Why are our theatre utilization rates below 85%?

Theatre utilization below the 85% NHS benchmark typically stems from late starts (averaging 22 minutes nationally), overrun cases creating downstream cancellations, and underbooked lists where case scheduling doesn't account for actual procedure duration. The data usually shows that 3–4 specific surgeons or specialties account for 60%+ of lost theatre time.

Three mechanisms drive sub-85% theatre utilization. Late starts are the most visible: nationally, the average first-case delay is 22 minutes, driven by patient not being on the ward pre-operatively, anaesthetic consent not completed, equipment not available in theatre, or the surgeon arriving after scheduled start time. Most Trusts do not systematically record which reason drives each delay — they record that the start was late, not why. Without the reason data, improvement efforts are generic rather than targeted.

Overrun cases create downstream cancellations when the last case of a list cannot start because the preceding procedure exceeded its scheduled duration. Case duration estimates in Theatre Management Systems typically use the historic mean for each procedure code — but the variance around that mean is large. A procedure with a 90-minute average has a 30-minute standard deviation, meaning 16% of cases will take over 120 minutes. Schedulers booking lists to the mean rather than the 75th percentile systematically over-fill lists, causing end-of-list cancellations that count as utilization losses. Underbooking — schedulers adding buffer that accumulates to structural under-utilization — is the third mechanism, occurring when schedulers compensate for previous overruns by leaving unbooked gaps that remain unfilled.

Utilization is measured at the day level by specialty in most Theatre Management Systems — a figure like "Theatre 2, General Surgery, Tuesday: 74%." This masks the intraday loss pattern entirely. The primary utilization loss occurs at two specific points: the first case of the day (where late starts eliminate irreplaceable time at premium capacity) and the last case of the day (where overruns prevent the final case from starting or completing). A theatre with a 24-minute late start on the first case and a final-case cancellation has lost approximately 2.5 hours from its session — but the daily utilization figure shows 74% without indicating where the time went.

Consultant-level utilization data is almost never surfaced in standard reporting. The specialty aggregate of 74% conceals the fact that one consultant consistently starts 35 minutes late while another's list runs 15 minutes over mean duration on every case — together accounting for most of the specialty's utilization shortfall. GIRFT Getting It Right First Time theatre benchmarking data reveals this pattern repeatedly across NHS trusts: the performance gap at specialty level is attributable to a small number of individuals whose behaviour is invisible in aggregate data.

Implement a first-case-of-day start compliance dashboard that records the reason for every late start and tracks the first-case start time against the scheduled time for each surgeon and theatre. This single metric, reviewed weekly in the Theatre Governance meeting, creates the visibility and accountability structure that drives improvement. Trusts that implement first-case start compliance monitoring with named-surgeon accountability typically achieve a 12–18 minute reduction in average late starts within 3 months — recovering 1.5–2.5 hours of theatre time per theatre per week.

Switch case duration estimates to the 75th percentile rather than the mean for all booking purposes. This change immediately reduces end-of-list overrun cancellations. Pair this with a gap analysis that measures the difference between list completion time and session end time — gaps that average more than 20 minutes indicate structural underbooking and trigger a review of whether additional short cases can be added to the list. Reference NHS Scotland's 85% utilization benchmark methodology and the RCoA anaesthetic workforce utilization data, which both support 75th-percentile scheduling as the standard approach for reducing cancellation rates.