Primer on sedation, analgesia and local anesthetic for the IR: Part 1

by Christina Boyd, MD, Daniel Scheinberg, MD, Michael Prasad, MD, Jonathan Markley, DO, Thaddeus Yablonsky, MD, Sean Calhoun, DO

July 15, 2019

12:00 AM

Introduction

As interventional radiology becomes more clinically based, knowledge of pain management strategies becomes increasingly important. Pain management and sedation decisions for IRs begin at the initial patient consultation and continue through postprocedural recovery. The decision to consult anesthesia, sedate the patient unassisted or only provide local anesthetic is an important decision and all options should be considered. This article will review an IR’s role in analgesia, anxiolysis, sedation and consultation with an anesthesiologist, with knowledge of the guidelines set by the American Society of Anesthesiologists (ASA).

Sedation

Sedation is a medically induced decrease in central nervous system activity, resulting in decreased awareness. Sedation alone adds additional risk of morbidity and mortality to each procedure. The ASA produces guidelines for nonanesthesiologists who provide sedation or analgesia to minimize these risks.¹

In October 2014, the ASA released an updated description of sedation, detailing a continuum of depth from minimal sedation to general anesthesia.¹

The levels of sedation are:

Minimal sedation (anxiolysis): A state where patients can respond normally to verbal commands.
Moderate sedation/analgesia (“conscious sedation”): A state where patients can respond purposefully to verbal or light tactile commands. However, a reflex withdrawal from a painful stimulus in not considered a purposeful response. These patients are able to protect their own airway.
Deep sedation/analgesia: A state where patients cannot be easily aroused but can respond purposely to repeated or painful stimuli. Patients may need assistance with maintaining a patent airway; however, cardiovascular function is maintained.
General anesthesia: A state where patients are not aroused by painful stimuli. Patients will often need assistance maintaining a patent airway and positive pressure ventilation may be required. The patient’s cardiovascular function may be impaired. It is important to note that, if there is the potential for airway compromise (moderate and deep sedation), the Joint Commission requires a preoperative evaluation and continuous monitoring while receiving medications and in recovery.^1,2

Given that sedation depth is variable on the continuum, and that a patient’s response to medication is unpredictable, it is vital for the administering physician to be prepared to “rescue” a patient from a deeper-than-intended level of sedation.

Table 1. ASA classifications, I to VI

ASA I	Normal healthy patient	Patients with no systemic disease.
ASA II	Mild systemic disease without functional limitations.	Examples include current smoker, social alcohol drinker, pregnant, obese (BMI 30–40), well-controlled diabetes (DM), well-controlled hypertension (HTN) or mild lung disease.
ASA III	Severe systemic disease with functional limitations	Moderate or severe diseases including poorly controlled DM, HTN, chronic obstructive pulmonary disease, morbid obesity (BMI over 40), alcoholism, end-stage renal disease (ESRD) on regular dialysis, greater than 3 months prior had a myocardial infarction (MI), cerebral vascular accident (CVA), coronary artery disease (CAD) with stents.
ASA IV	Severe systemic disease that is a constant threat to life	Within the last 3 months the patient has had an MI, CVA or TIA, or CAD with recent stents. Severe cardiac dysfunction, sepsis, disseminated intravascular coagulopathy, acute renal failure or ESRD not on regular dialysis.
ASA V	Moribund patient who is not expected to survive without the procedure	Massive trauma, ruptured aneurysm, ischemic bowel with organ dysfunction.
ASA VI	Brain-dead patient for organ procurement

ASA classifications, I to VI

Pre-procedural patient selection

The ASA has set standard requirements that must be met prior to sedation or anesthesia. These requirements include a history and physical (H&P) performed or reviewed within the last 30 days with an interval update to the H&P within 24 hours of sedation. The H&P must include prior anesthesia or sedation experience, including any family history of issues with anesthesia. It must also include a history of severe gastroesophageal reflux or airway problems (such as sleep apnea). A nurse practitioner or physician assistant, under the administering physician, can perform the focused history and physical.^1,3

The initial evaluation should indicate the patient’s ASA physical status classification. The ASA classification is a subjective assessment of the patient’s overall health associated with the relative morbidity and mortality of anesthesia.¹ (See Table 1.) Cancer is by definition a systemic disease and patients are at a significantly increased risk for venous thromboembolism. It has been argued that systemic cancer alone makes them a higher ASA level; however, this is still debated.^1,4

The physician should also perform an airway evaluation during the pre-procedural physical. Assessment should include the Mallampati classification, which predicts airway obstruction and potential difficult intubation.¹ (See Fig. 1.)

The patient’s pre-procedure assessment should include the last time they ate or drank anything. The ASA has updated their preoperative fasting recommendations in March 2017 to decrease the risk of pulmonary aspiration during anesthesia. It is no longer recommended by the ASA to have “nothing by mouth after midnight” and clear liquids should be encouraged up until 2 hours prior to the patient’s procedure. The addition of clear liquids up to 2 hours preoperatively has been shown to decrease the risk of aspiration due to a decreased gastric volume and has resulted in a higher gastric pH (less harmful if aspirated).^1,3 (See Table 2.) However, the ASA guidelines refer to normal healthy patients and may not apply to those with risk factors for delayed gastric emptying. There are contemporary studies investigating the benefits of carbohydrate-rich clear liquids (such as Gatorade) given up to 2 hours preoperatively, which have shown early promising results including favorable patient satisfaction, decreased perioperative cortisol and decreased postoperative insulin resistance.⁵

Table 2. Updated ASA preoperative fasting recommendations for adults and children

Clear liquids	2 hours
Breast milk	4 hours
Light meal	6 hours
Full meal	8 hours

Updated ASA preoperative fasting

The pre-procedural evaluation should conclude with informed consent from the patient and a set of pre-sedation vital signs.1 Once this is complete, the information can be used to decide the sedation and anesthesia plan for the patient. Anesthesiology should be consulted if the patient has an ASA class of IV or V and a consult should be considered if the ASA class is III. Anesthesia should also be consulted for a Mallampati class of III or IV or if the patient has a significant oxygenation, airway or ventilation abnormality noted on history and physical including obstructive sleep apnea.^1,6 Interestingly, the single most sensitive and specific sign of difficult ventilation (and intubation) is a large neck circumference (17 inches in a male or 16 inches in a female), which is not routinely part of an IR pre-sedation evaluation.⁷

Summary points

Pre-sedation history and physical (H&P) needs to include an airway assessment (ASA classification, Mallampati score and large neck).
Anesthesiology should be consulted if a patient has an ASA class of IV or V (consider a consult for ASA III), Mallampati score of III or IV or significant oxygenation, ventilation or airway abnormality.
New ASA guidelines recommend clear liquids up to 2 hours prior to sedation to decrease morbidity and mortality associated with aspiration.

Part 2 of this article, which describes intra- and postprocedural management of sedation, analgesia and local anesthetic, appears in the fall 2019 issue of IR Quarterly.

References

Standards and Guidelines. American Society of Anesthesiologists. Retrieved from asahq.org/standards-and-guidelines.
The Joint Commission. Comprehensive accreditation manual for hospitals: The official handbook. Oakbrook Terrace, Ill.: The Joint Commission, 2018.
American College of Radiology and Society of Interventional Radiology. ACR-SIR practice guideline for sedation/analgesia. American College of Radiology website. acr.org/-/media/ACR/Files/Practice-Parameters/Sed-Analgesia.pdf. Revised 2015. Accessed Aug. 25, 2018.
Araujo, BL, Theobald, D. (2017). Letter to the Editor: ASA Physical Status Classification in Surgical Oncology and the Importance of Improving Inter-Rater Reliability. Journal of Korean Medical Science, 32(7), 1211. doi:10.336/jkms.2017.32.7.1211.
Nygren, J. et al. (1998). Preoperative oral carbohydrate administration reduces postoperative insulin resistance. Clinical Nutrition, 17(2), 65-71. doi:10.1016/s0261-5614(98)80307-5 Gross J, Bailey P, ConnisR et al. Practice Guidelines for Sedation and Analgesia by Non-Anesthesiologists. Journal of the American Society of Anesthesiologists. 2002, Vol.96, 1004–1017.
Riad W et al. Neck circumference as a predictor of difficult intubation and difficult mask ventilation in morbidly obese patients: A prospective observational study. European Journal of Anesthesiology 2016.
Jonathan O, Richard B, and Shashin D. Moderate Sedation: What radiologists need to know. American Journal of Roentgenology 2013; 201: 941–946.