Massachusetts General Hospital (MGH) physicians have a developed a safer, and novel general anaesthetic for critically ill patients.
Published in the journal Anesthesiology, the article describes the drug called MOC-etomidate as a chemically altered version of an exiting anaesthetic that does not cause the sudden drop in blood pressure seen with most anaesthetics, or prolonged suppression of adrenal gland activity, a problem with the original version of the drug.
"We have shown that making a version of etomidate that is broken down very quickly in the body reduces the duration of adrenal suppression while retaining etomidate's benefit of keeping blood pressure much more stable than other anaesthetics do," says lead researcher Dr. Douglas Raines, of the MGH Department of Anaesthesia, Critical Care and Pain Medicine.
Almost all general anaesthetic agents reduce blood pressure immediately after they are administered.
Though not a problem for young and healthy patients, it can have serious consequences for those who are elderly, critically ill or suffering from blood loss.
Etomidate is often used to induce anaesthesia in such patients, but since adrenal suppression sets in quickly and can last for several hours to days, other agents are used to maintain anaesthesia during a procedure, requiring very careful monitoring to avoid dangerous blood pressure drops.
In their search for a safer version of etomidate, the researchers mimicked the chemical structure of other "soft analogue" drugs - derivatives of parent drugs designed to be rapidly metabolized - by adding a molecule that causes the drug to broken down by natural enzymes soon after producing its effects.
When they conducted experiments on tadpoles and rats, they found that the new agent quickly produced anaesthesia from which the animals recovered rapidly after administration ceased.
The rat study verified that MOC-etomidate had little effect on blood pressure levels, and no effect on adrenal activity, even when administered at twice the dosage required to produce anaesthesia.
The researchers note that, since the study only examined the effect of a single dose of MOC-etomidate, their next step will be to study continuous infusion of the drug.
They further say that additional data must be gathered from animal studies before testing the agent in human patients is feasible.
"If all goes well, we expect that we could give a large dose of MOC-etomidate to induce anaesthesia and then run a continuous infusion to maintain anaesthesia without reducing blood pressure in even very sick patients. We also anticipate that patients will wake more quickly and with less sedation after surgery and anaesthesia," Raines says.