Surgery under Conscious Sedation

Introduction

Conscious sedation is a technique that combines the use of local anesthesia and intravenous sedation. It is defined as a depressed level of consciousness to the point that the patient is in a state of relaxation, but maintains respiratory drive and the ability to protect the airway. The patient is also capable of purposefully responding to physical and verbal stimulation. This is in contrast to deep sedation, in which the patient is unable to respond to verbal stimuli, will only respond to painful stimulation with withdrawal and has potential compromise of airway protection and respiratory drive. As opposed to monitored anesthesia care (MAC), in which an anesthesiologist or nurse anesthetist are required, conscious sedation can be performed by a nurse under the supervision of the operating surgeon.

Conscious sedation is rapidly gaining acceptance and popularity among plastic surgeons. It has been utilized for many years by other specialties, and now with the growth in office-based procedures and surgicenters, there has been a corresponding increase in the role of conscious sedation. Currently, almost all aesthetic procedures can be performed using a local anesthetic combined with some form of intravenous sedation. These include breast augmentation, breast reduction, mastopexy, abdominoplasty, rhytidectomy, rhinoplasty, blepharoplasty and liposuction.

Benefits and Disadvantages of Conscious Sedation

There are a number of benefits to the use of conscious sedation instead of general anesthesia or deep sedation. First, the complications associated directly with the administration of a general anesthetic are avoided. These are not negligible, and include adverse cardiopulmonary effects, airway injury and positional nerve injuries. Such complications occur in roughly 1-2% of aesthetic procedures performed under general anesthesia. The incidence of postoperative nausea and vomiting, which account for most unintended admissions after outpatient surgery, is much less than that associated with general anesthesia. Secondly, the risk of developing deep vein thrombosis (DVT) as a result of blood pooling in the lower extremities during general anesthesia is greatly reduced due to the continued contraction of leg muscles and the spontaneous shifting of the patient during the procedure. Third, as a result of the relatively large dose of an amnestic medication that is used, most patients have no memory of the procedure, no recollection of experiencing pain, and many choose to undergo conscious sedation at subsequent procedures. Finally, because it can be performed safely without the presence of an anesthesiologist, there is a considerable saving in cost to the patient.

Conscious sedation is not suited to all patients. Furthermore, the use of conscious sedation requires a surgeon who can “multi-task,” focusing on the operation

as well as on the vital signs and level of arousal of the patient. The fact that the patient is conscious and can shift position or move freely, necessitates that the surgeon be prepared to stop working at any moment. Nevertheless, many patients are well-suited for conscious sedation.

Preoperative Considerations

Prior to using conscious sedation for the first time, the surgeon must familiarize herself with the medications she will be using, as well as their side effects and reversal agents. She must also be familiar with ACLS protocol, airway management and have readily available resuscitation equipment. Immediate access to an anesthesiologist in case of emergency is strongly recommended.

Proper patient selection is an important preoperative decision. Those with moderate to significant cardiopulmonary disease are poor candidates. Patients should meet the criteria of the American Society of Anesthesiologists status I or II. This means that candidates for conscious sedation should be healthy or have only a mild systemic disease that results in no functional limitation (e.g., obesity, diabetes, hypertension and extremes of age). All other patients should receive monitored anesthesia care by an anesthesiologist or general anesthesia. Furthermore, individuals with anxiety disorders and extreme fear of the operating room may not be suited for conscious sedation.

Prior to the procedure, patients may benefit from premedication with intravenous diazepam (Valium), administered in increments of 5-10 mg. The dose administered usually ranges from 10 to 50 mg, with the goal being adequate preoperative subjective relaxation of the patient with the desired endpoint being of slurred speech. Oral diazepam is also an option; however, it has to be given almost an hour prior to the procedure in order to be effective. A second medication that should be administered preoperatively is an antiemetic. Ondansetron (Zofran), given as a single 4 mg intravenous injection is used routinely at our institution. Recently, we have found that clonidine (0.1-0.3 mg PO) given 30 minutes prior to the procedure is not only effective in lowering blood pressure during surgery, it also contributes significantly to patient relaxation during the procedure. It does, however, cause post-procedure orthostatic hypotension.

Intraoperative Considerations

Tumescent Anesthesia

As stated previously, conscious sedation—as it pertains to plastic surgery, involves the administration of local anesthesia in addition to the intravenous sedation. In fact, it is the methodical use of tumescent anesthesia that ensures a smooth, relatively pain free procedure. Tumescence, or wetting solution as it is more appropriately termed, should be infiltrated into the surgical field. Two goals should be kept in mind: anesthesia of the sensory nerves and vasoconstriction of the blood vessels in the region. Achieving these goals requires at least 10 minutes for the wetting solution to exert its effects. Two solutions are commonly used at our institution:

Liposuction solution 1 liter bag of Lactated Ringer’s solution

50 ml of 1% plain lidocaine

1 ml of epinephrine (1:100,000)

Face/breast solution 250 ml bag of normal saline

100 ml of 1% lidocaine + epinephrine (1:100,000)

10 ml of sodium bicarbonate

Table 9.1. Simple medication regimen that can be used for conscious sedation

Medication Dosage Range Purpose Reversal Agent Preoperative

Diazepam 5-10 mg Preoperative Flumazenil (0.2 mg/min; (up to 50 mg) sedation up to 5 doses; reversal in 1-2 min)

Ondansetron 2-4 mg Prevention of None postop nausea and vomiting

Intraoperative

Midazolam 0.5-2 mg Anxiolytic, Flumazenil (0.2 mg/min; sedative up to 5 doses; reversal in 1-2 min)

Fentanyl 12.5-50 mcg Analgesia Naloxone (0.1-0.2 mg/ 2 minutes) reversal in 2-3 minutes

Intravenous Sedation Regimens

Although there are a number of intravenous sedation regimens available, an excellent choice is the combined use of midazolam (Versed) and fentanyl (see Table 9.1). The advantage of using this combination is that midazolam has both anxiolytic and amnestic effects, whereas fentanyl is a potent, short-acting analgesic. The combination of fentanyl and midazolam is superior to midazolam alone in decreasing patients’ subjective report of pain and anxiety. The main drawback of fentanyl is respiratory depression; however unlike other commonly used intravenous opiates such as morphine, it does have a very short half life. Midazolam, in contrast, has minimal effects on the respiratory system except in the elderly, in which lower doses should be utilized. Both of these medications have antagonists. Flumazenil (Mazicon) and naloxone (Narcan), the antagonists of midazolam and fentanyl respectively, should be readily available in the operating room.

Another method of intravenous sedation involves the use of propofol in combination with an opiate and benzodiazepine. The fact that a deeper level of sedation can be maintained makes this technique preferable for selected patients who are very anxious. Nevertheless, the disadvantage of this combination is the higher risk of respiratory depression, and the lack of a reversal agent for propofol. This technique necessitates a higher degree of experience and training in anesthetic technique including the ability to intubate the patient if needed. The use of propofol is not discussed in this chapter.

In the operating room, one nurse should be responsible for continuously monitoring patient status using pulse oximetry, blood pressure and cardiac monitoring. This should be performed by a nurse with appropriate experience and background in continuous patient monitoring; however specialized anesthesia training is usually not needed. It is important to emphasize that this nurse should have no other duties to perform during the procedure. The patient’s oxygen saturation, blood pressure, heart rate, level of arousal and respiratory status should be monitored every 5 minutes. Changes in vital signs, level of arousal and the oxygen saturation are communicated to the surgeon. In addition, the surgeon should make his own assessment of arousal based on response to verbal stimulation, as well as the patient’s degree of discomfort.

Based on the patient’s condition, 0.5 to 2 mg of midazolam should be administered at the 5 minute intervals. In addition, fentanyl should be given in increments of 12.5 to 50 mcg. After local anesthetic is infiltrated, fentanyl administration is infrequently required, except in preparation for subsequent local anesthetic administration to a new surgical site. The total dose of fentanyl should rarely exceeded 200 mcg over the course of the procedure. Toward the end of the case, the amount of sedation should be decreased to allow the patient to slowly return to a normal state of arousal and awareness.

During conscious sedation, supplemental oxygen is usually not necessary. The ability of the patient to maintain an oxygen saturation over 95% without supplemental oxygen is a useful guideline to avoid oversedation (crossing from conscious to deep sedation). Occasional periods of deep sedation may occur, usually lasting for a few minutes at most. Brief stimulation and rarely jaw thrust may be required to maintain adequate ventilation. The use of small incremental doses of midazolam, limited use of narcotics and effective local anesthesia help to limit episodes of deep sedation. Nevertheless, as a safety measure, the capability to convert to general anesthesia or immediate assistance from an anesthesiologist should always be available. Foley catheters and sequential compression devices are generally not required due to the relatively short length of procedures utilizing conscious sedation, and the fact that venous stasis is minimal due to spontaneous patient movement and leg muscle contractions. For cases involving large volume liposuction or those that are longer than a few hours, a Foley catheter should be used to monitor fluid status and to allow greater flexibility in intraoperative fluid resuscitation.

Postoperative Considerations

Following the procedure, many hospitals will allow patients to bypass the recovery room and proceed directly to the outpatient day surgery area. This saves the patient the extra costs of recovery room care. Patients are monitored postoperatively in a standard manner. Those who choose to go home the day of surgery must meet criteria for discharge (ability to ambulate to a chair and the bathroom, bladder control, tolerate oral intake without emesis). Patients who received preoperative clonidine must be monitored for orthostatic hypotension.

Inpatient stay in an observation unit is appropriate for longer cases that involve multiple procedures, as well as for older patients who live alone. Postoperative nausea and vomiting is the major factor contributing to unintentional hospital admission after outpatient surgery. It begins shortly after arrival in the recovery room and usually lasts no longer than 12-24 hours postoperatively. A number of studies support the administration of a preoperative antiemetic (see preoperative considerations).

Pearls and Pitfalls

One of the risks of conscious sedation is crossing over into deep sedation. The responsible surgeon and monitoring nurse should be able to identify and handle patients who briefly slip into deep sedation. In very rare instances, a patient may require jaw thrust, mask ventilation or narcotic reversal. It is critical that the surgeon be comfortable performing these steps if necessary. A common pitfall leading to over sedation is to administer excessive amounts of fentanyl, instead of maximizing the use of the local anesthetic. Towards the end of the procedure, there is nothing wrong with cutting back on the amount of sedation, and allowing the patient to become more awake. In addition, excessive administration of versed can result in the opposite effect: an overly anxious, and occasionally claustrophobic patient. When this occurs, it is best to withhold sedation, reassure the patient and allow her to reorient herself.

Suggested Reading

1. American Society of Anesthesiologists task force on sedation and analgesia by nonanesthesiologists. Practice guidelines for sedation and analgesia by nonanesthesiologists. Anesthesiology 1996; 84:459.
2. Byun MY, Fine NA, Lee JY et al. The clinical outcome of abdominoplasty peformed under conscious sedation: Increased use of fentanyl correlated with longer stay in outpatient unit. Plast Reconstr Surg 1999; 103:1260.
3. Dionne RA, Yagiela JA, Moore PA et al. Comparing efficacy and safety of four intravenous sedation regimens in dental outpatients. J Am Dent Assoc 2001; 132:740.
4. Iverson RE. Sedation and analgesia in ambulatory settings. American society of plastic and reconstructive surgeons. Task force on sedation and analgesia in ambulatory settings. Plast Reconstr Surg 1999; 104:1559.
5. Finder RL, Moore PA. Benzodiazepines for intravenous conscious sedation: Agonists and antagonists. Compendium 1993; 14:972.
6. Kallar S. Conscious sedation in ambulatory surgery. Anesth Rev 1991; 18:9.
7. Klein JA. Tumescent technique for regional anesthesia permits lidocaine doses of 35 mg/kg for liposuction. J Dermatol Surg Oncol 1990; 16(3):248.
8. Marcus JR, Few JW, Chao JD et al. The prevention of emesis in plastic surgery: A randomized, prospective study. Plast Reconst Surg 2002; 109:2487.
9. Marcus JR, Tyrone JW, Few JW et al. Optimization of conscious sedation in plastic surgery. Plast Reconst Surg 1999; 104:1338.