Accuracy of hospital clocks

Health Service policy requires clinical staff to remove watches and be ‘bare below the elbows’, as an infection control measure [1]. Although the legitimacy of the evidence base supporting this hypothesis has been questioned, some National Health Service Trusts have made the wearing of wristwatches a disciplinary matter [2]. Concern has been raised that the removal of watches leaves staff reliant on hospital clocks for timing events, the accuracy of which have been queried. Any inaccuracy between clocks in different clinical areas (e.g. anaesthetic room and operating theatre) could cause staff to record contemporaneous events as if they occurred at different times, creating a potential medico-legal risk. The relevance of this risk has been discussed [3–5]. National time in the United Kingdom changes twice a year, cycling between British Summer Time and Greenwich Mean Time. If staff are to rely on clocks for timings, this switch-over would be an ideal opportunity to check that they are updated appropriately. A survey of clocks was performed at our Trust in June 2008; and repeated on March 30th, 2009, the first working day after the switch to British Summer Time. The time on the clocks in the anaesthetic room, the corresponding operating theatre and the computerised patient monitors were recorded, and compared to a watch that was synchronised with national UK time, using the BBC Radio 4 ‘pips’. In 2008, the average time difference between the theatre and anaesthetic room clocks was 1.7 min (range 0–7). The difference between the anaesthetic rooms and BST was 1 min (range 0–4) and that between theatres and British Summer Time was 1.4 min (range 0–7). During this process, the time recorded on the patient monitors was entirely accurate. In the second assessment, the anaesthetic room clocks, which were hand adjustable, were almost always an hour ahead of the theatre clocks, which were not hand adjustable. The average differences between the anaesthetic room clocks and theatre clocks was −26.5 min; and between the theatres and British Summer Time was −59.5 min. The patient monitors were almost entirely inaccurate by one hour, although a faulty one was 12 h behind. Inaccuracies between clocks in these areas, and therefore any medico-legal risk entailed in using them to time events, are probably minimal for most of the year. These risks are however exaggerated greatly at time zone change, an issue exacerbated by the length of time taken for National Health Service Trusts to normalise the clocks and monitors. If employers wish staff to have confidence in clocks and remove their watches, they should have assessed this possible medico legal risk with policy introduction. It is not acceptable for an anaesthetist and their patient to enter a different time zone by moving from one room to another.