Conscious Sedation

Conscious sedation is an older term from 1985 to describe lightly sedated dental patients.¹ It is defined as the sedation depth that permits appropriate response to physical stimulation or verbal command (e.g., “open your eyes”). Many groups, including the American Association of Anesthesiology and American College of Emergency Physicians believe that the term conscious sedation is imprecise and they propose terms such as sedation/analgesia² or procedural sedation and analgesia (PSAA),¹ or monitored anesthesia care (MAC).³ Indeed, in the first ASA guidelines from February 1996, a notable comment is that patients whose only response is reflex withdrawal from a painful stimulus are sedated to a greater degree than encompassed by sedation/analgesia.

A continuum of depth of sedation was described in the second ASA guidelines for sedation/analgesia.⁴ From Table 4-1, concepts ranging from minimal sedation (anxiolysis) through moderate sedation/analgesia (conscious sedation) to general anesthesia are described related to responsiveness and airway management. Of note, moderate sedation/analgesia is described as purposeful response to verbal or tactile stimulation and that no airway intervention is required. A more detailed sedation continuum (Table 4-1) is proposed in a Canadian Emergency Department consensus guideline.⁵ However, the transition between moderate sedation and deep sedation where airway management is required can be different with each patient.

The best approach is to establish a sedation/analgesia plan prior to starting the procedure. Optimal goals include the following⁶:

In addition, the complexity and duration of the procedure involved changes the sedation/analgesia plan. Simple and short procedures may require little or no sedation with only local or topical analgesia, such as trigger point injections or piriformis muscle injections. Many procedures requiring fluoroscopic guidance can be assisted with moderate sedation including midazolam and fentanyl. Although some interventional pain experts routinely perform medial branch blocks under local analgesia only, multiple-level procedures versus single-level procedures may require more than midazolam 2 mg and fentanyl 100 mcg IV, particularly at a training institution. Cancer neurolytic blocks that can be intensely stimulating often require deeper sedation. Prolonged sedation may be required for spinal cord stimulation trials or intrathecal catheter implants due to the duration of the procedure (see Table 4-1). Physician preparation and experience can decrease the duration of the procedure, thereby decreasing the need for sedation and analgesia.

Patient Preparation

One of the main ways of decreasing sedation and analgesia requirements is to prepare patients for what happens during the procedure and hence reducing their anxiety of the unknown. It is easiest for those patients who are returning for a series of the same procedure. Short procedural materials or websites describing the procedure can help patients with questions in the office or preoperative area. Although the literature is insufficient in supporting preprocedural preparation, the ASA consultants agree that “appropriate preprocedure counseling of patients regarding risks, benefits, and alternatives to sedation and analgesia increases patient satisfaction.”⁴

Table 4-2 ASA Classification

ASA, American Society of Anesthesiologists.

From Cohen MM, Duncan PG, Tate RB: Does anesthesia contribute to operative mortality? JAMA 1988;260:2859-2863.

ASA preoperative classification can help stratify a patient’s risk for a medical event during procedural sedation/analgesia. At one author’s institution, only ASA 1 and 2 (healthy, low health risk) patients are offered procedures at the outpatient surgery center. ASA 3 and higher patients have their procedures at the main hospital with a higher medical acuity support staff.

Because interventional pain procedures are almost always elective, particularly for chronic pain patients, ASA fasting guidelines should be observed as per Table 4-3. Of note, patients can have a small amount of clear liquids up to 2 hours prior to procedure. Otherwise, many surgery centers will allow the procedure to be performed only under local or topical analgesia.⁴

Table 4-3 Summary of ASA Preprocedure Fasting Guidelines^∗

ASA, American Society of Anesthesiologists.

(A light meal typically consists of toast and clear liquids. Meals that include fried or fatty foods or meat may prolong gastric emptying time. Both the amount and type of foods ingested must be considered when determining an appropriate fasting period.)

∗ These recommendations apply to healthy patients who are undergoing elective procedures. They are not intended for women in labor. Following the Guidelines does not guarantee a complete gastric emptying has occurred.

† The fasting periods apply to all ages.

‡ Examples of clear liquids include water, fruit juices without pulp, carbonated beverages, clear tea, and black coffee.

§ Since nonhuman milk is similar to solids in gastric emptying time, the amount ingested must be considered when determining an appropriate fasting period.

From American Society of Anesthesiologists Task Force on Sedation and Analgesia by Non-Anesthesiologists. Practice guidelines for sedation and analgesia by non-anesthesiologists. Anesthesiology 2002;96:1004-1017.

Medical morbid conditions, particularly cardiopulmonary disease, can be problematic for a nonanesthesiologist providing sedation. A history of sleep apnea and difficult airway physical habitus as specified by Table 4-4 may suggest less sedation or having a monitoring anesthesiologist for the procedure would be appropriate.

Table 4-4 Airway Assessment for Sedation and Analgesia

From American Society of Anesthesiologists Task Force on Sedation and Analgesia by Non-Anesthesiologists. Practice guidelines for sedation and analgesia by non-anesthesiologists. Anesthesiology 2002;96:1004-1017.

Allergies

The main allergies that most interventional pain management specialists encounter are allergies to latex, iodine/contrast, or to local anesthetics.

Latex and iodine allergies can be easily prevented with advanced notice. Most interventional pain procedures can document correct placement fluoroscopically without contrast patterns and by anatomical landmarks. Surface preparation solutions, such as chlorhexidine can be used instead. Indeed, the authors routinely use chlorhexidine because some literature suggests that it may be the best antiseptic for regional and interventional pain procedures.⁸

Most local anesthetic allergies are caused by amide local anesthetic compounds, such as lidocaine or bupivacaine. Some patients also describe an allergy from a combination of these agents mixed with epinephrine. Often the epinephrine in a prior event was absorbed intravascularly causing an increase in heart rate. An alternative to using amide local anesthetics are esters: chloroprocaine or procaine. The main question to ask is whether the patient had a “true” allergic reaction with skin rash, throat tightness, difficulty breathing or swallowing. If the patient has a rash caused by benzocaine, a common ester local anesthetic in suntan lotions, the patient may be allergic to esters. Typically, patients are allergic to one chemical structure of local anesthetic: amides or esters; so the other class may be dosed during procedures. Dosing recommendations will follow later in this chapter.

Monitoring and Room Set-Up

In general, a procedure room must be able to accommodate pulse oximetry, blood pressure, oxygen, intravenous access, and other monitors, a space for a designated health care provider to record the patient’s vital signs and provide medications, and enough room to place the patient on a gurney for transport.

According to Medicare guidelines: