CHAPTER 2 Patient evaluation and care

In 1967, Dr. Alexander Margulis proposed a new subspecialty within the family of imaging sciences which he called “interventional radiology.”¹ For some time thereafter, interventional radiologists (IRs) were consultants who performed minimally invasive angiographic procedures (at the request of clinicians) with little or no responsibility for patient care before or after. This practice model has been transformed over the past 40 years. Interventionalists (including the many subspecialists from other fields who also do this work) now assume full clinical responsibility for their patients—they are true “clinicians.” As such, IRs are obligated to conduct the initial patient assessment, determine the best course of therapy, and provide long-term care and management after the procedure is completed. Experienced interventionalists will agree that a successful and safe technical outcome depends as much on preprocedure and postprocedure care as it does on performing the case itself. The concepts set down in this chapter form the cornerstone of modern interventional radiology practice. The details and nuances may vary among institutions, but the principles are universal.

Preprocedure care

Patient referral and contact

For simple diagnostic and interventional procedures (e.g., vascular access placement), patient referral without direct contact between physicians is appropriate. For more complex or controversial clinical problems, a discussion between the interventionalist and the referring physician ensures that the appropriate procedure is done, the potential risks for the individual patient are appreciated by everyone involved, and the likely outcome is understood.

The interventionalist should review the medical history and all pertinent diagnostic tests and imaging studies before seeing the patient. With this approach, one can avoid raising the specter of an intervention that is ultimately not indicated. The initial conversation between patient and physician is vitally important and should occur as far away (in time and space) from the interventional suite as possible. The goals of the interview and examination are to establish rapport, review the history firsthand, explain the procedure in detail (and thus obtain informed consent), and reduce anxiety. Family and significant others are encouraged to participate in the discussion. Ideally, inpatients are assessed the day before the case is scheduled. Outpatients are evaluated in a clinic or office dedicated to this work, where support staff (trainees, nurses, physician extenders, and administrative assistants) are fully engaged in IR.²

History and physical examination

The clinical evaluation includes several components (Box 2-1). The physician must be confident that there are appropriate indications for the proposed intervention based on “best practice” criteria established in the medical literature or endorsement by the Society of Interventional Radiology (SIR) and the Cardiovascular and Interventional Radiology Society of Europe (CIRSE).³ Risk factors that may require a delay or modification of the proposed procedure or an alternative therapy are sought (Boxes 2-2 and 2-3). A focused physical examination is performed, but it is prudent to assess the airway, lungs, heart, and abdomen in almost all patients. For angiographic procedures, the interventionalist should evaluate and document the following parameters:

• Proposed puncture site (contraindications include, for example, groin infection, common femoral artery aneurysm, overlying hernia, fresh incision, recent injury)

• All extremity pulses, using a Doppler ultrasound probe when necessary

• Status of extremities (e.g., color, perfusion, presence of swelling, ulceration)

Box 2-2 PRIMARY RISK FACTORS FOR IODINATED CONTRAST MATERIAL REACTIONS

• Previous allergic reaction to iodinated contrast

• Other drug allergy

• Asthma

• Reaction to skin allergens

Thrombophilic (hypercoagulable) states are an important risk factor for vascular thrombosis and can be associated with significant complications from diagnostic and therapeutic vascular procedures.⁴^–⁶ The major hereditary and acquired disorders are listed in Chapter 1 (see Boxes 1-4and 1-5). These conditions should be suspected when thrombosis occurs in young patients, at atypical sites, in the absence of underlying vascular disease, with familial tendency, or with apparent resistance to anticoagulants.

Sedation and analgesia requirements

Most procedures on adults are performed with moderate sedation under the supervision of the operating physician. It is wise (and often hospital policy) to have an anesthesiologist or nurse anesthetist handle sedation and analgesia for sicker patients (e.g., American Society of Anesthesiology physical status classification system categories 3 or above ⁷ [Box 2-4]). In certain circumstances, regional, monitored, or general anesthesia is preferable (Box 2-5).

Informed consent

It is the obligation of the physician or physician extender performing any medical procedure to explain the proposed intervention to the patient, to the parent of a minor patient, or to the legal representative or the closest relative if the patient is not competent to give consent.⁸^,⁹ If the patient is not fluent in the native language of the health care team, a trained medical translator (not a relative or friend) should assist with consent. If telephone consent from a family member or legal representative is necessary, a witness must document the conversation. In the United States, the “implied consent” doctrine is considered to be in force with any medical procedure in which a delay could lead to severe disability, severe pain, or death. In this rare situation, consent is unnecessary if the patient cannot give his or her own approval and no legal representative is immediately available.⁹

To give informed consent, the patient must understand the need for undergoing the procedure, potential risks and expected immediate and long-term outcomes, the consequences of refusing the intervention, and the nature of alternative studies or therapies. To avoid “exceeding” consent, the discussion should include conceivable interventions (e.g., thrombolysis, angioplasty, or stent placement in a patient undergoing angiography for evaluation of peripheral vascular disease).

Informed consent is both a legal and medical concept. In the United States, some states have adopted a “prudent patient” standard that is based on the information an average patient needs to make a decision regarding medical care. Other states use a standard based on the information that a “prudent physician” in the community would have discussed for such a procedure. The interventionalist should explain the various elements of the intervention that could result in an untoward event:

• Access, including the possibility of local infection, bleeding, or hematoma formation (and pseudoaneurysm, arteriovenous fistula, thrombosis or dissection with arteriography)

• Needle, catheter, or guidewire manipulation en route to and at the intended site of angiography or intervention (e.g., risk of bleeding, organ injury, dissection, vessel perforation or thrombosis, nerve damage, arrhythmias, stroke)

• Administration of

• Contrast agents, including allergic reactions and nephrotoxicity

• Sedatives and analgesics (e.g., respiratory depression, hypotension)

• Other medications that may be required during or after the procedure (e.g., allergic reaction, bleeding from anticoagulants)

• Radiation injury from prolonged fluoroscopic procedures

The particular risks for specific diagnostic and interventional procedures are discussed in later chapters. As a rough guide, the overall incidence of major complications (Box 2-6) should be no more than 1% to 2% for the more common interventions (e.g., vascular access placement, inferior vena cava filter placement, percutaneous biopsy and drainage procedures, dialysis access interventions).¹⁰^–¹² However, older patients and those with established risk factors are more likely to suffer a bad outcome such as bleeding, infection, thrombosis, renal dysfunction, or allergic reactions to administered drugs.¹³

In addition to having the patient (or legal representative) sign a consent form, a preprocedure note stating that informed consent was obtained must be placed in the medical record before starting the case. Some practitioners list both common and serious (but rare) risks, but others prefer to be less specific. The thrust of the conversation and patient queries should be documented. The preprocedure note also includes a brief medical history, the specific indications for the procedure, directed physical examination, and results of relevant imaging and laboratory tests.

Laboratory testing

The purpose of preprocedure laboratory testing is to minimize risk by detecting (and when feasible correcting) relevant abnormalities, altering the technique as needed, or canceling the case and choosing a safer treatment. Preprocedure studies may be routine (screening) or selective (directed).¹⁴ Indiscriminate testing has proved to be of little value in virtually every medical and surgical study ever published.¹⁵^–¹⁷ However, selective testing is warranted before vascular and interventional procedures. Screening is generally unnecessary in otherwise healthy patients younger than 40 years of age. Testing is certainly advisable in older adults and those with predisposing risk factors. The acceptable interval between test result and procedure varies among hospitals and clinical situations and cannot be generalized.

Renal function

Serum creatinine is still widely used as a proxy for kidney function, but it is an imprecise measure of such. Estimated glomerular filtration rate (eGFR) is a more accurate indicator of renal insufficiency. Contrast-induced nephropathy (CIN) is marked by a significant rise in serum creatinine level (0.5 mg/dL or 25% of baseline) 1 to 3 days after intravascular administration and by resolution at 7 to 10 days. This (usually) transient dysfunction is related to direct toxic effects on the kidney by oxygen free radicals or ischemia of the renal medulla.¹⁸ In the general population and in patients with eGFR greater than 60 mL/min (stage 1 or 2 chronic kidney disease), the overall risk of CIN after diagnostic angiography is low (<2%). The risk increases to about 5% in patients with preexisting mild renal dysfunction and 33% or greater in patients with diabetes and severe renal insufficiency (eGFR <30 mL/min, stage 4 or 5 chronic kidney disease).¹⁹ Only a small fraction of patients who suffer this complication require long-term hemodialysis. However, some experts believe concerns about CIN are exaggerated and that use of iodinated contrast should not be avoided in patients with moderate renal dysfunction.¹⁹

The traditional approach to preventing CIN is hydration with intravenous (IV) saline (1 to 1.5 mL/kg/hr) for 6 to 12 hours before and at least several hours after intravascular contrast administration. In addition, several other measures should be considered when the risk is increased:

• The total volume of contrast agent is strictly limited. Contrast material is diluted as much as possible without compromising diagnostic quality.

• The lowest osmolality agent is used.

• Carbon dioxide may replace or supplement standard iodinated contrast in some situations (see Chapter 3).

Several pharmacologic regimens may reduce the likelihood of CIN (see discussion below).

Until recently, gadolinium-based contrast agents were favored as a safe alternative to iodinated materials during intravascular interventions in patients with baseline renal insufficiency. Some of these agents pose a risk (albeit very small) for causing nephrogenic systemic fibrosis in individuals with preexisting severe chronic or acute renal insufficiency (eGFR <30 mL/min.). This rare disorder is characterized by widespread and often debilitating dermal (and sometimes visceral organ) sclerosis.²⁰^,²¹ As such, gadolinium-based agents are no longer used during vascular procedures unless renal function is essentially normal.

Coagulation parameters

Significant bleeding from interventional procedures is uncommon. It is an axiom in interventional radiology (IR) that the individual risk is largely a function of the coagulation status of the patient (Box 2-7), the likelihood of traversing a major artery or vein, and the ability to detect and then manually control bleeding when it occurs. In fact, there are equivocal data regarding the value of coagulation screening tests in predicting the likelihood of bleeding from invasive procedures.²²^,²³ Nonetheless, routine screening for coagulopathy is the practice in many institutions based on tradition and sometimes stated policy. A more judicious approach is favored by some practitioners:

• For diagnostic and most therapeutic vascular procedures, individuals with known or suspected risk factors for bleeding should be tested (see Box 2-7).

• With thrombolytic therapy or endovascular interventions that may require parenteral antithrombin or antiplatelet agents, the substantial risk of local or remote bleeding supports routine testing.

• Many nonvascular interventional procedures (e.g., deep large-core biopsy or fluid drainage, nephrostomy, biliary drainage) can result in hemorrhage that is only apparent after substantial blood loss and is often difficult to control; thus, testing is done routinely. Other procedures (e.g., small-gauge superficial biopsy) do not require screening tests.

Commonly performed coagulation tests are outlined in Box 2-8. Thresholds for defining a coagulopathy and measures for correcting them²²^–²⁵ are outlined in Tables 2-1 and 2-2. Based on limited but promising experience using more relaxed parameters for tunneled central venous catheter placement, some practitioners insert such devices when the INR is less than 2.0 or the platelet count is greater than 25,000/dL.²⁶

Table 2-1 Safety Thresholds for Coagulation Parameters

Parameter	Threshold
International normalized ratio (INR)	1.6-1.8
Prothrombin time (PT)	<3 sec from control
Partial thromboplastin time (PTT)	<6 sec from control
Platelet count (normal INR/PTT)	>50,000/mm³
Platelet count (abnormal INR/PTT)	>50-100,000/mm³
Bleeding time	<8 min

Table 2-2 Correction of Coagulation Abnormalities

Parameter	Response
International normalized ratio	Withhold warfarin, bridge with heparin or low molecular weight heparin (see Box 2-9)
	Fresh-frozen plasma (FFP), 2-4 bags or 10-15 mL/kg
	Vitamin K, 1-3 mg IV; may be repeated after 6-8 hr
Partial thromboplastin time	Withhold heparin 2-6 hr before procedure
Partial thromboplastin time	FFP, 2-4 bags or 10-15 mL/kg
Platelet count	Platelet transfusion (10 units to increase count by 50,000-100,000/mm³)
Bleeding time	Cryoprecipitate (0.2 bag/kg)
	Desmopressin (DDAVP), 0.4 μg/kg over 30 min
	Platelet transfusion
Fibrinogen	FFP, 10-15 mL/kg