Surgical Stratification

Patients undergoing low-risk procedures do not require any further cardiac evaluation before surgery. Patients undergoing high-risk or intermediate-risk surgeries need further assessment ( Table 6-1 ). Most orthopedic surgeries fall under the intermediate-risk category and require this next step of cardiac evaluation. The fourth step according to the guidelines of the ACC/AHA is evaluation of the patient’s functional capacity. The idea is to try to gauge the patient’s cardiac reserve. Cardiac reserve is assessed by determining the highest level of activity a patient can perform without any cardiac signs or symptoms. It is measured in metabolic equivalents. A metabolic equivalent of 1 is the ability to eat, dress, and perform basic self-care; at the other end of the range, 10 metabolic equivalents would be participation in strenuous sports. Most surgeries put a strain on the heart of approximately 4 metabolic equivalents; this is equal to climbing a flight of stairs or walking on level ground at 4 mph. A patient who has a functional capacity greater than 4 metabolic equivalents is thought not to require any further cardiac evaluation and can proceed to surgery.

A patient’s functional capacity often is unknown because of dementia, sedation, or other causes of impaired cognition. Patients may have a poor functional capacity because of a sedentary lifestyle. These patients require step 5 evaluation, which is the determination of their clinical risk factors. Clinical risk factors have been defined differently depending on the source. The ACC/AHA derived the Revised Cardiac Risk Index, which includes the following risk factors:

• 1
  

  Any history of ischemic heart disease

  
  
• 2
  

  Any history of compensated or prior heart failure

  
  
• 3
  

  Any history of cerebrovascular disease

  
  
• 4
  

  Diabetes mellitus

  
  
• 5
  

  Renal failure

If a patient has none of the above-listed clinical risk factors, the cardiac evaluation is complete. If a patient has one or two risk factors, further cardiac evaluation needs to be considered “if it would change the management of the patient.” The physician’s knowledge of the patient and a full review of the patient’s history, especially a complete review of symptoms and physical examination, are essential for determining which patients need further cardiac assessment.

Patients with three or more risk factors are divided into vascular surgeries and intermediate-risk surgeries. Most elderly patients with trauma fit into this intermediate-risk surgery category. Similar to the previous category of one or two clinical risk factors, initiation of beta blocker therapy and need for further cardiac assessment must be individually determined.

The ACC/AHA algorithm is a comprehensive tool to help in the cardiac evaluation of a patient preparing for surgery. It does not replace individual assessment of the patient and the surgery.

Beta Blockers

Beta blockers are controversial in the perioperative arena. The idea is that noncardiac surgery increases levels of catecholamines, which causes increased heart rate, blood pressure, and free fatty acid concentrations, all of which increase myocardial oxygen demand. Beta blockers are thought to attenuate increased catecholamine levels and decrease myocardial consumption and ultimately decrease cardiovascular risk.

Numerous studies, including the Atenolol Study in 1996 and the Bisoprolol Study in 1999, showed a decrease in both overall mortality and cardiac death, concluding, “Bisoprolol reduces the perioperative incidence of death from cardiac causes and nonfatal MI (myocardial infarction) in high risk patients who are undergoing major vascular surgery.” A retrospective cohort study looked at patients undergoing noncardiac surgery from 2000-2001 at 329 hospitals in the United States. The risk of in-hospital mortality with beta blocker administration was based on calculation of the revised cardiac risk index for each patient (clinical risk factors). The investigators concluded that “Perioperative beta-blocker therapy is associated with a reduced risk of in-hospital death among high risk, but not low risk, patients undergoing major noncardiac surgery. Patient safety may be enhanced by increasing the use of beta-blockers in high risk patients.” The MaVS study published in 2006 randomly assigned patients undergoing vascular surgery to metoprolol or placebo. The study found no difference in cardiac events but an increase in bradycardia and hypotension. The investigators concluded, “Our results showed metoprolol was not effective in reducing 30 day and 6 month postoperative cardiac event rates. Prophylactic use of perioperative beta blockers in all vascular patients is not indicated.”

In 2007, the ACC published guideline recommendations for perioperative use of beta blockers. The ACC suggested that the only class I indication for perioperative beta blockers is to continue beta blockers in all patients undergoing surgery who are already taking them; also, beta blockers may be given to patients undergoing vascular surgery who are at high cardiac risk (ischemia on preoperative testing). In 2008, the PeriOperative ISchemic Evaluation (POISE) trial was published. This multicenter randomized controlled trial looked at metoprolol versus placebo in patients undergoing noncardiac surgery. The investigators found an overall reduction of myocardial infarction, cardiac revascularization, and clinically significant atrial fibrillation but a significant excess risk of death, stroke, and clinically significant hypotension and bradycardia.

These results led to the ACC publishing a focused update on perioperative use of beta blockers in 2009. The only class I recommendation is that beta blocker medications be continued in all patients undergoing surgery who are currently taking beta blockers. The routine use of high-dose beta blockers in the absence of titration is not useful and possibly harmful to patients not taking beta blockers preoperatively and undergoing noncardiac surgery. The recommendations for perioperative beta blockers at this time include the following:

• 1
  

  Continue beta blockers in patients already taking them preoperatively.

  
  
• 2
  

  Consider starting patients on perioperative beta blockers if their modified cardiac risk index is at least 2 (clinical risk factors).

  
  
• 3
  

  Preoperative beta blockers are best started at least 2 weeks before surgery and titrated to a heart rate of 55 to 65 beats/min.

Hyperglycemic Medications

Oral hypoglycemic medications are generally held the morning of surgery to help prevent perioperative hypoglycemia. They are restarted when the patient is tolerating adequate oral intake. However, metformin (Glucophage) requires special consideration. The manufacturer warning lists lactic acidosis as a possible side effect of using metformin during the perioperative time frame. Although lactic acidosis is a rare side effect, it is a dangerous one, and the recommendation is to hold metformin 48 hours before surgery and continue to hold it for 48 hours after surgery. Lactic acidosis is increased in patients with renal insufficiency, and it is prudent that creatinine be assessed before restarting metformin. A creatinine level of 1.4 or greater in women or 1.5 or greater in men prevents reinitiating metformin.

Insulin regimens depend on the type of diabetes. A patient with insulin-dependent (type 1) diabetes requires more coordination with an endocrinologist and care in the perioperative period to avoid diabetic ketoacidosis. The details of type 1 diabetes management are beyond the scope of this chapter. The more common type 2 or non–insulin-dependent diabetes is addressed here. Patients taking oral hypoglycemic agents can follow the aforementioned recommendations. Patients taking insulin still have insulin requirements even without oral intake. The basal metabolic needs use approximately half of a patient’s total daily insulin requirements without oral intake.

Some general insulin recommendations are as follows:

• ▪
  

  Short-acting insulin is held the morning of surgery. Corrective doses can be given if the blood glucose levels are greater than 200 mg/dL.

  
  
• ▪
  

  Intermediate-acting insulin is given as a half to two-thirds dose the night before surgery, and half of the morning dose is given the day of surgery, provided that the patient is expected to eat after surgery. The decision to give the morning dose depends on how likely the patient will be able to eat after surgery versus the concern over sedation, nausea, or anorexia. It is often suggested that the morning dose of intermediate-acting insulin be held to avoid hypoglycemia because short-acting insulin can always be administered to prevent hyperglycemia.

  
  
• ▪
  

  Long-acting insulin is generally given at half or full dose the evening before surgery. If a patient takes long-acting insulin the morning of surgery, the same adjustments can be made. There is a lack of true consensus on what to do with long-acting insulin because controlled studies are still pending.

Glucocorticoids

To discuss glucocorticoid management in the perioperative period, it is essential to understand the basic pathophysiology of cortisol. The hypothalamus secretes corticotropin-releasing hormone, which causes secretion of adrenocorticotropic hormone from the pituitary, which stimulates the adrenal glands to secrete cortisol—hence the hypothalamic-pituitary-adrenal (HPA) axis. Cortisol secretion is involved in metabolism of carbohydrates, lipids, and proteins; in vascular tone and endothelial integrity; in sodium and potassium management; and in anti-inflammatory properties. Stress (i.e., surgery) causes a positive feedback on the HPA axis and increases corticotropin-releasing hormone and ultimately increases cortisol. Exogenous cortisol in the form of oral glucocorticoids imposes a negative feedback on the HPA axis and prevents the increased secretion of cortisol during the time of surgical stress. No randomized trials have illustrated the assumption that exogenous cortisol causes sufficient adrenal atrophy to prevent the generation of sufficient endogenous glucocorticoids to meet the demands of surgical stress. However, this assumption has permeated medical thinking from the early 1950s, when there were cases of adrenal insufficiency related to stopping exogenous glucocorticoid treatment perioperatively.

The question often arises regarding which patients receiving exogenous glucocorticoids are at risk for postoperative adrenal insufficiency and need extra stress dosing of glucocorticoids. All patients who are critically ill and have primary adrenal insufficiency or primary hypopituitary insufficiency should receive stress dose steroids before surgery. Identifying patients with secondary adrenal insufficiency is more controversial.

• ▪
  

  It has been found that patients taking at least 15 mg of oral prednisone or its equivalent for at least 3 weeks or patients with Cushing syndrome are likely to have adrenal suppression and to be unable to mount an endogenous response to the stress of surgery.

  
  
• ▪
  

  Patients taking less than 5 mg of prednisone or its equivalent, taking exogenous glucocorticoids for less than 3 weeks, or taking glucocorticoids on an alternate-day dosing schedule are unlikely to have had their HPA axis affected and need not be considered for stress dosing of steroids.

There is a large gray area of patients taking exogenous steroids for more than 3 weeks and taking more than 5 mg but less than 15 mg of oral prednisone. It has been suggested to check an adrenocorticotropic hormone stimulation test or 8 a . m . and 4 p . m . cortisol levels in such patients to determine if they have adrenal suppression.

With such a large population of patients with unclear adrenal status, why not just give every patient stress dose steroids? The problem is the large side-effect profile associated with cortisol. Side effects include the following:

• 1
  

  HPA axis suppression

  
  
• 2
  

  Impaired wound healing

  
  
• 3
  

  Fluid retention

  
  
• 4
  

  Weight gain

  
  
• 5
  

  Elevated blood pressure

  
  
• 6
  

  Low potassium

  
  
• 7
  

  Muscle weakness

  
  
• 8
  

  Diabetes exacerbation or hyperglycemia

  
  
• 9
  

  Obesity

  
  
• 10
  

  Cataracts

  
  
• 11
  

  Personality changes

  
  
• 12
  

  Increased friability of skin, blood vessels, and tissues

  
  
• 13
  

  Increased risk of bleeding and ulcers

  
  
• 14
  

  Increased risk of fracture and avascular necrosis

Emerging data indicate that the assumption of profound HPA axis suppression may be overstated. Marik and Varon did a literature review of two randomized controlled trials and seven cohort studies looking at stress dose steroids for secondary adrenal insufficiency. Only two patients (one each in two cohort trials) showed any signs of hypotensive collapse postoperatively. Both of these patients had their regular home regimen held 36 to 48 hours before surgery. The investigators also looked at urinary 11-hydroxycorticosteroid levels after surgery in patients treated with glucocorticoids compared with controls. Although the urinary levels in the corticosteroid-treated group were lower than the control group, levels were still sufficient to prevent signs and symptoms of secondary adrenal insufficiency. More studies are needed to define better which patients are at risk for secondary adrenal insufficiency during the stress of surgery.

There is insufficient scientific evidence to determine the route and amount of steroids to administer when a patient is determined to have adrenal suppression. Expert opinion and recommendations suggest the drug of choice is intravenous hydrocortisone to give both glucocorticoid and mineralocorticoid effects. Administration should begin within 1 hour of surgery. The initial dosing recommendations are as follows:

• 1
  

  For high-risk surgeries, the recommendation is to start with 100 to 150 mg of intravenous hydrocortisone at the induction of surgery.

  
  
• 2
  

  For intermediate-risk surgeries, the recommendation is to start with 50 to 75 mg of intravenous hydrocortisone at the induction of surgery.

  
  
• 3
  

  There is no general consensus for low-risk surgeries. Recommendations include no additional stress dosing of steroids, doubling the home dose, or giving 25 mg of intravenous hydrocortisone.

Similar to the wide spectrum of recommendations for low-risk surgeries, recommendations for how to taper the patient are also diverse. The general consensus is to taper extra steroids over the next 2 days, but it is up to the individual practitioner how this is done. Stress dose of hydrocortisone in patients is in addition to their home regimens.

Antihypertensive Medications

Perioperative hypotension is always a concern, especially because anesthetic agents often decrease blood pressure. Renal hypoperfusion and electrolyte abnormalities are additional considerations in recommending changes to a patient’s perioperative medication regimen. There is no clear evidence on perioperative side effects of antihypertensive medications. Generally, diuretics are held the morning of surgery to help prevent electrolyte abnormalities. Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are also held the morning of surgery to prevent renal hypoperfusion and postoperative renal insufficiency. Beta blockers should be continued but may need to be switched to intravenous forms if the patient is unable to take oral medications preoperatively. The other antihypertensive medication classes are typically continued through surgery with close monitoring of blood pressure perioperatively.

Anticoagulation Medications

Warfarin (Coumadin) is the anticoagulant most commonly encountered during the perioperative time period. In a trauma patient, time does not allow for the slow discontinuation of the effects of warfarin. In all patients, the risk of bleeding and the type of surgery need to be weighed against the patient’s own risk factors. Joint and soft tissue injections do not require any alteration of a patient’s routine anticoagulation. However, patients undergoing surgery need warfarin discontinued with an international normalized ratio (INR) of 1.5 or less as goal.

Reversal of warfarin can be accomplished several ways. If time allows, the medication can be discontinued 5 days before surgery. In elderly patients with trauma who require surgery, waiting 5 days for the INR to become less than 1.5 is generally not a management option. Vitamin K and fresh frozen plasma are other methods that allow reversal of the anticoagulant effect of warfarin. Fresh frozen plasma works quickly but has a half-life of only approximately 4 to 6 hours, and the effects of warfarin are in effect 12 to 24 hours later. Vitamin K initiation can take hours to work but has long-lasting effects and can affect the ability to anticoagulate the patient again after the surgery. The recommended dose is 1 to 2 mg of oral vitamin K or 2.5 to 5 mg of intravenous vitamin K.

Bridging anticoagulation needs to be determined at this stage. Which patients need low-molecular-weight heparin (LMWH) or a heparin drip to reduce their risk of thromboembolism, and which patients can safely stop their anticoagulation until after surgery? Bridging anticoagulation is recommended for patients with the following conditions:

• 1
  

  Acute venous or arterial thromboembolism within the past 3 months

  
  
• 2
  

  Atrial fibrillation with a history of a cerebrovascular event or transient ischemic event (congestive heart failure, hypertension, age, diabetes, stroke [CHADS] score 5 to 6)

  
  
• 3
  

  Prior recurrent venous thromboembolism

  
  
• 4
  

  Mechanical mitral valve

  
  
• 5
  

  Caged-ball type of prosthetic heart valve

  
  
• 6
  

  Recent stroke or transient ischemic attack within 6 months

  
  
• 7
  

  Rheumatic heart disease

  
  
• 8
  

  Severe thrombophilia

Patients with a history of antiphospholipid syndrome, particularly patients who have had thromboembolism; cancer patients; and patients with low cardiac ejection fractions should be individually considered for bridging anticoagulation.

The generally accepted methods to accomplish INR reversal and bridging anticoagulation include the following:

• ▪
  

  Stop warfarin 5 days before the procedure (if time allows).

  
  
• ▪
  

  Initiate LMWH (typically start the next day for simplicity but can wait until 2 to 3 days before the procedure) at full treatment dose. In trauma patients, this step is unnecessary.

  
  
• ▪
  

  Stop LMWH 12 to 18 hours before procedure. The anesthesiologist should be consulted if spinal anesthesia or an epidural is being considered because these anesthetics often require cessation of LMWH 24 hours before surgery.

  
  
• ▪
  

  If bleeding is minimal, restart warfarin 12 to 24 hours after surgery.

  
  
• ▪
  

  Restart LMWH (full dose) 12 to 24 hours after hemostasis is achieved.

  
  
• ▪
  

  Continue LMWH until warfarin is at a therapeutic level (INR 2 to 3).

  
  
• ▪
  

  If using unfractionated heparin, stop 4 to 6 hours before surgery and restart within 12 hours postoperatively, provided that adequate hemostasis is achieved. Continue until warfarin is at a therapeutic level.

The overlap between either LMWH or a heparin drip is continued until the patient has a therapeutic level of warfarin (typically INR 2 to 3).

Other anticoagulants are typically held depending on their half-life. Aspirin and clopidogrel are irreversible platelet inhibitors and need to be held 7 to 10 days before surgery. There are no medications to reverse these platelet effects in a patient with trauma. Patients with recent coronary angioplasty or stent placement need special consideration when holding these medications.

• ▪
  

  Patients with coronary angioplasty require uninterrupted aspirin and clopidogrel for 7 to 14 days.

  
  
• ▪
  

  Patients with bare metal stent placement require uninterrupted aspirin and clopidogrel for 6 to 8 weeks.

  
  
• ▪
  

  Patients with drug-eluting stent placement require 1 year of uninterrupted treatment.

Nonsteroidal anti-inflammatory drugs are typically held 3 to 4 days before surgery. There is no recommendation of routine use of platelet function assays or platelet transfusion in patients taking these medications.

Herbal Supplements

Use of herbal remedies and vitamin supplementation has increased vastly in recent years. Patients often take these additional supplements without the knowledge of their health care providers and often do not mention these supplements when providing a medication history.

Many of these herbal supplements are cytochrome P450 inducers and affect the metabolism of medications. Ginkgo biloba, garlic, and ginseng have been implemented in increased bleeding risk because they are believed to affect platelet aggregation. Echinacea can cause immunosuppression increasing the risk of postoperative infection. Valerian has been shown to have withdrawal symptoms, and ephedra can cause hypertension, tachycardia, and ventricular arrhythmias with halothane. Ideally, these supplements are stopped 7 to 10 days before surgery. In an elderly patient with trauma, it is essential to know about additional supplements to monitor for their potential side effects.

Other Medications

Selective serotonin receptor inhibitors have the potential to increase the risk of bleeding and serotonin syndrome with certain anesthetics. However, they have a long half-life and a withdrawal syndrome if abruptly discontinued. Trauma patients need to be monitored because 1-day cessation makes no difference in the drug levels.

Tamoxifen and other hormone replacement medications can increase the risk of deep venous thrombosis perioperatively. Bisphosphonates have a risk of pill esophagitis if a patient is unable to sit upright and have a full glass of water after medication administration.

Cholesterol-lowering agents in the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) inhibitor family have shown some promise as anti-inflammatory agents. Studies suggest that this class of medications may reduce the risk of postoperative atrial fibrillation and possibly even cardiac events. A patient currently taking this class of medication should continue it throughout the perioperative period.