Simon Hendel: Protecting memories

MEMORY is complicated, yet it is fundamental to our sense of self and also to our identity within society.

We share it — our relationships with others are built on memories. But some memories we shield from the outside world, for many reasons, and other memories we’d prefer not to have at all.

In no small way, memories make us … us.

Which is why having our memories taken away or manipulated is such a frightening concept and the topic of many a Hollywood thriller. Who would we be without our memories?

Defining memory can be difficult and understanding its mechanics even more so. Beyond rudimentary concepts of short-term and long-term memory, or vague recollections from university of procedural, semantic and episodic memory, I really don’t know the details of how memory works. Rather than having forgotten them — I’m slightly ashamed to admit — I never committed these details of memory … to memory.

Thankfully, however, my inattention at university does provide an important illustration of how “memory loss” in anaesthesia works.

I may not be a memory expert, but as an anaesthetist, I am a drug expert. Every day I combine a cocktail of drugs to keep people safe and comfortable during painful procedures or surgery.

Often these drugs affect patients’ memories.

I have previously written in MJA InSight about anaesthesia awareness and the overall safety of anaesthesia in Australia, so I won’t harp on it again. But I would like to set the record straight about some common misconceptions when it comes to memory loss and anaesthesia.

With the one important exception of postoperative cognitive decline, which I won’t discuss here, memory loss per se doesn’t happen as a result of anaesthesia.

To lose something you must first have had it. There are no drugs in anaesthetic practice that take memories away once they’ve been formed. This is the important distinction between retrograde and anterograde amnesia.

Anaesthetists regularly use drugs like midazolam (a short-acting benzodiazepine) or induction agents like propofol for their amnestic properties, but none of them cause retrograde amnesia. Instead, we use them to stop unpleasant memories forming in the first place. For example, of invasive lines being placed or regional nerve blocks being performed before the induction of general anaesthesia.

The distinction is important because a loss of control is one of the common fears patients have about anaesthesia. Being able to reassure patients that their memories of the past can’t be removed but also that they are unlikely to remember stressful experiences of the procedure can help to defuse some preop anxiety.

This doesn’t mean that if patients remember something of a procedure that anything has necessarily gone wrong. As doctors, our definition — and therefore our explanation to patients — of anaesthesia is important.

Procedural sedation for a colonoscopy is different to general anaesthesia for a bowel resection. Indeed, the very aim of procedural sedation is to have a cooperative but comfortable patient, so if they recall snippets of their procedure that’s OK — it doesn’t mean they had other memories removed or conversely that they weren’t “under” deeply enough.

It’s also important for all doctors to remember moments their patients are unlikely to recall. The anterograde amnestic effects of anaesthetic and sedative drugs persist for short but variable lengths of time once the procedure is over and patients appear “awake”. That makes the recovery room a good place for reassurance of immediate safety but not for in-depth — or even brief —discussion of a new diagnosis.

At the very least it calls for a level of awareness (pardon the pun) on our part that little will be remembered the next day, and the discussion will need to be wholly repeated when it can be committed to memory.
 

Dr Simon Hendel is an anaesthetist.