The ASA recommends that anesthetics be provided or supervised by an anesthesiologist. The ASA has developed definitions regarding depths of anesthesia (Table 31-10: Definitions of Levels of Sedation/Analgesia by the American Society of Anesthesiologists). When formulating an anesthetic plan, one must consider that all agents and techniques used should be short acting, and the patient should be ready for discharge home soon after the completion of the procedure.
- Anesthetic Agents. Intravenous sedation (propofol, barbiturates, midazolam, fentanyl, meperidine) is the most commonly used anesthetic technique in the OBA setting. Drugs should have short half-lives, be inexpensive, and not be associated with undesirable side effects such as nausea and vomiting.
- Remifentanil is an ultra-short-acting opioid that, in combination with propofol for conscious sedation, provides discharge readiness within 15 minutes after colonoscopy (48–80 minutes after meperidine or midazolam administration).
- Remifentanil is an ideal drug for use during many office-based procedures (facial cosmetic surgery) that may be painful during injection of the local anesthetic.
- Disadvantages of remifentanil are possible nausea and vomiting, risk of drug-induced apnea, and the need for an infusion pump.
- Ketamine functions as both an anesthetic and an analgesic. It is particularly useful because it does not depress respirations and is not associated with nausea and vomiting. Ketamine may cause an increase in secretions as well as cause hallucinations. Another advantage of ketamine is that it is relatively inexpensive.
- Clonidine facilitates blood pressure control throughout the perioperative period and may decrease the total propofol usage.
- It is vital that the office be adequately equipped and staffed to rescue patients from a deeper stage of anesthesia. (MAC is planned, but general anesthesia must be anticipated.)
- Depth of anesthesia monitoring during MAC procedures has been shown to decrease the total propofol usage.