Systemic Anesthetic Agents
The use of balanced general anesthesia, in which small amounts of several different types of medications are titrated to avoid the adverse effects of a large dose of any one type, has been effective in reducing prolonged anesthesia and prolonged recovery time. The use of neuromuscular blocking agents of short duration (12 minutes for mivacurium and 30 minutes for atracurium and vecuronium) administered with an infusion pump allow the anesthesiologist to fine-tune the degree of neuromuscular blockade during balanced anesthesia.
The shorter-acting narcotics such as sufentanil have potencies up to 1000 times those of morphine. These agents help provide short-term stability of hemodynamics during intensive stimulation without prolonged excessive postoperative sedation, as seen with fentanyl. Using such agents immediately before intubation as part of an anesthetic induction has become nearly universal.
Management of postoperative nausea and vomiting after general anesthesia has become easier with the use of more powerful antinausea medications such as ondansetron. Postoperative pain can be prophylactically treated during the procedure with IV ketorolac in a 30-mg to 60-mg dose or with small titrated doses of IV fentanyl in the range of 50–100 μg. Because of its pain-reducing qualities, there is evidence that IV ketorolac can also reduce the amount of postoperative nausea and vomiting in patients who have undergone strabismus surgery or other procedures requiring general anesthesia. There is no evidence that this particular nonsteroidal anti-inflammatory drug increases postoperative bleeding after ophthalmic surgery. However, because of the reported gastrointestinal complications of higher doses of ketorolac, patients older than 60 years should receive a total of no more than 30 mg of IV ketorolac.
Sedation is an important part of comfortable regional or general anesthesia in a patient undergoing elective surgery. Anxiolytics such as midazolam can be given intramuscularly (1–4 mg) 30–60 minutes before the procedure or intravenously (0.5–2.0 mg) 2–3 minutes before the stimulus of the anesthetic block. Midazolam is a more appropriate sedative than diazepam for outpatient surgery because its elimination half-life is 2–4 hours whereas diazepam’s half-life is 20–40 hours. The effects of midazolam can also be reversed with flumazenil. Careful IV titration of sedatives and narcotics is important in older patients to avoid oversedation or respiratory depression.
Alfentanil can be given intravenously in titrated doses with appropriate anesthesia monitoring. Its peak effect occurs in 1–2 minutes and lasts 10–20 minutes. Fentanyl citrate, which has a peak effect in 3–5 minutes and lasts approximately 30 minutes, is also given in titrated doses during regional or topical anesthesia. These agents are used for sedation as well as for their analgesic properties. The effects of narcotics can be reversed with the antagonist naloxone, given intravenously.
Thiopental sodium, a barbiturate used for rapid sequence induction, is no longer available in the United States. Propofol is the drug of choice for most patients due to its rapid hypnotic effect, antiemetic effects, rapid clearance, and fast recovery. It must be given through a large-bore vein or administered after a lidocaine flush of the IV line to avoid significant burning on administration. Propofol is a lipid-based medication that supports rapid bacterial growth at room temperature. Extrinsically contaminated propofol has been associated with postoperative infections, including endogenous endophthalmitis. It is therefore imperative that hospital personnel involved in the preparation, handling, and administration of this drug adhere to strict aseptic technique during its use.
Excerpted from BCSC 2020-2021 series: Section 1 - Update on General Medicine. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.