Patient Safety Tip of the Week

May 3, 2011          It’s All in the Timing



In our April 26, 2011 Patient Safety Tip of the Week “Sleeping Air Traffic Controllers: What About Healthcare?” we discussed the issue of fatigue on the night shift and the potential role it may play in patient care errors. That may apply to both nurses and physicians. And in this month’s What’s New in the Patient Safety World column “More on Nursing Workload and Patient Outcomes” we noted that patient ER visits and hospital readmissions are increased when nurses are working overtime.


Are there other examples where duration worked may have a detrimental effect on patient safety? It turns out there are several good examples. For a number of years now it has been pointed out that endoscopists tend to detect fewer colonic polyps or adenomas later in the day. Also, completeness of colonoscopy may fall off later in the day. In both examples patient characteristics and patient preparation probably do not explain the phenomenon and quite likely a factor related to operator fatigue is in play.


It was noted that the number of incomplete colonoscopies was about 60% higher when done in the afternoon than the morning, even after adjustment for patient characteristics and inadequate bowel preps (Sanaka 2007). The implication was that operator fatigue may play a role in this poorer performance in the afternoon.


Similarly, adenoma detection on colonoscopy also declined about 20% in the afternoon compared to the morning (Sanaka 2009). There was actually a trend to declining adenoma detection by each hour elapsed. A more recent study (Lee 2011) confirmed this and demonstrated that there was a 4.6% reduction in polyp detection for each elapsed hour of the day. And, if you look at it from the patient’s perspective, each position you are in the queue successively is associated with a 5.4% reduction in polyp detection.


Note that the above studies do not necessarily imply fatigue. Alternate explanations might be due to the monotony of the procedures causing inattentiveness or even time pressures to finish the day leading to less thorough evaluations. Whether it is operator fatigue, monotony, or time pressure the net effect seems to be the same and interventions to improve successful exams should be considered. Another recent study (Gurudu 2011) looked at the difference between colonoscopies scheduled in half-day blocks vs. full-day blocks and concluded that adenoma detection rate was not different in the afternoon compared to morning if endoscopists were each working just a half-day but the rate of adenoma detection was significantly lower in the afternoon if the same endoscopist did both morning and afternoon blocks. Another study done at the Mayo Clinic (Munson 2011) showed that the reduction in adenoma detection rates did not fall off when colonoscopists worked 3-hour shifts. And another new study (Freedman 2011) showed stable polyp detection rates throughout the day when moderated colonoscopist procedure loads were used in conjunction with split-dose bowel preparations.


An editorial by Spiegel (Spiegel 2011) summarizes the literature on this variation of detection of polyps or adenomas by time of day and notes it has occurred in almost all settings where colonoscopies are done. He even points out the in the Munson study noted above, though there was no hourly dropoff  in detection rates for the first two shifts, there was a dropoff in detection rates between the start and end of the third shift. He notes, however, that setting caps on endoscopic work shifts such as done at the Mayo Clinic may be helpful in reducing the dropoff in detection rates.


What about other specialties? A similar phenomenon has been reported in radiology. One study (Krupinski 2010) showed a significant reduction in diagnostic accuracy of radiologists after a day of clinical reading (average 8 hours), as measured by reduced ability to detect fractures. This correlated with subjective ratings of fatigue and eyestrain and objective errors in (ocular) accommodation. Even though radiologists recognized the eyestrain and/or fatigue they did not take any longer to interpret films at the end of the day.


But fatigue, per se, may not be the sole cause of errors in such cases. Monotony certainly also may play a role. It’s well known that fewer abnormalities are found by pathologists or cytology techs looking at slides for long periods (hence the interest in automated procedures to screen specimens for abnormalities). Nurses or technicians monitoring telemetry screens are also less likely to detect abnormalities when watching monitors for long periods. Errors related to monotony have been seen in other industries such as trucking, banking, inspecting goods, measuring parts, lifeguard surveillance, railway transportation, etc.


A study looking at the effects of sleep debt and monotonous work in process operators working 12-hour shifts (Sallinen 2004) showed that the effects of monotonous work are at least as harmful as moderate sleep debt. They called for more attention to the activity-provoking nature of work as a means to maintain alertness at work. They also note that our ever-increasing automation and introduction of computer technology may contribute to monotony and diminished pace of work, perhaps increasing the risk of sleepiness.


So what are the take-home lessons from all this (other than that we’ll be sure to have our next colonoscopies early in the day!)? First, there is obvious utility in looking at various outcome measures not just in the aggregate but also by time of day (and maybe day of the week as well). Second, limiting the workload in some circumstances may make sense. The cap of 3-hours per session for individual colononoscopists, as done at the Mayo Clinic, may make sense. Thirdly, we need to take a closer look at the issue of monotony in a whole variety of processes and look for ways to better break up the day and vary the “pace” of many of our healthcare workers to minimize the potentially fatiguing effect of monotony.







Sanaka MR, Shah N, Mullen KD, et al. Afternoon Colonoscopies Have Higher Failure Rates than Morning Colonoscopies. The American Journal of Gastroenterology 2006; 101: 2726-2730



Sanaka MR, Deepinder F, Thota PN, et al. Adenomas Are Detected More Often in Morning Than in Afternoon Colonoscopy. The American Journal of Gastroenterology 2009; 104: 1659-1664



Lee A, Iskander JM, Gupta N, et al. Queue Position in the Endoscopic Schedule Impacts Effectiveness of Colonoscopy. The American Journal of Gastroenterology 2011 (published online March 29, 2011)



Gurudu SR, Ratuapli SK, Leighton JA, et al. Adenoma Detection Rate Is Not Influenced by the Timing of Colonoscopy When Performed in Half-Day Blocks. The American Journal of Gastroenterology (published online April 19, 2011)



Munson GW, Harewood GC, Francis DL, et al. Time of day variation in polyp detection rate for colonoscopies performed on a 3-hour shift schedule. Gastrointestinal Endoscopy 2011; 73(3): 467-475



Freedman JS, Harari DY, Bamji ND, et al. The detection of premalignant colon polyps during colonoscopy is stable throughout the workday.

Gastrointestinal Endoscopy 2011; (published online March 14, 2011. )



Spiegel BMR. Does time of day affect polyp detection rates from colonoscopy?

Gastrointestinal Endoscopy 2011; 73(3): 476-479



Krupinski EA, Berbaum KS, Caldwell RT, et al. Long Radiology Workdays Reduce Detection and Accommodation Accuracy. Journal of the American College of Radiology 2010; 7(9): 698-704



Sallinen M, Harma M, Akila R, et al. The effects of sleep debt and monotonous work on sleepiness and performance during a 12-h dayshift. J. Sleep Res. 2004; 13(4): 285–294













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