Drug-induced comas: Miracles on the edge of oblivion
A colleague liked to say, only partially in jest: “I just put people to sleep; God wakes them up again”
When the mask swooped from above and was clamped tightly to my face I remember screaming. I was five years old at the time and in the room there were pipes and people staring down, and a black, sinister balloon.
The smell in the mask was very strong and stung my eyes.
The light was bright.
My mother had not been allowed to come with me, and as I fought the mask I pictured her vividly, unable to hear my screams as she walked away through the open doors of the hospital into a late summer afternoon, leaving me abandoned. Then a dark cloud ate me and there was nothing.
As an adult it was easier. The anaesthetist injected a premed beforehand that lent everything in theatre – the nurses, the doctors, the anaesthetic machine – fuzzy edges, and left me feeling woolly and unconcerned.
Somehow, as they upped the drugs, I was transformed into a bit of flotsam bobbing in warm bathwater. Then the plug was pulled and my flotsam self approached the swirling drain, where it started spinning as it fell into the vortex.
I was already a medical student when I underwent that second anaesthetic and I had studied anatomy and physiology. The second year of my studies had been spent in the dissection halls, carefully taking apart a fine-boned cadaver as the embalming fluid turned my white coat yellow and seeped into my very pores.
Months passed and I grew to know the cadaver with a rare intimacy. I peered into the chambers of his heart, dissected his peripheral nerves, and held his kidneys in my hands. I traced the arc of his aorta and learned to name its branches. In physiology classes we studied how the organs functioned.
Unlocking the secrets of the brain
When technicians sawed open our cadavers’ craniums to remove the brains, I learned to distinguish white matter from grey, and to name the sulci and gyri. I identified the hippocampus and the corpus callosum.
I examined brain slices under the microscope, looking at neurones, glial cells and myelin. In physiology class I memorised neurotransmitters: noradrenalin, GABA, dopamine and serotonin.
And as I amassed information about the strange sack of jelly we carry in our skulls, my frustration grew with the knowledge that none of it was enough to unlock the true secrets of the brain.
Pry as I might into his neural matter, I would never access my cadaver’s language, culture and childhood memories, or discover how he had come to die alone in hospital. We did not even understand how the brain went to sleep and woke up again.
Twenty years have passed since I entered a dissection hall, and I have drifted into the field of anaesthesia. The brain remains mysterious. The first general anaesthetic was performed in 1846, when a jar of ether was held to a patient’s nose until he passed out. Almost a fifth of patients never came back from those early forays into unconsciousness, which still remained an attractive alternative to undergoing surgery tied screaming to a table.
Improvements in monitoring and pharmacokinetics have now made general anaesthesia statistically safer than crossing a road for healthy people, but we are still not completely sure how our drugs cause loss of consciousness. And scientists have yet to agree on a definition of consciousness – that occasionally wonderful state most of us enjoy on a daily basis.
When I pick up a syringe and begin injecting a patient, I often say: “Now you’re off to sleep.” But this is not accurate. General anaesthesia is not sleep; it is a chemically induced, reversible coma, and the desired end point of our drug and gas cocktails is oblivion.
Patterns of on-off activity
For the recipient, one minute you are lying on the table, oxygen mask on your face, looking up at the anaesthetist’s nostrils. Perhaps you feel a little light-headed or a slight sting in the hand, and then suddenly it is two hours later, or four or even 12, and you have a sore throat and a cast on your leg or stitches in your belly or craters in your jaw where your wisdom teeth used to be. Or you might have had major brain surgery, in which case you may no longer be the person you once were.
Of course, general anaesthesia does not always go according to plan. Awareness is a very rare, nightmarish condition of being paralysed and unable to respond, while feeling and hearing every aspect of surgery. But awareness is a failure of anaesthesia, a result of mishap or negligence. Awareness occurs when just the muscle relaxant part of an anaesthetic is given, without enough of the stuff that sends you into a dreamless state of unresponsiveness.
Neuroscientists initially sought a seat of consciousness within the brain, hoping to discover a demarcated structure responsible for wakefulness, one with clear patterns of on-off activity.
As the sophistication of brain imaging techniques has evolved, however, consciousness is showing itself to be a more global phenomenon, related to interaction between different parts of the brain, rather than activity in a specific area.
And as anybody who has dabbled injudiciously in alcohol knows, consciousness is also not an all-or-nothing state, but rather a continuum.
Consciousness: not all-or-nothing
Using a machine called a syringe driver, which is linked to a computer program, I am able to deliver a specific dose of certain drugs. Loading the syringe with propofol, (the drug Michael Jackson grew so inordinately fond of), I dial in a low level. My patient becomes slightly drowsy, talkative and generous.
At slightly higher doses, my patient opens his eyes and gives me a thumbs-up when I ask how he feels. At increasing doses my patient no longer responds, and although a brain scan would show activity in reaction to speech, there is no awareness, no dreaming or visions, no recall.
Somewhere among these levels is the state neuroscientists believe to be responsible for the reports of serenity, levitation and bright lights that people bring back after near- death experiences. Unlike loss of consciousness from a lack of oxygen, however, anaesthetic drugs interfere with memory, which makes such reports rare. At higher doses of propofol patients will stop breathing, a not unusual event in general anaesthesia, and the reason anaesthetic machines come with ventilators. Deeper still, and brain activity disappears.
Cardiac anaesthetists go a step further, cooling the body and stopping not just breathing, but also the heart. With a patient on bypass, the cardiac theatre is eerily silent, without a reassuring beep-beep from the monitor. A flat line runs on the screen. There is nothing to suggest the person is alive.
At the end of the procedure, the surgeon applies tiny paddles to the ventricles, delivers a shock, and the heart, which was once believed to house the soul, resumes beating. Done properly, the patient experiences these momentous events as nothing. A void.
Turn off the gas and the patient comes back, the drugs metabolised and shifted around by the body. As a fellow anaesthetist liked to say, only partially in jest: “I just put people to sleep; God wakes them up again.”
Those who do not believe in God must be content with the intricacies of a physiology we do not fully understand, yet to explain our visit to, and return from, that sweet zone somewhere between being wide awake, fully alive, and death: the zone of general anaesthesia, which these days is as miraculous and commonplace as flying.
Martinique Stilwell is a medical doctor and an occasional contributor to the Mail & Guardian. She is the author of Thinking up a Hurricane, a memoir of her childhood at sea, published by Penguin.