Conscious sedation and analgesia are often overlooked aspects of interventional pain procedures. Patients expect to be comfortable during their injections. Physicians tend to concentrate more on the procedure with the sedation becoming secondary. However, when the procedure is not going smoothly, oversedation and analgesia can add problems, such as interpreting paresthesias, intraneural injections, and even loss of airway reflexes—particularly problematic at outpatient surgery centers where airway specialists may not be available.
The authors of this chapter are board-certified anesthesiologists and pain medicine specialists. It may be interesting to note that the optimal sedation and analgesia seems to be the least amount possible! One of the caveats of anesthesia training is that sedation and analgesia can always be titrated to effect for the individual patient. Although anesthesiologists can induce the full spectrum of sedation including general anesthesia, most elective pain procedures require far less.
The following chapter is for safety guidelines and recommendations and not a “cookbook” on set dosages for sedation and analgesia. Appropriate preparation of the patient, procedural facility, medical support teams, and physicians with procedural techniques can make the scheduled interventions safe and relatively “pain-free” for everyone involved.
Conscious Sedation
Conscious sedation is an older term from 1985 to describe lightly sedated dental patients. 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/analgesia or procedural sedation and analgesia (PSAA), or monitored anesthesia care (MAC). 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. 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. However, the transition between moderate sedation and deep sedation where airway management is required can be different with each patient.
| Area | Minimal Sedation | Moderate Sedation | Deeper Sedation | General Anesthesia |
|---|---|---|---|---|
| Cervical | Occipital block, stellate block | Cervical medial branch blocks, cervical epidural | Cervical discogram | |
| Thoracic | Intercostal block | Thoracic facet and transforaminal epidurals | Thoracic sympathectomy, thoracic discogram | Spinal cord stimulator implant (after location is verified) |
| Lumbar | Lumbar psoas block | Lumbar sympathetic, median branch, transforaminal epidurals | Celiac plexus block, lumbar discograms | Intraspinal pump placement (after catheter placement) |
| Sacral | Piriformis block, sacroiliac joint injection | Sacral nerve root blocks, impar ganglion block | Superior hypogastric plexus block, epiduroscopy |
The best approach is to establish a sedation/analgesia plan prior to starting the procedure. Optimal goals include the following :
- 1.
To provide adequate analgesia, sedation, anxiolysis, and amnesia during the performance of painful diagnostic or therapeutic procedures
- 2.
To control unwanted motor behavior that inhibits the performance of diagnostic procedures or image-guided interventions
- 3.
To rapidly return the patient to a state of consciousness
- 4.
To minimize the risks of adverse events related to the provision of sedation and analgesia
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.”
| Class | Systemic Disturbance | Mortality |
|---|---|---|
| 1 | Healthy patient with no disease outside of the surgical process | <0.03% |
| 2 | Mild-to-moderate systemic disease caused by the surgical condition or by other pathologic processes | 0.2% |
| 3 | Severe disease process that limits activity but is not incapacitating | 1.2% |
| 4 | Severe incapacitating disease process that is a constant threat to life | 8% |
| 5 | Moribund patient not expected to survive 24 hours with or without an operation | 34% |
| E | Suffix to indicate an emergency surgery for any class | Increased |
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.
∗ 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.
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.
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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.
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:
- •
Moderate Sedation should be provided by a qualified physician. Physician must be continuously present to monitor the patient and personally provide care.
- •
During Moderate Sedation, the patient’s oxygenation, ventilation, circulation, and temperature should be evaluated by whatever method is deemed most suitable by the attending physician.
- •
The following Centers for Medicare & Medicaid Services (CMS) requirements for Moderate Sedation should be the same as for MAC and general anesthesia with regard to the performance of presedation examination and evaluation, prescription of the sedation, care required for the completion of a record, the administration of necessary oral or parenteral medications, and the provision of indicated postoperative care. Appropriate documentation must be available to reflect pre- and postsedation evaluations and intraoperative monitoring.
- •
The Moderate Sedation service rendered must be appropriate and medically reasonable and necessary.
The provider who monitors the patient should have training and understanding of the agents that are administered and they should be readily available. Emergency equipment should be available as listed on example III from ASA guidelines. Most outpatient surgery centers require on-site staff with ACLS certification and/or physicians trained in anesthesiology or emergency medicine who can manage airway emergencies ( Table 4-5 ).
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