Anesthesia Could Be Made More Accurate with a Brain-Monitoring Device in the Future

A pioneering brain-monitoring device has the ambition to perfect the delivery of anesthesia drugs by dispensing just the right dosage.

Patients waking up during surgery is every doctor's worst nightmare, leading anesthesiologists to usually dispense more anesthesia than is perhaps needed. They do this to ensure patients stay sedated during surgeries or when on critical life support equipment such as ventilators.

Nevertheless, according to David Mintz, an anesthesiologist at Johns Hopkins University, giving anesthetic drugs in excess can sometimes be risky. Elderly individuals with cognitive conditions like dementia or cognitive decline due to aging can be at an increased risk of confusion after surgery. Moreover, extended periods of use in very young children might lead to behavioral problems. Mintz adds that it would be beneficial to give as little of these drugs as possible.

The efficient application of an automated anesthesia delivery system could enable doctors to find the accurate drug dosage. A recent experiment monitored the brain activity of rhesus macaques using the innovative device and provided them with adjusted quantities of a commonly used anesthetic labeled propofol every 20 seconds. It ensured that the animals received just enough drug to keep them sedated for 125 minutes, and it's considered a significant step towards creating a system fit for human patients.

Typically, the dosage of an anesthetic is estimated based on factors such as body weight and age. However, the exact science behind this calculation is unclear. The correlation between the amount of drug given and the probability of patients being successfully anesthetized using propofol and similar drugs is not explicit. Hence, to secure the unconsciousness of their patients, anesthesiologists often prescribe larger amounts of the drug.

According to Mintz, administering dosages that may not work for everyone is not acceptable. He puts forth the necessity for anesthesia to effectively work for virtually all patients. During anesthesia, doctors closely monitor indirect markers of consciousness such as the breathing and heart rate of the patient. Anesthetics like propofol can also change brainwaves, so observing brain activity can assist anesthesiologists in managing patient consciousness. Nonetheless, Very few physicians are equipped with the right training to do so.

Anesthesiologist Emery Brown and his colleagues introduced a device that could assist doctors in this process. This system combines brain-monitoring medical equipment with a computer that employs algorithms to keep track of how the body metabolizes propofol. Every 20 seconds, it determines the amount of drug needed to sustain a preset level of brain activity that earlier studies have shown to signify unconsciousness in macaques.

The team of researchers administered anesthesia to the macaques for the first half-hour manually, followed by the use of the automated system for the next 125 minutes. In every trial, the system effectively switched the macaques between lighter sedation and a deeper sleep, with each phase lasting 40 or 45 minutes.

Although Brown's system isn't the first of its kind, what sets it apart is its reliance on brain feedback. Brown, who works at MIT, Massachusetts General Hospital, and Harvard Medical School, compares it to using autopilot technology on a flight. An autopilot function is crucial for managing long flights, similarly using a brain-monitoring machine for adjusting anesthetic dosages automatically could be helpful during long surgeries and most likely minimize patients’ post-surgery delirium.

Mintz puts forward that, even with the advent of this technology, a pilot cannot decide to retire. However, he also notes that machines don't tire or need a break - the new device is a valuable tool as it can account for human limitations.

Going forward, the researchers intend to recreate the experiments using more animals for refining the system and making the brain monitoring steps less invasive. The study used electrodes implanted directly into the monkeys’ brains, but the aim is to shift towards non-invasive EEG electrodes, which are placed on the scalp.

Defining consciousness is challenging, and even EEGs are not a flawless tool, according to Mintz. People with brain diseases might have slightly unusual EEG results compared to healthy individuals. However, combining technology like EEGs with the watchful eyes of anesthesiologists can reduce the unpredictability of anesthetizing patients appropriately.