Monday, June 18, 2007

Errors of Misperception

OK, back to hospitals (you will be happy to know!) One of our surgeons recently gave me an article about types of errors made in surgery, with particular attention to bile duct injuries that occur during laparoscopic removal of gall bladders (cholecystectomies).

I don't think the article is generally available to the public. It is from the Annals of Surgery, Volume 237, Number 4, pages 460-469 and is entitled "Causes and Prevention of Laparoscopic Bile Duct Injuries". I quote the conclusions:

These data show that errors leading to laparoscopic bile duct injuries stem principally from misperception, not errors of skill, knowledge, or judgment. The misperception was so compelling that in most cases the surgeon did not recognize a problem. Even when irregularities were identified, corrective feedback did not occur, which is characteristic of human thinking under firmly held assumptions. These findings illustrate the complexity of human error in surgery while simultaneously providing insights. They demonstrate that automatically attributing technical complications to behavioral factors that rely on the assumption of control is likely to be wrong. Finally, this study shows that there are only a few points within laparoscopic cholecstectomy where the complication-causing errors occur, which suggest that focused training to heighten vigilance might be able to decrease the incidence of bile duct injury.

I don't know about you, but I think this is really fascinating. The article explains:

Mental procedures that solve problems by making use of uncertain, probabilistic information are called heuristic processes. Heuristics are normal, unconscious decision-making algorithms that work quickly and relatively effectively, but they do not always provide correct solutions. Visual perception is one example. The visual system implicitly makes plausible assumptions about the environment as it analyzes the imaging information being processed on its way towards the conscious mind. Because the assumptions are simplifications, visual perception provides an estimate of reality, not a replica.

...[I]nnate neurophysiological assumptions governing heuristic perception make the process vulnerable to the creation of false images. Our conscious minds are at the mercy of the subconscious heuristics. ....[P]erception of form can be faulty and beyond the individual's knowledge or control. This is central to the mechanism of bile duct injuries.

Think about this. We cannot be satisfied with avoiding only errors of skill, knowledge, and judgment -- arguably where we spend most time in surgical training. We need to understand enough about neurophysiology to devise mechanisms to avoid errors of misperception, as well. A powerful addition to the quality and safety agenda.


Anonymous said...


Being able to read the whole article myself might obviate my comment, but I am gathering that the "misperception" had to do with the surgeon visually mistaking one structure (e.g., the common bile duct) for another? The real question in my mind is, is that misperception caused by the reduced visualization ability inherent in a laparoscopic procedure vs. an open procedure?
Therefore, does that mean common bile duct injuries are more common in lap procedures vs. open procedures? Or, are certain surgeons more prone to misperception errors due to a poorer "eye-brain" connection, similar to variations in eye-hand coordination?

The reason I ask is because laparoscopic procedures are always touted as much better for the patient in terms of pain, recovery time, etc. - but, like stents, is this just another example of medical groupthink?

This may be a question the surgical profession needs to carefully consider, since laparoscopic procedures are spreading far and wide to other organs. A risk-benefit ratio calculation considering all factors might be in order, to truly evaluate patient safety.

Anonymous said...

It seems to me I skimmed something about this before--and one conclusion was that people's innards are all in subtly different positions and juxtapositions to each other. In other words, circumstances alter cases. Yet, with the small field of the laparscopic procedure, it's harder to take a good look. In other it's harder to meausure twice, cut once.

Anonymous said...

A physician I work with told me that she sends one group of our residents (medical-pediatric residents) for a neuro-psych assessment in their first year of residency. Having gone through a neuro-psych eval myself and having read multiple pediatric assessment reports, I know that the yield is likely to be very valuable in helping one understand how one thinks, uses information, processes information, etc. This is exactly her purpose in sending the residents.

I cannot help but wonder if we should make this a mandatory requirement in either med school or the intern year. If we globally gain self awareness about our own neuro-psychology we will better understand how we think. If our physicians better understand HOW they think and arrive at decisions, I wonder if this would translate into globally safer care. I am 95% convinced it would.

Anonymous said...

Most of them are actually online!

Anonymous said...

Wow, many thanks to anon 12:13 for the reference; I recommend it to all! Reading the entire article is even more illuminating, for it addresses the issue of the inevitability of human error. The authors make a statement that surgeons often don't recognize; that human error is inevitable due to the heuristics described by Paul, and that it is more useful to change the SYSTEM (e.g., the procedure sequence or the technology used) rather than try to retrain the error-maker. I believe this is a fundamental principle that everyone responsible for designing processes in hospitals must have burned into their brains. (My personal experience with it has to do with transfusing the wrong blood to the wrong patient; another area where human error is inevitable and there must be a fail-safe system to prevent it from happening.)

Fascinating post once again, Paul!

Anonymous said...

The article is interesting, no doubt. Whether it is true is another matter. Whether actions can be taken based on the results is a further issue. As a medical community we must be skeptical. I am not sure there is any new information in this article. Most of us who perform this operation know that injuries are almost always the result of misidentification of the anatomy. Simply saying that 'cognitive psychology' was used to analyze the results does not improve our fundamental understanding of why the problem occurs, though it makes for 'scholarly research'.

Anonymous said...

Anon 4:03; the editorials accompanying the article largely take your approach and, of course, many surgical misdaventures in general result from misidentification of the anatomy. As a pathologist, I have always respected surgeons' unsurpassed knowledge of anatomy and the small exposures they work with, compared to my autopsies. (:

However, I don't think that takes away from the authors' conclusion that no (human) surgeon is immune from error, exacerbated by the limited exposures due to modern minimally invasive techniques. What if, for instance, the laparoscopy equipment or procedures could be improved so that there is better ability to ID the anatomy, instead of just blaming it on the surgeon? This may become imperative as more widely applied laparoscopy and robotic technology inhibit the "haptic touch" (ability to feel and therefore "see" the anatomy/pathology of the tissue) available in an open procedure of any kind, be it orthopedic, gyn, cardiac, etc.

Pathologists have similar issues where an experienced pathologist can inexplicably miss or misinterpret something bad staring right at them on the slide. New technologies are exploring computer scanning to help with these issues, if molecular testing doesn't get there first.
My point remains: we all do the best we can and take the blame when we can't, but let's invent better systems to help us be perfect.

Anonymous said...

Powerful thinking. So what does this imply for the increasing (or so I understand, although the prospect feels a little creepy to me) popularity of lap-cholys performed by robot?

Anonymous said...

I am one of the authors and a practicing surgeon and I wanted to address a few issues that others have commented on.

1) Yes, laparoscopic cholecystectomy is superior to the open approach even though the incidence of bile duct injury (BDI) is approximately double with the laparoscopic technique (incidence of approx 0.4-0.8%). The reason why laparoscopic surgery is superior is that BDI is only one of many complications that occur more commonly after cholecystectomy. Even though the incidence of BDI is almost double it is a fairly rare compared to other complications that occur with greater freqency after open surgery, e.g. pneumonia, deep venous thrombosis, wound infections. A study of almost 31,000 patients demonstrated a mortality rate of about 1/8th after lap chole vs open (0.23% vs 1.9%, P<0.0001) [Hannan, Surgery 1999, 125(2); 223-3]. Other papers report lower complication rates, 2-9% after lap vs. 8-16% after open.

2) While injuries are due to misidentification of the anatomy his does not imply the surgeon is negligent. They may be fantastic surgeons, well-intentioned, well-trained, technically-facile and have done 500 cholecystectomies but there are certain surgical situations where the anatomy is more likely to be misperceived. In those situations it might be that say, 90 of 100 surgeons would also misperceive the anatomy - and the 'fault' should not ascribed to the surgeon but the situation or 'system'. There is a phenomenon in aviation called the 'graveyard spiral' where the pilot is misled by his or her senses to misperceive what is actually happening. A faulty correction is then made for this misperception which can lead to a crash. In both of these situations your senses are misleading you into making incorrect decisions. This is not to say that all surgeons are skilled and well-trained, but the lap cholecystomy is a basic operation and the truth is almost (my guess is 99%+) of all surgeons have the requisite skills to do the operation, but are misinterpreting their senses when a BDI occurs.

3) Can we reduce the number of BDIs? Yes, it can be reduced by knowing that the potential for misperception exists, taking special care during these parts of the operation, retracting the gallbladder in certain ways, and performing a procedure called a cholangiogram during the operation. Lawsuits DO NOT help surgeons reduce the number of BDIs. Lawsuits target individual surgeons and as such do not result in better systems. They may weed out the few incompetent surgeons but not very efficiently, for every incompetent surgeon who leave the practice of surgery, several good surgeons also leave for lower risk and lower stress careers.

4) Right now there are no cholecystectomies that are being done by a self-controlled robot. In all cases a surgeon controls the robot, although there are very few operations (e.g. prostatectomy) where robotic surgery is even comparable to laparoscopic or open surgery.

I'm glad to hear the responses and answer questions I can.

Anonymous said...

Dr. Lee;

Thanks for that edifying comment.
I am a physician but not a surgeon. Question - what is the outcome of repairing the BDI's (when they are discovered postoperatively) - e.g. is there an incidence of subsequent stenosis/obstruction, or does the repair fix the problem in every case? And, what is the mortality rate with BDI that is not discovered and repaired intraoperatively? Although I accept your data in #1 at face value, I am trying to get at what happens if you are the rare unfortunate patient to sustain a BDI.

Second, I would like all surgeons to read and believe your comments about the fact that a) any surgeon can make a human error and b) that doesn't mean it's his/her fault. In my hospital work with performance improvement, it seemed to be the surgeons who were the most resistant to attempts to find "system solutions" - they all took the attitude that if you were smart and careful enough, this wouldn't happen. I think M and M conferences sometimes tend to reinforce this attitude. We need more objective and rational thinking such as your article portrays. It is also important to have such a body of research to help repel the malpractice attorneys.

Third, don't let the vendors off the hook. No one is better qualified than a surgeon to suggest better designed equipment to perform a procedure.

Anonymous said...

There is indeed an incidence of bile duct stenosis and obstruction if the repair is not done well.

CBD injury occurs in about 1 in 200 cholecystectomies.

Dr Flum at U of Washington studied Medicare patients who underwent cholecystectomy. More than half of the patients without a CBD injury were alive at the last follow-up point, nearly 10 years after surgery, while only about one-fifth of those suffering the CBD injury were still alive then.

I agree that there is a culture amongst surgeons that works counter to finding solutions to system errors. Malpractice suits contribute to the problem because physicians will tend to underreport problems because they are worried about exposure to lawsuits.

Anonymous said...

Dr. Lee;

Thanks for your response. Interesting long term followup data. And certainly, all plaintiff's attorneys equate a poor outcome with medical error. I am told that "experts" have shown with statistics that defensive medicine does not exist and therefore does not contribute to increased costs. Any of us in the profession know that's a joke.