Adverse Occurrences in the Intensive Care Unit

To the Editor.— Inasmuch as we have been studying the frequency of human error in the emergency center as a basis for improving the quality of medical care, we welcome this splendid article (1980;244:1582) that recommends vigorous investigation of hazards in hospital. We would like to call the attention of the Pittsburgh group to the well-documented diurnal rise in human error that peaks at about 3 AM and 3 PM. This interesting phenomenon has been confirmed in a variety of settings including gas company personnel reading meters, automatic train breakers, and near-misses in train and truck operators. It is perhaps more pertinent to point out that at 3 PM, detection of hypertension in the emergency center of a university-affiliated public general hospital fell to one third its previous rate. 1 We would like the authors' opinion as to the relevance of these findings to their observation that intensive care unit