In the very early years of open-heart surgery, when the supply of surgeons failed to meet the demand for their services, the giants of cardiovascular surgery would walk from operating room to operating room carrying out the delicate, critical parts of care and leaving their trainees to open or close the patient’s chest. This was an early form of overlapping surgery. It would not be its last. As the waiting list for surgery in the UK’s National Health System exceeds six million, two anesthesiologists attempt a pre-emptive cautioning against adopting overlapping surgery.
How overlapping surgery works
The idea is straightforward. A surgeon begins an operation in theatre, well the US term would be in an OR room. After performing the critical portions of the surgery, basically everything up to the closure of the wounds and removal of equipment, they would enter room 2. Here, another patient already anesthetized, with the operative field exposed (opened and prepared) would be waiting for the surgeon to again perform the critical portions of the operation. The surgeon would then return to room 1 where a third patient was awaiting their critical portions. Lather, rinse, repeat.
The rationale for this was to increase the surgeon's productivity, their patient “touch time,” and the productivity of the operating room, a very significant source of hospital revenue. It performed this mathmagic by eliminating “turnover” time – the time between cases needed to clean and restock the room, open, sterilely, the necessary instruments for the subsequent surgery, bring the patient into the room, position them on the operating table and induce anesthesia. Turnover time is measured from when the first patient leaves the room until the next patient enters the room. It may be as short as fifteen minutes and as long as an hour.  The productivity gains of overlapping surgery come from eliminating those turnover times. But as the review article points out, there are no productivity gains, except maybe for the surgeon. Why would that be?
Mathmagic meets reality
Consider a surgeon who routinely operates, skin to skin, in 3 hours, with a 45-minute turnover time. A single surgeon, working in only one operating room could complete three procedures between 7 AM and 5:30 PM. By allowing a 30-minute overlap, starting case 2, 30 minutes before case 1 ends, and using two rooms, the surgeon can perform four procedures in the same period – in MBA land this is an increase in productivity by 25%, a significant improvement, especially for a procedure like surgery, that is bespoke rather than automated.
This productivity gain rests on two assumptions. First, the operating rooms have unused capacity; they are not fully occupied. On a 24-hour basis, this is true because very few patients and surgeons like to do elective surgery in the late evening or overnight. OR utilization may drop to 10 or 15% in the evening and overnight as only emergencies and urgent surgery are performed. To an administrator who calculates the 24-hour-a-day cost of the OR against the 24-hour-a-day revenue, the cash cow is doing nothing a third or more of the day. That is partly why many hospitals are now offering elective care on Saturday; patients are told it is for their convenience, which it is, but it also enhances hospital revenue.
The problem with the assumption of unused capacity is that those second rooms necessary for overlapping surgery are usually not available during daylight when the surgeons who overlap choose to work.
The second assumption is that a second surgeon is not available to perform those same procedures in the second room – the supply of surgeons is the rate-limiting factor. In the presence of a second surgeon, productivity would increase by 100%; there would be six procedures, not three or four. This assumption is more accurate, there is a mismatch between surgeons and patients, less of us, more of you – but the Goldilocks ratio is hard to find; surgeons need enough “experience” to be proficient, and patients want their elective needs to be treated now, and not be on a waiting list and there are only so many hours in the day.
The benefit of overlapping surgery to the individual surgeon is perhaps the greatest. They increased their income by 25% for the same time effort. You can see why surgeons might be in favor of overlapping cases. But as with all tradeoffs, there may be a downside.
What is the “critical part” of the surgery?
From the patient perspective, the whole damn thing.
For the surgeon trying to deliver an entirely personalized procedure, say a plastic surgeon doing aesthetic surgery, it is the entire procedure, skin to skin. For many of us, the critical part is really the fun part. Exposing and then closing the operative field is, most often, the price you pay to get to the fun part. Why not if opening and closing can be offloaded onto a qualified assistant?
But to the careful reader, we must consider that sometimes creating the operative field is critical because it makes the fun part easier and safer. Putting everything back where we found it, except the parts we changed, and making sure that there is no slow bleeding (everyone sees fast bleeding) would be considered critical by many surgeons, and certainly by their patients, but that is the very time when the surgeon is next door beginning the fun parts of patient 2 or 3 or 4. While that is not how I trained, I recognize it as a judgment call.
These types of judgment calls may only raise an eyebrow when they work out, but when they don’t there can be recriminations. And blame begins with what the “critical parts” of the surgery entail. As I said, the critical parts are often in the eye of the beholder. In some circumstances, they can be those simple acts of exposing and closing the operative field – small missteps have a way of cascading, over time, into complications, or worse.
Who is the arbiter of “critical parts?” In the most famous case in the US, it was a federal court acting upon a “whistle-blower complaint,” of overlapping surgery at Harvard’s Massachusetts General Hospital. Medicare, the ultimate payor, disagreed with the surgeons as to what they considered required to be paid for surgical care. As the authors of this review note,
“Any financial gains conceived by the policy have been wiped out several times over, by the $33 million required to settle cases resulting from that overlapping surgery."
 The time variation is due to any number of day-to-day factors including how many instrument packs need to be opened, what type of anesthesia the patient is receiving, how long it takes to clean up the room and restock it from the prior procedure, and to herd the surgeons and anesthesiologists, who tend to wander back into the room.
Source: The effect of overlapping surgical scheduling on operating theatre productivity: a narrative review Anesthesia DOI:10.1111/anes15797