Conscious Sedation: Practical Pointers and Pitfalls
February 1, 1998 9 minutes read
Conscious Sedation: Practical Pointers and Pitfalls
By John O’Donnell, MSN, CRNA, and Leslie A. Hoffman, RN, PhD
Conscious sedation (CS) is defined as "a minimally depressed level of consciousness that retains the patient’s ability to maintain the airway independently and continuously, and respond appropriately to physical stimulation and verbal commands, that is produced by pharmacologic or non-pharmacologic methods, alone or in combination."1 The primary goals of CS are to achieve anxiolysis, amnesia, and analgesia, while avoiding a depth of sedation that requires resuscitation.2 Benefits to the patient include less discomfort from the procedure and less fear and anxiety from anticipation of subsequent procedures.3 Benefits to providers include a patient who is cooperative, able to follow directions, less agitated, and less likely to move, allowing the procedure to be performed in a low-stress, timely, and efficient manner.4 CS is increasingly being used outside of the controlled setting of the operating room, introducing the potential for complications if appropriate practices are not followed. The following examples illustrate pitfalls during administration of CS and practical pointers to improve safety.
Case 1: A respiratory arrest was called in the radiology department for a 77-year-old, 48 kg, female patient having a percutaneous nephrostomy tube placed under fluoroscopy. History was significant for renal cancer with metastasis to the brain, a depressed neurologic status with response only to persistent verbal stimuli, and chronic aspiration due to decreased airway reflexes. When the anesthesia team arrived, the radiologist was attempting to mask-ventilate the patient. The radiologist reported that the patient was agitated prior to the procedure, and during attempted placement of the nephrostomy tube, agitation increased to the point that insertion was stopped. CS was then induced. Midazolam 2 mg was given via a 20 gauge peripheral IV by the radiology resident, followed almost immediately by fentanyl citrate, 100 micrograms IV. Shortly thereafter, the patient stopped breathing, and a respiratory arrest was called. The only monitor, a pulse oximeter, was intermittently functioning. The patient was intubated by the anesthesia team, but intubation was delayed because suction was not available.
This case prompts us to ask four questions. Was this patient an appropriate candidate for CS? Were clear goals for the level of sedation identified? Were the doses and sequence of medications appropriate? Was appropriate equipment available? In the following paragraphs, we briefly review the issues raised by these questions.
Select Appropriate Candidates
Patient selection is a key aspect to the success of CS. A history with attention to assessment of major organ function, prior response to anesthesia, current medications, allergies, whether the patient can take oral medication, and prior substance abuse should be obtained prior to administering any sedative agent. A focused physical exam should be used to evaluate the airway, lungs, and heart. Airway evaluation is critical and should be performed by an individual with experience in endotracheal intubation. All adult patients should fast from solid food for at least 6-8 hours prior to the procedure.5 Several factors made this patient a poor candidate for CS, including her depressed neurologic status, history of chronic aspiration, and physical condition.
Establish Clear Goals
If analgesia is the main concern during the procedure, judicious administration of a local anesthetic, in combination with verbal and tactile reassurance, can sometimes meet patient needs. Explanations about pain and discomfort, reassurance, and therapeutic touch can be used as alternatives to pharmacologic measures. Stoic adult patients and patients schooled in self-relaxation are appropriate candidates for this approach.4
Alternatively, the desired state may be a brief period of "unconscious" sedation, in which the patient experiences analgesia, amnesia, loss of consciousness, and some blunting of the autonomic response to pain or discomfort. However brief the period, this description fits the definition of general anesthesia and should, therefore, involve a provider who is trained in anesthesia and able to immediately manage the airway. Because many CS procedures are considered "minor," practitioners tend to relax and assume that patient risk is also minimal. Possible complications are as serious as for any general anesthetic. When providing CS, a good rule of thumb is to "expect the best but prepare for the worst."2
Titrating Medications: Sedate and Wait
Desirable characteristics of CS agents include specificity, titratability, and predictability. Slow, careful titration during CS administration is necessary to observe the drug’s effect. Elderly patients and patients with poor cardiovascular function often demonstrate a delayed response to sedative agents. Novice practitioners often give a second dose prior to determining effects of the first dose. An old axiom in anesthesia care is that you can always give more.
A wide range of drugs for CS are available, and this diversity can be seductive. Variability in response between patients is the rule, not the exception. Consider side effects and possible drug interactions. If opioids or benzodiazepines are used, the antagonists, naloxone and flumazenil, should be readily available. Combinations of agents are frequently used during CS. The benefits of combining agents include achieving multiple goals (sedation and analgesia), synergistic sedative effects, and minimizing the total amount of each drug used. However, synergism is not consistently predictable. Pharmacokinetics may be unpredictably altered, and toxicity may be cumulative. It may also be more difficult to identify the specific agent responsible for residual sedation.6 When selecting medications, focus on familiarity with the medication, patient condition, and clear goals.
Equipment Requirements
All equipment should be assembled, and the function should be verified prior to the procedure. The simple mnemonic, S.O.A.P.I.E.R., assists practitioners to assemble the necessary equipment for safe CS administration:
Suction: Wall mounted or portable, high continuous setting available, tubing, and appropriate suction head;
Oxygen: Pipeline or tank oxygen source, adequate supply, and pressure verified;
Airway: Laryngoscope handle and backup (charged), varied working blades (Miller and Macintosh), varied endotracheal tubes and stylets, oral and nasal airways, bag-valve mask unit and assorted masks, simple face mask, non-rebreathing mask, nasal cannulae, stethoscope, and laminated American Society of Anesthesiologists difficult airway algorithm card;
Pharmacy: Syringes (3 and 10 mL), needles, emergency medications, muscle relaxants (depolarizing and non-depolarizing), and muscle relaxant reversal agents, (naloxone, flumazenil);
Intravenous: Reliable IV, additional peripheral/central catheters, and IV fluids and tubing;
Equipment: Continuous pulse oximeter, electrocardiograph, infusion pump, temperature monitor, end-tidal CO2 detector, and blood pressure cuff/monitor;
Rescue: Mechanism to summon help.
In this case, synergism between the midazolam and fentanyl resulted in a respiratory arrest. Profound cardiovascular and respiratory embarrassment, especially in debilitated or physiologically unstable patients, has been well-documented when concurrently administering these two agents, and patients should be carefully monitored for this possibility. Proper equipment was not assembled, the oximeter was not functioning, and the reason was not determined.
Case 2: A 38-year-old, 70 kg female patient presented for an evaluative endoscopy to a busy gastroenterology practice. A newly employed RN was assigned responsibility for assisting with the procedure, administering CS medications, and monitoring response. Monitors were: pulse oximetry, EKG, and blood pressure. After some difficulty, an antecubital IV was started. CS was initiated using IV meperidine 75 mg and diazepam 10 mg. When the endoscopy began, the RN noted the patient was uncomfortable, but no attempt was made to remove the endoscope or communicate with the patient. During the 15-minute procedure, the patient progressively became more agitated. SaO2 remained 95-99%. Additional meperidine (25 mg) was given to deepen sedation. After the procedure was completed, the patient complained of excruciating arm and IV site pain. The arm appeared flushed. A diagnosis of local meperidine reaction was made. The patient was discharged, but the symptoms continued. The patient contacted her primary physician who immediately consulted a vascular surgeon. Inadvertent intra-arterial injection was diagnosed, and an emergency vascular procedure was performed to restore blood flow to the extremity.
Three additional questions merit discussion. What policies and guidelines should regulate CS provision? Was monitoring of the sedation, and patient-provider interaction appropriate? Should a RN newly assigned to the unit have been given the responsibilities described?
Guidelines and Policies
There is no mention of the term "conscious sedation" in the 1997 JCAHO Comprehensive Accreditation Manual for Hospitals. However, the JCAHO manual notes that standards for the delivery of anesthesia apply when "patients, in any setting, receive for any purpose, by any route . . . sedation (with or without analgesia) which, in the manner used, may be reasonably expected to result in the loss of protective reflexes." Because CS occurs along a continuum from full consciousness to general anesthesia, each institution is expected to develop protocols for patients receiving sedation that may result in a loss of protective reflexes. These protocols are expected to be multidisciplinary and to clearly delineate standards for all personnel engaged in delivering CS.7
To assist in developing policies and procedures for sedation and analgesia in non-operating room settings, the American Society of Anesthesiologists recently published practice guidelines for sedation and analgesia by non-anesthesiologists, which provide recommendations for pre-procedure evaluation, physical examination, laboratory testing, patient counseling, nothing-by-mouth status, monitoring, personnel, training, emergency equipment, oxygen, agents, IV access, recovery, and special situations.5 The American Association of Nurse Anesthetists (AANA) has also developed guidelines for non-CRNA professional nurses who provide CS. These guidelines identify: 1) prerequisite knowledge and skills; 2) necessary resuscitative equipment and emergency drugs; and 3) requirements for adequate back-up from expert emergency support personnel.8
Monitoring During CS
During CS, monitoring requirements are the same as for general anesthesia. Arterial oxygen saturation, cardiac rhythm, and ventilation (breath sounds/observation) should be continuously assessed, and blood pressure and level of consciousness should be evaluated on a periodic, ongoing basis. The individual performing the invasive procedure should not be the person delivering or monitoring CS. The individual who administers and monitors CS should have no other significant responsibilities and should be able to respond appropriately in an emergency situation. Monitoring is most easily done through verbal and tactile contact with the patient. Signals should be agreed upon before CS begins. A "thumbs up/down" sign or hand squeeze is commonly used to signal patient comfort. Alternately, sedation may be monitored using one of several scales (i.e., Ramsay scale, observer assessment of alertness and sedation [OAA/S], the digit symbol substitution test [DSST], or a visual analog scale [VAS]). All of the scales are easy to use, but none detect subtle changes in sedation level.9
The bispectral index (Bis), a relatively new assessment method, uses a monitor to display a single number derived from bispectral analysis of the electroencephalogram.9 Bis provides a single quantifiable number that correlates well to sedation depth (the range is 0-100 with 100 being full consciousness). A Bis of 60 indicates an adequate level of general anesthesia, and a reading somewhere between 60 and 100 (~80) represents an appropriate level of CS. The system is very user friendly but costly.
In this case, the nurse was inexperienced, had started IVs on only rare occasions, and was not ACLS-certified. No verbal or tactile clues were used, and the patient’s agitation was incorrectly attributed to distress over the procedure. The nurse was inappropriately given responsibility for assisting with the procedure, administering sedation, and monitoring the patient.
Summary
In order to provide safe and effective CS, providers must be familiar with guidelines, policies, monitoring needs, equipment, and advances in pharmacology related to CS. New drugs and new methods of drug delivery will continue to provide challenges. By selecting appropriate candidates, clearly defining goals, and conscientiously applying guidelines, pitfalls can be avoided, and these practical tips can be used to improve patient outcomes. (Mr. O’Donnell is Instructor, University of Pittsburgh School of Nursing, and Director, Nurse Anesthesia Program.)
References
1. ADSA: ADSA Guidelines for intraoperative monitoring of patients undergoing conscious sedation, deep sedation, general anesthesia. ADSA Newsletter 1988;20:2.
2. Scanman FL, et al. Conscious sedation for procedures under local or topical anesthesia. Ann Otol Rhinol Laryngol 1985;94:21.
3. Tung A, Rosenthal M. Patients requiring sedation. Crit Care Clin 1995;11(4):849-873.
4. Higgins TL, et al. Conscious sedation: What an internist needs to know. Cleve Clin J Med 1996;63(6): 355-361.
5. Practice guidelines for sedation and analgesia by non-anesthesiologists: A report by the American Society of Anesthesiologists Task Force on Sedation and Analgesia by Non-Anesthesiologists. Anesthesiology 1996;84: 459-471.
6. Stoltzfus DP. Advantages and disadvantages of combining sedative agents. Crit Care Clin 1995;11(4): 903-912.
7. Kobs A. "Conscious sedation." Questions about the anesthesia continuum. Nurs Man 1997;28(4):14-17.
8. Booth M. Clinical aspects of nurse anesthesia practice. Sedation and monitored anesthesia care. Nurs Clin North Am 1996;31(3):667-682.
9. Avramov MN, White PF. Methods for monitoring the level of sedation. Crit Care Clin 1995;11(4):803-826.
Benefits of conscious sedation include all of the following except:
a. less discomfort from the procedure.
b. less fear and anxiety during subsequent procedures.
c. the ability to respond to commands.
d. few potential complications.
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