The anaesthetist leans over you and smiles. You breathe deeply and feel yourself falling into that deep nothingness.
If things go to plan, you will gently wake up later in a ward, with flowers and family lined up by your bedside. But things don't always go as planned.
Instead, you might wake up to excruciating pain. You hear the whine of the sternal saw as it splits your breast bone; you scream, but no sound comes out. You can't move. When the sawing abates, you hear the doctors talking as if it is the most natural thing in the world. They have no idea you can hear them. You feel like you've been buried alive.
A nightmare? No, a reality
Awareness during anaesthesia may sound like a horror movie, but it is very much a reality.
Overall, it occurs in about one out of every 1 000 cases. In high-risk settings, however, such as open-heart surgery, caesarean sections, and trauma surgery, the risk rises to about 1 in 100, says Professor Paul Myles, director of the Department of Anaesthesia and Perioperative Medicine at Alfred Hospital and Monash University in Australia.
Far from being just a bad dream, the effects of awareness during anaesthesia can be debilitating. According to Myles, it can result in post-traumatic stress disorder, sometimes lasting for the remainder of one's life. "Such symptoms are found in about 25 - 40 percent of cases," he says.
How it works
Awareness during anaesthesia occurs when the brain is not sufficiently sedated while a muscle relaxant has made movement impossible.
Since movement is impossible, there is no way to let the anaesthetist know that you are awake and that you can feel pain. It's a straightforward matter for the anaesthetist to increase the drug load in order to make sure you are unconscious, but if he or she is unaware of your situation, that may not happen.
The most distressing thing for the patient is a sense of isolation and helplessness – it's "like being buried alive", says Myles. "Hearing sounds and conversation is very common (and this can be frightening)."
Most patients can hear during these episodes, while about half feel pain. Smelling is not reported.
The following are some of the accounts reported in an article published in the medical journal, The Lancet:
- during the removal of a pancreatic tumour, the patient heard the anaesthetist say: “The pressure is really low,” and the surgeon respond: “Can you do something about it?”. The patient recalls movement and pain within the abdomen, tried to move, but was unable to.
- during a laparotomy, the patient remembers going “half asleep”, then hearing shouting, including the words “…do things faster… because things are crashing…”.
- during coronary artery surgery, the patient heard noises and voices during surgery, and the pain of “people trying to tear my chest apart”.
- during a single lung transplant, a patient heard conversations about war in Afghanistan, and recalled that she disagreed with the views being put forward; but was unable to move or speak. She also remembered a suction tube being placed in her throat later, and someone saying: “There are lots of secretions.” This was uncomfortable.
Scanning for awareness
According to the Lancet study quoted above, clinical signs such as blood pressure and heart rate are routinely used by anaesthetists to monitor anaesthetic depth, but such methods are unreliable.
Research suggests that a special brainwave monitor that interprets readings from an electroencephalogram, or EEG, is significantly more reliable.
The brainwave analysis, known as bispectral index (BIS), reduced the risk of awareness by 82 percent in high-risk patients. The study looked at a sample of 2 463 patients who were randomly assigned to either receive BIS monitoring or not.
The BIS uses various measures to produce a single score between 0 (deep anaesthesia) and 100 (awake). Scores between 40 and 60 are considered suitable for surgical anaesthesia.
With study results such as those reported in the Lancet the case for brainwave monitoring is certainly growing. Yet take-up has been variable, for a number of reasons. One problem is reportedly that many anaesthetists underestimate the prevalence of awareness during anaesthesia.
According to Myles, only about one third of patients tell their doctor (and less often their anaesthetist). "They don't think they will be believed," Myles says.
The cost of BIS monitoring is estimated at about $20 (roughly R150) per operation. "But," says Myles, "this is small relative to the costs of surgery (and the costs of managing a patient with PTSD)."
He also says that some countries and some anaesthetists are sceptical of the value of BIS monitoring.
Such doubts have further been fuelled by a recent study published in the New England Journal of Medicine that suggested that BIS monitoring was no more effective than traditional monitoring in detecting awareness during inhaled anaesthesia (the findings do not apply to intravenous anaesthesia).
According to Myles, awareness and anaesthesia has become a "hotly debated issue".
Is it used in SA?
Not widely, says David Morrell, chairman of the 2008 World Congress of Anaesthesia, citing the expense and some reservations: the "reliability of the signal as a measure of awareness is still debated", he says.
Guidelines from the South African Society of Anaesthesiologists classify it as neither a "desirable" or "essential" form of monitoring.
"I have two such monitors for my four theatres, and they are in fact only used on isolated occasions when the anaesthetic technique involves the risk of awareness, or in cases where we suspect that the patient’s age or condition are such that we can reduce the dose of anaesthetic agent and still have the patient adequately anaesthetised," says Morrell.
(Marcus Low, Health24, updated January 2014)
Bispectral index monitoring to prevent awareness during anaesthesia: the B-Aware randomised controlled trial. Lancet. 2004 May 29;363(9423):1757-63.
Anesthesia awareness and the bispectral index. N Engl J Med. 2008 Mar 13;358(11):1097-108.