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Yosemite - photo by JoAnn Sturman
"Deep anesthesia is your friend." -- Burnell Brown, M.D., "The Chief"
Years ago I learned most patients did not seek anesthesia services for my conversational ability. During MAC anesthesia an anesthesiologist is judged by only two measures–the patient's demand for total amnesia during the perioperative period and the surgeon's desire for a motionless patient during the procedure. With these two benchmarks in mind, IV general anesthesia rather than MAC has been the preferred approach. I inform patients, if I do my job right, at the end of the case before leaving the operating room I will tell you the operation is finished, and you invariably will reply, “You’re kidding me!”
Most of the action occurs at the beginning of the case during injection of the local anesthetic, consequently the pharmacodynamics of the drugs given must match the anticipated time of injection. Fentanyl is not going to do much good if it is given and 30 seconds later the surgeon is sticking a needle into the operative site. Alfentanyl is a better choice under these circumstances.
As soon as a reasonably healthy patient enters the room midazolam 2mg + either fentanyl 100ug or alfentanyl 1000ug are given. Frail patients including those with ESRD, extreme old age, or diminished level of consciousness, often require no narcotics. A propofol bolus is administered to ablate the lid reflex, and the surgeon is ready to roll. The anesthesia circuit is readily available to assist ventilation, for there is a good chance the patient will become apneic until stimulated. After injection allow the patient to resume spontaneous ventilation and begin a propofol infusion to squelch the lid reflex. An oral airway is often handy for this depth of anesthesia, especially with the proliferation of OSA.
Encouraging surgeons to use bicarbonate with the local anesthetic at the beginning of the case will reduce the pain of injection and the amount of anesthesia needed to keep patients immovable. For those patients with large medication needs who threaten to empty the pharmacy of all propofol stores, the propofol-ketamine infusion works wonders.
In the special case of EDGs and most colonoscopies, propofol alone is quite satisfactory. The infusion pump is often too slow to respond to the patient's needs and the speed of the procedure. A thumb on a large propofol syringe connected to a well flowing IV allows for a near instantaneous response to the level of stimulation.
There is a perception that MAC anesthesia is simple, foolproof, and ultimately safe, but in our department disasters have repeatedly occurred. Over sedation, poor airway control, and the lack of immediate recognition are to blame. In these cases it is always best to tell the surgeon to stop and convert to general anesthesia, which ironically is the safer of the two options.
Yosemite - photo by JoAnn Sturman
