for bacterial endocarditis is remembering to think about it in every preoperative patient.   A basic outline of the 1997 AHA guidelines is as follows:

 

2.      Who should get prophylaxis?  Patients with…

• All prosthetic cardiac valves (high risk)
• Previous endocarditis (high risk)
• Surgical systemic pulmonary shunts (high risk)
• Most congenital heart defects (complex defects are at high risk)
• Acquired valve dysfunction (moderate risk)
• Hypertrophic cardiomyopathy (HCM) (moderate risk)
• Mitral valve prolapse with regurgitation (moderate risk)

 

3.      What procedures need prophylaxis?  Basically, procedures that need prophylaxis are those where there is a high chance of invading a bacteria-rich area that predisposes the patient to bacteremia.

• Surgery involving the GI mucosa
• Biliary tract surgery or ERCP
• Esophageal sclerotherapy or dilatation
• Surgery involving the respiratory mucosa or rigid bronchoscopy
• Prostate surgery or cystoscopy
• Any dental procedure likely to cause bleeding (e.g. dental extraction)
• Tonsillectomy & adenoidectomy

 

4.      What are the recommended prophylaxis regimens?

• Dental and upper respiratory tract: amoxicillin 2 g PO or clindamycin 600 mg PO 1 hour prior to procedure; if giving parenteral antibiotics, use ampicillin 2 g IV or clindamycin 600 mg IV 30 minutes prior to procedure.
• GI/GU: if the patient is at moderate risk, use amoxicillin or ampicillin as above.  Vancomycin 1 g IV can be given if the patient is penicillin-allergic.  If the patient is high risk, give ampicillin 2 g IV + Gentamicin 1.5 mg/kg (up to 120 mg) 30 minutes prior to procedure, followed in 6 hours by ampicillin 2 g IV or amoxicillin 2 g PO.  If the patient is penicillin-allergic, give Vancomycin 1 g IV + Gentamicin 1.5 mg/kg (up to 120 mg).
• Note: if using vancomycin, use a slow infusion that ends 30 minutes prior to procedure

 

Dajani AS, Taubert KA, Wilson W, et al. Prevention of bacterial endocarditis. Recommendations by the American Heart Association. JAMA 1997; 277:1794-801.