Senate Majority Leader Mitch McConnell (R-Ky.), accompanied by Sen. Mike Enzi (R-Wyo.), speaks to reporters on Capitol Hill on March 24. (Pablo Martinez Monsivais/AP)

House members spent a lot of time last week congratulating themselves for passing a permanent "doc fix" -- that is, an end to the yearly ritual of readjusting the rates Medicare pays to health care providers in order to avoid drastic cuts that could cause them to stop treating elderly patients.

One problem: The "doc fix" isn't actually fixed. While the House overwhelmingly passed the bipartisan deal that permanently changed the formula ahead of the April 1 deadline while also reauthorizing key health programs supported by Democrats, the Senate did not act on the House bill after completing budget votes in the wee hours Friday morning -- postponing action until senators return from recess on April 13.

Now the federal agency that administers Medicare is warning doctors that if the deal isn't passed by April 15, they will face a 21 percent cut in payments for service they've already rendered to Medicare patients.

[Congress congratulates itself for the ‘doc fix’ deal, but can it happen again?]

The Centers for Medicare and Medicaid Services said it "must take steps to implement the negative update" even if Congress is certain to pass the bill. "We are working to limit any impact to Medicare providers and beneficiaries as much as possible," an e-mail to providers said.

If the Senate fails to pass the House bill immediately, or if it amends the bill, thus delaying final passage, the agency will reprocess post-April 1 claims that were paid at the lower rate, an official said.

While the legislation does indeed enjoy vast bipartisan support, nothing is ever certain in the Senate, where a single senator's objections can slow a bill's advance to a crawl. As shown in recent weeks, even a measure cracking down on human trafficking can get bogged down in partisan rancor.

Some Democrats had raised issues about abortion restrictions embedded in the "doc fix" deal, while others wanted to see a longer reauthorization of the Children's Health Insurance Program. On the Republican side, there are a few senators who remained uneasy last week with the cost of the deal, which stands to add to the federal deficit in the short run.

But it appears that House Speaker John A. Boehner (R-Ohio) has successfully managed to "jam the Senate" -- which is how a Republican House member described Boehner's strategy to the National Journal last month -- leaving the upper chamber without time or options to unravel the House deal.

The federal announcement -- somewhat akin to holding a loaded gun to Congress's collective head -- could also help smooth passage once the Senate returns on April 13. President Obama has said he plans to sign the bill."

After the budget was disposed of early Friday morning, Minority Leader Harry M. Reid (D-Nev.) said he was ready to move immediately to the health-care bill, but wished to offer "a very limited number of amendments" to the bill.

"This would have been done before the break if it weren't for Republican objections," Reid spokesman Adam Jentleson said Thursday.

Majority Leader Mitch McConnell (R-Ky.) said at the time that the Senate would "turn to this legislation very quickly when we get back. I think there is every reason to believe it will pass the Senate by a very large majority."

McConnell spokesman Don Stewart said Thursday that "members will discuss the path forward, but we expect it will be done quickly."