They're a staple of hospital treatment: the clear plastic bags of saline solution hanging on poles above the patients' beds. They're used to deliver medications ranging from antibiotics to chemotherapy, or simply to infuse fluid into patients who need it.

And they're now in short supply around the country — including at Massachusetts General Hospital, which is raising a red flag about the ongoing inconsistency in supplies of intravenous fluid.

"There's a general worry — and no one wants to run out of IV fluids," says the hospital's chief medical officer, Dr. O'Neil Britton. "Even though we have run very low in certain sections, we have not run out of any IV fluids, and none of this has impacted patient care, but it remains on what we call a high watch risk list."

The situation is concerning enough that Mass. General has brought in its Hospital Incident Command System — used for responses to emergency events — to ensure efficient communication with the staff about how to cope with the shortage as it changes day to day, Britton says.

The industry that produces the IV fluid bags has been troubled for years, from moldy bags to a criminal probe, but the current shortage stems from Hurricane Maria: It knocked out plants in Puerto Rico that belong to the pharmaceutical company Baxter, which makes the bags.

At Mass. General, Britton says, the supply problems have come in waves. First came the shortage of "mini-bags" — little bags smaller than a mini-can of soda — used for various medications. The hospital coped in part by shifting to more IV "pushes" — injecting a medication into a line using a syringe instead of using an IV bag.

"Now, clearly this requires a change in nursing workflow," Britton says. "It certainly requires more time than a nurse just hanging an IV and then being able to do other things. And so on the front lines, this has translated into some adjustments from a nursing perspective, but we have been able to train and our nurses have stepped up wonderfully and managed that."

The hospital took other measures as well, such as asking the staff to give medications and fluids orally instead of by IV wherever possible. And the pharmacists adjusted too, Britton says — the small IV bags were in short supply, but they had large bags of fluid and the needed medications, so they started working overtime to mix the small bags themselves.

"Our pharmacists started doing what we call compounding," he says. "[They] mix the medication themselves in the pharmacy, label it and send it to the floor. So this would be more like baking a cake from scratch rather than using cake mix."

The trouble is, whatever alternatives MGH comes up with to cope with the crisis are likely to be tried by other hospitals as well, raising the demand for those substitutes. So, Britton says, soon, the large bags became harder to get, too.

"We have smaller bags gone," he says. "We’ve made adjustments trying to compensate for that, and now the larger bags, which we use as a stopgap measure, now they’re being inconsistent, and that’s what, I think, set off alarm bells."

The alarm bells are sounding loudly enough for the government to hear: At the state level, the Department of Public Health says it's actively working to understand how the shortage is impacting Massachusetts hospitals, and it has been directing hospitals to follow recommendations by the Food and Drug Administration.

At the national level, the FDA is monitoring the shortages. The agency says it is working with Baxter to help the company get its production back online in Puerto Rico, and it has approved imports of IV fluid products from two foreign companies.

"We now believe that the shortage situation related to IV solution products will improve by the end of 2017," the agency says in an email.

But judging by what Britton has been told, the crisis is not likely to be resolved so quickly. "Now we have been told by the manufacturers that about mid- to late-January, early February, the productivity of everything should be back to normal," he says. "And it may not actually exactly be back to normal."

Britton worries about smaller hospitals that could be having an even harder time with supplies than big places like MGH, he says. The FDA is begging hospitals not to hoard the IV fluid because that could stress the system even more, he says, and the manufacturers have put hospitals on quota systems based on how much they ordered historically.

Still, he emphasizes, patient care has not been affected.

Perhaps what is suffering most is confidence in the resilience of the health care supply system. There have been shortages of drugs and vaccines before, but this one is especially daunting because it affects such a core component of hospital care.

The shortage "does point to the relative fragility of the medical and pharmaceutical supply-demand system," Britton says. "We spend a ton of money on the national strategic oil reserves, but there’s no such thing in health care, and maybe we should think about that.”