The operator’s guide to improving OR utilization in an ASC

Operating rooms are the revenue-generating asset of a surgery center, and across the industry they sit idle about a third of the time: typical ASC utilization runs 60–65%. This guide is the practical version of the conversation we have with operators constantly — how to measure the number accurately, why it gets stuck, and which levers actually move it.

First, measure it accurately

Utilization debates are usually definition debates in disguise. Three rules make the number trustworthy:

• Use staffed prime-time hours as the denominator. Utilization = hours of wheels-in to wheels-out case time ÷ hours your ORs were staffed and available during prime time. Measured against booked hours instead, everyone looks great and nothing is learned.
• Separate OR utilization from block utilization. OR utilization asks “how full were my rooms?” Block utilization asks “how well did each surgeon use the time reserved for them?” A center can fail the first while every surgeon defends the second — because the problem lives in blocks granted years ago that no longer match practice patterns.
• Track the components, not just the headline. First-case on-time starts, turnover time, cancellation rate, and backfill rate each explain a piece of the gap. A single blended percentage hides which problem you have.

Why the number gets stuck at 60–65%

Utilization isn’t low because people aren’t trying. It’s low because the causes are structural and none of them announces itself:

• Block inertia. Block time is granted, defended, and almost never re-earned. Chronically under-used blocks are the single largest reservoir of idle prime time.
• Padded durations. Schedulers pad case estimates to be safe, the padding compounds across a day, and the schedule “fills” on paper while rooms sit empty in fact.
• Unfilled cancellations. A case that falls off 48 hours out is recoverable — if someone has time to find the fit. Usually nobody does, and the gap is absorbed as lost hours.
• Slow mornings and slow turnovers. A late first start cascades through every case behind it; turnover minutes multiply across the schedule.

The six levers, ranked

1. Block release and reallocation. The highest-value lever and the most politically loaded. Set a written release policy (auto-release at a defined horizon if unused), then bring data — not opinions — to reallocation conversations. Surgeons respond to their own utilization numbers far better than to appeals.
2. Duration accuracy. Replace padded defaults with estimates from your own history — this surgeon, this procedure, this time of day. Recovered padding is pure schedule capacity, with no one’s behavior changed.
3. Cancellation backfill. Make backfill a process, not a heroic scramble: a standing list of flexible cases and patients, and a defined owner who works every gap over a threshold.
4. First-case on-time starts.Measure it, post it, and fix the recurring causes (consents, H&Ps, anesthesia availability). The morning sets the day’s ceiling.
5. Turnover discipline. Worth real minutes, but chase it after the bigger levers — five turnovers of five saved minutes is 25 minutes; one released block is an afternoon.
6. Multi-site balancing. For groups: demand rarely distributes itself optimally across facilities. Visibility across sites turns one center’s overflow into another’s backfill.

What five points is worth

The math is worth doing precisely, because it changes how the whole effort gets prioritized. A worked example: a center running 4 ORs, 8 prime-time hours a day, 250 days a year has 8,000 staffed OR-hours annually. Five points of utilization is 400 hours — at a blended 90 minutes per case including turnover, roughly 265 additional cases a year from the same rooms, the same staff, and the same fixed costs. Run the numbers for your own center with the utilization calculator.

When spreadsheets stop scaling

Everything above can be started manually, and good administrators have been doing pieces of it for years. The ceiling is coordination: duration modeling, block scoring, backfill matching, and staffing alignment are each a part-time analyst job, and they interact — a released block is only valuable if staffing and supplies follow it. That coordination layer is what we’re building Perivanta to be. But the levers work regardless of whose tooling you use — start with the measurement, and start this quarter.