Preoperative Medical Evaluation

Fabio Orozco

Sergio Pulido

Alvin C. Ong

Introduction

Total hip arthroplasty (THA) has been proven to increase the quality of life and be a valuable method to manage pain in patients with advanced joint degenerative disease (1). This is an elective procedure and should only be performed after full evaluation of the patient’s risk factors and the benefits that the procedure might bring to the patient. This chapter focuses on the preoperative evaluation of the patient who will be undergoing THA. The goal of preoperative assessment is to identify the patient’s known and occult medical conditions, optimize medical care, and intervene with therapy to improve the surgical outcome. An organized approach to assessing the patient must be obtained. First of all, it is important to assess the risk factors that each individual patient might have before ordering unnecessary testing. This indicates that obtaining a good medical history is one of the most valuable tools to evaluate the patient.

Most orthopedic surgeries are considered to have an intermediate cardiac risk. Assessing the functional capacity of the patient is important to determine the risk of cardiac complications during and after surgery. Patients who are unable to walk four blocks or climb two flights of stairs due to chest pain or shortness of breath are thought to have poor exercise tolerance and as a result, they have increase risk of perioperative cardiac ischemia and cardiovascular events of perioperative cardiac ischemia and cardiovascular events. The metabolic equivalent of task (MET) level provides a great guidance to assess function capacity (see Table 26.1). Further cardiac testing is warranted in patients who have METs equal to or less than 4. Examples of leisure activities associated with less than 4 METs are baking, slow ballroom dancing, golfing with a cart, playing a musical instrument, and walking at a speed of approximately 2 to 3 mph. Activities that require more than 4 METs include moderate cycling, climbing hills, ice skating, rollerblading, skiing, singles tennis, and jogging (2).

Table 26.1 Metabolic Equivalent of Task (MET) for Various Activities (3)

Required Exercise Capacity	Activity
1 MET	Lying down
4 METs	Climb two flights of stairs, work in the yard
10 METs	Jogging 6 mph, strenuous sports

Laboratory, ECG, and Chest X-Ray

Laboratory testing is an important tool that the physician has in their arsenal to evaluate the risk a patient has if hip surgery is performed. Nevertheless, instead of making tests routine, it must be selective and individualized to the specific needs and medical history of each patient. It is extremely important to obtain a thorough history—it needs to be one of the main components of the preoperative management to prevent unnecessary laboratory testing in patients without the appropriate risk factors (4,5). This section will focus on the specific tests that are needed to help assess and establish management to lower the risk of undergoing hip surgery. Table 26.2 gives a summary of preoperative testing depending on specific conditions.

Complete blood count is one of the most important laboratory tests for patients undergoing orthopedic surgery. Hip arthroplasty could be associated with significant blood loss and as a result it is important to know the baseline of the patient. Studies have shown that a hematocrit count less than 28% increases the cardiovascular risk (5). To help prevent drastic decrease in hemoglobin and hematocrit postoperatively, patients may choose to undergo preoperative autologous blood donation or participate in a bloodless program with use of erythropoietin and iron. With autologous blood donation, blood is collected from the patient at weekly intervals with the last donation being at least 2 weeks before the surgery to allow for red blood cells to replenish (7).

It is important to assess if the patient is on medications that can lead to leukopenia. This could be seen in patients with a history of rheumatoid arthritis (RA) from the use of methotrexate, infliximab, and nonsteroidal anti-inflammatory agents (8). To prevent a postoperative prosthetic joint infection, surgery should be delayed until any active infections, such as a urinary tract infection, have resolved (9).

To prevent postoperative infections associated with surgery, The National Surgical Prevention Project 2004 guidelines recommend the use of cefazolin 1 g IV in patients less than 80 kg
and 2 g IV in patients more than 80 kg at induction of anesthesia. Two more dosages are given postoperatively (9).

Table 26.2 Preoperative Testing Schedule (6)

Preoperative Condition	HCT	PT	PTT	Na, K	Creat, BUN	Glucose	X-ray	ECG	Urine Pregnancy Test	T/S
Procedure with blood loss	X									X
Procedure without blood loss
40–49 yrs								X^a
50–64 yrs								X
65 yrs and over					X			X
Cardiovascular disease
Hypertension
Mild
Moderate to severe							X	X
Congestive heart failure	X						X	X
Ischemic heart disease	X							X
Vascular disease
Carotid disease								X
Abdominal aorta disease								X
Peripheral vascular disease								X
Pulmonary disease							X	X
Hepatic disease	X	X
Renal disease	X			X	X
Suspected pregnancy									X
Diabetes				X	X	X		X
Use of diuretics				X	X
Use of digoxin				X	X			X
Use of steroids				X		X
Use of tegretol				X
Use of coumadin		X
Use of heparin			X
^a Males. HCT, hematocrit; PT, prothrombin time; PTT, partial thromboplastin time; Na, sodium; K, potassium; Creat, creatinine; BUN, blood urea nitrogen; T/S, type and screen units of red blood cells.

Coagulation studies are not indicated to diagnose a new bleeding problem in patients who are asymptomatic. A history and physical examination can be more useful in assessing a patient with bleeding disorders. It is of little utility to obtain a bleeding time, prothrombin time, and partial thromboplastin time to predict postoperative hemorrhage in a patient without a history of hemostatic disease. It is more important to assess if the patient is taking chronic nonsteroidal anti-inflammatory medications since they inhibit platelet aggregation, potentially prolonging bleeding (10).

The presence of Q waves or significant ST segment elevations/depression in ECGs have been associated with an increased incidence of perioperative myocardial complications. However, Van Klei et al. stated that even though a right or left bundle branch block is associated with perioperative myocardial infarction (MI), there was no additional predictive value for perioperative MI with not a single abnormal ECG (11). The 2007 ACC/AHA guidelines on perioperative cardiovascular evaluation recommends obtaining a resting ECG in patients undergoing orthopedic surgery if they have known cardiovascular disease, peripheral artery disease, or cerebrovascular disease (2).

There is limited usefulness to screen for asymptomatic disease with chemistry studies that assess renal function, hepatic enzyme abnormalities, serum glucose levels, and electrolyte abnormalities. However, renal function can decrease postoperatively in older patients who have chronic diseases such as congestive heart failure (CHF), diabetes mellitus, or hypertension. Therefore, it is important to obtain a baseline blood urea nitrogen (BUN), creatinine, and urine analysis prior to hip replacement surgery in this population. Patients with hepatitis secondary to acute viral disease and alcohol can have adverse effects on morbidity and mortality during surgery. An underlying hepatic disease can be identified with a thorough history and help recognize those patients who should have liver function testing performed prior to surgery (12).

Chest x-rays aid in supporting the history and physical examination in patients who have chronic obstructive lung disease and abnormalities consistent with heart failure. In asymptomatic older patients, a chest x-ray may be abnormal but be inconsistent with the clinical picture. A chest x-ray can be a valuable tool to help guide management in patients who have been diagnosed with the diseases mentioned above. It is important to obtain a chest x-ray if it is only clinically indicated (13).

Risk Classification

The American Society of Anesthesiology (ASA) has adopted Dripps’ stratification system (4) (Table 26.3) to predict perioperative mortality. This system was originally designed to
classify patients for a research protocol, but it was found to have predictive value for clinical outcomes.

Table 26.3 Preoperative Assessment Classification

ASA Status	Examples of Preoperative Patients
Class 1: No disease	Healthy 25-year-old
Class 2: Mild to moderate systemic disease	65-year-old with well-controlled DM type II
Class 3: Severe systemic disease	70-year-old with CHF and rest angina
Class 4: Life-threatening systemic disease	30-year-old with DM type I in ketoacidosis
Class 5: Morbidly ill	70-year-old with angina and mesenteric ischemia
E is added to each class if surgery is an emergency. ASA, American Society of Anesthesiology; DM, diabetes mellitus; CHF, congestive heart failure Reproduced from Dripps RD. New classification of physical status. Anesthesiology. 1963;24:111.

Cardiac Risk

The patient undergoing hip replacement often has limited functional capacity because of age or arthritis, making cardiovascular fitness assessment difficult. In 2009 the American College of Cardiology Foundation (ACCF) and the American Heart Association (AHA) updated current recommendations to stratify cardiac risk for patients who will undergo noncardiac surgery. According to these guidelines, cardiac evaluation and treatment before any noncardiac surgery is warranted in patients who have the following four active cardiac conditions: unstable coronary syndromes, decompensated heart failure, significant arrhythmias, and severe valvular disease. Recent MIs and severe angina are considered to be unstable coronary syndromes. A hypercoagulable state arises in an acute unstable coronary syndrome as well and as a result, surgery needs to be delayed if it is not considered to be an emergence. Patients who have a New York Heart Association functional class IV heart disease or have a worsening or new-onset of heart failure are categorized as having decompensated heart failure. The following are considered to be significant arrhythmias that warrant further evaluation and treatment: Mobitz II atrioventricular block, third-degree atrioventricular block, symptomatic ventricular arrhythmias, supraventricular arrhythmias with uncontrolled ventricular rate, and novel ventricular tachycardia (2).

Noninvasive pharmacologic stress test can be used to evaluate patients who qualify for further cardiac evaluation. Dipyridamole, adenosine thallium, or dobutamine echocardiography has been helpful in assessing patients undergoing vascular or noncardiac surgery. Dipyridamole increases intracoronary adenosine, leading to vasodilatation of the coronary circulation. This creates an intracoronary steal in areas of fixed coronary obstruction, leading to a relative decrease in perfusion that can be detected with thallium, and more recently on echocardiography, as segmental wall motion abnormalities. These techniques have limitations, particularly in determining who to screen and then what to do with the information obtained. All of the modalities available have good sensitivity and specificity for detection of coronary disease, but they do not give an ischemic threshold (2,14).

Table 26.4 Clinical Risk Factors as Described by the 2009 ACCF/AHA (15)

Clinical Risk Factors
History of ischemic heart disease
History of compensated or prior HF
History of cerebrovascular disease
Diabetes mellitus
Renal insufficiency

Orthopedic surgery is considered to be an intermediate-risk surgery with a cardiac predicted risk of 1% to 5% (3). Patients without any active cardiac conditions must have a functional capacity of 4 METs or greater in order for surgery to proceed (15). Table 26.3 shows the estimated functional capacity for various activities.

Patients who are in need of hip surgery and have unknown functional capacity or a MET score less than 4 must be further evaluated. Noninvasive testing that may change management is recommended in patients who have more than one clinical risk factor (Table 26.4) (15).

Recent Myocardial Infarction

Recent MI and unstable or severe angina have been found to be associated with severe perioperative risk (15). In the past, it was customary to wait until 6 months after an MI before proceeding with elective orthopedic surgery. This practice was based on the work of Tahran et al. in the early 1970s and was validated by Goldman et al. in 1977 and then by Steen et al. (16,17). Tahran et al. studied 38,877 patients who had undergone anesthesia and found 422 with prior infarction. Of these 422, 37% had another infarction if they had surgery within 3 months of the prior infarction, 16% if the surgery was within 3 to 6 months, and 5% if the surgery was after 6 months. Tahran et al. obtained statistically similar results 6 years later (16). Rao et al. used invasive hemodynamic monitoring in patients with a recent MI and demonstrated a 5.7% risk of MI when surgery followed the MI by 3 months or less and a 2.3% risk when the surgery was within 3 to 6 months of the MI (18).

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