Sedation for Percutaneous Procedures

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CHAPTER 22 Sedation for Percutaneous Procedures

Mohammad Uddin, Salahadin Abdi

INTRODUCTION

‘Sedation and analgesia’ describe a state in which patients can tolerate unpleasant procedures while maintaining cardiac and respiratory function and still maintain the ability to respond purposefully to both verbal commands and tactile stimulation. The Task Force on sedation and analgesia decided that the term ‘sedation and analgesia’ (sedation/analgesia) more accurately defines this therapeutic goal than does the commonly used but imprecise term ‘conscious sedation.’ This level of sedation does not include a level in which the only intact reflex is withdrawal from a painful stimulus.1 Although sedation has been described as ‘light sleep’2 and textbooks note that ‘the terms sleep, hypnosis, and unconsciousness are used interchangeably in anesthesia literature to refer to the state of drug-induced sleep,’3 pharmacological sedation is not the same as physiological sleep.

During interventional procedures the goal is to provide enough sedation to keep the patient comfortable, relaxed, and communicative. Even though this preferred light sedation is relatively safe, rescue medications and equipment to support respiration and circulation should be readily available.

LEVELS OF SEDATION

See Table 22.1.

Table 22.1 Definition of General Anesthesia and Levels of Sedation/Analgesia1

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Minimal sedation (anxiolysis) is a drug-induced state during which patients respond normally to verbal commands. Although cognitive function and coordination may be impaired, ventilatory and cardiovascular functions are unaffected.

Moderate sedation/analgesia (i.e. ‘conscious sedation’) is a drug-induced depression of consciousness during which patients respond purposefully* to verbal commands, either alone or accompanied by light tactile stimulation. No interventions are required to maintain a patent airway, and spontaneous ventilation is adequate. Cardiovascular function is usually maintained.

Deep sedation/analgesia is a drug-induced depression of consciousness during which patients cannot be easily aroused but respond purposefully* following repeated verbal or painful stimulation. The ability to independently maintain ventilatory function may be impaired, necessitating assisted airway support. Cardiovascular function is usually maintained.

General anesthesia is a drug-induced loss of consciousness during which patients are not arousable, even by painful stimulation. The ability to independently maintain ventilatory function is often impaired. Patients often require assistance in maintaining a patent airway, and positive-pressure ventilation may be required because of depressed respiration or drug-induced neuromuscular depression. Cardiovascular function may be impaired. Because sedation is a continuum, it is not always possible to predict how an individual patient will respond. Hence, practitioners intending to produce a given level of sedation should be able to rescue patients whose level of sedation becomes deeper than initially intended. Individuals administering moderate sedation/analgesia (i.e. ‘conscious sedation’) should be able to rescue patients who enter a state of deep sedation/analgesia, while those administering deep sedation/analgesia should be able to rescue patients who enter a state of general anesthesia.

Deep sedation and general anesthesia are not usually recommended for most of pain management procedures, as an awake, cooperative patient is needed to prevent complications related to nerve injury, allergic reactions, or medication toxicity (Table 22.2).

Table 22.2 Ramsay Level of Sedation Scale2

Clinical Score Level of Sedation Achieved
6 Asleep, no response
5 Asleep, sluggish response to light glabellar tap or loud auditory stimulus
4 Asleep, but with brisk response to light glabellar tap or loud auditory stimulus
3 Sleepy, but responds to commands
2 Patient cooperative, oriented and tranquil
1 Patient anxious, agitated or restless

GENERAL PREPARATION

The risks, benefits, and alternatives of sedation should be explained to the patient in lay terms. The main goals in administering sedatives and analgesic medications are to facilitate the completion of a potentially difficult procedure and to provide a safe and comfortable environment for the patient. The most feared risk of sedation is respiratory depression, which can result in catastrophic consequences if not recognized and treated promptly. The patient may also decline sedation, at which point alternatives can be considered including local anesthesia, relaxation techniques and, for pediatric patients, general anesthesia. After thorough explanation is provided and all questions are answered, informed consent is obtained before any sedation is administered.

Preprocedural assessment

All patients who are scheduled to receive sedation should be thoroughly evaluated prior to the procedure. Relevant issues that should be addressed include past medical history, past surgical history to include any anesthetic complications, drug allergies, and current medications to include anticoagulants, smoking, alcohol use and recreational drug history, and NPO status. The risk stratification classification of the American Society of Anesthesiologists (ASA) provides an excellent preprocedure assessment tool for this purpose (Table 22.3).

Table 22.3 American Society of Anesthesiologist Physical Class Risk Stratification

Class I Normal healthy patient
Class II Mild systemic disease
Class III Severe systemic disease
Class IV Life-threatening illness
Class V Moribund patient

Table 22.4 provides a summary of the American Society of Anesthesiologists preprocedure fasting guidelines. The recommendations apply to healthy patients who are undergoing elective procedures. They are not intended for women in labor. Following the guidelines does not guarantee complete gastric emptying has occurred.

Table 22.4 Summary of American Society of Anesthesiologists Preprocedure Fasting Guidelines for Healthy Patients Who Are Undergoing Elective Procedures

Ingested Material Minimum Fasting Period
Clear liquids 2 h
Nonhuman milk 6 h
Light meal 6 h

The fasting periods noted in Table 22.4 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.

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 types of foods ingested must be considered when determining an appropriate fasting period.

Airway assessment procedures for sedation and analgesia

The airway should be evaluated prior to giving sedative medications. Oversedation will cause respiratory depression and may require respiratory support. Oversedation can also cause aspiration, obstruction, bronchospasm, and laryngospasm requiring tracheal intubation and ventilatory support. Intubation may be especially difficult in patients with atypical airway anatomy. Airway abnormalities may also increase the likelihood of airway obstruction following the administration of sedatives and analgesics. Warning signs of a difficult airway are listed in Table 22.5. Recommendations for frequency of monitoring and documentation during sedation/analgesia are listed in Table 22.6.

Table 22.5 Warning Signs of a Difficult Airway

Previous problems with sedation
Stridor, snoring, or sleep apnea
Advanced rheumatoid arthritis
Chromosomal abnormality (e.g. trisomy 21)
Significant obesity (especially involving the neck and facial structures)
Short neck and limited neck extension
Decreased hyoid-mental distance (<3 cm in an adult)
Neck or anterior mediastinal mass
Cervical spine disease or trauma
Tracheal deviation
Dysmorphic facial features (e.g. Pierre–Robin syndrome)
Small opening (< 3 cm in an adult)
Edentulous
Protruding incisors
Loose or capped teeth
Dental appliances
High, arched palate
Macroglossia
Tonsillar hypertrophy
Nonvisible uvula
Micrognathia
Retrognathia
Trismus and significant malocclusion

Table 22.6 Recommendations for Frequency of Monitoring and Documentation During Sedation/Analgesia1

Monitoring Conscious Sedation Deep Sedation
Heart rate Continuous Continuous
Oxygen saturation Continuous Continuous
Respiratory rate Minimum of every 15 min Minimum of every 5 min
Noninvasive blood pressure Minimum of every 15 min Minimum of every 5 min
Level of consciousness Minimum of every 5 min Minimum of every 5 min

EMERGENCY EQUIPMENT FOR SEDATION AND ANALGESIA

Appropriate emergency equipment should be available whenever sedative or analgesic drugs capable of causing cardiorespiratory depression are administered. Items in brackets are recommended when infants or children are sedated (Tables 22.7, 22.8).

Table 22.7 Emergency Equipment

BASIC AIRWAY MANAGEMENT EQUIPMENT
  Compressed oxygen (tank with regulator or pipeline supply with flow meter)
Ambu-bag
Suction
Suction catheters (pediatric suction catheters)
Yankauer-type suction
Face masks (various sizes)
Oral and nasal airways (various sizes)
Lubricant
ADVANCED AIRWAY MANAGEMENT EQUIPMENT (in addition to the above listed equipment)
  For practitioners with intubation skills, laryngeal mask airways
Rescue airways such as Combitube and esophageal obturatory airway
Laryngoscope handles (tested) and laryngoscope blades
Endotracheal tubes
Cuffed # 6.0, 7.0, 7.5, 8.0
Uncuffed # 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0
Stylets

Table 22.8 Emergency Medications

Amiodarone
Atropine
Diazepam
Diphenhydramine
Ephedrine
Epinephrine
Glucose (50%) (10% or 25% glucose)
Hydrocortisone, methylprednisolone, or dexamethasone
Lidocaine
Midazolam
Nitroglycerin (tablets or sprays)
Vasopressin

DRUG PRINCIPLES FOR SEDATION AND ANALGESIA

1. Always titrate to effect rather than using predetermined dosing guidelines.
2. Use the safest intravenous drug with the shortest duration of effect appropriate for the procedure.
3. Avoid using drugs that require infusion pumps for administration.
4. Benzodiazepines alone rarely cause apnea.
5. Benzodiazepines produce anxiolysis and amnesia, not analgesia.
6. The shortest-acting benzodiazepines have durations of action considerably longer than the shortest-acting opioids.
7. Opioid-induced apnea frequently responds to tactile stimulation.
8. Opioids produce analgesia, not amnesia. They may produce apnea prior to sedation.
9. Benzodiazepines markedly potentiate opioid-induced respiratory depression.
10. Flumazenil antagonizes benzodiazepines; naloxone antagonizes opioids.
11. Propofol is an intravenous general anesthetic with a narrow therapeutic index that is sometimes used for sedation. Its use should be restricted to individuals with the expertise and privileges to use such agents.
12. Ketamine is an intravenous induction agent with profound analgesic effects that is frequently used for painful procedures in ICUs and burn units. Advantages over opioids include better preservation of ventilation and airway reflexes, and stimulation of the cardiovascular system. Psychomimetic effects are common with ketamine, but may be prevented by coadministration of a benzodiazepine.

Common drugs for sedation

There is a variety of pharmacological agents commonly used for sedation/analgesia during interventional procedures. The most common reasons for using these agents are to promote anxiolysis, amnesia, analgesia, and sedation. Each of these agents have the potential to cause sedation and all can effect respiratory and cardiovascular function. The choice of the drug depends on whether the primary goal is anxiolysis, analgesia, or both. Generally, short-acting drugs are recommended for early recovery. In cases when polypharmacy is required, physicians must be aware of the synergistic and/or additive effects of these drugs. Sedating drugs should be administered slowly, with enough time for absorption. Only one drug should be administered at a time and the doses should be conservative. If necessary, a moderate dose of an additional drug may be added, but always infused slowly (Tables 22.9, 22.10).

Table 22.9 The Most Commonly Used Opioid Analgesics

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Table 22.10 Sedatives

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As previously mentioned, pharmacological antagonists or ‘reversal agents,’ such naloxone and flumazenil, must be readily available. Because these reversal drugs have their own side effects and complications, their routine use is discouraged. When used, the patients must remain for an extended duration to allow for monitoring of cardiovascular and respiratory depression, until the effects of the reversal agents dissipate (Table 22.11).

Table 22.11 Reversal Agents

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Because propofol, ketamine, pentothal, methohexial, and etomidate can easily and quickly result in general anesthesia for which no reversal agent is available, the authors recommend that these drugs should only be used by an anesthesia team.

Complications

The main complication of the sedation is oversedation. Since oversedation can cause respiratory and cardiovascular depression, the person responsible for monitoring the patient must be capable of rescuing the patient. Other side effects include irritation of the injection site, cognitive impairment and, rarely, allergic reactions.

POSTOPERATIVE CARE

It is important for the recovery room personnel to monitor vital signs and neurological condition of the patient. The duration in recovery room is determined by the both the condition of the patient and institution protocols. When necessary, a wheelchair can be used fortransporting patients until full motor strength and recovery from the sedation is achieved. Then patients should be discharged from the recovery room with an escort.

Recovery and discharge criteria following sedation and analgesia1

Patient care facilities administering sedation/analgesia must each develop recovery and discharge criteria based on the type of patients seen and the type of procedures performed. Some of the basic principles are detailed below.

General principles

1. Medical supervision of recovery and discharge following moderate or deep sedation is the responsibility of the operating practitioner or a licensed physician.
2. The recovery area should be equipped with or have direct access to appropriate monitoring and resuscitation equipment.
3. Patients receiving moderate or deep sedation should be monitored until appropriate discharge criteria are satisfied. The duration and frequency of monitoring should be individualized depending upon the level of sedation achieved, the overall condition of the patient, and the nature of the intervention for which sedation/analgesia was administered. Oxygenation should be monitored until patients are no longer at risk for respiratory depression.
4. Level of consciousness, vital signs and oxygenation (when indicated) should be recorded at regular intervals.
5. A nurse or other individual trained to monitor patients and recognize complications should be in attendance until discharge criteria are fulfilled.
6. An individual capable of managing complications (e.g., establishing a patent airway and providing positive-pressure ventilation) should be immediately available until discharge criteria are fulfilled.

Guidelines for discharge

1. Patients should be alert and oriented; infants and patients whose mental status was initially abnormal should have returned to their baseline. Practitioners and parents must be aware that pediatric patients are at risk for airway obstruction should the head fall forward while the child is secured in a car seat.
2. Vital signs should be stable and within acceptable limits.
3. Use of scoring systems may assist in documentation of fitness for discharge.
4. Sufficient time (up to 2 hours) should have elapsed following the last administration of reversal agents (naloxone, flumazenil) to ensure that patients do not deteriorate after reversal effects have worn off.
5. Outpatients should be discharged in the presence of a responsible adult who will accompany them home and be able to report any postprocedure complications.
6. Outpatients and their escorts should be provided with written instructions regarding postprocedure diet, medications, and activities, and a phone number to be called in case of emergency.

Continuing quality improvement indicators8

If any of the following occur and are caused by the sedatives and/or analgesics administered, and not the preexisting and underlying disease or its treatment, a review of the chart must be performed and appropriate action taken immediately.

1. Oxygen saturation 90% and a drop of 5% from baseline for longer than 1 min.
2. Use of opioid or benzodiazepine reversal agents.
3. A decrease in blood pressure or heart rate requiring pharmacologic intervention or rapid fluid administration.
4. Failure to respond to physical stimulation.
5. Assisted ventilation and/or unanticipated endotracheal intubation.
6. Unplanned admission.
7. Cardiac or respiratory arrest.

SUMMARY

The choice of sedating drugs is based on patient health, type of procedure, and the level of cooperation needed. Each of the sedative agents has advantages and disadvantages. There are no perfect agents. Physicians administering sedation should follow national and institutional guidelines throughout the sedation period. Sedated patient require vigilant monitoring by trained professionals during the entire period of sedation. Monitoring is required during the procedure, during transport, and during recovery. Finally, using strict discharge criteria and warning the patient about possible delayed side effects will further decrease sedation-related complications.

References

1 Gross JB, Bailey PL, Caplan RA, et al. Practice guidelines for Sedation and Analgesia by Non-Anesthesiologist. A report developed by the Task Force on Sedation and Analgesia by Non-Anesthesiologists. Anesthesiology. 1996;84:459-471.

2 Lydic R, Baghdoyan HA, editors. Handbook of behavioral state control: cellular and molecular mechanisms. Boca Raton, FL: CRC Press, 1999.

3 Lydic R, Biebuyck JF. Sleep neurobiology; relevance for mechanistic studies of anesthesia. Br J Anesth. 1994;72:506-508.

4 Warner MA, Robert A. Caplan RA, Burton S, Epstein BS, et al. Practice guidelines for preoperative fasting and the use of pharmacologic agents to reduce the risk of pulmonary aspiration: Application to healthy patients undergoing elective procedures. A report by the American Society of Anesthesiologists. Developed by the Task Force on Preoperative Fasting and the Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration.

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