Saturday, July 14, 2012

Are We On The Threshold Of Perfect Anesthesia?

We are currently tantalizingly close to achieving perfect anesthesia. What is a perfect anesthetic? In my opinion, it should be a substance that has a rapid onset, zero to minimal side effects, and fast elimination. Several substances that are in the experimental stages are leading us toward this holy grail.

I recently mentioned the finding that methylphenidate, or Ritalin, has been discovered to quickly reverse the effects of propofol. The problem with giving propofol was that a patient's ability to regain consciousness depended on how quickly the drug is eliminated from the blood. Ritalin appears to stimulate the upper neural pathways that leads to more rapid emergence. Now with a combination of propofol and methylphenidate, a patient can be awakened at will without the anesthesiologist guessing how long the elimination time is for a particular person.

The next drug that will lead to the perfect anesthesia is Sugammadex. Even though Sugammadex has not been approved by the FDA for use in the United States, it has already been used in Europe for years. The drug rapidly reverses the paralyzing effects of rocuronium by wrapping itself around the rocuronium molecule, quickly making it unavailable to cause paralysis. Its effect works faster than even succinylcholine elimination, the current gold standard. The FDA denied Sugammadex approval because of some reported allergic reactions, which have been found to be minimal in medical studies. By contrast, succinylcholine is known to cause profound and feared complications, including hyperkalemia, muscle rigidity, cardiac arrhythmias, allergic reactions, and even death. Sux is one of those drugs that, if it had not been grandfathered in by the FDA decades ago, would never be approved today. But it is the only muscle relaxant that can achieve such rapid onset of paralysis required for emergency endotracheal intubation. Rocuronium can achieve similar onset of paralysis with none of the side effects of succinycholine. But its drawback has always been its prolonged effects. Now with Sugammadex, that will no longer be an issue and another dangerous drug can be taken out of the anesthesia cart and put into the museum of outdated drugs like ether and methoxyflurane.

With a combination of these two pairs of drugs, we can finally eliminate the expensive anesthesia machines and its complicated vaporizer system. Total IV anesthesia will be the way to go. Volatile agents such as sevoflurane and desflurane require vaporizers that are expensive to maintain. Refilling them can contaminate the air in the operating room. And they can fail leading to overdosage to the patient. Inhalational agents also cause malignant hyperthermia, the much dreaded nightmare of every anesthesiologist. Plus, what anesthesiologist hasn't walked into an operating room in the morning and found the the previous night's anesthesiologist forgot to turn off the vaporizer completely, gassing the OR all night? Vaporizers are difficult mechanical devices that can be easily removed and not missed at all with the use of TIVA.

What will be left is just a ventilator. By using TIVA, the OR can use the same ventilators as the ICU and eliminate the anesthesia machine. All we need is an Ambu bag to mask the patient then connect him to a regular ventilator with its myriad of vent settings at our disposal. This will save money by getting rid of the anesthesia machine and standardizing ventilators througout the hospital. If we ever get approval for injectable oxygen, conceivably the ventilator could be history too. Yes these are exciting times for anesthesia.

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